<p>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?</p>
<p>Am I way off? Could it be 5 billion light years?</p>

CC BY-SA 4.0
2020-11-04T20:32:24.740Z
When the hydrogen atoms formed, so about  3-20 min after the big bang
seVenVo1d
CC BY-SA 4.0
2020-11-04T22:18:37.563Z
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.
bandybabboon
CC BY-SA 4.0
2020-11-04T23:10:50.703Z
FWIW, Wikipedia has a nice table of the [major elements in the human body](https://en.wikipedia.org/wiki/Composition_of_the_human_body#Elements), giving percentages in both mass and number of atoms.
PM 2Ring
CC BY-SA 4.0
2020-11-04T23:22:00.930Z
Sort of related: https://astronomy.stackexchange.com/q/16311/16685 Also see this [periodic table indicating the origins of the elements](https://en.wikipedia.org/wiki/Stellar_nucleosynthesis#Key_reactions).
PM 2Ring
CC BY-SA 4.0
2020-11-05T00:10:11.407Z
I had no idea that my [magnetron](https://en.wikipedia.org/wiki/Cavity_magnetron) was making human atoms, no wonder my food tastes so funny!
uhoh
CC BY-SA 4.0
2020-11-05T21:15:11.783Z
There are [Extragalactic cosmic rays](https://en.wikipedia.org/wiki/Extragalactic_cosmic_ray#ref_3) that may be from far away, but their flux is quite low, so you might not have any in you.
Keith McClary
CC BY-SA 4.0
2020-11-06T02:09:01.447Z
@keithMcClary Yes indeed, so the early solar system would have had extragalactic  10^12 cosmic rays per m2 when it was planetesmals. That can be an answer, it suggests that some of our atoms come from very far away.
bandybabboon
<star><galaxy><cosmology><distances><big-bang-theory>
From what distances do the atoms in you come from?
bandybabboon
# From what distances do the atoms in you come from?

(Asked by: username_0 on 2020-11-04)

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?

**Tags:** star, galaxy, cosmology, distances, big-bang-theory
> **Comments:**
> **username_1**: When the hydrogen atoms formed, so about  3-20 min after the big bang  
> **username_0**: 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.  
> **username_2**: FWIW, Wikipedia has a nice table of the [major elements in the human body](https://en.wikipedia.org/wiki/Composition_of_the_human_body#Elements), giving percentages in both mass and number of atoms.  
> **username_2**: Sort of related: https://astronomy.stackexchange.com/q/16311/16685 Also see this [periodic table indicating the origins of the elements](https://en.wikipedia.org/wiki/Stellar_nucleosynthesis#Key_reactions).  
> **username_3**: I had no idea that my [magnetron](https://en.wikipedia.org/wiki/Cavity_magnetron) was making human atoms, no wonder my food tastes so funny!  
> **username_4**: There are [Extragalactic cosmic rays](https://en.wikipedia.org/wiki/Extragalactic_cosmic_ray#ref_3) that may be from far away, but their flux is quite low, so you might not have any in you.  
> **username_0**: @keithMcClary Yes indeed, so the early solar system would have had extragalactic  10^12 cosmic rays per m2 when it was planetesmals. That can be an answer, it suggests that some of our atoms come from very far away.  

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## 0 answers

