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Thread: We are stardust

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    We are stardust

    I finally got around to a little project I promised myself after seeing The Origin Of The Elements on APOD. With a table of the atomic composition of the human body and a spreadsheet, I came up with this:
    pioneer.jpg

    Grant Hutchison

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    Very interesting. Iím a little surprised - I naively thought there would be more hydrogen/big bang original material, but I expect the percentages would be a tad different if by number of atoms vs. mass percentage. The Pioneer plaque graphics are appropriate. Nice.

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    Oh, I just saw the “pioneer.jpg” at the bottom. Is that your way of giving credit? It isn’t really that Jpeg any more, maybe just a small credit would be better? Edit - I see that’s the name of the file.

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    We really are stardust! And neutron-star dust. And primordial hydrogen and cosmic spallation stuff.

    Mix, heat, and let ferment for a few billion years. Do not boil.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Van Rijn View Post
    Very interesting. I’m a little surprised - I naively thought there would be more hydrogen/big bang original material, but I expect the percentages would be a tad different if by number of atoms vs. mass percentage. The Pioneer plaque graphics are appropriate. Nice.
    Yes, hydrogen dominates in moles, oxygen in kilograms.

    Quote Originally Posted by Van Rijn View Post
    Oh, I just saw the “pioneer.jpg” at the bottom. Is that your way of giving credit? It isn’t really that Jpeg any more, maybe just a small credit would be better? Edit - I see that’s the name of the file.
    The file name is just my way of tracking this image on my hard drive. The Pioneer plaque image is public domain, so the iconic silhouettes are intended a sort of Easter egg for people (like you) who recognize them. I wanted public domain + nude human silhouette + no sexist choice + relevance to topic. After about ten seconds of reflection, the choice seemed clear.
    (OK, there's actually still significant sexism in the Pioneer plaque, part of which is evident in the silhouettes, but the iconic relevance drew me in.)

    Grant Hutchison
    Last edited by grant hutchison; 2020-Dec-23 at 02:39 AM.

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    Lovely work there.

    As an addition to the chart, maybe the amount of electrical power our bodies generate that could be picked up by a dish if transmitted?

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    Quote Originally Posted by publiusr View Post

    As an addition to the chart, maybe the amount of electrical power our bodies generate that could be picked up by a dish if transmitted?
    Probably not. The level of bioelectricity from a human body is barely detectable even a few inches from the skin. It would be quickly lost in background noise at greater distances.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    In describing the stardust, we see the stuff, the life within is a bunch of processes and functions, many of which could be detected at a distance in principle. But that is another story.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
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    Lots of hydrogen and oxygen. It's a warning to aliens that we are composed of deadly dihydrogen monoxide!
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

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    Quote Originally Posted by Trebuchet View Post
    Lots of hydrogen and oxygen. It's a warning to aliens that we are composed of deadly dihydrogen monoxide!
    We need bright stripes like a poisonous insect.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    We're made of rocket fuel?

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    Quote Originally Posted by Chuck View Post
    We're made of rocket fuel?
    They want us for our water! Shades of the 1980s.

    I thought Mars Needs Women, not water...
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Van Rijn View Post
    Very interesting. I’m a little surprised - I naively thought there would be more hydrogen/big bang original material, but I expect the percentages would be a tad different if by number of atoms vs. mass percentage.
    So I belatedly followed up with a calculation and graphic showing the cosmic origin of the elements in the human body, by atom:
    pioneeratoms.jpg
    As you predicted, we're mainly composed of Big Bang hydrogen.

    I also revised the original "by weight" graphic to correct an error--I wrote "sodium" when I meant "potassium". (They're both physiologically important ions with to some extent complementary roles, so I mixed them up at the critical moment of actually typing the caption. But sodium is produced almost entirely by core-collapse supernovae, so shouldn't have found its way on to the Type Ia list.)
    pioneerweight.jpg
    By my reckoning, we're actually 62% hydrogen, 24% oxygen, 12% carbon, and 1% nitrogen. Another 0.5% comes from the calcium and phosphorus in our bones and tissues.

