Montshire Minute: Black Holes

Originally aired during the week of December 14, 1998

Monday

Imagine you're skippering a research mission on an interstellar starship. On the navigation screen you detect something very weird up ahead. It appears to be a big black blob, with streams of matter being pulled in it. It is strangely beautiful, different form anything you've seen in your travels. And, because you were paying attention in high school physics class, you know you are also looking at a potential danger to the well-being of your craft and its crew. You are looking at a black hole, a place where gravity is so strong that everything around it - your ship, and even light itself - gets sucked in, never to return. Getting sucked into a black hole is a one-way ticket to nowhere. Anything that enters the hole gets crushed into what astronomers call "infinite density" - that's the smallest area you can be crushed into. Ouch!

Tuesday

It's hard to prove the existence of black holes because they are, well, because they are so black. After all, the way most astronomers learn is by observing the light given off or reflected by celestial bodies. There may be several kinds of black holes - one kind forms after the death of a star. Let's say a star much bigger than our own sun ends its life in a tremendous explosion. What's left of the star collapses in on itself - in other words, stuff that was part of the star gets pulled tighter and tighter together. The more matter packed into one area, the stronger the area's gravitational pull becomes. Eventually the exploded star becomes a black hole that exerts such a strong gravitational force that it pulls other particles into it. Even light itself can't escape. A black hole originating from a star five times as big as our sun could end up having a radius of only about 12 miles!

Wednesday

The star of our solar system is, of course, the sun. It was the star before any humans on earth existed to marvel at its performance, and it will still be burning brightly for another 5 billion years or so. Many astronomers believe the final role for our sun will be as a "white dwarf." A star becomes a white dwarf when the electrons in its core refuse to be compressed any more. Although the white dwarf has run out of fuel and is much smaller than the star was originally, it continues to shine brightly as it cools. For many stars, the final performance takes on a darker visage. These stars become black holes! It sounds sinister, but astronomers believe it is a natural development in the course of a star's life. Or death. Black holes are created when the star, no longer able to resist the inward pull of its own gravity, implodes on itself. Wow! What an encore!

Thursday

Stars are born. Stars die. And many of them end up as black holes, which continue to draw matter into themselves, like a storm drain pulls in water after a thunderstorm. Even light itself gets absorbed by the black hole, never to return. As exotic as they seem, black holes, as far as we know, still conform to the laws of gravitation that Einstein explained earlier in this century. The mass of the hole will be the same as the mass of the star that gave it birth. If the star was spinning when it exploded, the resulting black hole will also spin. Scientists believe there may be many very small black holes out there, formed by the pressures that existed seconds after the Big Bang. Our planet could become a black hole, if the earth and everything on it were compressed into an area the size of a Ping-Pong ball.

Friday

We've been talking about "black holes" on the program this week, and marveling at how all the stuff in a star could be compressed into something so dense. But many scientists subscribe to the Big Bang theory as the explanation for how our universe began. And according to Big Bang, every piece of matter - matter that makes up you, me, planet earth, and all the millions and billions of stars and planets in the universe - could have fit into a space smaller than the period at the end of a sentence! About 15 billion years ago, this atomic nucleus exploded, creating all the subatomic particles in the universe, as well as space and time itself. Wow! The stars, the galaxies, and the planets that were formed from this material are still flying out from the point where the explosion took place. In other words, the Big Bang Theory says that the universe is still expanding today.