Expansion Rate at the Big Bang: Uncovering the Role of Dark Matter

In summary, the conversation discusses the concept of dark matter accelerating the expansion of the universe and questions how fast the universe started expanding at the point of the Big Bang. It is noted that the expansion rate may have been slower in the past, but it did not go to zero. Dark energy, specifically the cosmological constant, is mentioned as the force behind the early expansion. There is a graph showing the evolution of the universe's size, which can be found in a sticky thread or through a link provided by one of the speakers. It is also mentioned that there is another graph showing the scalefactor over time, which shows a slowing down until around 7 billion years and then a speeding up.
  • #1
Perchie
20
1
If dark matter is accelerating the expansion of the universe, then how fast did the universe start expanding at the point of the Big Bang ?

The pre-Standard Candle model of the Big Bang held that the expansion rate had always been declining and by backward interpolation, must have been very much faster at the BB.

But if the reverse is true, how did the BB even happen - if the expansion rate was slow to zero ?

I've never heard anyone ask this question, as yet.
 
Space news on Phys.org
  • #2
Currently, expansion is accelerating - but some billion years ago, matter dominated and acceleration was slowing down. Expansion was quicker in the early universe.

We have a calculator here, and some nice graph showing the evolution of the size of the universe which I do not find at the moment.

But if the reverse is true, how did the BB even happen - if the expansion rate was slow to zero ?
Note that "slower in the past" (if that would be true) does not mean "goes to zero". f(x)=x+x^2 has an increasing derivative (for increasing x) as well, but its derivative is not zero at x=0.
 
  • #3
mfb said:
Currently, expansion is accelerating - but some billion years ago, matter dominated and acceleration was slowing down. Expansion was quicker in the early universe.

We have a calculator here, and some nice graph showing the evolution of the size of the universe which I do not find at the moment.
Thanks.
:)
 
  • #4
then how fast did the universe start expanding at the point of the Big Bang ?

faster than light...there was a huge negative pressure... a high energy unstable scalar [Higgs type] field...which powered early expansion.
 
  • #5
If dark matter is accelerating the expansion of the universe,

you mean dark energy...the cosmological constant...
 
  • #6
mfb said:
We have a calculator here, and some nice graph showing the evolution of the size of the universe which I do not find at the moment.

...

Jorrie has some nice color-coded curves showing evolution of various things. If that's what you had in mind just say. I think they might be in one of the sticky threads and I'll hunt for them.

There is a much plainer graph of the scalefactor over time that is here
http://ned.ipac.caltech.edu/level5/March03/Lineweaver/Figures/figure14.jpg

It shows slowing down until around year 7 billion and then speeding up after that.

I didn't have room in my signature for it, but I already had a different figure from the same article in my signature
http://ned.ipac.caltech.edu/level5/March03/Lineweaver/Figures/figure1.jpg

so I get it by clicking on that (which is "Figure 1") and then changing the 1 to a 14.
 

1. What is the expansion rate of the universe?

The expansion rate of the universe is a measure of how quickly the universe is expanding. It is typically measured in terms of kilometers per second per megaparsec (km/s/Mpc) and is currently estimated to be around 70 km/s/Mpc.

2. How does the expansion rate of the universe affect the distance between galaxies?

The expansion rate of the universe causes the distance between galaxies to increase over time. This is because as the universe expands, it carries galaxies along with it, causing them to move away from each other.

3. What is the corollary of the expansion rate of the universe?

The corollary of the expansion rate of the universe is the age of the universe. By measuring the expansion rate, scientists can estimate the age of the universe, which is currently around 13.8 billion years.

4. How is the expansion rate of the universe measured?

The expansion rate of the universe is measured using various techniques, including the redshift of galaxies, the cosmic microwave background radiation, and the brightness of supernovae. These measurements can then be used to calculate the expansion rate.

5. Is the expansion rate of the universe constant?

No, the expansion rate of the universe is not constant. It is believed to have changed over time, with the universe initially expanding at an accelerated rate and then slowing down due to the influence of dark matter and dark energy. However, more research is needed to fully understand the nature of the expansion rate.

Similar threads

Replies
11
Views
2K
Replies
33
Views
1K
Replies
37
Views
2K
Replies
69
Views
4K
Replies
4
Views
1K
  • Cosmology
Replies
4
Views
1K
Replies
14
Views
1K
Replies
14
Views
2K
  • Cosmology
Replies
24
Views
2K
Back
Top