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Explaining the tides [Physics]
posted February 5 2013 18:54.35 by Giorgos Lazaridis

Every body knows that the Moon is responsible for the tides, which is true indeed. But since the earth rotates once per day, and the Moon "passes" from the same spot once per day (approximately), how comes and we have two high tides per day? The next video explains this phenomenon:

The water that is close to the Moon, is pulled by the gravitational pull of the Moon, so we have the first high tide which is easy to explain. Now, the water on the other side is pulled with a weaker force because of its greater distance (there is an Earth between....). But this alone does not explain the high tide at the other side right? Right!

This phenomenon was first explained by Newton in 1687. Its not the Moon that rotates around Earth, rather, the Moon AND the Earth rotate around a common center of gravity. Since Earth is bigger, much bigger, this center of gravity is much closer to the Earth, therefore we falsely perceive this motion as being the Moon that rotates around the Earth.

Therefore, the water on the far side is "pushed" towards space due to this rotation of the Earth around the Moon.

Others tried to explain this far-side high tide as a result of the rotation of the Earth around its axis of rotation, but this is absolutely false.

Bonus video - Two of the world-record breaking high tides!

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