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Earth Science > The Moon > Flashcards

The Moon Flashcards

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1
Q

How old is the Moon?

A

4.5 billion years old (within 50 million years of Earth’s formation)

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2
Q

How far away is the Moon from the Earth?

A

384,000 km

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3
Q

How large is the Moon relative to Earth?

A

Moon diameter: 3,474 km
Earth diameter: 12,742 km
Earth is 3.67 times larger

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4
Q

How long does it take the Moon to revolve around the Earth?

A

27.32 days

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5
Q

How long does it take the Moon to revolve around its axis?

A

27.32 days

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6
Q

Why does the Moon rise 50 minutes later each night?

A
  • Because of Earth’s rotation and the Moon’s revolution
  • Earth rotates CC, Moon orbits CC, Moon appear to move east to west- Moon moves slower in sky
  • Takes an extra 1/29 of Earth’s rotation (50 min) for the horizon to catch up to the moon
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7
Q

Why does the Moon have phases?

A
  • The Moon shines by reflected light
  • The changing relative positions of the sun, Earth, and Moon
  • The sun’s light always illuminates half of the moon
  • As the Moon revolves around Earth, different amounts of the near side of the Moon, which faces Earth, are lighted
  • The apparent shape of the visible part of the moon varies
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8
Q

What are various phases of the Moon?

A 
New moon
Waxing crescent
First quarter
Waxing gibbous
Full moon
Waning gibbous
Third quarter
Waning crescent
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9
Q

What is the time period from one full moon to the next full moon?

A

29.5306 days

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10
Q

Why is the time from one full moon to the next different from one revolution around Earth?

A
  • The difference of 2.2 days is due to the orbiting of the Earth-Moon system around the sun
  • In 27.3 days (Moon orbits Earth) the two bodies move slightly farther along their orbit around the sun
  • The Moon must go a little farther to be directly between Earth and the Sun (2.2 days)
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11
Q

What is the relationship between time of day, phase of Moon, and where the Moon is in the sky?

A
  • A new moon rises when the sun rises
  • A full moon rises when the sun sets
  • A first quarter moon rises at noon
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12
Q

How do you determine the phase of the Earth as seen from the Moon?

A 
Opposite of the phase of the Moon as seen from Earth
new moon - full moon
waxing crescent - waning gibbous
first quarter - third quarter
waxing gibbous - waning crescent
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13
Q

How do you calculate the phase of the Moon for any date in the past?

A

1) Calculate the number of days between the two dates:
- number of days divided by 4, leap years times 366, non leap years times of 365
- number of days in each month up to the date
2) Days divided by 29.5306
3) Decimal point on the clock

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14
Q

What are the differences between a solar eclipse and a lunar eclipse? (geometry of the Earth-Sun-Moon system, phase of the Moon, etc)

A

Solar: new moon, Earth-Moon-Sun
Lunar: full moon, Moon-Earth-Sun

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15
Q

Why don’t we have eclipses every month?

A
  • The orbit of the Moon is not on the same plane as the orbit of Earth around the sun
  • The Moon crosses Earth’s plane twice a month but there will only be an eclipse if the phase is full or new
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16
Q

Why is someone more likely to have seen a total lunar eclipse than a total solar eclipse?

A
  • Lunar eclipses are visible everywhere on the dark side of Earth
  • A total solar eclipse can only be seen by observers in the small path of the Moon’s shadow as it moves across Earth’s lighted surface
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17
Q

What are maria and how did they form?

A
  • Large, dark, round, flat areas of basalt on the moon formed when:
    a) planetesimals crashed into the Moon when it was very young (4-4.5 billion years ago)
    b) the huge depressions (from asteroid impacts) filled with lava which cooled to form a dark volcanic rock (basalt) 3.2-3.9 billion years ago (lava gushed up from the Moon’s melted interior)
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18
Q

What are craters and how did they form?

A
  • A bowl-shaped depression that forms on the surface of the moon when from the impact of asteroids and comets
  • Formed 4 billion years ago when debris left over from the formation of the solar system struck the Moon
  • 240 km to microscopic
  • Most obvious craters- less than 1 billion years old
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19
Q

What are simple craters and how did they form?

