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April 17

How do they make sure radio waves won't overlap each other?

We watch Televising by grabbing radio waves that carry a video signal representing moving images, along with a synchronized audio channel. How do they make sure this radio waves won't overlap each other? Rizosome (talk) 17:14, 17 April 2021 (UTC)

Three answers, depending on what you mean by "overlap";

• If you are in a room with two light bulbs, how do you make sure the light waves won't overlap each other?
• Different TV and radio stations are on different frequencies, and (in the US) the FCC makes sure that they don't interfere with each others signals on a particular frequency.
• See Television transmitter#Combining aural and visual signals for analog TV. With digital TV it's all bits and the computer in the TV figures out which bits are which.

--Guy Macon (talk) 17:26, 17 April 2021 (UTC)

Its actually incredibly complex, there is so much engineering going on behind the scenes it's unreal. See radio resource management and the plethora of techniques listed that are used to prevent co-channel interference. Jules (Mrjulesd) 17:49, 17 April 2021 (UTC)

This specific case showing how politics can come into it may be of interest. --184.147.181.129 (talk) 06:44, 18 April 2021 (UTC)

Regarding radio, if you've ever had your car radio on when you were close to a broadcasting antenna, you might observe that it overwhelms every channel on your dial. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:24, 18 April 2021 (UTC)

That's because the signal is strong enough to bypass the antenna circuit and begin to drive the speaker circuit directly. The purpose of the antenna circuit is to amplify a specific signal and send that amplified signal to your speakers. If the signal in the air is already stronger than the amplified signal from the antenna circuit, then it will be broadcast instead of your antenna signal. This is more pronounced with AM radio than with FM radio; indeed, with AM radio, you can build a simple receiver without a battery; if you're close to the transmitter it will broadcast the signal without any external power source at all; the RF signal is sufficient to drive a small speaker itself. This page describes building simple radio receivers that don't require any power source. --Jayron32 14:05, 19 April 2021 (UTC)

For radio waves in vacuum, or air, or on the surface of metal, or in common insulators, the response is linear so that the superposition principle applies. This means that the waves can be separated out again and can pass through each other without affecting each other. Some materials are non-linear. (see Nonlinear optics) These include semiconductors with junctions or some kinds of crystals. In these the waves can mix to make difference and sum outputs, and also harmonics. But the TV will make sure that these are only used by design and not by mistake. Baseball Bugs' example will be due to a non-linearity in the first stage of the receiver that is loaded beyond its design limit. Graeme Bartlett (talk) 12:47, 19 April 2021 (UTC)

Another answer: Radio antennae use something called a LC circuit, or inductor-capacitor circuits. Both electronic components have a certain frequency, and when they are the same, the LC circuit enters a 'resonance' state, where the inductor and capacitor are synchronized. This leads to them receiving only a certain frequency of wave (see LC circuit#Applications). This can tune the receiver to whatever frequency you want. I don't know if that's what you're asking, but there's my two cents. Sungodtemple a tcg fan!!1!11!! (talk) 14:07, 20 April 2021 (UTC)

April 18

Are there any biological advantage behind males incapable of reaching multiple orgasms like females?

Are there any biological advantage behind males incapable of reaching multiple orgasms like females? Rizosome (talk) 16:06, 18 April 2021 (UTC)

The short answer is probably conservation of energy, but men are actually capable of multiple orgasms.[1] See Orgasm#Subsequent and multiple orgasms. nagualdesign 18:42, 18 April 2021 (UTC)

The obvious answer is that the men would never get any work done, and everyone would starve. Maybe that's what did in the Neanderthals. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:49, 19 April 2021 (UTC)

I didn't understand this part "men would never get any work done". What do you mean by that? Rizosome (talk) 18:59, 19 April 2021 (UTC)

Two choices: (1) get to work; or (2) get another orgasm. Which one would you opt for? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:07, 19 April 2021 (UTC)

Then how do you explain women working at all??? 2601:646:8A01:B180:8DAE:8B87:A52D:42A0 (talk) 05:55, 20 April 2021 (UTC)

Are you talking about now? Or thousands of years ago? ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:05, 20 April 2021 (UTC)

Is it possible to create a male calico cat that can reproduce by changing its genes, or would that kill the cat?

