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Found Another (Astrophysical) Error in Science Television!

  1. Oct 5, 2011 #1
    Like they're difficult to find!

    (OK, so I realize I'm going out on a limb here, considering the pounding I recently took in the "The Nobel Prize in Physics 2011 goes to Saul Perlmutter Brian Schmidt and Adam Riess" thread under General Discussion in the Lounge, but, well, I'll cast caution to the wind here.)


    Anyways, on the Science Channel's show "How the Universe Works" episode entitled "Extreme Stars", somebody said that all the atoms in your body were manufactured inside stars.

    This seems, to me, to be extremely unlikely, as 80% of our bodies consists of water, each molecule of which contains two hydrogen atoms.

    If hydrogen is, at least in the non-decadent stages of their lives, the primary fuel of stars, then how can the existence of hydrogen be dependent on the existence of stars, or logically precede them temporally?

    This is no chicken-and-egg question, as it's a bit like saying that the existence of petroleum is dependent upon the existence of automobiles.

    (I really hope I got this one right!!)
  2. jcsd
  3. Oct 5, 2011 #2
    That's interesting, I've never thought of that. The one thing I can think of is that just because a molecule didn't undergo at least one part of the fusion cycle doesn't mean that it wasn't inside a star at one point.
  4. Oct 5, 2011 #3
    Quite right you are!

    But what I'm saying (besides the fact that I'm primarily talking about atomic hydrogen here, in addition to molecular hydrogen) is that, whether or not an atom was ever inside a star is irrelevant to whether or not the atom was MADE inside the star; as hydrogen is necessary to the existence of stars, how can one guarantee that any hydrogen atom was created inside a star, as opposed to having aided in the creation of that star?
  5. Oct 5, 2011 #4
  6. Oct 5, 2011 #5
    But hydrogen is never made anywhere.

    Hydrogen is made out of it's composite quarks, and from what I understand it hasn't been hot enough since the seconds after the Big Bang for hydrogen to naturally synthesize.

    I think the point is that there was a set amount of hydrogen from the beginning of the universe. Anything slightly larger than that (i.e. Helium/Lithium) was either also made directly after the big bang (very unlikely) or made in stars via the fusion process. Anything slightly larger than that was definitely made in the fusion process. And anything much larger than that were made in novae/supernovae.

    To so say the statement "everything in your body was made from stars" is incorrect because Hydrogen wasn't made in stars, is invalid because that statement by nature can't include Hydrogen in the first place! A much more valid statement might be that "a large majority of atoms in you body was contained within a star at some point in its life".

    However that's not quite as catchy, so I doubt it'll take :)
  7. Oct 5, 2011 #6
    You're right! You've stated my essential theory better than I did.

    Except that I don't understand why my original statement can't include hydrogen in the first place.

    Please explain.
  8. Oct 5, 2011 #7


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    I think it's just a minor mix up in wording. I wouldn't worry too much about it.
  9. Oct 5, 2011 #8
    It's not that you're statement was wrong, It exposed a good hole in that statement.

    All I was saying was that because Hydrogen can't actually be made (at least not since the Big Bang), the statement [that all the atoms in our body were made in stars] was less of an incorrect statement, and more of an oversimplification that led to mistakes.
  10. Oct 5, 2011 #9
    Gotchya! Agreed!
  11. Oct 5, 2011 #10


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    When stars 'die' [e.g., supernova], they expel their outer envelope - which still contains a large amount of 'unburnt' hydrogen. There also remains vast quantities of 'virgin' [primordial] hydrogen in the universe. Water, however, is also composed of oxygen and virtully all oxygen atoms are manufactured in stars.
  12. Oct 5, 2011 #11
    Correct you are! But hydrogen, two of whose atoms are a component of water along with each oxygen atom, is not made in stars, which still makes the talking-head scientist's statement wrong!
  13. Oct 6, 2011 #12
    Yup. I think you are correct. Also some of the lighter elements such as lithum and beryllium come about through cosmic ray spallation.
  14. Oct 6, 2011 #13


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    I think the point is not a molecule in your body does not contain atoms manufactured in stars. Perhaps that is a more accurate characterization.
  15. Oct 6, 2011 #14


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    I hadn't thought about it that way and I find that to be a very helpful way to look at it. Thanks for that insight.
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