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Atmospheric_physics | Atmospheric physics is the application of physics to the study of the atmosphere . Atmospheric physicists attempt to model Earth 's atmosphere and the atmospheres of the other planets using fluid flow equations , chemical models , radiation budget , and energy transfer processes in the atmosphere ( as well as how these tie into other systems such as the oceans ) . In order to model weather systems , atmospheric physicists employ elements of scattering theory , wave propagation models , cloud physics , statistical mechanics and spatial statistics which are highly mathematical and related to physics . It has close links to meteorology and climatology and also covers the design and construction of instruments for studying the atmosphere and the interpretation of the data they provide , including remote sensing instruments . At the dawn of the space age and the introduction of sounding rockets , aeronomy became a subdiscipline concerning the upper layers of the atmosphere , where dissociation and ionization are important . |
Baffin_Bay | Baffin Bay ( Inuktitut : Saknirutiak Imanga ; Avannaata Imaa Baie de Baffin ) , located between Baffin Island and the southwest coast of Greenland , is a marginal sea of the North Atlantic Ocean . It is connected to the Atlantic via Davis Strait and the Labrador Sea . The narrower Nares Strait connects Baffin Bay with the Arctic Ocean . The bay is not navigable most of the year because of the ice cover and high density of floating ice and icebergs in the open areas . However , a polynya of about 80,000 km2 , known as the North Water , opens in summer on the north near Smith Sound . Most of the aquatic life of the bay is concentrated near that region . |
Atmospheric_Model_Intercomparison_Project | Atmospheric Model Intercomparison Project ( AMIP ) is a standard experimental protocol for global atmospheric general circulation models ( AGCMs ) . It provides a community-based infrastructure in support of climate model diagnosis , validation , intercomparison , documentation and data access . Virtually the entire international climate modeling community has participated in this project since its inception in 1990 . AMIP is endorsed by the Working Group on Numerical Experimentation ( WGNE ) of the World Climate Research Programme , and is managed by the Program for Climate Model Diagnosis and Intercomparison with the guidance of the WGNE AMIP Panel . The AMIP experiment itself is simple by design ; an AGCM is constrained by realistic sea surface temperature and sea ice from 1979 to near present , with a comprehensive set of fields saved for diagnostic research . This model configuration removes the added complexity of ocean-atmosphere feedbacks in the climate system . It is not meant to be used for climate change prediction , an endeavor that requires a coupled atmosphere-ocean model ( e.g. , see AMIP 's sister project CMIP ) . |
Atmospheric_model | An atmospheric model is a mathematical model constructed around the full set of primitive dynamical equations which govern atmospheric motions . It can supplement these equations with parameterizations for turbulent diffusion , radiation , moist processes ( clouds and precipitation ) , heat exchange , soil , vegetation , surface water , the kinematic effects of terrain , and convection . Most atmospheric models are numerical , i.e. they discretize equations of motion . They can predict microscale phenomena such as tornadoes and boundary layer eddies , sub-microscale turbulent flow over buildings , as well as synoptic and global flows . The horizontal domain of a model is either global , covering the entire Earth , or regional ( limited-area ) , covering only part of the Earth . The different types of models run are thermotropic , barotropic , hydrostatic , and nonhydrostatic . Some of the model types make assumptions about the atmosphere which lengthens the time steps used and increases computational speed . Forecasts are computed using mathematical equations for the physics and dynamics of the atmosphere . These equations are nonlinear and are impossible to solve exactly . Therefore , numerical methods obtain approximate solutions . Different models use different solution methods . Global models often use spectral methods for the horizontal dimensions and finite-difference methods for the vertical dimension , while regional models usually use finite-difference methods in all three dimensions . For specific locations , model output statistics use climate information , output from numerical weather prediction , and current surface weather observations to develop statistical relationships which account for model bias and resolution issues . |
Axiom | An axiom or postulate is a statement that is taken to be true , to serve as a premise or starting point for further reasoning and arguments . The word comes from the Greek axíōma ( -LSB- ) ` that which is thought worthy or fit ' or ` that which commends itself as evident . ' The term has subtle differences in definition when used in the context of different fields of study . As defined in classic philosophy , an axiom is a statement that is so evident or well-established , that it is accepted without controversy or question . As used in modern logic , an axiom is simply a premise or starting point for reasoning . As used in mathematics , the term axiom is used in two related but distinguishable senses : `` logical axioms '' and `` non-logical axioms '' . Logical axioms are usually statements that are taken to be true within the system of logic they define ( e.g. , ( A and B ) implies A ) , often shown in symbolic form , while non-logical axioms ( e.g. , ) are actually substantive assertions about the elements of the domain of a specific mathematical theory ( such as arithmetic ) . When used in the latter sense , `` axiom '' , `` postulate '' , and `` assumption '' may be used interchangeably . In general , a non-logical axiom is not a self-evident truth , but rather a formal logical expression used in deduction to build a mathematical theory . To axiomatize a system of knowledge is to show that its claims can be derived from a small , well-understood set of sentences ( the axioms ) . There are typically multiple ways to axiomatize a given mathematical domain . In both senses , an axiom is any mathematical statement that serves as a starting point from which other statements are logically derived . Whether it is meaningful ( and , if so , what it means ) for an axiom , or any mathematical statement , to be `` true '' is an open question in the philosophy of mathematics . |
Atmospheric_instability | Atmospheric instability is a condition where the Earth 's atmosphere is generally considered to be unstable and as a result the weather is subjected to a high degree of variability through distance and time . Atmospheric stability is a measure of the atmosphere 's tendency to encourage or deter vertical motion , and vertical motion is directly correlated to different types of weather systems and their severity . In unstable conditions , a lifted thing , such as a parcel of air will be warmer than the surrounding air at altitude . Because it is warmer , it is less dense and is prone to further ascent . In meteorology , instability can be described by various indices such as the Bulk Richardson Number , lifted index , K-index , convective available potential energy ( CAPE ) , the Showalter , and the Vertical totals . These indices , as well as atmospheric instability itself , involve temperature changes through the troposphere with height , or lapse rate . Effects of atmospheric instability in moist atmospheres include thunderstorm development , which over warm oceans can lead to tropical cyclogenesis , and turbulence . In dry atmospheres , inferior mirages , dust devils , steam devils , and fire whirls can form . Stable atmospheres can be associated with drizzle , fog , increased air pollution , a lack of turbulence , and undular bore formation . |
Banff_National_Park | Banff National Park -LSB- ˈbæmf -RSB- is Canada 's oldest national park , established in 1885 in the Rocky Mountains . The park , located 110 -- west of Calgary in the province of Alberta , encompasses 6,641 km2 of mountainous terrain , with numerous glaciers and ice fields , dense coniferous forest , and alpine landscapes . The Icefields Parkway extends from Lake Louise , connecting to Jasper National Park in the north . Provincial forests and Yoho National Park are neighbours to the west , while Kootenay National Park is located to the south and Kananaskis Country to the southeast . The main commercial centre of the park is the town of Banff , in the Bow River valley . The Canadian Pacific Railway was instrumental in Banff 's early years , building the Banff Springs Hotel and Lake Louise Chalet , and attracting tourists through extensive advertising . In the early 20th century , roads were built in Banff , at times by war internees from World War I , and through Great Depression-era public works projects . Since the 1960s , park accommodations have been open all year , with annual tourism visits to Banff increasing to over 5 million in the 1990s . Millions more pass through the park on the Trans-Canada Highway . As Banff has over three million visitors annually , the health of its ecosystem has been threatened . In the mid-1990s , Parks Canada responded by initiating a two-year study , which resulted in management recommendations , and new policies that aim to preserve ecological integrity . Banff National Park has a subarctic climate with three ecoregions , including montane , subalpine , and alpine . The forests are dominated by Lodgepole pine at lower elevations and Engelmann spruce in higher ones below the treeline , above which is primarily rocks and ice . Mammal species such as the grizzly , cougar , wolverine , elk , bighorn sheep and moose are found , along with hundreds of bird species . Reptiles and amphibians are also found but only a limited number of species have been recorded . The mountains are formed from sedimentary rocks which were pushed east and over newer rock strata between 80 and 55 million years ago . Over the past few million years , glaciers have at times covered most of the park , but today are found only on the mountain slopes though they include the Columbia Icefield , the largest uninterrupted glacial mass in the Rockies . Erosion from water and ice have carved the mountains into their current shapes . |
Autonomous_building | An autonomous building is a building designed to be operated independently from infrastructural support services such as the electric power grid , gas grid , municipal water systems , sewage treatment systems , storm drains , communication services , and in some cases , public roads . Advocates of autonomous building describe advantages that include reduced environmental impacts , increased security , and lower costs of ownership . Some cited advantages satisfy tenets of green building , not independence per se ( see below ) . Off-grid buildings often rely very little on civil services and are therefore safer and more comfortable during civil disaster or military attacks . ( Off-grid buildings would not lose power or water if public supplies were compromised for some reason . ) Most of the research and published articles concerning autonomous building focus on residential homes . British architects Brenda and Robert Vale have said that , as of 2002 , `` It is quite possible in all parts of Australia to construct a ` house with no bills ' , which would be comfortable without heating and cooling , which would make its own electricity , collect its own water and deal with its own waste ... These houses can be built now , using off-the-shelf techniques . It is possible to build a `` house with no bills '' for the same price as a conventional house , but it would be ( 25 % ) smaller . '' |
Bank_of_Canada | The Bank of Canada ( or simply BoC ) ( Banque du Canada ) is Canada 's central bank . The bank was chartered by and under the Bank of Canada Act on July 3 , 1934 , as a privately owned corporation . In 1938 , the bank was legally designated a federal Crown corporation . The Minister of Finance holds the entire share capital issued by the bank . `` The capital shall be divided into one hundred thousand shares of the par value of fifty dollars each , which shall be issued to the Minister to be held by the Minister on behalf of Her Majesty in right of Canada . '' The essential role of the bank , as Canada 's central bank , is to `` promote the economic and financial well-being of Canada . '' This role follows from the purpose of the Bank as set out in the preamble to the Bank of Canada Act : `` to regulate credit and currency in the best interests of the economic life of the nation , to control and protect the external value of the national monetary unit and to mitigate by its influence fluctuations in the general level of production , trade , prices and employment , so far as may be possible within the scope of monetary action , and generally to promote the economic and financial welfare of Canada '' . With the exception of the word `` Canada '' replacing the word `` Dominion '' the wording today is identical to the 1934 legislation which created the bank . Changes to make the bank a government-owned institution in 1938 did not alter the purpose of the Bank as set out in the preamble to the Bank of Canada Act . More specifically , the responsibilities of the bank are : the formulation of monetary policy ; as the sole issuing authority of Canadian banknotes ; the promotion of a safe , sound financial system within Canada ; and funds management and central banking services `` for the federal government , the Bank and other clients . '' The Bank of Canada headquarters are located at the Bank of Canada Building , 234 Wellington Street in the nation 's capital , Ottawa . The edifice also houses the Currency Museum , which opened in December , 1980 . Between 2013 and 2017 , the Bank of Canada temporarily moved its offices to 234 Laurier Street in Ottawa to allow major renovations to its headquarters building . |
Atmospheric_circulation | Atmospheric circulation is the large-scale movement of air , and together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth . The Earth 's atmospheric circulation varies from year to year , but the large scale structure of its circulation remains fairly constant . The smaller scale weather systems -- mid-latitude depressions , or tropical convective cells -- occur `` randomly '' , and long range weather predictions of those can not be made beyond ten days in practice , or a month in theory ( see Chaos theory and Butterfly effect ) . The Earth 's weather is a consequence of its illumination by the Sun , and the laws of thermodynamics . The atmospheric circulation can be viewed as a heat engine driven by the Sun 's energy , and whose energy sink , ultimately , is the blackness of space . The work produced by that engine causes the motion of the masses of air and in that process it redistributes the energy absorbed by the Earth 's surface near the tropics to space and incidentally to the latitudes nearer the poles . The large scale atmospheric circulation `` cells '' shift polewards in warmer periods ( for example , interglacials compared to glacials ) , but remain largely constant as they are , fundamentally , a property of the Earth 's size , rotation rate , heating and atmospheric depth , all of which change little . Over very long time periods ( hundreds of millions of years ) , a tectonic uplift can significantly alter their major elements , such as the jet stream , and plate tectonics may shift ocean currents . During the extremely hot climates of the Mesozoic , a third desert belt may have existed at the Equator . |
Barents_Basin | The Barents Basin or East Barents Basin is a sedimentary basin underlying the eastern half of the Barents Sea . Lying off Russia on the continental shelf between the Kola Peninsula and Novaya Zemlya , it produces oil and gas . The Barents Basin is bordered by land and the Timan-Pechora Basin to the south , the Murmansk Rise and Murmansk Plateau to the west , the Admiralty High and the island of Novaya Zemlya to the east , and rise of Franz Josef Land to the north . The Barents Basin is subdivided into the South Barents Basin ( south of the Ludlov Saddle ) , the North Barents Basin , and the North Novaya Zemlya Basin . The latter two are separated by a major NW -- SE fault . |
Attorney_General_of_Virginia's_climate_science_investigation | The Attorney General of Virginia 's climate science investigation was a `` Civil Investigative Demand '' initiated in April 2010 by Virginia Attorney General Ken Cuccinelli for a wide range of records held by the University of Virginia related to five grant applications for research work by a leading climate scientist Michael E. Mann , who was an assistant professor at the university from 1999 to 2005 . The demand was issued under the Virginia Fraud Against Taxpayers Act in connection with claims by Cuccinnelli that Mann had possibly violated state fraud laws in relation to five research grants , by allegedly manipulating data . No evidence of wrongdoing was presented to support the claim . Mann 's earlier work had been targeted by climate change skeptics in the hockey stick controversy , and allegations against him were renewed in late 2009 in the Climatic Research Unit email controversy but found to be groundless in a series of investigations . Widespread concerns were raised by University of Virginia 's faculty and numerous scientists and science organizations that Cuccinelli 's actions posed a threat to academic freedom , and would have a chilling effect on research in the state . The university filed a court petition and the judge dismissed Cuccinelli 's demand on the grounds that no justification had been shown for the investigation . Cuccinelli tried to re-open his case by issuing a revised subpoena , and appealed the case to the Virginia Supreme Court . The case was defended by the university , and the court ruled that Cuccinelli did not have the authority to make these demands . The outcome was hailed as a victory for academic freedom . |
Barack_Obama_citizenship_conspiracy_theories | During Barack Obama 's campaign for president in 2008 , through his presidency , and afterwards , many conspiracy theories were circulated , falsely asserting that he was not a natural-born citizen of the United States and consequently , under Article Two of the U.S. Constitution , that he was ineligible to be President of the United States . Theories alleged that Obama 's published birth certificate was a forgery -- that his actual birthplace was not Hawaii but Kenya . Other theories alleged that Obama became a citizen of Indonesia in childhood , thereby losing his U.S. citizenship . Still others claimed that Obama was not a natural-born U.S. citizen because he was born a dual citizen ( British and American ) . A number of political commentators have characterized these various claims as a racist reaction to Obama 's status as the first African American President of the United States . Such claims were promoted by fringe theorists ( pejoratively referred to as `` birther '' ) , some of whom sought court rulings either declaring Obama ineligible to take office , or granting access to various documents which they claimed would evidence such ineligibility ; none of these efforts were successful . Some political opponents , especially in the Republican Party , have expressed skepticism about Obama 's citizenship or been unwilling to acknowledge it ; some have proposed legislation which would require presidential candidates to provide proof of eligibility . Expressed belief in such theories has persisted despite Obama 's pre-election release of his official Hawaiian birth certificate in 2008 ; confirmation , based on the original documents , by the Hawaii Department of Health ; the April 2011 release of a certified copy of Obama 's original Certificate of Live Birth ( or long-form birth certificate ) ; and contemporaneous birth announcements published in Hawaii newspapers . Polls conducted in 2010 suggested that at least one quarter of adult Americans said that they doubted Obama 's U.S. birth , while a May 2011 Gallup poll found that 13 % of American adults ( 23 % of Republicans ) continued to express such doubts . |
