The Self-Consistency Solution

Physicist Igor Novikov proposed the self-consistency principle: if time travel exists, events must form a consistent loop. You can travel to the past, but you cannot change it. Everything you do there already happened. Your trip was always part of history.

Under Novikov's principle, if you tried to prevent your grandparents from meeting, something would always go wrong. Your gun would jam. You would go to the wrong address. You might even introduce them by accident while trying to keep them apart. The past you visit is the past that already produced you, so it cannot turn out any other way.