What causes high and low tide?
The gravitational pull of the moon causes the mass of water to be pulled towards it causing a high tide. The body of water on the opposite side of the earth also bulges due to the earth being pulled towards the moon – imagine the body of water over the whole earth as being oval with one high towards the moon and one high opposite. As the earth rotates we get two tides per day – if it was just the moon pulling on the water as most people think we would only get one tide per day!. We also have some interaction between the Sun and the Moon, if they are perpendicular, ie Pulling against each other, the pull on the body of water is less so we have ‘Neap tides’ if they are working together to pull the body of water we have higher than normal tides called Spring tides ….. The position of the moon in its orbit will also determine the amount of gravitational force on the body of water and thus the extent of the tide.
