Here’s what you’ll learn when you read this story:Scientists now have multiple lines of evidence that black holes exist. Aside from better understanding them, we could even use black holes as cosmic tools one day. Arguably the most extreme objects in the universe, black holes have fascinated us since John Michell, an English astronomer, first proposed their possibility in 1783. Now, if we had two black holes orbiting one another, this would give us a more powerful slingshot. We don’t even understand black holes theoretically yet, let alone know how to engineer them artificially.