I just read about quantum entanglement. Simply (and possibly incorrectly), two electrons can be entangled. If you make one of these electrons spin in a particular way, the other electron will match its movement. And even if these electrons are moved many lightyears apart, any change will be instantly reflected.

In theory, this could enable instant communication over vast distances.

This kind of thing hurts my brain. There are average people (where I am), smart people, and then a whole other tier of people who are able to theorise and and harness this kind of thing.