Finitism and Cosmology

> [jim]: You seem to be using BB model figures and terms in estimating the density of the universe. If a sample of the universe was examined the density is greater than predicted by BB. For example, say 10E80 cubic meters was the sample. It will on average contain 10E12 galaxies each with 10E11 stars with 10E57 protons. So, then the total proton count in the stars alone for the sample is 10E80. That means 2/3s of the stars do not really exist and all of space is empty if the BB estimate is correct.

When I said "a few", that was not a mathematically precise estimate. I was then trying to distinguish between the two choices you offered that differed by a factor of a million. When all the figures are redone more carefully, the mean density figure is slightly higher, the galaxy count significantly lower, and the average "stars per galaxy" figure slightly lower, so that your calculation and the BB estimates will agree. -|Tom|-

None of these numbers are mine-they are well established average star/galaxy/volume ratios. The way I do the math here there are more galaxies by a factor of 3 in the volume suggested and 10E11 stars per galaxy is average as far as I know(that ain't much)and the IGM has 10 times more mass than this.

> [jim]: None of these numbers are mine-they are well established average star/galaxy/volume ratios. The way I do the math here there are more galaxies by a factor of 3 in the volume suggested and 10E11 stars per galaxy is average as far as I know(that ain't much)and the IGM has 10 times more mass than this.

Okay, if you must have these figures: From Allen's "Astrophysical Quantities" (4th ed. - 2000), the critical density is 11 h^2 protons/m^3 [p. 649], where h = ratio of real Hubble constant to 100 km/s/Mpc (probably in the range 0.5-0.. The portion of that in stars is 0.005/h [p. 661]. The gas fraction in clusters is about a factor of 11 higher than the star fraction. The total mass, including dark matter, is presnntly believed to be 0.3 of the critical density, with the remaining 0.7 supported by the cosmological constant.

If those number were translated into SI units so anyone could read what is said I would be greatful to have this info. As it is I have no idea what they mean if anything at all. My point is the density is much greater than theories say it should be and this can be shown in very simple numbers in the SI system.

> [jim]: If those number were translated into SI units so anyone could read what is said I would be greatful to have this info. As it is I have no idea what they mean if anything at all. My point is the density is much greater than theories say it should be and this can be shown in very simple numbers in the SI system.

All my numbers can be translated into SI units by plugging in the proton mass, 1.7x10^-27 kg. You must also adopt a value for h to set teh Hubble constant. Let's not get into that debate, and simply agree to use a medium value of h = 0.65.

The main problem with your numbers appears to be the galaxy count, which should be roughly a factor of 50 smaller. Your number may include many of the far more numerous dwarf galaxies, but these contribute little to the total mass. If your galaxies are going to have 10^11 stars on average, then the counts are much smaller than your number. -|Tom|-

Table:
critical density = 8x10^-27 kg/m^3
star density = 0.04^-27 kg/m^3
gas+star density = 0.43^-27 kg/m^3
Total mass density = 2.4^-27 kg/m^3

This is a very neat calculation and makes sense for a model. The facts do not fit with this in my opinion, so I'll not debate the details of the Hubble Constant but, explain the sample I proposed. 10E80 cubic meters is actually a bigger volume than the BB allows at the current era. The number of galaxies in that volume is ~3x10E12 allowing an average of 10E19 cubic lightyears of space per galaxy. This can be adjusted to what ever volume is correct and the basic fact remains that the totals don't come out anywhere near the model. The BB is well designed and should have an explaination of why all the mass required by the calculations is 1/3rd the mass observed. And this is allowing nothing for the mass of the IGM.