Atlantic_Ocean | The Atlantic Ocean is the second largest of the world 's oceans with a total area of about 106,460,000 km2 . It covers approximately 20 percent of the Earth 's surface and about 29 percent of its water surface area . It separates the `` Old World '' from the `` New World '' . The Atlantic Ocean occupies an elongated , S-shaped basin extending longitudinally between Eurasia and Africa to the east , and the Americas to the west . As one component of the interconnected global ocean , it is connected in the north to the Arctic Ocean , to the Pacific Ocean in the southwest , the Indian Ocean in the southeast , and the Southern Ocean in the south ( other definitions describe the Atlantic as extending southward to Antarctica ) . The Equatorial Counter Current subdivides it into the North Atlantic Ocean and South Atlantic Ocean at about 8 ° N. Scientific explorations of the Atlantic include the Challenger expedition , the German Meteor expedition , Columbia University 's Lamont-Doherty Earth Observatory and the United States Navy Hydrographic Office . |
Atlantic_Plain | The Atlantic Plain is one of eight distinct United States physiographic regions . This major division consists of the Continental Shelf and Coastal Plain physiographic provinces . It is the flattest of the U.S. physiographic divisions and stretches over 2200 mi in length from Cape Cod to the Mexican border and southward another 1000 mi to the Yucatán Peninsula . The central and southern Atlantic Coast is characterized by barrier and drowned valley coasts . The coastal Atlantic plain features nearly continuous barriers interrupted by inlets , large embayments with drowned river valleys , and extensive wetlands and marshes . The Atlantic plain slopes gently seaward from the inland highlands in a series of terraces . This gentle slope continues far into the Atlantic and Gulf of Mexico , forming the continental shelf . The relief at the land-sea interface is so low that the boundary between them is often blurry and indistinct , especially along stretches of the Louisiana bayous and the Florida Everglades . |
Atmospheric_carbon_cycle | The atmosphere is one of the Earth 's major carbon reservoirs and an important component of the global carbon cycle , holding approximately 720 gigatons of carbon . Atmospheric carbon plays an important role in the greenhouse effect . The most important carbon compound in this respect is the gas carbon dioxide . Although it is a small percentage of the atmosphere ( approximately 0.04 % on a molar basis ) , it plays a vital role in retaining heat in the atmosphere and thus in the greenhouse effect . Other gases with effects on the climate containing carbon in the atmosphere are methane and chlorofluorocarbons ( the latter is entirely anthropogenic ) . Emissions by humans in the past 200 years have almost doubled the amount carbon dioxide in the atmosphere . |
Bad_faith | Bad faith ( Latin : mala fides ) is double mindedness or double heartedness in duplicity , fraud , or deception . It may involve intentional deceit of others , or self-deception . The expression `` bad faith '' is associated with `` double heartedness '' , which is also translated as `` double mindedness '' . A bad faith belief may be formed through self-deception , being double minded , or `` of two minds '' , which is associated with faith , belief , attitude , and loyalty . In the 1913 Webster 's Dictionary , bad faith was equated with being double hearted , `` of two hearts '' , or `` a sustained form of deception which consists in entertaining or pretending to entertain one set of feelings , and acting as if influenced by another '' . The concept is similar to perfidy , or being `` without faith '' , in which deception is achieved when one side in a conflict promises to act in good faith ( e.g. by raising a flag of surrender ) with the intention of breaking that promise once the enemy has exposed himself . After Jean-Paul Sartre 's analysis of the concepts of self-deception and bad faith , bad faith has been examined in specialized fields as it pertains to self-deception as two semi-independently acting minds within one mind , with one deceiving the other . Some examples of bad faith include : a company representative who negotiates with union workers while having no intent of compromising ; a prosecutor who argues a legal position that he knows to be false ; an insurer who uses language and reasoning which are deliberately misleading in order to deny a claim . Bad faith may be viewed in some cases to not involve deception , as in some kinds of hypochondria with actual physical manifestations . There is a question about the truth or falsity of statements made in bad faith self-deception ; for example , if a hypochondriac makes a complaint about their psychosomatic condition , is it true or false ? Bad faith has been used as a term of art in diverse areas involving feminism , racial supremacism , political negotiation , insurance claims processing , intentionality , ethics , existentialism , and the law . |
Automated_Payment_Transaction_tax | The Automated Payment Transaction ( APT ) tax is a proposal to replace all United States taxes with a single tax ( using a low rate ) on every transaction in the economy . The system was developed by University of Wisconsin -- Madison Professor of Economics Dr. Edgar L. Feige . The foundations of the APT tax proposal -- a small , uniform tax on all economic transactions -- involve simplification , base broadening , reductions in marginal tax rates , the elimination of tax and information returns and the automatic collection of tax revenues at the payment source . The APT approach would extend the tax base from income , consumption and wealth to all transactions . Proponents regard it as a revenue neutral transactions tax , whose tax base is primarily made up of financial transactions . The APT tax extends the tax reform ideas of John Maynard Keynes , James Tobin and Lawrence Summers , to their logical conclusion , namely to tax the broadest possible tax base at the lowest possible tax rate . The goal to significantly improve economic efficiency , enhance stability in financial markets , and reduce to a minimum the costs of tax administration ( assessment , collection , and compliance costs ) . There is disagreement over whether the tax is progressive , with the debate primarily centered on whether the volume of taxed transactions rise disproportionately with a person 's income and net worth . Simulations of the Federal Reserve 's Survey of Consumer Finances demonstrate that high income and wealthy individuals undertake a disproportionate volume of transactions since they own a disproportionate share of financial assets that have relatively high turnover rates . However , since the APT tax has not yet been adopted , some argue that one can not predict whether the tax will be progressive or not . Daniel Akst , writing in the New York Times , wrote `` the Automated Payment Transaction tax offers fairness , simplicity , and efficiency . It may not be a free lunch . But it sure smells better than the one we eat now . '' On April 28 , 2005 , the APT proposal was presented to the President 's Advisory Panel on Federal Tax Reform in Washington , DC . |
Autotroph | An autotroph ( `` self-feeding '' , from the Greek autos `` self '' and trophe `` nourishing '' ) or producer , is an organism that produces complex organic compounds ( such as carbohydrates , fats , and proteins ) from simple substances present in its surroundings , generally using energy from light ( photosynthesis ) or inorganic chemical reactions ( chemosynthesis ) . They are the producers in a food chain , such as plants on land or contrast to heterotrophs as consumers of autotrophs ) . They do not need a living source of energy or organic carbon . Autotrophs can reduce carbon dioxide to make organic compounds for biosynthesis and also create a store of chemical energy . Most autotrophs use water as the reducing agent , but some can use other hydrogen compounds such as hydrogen sulfide . Some autotrophs , like green plants and algae , are phototrophs , meaning that they convert electromagnetic energy from sunlight into chemical energy in the form of reduced carbon . Autotrophs can be photoautotrophs or chemoautotrophs . Phototrophs use light as an energy source , while chemotrophs utilize electron donors as a source of energy , whether from organic or inorganic sources ; however in the case of autotrophs , these electron donors come from inorganic chemical sources . Such chemotrophs are lithotrophs . Lithotrophs use inorganic compounds , such as hydrogen sulfide , elemental sulfur , ammonium and ferrous iron , as reducing agents for biosynthesis and chemical energy storage . Photoautotrophs and lithoautotrophs use a portion of the ATP produced during photosynthesis or the oxidation of inorganic compounds to reduce NADP + to NADPH to form organic compounds . |
Axial_precession | In astronomy , axial precession is a gravity-induced , slow , and continuous change in the orientation of an astronomical body 's rotational axis . In particular , it can refer to the gradual shift in the orientation of Earth 's axis of rotation , which , similar to a wobbling top , traces out a pair of cones joined at their apices in a cycle of approximately 26,000 years . The term `` precession '' typically refers only to this largest part of the motion ; other changes in the alignment of Earth 's axis -- nutation and polar motion -- are much smaller in magnitude . Earth 's precession was historically called the precession of the equinoxes , because the equinoxes moved westward along the ecliptic relative to the fixed stars , opposite to the yearly motion of the Sun along the ecliptic . This term is still used in non-technical discussions , that is , when detailed mathematics are absent . Historically , the discovery of the precession of the equinoxes is usually attributed in the west to the Hellenistic-era ( 2nd century BC ) astronomer , Hipparchus , although there are claims of its earlier discovery , such as in the Indian text , Vedanga Jyotisha , dating from 700 BC . With improvements in the ability to calculate the gravitational force between and among planets during the first half of the nineteenth century , it was recognized that the ecliptic itself moved slightly , which was named planetary precession , as early as 1863 , while the dominant component was named lunisolar precession . Their combination was named general precession , instead of precession of the equinoxes . Lunisolar precession is caused by the gravitational forces of the Moon and Sun on Earth 's equatorial bulge , causing Earth 's axis to move with respect to inertial space . Planetary precession ( an advance ) is due to the small angle between the gravitational force of the other planets on Earth and its orbital plane ( the ecliptic ) , causing the plane of the ecliptic to shift slightly relative to inertial space . Lunisolar precession is about 500 times greater than planetary precession . In addition to the Moon and Sun , the other planets also cause a small movement of Earth 's axis in inertial space , making the contrast in the terms lunisolar versus planetary misleading , so in 2006 the International Astronomical Union recommended that the dominant component be renamed , the precession of the equator , and the minor component be renamed , precession of the ecliptic , but their combination is still named general precession . Many references to the old terms exist in publications predating the change . |
Atomic_theory | In chemistry and physics , atomic theory is a scientific theory of the nature of matter , which states that matter is composed of discrete units called atoms . It began as a philosophical concept in ancient Greece and entered the scientific mainstream in the early 19th century when discoveries in the field of chemistry showed that matter did indeed behave as if it were made up of atoms . The word atom comes from the Ancient Greek adjective atomos , meaning `` indivisible '' . 19th century chemists began using the term in connection with the growing number of irreducible chemical elements . While seemingly apropos , around the turn of the 20th century , through various experiments with electromagnetism and radioactivity , physicists discovered that the so-called `` uncuttable atom '' was actually a conglomerate of various subatomic particles ( chiefly , electrons , protons and neutrons ) which can exist separately from each other . In fact , in certain extreme environments , such as neutron stars , extreme temperature and pressure prevents atoms from existing at all . Since atoms were found to be divisible , physicists later invented the term `` elementary particles '' to describe the `` uncuttable '' , though not indestructible , parts of an atom . The field of science which studies subatomic particles is particle physics , and it is in this field that physicists hope to discover the true fundamental nature of matter . |
Avoiding_Dangerous_Climate_Change | Avoiding Dangerous Climate Change : A Scientific Symposium on Stabilisation of Greenhouse Gases was a 2005 international conference that examined the link between atmospheric greenhouse gas concentration , and the 2 ° C ( 3.6 ° F ) ceiling on global warming thought necessary to avoid the most serious effects of global warming . Previously this had generally been accepted as being 550 ppm . The conference took place under the United Kingdom 's presidency of the G8 , with the participation of around 200 ` internationally renowned ' scientists from 30 countries . It was chaired by Dennis Tirpak and hosted by the Hadley Centre for Climate Prediction and Research in Exeter , from 1 February to 3 February . |
Atmospheric_sciences | Atmospheric sciences is an umbrella term for the study of the Earth 's atmosphere , its processes , the effects other systems have on the atmosphere , and the effects of the atmosphere on these other systems . Meteorology includes atmospheric chemistry and atmospheric physics with a major focus on weather forecasting . Climatology is the study of atmospheric changes ( both long and short-term ) that define average climates and their change over time , due to both natural and anthropogenic climate variability . Aeronomy is the study of the upper layers of the atmosphere , where dissociation and ionization are important . Atmospheric science has been extended to the field of planetary science and the study of the atmospheres of the planets of the solar system . Experimental instruments used in atmospheric sciences include satellites , rocketsondes , radiosondes , weather balloons , and lasers . The term aerology ( from Greek ἀήρ , aēr , `` air '' ; and - λογία , - logia ) is sometimes used as an alternative term for the study of Earth 's atmosphere . Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann . |
Atmosphere_of_Mars | The atmosphere of Mars is the layer of gases surrounding Mars . It is composed mostly of carbon dioxide . The atmospheric pressure on the Martian surface averages 600 Pa , about 0.6 % of Earth 's mean sea level pressure of 101.3 kPa . It ranges from a low of 30 Pa on Olympus Mons 's peak to over 1155 Pa in the depths of Hellas Planitia . This pressure is well below the Armstrong limit for the unprotected human body . Mars 's atmospheric mass of 25 teratonnes compares to Earth 's 5148 teratonnes with a scale height of about 11 km versus Earth 's 7 km . The Martian atmosphere consists of approximately 96 % carbon dioxide , 1.9 % argon , 1.9 % nitrogen , and traces of free oxygen , carbon monoxide , water and methane , among other gases , for a mean molar mass of 43.34 g/mol . There has been renewed interest in its composition since the detection of traces of methane in 2003 that may indicate life but may also be produced by a geochemical process , volcanic or hydrothermal activity . The atmosphere is quite dusty , giving the Martian sky a light brown or orange-red color when seen from the surface ; data from the Mars Exploration Rovers indicate suspended particles of roughly 1.5 micrometres in diameter . On 16 December 2014 , NASA reported detecting an unusual increase , then decrease , in the amounts of methane in the atmosphere of the planet Mars . Organic chemicals have been detected in powder drilled from a rock by the Curiosity rover . Based on deuterium to hydrogen ratio studies , much of the water at Gale Crater on Mars was found to have been lost during ancient times , before the lakebed in the crater was formed ; afterwards , large amounts of water continued to be lost . On 18 March 2015 , NASA reported the detection of an aurora that is not fully understood and an unexplained dust cloud in the atmosphere of Mars . On 4 April 2015 , NASA reported studies , based on measurements by the Sample Analysis at Mars ( SAM ) instrument on the Curiosity rover , of the Martian atmosphere using xenon and argon isotopes . Results provided support for a `` vigorous '' loss of atmosphere early in the history of Mars and were consistent with an atmospheric signature found in bits of atmosphere captured in some Martian meteorites found on Earth . This was further supported by results from the MAVEN orbiter circling Mars , that the solar wind is responsible for stripping away the atmosphere of Mars over the years . |
Astrology | Astrology is the study of the movements and relative positions of celestial objects as a means for divining information about human affairs and terrestrial events . Astrology has been dated to at least the 2nd millennium BCE , and has its roots in calendrical systems used to predict seasonal shifts and to interpret celestial cycles as signs of divine communications . Many cultures have attached importance to astronomical events , and some -- such as the Indians , Chinese , and Maya -- developed elaborate systems for predicting terrestrial events from celestial observations . Western astrology , one of the oldest astrological systems still in use , can trace its roots to 19th-17th century BCE Mesopotamia , from which it spread to Ancient Greece , Rome , the Arab world and eventually Central and Western Europe . Contemporary Western astrology is often associated with systems of horoscopes that purport to explain aspects of a person 's personality and predict significant events in their lives based on the positions of celestial objects ; the majority of professional astrologers rely on such systems . Throughout most of its history astrology was considered a scholarly tradition and was common in academic circles , often in close relation with astronomy , alchemy , meteorology , and medicine . It was present in political circles , and is mentioned in various works of literature , from Dante Alighieri and Geoffrey Chaucer to William Shakespeare , Lope de Vega and Calderón de la Barca . During the 20th century and following the wide-scale adoption of the scientific method , astrology has been challenged successfully on both theoretical and experimental grounds , and has been shown to have no scientific validity or explanatory power . Astrology thus lost its academic and theoretical standing , and common belief in it has largely declined . Astrology is now recognized as pseudoscience . |
Avalanche | An avalanche ( also called a snowslide or snowslip ) is a rapid flow of snow down a sloping surface . Avalanches are typically triggered in a starting zone from a mechanical failure in the snowpack ( slab avalanche ) when the forces on the snow exceed its strength but sometimes only with gradually widening ( loose snow avalanche ) . After initiation , avalanches usually accelerate rapidly and grow in mass and volume as they entrain more snow . If the avalanche moves fast enough some of the snow may mix with the air forming a powder snow avalanche , which is a type of gravity current . Slides of rocks or debris , behaving in a similar way to snow , are also referred to as avalanches ( see rockslide ) . The remainder of this article refers to snow avalanches . The load on the snowpack may be only due to gravity , in which case failure may result either from weakening in the snowpack or increased load due to precipitation . Avalanches initiated by this process are known as spontaneous avalanches . Avalanches can also be triggered by other loading conditions such as human or biologically related activities . Seismic activity may also trigger the failure in the snowpack and avalanches . Although primarily composed of flowing snow and air , large avalanches have the capability to entrain ice , rocks , trees , and other surficial material . However , they are distinct from mudslides which have greater fluidity , rock slides which are often ice free , and serac collapses during an icefall . Avalanches are not rare or random events and are endemic to any mountain range that accumulates a standing snowpack . Avalanches are most common during winter or spring but glacier movements may cause ice and snow avalanches at any time of year . In mountainous terrain , avalanches are among the most serious objective natural hazards to life and property , with their destructive capability resulting from their potential to carry enormous masses of snow at high speeds . There is no universally accepted classification system for different forms of avalanches . Avalanches can be described by their size , their destructive potential , their initiation mechanism , their composition and their dynamics . |
