Was Einstein Right? Putting General Relativity to the Test by Clifford M. Will (Basic Books: $16.95)
First things first. The answer to the question posed by the title of this book is yes, Albert Einstein was right. If Clifford M. Will, a physicist at Washington University in St. Louis, had come to a different conclusion, he and his book could be dismissed; there would be no need to say any more about them.
The purpose of Will's book is to accumulate and explain for general readers the wealth of experimental data that has been gathered since 1960 that supports the general theory of relativity that Einstein proposed in 1915 and put before the world the following year.
It is a remarkable story made no less remarkable by the fact that Einstein's theory, which profoundly affects the way we understand the physical universe we inhabit, has developed, been tested and been accepted according to the classical principles of the scientific method--a textbook study of science in action.
Among other things, it shows once again the symbiotic relationship of science to technology--pure science and applied science, as it were. It is obvious that pure science enables applied science to progress, but it is not so obvious that applied science--machinery and the like--do the same for pure science.
For example, the invention of the telescope gave Galileo a close-up look at the planets, which enabled him to conclude that Copernicus was right. And the invention of the microscope allowed Anton van Leeuwenhoek to see tiny organisms living in water, which was the start of modern biology.
Waiting for Technology
So, too, the full testing and confirmation of Einstein's theory of relativity had to wait for the start of the space age and for the development of very sophisticated technologies that made possible incredibly precise measurements of minuscule relativistic effects.
There is also in this book a reminder that no question in science is ever settled for all time. The theory of relativity got its first--and for a long time its only--experimental confirmation during the 1919 total eclipse of the sun, when light from distant stars was shown to bend as it passed near the sun exactly in accord with Einstein's theory.
The event established the theory in the public mind and gave Einstein the superstar status that stayed with him the rest of his life. But as Will points out, the conclusions of that experiment were by no means as conclusive as originally thought, and the experiment was repeated during several subsequent eclipses, most recently in 1973.
Similarly, the long-known anomaly in the so-called perihelion shift of the planet Mercury, which had been fretted about since the middle of the 19th Century, was almost perfectly explained by the theory of relativity. This was a tremendous improvement over the Newtonian theory of the universe, which could not explain the discrepancy between prediction and observation.
As things turned out, however, the data involving the perihelion shift of Mercury was not as conclusive as originally thought, and alternate explanations were put forward, not all of which have been completely laid to rest.
Now, if the last two paragraphs have left you somewhat befuddled--what is meant by the perihelion shift of Mercury and what is meant by the anomaly in the perihelion shift of Mercury --don't be alarmed. These are not difficult ideas, but space prevents a full explanation. Will does a very good job of it in a few pages.
But he does not completely solve the more general problem of making difficult ideas accessible to interested readers who did not major in physics.
Perhaps that judgment is too harsh. The author tries very hard. The book contains no advanced mathematics, no formulas and very little jargon. But the underlying ideas of general relativity and of the experiments designed to test it are still not easy to explain or understand.
It's not Will's fault. There is probably no way that theoretical physics can be made simple. The book demands attention, and the interested reader may find himself having to reread certain pages or chapters to make sure he got it right. Even then, it's a good thing that no final exam is going to be given to the readers.
Of course, it isn't necessary to understand all of the ins and outs of the experiments to appreciate the achievements that they represent or their significance in confirming Einstein's theory. As Will makes clear, disagreements notwithstanding, every piece of experimental evidence gathered over the last 70 years supports the general theory of relativity.
"It bent and delayed light just right, it advanced Mercury's perihelion at just the observed rate . . . it made the Earth and the Moon fall the same, and it caused a binary system to lose energy to gravitational waves at precisely the right rate."