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September 9

Covid question

We know that if a vaccinated person catches Covid, the risk of long Covid or complications is much lower compared to if an unvaccinated person catches Covid.

But is catching Covid from a vaccinated person less dangerous than catching Covid from an unvaccinated person?

Logic is the virus would be weakened by the vaccinated person's immune system.

--219.75.107.21 (talk) 09:36, 9 September 2021 (UTC)

The immune system doesn't weaken the virus per se: the virus particle should be exactly the same whether it comes from an unvaccinated person or a vaccinated breakthrough case. Virus particles are made new each time, it's not like they're "worn out" from fighting the vaccinated person's immune system. However, there's evidence that people who've been vaccinated tend to produce less virus and for a shorter period of time, figure 1 of this pdf. I can't find the specific graph I'm thinking of though annoyingly. It shows virus levels produced dropping much faster in vaccinated people on average than unvaccinated. How much this matters depends on the question of exactly how many virus particles are needed to infect someone.

One scenario people worry about with vaccines is Marek's disease, in which it's been suggested that a weak vaccine used on battery chickens has encouraged the evolution of more aggressive virus variants to beat the effect of vaccination. However, it's important to note that i) the vaccine still works very well in stopping the disease, and ii) this is a one-off, there are dozens and dozens of other vaccines which have been used for decades without seeing anything like this kind of effect. Although I haven't found a source specifically pointing to this, my guess is that a major factor there is the tremendously confined nature of battery farming, that squashing huge numbers of chickens together makes it easier for the virus to spread from infected chickens to uninfected ones quickly. Blythwood (talk) 11:03, 9 September 2021 (UTC)

What's a battery chicken? ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:05, 9 September 2021 (UTC)

See Battery cage. --Wrongfilter (talk) 11:23, 9 September 2021 (UTC)

On that point, challenge studies have started in Britain to study questions like this. They seem to be way more altruistic than I to allow a pandemic infection on purpose. Imagine Reason (talk) 20:53, 11 September 2021 (UTC)

Link to uk gov PR. I would imagine that the protocol or/and ethics approval includes some risk assessment, but I could not get my hands on it. (In my opinion, such a document should be public, or at least accessible before registering to be a subject, but I could not find it on the website.)

The argument seems to be that a challenge trial will allow much quicker development of vaccines/treatment and therefore we are in a trolley problem situation, where action might harm a few specific individuals to save many more. I do not really buy it; by the same argument, one could argue to force prison inmates to register for that challenge trial, which would be highly unethical by post-1945 standards. By the way, Human_challenge_study#Ethics is a rather poor section at the moment. Tigraan^{Click here for my talk page ("private" contact)} 09:27, 13 September 2021 (UTC)

September 10

Why did NASA planned JWST deployment for 3 weeks process?

Here it says: Once in position, JWST will go through the process of deploying its sunshade, mirror, and arm, which will take around three weeks.

Why three weeks instead of deployment right after entering into Halo orbit? Rizosome (talk) 00:22, 10 September 2021 (UTC)

It's not saying that they're waiting 3 weeks and then they begin the deployment; it's saying the deployment takes 3 weeks to complete. The deployment process begins a few hours after launch, long before the telescope reaches its final halo orbit, as the diagram shows in the article that you linked to. Part of the time required for the process is apparently waiting for the telescope to cool down after the sun shade is deployed. There's a more detailed timeline here. CodeTalker (talk) 01:04, 10 September 2021 (UTC)

Apollo failure plan

If Armstrong & Aldrin (or any pair of their successors) could not leave the Moon, I guess they'd carry on doing whatever science they could until they ran out of air or water, and then open their helmets to vacuum; but has anyone in a position to know said anything publicly? —Tamfang (talk) 00:37, 10 September 2021 (UTC)

I think the contingency plan for Apollo 11 was to close down communications. The scientific part of the mission was extremely limited, after quickly deploying a seismometer and a laser ranger and collecting a few rocks to be analyzed back on Earth, there was nothing left to do for Armstrong and Aldrin in the way of science.  --Lambiam 08:23, 10 September 2021 (UTC)

Plenty of hits if you google "apollo failure plan". I don't know how much is accurate. This https://www.space.com/if-apollo-11-astronauts-died-nixon-contingency-speech.html mentions a contingency speech by Nixon; this was also mentioned in an Apollo documentary I saw recently on the Smithsonian TV channel. Thankfully, the Apollo missions were successful. I remember in the Australian news, speculation that Luna 15 might have been an emergency escape plan. --TrogWoolley (talk) 09:48, 10 September 2021 (UTC)

Thanks to MIT, we can hear Nixon deliver that speech. —Tamfang (talk) 01:01, 14 September 2021 (UTC)

I'm not sure they'd need to expose themselves to vacuum as both their spacesuits and the lander itself both used recycler technology to maintain a breatable atmosphere. So if the Oxygen supply ran out before the scrubber the astronauts would have lost conciousness and died due to hypoxia without the unpleasant sensation associated with asphyxiation caused by hypercapnia. 2A01:E34:EF5E:4640:9CF5:EEC0:F336:157F (talk) 13:49, 10 September 2021 (UTC)

