# Doubt in the calculation of the age of the universe?

1. Dec 17, 2012

### Vineeth T

Hi guys! I have a small doubt in the concept of age of our universe.Everyone say that our universe is 14.4 billion years old.Now I can't understand with what frame as reference this calculation is made.

Is there any global reference frame with which these calculations are made?

2. Dec 17, 2012

### Staff: Mentor

The frame of the cosmic microwave background can be used - it is the unique frame (for a specific location) where the universe looks the same in all directions. You get the same value for the age of the universe everywhere (within measurement uncertainties of course).

Alternatively, you can use earth, or any other star or planet - their velocity relative to the cosmic microwave background is so slow (~400km/s for earth) that time dilation is negligible with the current level of precision.

3. Dec 17, 2012

### Bill_K

The latest determination from WMAP7 is 13.77 ± 0.13 Gyr. But that was reported in Oct 2011, so add a year.

4. Dec 17, 2012

### Lino

MFB, I thought that the CMB reference frame would only get us back to the age, less 380k years. Does it actually get us back to (just after) the big bang / start?

Regards,

Noel.

5. Dec 17, 2012

### bcrowell

Staff Emeritus
6. Dec 17, 2012

### Naty1

Yes, the CMBR only goes back to some 380,000 years after the big bang. The CMBR confirmation means we have experimental confirmation from WMAP about the age of the relic radiation itself.

The "age of the universe" is usually taken to mean the duration of the 'Lambda-CDM' expansion, that is, the elapsed time since [just after] the Big Bang. [Other models yield different calculated ages for our universe.]

You can get an explanation of the standard [FLR, or FLRW] model used.

http://en.wikipedia.org/wiki/Freidmann_equation

Alexander Friedmann found an exact solution of the Einstein Field Equations
[ Equations of General Relativity] using the assumptions of large scale homogeneous and isotropic characteristics for our universe. These findings scrubbed Einstein's attempt to force a 'static' universe and strongly suggested the universe would either expand or contract. Hubble confirmed expansion by his observations.

The modern version of the FLRW solution is called the lambda-CDM model.....

http://en.wikipedia.org/wiki/LCDM_model

where parameters have been developed to 'fine tune the FLRW model to better match modern experimental observations.

7. Dec 18, 2012

### Lino

Thanks Bcrowell & Naty1.

Regards,

Noel.

8. Dec 18, 2012

### Staff: Mentor

Note that 380k is a couple of orders of magnitude short of mattering to the precision with which the universe's age has been measured...

9. Dec 18, 2012

### Lino

Thanks Russ. Do you know why it is generally quoted so frequently (with such certainty and without caveats)?

Regards,

Noel.

10. Dec 18, 2012

### Naty1

you mean the 380,000 years, right?

That's based on different modeling, of 'recombination' of charged particles, rather than the GR based FLRW overall 'age of the universe' model.

It's based on quantum modeling and has its own set of approximations about when photons could escape from the charged plasma of the big bang....which blocked photon emission for approximately the first 380,000 years.

More here: http://en.wikipedia.org/wiki/Recombination_(cosmology [Broken])

edit: A number of of our scientific models are glued together like this...with different parts explained via different theories and mathematics. We await a unified 'theory of everything'.

Last edited by a moderator: May 6, 2017
11. Dec 18, 2012

### Naty1

Lino, Vineeth....PS:

Marcus, of these forums, has posted great and numerous explanations over the years, about 'age of the universe calculations' ...assumptions,methods,models,etc...

If you are interested, here are a few I saved for my notes:

Last edited: Dec 18, 2012
12. Dec 18, 2012

### Lino

Thanks Naty1. Much appreciated.

Regards,

Noel.