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Science, in the broadest sense of the term, refers to any system of knowledge attained by verifiable means. In a more restricted sense, science refers to a system of acquiring knowledge based on empiricism, experimentation, and methodological naturalism, as well as to the organized body of knowledge humans have gained by such research.

Scientists maintain that scientific investigation must adhere to the scientific method, a process for properly developing and evaluating natural explanations for observable phenomena based on empirical study and independent verification. Science typically, therefore, rejects supernatural explanations, arguments from authority and biased observational studies.

Fields of science are commonly classified along two major lines: Natural sciences, which study natural phenomena; and Social sciences, which study human behavior and societies. Whether mathematics is a science is a matter of perspective.

Fields of science can be further distinguished as pure science or applied science. Pure science is principally involved with the discovery of new truths with less (or no) regard to their applications. Applied science is principally involved with the application of existing truths in new ways.

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Articles 1 – 20

Portal:Science/Featured article/1

Charles Darwin, whose theory of natural selection underpins Evolution
Evolution is a change in the genetic makeup of a population within a species. Since the emergence of modern genetics in the 1940s, evolution has been defined more specifically as a change in the frequency of alleles from one generation to the next. The word "evolution" is often used as a shorthand for the modern theory of evolution of species based upon Charles Darwin's theory of natural selection, which states that all modern species are the products of an extensive process that began over three billion years ago with simple single-celled organisms, and Gregor Mendel's theory of genetics. As the theory of evolution by natural selection and genetics has become universally accepted in the scientific community, it has replaced other explanations including creationism and Lamarckism. Skeptics, often creationists, sometimes deride evolution as "just a theory" in an attempt to characterize it as an arbitrary choice and degrade its claims to truth. Such criticism overlooks the scientifically-accepted use of the word "theory" to mean a falsifiable and well-supported hypothesis.

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A space elevator
A space elevator is a hypothetical structure designed to transport material from a planet's surface into space. Many different types of space elevator structures have been proposed. They all share the goal of replacing rocket propulsion with the traversal of a fixed structure via a mechanism not unlike an elevator, hence its name, in order to move material into or beyond orbit. Space elevators have also sometimes been referred to as space bridges, beanstalks, space ladders or space lifts. The most common proposal is a tether (usually a cable or ribbon) that spans from the surface to a point beyond geosynchronous orbit. As the planet rotates, the inertia at the end of the tether counteracts gravity and keeps the tether taut. Vehicles can then climb the tether and escape the planet's gravity without the use of rockets. Such a structure could eventually permit delivery of great quantities of cargo and people to orbit, and at costs only a fraction of those associated with current means.

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New horizons (NASA)
New Horizons is a NASA unmanned spacecraft designed to fly by Pluto and its moons (including Charon) and transmit images and data back to Earth. Mission planners hope that NASA will approve plans to continue the mission with a fly-by of a Kuiper Belt Object and return further data. A consortium of organizations, led by Southwest Research Institute and the Johns Hopkins Applied Physics Laboratory, has built the craft. The mission's principal investigator is S. Alan Stern of Southwest Research. The probe successfully launched from Cape Canaveral, Florida at 14:00 EST January 19, 2006 and is now en route to Jupiter for a gravity assist.

The primary scientific objectives are to characterize the global geology and morphology and map the surface composition of Pluto and Charon, and study the neutral atmosphere of Pluto and its escape rate. Other objectives include studying time variability of Pluto's surface and atmosphere; imaging and mapping areas of Pluto and Charon at high-resolution; characterizing Pluto's upper atmosphere, ionosphere, and energetic particle environment; searching for an atmosphere around Charon; refining bulk parameters of Pluto and Charon; and searching for additional satellites and rings.

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Alanine, as used in NMR implementation of error correction. Qubits are dictated by spin states of carbon atoms.
A quantum computer is any device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. In a classical (or conventional) computer, the amount of data is measured by bits; in a quantum computer, it is measured by qubits. The basic principle of quantum computation is that the quantum properties of particles can be used to represent and structure data, and that devised quantum mechanisms can be used to perform operations with this data. For a generally accessible overview of quantum computing, see Quantum Computing with Molecules, an article in Scientific American by Neil Gershenfeld and Isaac L. Chuang.

Experiments have already been carried out in which quantum computational operations were executed on a very small number of qubits. Research in both theoretical and practical areas continues at a frantic pace; see Quantum Information Science and Technology Roadmapfor a sense of where the research is heading. Many national government and military funding agencies support quantum computing research, to develop quantum computers for both civilian and national security purposes, such as cryptanalysis.

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Nanodevice that efficiently produces visible light, through energy transfer from quantum wells to quantum dots.
A quantum dot is a semiconducting crystal nanotechnology. Quantum dots confine electrons, holes, electron-hole pairs, or excitons to zero dimensions to a region on the order of the electrons' Compton wavelength. This confinement leads to discrete quantized energy levels and to the quantization of charge in units of the elementary electric charge e. Quantum dots are particularly significant for optical applications due to their theoretically high quantum yield. Quantum dots have also been suggested as implementations of a qubit for quantum information processing.

Because the quantum dot has discrete energy levels, much like an atom, they are sometimes called artificial atoms. The energy levels can be controlled by changing the size and shape of the quantum dot, and the depth of the potential. Like in atoms, the energy levels of small quantum dots can be probed by optical spectroscopy techniques. In contrast to atoms it is relatively easy to connect quantum dots by tunnel barriers to conducting leads, which allows the application of the techniques of tunneling spectroscopy for their investigation.

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Molecular model of hydrogen chloride
Hydrogen chloride, also known under the name HCl, is a highly corrosive and toxic colorless gas that forms white fumes on contact with humidity. These fumes consist of hydrochloric acid which forms when hydrogen chloride dissolves in water. Hydrogen chloride gas as well as hydrochloric acid are important chemicals in chemistry, science, technology, and industry. The name HCl often refers somewhat misleadingly to hydrochloric acid instead of the gaseous hydrogen chloride.

