Ch. 2 Discovering the Universe for YourselfMoon Phases

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Ch. 2.3 The Moon, Our Constant Companion

• Why do we see phases of the Moon?• What causes eclipses?

Our goals for learning:

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Watch Movie at:http://antwrp.gsfc.nasa.gov/apod/image/9911/lunation_ajc.gif

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How long does it take to complete the full cycle of Moon Phases?

(A) About a day(B) About a week(C) About a month(D) About a year(E) None of the above

Quiz

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Why do we see phases of the Moon?

• Lunar phases are a consequence of the Moon’s 27.3 day orbit around Earth

The Moon takes 27.3 days to orbit Earth, but the lunar phase cycle (from new Moon to new Moon) is 29.5 days. The Moon spends the extra 2.2 days "catching up" because Earth travels about 45 million miles around the Sun during the time the Moon completes one orbit around Earth.

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Phases of Moon• Half of Moon is

always illuminated by Sun and half is dark

• We see a changing combination of the bright and dark faces as Moon orbits

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Moon Phase Simulation Clip

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Lecture-Tutorial (LT):The Cause of Moon Phase (pp. 79-82)

• Work with a partner!

• Read the instructions and questions carefully.

• Discuss the concepts and your answers with one another.

• Come to a consensus answer you both agree on.

• If you get stuck or are not sure of your answer, ask another group.

• If you get really stuck or don’t understand what the LT is asking, ask for a help.

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Phases of the Moon: 29.5-day cyclenew

crescent

first quarter

gibbous

full

gibbous

last quarter

crescent

waxing• Moon visible in afternoon/evening.• Gets “fuller” and rises later each day.

waning• Moon visible in late night/morning.• Gets “less” and sets later each day.

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Although the Moon is always ½ lit by the Sun, we see

different amounts of the lit portion from

Earth depending on

where the Moon is

located in its month-long

orbit.

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How many phases shown in the picture at the right will the Moon go through in one day?

How long does it take the Earth to complete one rotation? How far will the Moon have moved?

How long does it take the Moon to complete one orbit? How many of the phases will the Moon have gone through in this time?

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How much of the Moons total surface is illuminated when it is in the New Phase? Full Phase?

How much of the illuminated surface of the Moon is visible from Earth when it is in the First Quarter Phase, Full Phase?

What time is it when the Waxing Gibbous Phase is highest in the sky, Rising? Setting? What phase will it be in one week later….

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Phases of the Moon Clip

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Lecture-Tutorial (LT):Predicting the Moon Phase (pp. 83-85)

• Work with a partner!

• Read the instructions and questions carefully.

• Discuss the concepts and your answers with one another.

• Come to a consensus answer you both agree on.

• If you get stuck or are not sure of your answer, ask another group.

• If you get really stuck or don’t understand what the LT is asking, ask for a help.

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