Between us here on Earth and those things you can see in the sky, there is a layer of gases that we call air or atmosphere. The most important gas in that layer is oxygen. Every person, animal, and plant needs oxygen to stay alive. The higher up you go, the less oxygen there is. Airplanes and spaceships and people who climb very tall mountains have to carry their own supply of oxygen because once you reach about 60 miles (100 km) above earth, there is no oxygen at all. That’s where space begins.

Everything that Hashem created in and out of space is known as the universe. We cannot even start to imagine how big the universe is. It contains billions of galaxies, each one a system of stars and other objects in space. The solar system belongs to the Milky Way galaxy. The huge stars that look so tiny when we see them twinkling so far away also belong to the Milky Way galaxy but they are not a part of the solar system.

The people of Ancient Rome called the Sun “sol,” so the word solar means “of the Sun.” The solar system is the name given to all the different planets and other objects out there in space that move in a set path (called an orbit) around the Sun. One of those planets is Earth.