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March 3

Aqueous AlCl3

What's the Ka or pKa of AlCl₃ in water? (Not homework -- I need to make sure I'm mixing my chemicals right, but I can't find a reliable value for this parameter anywhere!) 2601:646:9882:46E0:A9DB:D35F:F7B8:E80B (talk) 06:13, 3 March 2023 (UTC)[]

The acid in this reaction is the hexahyrdate aluminum complex ion, Al(H₂O)₆³⁺. According to This, the Ka of this ion is 1.4 x 10^-5. --Jayron 32 11:53, 3 March 2023 (UTC)[]

Thanks! 2601:646:9882:46E0:780E:6C08:3DB3:8473 (talk) 05:29, 4 March 2023 (UTC)[]

Wristwatch gears

Wristwatches have tiny gears which have been made for more than a hundred years. How have these gears been made so accurately? If they are stamped, how is the master punch made? 24.72.82.173 (talk) 17:36, 3 March 2023 (UTC)[]

Does This help you with your research? --Jayron 32 18:13, 3 March 2023 (UTC)[]

Here is a manual demonstration; the commentary suggests that high-quality commercial gears are made by CNC machines rather than stamped out. -- Verbarson ^talk_edits 23:35, 3 March 2023 (UTC)[]

These were, however, not available in the 19th century, so the question remains which techniques were employed by 19th-century watchmakers. --Lambiam 14:59, 4 March 2023 (UTC)[]

One of the sources in the article Watchmaker is this interesting book Practical Watchmaking, first published 1788. Chapter IV, "The Wheels", has a subheading "The Teeth", which says:

To split wheels one uses the tool, Pl. 12, Fig. 1. See its description in the Vocabulary, the article on wheel cutting machines.

In the Vocabulary under Wheel cutting machine there is this description:

It is composed of a frame in the shape of triangle, in which the arbor A is so skilfully adjusted that it turns exactly and free in this type of frame. It carries a bass plate called the dividing plate (plate-forme), which is fixed immovably to the base of the arbor so that these two parts turn in unison. Surface B of the dividing plate has several divided and numbered concentric circles of different numbers, in order to give a wheel the number of teeth which it needs. The part K, called the alidade, is a steel arm which springs. One end is fixed at the point N, on one of the pillars of the frame. It carries a pointed screw L, which enters the divisions of the dividing plate and holds it fixed at this point. The carriage F slides on the arm O of the frame, on which the carriage can come and go by means of a screw which moves it towards or away from the arbor A, according to the size of the wheel. Fixed on the carriage is a hinge Q, which holds a toothed wheel, mounted on an arbor, on the end of which the crank I is placed. This wheel meshes with a pinion P which carries a steel wheel cut in the shape of file, called a fraise or cutter. So when the crank I is turned, the wheel turns the cutter R. Let us suppose that you want to split a wheel. Enlarge the hole until it enters the pivot of the screw H and fix it there with the nut M. Then place the alidade on the line of the plate No . 60. Approach the carriage of the wheel little by little, to be sure that the teeth of the wheel will be neither too long nor too short. Then fix the carriage by means of the lock screw E, and turn the crank while pressing the hinge Q lightly against the wheel. The cutter, by filing the wheel, will split a tooth. That one split, change the alidade point to split another, and continue until you have made a full turn of the dividing plate.

I hope you can picture that clearly in your mind. :) Obviously it goes along with the illustration plate 12, where we can see that this device looks somewhat like a record turntable. I'm not certain how big it is in relation to the toothed wheel being created. I wonder if it has some aspect of a pantograph for the purpose of scaling down a design? (The arm is suggestive of that.) It's evidently a species of lathe, and the thing which always impressed me about lathes is that the parts for lathes are made using other lathes: thus they went through a kind of evolutionary or bootstrapping process.

I also did an image search and found a series of pictures titled Rare and antique Watchmaker Milling Machine with wheel cutting attachment. I don't know how antique is "antique" but it gives you a general idea of the shape and size of this kind of machine. I imagine it descends from a series of cruder ancestors, starting with one that made the gears for clocks (and for the next, slightly more accurate wheel cutting machine). Card Zero (talk) 16:23, 4 March 2023 (UTC)[]

Thanks for taking the time to reply. Unfortunately, I couldn't clearly (in fact not even nebulously!) picture the device in my mind. The gears I saw on the TV program "How Do They Do It?" were about 2 mm in diameter, which seems smaller than what the machine in the videos would be capable of. 24.72.82.173 (talk) 19:44, 4 March 2023 (UTC)[]

What time is it on the Moon?

