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More About Eclipses

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What Eclipses meant in Ancient Times

• pomo tribe: The sun got bit by a bear and they are fighting

• Chinese: dragon/demon eating sun• Tahitians: moon and sun making love• Eskimos: divine province: God is checking in to

see everything is okay. • Ancient Greeks believed it was a sign the gods

were angry and therefore was a bad omen.

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Eclipses

• Although the Sun is about 400 times larger than the Moon, it is also about 400 times further away.– Both appear to be about ½ degree across.– As a result of this coincidence, the Moon can

completely cover the Sun, producing a total solar eclipse.

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Eclipses

• The shadow of any body consists of two parts:– The umbra is where the Sun is completely blocked

from view.– The penumbra is where the Sun is only partially

blocked.

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Shadows and Eclipses

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Line up of Solar Eclipse

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The Modern ViewThe answer lies hidden among the shadows.

Earth

Moon

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Shadow Structure

Penumbra

Penumbra

Umbra

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South Pole

North Pole

Solar Eclipse Details

SunMoon

What is the phase of the moon?

New Moon!

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Total Solar Eclipse

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Solar Eclipse

• A total solar eclipse occurs about once every 18 months somewhere in the world.

• At any given location, a total solar eclipse occurs once every 360 years.– The next total solar eclipse in the U.S. is on Aug. 21 2017.

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Path of Solar Eclipses

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Solar Eclipse Images

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Total Solar Eclipse

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Total Solar

Eclipse

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Diamond Ring Effect

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Bailey’s Beads

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Solar Corona During Eclipse

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Total Solar Eclipse

• As the Moon orbits the Earth, its apparent size varies.– Only when the Moon is closest to the Earth can it

completely block the Sun.– If the Moon does not completely cover the Sun we

get an annular eclipse.

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Annular Solar Eclipse

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Why not a solar eclipse every month then?

Sun

Ecliptic

Moon

Moon’s Orbit

Earth5o

Moon's orbit is tilted about 5o with respect to the Earth's orbit (ecliptic), so the shadows usually miss!

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Frequency of Solar Eclipses

• We do not get solar eclipses at every new moon because the orbit of the Moon is tilted by about 5 degrees with respect to the ecliptic.– At most new moons the Moon is either above or below the

Sun.– The tilted orbit of the Moon crosses the ecliptic at two

points. When the Sun approaches these points, eclipses are possible. This will happen twice a year.

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·  But, the Moon passes through the ecliptic twice a month.

· *IF* at new moon – there is SOLAR ECLIPSE probability.

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Partial Solar Eclipse

During a total solar eclipse, depending on your location during the event, you might only see part of the Sun’s face blocked because of your observing vantage point.

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Lunar Eclipses

• A lunar eclipse occurs when the Moon passes into the shadow of the Earth.

• The lunar eclipse is visible to everyone on the night side of the Earth.

• Aristotle (384-322 B.C.) used the apparent shape of the Earth’s shadow to show that the Earth is a sphere.

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Line Up of Lunar Eclipse

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Lunar Eclipse

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Lunar Eclipse

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Lunar Eclipse Showing Earth’s Shadow

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The moon becomes a blood red color during a total lunar eclipse. No wonder that ancient cultures feared the appearance of the moon during a lunar eclipse.

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Lunar Eclipse Types

Total Penumbral Eclipse

Total Lunar Eclipse

Partial Lunar Eclipse

Partial Penumbral Eclipse

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Earth’s Atmosphere

Sunlight

MoonEarth

The Blood Moon

The moon often does not totally disappear during a total lunar eclipse. Instead it can be seen as a very dark red color because of the refraction of sunlight through the Earth's atmosphere.

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