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Astronomy GCSE > Topic 1 - Earth, Moon and Sun > Flashcards

Topic 1 - Earth, Moon and Sun Flashcards

1
Q

Describe 3 features of the earth that distinguish it from other planets

A
  • Earth has an atmosphere of mainly nitrogen (78%) and oxygen (21%)
  • Earth has liquid water which covers around 70% of the surface of the Earth
  • Earth has the ability to facilitate diverse forms of life
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2
Q

Why is the sky blue?

A

When photons from the Sun travel into Earth’s atmosphere some of this light hits and bounces off the nitrogen and oxygen molecules there. The result is that light is split up and scattered.
Red, orange, yellow and green light carries straight on through this atmosphere but blue, violet and indigo get reflected between the molecules.
We see a blue sky as a result of all this reflection and absorption around.

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3
Q

Describe 4 of the benefits of the Earth’s atmosphere to humankind

A
  • The atmosphere absorbs harmful radiation from the sun’s light (e.g. ultraviolet: accelerated skin aging + cancer)
  • Absorbs harmful x rays and gamma rays from space
  • Regulates temperature so that the Earth rarely experiences extreme temperatures, allowing liquid water to exist on Earth
  • Provides oxygen for respiration
  • Partly protects us from meteoroids as they burn up when they pass through the atmosphere - shooting stars
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4
Q

Name 3 sources of light pollution

A
  • Commercial and sports floodlights
  • Urban street lamps
  • Domestic and industrial security lamps
  • Lights above car parks and shopping centres
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5
Q

How does light pollution hinder astronomical observations?

A

Observations of the night sky are hindered by light pollution in the form of skyglow. Unwanted light shines up onto the sky and causes an orange background haze reducing the contrast between the sky and stars which means that astronomers cannot see some of the dimmer stars or other celestial objects such as nebulae in the sky.

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6
Q

How did Eratosthenes make the first accurate calculation of the circumference of the Earth?

A

He read that the sun was directly over Syene, which is on the tropic of cancer, on the summer solstice at noon as temples and pillars did not cast any shadows at that time.

He then calculated that the Sun was 7° from his zenith at Alexandria which is almost exactly 1/50 of a circle.

He knew that Syene was 790km further south than Alexandria (how? Subject to debate).

Using simple geometry he deduced that the circumference of the Earth was 50 x 790km = 39500km

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7
Q

Give 4 reasons why we know that the Earth is approximately spherical

A
  • Ships appear to disappear over the horizon
  • Satellites orbit the Earth which could not happen if the earth was flat
  • The curvature of the Earth’s shadow during a partial lunar eclipse
  • Airplanes fly in arcs not straight lines
  • Images of the earth from space
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8
Q

What is the rotation period of the Earth?

A

23h 56mins

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9
Q

How long does it take for the Earth to rotate through 1 degree?

A

4 mins

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10
Q

What is the equator?

A

The line on the earth equidistant from both poles dividing the earth into two hemispheres (north and south) and marking the point of 0° latitude.

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11
Q

What is the Tropic of Cancer?

A

At 23.5°N, the Sun is directly overhead on the summer solstice.

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12
Q

What is the Tropic of Capricorn?

A

At 23.5°S, the Sun is directly overhead on the winter solstice.

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13
Q

What is latitude?

A

The amount of degrees north or south a point on Earth is from the equator.

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14
Q

What is longitude?

A

The amount of degrees east or west a point on Earth is from the prime meridian.

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15
Q

What are the North and South Poles?

A

The northern and southern ends of the axis of rotation.

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16
Q

What is the horizon?

A

The point at which the Earth’s surface and the sky appear to meet.

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17
Q

What is a meridian?

A

A line of longitude connecting the 2 poles.

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18
Q

What is an observer’s zenith?

A

The point directly above them.

