The Experiment That Breaks Relativity

In this video, Derek Muller walks us through the legendary Einstein–Bohr showdown over quantum mechanics—starting with the speed of gravity and “spooky action at a distance,” then unpacking the Copenhagen interpretation, the EPR paradox, and the hunt for hidden variables. Along the way we meet John Bell and his revolutionary theorem on entanglement, showing that measuring one particle can instantaneously affect its partner, even light-years away.

Armed with Bell’s inequality tests (and lots of clever Stern–Gerlach setups), experimenters have now confirmed that nature really is non-local—forcing us to rethink the core of relativity’s no-faster-than-light rule. From the stubborn locality problem to the wilder Many-Worlds take, this saga proves quantum mechanics is as mind-bending today as it was 90 years ago.

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