They came very close to being stuck on the Moon. Count Iblis (talk) 17:07, 10 September 2021 (UTC)

I think they had backup methods. I think they could simply turn some valves by hand to start the engine. Bubba73 ^{You talkin' to me?} 04:05, 12 September 2021 (UTC)

If a freak meteorite destroyed the CM at touchdown how far from the landing site could they get, if they decided on a whim to make the distance record as hard to break as possible? Is the rover faster with one man or two? (for traction or balance or something) Could the throttle control be tied, taped or jammed in the "on" position? Sagittarian Milky Way (talk) 21:36, 10 September 2021 (UTC)

Perpetual motion of water

Greetings!

I found this video of perpetual motion (here) in which 4 watering cans are situated so that siphoning water through the spout of one can into the filling hole of another permits one to link a a number of cans so that they fill one another without any intervention and will continue to do so ad infinitum unless disturbed.

Why can't we harness the falling water with a water wheel and draw power from such a system? If we did, it seems we'd be drawing power from a perpetual motion machine, which seems to be a violation of the first law of thermodynamics.

Thanks!

DRosenbach ^{(Talk | Contribs)} 13:00, 10 September 2021 (UTC)

The first law of thermodynamics tells us this cannot be a source of perpetual motion. There is some "trick" involved as can be seen in the video - notice that when the operator sets the water in the first 3 watering cans into motion, he then steps backwards and stops adding water to the 1st can but the 1st can continues to pour water into the 2nd can, even though water hasn't started flowing from the 4th can into the 1st can! Notice that after the operator first stops adding water to the 1st can the water level in that can remains completely full even though water is pouring out of the 1st can into the 2nd. Some sort of trick must be involved because how could water be flowing from the 1st can into the 2nd when no water is yet flowing into the 1st from the 4th? The trick may be that there is a cut in the filming which is not detectable to anyone watching the video, but during the cut some other source of water (not visible to the viewer) is connected to the 1st can, and then filming resumes. Dolphin (t) 13:24, 10 September 2021 (UTC)

Funny, when I overfill a watering can, the extra water just spills out of the filling hole. Water only starts to come out of the spout if I tilt the can. The person in the video seems to be playing with a different physics ruleset. --Amble (talk) 22:37, 10 September 2021 (UTC)

Any holes below your filling hole? Sagittarian Milky Way (talk) 01:16, 11 September 2021 (UTC)

No, which is why pouring water in the filling hole of a real watering can sitting flat on the ground doesn’t cause water to come gushing out of the higher spout, as it appears to do in the video. —Amble (talk) 02:21, 11 September 2021 (UTC)

I wonder if there's a hosepipe hidden inside one of the watering cans feeding out the spout. Sort of like Brian Wansink's (supposed) bottomless soup bowl experiment. Blythwood (talk) 03:48, 11 September 2021 (UTC)

I think it was probably done with video editing. But if not, maybe a small submersible pump hidden inside the can? --Amble (talk) 22:13, 11 September 2021 (UTC)

Are short codons possible?

I just can't seem to find any references for this. My question is relatively simple. Is it possible for a codon to consist of less than three bases? Earl of Arundel (talk) 13:29, 10 September 2021 (UTC)

I'm not sure I understand your meaning. Do you mean "Could someone imagine a fictional biological system that used two- or one-base codons" or do you mean "are there examples of exotic forms of life that use two- or one-base codons that we know about"? --Jayron32 13:33, 10 September 2021 (UTC)

Precisely, the latter. And moreover what might happen if the DNA/RNA "machinery" actually did encounter a shorter snippet at the end of a chain? Eg. Would it destroy the strand, ignore the snippet, make an amino acid anyway, just get confused? Earl of Arundel (talk) 13:50, 10 September 2021 (UTC)

Our Genetic code article has a section on variants of the code, but the variants mostly involve changing the meaning of a small number of 3-base codons. The article says Despite these differences, all known naturally occurring codes are very similar. The coding mechanism is the same for all organisms: three-base codons, tRNA, ribosomes, single direction reading and translating single codons into single amino acids. (emphasis added) CodeTalker (talk) 20:12, 10 September 2021 (UTC)

Of course it isn't much of a stretch to imagine some rare cases where physical damage to a strand of DNA (due to radiation or what have you) could however cause that sort of thing to happen. Surely the cells have some way of dealing with those kinds of errors. Earl of Arundel (talk) 15:17, 11 September 2021 (UTC)

Not very good ways; see frameshift mutation, Earl of Arundel. HLHJ (talk) 20:32, 12 September 2021 (UTC)

I see. So in some extreme cases it really can cause serious problems. Well I guess that answers my second question! Earl of Arundel (talk) 15:22, 13 September 2021 (UTC)

Our Codon degeneracy article notes the important point that the number of codons sets a limit on the number of different amino acids that can be encoded. Going the other way (and drifting off the original specific question), doi:10.1093/nar/gnj003 demonstrates development of four-base codons. DMacks (talk) 15:26, 11 September 2021 (UTC)

Okay, so cells are often able to mitigate for these irregular chains, but mutations sometimes do occur instead. Well that makes sense. And thank you for the links! Earl of Arundel (talk) 19:45, 11 September 2021 (UTC)

What if they'd used respirators?