Atmospheric_chemistry | Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth 's atmosphere and that of other planets is studied . It is a multidisciplinary approach of research and draws on environmental chemistry , physics , meteorology , computer modeling , oceanography , geology and volcanology and other disciplines . Research is increasingly connected with other arenas of study such as climatology . The composition and chemistry of the Earth 's atmosphere is of importance for several reasons , but primarily because of the interactions between the atmosphere and living organisms . The composition of the Earth 's atmosphere changes as result of natural processes such as volcano emissions , lightning and bombardment by solar particles from corona . It has also been changed by human activity and some of these changes are harmful to human health , crops and ecosystems . Examples of problems which have been addressed by atmospheric chemistry include acid rain , ozone depletion , photochemical smog , greenhouse gases and global warming . Atmospheric chemists seek to understand the causes of these problems , and by obtaining a theoretical understanding of them , allow possible solutions to be tested and the effects of changes in government policy evaluated . |
Artificial_demand | Artificial demand constitutes demand for something that , in the absence of exposure to the vehicle of creating demand , would not exist . It has controversial applications in microeconomics ( pump and dump strategy ) and advertising . A demand is usually seen as artificial when it increases consumer utility very inefficiently ; for example , a physician prescribing unnecessary surgeries would create artificial demand . Government spending with the primary purpose of providing jobs ( rather than deliverying any other end product ) has been labelled `` artificial demand '' . Similarly Noam Chomsky has suggested that unchecked militarism is a type of government-created artificial demand , a `` system of state planning ... oriented toward military production , in effect , the production of high technology waste '' , with military Keynesianism or a powerful military industrial complex amounts to the `` creation of state-guaranteed markets for high technology waste ( armaments ) . '' Vehicles of creating artificial demand can include mass media advertising , which can create demand for goods , services , political policies or platforms , and other entities . Another example of artificial demand can be seen in penny stock spam . After purchasing a large number of shares of an extremely low-value stock , the spammer attempts to create artificial demand by implementing a spam-based guerrilla marketing strategy . |
Azores | The Azores ( -LSB- əˈzɔərz -RSB- or -LSB- ˈeɪzɔərz -RSB- ; Açores , -LSB- ɐˈsoɾɨʃ -RSB- ) , officially the Autonomous Region of the Azores ( Região Autónoma dos Açores ) , is one of the two autonomous regions of Portugal , an archipelago composed of nine volcanic islands in the North Atlantic Ocean about 1360 km west of continental Portugal , about 1643 km west of Lisbon , in continental Portugal , about 1507 km from the African coast , and about 1925 km southeast of Newfoundland , Canada . Its main industries are agriculture , dairy farming , livestock , fishing , and tourism , which is becoming the major service activity in the region . In addition , the government of the Azores employs a large percentage of the population directly or indirectly in the service and tertiary sectors . The main settlement of the Azores is Ponta Delgada . There are nine major Azorean islands and an islet cluster , in three main groups . These are Flores and Corvo , to the west ; Graciosa , Terceira , São Jorge , Pico , and Faial in the centre ; and São Miguel , Santa Maria , and the Formigas Reef to the east . They extend for more than 600 km and lie in a northwest-southeast direction . All the islands have volcanic origins , although some , such as Santa Maria , have had no recorded activity since the islands were settled . Mount Pico , on the island of Pico , is the highest point in Portugal , at 2351 m . The Azores are actually some of the tallest mountains on the planet , measured from their base at the bottom of the ocean to their peaks , which thrust high above the surface of the Atlantic . The climate of the Azores is very mild for such a northerly location , being influenced by its distance to continents and the passing Gulf Stream . Due to the marine influence , temperatures remain mild year-round . Daytime temperatures normally fluctuate between 16 C and 25 C depending on season . Temperatures above 30 C or below 3 C are unknown in the major population centres . It is also generally wet and cloudy . The culture , dialect , cuisine , and traditions of the Azorean islands vary considerably , because these once-uninhabited and remote islands were settled sporadically over a span of two centuries . |
Backward_bending_supply_curve_of_labour | In economics , a backward-bending supply curve of labour , or backward-bending labour supply curve , is a graphical device showing a situation in which as real , or inflation-corrected , wages increase beyond a certain level , people will substitute leisure ( non-paid time ) for paid worktime and so higher wages lead to a decrease in the labour supply and so less labour-time being offered for sale . The `` labour-leisure '' tradeoff is the tradeoff faced by wage-earning human beings between the amount of time spent engaged in wage-paying work ( assumed to be unpleasant ) and satisfaction-generating unpaid time , which allows participation in `` leisure '' activities and the use of time to do necessary self-maintenance , such as sleep . The key to the tradeoff is a comparison between the wage received from each hour of working and the amount of satisfaction generated by the use of unpaid time . Such a comparison generally means that a higher wage entices people to spend more time working for pay ; the substitution effect implies a positively sloped labour supply curve . However , the backward-bending labour supply curve occurs when an even higher wage actually entices people to work less and consume more leisure or unpaid time . |
Atacama_Cosmology_Telescope | The Atacama Cosmology Telescope ( ACT ) is a six-metre telescope on Cerro Toco in the Atacama Desert in the north of Chile , near the Llano de Chajnantor Observatory . It is designed to make high-resolution , microwave-wavelength surveys of the sky in order to study the cosmic microwave background radiation ( CMB ) . At an altitude of 5190 metres ( 17,030 feet ) , it is one of the highest permanent , ground-based telescopes in the world . Erected in the ( austral ) autumn of 2007 , ACT saw first light on 22 October 2007 with its science receiver , the Millimeter Bolometer Array Camera ( MBAC ) , and completed its first season in December 2007 . It began its second season of observations in June 2008 . The project is a collaboration between Princeton University , Cornell University , the University of Pennsylvania , NASA/GSFC , the Johns Hopkins University , the University of British Columbia , NIST , the Pontificia Universidad Católica de Chile , the University of KwaZulu-Natal , Cardiff University , Rutgers University , the University of Pittsburgh , Columbia University , Haverford College , West Chester University , INAOE , LLNL , NASA/JPL , the University of Toronto , the University of Cape Town , the University of Massachusetts Amherst and York College , CUNY . It is funded by the US National Science Foundation . |
Astra_(satellite) | Astra is the brand name for a number of geostationary communication satellites , both individually and as a group , which are owned and operated by SES S.A. , a global satellite operator based in Betzdorf , in eastern Luxembourg . The name is also used to describe the pan-European broadcasting system provided by these satellites , the channels carried on them , and even the reception equipment . At the time of the launch of the first Astra satellite , Astra 1A in 1988 , the satellite 's operator was known as Société Européenne des Satellites . In 2001 SES Astra , a newly formed subsidiary of SES , operated the Astra satellites and in September 2011 , SES Astra was consolidated back into the parent company , which by this time also operated other satellite families such as AMC , and NSS . Astra satellites broadcast 2,600 digital television channels ( 675 in high definition ) via five main satellite orbital positions to households across Europe and North Africa . The satellites have been instrumental in the establishment of satellite TV and the introduction of digital TV , HDTV , 3D TV , and HbbTV in Europe . A book , High Above , telling the story of the creation and development of the Astra satellites and their contribution to developments in the European TV and media industry , was published in April 2010 to mark the 25th Anniversary of SES . |
Automobile_air_conditioning | Automobile air conditioning ( also called A/C ) systems use air conditioning to cool the air in a vehicle . |
Baby_boom | A baby boom is any period marked by a significant increase of birth rate . This demographic phenomenon is usually ascribed within certain geographical bounds . People born during this period are often called baby boomers ; however , some experts distinguish between those born during such demographic baby booms and those who identify with the overlapping cultural generations . The causes of baby booms involves various fertility factors . The most well-known baby boom occurred immediately after World War II during the Cold War . It was a change of trend that was largely unexpected , because in most countries it occurred in the midst of a period of improving economies and rising living standards . The baby boom most often occurred in countries that experienced tremendous damage from the war and were going through dramatic economic hardships . These countries include Germany and Poland . In 1945 when the war ended , a huge amount of veterans returned home and began living as civilians . In order to make this process as smooth as possible in the US , Congress passed the G.I. Bill of Rights . The purpose of the G.I. Bill of Rights was to encourage home ownership and higher levels of education by charging very low or no interest at all on loans for veterans . Getting settled in with a more comfortable economic position allowed families to form , have a place to live , be educated , and start having babies . `` Now thriving on the American Dream , life was simple , jobs were plentiful , and a record number of babies were born . '' The U.S. birthrate exploded after World War II . From 1945 to 1961 , more than 65 million children were born in the United States . At the height of this baby boom , a child was born every seven seconds . Factors that contributed to the baby boom consisted of young couples who started families after putting off marriage during the War , government encouragement of growth of families through the aid of GI benefits , and popular culture that celebrated pregnancy , parenthood , and large families . Historians say that the baby boom was the result of couples holding off on having children due to the Great Depression and World War II . Once the baby boom began , the average woman started getting married around the age of 20 instead of 22 . Couples were very eager to have babies after the war ended because they knew that the world would be a much better place to start a family . Another leading cause that led to the baby boom was that people were able to afford moving out to the suburbs to raise a family instead of living in the city . Additionally , the cost of living in the suburbs was very low , especially for those returning from the military . This was also the time period where women were encouraged to take on their `` roles '' , meaning that they were encouraged to stay home and be householders along with being a mother while the husband worked . The market became a seller 's market . Many families were adapting to popular culture changes that included purchasing TVs , opening credit card accounts , and little things like buying mouse ears to wear while watching Mickey Mouse . Overall , the baby boom time period was a blessing but it also had its flaws once economists realized how many children were being born . Concern arose about enough resources being available , especially when those born in the baby boom time period started having kids of their own . The issues of the baby boom time period are that it could hugely impact the population change and cause social and economic impacts . One economic impact of the baby boom is the concern that when baby boomers get older and retire , the dependency ratio will increase . The Census Bureau estimates that the dependency ratio in the United States will be 65 by 2020 and reach a record-breaking high of 75 , the highest it has been since the 1960s and 1970s when those baby boomers were children . The economics of an area or country could benefit from the baby boom : It could increase the demand of housing , transportation , facilities and more for the increasing population . With an increase in population , the demand for food also increased . If a country can not keep up with a rapidly increasing population , it could cause a food shortage and insufficient health care facilities . Without the sufficient supplies needed for the population , it could cause poor health that could lead to deaths in the population . |
Atmosphere_of_Earth | The atmosphere of Earth is the layer of gases , commonly known as air , that surrounds the planet Earth and is retained by Earth 's gravity . The atmosphere of Earth protects life on Earth by absorbing ultraviolet solar radiation , warming the surface through heat retention ( greenhouse effect ) , and reducing temperature extremes between day and night ( the diurnal temperature variation ) . By volume , dry air contains 78.09 % nitrogen , 20.95 % oxygen , 0.93 % argon , 0.04 % carbon dioxide , and small amounts of other gases . Air also contains a variable amount of water vapor , on average around 1 % at sea level , and 0.4 % over the entire atmosphere . Air content and atmospheric pressure vary at different layers , and air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth 's troposphere and in artificial atmospheres . The atmosphere has a mass of about 5.15 kg , three quarters of which is within about 11 km of the surface . The atmosphere becomes thinner and thinner with increasing altitude , with no definite boundary between the atmosphere and outer space . The Kármán line , at 100 km , or 1.57 % of Earth 's radius , is often used as the border between the atmosphere and outer space . Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km . Several layers can be distinguished in the atmosphere , based on characteristics such as temperature and composition . The study of Earth 's atmosphere and its processes is called atmospheric science ( aerology ) . Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann . |
BP | BP P.L.C. , formerly British Petroleum , is a British multinational oil and gas company headquartered in London , England . It is one of the world 's seven oil and gas `` supermajors '' , whose performance in 2012 made it the world 's sixth-largest oil and gas company , the sixth-largest energy company by market capitalization and the company with the world 's fifth-largest revenue ( turnover ) . It is a vertically integrated company operating in all areas of the oil and gas industry , including exploration and production , refining , distribution and marketing , petrochemicals , power generation and trading . It also has renewable energy interests in biofuels and wind power . As of 31 December 2016 , BP had operations in 72 countries worldwide , produced around 3.3 e6oilbbl/d of oil equivalent , and had total proved reserves of 17.81 e9oilbbl of oil equivalent . The company has around 18,000 service stations worldwide . Its largest division is BP America in the United States . In Russia BP owns a 19.75 % stake in Rosneft , the world 's largest publicly traded oil and gas company by hydrocarbon reserves and production . BP has a primary listing on the London Stock Exchange and is a constituent of the FTSE 100 Index . It has secondary listings on the Frankfurt Stock Exchange and the New York Stock Exchange . BP 's origins date back to the founding of the Anglo-Persian Oil Company in 1908 , established as a subsidiary of Burmah Oil Company to exploit oil discoveries in Iran . In 1935 , it became the Anglo-Iranian Oil Company and in 1954 British Petroleum . In 1959 , the company expanded beyond the Middle East to Alaska and it was one of the first companies to strike oil in the North Sea . British Petroleum acquired majority control of Standard Oil of Ohio in 1978 . Formerly majority state-owned , the British government privatised the company in stages between 1979 and 1987 . British Petroleum merged with Amoco in 1998 , becoming BP Amoco plc , and acquired ARCO and Burmah Castrol in 2000 , becoming BP plc in 2001 . From 2003 to 2013 , BP was a partner in the TNK-BP joint venture in Russia . BP has been directly involved in several major environmental and safety incidents . Among them were the 2005 Texas City Refinery explosion , which caused the death of 15 workers and resulted in a record-setting OSHA fine ; Britain 's largest oil spill , the wreck of Torrey Canyon ; and the 2006 Prudhoe Bay oil spill , the largest oil spill on Alaska 's North Slope , which resulted in a US$ 25 million civil penalty , the largest per-barrel penalty at that time for an oil spill . The 2010 Deepwater Horizon oil spill , the largest accidental release of oil into marine waters in history , resulted in severe environmental , health and economic consequences , and serious legal and public relations repercussions for BP . 1.8 million gallons of Corexit oil dispersant were used in the cleanup response , becoming the largest application of such chemicals in US history . The company pleaded guilty to 11 counts of felony manslaughter , two misdemeanors , one felony count of lying to Congress , and agreed to pay more than $ 4.5 billion in fines and penalties , the largest criminal resolution in US history . On July 2 , 2015 , BP and five states announced an $ 18.5 billion settlement to be used for Clean Water Act penalties and various claims . |
BOOMERanG_experiment | In astronomy and observational cosmology , The BOOMERanG experiment ( Balloon Observations Of Millimetric Extragalactic Radiation ANd Geophysics ) was an experiment which measured the cosmic microwave background radiation of a part of the sky during three sub-orbital ( high-altitude ) balloon flights . It was the first experiment to make large , high-fidelity images of the CMB temperature anisotropies , and is best known for the discovery in 2000 that the geometry of the universe is close to flat , with similar results from the competing MAXIMA experiment . By using a telescope which flew at over 42,000 meters high , it was possible to reduce the atmospheric absorption of microwaves to a minimum . This allowed massive cost reduction compared to a satellite probe , though only a tiny part of the sky could be scanned . The first was a test flight over North America in 1997 . In the two subsequent flights in 1998 and 2003 the balloon was launched from McMurdo Station in the Antarctic . It was carried by the Polar vortex winds in a circle around the South Pole , returning after two weeks . From this phenomenon the telescope took its name . The BOOMERanG team was led by Andrew E. Lange of Caltech and Paolo de Bernardis of the University of Rome La Sapienza . |
