Tides

Depending on what time you went to Redcar beach the tide might be in or out. There are 2 high and 2 low tides every day. What causes the tides?

pic   Ian Britton - Freefoto.com

The Moon is kept in orbit around the Earth by the force due to gravity between them. One effect of the Moon's gravitational pull on the Earth is to cause the tides.

The pull of the Moon causes the water on the Surface of the Earth to bulge as shown below. As the Earth rotates a bulge passes over each place twice a day. Hence there are two high tides every day.

The gravitational pull of the Sun is also important, it pulls on the Earth's water in the same way. When the two pulls are in the same line, which occurs twice a month, there is a very high tide called a spring tide. When the two pulls are at right angles, which occurs twice a month, the high tide is at its lowest, this is called a neap tide.

Draw your own diagram showing the positions of the Earth, Moon and Sun when there is a spring tide and a neap tide.

Why do spring tides occur twice a month?