Wikipedia:Reference desk/Archives/Science/2020 February 22

= February 22 =

Human anatomy questions.
You know how the heart is in the left chest? Well are there people born with a reverse direction, so that their heart is on their right side chest instead? Or how about our right-lung has 3 sacs and our left lung 2-sacs, can there be people born with it reversed? Heh. 67.175.224.138 (talk) 06:13, 22 February 2020 (UTC).


 * See Situs inversus Rojomoke (talk) 06:49, 22 February 2020 (UTC)
 * Note that the structure of the lungs and the orientation of the heart are correlated, so that if the heart is on the right the right lung has 2 sacs and the left has 3. --Khajidha (talk) 14:15, 22 February 2020 (UTC)
 * I wonder if I was actually referring to dextrocardia, and why is it not the same as Situs inversus. 67.175.224.138 (talk) 16:45, 22 February 2020 (UTC).
 * I'm a little amused by one of the sources in dextrocardia, telling us it is "believed" (why is belief necessary in statistical analysis? I changed that) to occur 1 out of 12,019 pregnancies. Weirdly precise. --jpgordon&#x1d122;&#x1d106; &#x1D110;&#x1d107; 19:00, 22 February 2020 (UTC)
 * Situs inversus is one type of dextrocardia.--Khajidha (talk) 19:17, 22 February 2020 (UTC)

Meteorology and vegetation
Irregardless of humidity, climates with seasons averaging 30-35°C or higher temperatures on Earth don't seem to have enough rainfall to overcome evapotranspiration or enough water vapor to maintain high humidity, and so always have a desert or scrubland landscape. But if there is enough rainfall and water vapor, could a climate averaging let's say 45°C maintain a jungle? Or is there a lower hard limit, like with body temperature and protein denaturation? 93.136.62.99 (talk) 19:20, 22 February 2020 (UTC)
 * Amazon rainforest has 27° C year average with max registered temperature over 44° C, Bangkok monthly average is minimum 21° C in November, max 35° C in April. World rainforest average vary between 21° and 30° C. "The optimum temperature for photosynthesis is 77°F (25°C). (Plants growing in a CO2 enriched environment thrive in slightly warmer conditions-82°F (28°C.)"
 * And it seems that no plant with leaves can grow when the temperature exceeds permanently 90° F, that is about 32° C.
 * That said, I'm not sure that deserts have not enough humidity (and vegetation) just because they are so hot, but they are possibly so hot (at least during the day) also because they have not enough humidity. 2003:F5:6F06:E500:5556:A588:A82B:6270 (talk) 21:04, 22 February 2020 (UTC) MPB
 * Very interesting! Is it known why 32°C is the limit? Does this also happen in a laboratory if they simulate a ~ 32°C dewpoint environment with sufficiently high rainfall? For example if we had a microclimate with 35 ~ 45°C daily temperatures year-round and let's say 4000 mm rainfall (or w/e is necessary to cover evapotranspiration), what kind of vegetation (if any) would we have?
 * For clarity I was talking about daily average, not average high, though yes places exist with 30°C averages and high humidity and rainfall with lush vegetation, I should've set my numbers higher. With high enough air temperatures, I suppose the reason you can't get both high humidity and rainfall is because there's only so much water vapor on Earth and apparently no process to draw so much of it into one place, but I wonder if you could (or if you were on a hotter and wetter planet), would rainforests form there or would it even be physiologically too hot for the form of plant life we know. 93.142.87.124 (talk) 23:45, 22 February 2020 (UTC)
 * About the reason of the limit I found this explanation: "At a temperature above 104 degrees Fahrenheit – 40 degrees Celsius – the enzymes that carry out photosynthesis lose their shape and functionality, and the photosynthetic rate declines rapidly". So the answer to your question seems to be that green plants as we know them could not live on your hot planet (but maybe photosynthetic enzymes capable of functioning at higher temperature are possible, even if it was not necessary for our green plants to develop them. See e.g. the DNA Polymerases from yeast, some of which can already denaturate at 35° C, and the DNA Polymerase from Archaea, which functions best at 75-80° C and does not denaturate even at 95° C)
 * To the other point: most deserts on our planet are deserts not really because there is not enough water vapor on Earth, but because geography and specially mountain chains and prevailing winds prevent very humid air from reaching them or from condensing into rain above them if they do. For this reason for example you find on the western side of the Andes the Atacama Desert, one of the driest places on Earth. This is due to the very cold Pacific Ocean and a dominant high pressure anticyclone west off the coast, together with the Andes chain blocking the western wet winds and forcing them to discharge all their humidity onto the regions of the Atlantic side, like Mato Grosso and Amazon rain forests. 2003:F5:6F06:E500:5556:A588:A82B:6270 (talk) 01:25, 23 February 2020 (UTC) MPB
 * What I wanted to say is that if you want a climate that's very hot and also humid, you need a very high dewpoint, and the dewpoint is very nearly a function of water vapor concentration. And there's apparently not enough water vapor or no strong enough air currents to amass such water vapor concentrations anywhere on Earth to have a climate that regularly reaches 40°C dewpoints for example. If there were, dry climates would still exist and form as you describe, I was really just thinking that the Earth is not wet enough for this kind of extreme humidity to regularly happen in places like the Amazon or Persian Gulf.
 * Regarding plants, that's interesting. I was hoping this wouldn't be the case but I suppose I should've expected it considering I know it happens to warm-blooded animals. I wonder if these plants could still be green. Judging from this link I found on Duckduckgo chlorophyll might still be useful at 45°C. 93.142.87.124 (talk) 02:07, 23 February 2020 (UTC)
 * Rain falls from clouds. To get high rainfall, you need high cloudcover. Clouds reflect sunlight back into space, which has a cooling effect, so a place with high cloudcover cannot be much hotter than 30°C average (unless you make the sun more powerful or increase the greenhouse effect). So precisely as 2003:F5 says, deserts are hotter than rainforests because they are drier, they are not drier because they are hotter. PiusImpavidus (talk) 11:41, 23 February 2020 (UTC)

