On Apollo 13, did the severe cold conditions (caused by the need to turn off all non-essential systems such as heating in order to conserve power) contribute to the premature failure of the CO2 scrubbers, as was the case on the Johnson Sea Link? 2601:646:8A81:6070:6C67:B2B6:D530:3F2A (talk) 10:20, 6 February 2022 (UTC) Reply

My understanding is the scrubbers did not fail prematurely. The LEM filters were only designed to support two men for two days, and it instead had to support three men for four days, thus the need for adapting the filters from the command module. Do you have a source that says they failed prematurely? RudolfRed (talk) 22:32, 6 February 2022 (UTC) Reply

That's what I was asking about -- was it only the increased load, or did the cold contribute as well? 69.181.91.208 (talk) 07:41, 7 February 2022 (UTC) Reply

The lithium hydroxide in the canisters could only bind a limited amount of CO₂ and needed to be replaced regularly. At some point, the crew ran out of the limited supply of canisters that fit into the LM system. The scrubber itself did not fail, and while most LM systems were shut down, this would not have included the scrubber. I suppose (but cannot find definitive confirmation) that the scrubber may have included an internal heating system. But another issue is that the temperature-dependency properties of LiOH granules are rather different from those of the Baralyme used in the Johnson Sea Link scrubber. At a relative humidity in the air stream above 40%, LiOH is even reported to have a higher CO₂ absorption capacity at lower temperatures. --Lambiam 09:55, 7 February 2022 (UTC) Reply

So are you saying that the cold, damp conditions which prevailed in the LM actually stretched the scrubber's capacity longer? 69.181.91.208 (talk) 10:33, 7 February 2022 (UTC) Reply

It would not have changed the capacity, which is only dependent on the stoichiometry of the reactants (which is to say, there are only so many formula units of LiOH available to react with CO₂), and temperature doesn't change that. The temperature would have affected only the kinetics of the reaction, which is to say the speed at which the reaction would have happened. AFAIK, the problem was not the kinetics, it is that they were literally out of usable LiOH in the LM scrubber system; which is why they needed to use the Command Module canisters. --Jayron 32 13:39, 7 February 2022 (UTC) Reply

I couldn't find any specific information on nuclear bombs that answered this question.

"The world's first nuclear explosion occurred on July 16, 1945, when a plutonium implosion device was tested ..." Clarityfiend (talk) 07:48, 9 February 2022 (UTC) Reply

I don't think radium has ever been used to create a nuclear bomb. Clarityfiend (talk) 07:50, 9 February 2022 (UTC) Reply

Radium is not particularly fissile, which means it does not undergo a spontaneous fission reaction. Not all radioactive materials do so. Generally speaking, most fissile elements are isotopes of actinides with odd mass numbers. Radium is not an actinide, and has only 5 isotopes that have a halflife of more than a few seconds; of those only two have halflives measured in years; radium-228 and radium-226, both of which are even mass number. --Jayron 32 12:10, 9 February 2022 (UTC) Reply

The OP was probably thinking of "uradium". Clarityfiend (talk) 22:10, 9 February 2022 (UTC) Reply

See Trinity (nuclear test). The Manhattan Project created two bomb designs: a uranium gun-type bomb ("Little Boy"), and a more complicated plutonium implosion type bomb ("Fat Man"). Little Boy was simple enough that they were sure it would work on the first try, but Fat Man had to be tested first, just in case. So the first three explosions were 1) Trinity, a test explosion in New Mexico of the Fat Man design, mentioned above as the first nuclear explosion; 2) Little Boy, dropped on Hiroshima and therefore the first atom bomb actually dropped in a war; and 3) Fat Man, a second copy of the implosion design, dropped on Nagasaki. I'm sure Wikipedia's articles cover this stuff in detail, but a very thorough history is the 1987 book The Making of the Atomic Bomb . 2602:24A:DE47:B8E0:1B43:29FD:A863:33CA (talk) 09:42, 13 February 2022 (UTC) Reply

In chemical equation are there any symbols / special characters to indicate that the reaction produces an explosion, vigorous burning or similar hazard? Googling only suggested that "gas explosion can be simplified as an one-step, exothermic chemical reaction: CH4 + 2O2 → CO2 + 2H2O + 886.2kJ/mol". Thanks. 212.180.235.46 (talk) 12:16, 9 February 2022 (UTC) Reply

