December 2, 2019 0

Astronomers vs. Kids – The Expanding Universe

Astronomers vs. Kids – The Expanding Universe

Did you know that the Universe is flying apart and it’s getting faster all the time? Professor Brian Schmidt is here to tell you why. Space is really big, and that’s what I study. I try to study how the Universe works and what’s going to happen to it in the future to it. What I’ve discovered is that the Universe is getting bigger faster and faster over time. The way I do that is that I go out and look at stars. Actually, I don’t look at stars, I look at galaxies that are much farther away than stars. So, we live in a galaxy called the Milky Way. Have you ever seen, when you look up on a dark night, you can see that fuzzy cloud? That’s billions of stars you’re seeing, all merged into a mess because you can’t see one from another. Our Milky Way has 100 billion stars. That’s a lot of stars. That’s a one with 11 zeros behind it. Our Milky Way is just one of billions of galaxies we can see in the sky. So, what I do is I go out and look at these galaxies. It’s really interesting because all the galaxies are moving away from us. The faster these galaxies are moving away from us, the further away that are. That’s why we think the Universe is expanding. When the Big Bang exploded, the Universe was created and then it began expanding and expanding, faster and faster. So imagine the Universe is expanding. I want you to look at all these stars. Now I’m going to blow the Universe up. Did you notice that all the stars moved away from all the other stars? Imagine we’re right here and we’re looking out, what would we see? As the Universe expanded the nearby stars only moved a little bit but the distant stars, they moved a lot. If I let all the air out and go back to the past, things were really close and now they’re really far away. If I could measure the speed that things are moving away, those things would be moving away really quickly compared to the less distant ones. That’s what we see in the Universe, we see that everything is moving away from everything else. What I was able to do with a group of astronomers is to measure how that was happening back in time. I can look back in time as an astronomer, because light takes time to reach me. When I look at the nearest star, I see it 4.3 years ago. If someone said “hello†right now on Alpha Centauri, I wouldn’t know about it for 4.3 years. But, when I look at distant galaxies I can see billions of years into the past. I can look back before the dinosaurs I can even look back before the Earth was formed and I can measure how fast the Universe is stretching apart now and back in the past. There’s this thing called dark energy which is the opposite of gravity and that’s why the Universe is expanding Gravity is a sort of force that pulls two objects together. Dark energy is a force that acts the opposite of gravity, so basically it pulls things away from each other. It turns out that Albert Einstein, back in 1917 realised that if the Universe was full of this stuff it would make his version of gravity and that’s how we understand gravity now, not Isaac Newton but Einstein his version of gravity would actually work in reverse with this stuff. So, the atoms that you and I are made out of gravity pulls us together, but dark energy pushes things apart. Fortunately, here on Earth there’s a lot more atoms than there is Dark Energy because our part of the Universe collapsed because of gravity billions of years ago. So, right here in this room for every piece of dark energy there’s one with 30 zeros behind it, atoms. A lot of atoms. That’s why things aren’t flowing apart here, because in our part of the Universe there’s a lot of gravity that pulls. It’s only in the vastness of space remember how far apart those stars were? Well, think of all the space between galaxies, there’s a lot of space where there’s nothing except for the dark energy That’s where it can add up and start pushing things apart. Subtitles by the community

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