Wikipedia:Reference desk/Archives/Science/2017 July 21

= July 21 =

Is water's high surface tension compared to say ethanol another plus for life like it's "universal" solventness/heat capacity etc.?
I read a college biology book at age 8 but forgot half as soon as I read it (and didn't understand some anyway). Maybe this is where I got the vague idea I might've heard this before. Sagittarian Milky Way (talk) 14:30, 21 July 2017 (UTC)


 * The surface tension of water (as well as the fact that ice floats in water) is critical to life on Earth because life on Earth evolved to exploit the surface tension of water. It filters pollutants by keeping them from entering water easily. It allows plants to pull water upward and distribute it through the plant. It effects flow of all water-based systems (such as blood flow). If water had very little surface tension, life would have had to form without it and it wouldn't be critical. 209.149.113.5 (talk) 15:05, 21 July 2017 (UTC)
 * To the more general concept, questions of the form "Why is X necessary for life" the answer is "Because life evolved in a universe where X exists". It's a sort of tautology known as the weak anthropic principle, which is to say that the properties to support life in our current universe have created a form of life which is dependent on those properties being what they are.  In simple terms of water; water and its specific properties are necessary to life (at least, the life we know) because it evolved with water, and its specific properties.  If water had different properties, then life as we know it would not have evolved along the same lines (if at all).  Note that this is the weak anthropic principle.  The strong anthropic principle is quite different, in that it doesn't start from life and work backwards to the conditions that created it, but starts from the initial conditions, and posits not just that it makes life as we know it possible, but instead holds that those conditions make life necessary; that is life couldn't have not happened.  -- Jayron 32 15:36, 21 July 2017 (UTC)


 * People are still so creationist, even when they believe and teach they are not. Your question is typically anti-evolutionist, as it imbue water some god-given better life-support quality than other thing, whereas it is just the other way round in an evolution point of view: life forms evolved to exploit/cope with water as it is, not to exploit, say, ethanol (well, some life forms do exploit ethanol, that is, but rather as some food; use it just as solvent would but such a waste!). So it makes little sense to say "look, water has better [insert quality] than [insert other thing] for life support". The correct way to say the very same thing (better fitness of life forms to water than to other things) would be "look, life forms exploit [insert quality] of water more than they do for [insert other, less common, thing]" Of course they do: that's what evolution implies!
 * Moreover, surface tension says that "[it] is not a property of the liquid alone, but a property of the liquid's interface with another medium". So it requires an interface to apply.
 * Now, surface tension also gives examples of the way life forms exploit it to their advantage.
 * But life forms also use surfactants to lower surface tension (Sophorolipid, lecithin, ...), so high surface tension is not always an advantage.
 * Then again, life forms exploit/cope with water as it is, and they have to, because water is so abundant ; they usually don't need to be adapted to ethanol (but for sure they would, if required)...
 * Gem fr (talk) 15:49, 21 July 2017 (UTC)
 * That comment got me wondering whether the water/air surface tension is noticeably different from, say, water/CO2 or water/CH4 etc. It turns out yes (paywall); it varies with pressure as well. I could not find quickly any data about surface tension when the liquid and the gas are non-trivial (well, there is this but supercritical gases do weird stuff), but it might be than on Mars (where atmosphere is basically CO2) some other liquid (even excluding mercury) has a higher-surface-tension. Tigraan Click here to contact me 16:54, 21 July 2017 (UTC)
 * I think the problem, Gem fr, is more that they are teleological than necessarily creationist per se. Kind of the way most people are still dualistic, even if atheist, accepting a mind/body dichotomy where they "explain" consciousness as a quantuum mechanical effect, like modern day Cartesian pinealism. Given SMW's understanding is on the level of a 9 year-old, he should be patient, and learn basic chemistry and planetology (for example, ethanol oceans would be highly unstable, and quickly reduced to water and CO2).  His entire premise is simply magical thinking, the manipulation of words, not the understanding of concepts.  Entertaining such random concatenations of floating abstractions is a disservice to children who haven't yet mastered the concrete basics. μηδείς (talk) 03:00, 22 July 2017 (UTC)
 * I see no basis for these assertions, personal or otherwise. CH3CH2OH clearly cannot decompose to CO2+H2O, though of course hydrogen is lost from some developing atmospheres, which might gradually oxidize ethanol to that mixture of products.  Ethanol oceans seem unlikely to me, but I would have said the same thing about carbon planets a decade ago.  Tell me how I can know there are no ethanol oceans in the cosmos. Wnt (talk) 13:20, 22 July 2017 (UTC)
 * Obviously there would be other products, but ethanol is much more reactive than CO2 and H2O. I used the term decompose rater than a technical term like oxidize since SMW has advised us he was 8 the last time he read a chemistry book, half of which he didn't understand.  I assume he's 9 now, since it would seem odd he hadn't read more on the topic within the last year.  Perhaps you could offer a curriculum for such a curious juvenile to study? μηδείς (talk) 14:07, 22 July 2017 (UTC)
 * Where are you going to get the oxidizer in a reducing atmosphere? All the lightning in the world will not set an alcohol ocean on fire if the atmosphere's like Jupiter. I have read my high school chemistry book after high school thank you very much. If I didn't drop out I would've had a high school biology textbook too. My middle school "biology textbook" was environmental science. (Hunter College High School) Hypothetical biochemistries with methanol as solvent have been proposed. Oceans of the higher atom-count ethanol seem less likely than methanol but at any rate their surface tensions are almost the same. (could a mostly methanol ocean evaporate to a smaller one that's mostly ethanol without a runaway greenhouse effect? No idea) Sagittarian Milky Way (talk) 15:17, 22 July 2017 (UTC)


