It's the philosophical question that keeps cropping up - if you could travel back in time, would you kill baby Hitler? Okay, let's be honest, the first thing you'd do is go and see the dinosaurs, but would killing one of history's worst babies be the second thing?
Of course, at first glance, there's no right answer to the question. If you say yes, you'll have stopped one of the worst periods of human history from occurring, but what would the effects of changing the course of history be? Maybe things will turn out worse?
And if you say no, well, you could have stopped one of the worst periods in human history, and you didn't.
As the Vox video above explains, the question of travelling back in time to change the past really came to the fore in 1895, when H. G. Wells published his novel, The Time Machine, it was one of the first times that the phrase "time travel" really hit the public consciousness.
It was a real sign of the times - back in the 1600s, technology was, for the most part, something that happened by accident, because people would stumble on a better design for a plough rather than sit down and try to figure one out.
But during the 1800s, the vast possibilities of new technology were at the forefront of everyone's mind, and the time was right to consider a machine that could bend time.
Fast-forward to 1941, and that's when we get the first real mention of travelling back in time to kill Hitler, and all the problems that come with that.
"It's two problems at once," says author James Gleick, an expert on the cultural impact of modern technology.
"There's a scientific problem - you can set your mind to work imagining could such a thing be possible, and how would that work - and there's the ethical problem, if I could, would I, should I?"
A lot of what we think about when we consider changing things through time travel is about regret, and just as dwelling on regret can often be counter-productive, it could actually solve this conundrum for us.
"The moral of the story is that I find, somehow, most believable, is that when you change history, you don't get the result you were looking for," says Gleick in the Vox video above.
And the reason for that is fascinating. I won't give it away, you should watch the video to find out, but let's just say that every day, every second, we're all at a turning point, and there's no way of knowing which of those turning points will really matter.
So maybe don't kill Hitler if you make a time machine, but you could still probably see the dinosaurs. Just don't step on anything, you big klutz.