How to Measure the Size of a Black Hole?

Astronomers used the lucky lining up of these two objects to learn something about them. They learned that this disk is about seven AU wide, where AU is the distance from the earth to the sun. And so if you put this thing in our solar system and you extend out past the Earth's orbit and out past Mars,. So this thing is really pretty big. The final question is whether a black hole could eclipse something else? Like if there's a star or a sun out there and a black hole passes in between it and us, would it create an eclipse? That would be pretty dramatic, wouldn't it? But it's almost impossible. If somebody standing on the other side of