The Self Consistency Problem in Time Travel

i love this because i have a long kind of been sceptical about the idea of time travel into the past. So going back and changing something in the past really just makes no sense from a physic's point of view. I mean, it just sort of all becomes very complicated and falls apart as soon as you start thinking about it carefully. It reminds me of stephen hawkins famous invitation to time travellers,. where he threw a party, and then he posted the invitation later after the party. But of course, nobody should have his party about thi we know of he might have dispensed withen.