Einstein’s Theory of Gravity Passes Enormous Test on a Galaxy

By Ryan F. Mandelbaum

It would be hard to overstate how resilient the theory of general relativity has been. In its hundred-plus-year history, it’s managed to predict things far beyond the capabilities of 1910s experiments, and it withstands every new test scientists throw at it.

This time around, researchers flipped typical experiments on their head. Often, scientists look at how much an object bends the fabric of space itself to determine its mass. A new experiment reverses that idea, using an already-calculated mass to see whether the predictions of general relativity held up. Spoiler: They did. But interestingly, the finding could spell trouble for physicists hoping to solve certain other mysteries of the universe.

That mass can warp of the shape of space itself is a fundamental part of general relativity. Scientists have observed it repeatedly by looking at how heavy objects in space, like clusters of galaxies, warp the light passing around them. Scientists first spotted this during a 1919 solar eclipse, during which the blacked-out sun appeared to have slightly shifted the position of background star. They continue to spot this phenomenon today, and now know that heavy foreground objects can warp light so much that background stars and galaxies appear like a ring in the sky.

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