Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

June 21

When will a F-35 be fully ready? Why does the USS Gerald Ford take so long to deploy?

The article doesn't say on the first one and says she'll spend 2016-2019 doing.. something on the second. Why does it take 3 years between being commissioned into the Navy and being deployed? The 2005 article said the F-35 will enter service in... 2008. Sagittarian Milky Way (talk) 00:41, 21 June 2016 (UTC)

For the F-35, it depends on what you mean by "fully ready". The F-35B is currently at initial operating capability with the USMC and is deployed with VMFA-121. Deliveries are currently scheduled for the next 20 years; undoubtedly, the aircraft will receive upgrades during that time (it's the case with all other major aircraft). Service life is anticipated for another 35 years beyond that; undoubtedly, the aircraft will receive upgrades then, too. Full operational capability is currently forecast for 2021 per several search results, but that definition means (among other thing) "all units scheduled to receive a system have received it" -- is that a precursor to say that the aircraft is "fully ready" by your standards?

For the USS Gerald Ford, I'm doing more guesswork, but I suspect the long working-out process is because this is the USN's first new class of carrier in about 45 years (depending on where you want to snap the line on the USS Nimitz) — the gap between the Ford and the Nimitz is the same as that between the Nimitz and the USN's first fleet carrier, the USS Lexington. Per the Ford's article, there's a lot of testing to wring out all of the new tech so that future ships in the class don't have the same growing pains. — Lomn 02:03, 21 June 2016 (UTC)

When will testing finish on at least one variant and the first individual aircraft go "on duty" and have all its version 1.0 capability available to be used within about whatever the in service scrambling time's supposed to be? No taking an extra hour cause "Oh shit, it's not fueled, the non-trainers weren't supposed to be fueled for another 3 months, somebody get a fuel truck! Who here has finished training? Somebody arm the weapons! Find the guy with the other arming key!..." (however unlikely it is that we'd be threatened by something that needs an F-35 that early in the product lifecycle) Sagittarian Milky Way (talk) 05:55, 21 June 2016 (UTC)

The problem with the Ford deploying is... μηδείς (talk) 12:41 am, Yesterday (UTC−4)

Ah, I didn't realize the infobox's "status: testing, training" only means the A & C are testing and they don't have a B to spare from training (with the F-35 pilot cadre growing for decades and low immediate battlefield need and all). I guess it's happened already then. Sagittarian Milky Way (talk) 21:01, 21 June 2016 (UTC)

How to label a 0 distance in an engineer drawing

Let's say I have a starting raw material that looks like the first frame[1]. If I want the left half to be machined so that it's 10 units higher than the right half, I would draw it like the second frame.

But what about the case when that distance is 0? As in, I want the left half to be flush with the right half like the third frame? How do I draw that? Any similar example would be welcome. Johnson&Johnson&Son (talk) 01:44, 21 June 2016 (UTC)

have a look at these examples. I'm not sure there is precisely such a thing as you are asking, I think you would simply include the dimension on the side as normal and an axis line, to make it clear you could include a "right angle" mark in the corner of the object and then if you've drawn a straight line, it's assumed the line is straight. If you want to you could probably include a dimension on both sides, but I don't think it's necessary. You could draw a "ghost" of where the material you need removed is, with the original dimension. Vespine (talk) 02:22, 21 June 2016 (UTC)

Thanks for the help.

>I think you would simply include the dimension on the side as normal and an axis line

>If you want to you could probably include a dimension on both sides

I cannot dimension the left side against the bottom nor the right side against the bottom due to variation of the material. I would love to if I could, but I can't, hence the tricky problem.

I can only dimension the left side with respect to the right side. Johnson&Johnson&Son (talk) 03:11, 21 June 2016 (UTC)

Basically imagine the bottom as a rough irregular shape like this[2], impossible to reference against.

But I do have a nice flat repeatable reference surface, which is the right side. So I'm forced to rely on only referencing against it and nothing else. Johnson&Johnson&Son (talk) 03:16, 21 June 2016 (UTC)

It's rather unusual to mill both sides down independently when you want them both to be flush, as this process is likely to leave a discontinuity between them. But, if this is the only machining possible, an engineering note, perhaps with leaders pointing to both sides, might be in order. It could say something like "Mill both sides flush to each other and sand out any discontinuity." StuRat (talk) 04:40, 21 June 2016 (UTC)

Only the left side is milled. The right side is simply the shape of the stock. It's like a L channel.

