|
Laser Guide Star
A laser guide star is an artificial star image created for use in astronomical adaptive optics systems, which are employed in large telescopes in order to correct atmospheric distortion of light (called '' astronomical seeing''). Adaptive optics (AO) systems require a wavefront reference source of light called a guide star. Natural stars can serve as point sources for this purpose, but sufficiently bright stars are not available in all parts of the sky, which greatly limits the usefulness of natural guide star adaptive optics. Instead, one can create an artificial guide star by shining a laser into the atmosphere. Light from the beam is reflected by components in the upper atmosphere back into the telescope. This star can be positioned anywhere the telescope desires to point, opening up much greater amounts of the sky to adaptive optics. Because the laser beam is deflected by astronomical seeing on the way up, the returning laser light does not move around in the sky as as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Most Powerful Laser Guide Star System In The World Sees First Light At The Paranal Observatory
''The'' is a grammatical Article (grammar), article in English language, English, denoting nouns that are already or about to be mentioned, under discussion, implied or otherwise presumed familiar to listeners, readers, or speakers. It is the definite article in English. ''The'' is the Most common words in English, most frequently used word in the English language; studies and analyses of texts have found it to account for seven percent of all printed English-language words. It is derived from gendered articles in Old English which combined in Middle English and now has a single form used with nouns of any gender. The word can be used with both singular and plural nouns, and with a noun that starts with any letter. This is different from many other languages, which have different forms of the definite article for different genders or numbers. Pronunciation In most dialects, "the" is pronounced as (with the voiced dental fricative followed by a schwa) when followed by a con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanometer
330px, Different lengths as in respect to the Molecule">molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling Despite the various list of dialects of English, English dialects spoken from country to country and within different regions of the same country, there are only slight regional variations in English orthography, the two most notable variati ...), is a units of measurement, unit of length in the International System of Units (SI), equal to one billionth (short scale) or one thousand million (long scale) of a metre, meter (0.000000001 m) and to 1000 picometres. One nanometre can be expressed in scientific notation as 1 × 10−9 m and as m. History The nanometre was formerly known as the "''millimicrometre''" – or, more commonly, the "''millimicron''" for short – since it is of a micrometre, micrometer. It was often de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lick Observatory
The Lick Observatory is an astronomical observatory owned and operated by the University of California. It is on the summit of Mount Hamilton (California), Mount Hamilton, in the Diablo Range just east of San Jose, California, United States. The observatory is managed by the University of California Observatories, with headquarters on the University of California, Santa Cruz campus, where its scientific staff moved in the mid-1960s. It is named after James Lick. The first new moon of Jupiter to be identified since the time of Galileo, Amalthea (moon), Amalthea, the planet's fifth moon, was discovered at this observatory in 1892. Early history Lick Observatory is the world's first permanently occupied mountain-top observatory. The observatory, in a Classical Revival architecture, Classical Revival style structure, was constructed between 1876 and 1887, from a bequest from James Lick of $700,000, . Lick, originally a carpenter and piano maker, had arrived from Peru in San Franc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peer-review
Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work ( peers). It functions as a form of self-regulation by qualified members of a profession within the relevant field. Peer review methods are used to maintain quality standards, improve performance, and provide credibility. In academia An academy (Attic Greek: Ἀκαδήμεια; Koine Greek Ἀκαδημία) is an institution of tertiary education. The name traces back to Plato's school of philosophy, founded approximately 386 BC at Akademia, a sanctuary of Athena, the go ..., scholarly peer review is often used to determine an academic paper's suitability for publication. Peer review can be categorized by the type and by the field or profession in which the activity occurs, e.g., #Medical, medical peer review. It can also be used as a teaching tool to help students improve writing assignments. Henry Oldenburg (1619–1677) was a German-born British philosop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Classified Information
Classified information is confidential material that a government deems to be sensitive information which must be protected from unauthorized disclosure that requires special handling and dissemination controls. Access is restricted by law or regulation to particular groups of individuals with the necessary security clearance with a need to know. A formal security clearance is required to view or handle classified material. The clearance process requires a satisfactory background investigation. Documents and other information must be properly marked "by the author" with one of several (hierarchical) levels of sensitivity—e.g. Confidential (C), Secret (S), and Top Secret (S). All classified documents require designation markings on the technical file which is usually located either on the cover sheet, header and footer of page. The choice of level is based on an impact assessment; governments have their own criteria, including how to determine the classification of an inf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strategic Defense Initiative