[1] Imagine Reason (talk) 14:40, 10 September 2021 (UTC)

Is there a question? --OuroborosCobra (talk) 17:54, 10 September 2021 (UTC)

Inaccessible link. --CiaPan (talk) 20:54, 10 September 2021 (UTC)

9/11 Survivors Are Still Getting Sick Decades Later: ‘Am I Next?’ It's an interesting question, but is either trivial or calls for speculation, which we won't do here. Certainly hazmat suits would have resulted in fewer people being exposed to toxins and thus fewer long-term problems. --jpgordon^{𝄢𝄆𝄐𝄇} 22:26, 10 September 2021 (UTC)

I'd have thought that there'd be a lot of science done now on the effects of building destructions on air quality and the usefulness of filtering masks in such air. Imagine Reason (talk) 20:49, 11 September 2021 (UTC)

Perhaps it doesn't require much research to conclude that breathing building debris is bad for you. This article from the American Lung Association sums up:

1) Most people who had intense early exposure did sustain around a 10 percent reduction in lung function and this reduction was sustained after more than a decade. 2) Some of the effects could have been reduced with widespread use of personal protective respiratory equipment. 3) Persons most affected generally had pre-existing lung problems. Smokers were harder hit than non-smokers.

Alansplodge (talk) 17:15, 12 September 2021 (UTC)

See respirator. Emergency responders often did use elastomeric respirators. Filtering out particulates can be done with a mechanical filter respirator (or, less efficiently, with almost any type of cloth mask), but filtering out gaseous toxins requires different types of chemical cartridges for different chemicals. Since the NYT does not make it clear what it is that is causing the symptoms, and OuroborosCobra did not specify the type of respirator, it's not possible to predict the exact effects. The Lung Association article mentions alkaline dust and silica dust (which can be kept out with a mechanical filter, since they're solid dust) and acrolein (which can be kept out with a mechanical filter if it's in liquid droplets, but it's fairly volatile, and so some of it will have been a gas that can go through a mechanical filter). But there were obviously lots of other chemicals, depending on when you were where. HLHJ (talk) 20:29, 12 September 2021 (UTC)

Why would I have specified anything, including respirator type? I responded to the fact that the original poster had not actually posed a question in starting this discussion. --OuroborosCobra (talk) 14:55, 13 September 2021 (UTC)

Apologies, OuroborosCobra; I meant to ping Imagine Reason, the OP, and messed up. Obviously this is because you have a boring name and not a vivid, evocative one like four random letters. HLHJ (talk) 03:56, 15 September 2021 (UTC)

Do vaccine booster shots need to be same as original vaccine?

Not a request for medical advice, but rather a general question. When a vaccine booster shot is given, does it need to be the same as the original vaccine? COVID vaccine booster shot is what brings this to mind (if someone had the Pfiser vaccine originally, can they get Moderna as the booster?) but also curious about other vaccines that require booster shots. RudolfRed (talk) 20:12, 10 September 2021 (UTC)

By "booster" I mean, for example, a third shot of a two-shot series given some time (6+ months) after the original. RudolfRed (talk) 20:22, 10 September 2021 (UTC)

See Mix-and-match COVID vaccines trigger potent immune response (19 May 2021). Alansplodge (talk) 21:58, 10 September 2021 (UTC)

As to COVID vaccines, the three vaccines principally used here in Canada fall into two major types: the Pfizer and Moderna vaccines are mRNA vaccines while AstraZeneca's is a viral vector vaccine. The Advisory Committee on Immunization recommended in June that "When the first dose in a COVID-19 vaccine series is an mRNA vaccine, the same mRNA vaccine product should be offered for the subsequent dose if readily available. When the same mRNA vaccine product is not readily available, or is unknown, another mRNA COVID-19 vaccine product recommended in that age group can be considered interchangeable and should be offered to complete the series"; and that "When the first dose in a COVID-19 vaccine series is the AstraZeneca/COVISHIELD vaccine, either the AstraZeneca/COVISHIELD vaccine or an mRNA vaccine product may be offered for the subsequent dose to complete the series, however an mRNA vaccine product is preferred as a subsequent dose due to emerging evidence including the possibility of better immune response...". As far as I know this advice hasn't changed. --184.144.99.72 (talk) 04:29, 11 September 2021 (UTC)

As a majority of COVID vaccines is based on the full length spike protein (or even on the whole virus) they are probably interchangeable. Ruslik_Zero 20:16, 11 September 2021 (UTC)

Thanks, everyone, for the information and replies. RudolfRed (talk) 21:36, 11 September 2021 (UTC)

September 11

Which ship would be drowned faster in case of raging / stormy sea?

