Lecture 6: Phases of the Moon

What is the moon?

a cooled, solidified piece of rock from molten lava - whiter parts of the moon = older surfaces of the moon - darker parts of the moon = newer parts of the moon formed from other rock impacts & it changes the mineral composition of that specific surface on the moon

How much of the moon is lit at any time?

half

If you wanted to see the third quarter moon rising, what time would you need to walk outside?

midnight

What are the phases of the moon in order?

new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter, waning crescent, then back to new moon to repeat

What affects how much of the Moon we see at a given time?

the Moon's orbit around Earth and Earth's rotation on its axis affects how/which part we see of the Moon

What other phases would be visible somewhere in your sky at noon?

waxing crescent & waning crescent

Notes about the Moon's motion:

- The Moon is constantly moving - It moves about 1/30th of its orbit every day - However, for the purposes of trying to observe the Moon on any given day, we generally ignore the Moon's daily motion around the Earth and instead focus just on the rotation of the Earth.

Key Points:

- The Moon reflects sunlight. - The Moon orbits Earth. - What phase the Moon is in depends on where it is in its orbit. - If and where we can see the Moon in our sky depends on the phase and what time of day we look for it.

In this top-down view, the Earth spins counterclockwise on its axis and the north pole points out of the screen. What is the phase of the moon at position 1? 2? 3? 4?

1) New Moon 2) First Quarter 3) Full Moon 4) Third Quarter

If and where the Moon will be visible in your sky depends on what two things?

1) the phases of the moon - or, more specifically, where it is in its orbit 2) the time of day that you try to look for it - this determines your horizon

How long does one complete cycle of the phases of the moon take?

29.5 days (just shy of one month)

During the waxing crescent phase, how much of the moon's surface is illuminated by the sun? A. Exactly half B. Less than half C. More than half D. All of it E. None of the above

A

You walk outside at sunset and see the moon straight overhead. What is the phase of the moon? A) 1st quarter B) 3rd quarter C) full D) new E) I'm confused...

A

You walk outside at sunset and see the moon straight overhead. What is the phase of the moon? A) 1st quarter B) 3rd quarter C) full D) new

A

You walk outside at sunset. Your position is marked by the "X". Which letter marks a position of the Moon that cannot be seen at sunset?

A

In this top-down view, the Earth spins counterclockwise on its axis and the north pole points out of the screen. Imagine you have friends standing on Earth at the four positions marked above. If you called them up and asked them to tell you the time, what would they say?

A) Midnight (12:00 am) B) Sunrise (6:00 am) C) Noon (12:00 pm) D) Sunset (6:00 pm)

How does the moon move through space?

As the Earth rotates, it also moves, or revolves, around the Sun. ... As the Earth orbits the Sun, the Moon orbits the Earth. The Moon's orbit lasts 27 1/2 days, but because the Earth keeps moving, it takes the Moon two extra days, 29 1/2, to come back to the same place in our sky.

During the waxing crescent phase, how much of the illuminated surface of the moon can we see? A. None B. Less than half C. More than half D. All of it

B

You walk outside at sunset. Your position is marked by the "X". Which letter marks the position of the Moon that you would see as being straight overhead?

C

Which of the following best describes why the Moon goes through phases? A. Earth's shadow falls on different parts of the Moon at different times. B. The Moon receives different amounts of sunlight throughout the course of its orbit. C. Earth's clouds cover potions of the Moon at various times resulting in the changing phases that we see. D. We see only part of the illuminated side of the Moon depending on its position relative to Earth and the Sun.

D

Your roommate texts you during astronomy class to tell you there's an awesome full moon outside. You should text your friend back and say: a) Awesome, I'll go take a look right now. b) Great, I'll check it out after class. c) You're full of crap. d) What are you doing in Australia? f) Why are you reading texts during my class?

D

You walk outside at sunset. Which letter represents a person standing on Earth at sunset?

D (first quarter)

Which letter represents the position of the Moon when it is in the waining gibbous phase?

E

Where does moonlight come from?

Moonlight comes from the light of the sun reflecting of the moon.

If you walk outside at noon, what phase of the moon would be straight overhead?

New Moon

Can you see the new moon at midnight?

No

The Moon is illuminated by light from the __________ and orbits around the ___________ about once every ___________.

Sun, Earth, month

Common misconceptions about the Moon... that all are (relatively) easily disproven:

- The Moon can only be seen at night. - The Moon makes its own light, instead of reflecting sunlight. - The Moon takes one day to orbit the Earth.The Moon orbits the Sun, not the Earth. - The Moon's phases are caused by clouds. - The Moon's phases are caused by Earth's rotation on its axis. - The Moon's phases are caused by the Moon's rotation on its axis. - The Moon's phases are caused by the Earth's shadow.