r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.
You don't need a time machine to go forward in time - you can just wait. A'' cant leave everything to A' because A' will disappear within three hours when he goes back to become A''. If A' knows A wasn't reminded the A' can't remind A. the other three Harrys use their time turners to go backwards and close the loop. You do need both forward and backward time travel to create a closed loop, but the forward time travel can just be waiting; it doesn't require a machine.
I think I get it, but I'm still a bit confused, because both A' and A'' are moving forward at the same rate, which means since A'' started off older, A' will never really "catch up to" and become A'', because A'' continues to age. A'' is still three hours older than A', right, forever and ever?
To consider a weird example, what about a six hour old baby going back in time to witness her own birth? Once the fetus comes out, wouldn't there just be two babies, one six hours older than the other? Since they're both there and they're both experiencing... (read more)