Is this something that belongs in the Moon or in another one?— Vchimpanzee • talk • contributions • 22:53, 3 March 2023 (UTC)[]

Has anything actually happened yet? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:12, 3 March 2023 (UTC)[]

I guess it's too early, but certainly the proposal needs to have a brief mention at some point.— Vchimpanzee • talk • contributions • 23:21, 3 March 2023 (UTC)[]

They could use local time until the infrastructure is set up, see Railway time. Martin of Sheffield (talk) 08:31, 4 March 2023 (UTC)[]

19th Century railways initially lacked a seconds-accurate clock distribution but everyone was sure about their longitude, and therefore which time zone they occupied. 21st Century Moon-walkers will have near-instant data communications but the Moon's Earth-referenced Earth-fixed longitude, and therefore which Earth time zone might be relevant, keeps varying. A good solution to timekeeping on 19th century railways therefore doesn't address the issue of Moon timekeeping.

A possible solution is to adopt Earth GPS (Global Positioning System) time for the whole Moon. Sensitive GPS receivers may be able to provide surface locations on the Moon, necessarily for Earth-facing fixed locations using long integration times and Kalman filtering, because the GPS satellites (4 are needed for a trilateral location fix) were designed to transmit to Earth with only incidental stray radiation towards the Moon. The concept is credible enough for tests planned by a NASA Lunar GNSS Receiver Experiment (LuGRE) in 2023 and by ESA in 2024. Given a lock on GPS time that can certainly be distributed all over the Moon using local radio clocks, I think any subdivision into local time zones would be as premature as are plans for Colonization of the Moon. Philvoids (talk) 13:10, 4 March 2023 (UTC)[]

My question was where to put this information on Wikipedia.— Vchimpanzee • talk • contributions • 16:15, 4 March 2023 (UTC)[]

Until or unless they come up with a solid plan that has a reasonable chance of approval, the answer is "nowhere". One thing to keep in mind is that a "day" on the moon is about a month on earth. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:04, 4 March 2023 (UTC)[]

Perhaps European Space Agency as it seems to be their baby. Curious that they have nothing more urgent to discuss. Alansplodge (talk) 21:02, 4 March 2023 (UTC)[]

Urgent? I first raised this issue in 2005. -- Jack of Oz ^{[pleasantries]} 21:43, 4 March 2023 (UTC)[]

It probably won't be a thing until or if we start forming permanent settlements on the moon. And maybe not even then. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:02, 4 March 2023 (UTC)[]

The Apollo 11 article timings are all given in UTC. This was presumably UTC as recorded by the ground station, so about 1.25 seconds behind Moon time? -- Verbarson ^talk_edits 23:29, 4 March 2023 (UTC)[]

I expect that the JWST scientists have figured out a way to sync the clocks here and there, possibly with microsecond accuracy, in spite of the communication delay (about 5 seconds). It may not be exactly rocket science to get this working. --Lambiam 09:52, 5 March 2023 (UTC)[]

Plain old-fashioned ntp (or it's offspring chrony) would do that. It is specifically designed to allow for delays between the primary source and the local clock. Martin of Sheffield (talk) 11:13, 5 March 2023 (UTC)[]

Because the gravitational potential on the moon is less than on Earth, clock will run faster there. So if you try to sync from Earth, it will try to keep slowing down the faster clock on the moon. With microsecond accuracy this will be noticed. So do you want to say a second is longer on the moon, or allow clocks to drift apart? There is a system for the solar system called Barycentric Coordinate Time. Graeme Bartlett (talk) 23:57, 7 March 2023 (UTC)[]

March 4

Oil packets for instant soups

When preparing an instant soup I've noticed that the oil/fat from the plastic packet comes out with difficulties when squeezed, recently I used a toothpick to pick up the oil remnants and drop them into the soup. Is it theoretically possible to design a packet from lipophobic material or in some other manner so that the oil/fat would come out easily? 212.180.235.46 (talk) 13:21, 4 March 2023 (UTC)[]

Not an answer but a tip. If you first immerse the packet in hot water (or soup), the contents will come out more easily. --Lambiam 14:40, 4 March 2023 (UTC)[]

