Download - Lunar Phases and Eclipses
Lunar Phases
and Eclipses
http://solarsystem.nasa.gov/multimedia/gallery/Earth_Moon.jpg
Created by the Lunar and Planetary InstituteFor Educational Use Only
LPI is not responsible for the ways in which this powerpoint may be used or altered.
Preliminary TopicsBefore 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 Earth’s orbit around the Sun
• The Moon doesn’t shine on its own; it reflects sunlight
• The scale of the Moon and Earth’s sizes and distance
Please go through Earth and Moon statistics before trying to cover the reason for phases or eclipses.
Ecliptic planeMoon’s orbital plane
The Moon
• The Moon shines by reflected sunlight.
– On average, it reflects about 7% of the incident
sunlight.
– The Moon appears about 400,000 times fainter
than the Sun in the sky.
• The phases of the Moon are the result of
varying viewing angles throughout the
month.
– A common misconception is that the phases of the
Moon are caused by the shadow of the Earth.
Moon Size
~ 1/4 width of Earth
Radius of 1080 miles
Gravity ~1/6 of Earth’s
http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-001444.jpg
http://visibleearth.nasa.gov/view_rec.php?id=1624
Earth and Moon to Scale
If Earth were a basketball, then the Moon would be a
tennis ball,
23.5 feet away
Moon Rotation Spins on axis (rotates) once every 27.3 days
Tilted ~1.5 degrees
(Earth = 23.5)
Moon’s Orbit Orbits (revolves around) Earth every 27.3 days
Elliptical orbit (not a perfect circle)
360,000 km 406,000 km 224,000 miles 252,000 miles http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=442
Moon Stats Moon’s orbit around Earth is inclined about 5 degrees to Earth’s plane of orbit around the Sun
Ecliptic plane
Sun EarthMoon
Moon’s orbital plane
Image created by LPI staff
New (couple days)
Waxing Crescent (several days)
1st Quarter
Waxing Gibbous (several days)
Full
Waning Gibbous (several days)
3rd Quarter
Waning Crescent (several days)
New
Phases: Observing and Identifying
http://www.lpi.usra.edu/education/skytellers/moon_phases/about.shtml
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
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Please do NOT use this to teach phases;
use to test for comprehension
http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question3.html
starchild.gsfc.nasa.gov/docs/StarChild/questions/phases.html
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
14When the Earth’s shadow covers the Moon, we have a lunar eclipse
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
• 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)
Images from Fred Espenakhttp://www.mreclipse.com/LEphoto/LEgallery1/LEgallery1.html
Why is the Moon red during an eclipse?
• The Earth’s atmosphere filters some sunlight and allows it to reach the Moon’s surface
• The blue light is removed—scattered 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 Earth’s atmosphere
Upcoming Lunar Eclipses
• June 15, 2011, Total lunar eclipse (not visible in US_
• Dec 10, 2011, Total lunar eclipse (mostly not visible in US)
• June 4, 2012, Partial eclipse • Nov. 28, 2012, Penumbral eclipse• Apr. 25, 2013, Partial eclipse (not visible in US)• May 25, 2013, Penumbral eclipse• Oct. 18, 2013, Penumbral eclipse• Apr 15, 2014, TOTAL ECLIPSE –visible here
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Solar Eclipses• When the Moon’s shadow covers part of the Earth• Only happens at New Moon• Three types: Annular, Partial, and Total
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
Photo of a Total Eclipse
http://sunearthday.nasa.gov/2006/multimedia/gal_008.php
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
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Photos of an Annular Eclipse
http://sunearthday.nasa.gov/2006/multimedia/gal_010.php; photos taken by Fred Espenak
Upcoming Solar Eclipses• Nov. 25, 2011, partial solar eclipse—not visible
in USA• May 20, 2012 (annular)—VISIBLE In USA• Nov. 13, 2012, total eclipse—not visible in USA• May 10, 2013, annular eclipse—not visible in
USA
• Next Total Solar Eclipse in continental USA—August 21, 2017
Tides
• The Moon’s 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 that’s farthest, which allows the oceans and atmosphere to be further from the Moon (and higher)
– The Sun’s gravity does the same thing, but to a lesser extent
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• St. Michel, N. coast of France
• ~16.8 m highest tidal range in Nova Scotia
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Nova Scotia Tides
• Wolfville, NS (16 m tidal range)• Diurnal Tides (one high and one low
every 12 hours and 25 minutes
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Sun and moon effects can be additive or not…
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Force imbalance in earth-moon system creates tidal bulges
Tides and the Moon
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• Second highest tidal range at Ancorage Alaska ~ 12 m