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Edexcel GCSE (9-1) Astronomy > 1 Planet Earth > Flashcards

1 Planet Earth Flashcards

1
Q

What is the Earth’s mean diameter?

A

13 000 km

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2
Q

What is the largest terrestrial planet?

A

Earth

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3
Q

What shape is the Earth?

A

Oblate Spheroid

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4
Q

How is the Earth an oblate spheroid?

A

The polar diameter is smaller than the equatorial diameter by 42km

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5
Q

How much of the Earth is covered by the water?

A

~70% (71%)

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6
Q

What are the Earth’s four major internal divisions?

A

Crust, Mantle, Outer Core, Inner Core

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7
Q

What is the thickness of the Earth’s crust?

A

The Earth’s crust ranges in thickness from 0-70km thick

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8
Q

What is the continental crust made up of?

A

low-density rocks such as granite

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9
Q

What is the thickness of the Oceanic crust?

A

Up to 10km thick

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10
Q

What is the Oceanic crust made up of?

A

Denser rocks such as basalt

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11
Q

What does the crust float on?

A

The silicate mantle

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12
Q

How much of the Earth does the mantle make up?

A

~80% of the Earth’s volume

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13
Q

What is the state of the mantle?

A

semi-molten/Liquid

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14
Q

Why do the tectonic plates move?

A

As the upper mantle is semi-molten, the thermal convection currents rise and fall, driving the sideways motion of the tectonic plates

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15
Q

How hot is the outer core of the Earth?

A

~5000 K

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16
Q

What materials is the outer core made out of?

A

liquid iron and nickel

17
Q

How is the Earth’s magnetic field created?

A

Currents of charged particles that flow in the outer core are responsible for the Earth’s magnetic field

18
Q

What is the state of the inner core?

A

solid

19
Q

What is the temperature of the inner core?

A

~5500 K

20
Q

Why is the inner core solid?

A

The high pressure prevents the iron and nickel from melting

21
Q

What is Latitude measured in?

A

Degrees North or South of the equator

22
Q

How is Longitude measured?

A

East or West of the Prime Meridian

23
Q

Where is the Prime Meridian?

A

In 1884, the meridian passing through the Observatory of Greenwich was globally adopted as the zero of longitude

24
Q

How much is the Earth’s polar axis tilted by?

A

23.5° to the vertical

25
Q

When does the Sun lie directly over the equator?

A

March 21st and September 23rd; these dates also correspond to the vernal and autumnal equinoxes

26
Q

When does the Sun lie directly over the Tropics Of Cancer (23.5°N)?

A

21st June; this is also the summer solstice

27
Q

When does the Sun lie directly over the Tropics Of Capricorn (23.5°S)?

A

21st December; this is also the winter solstice

28
Q

What are the Arctic and Antarctic Circles?

A

The Arctic and Antarctic Circles represent the most northern (66.5°N) and southern (66.5°S) latitudes

29
Q

Why is the atmosphere important?

A

The atmosphere:

  • Provides us with oxygen to breathe
  • Absorbs harmful solar UV and X-radiation
  • Regulates our planet’s temperature to mean 15°C
  • Protects us from most meteoroid strikes
30
Q

What are the drawbacks for the atmosphere?

A

The drawbacks of the atmosphere are:

  • The sky is blue restricting observations to night time.
  • Light is scattered by oxygen and nitrogen molecules in our air: most scattering occurs at shortest (blue) wavelengths so the sky is blue
  • Air is in the atmosphere and is continuously in turbulent motion. Different densities of air rise and fall on a variety of scales causing light to react and change direction as it passes through the different layers making the stars ‘twinkle’
31
Q

What difficulties are there from observations for astronomers?

A

Some major problems are:

  • Skyglow is the rusty orange haze caused by lights near urban communities
  • Local glare from things like streetlights ruin our dark adaptation
32
Q

What are the two most common elements in the Earth’s core?

A

Iron and Nickel

33
Q

What are the two most common common elements in the Earth’s crust?

A

Silicon and Oxygen

34
Q

What evidence is there that proves the Earth is a sphere?

A
  • Satellites orbit the Earth
  • Ships disappear over the horizon
  • The Earth casts a curved shadow during an eclipse
  • Aircraft fly in arcs (not straight lines)
  • Images of the Earth from space
35
Q

What is the polar axis of the Earth?

A

The line around which the Earth rotates

36
Q

How much is the Earth’s axis inclined to the ecliptic?

A

66.5°

37
Q

Which direction does Right Ascension move?

A

Eastwards

Edexcel GCSE (9-1) Astronomy (20 decks)

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