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Tides. Gravity. Remember gravity is an invisible force of attraction between two objects. What celestial object is attracted to the Earth? The moon What celestial object is the Earth attracted to? The Sun. Effect of the moon on the Earth.
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Gravity • Remember gravity is an invisible force of attraction between two objects. • What celestial object is attracted to the Earth? • The moon • What celestial object is the Earth attracted to? • The Sun
Effect of the moon on the Earth • The moon’s gravity also pulls on the Earth, but because the Earth is solid, it doesn’t seem to respond. • However, the Earth is mostly covered with water. Water is a liquid and does respond to the pull of the moon. This response creates tides.
Tides • The how and the why of tide formation is very complex. • This presentation will try to simplify how and why tides form. • To do this….
Now imagine looking at the Earth from above the North Pole. N
The moon pulls on the water. N This creates a bulge.
But because the Earth is spinning there are actually 2 bulges created. N You’ll learn more about this in a course called Physics.
This bulge of water follows the moon as it orbits the Earth. N
It takes the moon about 28 days to revolve around the Earth. N
This makes the times that the tides occur change in a predictable pattern.
But there is more going on than just the revolution of the moon around the Earth . N The Earth rotates every day.
Let’s put a person on the equator of the Earth. Remember you are looking at the Earth from the North Pole, so this person appears to be on the edge of the Earth.
As the Earth rotates, the person will move through two very high bulges of water and two areas of low water each day.
We call these areas high tide and low tide. Remember in a 24 hour period of rotation, there are 2 high tides and 2 low tides.
Spring Tides • When the Sun, Earth, and Moon are in a straight line- the variation between high tide and low tide is greatest. This occurs during the full moon and new moon. Low Tide High Tide
Neap Tides • When the Sun, Earth, and Moon are in a perpendicular arrangement- the variation between high tide and low tide is not great. This occurs during the first and third quarter moon. Low Tide High Tide