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19
Q

Describe 3 drawbacks to astronomers of the Earth’s atmosphere

A
  • The atmosphere causes stars to twinkle as the light passes through the turbulence of our atmosphere and so refracts, this limits the resolution at which we can see the stars
  • The selective scattering of shorter wavelengths by our atmosphere causes the sky to be blue preventing observations of stars during the day
  • The atmosphere absorbs or reflects most electromagnetic radiation and so observations of this radiation (gamma and x rays), can only take place outside the atmosphere
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20
Q

Why do optical and infrared observatories need to be sited on high mountains or in space?

A

Less infrared radiation penetrates through the atmosphere and onto the surface so infrared observatories should be located on higher mountains, they could also be in space as there is little interference outside the atmosphere

Optical observatories are also placed on high mountains or in space in order to reduce the amount of turbulence in the atmosphere the light being observed goes through and so limits twinkling.

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21
Q

What is the shape of the Earth?

A

oblate spheroid/flattened sphere

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22
Q

What is the diameter of the Earth?

A

13000km

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23
Q

How does a refracting telescope work?

A

A glass convex lens collects the light and brings it to focus.

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24
Q

How does a reflecting telescope work?

A

A curved mirror collects the light.

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25
Q

Is the Earth’s atmosphere transparent to visible light, microwaves and radio waves?

A

Yes, visible light, microwaves and some radio waves.

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26
Q

Where are infrared observatories sited and why?

A

Infrared radiation is blocked by water vapour which is in the lower atmosphere. It can be observed on high mountains as this is over the water vapour which blocks it.

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27
Q

Where are ultraviolet observatories sited and why?

A

They are often sited in space as most ultraviolet radiation is absorbed by ozone or oxygen.

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28
Q

Where are X-ray observatories sited and why?

A

X-rays are completely blocked by the Earth’s atmosphere and so are only observed by space telescopes.

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29
Q

What are the Van Allen Belts?

A

Two doughnut-shaped rings of spiralling high-energy particles comprising of inner and outer belts held in place by the Earth’s magnetic field.

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30
Q

How were the Van Allen Belts discovered?

A

The inner belt was discovered by a geiger counter on the satellite Explorer 1. The outer belt was discovered by similar instruments on the US probe Pioneer 3.

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31
Q

Identify the Sea of Tranquility, Ocean of Storms, Sea of Crises, Tycho Crater, Copernicus Crater, Kepler Crater, and the Apennine Mountains on tinyurl.com/moonfeatures

A

See book or

tinyurl.com/moonanswers

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32
Q

What is the Moon’s diameter?

A

3,500km

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33
Q

What is the Moon’s distance from Earth

A

380,000km

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34
Q

What is the Moon’s rotation period?

A

27.3 days

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35
Q

What is the Moon’s orbital period?

A

27.3 days

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36
Q

Why is the far side of the Moon not visible from Earth?

A

The Moon rotates whilst it orbits the earth and so we can always only see one face of the Moon from the earth.

37
Q

How do astronomers know the appearance of the Moon’s far side?

A

A space probe was sent called Luna 3 which sent 17 images of the far side of the Moon back to Earth.

38
Q

How does the far side of the Moon differ from the near side?

A

The far side has fewer seas, but more mountains and craters than the near side.

39
Q

How do the appearances of lunar seas (maria) and highlands (terrae) differ?

A

Lunar seas look like large, dark grey, smooth ‘seas’; highlands look like lighter grey, mountainous areas.

40
Q

How are lunar seas formed?

A

From giant impacts resulting in molten rock rising to the surface

41
Q

How are lunar craters formed?

A

By impacts with meteors and meteoroids

42
Q

If there are more craters on a feature of the Moon, does that mean it is probably older or younger and why?

A

It is likely to be older, as more time passed allowing craters to form.

43
Q

Do highlands or seas tend to have more craters?

A

Highlands tend to have more craters and so are usually older.

44
Q

What are rilles?

A

Narrow channels in lunar seas formed by flowing molten rock

45
Q

What are wrinkle ridges?

A

Long ridges above ground from when the seas of molten rock cooled and contracted

46
Q

What is the cause of the Moon’s lack of atmosphere?

A

The Moon has a gravitational field strength of about 1/6 that of the Earth and so has less gravity holding gas together to make an atmosphere.

47
Q

What were the purposes of the Apollo space programme?

