Gravitational Physics Exploring the Structure of Space and Time (1999) / Chapter Skim
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1 Introduction, Overview, and Recommendations
1 Introduction, Overview, and Recommendations
Pages 7-23
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From page 7... ...
Gravitational physics has given us some of the most accurately tested principles in the history of science, yet gravitational waves one of its most basic predictions have never been detected by a receiver on Earth. Gravitational physics is concerned with some of the most exotic phenomena in the universeblack holes, pulsars, quasars, the big bang, the final destiny of stars, gravitational waves, the microscopic structure of space and time, and the unification of all forces challenges to understanding that have captured the imaginations of physicists and lay persons alike.
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From page 8... ...
But general relativity also predicts new strong-gravity phenomena such as gravitational waves, black holes, and the big bang that are quantitatively and qualitatively different from those accounted for in Newtonian gravity. Modern gravitational physics focuses on these new phenomena and on high-precision tests of general relativity.
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From page 9... ...
Representative ones are indicated by filled circles; other illustrative phenomena in which gravitation plays little role are shown by filled squares and italics. Phenomena above the diagonal line are unobservable, because they take place inside black holes.
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From page 10... ...
Any short list of highlights would include the following: . The confirmation of the existence of gravitational waves by the detailed analysis of the shortening of the orbital period of the Hulse-Taylor binary pulsar, showing that the radiated power in gravitational waves agrees with the prediction of general relativity to within a third of a percent.
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From page 11... ...
· The development of string theory and the quantum theory of geometry as promising candidates for a finite, workable theory that unifies quantum mechanics and general relativity. The first descriptions, in the above theories, of the quantum states of black holes.
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From page 12... ...
· The use of gravitational waves to probe the universe of complex astronomical phenomena by the decoding of the details of the gravitational wave signals from particular sources. · The continuing transformation of cosmology into a data-driven science by the wealth of measurements expected from new cosmic background radiation satellites, new telescopes in space and on the ground, and new systematic surveys of the large-scale arrangements of the galaxies.
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From page 13... ...
This will be ensured by the new data from the worldwide network of gravitational wave detectors now under construction, from the cosmic background radiation satellites now planned, and from new gamma-ray, x-ray, optical, infrared, and radio telescopes on Earth and in space. The CGP expects these phenomena to yield increasingly accurate tests and demonstrations of strong-field gravitational theory.
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From page 14... ...
In Chapter 3 the CGP analyzes the achievements of the past and opportunities for the future in gravitational waves, black holes, cosmology, testing general relativity, and quantum gravity. The COP's recommendations arising from this analysis of the most promising scientific opportunities to pursue are described immediately below.
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From page 15... ...
Gravitational waves can provide unique signatures for the existence of black holes. They can also be used to test the validity of general relativity.
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From page 16... ...
Despite the outstanding success of general relativity, this theory is not able to describe the strongest gravitational fields in the universe, such as the earliest moments of the big bang, or the ultimate fate of a star that collapses to form a black hole. To describe these situations, a quantum extension of Einstein's theory is needed.
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From page 17... ...
The discovery of waves from binary neutron star inspirals can reveal information about the nature of matter at supernuclear densities and could shed light on the origin of gamma-ray bursts, while waves from merging double black holes could show how event horizons coalesce and provide proof of their existence. Detection of gravitational waves from pulsars would reveal whether or not their surfaces are distorted and provide key clues as to their internal structure.
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From page 18... ...
In physics, observations in this window would allow precision tests of the properties of gravitational waves, tests of strong-field theories of the production of these waves, detailed confirmations of the predicted properties of black holes in general relativity, and observational tests of the theory of gravitational collapse. Limits on the gravitational waves from the big bang would constrain the physics of the fundamental interactions at the ultrahigh energies realized in the early universe.
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From page 19... ...
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From page 20... ...
The most urgent of these is to understand quantitatively the outcome of black hole and neutron star collisions. If these calculations are to supply predictions of the gravitational waves produced by such events by the time LIGO is on line, an expanded effort is required, including adequate human resources and increased access to supercomputer facilities.
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From page 21... ...
. Use gamma-ray, x-ray, optical, infrared, and radio telescopes on Earth and in space to study the environment near black holes.
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From page 22... ...
A black holepulsar binary system would be a powerful laboratory for gravitational physics, testing with high precision whether the orbital motion and gravitational wave generation of black holes conform to the general relativistic predictions.
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From page 23... ...
reduce both statistical and systematic errors in these results. Observations of gravitational lenses can map the distribution of dark matter.
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