Wikipedia:Reference desk/Archives/Science/2017 January 20

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January 20

Blood and wounds

Why is coagulated blood the best protective layer for a wound to crust (to skin over)?

Additionally, what about blood from another body, placed on the wound that tries to skin over? 185.27.105.90 (talk) 08:34, 20 January 2017 (UTC)

Since coagulation developed through evolution, it doesn't need to have anything do do with being the best. It's just what we got. Makes sense - coagulated blood is tough, but a bit flexible, and it's right there anyway after a wound. As for someone else's blood? Sounds like an excellent way to spread a bloodborne infection. Better to stick with sterile methods of wound bandaging. Someguy1221 (talk) 10:25, 20 January 2017 (UTC)

Per Someguy1221, evolution doesn't produce the "best" in a Panglossian sense, which would imply that it was under some intelligent control. Evolution produces better traits, in a very rough sense. It actually produces entirely random traits, and over time, the better traits will tend to edge out the worse traits, but there's no plan involved. Stuff happens, and if it works better than what is already existing, it tends to keep working until it isn't better anymore. --Jayron32 13:11, 20 January 2017 (UTC)

Given an infinite amount of time, evolution should produce the best possible result. But, of course, we don't have an infinite amount of time. StuRat (talk) 16:35, 20 January 2017 (UTC)

That might be true if the world was a constant. It is not. Rather, it is constantly changing and so there is always another "best" solution just around the corner. DrChrissy ^(talk) 19:01, 20 January 2017 (UTC)

Yes, you would need an infinite amount of time at each set of conditions to get the perfect solution for that set. StuRat (talk) 02:27, 21 January 2017 (UTC)

I believe that you are mistaken. Evolution typically only finds the local maximum. For example, squid eyes have the blood vessels on the back side, while human eyes have them on the front side, causing blind spots and other less-than-ideal effects on vision. Evolution is very unlikely to result in human blood vessels moving to the rear of the retina, because there is no minor change that cause a minor improvement. Another classic example is the panda's thumb. --Guy Macon (talk) 19:05, 20 January 2017 (UTC)

Given an infinite amount of time, you would eventually get "mutation combos", where many traits change at once. In the case of the eye, all the mutations required to move the blood vessels to the other side would eventually occur all at once, in a single individual. (Yes, it's like monkeys typing at random eventually typing a work by Shakespeare, in that it would take very long time.) StuRat (talk) 02:27, 21 January 2017 (UTC)

Are you suggesting that one day a horse-like female gave birth to a baby that had a 2 m neck and suddenly we had giraffes? DrChrissy ^(talk) 19:13, 21 January 2017 (UTC)

No, but given an infinite amount of time it would happen. You seem to be unfamiliar with the concept that over an infinite time period anything that can possible happen will happen, even incredibly unlikely events. See infinite monkey theorem. StuRat (talk) 01:39, 22 January 2017 (UTC)

You seem to be unfamiliar with the concept that the evolutionary pressures on an animal are in eternal flux - there are no constants. Comparing evolution with the infinite monkey theorem is flawed because the latter has a constant - the works of Shakespeare. Evolution does not work in this way. It does not have a template which it is working towards. There are many other (biological) factors to be considered. For example, in the farcical example I gave above about a horse-like animal giving birth to a giraffe, this simply would not happen because offspring with a 2m neck would kill the mother before birth. So, no giraffes from a one-off series of multiple mutations. So are you suggesting that if a suit of metal armour is the best protective mechanism, given infinite time, prey animals would evolve a mechanism of producing a metal suit of armour? DrChrissy ^(talk) 18:43, 22 January 2017 (UTC)

I had a totally different interpretation of the question, I thought it was just about how wounds heal, and didn't get hung up on "best". Rather than talk of evolution, I'd suggest OP read up on scab formation and wound healing. Here [1] is a very good general reference on the process of wound healing and treating wounds, that is more reliable than our articles. SemanticMantis (talk) 17:46, 20 January 2017 (UTC)