Indeed. Another solution would be a disc shaped bag, no corners.Greglocock (talk) 20:47, 4 March 2023 (UTC)[]

The packet soups I use are dry powder, which leaves almost no residue in the packet, but being stingy I like to extract the last traces by pouring a small amount (say a tablespoon / ¹/₂oz / 15ml) of hottish water (from an electric kettle) into the packet, slosh it about, and then add it to the soup. I imagine this would also work to extract more liquid oil/fat residues. {The poster formerly known as 87.81.230.195} 51.198.55.125 (talk) 23:10, 4 March 2023 (UTC)[]

A problem with the plastic oil packets is that they are too tight for sloshing, especially in the corners. It may be theoretically possible to apply an oleophobic coating to the plastic, but packing just a wee bit more oil for less toothpicky customers is almost certainly less costly. --Lambiam 09:12, 5 March 2023 (UTC)[]

Rolling vs wind resistence

If I stand near a highway and a relatively unaerodynamic vehicle like a pickup truck appoaches at 70 mph, I hear mainly tire noise, even though the wind resistence increases as v squared. Under these conditions, how do the energies required to overcome rolling and wind resistences compare? 24.72.82.173 (talk) 19:28, 4 March 2023 (UTC)[]

Must be road surface dependent, at 60 kph full throttle on asphalt a modern car generates roughly equal amounts of engine-related, tire, and aero noise. Tire noise is probably linear with speed, aero v^2, and engine noise is irrelevant on flat roads at constant speed. Hence at high speeds I'd expect aero noise to dominate. Greglocock (talk) 21:48, 4 March 2023 (UTC)[]

Tyre noise and rolling resistance both depend on the tyres and road surface, but in different ways. A soft rubber mat would give low tyre noise, but high rolling resistance. Porous asphalt-concrete (popular here on motorways) gives much less noise than cobblestones, but I don't expect a large difference in rolling resistance. Air drag is mainly determined by the main body of the vehicle, wind noise largely comes from small gaps, antennas and mirrors sticking out, grilles etc.; stuff that creates vibrations in the audible range. Turbulence around the main body also creates acoustic waves, but those are infrasonic, so you don't hear them. Conclusion: the ratio between tyre noise and wind noise says nothing about the ratio between rolling resistance and wind resistance. I'm quite sure that for most road vehicles at motorway speeds, wind resistance dominates over rolling resistance. PiusImpavidus (talk) 10:33, 6 March 2023 (UTC)[]

March 6

Plastic sheet pickup truck bed cover vs rigid?

I always wondered what city/highway mpg you'd get with a light rigid cab top to tailgate end hypotenuse wedge (hollow wedge not solid, only thick enough to minimize drag) vs a few pieces of flappy plastic glued on in the same shape maybe with a few rods to keep the shape (the thinnest plastic that wouldn't tear). If your aero shield is flapping in the wind how bad is that? Are all the energy savings of the shape being wasted on the flapping and tugging or only some of it and how much? Rigid aerodynamic shields obviously work so how rigid do they have to be before energy stops being wasted in flappiness or the chemical bonds being stretched by the vacuum and turbulence futile-y trying to tear something? Sagittarian Milky Way (talk) 04:05, 6 March 2023 (UTC)[]

Do Tonneau Covers Really Save Gas? Alansplodge (talk) 11:01, 6 March 2023 (UTC)[]

That's a horizontal cover not a full four-sided wedge or pyramid, or even a frustum ending at the stern flap in a vertical position. The largest increase in length and presumably aerodynamics would be an inclined plane coming from the roof till at least the top of the vertical stern flap and continuing on the same angle till it meets the horizontal continuation of the bottom of the bed in a horizontal line segment as wide as the width of the rearmost lip, I've never seen a tail wedge or tail pyramid but they're already hard to park even without anything behind the stern hinge, and rearward visibility would be bad) Sagittarian Milky Way (talk) 14:17, 6 March 2023 (UTC)[]

Short answer, probably no-one knows because no-one has ever wanted to make one. Perhaps you should make friends with someone with access to Computational fluid dynamics computer modelling (any Formula 1 team headquarters in your vicinity?) or other Automotive aerodynamics tools and get them to run a simulation. Or you could make one to fit your truck and perform comparative runs. {The poster formerly known as 87.81.230.195} 51.198.55.125 (talk) 20:12, 6 March 2023 (UTC)[]

