6 ms·
Every once in a while, I get reminded that people don’t necessarily have a scientific background. 1. Water molecules are not indivisible, of course. Many biolo
by jychang 3y ago
Every once in a while, I get reminded that people don’t necessarily have a scientific background.
1. Water molecules are not indivisible, of course. Many biological processes will rip apart hydrogen and oxygen, or combine them back together, and have been doing so for billions of years. Industrial processes do the same. So there’s plenty of “new water” from oxygen in the air, etc.
2. New water/oxygen/hydrogen land on earth fairly regularly due to comets, which are usually slushy balls of ice.
- deleted 3y ago[deleted]
- kcarter80 3y agoAs a percentage of total water on earth, how many of the H2O molecules do you speculate came from comets or industrial processes? Same question for the biological processes you mention.
- ramraj07 3y agoDefinitely more than a glass of water which was the original question anyway.
- foota 3y agoI'm not a scientist; but water is used in photosynthesis, which is probably the main chemical reaction it undergoes. [1] says that the C3 cycle consumes 120 GT of CO2 per year, that's 2.7267×10^15 mols of CO2. C3 carbon fixation consumes one mol of H2O per mol of CO2, so that's 2.7267×10^15 mols of H2O. That's 5 * 10^13 liters. The USGS says there's ~1.4 billion cubic kilometers of water on earth (who chose that unit?), compared to 50 cubic kilometers for the C3 fixation. That's a lot of glasses, but not many oceans. Perhaps a bigger factor might be from back and forth reactions in the oceans and atmosphere, but I'm not sure how to estimate those (e.g., water converting between different acids or getting hit by light in the atmosphere). [1]: https://bio.libretexts.org/Bookshelves/Biochemistry/Fundamentals_of_Biochemistry_(Jakubowski_and_Flatt)/02%3A_Unit_II-_Bioenergetics_and_Metabolism/20%3A_Photosynthesis_and_Carbohydrate_Synthesis_in_Plants/20.04%3A_CO_uptake_-_Calvin_Cycle_and_C3_organisms https://bio.libretexts.org/Bookshelves/Biochemistry/Fundamen...
- labster 3y agoPoint 1 above greatly understates the case. Water just sitting in a glass is constantly creating and destroying hydronium and hydroxide ions, and bare protons. Not to mention the carbon dioxide that gets dissolved as carbonic acid which can dissociate to bicarbonate. On the other hand, its tough to talk about new water because under thermodynamics, all atoms of the same isotope at the same energy state are completely fungible, so it’s hard to say anything meaningful about the history of a molecule.
- rcpt 3y agoIf a few water molecules are destroyed and replaced created over a long time then is it still the same glass of water?
- mensetmanusman 3y agoNothing is ever the same at room temperature if you are counting atoms.
- alex_young 3y agoThe famous glass of Theseus’ water eh? https://en.m.wikipedia.org/wiki/Ship_of_Theseus https://en.m.wikipedia.org/wiki/Ship_of_Theseus
- deleted 3y ago[deleted]
- labster 3y agoIs the Glass of Theseus half-full or half-empty?
- developer93 3y agoTwice as big as it needs to be
- adonovan 3y ago
- jvm___ 3y agoIs the water I drink the same water I pee? Or does it get taken apart and put back together with different pieces?
- nojvek 3y agoSame H2O molecules, different levels of other molecules mixed in with it. It is possible to recycle urine into drinkable water. That’s what they do in international space station where water is very precious. https://www.nasa.gov/mission_pages/station/research/news/water_recovery_milestone https://www.nasa.gov/mission_pages/station/research/news/wat...
- kolinko 3y agoThey also do it in Singapore iirc.
- thombat 3y agoI'm curious why this would be worthwhile: since Singapore is an island conventional desalination would seem easier than either coping with the witches' brew of sewage (random amounts of random chemicals) or the expense of plumbing urine separately.
- Cthulhu_ 3y agoSeem being the key word here; if it's plain sewage, there's affordable, scalable and relatively low energy ways to turn it back into clean drinking water, vs desalinization which requires a lot of energy still. But it's not just sewage though, it's chemicals as well, e.g. from medication, plus whatever else gets flushed.
- thombat 3y agoExactly: all the sewage systems I know of process it enough to dump into a sea or river, where even if a downstream town draws drinking water from it the dilution with other water plus additional environmental chemistry reduces the purification problem. In Singapore's case the sea is the obvious sink for treated sewage, which kicks it back to desalination. Except that I believe that Singapore's water comes across the causeway to the mainland in a pipe.
- bmitc 3y ago> Every once in a while, I get reminded that people don’t necessarily have a scientific background. This isn't necessary for your point and detracts from an otherwise useful clarification.
- TheHappyOddish 3y agoAs a non scientific person, I took no offense. Whilst it's fine to point these things out, it's important to remember that people come from different cultures, and often the intent is unlikely to be there to offend.
- jimkleiber 3y agoI find it helpful to remember. When covid was starting to spread I worried a lot about potential exponential growth and was confused why a lot of others didn't seem so worried. While there may be many reasons, one that came to mind is that they may not have learned as much about exponential growth as I had in electrical and computer engineering and in working with startups. So it helped me to remember not everyone has the same education and experience that I do, that we're all relatively ignorant, depending on the field.
- bmitc 3y agoThere will always be people that don't know what you know and vice versa. It's a given fact of life. It's like forgetting that the sky is blue. Haha. I.e., I agree with you, but your statement is more humble than the last.
- rpwverheij 3y ago> 2. New water/oxygen/hydrogen land on earth fairly regularly due to comets, which are usually slushy balls of ice. This + the fact that we've seen microbes come back to life after being frozen in polar ice for millions of years always seems like the most obvious explanation for the origins of cellular life on earth to me. In other words, what's the chance that the immense complexity of cells did evolve from a molecular soup here on earth VS the chance that it formed somewhere in the universe and found its way here (and many other places)