For the question "Can we use blood from person A to help heal a wound on person B?" -I'm not sure, but it's certainly not impossible, though there may be risks, as mentioned above. However, there is some precedent for using a patient's own processed blood to tread wounds. Here [2] is a 2010 review article about the use of platelet-rich plasma to treat wounds, including wounding occurring as part of surgery. The "platelets initiate wound repair by releasing locally active growth factors". We do use blood transfusions between people all the time, so it's not like infectious disease completely prevents us from using one person's blood to help another. SemanticMantis (talk) 17:48, 20 January 2017 (UTC)

Blood type could matter. (That's fairly basic stuff, but I see no reason to assume the OP knows about it.) Tigraan^{Click here to contact me} 14:20, 21 January 2017 (UTC)

You also have no reason to assume I was not aware of this basic stuff (hemm...really basic...). I was only asking about coagulated blood as a protective layer for a wound that tries to heal. As for the blood type, you might assume I was asking about someone else's (coagulated) blood of the same blood type, and again: as a protective layer only. 185.27.105.90 (talk) 17:42, 21 January 2017 (UTC)

Rant by TigraanClick here to contact me 19:00, 21 January 2017 (UTC)

If you had not been aware of blood groups and none had mentioned it, you would have left just as unaware. What you consider "really basic" is known only by those who have had a decent education. I suspect that among citizens of Zimbabwe, where according to our article the literacy rate is about 85%, more have access to Wikipedia's reference desk on a smartphone with internet than to proper biology courses at school. The assymetry between assuming knowledge when there is not and the reverse (which causes in the worst case a few more bytes on Wikimedia's servers and hurt egos) justifies to assume the latter unless the question justifies it. You have described it as a "fairly basic stuff", and I only agreed. However, I don't agree with you about the assymetry: In my opinion, it's entirely symetrical. 185.27.105.90 (talk) 20:14, 21 January 2017 (UTC)

Note: The OP is fooling around with his signatures. He's now editing as 185.27.105.82 (talk · contribs) but keeps erasing that fact. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:04, 21 January 2017 (UTC)

Since the address is in a close IP range, I don't think such "anti-sockpuppetry" deserves any blame. It may be harder to follow for future page history archeologists, but it is arguably better to follow the discussion. Tigraan^{Click here to contact me} 21:25, 21 January 2017 (UTC)

Exactly.

Sincerely, my aim was "anti-sockpuppetry" (after my computer lost my first IP), just to make the discussion easy to follow. 185.27.105.90 (talk) 10:29, 22 January 2017 (UTC)

You could simply start each comment with "OP here" or words to that effect. Then there should be no confusion. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:20, 22 January 2017 (UTC)

• StuRat's claim that an infinite amount of time, even when qualified, would lead to perfection is false, a layman's simplification. Evolution is both random and historical. GM is correct that it is largely limited to local maxima. The ontogeny of an organism depends on the matter it has to work with. This is why humans still develop gill arches as embryos, even though a smart designer would have the organsof the ear and throat develop directly.

Also, there is no way for macroorganisms to develop wheels for limbs, even though they might be ideal for locomotion in certain environments.

Look at the pathway of the laryngeal nerve of the giraffe, which travels twice the full length of the neck. In short-necked animals this design fluke is not obvious, but there is no way for the giraffe to overcome this obvious imperfection given they evolved from short-necked ancesstors and are stuck with that developmental path.

Finally, the closest you come to "perfection" in palaeontological history is the dinosaurs, but the Chixulub impactor basically killed off anything over a certain mass or inability to burrow or survive in the water. No matter how well adapted Tyrranosaurus was, it wasn't evolved to handle meteoric incineration.

μηδείς (talk) 01:23, 24 January 2017 (UTC)

Dispersion of atmospheric greenhouse gases

Is it potentially feasible to disperse or dilute excessive greenhouse gases (including CO2) by releasing more oxygen/other gases to the atmosphere (and thus eventually offset the emissions to counter global warming)? Perhaps this could be done regularly. Thanks.--93.174.25.12 (talk) 13:19, 20 January 2017 (UTC)

No, because:

(a) This would produce an overall thicker atmosphere, which would itself increase global warming – all gases have some greenhouse effect, it's just that some of them, like carbon dioxide and methane, have much more effect per molecule (so to speak) than others like oxygen and nitrogen.

