But that's a lot of information. It's a very short interval. Since it's so unlikely to be in that interval, this is large evidence against easy space travel.

I agree that it's a lot of information. But it's also the case that we have a lot of information about physics, such that interstellar space travel being difficult is also unlikely. Which unlikelihood is larger? That's the question we need to ask and answer, not "the left side of the balance is very heavy."