User blocked
The following discussion has been closed. Please do not modify it.
Also, if the cat had a baby, would it be female or male? Answermeplease11 (talk) 20:43, 18 April 2021 (UTC) Changing an individual's sex chromosomes from XX to XY is not possible with current technology. Even if it was, one cannot expect the ovary to thereby change into a pair of testicles.  --Lambiam 22:33, 18 April 2021 (UTC) Lambiam, does this mean that you dont know. And if you dont know, I dont care! Answermeplease11 (talk) 22:46, 18 April 2021 (UTC) Answermeplease11 You just convinced me not to put any effort in finding an answer to any future questions you may have.  --Lambiam 22:55, 18 April 2021 (UTC) Sorry Lambiam, that was a mistake. I would actually like to put in effort for my future questions! Answermeplease11 (talk) 23:29, 18 April 2021 (UTC) Then you won't mind using Google! ←Baseball Bugs What's up, Doc? carrots→ 01:48, 19 April 2021 (UTC) Or, failing that, read what Calico cat has to say about male Calicos. ←Baseball Bugs What's up, Doc? carrots→ 21:53, 19 April 2021 (UTC)

April 19

Over-current in lamp socket?

So, there's one particular lamp socket in my home where the bulb burns out much faster than in any other fixture (and once, when it burned out, it actually made a loud popping noise, almost like a blasting cap) -- which makes me think, could it be that this one fixture draws much more current than the others (despite the bulb being a standard 40-watt one)? What could possibly cause that? 2601:646:8A01:B180:8884:2B54:C0AA:7CD0 (talk) 09:04, 19 April 2021 (UTC)

• I seem to recall that an incandescent bulb would burn twice as bright if there was twice the current. Or maybe 4 times as bright. Abductive (reasoning) 09:26, 19 April 2021 (UTC)

To get twice the current, you also need twice the voltage. Actually a bit more, as resistance increases with temperature. So that's a bit more than 4 times the power. Brightness will increase stronger than power, as there'll be more visible light compared to infrared. Temperature will rise by over 40%, which means very quick failure. PiusImpavidus (talk) 18:18, 19 April 2021 (UTC)

Have you checked the wattage rating of that fixture? Some fittings don't permit much air flow which can result in the bulb overheating.--Shantavira|^{feed me} 11:59, 19 April 2021 (UTC)

It's a while ago that I used any of those incandescent light bulbs (they've been banned in Europe for quite a while), but I remember that they can fail with a bang – not the kind of bang shattering the glass. I've got no experience with blasting caps, so can't compare, but I think electric blasting caps work the same way as failing incandescant lights. My first guess is that you (or someone else in the house) use the light in that particular socket a bit more than you thought. They usually work for about 1000 hours or so, so the more hours per week it's on, the fewer weeks until it fails. Another possibility is vibration. In any case, the current drawn by the bulb is set by the bulb itself (and the power supply, which is the same for all sockets). The socket should have no influence on the current – and if it has, by having extra resistance, it lowers the current, making the light dim and longer lasting. PiusImpavidus (talk) 18:18, 19 April 2021 (UTC)

I've seen an incandescent light bulb fail in a way that broke the glass. Because the filament can be made in various shapes, it's possible for it to break and one of the broken pieces to form a short-circuit with the other one. In this case it apparently did that, lit up more brightly than normal and made a humming sound for a few seconds, then part of the overheated filament broke and burst through the glass. From the distance the fragments traveled, I estimated that they left the bulb at about 12 mph.

As Pius says, the socket should have no influence on the amount of current -- unless the voltage is higher than at other sockets (but that would imply a wiring fault and would not likely be a permanent condition, and you'd notice the bulb being brighter than normal). Vibration or insufficient airflow seem more likely. --184.147.181.129 (talk) 01:20, 20 April 2021 (UTC)

Does it pop while the light is already on, or does it pop the moment you turn the light on? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:27, 19 April 2021 (UTC)

As far as usage, that particular fixture is on the same switch as another identical fixture (so the amount of use they get is identical), but burns out more than twice as fast as the other one -- so usage in and of itself is not the problem. Nor is there any vibration (which, moreover, would once again have affected the 2 fixtures in the same way) -- however, overheating could be the problem (I checked the problem fixture just today and found a fairly large (2 inches), dead moth inside it -- which could in principle disrupt the airflow!) 2601:646:8A01:B180:8DAE:8B87:A52D:42A0 (talk) 05:53, 20 April 2021 (UTC)

Is it possible someone has done something completely dumb like wired the faster one to the two phases of the Split-phase electric power (as this seems to be in the US)? It's should be possible to do this even with a shared switch depending on the design of the switch. Nil Einne (talk) 13:16, 21 April 2021 (UTC)