(b) To have any significant effect, vast quantities would be needed, far more than we could possibly generate. To dilute the present excessive carbon dioxide level (approx. 400ppm) caused (we mostly think) by human agriculture and industry back to its previous level (of approx. 200ppm – exact numbers don't matter, so don't let's quibble *), you would have to roughly double the volume of oxygen and nitrogen. Where are you going to get a whole second Earth's worth of atmosphere?

(* NB: our article takes a pre-industrial starting point of 280ppm in 1750, but recent studies suggest that farming practices since the beginning of agriculture had by that time already contributed to a significant rise, hence my taking 200ppm as a mathematically convenient approximation). {The poster formerly known as 97.81.230.195} 94.12.94.189 (talk) 15:15, 20 January 2017 (UTC)

• One might argue that if we had the magical portal that allows to conjure up oxygen and nitrogen from the netherworld and pump it into the atmosphere, atmospheric escape would allow the total mass/volume/whatever of atmosphere to stay roughly constant by sending the surplus to space. I have no idea whether that argument is actually supported by the math, but it is at least within the realm of possibilities.

Of course, the big problem is point (b) - we don't have a portal to the netherworld, nor any industrial process that emits enough gases (let alone the ones we want) to double Earth's atmosphere. Tigraan^{Click here to contact me} 16:16, 20 January 2017 (UTC)

Even if we could dilute the concentration of carbon dioxide, hypothetically by doubling the total quantity of gas in the atmosphere - the outcome would be very hard to predict. Concentration is not the only parameter that affects the greenhouse effect or the average planet surface temperature. The greenhouse effect is driven by many factors, including the total optical depth of the atmosphere at particular infrared wavelengths. Diluting the greenhouse gases, without actually reducing the total quantity, might make for some really complicated dynamics - it might redistribute where the heat goes, and where it gets reabsorbed and recirculated - but it's not clear that we can draw a straightforward conclusion about how it would affect the climate. Bluntly: diluting the CO2 concentration by increasing the other atmospheric species might make the greenhouse effect stronger, weaker, or might have no change - and that complete non-answer is probably the most scientifically accurate conclusion we can draw!

You'd have to do some very sophisticated research on atmospheric modeling to figure out what would happen; and because we have very little useful data about how hypothetical atmospheres would behave, we don't have a great wealth of data to inform our models and figure out where they go awry.

For what it's worth, I spent all weekend learning about the Skew-T/Log-P approach to plotting and analyzing weather. Here's a great resource on Skew-T Log-P Diagrams from the National Weather Service; here's the current database. Anyone want to take a stab at analyzing how concentration and total quantity of our most abundant greenhouse gas, water vapor, affects the weather? Hint: we measure both - TPW and RH - and feed both into our most accurate models, including the NAM and the HRRR....

...and even then, I can't predict with perfect certainty whether it's going to be warm or cold, wet or dry, even in the short term. As a bike commuter, this uncertainty is troublesome - as an aviator, this uncertainty is a factor in my decision-making - as a scientist, it gives me great insight into the difficulty faced by medium- and long-range climate modelers.

The take-away message is that atmospheric dynamics is non-obvious - simple stimuli yield complicated behaviors. Dramatic changes - like changing the total quantity of gas in our atmosphere - start to fall outside of our established models, and responsible scientists won't make strong predictions about what would happen if we hypothetically changed our atmosphere in a way that is so far from physical reality.

You might be able to find great resources on planetary dynamics modeling if you extend your literature survey to include scientific study of planets-other-than-Earth. Here's a fun research paper that clearly resounds in the shadows of Carl Sagan's excellent book, Pale Blue Dot, and his 1993 paper A search for life on Earth:

• Earth as an Extrasolar Planet: Earth Model Validation Using EPOXI Earth Observations (2011).

Look how hard it is to characterize a planet when you have even a few percentage points of uncertainty about its atmospheric parameters!