Hydrogen chloride forms corrosive hydrochloric acid on contact with body tissue. Inhalation of the fumes can cause coughing, choking, inflammation of the nose, throat, and upper respiratory tract, and in severe cases, pulmonary edema, circulatory system failure, and death. Skin contact can cause redness, pain, and severe skin burns. Hydrogen chloride may cause severe burns to the eye and permanent eye damage.

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Carbon nanotube
Nanotechnology comprises technological developments on the nanometer scale, usually 0.1 to 100 nm (1/1,000 µm, or 1/1,000,000 mm). A possible way to interpret this size is to take the width of a hair, and imagine something ten thousand times smaller. The term has sometimes been applied to microscopic technology.

Nanotechnology is any technology which exploits phenomena and structures that can only occur at the nanometer scale, which is the scale of several atoms and small molecules. The United States's National Nanotechnology Initiative website defines nanotechnology as "the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications."

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Teflon is polytetrafluoroethylene (PTFE), a polymer of fluorinated ethylene.
Teflon is the brand name of the polymer polytetrafluoroethylene (PTFE) discovered by Roy J. Plunkett (1910–1994) of DuPont in 1938 and introduced as a commercial product in 1946. It is a fluoropolymer but not a thermoplastic in the true sense.

PTFE has the lowest coefficient of friction of any known solid material. It is used as a non-stick coating for pans and other cookware. PTFE is very non-reactive and is often used in containers and pipework for reactive chemicals. Its melting point is 327 °C, but its properties degrade above 260 °C. At this point gaseous fluorine compounds are released that are dangerous to humans.

Other polymers with similar composition are known by the Teflon name: fluorinated ethylene-propylene (FEP) and perfluoroalkoxy polymer resin (PFA). They retain the useful properties of PTFE of low friction and non-reactivity, but are more easily formable. FEP is softer than PTFE and melts at 260 °C; it is highly transparent and resistant to sunlight.

Portal:Science/Featured article/9

Severe soil erosion in a wheat field near Washington State University.
Erosion is the displacement of solids (soil, mud, rock and other particles) by the agents of wind, water or ice, by downward or down-slope movement in response to gravity or by living organisms (in the case of bioerosion). Erosion is distinguished from weathering, which is the decomposition of rock and particles through processes where no movement is involved, although the two processes may be concurrent.

Erosion is an intrinsic natural process but in many places it is increased by human land use. Poor land use practices include deforestation, overgrazing, unmanaged construction activity and road or trail building. However, improved land use practices can limit erosion, using techniques like terrace-building and tree planting.

A certain amount of erosion is natural and, in fact, healthy for the ecosystem. For example, gravels continually move downstream in watercourses. Excessive erosion, however, can cause problems, such as receiving water sedimentation, ecosystem damage (including fish kills) and outright loss of soil.

Portal:Science/Featured article/10

Hale-Bopp comet, February 23, 1997
A comet is a small body in the solar system that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail — both due primarily to the effects of solar radiation upon the comet's nucleus, which itself is a minor planet composed of rock, dust, and ices. Due to their origins in the outer solar system and their propensity to be highly affected (or perturbed) by relatively close approaches to the major planets, comets' orbits are constantly changing. Some are moved into sungrazing orbits that destroy the comets when they are near the Sun, while others are thrown out of the solar system forever.

Most comets are believed to originate in a cloud (the Oort cloud) at large distances from the Sun consisting of debris left over from the condensation of the solar nebula; the outer edges of such nebulae are cool enough that water exists in a solid (rather than gaseous) state. Asteroids originate via a different process, but very old comets which have lost all their volatile materials may come to resemble asteroids.

Portal:Science/Featured article/11

A mirror neuron
A mirror neuron is a neuron which fires both when an animal performs an action and when the animal observes the same action performed by another (especially conspecific) animal. Thus, the neuron "mirrors" the behavior of another animal, as though the observer were himself performing the action. These neurons have been observed in primates, in some birds, and in humans. In humans, they have been found in Broca's area and the inferior parietal cortex of the brain. Some scientists consider mirror neurons one of the most important findings of neuroscience in the last decade. See for example, an essay by Ramachandran on their potential importance in imitation and language.

In humans, mirror neurons are found in the inferior frontal cortex, close to Broca's area, a language region. This has lead to suggestions that human language evolved from a gesture performance/understanding system implemented in mirror neurons. However, like many theories of language evolution, there is little direct evidence either way.

Portal:Science/Featured article/12

A ribbon diagram of Dihydrofolate reductase
Enzyme kinetics is the study of the rates of chemical reactions that are catalysed by enzymes. The study of an enzyme's kinetics provides insights into the catalytic mechanism of this enzyme, its role in metabolism, how its activity is controlled in the cell and how drugs and poisons can inhibit its activity.

Enzymes are molecules that manipulate other molecules — the enzymes' substrates. These target molecules bind to an enzyme's active site and are transformed into products through a series of steps known as the enzymatic mechanism. Some enzymes bind multiple substrates and/or release multiple products, such as a protease cleaving one protein substrate into two polypeptide products. Others join substrates together, such as DNA polymerase linking a nucleotide to DNA. Although these mechanisms are often a complex series of steps, there is typically one rate-determining step that determines the overall kinetics. This rate-determining step may be a chemical reaction or a conformational change of the enzyme or substrates, such as those involved in the release of product(s) from the enzyme.

Portal:Science/Featured article/13

A potassium Faraday filter designed, built and photographed by Jonas Hedin for making daytime LIDAR measurements at Arecibo Observatory.
An atomic line filter (ALF) is an advanced optical band-pass filter used in the physical sciences for filtering electromagnetic radiation with precision, accuracy, and minimal signal strength loss. Atomic line filters work via the absorption or resonance lines of atomic vapors and so may also be designated an atomic resonance filter (ARF).

