# How Tides Happen

Tides are gravitational forces of the heavenly bodies interacting on the oceans of the earth causing the water to be drawn in one direction or another in a relationship to those bodies. Normal daily tides happen twice a day due to the gravitational pull of the sun and moon and the rotation of the earth. Some places on the earth have one high tide and one low tide a day (diurnal). Other places have two high tides and two low tides per day (semidiurnal).

Sir Isaac Newton wrote the Philosophiae Naturalis Principia Mathematica to explain it all. In this book he was the first to show that the motion of objects on Earth and of the planets were governed by the same set of natural laws and came up with the math to prove it. Not only did he discover gravity on the earth from the apple falling on him, he had the brainchild of tides too. Sir Isaac came up with a whole lot of other things too, like calculus. The fantastic things he proposed were such a leap from the thinking of his contemporaries that it reminds me of the touching of the obelisk in the movie ” 2001-A Space odyssey”. That will be for another writing.

At times there can be a very high tide (spring tide). When the sun and the moon line up together and their gravitational pull is added together, then the ocean waters will be pulled exceptionally far onto the land. These spring tides do not necessarily happen in the season of spring. They are called spring tides because of the action of water springing up. These spring tides can cause damage to structures not affected by normal high tides.

The moon travels around the earth in an elliptical egg shaped orbit. About every year and a half it just happens to travel approximately 7 to 8 percent closer to earth than normal. At the time that this happens, the sun will also line up and add its pull to that of the moons increased pull. When conditions are right, everything lines up, there occurs such a high tide that coastal flooding and extremely damaging storms all happen at once. This is called a Proxigean Spring Tide.

When conditions are such that you have only the pull of the sun on one part of the earth. The moon pulling on another part of the earth. the gravitational pull is nullified a great deal when this happens. The result is called a Neap tide and it is an exceptionally weak tide.

Because of the cyclic nature of the universe, seasons, motion of the earth the tides are also cyclic in nature. The tides can be predetermined by mathematics (designed of course by Sir Isaac). There are almanacs that are printed up each year that list the various tide heights in different areas of the world and the information will only vary slightly from year to year. There are tides in all the lakes too. There is not the volume of water in the lakes as in the oceans and seas of the world so there will not be the huge difference in tidal motion there but it does happen.