Squirrel Memes

The philosophical squirrel raises one of theoretical physics' greatest paradoxes! If backward time travel were possible, we should be swimming in tourists from the 22nd century taking selfies at the pyramids. The absence of future visitors suggests either: 1) time travel is physically impossible, 2) humans don't survive long enough to invent it, or 3) the Time Travelers' Convention hasn't been properly advertised yet. This is actually called the Fermi Paradox of time travel - same energy as asking "if aliens exist, where are they?" but with a furry woodland creature doing the heavy existential lifting.