The Strategic Defense Initiative (SDI) was a proposed missile defense system intended to protect the United States from attack by ballistic nuclear missiles. The program was announced in 1983, by President Ronald Reagan. Reagan called for a system that would render nuclear weapons obsolete, and to end the doctrine of mutual assured destruction (MAD), which he described as a " suicide pact". Elements of the program reemerged in 2019 under the Space Development Agency (SDA). The Strategic Defense Initiative Organization (SDIO) was set up in 1984 within the US Department of Defense to oversee development. Advanced weapon concepts, including lasers, particle-beam weapons, and ground and space-based missile systems were studied, along with sensor, command and control, and computer systems needed to control a system consisting of hundreds of combat centers and satellites spanning the globe. The US held a significant advantage in advanced missile defense systems through decades ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Will Happer
William Happer (born July 27, 1939) is an American physicist who has specialized in the study of atomic physics, optics and spectroscopy. He is the Cyrus Fogg Brackett Professor of Physics, emeritus, at Princeton University, and a long-term member of the JASON advisory group, where he pioneered the development of adaptive optics. From 1991 to 1993, Happer served as director of the Department of Energy's Office of Science as part of the George H.W. Bush administration. He was dismissed from the Department of Energy in 1993 by the Clinton Administration after disagreements on the ozone hole. Happer, who is not a climate scientist, rejects the scientific consensus on climate change. In 2018, Donald Trump appointed him to the National Security Council to counter evidence linking carbon dioxide emissions to global warming.Niina Farah and Robin BravenderEmails reveal behind-the-scenes plans for climate debate ''ClimateWire'', May 10, 2018. He resigned from the council in 2019. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Artificial Stars Over Paranal
Artificiality (the state of being artificial, anthropogenic, or man-made) is the state of being the product of intentional human manufacture, rather than occurring naturally through processes not involving or requiring human activity. Connotations Artificiality often carries with it the implication of being false, counterfeit, or deceptive. The philosopher Aristotle wrote in his ''Rhetoric'': However, artificiality does not necessarily have a negative connotation, as it may also reflect the ability of humans to replicate forms or functions arising in nature, as with an artificial heart or artificial intelligence. Political scientist and artificial intelligence expert Herbert A. Simon observes that "some artificial things are imitations of things in nature, and the imitation may use either the same basic materials as those in the natural object or quite different materials.Herbert A. Simon, ''The Sciences of the Artificial'' (1996), p. 4. Simon distinguishes between the artific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tunable Laser
A tunable laser is a laser whose wavelength of operation can be altered in a controlled manner. While all active laser medium, laser gain media allow small shifts in output wavelength, only a few types of lasers allow continuous tuning over a significant wavelength range. There are many types and categories of tunable lasers. They exist in the gas, liquid, and solid states. Among the types of tunable lasers are excimer lasers, gas lasers (such as CO2 laser, CO2 and helium–neon laser, He-Ne lasers), dye lasers (liquid and solid state), transition-metal solid-state lasers, semiconductor crystal and diode lasers, and free electron laser, free-electron lasers. Tunable lasers find applications in spectroscopy, photochemistry, atomic vapor laser isotope separation, and optical communications. Types of tunability Single line tuning No real laser is truly monochromatic#In physics, monochromatic; all lasers can emit light over some range of frequencies, known as the linewidth of the las ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dye Laser
A dye laser is a laser that uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths, often spanning 50 to 100 nanometers or more. The wide bandwidth makes them particularly suitable for tunable lasers and pulsed lasers. The dye rhodamine 6G, for example, can be tuned from 635 nm (orangish-red) to 560 nm (greenish-yellow), and produce pulses as short as 16 femtoseconds. Moreover, the dye can be replaced by another type in order to generate an even broader range of wavelengths with the same laser, from the near-infrared to the near-ultraviolet, although this usually requires replacing other optical components in the laser as well, such as dielectric mirrors or pump lasers. Dye lasers were independently discovered by P. P. Sorokin and F. P. Schäfer (and colleagues) in 1966. In addition to the usual liquid state, dye lasers are also avail ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rayleigh Scattering
Rayleigh scattering ( ) is the scattering or deflection of light, or other electromagnetic radiation, by particles with a size much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scattering medium (normal dispersion relation, dispersion regime), the amount of scattering is inversely proportional to the fourth power of the wavelength (e.g., a blue color is scattered much more than a red color as light propagates through air). The phenomenon is named after the 19th-century British physicist Lord Rayleigh (John William Strutt). Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency. The particle, therefore, becomes a small radiating dipole whose radiation we see as scattered light. The particles may be individual atoms or molecules; it can occur when light travels throu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Street Light
A street light, light pole, lamp pole, lamppost, streetlamp, light standard, or lamp standard is a raised source of light on the edge of a road or path. Similar lights may be found on a railway platform. When urban electric power distribution became ubiquitous in developed countries in the 20th century, lights for urban streets followed, or sometimes led. Many lamps have light-sensitive photocells that activate the lamp automatically when needed, at times when there is little-to-no ambient light, such as at dusk, dawn, or the onset of dark weather conditions. This function in older lighting systems could be performed with the aid of a solar dial. Many street light systems are being connected underground instead of wiring from one utility post to another. Street lights are an important source of public security lighting intended to reduce crime. History Preindustrial era Early lamps were used in the Ancient Greek and Ancient Roman civilizations, where light primarily ser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
