About a week later, when the Sun and Moon are at right angles to each other, the Sun’s gravitational pull works against the Moon’s gravitational tug and partially cancels it out, creating the moderate tides called neap tides. Twice a month, when the Earth, Sun, and Moon line up, their gravitational power combines to make exceptionally high tides where the bulges occur, called spring tides, as well as very low tides where the water has been displaced. But it’s a distant gorilla, about 390 times farther away than the Moon, which gives it a little less than half of the Moon’s tide-generating force. The Sun ― with about 27 million times the mass of the Moon ― is always the gorilla in the room when it comes to solar system equations. Now, the Moon is the biggest influence on Earth’s tides because of its proximity ― but it isn’t the only influence. To get a true estimate of the tides near you, you’ll have to check the local tides forecast. The tides we actually see at our shores are affected by everything from the shape of Earth’s continents to wind and storms. In addition, Earth isn’t a perfect, smooth sphere. This means that the high tide bulges are never directly lined up with the Moon, but a little ahead of it. When the Moon’s gravity pulls at Earth, the water doesn’t float outward, it just gets pushed and squeezed around on the globe, directed by both gravitational pull and other forces, until it ultimately ends up bulging out on the side closest to the Moon and the side farthest away.Ĭan you easily predict the tides by following the path of the Moon? Not really! First of all, because the Moon is orbiting in the same direction as the Earth rotates, it takes extra time for any point on our planet to rotate and end up exactly below the Moon. It’s easier to slide the water around on the table rather than lift it directly upwards. Now think about pouring a bucket of water out on a table.
The strongest pull occurs on the points closest to the Moon, and the weakest on the points farthest away, but every bit of water is affected. This happens because the Moon’s gravity affects the entire Earth, pulling at every point on our planet. It might seem strange that the ocean would bulge on the side farthest from the Moon as well as the side closest to it. The low points are where low tides occur. In this simplified animation, Earth’s oceans bulge out on both the side closest to the Moon and the side farthest from the Moon.
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