Of all planets in our solar system, Mercury is closest to the Sun. Then comes Venus, and Earth is next.
We’re number three! That should be an Earthling’s loudest cheer. Everything about Earth is just right to support life as we know it. It’s the right distance from the Sun for water to stay liquid, rather than freeze or turn to gas. All life as we know it needs water.
We’re not the smallest! That’s our next loudest cheer. Small planets have weak gravity, and weak gravity can’t hold on to an atmosphere. Gases just fly out into space. Earth’s gravity is strong enough to keep hold of a thin layer of gases, or an atmosphere. This atmosphere is the air we breathe. It protects us from deadly solar rays and keeps the planet from freezing solid.
We’re just right! If Earth were a tiny bit “wrong,” life could not exist.