I had an apartment that had a recepticle with 120 V slot configuration that was wired with 240 V split-phase, and a relative also had a house with this...feature. In both cases, it was an recepticle under a window. Best we can tell, the purpose of having 240 V available there was for higher-voltate window air conditioner units. We don't know if previously someone had altered the wire on a 240 V A/C to fit the 120 V recepticle or if someone used the wrong wiring when intending it for 120 V uses. Blew out a few appliances before someone with a volt-meter tested and found the mistake. DMacks (talk) 06:10, 22 April 2021 (UTC)

Not possible -- I've lived in the same place for many years and the problem has only appeared recently, and there have been no recent changes in the wiring. So I think only the moth could possibly be to blame after all! 2601:646:8A01:B180:817E:DAE9:6844:2CB0 (talk) 11:00, 22 April 2021 (UTC)

Is it possible to restore DMX’s dead body?

Asked and answered.
The following discussion has been closed. Please do not modify it.
I came up with this idea a few minutes after I heard that he died, which was about 3 days ago. I think that DMX’s body can be revived with these steps, which can be solved after we know what has happened to his dead body. (Unless his body has been incinerated) Answermeplease11 (talk) 18:11, 19 April 2021 (UTC) @Answermeplease11: Although there have been several instances of people recovering after being declared dead (see Lazarus syndrome), there are no known methods for resurrecting or reanimating deceased humans. Within hours of an individual being declared clinically dead, vital organs such as their brain and heart begin to fail on a cellular level, known as "molecular death". Beyond this point, it is unlikely that their organs could be procured for transplanting, and absolutely impossible that they could be resuscitated or restored. The rapper known as DMX was declared dead on April 9, 2021 at the age of 50. Barring a sudden technological breakthrough in artificial intelligence (see Mind uploading) and/or time travel (see Technological resurrection), I am sad to say that it is very unlikely that he could be restored to life by any method. RoxySaunders (talk · contribs) 19:26, 19 April 2021 (UTC) @RoxySaunders: you havent told me what happened to DMX’s dead body. I would still like know what happened to it, even if want to restore the body. Just please, tell me what happened to it, then I can come up with my solution. (I will possibly be well known in the future for coming up with strategies and solutions) Answermeplease11 (talk) 20:34, 19 April 2021 (UTC) At the moment, at least, his Findagrave entry says "burial details unknown".[2] ←Baseball Bugs What's up, Doc? carrots→ 21:02, 19 April 2021 (UTC) @Answermeplease11: I do not know. The exact state of Mr. Simmons' remains (embalming, cremation, burial, etc.) is a private matter which has not been reported by any media sources. His family have requested privacy in their time of grief, so it would be inappropriate for me to speculate. While the Reference Desk is not a credible fount for legal or medical advice, I would strongly advise against any futile attempt to steal and resurrect the body of any deceased individual against their wishes. Yours truly, RoxySaunders (talk · contribs) 21:03, 19 April 2021 (UTC) @RoxySaunders:, I dont want to steal the body! I just want to call their family, just to ask them if his body can be restored. If they say no, I dont care. But at least he has kids which will continue his legacy! (And learn not to take drugs) Answermeplease11 (talk) 21:17, 19 April 2021 (UTC) You're wandering into inappropriate territory. You had best close out this section. ←Baseball Bugs What's up, Doc? carrots→ 21:26, 19 April 2021 (UTC) Sorry, @Baseball Bugs:, just got stuck in a thought. But was my thought a bad one, or a good one? Answermeplease11 (talk) 21:30, 19 April 2021 (UTC) Good if kept to yourself. Bad if openly stated. ←Baseball Bugs What's up, Doc? carrots→ 21:45, 19 April 2021 (UTC) So, Baseball Bugs, should I delete this talk? Answermeplease11 (talk) 21:49, 19 April 2021 (UTC)

April 20

Where are the whitest people in the world?

In this article, it's written that "the native people of Bougainville, Papua New Guinea, have some of the darkest skin pigmentation in the world". But where are the whitest people located in the world? (I guess in Europe, but even as an European I'm not sure where exactly it is).--ThePupil (talk) 00:41, 20 April 2021 (UTC)

Jablonski and Chaplin have collected and reported published information on the skin color of indigenous populations of 85 locations spread over more than 50 countries (ref. [20] in our article Light skin). Based on the measured skin reflectance at 685 nm (red), where higher reflectance corresponds to a lighter skin tone, the top 40 are all in the Northern Hemisphere, followed by "South Africa (Cape)". (This raises the question how "indigenous" was defined.) The top 13 are all in Western Europe, with the Netherlands heading the list. Scandinavia and Iceland are not represented, though.  --Lambiam 09:55, 20 April 2021 (UTC)

