Me: So you all know about the planets orbiting the Sun right?
Kids: Yea, like Mars and Jupiter?
Me: Correct, just like Mars and Jupiter, but don’t forget about Mercury, Venus, Earth, Saturn, Uranus and Neptune. Planets are pretty big aren’t they?
Kids: They’re huge!
Me: Right, they’re huge. And that means they are very heavy. They weigh a lot. But did you know that there are things in space that weigh even more than a planet, even more than the Sun?
Kids: Really? Wow, that’s cool. How much bigger?
Me: Well that’s a good question class. There is something called a black hole that can weigh 20 times as much as the Sun, and really big black holes can weigh more than a billion times as much as the Sun. Incredible huh?
Kids: No way, really? That’s big.
Me: And who knows how many stars we have in our solar system?
Kids: [After a moment of hesitation] We have a star in our solar system?
Me: Sure we do. It is called “the Sun!” The Sun is a star.
Kids: Oh yea, right, we knew that!
Me: Well, maybe you didn’t know that most stars (but not our Sun) have companions, and the two stars circle around each other. And many black holes circle around each other.
Kids: Oooh, that’s awesome. Do they go around very fast?
Me: You bet they do! In fact, they go faster and faster over time, and eventually they crash into each other making an even bigger black hole. But right before they crash, they throw out a lot of energy, sort of like a blast, and the energy is called “gravitational waves.” After millions of years travelling to reach us they rain down on Earth.
Kids: You mean the waves are hitting us now? Does it hurt?
Me: Exactly! They are always raining down on us, constantly, but they are so weak we never notice them at all. In fact, we have to try very hard to notice them at all. So far nobody has actually found one.
Kids: So how do we know they’re real if we can find them?
Me: Good question! It is because nearly 100 years ago, a great scientist named Albert Einstein stayed up late one night and thought about this, and he said the waves should exist. One day soon, we’ll be able to find the waves and prove Albert was right.
Kids: We’ve heard of Albert Einstein. He was very smart so he must be right.
Me: Yes, he was smart, but the way science works is that thinking something isn’t enough. You must figure out how to prove it. You have to figure out an experiment to prove it. So a lot of very smart scientists from around the world are working on this big problem.
Kids: This sounds like fun. We want to become scientists one day too so we can prove things like the waves.