[off topic]

“The Big Time” by Fritz Leiber is one of my all time favorite novels. His time travel works on the principle of 'The Law Of Conservation Of Reality." There’s only one timeline, and it’s possible to change it, but it requires a lot of work.

If you go back and kill baby Hitler, he’ll come back to life and no one will remember anything. It takes vast armies fighting thousands of secret battles to change one thing. But when a Big Change hits, look out!