What a Long, Strange Trip It Still Is

Quantum entanglement theory: I say that no two quantum systems or particles can ever be measured separately again once they've interacted, no matter how far apart they get. Changing one means instantaneously changing the other. I'm about as weird an idea as you can get.

Quantum temporal entanglement theory: Hold my beer.

As stated above, entanglement theory has been a part of observed quantum phenomena since the early days of quantum physics. Take two electrons and let them interact. They have, among other qualities, one called "spin." Any pair of electrons will have one of one spin and one of another; change the spin of one and the other one switches. So far so good, except the electrons will continue to interact in that way at any distance. Which means they somehow transmit information between them instantaneously, paying no attention to the fact that nothing can travel faster than light in normal space. Move the two electrons one light-minute apart (about 11 million miles) and flick on a light at the very instant you change the spin of one of them. By the time the light reaches the second electron -- a minute, naturally -- it will have already changed its spin. Albert Einstein called entanglement "spooky" and considered it evidence that quantum physics had a flaw. It's also sometimes called "quantum nonlocality."

Physicists at the Hebrew University of Jerusalem did an experiment in which entangled particles affected each other even when their existence did not overlap in time. Team leader Eli Megidish playfully asks if the experiment means that the photon from the past reached into the future and affected the photon there, or if the changing photon of the future reached back in time to affect the photon of the past.

Now technically, Einstein's theory of relativity points out that the future and past talk is in the eye of the beholder. From the perspective of the person with the first photon, the change made reaches into the future. But from the perspective of the person with the final photon, the change reaches back into the past. And, relativity tells us, they are both right because scientific laws are the same everywhere and no point of view can take precedence over another.

But all that does, it seems, is make entanglement an idea that's weird, instead of an idea that's mega-hyper-super-duper-flipping weird. Which is, of course, where the fun is for physicists.