Now, I remember some time within the last three years that one of my teachers in high school said that the number of atoms in the universe is about 10^? . I've forgotten what the number was. Is there an absolute number of atoms in the universe? I thought atoms decay and split apart. Although I suppose if a fission occurred for every fusion, there would be an absolute number. I'm also curious to know how this giant number could be obtained. I was reading Archimedes' The Sand Reckoner and it reminded me of the day my teacher told us the number of atoms in the universe.

It is possible that there is some estimation.

 

As you said the number of atoms is increasing due to pair production or one bigger atom splitting into two smaller however there are of course the reverse effects which lower the number of atoms. I guess the approximation (if there is one) assumes that the two effects cancel each other out, or do in the short term anyway.

I'm sorry, but under the latest scientific technology, it is impossible to find out even a rough estimate of how many atoms there are!

How do u know how many atoms exist in far away galaxies, that haven't even been discovered!

How do u know how many atoms exist in far away galaxies, that haven't even been discovered!

 

If you want an estimate, you assume that other regions of the galaxy aren't all that different than the ones we can see. Estimates for the number of protons range from 10⁷⁸ - 10⁸⁰