Einstein hated this idea so much he called it spooky. It turned out to be completely real

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In 1935, Albert Einstein and two colleagues published a paper trying to prove that quantum mechanics was missing something, using a strange consequence of the theory to argue it simply could not be a complete description of reality. That consequence is what we now call quantum entanglement, a connection between two particles so strong that measuring one instantly tells you something about the other, no matter how far apart they are, even if they are on opposite sides of the universe. Einstein dismissed it as spooky action at a distance, convinced that nature could not possibly work this way

Decades of experiments eventually proved Einstein wrong about the wrongness, entanglement is genuinely real, and it does not actually let information travel faster than light or violate his own theory of relativity, despite how strange it sounds. What actually happens is subtler, when two particles become entangled, they stop being two fully separate objects and start behaving as one connected system, so learning about one half instantly tells you something true about the other half, without anything physically traveling between them at all

This is not just a philosophical curiosity anymore, it is the working foundation underneath quantum computing, quantum cryptography, and the early quantum internet researchers are trying to build. The 2022 Nobel Prize in Physics went to three scientists specifically for experiments confirming entanglement holds up even under the strictest possible tests, closing the door on any lingering hope that Einstein might have been right after all

What is quantum entanglement? A physicist explains Einstein's 'spooky action at a distance'www.astronomy.com