> -----Original Message----- > From: brin-l-boun...@mccmedia.com [mailto:brin-l-boun...@mccmedia.com] On > Behalf Of Doug Pensinger > Sent: Friday, January 23, 2009 10:36 PM > To: Killer Bs (David Brin et al) Discussion > Subject: Re: Galactic Effect On Biodiversity > > Dan wrote: > > Even really revolutionary data, like the data that suggests dark energy, > are > > written up in such a way that it implies that the big bang is now in > > question. That drives me crazy in the same way. > > > Yea, god forbid scientists that are skeptical about the big bang! >
I was flip and trying to be humorous in my reply, but was then thinking that you might be referring to questions that exist about the initial big bang theory that are being looked at. For the general outline of the big bang and the evidence for it, UCLA has a nice site: http://www.astro.ucla.edu/~wright/cosmology_faq.html#bestfit But, the very start of the big bang, without modification from the original idea, is known to be problematic. I found a good site for discussing those difficulties: which are mainly the non-existence of relic exotic particles, (e.g. magnetic monopoles) that would have been expected to have been produced at ultra-high densities. http://www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/inflat ion.html Well, I should say those are the problems that place a limit on how far back we can extrapolate. Things are clearly problematic at the Planck density, about 10^93 g/cc. On the other end, the big bang theory describes conditions very well back to nuclearsynthesis. For the time in between the theory of inflation has been developed. <quote from the last article> As I said before, it is almost certain that the big bang model gives an accurate description of the universe back at least as far as the time of nucleosynthesis. The earliest it could possibly be applied would be the Planck era. If we were to consider it valid all the way back to the Planck era we would have to suppose that all the very fine-tuned initial conditions we observe such as homogeneity and flatness were present from the beginning, presumably as a result of some unknown quantum gravity effects. Even given this assumption, however, it is unclear how the theory could avoid the production of relic particles that would destroy the successful description it has made of the later universe. It would be wonderful if a theory existed that with a minimum of assumptions could explain the initial conditions such as flatness and homogeneity, eliminate all high energy relic particles, and then segue into the big bang model itself by the time of nucleosynthesis. In 1980 Alan Guth proposed such a theory, known as inflation, <end quote> The actual process of nucleosynthesis is though to have stopped 20 minutes after the big bang. We know that the inflationary period had to end after densities were below those sufficient to produce magnetic monopoles. So, if you are arguing that the big bang did not survive without modifications, and that some tweaking may still be needed, then that's not problematic. The common nomenclature for this is that the big bang needed to be modified to handle these problems, not that it is false. False would be, for example, finding the steady state universe to be correct. So, I think you had been arguing more towards something of the latter, but if it is the former, than our differences are mainly semantic. Dan M. _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
