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Physics 21st Century > The Earth in the Universe > Flashcards

The Earth in the Universe Flashcards

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1
Q

What is at the centre of the solar system

A

A star called the sun

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2
Q

How many planets in the solar system?

A

8

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3
Q

Make up a way of remembering the planets MVEMJSUN

A

eg My Vicious Earthworm Might Just Swallow Us Now

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4
Q

What is the planet nearest to the sun?

A

Mercury

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5
Q

Name the planets in order, starting at the sun

A

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

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6
Q

What is a moon?

A

A ball of rock in an orbit around a planet

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7
Q

What is a comet?

A

A small lump of ice and rock in a very elongated orbit around the sun

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8
Q

What is an asteroid?

A

Irregular lumps of rock, mainly found in orbit around the sun in a belt between Mars and Jupiter

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9
Q

Where are the dwarf planets?

A

Beyond Neptune (though Pluto can go inside the orbit of Neptune)

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10
Q

How much of the mass of the solar system is in the sun?

A

99%

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11
Q

Which is the heaviest planet?

A

Jupiter

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12
Q

Earth is larger than?

A

Venus, Mars, Mercury

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13
Q

What is the Milky Way?

A

Our galaxy

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14
Q

What is a galaxy?

A

A group of stars

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15
Q

What is the speed of light?

A

3x10 ^ 5 km/s.

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16
Q

What is a light year?

A

The distance light travels in a year - about 9.5 million million km.

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17
Q

What evidence can we collect from distant stars?

A

Only the radiation they emit.

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18
Q

What is the difference between brightness and relative brightness?

A

Brightness is what the star is giving out, relative brightness is what we see from earth.

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19
Q

What happens to relative brightness as stars are further away?

A

It reduces.

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20
Q

How can relative brightness be used to calculate the distance of stars?

A

The difference of relative brightness can be used to calculate the difference between two similar stars

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21
Q

What are the problems of using relative brightness to calculate the distance to a star?

A

It is based on the assumption that the same type of star has a constant brightness. It is based on an estimate of the distance to one of the stars. Brightness can be affected by many things on earth, eg light pollution, dust.

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22
Q

Where are telescopes placed to avoid the distortion of earth’s atmosphere?

A

Space

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23
Q

How else can the distance of a star be measured?

A

Parallax

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24
Q

How is parallax used?

A

The earth moves in orbit, so the star is observed 6 months apart, and it appears to move relative to stars that are further away. The amount of movement can be used to calculate the distance.

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25
Q

What are the problems of using parallax?

A

Only close stars appear to move as the earth orbit is small compared to interstellar distances.

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26
Q

How does the sun generate energy?

A

Nuclear fusion.

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27
Q

What nuclear fusion takes place in the sun?

A

4 hydrogen nuclei are fused to form helium

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28
Q

What elements are believed to have been present in the early universe?

A

Only hydrogen

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29
Q

Where do all the elements from hydrogen up to iron come from?

A

They have been produced by nuclear fusion in stars, then spread through the universe by stellar explosions.

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30
Q

Where are the elements heavier than iron made?

A

In a supernova

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31
Q

Where in the star does nuclear fusion take place?

A

In the centre

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32
Q

What is needed for nuclear fusion to take place?

A

High pressure and temperature

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33
Q

How was the solar system made?

A

From a collapsing cloud of dust,

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34
Q

When was the solar system made?

A

About 5000 million years ago

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35
Q

Why do we believe that the universe is expanding?

A

Most galaxies are moving away from us.

36
Q

How do we know when a galaxy is moving away from us?

A

The wavelength of the light is longer, known as redshift.

37
Q

How do we know when a galaxy is coming towards us?

A

The wavelength of the light becomes shorter.

38
Q

Where are the galaxies that are moving towards us?

A

They are all close to us, part of the close cluster and are believed to be gravitationally locked to us.

39
Q

What is believed to have happened at the beginning of the universe?

A

The big bang?

40
Q

Was there a bang at the big bang?

A

Sound cannot travel through a vacuum

41
Q

How is it possible to know how quickly a galaxy is moving away from us?

A

The amount of redshift increases with speed.

42
Q

When was the sun created?

A

About 5000 million years ago.

43
Q

When was earth created?

A

About 4500 million years ago.