I've seen extremely pale people in Northern Norway, you don't see people with such light skin color outside of Scandinavia. If you saw someone like that elsewhere, you'd think that the person was anemic. Count Iblis (talk) 17:15, 20 April 2021 (UTC)

It's not a location, but a genetic condition. See Albinism in humans. --OuroborosCobra (talk) 17:57, 20 April 2021 (UTC)

Like Nói albinói.  --Lambiam 12:03, 21 April 2021 (UTC)

The comparison with "people [who] have some of the darkest skin pigmentation in the world" tells me that the OP is asking about overall populations, not albinos. There are people in Ireland who (outside of some freckles) appear to be very pale. I wonder if anyone has compared them with a true albino to estimate how close they are to zero pigment? Are there people other than albinos who are totally unable to form a tan?

Related question: is there a genetic condition that is the opposite of albinism? I suppose that Addison's disease may come close, but the darkening seems to be a side effect with that condition. --Guy Macon (talk)

Various other conditions are described under Hyperpigmentation, though none are really "opposite" to albinism. See also List of skin conditions#Disturbances of pigmentation. {The poster formerly known as 87.81.230.195} 2.219.35.136 (talk) 05:25, 21 April 2021 (UTC)

Revealed: Why the Irish are the most fair-skinned people in the world:-

"In 2016, scientists found that our [Irish} pale skin complexion is inherited from just one man who lived thousands of years ago. Researches at Penn State University identified SLC24A5 as the gene responsible for skin pigmentation, and a specific mutation within it responsible for fair skin. The mutation, A111T, is found most commonly in Ireland and all who possess it share a common genetic code descended from the same ONE person. We don't know his name, but he lived in India or the Middle East around 10,000 years ago, before his ancestors eventually brought the gene to Ireland via the Iberian Peninsula".

Alansplodge (talk) 18:13, 21 April 2021 (UTC)

To be sure, the place also has more than it's fair share of gingers. Martinevans123 (talk) 21:33, 21 April 2021 (UTC)

@Guy Macon The closest concept is probably melanism. Matt Deres (talk) 19:53, 21 April 2021 (UTC)

Realism in "Godzilla vs. Kong (2021)"

Dr Nathan: Are you guys familiar with genetic memory? It's a theory that all Titans share a common impulse to return to their evolutionary source.

Ren Serizawa: Like spawning salmon.

Is "spawning salmon" good example for return to their evolutionary source? Rizosome (talk) 15:13, 20 April 2021 (UTC)

No, because "evolutionary source" is a meaningless concept in this context. It sounds all "sciency" but it really doesn't make sense; the dialogue makes it sound like a geographic location from which a species originated, but that's not how evolution works, nor is it why some species of salmon return to where they spawn. While it is broadly true that the defining characteristic of Salmonidae (the salmon family) is that they spawn in fresh water; it does not mean that the place they return is the location where the species evolved; if that were so literally every salmon in the world would be heading up the exact same river, and would continue to do so forever. They don't do that. I mean, people generally understand how salmon spawning works, so it's the sort of thing that does make sense for the audience, as long as you don't think about it too hard. Like pretty much all movie dialogue, especially as it relates to science. --Jayron32 15:42, 20 April 2021 (UTC)

Wait...what? Are you saying Godzilla isn't real? We have him on film! Excuse me, I have to inform the other engineers who are working with me on the Mechagodzilla project. We may have wasted a large amount of the taxpayer's money.   :(   -Guy Macon (talk) 19:36, 20 April 2021 (UTC)

Not to mention that Titans are also not real, with the possible exception of the New York Titans. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:56, 20 April 2021 (UTC)

Well, the Titans evolved into only a marginally real football team; some might even say their annual chances of success are purely fictional. The Tennessee Titans, on the other hand, have had more recent successes. --Jayron32 12:50, 21 April 2021 (UTC)

AFAIK there are no titans at all in reality, so there is no titan-related science in reality, either. The more in the Godzilla series, which is fantastic, not real. Hence its content is not real, too. Any 'science' provided there serves as explanation for fantasy, as such it makes no real sense. Searching for it is futile. --CiaPan (talk) 23:34, 20 April 2021 (UTC)

I recall seeing an early Godzilla movie in which one thing seemed real: The Kenner Girder and Panel building sets being destroyed by the monster. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:41, 21 April 2021 (UTC)

April 21

Do other species of Feline require Taurine?

