Was Einstein wrong? New doubts about relativity theory
Alas, Albert Einstein.
Could it be that his crowning work of genius, the theory of general relativity, may be proved in error?
For 66 years now a large number of reputable scientists and a legion of crackpots have been working diligently to discredit his work without success. But last week a careful and clever US physicist, Prof. Henry A. Hill of the University of Arizona, presented findings that cast measurable doubt on the accuracy of one of relativity's first successes, its explanation of the peculiarities in the planet Mercury's orbit.
Mercury's strange course has excited scientific curiosity for nearly a century and a half. The sun's closest planet traces out an elliptical path. This is not unusual in itself. What perplexed generations of astronomers is the fact that the pattern of Mercury's elliptical orbit moves, or precesses. Thus, each year when the tiny world has reached the point in its orbit farthest from the sun, it is in a slightly different position than it was the year before. Although most of this precession can be explained by the gravitational action of the other planets on Mercury, there is a residual amount that could not be accounted for until 1916.
It was then that Albert Einstein demonstrated that this discrepancy could be explained by his revolutionary theory of gravitation. The previous theory, that of Sir Isaac Newton, conceived of gravity as a force that acted instantaneously throughout space. This so-called ''action at a distance'' was rejected by Einstein. He was convinced that no form of force or energy could travel faster than the speed of light. Instead, he argued that gravity arose because every object that has mass warps the basic fabric of space. This warping results in the attraction between massive objects, which we call gravity.
For most cases, Einstein's equations give virtually the same result as Newton's. It is only in very special circumstances or where gravity is far stronger than it is on Earth that the differences become large enough for even the most sensitive experiments to measure. One case is the precession of Mercury's orbit. Another is the bending of star light when it passes near the sun.
The advent of the space age has given scientists a number of new ways to test Einstein's theory at ever greater levels of precision. It has withstood every test while a number of newer, competing theories have failed. For instance, the Viking spacecraft on Mars made possible one of the most accurate tests to date, verifying the relativity equations to within 0.2 percent.
Now comes Professor Hill who, with his colleagues Phillip R. Goode of the University of Arizona's Research Laboratories and graduate student Randall J. Bos, have announced findings that call relativity once more into question. They have reexamined Mercury's precession in light of painstaking solar measurements they have made using a special telescope.
While trying to measure the shape of the sun--a difficult task because of its brilliant and gaseous nature--the scientists found that the solar ''surface'' is vibrating like a disturbed ball of gelatin. Further, it oscillates in a number of well-defined ways.
Although the sun's visible surface, or chromosphere, appears to be nearly spherical in shape, by carefully examining these vibrations the scientists believe they can prove that 95 percent of the mass of the sun is caught up in a hidden core rotating more than six times faster than the solar surface. At this rate, the core would be flattened at the poles and bulging at the equator. This, in turn, would alter the Newtonian description of the sun's gravitational field in the vicinity of Mercury.
Thus, the picture of the sun's interior which best explains the ''sunquakes'' on its surface increases the precession rate of Mercury's orbit by 1.7 percent, explains Dr. Goode. Because the theory of relativity makes an absolute prediction of this excess precession and because the well-established solar models on which the Arizona physicists' calculations are based would have to be severely ''distorted'' to give a result which confirms relativity, one or the other must give, Dr. Goode asserts.
Actually, there is another uncertainty that could resolve this apparent impasse: Mercury's orbit is not as well known as it could be. This uncertainty is just large enough so that it is possible that both relativity and Hill's nonspherical solar model are true, explains John D. Anderson of the Jet Propulsion Laboratory (JPL).