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:[1]
- 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 be in an inverted population, where more are in the excited state than the ground state. This typically requires some type of pumping, such as optical pumping.
- The lasing medium must be long enough for the radiation to persist and excite more of the same. In optical systems this can typically be created by mirrors, effectively making a larger optical path length. For a gaser, a large-scale, slowly spatially varying gravitational potential could act as a mirror (by the WKB approximation). Alternately, a hypothetical gaser could simply be built with sufficient length to begin with.
Alternate design proposals involve free undulators akin to a free-electron laser.[2][3] Several proposals involve exploiting the momentum transport properties of superconductors, where s-waves and d-waves couple distinctly to gravitational radiation.[4][5]
As of 2019, there are no plans to construct a gravity laser.
Use in Science Fiction
The idea of gravity lasers has been in part popularized by science fiction works such as Earth Unaware where glasers are used as a plot device to enable planetary-scale manipulation of matter, akin to gravity guns. In other works such as Star Ocean they may be a hypothetical weapon.[6] They are also commonly employed as a proposed mechanism for tractor beams, antigravity, and space propulsion.
See also
External links
References
- ^ Killus, James (2007-01-19). "Unintentional Irony: The Gamma Laser". Unintentional Irony. Retrieved 2019-07-14.
- ^ Bessonov, E. G. (1998-02-19). "Grasers based on particle accelerators and on lasers". arXiv:physics/9802037. Bibcode:1998physics...2037B.
{{cite journal}}: Cite journal requires|journal=(help) - ^ Strelkov, Alexander V.; Petrov, Guennady A.; Gagarski, Alexei M.; Westphal, Alexander; Stöferle, Thilo; Rueß, Frank J.; Baeßler, Stefan; Abele, Hartmut; Petukhov, Alexander K. (2002). "Quantum states of neutrons in the Earth's gravitational field". Nature. 415 (6869): 297–299. Bibcode:2002Natur.415..297N. doi:10.1038/415297a. ISSN 1476-4687. PMID 11797001.
- ^ Fontana, Giorgio (2004). "Design of a Quantum Source of High-Frequency Gravitational Waves (HFGW) and Test Methodology". AIP Conference Proceedings. 699. Albuquerque, New Mexico (USA): AIP: 1114–1121. arXiv:physics/0410022. Bibcode:2004AIPC..699.1114F. doi:10.1063/1.1649680.
- ^ Modanese, Giovanni; Robertson, Glen A. (2012). Gravity-superconductors Interactions: Theory and Experiment. Bentham Science Publishers. ISBN 9781608053995.
- ^ Weapons and Armor - Star Ocean: Till the End of Time Wiki Guide - IGN, retrieved 2019-07-14