 * Now you are adding the ad hoc presence of a reducing atmosphere? I suppose you will also next add that the planet has a higher gravity than the earth, so that unlike here, excess H2 can't reach escape velocity, and be lost to space?  Or replenishing photosynthetic quasi-yeast algae will convert molasses lava into seas of vodka?  And let me get the bio straight.  You are actually a college drop-out who last read chemistry when he was in middle school at "age 8"?  The simple answer is that an ethanol ocean is not at equilibrium under any earth-like circumstances, and would be converted to more stable and simple molecules by volcanism, lightning, UV, and other oxidizing elements in short order.  Your premise fails on the basis that a little knowledge is a dangerous thing. μηδείς (talk) 19:29, 23 July 2017 (UTC)
 * I dropped out of high school, not college. Because I'm a lazy idiot not because I'm a retard. At 8 years old I was in.. elementary school (shocking!). P.S. Since you're so much more knowledgeable and interested in biology and chemistry than me why'd you think the ozone hole might've existed for millions of years? Wouldn't an ozone hole have been mentioned when your paleontology class covered Cenozoic Antarctica? Sagittarian Milky Way (talk) 03:20, 25 July 2017 (UTC)


 * My impression (which is to be sure not an expert one) is that over a long enough time scale, you can simply look at atom count. If there is enough carbon, enough oxygen, and a whole lot of hydrogen, so that you have a net 2 C/6 H/1 O ratio, you should get a large amount of ethanol, plus of course various other hydrocarbons that you can make with this blend of components - methanol here, propanol there, ethers and aromatics and so forth.  Presumably the planet would have a highly reducing atmosphere with methane and water components, and with the loss of hydrogen atoms from the upper atmosphere, those compounds need to join up in new ways.  According to  ethanol can be catalytically destroyed (at high temperature) or created (at low temperature) from methane and carbon monoxide.  You would have to hypothesize a new geology and ... "ethanology" to explain how fairly pure ethanol would accumulate in one place.  Now to be sure, petroleum is heterogeneous without ethanol that I know of; but petroleum only gets up to 1.5% oxygen by weight, and it takes 16 hydrogens to balance one oxygen by weight - I presume such rare oxygens are unlikely to end up in the rare short chain hydrocarbons in petroleum, plus they may be more stable as furans?  But the brew will differ depending on the ingredients and the manner of their distillation. Wnt (talk) 19:58, 22 July 2017 (UTC)
 * According to A. Hanslmeier, "In order to form aggregates of organic compounds, the surface tension of a solvent is relevant and water has a high surface tension. Thus water is much more appropriate for life regarding its heat capacity, heat of vaporization, surface tension and dissolving capability than other substances." A topic of special relevance is the water-lipid surface tension in formation of cells or protocells.   Personally I would downplay the importance of this phenomenon because I don't believe the "membrane-first" model of abiogenesis (I think it was a network of RNA functionalized with catalytic cofactors), but I can't give you a guarantee on that! Wnt (talk) 13:15, 22 July 2017 (UTC)
 * which tell us that creationist (or at least teleological as pointed by μηδείς) is just everywhere, indeed. Because:
 * Obviously Hanslmeier overlooks that "surface tension" and "dissolving capability" are just the exact opposite of each other (surface tension occurs when solvent and solute molecule have rather have homologue neighbors so they refuse to mix, dissolution occurs when these molecules are eager to mix, so interface quickly disappear, and you could say that surface tension is negative).
 * And, again, "surface tension" and "dissolving capability" are not a property of a substance alone, but a property of a pair of substance regarding each other.
 * So stating that water per se has, or rather would have, both high surface tension and high dissolving capability is just ... WTF?
 * For sure, water-lipid surface tension is important for cells right now (whether it was in formation of protocells or not), but note that to get cells you don't need high tension surface, you need surfactants (phospholipids), lots of, that reduce surface tension. Otherwise lipids and water (and their respective solute) would just separate into two giant bubbles, preventing polar and oily components to react with each other.
 * Gem fr (talk) 15:11, 25 July 2017 (UTC)

How far in the future can air temp+sunniness anomalies cause sea surf temp anomalies?
If it varies too much by location then how about just the non-tropical North Atlantic west of the 70th meridian? Sagittarian Milky Way (talk) 16:43, 21 July 2017 (UTC)


 * I wouldn't expect air temp to make much diff in heating the water, since water has a much greater density. Sunlight, on the other hand, should have a major effect.


