Garth said:
The fact that the universe is bathed in a sea of isotropic microwave radiation
http://xxx.lanl.gov/PS_cache/arxiv/pdf/0704/0704.0908v2.pdf
How likely is such a large underdense region in a concordance cosmology? Suppose there is only one such large underdense region in the whole volume up to z=1. The corresponding void frequency is then the ratio of the comoving volume of the void to the comoving volume of the Universe to z=1, which is roughly 3 × 10−5. Is this consistent with CDM? Void statistics have been done for a number of optical galaxy surveys, as well as numerical structure formation simulations. Taking the most optimistic void statistics (filled dots in Fig. 9 of Hoyle & Vogeley, 2004) which can be approximated by log P = −(r/Mpc)/15, a 140 Mpc void would occur with a probability of 5 × 10−10, considerably more rare than our estimate for our Universe (3×10−5) based on the existence of the cold spot. One must keep in mind, however, that observational and numerical void probability studies are limited to rc ~30 Mpc; it is not yet clear how these should be extrapolated to rc > 100 Mpc.
I got involved in this thread by pointing out that the background radiation is *not* isotropic, and according to Lambda-CDM theory, a hole of this size was never "predicted" to exist.
and comprises of roughly 3/4 hydrogen and 1/4 helium and 2% everything else
These percentages that you mention are based upon the belief that plasmas do not mass separate in suns, and that the elements stay relatively "mixed". That is in spite of the fact that plasmas tend to separate in the presence of strong gravitational and magnetic fields. If you remove that single assumption, those elemental abundance numbers become highly suspect. Here's what I mean:
http://archives.cnn.com/2002/TECH/space/07/23/sun.iron/index.html
is good evidence that the universe went through a very compact, hot and dense phase that we call the Big Bang from which it has expanded.
Only if we "assume" that the redshifting phenomenon is related *exclusively* to distance and velocity can we "assume" that the universe is expanding. There have been a number of tired light theories proposed over the years and I have posted links to such theories in this thread. If Arp is correct, and objects have an intrinsic redshift component, then we can't even be sure that we're expanding at all. I'll grant you that the expansion "interpretation" of the evidence is valid (to a point), but Arp has shown physical connections to objects with different redshifts, and MECO theories suggest that heavy objects *can* have an intrinsic redshift. What do we do with that information? Just toss it out?
Whether extrapolating further back leads to a singularity of infinite density, pressure and temperature, or not, is a matter of conjecture that will not be resolved until a quantum gravity theory is established.
Even is we have some evidence that our visible physical universe is expanding *right now*, we do not know that it all was concentrated to a "point" or that it was all concentrated to something the size of a couple hundred light years across, or that all matter (even the stuff we can't see anymore) has always expanded. We don't know that all mass came from a "point", even if we assume that our part of the physical universe is expanding right now.
There is a lot of empirical evidence to support the mainstream model. That does not mean questions are not asked about it,
We also cannot simply assume that one "big picture" theory is right based on a single "interpretation" of the "evidence". Even if we assume that redshift is related to distance and velocity, we still cannot be sure that the universe was ever collected to a single point. All we can know is what our little visible sliver of the physical universe is doing at the moment. We can't even see the vast majority of the physical universe, so how could we even know what that matter happens to be doing right now?
but anyone who dismisses it as 'just a theory' is misunderstanding what a scientific theory actually is, that is, a tried and tested body of ideas supported by observational evidence, and also shows themselves to be ignorant of all the observations made in the last thirty years or so.
Ignorance is a funny thing because new knowledge changes our opinions over time. I've seen it change a whole lot in my time. That hole in the universe is an example of data that simply doesn't "fit" with Lambda-CDM predictions. We were ignorant of that hole in the universe until very recently. I could rightfully also claim that faith in Lambda-CDM theory is based on ignorance of this most recent data.
It is only when you fully understand something that you can criticize it!
I agree. I've been studying astronomy and BB theory now for more than 30 years. Astronomy has always interested me, probably because I was nine when we landed people on the moon, and it was forever hooked. Over that thirty years I've seen many theories come and go, and I've seen many new ideas put on the table, some that I agree with, and some that I do not. I see plenty of folks criticize plasma cosmology theory without studying it for a single day. I've been studying BB theories before inflation theories became vogue, and before dark matter theories existed, and before many of you here were even born. Trust me when I tell you that I know a lot more about Lambda-CDM theory than most folks know about plasma cosmology theory. My criticisms of Lambda-CDM are valid scientific criticisms, and I'm not the only one who has criticized that particular theory.
http://www.cosmologystatement.org/
I want to clearly state that plasma cosmology theory (my theory of preference) does not preclude a "Big Bang" type of event. My aversion to Lambda-CDM theory is based on my aversion to metaphysical constructs, not to the philosophical notion of a "Big Bang". It's entirely possible that something like a "bang" took place, but I have no evidence that our physical universe was ever condensed to a point, nor do I have any empirical evidence that inflation, dark energy or dark matter exist, or that these things have any influence on nature or matter. If and when you can show me empirical evidence of inflation or dark energy or dark matter (rather than missing mass) have an effect on nature in controlled scientific conditions, then I may change my opinions about these metaphysical constructs. Until I see that kind of evidence however, I'm going to be far more skeptical of these metaphysical theories than I am skeptical of BB theory in a general sense.