Cosmology (20) Flashcards
What is the cosmological principle
The universe is homogenous and isotropic
Define homogenous
Uniform distribution of mass on a large scale
Define isotropic
Same in all directions (regardless of position)
What is an arc minute
60th of a degree
Define an AU
distance from earth to sun
What is an AU
1.5x10^11m
What is a light year
distance travelled by light in a year in a vacuum
What is a parsec
The distance at which the length of the distance between the earth and sun is 1 arc second
How many ly is a parsec
~3.26ly
What is the distance and angle relationship
d (parsecs) =1/p (arcseconds)
Explain parallex
Using the earth’s orbital period to note the movement of a nearby star compared to the fixed background, to determine how far away
When does the doppler effect occur
When a wave source moves relative to an observer
Why does doppler effect
wavelength changes due to movement, speed stays constant so the frequency changes
D Red shift
wavelength appear longer as moving away
What do you remember about red shift
Not linear
What is v in the doppler equation
magnitude of relative velocity
What did Hubble notice
Recessional velocity is proportional to distance
What is Hubble’s Law evidence for
An expanding universe
Key bits of evidence for expanding universe
Hubbles law
CMB
What does the CMB provide evidence for
Young hot universe
rapid inflation
uniform temperature
How can Hubble’s law be used to work out age of the universe
Assumes constant speed
t=1/H0
New information about the universe
Expanding at an increasing rate
Dark energy and dark matter
What percentage is normal matter
5%
Describe the story of the universe (9)
Big bang Inflation Fundametal particles gain mass Hadrons are made Matter stops being created nucleosynthesis atoms form, photons can travel stars galaxies
When did inflation occur
10^-35 seconds
when did matter stops being created
1 second
When did nucleosynthesis occur
100 seconds
When did photons begin to be able to travel
380000 years
Stars when
30 mil
Galaxies when
200 mil
