The Moon

The Moon is Earth's only natural satellite. It's the brightest thing in the night sky (well, ignoring the Sun). The Moon's gravity creates the ocean's tides on Earth. It also makes the day a liiiiitle longer. The Moon looks about the same size as the Sun when it's in the sky, and this allows it to cover the Sun almost exactly, and this results in total solar eclipses. The dark spots you see on the Moon are called 'maria'. The word 'maria' is Latin for 'seas', because ancient astronomers thought they were filled with water. We now know that they are big solidified pools of ancient basaltic lava. The Moon is the only celestial body that humans have landed on.