Black holes are some of the most extreme objects in the universe.
They contain such enormous amounts of mass concentrated in such a small volume of space they create a gravitational field from which nothing can escape - not even light itself.
But there are some other things that absorb light nearly as much light- 99.5% in fact.
But you won’t find them in deep space, you’ll find them in the dpeths of our seas and oceans.
Karen Osborn, is a marine biologist at the Smithsonian National Museum of Natural History in Washington, D.C - she joined Jonathan to discuss.
Image: (Karen Osborn / Smithsonian NMNH)