But Why explores the Big Bang, earth, stars and black holes in this call-in episode that aired live on Vermont Public Radio. Astronomer John O'Meara tackles the big bang, the origins of the universe and how we know humans landed on the moon. Plus, why is the earth round? What is space made out of? How are stars formed? Why do the stars shine so bright? What's beyond space? How long does it take to get to outer space? Will humans ever be able to go to Mars?
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"What's beyond space?" - Amelia, 5, Germany
O'Meara says explaining what's beyond space depends on how you define the question. One way of thinking about the extent of the universe is to define it by farthest thing we can see with our telescopes.
"The other way to think about the universe is as if you're standing on a globe," O'Meara says. "If you started walking, when would you stop?"
You wouldn't, right? You can just keep walking around and around the globe. "That globe has a size. It has a shape that is limited. But if you want to keep walking on it you could walk forever. So it's an example of a thing that has a size but is limitless, depending on how you want to talk about it. And that's one of the models that we have for the universe." O'Meara says we definitely don't know the shape of the universe, but it has a size and it is expanding in both shape and time. That's a really hard thing to visualize, so mostly it's done by computers.
As far as what's on the other side, the universe is everything that is in all of space and time, so it doesn't really have something outside of it. We're used to things that have boundaries and edges and tops and bottoms. We want to say what's in the box and what's outside of the box, but the universe is the box and the room and the stuff inside the box. It is everything.
WATCH — Behind the scenes in the studio for this But Why:
