GRAVITY WAVES SET TO BE DISCOVERED
For the world of physics, a quiet revolution may very well be set to begin at the end of this year. December 28, 2001, will see the activation of two separate devices, the
LIGO in America and the
GEO 600 in Germany, in the first large-scale attempt to detect
gravity waves. If all goes well and detection ensues, the discovery and confirmation of the existence of gravity waves will qualify as a Really Big Deal for science nerds everywhere. Gravity is arguably the least understood of the physical forces. We know that it works, but not how it works. Drop an apple and it�ll fall; beyond that the best and brightest minds in physics are pretty much stumped. And while this upcoming project to find gravity waves won�t spell out for us how this essential quality of the universe operates, it should provide some fascinating hints, as well as some unexpected discoveries about the cosmos.
Predicted by Albert Einstein�s general
theory of relativity but never detected, gravity waves are produced by everything in the universe in any state of motion. This is as true for a collapsing black hole as it is for the simple motion of opening and closing your fist. When you clench your palm, you are actually bending the fabric of space-time and affecting the position of every particle in the universe, albeit to a very, very, very small degree. It is the fact that these distortions occur on such infinitesimal scales that makes the detection of gravity waves fiendishly difficult. Research toward that end was spurred in the 1960s after Joseph Weber, a respected scientist at Princeton�s Institute for Advanced Study and a pioneer of lasers, reported detecting gravity waves with a device that he built himself. However, subsequent independent experiments failed to confirm his results and stymied research for decades. It seems that the problem in detecting these waves lies not with the theory, but with the limitations in our own ability to take measurements of distance at very tiny scales. Essentially, what we need is a tape measure that has the width of atoms in place on inches. Over the years there have been some ingenious but difficult proposals, some funny ideas and
claims from the fringe, and even an
Italian experiment that failed to detect gravity waves but, surprisingly, revealed interesting information about background radiation unrelated to the study!
We have recently reached the point where it is thought we can detect gravity waves by measuring the minute changes in distance they will create in a structure, by using a technique that has progressed significantly of late, laser interferometrics. According to theory, gravity waves will radiate outward from the point of creation at about the speed of light (186,000 miles per second), but their signal strength will dissipate the further they travel. However, gravity waves will pass unhindered through matter, unlike light. When a wave passes through an object, for example our planet, it bends all the atoms in that object, and then they �snap� back into place after the wave passes. Don�t notice it too often? That�s because even the most powerful gravity waves physicists can imagine, such as those produced when two dying
neutron stars collide, would �bend� our planet by such a small distance that it would be just a few tenths of a trillionth of the width of a human hair. Put simply, two separate lasers having the exact same wavelength can be placed opposingly such that their waves cancel each other out, but if a gravity wave passes it will ever so slightly lengthen one laser�s path while shortening another. A computer will detect this discrepancy and the experiment, after scrutiny, will be declared a success. So the theory goes, and we�ll see if it holds up in a couple weeks.
So keep your fingers crossed. The successful detection of gravity waves will usher in a brand new era of exploring the universe. Our exploration of the cosmos thus far has been limited to what we can see; studying gravity waves can be imagined as gaining a sense of hearing the phenomena that surround us in the stars.
For a cool video download of a gravity wave bending spacetime, click
here!
current science news posted by ted at 12/10/2001 09:03:00 PM
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