Science Of The Day
Out of context: Reply #152
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- Gnash2
I good analogue of quantum entanglement not breaking the speed of light law...
The way people get around the idea that entanglement implies instantaneous communication is that no actual information is passed when the entangled particles affect each other. The argument is as follows (using a non-QM example):
Say you agree to send out two beams of light to your two friends who live on opposite sides of the galaxy (you live in the middle). Ahead of time you tell them that if one of the beams of light is red the other will be blue. So you send the blue beam to your friend on one side and immediately she knows that your other friend is receiving a red beam at the same time. Aha! You say, my friends have now communicated at a speed faster than the speed of light and violated relativity, but no real information has been passed between them. You have told both of them at a normal sub-luminal speed about what you just did and that's all. (A way of proving there's no faster than light communication is that you could lie and send them both the same coloured beam of light and they would never know!).
With QM is gets a bit more complicated because theoretically no-one knows the state of the particle until it has been observed, but you still cannot affect the state of the particle so the argument is the same.