This episode looks at a big question, a really big question. It's about the end of the world and what it might feel like. Parents: this episode is about asteroids and supernovas; some kids may find this episode a bit scary, or may have never considered those possibilities before, so you may want to listen first on your own.
Our first answer comes from John O’Meara, professor of physics and astronomy at St. Michael’s College.
"That’s a question that’s very interesting because it depends on how the world ends...How we answer that question depends on which end of the world you mean: actually the end of the entire earth or do you mean the end of all living beings?
"As an astronomer I can think of a couple of different ways. One of them is something that you probably already know about: when something big hits the Earth. We have neat evidence that the reason why we have the moon is that very early on in the solar system, something about the size of Mars hit the earth and broke off and solidified and formed the moon that we have today.
"We also have giant crater features on the earth, and crater features all over all of the bodies in the solar system. That tells us that big things hit planets all the time. Many hundreds of millions of years ago and 65 million years ago, big things hit the earth and did a lot of damage. If they smack into the ground, they kick up huge amounts of dirt into the atmosphere and that dirt blocks the sunlight.
"If you don’t have sunlight, the plants can’t grow. If the plants can’t grow, the things that eat the plants can’t grow and if they can’t grow, the things that eat the things that the plants can’t grow. Lots of life on the surface of the earth ends. This is probably what happened to the dinosaurs about 65 million years ago.
"We don’t know for sure whether it was a meteor or a comet or something like that, but we do know something big hit the earth and that caused a lot of the organisms on the planet to die off."
"The other kind of thing that can happen is that very large stars can explode. We see it happen all of the time in other galaxies and in other parts of the universe. This is called a supernova and it’s one of the biggest explosions you can possibly think of: stars 100 times as big as the sun, exploding.
"When they do this, they make a lot of energy. The sun gives off a lot of energy right now. When something like that blows off, it gives 100 billion times the amount of energy the sun is giving off right now. You don’t want to be near that kind of star when it happens!
"When it does, if the Earth was too close to a supernova type event, bad things happen to the atmosphere. The atmosphere is made up of lots of different types of elements, nitrogen and oxygen. Those elements are very happy in the way they are right now, but if you whack them with a lot of energy, those elements can go haywire and once again, that affects the plant life and the things that eat the plants.
"The good news is we know where most of the really big stars are and none of them are close enough to use to be a really big danger. What we don’t know is where all of the tiny stars are. But we’re not concerned because we’re building better and better telescopes and finding all of those things.”
Sun Runs Out Of Gas
"Eventually the sun will run out of fuel. Right now, the sun is kind of like an engine that takes the element hydrogen and turns it into helium in a process called fusion. That’s what powers the sun and gives off all the light energy that we then take in.
"Unfortunately, the sun is also its own gas tank. It will run out of its own fuel because it will have turned all the hydrogen into helium. When it runs out of fuel, the inside of the star starts to crunch down and the outside of the star starts to expand. It gets really big. It gets so big that both Mercury and Venus would be stuck inside the sun’s atmosphere. It could get so big that something like the earth could get stuck inside the star! But we know when this is going to happen and it’s not going to happen for at least 5 billion years. The solar system is only 4.5 billion years old. We’ve still got over half of the lifetime of the whole solar system left."
— John O’Meara, Physics and Astronomy Professor at St. Michael’s College.
Listen to the full episode to hear how authors have imagined the end of the world. We hear from S.S Taylor, author of the Expeditioners, and science fiction author M.T. Anderson, author of Pals in Peril, Feed, and other works for kids and young adults.
Want to learn more about space? John O’Meara recommends the NASA Kids Club website.