Wikipedia:Reference desk/Archives/Science/2021 April 21

= 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. -- Jayron 32 12:48, 21 April 2021 (UTC)
 * Thanx. Which as far as I can tell makes all of Felidae obligate meat eaters.Naraht (talk) 14:06, 26 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?? 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.  -- Jayron 32 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)
 * Unless the drum has a serious manufacturing defect, no load means an optimally balanced load and should not lead to oscillations, thus not requiring springs to dampen the oscillations. So the theory of shipping bolts having remained cannot be seriously tested this way. Can the tub be moved at all by pushing elsewhere, and is there an asymmetry consistent with the naughty bolts theory? --Lambiam 09:28, 23 April 2021 (UTC)
 * I can move the drum to back and front a little bit. No apparent asymmetry. Imagine Reason (talk) 13:59, 23 April 2021 (UTC)


 * At what point in the cycle does it start to shake? I've had shaking washing machines problems on two occasions:
 * On an older, cheap machine, caused by the concrete weight inside coming loose. This resulted in it shaking throughout the wash cycle.
 * On my current machine, caused by a blockage (specifically a screw that had accidently been included in the laundry) getting trapped in the drain pump. This caused the machine to shake violently, but only towards the end of the cycle when the water started draining.
 * The former necessitated replacing the washing machine, the latter took the repairman about 5 minutes to identify and fix. Iapetus (talk) 13:19, 23 April 2021 (UTC)
 * I just finished a load with a bedsheet, two t-shirts, and a boxer. It went swimmingly until 4 seconds left in the cycle. The spinning got so violent I stopped it. The machine said "unbalanced load". Indeed the bedsheet was bunched to the front. I couldn't fix it by spreading it towards the back, so I ended the wash. Previously it was also the spinning cycle that caused the shaking, but I didn't know about unbalanced loads then and forgot if the display said anything.
 * I'm confused about people throwing in items to balance an unbalanced load. Do they throw in clean clothes? Doesn't make sense to dirty the load just to balance the machine. Imagine Reason (talk) 13:59, 23 April 2021 (UTC)
 * When I bought my (front loading) washing machine, the salesperson claimed that one of their customers found their washing machine was moving around the floor, and it was because they didn't remove the bolts. Whether this was true or a story told just to emphasise the importance of removing the bolts I don't know. Nil Einne (talk) 14:59, 23 April 2021 (UTC)
 * Washed another couple of loads. Spinning at max. spin didn't matter until the last load, when it started shaking with over two minutes left. I took out the pair of jeans that didn't fit with the other light articles of clothing, and the machine was able to finish the load without a problem, although it never complained about unbalanced loads. Imagine Reason (talk) 17:33, 24 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.  -- Jayron 32 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.  -- Jayron 32 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"). --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.  -- Jayron 32 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)
 * I must have missed the strawman presenting that claim; all I got was that some forces don't care what names they are called. Executing prisoners by hanging wouldn't work in zero gravity, so this particular form of punishment could be called a "gravity assist". Is the termination of life caused by the hanging, or by the "orbit" (trajectory in spacetime) of the condemned's body? --Lambiam 08:38, 23 April 2021 (UTC)