Astrophysicists tell us there is a supermassive black hole at the center of the Milky Way Galaxy. They theorize its formidable gravitational pull originally helped form our galaxy.
Readers, I know I've joked previously about black hole theories having been debunked, but truthfully I'm a big fan of all this exotic dark matter and quantum energy stuff, especially black holes. You might even describe me as a supermassive black hole fan. (Couldn't resist.)
Of course, black holes are black because their immense gravity curves nearby space so profoundly that nothing—not even light, the fastest moving stuff there is—can move fast enough to escape the curved region. It just swirls around and around like a coin in one of those funnel-shaped gravity wells you've probably seen at the museum.
You say, "Will, I've seen those gravity wells you're describing. It's so much fun to watch the coin go around and around! But then I get so sad when the coin drops down out of view into the donation bin underneath the funnel."
And then I say, "I would like to explain to you why the coin goes around and around, but I'm concerned you'll question my circular reasoning."
And then you say, "I get so sad when you make terrible jokes. Please stop at once."
Two More Fun Facts About Black Holes
At the center of a black hole is a singularity, a dimensionless point in space-time, which contains a huge mass in an infinitely small space. At the point of the singularity, density and gravity become infinite and space-time curves infinitely. (Wow! Now that's overcrowding!)
There's a spherical region known as the event horizon that surrounds the singularity, kind of like a soap bubble might surround a tiny speck of dust floating at the bubble's center. Think of the event horizon as the final place where you can say goodbye to anything being swirled into the black hole. Once something crosses the event horizon, there will never be any further information about it available in this reality.
And then you say, "Will, I get so sad when you describe the event horizon. It reminds me of the coin dropping down into the donation bin below the gravity well."
And then I say, "Ah ha! Exactly!"
(Black hole illustration courtesy of NASA; Jörn Wilms (Tübingen) et al.; ESA. And thanks to Chris Lanham for letting me link to his YouTube video of the gravity well.)