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Topic Review
Virgo Interferometer
The Virgo interferometer is a large interferometer designed to detect gravitational waves predicted by the general theory of relativity. Virgo is a Michelson interferometer that is isolated from external disturbances: its mirrors and instrumentation are suspended and its laser beam operates in a vacuum. The instrument's two arms are three kilometres long and located near Pisa, Italy. Virgo is part of a scientific collaboration of laboratories from six countries: Italy and France (the two countries behind the project), the Netherlands, Poland, Hungary and Spain. Other interferometers similar to Virgo have the same goal of detecting gravitational waves, including the two LIGO interferometers in the United States (at the Hanford Site and in Livingston, Louisiana). Since 2007, Virgo and LIGO have agreed to share and jointly analyze the data recorded by their detectors and to jointly publish their results. Because the interferometric detectors are not directional (they survey the whole sky) and they are looking for signals which are weak, infrequent, one-time events, simultaneous detection of a gravitational wave in multiple instruments is necessary to confirm the signal validity and to deduce the angular direction of its source. The interferometer is named for the Virgo Cluster of about 1,500 galaxies in the Virgo constellation, about 50 million light-years from Earth. As no terrestrial source of gravitational wave is powerful enough to produce a detectable signal, Virgo must observe the Universe. The more sensitive the detector, the further it can see gravitational waves, which then increases the number of potential sources. This is relevant as the violent phenomena Virgo is potentially sensitive to (coalescence of a compact binary system, neutron stars or black holes; supernova explosion; etc.) are rare: the more galaxies Virgo is surveying, the larger the probability of a detection.
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Topic Review
Red Supergiant Star
Red supergiants (RSGs) are stars with a supergiant luminosity class (Yerkes class I) of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Antares are the brightest and best known red supergiants (RSGs), indeed the only first magnitude red supergiant stars.
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Topic Review
Barrier Grid Animation and Stereography
Barrier-grid animation, also known as a kinegram, and "picket fence" animation, which was originated in the late 1890s and then re-popularized by Rufus Butler Seder's trademarked "Scanimation(r)" books in the early 2,000s, is an animation effect created by moving a striped transparent overlay across an interlaced image. The barrier-grid technique and its history overlap with parallax stereography (also known as "Relièphographie") for 3D autostereograms. The technique has also been used for color-changing pictures, but to a much lesser extent. The development of barrier-grid technologies can also be regarded as a step towards lenticular printing, although the technique has remained after the invention of lenticular technologies as a relatively cheap and simple way to produce animated images in print.
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Topic Review
Public Utility Holding Company Act of 1935
The Public Utility Holding Company Act of 1935 (PUHCA), also known as the Wheeler-Rayburn Act, was a US federal law giving the Securities and Exchange Commission authority to regulate, license, and break up electric utility holding companies. It limited holding company operations to a single state, thus subjecting them to effective state regulation. It also broke up any holding companies with more than two tiers, forcing divestitures so that each became a single integrated system serving a limited geographic area. Another purpose of the PUHCA was to keep utility holding companies engaged in regulated businesses from also engaging in unregulated businesses. The act was based on the conclusions and recommendations of the 1928-35 Federal Trade Commission investigation of the electric industry. On March 12, 1935, President Franklin D. Roosevelt released a report he commissioned by the National Power Policy Committee. This report became the template for the PUHCA. The political battle over its passage was one of the bitterest of the New Deal, and was followed by eleven years of legal appeals by holding companies led by the Electric Bond and Share Company, which finally completed its breakup in 1961. On August 26, 1935, President Franklin D. Roosevelt signed the bill into law. The Energy Policy Act of 2005 repealed the PUHCA.
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Topic Review
Lagrangian Point
In celestial mechanics, the Lagrangian points (/ləˈɡrɑːndʒiən/ also Lagrange points, L-points, or libration points) are the points near two large bodies in orbit where a smaller object will maintain its position relative to the large orbiting bodies. At other locations, a small object would go into its own orbit around one of the large bodies, but at the Lagrangian points the gravitational forces of the two large bodies, the centripetal force of orbital motion, and (for certain points) the Coriolis acceleration all match up in a way that cause the small object to maintain a stable or nearly stable position relative to the large bodies. There are five such points, labeled L1 to L5, all in the orbital plane of the two large bodies, for each given combination of two orbital bodies. For instance, there are five Lagrangian points L1 to L5 for the Sun–Earth system, and in a similar way there are five different Lagrangian points for the Earth–Moon system. L1, L2, and L3 are on the line through the centers of the two large bodies, while L4 and L5 each act as the third vertex of an equilateral triangle formed with the centers of the two large bodies. L4 and L5 are stable, which implies that objects can orbit around them in a rotating coordinate system tied to the two large bodies. Several planets have trojan satellites near their L4 and L5 points with respect to the Sun. Jupiter has more than a million of these trojans. Artificial satellites have been placed at L1 and L2 with respect to the Sun and Earth, and with respect to the Earth and the Moon. The Lagrangian points have been proposed for uses in space exploration.
