Like bowlers trying to pick up a spare, physicists keep trying to knock down general relativity — Albert Einstein’s theory of gravity. But they keep throwing gutter balls. The theory has withstood every test.

Einstein developed the theory in the early 1900s. It passed its first big test 100 years ago yesterday, during a solar eclipse. Relativity predicted that the light of stars that appeared near the Sun would be deflected a bit by the curvature of space around the Sun. Astronomers observed that effect — turning Einstein into a major celebrity.

Since then, relativity has been confirmed in many ways. Astronomers found, for example, that gravity causes a shift in the wavelength of light leaving stars and other massive objects. They’ve discovered that galaxies and clusters of galaxies act as gravitational lenses, bending the light of galaxies behind them. And they’ve discovered the “jiggles” in spacetime known as gravitational waves — something predicted by Einstein’s equations.

And astronomers at McDonald Observatory and elsewhere have bounced laser beams off reflectors on the Moon. Those observations show that Earth and the Moon “fall” toward the Sun in the same way — gravity treats them equally, just as predicted.

While general relativity works well at large scales, it falls apart at the smallest scales. So scientists keep probing its limits — trying to unify the science of the big with the science of the small.

Script by Damond Benningfield