Calculating Age of Universe Using Redshift: 0.6

In summary, calculating the age of the universe with redshift involves knowing the ratio of scale factors, which can be found using the Friedmann equation. In a matter-dominated universe, the scale factor is proportional to t^(2/3). Therefore, using the formula z=(t0/t)^(2/3)-1, we can approximate the age of the universe at a given redshift. However, this may be a difficult concept for someone without a background in science courses.
  • #1
b_o3
52
0
Hi i am confused as to how to calculate the age of the universe with redshift
say for example

The age of the universe now is 13.4 billion years old (and a critical universe).
How do i find the age of the universe if it was a redshift at say 0.6??

Do i have to find the scale factor first?
I am not very sure, please help!
 
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  • #2
You need to know the ratio of the scale factors. z=(a0/a)-1 where a is the scale factor then and a0 is the scale factor now.
 
  • #3
how do i get that? do i have to integrate first
 
  • #4
No. To a good approximation the universe has been matter dominated all of it's history. What does a(t) look like as a function of t in this case?
 
  • #5
so how would that work then?
 
  • #6
What does a(t) look like as a function of t in a matter dominated universe? You can look it up, it's a power law.
 
  • #7
to the power of 4
 
  • #8
Nope. Use the Friedmann equation. H^2 is proportional to rho. If a(t)=t^n. H is proportional to 1/t. rho is proportional to 1/a(t)^3. So 1/t^2 is proportional to 1/a(t)^3. So a(t) is proportional to t^(2/3).
 
  • #9
I'm sorry I'm not an expert on this I don't usually take science courses... but are u saying I'm gna take a(t)= k * t^(2/3) . and that gives me the answer?
 
  • #10
Yes. Since z=(a0/a)-1, this gives z=(t0/t)^(2/3)-1. (t0 is the age of the universe and t is time at redshift z. It's an approximation but it should do. You are asking some pretty hard questions for a non-science course person. What's the course?
 

1. How is redshift used to calculate the age of the universe?

Redshift is a phenomenon in which light from distant galaxies or objects appears to be shifted towards the red end of the spectrum. This is caused by the expansion of the universe, which stretches out the wavelengths of light as it travels. By measuring the amount of redshift, scientists can calculate the distance to the object and use this information to estimate the age of the universe.

2. What is the redshift value of 0.6 and how does it relate to the age of the universe?

A redshift value of 0.6 means that the light from the object has been shifted by 60% towards the red end of the spectrum. This corresponds to a distance of approximately 6 billion light years, which is the distance light has traveled since the Big Bang. Therefore, the age of the universe can be estimated to be around 6 billion years.

3. How accurate is the calculation of the age of the universe using redshift?

The calculation of the age of the universe using redshift is based on the current understanding of the expansion of the universe and the speed of light. While it is considered to be a reliable method, there may be some margin of error due to factors such as the uncertainty of the exact value of the Hubble constant (which is used in the calculation) and potential biases in measuring redshift.

4. Can redshift be used to calculate the age of the universe for all objects?

Redshift can only be used to calculate the age of the universe for objects that are far enough away for their light to have been significantly redshifted. For objects that are closer to us, other methods such as the cosmic microwave background radiation must be used to estimate the age of the universe.

5. How does the age of the universe calculated using redshift compare to other methods?

The age of the universe calculated using redshift is consistent with other methods such as the cosmic microwave background radiation and the ages of the oldest stars in our galaxy. This helps to validate the accuracy of the calculation and our understanding of the expansion of the universe.

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