    Grant Hutchison
    Last edited by grant hutchison; 2021-May-25 at 10:07 PM.

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    Thatís a nice alternate view, thanks for presenting it. We arenít just stardust, we are the universe (well, in a sense at least). These feel to me like something that should make it into an article somewhere for wider distribution. Easy to understand and make an interesting point.

    "The problem with quotes on the Internet is that it is hard to verify their authenticity." ó Abraham Lincoln

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    Quote Originally Posted by Van Rijn View Post
    That’s a nice alternate view, thanks for presenting it. We aren’t just stardust, we are the universe (well, in a sense at least). These feel to me like something that should make it into an article somewhere for wider distribution. Easy to understand and make an interesting point.
    The "by weight" graphic went up on the blog last week, and was picked up by Damn Interesting, so is getting a reasonable amount of traffic. I wrote accompanying text giving some detail of how different stellar processes give rise to different groups of elements, and describing the biological role of the various elements in our bodies. You can find that here.
    The "by atom" graphic will be the focus of another post in the future--it's already written, but there's a lot of stuff queued at present.

    Grant Hutchison

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    I think this is my favorite thread on the whole forum!
    Thanks, grant.
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

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    Afterthought:
    What about novae?
    What about pair-production supernovae?
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

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    Quote Originally Posted by Tom Mazanec View Post
    Afterthought:
    What about novae?
    What about pair-production supernovae?
    Others may have more to say about this, but as far as Iím aware, novae contribute relatively little material and it is typically from the lower end of the periodic table, so maybe some small fraction of (for instance) carbon could be from them, but most will come from red giants.

    And I believe pair-production supernovae are quite rare.

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    You can read Jennifer Johnson's short explanatory paper in Science here. Some more information about the processes involved here (some details are in conflict with Johnson's).

    Novae contribute only about 0.3% of the interstellar medium, though they significantly enrich some rare isotopes of C, N & O.

    Pair-instability supernovae are rare and poorly modelled--they're specifically excluded from my second reference for that reason. (On a separate note, sometimes I see pair-instability supernovae included under the umbrella of core-collapse supernovae, as part of a continuum with classical "iron core-collapse supernovae", and pulsational pair-instability supernovae linking the two groups; sometimes I see them treated as a separate category. So it's difficult to know what people are talking about when they say "core-collapse supernovae".)

    Grant Hutchison

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    Interestingly from this graphic (thank you Grant!) the term "carbon based life" seems a bit odd. I realise that the carbon forms an important part in life development due to the bonding characterists etc... and that life as we know it would not be possible without carbon. But if we are predominently Hydrogen (62%) which is the majority, greater than all the other elements combined, then in fact are we actually hydrogen based life?

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    I'd need to check, but I suspect if you removed water, which accounts for most of our weight, carbon would be the dominant atom by mass.

    We really need experience of other forms of life before we decide what the important differentiators are--I suspect it would be according to molecular species, rather than chemical elements. And it might even turn out that the solvent is more important as a way of classifying life, so we'd end up under the broad heading "water-based biochemistry".

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    I'd need to check, but I suspect if you removed water, which accounts for most of our weight, carbon would be the dominant atom by mass.

    We really need experience of other forms of life before we decide what the important differentiators are--I suspect it would be according to molecular species, rather than chemical elements. And it might even turn out that the solvent is more important as a way of classifying life, so we'd end up under the broad heading "water-based biochemistry".

