My Supermodel Girlfriend and Other Things that Will Never Exist
The Isaac Arthur video I watched today had a very basic premise: Things that will never exist. It also has some basic assumptions built around known limits in physics.
Entropy will not allow "true" immortality. Everything breaks down.
The Planck constants limit how small something can be physically existing in the universe. Most likely nothing can have a higher temperature than 1000 trillion degrees Celsius because that's the estimated temperature of the entire universe a fraction of a second after the Big Bang. Because of the speed of light it's not possible to have a fully accurate map of the universe at any given time.
One of the basic assumptions the video makes is that causality can't be violated. Without a unified theory of quantum gravity to prove that though that can't be stated as an absolute certainty.