An astronomy book from several years ago said there are ten to the eightith power hydrogen atoms (10^80), and that hydrogen made up 90% of the universe. From this we could use simple algebra to solve for the other 10% and then add it to 10^80, but I forget exactly how to do this, so I will not. :(

Any other figures for exactly how many atoms are in the universe? Precise figures for each element?

Hi eddie monkey:

10^80 = 90%
10^80/90 = 1%
100 *10^80/90 = 100%

Answer: 10/9 * 10^80
Approximate answer: 10^80.
Intuitive answer: A lot.

I don't think you will find any concrete results on the division by element; as a matter of fact, I think accurate results on the mass-distribution on a per-element basis would be worth quite some fame and fortune. There is a terrible amount of mass that is unaccounted for, and that these kind of tables would explain.

Also, current (gu)estimates on the number of hydrogen atoms are derived indirectly from cosmological theories (i.e. the amount of matter required to reproduce a universe we see now), so I wouldn't bet too much money on the number being very accurate either.

Bye!

Crisp

Tables of relative element abundances for both the universe and the Earth are available. Just search the web.

How do we know the proportions of the entire universe? Are they based on proportions that we have been able to directly observe?

Perhaps the universe there are in the order of 10 billion galaxies each containing about 10 billion stars. (guess)
This adds up to 10^22 total stars in the universe.
The sun weighs in the order of 10^40 kg .
If we take the Sun to be the average star by weight, and the total mass of the universe is estimated to be 10 times the mass of the stars, we obtain the total mass of matter in the universe to be in the order of 10^53 kg, or 10^56 g.
If all the matter in the universe consisted of the lightest periodic element (H) in its elementary (uncombined) form.
Then the total number of atoms present in the universe would be in the order of 10^56; each mole contains in the order of 10^23 molecules, making the total number of atoms in the universe 10^79.

Another way to derive the number would be to calculate it from the average photon density of the universe. There are a billion times more photons than protons.

Nebula:

Yep.

Hi James,

"Tables of relative element abundances for both the universe and the Earth are available. Just search the web."

Okay, but I would never believe these to be accurate enough for any scientific purposes... You said it is an extrapolation of what we see around us; I agree that for most solar systems doing a spectral analysis of the star would give 99,9% of the mass in that solar system, but what about all the matter that we can't see (guestimates of the fraction of dark matter versus the amount of visible matter vary up to almost 1 if I remember correctly (I remember reading that 40% of the matter is dark))... This could totally overthrow the balance in these kind of histograms...

I would agree that the amount of visible matter can be catalogued up to a fair amount of accuracy.

Bye!

Crisp

Keep in mind that the “universe” here is limited to the observable universe. Beyond that sphere, the number of atoms may be infinite.