A delightful quirk of relativity theory
This would be more fun in a blog post. Twitter is a fucking horrible format for a complex analysis of special relativity.That aside, my favourite quirk from relativity is this:  "The more you move in space, the less you move in time."

Like relativity in general, it sounds simple enough, but it's consequences are profoundly shocking. (That is, if you take the time to understand it, and don't leap to the conclusion that you know relativity better than Einstein or Penrose ;)Take the case of two people on Earth, one stationary and one travelling past in a car. They each have a different reference frame, and a different set events which make up their present. Now imagine that there is an alien government in Andromeda debating a possible invasion of Earth. In the reference frame of the person on Earth who is moving, the debate is still going on. But, in the reference frame of the stationary person, it is a day or so later in Andromeda, and the invasion fleet is already on it's way! In nature there is no absolute reference frame we can call base reality, and both observers reference frames are equally valid. Then the outcome of the invasion debate is a foregone conclusion. How can there be any room for free will in the deliberations of the alien government? This is the crux of the Andromeda Paradox and the Reitdijk-Putnam-Penrose argument.BTW:  "Notice that neither observer can actually "see" what is happening in Andromeda, because light from Andromeda (and the hypothetical alien fleet) will take 2.5 million years to reach Earth. The argument is not about what can be "seen"; it is purely about what events different observers consider to occur in the present moment."

https://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argume...More info
https://en.m.wikipedia.org/wiki/Relativity_of_simultaneityEdit: If you know of any serious alternatives to the 4D spacetime/ block universe theory then I would love to read it. Rescuing free-will from the jaws of spacetime would be cool!