© K. Coder 2015

Guided Notes

Astronomy

Earth’s Moon

Formation

OrbitCraters

Motions

Phases

Tides

Eclipses

© K. Coder 2015

1. What is the Moon? • The Moon: the Earth's only natural

satellite. See ESRT page 15 for data on Earth’s Moon.

o Satellite: an object in space that revolves around another object due to gravity

© K. Coder 2015

2. How did the Moon form?• Giant Impact Hypothesis: the Moon was

created from debris left over from a collision between young Earth and a Mars-sized body approximately 4.5 billion years ago.

3. How does the Moon orbit the Earth?

• The Moon revolves around the Earth in an elliptical (oval) orbit with the Earth at one focus.

Perihelion: Moon is closest to Earth

Aphelion: Moon is farthest from

Earth

3. How does the Moon orbit the Earth?

• Evidence: The apparent diameter of the Moon changes.

o Photographs A: Moon appears smaller during Aphelion

o Photograph B: Moon appears larger during Perihelion

© K. Coder 2015

4. Why are there so many craters on the Moon (and other planets) but not on Earth?

4. Why are there so many craters on the Moon (and other planets) but not on Earth?

• Earth has a hydrosphere (water) & atmosphere (gases).

o The Earth’s atmosphere allows it to have weather like wind, rain, and snow. All factors that lead to erosion and weathering, which wear away any craters on Earth.

© K. Coder 2015

4. Why are there so many craters on the Moon (and other planets) but not on Earth?

• The Moon (and other small planets) have lost their atmosphere because they are smaller and have less gravity.

© K. Coder 2015

5. Why do we always see the same side of the moon?

We always see this side. We never see this side!

5. Why do we always see the same side of the moon? • The moon’s period of rotation (27.3 days)

is equal to the moon’s period of revolution (27.3 days). See ESRT page 15.

Synchronous Rotation Animations: http://www.webassign.net/fkastro9/animations/Animation03-02.htm

6. Why does the Moon appear differently on different days?

• Phases of the moon: the observed shape of the lighted portion of the Moon

6. Why does the Moon appear differently on different days?

• Caused by the Moon’s revolution around the Earth which causes the amount of the lit half of the Moon visible to observers on Earth to change.

• A complete cycle of phases takes 29.5 days (one “moonth")

• The phases of the Moon are cyclic and predictable because they repeat in a pattern.

© K. Coder 2015

7. Why is the Moon’s period of revolution not the same as the amount of time it takes to view one full cycle of Moon phases?

• As the Moon is orbiting the Earth, the Earth is orbiting the Sun. Thus, it takes 2.2 more days for the Moon to reach the same position in relation to the Earth and the Sun.

Go back to packet for next steps

Stop!

8. How can you determine the phase of the Moon as viewed from Earth using a diagram of the Moon-Earth-Sun as viewed from space?

The diagram below represents the Moon at eight numbered positions in its orbit around Earth. The nighttime sides of the Moon and Earth are shaded.

© K. Coder 2015

© K. Coder 2015

Here is what you’re actually seeing…

Direction the Sun is coming from

North Pole

Moon in 8 orbit positions around the Earth.

It takes about 3.5 days for the Moon to move from one position to the next.

One half of the Moon and the Earth is always illuminated. The other half (facing away from the Sun) is always dark.

Because the Moon’s position relative to Earth changes, the amount of lighted Moon we see also changes.

© K. Coder 2015

Steps to determine the Phase of the Moon:

1. Draw an arrow from the observer on Earth’s North Pole to the selected position.

2. Turn your paper so that the arrow is pointed directly away from you.

3. Block the far half of the moon.

4. Draw the amount of light and dark you see on the same side as you view it.

View from SpaceCompletely dark

© K. Coder 2015

Mostly dark on left, a little light on right

View from Space

Steps to determine the Phase of the Moon:

1. Draw an arrow from the observer on Earth’s North Pole to the selected position.

2. Turn your paper so that the arrow is pointed directly away from you.

3. Block the far half of the moon.

4. Draw the amount of light and dark you see on the same side as you view it.

Follow the same steps and complete the rest of the moon phases in your

packet.

New Moon

1st Quarter

Full Moon

3rd Quarter

Practice #1

Answer in Packet

Locations of Major Phases:1 The New Moon will always be directly

between the Earth and Sun.

2 The Full Moon will always be on the opposite side of Earth than the Sun.

3 First quarter and third quarter are always at a right angle to the Earth and Sun.

© K. Coder 2015

Here is another perspective with Sunlight coming from the right…

Direction the Sun is

coming from

Notice the same phase occurs in the same position, relative to the Earth and Sun.

9. How does the Moon affect our oceans?• Tides: cyclic rise and fall of sea level

under gravitational pull

© K. Coder 2015

9. How does the Moon affect our oceans?

oCaused by the pull of the Moon’s gravity and the Sun’s gravity on the Earth

▪ The Moon has more of an effect on the tides because it is closer to Earth.

10. How often do the tides change?• Each day, all coastal locations experience 2 high

tides and 2 low tides.

Lunar Day Animation

o One high tide to the next high tide takes 12 hours and 26 minutes (or from one low tide to the next low tide).

o One high tide to the next low tide (or vice-versa) takes 6 hours and 13 minutes.

11. How can you plot a tidal change graph?

Based on the tidal information, at what time will the next low tide and high tide occur on November 27? Low tide: High tide:

© K. Coder 2015

12. Why does the height of the tide change throughout the month?• Spring Tides: highest high tides and

lowest low tidesLowest

Low TideHighest

High Tide

© K. Coder 2015

Mont St. Michel Spring Tides

© K. Coder 2015

Mont St. Michel Spring Tides

Mont St. Michel Spring Tides

© K. Coder 2015

Mont St. Michel Spring Tides

© K. Coder 2015

12. Why does the height of the tide change throughout the month?o Occurs when Earth, Sun and Moon are in a

straight line (during New and Full Moons)

Spring Tides = Strong = Straight

FullMoon

NewMoon

12. Why does the height of the tide change throughout the month?• Neap Tides: lowest high tides and highest

low tidesHighest

Low TideLowest

High Tide

© K. Coder 2015

12. Why does the height of the tide change throughout the month?o Occurs when Earth, Sun, and Moon are at a 90˚

angle (1st and 3rd Quarter Moons)

Neap Tides = Not Strong = Ninety Degree Angle1st

Quarter

3rd Quarter

13. Why are there eclipses?• Eclipse: an object is blocked from view

13. Why are there eclipses?o Solar Eclipse: Cannot see the Sun

• Occurs when Moon is directly between the Sun and Earth (New Moon)

• Can only see on the daylight side of Earth

© K. Coder 2015

13. Why are there eclipses?oLunar Eclipse: Cannot see the Moon

• Occurs when Earth is directly between the Sun and Moon (Full Moon)

• Can only see on the nighttime side of Earth

14. Why aren’t there eclipses each month during the Full Moon and New Moon?

• The Moon orbit around the Earth at a 5˚ incline.

Practice #2 in Packet