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Physics A level OCR > Cosmology (20) > Flashcards

Cosmology (20) Flashcards

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1
Q

What is the cosmological principle

A

The universe is homogenous and isotropic

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2
Q

Define homogenous

A

Uniform distribution of mass on a large scale

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3
Q

Define isotropic

A

Same in all directions (regardless of position)

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4
Q

What is an arc minute

A

60th of a degree

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5
Q

Define an AU

A

distance from earth to sun

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6
Q

What is an AU

A

1.5x10^11m

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7
Q

What is a light year

A

distance travelled by light in a year in a vacuum

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8
Q

What is a parsec

A

The distance at which the length of the distance between the earth and sun is 1 arc second

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9
Q

How many ly is a parsec

A

~3.26ly

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10
Q

What is the distance and angle relationship

A

d (parsecs) =1/p (arcseconds)

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11
Q

Explain parallex

A

Using the earth’s orbital period to note the movement of a nearby star compared to the fixed background, to determine how far away

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12
Q

When does the doppler effect occur

A

When a wave source moves relative to an observer

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13
Q

Why does doppler effect

A

wavelength changes due to movement, speed stays constant so the frequency changes

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14
Q

D Red shift

A

wavelength appear longer as moving away

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15
Q

What do you remember about red shift

A

Not linear

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16
Q

What is v in the doppler equation

A

magnitude of relative velocity

17
Q

What did Hubble notice

A

Recessional velocity is proportional to distance

18
Q

What is Hubble’s Law evidence for

A

An expanding universe

19
Q

Key bits of evidence for expanding universe

A

Hubbles law

CMB

20
Q

What does the CMB provide evidence for

A

Young hot universe
rapid inflation
uniform temperature

21
Q

How can Hubble’s law be used to work out age of the universe

A

Assumes constant speed

t=1/H0

22
Q

New information about the universe

A

Expanding at an increasing rate

Dark energy and dark matter

23
Q

What percentage is normal matter

A

5%

24
Q

Describe the story of the universe (9)

A 
Big bang
Inflation
Fundametal particles gain mass
Hadrons are made
Matter stops being created
nucleosynthesis
atoms form, photons can travel
stars 
galaxies
25
Q

When did inflation occur

A

10^-35 seconds

26
Q

when did matter stops being created

A

1 second

27
Q

When did nucleosynthesis occur

A

100 seconds

28
Q

When did photons begin to be able to travel

A

380000 years

29
Q

Stars when

A

30 mil

30
Q

Galaxies when

A

200 mil

Physics A level OCR (23 decks)

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