When I was an undergrad at the University of Chicago, I had the opportunity to join a small gathering one evening listening to Nobel Prize winner Subrahmanyan Chandrasekhar. We students all sat on the floor while Professor Chandrasekhar sat on a sunken couch with his knees up to his chest. He looked terribly uncomfortable. Someone passed a plate of Oreo cookies to him and before he could take a bite, we began peppering him with questions about black holes. The poor man spent the next two hours explaining black holes, having to use the Oreo as an example of a black hole in space.
A black hole is a region of space where gravity pulls so much that nothing, not even light, can escape. The gravity is strong because matter has been squeezed into a small space. This can happen because a star implodes, or falls in on itself, when it is dying. Other black holes formed when the universe began. Black holes will pull objects into them including comets, stellar gases, planets and even other stars. During the evening, Professor Chandrasekhar frequently used the cookie to represent a black hole and showed how celestial bodies would disappear into the Oreo.
Today, NASA.gov has great videos and articles on black holes so no cookies needed! Click here to go to NASA.gov to see a great video on the formation of birth of a black hole.