How the Moon Influences Earth's Ocean

Ever wonder how the tides in the sea change their levels almost everyday? The Sun and Moon both play a great part in that change.

The bulge created in the ocean is due to the gravitational pull of the Sun and Moon. The tidal effect of the Moon is two times stronger than the Sun’s, though the Sun’s gravitational pull is 178 times more powerful than the Moon’s. This is because the Moon is closer to the Earth than the Sun. The gravitational force of the Sun and Moon pull the water toward them, making the ocean rise. This creates high tides on the side of Earth that faces the Moon and the opposite side. On the other unoccupied sides, the ocean's water drains away to fill in the bulges, which creates low tides. Since the Moon goes around the Earth about once a day, that causes high tides and low tides to occur twice a day.

A solar day is when Earth spins around its own axis and returns again. This lasts for 24 hours. It takes Earth to reach the same position in relation to the Moon around 24 hours and 50 minutes. This is called a lunar day. The tides follow the lunar day, not the solar day.

Astronomical forces that create the tides are often predicted correctly. Sea levels could be affected by distinct weather conditions, and could cause lower and higher tides than normal. Storm tides are caused by both storm surges and tidal movements, that increase the seawater levels. Onshore winds cause water to collect on the shoreline, while powerful offshore winds move water away from the shores.

The Sun and Moon not only influence the tidal seas and oceans but the daily lives of living things as well. Next time you’re in a large body of water, you have the Sun and the Moon to thank for the waves.