How would the leaders look like? If you don't mind, could you please take a screenshot or even just make a rough paint drawing like mine would be fine.Johnson&Johnson&Son (talk) 05:58, 21 June 2016 (UTC)

That's a fairly useless suggestion if you are dealing with a professional machine shop, they could quite rightly charge you ten thousand dollars for that. The correct solution is to define the 'as is' surface as a reference plane, and then define the machined plane relative to that using the appropriate tolerance form and value, depending on what you need from the machined surface. http://www.gdandtbasics.com/parallelism/ would be a place to start, but you could just apply a flatness tolerance to the entire contiguous surface, ie bothte machined and unmachined parts. Greglocock (talk) 07:16, 21 June 2016 (UTC)

Here's some examples: [3] (straight leader lines, at low resolution, unfortunately), [4] (curved leader lines). The note can either be placed directly, or a number can be placed there, and circled. That number then references a note on either the side of that page or on another page. StuRat (talk) 13:59, 21 June 2016 (UTC)

Voltaic Cell

Hello, I am having trouble wrapping my head around the chemistry/physics behind lead-acid batteries. A textbook I'm reading tells me that in a battery (which is not hooked up to anything) maintains a potential difference (the cell potential difference, determined entirely by the chemical's redox potentials). It does so by having the following half-cell reactions occur on the electrodes, which again are not in contact (except by the electrolyte):

${\ce {{HSO4^{-}}+Pb->{PbSO4}+{H+}+2e^{-}}}$ (anode)
${\ce {{PbO2}+{HSO4^{-}}+3{H+}+2e^{-}->{PbSO4}+2H2O}}$ (cathode)

I have two questions:

• I would say, if the reaction were to theoretically start on the anode, then the anode reaction makes perfect sense; the reaction will produce two electrons that travel through the lead metal, and end up at the terminal. However, the positive and negative terminals are not in contact; my question is then, where do the 2 electrons come from on the cathode reaction? I have tried to come up with a reaction mechanism for how these two electrons could have perhaps come from the electrolyte, but I am stumped.
• Say the cell is at its cell potential difference, with the electrons at the anode terminal and the deficit of electrons on the cathode terminal. If the battery were to be attached to a load, would it be more correct to say that the battery "produces a force" that moves the electrons (from within the wire) through the circuit, or would it be more correct to say that the excess electrons originally on the anode terminal move through the circuit instead?

Thanks for the help. 74.15.5.167 (talk) 03:29, 21 June 2016 (UTC)

Does this answer your question ? The cathode and the anode ARE in contact, through the electrolyte. Vespine (talk) 04:35, 21 June 2016 (UTC)

Elecrons travel from anode to cathode through the load by wires (when there is one). The battery produces the electromotive force. Ruslik_Zero 17:23, 21 June 2016 (UTC)

Okay, but does that mean there is no chemical reaction that transfers these electrons through the electrolyte? That is, it sounds to me like, if the battery was not hooked up to any load or wires, then the anode could produce its chemical reaction but the cathode could not (as it requires the anode's electrons). Would that not imply that a battery on its own has no potential difference if it weren't hooked up to a load? 74.15.5.167 (talk) 23:59, 21 June 2016 (UTC)

The key thing to grok here is that electrons carry a LOT of charge. So an undetectable shift in the proportion of how many + ions and how many - ions are in a given part of a solution adds up to a huge change in voltage. This is how an electrolyte works - the ions can simply move back and forth. They can "brigade", too - if one negative ion moves a few angstroms one way, and the next one down the line does the same, and the one after that... all the way to the far end of the electrolyte, then the charge effectively moves long before any one ion could ever cross the distance. So in practice, you have an electrolyte with a certain voltage here and there within it, and that is putting an electromotive force on the ions, and you can measure that in aggregate without tracing a single completed motion that takes the electron from one end to the other.

Now the battery therefore can have a difference in charge without having any noticeable effect on how many electrons or lead ions are present at each end, because only an undetectably tiny fraction have to change before there is a voltage difference. Once there is a voltage difference, that difference is pushing back against the electrons, against the electrolyte, so that the equilibrium no longer favors any further reaction at either end. I think -- I might be saying more than I know about this part, because there's a distinction between discharging and recharging a non-rechargeable battery and simply having it sit on a shelf. I think this is because the equilibrium occurs at a very small scale, whereas discharging the battery substantially creates macroscopic (or at least microscopic) changes in its structure. Wnt (talk) 00:10, 22 June 2016 (UTC)

Freezing water and oil

What aspect has the solid obtained by freezing an emulsion of water and oil? Are the oil bubbles traped in ice? What is the difference from the case of two distinct layers of water and oil? Does the heat transfer between layers of water and oil play affect the structure of the solid obtained?--5.2.200.163 (talk) 15:36, 21 June 2016 (UTC)

It depends on the type of emulsion and how it is frozen. It seems pretty complicated. Here are two research articles about the freezing of oil/water emulsions [5] [6]. Here's [7] another that is freely accessible. SemanticMantis (talk) 17:05, 21 June 2016 (UTC)

Thanks for answer. I see that coalescence (chemistry) is mentioned in the summary of one of this articles.--5.2.200.163 (talk) 11:07, 24 June 2016 (UTC)

In the scientific name Sus scrofa L., what does the L. denote?

