Unraveling Hypertext_ Analyzing Postmodern Elements in Literature.pptx
Astronomy lunar phases eclipses and tides
1. Eclipses and Lunar Phases and Tides http://solarsystem.nasa.gov/multimedia/gallery/Earth_Moon.jpg
2. What does “Phases of the Moon” mean? The positions of the moon, Earth, and the sun cause the phases of the moon, eclipses, and tides. The phase of the moon you see depends on how much of the sunlit side of the moon faces Earth. The moon does not have it’s own light, it reflects light from the sun. This determines its phase.
3. Moon Facts The moon goes through a whole set of phases about once a month. The Moon orbit at an angle with respect to the Earth’s orbit around the Sun Rotation : Day :: Revolution : year Since it takes 27.3 Earth days for the moon to rotate (day) and 27.3 Earth days for the moon to revolve (year), the day and a year are the same length
6. Phases--Causes The Sun shines on the Moon. When the sunlight reflects off the Moon’s far side, we call it a New Moon When the sunlight reflects off on the Moon’s near side, we call it a Full Moon Between New and Full, we see parts of the daytime side of the Moon. Golfball and Blacklight Activity
7. Eclipses The Sun and Moon occasionally line up so that we have an eclipse. These eclipses happen every year To see a solar eclipse, you need to be on a particular part of the Earth
9. Three types of Lunar Eclipses Penumbral lunar eclipse—the Moon only passes through the penumbra of Earth’s shadow Partial lunar eclipse—part of the Moon passes through the umbra of Earth’s shadow Total lunar eclipse—the entire Moon passes through the umbra of Earth’s shadow Anyone who can see the Moon (anyone who is on the nighttime side of the Earth during the eclipse)
10. Images from Fred Espenak http://www.mreclipse.com/LEphoto/LEgallery1/LEgallery1.html
11. Solar Eclipses When the Moon’s shadow covers part of the Earth Only happens at New Moon Three types: Annular, Partial, and Total
12. Total Solar Eclipse Observers in the “umbra” shadow see a total eclipse (safe to view the Sun); can see the corona Those in “penumbra” see a partial eclipse—not safe to look directly at Sun Only lasts a few minutes Path of Totality about 10,000 miles long, only 100 miles wide
13. Photo of a Total Eclipse http://sunearthday.nasa.gov/2006/multimedia/gal_008.php
14. Annular Solar Eclipse When the Moon is too far to completely cover the Sun—the umbra doesn’t reach the Earth Sun appears as a donut around the Moon
15. Photos of an Annular Eclipse http://sunearthday.nasa.gov/2006/multimedia/gal_010.php; photos taken by Fred Espenak
16. Solar and Lunar Eclipses Solar Eclipse A solar eclipse occurs when the moon passes between the Earth and the sun, blocking the sunlight from reaching the Earth. Lunar Eclipse A lunar eclipse occurs at a full moon when Earth is directly between the moon and the sun. Next Total Solar Eclipse in USA—August 21, 2017
17. What is a tide? A tide is the rise and fall of water every 12.5 hours. The water rises for about 6 hours and then falls for about 6 hours.
18. What causes the tides? The force of the gravity pulls the moon Earth (especially the water on Earth’s surface) toward each other. Tides occur mainly because of differences in how much the moon pulls on different parts of the Earth.
19. Spring and Neap Tides Spring Tides Once a month, at a new moon, the sun, Earth, and moon are nearly in a line. The gravity of the sun and moon pull in the same direction causing a tide with the greatest difference between low and high tide. Neap Tides Twice a month when the Earth and sun are at right angles to line between the Earth and moon. The sun and moon pulling in these directions causes a tide with the least difference between low and high tide.
21. Class Review Why does the moon change its phases as the month progresses? Why are a day and a year on the moon the same length?
Editor's Notes
Information at http://sunearth.gsfc.nasa.gov/eclipse/solar.html
It's not a question of mass, but of energy! The tidal force exerted by the Moon on the Earth causes the oceans to bulge. The Earth rotates about its axis faster than the Moon revolves around the Earth, and this rapid rotation carries the tidal bulge of the oceans forward of the Moon in its orbit. So the tidal bulge on the Earth is always slightly ahead of the Moon's own position. This bulge is continuously tugging the Moon forward, increasing the Moon's total energy. Imagine a cowboy's lasso. As the cowboy spins the lasso faster and faster (increasing its total energy), the loop gets wider. The same thing essentially happens to the Moon. The tugging of the Earth's bulge lifts it into a wider orbit around the Earth.
