Wikipedia:Reference desk/Archives/Science/2017 December 31

= December 31 =

How many of a 100 year old's atoms have been in their body their whole adult life?


Do weight changes or yo-yo dieting affect this or is lipid storage an unlikely place for atoms that don't leave the body for decades to have been?

2. Could their body at this instant have an atom that has spent at least 1/2 continuous centuries outside and came back? Well of course it can but is this almost certain, almost certainly false or in between? How is such an atom most likely to leave and return? (i.e exhalation, food, water) Sagittarian Milky Way (talk) 01:00, 31 December 2017 (UTC)

Seriously, SMW, this is the sort of nonsense that made User:Floquenbeam suggest that you might be a candidate for a topic ban. We don't do predictions or debate. This is not a forum. I suggest you do with this what you did with your enquiry on the Klingon word for diaper. μηδείς (talk) 01:07, 31 December 2017 (UTC)


 * When did I ask about Klingon? I've never asked about Klingon. Sagittarian Milky Way (talk) 01:13, 31 December 2017 (UTC)


 * Medeis might have been thinking of this, which was posed by a 140 IP. Floq's comment came in reference to SMW's Muzak question. ←Baseball Bugs What's up, Doc? carrots→ 02:10, 31 December 2017 (UTC)


 * Oh, my. I think the question speaks for itself μηδείς (talk) 17:22, 31 December 2017 (UTC)


 * I would say virtually none remain. Cells die, even fat cells.  Cells respirate.  It's hard to imagine that a cell lives without exchanging atoms.  --DHeyward (talk) 02:34, 31 December 2017 (UTC)


 * Exhalation is the dominant effect here, you can use the information in this article to calculate the exhaled body mass per unit time for some given metabolic rate. This is the same as the absorbed body mass from carbs and fats in food for someone who has a stable body weight. If you then assume that the exhaled CO2 mixes with the atmosphere, then it's easy to compute the fraction of the carbon that comes back later from the food you eat. Count Iblis (talk) 02:37, 31 December 2017 (UTC)
 * User:Sagittarian Milky Way is not asking about that. He is interested in turnover time. For example, collagen molecules in cartilage have a 400 year median turnover time. So some of them remain in your body for your whole life. Abductive  (reasoning) 05:45, 31 December 2017 (UTC)
 * The question as posed is meaningless. All atoms of the same sort are identical to each other. Therefore one can not distinguish "old atoms" from "new atoms". On the hand complex molecules can be "old" as they can carry some defects which can be used to distinguish them from other molecules of the same sort. Please, see this. Ruslik_ Zero 17:15, 31 December 2017 (UTC)
 * Fundamental particles are identical, yet the ways they are assembled are not - which includes atoms, since there are isotopes. Count Iblis gave an excellent example above -- the amount of carbon-14 in hippocampus DNA depends on date of birth, even though there is some turnover. Wnt (talk) 17:50, 31 December 2017 (UTC)
 * Note: the excellent answer was given by User:Fgf10 and promptly removed by some drama asshole with nothing to contribute . Here it is:  Another possibility for long lived atoms is in the DNA of non-dividing cells, such as neurons. This has been used to carbon date cells, and see here for an example of cells with DNA containing carbon incorporated well before the onset of atmospheric nuclear testing. Fgf10 (talk) 15:09, 31 December 2017 (UTC)


 * See the Biology section of the Bomb pulse article --catslash (talk) 19:20, 31 December 2017 (UTC)


 * Ruslik is correct, the question as posed is rambling and meaningless. We have no way of determining how many of the atoms of you are born with will last over any period, or especially whether "their body at this instant have an atom that has spent at least 1/2 continuous centuries outside and came back?"  Iblis hasn't addressed that by pointing out that people born at certain times have more or less of certain isotopes, it doesn't generalize into anything other than a sophomore bullshit session. μηδείς (talk) 00:56, 1 January 2018 (UTC)
 * I'm not sure I understand the hostility to the question. Carbon dating is based on the exchange of atoms.  How close the body and its parts resemble natural radioisotopes is very meaningful.  Radioisotopes are also not chemically identical to each other as carbon uptake by plants is different for different carbon isotopes.  --DHeyward (talk) 01:12, 1 January 2018 (UTC)