Atlantic_hurricane_season | The Atlantic hurricane season is the period in a year when hurricanes usually form in the Atlantic Ocean . Tropical cyclones in the North Atlantic are called hurricanes , tropical storms , or tropical depressions . In addition , there have been several storms over the years that have not been fully tropical and are categorized as subtropical depressions and subtropical storms . Worldwide , tropical cyclone activity peaks in late summer , when the difference between temperatures aloft and sea surface temperatures is the greatest . However , each particular basin has its own seasonal patterns . On a worldwide scale , May is the least active month , while September is the most active . In the Northern Atlantic Ocean , a distinct hurricane season occurs from June 1 to November 30 , sharply peaking from late August through September ; the season 's climatological peak of activity occurs around September 10 each season . Tropical disturbances that reach tropical storm intensity are named from a pre-determined list . On average , 10.1 named storms occur each season , with an average of 5.9 becoming hurricanes and 2.5 becoming major hurricanes ( Category 3 or greater ) . The most active season was 2005 , during which 28 tropical cyclones formed , of which a record 15 became hurricanes . The least active season was 1914 , with only one known tropical cyclone developing during that year . The Atlantic hurricane season is a time when most tropical cyclones are expected to develop across the northern Atlantic Ocean . It is currently defined as the time frame from June 1 through November 30 , though in the past the season was defined as a shorter time frame . During the season , regular tropical weather outlooks are issued by the National Hurricane Center , and coordination between the Hydrometeorological Prediction Center and National Hurricane Center occurs for systems which have not formed yet , but could develop during the next three to seven days . |
Backcasting | Backcasting is a planning method that starts with defining a desirable future and then works backwards to identify policies and programs that will connect that specified future to the present . The fundamentals of the method were outlined by John . B Robinson from the University of Waterloo in 1990 . The fundamental question of backcasting asks : `` if we want to attain a certain goal , what actions must be taken to get there ? '' Forecasting is the process of predicting the future based on current trend analysis . Backcasting approaches the challenge of discussing the future from the opposite direction . In statistics and data analysis , backcasting can be considered the opposite of forecasting . Whereas forecasting is predicting the future ( unknown ) values of the dependent variables based on known values of the independent variable , backcasting can be considered the prediction of the unknown values of the independent variables that might have existed to explain the known values of the dependent variable . |
Astronomical_seeing | Astronomical seeing refers to the blurring and twinkling of astronomical objects such as stars caused by turbulent mixing in the Earth 's atmosphere that causes variations of the optical refractive index . The astronomical seeing conditions on a given night at a given location describe how much the Earth 's atmosphere perturbs the images of stars as seen through a telescope . The most common seeing measurement is the diameter ( or more correctly the full width at half maximum or FWHM ) of the optical intensity across the seeing disc ( the point spread function for imaging through the atmosphere ) . The FWHM of the point spread function ( loosely called seeing disc diameter or `` seeing '' ) is a reference to the best possible angular resolution which can be achieved by an optical telescope in a long photographic exposure , and corresponds to the FWHM of the fuzzy blob seen when observing a point-like source ( such as a star ) through the atmosphere . The size of the seeing disc is determined by the astronomical seeing conditions at the time of the observation . The best conditions give a seeing disk diameter of ~ 0.4 arcseconds and are found at high-altitude observatories on small islands such as Mauna Kea or La Palma . Seeing is one of the biggest problems for Earth-based astronomy : while large telescopes have theoretically milli-arcsecond resolution , the real image will never be better than the average seeing disc during the observation . This can easily mean a factor of 100 between the potential and practical resolution . Starting in the 1990s , new adaptive optics have been introduced that can help correct for these effects , dramatically improving the resolution of ground based telescopes . |
Atmospheric_methane | Atmospheric methane is the methane present in Earth 's atmosphere . Atmospheric methane concentrations are of interest because it is one of the most potent greenhouse gases in Earth 's atmosphere . The 100-year global warming potential of methane is 28 . That is , over a 100-year period , it traps 28 times more heat per mass unit than carbon dioxide and 32 times the effect when accounted for aerosol interactions . Global methane levels , had risen to 1800 parts per billion ( ppb ) by 2011 , an increase by a factor of 2.5 since pre-industrial times , from 722 ppb , the highest value in at least 800,000 years . Its concentration is higher in the Northern Hemisphere since most sources ( both natural and human ) are located on land and the Northern Hemisphere has more land mass . The concentrations vary seasonally , with , for example , a minimum in the northern tropics during April − May mainly due to removal by the hydroxyl radical . Early in the Earth 's history carbon dioxide and methane likely produced a greenhouse effect . The carbon dioxide would have been produced by volcanoes and the methane by early microbes . During this time , Earth 's earliest life appeared . These first , ancient bacteria added to the methane concentration by converting hydrogen and carbon dioxide into methane and water . Oxygen did not become a major part of the atmosphere until photosynthetic organisms evolved later in Earth 's history . With no oxygen , methane stayed in the atmosphere longer and at higher concentrations than it does today . Methane is created near the surface , and it is carried into the stratosphere by rising air in the tropics . Uncontrolled build-up of methane in Earth 's atmosphere is naturally checked -- although human influence can upset this natural regulation -- by methane 's reaction with hydroxyl radicals formed from singlet oxygen atoms and with water vapor . |
Asteroid_belt | The asteroid belt is the circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter . It is occupied by numerous irregularly shaped bodies called asteroids or minor planets . The asteroid belt is also termed the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such as near-Earth asteroids and trojan asteroids . About half the mass of the belt is contained in the four largest asteroids : Ceres , Vesta , Pallas , and Hygiea . The total mass of the asteroid belt is approximately 4 % that of the Moon , or 22 % that of Pluto , and roughly twice that of Pluto 's moon Charon ( whose diameter is 1200 km ) . Ceres , the asteroid belt 's only dwarf planet , is about 950 km in diameter , whereas 4 Vesta , 2 Pallas , and 10 Hygiea have mean diameters of less than 600 km . The remaining bodies range down to the size of a dust particle . The asteroid material is so thinly distributed that numerous unmanned spacecraft have traversed it without incident . Nonetheless , collisions between large asteroids do occur , and these can form an asteroid family whose members have similar orbital characteristics and compositions . Individual asteroids within the asteroid belt are categorized by their spectra , with most falling into three basic groups : carbonaceous ( C-type ) , silicate ( S-type ) , and metal-rich ( M-type ) . The asteroid belt formed from the primordial solar nebula as a group of planetesimals . Planetesimals are the smaller precursors of the protoplanets . Between Mars and Jupiter , however , gravitational perturbations from Jupiter imbued the protoplanets with too much orbital energy for them to accrete into a planet . Collisions became too violent , and instead of fusing together , the planetesimals and most of the protoplanets shattered . As a result , 99.9 % of the asteroid belt 's original mass was lost in the first 100 million years of the Solar System 's history . Some fragments eventually found their way into the inner Solar System , leading to meteorite impacts with the inner planets . Asteroid orbits continue to be appreciably perturbed whenever their period of revolution about the Sun forms an orbital resonance with Jupiter . At these orbital distances , a Kirkwood gap occurs as they are swept into other orbits . Classes of small Solar System bodies in other regions are the near-Earth objects , the centaurs , the Kuiper belt objects , the scattered disc objects , the sednoids , and the Oort cloud objects . On 22 January 2014 , ESA scientists reported the detection , for the first definitive time , of water vapor on Ceres , the largest object in the asteroid belt . The detection was made by using the far-infrared abilities of the Herschel Space Observatory . The finding was unexpected because comets , not asteroids , are typically considered to `` sprout jets and plumes '' . According to one of the scientists , `` The lines are becoming more and more blurred between comets and asteroids . '' |
Atmospheric_electricity | Atmospheric electricity is the study of electrical charges in the Earth 's atmosphere ( or that of another planet ) . The movement of charge between the Earth 's surface , the atmosphere , and the ionosphere is known as the global atmospheric electrical circuit . Atmospheric electricity is an interdisciplinary topic , involving concepts from electrostatics , atmospheric physics , meteorology and Earth science . Thunderstorms act as a giant battery in the atmosphere , charging up the ionosphere to about 400,000 volts with respect to the surface . This sets up an electric field throughout the atmosphere , which decreases with increase in altitude . Atmospheric ions created by cosmic rays and natural radioactivity move in the electric field , so a very small current flows through the atmosphere , even away from thunderstorms . Near the surface of the earth , the magnitude of the field is around 100 V/m . Atmospheric electricity involves both thunderstorms , which create lightning bolts to rapidly discharge huge amounts of atmospheric charge stored in storm clouds , and the continual electrification of the air due to ionization from cosmic rays and natural radioactivity , which ensure that the atmosphere is never quite neutral . |
Australian_Skeptics | Australian Skeptics is a loose confederation of like-minded organisations across Australia that began in 1980 . Australian Skeptics investigate paranormal and pseudoscientific claims using scientific methodologies . This page covers all Australian skeptical groups who are of this mindset . The title `` Australian Skeptics '' can be easily confused with one of the more prominent groups , `` Australian Skeptics Inc. '' which is based in Sydney and is one of the central organising groups within the Australian Skeptics . |
Atmosphere | An atmosphere is a layer of gases surrounding a planet or other material body , that is held in place by the gravity of that body . An atmosphere is more likely to be retained if the gravity it is subject to is high and the temperature of the atmosphere is low . The atmosphere of Earth is mostly composed of nitrogen ( about 78 % ) , oxygen ( about 21 % ) , argon ( about 0.9 % ) with carbon dioxide and other gases in trace amounts . Oxygen is used by most organisms for respiration , nitrogen is fixed by bacteria and lightning to produce ammonia used in the construction of nucleotides and amino acids and carbon dioxide is used by plants , algae and cyanobacteria for photosynthesis . The atmosphere helps protect living organisms from genetic damage by solar ultraviolet radiation , solar wind and cosmic rays . Its current composition is the product of billions of years of biochemical modification of the paleoatmosphere by living organisms . The term stellar atmosphere describes the outer region of a star , and typically includes the portion starting from the opaque photosphere outwards . Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere . |
Atmospheric_thermodynamics | Atmospheric thermodynamics is the study of heat-to-work transformations ( and their reverse ) that take place in the earth 's atmosphere and manifest as weather or climate . Atmospheric thermodynamics use the laws of classical thermodynamics , to describe and explain such phenomena as the properties of moist air , the formation of clouds , atmospheric convection , boundary layer meteorology , and vertical instabilities in the atmosphere . Atmospheric thermodynamic diagrams are used as tools in the forecasting of storm development . Atmospheric thermodynamics forms a basis for cloud microphysics and convection parameterizations used in numerical weather models and is used in many climate considerations , including convective-equilibrium climate models . |
Bee | Bees are flying insects closely related to wasps and ants , known for their role in pollination and , in the case of the best-known bee species , the European honey bee , for producing honey and beeswax . Bees are a monophyletic lineage within the superfamily Apoidea and are presently considered a clade , called Anthophila . There are nearly 20,000 known species of bees in seven recognized biological families . They are found on every continent except Antarctica , in every habitat on the planet that contains insect-pollinated flowering plants . Some species including honey bees , bumblebees , and stingless bees live socially in colonies . Bees are adapted for feeding on nectar and pollen , the former primarily as an energy source and the latter primarily for protein and other nutrients . Most pollen is used as food for larvae . Bee pollination is important both ecologically and commercially ; the decline in wild bees has increased the value of pollination by commercially managed hives of honey bees . Bees range in size from tiny stingless bee species whose workers are less than 2 mm long , to Megachile pluto , the largest species of leafcutter bee , whose females can attain a length of 39 mm . The most common bees in the Northern Hemisphere are the Halictidae , or sweat bees , but they are small and often mistaken for wasps or flies . Vertebrate predators of bees include birds such as bee-eaters ; insect predators include beewolves and dragonflies . Human beekeeping or apiculture has been practised for millennia , since at least the times of Ancient Egypt and Ancient Greece . Apart from honey and pollination , honey bees produce beeswax , royal jelly and propolis . Bees have appeared in mythology and folklore , again since ancient times , and they feature in works of literature as varied as Virgil 's Georgics , Beatrix Potter 's The Tale of Mrs Tittlemouse , and W. B. Yeats 's poem The Lake Isle of Innisfree . Bee larvae are included in the Javanese dish botok tawon , where they are eaten steamed with shredded coconut . |
Bile_bear | Bile bears , sometimes called battery bears , are bears kept in captivity to harvest their bile , a digestive fluid produced by the liver and stored in the gallbladder , which is used by some traditional Chinese medicine practitioners . It is estimated that 12,000 bears are farmed for bile in China , South Korea , Laos , Vietnam , and Myanmar . The bear species most commonly farmed for bile is the Asiatic black bear ( Ursus thibetanus ) , although the sun bear ( Helarctos malayanus ) and the brown bear ( Ursus arctos ) are also used . Both the Asiatic black bear and the sun bear are listed as Vulnerable on the Red List of Threatened Animals published by the International Union for Conservation of Nature . They were previously hunted for bile but factory farming has become common since hunting was banned in the 1980s . The bile can be harvested using several techniques , all of which require some degree of surgery , and may leave a permanent fistula or inserted catheter . A significant proportion of the bears die because of the stress of unskilled surgery or the infections which may occur . Farmed bile bears are housed continuously in small cages which often prevent them from standing or sitting upright , or from turning around . These highly restrictive cage systems and the low level of skilled husbandry can lead to a wide range of welfare concerns including physical injuries , pain , severe mental stress and muscle atrophy . Some bears are caught as cubs and may be kept in these conditions for over 20 years . Though the value of the bear products trade is estimated as high as $ 2 billion , there is no evidence that bear bile has any medicinal effect . The practice of factory farming bears for bile has been extensively condemned , including by Chinese physicians . |
Beringia_lowland_tundra | The Beringia lowland tundra is a tundra ecoregion of North America , on the west coast of Alaska , mostly covered in wetland . |
Biotic_material | Biotic material or biological derived material is any material that originates from living organisms . Most such materials contain carbon and are capable of decay . The earliest life on Earth arose at least 3.5 billion years ago . Earlier physical evidences of life include graphite , a biogenic substance , in 3.7 billion-year-old metasedimentary rocks discovered in southwestern Greenland , as well as , `` remains of biotic life '' found in 4.1 billion-year-old rocks in Western Australia . Earth 's biodiversity has expanded continually except when interrupted by mass extinctions . Although scholars estimate that over 99 percent of all species of life ( over five billion ) that ever lived on Earth are extinct , there are still an estimated 10 -- 14 million extant species , of which about 1.2 million have been documented and over 86 % have not yet been described . Examples of biotic materials are wood , straw , humus , manure , bark , crude oil , cotton , spider silk , chitin , fibrin , and bone . The use of biotic materials , and processed biotic materials ( bio-based material ) as alternative natural materials , over synthetics is popular with those who are environmentally conscious because such materials are usually biodegradable , renewable , and the processing is commonly understood and has minimal environmental impact . However , not all biotic materials are used in an environmentally friendly way , such as those that require high levels of processing , are harvested unsustainably , or are used to produce carbon emissions . When the source of the recently living material has little importance to the product produced , such as in the production of biofuels , biotic material is simply called biomass . Many fuel sources may have biological sources , and may be divided roughly into fossil fuels , and biofuel . In soil science , biotic material is often referred to as organic matter . Biotic materials in soil include glomalin , Dopplerite and humic acid . Some biotic material may not be considered to be organic matter if it is low in organic compounds , such as a clam 's shell , which is an essential component of the living organism , but contains little organic carbon . Examples of the use of biotic materials include : Alternative natural materials Building material , for a stylistic reasons , or to reduce allergic reactions Clothing energy production Food medicine Ink Composting and mulch |
Beach_ridge | A beach ridge is a wave-swept or wave-deposited ridge running parallel to a shoreline . It is commonly composed of sand as well as sediment worked from underlying beach material . The movement of sediment by wave action is called littoral transport . Movement of material parallel to the shoreline is called longshore transport . Movement perpendicular to the shore is called on-offshore transport . A beach ridge may be capped by , or associated with , sand dunes . The height of a beach ridge is affected by wave size and energy . A fall in water level ( or an uplift of land ) can isolate a beach ridge from the body of water that created it . Isolated beach ridges may be found along dry lakes in the western United States and inland of the Great Lakes of North America , where they formed at the end of the last ice age when lake levels were much higher due to glacial melting and obstructed outflow caused by glacial ice . Some isolated beach ridges are found in parts of Scandinavia , where glacial melting relieved pressure on land masses and resulted in subsequent crustal lifting or post-glacial rebound . A rise in water level can submerge beach ridges created at an earlier stage , causing them to erode and become less distinct . Beach ridges can become routes for roads and trails . |
