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Gravitational waves have opened up new ways to test the properties of black holes — and Einstein’s theory of gravity along with them.
By 1913, Albert Einstein had nearly completed general relativity. But a simple mistake set him on a tortured, two-year reconsideration of his theory. Today, mathematicians still grapple with the issues he confronted.
A recently proposed experiment would confirm that gravity is a quantum force.
Physicists theorize that a new “traversable” kind of wormhole could resolve a baffling paradox and rescue information that falls into black holes.