Eclipses and Tides

1. Eclipses and Tides

2. Eclipses

3. There are 2 types of eclipses… Solar eclipse occurs when the Moon passes between the Sun and the Earth. The Moon fully or partially covers the Sun as viewed from some location on Earth. Lunar eclipse occurs when the moon passes behind the earth so that the earth blocks the sun's rays from striking the moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle.

4. Solar Eclipse The Moon moves directly between the Sun and Earth. The Moon casts a shadow on the Earth; only occurs with a new moon. This does not occur with every new moon due to the moon being 10o off from the orbit of the Earth.

5. Solar Eclipse

6. Lunar Eclipse The Earth, Sun, and Moon are directly lined up in the center. The Earth casts a shadow on the Moon; only occurs with a full moon. This does not occur with every full moon due to the Moon being 10o off from the orbit of the Earth.

7. Lunar Eclipse

8. Tides

9. 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

10. 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.

11. Tides • The how and why of tide formation is very complex. • This presentation will try to simplify how and why tides form. • To do this….

12. IMAGINE THAT THERE IS NOTHING BUT WATER COVERING THE EARTH.

13. NOW, IMAGINE LOOKING AT THE EARTH FROM ABOVE THE NORTH POLE. N

14. Let’s add the moon to this system. N

15. THE MOON PULLS ON THE WATER. N This creates a bulge.

16. BUT BECAUSE THE EARTH IS SPINNING, THERE ARE ACTUALLY 2 BULGES CREATED. N You’ll learn more about this in a course called Physics.

17. THIS BULGE OF WATER FOLLOWS THE MOON AS IT ORBITS THE EARTH. N

18. IT TAKES THE MOON ABOUT 28 DAYS TO REVOLVE AROUND THE EARTH. N

19. THIS MAKES THE TIMES THAT THE TIDES OCCUR CHANGE IN A PREDICTABLE PATTERN.

20. BUT THERE IS MORE GOING ON THAN JUST THE REVOLUTION OF THE MOON AROUND THE EARTH . N N The Earth rotates every day.

21. LET’S PUT A PERSON ON THE EQUATOR OF THE EARTH. N Remember, you are looking at the Earth from the North Pole, so this person appears to be on the edge of the Earth.

22. AS THE EARTH ROTATES, THE PERSON WILL MOVE THROUGH TWO VERY HIGH BULGES OF WATER AND TWO AREAS OF LOW WATER EACH DAY. N

23. We call these areas high tide and low tide. N Remember, in a 24 hour period of rotation, there are two high tides and two low tides.

24. This is what it looks like with both motions. N

25. Illustration of high and low tides

26. 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 N High Tide

27. 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 N High Tide