Beringian_wolf | The Beringian wolf was an Ice Age gray wolf ( Canis lupus ) that once inhabited modern day eastern Alaska , the Yukon and northern Wyoming . Some of these wolves survived well into the Holocene but they are now extinct . The Beringian wolf is notable because it was the first gray wolf ecomorph to be identified and comprehensively studied using a range of scientific techniques , which revealed the prey species and feeding behavior of prehistoric wolves . Compared with the modern Yukon wolf and other Late Pleistocene gray wolves , the Beringian wolf was similar in size but was more robust with stronger jaws and teeth , a broader palate and larger carnassial teeth relative to its skull size . In comparison with the Beringian wolf the more southerly occurring dire wolf ( Canis dirus ) was the same size but heavier and possessed a more robust skull and dentition . The unique adaptation of the skull and dentition of the Beringian wolf allowed it to produce relatively large bite forces , grapple with large struggling prey , and therefore to predate and scavenge on megafauna . The Beringian wolf preyed most often on horse and steppe bison , and also on caribou , mammoth , and woodland muskox . At the close of the Ice Age with the loss of cold and dry conditions and the extinction of much of its prey , the Beringian wolf became extinct . Multiple events appear to have caused the rapid replacement of one species by one within the same genus , or one population by another within the same species , across a broad area . Of the North American wolves , only the ancestor of the modern North American gray wolf survived . |
Beyond_Coal | The Beyond Coal movement is a campaign by environmental group the Sierra Club to promote renewable energy instead of coal . Their primary objective is to close coal power plants in the United States , including at least one-third of the country 's more than 500 coal plants by 2020 , and to replace them with renewable energy sources . The campaign is also active in other countries ; for example they are trying to prevent the construction of the Kosovo C thermal power plant near Pristina , Kosovo ; to this end they have collaborated with academic and Obama administration climate advisor Dan Kammen . Other objectives include keeping coal in the ground , specifically in Appalachia and the Powder River Basin , where the majority of American coal reserves are located , and preventing coal from being exported from America . The campaign has received at least $ 80 million from Michael Bloomberg and his philanthropic foundation , Bloomberg Philanthropies . During the early Presidency of George W. Bush , an energy task force convened by Dick Cheney advocated the construction of 200 new coal plants in the United States , warning that if they were not built the entire country would face load shedding as California had just seen . During the Bush administration , the Beyond Coal campaign prevented 170 of the 200 plants from being built . |
Bio-geoengineering | Bio-geoengineering is a form of climate engineering which seeks to use or modify plants or other living things to modify the Earth 's climate . Bio-energy with carbon storage , afforestation projects , and ocean nourishment ( including iron fertilization ) could be considered examples of bio-geoengineering . Biogenic aerosols can be grown to replace those beneficial aerosols lost as the result of the death of 50 % of Earth 's boreal forests . Agricultural production of atmospheric aerosols called `` monoterpenes '' is possible if crops that are rich in monoterpenes are grown . |
Benchmark_(surveying) | The term bench mark , or benchmark , originates from the chiseled horizontal marks that surveyors made in stone structures , into which an angle-iron could be placed to form a `` bench '' for a leveling rod , thus ensuring that a leveling rod could be accurately repositioned in the same place in the future . These marks were usually indicated with a chiseled arrow below the horizontal line . The term is generally applied to any item used to mark a point as an elevation reference . Frequently , bronze or aluminum disks are set in stone or concrete , or on rods driven deeply into the earth to provide a stable elevation point . If an elevation is marked on a map , but there is no physical mark on the ground , it is a spot height . The height of a benchmark is calculated relative to the heights of nearby benchmarks in a network extending from a fundamental benchmark . A fundamental benchmark is a point with a precisely known relationship to the level datum of the area , typically mean sea level . The position and height of each benchmark is shown on large-scale maps . The terms `` height '' and `` elevation '' are often used interchangeably , but in many jurisdictions they have specific meanings ; `` height '' commonly refers to a local or relative difference in the vertical ( such as the height of a building ) , whereas `` elevation '' refers to the difference from a nominated reference surface ( such as sea-level , or a mathematical/geodetic model that approximates the sea level known as the geoid ) . Elevation may be specified as normal height ( above a reference ellipsoid ) , orthometric height , or dynamic height which have slightly different definitions . |
Biomass_(ecology) | Biomass , is the mass of living biological organisms in a given area or ecosystem at a given time . Biomass can refer to species biomass , which is the mass of one or more species , or to community biomass , which is the mass of all species in the community . It can include microorganisms , plants or animals . The mass can be expressed as the average mass per unit area , or as the total mass in the community . How biomass is measured depends on why it is being measured . Sometimes , the biomass is regarded as the natural mass of organisms in situ , just as they are . For example , in a salmon fishery , the salmon biomass might be regarded as the total wet weight the salmon would have if they were taken out of the water . In other contexts , biomass can be measured in terms of the dried organic mass , so perhaps only 30 % of the actual weight might count , the rest being water . For other purposes , only biological tissues count , and teeth , bones and shells are excluded . In some applications , biomass is measured as the mass of organically bound carbon ( C ) that is present . Apart from bacteria , the total live biomass on Earth is about 560 billion tonnes C , and the total annual primary production of biomass is just over 100 billion tonnes C/yr . The total live biomass of bacteria may be as much as that of plants and animals or may be much less . The total amount of DNA base pairs on Earth , as a possible approximation of global biodiversity , is estimated at 5.0 x 1037 , and weighs 50 billion tonnes . In comparison , the total mass of the biosphere has been estimated to be as much as 4 TtC ( trillion tons of carbon ) . |
Beaufort_Sea | The Beaufort Sea ( mer de Beaufort ) is a marginal sea of the Arctic Ocean , located north of the Northwest Territories , the Yukon , and Alaska , west of Canada 's Arctic islands . The sea is named after hydrographer Sir Francis Beaufort . The major Mackenzie River empties into the Canadian part of the sea , west of Tuktoyaktuk , which is one of the few permanent settlements on the sea shores . The sea , characterized by severe climate , is frozen over most of the year . Historically , only a narrow pass up to 100 km opened in August -- September near its shores , but recently due to climate change in the Arctic the ice-free area in late summer has greatly enlarged . Claims that the seacoast was populated about 30,000 years ago have been largely discredited ( see below ) ; present population density is very low . The sea contains significant resources of petroleum and natural gas under its shelf , such as the Amauligak field . They were discovered in the period between the 1950s and 1980s , and their exploration became the major human activity in the area since the 1980s . The traditional occupations of fishery and whale and seal hunting are practiced only locally , and have no commercial significance . As a result , the sea hosts one of the largest colonies of beluga whales , and there is no sign of overfishing . To prevent overfishing in its waters , the US adopted precautionary commercial fisheries management plan in August 2009 . In April 2011 the Canadian government signed a memorandum of understanding with the Inuvialuit as a first step in developing a larger ocean management plan . The Canadian government announced in October 2014 that no new commercial fisheries in the Beaufort Sea will be considered until research has shown sustainable stocks that would be made available to Inuvialuit first . The Canadian government has set a new block of the Beaufort Sea off the Parry Peninsula in the Amundsen as a Marine Protected Area ( MPA ) . The protected area is set to protect species and habits for the Inuvialuit community . |
Biological_aspects_of_fluorine | Fluorine , a poisonous gas in its elemental form at biological temperatures , has been a subject of significant interest for a broad range of biological applications , including ecology , medical science , and biochemical engineering . Among the most reactive of the elements , it has proven valuable in many potent industrial compounds that are quite dangerous to living organisms , such as the weak ( but very toxic ) acid hydrogen fluoride . Fluorine is a component of so-called `` 1080 '' poison , a mammal-killer banned in much of the world but still used to control populations of Australian foxes and American coyotes . Because carbon-fluorine bonds are difficult to form , they are seldom found in nature . A few species of plants and bacteria found in the tropics make fluorine-containing poisons to deter predators from eating them . The same bond makes fluorination a powerful lever for new drug design , allowing the tweaking of organic molecules in innovative ways , which has led to several blockbuster commercial successes , such as Lipitor and Prozac . When applied topically in dental products , the fluoride ion chemically binds to surface tooth enamel , making it marginally more acid-resistant . Although politically controversial , fluoridation of public water supplies has shown consistent benefits to dental hygiene , especially for poor children . Manmade fluorinated compounds have also played a role in several noteworthy environmental concerns . Chlorofluorocarbons , once major components of numerous commercial aerosol products , have proven damaging to Earth 's ozone layer and resulted in the wide-reaching Montreal Protocol ( though in truth the chlorine in CFCs is the destructive actor , fluorine is an important part of these molecules because it makes them very stable and long-lived ) . Similarly , the stability of many organofluorines has raised the issue of biopersistence . Long-lived molecules from waterproofing sprays , for example PFOA and PFOS , are found worldwide in the tissues of wildlife and humans , including newborn children . Fluorine biology is also relevant to a number of cutting-edge technologies . PFCs ( perfluorocarbons ) are capable of holding enough oxygen to support human liquid breathing . Several works of science fiction have touched on this application , but in the real world , researchers have experimented with PFCs for burned lung care and as blood substitutes . Fluorine in the form of its radioisotope 18F is also at the heart of a modern medical imaging technique known as positron emission tomography ( PET ) . A PET scan produces three-dimensional colored images of parts of the body that use a lot of sugar , particularly the brain or tumors . |
Biotic_component | Biotic components are the living things that shape an ecosystem . Biotic components usually include : Producers , i.e. autotrophs : e.g. plants , convert the energy -LSB- from photosynthesis ( the transfer of sunlight , water , and carbon dioxide into energy ) , or other sources such as hydrothermal vents -RSB- into food . Consumers , i.e. heterotrophs : e.g. animals , depend upon producers ( occasionally other consumers ) for food . Decomposers , i.e. detritivores : e.g. fungi and bacteria , break down chemicals from producers and consumers ( usually dead ) into simpler form which can be reused . A biotic factor is any living component that affects the population of another organism , or the environment . This includes animals that consume the organism , and the living food that the organism consumes . Biotic factors also include human influence , pathogens , and disease outbreaks . Each biotic factor needs energy to do work and food for proper growth . All species are influenced by biotic factors in one way or another . For example , if the number of predators will increase , the whole food web will be affected as the population number of organisms that are lower in the food web will decrease due to predation . Similarly , when organisms have more food to eat , they will grow quicker and will be more likely to reproduce , so the population size will increase . Pathogens and disease outbreaks , however , are most likely to cause a decrease in population size . Humans make the most sudden changes in an environment ( e.g. building cities and factories , disposing of waste into the water ) . These changes are most likely to cause a decrease in the population of any species , due to the sudden appearance of pollutants . Biotic components are contrasted to abiotic components , which are non-living components that influence population size and the environment . Examples of abiotic factors are : temperature , light intensity , moisture and water levels , air currents , carbon dioxide levels and the pH of water and soil . An additional abiotic factor include minerals as they are nonliving and make up the composition of the soil . The factors mentioned above may either cause an increase or a decrease in population size , depending on the organism . For example , rainfall may encourage the growth of new plants , but too much of it may cause flooding , which may drastically decrease the population size . |
Behavior-based_safety | Behavior-Based Safety ( BBS ) is the `` application of science of behavior change to real world problems '' . or `` A process that creates a safety partnership between management and employees that continually focuses people 's attentions and actions on theirs , and others , daily safety behavior . '' BBS `` focuses on what people do , analyzes why they do it , and then applies a research-supported intervention strategy to improve what people do '' . At its very core BBS is based on a larger scientific field called organizational behavior management . In a safety management system based upon the hierarchy of hazard control , BBS may be applied to internalise hazard avoidance strategies or administrative controls ( including use of personal protective equipment ) , but should not be used in preference to the implementation of reasonably practicable safety measures further up the hierarchy . To be successful a BBS program must include all employees , from the CEO to the front line workers including hourly , salary , union employees , contractors and sub-contractors . To achieve changes in behavior , a change in policy , procedures and/or systems most assuredly will also need some change . Those changes can not be done without buy-in and support from all involved in making those decisions . BBS is not based on assumptions , personal feeling , and/or common knowledge . To be successful , the BBS program used must be based on scientific knowledge . |
Biodilution | Biodilution is the decrease in concentration of an element or pollutant with an increase in trophic level . This effect is primarily caused by the observed trend that an increase in algal biomass will reduce the overall concentration of a pollutant per cell , which ultimately contributes to a lower dietary input to grazers ( and higher-level aquatic organisms ) . The primary elements and pollutants of concern are heavy metals such as mercury , cadmium , and lead . These toxins have been shown to bioaccumulate up a food web . In some cases , metals , such as mercury , can biomagnify . This is a major concern since methylmercury , the most toxic mercury species , can be found in high concentrations in human-consumed fish and other aquatic organisms . Persistent organic pollutants , such as carcinogenic polycyclic aromatic hydrocarbons and alkylphenols , have also shown to biodilute in the marine environment . Numerous studies have linked lower mercury concentrations in zooplankton found in eutrophic ( nutrient-rich and highly productive ) as compared to oligotrophic ( low nutrient ) aquatic environments . Nutrient enrichment ( mainly phosphorus and nitrogen ) reduce the input of mercury , and other heavy metals , into aquatic food webs through this biodilution effect . Primary producers , such as phytoplankton , uptake these heavy metals and accumulate them into their cells . The higher the population of phytoplankton , the less concentrated these pollutants will be in their cells . Once consumed by primary consumers , such as zooplankton , these phytoplankton-bound pollutants are incorporated into the consumer 's cells . Higher phytoplankton biomass means a lower concentration of pollutants accumulated by the zooplankton , and so on up the food web . This effect causes an overall dilution of the original concentration up the food web . That is , the concentration of a pollutant will be lower in the zooplankton than the phytoplankton in a high bloom condition . Although most biodilution studies have been on freshwater environments , biodilution has been shown to occur in the marine environment as well . The Northwater Polynya , located in Baffin Bay , was found to have a negative correlation of cadmium , lead , and nickel with an increase in trophic level Cadmium and lead are both non-essential metals that will compete for calcium within an organism , which is detrimental for organism growth . Most studies measure bioaccumulation and biodilution using the δ15N isotope of nitrogen . The δ15N isotopic signature is enriched up the food web . A predator will have a higher δ15N as compared to its prey . This trend allows the tropic position of an organism to be derived . Coupled to the concentration of a specific pollutant , such as mercury , the concentration verses trophic position can be accessed . While most heavy metals bioaccumulate , under certain conditions , heavy metals and organic pollutants have the potential to biodilute , making a higher organism less exposed to the toxin . |
Beach | A beach is a landform along a body of water . It usually consists of loose particles , which are often composed of rock , such as sand , gravel , shingle , pebbles , or cobblestones . The particles composing a beach are occasionally biological in origin , such as mollusc shells or coralline algae . Some beaches have man-made infrastructure , such as lifeguard posts , changing rooms , and showers . They may also have hospitality venues ( such as resorts , camps , hotels , and restaurants ) nearby . Wild beaches , also known as undeveloped or undiscovered beaches , are not developed in this manner . Wild beaches can be valued for their untouched beauty and preserved nature . Beaches typically occur in areas along the coast where wave or current action deposits and reworks sediments . |
Bioenergy_in_China | China has set the goal of attaining one percent of its renewable energy generation through bioenergy in 2020 . The development of bioenergy in China is needed to meet the rising energy demand . Several institutions are involved in this development , most notably the Asian Development Bank and China 's Ministry of Agriculture . There is also an added incentive to develop the bioenergy sector which is to increase the development of the rural agricultural sector . As of 2005 , bioenergy use has reached more than 20 million households in the rural areas , with methane gas as the main biofuel . Also more than 4000 bioenergy facilities produce 8 billion cubic metres every year of methane gas . By 2006 20 % of `` gasoline '' consumed was actually a 10 % ethanol-gasoline blend . ( People 's Daily Online ) As of 2010 , electricity generation by bioenergy is expected to reach 5 GW , and 30 GW by 2020 . The annual use of methane gas is expected to be 19 cubic kilometers by 2010 , and 40 cubic kilometers by 2020 . China is the world 's third-largest producer of ethanol , after Brazil and the United States . ( RFA ) Although only 0.71 % of the country 's grain yield ( 3.366 million tons of grain ) in 2006 was used for production of ethanol , concern has been expressed over potential conflicts between demands for food and fuel , as crop prices rose in late 2006 . |