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Biography
Hans-Peter Dürr
Hans-Peter Dürr (7 October 1929 – 18 May 2014) was a German physicist. He worked on nuclear and quantum physics, elementary particles and gravitation, epistemology, and philosophy, and he has advocated responsible scientific and energy policies.[1] In 1987, he was awarded the Right Livelihood Award for "his profound critique of the Strategic Defense Initiative (SDI) and his work to convert hi
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Topic Review
Soyuz TMA-20
Soyuz TMA-20 was a human spaceflight to the International Space Station (ISS) and was part of the Soyuz programme. It lifted off from the Baikonur Cosmodrome in Kazakhstan on December 15, 2010, and docked with the ISS two days later. The three-person crew of Soyuz TMA-20 – Dmitri Kondratyev, Catherine Coleman and Paolo Nespoli – represented the ISS partner organizations of Roscosmos, NASA and the European Space Agency (ESA). Soyuz TMA-20's crew represented half of the members of Expedition 27; the other three members of the expedition arrived at the station on board Soyuz TMA-21 on April 6, 2011. The COSPAR ID of Soyuz TMA-20 was 2010-067A. It is ISS flight 25S. On May 24, 2011, after spending 159 days in space, the Soyuz TMA-20 descent module landed safely in Zhezkazgan, Kazakhstan, carrying Kondratyev, Coleman and Nespoli.
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Topic Review
Mechanistic Organic Photochemistry
Some chemical reactions take place by the action of light. These are called, "photochemical reactions", or "photolysis". Mechanistic organic photochemistry is the aspect of organic photochemistry which seeks to explain the mechanisms of organic photochemical reactions. The absorption of ultraviolet light by organic molecules often leads to reactions. In the earliest days, sunlight was employed, while in more modern times ultraviolet lamps are employed. Organic photochemistry has proven to be a very useful synthetic tool. Complex organic products can be obtained simply. Over the last century and earlier an immense number of photochemical reactions have been uncovered. In modern times the field is quite well understood and is used in organic synthesis and industrially. The utility of organic photochemistry has arisen only by virtue of the available mechanistic treatment; reactions which appear unlikely in ground-state understanding become understandable and accessible in terms of electronic excited-state consideration.
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Topic Review
Large Strategic Science Missions
NASA's Large Strategic Science Missions, formerly known as Flagship missions or Flagship-class missions, are the costliest and most capable NASA science spacecraft. Flagship missions exist within all four divisions of NASA's Science Mission Directorate: the astrophysics, Earth science, heliophysics and planetary science divisions. "Large" refers to the budget of each mission, typically the most expensive mission in the scientific discipline. Within the Astrophysics Division and the Planetary Science Division, the large strategic missions are usually in excess of $1 billion. Within Earth Science Division and Heliophysics Division, the large strategic missions are usually in excess of $500 million. "Strategic" refers to their role advancing multiple strategic priorities set forth in plans such as the Decadal Surveys. "Science" marks these missions as primarily scientific in nature, under the Science Mission Directorate (SMD), as opposed to, e.g., human exploration missions under the Human Exploration and Operations Mission Directorate (HEOMD). The lines can be blurred, as when the Lunar Reconnaissance Orbiter began as a directed mission from the HEOMD, and was later transferred to the SMD. Flagship missions are not under the purview of any larger "Flagship Program", unlike, e.g., Discovery-class missions that are under the purview of the Discovery Program. Unlike these competed classes that tender proposals through a competitive selection process, the development of Flagship missions is directed to a specific institution — usually a NASA center or the Jet Propulsion Laboratory — by the Science Mission Directorate. Flagship missions are developed ad-hoc, with no predetermined launch cadence or uniform budget size. Flagship missions are always Class A missions: high priority, very low risk.
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Topic Review
Carbon-Burning Process
The carbon-burning process or carbon fusion is a set of nuclear fusion reactions that take place in the cores of massive stars (at least 8 [math]\displaystyle{ \begin{smallmatrix}M \odot\end{smallmatrix} }[/math] at birth) that combines carbon into other elements. It requires high temperatures (> 5×108 K or 50 keV) and densities (> 3×109 kg/m3). These figures for temperature and density are only a guide. More massive stars burn their nuclear fuel more quickly, since they have to offset greater gravitational forces to stay in (approximate) hydrostatic equilibrium. That generally means higher temperatures, although lower densities, than for less massive stars. To get the right figures for a particular mass, and a particular stage of evolution, it is necessary to use a numerical stellar model computed with computer algorithms. Such models are continually being refined based on nuclear physics experiments (which measure nuclear reaction rates) and astronomical observations (which include direct observation of mass loss, detection of nuclear products from spectrum observations after convection zones develop from the surface to fusion-burning regions – known as dredge-up events – and so bring nuclear products to the surface, and many other observations relevant to models).
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