I've only ever seen that denoted using ${\displaystyle \Delta H_{\text{reaction}}^{\ominus }}${\displaystyle \Delta H_{\text{reaction}}^{\ominus }}. Professional chemists will do a hazard/risk assessment (similar to HACCP) before they attempt any lab-work since having a career in chemistry means avoiding blowing up oneself or colleagues. In my industrial lab it was, for example, prohibited to do anything for the first time on a scale greater than 0.1 mol so that even if the hazard were underestimated the resulting exotherm would be unlikely to do much damage. Mike Turnbull (talk) 12:44, 9 February 2022 (UTC) Reply

The ${\displaystyle \Delta H}${\displaystyle \Delta H} of a reaction only tells the difference between the starting and ending points, not how fast it got there. There are many reactions which are highly exothermic (rusting, for example), but which have very slow kinetics; if a massive amount of energy is released, but it does so over years, than the reaction is not described as explosive. Even if less energy is released, if the energy is released in fractions of a second, and if the energy does pressure volume work, only THEN could it be described as an explosion. To answer the OP's question, no, there is not any particular way to indicate "explosiveness" in a chemical equation. --Jayron 32 13:09, 9 February 2022 (UTC) Reply

Thanks, Jayron32, that reminds me that that the thermite reaction converting the rust back to iron can also be fast and furious. Also worth mentioning for the OP is that in many lab reactions the real hazard is any flammable solvent, which is usually present in much larger amounts than the reagent and if set alight can give many times more than the reaction's exotherm. Mike Turnbull (talk) 13:38, 9 February 2022 (UTC) Reply

Just a side note, taking the oxygen out of rust is still endothermic in that half of the Thermite reaction. It's the putting the oxygen on aluminum in the other part which is so exothermic. And yes, the reaction is vigorous because the kinetics are rather rapid. --Jayron 32 14:10, 9 February 2022 (UTC) Reply

• In addition to the considerations of kinetics, "explosion" is not really a scientific term, so there is no real demarcation between burning and exploding. There is a scientifically-meaningful distinction between deflagration and detonation depending on whether the flame propagates slower or quicker than sound in the medium (the latter allows for a shock wave to form, among other things).

Tigraan ^{Click here for my talk page ("private" contact)} 17:58, 9 February 2022 (UTC) Reply

There are no rigorous rules, but if a single molecule of a material in the solid or liquid state releases multiple gas molecules during the reaction (e.g. TNT), it indicates the reaction is potentially explosive, due to the sudden increase in atmospheric pressure. 51.155.110.141 (talk) 22:59, 10 February 2022 (UTC) Reply

Amongst drugs where the active ingredient is an exact compound and not a mixture. Sagittarian Milky Way (talk) 20:49, 10 February 2022 (UTC) Reply

Are we including macro-molecule therapies, such as ones using a protein? A protein is technically a single molecule, and it can have a LOT of rings. Also, are we talking aromatic or not? --OuroborosCobra (talk) 21:01, 10 February 2022 (UTC) Reply

The Pfizer-BioNTech COVID-19 vaccine has an RNA sequence with 4284 nucleotides, each with several rings. --Amble (talk) 21:48, 10 February 2022 (UTC) Reply

Proteins made of amino acids, several of which (proline, phenylalanine, histidine and tyrosine) contain 1 ring, and one (tryptophan) contains two. While insulin, a necessary medication for people with diabetes, is a relatively small protein (only 51 amino acids), the broad class of proteins known as interferons can get MUCH larger, and many have therapeutic uses. --Jayron 32 16:22, 11 February 2022 (UTC) Reply

While peptides/proteins are clearly going to set the record, Sagittarian Milky Way, maybe you meant to exclude them. There is then a different problem: you could go through Category:World Health Organization essential medicines and look for those with a large number of rings. But how many will you count for compounds like vancomycin which has one very large ring, if you choose to take the maximal periphery, plus numerous smaller rings? Or morphine with its interlocking bridged system? Mike Turnbull (talk) 16:43, 11 February 2022 (UTC) Reply

