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"Major" Epochs of the Universe
- Planck Era
- Inflationary Epoch
- Neucleosynthesis Era
- Recombination, and the Cosmic Microwave Background Radiation
- Cosmic Dark Ages
- Era of Galaxy formation
The Inflationary Epoch
Between 10-38 and 10-36 seconds, the scale factor of the universe expanded by a factor of 1026 - faster than the speed of light
this is the same scale factor as in general relativity, which is responsible for the Hubble Constant today. It is the expansion of space itself
explains how all parts of the universe are the same temperature
Inflationary Epoch explains three things:
- 1. Where does structure come from
- 2. Why is the large scale universe so uniform? Why is the CMBR temperature so similar (2.73 K) everywhere
- 3. Why is the density of the universe so close to the critical density
Where does structure come from?
- - we see galaxies everywhere. Galaxies form when there is an enhancement of density over the average density. We can see density enhancement in the temp. map of the CBMR.
- - hot spots (yellow/red) - greater density, cool - lower density
- - these are the seeds of mass from which galaxies later grow
but where do these density enhancements come from?
Why is the large scale universe so uniform?
- - on opposite sides of the universe, 27.4 bill. ly away from eachother, the temperature and density of the universe are extremely similar
- - a signal traveling at the speed of light from one side will not have reached the other side - so how do we know theyre the same?
- the effect of an inflationary epoch would be that those distant areas of the universe were in causal contact, then the universe expanded exponentially, placing them so far apart that they appear to be out of contact.
Why is the density of the universe so close to the critical density?
An inflationary epoch would "flatten" the universe: if Omega >1 or Omega < 1 before inflation, an inflationary epoch would drive Omega to = 1 - that plus the hubble constant, tells us how big the universe was at the time of recombination.
Thereafter Omega = 1 for all time
Has inflation ever been proven correct
no. never been proven, but still explains those three questions, so useful theory to drive observations
Inflation predicts: how big the temperature fluctuations on the sky should be
- if the temperature patches are smaller, then Omega > 1. If the temperature patches are larger, then Omega < 1
Inflation drives the value of Omega to 1. That, plus the hubble constant, tells us how big the universe was at the time of recombination