Do animals like Lions, Tigers, and Ocelots require Taurine in their diet like House cats do? The Vitamin C article deals with which of the Primates can and can't make Vitamin C (Wet nosed apes can, dry nose apes like humans can't), but doesn't say how much of Felidae requires Taurine.Naraht (talk) 12:38, 21 April 2021 (UTC)

This paper seems to indicate that all members of Felidae require dietary Taurine. --Jayron32 12:48, 21 April 2021 (UTC)

Washing machine shakes violently

I'll call them up in a few days, but something needs to be done with my new Haier washer (they also make GE Appliances, Monogram, etc., I've learned). It shakes so badly even at the second highest of five spin settings that I can't put anything on it without worrying about it falling off. I worry about damage to the machine and the floor. Their website indicates that it's supposed to walk 0.25" per cycle?? [3] I used a level (well a pen with a level built in) and it seemed to be level. A plumber had also adjusted it while connecting the pipes to the under-the-sink inlets, something the GE installers wouldn't touch. Imagine Reason (talk) 14:25, 21 April 2021 (UTC)

Had you considered getting in an exorcist? Martinevans123 (talk) 14:30, 21 April 2021 (UTC)

Yes, but then I figured that it's unlikely for an evil spirit to have taken up residence in the machine so soon after it was delivered, and also to infect a machine at all. Also, I'd have to consider which exorcism tradition I'd have to follow. Imagine Reason (talk) 14:44, 21 April 2021 (UTC)

I hear the Polish ones are very reasonable. Martinevans123 (talk) 15:18, 21 April 2021 (UTC)

Mine will do this if there is an unbalanced clothes load in the machine. It may be that it isn't that the exterior casing of the machine isn't level, it's likely that the clothes inside of the drum aren't evenly distributed, which can unbalance the machine during the spin cycle and cause all sorts of havoc. This page has some guidance on how to correct for the problem, but the simplest one is simply to take the clothes out and re-arrange them so they are evenly distributed in the drum. --Jayron32 14:35, 21 April 2021 (UTC)

My compact model is listed as having a weight of 249 lbs. For a few pieces of clothing to cause such havoc...I don't want to have to adjust things for every wash. Imagine Reason (talk) 14:44, 21 April 2021 (UTC)

Unbalanced load can cause a lot of vibration. The mass may not be huge, but the drum spins quite fast, causing large and fast changes in momentum. I always just throw the stuff in, as no arrangement of clothes would hold and the machine is designed to shake it up to get a decent distribution of the load, but that would depend on the type of washing machine. There are 3 basic types: top loading vertical axis, top loading horizontal axis and front loading horizontal axis. You didn't specify which variety you use. I guess the horizontal axis machines are better at distributing the load. The top loading variety combines that with proper suspension of the drum. PiusImpavidus (talk) 15:43, 21 April 2021 (UTC)

It's a front loader. Imagine Reason (talk) 16:05, 21 April 2021 (UTC)

Could it be that I've vertical loops in my drain tube extension? The 4' drain tube from the washer is just short of my sink, so I had to buy a tube extension with a clamp, and I haven't tried to cut the 6' extension to half a foot (what a waste). Imagine Reason (talk) 14:50, 21 April 2021 (UTC)

Almost certainly not. It pretty much has to be something that rotates. If you run a cycle with nothing but water is is silky smooth? It should be. If it isn't it needs to be repaired. If you put in just one item you should see the tub oscillating a bit with the cabinet not moving. It should only be when you have a major unbalance that the oscillation becomes large enough to shake the entire machine. I suspect that one of the bolts holding the mechanism has worked its way loose. You may even find a bolt or a nut under the machine. --Guy Macon (talk) 17:33, 21 April 2021 (UTC)

I can't speak to the exact technical reasons behind your problem, but I can tell you that this may be a manufacturing defect issue of some kind. My nearest neighbor and myself both have GE washers that are about three years old and we are unable to use the highest (heavy) spin settings for this reason. I'm thinking it can't be a coincidence. Viriditas (talk) 21:45, 21 April 2021 (UTC)

Nooo, I got a great deal on a non-cheap model. Imagine Reason (talk) 22:53, 21 April 2021 (UTC)

My neighbor had the GE washer that was recalled due to potential fires. Check online for recall info. Viriditas (talk) 05:55, 22 April 2021 (UTC)

Washing machines come with bolts fitted so that during transport the drum part does not bounce up and down, overloading the springs that suspend it when in use. Sorry to risk suggesting something obvious to all, but you did remove all these bolts after delivery, didn't you? Without the springs being able to dampen the oscillations, I could imagine that the machine gets pretty violent. Jmchutchinson (talk) 13:17, 22 April 2021 (UTC)

