View Full Version : Cosmic Baryons , light elements, BBN

steve newman
2008-Jan-02, 07:01 AM
Over at least the last 5 years, there have been mixed messages about the amount of observed baryons.

two recent articles are



The BB theory of nucleogenesis predicts amounts
of primordial light elements as a function of the
baryon density. A baryon density of about .04 x the critical mass density is what is said to be consistent with observations of H, He, D and Li.

The articles linked say that before 2005, only
about half the baryons predicted by BBN have been observed. The others are referred to as "missing". Then x-ray observations by chandra inferred that the missing baryons exist in the form of hot gases that fill the intergalactic space.
Now the latest article, 2007, retracts that and says the baryons are probably still missing.

This raises the following question-
1. BBN starts with observed light element abundances and predicts a baryon density.
2. That density is about twice the observed amount of baryons that were used in 1.

This is not good.

Since half the predicted baryons have never been seen, (or exist in intergalactic gas of unknown composition), then how does one know
what the cosmic light element abundances really are? ( this is like - if half the people in a group
are not seen, how do you know what is the ratio of men to women in the group).

If one doesnt know what the light element abunances are, how can one decide what the baryon density must be to make BBN agree with
these unknown abundances.

We have a circular mishmash-

i) You determine the light element densities by observation.

ii)You predict a baryon density consistent with (i).

iii) the baryon density you come up with in (ii),
predicts that your observations in (i) are unreliable because you only observed half of what you needed to observe.

The above inconsistency seems to contradict the
claim that BB theory explains the cosmic light element abundances.

2008-Jan-02, 02:35 PM
Hi, Steve! Welcome to BAUT.

Is this the right forum for your post? It seems you are posing a question about BBT rather than proposing an alternate to it.

Halcyon Dayz
2008-Jan-03, 05:48 AM
How come that Steve Newman has 0 posts? :confused:

steve newman
2008-Jan-03, 07:04 AM
i assume that all newcomers start out with zero posts. i am new to baut, so i have zero posts so far.

2008-Jan-03, 01:35 PM
i assume that all newcomers start out with zero posts. i am new to baut, so i have zero posts so far.
What happened is this:
- New members are not allowed to make unmoderated posts with links
- Your first post had a link
- I had to approve or reject it (approved!)
- The post counter registered you as having zero posts because your first post had to be moderated
- There is a quirk in the forum software that doesn't update your post-count when the moderator approves it.

Eta C
2008-Jan-04, 02:11 PM
Steve, beware of press releases. Even from a source like Science Daily they tend to be dramatic, overstating, and misleading. They often describe cutting edge research that may or may not be validated.

As to the status of nucleosynthesis, you can get the word from the horse's mouth from the Particle Data Group here. (http://www-pdg.lbl.gov/2007/reviews/bigbangnucrpp.pdf)