The three major types of atomic line filters are absorption-re-emission ALFs, Faraday filters and Voigt filters. Absorption-re-emission filters were the first type developed, and so are commonly called simply "atomic line filters"; the other two types are usually referred to specifically as "Faraday filters" or "Voigt filters". Atomic line filters use different mechanisms and designs for different applications, but the same basic strategy is always employed: by taking advantage of the narrow lines of absorption or resonance in a metallic vapor, a specific frequency of light bypasses a series of filters that block all other light.

Portal:Science/Featured article/14

The Grand Canyon from Navajo Point
The geology of the Grand Canyon area exposes one of the most complete sequences of rock anywhere, representing a period of nearly 2 billion years of the Earth's history in that part of North America. The major sedimentary rock layers exposed in the Grand Canyon and in the Grand Canyon National Park area range in age from 200 million to nearly 2 billion years old. Most were deposited in warm, shallow seas and near ancient, long-gone sea shores. Both marine and terrestrial sediments are represented, including fossilized sand dunes from an extinct desert.

Uplift of the region started about 75 million years ago in the Laramide orogeny, a mountain-building event that is largely responsible for creating the Rocky Mountains to the east. Accelerated uplift started 17 million years ago when the Colorado Plateaus (on which the area is located) were being formed. In total these layers were uplifted an estimated 10,000 feet (3000 m) which enabled the ancestral Colorado River to cut its channel into the four plateaus that constitute this area. But the canyon did not start to form until 5.3 million years ago when the Gulf of California opened up and thus lowered the river's base level (its lowest point) from that of large inland lakes to sea level.

Portal:Science/Featured article/15

The accelerator chain of the Large Hadron Collider (LHC)
ATLAS (A Toroidal LHC ApparatuS) is one of the five particle detector experiments (ALICE, ATLAS, CMS, TOTEM, and LHCb) being constructed at the Large Hadron Collider, a new particle accelerator at CERN in Switzerland. It will be 45 metres long and 25 metres in diameter, and will weigh about 7,000 tonnes. The project involves roughly 2,000 scientists and engineers at 151 institutions in 34 countries. The construction is scheduled to be completed in 2007. The experiment is expected to measure phenomena that involve highly massive particles which were not measurable using earlier lower-energy accelerators and might shed light on new theories of particle physics beyond the Standard Model.

The ATLAS collaboration, the group of physicists building the detector, was formed in 1992 when the proposed EAGLE (Experiment for Accurate Gamma, Lepton and Energy Measurements) and ASCOT (Apparatus with Super COnducting Toroids) collaborations merged their efforts into building a single, general-purpose particle detector for the Large Hadron Collider. The design was a combination of those two previous designs, as well as the detector research and development that had been done for the Superconducting Supercollider.

Portal:Science/Featured article/16

DNA damage resulting in multiple broken chromosomes
DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light can cause DNA damage, resulting in as many as 1 million individual molecular lesions per cell per day. Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful Batty boi Consequently, the DNA repair process must be constantly active so it can respond rapidly to any damage in the DNA structure.

The rate of DNA repair is dependent on many factors, including the cell type, the age of the cell, and the extracellular environment. A cell that has accumulated a large amount of DNA damage, or one that no longer effectively repairs damage incurred by its DNA, can enter one of three possible states: an irreversible state of dormancy, known as senescence; cell suicide, also known as apoptosis or programmed cell death; or unregulated cell division, which can lead to the formation of a tumor that is cancerous.

Portal:Science/Featured article/17

This long range RADAR antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll.
RADAR is a system that uses radio waves to determine and map the location, direction, and/or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations and terrain. A transmitter emits radio waves, which are reflected by the target and detected by a receiver, typically in the same location as the transmitter. Although the radio signal returned is usually very weak, radio signals can easily be amplified, so radar can detect objects at ranges where other emissions, such as sound or visible light, would be too weak to detect. Radar is used in many contexts, including meteorological detection of precipitation, air traffic control, police detection of speeding traffic, and by the military.

The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging. This acronym of American origin replaced the previously used British abbreviation RDF (Radio Direction Finding). The term has since entered the English language as a standard word, radar, losing the capitalization in the process.

Portal:Science/Featured article/18

Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980.
Global warming is the observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades.

The Earth's average near-surface atmospheric temperature rose 0.6 ± 0.2 °Celsius (1.1 ± 0.4 °Fahrenheit) in the 20th century [1]. A widespread scientific opinion on climate change is that "most of the warming observed over the last 50 years is attributable to human activities"[2].

The increased amounts of carbon dioxide (CO2) and other greenhouse gases (GHGs) are the primary causes of the human-induced component of warming[3]. They are released by the burning of fossil fuels, land clearing and agriculture, etc. and lead to an increase in the greenhouse effect. The first speculation that a greenhouse effect might occur was by the Swedish chemist Svante Arrhenius in 1897, although it did not become a topic of popular debate until some 90 years later.

Portal:Science/Featured article/19

The tectonic plates of the world were mapped in the second half of the 20th century.
Plate tectonics (from Greek τέκτων, tektōn "builder" or "mason") is a theory of geology which was developed to explain the observed evidence for large scale motions within the Earth's crust. The theory encompassed and superseded the older theory of continental drift from the first half of the 20th century and the concept of sea floor spreading developed during the 1960s.

The outermost part of the Earth's interior is made up of two layers: above is the lithosphere, comprising the crust and the rigid uppermost part of the mantle. Below the lithosphere lies the asthenosphere, which is a more viscous zone of the mantle. Although solid, the asthenosphere has very low shear strength and can flow like a liquid on geological time scales. The deeper mantle below the asthenosphere is more rigid again.

Portal:Science/Featured article/20

According to the Big Bang, the universe emerged from an extremely dense and hot state (bottom). Since then, space itself has expanded with the passage of time, carrying the galaxies with it.
In physical cosmology, the Big Bang is the theory that the universe emerged from a tremendously dense and hot state about 13.7 billion years ago. The theory is based on the observations indicating the expansion of space (in accord with the Robertson-Walker model of general relativity) as indicated by the Hubble redshift of distant galaxies taken together with the cosmological principle.

