Tuesday Fact Checking: Black Holes

Black holes: what's the deal? I said that black holes are something from which nothing can escape, not even light. (true) Also they don't act like a drain on a cosmic bathtub. (true) Then I said that as one gets closer to a black hole, things get really strange and mumbled something about time slowing down. Not entirely accurate. It has to do with Einstein's Theory of Relativity (specifically special relativity). Don't worry, we'll keep things simple. Well, as simple as gravitational time dilation gets, anyway.

Light is affected by gravity. That's what makes a black hole black, the velocity needed to escape the gravitational pull of the center is greater than the speed of light. But before light reaches the "point of no return" (what's call the event horizon) it's still affected by gravity. In fact, gravity can shift the color of light as it slows down. Imagine a person standing on a nearby planet watching a spaceship fall into a black hole. As the spaceship gets closer to the center of the black hole, the light emmited from the spaceship gets slower and thus takes longer to reach the eyes of the observer. In fact, since the closer it gets the slower light travels, to the person watching the spaceship will never fall into the black hole. Does this mean the occupants of the spaceship can start breathing easy? Nope. To them, time is still traveling at the normal rate of speed. I wouldn't think it would take more than a few minutes to crash into such an object.

The above image is from Step by Step into a Black Hole showing what one would see if one were to be so unlucky as to stray into the gravity well of a black hole.

For further information regarding black holes, Disney's first PG movie The Black Hole is pretty exciting. Plus, Slim Pickens and Roddy McDowall voice the robots!