 * I apologize for inadvertently deleting FGF's comment when I reverted his busy-body hatting.
 * ":Another possibility for long lived atoms is in the DNA of non-dividing cells, such as neurons. This has been used to carbon date cells, and see here for an example of cells with DNA containing carbon incorporated well before the onset of atmospheric nuclear testing. Fgf10 (talk) 15:09, 31 December 2017 (UTC)"
 * Thankfully, I am not inclined to sink to his level of arrogance and low-life chatter. ←Baseball Bugs What's up, Doc? carrots→ 04:14, 1 January 2018 (UTC)
 * Lest there be any confusion, this is my level of annoyance, expressed before I quoted his posting above. We do not need trolls who don't answer the questions and do destroy the good answers to the questions while waving bogus administrative claims against people who asked good questions; people who win every debate on what gets "hatted" and one doesn't according to one simple policy, namely that the race goes not to the swift nor the strong but to him that edit-wars unto the end.  This is a classic good question, asked fairly often in biological circles and answered with varying degrees of persuasiveness, and Fgf10 provided a decent example. Wnt (talk) 04:51, 1 January 2018 (UTC)
 * No one is stopping you, Wnt. Please do answer "How many of a 100 year old's atoms have been in their body their whole adult life" and whether "their body at this instant have an atom that has spent at least 1/2 continuous centuries outside and came back?" μηδείς (talk) 05:14, 1 January 2018 (UTC)
 * Just because you lack to knowledge to awnser the question doesn't mean everybody else does. Please don't troll. Thank you! Fgf10 (talk) 10:15, 1 January 2018 (UTC)
 * Just because a question is difficult to answer does not mean that it should not be asked. I've learned a lot about neurons and collagen reading this debate and it's possible that others might contribute  further insights.  Someone might post an approximate answer or be able to answer a different but related question.  It was a perfectly sensible question (to which I don't know the answer). Robinh (talk) 07:31, 1 January 2018 (UTC)




 * The question about atoms leaving and returning is harder to answer, but we can certainly lay down some approximations. If we suppose that products leaving the body are perfectly mixed into the rest of the world, then we can say that people take about 9 kilograms of nitrogen gas into their body daily (promptly expelling it again)  and release about 1 kg of CO2 daily  and drink about 3 liters = 3 kg of water a day .  These are all very approximate figures, but for reasons we'll see below even an order of magnitude is more accuracy than we need.  The global carbon pool in the atmosphere is 750 Pg (that's petagram, x 10^15 g) ; obviously there's some exchange out of that to the oceans and crust but again, order of magnitude argument here.  The pool of water is 1,338,000,000 km^3 = 1.3 x 10^18 m^3 = 1.3 x 10^21 dm^3 = 1.3 x 10^21 kg.   for the first.  And Earth's atmosphere should have about 4 x 10^18 kg of nitrogen.  (see atmosphere of Earth, multiply by 78% or so - also confirmed here)  Now taking each of these dilutions, we see that the water is diluted 3 kg in 1.3 x 10^21 kg is about 1 in 2 x 10^21, the CO2 is diluted 1 kg in (7.5 x 10^17 g C = 7.5 x 10^14 kg C x (48 g CO2/12 g C) = 3 x 10^15 kg CO2) or 1 in 3 x 10^15, the nitrogen is diluted 9 kg in 4 x 10^18 kg is about 1 in 5 x 10^17.  Now Avogadro's number is 6.022 x 10^23 atoms per mol; a mol of water is 18 g, a mol of CO2 is 48 g, a mol of nitrogen is 28 g.  So 9 kg of nitrogen contains about 300 mol, which means it has 1.8 x 10^26 molecules (multiplying by Avogadro's number).  If these are perfectly diluted into the nitrogen of the atmosphere and rebreathed, you get that diluted by a factor of 5x10^17, which means you're still breathing in, oh, close to 4 x 10^8 = 400,000,000 molecules that you breathed on some day in the distant past; double that for atoms.  (For this purpose it doesn't really matter if they've found new partners in the meanwhile).  Likewise you're breathing that many atoms breathed by Jesus on the day of the Sermon on the Mount or whatever, because according to  all the other non-geologic nitrogen pools are pretty small compared to atmosphere.  I'll leave the others as an exercise, though tracing the CO2 involves some more figuring since so much of the carbon and oxygen end up in other forms.