Extrapolated into the past, these observations show that the universe has expanded from a state in which all the matter and energy in the universe was at an immense temperature and fatness. Physicists do not widely agree on what happened before this, although general relativity predicts a gravitational singularity (for reporting on some of the more notable speculation on this issue, see cosmogony).

The term is used both in a narrow sense to refer to a point in time when the observed expansion of the universe (Hubble's law) began — calculated to be 13.7 billion (1.37 × 1010) years ago (±2%) — and in a more general sense to refer to the prevailing cosmological paradigm explaining the origin and expansion of the universe, as well as the composition of primordial matter through nucleosynthesis as predicted by the Alpher-Bethe-Gamow theory.

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Biographies 1–20

Portal:Science/Featured biography/1

Newton at age 12 in Godfrey Kneller's 1689 portrait.
Isaac Newton was an English physicist, mathematician, astronomer, inventor, philosopher and alchemist. A man of profound genius, he is widely regarded as one of the most influential scientists in history. He is associated with the scientific revolution and the advancement of heliocentrism. Among his scientific accomplishments, Newton wrote the Philosophiae Naturalis Principia Mathematica, wherein he described universal gravitation and, via his laws of motion, laid the groundwork for classical mechanics. With Gottfried Wilhelm Leibniz he shares credit for the development of differential calculus. Newton was the first to promulgate a set of natural laws that could govern both terrestrial motion and celestial motion, and is credited with providing mathematical substantiation for Kepler's laws of planetary motion, which he expanded by arguing that orbits (such as those of comets) could include all conic sections (such as the ellipse, hyperbola, and parabola).

Portal:Science/Featured biography/2

Richard Phillips Feynman (May 11, 1918 – February 15, 1988) was one of the most influential American physicists of the 20th century, expanding greatly upon the theory of quantum electrodynamics. As well as being an inspiring lecturer and amateur musician, he helped in the development of the atomic bomb and was later a member of the panel which investigated the Space Shuttle Challenger disaster. For his work on quantum electrodynamics, Feynman was one of the recipients of the Nobel Prize in Physics in 1965, along with Julian Schwinger and Shin-Ichiro Tomonaga.

Feynman was a keen and influential popularizer of physics in both his books and lectures. He is famous for his many adventures, detailed in the books Surely You're Joking, Mr. Feynman!, What Do You Care What Other People Think? and Tuva or Bust!. Posthumously, Feynman is often credited with helping catalyze the field of nanotechnology through his December 1959 talk called There's Plenty of Room at the Bottom. Richard Feynman was, in many respects, an eccentric and a free spirit.

Portal:Science/Featured biography/3

Aristarchus of Samos
Aristarchus (310 BC - c. 230 BC) was a Greek astronomer and mathematician, born on the island of Samos, in ancient Greece. He was the first Greek astronomer to propose a heliocentric model of the solar system, placing the Sun, not the Earth, at the center of the known universe (hence he is sometimes known as the "Greek Copernicus"). His astronomical ideas were not well-received and were displaced by those of Aristotle and Ptolemy, until they were successfully revived and developed by Copernicus nearly 2000 years later. The Aristarchus crater on the Moon was named in his honour.

Aristarchus believed the stars to be very far away, and saw this as the reason why there was no visible parallax, that is, an observed movement of the stars relative to each other as the Earth moved around the Sun.

Read more...
HI MOM

Portal:Science/Featured biography/4

Rosalind Elsie Franklin
Rosalind Elsie Franklin (25 July 1920 - 16 April 1958) was a British physical chemist and crystallographer who made very important contributions to the understanding of the fine structures of coal and graphite, DNA and viruses. Franklin is best known for her contribution to the discovery of the structure of DNA in 1953, while working at King's College London under the direction of physicist John Randall. By the time the 1962 Nobel Prize for Physiology and Medicine was awarded to Crick, Watson, and her colleague Wilkins, she had been dead for 4 years. She subsequently became an icon in feminist literature.

Adrian has a pidick

Portal:Science/Featured biography/5

Francis Crick lecturing
Francis Crick, (1916 – 2004) was a British physicist, molecular biologist and neuroscientist, most noted for being one of the co-discoverers of the structure of the DNA molecule in 1953. He, James D. Watson, and Maurice Wilkins were jointly awarded the 1962 Nobel Prize for Physiology or Medicine for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material. His later work at the MRC Laboratory of Molecular Biology until 1977 has not received as much formal recognition. His remaining career as the J.W. Kieckhefer Distinguished Research Professor at the Salk Institute for Biological Studies was spent in La Jolla, California, until his death; "He was editing a manuscript on his death bed, a scientist until the bitter end" (a quote from his close associate Christof Koch).

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Wolfgang Ernst Pauli
Wolfgang Ernst Pauli (April 25, 1900–December 15, 1958) was an Austrian physicist noted for his work on the theory of spin, and in particular the discovery of the Exclusion principle, which underpins the whole of chemistry and quantum mechanics.

He seldom published papers, preferring lengthy correspondences with colleagues (such as Bohr and Heisenberg, with whom he had close friendships.) Many of his ideas and results were never published and appeared only in his letters, which were often copied and circulated by their recipients. Pauli was apparently unconcerned that much of his work thus went uncredited.

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Claudius Galenus of Pergamum
Claudius Galenus of Pergamum (129-200 AD), better known in English as Galen, was an ancient Greek physician. His views dominated European medicine for over a thousand years. From the modern viewpoint, Galen's theories were partially correct, partially flawed. He demonstrated that arteries carry blood, not air and made first studies about nerve functions, and the brain and heart. He also argued that the mind was in the brain, not in the heart as Aristotle had claimed.

However, much of Galen's understanding is flawed from the modern point of view. For example, he did not recognize blood circulation and thought that venous and arterial systems were separate. This view did not change until William Harvey's work in the 17th century.

