Tides

ocean · moon · gravity · cycles

The Moon pulls water. The Moon's gravity tugs on Earth's oceans, making the water bulge out on the side facing the Moon. This creates a high tide, where sea level rises.

Two tides a day. As Earth spins, different parts of the ocean face the Moon at different times. Most coastlines experience two high tides and two low tides every 24 hours.

The Sun helps too. The Sun also pulls on Earth's oceans with its gravity, though not as strongly as the Moon. When the Sun and Moon line up, their combined pull creates extra-high tides called spring tides.

Life depends on tides. Creatures living on beaches, like crabs and seaweed, have adapted to survive the twice-daily changes in water level. Fishers also use tide charts to find the best time to catch fish.

Tides give us power. Scientists are learning to capture the energy of moving tidewater to generate electricity, creating a clean energy source from the Moon's ancient pull.