• Question: How many hydrogen atoms are there in the universe?

    Asked by evilevo to Sarah, Tim, Tom on 24 Jun 2011.
    • Photo: Sarah Thomas

      Sarah Thomas answered on 23 Jun 2011:

      I really don’t know! And I couldn’t even begin to figure out how to calculate that!

      Sorry! Hopefully Tom the maths and physics genius will know! (No pressure heehee!) 🙂

    • Photo: Tom Crick

      Tom Crick answered on 24 Jun 2011:

      Haha, thanks Sarah! 🙂

      The visible universe is estimated to contain between 10^78 and 10^80 atoms (e.g. 10 followed by 80 zeros!). This is the estimated number of atoms in the observable universe, but since we do not know the absolute size of the universe, we cannot be certain. Most of the matter in the universe is still hydrogen, so this gives us a rough approximation.