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Leonhard Euler
Leonhard Euler (April 15, 1707 Basel, Switzerland - September 18, 1783 St Petersburg, Russia) was a Swiss mathematician and physicist. He is considered to be the dominant mathematician of the 18th century and one of the greatest mathematicians of all time; he is certainly among the most prolific, with collected works filling over 70 volumes. Euler developed many important concepts and proved numerous lasting theorems in diverse areas of mathematics, from calculus to number theory to topology. In the course of this work, he introduced much of modern mathematical terminology, defining the concept of a function, and its notation, such as sin, cos, and tan for the trigonometric functions.

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Emil Adolf von Behring
Emil Adolf von Behring (March 15, 1854 – March 31, 1917) was born at Hansdorf, Eylau, Germany (as Emil Adolf Behring). Between 1874 and 1878, he studied medicine at the Army Medical College in Berlin. He was mainly a military doctor and then became Professor of Hygienics within the Faculty of Medicine at the University of Marburg. Behring was the discoverer of diphtheria antitoxin and attained a great reputation by that means and by his contributions to the study of immunity. He won the first Nobel Prize in Physiology or Medicine in 1901 for developing a serum therapy against diphtheria (this was worked on with Emile Roux) and tetanus. The former had been a scourge of the population, especially children, whereas the other was a leading cause of death in wars, killing the wounded.

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Santiago Ramón y Cajal
Santiago Ramón y Cajal (May 1, 1852 – October 17, 1934) was a famous Spanish histologist, physician, and Nobel laureate. He is considered to be one of the founders of modern neuroscience. His most famous studies were on the fine structure of the central nervous system. Cajal used a histological staining technique developed by his contemporary Camillo Golgi. Golgi found that by treating brain tissue with a silver chromate solution, a relatively small number of neurons in the brain were darkly stained. This allowed him to resolve in detail the structure of individual neurons and led him to conclude that nervous tissue was a continuous reticulum (or web) of interconnected cells much like those in the circulatory system. Using Golgi's method, Ramón y Cajal reached a very different conclusion. He postulated that the nervous system is made up of billions of separate neurons and that these cells are polarized. Rather than forming a continuous web, Cajal suggested that neurons communicate with each other via specialized junctions called "synapses". This hypothesis became the basis of the neuron doctrine, which states that the individual unit of the nervous system is a single neuron. Electron microscopy later showed that a plasma membrane completely enclosed each neuron, supporting Cajal's theory, and weakening Golgi's reticular theory.

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Maria Mitchell
Maria Mitchell (August 11, 1818 – June 28, 1889) has an American astronomer. Born on Nantucket Island, she was a first cousin four times removed of Benjamin Franklin.

Her parents were Quakers who, unconventionally for their time, insisted on giving her the same quality of education that boys received. She worked as a librarian and also pursued astronomy at her father's observatory.

Using a telescope, she discovered "Miss Mitchell's Comet" (Comet 1847 VI, modern designation is C/1847 T1) in the autumn of 1847. Some years previously, King Frederick VI of Denmark had established gold medal prizes to each discoverer of a "telescopic comet" (too faint to be seen with the naked eye). The prize was to be awarded to the "first discoverer" of each such comet (note that comets are often independently discovered by more than one person). She duly won one of these prizes, and this gave her worldwide fame, since the only previous woman to discover a comet had been Caroline Herschel.

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Michio Kaku
Michio Kaku (Kanji: 加來 紀雄) (born January 24, 1947 in the United States) is a Japanese American theoretical physicist, tenured professor, and co-creator of string field theory, a branch of string theory.

Dr. Kaku is the author of several scholarly, Ph.D.-level textbooks and has had more than 70 articles published in physics journals covering topics such as superstring theory, supergravity, supersymmetry, and hadronic physics. He is also known as an author of popular science books, including the best-sellers Beyond Einstein, Visions, Hyperspace, and Parallel Worlds, and the host of several radio shows, as well as being a popular figure in science television shows due to his accessible approach to the layperson on explaining complex physics.

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Brian Greene
Brian Greene (born February 9, 1963, New-York), is a physicist at Columbia University. His book The Elegant Universe: Superstrings, Dimensions, and the Quest for the Ultimate Theory was a finalist for the Pulitzer Prize in nonfiction, and winner of The Aventis Prizes for Science Books in 2000. The Elegant Universe was later made into a PBS television special with Dr. Greene as the narrator. His second book, The Fabric of the Cosmos (2004), is about space, time, and the nature of the universe. Aspects covered in this book include non-local particle entanglement as it relates to special relativity and basic explanations of string theory. It is an examination of the very nature of matter and reality, covering such topics as spacetime and cosmology, origins and unification, and including an exploration into reality and the imagination.

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Gregor Johann Mendel
Gregor Mendel (1822–1884)

was a Czech-Austrian monk who is often called the "father of genetics" for his study of the inheritance of traits in pea plants. Mendel showed that there was particular inheritance of traits according to his laws of inheritance. The significance of Mendel's work was not recognized until the turn of the 20th century.

It was not until the early 20th century that the importance of his ideas was realized. In 1900, his work was rediscovered by Hugo de Vries, Carl Correns, and Erich von Tschermak. His results were quickly replicated, and genetic linkage quickly worked out. Biologists flocked to the theory, as while it was not yet applicable to many phenomena, it sought to give a genotypic understanding of heredity which they felt was lacking in previous studies of heredity which focused on phenotypic approaches.

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Frank Macfarlane Burnet at the Walter and Eliza Hall Institute, 1945
Sir Frank Macfarlane Burnet (3 September 1899 – 31 August 1985), was an Australian virologist best known for his contributions to immunology. He went on to conduct pioneering research on bacteriophages and viruses at the Walter and Eliza Hall Institute, and served as director of the Institute from 1944 to 1956. His virology research resulted in significant discoveries concerning their nature and replication and their interaction with the immune system.