Sword-breaking during cashiering
Is a sword or a similar blade weapon that easy to break during cashiering (eg. by snapping on a knee), given they are reportedly made durable and hard to break? 212.180.235.46 (talk) 22:43, 22 February 2020 (UTC)
 * Yes! Swords (US Civil War era) were working swords and were made hard and sharp - which does tend to imply brittle, particularly with the simple non-alloy high carbon steels of the period. The best were forge-welded to give a composite structure which was much more resilient (this goes back to the Viking period), but by the Civil War they had simplified most of them to homogeneous industrial steel and they now gained much of their strength from their shape, as something of a girder in cross section. They were sold as 'modern' and with all the superiority that implied, but in fact they were more fragile. For stresses edge-on, the blade was deep and strong. For bending sideways across narrow section, they could indeed snap. This was particularly noted in Japan post 1868, where the kyū guntō was a new Westernised design, with Western mounts (i.e. the grip, hand guard and purely single handed use). Many of the best swords of that style though were old blades, re-mounted, and following the old (and superior) construction techniques.
 * See maraging steel for a modern solution to making fencing foils safer, by resisting this snapping. Andy Dingley (talk) 23:59, 22 February 2020 (UTC)


 * Yes, but there could be an element of theatrical cheating; see this account of the notorious cashiering of Alfred Dreyfus in 1894:
 * "To prepare for stripping the prisoner of his insignia of rank, the prison tailor yesterday removed all the buttons and stripes from Dreyfus’ tunic, the red stripes from his trousers and the regimental number and braid from his collar and cap. These were all replaced with a single stitch so that they could be torn away readily. The condemned man’s sword was also filed almost in two, in order that it might be easily broken. The Adjutant’s quick movement and apparent effort in breaking the sword was consequently mere pretense, as only a mere touch was necessary."
 * The same article also mentions Francis Mitchell, in 1621 the last English knight to be publicly degraded, who had his sword broken over his head. Alansplodge (talk) 12:28, 23 February 2020 (UTC)
 * Good point, but I don't know to what extent that went on. Also the only broken sword I have is a French cabbage-chopper of around that period (bit earlier), with a crack in it. An infamously poor sword for just that sort of failure.Andy Dingley (talk) 13:01, 23 February 2020 (UTC)
 * Still, I expect you wouldn't want to wait until the big moment to find out if it was going to break or not. Imagine the sniggering in the ranks... Alansplodge (talk) 15:58, 23 February 2020 (UTC)
 * How far do you go? Half-saw Marie Antoinette's head off the night before, in case the guillotine sticks?  You can break such a sword easily enough, although you might need a Pioneer Sergeant to do it with some grunting, rather than getting an adjutant's gloves dirty. Andy Dingley (talk) 16:41, 23 February 2020 (UTC)
 * Well maybe. It's always harder to prove that something didn't happen, than to prove that something did. Alansplodge (talk) 18:09, 24 February 2020 (UTC)

