Gravitational Radiation - A New Way To See The Cosmos
When Albert Einstein formulated his general theory of relativity in 1916, he noted that the theory predicts the existence of an entirely new form of cosmic radiation. Gravitational radiation, unlike the electromagnetic radiation we know as visible light, radio,and other now-familiar types, consists of ripples in the fabric of space itself, produced by the motion of large amounts of matter. When a star explodes, or when two black holes collide and merge, these episodes of cosmic violence shake the vacuum of space around them. This shaking generates waves that travel outward in all directions through space at the speed of light. When this gravitational radiation encounters another object, its waves distort it. But they do so in ways that challenge our ability to detect the distortion, because they stretch and shrink space (and any objects within it) by amounts that span only a tiny fraction of the size of a single atom!
Astronomers and physicists have long known that the detection of gravitational radiation will allow us to probe deeply into the violent events that produce it. Because this type of radiation interacts only weakly with matter, its waves will emerge relatively unaffected from the heart of catastrophic events in the cosmos. In contrast, light waves and other forms of electromagnetic radiation must slowly leak through masses of material blocking their passage. They inevitably lose much of the information that they originally carried in this passage.
Observation of gravitational radiation requires isolating precisely manufactured objects so that they remain as free as possible from all outside influences. Monitoring with extreme accuracy the shape or the separation of pairs of these objects then allows us to detect the nearly infinitesimal movements that arise from the shaking of space-time by the radiation as it passes by. If we can detect them, the waves of gravitational radiation offer a new, clear view of some of the most exciting events in the cosmos, some of which are otherwise unobservable.
Future generations of detectors may offer the earliest view of the universe from a time just after the Big Bang and well before the first possible moment from which we can see electromagnetic radiation.
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