We are still exploring the universe along with the contrary of multi-verse, then how one estimated total no. of atoms? Is it just consideration of matter or also anti matter?
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There are up to $100$ billion galaxies in the observable universe. Let me assume each of these has $100$ billion stars with a mass comparable to the sun $2\times 10^{30}kg$. A proton weighs about $10^{-27}kg$. So with a total of $10^{22}$ stars this is $10^{52}kg$ and so there are on the order of $10^{79}$ protons in the observable universe.
There are more however, for the CMB is at $45\times 10^{10}$ light years and our survey of stars goes out to about $12$ billion light years. This is a volume increase of $52$, which means an estimate of around $10^{81}$ protons on the Hubble frame is not a bad estimate. Yet there is even more, for the CMB is just a period in the past where the radiation dominated universe was opaque. The number could then actually be infinite if the universe is flat. However, for the CMB the redshift factor is $z~=~1100$, and we could guess what it would take to redshift the Planck scale to some figure. The Planck epoch might have Planck scale quanta (gravitons etc) red shifted by a factor of $10^{30}$ or so. There might then be proportionately more volume expanded by $\sim~10^{100}$ on the Hubble frame.
Lawrence B. Crowell
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"Multiverse" is more like a sci-fi or phylosophic thing as mainstream physics.
The size of the whole Universe is unknown, maybe infinite.
The total number of atoms in the visible universe is estimated by adding the stars (with their known sizes), the interstellar gas, the intergalactic gas, etc.
Note, only around 5% of the matter in the Universe is baryonic (= can produce atoms). Btw, most of it isn't part of atoms, because it is plasma in the stars.
peterh
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