A
  • To send humans to the Moon and return them back to Earth safely
  • To collect lunar soil and rock for analysis
  • To deploy scientific experiments on the lunar surface
  • To win the ‘race’ to the Moon against Russia
48
Q

When was the Apollo space programme conceived?

A

1960

49
Q

Who were the first two men to walk on the Moon?

A

Neil Armstrong, then Buzz Aldrin

50
Q

What year did the first man walk on the Moon?

A

1969

51
Q

What was the name of the spacecraft that took the first men to the Moon?

A

Apollo 11

52
Q

What was the aim of the ALSEPs (Apollo Lunar Surface Experiment Packages)?

A

To perform long term studies of internal structure and local environment of the Moon

53
Q

What did the ALSEPs measure?

A
  • Lunar dust
  • Structure of the Moon’s interior
  • Intensity and direction of solar wind
  • Composition and pressure of lunar atmosphere
  • Minute changes in lunar gravity
54
Q

What is the likely origin of the Moon and what is this theory called?

A

Giant impact hypothesis - the theory suggests that that an object the size of mars collided with the Earth and debris was thrown out into orbit of the Earth. This formed a disk around the earth which, with gravity, gradually formed the Moon.

55
Q

What evidence allowed astronomers to develop the giant impact hypothesis?

A
  • The rocks on the Moon have the same oxygen isotope as Earth, showing they may have a common origin.
  • The Moon’s surface was once molten and the giant impact could have provided the energy needed to melt it
56
Q

How can the Sun can be observed safely by amateur astronomers?

A
  • Use of a high quality H-alpha filter or Mylar filter on the telescope (but the condition of the filter must be checked before use)
  • Indirect projection - using a pin hole camera or a pair of binoculars or a telescope to focus an enlarged image of the sun onto a screen
57
Q

What is the Sun’s diameter?

A

1.4 million km

58
Q

What is the Sun’s distance from Earth?

A

150 million km or 1AU

59
Q

What is the temperature of the Sun’s photosphere?

A

5,800K

60
Q

What are the two main elements of the solar atmosphere?

A

The chromosphere and the corona

61
Q

What is the chromosphere?

A

The chromosphere is a layer of the atmosphere where the heated hydrogen emits a red glow, however this can only be seen near totality during a full solar eclipse.

62
Q

What is the corona?

A

The corona is the outer layer of the Sun’s atmosphere which emits ionized gas which, when cooled, forms solar winds. It is hot enough to emit X-rays (only visible in a solar eclipse).

63
Q

What is the temperature of the corona?

A

Around 2 million Kelvin

64
Q

What are sunspots and what do they look like? (Describe the umbra and penumbra)

A

Sunspots are small dark, cooler patches on the sun’s photosphere.

They contain an umbra, the central dark section with a temperature 2000K cooler than the photosphere around it (about 3800k).

They also contain a penumbra which is a brighter area than the umbra with a temperature only around 200K less than the photosphere (about 5600k).

65
Q

What is the cause of sunspots?

A

Sunspots are caused by areas of high magnetic activity on the sun’s surface which hinders the sun’s ability for convection in that area meaning that the hot gas does not reach the sunspot as much and so it is cooler.

66
Q

What is the Sun’s rotation period?

A

It varies from 25 days at the equator to 36 days at its poles as the sun does not rotate as a solid body.

67
Q

How do astronomers use observations of sunspots to determine the Sun’s rotation period?

A

Astronomers observed the time taken for sunspots at different points to travel across the sun’s photosphere and then multiplied the time taken for them to appear to travel once across the photosphere by 2 to account for the rotation along the opposite side.

68
Q

Describe the solar cycle

A

The amount of sun spots and their solar latitudes follow a particular 11 year cycle known as the solar cycle.

The cycle begins with few sunspots at high latitudes, 35-40 degrees north or south of the equator.

They gradually move closer to the solar equator with latitudes between 5-10 degrees north or south.

The solar cycle has a peak number of sunspots in the middle of the 11 year cycle known as the solar maximum and then the number falls again.