 * The catch to all this though is that the mixing isn't random, especially with non-nitrogen elements that can more readily react close to the site of production. If you end up living in the same house after 50 years somehow, a drop of boyhood pee on the floor may have combined with some calcium in grout or cement or something, to release countless billions of oxygen atoms on a warm day fifty years later.  Seems absurd, but think of the levels of dilution we're talking about here!  You can release billions of atoms from a spot on a floor and not notice *any* difference in what is left.  As a result, the non-random flows seem likely, by idiosyncratic and bizarre means, to swamp the smaller random flows. Wnt (talk) 16:52, 1 January 2018 (UTC)


 * It is precisely because I do know the absurd number of variables involved in this arbitrary question with so many undefined parameters, (I majored in biology as an undergrad, did the air Jesus breathed calculation four decades ago, tested out of Chemistry 101 & 102, having gotten a 5 on AP chem, and understand the conservation of DNA molecules versus the recycling of red blood cells) and the fact that not a single RS is going to answer it, that I am closing this bullshit session as a request for prediction and debate. μηδείς (talk) 17:08, 1 January 2018 (UTC)
 * Stop your disruptive behaviour or I will be forced to take this to ANI. Several people have provided partial answers, something you have neglected to do. The vendetta you and BB have against Sagittarian is ridiculous. Fgf10 (talk) 18:23, 1 January 2018 (UTC)
 * You have jumped to a false conclusion. And you need to fix your own vendettas before worrying about someone else's alleged vendettas. ←Baseball Bugs What's up, Doc? carrots→ 21:44, 4 January 2018 (UTC)


 * I'm still wondering, "Why do tea parties serve air?" Unless we know that, we won't be able to generalize between men and women who did and did not serve tea parties when they were little girls as regards to their oxygen isotope ratios at age 100. μηδείς (talk) 01:20, 5 January 2018 (UTC)
 * And I'm wondering where FGF attacked Floquenbeam for making the actual suggestion of a ban for SMW. However, Floq is an admin and might be able to put FGF in his place, which is something us peons cannot do. ←Baseball Bugs What's up, Doc? carrots→ 01:33, 5 January 2018 (UTC)


 * Earth science not biology might be the biggest problem with 2. for water. Most of the industrialized world doesn't fertilize their food with their waste or drink their recycled pee and breath but flushes it far away so if rebreathing your own water vapor isn't considered becoming part of the body if it doesn't reenter the blood then perhaps random mixing isn't so far off for them. Then the chance of ~1030 water atoms/decade shuffling between pools of ~1047 and ~1027.2 water atoms causing at least one of them to be in the smaller one now and the bigger one for at least 50 contiguous years of the last 100 seems possible to estimate with mathematics. The worldwide tropospheric mixing time is only about a year but most water is sea and the thermohaline circulation takes a millennium so even if that calculation showed a high probability 2. is true it'd require more earth science than I know to know to see if that answer isn't bullshit. Sagittarian Milky Way (talk) 20:17, 2 January 2018 (UTC)
 * If it is so obvious that this is an unanswerable question, then presumably there will be reliable sources stating that it is an unanswerable question. In which case surely the appropriate way to treat this question is to link to the source that states it is unanswerable. Iapetus (talk) 14:40, 3 January 2018 (UTC)
 * The burden lie on him who makes the positive assertion. μηδείς (talk) 00:57, 7 January 2018 (UTC)


 * That would be you, if you say it is unanswerable. There is no lack of BOTE calculation on the topic.  For example,  finds that 8100 molecules are shared between two random pints drawn from the ocean....   claims to have done the math and found 2100 shared between two cups, though these results align too closely afaict.  This finds that there are a million molecules of Jesus in every liter of ocean, in the sense of water that passed through during a lifetime.  I'll admit I don't much believe  or ; they seem too confused to generate a clear answer.   finds that there are 1000 to 1,000,000 more drops of water in the ocean than atoms in a drop.
 * Now whether such sources are reliable is a pickle, but there are a lot of people doing parallel math here, using various sourced estimates and simple calculation, as I did above, and coming to relatively similar answers. Since the problem cannot be approached experimentally and is of little interest to real science, that's the best I reasonably hope for. Wnt (talk) 06:50, 7 January 2018 (UTC)