Bicarbonate | In inorganic chemistry , bicarbonate ( IUPAC-recommended nomenclature : hydrogen carbonate ) is an intermediate form in the deprotonation of carbonic acid . It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochemical role in the physiological pH buffering system . The term `` bicarbonate '' was coined in 1814 by the English chemist William Hyde Wollaston . The prefix `` bi '' in `` bicarbonate '' comes from an outdated naming system and is based on the observation that there is twice as much carbonate per sodium ion in sodium bicarbonate ( NaHCO3 ) and other bicarbonates than in sodium carbonate ( Na2CO3 ) and other carbonates . The name lives on as a trivial name . |
Biodegradation | Biodegradation is the disintegration of materials by bacteria , fungi , or other biological means . Although often conflated , biodegradable is distinct in meaning from compostable . While biodegradable simply means to be consumed by microorganisms , `` compostable '' makes the srial can be degraded aerobically with oxygen , or anaerobically , without oxygen . Biosurfactant , an extracellular surfactant secreted by microorganisms , enhances the biodegradation process . Biodegradable matter is generally organic material that serves as a nutrient for microorganisms . Microorganisms are so numerous and diverse that , a huge range of compounds are biodegraded , including hydrocarbons ( e.g. oil ) , polychlorinated biphenyls ( PCBs ) , polycyclic aromatic hydrocarbons ( PAHs ) , pharmaceutical substances . Decomposition of biodegradable substances may include both biological and abiotic steps . |
Bear_River_(Michigan) | Bear River is a small clear slow-moving river in the U.S. state of Michigan . 14.7 mi long , it is the largest tributary of Little Traverse Bay in the northwest of the lower peninsula . Traverse Bay is on Lake Michigan . The river is formed as the outflow of Walloon Lake on the boundary between Charlevoix County and Emmet County , draining from the southeast end of the lake at near the community of Walloon Lake in Melrose Township . M-75 has its northern terminus in a junction with US 131 nearby . The river flows east for about 2 mi before turning north through Bear Creek Township , angling northwest to empty into Little Traverse Bay in Petoskey at . Petoskey was at first known as `` Bear River '' until being renamed in 1873 . The Bear River itself has also been known as `` Bear Creek '' and `` Ellis Creek '' . The river has excellent fishing and provides opportunities for peaceful canoeing or kayaking . The river is great for smelt fishing . For most of its path in Emmet County , River Road and the Tuscola and Saginaw Bay Railway parallel the river on its west banks . |
Big_Bang_nucleosynthesis | In physical cosmology , Big Bang nucleosynthesis ( abbreviated BBN , also known as primordial nucleosynthesis , arch ( a ) eonucleosynthesis , archonucleosynthesis , protonucleosynthesis and pal ( a ) eonucleosynthesis ) refers to the production of nuclei other than those of the lightest isotope of hydrogen ( hydrogen-1 , 1H , having a single proton as a nucleus ) during the early phases of the Universe . Primordial nucleosynthesis is believed by most cosmologists to have taken place in the interval from roughly 10 seconds to 20 minutes after the Big Bang , and is calculated to be responsible for the formation of most of the universe 's helium as the isotope helium-4 ( 4He ) , along with small amounts of the hydrogen isotope deuterium ( 2H or D ) , the helium isotope helium-3 ( 3He ) , and a very small amount of the lithium isotope lithium-7 ( 7Li ) . In addition to these stable nuclei , two unstable or radioactive isotopes were also produced : the heavy hydrogen isotope tritium ( 3H or T ) ; and the beryllium isotope beryllium-7 ( 7Be ) ; but these unstable isotopes later decayed into 3He and 7Li , as above . Essentially all of the elements that are heavier than lithium were created much later , by stellar nucleosynthesis in evolving and exploding stars . |
Bay | A bay is a recessed , coastal body of water that directly connects to a larger main body of water , such as an ocean , lake , or another bay . A large bay may be called a gulf , sea , sound , or bight . A cove is a type of smaller bay with a circular inlet and narrow entrance . A fjord is a particularly steep bay shaped by glacial activity . Bays can be the estuary of a river , such as the Chesapeake Bay , an estuary of the Susquehanna River . Bays may also be nested within each other ; for example , James Bay is an arm of Hudson Bay in northeastern Canada . Some large bays , such as the Bay of Bengal and the Hudson Bay , have varied marine geology . The land surrounding a bay often reduces the strength of winds and blocks waves . Bays were significant in the history of human settlement because they provided a safe place for fishing . Later they were important in the development of sea trade as the safe anchorage they provide encouraged their selection as ports . The United Nations Convention on the Law of the Sea ( UNCLOS ) , also called the Law of the Sea defines a bay as a well-marked indentation whose penetration is in such proportion to the width of its mouth as to contain land-locked waters and constitute more than a mere curvature of the coast . An indentation shall not , however , be regarded as a bay unless its area is as large as , or larger than , that of the semi-circle whose diameter is a line drawn across the mouth of that indentation . |
Biogas | Biogas typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen . Biogas can be produced from raw materials such as agricultural waste , manure , municipal waste , plant material , sewage , green waste or food waste . Biogas is a renewable energy source . Biogas can be produced by anaerobic digestion with anaerobic organisms , which digest material inside a closed system , or fermentation of biodegradable materials . Biogas is primarily methane and carbon dioxide and may have small amounts of hydrogen sulfide , moisture and siloxanes . The gases methane , hydrogen , and carbon monoxide can be combusted or oxidized with oxygen . This energy release allows biogas to be used as a fuel ; it can be used for any heating purpose , such as cooking . It can also be used in a gas engine to convert the energy in the gas into electricity and heat . Biogas can be compressed , the same way natural gas is compressed to CNG , and used to power motor vehicles . In the UK , for example , biogas is estimated to have the potential to replace around 17 % of vehicle fuel . It qualifies for renewable energy subsidies in some parts of the world . Biogas can be cleaned and upgraded to natural gas standards , when it becomes bio-methane . Biogas is considered to be a renewable resource because its production-and-use cycle is continuous , and it generates no net carbon dioxide . Organic material grows , is converted and used and then regrows in a continually repeating cycle . From a carbon perspective , as much carbon dioxide is absorbed from the atmosphere in the growth of the primary bio-resource as is released when the material is ultimately converted to energy . |
Bioremediation | Bioremediation is a waste management technique that involves the use of organisms to neutralize pollutants from a contaminated site . According to the United States EPA , bioremediation is a `` treatment that uses naturally occurring organisms to break down hazardous substances into less toxic or non toxic substances '' . Technologies can be generally classified as in situ or ex situ . In situ bioremediation involves treating the contaminated material at the site , while ex situ '' involves the removal of the contaminated material to be treated elsewhere . Some examples of bioremediation related technologies are phytoremediation , bioventing , bioleaching , landfarming , bioreactor , composting , bioaugmentation , rhizofiltration , and biostimulation . Bioremediation may occur on its own ( natural attenuation or intrinsic bioremediation ) or may only effectively occur through the addition of fertilizers , oxygen , etc. , that help in enhancing the growth of the pollution-eating microbes within the medium ( biostimulation ) . For example , the US Army Corps of Engineers demonstrated that windrowing and aeration of petroleum-contaminated soils enhanced bioremediation using the technique of landfarming . Depleted soil nitrogen status may encourage biodegradation of some nitrogenous organic chemicals , and soil materials with a high capacity to adsorb pollutants may slow down biodegradation owing to limited bioavailability of the chemicals to microbes . Recent advancements have also proven successful via the addition of matched microbe strains to the medium to enhance the resident microbe population 's ability to break down contaminants . Microorganisms used to perform the function of bioremediation are known as bioremediators . However , not all contaminants are easily treated by bioremediation using microorganisms . For example , heavy metals such as cadmium and lead are not readily absorbed or captured by microorganisms . A recent experiment , however , suggests that fish bones have some success absorbing lead from contaminated soil . Bone char has been shown to bioremediate small amounts of cadmium , copper , and zinc . A recent experiment suggests that the removals of pollutants ( nitrate , silicate , chromium and sulphide ) from tannery wastewater were studied in batch experiments using marine microalgae . The assimilation of metals such as mercury into the food chain may worsen matters . Phytoremediation is useful in these circumstances because natural plants or transgenic plants are able to bioaccumulate these toxins in their above-ground parts , which are then harvested for removal . The heavy metals in the harvested biomass may be further concentrated by incineration or even recycled for industrial use . Some damaged artifacts at museums contain microbes which could be specified as bio remediating agents . In contrast to this situation , other contaminants , such as aromatic hydrocarbons as are common in petroleum , are relatively simple targets for microbial degradation , and some soils may even have some capacity to autoremediate , as it were , owing to the presence of autochthonous microbial communities capable of degrading these compounds . The elimination of a wide range of pollutants and wastes from the environment requires increasing our understanding of the relative importance of different pathways and regulatory networks to carbon flux in particular environments and for particular compounds , and they will certainly accelerate the development of bioremediation technologies and biotransformation processes . |
Beringia | Beringia is defined today as the land and maritime area bounded on the west by the Lena River in Russia ; on the east by the Mackenzie River in Canada ; on the north by 72 degrees north latitude in the Chukchi Sea ; and on the south by the tip of the Kamchatka Peninsula . It includes the Chukchi Sea , the Bering Sea , the Bering Strait , the Chukchi and Kamchatka Peninsulas in Russia as well as Alaska in the United States . The area includes land lying on the North American Plate and Siberian land east of the Chersky Range . Historically , it formed a land bridge that was up to 1000 km wide at its greatest extent and which covered an area as large as British Columbia and Alberta together , totaling at approximately 1600000 km2 . Today , the only land that is visible from the central part of the Bering land bridge are the Diomede Islands , the Pribilof Islands of St. Paul and St. George , St. Lawrence Island , and King Island . The term Beringia was coined by the Swedish botanist Eric Hultén in 1937 . During the ice ages , Beringia , like most of Siberia and all of North and Northeast China , was not glaciated because snowfall was very light . It was a grassland steppe , including the land bridge , that stretched for hundreds of kilometres into the continents on either side . It is believed that a small human population of at most a few thousand arrived in Beringia from eastern Siberia during the Last Glacial Maximum before expanding into the settlement of the Americas sometime after 16,500 years ago during the Late Glacial Maximum as the American glaciers blocking the way southward melted , but before the bridge was covered by the sea about 11,000 years BP . Before European colonization , Beringia was inhabited by the Yupik peoples on both sides of the straits . This culture remains in the region today along with others . In 2012 , the governments of Russia and the United States announced a plan to formally establish `` a transboundary area of shared Beringian heritage '' . Among other things this agreement would establish close ties between the Bering Land Bridge National Preserve and the Cape Krusenstern National Monument in the United States and the planned Beringia National Park in Russia . |
Biosequestration | Biosequestration is the capture and storage of the atmospheric greenhouse gas carbon dioxide by biological processes . This may be by increased photosynthesis ( through practices such as reforestation / preventing deforestation and genetic engineering ) ; by enhanced soil carbon trapping in agriculture ; or by the use of algal bio sequestration ( see algae bioreactor ) to absorb the carbon dioxide emissions from coal , petroleum ( oil ) or natural gas-fired electricity generation . Biosequestration as a natural process has occurred in the past , and was responsible for the formation of the extensive coal and oil deposits which are now being burned . It is a key policy concept in the climate change mitigation debate . It does not generally refer to the sequestering of carbon dioxide in oceans ( see carbon sequestration and ocean acidification ) or rock formations , depleted oil or gas reservoirs ( see oil depletion and peak oil ) , deep saline aquifers , or deep coal seams ( see coal mining ) ( for all see geosequestration ) or through the use of industrial chemical carbon dioxide scrubbing . |
Bear_attack | A bear attack is an attack by any mammal of the family Ursidae , on another animal , although it usually refers to bears attacking humans or domestic pets . Bear attacks are relatively rare , but frequent enough to be of concern for those who are in bear habitats . Bear attacks can be fatal and often hikers , hunters , fisherman , and others in bear country take precautions against bear attacks . According to Taylor Y. Cardall and Peter Rosen , in their article `` Grizzly Bear Attack '' published in the The Journal of Emergency Medicine , there were 162 bear-inflicted injuries reported in the United States between 1900 and 1985 . This constitutes approximately two reported bear-inflicted injuries per year . Likewise , Stephen Herrero , a Canadian biologist , reports that during the 1990s bears killed around three people a year in the U.S. and Canada , as compared to the 15 people killed every year by dogs . Multiple reports remark that one is more likely to be struck by lightning than to be attacked by a bear when outdoors ; around 90 people are killed by lightning each year . However , with the increase in habitat destruction , interactions between bears and humans have increased and one would expect bear attacks to likewise be on the rise . |
Biodiversity | Biodiversity a portmanteau of `` biological diversity , '' generally refers to the variety and variability of life on Earth . According to the United Nations Environment Programme , biodiversity typically measures variation at the genetic , the species , and the ecosystem level . Terrestrial biodiversity tends to be greater near the equator , which seems to be the result of the warm climate and high primary productivity . Biodiversity is not distributed evenly on Earth , and is richest in the tropics . These tropical forest ecosystems cover less than 10 per cent of earth 's surface , and contain about 90 percent of the world 's species . Marine biodiversity tends to be highest along coasts in the Western Pacific , where sea surface temperature is highest and in the mid-latitudinal band in all oceans . There are latitudinal gradients in species diversity . Biodiversity generally tends to cluster in hotspots , and has been increasing through time , but will be likely to slow in the future . Rapid environmental changes typically cause mass extinctions . More than 99.9 percent of all species , amounting to over five billion species , that ever lived on Earth are estimated to be extinct . Estimates on the number of Earth 's current species range from 10 million to 14 million , of which about 1.2 million have been documented and over 86 percent have not yet been described . More recently , in May 2016 , scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described . The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes . In comparison , the total mass of the biosphere has been estimated to be as much as 4 TtC ( trillion tons of carbon ) . In July 2016 , scientists reported identifying a set of 355 genes from the Last Universal Common Ancestor ( LUCA ) of all organisms living on Earth . The age of the Earth is about 4.54 billion years old . The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago , during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon . There are microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia . Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old meta-sedimentary rocks discovered in Western Greenland . More recently , in 2015 , `` remains of biotic life '' were found in 4.1 billion-year-old rocks in Western Australia . According to one of the researchers , `` If life arose relatively quickly on Earth . . then it could be common in the universe . '' Since life began on Earth , five major mass extinctions and several minor events have led to large and sudden drops in biodiversity . The Phanerozoic eon ( the last 540 million years ) marked a rapid growth in biodiversity via the Cambrian explosion -- a period during which the majority of multicellular phyla first appeared . The next 400 million years included repeated , massive biodiversity losses classified as mass extinction events . In the Carboniferous , rainforest collapse led to a great loss of plant and animal life . The Permian -- Triassic extinction event , 251 million years ago , was the worst ; vertebrate recovery took 30 million years . The most recent , the Cretaceous -- Paleogene extinction event , occurred 65 million years ago and has often attracted more attention than others because it resulted in the extinction of the dinosaurs . The period since the emergence of humans has displayed an ongoing biodiversity reduction and an accompanying loss of genetic diversity . Named the Holocene extinction , the reduction is caused primarily by human impacts , particularly habitat destruction . Conversely , biodiversity impacts human health in a number of ways , both positively and negatively . The United Nations designated 2011 -- 2020 as the United Nations Decade on Biodiversity . |
Bayou | In usage in the United States , a bayou ( -LSB- ˈbaɪ.uː -RSB- or -LSB- ˈbaɪ.oʊ -RSB- , from Cajun French ) is a body of water typically found in a flat , low-lying area , and can be either an extremely slow-moving stream or river ( often with a poorly defined shoreline ) , or a marshy lake or wetland . The name `` bayou '' can also refer to a creek whose current reverses daily due to tides and which contains brackish water highly conducive to fish life and plankton . Bayous are commonly found in the Gulf Coast region of the southern United States , notably the Mississippi River Delta , with the states of Louisiana and Texas being famous for them . A bayou is frequently an anabranch or minor braid of a braided channel that is moving much more slowly than the mainstem , often becoming boggy and stagnant . Though fauna varies by region , many bayous are home to crawfish , certain species of shrimp , other shellfish , catfish , frogs , toads , American alligators , American crocodiles , herons , turtles , spoonbills , snakes , leeches , and many other species . |