Two of the four bolts have been removed. The other two probably as well, but I can't pry open the plastic cover to make sure (I'll use my phone to take photos later as I can't move the machine). Weird thing is, I try to push down the front of the tub and it doesn't move, which would seem to indicate that the bolts had not been removed. Yet when I ran an empty cycle, there was no shaking, which would seem to indicate unbalanced loads. Also, I just ran another load at medium spin and it worked fine. But my previous loads weren't that abnormal... Imagine Reason (talk) 14:21, 22 April 2021 (UTC)

Actually I only ran Max. Spin, no washing cycle. Is that sufficient to rule out shipping bolts? Imagine Reason (talk) 15:36, 22 April 2021 (UTC)

Why AC current good for home appliances if it has huge fluctuation in it?

In DC current, frequency is zero. But AC current frequency is not equal to zero. So why we prefer AC current for home appliances? Rizosome (talk) 15:41, 21 April 2021 (UTC)

See war of the currents. PiusImpavidus (talk) 15:52, 21 April 2021 (UTC)

It doesn't have a huge fluctuation. It operates on an incredibly regular frequency. --OuroborosCobra (talk) 16:32, 21 April 2021 (UTC)

There is an interesting attribute of AC power frequency. If you measure the frequency over, say, a ten minute period, you get a certain (low) deviation from a perfect 50Hz or 60Hz frequency. If you measure it over a month the error in percent is far smaller, and over several years it is smaller still. This is because AC power frequency variations are not a percentage, the way most errors in most things are. Instead, the frequency is sped up or slowed down ever so slightly so that the error is always a small fraction of a cycle no matter how much time goes by. The actual error in percentage equals that of the best atomic clocks -- because the engineers constantly adjust it to match the atomic clock within a fraction of a cycle. --Guy Macon (talk) 17:25, 21 April 2021 (UTC)

That's less often the case now -- some power companies (including where I live) have given up doing this... AnonMoos (talk) 03:12, 22 April 2021 (UTC)

Seriously? That would imply that they have no connections (or perhaps only high voltage DC connections) to the rest of the power grid. Is this on an island or some other remote location?

If you have a source for that claim we may wish to update our Synchronization (alternating current) page with it. --Guy Macon (talk) 03:37, 22 April 2021 (UTC)

Could be Texas ;-) --OuroborosCobra (talk) 03:39, 22 April 2021 (UTC)

Guy Macon -- I don't think that synchronizing a power plant with the rest of the electric grid requires atomic-clock correctness, or anything close to it. That was more of a consumer service, since many devices in homes had clocks. However, nowadays the clocks which depend on AC power cycling to count time are in microwaves and such (i.e. less essential), and people rely more on cell-phones etc to keep track of time... AnonMoos (talk) 23:17, 22 April 2021 (UTC)

You misunderstood my comment. I clearly said the short term error was "a fraction of a cycle". Even 1% of an AC cycle is huge compared to the error of an atomic clock. My point is that even if you measured over a period of hundreds of years the error would still be the same fraction of a cycle.

Consider if I measured the length of your index finger with an instrument that might read an inch too high or an inch too low. The error in percent would be huge. Now I measure the distance to the nearest star with the same plus or minus one inch accuracy. The error in percent would be tiny. That's what AC power is like; same absolute error no matter how long you measure it.

So does AC power have zero actual drift? No. The frequency over the long term has an error in percent equal to that of an atomic clock on top of the fraction of a cycle short term error.

And by the way, wall clocks and alarm clocks that use synchronous motors and thus have the same error as the AC that powers them are still very common. --Guy Macon (talk) 00:45, 23 April 2021 (UTC)

Then why did you even mention article "Synchronization (alternating current)" at all, if you already knew that it was irrelevant to my point??? AnonMoos (talk) 02:11, 23 April 2021 (UTC)

It isn't always about you. Other editors are free to discuss several related aspects of a question without each of those aspects being relevant to whatever pearls of wisdom you have blessed us all with. I am still wondering how you know that your local power company isn't synchronized with the rest of the grid. Did you read it somewhere? Personally make some phase measurements? Hear it from someone who is in a position to know? --Guy Macon (talk) 02:38, 23 April 2021 (UTC)

Whatever -- why should I exert the slightest effort to research anything to satisfy the objections of someone who is radically inconsistent from one comment to the next? There's really no point to it, when I have no idea which direction you're going to veer in by the time I would finish such research. AnonMoos (talk) 02:52, 23 April 2021 (UTC)