Nimur (talk) 20:21, 20 January 2017 (UTC)

BTW although as mentioned above simply adding more gases isn't considered a viable or useful proposition, Climate engineering via Greenhouse gas removal including Carbon dioxide removal and Carbon sequestration is at least considered potentially feasible enough to have some research. As our articles mentions, although there is some overlap with Carbon capture and storage and distinction is sometimes made between projects aiming to capture carbon dioxide or carbon once after it's released to the atmosphere versus during production. Nil Einne (talk) 22:51, 20 January 2017 (UTC)

There is no relevant dilution effect here. The gases in the atmosphere can be treated to a very good approximation as independent components, they satisfy the ideal gas law to a very good approximation, the partial pressure of each component equals the concentration (molecules per unit volume) times Boltzmann's constant times the absolute temperature. So, the CO2 in the atmosphere is not going to behave differently just because you put in a lot more oxygen or nitrogen. This means that you're not going to change the mean free path of infrared photons (they have very little interactions with diatomic molecules), so they'll still escape to space from the same mean free path into the atmosphere as before. If you instead increase the CO2 concentration, you're going to reduce this mean free path, so the photons escaping into space will on average come from higher in the atmosphere. If you then balance this energy loss with the absorbed energy from from the Sun and take into account that the escaping photons are in thermal equilibrium with the part of the atmosphere from where they are escaping and that its colder at higher altitudes, then you'll find that the temperature at the surface will increase. Count Iblis (talk) 00:33, 21 January 2017 (UTC)

...and by direct application of the Stefan-Boltzmann equation in tandem with the solar constant, the effective planetary temperature of Earth is guaranteed to oscillate around a stable equilibrium irrespective of any other atmospheric condition and ... hence global warming is a complete myth! In case this isn't obvious, I'm being facetious. Global climate does change - and we know it changes - and these changes are hard to predict because they depend on so many deep and non-obvious interconnections between physical and chemical processes. We can not draw simple conclusions about planet-scale behaviors by naively applying equations from high-school physics. The atmosphere is really complicated, and the experts who spend their careers studying it generally agree that our models are only accurate within certain bounds. The OP asked us for references on atmospheric modification. I don't think you'll be able to find a single peer-reviewed paper that attempts to predict Earth surface temperature trend after applying some hypothetical process to dilute the greenhouse gas species by anthropogenically increasing the quantity of inert gas species. This kind of modeling work is interesting to geologists, planetary scientists, and so on; and in a world where all our information about the atmosphere comes from a single pixel, we can make fantastic speculations about atmospheric chemistry and temperature! But we have to be responsible: when we speculate about an environment so different from the empircal observations of our own atmosphere, our error bars are huge. Per the paper I linked earlier, if you use overly-simplified physics for a hypothetical atmosphere, your temperature estimates can and do err by hundreds of kelvins. If we model Earth's surface temperature dynamics for the proposed hypothetical atmosphere, the surface temperature will probably fall somewhere between zero and a thousand kelvins, if there is even a planetary surface anymore! One cannot casually change the stoichiometry of an entire planet! As we already know, Earth's climate is dramatically affected even by a tiny atmospheric change, such as the carbon-dioxide emitted by normal biological human behaviors - including, but not limited to, technological industrialism. We don't know what would happen if our anthropogenic atmospheric changes were millions of times bigger - and our best scientists don't even try to predict it.

Nimur (talk) 18:44, 22 January 2017 (UTC)

Mathematical physicist Freeman Dyson, FRS questions the mathematical models used to predict global warming on the grounds that necessary data to support global warming are not available, having created similar models to estimate the Earth's environment after a nuclear war for thirty years while working with Los Alamos National Laboratory and the JASON group of the Institute for Defense Analysis. However, he agrees that continued use of petroleum and other hydrocarbons from drilling is bad for the environment and has proposed intensive and vast planting of fast-growing trees to sequester carbon dioxide from the environment. He also predicts that these trees can be genetically altered to serve as an interim fuel source to replace petroleum and natural gas. loupgarous (talk) 21:15, 24 January 2017 (UTC)