Biosphere | The biosphere ( from Greek βίος bíos `` life '' and σφαῖρα sphaira `` sphere '' ) also known as the ecosphere ( from Greek οἶκος oîkos `` environment '' and σφαῖρα ) , is the worldwide sum of all ecosystems . The two joined words are `` bio '' and `` sphere '' . It can also be termed as the zone of life on Earth , a closed system ( apart from solar and cosmic radiation and heat from the interior of the Earth ) , and largely self-regulating . By the most general biophysiological definition , the biosphere is the global ecological system integrating all living beings and their relationships , including their interaction with the elements of the lithosphere , geosphere , hydrosphere , and atmosphere . The biosphere is postulated to have evolved , beginning with a process of biopoiesis ( life created naturally from non-living matter , such as simple organic compounds ) or biogenesis ( life created from living matter ) , at least some 3.5 billion years ago . The earliest evidence for life on Earth includes biogenic graphite found in 3.7 billion-year-old metasedimentary rocks from Western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone from Western Australia . More recently , in 2015 , `` remains of biotic life '' were found in 4.1 billion-year-old rocks in Western Australia . In 2017 , putative fossilized microorganisms ( or microfossils ) were announced to have been discovered in hydrothermal vent precipitates in the Nuvvuagittuq Belt of Quebec , Canada that were as old as 4.28 billion years , the oldest record of life on earth , suggesting `` an almost instantaneous emergence of life '' after ocean formation 4.4 billion years ago , and not long after the formation of the Earth 4.54 billion years ago . According to one of the researchers , `` If life arose relatively quickly on Earth ... then it could be common in the universe . '' In a general sense , biospheres are any closed , self-regulating systems containing ecosystems . This includes artificial biospheres such as Biosphere 2 and BIOS-3 , and potentially ones on other planets or moons . |
Betz's_law | Betz 's law indicates the maximum power that can be extracted from the wind , independent of the design of a wind turbine in open flow . It was published in 1919 , by the German physicist Albert Betz . The law is derived from the principles of conservation of mass and momentum of the air stream flowing through an idealized `` actuator disk '' that extracts energy from the wind stream . According to Betz 's law , no turbine can capture more than 16/27 ( 59.3 % ) of the kinetic energy in wind . The factor 16/27 ( 0.593 ) is known as Betz 's coefficient . Practical utility-scale wind turbines achieve at peak 75 % to 80 % of the Betz limit . The Betz limit is based on an open disk actuator . If a diffuser is used to collect additional wind flow and direct it through the turbine , more energy can be extracted , but the limit still applies to the cross-section of the entire structure . |
Bay_of_Saint_Louis | The Bay of Saint Louis ( Bay of St. Louis , St. Louis Bay ) is a shallow-water , partially enclosed estuary of the northeast Gulf of Mexico along the southwestern coast of Mississippi . The estuary receives freshwater input from two blackwater , or swamp-land , tributaries of the Mississippi River , the Jourdan River on the west and the Wolf River on the east and some smaller streams ( Bayou Portage ) ; these are mixed in the bay with salt water from Mississippi Sound and the Mississippi Bight . The waters are comparatively well mixed , with an average salinity of less than 20 . The Bay of Saint Louis is classified as an `` impaired '' waterway by the United States Environmental Protection Agency due to high fecal coliform levels in the waters from urban development on the bay and surrounding waters . |
Base_station | Base station ( or base radio station ) is -- according to the International Telecommunication Union 's ( ITU ) Radio Regulations ( RR ) -- a `` land station in the land mobile service . '' The term is used in the context of mobile telephony , wireless computer networking and other wireless communications and in land surveying . In surveying , it is a GPS receiver at a known position , while in wireless communications it is a transceiver connecting a number of other devices to one another and/or to a wider area . In mobile telephony , it provides the connection between mobile phones and the wider telephone network . In a computer network , it is a transceiver acting as a router for computers in the network , possibly connecting them to a local area network and/or the internet . In traditional wireless communications , it can refer to the hub of a dispatch fleet such as a taxi or delivery fleet , the base of a TETRA network as used by government and emergency services or a CB shack . |
Biofuel_in_the_United_States | The United States produces mainly biodiesel and ethanol fuel , which uses corn as the main feedstock . In 2005 the US overtook Brazil as the world 's largest ethanol producer . In 2006 the US produced 4.855 e9USgal of ethanol . The United States , together with Brazil accounted for 70 percent of all ethanol production , with total world production of 13.5 e9USgal ( 40 million metric tons ) . When accounting just for fuel ethanol production in 2007 , the U.S. and Brazil are responsible for 88 % of the 13.1 e9USgal total world production . Biodiesel is commercially available in most oilseed-producing states . , it was somewhat more expensive than fossil diesel , though it is still commonly produced in relatively small quantities ( in comparison to petroleum products and ethanol fuel ) . Due to increasing pollution control and climate change requirements and tax relief , the U.S. market is expected to grow to 1 to by 2010 . Biofuels are mainly used mixed with fossil fuels . They are also used as additives . The largest biodiesel consumer is the U.S. Army . Most light vehicles on the road today in the US can run on blends of up to 10 % ethanol , and motor vehicle manufacturers already produce vehicles designed to run on much higher ethanol blends . The demand for bioethanol fuel in the United States was stimulated by the discovery in the late 90s that methyl tertiary butyl ether ( MTBE ) , an oxygenate additive in gasoline , was contaminating groundwater . Cellulosic biofuels are under development , to avoid upward pressure on food prices and land use changes that would be expected to result from a major increase in use of food biofuels . Biofuels are not just limited to liquid fuels . One of the often overlooked uses of biomass in the United States is in the gasification of biomass . There is a small , but growing number of people using woodgas to fuel cars and trucks all across America . The challenge is to expand the market for biofuels beyond the farm states where they have been most popular to date . Flex-fuel vehicles are assisting in this transition because they allow drivers to choose different fuels based on price and availability . It should also be noted that the growing ethanol and biodiesel industries are providing jobs in plant construction , operations , and maintenance , mostly in rural communities . According to the Renewable Fuels Association , the ethanol industry created almost 154,000 U.S. jobs in 2005 alone , boosting household income by $ 5.7 billion . It also contributed about $ 3.5 billion in tax revenues at the local , state , and federal levels . On the other hand , in 2010 , the industry received $ 6.646 billion in federal support ( not counting state and local support ) . Based upon average U.S. corn yields for the years 2007 through 2012 , conversion of the entire US corn crop would yield 34.4 billion gallons of ethanol which is approximately 25 % of 2012 finished motor fuel demand . |
Bird | Birds ( Aves ) , a subgroup of reptiles , are the last living examples of dinosaurs . They are a group of endothermic vertebrates , characterised by feathers , toothless beaked jaws , the laying of hard-shelled eggs , a high metabolic rate , a four-chambered heart , and a strong yet lightweight skeleton . Birds live worldwide and range in size from the 5 cm bee hummingbird to the 2.75 m ostrich . They rank as the class of tetrapods with the most living species , at approximately ten thousand , with more than half of these being passerines , sometimes known as perching birds . Birds are the closest living relatives of crocodilians . The fossil record indicates that birds evolved from feathered ancestors within the theropod group of saurischian dinosaurs . True birds first appeared during the Cretaceous period , around 100 million years ago . DNA-based evidence finds that birds diversified dramatically around the time of the Cretaceous -- Palaeogene extinction event 66 million years ago , which reduced the Pterosaurs , and killed off all the non-avian dinosaur lineages . Birds , especially those in the southern continents , survived this event and then migrated to other parts of the world while diversifying during periods of global cooling . Primitive bird-like dinosaurs that lie outside class Aves proper , in the broader group Avialae , have been found dating back to the mid-Jurassic period , around 170 million years ago . Many of these early `` stem-birds '' , such as Archaeopteryx , were not yet capable of fully powered flight , and many retained primitive characteristics like toothy jaws in place of beaks , and long bony tails . Birds have wings which are more or less developed depending on the species ; the only known groups without wings are the extinct moa and elephant birds . Wings , which evolved from forelimbs , gave birds the ability to fly , although further evolution has led to the loss of flight in flightless birds , including ratites , penguins , and diverse endemic island species of birds . The digestive and respiratory systems of birds are also uniquely adapted for flight . Some bird species of aquatic environments , particularly seabirds and some waterbirds , have further evolved for swimming . Some birds , especially corvids and parrots , are among the most intelligent animals ; several bird species make and use tools , and many social species pass on knowledge across generations , which is considered a form of culture . Many species annually migrate great distances . Birds are social , communicating with visual signals , calls , and bird songs , and participating in such social behaviours as cooperative breeding and hunting , flocking , and mobbing of predators . The vast majority of bird species are socially monogamous ( referring to social living arrangement , distinct from genetic monogamy ) , usually for one breeding season at a time , sometimes for years , but rarely for life . Other species have breeding systems that are polygynous ( arrangement of one male with many females ) or , rarely , polyandrous ( arrangement of one female with many males ) . Birds produce offspring by laying eggs which are fertilised through sexual reproduction . They are usually laid in a nest and incubated by the parents . Most birds have an extended period of parental care after hatching . Some birds , such as hens , lay eggs even when not fertilised , though unfertilised eggs do not produce offspring . Many species of birds are economically important as food for human consumption and raw material in manufacturing , with domesticated and undomesticated birds ( poultry and game ) being important sources of eggs , meat , and feathers . Songbirds , parrots , and other species are popular as pets . Guano ( bird excrement ) is harvested for use as a fertiliser . Birds prominently figure throughout human culture . About 120 -- 130 species have become extinct due to human activity since the 17th century , and hundreds more before then . Human activity threatens about 1,200 bird species with extinction , though efforts are underway to protect them . Recreational birdwatching is an important part of the ecotourism industry . |
Big_Sur | Big Sur is a lightly populated , unincorporated region on California 's Central Coast where the Santa Lucia Mountains rise abruptly from the Pacific Ocean . The coast is frequently praised for its rugged coastline and mountain views . As the `` longest and most scenic stretch of undeveloped coastline in the -LSB- contiguous -RSB- United States , '' it has been described as a `` national treasure that demands extraordinary procedures to protect it from development '' and `` one of the most beautiful coastlines anywhere in the world , an isolated stretch of road , mythic in reputation . '' Big Sur 's Cone Peak at 5,155 feet ( 1,571 m ) is only 3 miles ( 5 km ) from the ocean . The stunning views make Big Sur a popular tourist destination . The region is protected by the Big Sur Local Coastal Program which preserves the region as `` open space , a small residential community , and agricultural ranching . '' Approved in 1981 , it is one of the most restrictive local use programs in the state , and is widely regarded as one of the most restrictive documents of its kind anywhere . The program protects viewsheds from the highway and many vantage points , and restricts the density of development to one unit per acre in tourist areas or one dwelling per 10 acre in the far south . About 60 % of the coastal region is owned by a government or private agency that does not allow any development . The majority of the interior region is part of the Los Padres National Forest , the Ventana Wilderness , Silver Peak Wilderness , or Fort Hunter Liggett . When the region was ceded by Mexico to the United States in 1848 , it was the United States ' `` last frontier . '' The region remained one of the most isolated areas of California and the United States until , after 18 years of construction , the Carmel -- San Simeon Highway was completed in 1937 . The region does not have specific boundaries , but is generally considered to include the 76 mile segment of California State Route 1 from Carmel River south to San Carpóforo Creek near San Simeon and the entire Santa Lucia range between the rivers . The interior region is uninhabited , while the coast remains relatively isolated and sparsely populated with about 1,000 year-round residents and relatively few visitor accommodations . The original Spanish-language name for the unexplored mountainous terrain south of Monterey , the capital of Alta California , was `` el país grande del sur '' meaning , `` the big country of the south . '' It was Anglicized by English-speaking settlers as Big Sur . |
Bird_migration | Bird migration is the regular seasonal movement , often north and south along a flyway , between breeding and wintering grounds . Many species of bird migrate . Migration carries high costs in predation and mortality , including from hunting by humans , and is driven primarily by availability of food . It occurs mainly in the northern hemisphere , where birds are funnelled on to specific routes by natural barriers such as the Mediterranean Sea or the Caribbean Sea . Historically , migration has been recorded as much as 3,000 years ago by Ancient Greek authors including Homer and Aristotle , and in the Book of Job , for species such as storks , turtle doves , and swallows . More recently , Johannes Leche began recording dates of arrivals of spring migrants in Finland in 1749 , and scientific studies have used techniques including bird ringing and satellite tracking . Threats to migratory birds have grown with habitat destruction especially of stopover and wintering sites , as well as structures such as power lines and wind farms . The Arctic tern holds the long-distance migration record for birds , travelling between Arctic breeding grounds and the Antarctic each year . Some species of tubenoses ( Procellariiformes ) such as albatrosses circle the earth , flying over the southern oceans , while others such as Manx shearwaters migrate 14,000 km between their northern breeding grounds and the southern ocean . Shorter migrations are common , including altitudinal migrations on mountains such as the Andes and Himalayas . The timing of migration seems to be controlled primarily by changes in day length . Migrating birds navigate using celestial cues from the sun and stars , the earth 's magnetic field , and probably also mental maps . |
Biomedical_research_in_the_United_States | The USA carries out 46 % of global research and development ( R&D ) in life sciences , making it the world leader . |
Binomial_regression | In statistics , binomial regression is a technique in which the response ( often referred to as Y ) is the result of a series of Bernoulli trials , or a series of one of two possible disjoint outcomes ( traditionally denoted `` success '' or 1 , and `` failure '' or 0 ) . In binomial regression , the probability of a success is related to explanatory variables : the corresponding concept in ordinary regression is to relate the mean value of the unobserved response to explanatory variables . Binomial regression models are essentially the same as binary choice models , one type of discrete choice model . The primary difference is in the theoretical motivation : Discrete choice models are motivated using utility theory so as to handle various types of correlated and uncorrelated choices , while binomial regression models are generally described in terms of the generalized linear model , an attempt to generalize various types of linear regression models . As a result , discrete choice models are usually described primarily with a latent variable indicating the `` utility '' of making a choice , and with randomness introduced through an error variable distributed according to a specific probability distribution . Note that the latent variable itself is not observed , only the actual choice , which is assumed to have been made if the net utility was greater than 0 . Binary regression models , however , dispense with both the latent and error variable and assume that the choice itself is a random variable , with a link function that transforms the expected value of the choice variable into a value that is then predicted by the linear predictor . It can be shown that the two are equivalent , at least in the case of binary choice models : the link function corresponds to the quantile function of the distribution of the error variable , and the inverse link function to the cumulative distribution function ( CDF ) of the error variable . The latent variable has an equivalent if one imagines generating a uniformly distributed number between 0 and 1 , subtracting from it the mean ( in the form of the linear predictor transformed by the inverse link function ) , and inverting the sign . One then has a number whose probability of being greater than 0 is the same as the probability of success in the choice variable , and can be thought of as a latent variable indicating whether a 0 or 1 was chosen . In machine learning , binomial regression is considered a special case of probabilistic classification , and thus a generalization of binary classification . |
Bioregion | A bioregion is an ecologically and geographically defined area that is smaller than an ecozone , but larger than an ecoregion or an ecosystem , in WWF classification scheme . There is also an attempt to use the term in a rank-less generalist sense , similar to the terms `` biogeographic area '' or `` biogeographic unit '' . It may be conceptually similar to an ecoprovince . It is also differently used in the environmentalist context , being coined by Berg and Dasmann ( 1977 ) . |
Bilbao | Bilbao ( -LSB- bɪlˈbaʊ , _ - ˈbɑːəʊ -RSB- -LSB- bilˈβao -RSB- ; Bilbo -LSB- bilβo -RSB- ) is a city in northern Spain , the largest city in the province of Biscay and in the Basque Country as a whole . Bilbao is the tenth largest city in Spain , with a population of 345,141 as of 2015 . The Bilbao metropolitan area has roughly 1 million inhabitants , making it one of the most populous metropolitan areas in northern Spain ; with a population of 875,552 the comarca of Greater Bilbao is the fifth-largest urban area in Spain . Bilbao is also the main urban area in what is defined as the Greater Basque region . Bilbao is situated in the north-central part of Spain , some 16 km south of the Bay of Biscay , where the economic social development is located , where the estuary of Bilbao is formed . Its main urban core is surrounded by two small mountain ranges with an average elevation of 400 m. After its foundation in the early 14th century by Diego López V de Haro , head of the powerful Haro family , Bilbao was a commercial hub of the Basque Country that enjoyed significant importance in Green Spain . This was due to its port activity based on the export of iron extracted from the Biscayan quarries . Throughout the nineteenth century and the beginning of the twentieth , Bilbao experienced heavy industrialisation , making it the centre of the second-most industrialised region of Spain , behind Barcelona . At the same time an extraordinary population explosion prompted the annexation of several adjacent municipalities . Nowadays , Bilbao is a vigorous service city that is experiencing an ongoing social , economic , and aesthetic revitalisation process , started by the iconic Bilbao Guggenheim Museum , and continued by infrastructure investments , such as the airport terminal , the rapid transit system , the tram line , the Alhóndiga , and the currently under development Abandoibarra and Zorrozaurre renewal projects . Bilbao is also home to football club Athletic Club de Bilbao , a significant symbol for Basque nationalism due to its promotion of Basque players and one of the most successful clubs in Spanish football history . |
