# Dating techniques for our universe

1. Jan 26, 2006

### nnxion

Can someone tell me why people age our universe at about 13.7 billion years? I know this is done with WMAP, but I can't seem to make much of that. Is there a measurement that aims to explain the age of our universe with just the help of our solar system?

I know there are some methods of trying to find out it's age, with the following: globular clusters, radioactive elements, and Cosmic microwave background radiation (CMB) which is done by the Wilkinson Microwave Anisotropy Probe (WMAP) and tempature measurements.

The only star we can measure that is not light years away is our sun. The sun is supposed to be 4.5 billion years old measured through stellar evolution, and nucleocosmochronology. Do other techniques give us the same answer?

Can we prove that any of these techniques are truly true?

2. Jan 26, 2006

### hellfire

The age of the universe is basically determined by four parameters in the cosmological model under consideration: the energy density in the universe, the energy density of matter related to the critical density ($\Omega_M$), the energy density of the cosmological constant related to the critical density ($\Omega_{\Lambda}$) and the value of the Hubble parameter today ($H_0$). These parameters together with the Friedmann equations allow you to determine the age. For the estimation of these parameters the main source of information is the angular power spectrum of the anisotropies in the cosmic microwave background. One takes this as an input to put constraints on the parameter space that determine the whole cosmological model. By the way, the usual parameter set is far larger than just these four parameters and this it is not possible to determine all four values unequivocally with the data (there is some degeneracy). However, there are other sources of information that can be used to determine some of these four parameters, for example, the $\Omega_{\Lambda}$ can be estimated from the luminosity curves of the supernovae 1a.

Last edited: Jan 26, 2006
3. Jan 26, 2006

### SpaceTiger

Staff Emeritus
Well, our solar system only formed around 4.5 billion years ago, so most of the "structures" (planets, comets, the sun, asteroids, etc.) we see around us are of that age or less. The only things we find locally that could be much older than that would be the elements themselves. This might suggest that we could do radioactive dating on elements formed in some of the early supernovae, but in order to do that, we would need a sample of heavy elements that we could safely assume to have originated in the early universe. Since the contents of our solar system could have been enriched by supernovae of any age prior to its formation, I don't see how this could be done. We might be able to date something passing through our solar system, but I think we'd have to get pretty lucky.

If you haven't already done so, check out the age post in my Review of Mainstream Cosmology. There's also a link to a review paper with more information.

We can date the earth, which presumably formed at the same time. Here's a nice website discussing these measurements:

The Age of the Earth

I don't know what you mean. True in what sense? Most of them don't measure the age of the universe directly, but instead the age of something in the universe. This makes them lower limits (i.e. the universe must be older than these things). Also, the age of the universe obtained from cosmological measurements makes certain physical assumptions, like hellfire already pointed out, so it would be open to question, but for a different reason.