quote:
I thought they found black holes by looking for what was not there, no light where there should be some. I know they use x-rays and heat measurements also but I thought the absence of light was the main indicator.
Very good.
the point you're missing is that they knew
something is there, just not what it could be. If you look out into the depths of space at a black hole, you don't see much at all, and move on. If you see a star going in little circles, but nothing else, then you look closer and find that theres got to be a star-sized mass right there, but we don't see any light. Probably a black hole.
If the hole is sitting all alone, then it is almost impossible to detect. When your ship goes through the warp point, the hole is no longer alone, you and the warp point are there, & you can quickly see somethings amiss and conclude that it's a Black hole