For the Streamlining that the OP wonders about, this reference desk cannot evaluate aerodynamic drag values for varying vehicle designs and materials. Such values are found by tests in a Wind tunnel that is ideally large enough for the test vehicle (since not all aerodynamic phenomenae are scaleable to models), is equipped with means to study the wake pattern behind the vehicle and should include a rolling road surface to avoid unrepresentative friction under the vehicle. Wunibald Kamm investigated the drag coefficient obtainable in practical vehicles for which an ideal elongated "teardrop" tail would be impractical and arrived at the famed Kammback compromise that is to truncate the vehicle tail at the point where the cross section area is 50% of the maximum cross-section. This result continues to have widespread usage in car design. Philvoids (talk) 21:24, 6 March 2023 (UTC)[]

Heavy chain development mechanism reference

The section V(D)J recombination#Heavy chain does not cite any sources, and I was hoping to find some reference explaining the process at a similar level (I am an engineer, not a biologist). Specifically, how are each of the V, D, and J genes combined, and what is the end result of the recombination? RNA transcript? mRNA? I'd appreciate any help finding an article or book that doesn't get too deep into the molecular biology terminology! Trikekus (:3) 20:15, 6 March 2023 (UTC)[]

In a publication in Nature, "Somatic generation of antibody diversity", Susumu Tonegawa wrote in 1983: "The mechanism of V–J or V–D–J joining is not known and the main possibilities will be discussed in more detail below." I do not know if the precise mechanism has since been unraveled, but it operates directly on the DNA, changing the genome of a cell, and in the "main possibilities" discussed by Tonegawa it involves putative specific DNA-binding proteins (DNA polymerase, DNA ligase, ...). --Lambiam 11:05, 7 March 2023 (UTC)[]

unraveled ... :)

Thank you for your reply! In this book it seemed like some mechanism had been figured out, but I'm not sure I understand it. I think it's saying that V(D)J recombination results in a new chromosome present in the B cell, so I wonder how that will create an antibody protein eventually. Trikekus (:3) 19:31, 7 March 2023 (UTC)[]

"Somatic hypermutation and class switch recombination: After going through V(D)J recombination, B cells subsequently undergo two genetic modifications, SHM and CSR. The purpose of these alterations, mostly in the germinal center, is to increase the affinity and alter the biological properties of immunoglobulin but with a specificity for the antigen." from this 2020 review: V(D)J recombination, somatic hypermutation and class switch recombination of immunoglobulins: mechanism and regulation Modocc (talk) 20:08, 7 March 2023 (UTC)[]

The genome of a eukaryotic cell, in this case a B cell, is recorded in the collection of its chromosomes. V(D)J recombination operates on the genes of one chromosome at a time, so the change in the B cell's genome is a change in one of its chromosomes. Proteins are encoded in the genes of the genome and biosynthesized by translating the genes into a sequence of amino acids. The modified genes of the B cell encode antibody proteins. Different modifications give rise to different antibodies. --Lambiam 22:00, 7 March 2023 (UTC)[]

March 8

Safety procedures

Would the Piper Alfa (where the hell did the article I've just read go?!) disaster have been prevented if they had enforced proper lockout-tagout procedures (in particular with regard to condensate pump A)? 2601:646:9882:46E0:61CA:6F8B:E761:9E7E (talk) 07:28, 8 March 2023 (UTC)[]

Courtesy link - Piper Alpha. DuncanHill (talk) 07:35, 8 March 2023 (UTC)[]

I've put a redirect in: Piper Alfa → Piper Alpha. Martin of Sheffield (talk) 09:39, 8 March 2023 (UTC)[]

It certainly looks as though that would have prevented the disaster, but because the rig was completely destroyed, and most of the personnel died, we will never know the exactly sequence of events. Shantavira|^{feed me} 09:43, 8 March 2023 (UTC)[]

Lamp self-charging from solar panel

Suppose there's a lamp strong enough to charge an appropriately sized solar panel. There's also a battery charged by that panel and powering the lamp. The battery is fully charged and the lamp starts shining on solar panel. Would it create a self-sustaining loop where the lamp is continuously feeding the solar panel that in turn is constantly charging the battery that powers the lamp? 212.180.235.46 (talk) 14:46, 8 March 2023 (UTC)[]

