Tides

The force of gravity pulls the moon and Earth toward each other. Tides are caused mainly by differences in how much gravity from the moon and the sun pulls on different parts of Earth.

Tides happen during particular phases of the moon. Tides are caused by interactions between the moon in different parts of Earth.

How does the moon cause a high tide? The force of gravity from the moon pulls on Earth. The water on the side of Earth facing the moon is pulled toward the moon more strongly than is the rest of Earth. The water on the other side of Earth is pulled least of all, and is left behind. This produces bulges of water.

Earth has two basic types of motion Which of Earth’s two basic types of motion

affect the tide cycle? Rotation How? Ask Earth rotates one high tide stays on

the side of Earth facing the moon. The second high tide stays on the opposite side of Earth.

Why is it useful to know when high and low tides happen? People who fish need to know the tide cycle because it affects when they fish and what they catch. People who swim they also need to know the tide cycle so they can be safe.

In addition to the positions of Earth and the moon the position of the sun can also affect the heights of tides.

The sun is a great distance, 150,000,000 km, from Earth, so why does gravity affect the tides? Mass affects the force of strength of the gravitational force. The sun’s mass is immense.

Most coastal regions have two high tides and two low tides each day.

There are two types of tides; spring tides and neap tides. During the spring tide, high tides are higher than usual

and low tides are lower than usual. During an neap tide, high tides are lower than usual and

low tides are higher than usual. What causes the difference? The difference is caused by

the different positions of Earth, the moon and the sun relative to each other. When the sun the moon and Earth are in a straight line, spring tides happen.

Students page 198 look at the Sun’s role and tides relevance in new moon, first quarter, full moon, and third quarter.

What two factors determine how strong the force of gravity is between two objects? The mass of the object’s and the distance between them.

Which of those two factors explains variations in how much gravity from the moon pulls on each side of Earth? Distance

How do you know? The masses of the moon and Earth are always the same, but the distance between the moon and each side of Earth changes as Earth rotates.

The near side of the earth has the high tide. The far side of Earth has the low tide.

What is the angle formed by the Sun, Earth and the moon during a neap tide? During a neap tide the angle is 90°.

What is the angle formed by the Sun, Earth and the moon during the spring tide? During spring tide the angle is 0° or 180°.