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Comment by dmix | Hacker News Reader

> a fascinating world with a salty, subsurface ocean of liquid water—possibly twice as much as in all of Earth’s oceans combined.

If we brought water back a container of water from Europa would this be the largest amount of new water entering the earth since planets struck it billions of years ago?

I briefly googled it (I dont know much about this stuff tbh):

> The water on our Earth today is the same water that’s been here for nearly 5 billion years. So far, we haven’t managed to create any new water, and just a tiny fraction of our water has managed to escape out into space. The only thing that changes is the form that water takes as it travels through the water cycle.

Anyway interesting thought experiment.

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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.

As 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.

Definitely more than a glass of water which was the original question anyway.

I'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/Fundamen...

Point 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.

If a few water molecules are destroyed and replaced created over a long time then is it still the same glass of water?

Nothing is ever the same at room temperature if you are counting atoms.

The famous glass of Theseus’ water eh? https://en.m.wikipedia.org/wiki/Ship_of_Theseus

Is the Glass of Theseus half-full or half-empty?

Twice as big as it needs to be

True, but even Feynman talks about "new photons" when describing scattering.

Is the water I drink the same water I pee? Or does it get taken apart and put back together with different pieces?

Same 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/wat...

They also do it in Singapore iirc.

I'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.

Seem 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.

Exactly: 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.

https://eu.usatoday.com/story/tech/2015/06/02/singapore-wate...

context

Metabolism converts sugars and oxygen to carbon dioxide and water. Fire has the same inputs and outputs too! You can think of metabolism as releasing the same energy as fire but with more steps so our bodies can harness and use the energy via various other chemical reactions.

Most of the water from metabolism is released in your breath. Water you pee is mostly water you ingested via drinking and eating.

How do the kidneys identify the H2O molecules origin?

It’s a tagged Union with associated data (the molecule), released in edition Homo Erectus. Pretty nifty feature a lot of other species lack. Abstract Human Types are much more powerful than what Homo Go can offer, for example.

The water you exhale is just the amount of water that happens to evaporate in your respiratory tract/lungs. The water you urinate is whatever "extra" water is left over (based on a bunch of factors like blood pressure, how much stuff is dissolved in you blood, etc).

The water that leaves via your lungs and the water that leaves via your kidneys all had to get there via your blood. There's no distinction made based on the "source" of that water.

Yes agreed fair enough

> Most of the water from metabolism is released in your breath

And the reason for that is that air is bad for heat exchange and transport, water is much better, and evaporates! While the body passively cools in air (either directly when air is colder or via sweat evaporation when air is too hot) most of the heat exchange happens actively via breathing, which is nice because it's easy and quick to adjust, just by breathing faster or slower, so as to maintain 37ish C-100ish F while the body is continuously burning molecules. Without breathing we'd not only lack comburant (oxygen), we'd overheat pretty quickly!

The primary driver for your respiratory rate is the pH of your blood. For instance, metabolic disorders that result in a drop in blood pH will result in an increase in respiratory rate/depth (e.g. Kussmaul breathing). As far as I know (with a fairly deep anatomy and physiology background) there is no mechanism by which body temperature can directly influence respiratory rate. If your respiratory rate increased just to get rid of heat, you’d also be blowing off more carbon dioxide and would end up in a state of respiratory alkalosis.

As you mentioned, sweat is also evaporating water, and that is a much more effective way of dumping heat.

The Urine of Theseus, lol

> 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.

I 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.

There 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.

"but your statement is more humble than the last."

It also was a different person ..

I know it was a different person.

You are giving an example of the very issue you complain about. You worry about this not from a background of epidemiology, but another field entirely. Some of the people who were not worried were deferring to expert opinions they have read about the matter.

The vast majority of people dont really "get" functions or plots or line fitting

They took 7th grade math, but assert that y=mx is meaningless in real life and doesn't help them understand anything they have to deal with

Yeah. Originally when those people refused to wear masks I quietly wished them death. But after awhile I got more tired of hearing educated people pretend that their intellect was keeping them alive more than their economic leverage was. Rooting for the ignorant to die of covid was a bad look. Granted, we also had a president who said he loved the uneducated, so it all took place at a moment when that line could be drawn in a certain way. In any event, the snobbish castigation of people who don't understand science or math didn't help and actually hurt the cause of getting them to protect themselves and everyone else.

> detracts from it

I think you're assigning a moral quality to certain kinds of knowledge that isn't warranted.

I don't know what that means. The statement just wasn't useful and comes across as sassy and arrogant.

the most important thing though, is that that statement is true and verifiably so.

