'I am NOT an alcoholic': Gerard Butler reveals the real reason behind his stretch in rehab. Actor Gerard Butler has revealed his rehab agony and set the record straight over rumours of his alcoholism. The 42-year-old Scot checked into the Betty Ford Centre in February for three weeks after being injured in a surfing accident. He said: 'Maybe a stronger person wouldn't have needed to go. But I'm glad I did it.
Gravity is one major force that creates tides. In 1687, Sir Isaac Newton explained that ocean tides result from the gravitational attraction of the sun and moon on the oceans of the earth (Sumich, J.L., 1996).
Tides are daily changes in the level of ocean water. They occur all around the globe. High tides occur when the water reaches its highest level in a day. Low tides occur when the water reaches its lowest level in a day. Tides keep cycling from high to low and back again. In most places the water level rises and falls twice a day. So there are two high tides and two low tides approximately every 24 hours. In Figure 1, you can see the difference between high and low tides. This is called the tidal range.