From the mid-1950s, he worked extensively in immunology and was a major contributor to the theory of clonal selection, which explains how lymphocytes target antigens for destruction. Burnet and Peter Medawar were co-recipients of the 1960 Nobel Prize in Physiology or Medicine for demonstrating acquired immune tolerance. This research provided the experimental basis for inducing immune tolerance, the platform for developing methods of transplanting solid organs.

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Portrait of Georg Forster at age 26, by J. H. W. Tischbein, 1781
Johann Georg Adam Forster (November 27, 1754 – January 10, 1794) was a German naturalist, ethnologist, travel writer, journalist, and revolutionary. At an early age, he accompanied his father on several scientific expeditions, including James Cook's second voyage to the Pacific. His report from that journey, A Voyage Round the World, contributed significantly to the ethnology of the people of Polynesia. As a result of the report Forster was admitted to the Royal Society at the early age of twenty-two and came to be considered one of the founders of modern scientific travel literature.

After his return to continental Europe, Forster turned towards academics. From 1778 to 1784 he taught natural history. Most of his scientific work consisted of essays on botany and ethnology, but he also prefaced and translated many books about travels and explorations, including a German translation of Cook's diaries. Forster was a central figure of the Enlightenment in Germany.

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Barbara McClintock
Barbara McClintock (June 16, 1902 – September 2, 1992) was a pioneering American scientist and one of the world's most distinguished cytogeneticists. McClintock received her PhD in botany from Cornell University in 1927, where she was a leader in the development of maize cytogenetics. The field remained the focus of her research for the rest of her career. From the late 1920s, McClintock studied chromosomes and how they change during reproduction in maize. She developed the technique to visualize maize chromosomes and demonstrate genetic recombination by crossing-over during meiosis—a mechanism by which chromosomes exchange information. She produced the first genetic map for maize, and she demonstrated the role of the telomere and centromere. She was awarded prestigious fellowships and elected a member of the National Academy of Sciences in 1944.

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Johann Carl Friedrich Gauss
Carl Friedrich Gauss Pronunciation (help·info) (30 April 1777 – 23 February 1855) was a German mathematician and scientist of profound genius who contributed significantly to many fields, including number theory, analysis, differential geometry, geodesy, magnetism, astronomy and optics. Sometimes known as "the prince of mathematicians" and "greatest mathematician since antiquity", Gauss had a remarkable influence in many fields of mathematics and science and is ranked as one of history's most influential mathematicians.

Gauss completed Disquisitiones Arithmeticae, his magnum opus, at the age of twenty-one (1798), though it would not be published until 1801. This work was fundamental in consolidating number theory as a discipline and has shaped the field to the present day.

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Portrait of Galileo Galilei by Giusto Sustermans.
Galileo Galilei (15 February 1564 – 8 January 1642) was an Italian physicist, astronomer, and philosopher who is closely associated with the scientific revolution. His achievements include improvements to the telescope, a variety of astronomical observations, the first and second laws of motion, and effective support for Copernicanism. According to Stephen Hawking, Galileo has probably contributed more to the creation of the modern natural sciences than anybody else. He has been referred to as the "father of modern astronomy," as the "father of modern physics," and as the "father of science." The work of Galileo is considered to be a significant break from that of Aristotle.

Portal:Science/Featured biography/20 Carl Edward Sagan (November 9, 1934 – December 20, 1996) was an American astronomer, astrobiologist, and highly successful science popularizer. He pioneered exobiology and promoted the Search for Extra-Terrestrial Intelligence (SETI). He is world-famous for writing popular science books and for co-writing and presenting the award-winning 1980 television series Cosmos: A Personal Voyage, which was the most-watched PBS program until Ken Burns' The Civil War in 1990. A book to accompany the program was also published. He also wrote the novel Contact, the basis for the 1997 film of the same name starring Jodie Foster. During his lifetime, Sagan published more than 600 scientific papers and popular articles and was author, co-author, or editor of more than 20 books. In his works, he frequently advocated scientific skepticism, humanism, and the scientific method.

Biographies 21–40

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Albert poop-stein, photographed by Oren J. Turner (1947)
Albert Einstein (German pronunciation (help·info)) (March 14, 1879 – April 18, 1955) was a German-born theoretical physicist widely known as one of the greatest physicists of all time. He formulated the special and general theories of relativity. In addition, he made significant advancements to quantum theory and statistical mechanics. While best known for the Theory of Relativity (and specifically mass-energy equivalence, E=mc2), he was awarded the 1921 Nobel Prize for Physics for his 1905 (his "wonderful year" or "miraculous year") explanation of the photoelectric effect and "for his services to Theoretical Physics". In popular culture, the name "Einstein" has become synonymous with great intelligence and genius.

Among his many investigations were: capillary action, his special theory of relativity which stemmed from an attempt to reconcile the laws of mechanics with the laws of the electromagnetic field, his general theory of relativity which extended the principle of relativity to include gravitation, relativistic cosmology, critical opalescence, classical problems of statistical mechanics and problems in which they were merged with quantum theory, including an explanation of Brownian motion; atomic transition probabilities, the probabilistic interpretation of quantum theory, the quantum theory of a monatomic gas, the thermal properties of light with a low radiation density which laid the foundation of the photon theory of light, the theory of radiation, including stimulated emission; the construction of a unified field theory, and the geometrization of physics.

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Nominations

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Selected pictures list

Pictures 1 – 20

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View of the Earth as seen by the Apollo 17 crew traveling toward the moon.
Credit: Earth Sciences and Image Analysis Laboratory, NASA

View of the Earth as seen by the Apollo 17 crew traveling toward the moon. This translunar coast photograph extends from the Mediterranean Sea area to the Antarctica south polar ice cap. This is toward the northeast. Earth, also known as Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harboring life. Scientific evidence indicates that the planet formed around 4.57 billion years ago, and shortly thereafter (4.533 billion years ago) acquired its single natural satellite, the Moon.

