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Spooky connections: How tiny things link miles apart

When things are far apart, they can still be connected. It baffled Einstein!

By Smartasaurus· 1 min read Curious

If you tickle a single particle on your desk

Knowledge check

What happens when two quantum-entangled particles are separated by light years?

The short version
  • When things are far apart, they can still be connected. It baffled Einstein!
  • In 1964, John Bell devised a mathematical test that could tell the difference between hidden variables and genuine quantum weirdness.
  • Entanglement does not let anything travel faster than light.

Measure one particle here, and its partner - on the other side of the galaxy - answers the question in the same instant. No signal travels between them. Nothing crosses the gap. The correlation is simply there.

Einstein hated this. He called it "spooky action at a distance" and spent the last decades of his life insisting the universe could not work that way. There had to be, he argued, a hidden variable: some property the two particles secretly carried with them since their shared origin, predetermining how they would respond.

In 1964, John Bell devised a mathematical test that could tell the difference between hidden variables and genuine quantum weirdness. Experiments since the 1970s - culminating in the work that won the 2022 Nobel Prize in Physics - have ruled the hidden variables out. The particles are not carrying secret answers. The correlation is real, instantaneous, and impossible to use for sending a message.

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Entanglement does not let anything travel faster than light. It is stranger than that: two particles that are, in some deep sense, no longer separate things at all.

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