Do you know why astronauts float in space? The answer is the gravity (gra-vit-e) in space is not as strong as the gravity on earth. For example,if I kicked a ball up it would come down really slow or it would never, ever, ever, ever come back down to you. Even high tide and low tide involve the moon! The moon and sun pull in different directions. Did you know that? This creates the tides! So when the moon's gravity pulls on the sea, it is low tide. When it is high tide the Earth and sun's gravity pulls on the sea.