Meteorology and vegetation
Irregardless of humidity, climates with seasons averaging 30-35°C or higher temperatures on Earth don't seem to have enough rainfall to overcome evapotranspiration or enough water vapor to maintain high humidity, and so always have a desert or scrubland landscape. But if there is enough rainfall and water vapor, could a climate averaging let's say 45°C maintain a jungle? Or is there a lower hard limit, like with body temperature and protein denaturation? 93.136.62.99 (talk) 19:20, 22 February 2020 (UTC)
 * Amazon rainforest has 27° C year average with max registered temperature over 44° C, Bangkok monthly average is minimum 21° C in November, max 35° C in April. World rainforest average vary between 21° and 30° C. "The optimum temperature for photosynthesis is 77°F (25°C). (Plants growing in a CO2 enriched environment thrive in slightly warmer conditions-82°F (28°C.)"
 * And it seems that no plant with leaves can grow when the temperature exceeds permanently 90° F, that is about 32° C.
 * That said, I'm not sure that deserts have not enough humidity (and vegetation) just because they are so hot, but they are possibly so hot (at least during the day) also because they have not enough humidity. 2003:F5:6F06:E500:5556:A588:A82B:6270 (talk) 21:04, 22 February 2020 (UTC) MPB
 * Very interesting! Is it known why 32°C is the limit? Does this also happen in a laboratory if they simulate a ~ 32°C dewpoint environment with sufficiently high rainfall? For example if we had a microclimate with 35 ~ 45°C daily temperatures year-round and let's say 4000 mm rainfall (or w/e is necessary to cover evapotranspiration), what kind of vegetation (if any) would we have?
 * For clarity I was talking about daily average, not average high, though yes places exist with 30°C averages and high humidity and rainfall with lush vegetation, I should've set my numbers higher. With high enough air temperatures, I suppose the reason you can't get both high humidity and rainfall is because there's only so much water vapor on Earth and apparently no process to draw so much of it into one place, but I wonder if you could (or if you were on a hotter and wetter planet), would rainforests form there or would it even be physiologically too hot for the form of plant life we know. 93.142.87.124 (talk) 23:45, 22 February 2020 (UTC)
 * About the reason of the limit I found this explanation: "At a temperature above 104 degrees Fahrenheit – 40 degrees Celsius – the enzymes that carry out photosynthesis lose their shape and functionality, and the photosynthetic rate declines rapidly". So the answer to your question seems to be that green plants as we know them could not live on your hot planet (but maybe photosynthetic enzymes capable of functioning at higher temperature are possible, even if it was not necessary for our green plants to develop them. See e.g. the DNA Polymerases from yeast, some of which can already denaturate at 35° C, and the DNA Polymerase from Archaea, which functions best at 75-80° C and does not denaturate even at 95° C)
 * To the other point: most deserts on our planet are deserts not really because there is not enough water vapor on Earth, but because geography and specially mountain chains and prevailing winds prevent very humid air from reaching them or from condensing into rain above them if they do. For this reason for example you find on the western side of the Andes the Atacama Desert, one of the driest places on Earth. This is due to the very cold Pacific Ocean and a dominant high pressure anticyclone west off the coast, together with the Andes chain blocking the western wet winds and forcing them to discharge all their humidity onto the regions of the Atlantic side, like Mato Grosso and Amazon rain forests. 2003:F5:6F06:E500:5556:A588:A82B:6270 (talk) 01:25, 23 February 2020 (UTC) MPB
 * What I wanted to say is that if you want a climate that's very hot and also humid, you need a very high dewpoint, and the dewpoint is very nearly a function of water vapor concentration. And there's apparently not enough water vapor or no strong enough air currents to amass such water vapor concentrations anywhere on Earth to have a climate that regularly reaches 40°C dewpoints for example. If there were, dry climates would still exist and form as you describe, I was really just thinking that the Earth is not wet enough for this kind of extreme humidity to regularly happen in places like the Amazon or Persian Gulf.
 * Regarding plants, that's interesting. I was hoping this wouldn't be the case but I suppose I should've expected it considering I know it happens to warm-blooded animals. I wonder if these plants could still be green. Judging from this link I found on Duckduckgo chlorophyll might still be useful at 45°C. 93.142.87.124 (talk) 02:07, 23 February 2020 (UTC)
 * Rain falls from clouds. To get high rainfall, you need high cloudcover. Clouds reflect sunlight back into space, which has a cooling effect, so a place with high cloudcover cannot be much hotter than 30°C average (unless you make the sun more powerful or increase the greenhouse effect). So precisely as 2003:F5 says, deserts are hotter than rainforests because they are drier, they are not drier because they are hotter. PiusImpavidus (talk) 11:41, 23 February 2020 (UTC)
 * Yes, depending on how you define "desert", you can include polar deserts. They have low precipitation, but due to latitude or altitude are not hot. --47.146.63.87 (talk) 02:58, 28 February 2020 (UTC)