Tides

Tides are the rising of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. A tidal force is a secondary effect of the force of gravity. It arises because the gravitational force exerted on one body by a second body is not constant across its diameter. (http://oceanworld.tamu.edu/resources/ocng_textbook/chapter17/Images/Fig17-11s.jpg)

[|(http://home.hiwaay.net/~krcool/Astro/moon/moontides/)]
 * __-Types of Tides-__ **
 * **Spring tides**- occur when there is a full moon. The gravitational pull of the moon and sun are combined. At these times, the high tides are very high and the low tides are very low. This is known as a spring high tide. Spring tides are especially strong tides (they do not have anything to do with the season Spring). They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides.
 * **Neap tides-** During the moon's quarter phases the sun and moon work at right angles, causing the bulges to cancel each other. The result is a smaller difference between high and low tides and is known as a neap tide. Neap tides are especially weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another (with respect to the Earth).
 * **Proxigean Spring Tide-** is a rare, unusually high tide. This very high tide occurs when the moon is both unusually close to the Earth (at its closest perigee, called the proxigee) and in the New Moon phase (when the Moon is between the Sun and the Earth). The proxigean spring tide occurs at most once every 1.5 years.

**__GR A VI TY explains why we have tides on the earth's oceans__.***

One side of the earth is **closer** to the moon than the other side; this means there is a //large difference //in gravitational pull on each side. Shown in the diagram below, the moon pulls the tide toward itself.The ocean bulges .*



High tide and low tide are a result of the earth rotating beneath the tides. Most areas experience two tides a day, though some can experience up to four.*

*WSD Physics Notes  Isaac Newtons universal theory of gravitation is what first explained the reason for two tides a day. And adjustments in the heights of tides are based on the distances of the sun and moon. (http://en.wikipedia.org/wiki/Tide)

