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It's fall and many kids are headed back to school and they're on the hunt for the perfect book to read. Don't forget to check out our But Why book series. We have two books perfect for young readers about age 8 to 10. Look for Our Llamas Ticklish and Do Fish Breathe Underwater wherever you buy your books. And if you prefer to listen to books, check out the audiobook versions as well. You can find out more at butwhykids.org books.
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Today we're answering two questions that have to do with space. One about Saturn and one about a phenomenon a little closer to us, the sky that we see every day. Our first question comes from four-year-old Francisco who lives in Virgins, Vermont. How do Saturn's wings stay on it and go really fast? And how do they spin around?
Hi, this is Carolyn Porco. I'm the leader of the Cassini imaging team. Carolyn Porco is a really big deal in the world of astronomy. The Cassini mission is one of the U.S. Space Agency's biggest projects, and 16 other countries are involved too.
The Cassini spacecraft took off in 1997. That's probably before you were born. And it took seven years for it to get to Saturn. Imagine if your road trips with your family took seven years just to get to your destination. For one thing, you'd need a lot of snacks, and you'd probably get pretty sick of your siblings.
Luckily, Cassini is unmanned. That means no one is actually on board flying the spaceship. It's flown by a team on the ground on this planet.
Before Cassini reached Saturn's orbit, it did flybys of Earth, Venus, and Jupiter, and it sent pictures back to scientists on Earth so they could learn more about all of those planets. But Cassini's main mission is to let scientists learn more about Saturn, since it's the first spacecraft ever to enter Saturn's orbit and travel around it. It's been traveling around the ringed planet for more than a decade now, taking pictures the whole time.
And it's Carolyn Porco's job to be in charge of all those pictures, the imaging that Cassini sends back to Earth. Since Carolyn is an expert in Saturn and its rings, she took a stab at answering Francisco's question. Here's his question again. How do Saturn's rings stay on it and go really fast? And how do they spin around?
Well, Saturn's rings do go really fast, but they don't spin around. They, in fact, consist of countless particles, icy particles made of water ice,
that range in size from the tiniest particles you find in talcum powder all the way to the size of small apartment buildings. And each of these particles is in separate independent orbit around Saturn. You can think of each of them as being a moon of Saturn. There's just lots and lots of them, and they're all packed closely together. And that's what Saturn's rings really are. They are a disk of debris that
or collisional products from a breakup of a moon or a body in orbit around Saturn that happened a very, very long time ago. That was Carolyn Porco. She's a scientist working on the Cassini mission, which sent an unmanned spacecraft all the way to Saturn. In the two decades it has been up in space, Cassini has given astronomers some really amazing information about this mysterious planet.
For example, its pictures revealed several moons that scientists hadn't even known about before. But in 2017, next year, Cassini will plunge into Saturn's atmosphere and it will burn itself up on purpose. After 20 years, its mission will be over. One more fun fact about Saturn before we move on. Here on Earth, we have four seasons, of course, and each season lasts about three months, giving us a full year.
There are seasons on Saturn, too, but each season lasts seven years. Imagine seven years to get through one summer. That might sound great. Or one winter. Seven years of winter just for one season. Countdown commences. Seven. Coming up, we'll learn about why the sky is blue.
Maybe you've looked up at the sky and wondered, how did it get that color? And why isn't it white or green? Kabir, who lives in Austin, Texas and is six years old, sent us this question. Why is the sky blue? For an answer, we turned to NASA's Space Place. That's a great website that has answers to all kinds of space questions, and it's written just for kids.
Science writer Jessica Stahler Conrad just started working there, and we asked her to offer some thoughts. Well, Kabir, that's a really good question, and it's probably one that people have been asking for as long as people have been looking up at the sky. We see blue when we look up at the sky because of how the light from the sun interacts with our atmosphere. The atmosphere is the layer of gases that's above the Earth.
So Jessica said it's blue because of the way the light from the sun reacts with the gases in our atmosphere. The sky above us is filled with gases that we can't see. We typically just say it's air up there, but there are many types of gases that actually make up that air or atmosphere.
Sunlight is just plain white light, but white light is actually a mixture of all the colors of the rainbow. So one thing to remember is that light is a form of energy. So when a surge of energy passes through ocean water, you see that as a wave, right?
Well, light energy travels in waves too. And that's important in understanding the color of light that we see. As Jessica said, light energy travels in waves. We can't see those waves like we do in the ocean, but we can see the color they produce. For example, long, lazy, low-energy waves are seen as the color red, while the short, choppy, high-energy waves are seen as black.
blue light
When sunlight reaches the Earth's atmosphere, it hits gases and other particles that are in the air, and the light that's coming from the sun scatters. The shorter, smaller waves that we talked about, the short, choppy ones, are scattered more strongly than the other waves. And since the blue light are those short, choppy waves, the blue light is scattered most strongly, more than any of the other colors. And that's why we see...
the blue light in the sky. So what about at sunset when the sky turns red and orange and purple and all those other beautiful colors? As the sun sets, the sun looks like it's getting lower and lower in the sky, right? That's because the sun isn't directly above you anymore and the sunlight is coming at you from an angle.
So it means that the light waves have to pass through more of the atmosphere to reach you here on Earth. An analogy I like to think of when I'm thinking about this is that you
that you imagine the atmosphere is a block of cheese and the sunlight is a knife. If the knife is directly above the cheese and it's cutting through, it takes only a shortcut to get through the cheese to the cutting board. But if the knife is at an angle, it has to take a longer path through the cheese to get to the bottom.
The setting sun is like the angled knife. Light from the low setting sun must take a longer path to get through the atmosphere and to you on Earth. That means it hits even more gases and particles on its path through the atmosphere. And the more particles it's hitting, the more the blue light waves are scattering all over the place. And
almost all at sunset, almost all of the blue light is scattered away. But that means that the longer waves, like red and yellow light from the sunlight, are passing straight through the atmosphere and to your eyes. Why are the blue waves being scattered away? Blue waves are the short, choppy, high-energy waves. And they...
they're more likely to hit these particles in the atmosphere and be scattered. So we see these different sky colors at different times of the day because of where the sun is primarily. Right, where the sun is in relation to you. So if you're looking at the sunset, you're almost looking...
right straight across at the sun, whereas at noon, when it's really bright blue sky, you might be looking sort of directly up at the sun. So it's where the sun is in relation to your eyes that helps determine what colors we see in the sky. That's right. So there you have it. When the sun is high in the sky overhead, it's the blue waves from its light that are scattered away first, so you see the blue.
As the sun sets, those light particles pass through more atmosphere to reach you, so we see those longer waves of red instead. Do you have a question for us? Have an adult record it and send your file to questions at butwhykids.org. But Why is produced by Melody Beaudet and by me, Jane Lindholm, for Vermont Public Radio. Our theme music is by Luke Reynolds. We'll see you in two weeks. Until then, stay curious.
From PR.