Ive got some kinda theory that we can predict whether the time machine will be invented or not.
Firstly, there is the eventuality that the earth will end someday when sun depletes its hydrogen stock, or due to global warming, whichever comes first.
When such a time comes, well, if the time machine has already been invented, many people will travel back in time to develop their means of escape from disaster. This will cause a steep increase in the population very suddenly.
So, the point is, if whenever we experience a steep pop rise, we can be sure that t-m has been invented, if pop doesnt rise, then either panic that we're all gonna die or we will surely escape !
Hey, i know this is kinda naive, so, give me ur feedback