Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to [email protected] is beyond outer space? – Siah, age 11, Fremont, CaliforniaRight above you is the sky – or as scientists would call it, the atmosphere. It extends about 20 miles (32 kilometers) above the Earth. Floating around the atmosphere is a mixture of molecules – tiny bits of air so small you take in billions of them every time you breathe.Above the atmosphere is space. It’s called that because it has far fewer molecules, with lots of empty space between them.AdvertisementAdvertisementHave you ever wondered what it would be like to travel to outer space – and then keep going? What would you find? Scientists like me are able to explain a lot of what you’d see. But there are some things we don’t know yet, like whether space just goes on forever.Planets, stars and galaxiesAt the beginning of your trip through space, you might recognize some of the sights. The Earth is part of a group of planets that all orbit the Sun – with some orbiting asteroids and comets mixed in, too.You might know that the Sun is actually just an average star, and looks bigger and brighter than the other stars only because it is closer. To get to the next nearest star, you would have to travel through trillions of miles of space. If you could ride on the fastest space probe NASA has ever made, it would still take you thousands of years to get there.If stars are like houses, then galaxies are like cities full of houses. Scientists estimate there are 100 billion stars in Earth’s galaxy. If you could zoom out, way beyond Earth’s galaxy, those 100 billion stars would blend together – the way lights of city buildings do when viewed from an airplane.AdvertisementAdvertisementRecently astronomers have learned that many or even most stars have their own orbiting planets. Some are even like Earth, so it’s possible they might be home to other beings also wondering what’s out there.You would have to travel through millions of trillions more miles of space just to reach another galaxy. Most of that space is almost completely empty, with only some stray molecules and tiny mysterious invisible particles scientists call “dark matter.”Using big telescopes, astronomers see millions of galaxies out there – and they just keep going, in every direction.If you could watch for long enough, over millions of years, it would look like new space is gradually being added between all the galaxies. You can visualize this by imagining tiny dots on a deflated balloon and then thinking about blowing it up. The dots wou …