 * How long warmed surface waters remain warm is complex, as the water can "respond" with several cooling methods. There's increased evaporative cooling, increased thermal radiation into space, especially on cloudless nights, and possibly strengthened ocean currents to increase heat transfer by convection (although other factors, like ocean salinity, also contribute to that).  If the water surface temp gets hot enough, it will spawn a tropical storm, perhaps even a hurricane/cyclone, to cool the surface even faster. StuRat (talk) 18:20, 21 July 2017 (UTC)


 * I wouldn't expect air temp to make much diff in heating the water, since water has a much greater density. First of all density ≠ volumetric heat capacity, and regardless, the argument does not follow. Try making a simple model of heat exchange, and you will see that you need additional nontrivial hypotheses for the claim that water temperature will not change much. If you don't see why, try to find the flaw in "Convection heaters are a scam, since human bodies have a much greater density/heat capacity than air".  Tigraan Click here to contact me 20:06, 21 July 2017 (UTC)


 * The top 2.5 meters of the ocean has the same heat capacity as the entire atmosphere. For this reason we generally think of sea surface temperature driving the atmosphere rather than the other way around. The temperature of the air does have some effect on the temperature of the ocean, but it's pretty small except for extreme cases. The effect of the atmosphere on sea surface temperature arises mostly from latent heat exchange and the effect of wind on mixing and circulation. We have an OK article on sea surface temperature. Shock Brigade Harvester Boris (talk) 01:14, 22 July 2017 (UTC)


 * As for air temp changing human body temp, there's a couple factors:


 * 1) The volume of air is typically vastly more than the humans occupying a particular space. So, even with a much lower thermal capacity per unit volume, the total heat capacity of the air is still significant compared to that of the people in the space.  The volumes of the atmosphere and oceans are more similar, especially if the atmosphere was all compressed down to 1 atmosphere pressure.


 * 2) Humans (and endotherms in general) are quite sensitive to minor changes in their body temperature. So, even a 0.1 degree rise may be quite noticeable. StuRat (talk) 02:04, 22 July 2017 (UTC)
 * I think you missed my point. Of course convection heaters work (i.e. allow humans to live comfortably in a room for reasonable parameters of input power, room volume, mass exchange with the outside and temperature thereof, etc.). The point is that why they work is not completely obvious, and a comparison of a single parameter (be it volumetric or total heat capacity) is not enough.
 * Example of things to consider in the "heater problem": temperature felt by the human in the room comes from the air immediately surrounding them; this in turns depends of convection which does bring thermal energy from other parts of the room, but it is not clear that it does it quickly enough that air temperature in the room can be considered homogeneous for our purposes. Also, the convection heater is not heating the whole room, but only air that is present inside it at a given moment - which is circulated, sure, but the question becomes at which speed. The convection heater has to be of a certain power - many people have 60W radiation heaters on their ceilings, but those are insufficient as heaters.
 * Similarly for the atmosphere/ocean system, there are other key parameters at play. If we assume for the sake of the argument that a top layer of sea water of one millimeter does little or no thermal exchange with the rest of the ocean, then the heat capacity of the whole ocean does not matter - what matters is the effective heat capacity of that top layer. Of course that is an extreme case; in reality what really needs to be taken into account is how fast heat is exchanged between air and water vs. how fast it is exchanged within water vs. within air (and of course loads and loads of other parameters).
 * You can make simplifying assumptions on an underlying model which may lead you to the conclusion that comparing heat capacities is all that is needed to see how things will go. But the model (even extremely simplified) needs to be stated, unless it is particularly obvious. And it is not, as my "heater problem" was designed to demonstrate. Another example: temperature in underground grottos is quite constant during the year, while outside air is much colder in winter than in summer (take a location in Russia far from the sea, to eliminate water effects such as seasonal currents etc.) - in both cases I can make an explanatory model that will use "heat capacity of air is much smaller than that of solids such as rocks" at some point, but clearly the rest of the argument matters, since opposite conclusions are met for open air and underground grotto. Tigraan Click here to contact me 12:30, 25 July 2017 (UTC)