Which ship would be drowned faster in case of raging / stormy sea, a ship that has a heavy load or the similar ship that has lighter load? I'm not sure if a load plays a positive role in such a situation or not.--ThePupil (talk) 00:07, 11 September 2021 (UTC)

The Book of Jonah says heavier but take that with a grain of salt. Completely different technologies from that fable. Sagittarian Milky Way (talk) 01:14, 11 September 2021 (UTC)

Larger vessels, be they in the sea or the air, can usually handle storms better than smaller ones. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:23, 11 September 2021 (UTC)

The question was about similar ships, not smaller and larger ones. Cargo ships are designed to be able to operate in a "raging/stormy sea" if necessary: if they sink it's because something went wrong, for example a hatch cover breaking or coming unlatched, leading to flooding of a hold. Further, a lightly loaded ship may contain ballast that would affect the scenario. I don't think it's reasonable to speculate about specific possibilities: there is too much room for variation. --184.144.99.72 (talk) 04:37, 11 September 2021 (UTC)

The most likely doom scenario in a storm is the ship capsizing, which can happen if it is hit broadside by a large wave. The stability of the ship is related to the height of the centre of mass of the vessel together with its load. Relative to the height of the centre of mass of the unloaded vessel, the centre of mass of the loaded vessel will be higher if the load is all on deck, and lower if stowed in a below-deck cargo hold. So depending on how the ship is loaded, it may be less stable or more stable than when carrying no load. If the vessel is designed to be self-righting, a lower centre of mass (on the upright vessel) also supports its righting after capsizing, while a top-loaded ship, even if designed to be self-righting, may not overcome the capsizing – which can also be triggered by the load shifting on deck if it is not securely stowed. Capsizing does not necessarily imply that the ship will sink; the air that remains trapped, as well as any cargo whose density is less than that of the surrounding water, may provide enough buoyancy to keep it afloat.  --Lambiam 08:56, 11 September 2021 (UTC)

With a heavier load, the ship will be deeper in the water, with a smaller freeboard. That means that it will take smaller waves or list before the water washes over the deck, endangering the ship. Most capsizing ships suffered from shifting cargo, moving the centre of mass sideways, giving positive feedback to a list. Also see free surface effect. If the cargo holds are empty, this can't happen. If the cargo holds are full by volume, this can't happen either, but if full by mass well before they are full by volume (dense cargo), shifting cargo can be a large contributor to sinking. The cargo also increases the moment of inertia of the ship, but what effect this has on safety depends on the details. PiusImpavidus (talk) 10:38, 12 September 2021 (UTC)

Why can't they make the decks slightly sloped to a wall-less edge railing for drainage, the doors, bridge, inside etc watertight and anything that can't be put on snorkels? Similar to how modern lifeboats look more like enclosed pods than open rowboats. Sagittarian Milky Way (talk) 03:32, 14 September 2021 (UTC)

What's the point of poison fruits ?

What's the point of poison fruits if its main aim is to spread seeds by birds/animals? Rizosome (talk) 00:30, 11 September 2021 (UTC)

Most fruits have been evolved to be consumed by one or a few particular species, to whom they are not poisonous: a given substance can be non-poisonous (or distasteful) to some species of birds or animals, but poisonous (or distasteful) to others such as humans. Fruits that are poisonous to humans are not poisonous to the species that normally eat and thus propagate them in the wild.

Until very recently, in evolutionary terms, humans were so few in number compared to other species of animals and birds that it is unlikely any fruit evolved by natural selection to be non-poisonous specifically to humans. However, since agriculture was invented, humans have selectively bred some fruits, a process called artificial selection, to make them less or non-poisonous. Also, some fruits poisonous to humans in an unprepared state may be rendered edible by various methods of preparation. {The poster formerly known as 87.81.230.195} 90.200.67.3 (talk) 01:07, 11 September 2021 (UTC)

A great example is poison ivy. Although the urushiol is quite toxic to most people, birds can eat the berries with impunity. A similar example is with fruiting bodies that contain capsaicin (e.g. hot peppers) - the hot spice is meant as a deterrent, but again it is not detected by birds at all, who eat it without sensing the heat. As our article notes, in the wild, birds are the primary means of seed transport. On the other hand, we can eat chocolate with impunity while many mammals suffer from theobromine poisoning if they do. Matt Deres (talk) 14:38, 13 September 2021 (UTC)

Strictly speaking, urushiol isn't toxic in the sense of being poisonous (so "poison ivy" is a bit of a misnomer) - instead, it causes harm by producing a damaging allergic reaction. PaleCloudedWhite (talk) 21:00, 13 September 2021 (UTC)

Bear in mind that there is no "point" to evolution. It's a natural process. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:27, 11 September 2021 (UTC)

For "point" read "advantage". —Tamfang (talk) 01:37, 14 September 2021 (UTC)

By happenstance, not by conscious design. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:34, 14 September 2021 (UTC)

Which I think is covered by definitions 4.3 to 4.4 here. Iapetus (talk) 08:32, 15 September 2021 (UTC)

See also I have always wondered: why are some fruits poisonous?. Alansplodge (talk) 16:43, 11 September 2021 (UTC)

Lewis acids/base questions.