How many rings or cycles does vancomycin have in the most common counting convention? 11? If they counted rings that contained rings then olympicene would have a lot more than 5 rings. Sagittarian Milky Way (talk) 19:05, 11 February 2022 (UTC) Reply

Yes, I was pointing out that graph theory, as applied to chemicals is relevant. If you read International Chemical Identifier, you'll see why I chose morphine as an example. Your question interested me: having thought about it, I moved on to wonder which drug had the most ring bonds, as a proportion of all its bond (or maybe its non-CH bonds). That number, expressed as a %, can reach 100% for buckminsterfullerene (not a medicine!) and it is certain that the record-holder won't be one of the polymer-like materials of vaccines, peptides etc. Jayron32 makes a perfectly good point below but thinking about questions like this is good for my aging brain. Mike Turnbull (talk) 13:14, 12 February 2022 (UTC) Reply

As a percent of all or non-CH bonds is also interesting, if I had the last Physicians Desk Reference I could check some each day till I found the answers, at least for the subset of drugs that both show the structure sufficiently and weren't removed for obsolescence or missing the deadline for inclusion (I don't know if drugs that have been obsolete for many years are still listed). Sagittarian Milky Way (talk) 15:16, 12 February 2022 (UTC) Reply

You could instead start from Wikipedia entries that use Template:Infobox drug, of which there are apparently about 8000 which are not mixtures. Amantadine is a drug with a carbon framework of entirely ring bonds but it may not be the record holder even on the % criterion because of its attached -NH2 group. Good luck.... Mike Turnbull (talk) 18:06, 12 February 2022 (UTC) Reply

• The problem with a question like this is not "Is there a record?" Given that there are a finite (extremely large number, but still finite) number of different therapeutic compounds out there, there is going to be one "most" of any random property one could care to name. That such a "most number of rings record" exists does NOT mean that anyone has ever thought to note such a record before. Without sources to confirm that such a record has been noted before now, it is essentially impossible we're going to hit on that record by guessing random molecules we've heard about. Questions of this type are unanswerable, not necessarily because there isn't an answer, just because no one has ever figured it out, and we're for sure not going to reliably create that answer here. --Jayron 32 19:16, 11 February 2022 (UTC) Reply

You may wish to consult Category:Heterocyclic compounds with 7 or more rings. However I may not have all the compounds that could be there categorised. And I have not included biological macromolecules. DNA and RNA with their purines and bases have numerous rings, but not fused together. A seven ring heterocycle has seven rings interconnected, so you have to cut 7 bonds to turn this to a connected branching molecule. But for the category, it may additionally include other rings with lesser connection. Graeme Bartlett (talk) 02:24, 13 February 2022 (UTC) Reply

Our shower is supplied from the cold water supply only and it heats the water electrically. The temperature is thermostatically controlled so it does not matter if the water pressure varies. The knob setting the water temperature, although it has radial marker lines, turns smoothly with no sign of discrete positions. There is another knob for "high", "medium" and "cold" which we leave on high. How is the heater likely to be controlled? Will the power be being switched on and off fairly rapidly or will there be some sort of "analogue" control? Thincat (talk) 09:15, 11 February 2022 (UTC) Reply

One possibility, of many, is Infinite switch Greglocock (talk) 09:38, 11 February 2022 (UTC) Reply

Yes, that looks the sort of thing. Thank you. Thincat (talk) 09:52, 11 February 2022 (UTC) Reply

A device like that made today might instead use a potentiometer and sensor setup, maybe as part of a PID controller, rather than deal with the mechanical unreliability of the infinite bimetallic switch. 2602:24A:DE47:B8E0:1B43:29FD:A863:33CA (talk) 09:53, 13 February 2022 (UTC) Reply

A coral diagram seems to be a good way to depict speciation. In the illustration here, created by Lajos.rozsa, the first detail view appears to be at a moment just before the species are separating. But the magnified picture (second from top) looks pretty homogenous. Shouldn't there be some signs of the impending separation, such as a reduced reproduction rate in the middle of the top border? ◅ Sebastian 09:57, 11 February 2022 (UTC) Reply

