Page 10 - Curriculum Visions Dynamic Book

The importance of gravity
There are two high tides (and therefore two low tides) each day on Earth. One high and one low tide are caused by the gravitational pUll of the Moon and to a lesser extent
by the Sun, and the other high and low tide by the way the Earth and Moon together orbit the Sun.
As the Earth-Moon system orbits the Sun, centrifUgal force tends to throw everything in the direction away from the Sun, causing, for example, a high tide away from the Sun. Although they have quite different causes, the two high tides occur exactly at the same time on the opposing sides of the Earth.
The Earth spins around the Sun so fast that if it were not for the Earth’s gravity, the ocean waters would all flow to the side of the Earth that is facing away from the Sun and fly off into space.
Although the Earth’s gravity holds the ocean waters to the surface, the spinning effect of the Earth is powerful enough to ensure that there is always a high tide on the side of the Earth facing away from the Sun.
The interaction of the Moon and the Earth acts like a drag on the Earth through the Moon’s effect on the tides.
The Moon is not the only body to have an influence on the Earth’s tides. Even though the Sun is much farther away, its gravitational field is far stronger. Its effect is about half that of the Moon’s and acts in a different cycle. Even other planets feel the Sun’s gravity.
The combined cycles help produce the pattern of the tides. When they act together, they reinforce each other to cause a high-ranging or spring tide (maximum height difference from high to low tide) or a low-ranging neap tide (minimum height difference from high to low tide).
The seasons
The Earth moves in two ways—it tilts as it spins, and it travels around the Sun. These two movements produce the seasons—spring, summer, fall, and winter—for people who live away from the eqUator.
10
Northern summer