Article Outline Tidal forces. The forces that produce tides affect all objects on the earth, the atmosphere, and even the solid earth itself. The response to tidal forces is greatest in the oceans.
Tides are most noticeable at shorelines where oceans and continents meet.
There are one or two high tides and one or two low tides each day. The tides occur so regularly that they can be predicted many years in advance. The regularity of the tides has fascinated people since ancient times. Some Greek and Roman philosophers who lived between the 300's B.C. and the A.D. 300's thought that the earth was a living being whose breathing caused the tides. But other philosophers of ancient China, Greece, and Rome noticed that the times of high and low tides followed the crossing of the moon overhead.