This can be shown on a butterfly diagram: tinyurl.com/butterflydiagram

69
Q

Describe how the Sun’s energy is generated including the proton-proton cycle

A

The sun’s energy is generated by nuclear fusion, this follows a chain of events called the proton-proton cycle:

  1. Two hydrogen atoms collide forming deuterium, an isotope of hydrogen. A neutrino and a positron are released with radiation.
  2. Deuterium and hydrogen collide to form helium, more radiation released.
  3. 2 Helium atoms collide to make He4 and 2 protons are released with radiation
70
Q

How and why do astronomers observe the Sun at different wavelengths?

A

Humans only observe visible light; however, different activities take place on the sun which can only be observed with different wavelengths of light such as infrared. To observe the sun at these wavelengths, an optical filter can be fitted onto a telescope.

71
Q

What does the Sun look like in visible light?

A

Yellow with dark sunspots

72
Q

What does the Sun look like in infrared?

A

Orange/red with dark sunspots

73
Q

What does the Sun look like in ultraviolet?

A

Dark with bright sunspots

74
Q

What does the Sun look like through X-rays?

A

Dark with bright patches (exceptionally hot areas and luminous gas present around the sun)

75
Q

What does the Sun look like in H-alpha?

A

Pale orange, prominences (clouds of cool gas) and filaments (dark clouds silhouettes of clouds of dark gas) are visible

76
Q

What are solar winds and what is their cause?

A

Solar winds are streams of protons, electrons, ions and other charged particles with speeds of around 400km/s coming from the corona. The corona is very hot (2 million Kelvin) which gives the particles the kinetic energy to escape the Sun’s gravity.

77
Q

What is fast solar wind and what is its cause?

A

Fast solar wind is solar wind with a speed of around 850km/s. This increased speed is because the wind is released near the Sun’s magnetic pole which allows the particles to leave the Sun’s gravity more easily.

78
Q

Why do the Moon and Sun appear to be the same size when viewed from Earth?

A

The size of something that we observe is dependant on the distance from which it is observed. The Moon is about 400 times closer than the Sun; the Sun is about 400 times the size of the moon.

79
Q

What is the period of the lunar phase cycle?

A

29.5 days

80
Q

How many days are there per lunar phase?

A

3.5 days

81
Q

What is the position of the Moon during a full moon?

A

The Moon is on the opposite side of the Earth to the Sun.

82
Q

What is the position of the Moon during a new moon?

A

The Moon is on the same side of the Earth as the Sun.

83
Q

Label the lunar phases (tinyurl.com/lunarphasesblank)

A

tinyurl.com/lunarphasesanswers

84
Q

Why is the lunar phase cycle 2.2 days longer than the orbital period of the Moon?

A

The Earth has progressed in its orbit around the Sun as the Moon carries out its orbit around the Earth and so the moon must complete a little more than one orbit of the earth before the same phase appears in the sky. (refer to folder for diagram)

85
Q

What is a solar eclipse, what does it look like and during what lunar phase does it occur?

A

A solar eclipse is when the Moon is in between the Sun and the Earth which blocks out some or all of the Sun. It only occurs with a new moon.

86
Q

What is a lunar eclipse, what does it look like and during what lunar phase does it occur?

A

A lunar eclipse is when the Earth is in between the Sun and the Moon which makes the Moon appear as a red/copper-coloured full moon. It only occurs with a full moon.

87
Q

What are the two types of shadow cast by the Moon during a solar eclipse?

A

Umbra - a total shadow, an observer at a location under this would see a total solar eclipse.

Penumbra - a partial shadow, an observer at a location under this would see a partial solar eclipse.

88
Q

How long do solar and lunar eclipses take?

A

Solar - a few minutes

Lunar - between 30 minutes and 1 hour

89
Q

Why does a lunar eclipse change the apparent colour of the Moon?

A

The Earth’s atmosphere provides an orangish color to the moon during an eclipse.
The atmosphere acts like a filtered lens.
It bends red sunlight into our planet’s shadow and scatters out blue light.
It’s the same reason why sunrises and sunsets appear reddish.

Astronomy GCSE (4 decks)

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