Eclipses and Lunar Phases

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Eclipses and Lunar Phases
By the Lunar and Planetary Institute For use in
teacher workshops
http//solarsystem.nasa.gov/multimedia/gallery/Ear
th_Moon.jpg
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Preliminary Topics

• Before students can understand the reason for
  phases, they need to understand
• The Moon orbits the Earth
• The Moon orbit at an angle with respect
  to the Earths orbit around the Sun
• The Moon doesnt shine on its own it reflects
  sunlight
• The scale of the Moon and Earths sizes and
  distance
• Please go through Earth and Moon statistics
  before trying to cover the reason for phases or
  eclipses.

Ecliptic plane
Moons orbital plane
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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

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When the Earths shadow covers the Moon, we have
a lunar eclipse
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Three types of Lunar Eclipses

• Penumbral lunar eclipsethe Moon only passes
  through the penumbra of Earths shadow
• Partial lunar eclipsepart of the Moon passes
  through the umbra of Earths shadow
• Total lunar eclipsethe entire Moon passes
  through the umbra of Earths shadow
• Who on Earth will be able to see a lunar eclipse?

Anyone who can see the Moon (anyone who is on the
nighttime side of the Earth during the eclipse)
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Images from Fred Espenak http//www.mreclipse.com/
LEphoto/LEgallery1/LEgallery1.html
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Why is the Moon red during an eclipse?

• The Earths atmosphere filters some sunlight and
  allows it to reach the Moons surface
• The blue light is removedscattered down to make
  a blue sky over those in daytime
• Remaining light is red or orange
• Some of this remaining light is bent or refracted
  so that a small fraction of it reaches the Moon
• Exact appearance depends on dust and clouds in
  the Earths atmosphere

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Solar Eclipses

• When the Moons shadow covers part of the Earth
• Only happens at New Moon
• Three types Annular, Partial, and Total

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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 eclipsenot
  safe to look directly at Sun
• Only lasts a few minutes
• Path of Totality about 10,000 miles long, only
  100 miles wide

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Photo of a Total Eclipse
http//sunearthday.nasa.gov/2006/multimedia/gal_00
8.php
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Annular Solar Eclipse

• When the Moon is too far to completely cover the
  Sunthe umbra doesnt reach the Earth
• Sun appears as a donut around the Moon

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Photos of an Annular Eclipse
http//sunearthday.nasa.gov/2006/multimedia/gal_01
0.php photos taken by Fred Espenak
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Tides

• The Moons gravity tugs on the Earth.
• It pulls the most on the part of Earth closest,
  which raises the atmosphere, the oceans, and even
  the rocks (a little)
• It pulls the least on the part of Earth thats
  farthest, which allows the oceans and atmosphere
  to be further from the Moon (and higher)
• The Suns gravity does the same thing, but to a
  lesser extent