• I suspect (based on the nature of the question) that the OP is making a fundamental (but common) misconception about how electricity delivers energy to run devices. The model most people have in their head is the electrons are like little balls flowing down the wire, and the motion of those balls moving down the wire produces the energy to power your stuff. That introduces some contradictions when you consider AC power; which is to say that if energy is spent moving electrons in one direction, the same amount of energy would need to be expended moving them back, and where then is the energy to power your device if the electrons are just being driven back-and-forth in place. The energy to power your device doesn't come from the motion of the electrons in such a direct way; it comes from the interaction between moving electric charges and the electromagnetic field. If a picture is worth 1000 words, sometimes a video is worth a million words, and This video is undeniably the BEST explanation I have ever seen for alternating current and how it delivers energy. --Jayron32 12:24, 22 April 2021 (UTC)

Does Gravity assist heat/cools spacecraft?

Does gravity assist heat/cool down a spacecraft being accelerated/decelerated? --Bumptump (talk) 18:37, 21 April 2021 (UTC)

No. --Guy Macon (talk) 18:38, 21 April 2021 (UTC)

No, not significantly. Because friction is neglible, practically 100% of the potential energy is converted to kinetic energy. Exception: if the planet used for the gravity assist has an atmosphere and the spacecraft passed by that planet close enough to encounter said atmosphere, that would obviously result in friction/heat. - Lindert (talk) 18:43, 21 April 2021 (UTC)

I will have a caveat here, because the answer is not measurably, but there will be an unmeasurable non-zero heating occuring (which is to say, there is no way to even construct a device sensitive enough to measure it, but it will still be heated a tiny little bit) because every interaction that exchanges energy does result in some conversion of energy to heat (the second law of thermodynamics is a mean bitch). In this case, because the spacecraft is a 3-dimensional object, there will be some very very tiny amount of tidal forces exerted on the spacecraft (and conversely by the spacecraft on the planet) because the far side of the spacecraft experience a different gravitational effect than the near side, and that difference results in an imperceptible distortion in the shape of the spacecraft, and that distortion produces a tiny bit of heat. With a small spacecraft in the gravitational influence of a planet for a few days, it's negligible (i.e. not measurable, you can ignore it, etc.) but if we're being scrupulous it will still happen. Tidal heating is a real thing, and happens with quite dramatically with moons around the largest planets in the solar system, see for example Io (moon). So it depends on what level the OP is asking: are they asking purely theoretically? If so, the answer is "yes". Are they asking practically (i.e. would a thermometer be able to detect it?), then the answer is no. --Jayron32 12:09, 22 April 2021 (UTC)

True, but tidal heating can occur even if a moon is a uniform sphere in a perfectly circular orbit, so I would say that it was the orbit which cased the tides which caused the heating, not the gravity assist per se. The counterargument is that the gravity assist is a form of orbit (assuming that we define both ellipses and parabolas as "orbits"[4][5][6][7]). --Guy Macon (talk) 16:07, 22 April 2021 (UTC)

Spheres are still three dimensional, and will still experience differential gravity with the planet in question, the shape of either the orbit or the body is irrelevant, it's the fact that the close side and the far side have different gravitational effects on them that matters that leads to tidal heating. Regarding the word choice here; that's mostly an arbitrary linguistic convention; what an object actually does is not affected by the word or words we, as people observing the situation, use to describe it. The forces involved in gravity assist are no different whether or not we consider them to be an orbit or not; they care not one whit what words we use to describe them. --Jayron32 16:26, 22 April 2021 (UTC)

Playing the devil's advocate for a moment, the logical conclusion from the premise "what an object actually does is not affected by the word or words we, as people observing the situation, use to describe it" is that gravity assist heats the spacecraft a lot. The sun shines on the spacecraft and it heats up. That's literally "what the object actually does". Also, the side not facing the sun loses energy through radiation into the 2.7 degree kelvin interstellar space, so gravity assist cools the spacecraft a lot. Of course I am being silly and playing the Devil's advocate, but in a very real sense whether solar radiation is part of gravity assist and whether tidal heating is part of gravity assist really do depend on your definitions, not just "what the object actually does". --Guy Macon (talk)

A spacecraft can make a gravity assist manoeuvre around the shadow side of Neptune, or around the Sun side of Mercury. It is IMO confusing to ascribe the resulting cooling or heating due to differences in solar radiation received to the gravity assist.  --Lambiam 17:49, 22 April 2021 (UTC)

