This sounds like solid evidence for the fact that he won't ever get his hands on a time machine.

Or it'll be like the time machine in Primer, where you can't go back before the time machine was turned on.

That kinda only works if we’re the only civilization in the universe, right? What if some other civilization discovered it a long time ago?

Something something 'light cone.' If the machine was turned on a million years ago in another star system and then brought to Earth, the Primer model would put you in the other star system when you climb out of the machine. And then you'd need to make your way back to Earth. (It's unclear to me whether you would continue aging while sitting in the box and waiting for a million years to go by in reverse... But I assume you would.)

So I think the 'other civilization' thing only works if they're already approximately here with a running machine.

Then they might have been using it this whole time. If they kept to themselves we would have no idea.

I think we can tell for certain that time travel will never be invented because if it were to happen, then logically we’d already be experiencing people visiting us from the future.

Hello! It’s me, your visitor from 22 minutes into the future!

Hi! In a few other threads today people claimed that they / one can time the stock market.

Wanna start a trading venture with me? :-)

Since this is HN and we're playing the tbf game...

To be fair he'd only have to hit the FTL goal and then FTL can be used as a time machine.

Oh, good point!