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Gravity Laser
A gravity laser, also sometimes referred to as a Gaser, Graser, or Glaser, is a hypothetical device for stimulated emission of coherent gravitational radiation or gravitons, much in the same way that a standard laser produces coherent electromagnetic radiation. Principle of function While photons exist as excitations of a vector potential and so contain an oscillating dipole term, gravitons are a spin-2 field and so have an oscillating quadrupole term. For efficient lasing to occur, there are several conditions that must be met: # There must be particles in an excited state capable of emitting radiation at the desired frequency. In a normal laser, these would be valence electrons in an excited state. For a gaser, the more straightforward analog would be a binary system of massive bodies. # These particles must couple to supplied radiation, in order to provide stimulated emission. This could be possible in a gaser by a stimulated analog of the Penrose process. # The particles must ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma-ray Laser
A gamma-ray laser, or graser, is a hypothetical device that would produce coherent gamma rays, just as an ordinary laser produces coherent rays of visible light. Potential applications for gamma-ray lasers include medical imaging, spacecraft propulsion, and cancer treatment. In his 2003 Nobel lecture, Vitaly Ginzburg cited the gamma-ray laser as one of the 30 most important problems in physics. The effort to construct a practical gamma-ray laser is interdisciplinary, encompassing quantum mechanics, nuclear and optical spectroscopy, chemistry, solid-state physics, and metallurgy—as well as the generation, moderation, and interaction of neutrons—and involves specialized knowledge and research in all these fields. The subject involves both basic science and engineering technology. Research The problem of obtaining a sufficient concentration of resonant excited (isomeric) nuclear states for collective stimulated emission to occur turns on the broadening of the gamma- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser Pumping
Laser pumping is the act of energy transfer from an external source into the gain medium of a laser. The energy is absorbed in the medium, producing excited states in its atoms. When the number of particles in one excited state exceeds the number of particles in the ground state or a less-excited state, population inversion is achieved. In this condition, the mechanism of stimulated emission can take place and the medium can act as a laser or an optical amplifier. The pump power must be higher than the lasing threshold of the laser. The pump energy is usually provided in the form of light or electric current, but more exotic sources have been used, such as chemical or nuclear reactions. Optical pumping Pumping cavities A laser pumped with an arc lamp or a flashlamp is usually pumped through the lateral wall of the lasing medium, which is often in the form of a crystal rod containing a metallic impurity or a glass tube containing a liquid dye, in a condition known as "side-pump ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antigravity
Anti-gravity (also known as non-gravitational field) is a hypothetical phenomenon of creating a place or object that is free from the force of gravity. It does not refer to the lack of weight under gravity experienced in free fall or orbit, or to balancing the force of gravity with some other force, such as electromagnetism or aerodynamic lift. Anti-gravity is a recurring concept in science fiction. Examples are the gravity blocking substance "Cavorite" in H. G. Wells's ''The First Men in the Moon'' and the Spindizzy machines in James Blish's ''Cities in Flight''. "Anti-gravity" is often used to refer to devices that look as if they reverse gravity even though they operate through other means, such as lifters, which fly in the air by moving air with electromagnetic fields. Historical attempts at understanding gravity The possibility of creating anti-gravity depends upon a complete understanding and description of gravity and its interactions with other physical theories, such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tractor Beam
A tractor-beam is a device with the ability to attract one object to another from a distance. The concept originates in fiction: The term was coined by E. E. Smith (an update of his earlier "attractor-beam") in his novel ''Spacehounds of IPC'' (1931). Since the 1990s, technology and research has labored to make it a reality, and have had some success on a microscopic level. Less commonly, a similar beam that repels is called a pressor beam or repulsor-beam. Gravity impulse and gravity propulsion beams are traditionally areas of research from fringe physics that coincide with the concepts of tractor and repulsor-beams. Physics A force field confined to a collimated beam with clean borders is one of the principal characteristics of tractor and repulsor beams. Several theories that have predicted repulsive effects do not fall within the category of tractor and repulsor beams because of the absence of field collimation. For example, Robert L. Forward, Hughes Research Laboratories, Ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star Ocean
is a franchise of action role-playing video games developed by the Japanese company tri-Ace and published and owned by Square Enix (formerly Enix). Development History The series is also known for being some of the earliest action RPGs to allow players to alter the storyline's outcome through the player's actions and dialogue choices, mainly through a social relationship system referred to as "private actions". The original '' Star Ocean'', published by Enix in 1996, introduced a "private actions" social system, where the protagonist's relationship points with the other characters are affected by the player's choices, which in turn affects the storyline, leading to branching paths and multiple different endings. This was expanded in its 1999 sequel, '' Star Ocean: The Second Story'', which boasted as many as 86 different endings, with each of the possible permutations to these endings numbering in the hundreds, setting a benchmark for the number of outcomes possible for a video ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth (Brin Novel)