Of course is. That's why I used it as a counterexample to the claim that we just need to pay attention to the actual temperature of the spacecraft without defiding whether solar radiation and tidal heating are part of "heating caused by gravity assist". --Guy Macon (talk) 00:50, 23 April 2021 (UTC)

April 22

Earthquakes and magnetic field

Could it be argued that earthquakes is a certain tradeoff for having a magnetic field generated by geodynamo? That is, if the theoretical lack of earthquakes across entire Earth entails fixed, static tectonic plates, would this also mean the lack of magnetic field due to absence of plate-moving factors in the Earth's core? This is, of course, based on the assumption that magnetic field is vital for living organisms, otherwise it could be neglected. Thanks. 212.180.235.46 (talk) 15:17, 22 April 2021 (UTC)

Some points to consider:

• one might have an active core generating a magnetic field without this resulting in surface tectonic activity;
• a planetary magnetic field, once generated, might to a degree persist in the rocks even after the core activity ceased;
• lack of a (strong enough) magnetic field would expose the atmosphere and surface to the effects of cosmic rays and solar wind would likely have a detrimental effect on the existence and development of living organisms, both directly and through the results of atmospheric stripping;
• lack or cessation of tectonic activity to recycle absorbed water and atmospheric gases back into the hydrosphere and atmosphere via volcanoes might result (particularly when combined with atmospheric stripping) in a dry and near-airless surface, such as appears to have happened in the case of Mars. {The poster formerly known as 87.81.230.195} 2.219.35.136 (talk) 15:50, 22 April 2021 (UTC)

As far as we know, the magnetic field is not vital for most living organisms. If the core froze solid, earthquakes and the magnetic field would probably both cease. The term "tradeoff" is usually reserved for design decisions, which I think does not apply here.  --Lambiam 17:35, 22 April 2021 (UTC)

Doubt on current flow

From hereI learn that electric current flows positive to negative charge, does it mean current goes back to battery and recharges it? Rizosome (talk) 16:20, 22 April 2021 (UTC)

See Electric current#Conventions. Also see NASA's The Direction Assigned to Electric Currents and IOP's Electric charge and current - a short history --Guy Macon (talk) 16:51, 22 April 2021 (UTC)

Further, look at Electrochemical cell and Galvanic cell. Electrons aren't flowing out of a battery and into a battery. They are flowing around a circuit, all of the way around, and keep flowing as long as their is electrochemical force to keep driving the flow. That electromotive force is coming from the battery placed into the circuit. So, electrons flowing through the whole circuit, including the battery, do not recharge said battery, they are being "pushed" by the battery. That electrochemical force is driven by redox reactions in the battery (galvanic cell article shows this well). You have a redox reaction that starts under conditions far from equilibrium (i.e. most of what is getting oxidized is starting in its reduced form, and most of what is getting reduced starts in its oxidized form). The electrochemical "force" is the force of the system trying to reach equilibrium. As the reaction takes place to get to equilibrium, whatever side is being oxidized is "pushing" electrons to the side that is getting reduced, and we take advantage of this by placing a wire and all of our other electrical components between them. As the redox reaction approached equilibrium, the electrochemical force decreases, which we observe as the battery being "drained." Eventually, you reach equilibrium, and the battery is dead. The math for this can be found at Nernst equation. Since what is pushing those electrons is the reaction to bringing the system towards equilibrium, the electrons going back to the cathode doesn't recharge anything, as it is going to the cathode to reduce it. The only way to recharge the battery is to somehow re-oxidize the cathode and re-reduce the anode. --OuroborosCobra (talk) 17:35, 22 April 2021 (UTC)

@OuroborosCobra:Electrons aren't flowing out of a battery and into a battery. They are flowing around a circuit, all of the way around, and keep flowing as long as their is electrochemical force to keep driving the flow. You are saying electrons are not flowing and again flowing, so much contradiction in your edit. Rizosome (talk) 06:26, 23 April 2021 (UTC)

It sounds to me that you believe the SAME electrons are whizzing around the "circuit" like cars at the Indi 500. This is not the case. The positive and negative side of the battery itself are isolated/insulated from each other. The potential difference is what drives the electrons from the positive side of the battery through the circuit and to the negative side. 41.165.67.114 (talk) 07:03, 23 April 2021 (UTC)

April 23

Substance mixing and boundaries

Do all substances/materials, including solids, mix together or interact with their surroundings and thus have indefined boundaries, even if it's only by a tiny amount at the atomic/sub-atomic level? PaleCloudedWhite (talk) 06:53, 23 April 2021 (UTC)