Biome | A biome -LSB- ˈbaɪoʊm -RSB- is a community of plants and animals that have common characteristics for the environment they exist in , and can be found over a range of continents . Spanning continents , biomes are distinct biological communities that have formed in response to a shared physical climate . `` Biome '' is a broader term than `` habitat '' ; any biome can comprise a variety of habitats . While a biome can cover large areas , a microbiome is a mix of organisms that coexist in a defined space as well , but on a much smaller scale . For example , the human microbiome is the collection of bacteria , viruses , and other microorganisms that are present on a human . A ` biota ' is the total collection of organisms of a geographic region or a time period , from local geographic scales and instantaneous temporal scales all the way up to whole-planet and whole-timescale spatiotemporal scales . The biotas of the Earth make up the biosphere . |
Base_(chemistry) | In chemistry , bases are substances that , in aqueous solution , are slippery to the touch , taste astringent , change the color of indicators ( e.g. , turn red litmus paper blue ) , react with acids to form salts , promote certain chemical reactions ( base catalysis ) , accept protons from any proton donor , and/or contain completely or partially displaceable OH − ions . Examples of bases are the hydroxides of the alkali metals and alkaline earth metals ( NaOH , Ca ( OH ) 2 , etc. ) . These particular substances produce hydroxide ions ( OH − ) in aqueous solutions , and are thus classified as Arrhenius bases . For a substance to be classified as an Arrhenius base , it must produce hydroxide ions in an aqueous solution . In order to do so , Arrhenius believed the base must contain hydroxide in the formula . This makes the Arrhenius model limited , as it can not explain the basic properties of aqueous solutions of ammonia ( NH3 ) or its organic derivatives ( amines ) . There are also bases that do not contain a hydroxide ion but nevertheless react with water , resulting in an increase in the concentration of the hydroxide ion . An example of this is the reaction between ammonia and water to produce ammonium and hydroxide . In this reaction ammonia is the base because it accepts a proton from the water molecule . Ammonia and other bases similar to it usually have the ability to form a bond with a proton due to the unshared pair of electrons that they possess . In the more general Brønsted -- Lowry acid -- base theory , a base is a substance that can accept hydrogen cations ( H + ) -- otherwise known as protons . In the Lewis model , a base is an electron pair donor . In water , by altering the autoionization equilibrium , bases yield solutions in which the hydrogen ion activity is lower than it is in pure water , i.e. , the water has a pH higher than 7.0 at standard conditions . A soluble base is called an alkali if it contains and releases OH − ions quantitatively . However , it is important to realize that basicity is not the same as alkalinity . Metal oxides , hydroxides , and especially alkoxides are basic , and counteranions of weak acids are weak bases . Bases can be thought of as the chemical opposite of acids . However , some strong acids are able to act as bases . Bases and acids are seen as opposites because the effect of an acid is to increase the hydronium ( H3O + ) concentration in water , whereas bases reduce this concentration . A reaction between an acid and base is called neutralization . In a neutralization reaction , an aqueous solution of a base reacts with an aqueous solution of an acid to produce a solution of water and salt in which the salt separates into its component ions . If the aqueous solution is saturated with a given salt solute , any additional such salt precipitates out of the solution . The notion of a base as a concept in chemistry was first introduced by the French chemist Guillaume François Rouelle in 1754 . He noted that acids , which at that time were mostly volatile liquids ( like acetic acid ) , turned into solid salts only when combined with specific substances . Rouelle considered that such a substance serves as a `` base '' for the salt , giving the salt a `` concrete or solid form '' . |
Bering_Sea | The Bering Sea is a marginal sea of the Pacific Ocean . It comprises a deep water basin , which then rises through a narrow slope into the shallower water above the continental shelves The Bering Sea is separated from the Gulf of Alaska by the Alaska Peninsula . It covers over 2,000,000 km2 and is bordered on the east and northeast by Alaska , on the west by Russian Far East and Kamchatka Peninsula , on the south by the Alaska Peninsula and the Aleutian Islands and on the far north by the Bering Strait , which connects the Bering Sea to the Arctic Ocean 's Chukchi Sea . Bristol Bay is the portion of the Bering Sea which separates the Alaska Peninsula from mainland Alaska . The Bering Sea is named for Vitus Bering , a Danish navigator in Russian service , who in 1728 was the first European to systematically explore it , sailing from the Pacific Ocean northward to the Arctic Ocean . The Bering Sea ecosystem includes resources within the jurisdiction of the United States and Russia , as well as international waters in the middle of the sea ( known as the `` Donut Hole '' ) . The interaction between currents , sea ice , and weather makes for a vigorous and productive ecosystem . |
Bering_Glacier | Bering Glacier is a glacier in the U.S. state of Alaska . It currently terminates in Vitus Lake south of Alaska 's Wrangell-St . Elias National Park , about 10 km from the Gulf of Alaska . Combined with the Bagley Icefield , where the snow that feeds the glacier accumulates , the Bering is the largest glacier in North America . Warmer temperatures and changes in precipitation over the past century have thinned the Bering Glacier by several hundred meters . Since 1900 the terminus has retreated as much as 12 km . The Bering Glacier exhibits `` surges '' , acceleration events of the flow rate of the glacier , every 20 years or so . During these periods the glacier terminus advances . The surges are generally followed by periods of retreat , so despite the periodic advances the glacier has been shrinking overall . Most glaciers along the Alaskan coast have been retreating along with the Bering Glacier . The glacial retreat has an interesting side effect , an increase in the frequency of earthquakes in the region . The Wrangell and St. Elias mountain ranges that spawn the Bering Glacier were created by the collision of the Pacific and North American tectonic plates -LSB- the Pacific Plate is sliding underneath ( being subducted by ) the North American Plate -RSB- . The weight of the vast amount of ice in the Bering Glacier is enough to depress the Earth 's crust , stabilizing the boundary between the two plates . As the glaciers lose mass , the pressure of the ice is diminished . This reduced compression allows the rocks along faults to move more freely , resulting in more earthquakes . Scientists from the Michigan Tech Research Institute , working with U.S. Geological Survey and U.S. Bureau of Land Management have recently discovered that the glacier is releasing approximately 30 km3 of water a year , more than twice the amount of water in the entire Colorado River . Meltwater at the terminus collects in Vitus Lake , which flows via the Seal River to the Gulf of Alaska . |
Bill_Morneau | William Francis `` Bill '' Morneau ( born October 7 , 1962 ) is a Canadian politician and businessman , who was elected in the 2015 Canadian federal election as member of parliament for Toronto Centre . Morneau was executive chair of Canada 's largest human resources firm , Morneau Shepell , and the former chair of the C. D. Howe Institute . He has also been chair of the board at St. Michael 's Hospital , and Covenant House . Morneau was educated at the UWO and the London School of Economics ( LSE ) . Since November 4 , 2015 , he has been Canada 's Minister of Finance . |
Battery_(electricity) | An electric battery is a device consisting of one or more electrochemical cells with external connections provided to power electrical devices such as flashlights , smartphones , and electric cars . When a battery is supplying electric power , its positive terminal is the cathode and its negative terminal is the anode . The terminal marked negative is the source of electrons that when connected to an external circuit will flow and deliver energy to an external device . When a battery is connected to an external circuit , electrolytes are able to move as ions within , allowing the chemical reactions to be completed at the separate terminals and so deliver energy to the external circuit . It is the movement of those ions within the battery which allows current to flow out of the battery to perform work . Historically the term `` battery '' specifically referred to a device composed of multiple cells , however the usage has evolved additionally to include devices composed of a single cell . Primary ( single-use or `` disposable '' ) batteries are used once and discarded ; the electrode materials are irreversibly changed during discharge . Common examples are the alkaline battery used for flashlights and a multitude of portable electronic devices . Secondary ( rechargeable ) batteries can be discharged and recharged multiple times using mains power from a wall socket ; the original composition of the electrodes can be restored by reverse current . Examples include the lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics such as laptops and smartphones . Batteries come in many shapes and sizes , from miniature cells used to power hearing aids and wristwatches to small , thin cells used in smartphones , to large lead acid batteries used in cars and trucks , and at the largest extreme , huge battery banks the size of rooms that provide standby or emergency power for telephone exchanges and computer data centers . According to a 2005 estimate , the worldwide battery industry generates US$ 48 billion in sales each year , with 6 % annual growth . Batteries have much lower specific energy ( energy per unit mass ) than common fuels such as gasoline . This is somewhat offset by the higher efficiency of electric motors in producing mechanical work , compared to combustion engines . |
Bias | Bias is an inclination or outlook to present or hold a partial perspective , often accompanied by a refusal to consider the possible merits of alternative points of view . Biases can be learned implicitly within cultural contexts . People may develop biases toward or against an individual , an ethnic group , a nation , a religion , a social class , a political party , theoretical paradigms and ideologies within academic domains , or a species . Biased means one-sided , lacking a neutral viewpoint , or not having an open mind . Bias can come in many forms and is related to prejudice and intuition . In science and engineering , a bias is a systematic error . Statistical bias results from an unfair sampling of a population , or from an estimation process that does not give accurate results on average . |
Bering_Strait | The Bering Strait ( Берингов пролив , Beringov proliv , Yupik : Imakpik ) is a strait of the Pacific , which borders with the Arctic to north . It is located between Russia and the United States . Named after Vitus Bering , a Danish-born explorer in the service of the Russian Empire , it lies slightly south of the Arctic Circle being at about 65 ° 40 ' N latitude . The present Russia-US east-west boundary is at 168 ° 58 ' 37 '' W. The Strait has been the subject of the scientific hypothesis that humans migrated from Asia to North America across a land bridge known as Beringia when lower ocean levels -- perhaps a result of glaciers locking up vast amounts of water -- exposed a wide stretch of the sea floor , both at the present strait and in the shallow sea north and south of it . This view of how Paleo-Indians entered America has been the dominant one for several decades and continues to be the most accepted one . Numerous successful crossings without the use of a boat have also been recorded since at least the early 20th century . As of 2012 , the Russian coast of the Bering Strait has been a closed military zone . Through organized trips and the use of special permits , it is possible for foreigners to visit . All arrivals must be through an airport or a cruise port , near the Bering Strait only at Anadyr or Provideniya . Unauthorized travelers who arrive on shore after crossing the strait , even those with visas , may be arrested , imprisoned briefly , fined , deported and banned from future visas . |
Bergmann's_rule | Bergmann 's rule is an ecogeographical rule that states that within a broadly distributed taxonomic clade , populations and species of larger size are found in colder environments , and species of smaller size are found in warmer regions . Although originally formulated in terms of species within a genus , it has often been recast in terms of populations within a species . It is also often cast in terms of latitude . It is possible that the rule applies to some plants , such as Rapicactus . The rule is named after nineteenth century German biologist Carl Bergmann , who described the pattern in 1847 , although he was not the first to notice it . Bergmann 's rule is most often applied to mammals and birds which are endotherms , but some researchers have also found evidence for the rule in studies of ectothermic species . such as the ant Leptothorax acervorum . While Bergmann 's rule appears to hold true for many mammals and birds , there are exceptions . Larger-bodied animals tend to conform more closely to Bergmann 's rule than smaller-bodied animals , at least up to certain latitudes . This perhaps reflects a reduced ability to avoid stressful environments , such as by burrowing . In addition to being a general pattern across space , Bergmann 's rule has been reported in populations over historical and evolutionary time when exposed to varying thermal regimes . In particular , reversible dwarfing of mammals has been noted during two relatively brief upward excursions in temperature during the Paleogene : the Paleocene-Eocene thermal maximum and the Eocene Thermal Maximum 2 . |
Blue_whale | The blue whale ( Balaenoptera musculus ) is a marine mammal belonging to the baleen whales ( Mysticeti ) . At up to 29.9 m in length and with a maximum recorded weight of 173 tonne and probably reaching over 181 tonnes ( 200 short tons ) , it is the largest animal known to have ever existed . Long and slender , the blue whale 's body can be various shades of bluish-grey dorsally and somewhat lighter underneath . There are at least three distinct subspecies : B. m. musculus of the North Atlantic and North Pacific , B. m. intermedia of the Southern Ocean and B. m. brevicauda ( also known as the pygmy blue whale ) found in the Indian Ocean and South Pacific Ocean . B. m. indica , found in the Indian Ocean , may be another subspecies . As with other baleen whales , its diet consists almost exclusively of small crustaceans known as krill . Blue whales were abundant in nearly all the oceans on Earth until the beginning of the twentieth century . For over a century , they were hunted almost to extinction by whalers until protected by the international community in 1966 . A 2002 report estimated there were 5,000 to 12,000 blue whales worldwide , in at least five groups . The IUCN estimates that there are probably between 10,000 and 25,000 blue whales worldwide today . Before whaling , the largest population was in the Antarctic , numbering approximately 239,000 ( range 202,000 to 311,000 ) . There remain only much smaller ( around 2,000 ) concentrations in each of the eastern North Pacific , Antarctic , and Indian Ocean groups . There are two more groups in the North Atlantic , and at least two in the Southern Hemisphere . As of 2014 , the Eastern North Pacific blue whale population had rebounded to nearly its pre-hunting population . |
Block_(meteorology) | Blocks in meteorology are large-scale patterns in the atmospheric pressure field that are nearly stationary , effectively `` blocking '' or redirecting migratory cyclones . They are also known as blocking highs or blocking anticyclones . These blocks can remain in place for several days or even weeks , causing the areas affected by them to have the same kind of weather for an extended period of time ( e.g. precipitation for some areas , clear skies for others ) . In the Northern Hemisphere , extended blocking occurs most frequently in the spring over the eastern Pacific and Atlantic Oceans . |
Body_of_water | A body of water or waterbody ( often spelled water body ) is any significant accumulation of water , generally on a planet 's surface . The term most often refers to oceans , seas , and lakes , but it includes smaller pools of water such as ponds , wetlands , or more rarely , puddles . A body of water does not have to be still or contained ; Rivers , streams , canals , and other geographical features where water moves from one place to another are also considered bodies of water . Most are naturally occurring geographical features , but some are artificial . There are types that can be either . For example , most reservoirs are created by engineering dams , but some natural lakes are used as reservoirs . Similarly , most harbors are naturally occurring bays , but some harbors have been created through construction . Bodies of water that are navigable are known as waterways . Some bodies of water collect and move water , such as rivers and streams , and others primarily hold water , such as lakes and oceans . The term body of water can also refer to a reservoir of water held by a plant , technically known as a phytotelma . Bodies of water are effected by gravity which is what creates the tidal effects on Earth . |
Bivalvia | Bivalvia , in previous centuries referred to as the Lamellibranchiata and Pelecypoda , is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts . Bivalves as a group have no head and they lack some usual molluscan organs like the radula and the odontophore . They include the clams , oysters , cockles , mussels , scallops , and numerous other families that live in saltwater , as well as a number of families that live in freshwater . The majority are filter feeders . The gills have evolved into ctenidia , specialised organs for feeding and breathing . Most bivalves bury themselves in sediment where they are relatively safe from predation . Others lie on the sea floor or attach themselves to rocks or other hard surfaces . Some bivalves , such as the scallops and file shells , can swim . The shipworms bore into wood , clay , or stone and live inside these substances . The shell of a bivalve is composed of calcium carbonate , and consists of two , usually similar , parts called valves . These are joined together along one edge ( the hinge line ) by a flexible ligament that , usually in conjunction with interlocking `` teeth '' on each of the valves , forms the hinge . This arrangement allows the shell to be opened and closed without the two halves detaching . The shell is typically bilaterally symmetrical , with the hinge lying in the sagittal plane . Adult shell sizes of bivalves vary from fractions of a millimetre to over a metre in length , but the majority of species do not exceed 10 cm ( 4 in ) . Bivalves have long been a part of the diet of coastal and riparian human populations . Oysters were cultured in ponds by the Romans , and mariculture has more recently become an important source of bivalves for food . Modern knowledge of molluscan reproductive cycles has led to the development of hatcheries and new culture techniques . A better understanding of the potential hazards of eating raw or undercooked shellfish has led to improved storage and processing . Pearl oysters ( the common name of two very different families in salt water and fresh water ) are the most common source of natural pearls . The shells of bivalves are used in craftwork , and the manufacture of jewellery and buttons . Bivalves have also been used in the biocontrol of pollution . Bivalves appear in the fossil record first in the early Cambrian more than 500 million years ago . The total number of living species is about 9,200 . These species are placed within 1,260 genera and 106 families . Marine bivalves ( including brackish water and estuarine species ) represent about 8,000 species , combined in four subclasses and 99 families with 1,100 genera . The largest recent marine families are the Veneridae , with more than 680 species and the Tellinidae and Lucinidae , each with over 500 species . The freshwater bivalves include seven families , the largest of which are the Unionidae , with about 700 species . |