Ocean tides are one of the few phenomena that bring the workings of the sky down to Earth. The gravitational pull of the Moon, and to a lesser degree the Sun, tug on the world’s oceans while the Earth rotates under them, causing the ocean to appear to rise and fall twice each day. Isaac Newton applied his theory of gravitation to explain the tides. He reasoned that the Moon pulls on the ocean on the Moon-facing side of Earth, pulls on the Earth itself to a lesser degree because it’s further away, and pulls on the ocean on the far side of the Earth least of all. The effect is to cause the oceans to bulge slightly on a line towards the Moon as the earth rotates. So we see two tides each day spaced by 12 hours plus a little bit more to account for the Moon’s revolution around the Sun. Other than sunlight itself, tides are one of the most familiar astronomical phenomena we see around us.
In this time-lapse video by photographer Alan Dyer, you see the tides in action on the east coast of Canada, including the Bay of Fundy, a place in New Brunswick that boasts the highest tides in the world. It ends with a view of the Moon and Sun setting over the Bay of Fundy.
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