I have a hard time interpreting the diagram. Its caption in Coral of life says: "Zooming out from a network/tree of individuals to a coral diagram in 4 steps." Usually, in a stepwise zooming-out presentation, the full rectangle of the image of step N shrinks to a smaller rectangle embedded in the image of step N+1. So I guess the "zooming out" is bottom-to-top, which (I think) is unusual. Then, the image in the shrunk rectangle embedded in the image of step N+1 is usually still recognizable as a scaled version of the image of step N. Here, I don't see a correspondence. Also, the branches of what is supposedly a single tree overlap in the middle two images, making it difficult to see this as a tree diagram. As to your specific question: (a) is the reproduction rate in a population about to speciate known to be reduced? and (b) how is the rate supposed to be represented visually in such diagrams? --Lambiam 10:57, 11 February 2022 (UTC) Reply

Thanks for pointing out those two problems. I agree with your interpretation of the composite image being described bottom-to-top, which is also expressed by the direction of the arrows, and I agree that that's rather unusual. Maybe that could be added explicitly to the caption. The second problem is tougher, since it requires a thorough change of the image file. (Most obviously it can be seen in the last two sub-images: Whereas the smaller rectangle in the second last sub-image has only 3 lines entering the bottom edge, the last sub-image shows 7, and a much more even distribution.)

But the overlapping branches are not a problem: That is the whole point of a coral diagram as opposed to a tree diagram. That said, it is a weakness of the image file that it doesn't show any such case in the last sub-image.

As for the specific questions regarding the OP:

(a) I don't know. But: In the scale of the topmost sub-image, which we should call "sub-image 4", the two branches diverge right above the edge of rectangle for sub-image 3. That means that, If we moved sub-image 3 up just a millimeter or two, we should see no nodes in a wide stretch of the top edge. I can see two ways for that to happen: All the lines need to either suddenly die out or abruptly change course, deciding for one of the two branches. I avoided the second possibility in my question, since it's harder to explain. But let me try: While the diagram type has, to my knowledge, no explicit rule for the x-coordinate of any node, I would say that expediency demands that it represents the closeness (by phenotype or genotype) to any of the two resulting species, at least in the vicinity of a speciation event. Thus, all offspring of that generation would exhibit a sudden change, which violates my understanding of evolution, which is gradual under normal circumstances.

(b) As I understand it, the rate should be the average of lines pointing upward from each node (divided by the number of lines coming in from below, but that's mostly 1 here, so we're safe to neglect the deviations from 1). ◅ Sebastian 13:18, 11 February 2022 (UTC) Reply

Re. While the diagram type has, to my knowledge, no explicit rule for the x-coordinate of any node, I would say that expediency demands that it represents the closeness (by phenotype or genotype) to any of the two resulting species, at least in the vicinity of a speciation event. There's no such thing as "the vicinity of a speciation event". For speciation to occur two groups of the same species need to be geographically separated for a large number of generations. There's no 'split' in the family tree caused by a slow dwindling of reproduction rates in that 'area'. The x-coordinate in these diagrams (which are not graphs) is just an abstract way to visualize separateness. The way the lines waiver and go off at various angles is misleading. nagual design 15:44, 12 February 2022 (UTC) Reply

Sorry, the term "vicinity" wasn't as clear as I thought. Since none of the dimensions of the coral diagram are spatial, it didn't occur to me that anyone could read it as geographic vicinity. What I meant was: "any point within the same contiguous area of the branch whose time is much closer to the speciation event than to any other event". I hope this clears up the misunderstanding. ◅ Sebastian 23:09, 12 February 2022 (UTC) Reply

Been wondering which electrons of a metal atom contribute to the electron gas in metals and which ones remain attached to nuclei. I was wondering specifically for lithium. Jo-Jo Eumerus (talk) 13:41, 11 February 2022 (UTC) Reply

Articles like electron gas go way above my head but electrical resistivity and conductivity#In metals is a bit easier to understand. This suggests that it is the outermost shell of electrons that contribute to the conduction and for lithium it's pretty certain just to be its single 2s electron that matters. Note that no electron "attaches to the nucleus", they are all in atomic orbitals around it. Mike Turnbull (talk) 13:51, 11 February 2022 (UTC) Reply

It's also important to note that electrons are not individually identifiable; neither is their location knowable. In terms of modeling metals, the Valence and conduction bands matches up pretty well; in the sea of electrons model, the valence band is those electrons that are capable of participating in electrical conductivity, and gaining energy to reach the conduction band. --Jayron 32 16:14, 11 February 2022 (UTC) Reply

