Einstein’s Theory of Gravity Passes Toughest Test to Date

By Mike Wall

Einstein’s theory of general relativity has passed its toughest-ever test with flying colors, a new study reports.

General relativity, which the great physicist proposed in 1916, holds that gravity is a consequence of space-time’s inherent flexibility: Massive objects distort the cosmic fabric, creating a sort of well around which other bodies orbit.

Like all scientific theories, general relativity makes testable predictions. One of the most important is the “equivalence principle” — the notion that all objects fall in the same way, no matter how big they are or what they’re made of.

Researchers have confirmed the equivalence principle many times on Earth — and, famously, on the moon. In 1971, Apollo 15 astronaut David Scott dropped a feather and a hammer simultaneously; the two hit the gray lunar dirt at the same time. (On Earth, of course, the feather would flutter to the ground much later than the hammer, having been held up by our atmosphere.)

But it’s tough to know if the equivalence principle applies in all situations — when the objects involved are incredibly dense or massive, for example. This wiggle room has given hope to adherents of alternative gravity theories, though such folks remain in the minority.

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