No, even if you perfectly encased the solar panel around the lamp, so no light escaped, the panel does not convert 100% of the light into electricity. Only 15-20% of the light falling on a panel is converted to usable energy. The rest is likely lost to heat. --Jayron 32 14:58, 8 March 2023 (UTC)[]

You would effectively have invented a sort of perpetual motion, which is impossible in principle. As Jayron explained the culprit is heat (more technically: an increase in entropy). --Wrongfilter (talk) 15:03, 8 March 2023 (UTC)[]

Indeed, the second law of thermodynamics is a mean bitch. --Jayron 32 15:25, 8 March 2023 (UTC)[]

Yeah, however I see that particular configuration this way: even if only 15-20% of energy is converted, this implies that when a certain percentage of battery charge is spent to power the lamp (be it 20%, 50% or 80%), there should be enough time to regain at least 15% of spent energy. This would be mean that battery charge will never drop to zero or somewhat higher, so that the lamp will never (or at least after a very long time) discharge. Isn't it so? 212.180.235.46 (talk) 20:31, 8 March 2023 (UTC)[]

The issue here is that the amount of usable energy left in the system will drop exponentially over time. Because the amount of remaining energy drops so quickly, there will inevitably be a point in time after which there is no longer enough energy being emitted as light by the lamp to charge the solar panel at all (at least to any meaningful degree). I think I see where you're going with your statement that because the energy lost is a percentage of the remaining energy, there will never be a point after which there is none left, but there will indeed be a point after which there is no meaningful amount of energy remaining. Jguglielmin (talk) 20:37, 8 March 2023 (UTC)[]

No, the usable energy will drop linearly over time, not exponentially. PiusImpavidus (talk) 10:52, 9 March 2023 (UTC)[]

To provide an example: Suppose your battery holds 100 units of energy, you have a perfect lamp that emits all its input energy as light (which does not exist, but just for ease of math), and a solar panel that can capture 20% of incoming light. In just 5 cycles of the battery discharging and recharging, there will only be 0.032 units of energy left:

100\times 0.2^{5}=0.032

. Jguglielmin (talk) 20:45, 8 March 2023 (UTC)[]

"there should be enough time to regain at least 15% of spent energy. This would be mean that battery charge will never drop to zero". That's like saying that whenever Achilles reaches the place where the tortoise was before, the tortoise has always had time to cover at least 15% of the distance covered by Achilles, therefore Achilles can never overtake the tortoise. See Zeno's paradoxes; you're in good company to make that mistake. But if you reason that way, you take ever (exponentially) decreasing steps in time and therefore never reach the point in time when Achilles overtakes the tortoise or your battery is empty. In reality, the energy left in the battery decreases linearly and only a little slower than if there were no solar panel. Just as the separation between Achilles and the tortoise decreases linearly and just a little slower than if the tortoise hadn't run. PiusImpavidus (talk) 10:52, 9 March 2023 (UTC)[]

While it is true that a sum of infinite terms can sum to a finite value in a well-defined manner, math alone solves only a layman’s understanding of Zeno’s paradoxes. See Zeno's_paradoxes#In_modern_mathematics, in particular that ref (start reading from there's a tradition among some high school calculus teachers...). Tigraan^{Click here for my talk page ("private" contact)} 11:19, 9 March 2023 (UTC)[]

With respect to v<<c velocity addition, Zeno's The Stadium "half the time is equal to its double" is clearly bogus. Let d be the composite bodies' length and s their speed then passing by a point landmark A at the same time takes time t = d/s regardless of their direction of approach. Of course the stadium's space is filled in half the time, but that is on account of there being two bodies. More importantly, the time dilation of special relativity is insignificant when v<<c. Changing the reference frame to a body's proper rest frame the other opposing body's speed doubles to 2s (which is their relative speed) but the landmark is now moving with speed s (something that Zeno ignored? And Aristotle pointed out "The fallacy of the reasoning lies in the assumption that a body occupies an equal time in passing with equal velocity a body that is in motion and a body of equal size that is at rest; which is false."). Anyway, IMHO, PiusImpavidus's analysis of the OP's mistake is spot on. Modocc (talk) 16:00, 9 March 2023 (UTC)[]

From what I can tell, the cited www.mathpages.com article does not appear to meet WP:RS criteria. We can sometimes cite experts' self-published works, but only if we can ascertain their credentials and credibility. But I have not been able to do either with this source. Modocc (talk) 19:44, 9 March 2023 (UTC)[]