44
Q

What evidence is there for the big bang?

A

Cosmic background radiation.

45
Q

What will happen to the universe?

A

Either it will keep expanding (if not enough mass) or it will eventually contract again (if there is enough mass)

46
Q

Why are we unsure about the fate of the universe?

A

We only know about mass that emits radiation; precise measurements of speed and distance are very difficult due to the vast distances,

47
Q

What changes the surface of our earth?

A

Weather, water, continental drift

48
Q

What happens to mountains on earth?

A

They are slowly eroded and become sediments which make rocks again

49
Q

What spews out lava at plate boundaries?

A

Volcano

50
Q

What makes the mountain ridges at plate boundaries?

A

The pushing together of two plates.

51
Q

What transports eroded rock fragments?

A

Wind, water, ice.

52
Q

Where do eroded rock fragments end up?

A

In riverbeds and the sea

53
Q

What is the name for the rock fragments settling out in water?

A

Sedimentation

54
Q

What turns the sediment into a sedimentary rock?

A

Pressure

55
Q

How old are the oldest rocks on earth?

A

4000 million years

56
Q

Who came up with the theory of continental drift?

A

Alfred Wegener

57
Q

What year was the theory of continental drift suggested?

A

1915

58
Q

What did Wegener suggest in his theory of continental drift?

A

Millions of years ago there was a single land mass which has split into several continents

59
Q

What evidence did Wegener use for his theory?

A

The way continents fit together so well; similar rocks and fossils found on continents now separated by oceans.

60
Q

Why was Wegeners theory not accepted?

A

There were simpler theories that explained some of his observations; nobody could measure the movement of continents; nobody could think why the continents would move; Wegener was not even a geologist

61
Q

Why do continents move?

A

As a result of the slow convection currents in the mantle.

62
Q

What is the name given for the way the mid Atlantic rift behaves?

A

Seafloor spreading.

63
Q

Why do ridges form at the expanding seafloor?

A

Liquid rock from the mantle fills the gap left by the spreading seafloor.

64
Q

Why are rocks magnetised?

A

The earth’s magnetic field lines up their natural magnetism with itself.

65
Q

Why are the stripes of opposite magnetism on the sea floor?

A

The earth’s magnetic field switches. Rock remains with the magnetism lined up as it was when it set.

66
Q

What are the bits of crust that float past each other known as?

A

Tectonic plates

67
Q

What is the place where tectonic plates meet known as?

A

Plate boundary

68
Q

What forms when plates are moving apart?

A

Volcanoes - eg Iceland

69
Q

What forms when one plate is forced under another?

A

Volcanic mountains… the plate being forced down melts, with the water which tries to turn to steam.

70
Q

What forms when 2 plates meet head-on?

A

Fold mountains,

71
Q

What are earthquakes?

A

Release of energy from two plates sliding past each other, and getting “snagged”

72
Q

What explains the rock cycle?

A

Tectonic plate movements.

73
Q

What is the earth’s core made of?

A

Mainly iron

74
Q

What is the earth’s mantle made of?

A

Semi-liquid rock

75
Q

What is the inner core of the earth made of?

A

Solid nickel and iron.

76
Q

What is the crust?

A

A thin layer of solid rock that floats on the mantle.

77
Q

What are seismic waves caused by?

A

The sudden movement of tectonic plates?

78
Q

What are P waves?

A

Longitudinal, move quickly through solid crust and liquid core.

79
Q

What are S waves?

A

Transverse waves, only move through crust and mantle

80
Q

How do we know that the centre of the earth is liquid?

A

Only P waves can pass through it.

81
Q

What does a wave transfer in the direction of travel?

A

Only energy, no matter

82
Q

What is the amplitude of a wave?

A

The maximum height compared to the undisturbed level.

83
Q

What is the wavelength?

A

The distance from one maximum height to the next

84
Q

What is frequency?

A

The number of vibrations in a specific time, usually a second.

85
Q

What is 1Hz

A

1 vibration per second

86
Q

What is the wave equation?

A

wave speed (m/s) = frequency (Hz) x wavelength(m)

87
Q

If the speed of the wave is constant (eg light in a vacuum) what is the relationship between frequency and wavelength?

A

They are inversely proportional

Physics 21st Century (8 decks)

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