A
  • Bowl-shape
  • 15 km to microscopic
  • Raised rim
  • Floor filled with debris
  • Most common
20
Q

What are complex craters and how did they form?

A
  • Larger than simple craters
  • Terraced walls
  • Central peak- formed by larger object crashing into moon or a higher speed (rebound effect- liquid solidifies)
21
Q

What are multi-ringed basins and how did they form?

A
  • Huge object
  • Flat center (molten rock)
  • Mountain ranges around impact
  • Bulls-eye pattern
22
Q

Apogee

A

The point when the Moon is farthest from Earth in its orbit

23
Q

Corona

A
  • Outermost layer of the sun’s atmosphere
  • Magnetic field
  • Very dim- only visible during solar eclipse/total darkness
24
Q

Earthshine

A
  • Sunlight that is reflected off Earth
  • Reason that you can still see the darker part of the Moon
  • Sun - Earth - Moon - Earth
25
Q

Eclipse

A

-One celestial body passes through the shadow of another another

26
Q

Gibbous

A

The side of the Moon that is facing the Earth is mostly illuminated (more than half)

27
Q

Lunar highlands

A
  • Formed when the Moon did
  • Densely cratered regions on the Moon
  • Relatively light colored
  • Represent the first crust of the Moon
28
Q

Lunation

A

A lunar month, from one new moon to the next (29.53 days)

29
Q

Penumbra

A

The outer part of the Earth and Moon’s shadow, sunlight is only partially blocked

30
Q

Perigee

A

The point when the Moon is closest to Earth in its orbit

31
Q

Sidereal month

A
  • The time it takes for the Moon to make 1 orbit

- 27.32 Earth days

32
Q

Synodic month

A
  • One full moon to the next

- 29.5306

33
Q

Syzygy

A

When the Earth, Moon, and Sun are alligned

34
Q

Umbra

A

The inner, cone-shaped part of the shadow cast by the Earth and the Moon

35
Q

Solar eclipse

A

-Moon is directly between the sun and part of Earth, the umbra of the Moon falls on Earth
-New moon
-1-2 times per year
-Shadow 100 km or less on Earth
-Sun completely blocked for 7 minutes
-

36
Q

Lunar eclipse

A

-The passing of the Moon through Earth’s shadow at full moon
-1-2 times per year
-Seen by everyone of dark half of Earth
-Totality lasts for over an hour- Earth’s umbra 2 1/2 times larger than the Noon
-

37
Q

How did the Moon form?

A

1) Earth hit by a planet-size object 4.5 billion years ago
2) Impact was a glancing blow (no scar because Earth’s surface was liquid)
3) Impacting planet was obliterated (its core merged with core of Earth)
4) Much of the mantle + crust of Earth blown out into orbit around Earth (vaporized and then solidified)
5) Created Saturn-like ring around Earth
6) Over time, ring particles collided to form the Moon

38
Q

As the sun shines of any spherical object in the solar system, how much of the object is illuminated?

A
  • Half

- The half that is not facing the sun is in darkness

39
Q

Waxing

A

When more and more of the side of the Moon that is facing the Earth is lit from from day to day

40
Q

Waning

A

When less and less of the side of the Moon that is facing the Earth is lit from from day to day

41
Q

Why was the Moon hot 4.5 billion years ago after it formed?

A

1) Impacts from asteroids- transferred to heat energy

2) Earth was radioactive

42
Q

What is an annular eclipse?

A
  • Earth at perihelion
  • Moon at apogee
  • The Moon’s umbra does not reach Earth
  • Sun is never completely blocked out
  • Thin ring of sunlight visible around outer edges of the Moon
  • No corona visible
43
Q

Where do people see a partial solar eclipse?

A

Outside the umbra but within the penumbra

44
Q

What is a penumbral eclipse?

A
  • When the entire moon passes through Earth’s penumbra

- Eclipse is barely visible

45
Q

What is a partial lunar eclipse?

A

When only part of the moon passes into Earth’s umbra

46
Q

Why do totally eclipsed moons appear red?

A
  • Sunlight is bent around Earth through our atmosphere

- Mainly red light reaches the moon

47
Q

What is the diamond-ring effect?

A
  • The last bits of normal sunlight before darkness during a solar eclipse
  • Often glistens like a diamond on a ring

Earth Science (16 decks)

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