Yeah, my question is aimed at determining whether any of these electrons don't participate in conduction [and in superconductors, if any of the electrons don't form Cooper pairs] Jo-Jo Eumerus (talk) 16:59, 11 February 2022 (UTC) Reply

Is there a forum about biohacking that is reputable?--2A02:908:426:D280:E489:4BB:F7DD:7E43 (talk) 21:35, 11 February 2022 (UTC) Reply

I don't know, but if such a thing exists, gwern.net or erowid.org would likely have links to it someplace. 2602:24A:DE47:B8E0:1B43:29FD:A863:33CA (talk) 09:55, 13 February 2022 (UTC) Reply

Biohacking means different things to different people, as you'll see from that disambiguation page. If you mean specifically Do-it-yourself biology, that article has plenty of reliable sources and some links to organisations that should have discussion forum via their websites. Mike Turnbull (talk) 12:13, 13 February 2022 (UTC) Reply

My local water utility occasionally gives us a slug of extra chlorine, making my tap water smell like a swimming pool. Is there any science showing that drinking that water could be harmful?

Conflicting answers from the Internet:

https://www.cancerwa.asn.au/resources/cancermyths/chlorine-cancer-myth/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4824718/

https://www.scientificamerican.com/article/earth-talks-tapped-out/

03:06, 12 February 2022 (UTC)2600:1700:D0A0:21B0:D096:A2DF:EE0B:35D3 (talk)

You may wish to look at Monochloramine, one of the main things formed in the chlorination. It mentions cancer as a risk, and the references might tell you about testing and how much is safe. Graeme Bartlett (talk) 02:28, 13 February 2022 (UTC) Reply

In Einstein's theory of General Relativity, gravity is a fictional force arising from the curvature of spacetime. This curvature is said to be due to the presence of mass. But what is "mass"? Is it possible that what we call "mass" is actually nothing but this curvature, and that the conservation of mass is a geometric conservation of curvature? Thank you. Hevesli (talk) 12:52, 12 February 2022 (UTC) Reply

It's worth noting that the conservation of mass doesn't quite hold up, since matter and energy are interchangeable on a quantum scale. nagual design 15:56, 12 February 2022 (UTC) Reply

The lay-level (noon-mathematical) explanation of General relativity says that the curvature of spacetime is caused by mass. If mass is the curvature, what would be causing this curvature?

In Quantum mechanics, it is similarly suggested at the lay level that mass is a quality imparted to matter by the Higgs boson and Higgs field via the Higgs mechanism. It is widely stated that at present the two theories or models, Relativity and Quantumm mechanics, are incompatible even though each appears to be accurate within its own sphere of application and measurement. Your suggestion does not readily seem able to contribute to the reconciliation of the two. {The poster formerly known as 87.81.230.195} 90.193.130.191 (talk) 17:36, 12 February 2022 (UTC) Reply

Thank you. It is not my purpose to reconcile these theories. Nor do I strive for the Theory of Everything with this idea. The fundamental nature of energy is probably even more mysterious than that of mass. I believe that heat is kinetic energy and chemical energy is potential energy. Using the relativistic mass formula, maybe we can equate kinetic energy with mass. Maybe a curvature of spacetime moving through space (in a stationary observer frame) causes additional curvature. And maybe a photon is accompanied by a curvature that moves with it. For other fields than the gravitational field the force is very local because at longer distances the positive and negative forces cancel each other out, but perhaps all forces are accompanied by curvature, only the effect is so local that it has not been observed yet. My question is really not whether I am correct, but whether this idea or similar ones have ever been considered. Could they not be a basis for theories with experimentally testable prediction? Hevesli (talk) 13:52, 13 February 2022 (UTC) Reply

What do you call it where, you have a layer of walls, each with plants on it? Like these https://imagizer.imageshack.com/v2/714x657q90/923/WPNirL.jpg https://imagizer.imageshack.com/v2/960x643q90/924/HPW7mO.jpg Thanks. 67.165.185.178 (talk) 11:24, 13 February 2022 (UTC).Reply

Terracing. Bazza (talk) 11:55, 13 February 2022 (UTC) Reply