What are some examples of Lewis acids with basic pHs? Googling Lewis acids with basic pH didn't return anything that specific. So it recently occurred to me that Lewis bases can have acidic pHs, an example is hydrogen peroxide. Although hydrogen peroxide could be an Arrhenius acid, in actuality it is unstable in alkaline solutions rendering it not happening. So hydrogen peroxide is more of a Lewis base than a Arrhenius acid (thus Lewis acid). But its pH is in the weak acid range. Are there any other examples like this, as well as Lewis acids with weak-base pH? Thanks. 67.165.185.178 (talk) 05:38, 11 September 2021 (UTC).

Are you asking about amphoterism? DMacks (talk) 15:28, 11 September 2021 (UTC)

Sure. Should amphoterism be mostly about something that can be a Lewis acid and a Lewis base, or say, a Lewis acid and a Arrhenius base, and Lewis base and a Arrhenius acid? 67.165.185.178 (talk) 15:53, 11 September 2021 (UTC).

Aluminium hydroxide is a Brønsted–Lowry base, so an aqueous solution of it would have a high pH, but it also acts as a Lewis acid. --OuroborosCobra (talk) 21:40, 11 September 2021 (UTC)

September 12

heart condition from joke

There is a corny joke/prank that kids play on each other. You shake the other person's hand, but while doing so, you give it a series of pulsating squeezes, like a heartbeat, and say "Hi, I'm from the heart association". (I told you that the joke was corny).

I learned this joke in school and tried it on my dad, who got a chuckle out of it. It turns out he had a professional acquaintance who was a heart surgeon, so when the opportunity next came up, he tried the joke on the surgeon. The surgeon, without missing a (no pun intended) beat, said something like "you've got aortic deficiency" or some other such medical condition. One got the impression that the surgeon had been through this many times before, and had the answer worked out ahead of time.

I had remembered "aortic deficiency" but WP doesn't have an article about that, so maybe I have it wrong. Is there another condition that sounds like that, which would fit the situation? 2602:24A:DE47:B8E0:1B43:29FD:A863:33CA (talk) 01:32, 12 September 2021 (UTC)

• Aortic insufficiency. Abductive (reasoning) 04:12, 12 September 2021 (UTC)

• Thanks, that must be it, though the symptoms in the article don't match the joke afaict. Close enough though. 2602:24A:DE47:B8E0:1B43:29FD:A863:33CA (talk) 03:38, 13 September 2021 (UTC)

  An on-the-spot diagnosis matching the setting is cardiac arrhythmia. This is an umbrella designation for many more specific diagnoses, such as atrial tachycardia. Nothing with "aortic" or "-ficiency" in the lot, though.  --Lambiam 07:34, 13 September 2021 (UTC)

If acid/bases are opposites then why they react on human skin equally?

Endothermic and exothermic are treated opposite based on their hot and cold reactions but in case of acids/bases, they are treated as opposites in ph scale, but they react on human skin equally, why so? Rizosome (talk) 01:43, 12 September 2021 (UTC)

Each acid and base reacts differently to human skin. Some chemicals can cause what we call "chemical burns," and these injuries are in no way equal. An important feature of reality is that human language is inadequate in describing reality. 2600:1702:2670:B530:45D:3246:2D5F:FEC0 (talk) 02:46, 12 September 2021 (UTC)

True. The OP needs to keep in mind that the terms "acid" and "base" are general chemical classifications. The corrosive aspects of individual examples vary. One item is Citric acid, which is mild enough to be used in food, even though in its pure form it can be troublesome. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:42, 12 September 2021 (UTC)

The broad effects of acids and bases on skin are also different. [2]--Wikimedes (talk) 05:39, 12 September 2021 (UTC)

You probably meant or are talking about concentration. 67.165.185.178 (talk) 06:54, 12 September 2021 (UTC).

Concentration is distinct from Acid strength. If I remember my GCSE chemistry correctly, there are things that a strong acid can do that a weak acid simply cannot, no matter how concentrated that weak acid is. Iapetus (talk) 09:14, 13 September 2021 (UTC)

Well human skin is neither an acid or a base, or water, so you wouldn't expect acids and bases to react with human skin much differently. 67.165.185.178 (talk) 06:54, 12 September 2021 (UTC).

