Outer space

Outer space is everything beyond Earth's sky. It stretches between all the stars and planets. Space is almost completely empty. It has very few tiny bits of stuff floating around.

Space is extremely cold. It is colder than anything on Earth. The temperature is about minus 270 degrees. Most of space is just empty nothingness. Stars and galaxies are spread far apart. Between them is mostly just empty space. Scientists think there is invisible stuff in space. They call it dark matter and dark energy.

Space does not start at one exact height. Scientists say space begins about 62 miles up. That is very high above the ground. Many countries agreed to share space fairly. They said no country could own space. Everyone can explore it together.

People first thought about empty space long ago. In the 1600s, scientists wondered about the space between Earth and the Moon. In the 1900s, people learned how huge space really is. A man named Yuri Gagarin flew into space in 1961. He was the first human in space. Since then, many people have traveled to space.

Space is very dangerous for people. There is no air to breathe in space. There is also harmful radiation from the sun. People's muscles get weak in space. Their bones also get weaker. Robots can go to space more safely than people. Robots have visited all the planets around our sun.