Is Einstein Still Right?

June 8, 2020
Physicists Will (Theory and Experiment in Gravitational Physics) and Yunes take readers on an intellectually challenging but invigorating tour of experiments involving Einstein’s theory of general relativity. Despite the title’s question mark, they write in the preface that “general relativity has passed every experimental test to which it has been subjected,” so their concern is less with grappling with Einstein’s theory itself than with explaining the various methods used to verify it. Some are familiar, such as black holes and gravitational waves, while others, like the “Shapiro time delay,” a delay observed in radio waves traveling around the sun, or geodetic precession, the change in the axis of spin of a gyroscope traveling past a massive gravitational body, are less so. The authors put in yeomanlike work to explain each concept, and avoid using any mathematical formulas, other than the unavoidable E=mc². They also provide observations on the scientific process in general and on their own scientific careers (Yunes admits his initial inspiration came from reruns of Star Trek: The Next Generation.) The topic will still stretch the comprehension of general readers, but for those able to soldier through, this will be a valuable treatise on a foundational topic in modern physics.

September 1, 2020
The answer is yes, but plenty of work remains to confirm his predictions and fill in the gaps. Will, a professor of physics at the University of Florida, and Yunes, physics professor at the University of Illinois and founding director of the Illinois Center for Advanced Studies of the Universe, write that Einstein became a scientific superstar in 1919 when experiments showed that the sun's gravity bent a star's light when it passed nearby. The authors add that, unlike many other superstars, he deserved the acclaim because his discoveries--mostly relativity, but there were others--mark him as one of the most significant geniuses in human history. Besides his brilliant if unsettling descriptions of time and space, relativity predicts phenomena so bizarre that Einstein himself doubted their existence. Most scientists agreed until the 1960s, when they began turning up. Confronted with neutron stars, pulsars, quasars, gravitational lenses, cosmic background radiation, and black holes, relativists suddenly found themselves in great demand. By this time, other theories proposed to explain matters, but so far relativity enjoys a perfect record. "Experiment seems to really like Einstein's theory in spite of how crazy and wacky it seems," writes Yunes at the conclusion. The culmination was the 2015 detection of almost impossibly faint gravity waves, "the most important scientific discovery of the twenty-first century (at least so far)." Many books explain Einstein for a lay audience, and readers would be advised to consult one--perhaps Will's Was Einstein Right? (1986)--before tackling this challenging entry in the field. Justifiably excited by the past 50 years of astronomical spectaculars, the authors hurry past Einstein's basics (curvature of space, relativity of time), concentrating on his more complex predictions. They succeed superbly in describing the history and personalities behind them and work diligently, sometimes successfully, to explain the science. Solid insights into Einstein's dazzling discoveries, but not for the faint of heart.

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