See homeostasis. Excessive heat, insufficient heat, excessive pH, insufficient pH, excessive pressure, insufficient pressure, etc. will all damage skin. The differences between the types of damage may not be very obvious in some cases. So, for instance, "chemical burn" describes a lot of different types of skin damage. Chemicals have traits other than "will they hurt my skin?" (water and olive oil are both harmless, but anyone attempting to drink them will soon notice a difference). Distinguishing between chemicals, using measurements like pH, is useful, even if they have similar effects on skin. The treatment for acid burns generally depends on the substance causing the burn, though obviously removing the irritant is usually part of the treatment. Some antacids are pH buffers, designed make the pH of any solution they are added to change to a target pH (or close). I've answered several questions here because I'm not sure which one you are asking, Rizosome; please feel free to clarify. HLHJ (talk) 21:04, 12 September 2021 (UTC)

As sometimes happens, the OP started with a false premise, and it went downhill from there. :( ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:59, 12 September 2021 (UTC)

Should we generalize Coca trees, Cola trees, Cocoa trees, Coffea trees and Camelia Sinesis are all related?

Is it true to generalize that Coca trees, Cola trees, Cocoa trees, Coffea trees and Camelia Sinesis are all related?

If so, in what context could they be related?

• Significant evolutionary proximity
• Caffeine biosynthesis? (or other chemically similar stimulants biosynthesis?)

Thanks, 182.232.55.189 (talk) 08:36, 12 September 2021 (UTC)

Coca plants are in the genus Erythroxylum in the family Erythroxylaceae. Plants in the Cola genus are in the family Malvaceae, subfamily Sterculioideae. Also in the Malvaceae is Theobroma cacao, the 'cocoa tree'. Coffea is in the family Rubiaceae. Camellia sinensis is in the family Theaceae. So only cola and cocoa plants are in the same botanical family. PaleCloudedWhite (talk) 13:03, 12 September 2021 (UTC)

Glancing at the relevant articles, they are all eudicots. —Tamfang (talk) 01:41, 14 September 2021 (UTC)

Considering that the eudicots comprise about 75% of all flowering plants (about 175,000 species), that isn't narrowing down relatedness very much. PaleCloudedWhite (talk) 06:56, 14 September 2021 (UTC)

The thermometer in Leslie cubes

I recently learnt what a Leslie cube is and I wonder what John Leslie (physicist) used to compare the radiation. From reading Wikipedia, I understand it was some kind of differencial thermometer (no article?) or a pyrometer. But I don't know what Leslie had available in his time. He invented the aethrioscope, which our articles says "may be used as a pyrometer too.". So what did he use? Do we have an article about it? --Error (talk) 21:29, 12 September 2021 (UTC)

wikisource:1911 Encyclopædia Britannica/Leslie, Sir John says:

Leslie’s main contributions to physics were made by the help of the “differential thermometer,” an instrument whose invention was contested with him by Count Rumford. By adapting to this instrument various ingenious devices he was enabled to employ it in a great variety of investigations,

--Error (talk) 21:49, 12 September 2021 (UTC)

We have an article on the Beckmann thermometer, which is a differential thermometer. Apparently, Mortimer Granville also invented one.  --Lambiam 07:23, 13 September 2021 (UTC)

I have created a provisonal redirect for Differential thermometer.--Shantavira|^{feed me} 08:24, 13 September 2021 (UTC)

September 13

Environmental chem questions.

1. Can't we rebuild into the ozone layer, by flying up there and releasing ozone? Or does that take thousands of years?

2. What % is fuel efficiency for gasoline, is it like 99%? Meaning 1% is left as exhaust gas? Say, how much has it changed going back to the '70s, I'm hoping it went up gradually? Thanks. 67.165.185.178 (talk) 22:32, 13 September 2021 (UTC).

No. Over 99% becomes exhaust, but up to several tens of percent of the energy released becomes useful work, it has gone up gradually. Sagittarian Milky Way (talk) 23:14, 13 September 2021 (UTC)

1. The rate at which ozone is formed and destroyed naturally in the ozone layer is so high that it would be very hard to make an impact by adding ozone from an aircraft. Releasing catalysts that accelerate formation or destruction of ozone can have a significant effect. As it happens, the exhaust gases of combustion-powered aircraft contain catalysts destroying ozone, so the net effect of a high flying aircraft releasing ozone would be depletion of the ozone layer. Also see supersonic transport#History.

2. All atoms of the fuel end up in the exhaust gas; nothing remains in the engine. But that's not what fuel efficiency is about. Somewhere around 30% of the energy released by burning the fuel is turned into work done by the engine, the rest is waste heat in either the exhaust gas or engine cooling. That's what fuel efficiency of an engine is about: the fraction of the heat released by burning the fuel that gets applied as work at the driveshaft. It has improved a bit since the 1970s, but this is also offset somewhat by the increasing weight of our cars (a heavier car wastes more fuel on moving the car instead of its occupants), so the change in fuel efficiency of the car (fuel used to move a person from A to B) hasn't been very dramatic. PiusImpavidus (talk) 09:07, 14 September 2021 (UTC)

Unless you have soot deposits, those are gasoline atoms that didn't reach the air. Sagittarian Milky Way (talk) 13:34, 14 September 2021 (UTC)

Gasoline is a compound, or rather a mixture of compounds, not an element, it consists of molecules, not atoms. --CiaPan (talk) 17:55, 14 September 2021 (UTC)

Everyone knows that. Gasoline-derived mass that stuck to the vehicle parts. In this case, some of the carbons. A sign of imperfect stoichiometry. Sagittarian Milky Way (talk) 18:22, 14 September 2021 (UTC)

Are photovoltaics made for sunlight inefficient in low light?

