CMBR- How long ago are we observing?

[Sorcerer]

I was just quickly looking and couldn't find the answer, wiki says the age of the universe is 13.8 billion years. WMAP took observations of the CMBR and wiki says this:

"NASA's Wilkinson Microwave Anisotropy Probe (WMAP) project's nine-year data release in 2012 estimated the age of the universe to be (13.772±0.059)×10⁹ years (13.772 billion years, with an uncertainty of plus or minus 59 million years).^[2]

However, this age is based on the assumption that the project's underlying model is correct; other methods of estimating the age of the universe could give different ages. Assuming an extra background of relativistic particles, for example, can enlarge the error bars of the WMAP constraint by one order of magnitude.^[11]

This measurement is made by using the location of the first acoustic peak in the microwave background power spectrum to determine the size of the decoupling surface (size of the universe at the time of recombination). The light travel time to this surface (depending on the geometry used) yields a reliable age for the universe. Assuming the validity of the models used to determine this age, the residual accuracy yields a margin of error near one percent.<sup>[12]"


So when I talk about the age of the universe, what can I actually say for certain (ie the universe is atleast X years old), what is the length of time from now to the CMBR? I'm assuming there was time needed for the universe to cool down and light to permeate ofcourse.</sup>

 

^{What other models have been propsed which give different ages for the universe?}

Edited March 30, 2015 by Sorcerer

[Strange]

The CMB was released about 370,000 years after the (notional) start of the big bang. This is much, much less than the error in the age of the universe.

[Sorcerer]

Sorry people another wiki page gave me this:

"A few minutes into the expansion, when the temperature was about a billion (one thousand million; 10⁹; SI prefix giga-) kelvin and the density was about that of air, neutrons combined with protons to form the universe's deuterium and helium nuclei in a process called Big Bang nucleosynthesis.^[28] Most protons remained uncombined as hydrogen nuclei. As the universe cooled, the rest mass energy density of matter came to gravitationally dominate that of the photon radiation. After about 379,000 years the electrons and nuclei combined into atoms (mostly hydrogen); hence the radiation decoupled from matter and continued through space largely unimpeded. This relic radiation is known as the cosmic microwave background radiation.^[29] The chemistry of life may have begun shortly after the Big Bang, 13.8 billion years ago, during a habitable epoch when the universe was only 10–17 million years old.^[30][31][32]"

And this:

"

The theory of BBN gives a detailed mathematical description of the production of the light "elements" deuterium, helium-3, helium-4, and lithium-7. Specifically, the theory yields precise quantitative predictions for the mixture of these elements, that is, the primordial abundances at the end of the big-bang.

In order to test these predictions, it is necessary to reconstruct the primordial abundances as faithfully as possible, for instance by observing astronomical objects in which very little stellar nucleosynthesis has taken place (such as certain dwarf galaxies) or by observing objects that are very far away, and thus can be seen in a very early stage of their evolution (such as distant quasars).

As noted above, in the standard picture of BBN, all of the light element abundances depend on the amount of ordinary matter (baryons) relative to radiation (photons). Since the universe is presumed to be homogeneous, it has one unique value of the baryon-to-photon ratio. For a long time, this meant that to test BBN theory against observations one had to ask: can all of the light element observations be explained with a single value of the baryon-to-photon ratio? Or more precisely, allowing for the finite precision of both the predictions and the observations, one asks: is there some range of baryon-to-photon values which can account for all of the observations?

More recently, the question has changed: Precision observations of the cosmic microwave background radiation^[9][10] with the Wilkinson Microwave Anisotropy Probe (WMAP) give an independent value for the baryon-to-photon ratio. Using this value, are the BBN predictions for the abundances of light elements in agreement with the observations?

The present measurement of helium-4 indicates good agreement, and yet better agreement for helium-3. But for lithium-7, there is a significant discrepancy between BBN and WMAP, and the abundance derived from Population II stars. The discrepancy is a factor of 2.4―4.3 below the theoretically predicted value and is considered a problem for the original models,^[11] that have resulted in revised calculations of the standard BBN based on new nuclear data, and to various reevaluation proposals for primordial proton-proton nuclear reactions, especially the abundances of ⁷Be(n,p)⁷Li versus ⁷Be(d,p)⁸Be.<sup>[12]"

Is the LHC able to test this?</sup>

The CMB was released about 370,000 years after the (notional) start of the big bang. This is much, much less than the error in the age of the universe.

Do any hypotheses posit the universe could've began instanteously at the moment radiation "decoupled"? Why do we assume there was time before that if we can't observe anything?

Edited March 30, 2015 by Sorcerer

[Strange]

^{Is the LHC able to test this?}

 

I can't answer that (maybe someone else can). I don't know what energy levels the LHC can reach, and how that might relate to the early history of the universe.

 

Do any hypotheses posit the universe could've began instanteously at the moment radiation "decoupled"? Why do we assume there was time before that if we can't observe anything?

 

As the bits you quote say, it is possible to extrapolate further back in time and use the information about temperature, density, etc to calculate what would have happened. This predicts the proportions of hydrogen and helium that were formed, the temperature and characteristics of the CMB and various other things. These predictions are all consistent with observation.

[imatfaal]

...Do any hypotheses posit the universe could've began instanteously at the moment radiation "decoupled"? Why do we assume there was time before that if we can't observe anything?

 

To an extent we assume the existence of a time before the era of last scattering because our models have been proved correct so far. Bear in mind that the transition from an opaque glowing universe to a transparent universe at the surface of last scattering was a prediction of big bang theory - years later the highly red-shifted microwave radiation was discovered as the model predicted.

[Strange]

The idea that the universe just suddenly appeared at the point the CMB was released isn't really physics (as there is no mechanism for that).

[Sorcerer]

The idea that the universe just suddenly appeared at the point the CMB was released isn't really physics (as there is no mechanism for that).

Surely if there's a mechanism for a universe "just suddenly" appearing in the big bang, then also this mechanism could be expanded to a universe appearing in any form?

Something similar to this perhaps? http://www.space.com/17217-big-bang-phase-change-theory.html

[Spyman]

If you go down that route then you might as well claim that the Universe suddenly appeared yesterday, with Earth, life and everything.

 

Point is that scientist are trying to figure out the "mechanism" and to explain how a more complex universe instantly occurred we need much more complicated models and our current understanding and less complicated models that we can test, are already able to explain how the Universe has evolved over time and they work further back in time than the emission of the CMBR.

[Strange]

Surely if there's a mechanism for a universe "just suddenly" appearing in the big bang

There isn't.