I am one of those persons that learned something by reading that comment.

assuming arrogance and sassyness in an otherwise neutral exposition of a true fact, to me means that, as usually happens, arrogance and sassyness are in the eye of the beholder.

Is the most important thing in communication that each statement is true, or that true information is successfully conveyed? If I prefaced this comment with true facts about how bad your life in particular is, I doubt you'd be ready to read the rest of it :)

  arrogance and sassyness are in the eye of the beholder

very true - but true of all aspects of communication, I think

> Is the most important thing in communication that each statement is true, or that true information is successfully conveyed?

the former.

I, for example, am not native English speaker, so, for example, in this case should you learn Italian to the point where you are able to successfully convey the information to me, which could be "never"?

> f I prefaced this comment with true facts about how bad your life in particular is, I doubt you'd be ready to read the rest of it :)

you can try, but be ready to fail miserably. Also: I am very well aware how bad my life is, I would say that only an arrogant can think to know it better than me to the point that I will be surprised or shocked.

Do you think it's belittling to point out that someone may not have scientific knowledge? Ie, is the statement something beyond mere fact? What makes having scientific knowledge good, that you may infer that someone may think not having it is bad?

My first reading of the sentence in question was that it was patronising

In and of itself no. But in the context of responding to someone saying “your comment reminded me that some people don’t have a scientific background” can be read in a similar way to saying “your comment reminded me that not everyone on Hacker News is a genius”, even if that wasn’t the author’s intention.

I agree with you. I took it exactly the same way and thought it was unnecessary.

As 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.

> 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)

> The water on our Earth today is the same water that’s been here for nearly 5 billion years.

We create tons of water as a byproduct of many industrial processes, that's "new" water. Of course in the grand scheme of things the quantities are inconsequential, so the statement is probably still generally true...

Is it truer to say "the hydrogen and oxygen on our Earth today are the same [...] 5 billion years"?

If those hydrogen and oxygen atoms had not previously been bonded into H2O, you would have to say this is “new” water, right?

Water of Theseus!

What if they bonded with different atoms? To get truly duplicate water it would need to find its partner(s, who knew water was poly), I suspect the odds are low :-)

Except water is H2O where the oxygen comes from plants and plants get it from water and the hydrogen comes from hydrocarbon fuels where the hydrogen comes from water again. So technically you can never create new water on Earth but you can bring in more from the space.

> Except water is H2O where the oxygen comes from plants and plants get it from water and the hydrogen comes from hydrocarbon fuels where the hydrogen comes from water again

I'm not a chemist, so I may be totally wrong here, but does a water molecule "care" where the source of its oxygen and hydrogen come from? If you brought oxygen from space, and hydrogen from space, couldn't you then create new water on Earth?

Comets do fall from time to time, and Earth collects 5000 tons of debri from space each year. So I imagine Earth does gain a few tons of water from time to time.

Oh good point, I didn't think about Comets.

> Earth collects 5000 tons of debri from space each year

That is a lot more than I would have guessed. I had thought that we were very slowly leaking precious resources by sending rockets into space, but I guess we're actually still gaining resources on average.

(At least, I don't think we're sending 5000 tons beyond the atmosphere every year).

https://en.wikipedia.org/wiki/Earth_mass#Variation

It depends on your definition of creating new water.

When we extract crude oil from ground, hydrogen is made as byproduct. Similar with other industrial processes. That hydrogen released in atmosphere burns with oxygen to make water.

So one could say that is new water.

The sun is a big hydrogen ball, and some of the big sun flares may bring new hydrogen atoms to Earth. Which then end up oxidized into water, hence new water.

https://www.nasa.gov/mission_pages/stereo/news/Solar_Flare_S....

Hydrolox rockets have been making millions of gallons of new water on earth.

Even burning gasoline creates some new water.

Burning gasoline releases more h2o than co2 - think about that for scale

In fact all fossil fuels! When you split the carbon parts from the hydrocarbon, most of hydrogen parts end up as water. For every tonne of CO2 that's ever been emitted, there's a corresponding mass of water for which the hydrogen part was previously sequestered.

All fossil fuels except coal, which is a pretty big one.

Why not coal?

It's approximately pure carbon, not hydrocarbon.

Don’t commercial hydrogen fuel cells create water as a byproduct?

Yeah, but you make hydrogen fuel out of water, so you're kinda just playing accounting games with the water.

Hydrogen is mostly made by steam reforming methane, with half the hydrogen coming from the water and half from the methane.