Or is the watts per lux a constant if spectrum is sun-like?

2. Do incandescent, fluorescent, CFL, HPS, and LED lightbulbs and candles yield more watts per lux than sunlight or less?

3. What happens if you try to charge a battery with light and it's too dim to make the normal charging volts, amps or both? Is there a non-zero watt minimum to reverse the discharge chemical reaction? Sagittarian Milky Way (talk) 23:09, 13 September 2021 (UTC)

1. For the same spectrum and the same temperature, I don't think efficiency changes much with intensity. I wouldn't be surprised if there's some saturation effect at very high intensities. The temperature matters though; at higher temperature the efficiency drops. Under high light intensity, the panel tends to get hotter, so the efficiency is usually lower in brighter light.

2. It depends. If the band gap of the PV semiconductor is tuned to the spectrum of the light source, the efficiency could be higher. If not, it could be lower. Generally, turning electricity into light, then back into electricity is a very inefficient method of power transfer, so people don't really try to make this more efficient. It will never work well.

3. With less light, the PV panel will provide less current. The battery will charge slower. PV panels behave like a current source with a voltage cap. The current is proportional to the available light. PiusImpavidus (talk) 09:41, 14 September 2021 (UTC)

September 14

Red colored fabrics

Goodmorning! Why do red colored fabrics (e.g. a t-shirt) tend to fade more over time when exposed to light than those of other colors? Thank you--93.43.187.226 (talk) 05:42, 14 September 2021 (UTC)

Who says they do? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:47, 14 September 2021 (UTC)

There is a book called Red: The Art and Science of a Colour that discusses this issue. If you go to Google Scholar and search for "Fading of red dye" or "paint" or "objects" or "fabrics", you will get many hits in the academic literature. One I found began, "The irreversible fading of organic red colorants in art is well documented and greatly affects the perception of masterpieces from antiquity to the present day." So, there's that, Bugs. Cullen³²⁸ Let's discuss it 06:05, 14 September 2021 (UTC)

Thanks for the citation! ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:09, 14 September 2021 (UTC)

I was looking around WP for a discussion of the lightfastness of red pigments and didn’t’t find much. However, both red pigments and more particularly, red dyes (which would be the choice for fabrics) are notoriously fade-prone. Looking around elsewhere, this is commonly attributed to preferential absorption of UV, since red light is reflected for it to appear red. However, I think there’s more to it than just that. Acroterion (talk) 06:12, 14 September 2021 (UTC)

In connection with the fading of outdoor printed material (such as advertising posters) which, as commonplace observation reveals to anyone who actually looks, lose reds fastest and blues least fast, I once read an explanation that disruption of redder pigments inherently require less light energy than that of bluer ones, not unconnected with the fact that higher frequency (= shorter wavelength) blue photons are more energetic than lower frequency (= longer wavelength) red photons. However, I can't remember all the details or find the original source. Is there an optical physicist in the house? {The poster foremrly known as 87.81.230.195} 90.200.67.3 (talk) 07:42, 15 September 2021 (UTC)

Some time ago I read an explanation. I don't remember where I read it and can't guarantee it's true, but it made sense. Red pigments reflect red light and absorb green and blue, blue pigments reflect blue light and absorb red and green. Blue light, due to its higher energy per photon, does more damage when absorbed than red or green light, so the red pigments, absorbing more of the higher energetic radiation, are damaged faster. PiusImpavidus (talk) 08:32, 16 September 2021 (UTC)

How sweat comes out of human skin at the same time water can't go inside the skin?

I didn't understand the mechanism of human skin towards fluids. Rizosome (talk) 08:01, 14 September 2021 (UTC)

Who says skin does not absorb water? ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:27, 14 September 2021 (UTC)

One Dr Hoffman says: "The epidermis, the outermost layer of skin, provides a waterproof barrier" [3] Alansplodge (talk) 20:03, 14 September 2021 (UTC)

In any case, read Sweat gland for some answers on the first part of your question. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:29, 14 September 2021 (UTC)

Does it depend on whether or not you have anhidrosis? Martinevans123 (talk) 14:32, 14 September 2021 (UTC)

Courtesy link: Anhidrosis. hydnjo (talk) 16:47, 14 September 2021 (UTC)

Alansplodge "The epidermis, the outermost layer of skin, provides a waterproof barrier" is enough for me. Rizosome (talk) 00:09, 15 September 2021 (UTC)

That's why your fingertips don't wrinkle when they've been in water for a long time. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:23, 15 September 2021 (UTC)

Obviously you know that they do, and are presumably being sarcastic. However Alansplodge is correct – the epidermis does indeed prevent water from penetrating deeper into the dermis. However, the very outermost layer of the epidermis is made up of dead, dry cells made mostly of keratin; when these get wet they absorb water (which does not penetrate beyond them) and swell up, but since their attachment to the underlying dermis prevents them from expanding like a balloon, their increased volume instead forces the skin into wrinkles.

