If the atoms of a human come from stars, comets, nebulas and magnetrons, then what is the greatest distance that two atoms of a human can possibly have been away from each other previously? Perhaps the distance could be further than 4 million light years, because two galaxies further than Andromeda could have fallen into the Milky Way in the earlier universe? is that correct?

Am I way off? Could it be 5 billion light years?

  • 1
    $\begingroup$ When the hydrogen atoms formed, so about 3-20 min after the big bang $\endgroup$
    – seVenVo1d
    Commented Nov 4, 2020 at 20:32
  • $\begingroup$ The universe was about 20 light years at when the hydrogen atoms formed. There's a number compared to the size of the universe and a number compared to today's distances. $\endgroup$ Commented Nov 4, 2020 at 22:18
  • $\begingroup$ FWIW, Wikipedia has a nice table of the major elements in the human body, giving percentages in both mass and number of atoms. $\endgroup$
    – PM 2Ring
    Commented Nov 4, 2020 at 23:10
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    $\begingroup$ Sort of related: astronomy.stackexchange.com/q/16311/16685 Also see this periodic table indicating the origins of the elements. $\endgroup$
    – PM 2Ring
    Commented Nov 4, 2020 at 23:22
  • $\begingroup$ I had no idea that my magnetron was making human atoms, no wonder my food tastes so funny! $\endgroup$
    – uhoh
    Commented Nov 5, 2020 at 0:10


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