    Grant Hutchison
    I agree with everything Grant said, but I would add that yes, carbon's bonding characteristics are probably a significant part of its importance to life-as-we-know-it. Carbon has a remarkable ability both to bond to itself (as single, double, and triple bonds) and to a huge variety of other atoms, both ionically and covalently. Carbon has a fairly unique ability to form long-chain macromolecules (the only other thing that comes close are the silicon-oxygen silicones and silicates). It makes carbon fairly unique among the elements.
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    Quote Originally Posted by Swift View Post
    I agree with everything Grant said, but I would add that yes, carbon's bonding characteristics are probably a significant part of its importance to life-as-we-know-it. Carbon has a remarkable ability both to bond to itself (as single, double, and triple bonds) and to a huge variety of other atoms, both ionically and covalently. Carbon has a fairly unique ability to form long-chain macromolecules (the only other thing that comes close are the silicon-oxygen silicones and silicates). It makes carbon fairly unique among the elements.
    Fortunately, carbon is everywhere! We've found complex hydrocarbons, including ones associated with life, pretty much every place we look. That's the main reason I'm always skeptical about "silicon based life" tropes... why wouldn't silicon compounds be outcompeted by the more "useful" (for complex chemistry) and ubiquitous molecules?
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    Quote Originally Posted by Noclevername View Post
    Fortunately, carbon is everywhere! We've found complex hydrocarbons, including ones associated with life, pretty much every place we look. That's the main reason I'm always skeptical about "silicon based life" tropes... why wouldn't silicon compounds be outcompeted by the more "useful" (for complex chemistry) and ubiquitous molecules?
    But on (or in) Earth, silicon is much more abundant. If early life could take a turn towards using silicon as part of a backbone molecule, it would have an advantage in availability on Earthlike worlds.

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    Quote Originally Posted by Van Rijn View Post
    But on (or in) Earth, silicon is much more abundant. If early life could take a turn towards using silicon as part of a backbone molecule, it would have an advantage in availability on Earthlike worlds.
    Well Earth is an Earthlike world, and we don't have any silicate life. We have partially silicone life, but that's only by plastic surgery...
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    Quote Originally Posted by Noclevername View Post
    Well Earth is an Earthlike world, and we don't have any silicate life. We have partially silicone life, but that's only by plastic surgery...
    Sure, and Iíve read speculative articles on different life chemistries, with discussion of carbonís advantage. But silicon isnít something I would rule out entirely for other worlds, it does have its own advantages and conceivably life could start out differently elsewhere.

    One of the other interesting things would be what elements life might do without if they were much rarer than on Earth. We have a fair amount of heavy elements, for example, and use some of them. A system that didnít get enriched in the same way as ours might have life that focuses more on common light elements.

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    Quote Originally Posted by Van Rijn View Post
    Sure, and I’ve read speculative articles on different life chemistries, with discussion of carbon’s advantage. But silicon isn’t something I would rule out entirely for other worlds, it does have its own advantages and conceivably life could start out differently elsewhere.
    Well, as far as we can tell, complex organics are very very common around the Universe. I think a system would have to be specifically lacking in carbon compounds for silicates to have the advantage in forming self replicating molecules.

    For all we know silicate life did occur on Earth, and got left by the wayside by hydrocarbon life, which is us, which brings us neatly back on topic.
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    Quote Originally Posted by Van Rijn View Post
    But on (or in) Earth, silicon is much more abundant. If early life could take a turn towards using silicon as part of a backbone molecule, it would have an advantage in availability on Earthlike worlds.
    I wonder if Grant's point about solvent starts to become a critical difference between Si/O-based life or C-based life (and yes, I am differentiating between Si-based and Si/O-based; I think the former is very unlikely). There are not a lot of good solvents for Si-O compounds; silicates tend to be soluble only at very high pH in aqueous systems. The Si-O polymeric species tend to be very insoluble.
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    Quote Originally Posted by cosmocrazy View Post
    But if we are predominently Hydrogen (62%) which is the majority, greater than all the other elements combined, then in fact are we actually hydrogen based life?
    I think perhaps the reason we donít say that is that hydrogen is so ubiquitous and kind of insignificant. You canít really build a molecule around hydrogen, because itís essentially just a proton that attaches to anywhere where thereís an open space to bind with an electron, so in chemical structures you donít even write them in because theyíre assumed. So I think that you could possibly replace carbon with something else, but the hydrogen would still be there.


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    Quote Originally Posted by Jens View Post
    I think perhaps the reason we don’t say that is that hydrogen is so ubiquitous and kind of insignificant.
    Maybe, but I think it is a different and interesting way to look at it, which is what I like about this topic.

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