Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Recycling Atoms

  1. Jan 28, 2004 #1
    Also posted in skepticism forum:

    Hey everyone,

    Currently reading a new book by Bill Bryson, "A short history of nearly everything".

    Well, despite the title, clearly even a short history would be a very, very big book, still the read is quite addicting, and there are many scientific areas to which I was quite unfamiliar (Geophysics, Geology for example - Yellowstone is a big volcano!).

    There was one instance in the book, that gave me considerable pause - the author "states" that each one of us has up to a billion atoms that were once other humans, those who lived long ago. A specific example used was Shakespeare.

    At first glance, I thought, well, yeah, a billion atoms is an infinitesimal number that actually comprise us - and I'm assuming what they are referring to is oxygen/gas that people inhaled & exhaled.

    The little know about how dynamic the atmosphere is, not only with oxygen, nitrogen, but even carbon particulates, I wouldn't be surprised to learn that very quickly these become homogeneously distributed throughout the biosphere.

    I mentioned this little kernel to a friend, and they asked me if I was a member of a new religion! That this was time-worn cliche, not worthy of the effort to speak it.

    The little googling I did, I came up with a book by Harlow Shapley, "Beyond the Observatory", which delineates the journeys of the inert gas argon. We take in like 3x10^19 atoms in every breath, and in one week these atoms are already distributed through the country. And so on...

    Anyone have a little more ammunition, er, I mean info, that I might use to supplant my argument?

  2. jcsd
  3. Jan 29, 2004 #2
    I have heard of a similar situation, though probably not from the source you cited, as I have not read that book.
    In any event, but NOT to get into religion, I hear that many of us has breathed in some of the exact same atoms that Jesus breathed in and exhaled. "Touched by Jesus" taking on a new meaning?
    And I suppose that might also be true with regards to Hitler's exhaled air.
  4. Jan 29, 2004 #3
    I think the "new religion" comment to me was meant sarcastically, implying that idea had no merit. Frankly, I don't see any religious connotation; at most, it speaks to the issue that atoms are not "alive", alive in the sense we consider ourselves, :smile: , but that when we bring together a certain assembly of said atoms, bingo!. Ok, not exactly bingo, but perhaps some emergent state occurs - note, Im not suggesting a soul, merely musing why a rock *might* be different from a organic living thing.

  5. Jan 29, 2004 #4


    User Avatar
    Homework Helper

    When you start talking about things as small as atoms, then your in the identical particle arena of phenomena. In that case, it almost doesn't make sense to say that this H atom is the same as that H atom. Or, rather, it makes sense in the same way that the water on one side of the pool is the same water as the water on the other side of the pool, which is kind of trivial.
  6. Jan 30, 2004 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    What, exactly, are you looking for? Do you want an outline of the kind of calculation that leads to Bryson's conclusion? For just C, or O, N, H, etc? Or a general description of the processes which lead to the fact that there is a small part of every human who ever lived in you, right now? (almost ditto, for every trilobite which swam in the Cambrian oceans?)
  7. Jan 30, 2004 #6
    Re: Re: Recycling Atoms

    As you probably know, typical "Caesar breath" calculations show that in each breath we take, there is a large probability that at least one atom is one that Caesar shared.
    I have looked at the math here, and find it fairly reasonable - though being able to distinguish between any one particular atom is not allowable - so were only talking probabilities, right?

    What I'm wondering, is how bryson manages to calculate (or more accurately, parrot some other finding) that each of us has up to a billion atoms that once were part of others. If he is talking gas, and we can only count on acquiring 1 atom per breath, it would take nearly a lifetime to get a billion of them (approx). So, I wonder if he meant more than gas, perhaps that our cells being made up mostly of h2O, and since water is also heavily recycled, this is what he refers to?

    In the past, the only time recycling was calculated, it was with gas. I guess with gas, using ideal gas notions, we can better calculate the equilibrium & dynamics, in order to arrive at the reasonable proposition of the makeup of each breath. I would think any comparable analysis with other materials, i.e., water, would be far more difficult, perhaps unknowable?

    thanks for your time here,

  8. Jan 31, 2004 #7


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    If he didn't say, and he didn't quote his source, I guess we'll just have to make something up, won't we :wink:

    Sounds like an interesting exercise - if we follow the same sort of reasoning about Caeser's breath, we can see if we can come up with a number that's within an OOM (order of magnitude) of 1 billion.

    Just for fun then: if we absorb one atom from Caeser every day (assume it takes that many breaths before we get one atom that was part of Caeser to become part of us, e.g. a bone in my finger), then how many people's breath have I breathed in that day? Depends on how you do the 'Caeser's breath' calculation, but let's say it's ~1 billion. Voila!

    We can deal with the 'up to' by saying that some of the atoms have come from many people

    We could have all kinds of fun with metabolising the C in CO2, the H in H2O, etc; we could even go crazy over what we eat
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook