Why do we have tides?

Today I want to talk about tides! Above is this video of Clovelly, England and the drastic tide that they experience day in and day out, especially when it is spring tide, meaning the moon and sun’s tidal forces line up to create even more drastic tidal forces. What is amazing about that video is how the entire harbor empties during Spring tide and it’s actually completely a result of the sun and moon, objects that are thousands of kilometers away from us! Now what is actually causing these tides? Well it’s caused by the gravitational forces between Earth and the Sun and Moon. Essentially the gravitational force is different across the earth as the side closest to the moon and/or sun has a stronger attraction compared to the far side. Therefore, the difference between the attraction on opposite sides of the earth create what is known as a tidal force. This tidal force is essentially a stretching force that pulls the earth in the direction of the moon or sun. This is illustrated in the image below.

 

tide03_480
NOAA

 

We witness this tidal force most in the oceans because liquid is most easily affected by gravitational forces but the land moves as well, only a couple centimeters during spring tide, but still it moves! The entire sphere of the early is being stretched towards the moon or sun. Now, because of the distance to the moon, it has about double the effect on tidal forces the sun has but when they work in combination, which is known as spring tide, the force is strong enough to empty the harbor at Clovelly at low tide and be almost overflowing at high tide. This drastic distance is created by gravitational forces from objects hundreds of thousands of kilometers away. That’s pretty cool if I do say so myself.