Chapter 14 Flashcards
Who were the people who inadvertently discovered CMB?
Penzias and Wilson
When they first heard the consistent noise that eventually was proven to be CMB, what did they think it actually was?
The pigeons that had nested in the horn. However, when it was removed, the noise persisted
What can a radio signal such as CMB be characterised as?
A temperature
What was the temperature of the radiation that Penzias and Wilson detected?
3.5k
What does CMB tell us about the conditions in the early universe?
That it was very hot, consistent with the Big Bang model
At what stage is CMB created?
recombination
Why has CMB been redshifted?
Because the universe is expanding
What spectrum does the CMB have?
The same as that of a blackbody
Why is the CMB photon density redshifted?
Because of the cosmic expansion
What is the relationship of the CMB’s energy and time?
CMB loses energy over time
What did recombination of electrons with nuclei allow photons to do?
move freely throughout the universe
What principle does the existence of CMB back up?
The cosmological principle
What is the issue with observing CMB from Earth?
The atmosphere of Earth makes it very difficult to detect anything. It is opaque to many forms of radiation
What did COBE determine the CMB temperature to be?
2.725K (uncertainty of +/- 0.002K)
How well did COBE see CMB obeying the blackbody spectrum?
To a precision of 0.03%
What does the coherence with a blackbody spectrum mean about the source of CMB?
It comes from the universe and not other objects like gas
What did COBE find about the temperature of CMB across the whole sky?
That it was evenly distributed, showing isotropy of the universe
Are there fluctuations in the temperature of CMB?
Yes, some very small ones
COBE was too blurry to see this variation very well
What kind of thing affects the radiation fluctuations in the CMB?
The dust from places like the Milky Way can be seen to be emitting more radiation
What can COBE detect with regards to the motion of the solar system?
It can detect redshifts and blueshifts with respect to the cosmic background to show things like the motion of the Milky Way
Why does CMB and redshirting only tell us part of the story with regards to the speed of the universe?
It tells us if the universe is moving towards us or away from us, but does not give us a 3 dimensional sense of the movement
How are sound waves created in the universe?
Gravitational perturbations in the universe
What do CMB fluctuations reveal about the early universe?
They reveal perturbations in the early universe
What do the temperature fluctuations in the CMB appear to be?
Noise
What was WMAP
It measured temperature differences in the CMB more precisely than COBE
What can WMAP tell us about the shape of the universe?
The universe is flat to within 2%
What is reionisation
The hydrogen in the universe (which is mostly ionised) is recognising to help to form new stars
What was the superior satellite to WMAP and COBE?
Planck Satellite