With reference to the implied question in the title: sweat does not just ooze out of the skin randomly, it is formed in sweat glands and expelled out by internal pressure via sweat pores. Due at least in part to surface tension, this is a one-way process – water cannot enter the body via the pores. {The poster formerly known as 87.81.230.195} 90.200.67.3 (talk) 07:33, 15 September 2021 (UTC)

Your fingertips do not "swell up" when in water - if they did, your fingertips would be less wrinkled, not more wrinkled. And in fact "prune hands" has nothing to do with water being absorbed or released at all (cite). Matt Deres (talk) 17:43, 15 September 2021 (UTC)

I didn't say that the fingertips swell up, I said that the outermost keratinous cells swell up but do not expand outwards because of their attachment to the deeper epidermal (and indirectly dermal) cells, and since they can't cause the skin overall to expand, they must accommodate their larger size within the same lateral span, which forces the skin into wrinkles, thus: ---------- —> /\/\/\/\/\.

This is what your reference says scientists used to think, and I concede that you have found a more up-to-date reference. I'm reminded that the "half-life" of "facts" on the well-researched programme QI is said to be about 18 months (or something similar). {The poster formerly known as 87.81.230.195} 90.200.67.3 (talk) 22:50, 15 September 2021 (UTC)

18 months ago it was about 18 months. Now it is more like 9 months. Soon we'll have the 24/7 science cycle.  --Lambiam 08:21, 16 September 2021 (UTC)

That's fair. Apologies for misrepresenting your post. Matt Deres (talk) 13:53, 17 September 2021 (UTC)

September 16

Why there is no vent for medical oxygen tanks?

I remember seeing a vent on top of oxygen tanks at industries, but why there is no vent for medical oxygen tanks? Rizosome (talk) 03:49, 16 September 2021 (UTC)

Maybe the venting oxygen tanks you saw were for holding liquid oxygen, whereas medical oxygen tanks contain compressed gas. Here you can read about the need to vent liquid oxygen cylinders.  --Lambiam 07:05, 17 September 2021 (UTC)

A great link. Just to add that liquid oxygen would be far too cold to use in a medical setting, e.g. to assist breathing.--Shantavira|^{feed me} 08:28, 17 September 2021 (UTC)

For iron's metallic bond, what type of iron ion is present to bond with the delocalized electrons?

For sodium, each Na will lose 1 e- to form Na+. Then sodium ions are attracted to the delocalized electrons, and therefore there is metallic bond. However, for iron (and other transition metals), how many electrons will each iron atom lose? Will they lose all of the 4s electrons? Or, is the ion Fe(II) or Fe(III) ion? Thank you so much!!!! Jocosus2000 (talk) 15:04, 16 September 2021 (UTC)

• NaCl has ionic bonds. Those can be simplified as "one atom loses one (or more) electron(s) to another atom, and both stick together due to electromagnetic attraction". (For the longer explanation, see the linked article.)

Iron, on the other hand, has metallic bonding. A gross oversimplification is that iron atoms pool electrons together into a sea of free-moving electrons. Individual atoms do not really "lose" electrons in that process. How many free electrons per atom are yielded by that process is a good question, but not one I can answer - researching this probably goes through our article Valence and conduction bands; based on a sentence in Drude model I assume usually as many as the valence number (so, probably 3?).

Finally, many compounds have covalent bonding, where close-by atoms share some electrons, and shared electrons count for both atoms towards the "having a complete electronic shell" stability criterion. The difference with metallic bonding is that the electrons are not free-moving so the bond is really local. Tigraan^{Click here for my talk page ("private" contact)} 15:52, 16 September 2021 (UTC)

Thank you so much!!! By the way, is band similar to orbitals? Thanks:)Jocosus2000 (talk) 10:04, 17 September 2021 (UTC)

No. Atomic orbitals are a concept linked to a single atom (the "location" of a given electron, basically). The conduction/valence bands are macroscopic (or mesoscopic) concepts related to energy levels of a large number of electrons around a large number of atoms. Tigraan^{Click here for my talk page ("private" contact)} 12:06, 17 September 2021 (UTC)

Where an atom in a compound loses an electron to some other place in the structure, and it is just a single electron, that is called an electride. They're different to metals as they are insulators. Graeme Bartlett (talk) 12:41, 17 September 2021 (UTC)

Thank you so much! Jocosus2000 (talk) 15:20, 17 September 2021 (UTC)

Position of black hole event horizon

Is the event horizon (i.e. absolute horizon) of a black hole in the same place for all objects, or does it vary according to their mass or some other factor(s)? PaleCloudedWhite (talk) 07:17, 17 September 2021 (UTC)

The event horizon depends on the mass, charge, and angular momentum of the black hole. Dja1979 (talk) 17:09, 17 September 2021 (UTC)