Robert Nemiroff (Michigan Technology University)

A black hole is a rip in the fabric of spacetime, a place where anything that enters, including light, can never escape. If a black hole doesn't shine, how can we tell if we're looking at one? Often, black holes have very energetic environments—disks and jets surrounding the point of no return—that shine in X-rays and radio waves. But even if there is no such environment, we can still detect a black hole by the way it warps light around it (if we get close enough).

Warping space

According to Einstein's General Theory of Relativity, matter bends space, which in turn causes gravity. (We fall down, not up, because Earth's mass bends space down toward Earth's center.) Black holes are the ultimate manifestation of gravity; they bend space so much that nothing can ever come back once it falls in. Around such a strong gravitational force, space is twisted and distorted causing light to behave in strange ways. This movie gives us an idea of how just how odd the view might be.

What the movie demonstrates

This movie shows what a background sky might look like if you orbit a black hole from just above the event horizon, the imaginary line dividing the inside of the black hole from the outside. The gravity of the black hole is so great that it severely distorts the background starlight. Large light bending effects cause the background sky to appear to move in unusual ways as you circle the black hole. The stars opposite the black hole, with respect to the observer's position, appear to approach at very high speeds and are greatly magnified. If we were to move our vantage point closer to the black hole's horizon, the sky would apparently become flat and concentrate into one point on the opposite side of the black hole.

Gordon Myers