In his general theory of relativity, Albert Einstein postulated that many major celestial events, such as exploding stars, should flood the universe with gravity waves, causing objects trillions of miles away to move ever so slightly.
Recognizing that Einstein had come up with yet another idea that could tell much about the dynamics of some of the universe's most cataclysmic events, scientists around the world have spent the last few decades trying to prove that he was right.
As other elements in his astounding theories have been slowly confirmed, scientists have grown to believe that Einstein had to be right about gravity waves as well.
But all these years later, no one has been able to prove it.
Now, scientists at Caltech and the Massachusetts Institute of Technology, united in a shotgun marriage arranged by the National Science Foundation, plan to build two giant facilities to see if the great man was correct. If they are successful, they will open an entirely "new dimension" in astronomical research, according to Rochus (Robby) Vogt, former Caltech provost who is in charge of the project, which could cost as much as $150 million.
Gravity waves are not the same as the force of gravity that causes objects to attract each other. Instead, they are a very weak form of radiation beyond the range of the electromagnetic spectrum normally used in astronomy. The effort to prove that they exist, and thus open a new window on the universe, is extraordinarily challenging.
To succeed, the scientists will have to be able to measure movement so slight that it is almost unthinkable. A scale model of the two instruments that will be required for the project has been operating at Caltech for several years, and it is so sensitive that "it registers when a fly walks over it," Vogt said.
The prototype, consisting of two tubes 130 feet long laid out in the shape of an L, is the largest gravity wave detector in the world and it can measure movement one-millionth the diameter of an atom.
'Not Good Enough'
"But that's not good enough," Vogt said.
It, like other experimental detectors, has never detected a single gravity wave since it began operations in 1980. So Vogt and his colleagues hope to achieve sensitivities 100 times that great with two mammoth devices that will have tubes more than 2 1/2 miles long with suspended weights that the scientists hope will move either closer together or farther apart by a force that is so weak it defies imagination.
The idea behind the project is that a laser beam, bouncing back and forth between the suspended weights, will be thrown slightly out of phase in one tube compared to the other because the weights will move differently depending on the direction from which the wave enters the apparatus.
The concept is crudely analogous to two surfers riding a wave across an irregular shoreline. If rocks below the surface retard the wave beneath one of the surfers, the two will arrive on the beach at slightly different times because the crest of part of the wave will trail the other. In other words, the surfers will be out of phase.
The difference in the time of arrival of the two surfers would tell something about the nature of the obstruction.
That technique, called interferometry, has been used for years in radio astronomy to sharpen radio-wave images.
But applying that concept to the gravity wave search will take interferometry to new frontiers.
"Physics is the art of measurement," Vogt said. "That's what physics is all about. But this is the kind of thing that's almost scary."
To succeed, the scientists will have to break new ground in a number of fields.
But some of the best minds in physics, in this country as well as Japan and Europe, believe that it can be done even though all past efforts have failed.
'It's the Right Time'
"It's the right time to do it," said Ronald Drever, the wizard who is chiefly responsible for Caltech's prototype, which has convinced others that the incredible levels of control needed for a machine 100 times larger are at least theoretically possible. It has taken a long time to reach this point, and Drever is clearly ready to seize the moment.
"It's going to happen sometime," he said recently. "One mustn't die before then."
It has also pitted two great institutions in a battle that has left scars and bitterness on both sides. MIT and Caltech have both been working in the field, each competing for funds from the National Science Foundation.
And although $150 million may not sound like much compared to projects funded by other agencies--like the $6 billion-plus for the super collider envisioned by the Department of Energy--it is a lot for the NSF, which has a total annual budget of only $1.5 billion.