• Question: Is quantum entanglement faster than light

    Asked by craw532prop9 to Sebastian J, oscarchow, Martin M, Luke D, Joel, Indigo, ciarahurley, Alessio S on 2 Feb 2026.
    • Photo: Martin McCoustra

      Martin McCoustra answered on 2 Feb 2026:

      This idea that quantum entanglement is faster than the speed of light comes from the so-called spooky action at a distance concept in quantum mechanics. This is related to some extent to the famous Schrodinger’s Cat thought experiment. Consider a cat in a box with a bottle of poison that has a random timer able to open the box. Without looking in the box, is the cat dead or alive? We don’t know. In fact, we could consider the cat to be both dead and alive until we look. The act of looking forces the cat into one state – alive or dead. Before looking it is said to be in a superposition of states and both alive and dead at the same time. I know that’s weird but that’s quantum theory for you.

      Now image the cat and poison are entangled and in boxes at the opposite sides of the Universe. The same idea hold true… only when we look in one of the boxes and collapse to superposition into alive or dead will we know and we will know instantly (without the speed of light limit) due to the entanglement. This is the action at a distance that is so difficult to accept.

    • Photo: Luke Detraux

      Luke Detraux answered on 2 Feb 2026:

      Quantum Entanglement does at first seem to break Einstein’s rule than no information can be transmitted faster than the speed of light. This is because when two particles are entangled, measuring one particle can instantly determine the state of the other particle, even if its many light years away. So it seems like the particles have communicated faster than the speed of light.

      However there is a catch! Imagine you have a friend on Mars, who has a pair of entangled particles. Without measuring them, he sends one of the particles to you. At a random time, he’s going to measure his particle and he wants you to record the time when he does. Unfortunately there is no way for you to know when he measured the particle. Nothing changes from your perspective when your friend measures their particle, even if they’re entangled.

      So even through you and your friend might see the correlated results when you do look at your particles, you weren’t able to communicate anything faster than the speed of light.

Comments