The sun is a large ball of fire in the sky. The sun’s primary purpose for Earth is to help plants grow. It also provides people Vitamin D. However, too much sun can cause cancer or a sunburn. So, the sun can be hurtful as well. The moons appear in different phases in the night sky. Full moons look very bright in the night sky and can help somewhat to bring light at night. The Earth is a planet that rotates around the sun. It sustains life and is part of the Milky Way solar system.