Tides and Science

The main influence on the oceans is from the moon

The balance between the gravitational force of the moon and the rotation of the moon around the earth creates a force that acts on the oceans creating a bulge of water. So you get a hump or bulge of high water on either side of the earth. The moon also pulls the earth towards it but this is very small.

As the Earth spins, you, standing on the earth at one spot, experience high tide, low tide, high tide and then low tide.

The sun also has an effect on the ocean. When it is at 90 degrees to the moon it reduces the effect of the moon on the tide.
While the sun is much bigger than the moon it only pulls about half as hard as the moon because it is 400 times further away. So it lowers the effect of the tide.  When the Sun is in line with the moon it exerts a pull in the same direction and makes the tide much bigger. So you get very high tides and very low tides, called Spring Tides. These occur when the sun is on the same side as the moon or on the opposite side
The sun is higher in the sky in the summer than it is in the winter. Also the moon’s orbit isn’t actually circular, but an ellipse… so sometimes it’s further away from the earth and other times it is closer. There’s one cycle of the moon and Earth that only happens every 18.61 years. Like in 2015 when we'll be seeing a couple of media labelled 'Supertides'!

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