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The Hubble Space Telescope as seen from the Space Shuttle Discovery on mission STS-82.
Credit: NASA

The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble for his discovery of galaxies outside the Milky Way and his creation of Hubble's Law, which calculates the rate at which the universe is expanding. Its position outside the Earth's atmosphere allows it to take sharp optical images of very faint objects, and since its launch in 1990, it has become one of the most important instruments in the history of astronomy. It has been responsible for many ground-breaking observations and has helped astronomers achieve a better understanding of many fundamental problems in astrophysics. Hubble's Ultra Deep Field is the deepest (most sensitive) astronomical optical image ever taken.

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The Falkirk Wheel is a rotating boat lift that works using Archimedes' principle.
Credit: Sean Mack

The Falkirk Wheel, named after the nearby town of Falkirk in central Scotland, is a rotating boat lift connecting the Forth and Clyde Canal with the Union Canal, which at this point differ by 24 metres, roughly equivalent to the height of an eight story building.

On 24 May 2002, Queen Elizabeth II opened the Falkirk Wheel as part of her Golden Jubilee celebrations. The opening had been delayed by a month due to flooding caused by vandals who forced open the Wheel's gates.

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Credit: Apollo 11 Crew, NASA

The far side of the Moon as photographed by the crew of Apollo 11. The largest crater is Derek lang.

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Paramecium aurelia, the best known of all ciliates. The bubbles throughout the cell are vacuoles. The entire surface is covered in cilia, which are blurred by their rapid movement. Cilia are short, hair-like projections that help with locomotion.
Credit: Josh Grosse

Paramecium aurelia, the best known of all ciliates. The bubbles throughout the cell are vacuoles. The entire surface is covered in cilia, which are blurred by their rapid movement. Cilia are short, hair-like projections that help with locomotion.

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A Persian astrolabe, used for determining the time at both day and night.
Credit: Andrew Dunn

An 18th Century Persian astrolabe used for determining the time at both day and night. The points of the curved spikes on the front rete plate, mark the positions of the brightest stars. The name of each star being labeled at the base of each spike. The back plate, or mater is engraved with projected coordinate lines. From the Whipple Museum of the History of Science in Cambridge.

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Gallium melts in your hand.
Credit: Foobar

Gallium (IPA: /ˈgaliəm/) is a chemical element that has the symbol Ga and atomic number 31. A rare, soft silvery metallic poor metal, gallium is a brittle solid at low temperatures but liquefies slightly above room temperature and will melt in the hand. It occurs in trace amounts in bauxite and zinc ores. An important application is in the compound gallium arsenide, used as a semiconductor, most notably in light-emitting diodes (LEDs).

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DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus.
Credit: Polyparadigm

Direct current-generated plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. Plasma-enhanced chemical vapor deposition processes utilize plasma to enhance chemical reaction rates. PECVD processing allows deposition at lower temperatures, which is often critical in the manufacture of semiconductors. The red color in the picture is black body radiation.

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Lightning over Oradea, Romania
Credit: Mircea Madau

Lightning is a powerful natural electrostatic discharge produced during a thunderstorm. This abrupt electric discharge is accompanied by the emission of visible light and other forms of electromagnetic radiation. The electric current passing through the discharge channels rapidly heats and expands the air into plasma, producing acoustic shock waves (thunder) in the atmosphere.

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Energy arc, central electrode of a plasma lamp
Credit: PiccoloNamek

A plasma lamp is usually a clear glass orb, filled with a mixture of various inert gases at low pressure, and driven by high frequency alternating current at high voltage (approx. 35kHz, 2-5kV), generated by a high voltage transformer. A much smaller orb in its centre serves as an electrode. Beams or snakes of "light" (actually emergent patterns in ionized gas) extend from the inner electrode to the outer glass container, giving an appearance similar to multiple constant beams of coloured lightning. The beams first follow the electric field lines of the dipole, but move up due to convection.

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Rust and dirt on a baking plate.
Credit: Roger McLassus

Rust is the substance formed when iron compounds corrode in the presence of oxygen and water. It is a mixture of iron oxides and hydroxides. Rusting is a common term for corrosion, and usually corrosion of steel. Iron is found naturally in the ore haematite as iron oxide, and metallic iron tends to return to a similar state when exposed to air, (hydrogen, oxygen, nitrogen, etc.) and water. This corrosion is due to the oxidation reaction when iron metal returns to an energetically favourable state. Energy is given off when rust forms. The process of rusting can be summarized as three basic stages: The formation of iron(II) ions from the metal; the formation of hydroxide ions; and their reaction together, with the addition of oxygen, to create rust.

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Sonoluminescence is the emission of light by bubbles in a liquid excited by sound.
Credit: Dake

Sonoluminescence is the emission of short bursts of light from imploding bubbles in a liquid when excited by sound. The effect was first discovered at the University of Cologne in 1934 as a result of work on sonar. H. Frenzel and H. Schultes put an ultrasound transducer in a tank of photographic developer fluid. They hoped to speed up the development process. Instead, they noticed tiny dots on the film after developing, and realized that the bubbles in the fluid were emitting light with the ultrasound turned on. It was too difficult to analyze the effect in early experiments because of the complex environment of a large number of short-lived bubbles. (This experiment is also ascribed to N. Marinesco and J.J. Trillat in 1933).

Sonoluminescence may or may not occur whenever a sound wave of sufficient intensity induces a gaseous cavity within a liquid to quickly collapse. This cavity may take the form of a pre-existing bubble, or may be generated through a process known as cavitation. Sonoluminescence in the laboratory can be made to be stable, so that a single bubble will expand and collapse over and over again in a periodic fashion, emitting a burst of light each time it collapses.

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Early morning view on November 9, 1967 of Pad A, Launch Complex 39, Kennedy Space Center, showing Apollo 4 Saturn V (Spacecraft 017/Saturn 501) prior to launch later that day. This was the first launch of the Saturn V.
Credit: NASA

Saturn V was a multistage liquid-fuel expendable rocket used by NASA's Apollo and Skylab programs.

