From what we commonly understand, time has one direction and that direction is forward; past, present, future. But physicists are playing with the theory of “retrocausality”, which if real, is the idea that the future can influence the past.
That’s like if I spill coffee on my shirt tomorrow, but I will see the coffee stain on my shirt today. It’s an idea that has been around for a long time, but it never caught on, because why would it? We live on a cause-and-effect timeline and the theory of retrocausality didn’t really fit, until recently.
Some physicists think accepting retrocausality can answer a lot of unanswered questions in quantum mechanics, and deepen our understanding of “spooky action at a distance”. This is what Einstein called quantum entanglement back in the 1930’s.
He thought it was crazy that when two particles are created at the same time, they can be linked together, or entangled, even if they are then separated light-years apart. According to quantum theory, elementary particles like photons that are entangled, have no definite state until they are measured by us.
Special thanks to Dianna from Physics Girl for her help with this episode. Check out her YouTube channel, here!