What Does Redshift and Scale Factor Tell Us About the Size of the Universe?

In summary, the relationship between ##z## and ##a(t_e)## is defined as $$1+z=\frac {a(t_0)=1} {a(t_e)}$$ When assuming ##z=2##, this means that ##a(t_e)=\frac {1} {3}## and the universe was ##\frac {1} {3}## times smaller than it is now. Similarly, if we assume ##z=6##, the universe was ##\frac {1} {7}## times smaller. However, there is no upper limit for ##z## and it can reach values much larger than 10, as seen in the case of the redshift at the last scattering surface which
  • #1
Arman777
Insights Author
Gold Member
2,168
192
We can define the relationship between ##z## and ##a(t_e)## as,

$$1+z=\frac {a(t_0)=1} {a(t_e)}$$

When we assume ##z=2##, it means that ##a(t_e)=\frac {1} {3}##

Is this means that universe was ##\frac {1} {3}## times smaller then now ?

If its the case then let's suppose ##z=6## which means universe was ##\frac {1} {7}## times smaller, but even in this case it doesn't seem a huge difference between ##z=2## and ##z=6##. But I think there should be a lot of difference.

I am not sure what am I missing.

Thanks
 
Astronomy news on Phys.org
  • #2
Arman777 said:
But I think there should be a lot of difference.
Why?
 
  • #3
Orodruin said:
Why?
The largest value of z can be 10 and it that case universe was 1 billion years old maybe more young like a 500 million years old. I am not sure but in any case.

Lets suppose ##z=10##, in that time let's suppose radius of OU is ##r## and now its ##11r##?
Cause I was espanding like ##10^10## difference cause universe was so young those times.

For a current scale of the OU is 45 billion light year. 11 times smaller means 4 billion light year. But I was expanding like a million light year or maybe less If I think the time scale which it grow 11 times bigger in 13 billion years ?

I am not sure how can I explain it.
 
  • #4
Arman777 said:
The largest value of z can be 10
The CMBR is z = 1089. There is no upper limit for z.
 
  • Like
Likes Arman777
  • #5
Arman777 said:
The largest value of z can be 10
Why do you think that z cannot be larger than 10? It is false. The redshift at the last scattering surface is about 1000.
 
  • Like
Likes Arman777
  • #8
They are studying galaxies. It took some time for galaxies to evolve and you will not find galaxies with a redshift of z = 1000. This does not mean that redshifts larger than 10 does not exist.
 
  • Like
Likes Arman777
  • #9
Thanks for your replies. I understand it now
 

1. What is the relationship between redshift and scale factor?

The redshift of an object is directly proportional to its scale factor. This means that as the universe expands and the scale factor increases, the wavelength of light from an object stretches and its redshift increases.

2. How is redshift measured?

Redshift can be measured by comparing the observed wavelength of light from an object to its known rest wavelength. This difference is then divided by the rest wavelength to calculate the redshift value.

3. What does a high redshift indicate about an object?

A high redshift indicates that the object is moving away from us at a high speed, and therefore, is located at a large distance from us. This is due to the expansion of the universe, which causes the stretching of light and an increase in its wavelength.

4. Can redshift be used to determine the age of the universe?

Yes, redshift can be used to determine the age of the universe. By measuring the redshift of distant objects and using the known rate of expansion of the universe, scientists can estimate the age of the universe to be approximately 13.8 billion years.

5. How does the Hubble constant relate to redshift and scale factor?

The Hubble constant is a measure of the rate of expansion of the universe. It is directly related to both redshift and scale factor, as a higher Hubble constant indicates a faster expansion of the universe, which leads to a larger scale factor and higher redshift values.

Similar threads

  • Astronomy and Astrophysics
Replies
2
Views
2K
  • Astronomy and Astrophysics
Replies
5
Views
2K
  • Advanced Physics Homework Help
Replies
21
Views
2K
  • Astronomy and Astrophysics
Replies
2
Views
1K
  • Advanced Physics Homework Help
Replies
1
Views
765
  • Thermodynamics
Replies
2
Views
1K
Replies
2
Views
951
  • Astronomy and Astrophysics
Replies
2
Views
2K
  • Astronomy and Astrophysics
Replies
13
Views
1K
Replies
0
Views
515
Back
Top