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Astronomy 101 > Topic 1 - Planet Earth > Flashcards

Topic 1 - Planet Earth Flashcards

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1
Q

What is the shape of the Earth?

A

An oblate spheroid

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2
Q

What is the mean diameter of the Earth?

A

13,000km

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3
Q

What percentage of water vs land does the Earth contain?

A

71% Water and 29% Land

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4
Q

How much of the water that the Earth contains is saline?

A

97.5% of this water is saline and only 2.5% of this water is fresh water.

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5
Q

What inside the Earth’s core produces a magnetic field?

A

Large electrical currents which flow in complicated patterns produce a magnetic field.

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6
Q

What does the Earth’s magnetic field protect the Earth from?

A

The radiation that is emitted by the sun

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7
Q

What does the crust of the Earth contain?

A

Giant tectonic plates that are floating and moving on top of the mantle.

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8
Q

What does the movement of giant tectonic plates cause?

A

The creation of mountains and trenches.

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9
Q

What is the average thickness of the Earth’s crust?

A

50km (Although can vary between 0-70km)

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10
Q

What are the two types of crust that the Earth uses?

A

Continental Crust

Which consists of low density rocks, e.g. Granite

Oceanic Crust

Which consists of high density rocks e.g. Basalt

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11
Q

What is the thickness of the mantle, and how much of the Earth’s volume does it take up?

A

This is a silicate rocky shell with a thickness of about 2900km making up around 80% of the Earth’s volume.

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12
Q

What are the two divisions of the Earth’s upper mantle?

A

The lithosphere and the astenosphere

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13
Q

What is the state of the upper mantle of the Earth?

A

It is considered semi-molten, allowing for the rise and fall of convection currents - driving the movement of tectonic plates.

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14
Q

What does the lithosphere consist of?

A

The lithosphere is the upper section of the upper mantle, which is viscous and supports the crust.

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15
Q

What does the asthenosphere consist of?

A

Less mobile, mostly solid material

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16
Q

What is the state of the lower mantle of the Earth?

A

Solid

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17
Q

What elements is the Earth’s outer core made of?

A

It is a liquid layer of iron and nickel.

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18
Q

What is the thickness of the outer core?

A

2,266km thick

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19
Q

What is temperature of the outer core?

A

500 K

20
Q

What is the thickness of the inner core?

A

Solid ball of iron-nickel alloy

21
Q

What is the temperature of the Earth’s inner core?

A

5700 K - the high pressure prevents the nickel and iron from melting.

22
Q

What are lines of latitude parallel to?

A

The Earth’s equator.

23
Q

Where do lines of longitude run between?

A

North and South Poles

24
Q

What is the significance of the prime meridian and where is it?

A

The prime meridian is in Greenwich, and it is the line of zero degrees longitude.

25
Q

What is the largest value for latitude?

A

90 Degrees North or 90 Degrees South

26
Q

What is the largest value of longitude?

A

180 Degrees East or 180 Degrees West

27
Q

List the key locations of latitude, and their latitude?

A 
North Pole → 90º N
Arctic Circle → 66.5ºN
Tropic of Cancer → 23.5 º N
Equator → 0º
Tropic of Capricorn → 23.5ºS
Antarctic Circle → 66.5ºS
South Pole → 90ºS
28
Q

In order, list the sections of the atmosphere?

A

Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere

29
Q

Troposphere

A

Up to 20km from the Earth’s Surface

30
Q

Ozone Layer

A

In between the stratosphere, and the troposphere

31
Q

Stratosphere

A

20-50km

32
Q

Mesosphere

A

50-85km

33
Q

Thermosphere

A

85-690km

34
Q

Ionosphere

A

In the thermosphere, and contains highly charged particles from the solar wind

35
Q

Exosphere

A

690-10,000km above the Earth’s Surface

36
Q

What is the breakdown of the different gases in the Earth’s atmosphere?

A

78% Nitrogen
21% Oxygen
0.9% Argon
0.04% Carbon Dioxide

37
Q

Advantages of the Earth’s Atmosphere?

A
  • Oxygen allows humans and animals to breathe
  • Carbon dioxide allows plants to photosynthesise
  • Makes the climate and temperature of Earth consistent ( a mean of 15ºC)
  • The atmosphere spreads out and scatters the light from the sun
  • Protects us from micro meteorite collisions from space
  • The atmosphere protects us from harmful (ultraviolet) radiation from the sun.
38
Q

Explain the process of scattering in the atmosphere?

A

Light is scattered by oxygen and nitrogen molecules in the atmosphere; most scattering occurs at the shortest wavelength (blue) wavelengths so the sky is predominantly blue.

39
Q

Explain the process of skyglow in the atmosphere?

A

Skyglow is the rusty orange haze cast by lights near the urbanised areas.

40
Q

What is local glare?

A

The light from bright areas in our local vicinity that ruin the dark adaptation of the eyes.

41
Q

What is seeing?

A

Air in the atmosphere is continuously in turbulent motion: different densities of air rise and fall at different rates, causing light to refract and change direction as it passes through the different layers. This makes stars appear to “twinkle”.

42
Q

Why is seeing worse for stars lower on the horizon?

A

Light then has to travel through more atmosphere.

43
Q

How is seeing measured?

A

Seeing can be measured through the Antoniadi Scale.

44
Q

What is transmission?

A

Many of the objects in space are only visible in parts of the electromagnetic spectrum we can’t see: IR/UV etc. The atmosphere absorbs many of these and thus we can’t see them.

45
Q

Why is the weather bad for us?

A

The Earth’s weather can block our view of space - by clouds. Light can also be scattered by dust storms or other weather patterns.

Astronomy 101 (3 decks)

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