eli5: Why is the Kessler effect so dangerous? Won’t the space junk eventually fall out of orbit or drift off into space?

Question

I saw the opening of *Gravity* and it was pretty terrifying, but to quote Billy Bob Thornton in *Armageddon*, it’s a big-ass sky.

In: 14

Answer 1

Things don’t drift off into space when they are in orbit. It requires energy to do that.

It’s like expecting a ball to roll up a mountain.