Chris Murray says that if it's possible for there to be in the future a time machine configured to immediately travel back to the present, there should be infinitely many such machines in the far future like Boltzmann brains. The fact that our world is not densely packed with such time machines could be evidence that backward time machines are impossible. Jonathan Bird asks, why would abiogenesis ever stop? Abiogenesis is the origin of life. Shouldn't molecules still be coming together to form tiny living things somewhere on Earth? What are the chances that there were some initial conditions that no longer exist anywhere on Earth? Well, I mean, there's a lot we don't know about this also