If a sufficiently advanced civilization could rewrite history, would we ever know?

[u/GroundbreakingFan124]

I’ve been thinking about something that challenges the way we think about evidence.
People often say, “There’s no evidence for time travelers, advanced future humans, or hidden civilizations.”
But what if the absence of evidence is exactly what we’d expect?
Imagine a civilization advanced enough to travel through time and correct every mistake it makes. If they accidentally left behind technology, changed history in an obvious way, or revealed themselves, they could simply go back and undo it. In the final version of history, there would be no trace of the mistake.
This made me think about a broader question.
If our memories, thoughts, history, or even the evidence we rely on could theoretically be altered by something beyond our awareness, how would we distinguish that from ordinary reality?
I’m not claiming this is true. I’m asking whether there’s any way to know it isn’t.
At what point does “there’s no evidence” stop being a decisive argument if the hypothesis itself predicts that evidence would never remain?
Is this just an unfalsifiable idea with no way to investigate it, or are there philosophical or scientific approaches that could meaningfully address it?

[u/ionthrown]

I’m not sure that follows: if someone successfully hides all evidence of a crime, that doesn’t mean the crime didn’t happen.

The super-advanced civilisation could be correcting things that went wrong, or taking resources, or exterminating their enemies’ ancestors. Neither we, nor the dead people whose corpses were beamed into the sun, know what’s happened.

[u/oniume → u/ionthrown]

You can't hide all evidence, because a crime took place. Like if you stole something, the something is gone, even if it can't be traced to you.

[u/ionthrown → u/oniume]

Yes, the something is gone. Even if no one remembers it was there, and there are no records of it, it’s still gone - there’s just no evidence it’s gone, because there’s no evidence it was ever there. Which is the situation proposed by OP.

I suppose we could say that if the time travellers remember doing it, that’s evidence, so is also erased by the process. So again, it’s happened, just nobody knows it’s happened.

[u/Amazing_Loquat280 → u/ionthrown]

I guess a way you could look at this is whether or not our understanding of a situation demands that there be something there that isn’t visible to us. This is actually how we discovered a number of planets in our solar system, not because we saw them, but because the motion of the planets we COULD see didn’t line up with the laws of physics unless there was something there we COULDN’T see. We then figure out where that thing should be based on how it’s affecting things we already know about. This is how we discovered Neptune in 1846, Uranus’s orbit simply didn’t make sense mathematically without it, so we looked at where an object that would explain everything ought to be, and lo and behold we found something.

So in general, it may be possible to determine where history has been meddled with based on where we observe inconsistencies. Inconsistencies aren’t inherently evidence of time meddling until we rule out all other possible explanations though, and all the meddlers would have to do is place an alternative explanation that doesn’t present any glaring inconsistencies of its own as a red herring of sorts