''Earth'' is a 1990 science fiction novel by American writer David Brin. The book was nominated for the Hugo and Locus Awards in 1991. Plot summary Set in the year 2038, ''Earth'' is a cautionary tale of the harm humans can cause their planet via disregard for the environment and reckless scientific experiments. The book has a large cast of characters and Brin uses them to address a number of environmental issues, including endangered species, global warming, refugees from ecological disasters, ecoterrorism, and the social effects of overpopulation. The plot of the book involves an artificially created black hole which has been lost in the Earth's interior and the attempts to recover it before it destroys the planet. The events and revelations which follow reshape humanity and its future in the universe. It also includes a war pitting most of the Earth against Switzerland, fueled by outrage over the Swiss allowing generations of kleptocrats to hide their stolen wealth in the coun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unconventional Superconductors
Unconventional superconductors are materials that display superconductivity which does not conform to either the conventional BCS theory or Nikolay Bogolyubov's theory or its extensions. History The superconducting properties of CeCu2Si2, a type of heavy fermion material, were reported in 1979 by Frank Steglich. For a long time it was believed that CeCu2Si2 was a singlet d-wave superconductor, but since the mid 2010s, this notion has been strongly contested. In the early eighties, many more unconventional, heavy fermion superconductors were discovered, including UBe13, UPt3 and URu2Si2. In each of these materials, the anisotropic nature of the pairing was implicated by the power-law dependence of the nuclear magnetic resonance (NMR) relaxation rate and specific heat capacity on temperature. The presence of nodes in the superconducting gap of UPt3 was confirmed in 1986 from the polarization dependence of the ultrasound attenuation. The first unconventional triplet superconduc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superconductors
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source. The superconductivity phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon which can only be explained by quantum mechanics. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor during its transitions into the sup ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convective Momentum Transport
Convective momentum transport usually describes a vertical flux of the momentum of horizontal winds or currents. That momentum is carried like a non-conserved flow tracer by vertical air motions in convection. In the atmosphere, convective momentum transport by small but vigorous (cumulus type) cloudy updrafts can be understood as an interplay of three main mechanisms: *Vertical advection of ambient momentum due to subsidence of environmental air that compensates the in-cloud upward mass flux, *Detrainment of in-cloud momentum where updrafts stop ascending, *Accelerations by the pressure gradient force In fluid mechanics, the pressure-gradient force is the force that results when there is a difference in pressure across a surface. In general, a pressure is a force per unit area, across a surface. A difference in pressure across a surface t ... around clouds whose inner momentum differs from their environment. The net effect of these interacting mechanisms depends on the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free-electron Laser
A free-electron laser (FEL) is a (fourth generation) light source producing extremely brilliant and short pulses of radiation. An FEL functions and behaves in many ways like a laser, but instead of using stimulated emission from atomic or molecular excitations, it employs relativistic electrons as a gain medium. Radiation is generated by a ''bunch'' of electrons passing through a magnetic structure (called undulator or wiggler). In an FEL, this radiation is further amplified as the radiation re-interacts with the electron bunch such that the electrons start to emit coherently, thus allowing an exponential increase in overall radiation intensity. As electron kinetic energy and undulator parameters can be adapted as desired, free-electron lasers are tunable and can be built for a wider frequency range than any other type of laser, currently ranging in wavelength from microwaves, through terahertz radiation and infrared, to the visible spectrum, ultraviolet, and X-ray. The first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WKB Approximation
In mathematical physics, the WKB approximation or WKB method is a method for finding approximate solutions to linear differential equations with spatially varying coefficients. It is typically used for a semiclassical calculation in quantum mechanics in which the wavefunction is recast as an exponential function, semiclassically expanded, and then either the amplitude or the phase is taken to be changing slowly. The name is an initialism for Wentzel–Kramers–Brillouin. It is also known as the LG or Liouville–Green method. Other often-used letter combinations include JWKB and WKBJ, where the "J" stands for Jeffreys. Brief history This method is named after physicists Gregor Wentzel, Hendrik Anthony Kramers, and Léon Brillouin, who all developed it in 1926. In 1923, mathematician Harold Jeffreys had developed a general method of approximating solutions to linear, second-order differential equations, a class that includes the Schrödinger equation. The Schrödinger equati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitational Potential
In classical mechanics, the gravitational potential at a location is equal to the work (energy transferred) per unit mass that would be needed to move an object to that location from a fixed reference location. It is analogous to the electric potential with mass playing the role of charge. The reference location, where the potential is zero, is by convention infinitely far away from any mass, resulting in a negative potential at any finite distance. In mathematics, the gravitational potential is also known as the Newtonian potential and is fundamental in the study of potential theory. It may also be used for solving the electrostatic and magnetostatic fields generated by uniformly charged or polarized ellipsoidal bodies. Potential energy The gravitational potential (''V'') at a location is the gravitational potential energy (''U'') at that location per unit mass: V = \frac, where ''m'' is the mass of the object. Potential energy is equal (in magnitude, but negative) to the w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
