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

The Earth in the Universe Flashcards

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
What are the problems of using parallax?
Only close stars appear to move as the earth orbit is small compared to interstellar distances.
26
How does the sun generate energy?
Nuclear fusion.
27
What nuclear fusion takes place in the sun?
4 hydrogen nuclei are fused to form helium
28
What elements are believed to have been present in the early universe?
Only hydrogen
29
Where do all the elements from hydrogen up to iron come from?
They have been produced by nuclear fusion in stars, then spread through the universe by stellar explosions.
30
Where are the elements heavier than iron made?
In a supernova
31
Where in the star does nuclear fusion take place?
In the centre
32
What is needed for nuclear fusion to take place?
High pressure and temperature
33
How was the solar system made?
From a collapsing cloud of dust,
34
When was the solar system made?
About 5000 million years ago
35
Why do we believe that the universe is expanding?
Most galaxies are moving away from us.
36
How do we know when a galaxy is moving away from us?
The wavelength of the light is longer, known as redshift.
37
How do we know when a galaxy is coming towards us?
The wavelength of the light becomes shorter.
38
Where are the galaxies that are moving towards us?
They are all close to us, part of the close cluster and are believed to be gravitationally locked to us.
39
What is believed to have happened at the beginning of the universe?
The big bang?
40
Was there a bang at the big bang?
Sound cannot travel through a vacuum
41
How is it possible to know how quickly a galaxy is moving away from us?
The amount of redshift increases with speed.
42
When was the sun created?
About 5000 million years ago.
43
When was earth created?
About 4500 million years ago.
44
What evidence is there for the big bang?
Cosmic background radiation.
45
What will happen to the universe?
Either it will keep expanding (if not enough mass) or it will eventually contract again (if there is enough mass)
46
Why are we unsure about the fate of the universe?
We only know about mass that emits radiation; precise measurements of speed and distance are very difficult due to the vast distances,
47
What changes the surface of our earth?
Weather, water, continental drift
48
What happens to mountains on earth?
They are slowly eroded and become sediments which make rocks again
49
What spews out lava at plate boundaries?
Volcano
50
What makes the mountain ridges at plate boundaries?
The pushing together of two plates.
51
What transports eroded rock fragments?
Wind, water, ice.
52
Where do eroded rock fragments end up?
In riverbeds and the sea
53
What is the name for the rock fragments settling out in water?
Sedimentation
54
What turns the sediment into a sedimentary rock?
Pressure
55
How old are the oldest rocks on earth?
4000 million years
56
Who came up with the theory of continental drift?
Alfred Wegener
57
What year was the theory of continental drift suggested?
1915
58
What did Wegener suggest in his theory of continental drift?
Millions of years ago there was a single land mass which has split into several continents
59
What evidence did Wegener use for his theory?
The way continents fit together so well; similar rocks and fossils found on continents now separated by oceans.
60
Why was Wegeners theory not accepted?
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
Why do continents move?
As a result of the slow convection currents in the mantle.
62
What is the name given for the way the mid Atlantic rift behaves?
Seafloor spreading.
63
Why do ridges form at the expanding seafloor?
Liquid rock from the mantle fills the gap left by the spreading seafloor.
64
Why are rocks magnetised?
The earth's magnetic field lines up their natural magnetism with itself.
65
Why are the stripes of opposite magnetism on the sea floor?
The earth's magnetic field switches. Rock remains with the magnetism lined up as it was when it set.
66
What are the bits of crust that float past each other known as?
Tectonic plates
67
What is the place where tectonic plates meet known as?
Plate boundary
68
What forms when plates are moving apart?
Volcanoes - eg Iceland
69
What forms when one plate is forced under another?
Volcanic mountains... the plate being forced down melts, with the water which tries to turn to steam.
70
What forms when 2 plates meet head-on?
Fold mountains,
71
What are earthquakes?
Release of energy from two plates sliding past each other, and getting "snagged"
72
What explains the rock cycle?
Tectonic plate movements.
73
What is the earth's core made of?
Mainly iron
74
What is the earth's mantle made of?
Semi-liquid rock
75
What is the inner core of the earth made of?
Solid nickel and iron.
76
What is the crust?
A thin layer of solid rock that floats on the mantle.
77
What are seismic waves caused by?
The sudden movement of tectonic plates?
78
What are P waves?
Longitudinal, move quickly through solid crust and liquid core.
79
What are S waves?
Transverse waves, only move through crust and mantle
80
How do we know that the centre of the earth is liquid?
Only P waves can pass through it.
81
What does a wave transfer in the direction of travel?
Only energy, no matter
82
What is the amplitude of a wave?
The maximum height compared to the undisturbed level.
83
What is the wavelength?
The distance from one maximum height to the next
84
What is frequency?
The number of vibrations in a specific time, usually a second.
85
What is 1Hz
1 vibration per second
86
What is the wave equation?
wave speed (m/s) = frequency (Hz) x wavelength(m)
87
If the speed of the wave is constant (eg light in a vacuum) what is the relationship between frequency and wavelength?
They are inversely proportional

Physics 21st Century (8 decks)

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