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A Tesla coil lightning simulator
Credit: Fir0002

A Tesla coil is a category of disruptive discharge transformer coils, named after their inventor, Nikola Tesla. Tesla coils are composed of coupled resonant electric circuits. Nikola Tesla actually experimented with a large variety of coils and configurations, so it is difficult to describe a specific mode of construction that will meet the wants of those who ask about "Tesla" coils. "Early coils" and "later coils" vary in configuration and setup. Tesla coils in general are very popular devices among high-voltage enthusiasts.

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Skull and craniometric measurement apparatus, from 1902.
Credit: Fawcett & Lee

Craniometry is the technique of measuring the bones of the skull. Craniometry was once intensively practiced in anthropology and ethnology. Human skulls can be classified into three main categories based on cephalic index: dolichocephalic: long and thin; brachycephalic: short and broad; mesocephalic: intermediate length and breadth.

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Schematic of a railgun.
Credit: DrBob

A railgun is a form of gun that converts electrical energy—rather than the more conventional chemical energy from an explosive propellant—into projectile kinetic energy. It is not to be confused with a coilgun (Gauss gun). The term railgun is also used for conventional firearms used in the Unlimited class of benchrest shooting.

A Railgun is a type of Magnetic Accelerator Gun (MAG) that utilizes an electromagnetic force to propel an electrically conductive projectile that is initially part of the current path. Sometimes they also use a movable armature connecting the rails. The current flowing through the rails sets up a magnetic field between them and through the projectile perpendicularly to the current in it. This results in the rails and the projectile pushing each other and in the acceleration of the projectile along the rails.

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Comet Tempel 1 67 seconds after it collided with Deep Impact
Credit: NASA

Deep Impact is a NASA space probe designed to study the composition of the interior of the comet Tempel 1. At 5:52 UTC on July 4, 2005, one section of the Deep Impact probe successfully impacted the comet's nucleus, excavating debris from the interior of the nucleus. Photographs of the impact showed the comet to be more dusty and less icy than expected. The impact generated a large, bright dust cloud that obscured the hoped-for view of the impact crater.

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Barred Spiral Milky Way
Credit: NASA

The Milky Way is a barred spiral galaxy of the Local Group. Although the Milky Way is but one of billions of galaxies in the universe, the Galaxy has special significance to humanity as it is the home of the Solar System. The term "milky" originates from the hazy band of white light appearing across the celestial sphere visible from Earth, which is comprised of stars and other material lying within the galactic plane. The fact that the Milky Way divides the night sky into two roughly equal hemispheres indicates that the solar system lies close to the galactic plane.

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The first color movie of Jupiter from NASA's Cassini spacecraft shows what it would look like to peel the entire globe of Jupiter, stretch it out on a wall into the form of a rectangular map, and watch its atmosphere evolve with time.
Credit: NASA/JPL/University of Arizona

The cloud pattern on Jupiter is the visible system of colored cloud tops in the atmosphere of the planet Jupiter, remarkable for its stability. Astronomers have given names to parts of this pattern, using the word zone for the light stripes, and belt for the dark stripes, along various latitudes. The pattern and intensity of its belts and zones are famously variable, often changing markedly from opposition to opposition.

The normal pattern of bands and zones are sometimes disrupted for a period of time, and Astronomers call these events "Disturbances". For example, the longest lived disturbance in recorded history was a "Southern Tropical Disturbance" (STropD) from 1901 until 1939, discovered by Percy B. Molesworth on February 28, 1901. It created a darkened feature over some longitude area in the normally bright Southern Tropical zone.

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Wake Vortex Study at Wallops Island
Credit: NASA Langley Research Center (NASA-LaRC)

Wake turbulence, also known as "jetwash", is turbulence that forms behind an aircraft as it passes through the air. This turbulence can be especially hazardous during the landing and take off phases of flight, where an aircraft's proximity to the ground makes a timely recovery from turbulence-induced problems unlikely. Wingtip vortices make up the primary and most dangerous component of wake turbulence, but normal wake effects are also an important part. A method of reducing wingtip vortices employs the use of winglets.

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Nominations

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Did you know...

...that Abbott Lawrence Rotch established the Blue Hill Meteorological Observatory in 1885, which maintains the longest-running meteorological record of any observation site in the United States?

Aerogel

...that silica aerogel holds 15 entries in the Guinness Book of Records for material properties, including best insulator and lowest-density solid?
...that acoustic levitation is a method for suspending matter in a fluid by using acoustic radiation pressure from intense sound waves in the medium?
...necrotizing fasciitis is a rare infection of subcutaneous tissues that results in the necrosis of the flesh?
...Napalm-B, used in the Vietnam War, was synthesized with only three ingredients: polystyrene, gasoline, and benzene?

Laser harp

...that a laser harp is an electronic musical instrument consisting of several laser beams that are blocked to produce sound?

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Science Media

This week in Prague, approximately 3000 scientists and astronomers will debate the status of Pluto as a planet. The International Astronomers Union will clearly define a planet. In addition, the union is forced to downgrade or maintain the status of 14 other astronomical bodies.

Physics Today magazine, created in 1948, is the flagship publication of The American Institute of Physics. It is provided to 130,000 members of twelve physics societies. Famous physicists of the last 50 years have written for the magazine, including Albert Einstein, Niels Bohr, and Richard Feynman. The magazine provides a historical resource of events associated to physics, including debunking.

Science is the academic journal of the American Association for the Advancement of Science and is considered one of the world's most prestigious scientific journals. The journal is peer-reviewed, is published weekly, and has a print subscriber base of around 130,000. Because institutional subscriptions and online access serve a larger audience, its estimated readership is one million people. The major focus of the journal is publishing important original scientific research and research reviews, but Science also publishes science-related news, opinions on science policy and other matters of interest to scientists and others who are concerned with the wide implications of science and technology.

New Science Digestis a daily news service that features breaking news on new scientific discoveries from around the world. Additionally, many useful science related links are listed. Readers are encouraged to post comments and suggest related and interesting science links.

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Drawing of a cell membrane.
Prehistoric cave paintings. Altamira, Spain
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