The Moon's Pull: Why Tides Rise and Fall

The ocean moves up and down like a giant, slow-breathing animal, and this happens because the Moon’s gravity pulls on the water.

Imagine you are playing tug-of-war. The Moon grabs the ocean’s surface and gently tugs. On the side of the Earth facing the Moon, the water stretches out toward it. On the opposite side, the water bulges outward because the Earth is pulled harder than the water is. These bulges are called high tides. When your beach is in a bulge, the water covers the sand. When your beach is between the bulges, the water slides away. This is low tide.

The Earth spins like a top. As it spins, your spot on the beach moves through the bulges. It takes about twelve hours to go from high to low. The Sun also helps, but the Moon is the boss. Think of the Moon as a giant magnet for water. It doesn't push or pull with magic; it uses gravity, which is a force that pulls things together. When you jump, gravity pulls you back down. The Moon does the same thing to the ocean, just from very far away.

The tide comes in, then goes out, over and over, like a calm, rhythmic breath.