1. Tides

3. Gravity
Remember that 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

4. 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.

5. Tides A TIDE is the rise and fall of the sea level.
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….

6. Imagine that there is nothing but water covering the Earth.

7. Now imagine looking at the Earth from above the North Pole.

8. Let’s add the moon to this system.

9. The moon pulls on the water.
This creates a bulge.

10. But because the Earth is spinning there are actually 2 bulges created.
You’ll learn more about this in a course called Physics.

11. This bulge of water follows the moon as it orbits the Earth.

12. It takes the moon about 28 days to revolve around the Earth.

13. This makes the times that the tides occur change in a predictable pattern.

14. The Earth rotates every day.
But there is more going on than just the revolution of the moon around the Earth . N
The Earth rotates every day.

15. 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.

16. As the Earth rotates, the person will move through two very high bulges of water and two areas of low water each day.

17. 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.

19. This is what it looks like with both motions.

20. High Tide & Low Tide High tide
when the water is deeper and comes further onto the beach because of the gravitational pull of the moon.
Occurs two times every 24 hour period.

21. High Tide & Low Tide Low tide
when the water is more shallow and does not come as far onto the beach.
Occurs two times every 24 hour period.

23. That is a simplified version of how tides work.
There are many things that complicate this cycle.
Continents interfere with the movement of tides.
The alignment of the Sun, Earth, and moon

24. The Sun has a gravitational effect on the sea
The Sun has a gravitational effect on the sea. Although the Sun is larger than the Moon, it is further away from the Earth, which means that it has less effect on our tides.

25. Spring Tides
During the new moon and the full moon, the Moon and the Sun are in line with the Earth and so they pull together. This causes very high tides and very low tides called SPRING tides.

26. Neap Tides
During the first quarter and last quarter moon, the Sun and Moon are at right angles to each other, and so their pulls sort of cancel each other out, and are not as great.
This causes much smaller tides. These are called NEAP tides.

27. Spring & Neap Tide In Action
When the Sun, Moon, and Earth are in a Straight line, we have a Spring tide.
When the Sun, Moon, and Earth are perpendicular at a Ninety degree angle, we have a Neap tide.
Check this out! You will be amazed!