But then the fossil methane was made by bacteria decomposing carbohydrates and the carbohydrates were made by plants photosynthesising water and carbon dioxide.

So it all comes from water in the end, but some of it has not been water for hundreds of millions of years!

Great video I just happened to finish:

https://www.youtube.com/watch?v=vjDnh7zfO98

"Where did Earth's water come from?"

No, water is brought to earth by meteors and comets.

This is why I roll my eyes at alarmist talk of various processes "consuming X zillion gallons of water".

Water is much stronger than that. It just passes through our processes and will outlast us all.

Your sort of responses to climate alarms are always the most disingenuous.

We are consuming water from places where it has been relatively static, at rates far beyond its natural replenishment rate. THAT'S the issue. Yes, this is a closed system, and the human circulatory system is a closed system. But it's bad if you drain the blood from your brain faster than it is replenished.

It's only bad if there aren't undiscovered sources and/or processes we can use in the future to produce more water. It's technological optimism, not disingenuousness.

Saying there might be fixes for this in the future is also disingenuous.

It's like saying military burn pits are okay because there may be medical advancements in the future that can be used to treat afflicted soldiers.

Arguing against optimism is arguing against the history of science. We have cures to diseases that were declared unavoidable divine judgements, we have achieved feats of engineering that would be unimaginable a century ago. I am not arguing for the deapoilation of the planet. We should preserve our resources as best we can. But future growth requires the usage of what resources we do have, in to achieve outcomes and efficiencies far better than we can imagine.

I do agree though, if science wasn't verifiable, it would sound like a pyramid scheme.

Technological advances are nice, but you can’t just assume they will happen. There’s no law or axiom that says we will discover something new, and certainly not on any time scale that we could plan against to avoid problems we predict today.

Based on past trends, it's much more likely we will discover new sources and methods of resource generation, than not. Diamonds were rare, now lab created, electricity was once sparse now ubiquitous. The trend is obvious

Technological pessimism underestimates the rate of progress, but technological optimism routinely overestimates it. In the 50s people thought we would have superintelligent robots, flying cars, moon colonies and cold fusion by year 2000. In the 60s people were optimistic that we would eradicate all diseases in the near future. Right now some people believe the singularity will happen in the next decade. What could possibly happen in the next century that would be "unimaginable" to them?

If you showed today's world to an optimist from a century ago they would see many wondrous things they would never have thought of, but they would also fail to see many of their predicted advancements. And I do think that what optimists predict is usually far more impressive than what actually comes to fruition. That's not to say the pessimists are right, but the optimists simply don't have the track record you seem to think they have.

That sounds like it's beyond optimum into foolishness. I could possibly win the lottery one day, but I'm not going to live my life as if it's guaranteed.

Your analogy is an extreme example of the principle I'm referencing. Taken to a similar extreme, your argument is that we should choose who lives and who dies, through the limitation of the resources required for growth.

They are just being realistic, their example isn’t extreme (though yours is).

It is entirely possible with our current level of technology to adjust to the realities of the physical limitations in the world as we know it, without needing to resort to picking “who lives and dies”.

If those adjustments are to be made, they should be in increases in supply, not artificial constraints, that's my argument. Winning the lottery is imo more likely than finding a way to limit growth without draconian/totalitarian measures.

I'm not being disingenuous. I honestly have a different analysis and opinion than you.

And I roll my eyes at comments like this.

There's a huge difference of usability between different water sources. You can't irrigate your orchards with salt water from the ocean. You can't bathe in waste water from most manufacturing plants. You can't drink ground water that has been contaminated by fracking.

There is a finite amount of potable water. There is a finite amount of usable water for agriculture. Pointing at all of the water on earth and acting as if it's all immediately usable without significant, costly barriers is silly.

I wonder what the economics are of a massive centralized desalination plant in Africa powered by a Sahara mega-array of solar panels. Oil is transported via pipeline, what about water?

“Water” is overloaded. They may mean drinkable water.

Yeah man, water your vegetables with sea water, they'll love it.

You’re entirely missing the context of what you call “alarmist talk”.

The issue isn’t that the water will cease to exist, or that the planet will literally be destroyed. It is that our way of life is unsustainable and actively degrades the future quality of life for us in the future (and our children).

You can compare our mindless pumping of water from the ground to the ignorant farming practices that lead to the dust bowl. If we don’t use our knowledge to take steps to avoid running out of usable water by using it less and more intelligently now, we will come to a hard point in the future.

Which takes cooperation and empathy for everyone’s situations and the overall reality in front of us.

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