I would like to include the sub-species of wild boar found in the UK at the Wild boar article. This article states that it is Sus scrofa L. What does the L. denote? DrChrissy ^(talk) 20:20, 21 June 2016 (UTC)

Naming authority, i.e. described the species, and often who gave it the name that is being used. By convention, a simple 'L.' means the big guy, Linneaus himself. Kind of surprising at first how many things he got his mitts on, even from around the world. This is the simplest usage, there are all kinds of arcane variants supported by formal ICN/ICZN policy, but I don't see anyone other than systematists/taxonomists using those much. There are ways to describe who described it, who renamed it, and then how the genus was moved into another family, but that's way above my pay grade. Altogether a commonly confusing thing, one that's surprisingly hard to figure out if you can't just ask someone what's up :) SemanticMantis (talk) 20:23, 21 June 2016 (UTC)

Thanks and you deserve a prize for the speediest answer of the year! Looking back, I should perhaps have realised because the L. is not italicised; I had been thinking it was an abbreviation as part of the name, but obviously it would be italicised if it were. DrChrissy ^(talk) 20:30, 21 June 2016 (UTC)

Like my namesake, I strike quickly, especially on matters of meaning ;) SemanticMantis (talk) 20:37, 21 June 2016 (UTC)

References

I believe your aquatic namesakes can strike so quickly they make light (see Sonoluminescence)! How awesome is that! DrChrissy ^(talk) 20:48, 21 June 2016 (UTC)

And today I learned that there's a redirect from Linneaus. —Tamfang (talk) 08:32, 22 June 2016 (UTC)

Haha yeah I realized my typo eventually but then decided to rock the redirect from misspelling :) SemanticMantis (talk) 13:38, 22 June 2016 (UTC)

June 22

Refractometry, part 2

So how do they prepare a thin slice of a translucent/opaque mineral for refractometry? What special tools (if any) do they need for this? 67.164.54.236 (talk) 00:59, 22 June 2016 (UTC)

Normally they would cut off a slice with a diamond cutting wheel, then flatten a surface on a faceting machine. It can be glued to a glass slide with canada balsam. Then sliced off again, and then ground down to the thinness required. Lapidary is the topic about shaping stones and minerals. However to measure refractive index, it can also be done by crushing into small fragments that might be transparent, and then putting them in different immersion liquids, such as diiodomethane or α-monochloronaphthaline. There is the Duc de Chaulnes method, oblique illumination method, and Becke line method and observation of relief. My reference is "An Introduction to the Methods of Optical Crystallography" by F Donald Bloss.Graeme Bartlett (talk) 01:26, 22 June 2016 (UTC)

So is it possible to do the job with a glass-cutting knife and a sander/bench grinder? Or do you have to use a powered diamond cutter and a faceting machine? (Call me Mr. Cheapskate, but these specialized lapidary tools cost a lot more than the generic ones I hope to use -- and I'm not trying to make jewelry, but to make a thin slice for spectroscopic analysis.) 67.164.54.236 (talk) 11:26, 23 June 2016 (UTC)

It is possible to use cheap equipment, it depends on how much you want to do. Also how hard is your opaque mineral? A bench grinder may be emery, and same with the paper. So you could probably do minerals up to hardness 8.5, but the harder the longer it takes. Also the average bench grinder does not have sealed bearings, and if you get rock/mineral dust inside it will be destroyed. Also something may overheat without water cooling, so you will have to stop and start once again after the sample cools. It is a lot of work to polish by hand on emery paper. I have done this with marble and granite, which is not that hard, but it still takes a long time by hand. But a small area of a few square millimeters should be possible with a couple of hours of grinding and polishing. You will want to get a mirror smooth finish. Graeme Bartlett (talk) 13:26, 23 June 2016 (UTC)

Thank you! FYI, the mineral in question is (or, rather, should be) between 5 and 6 on the Mohs scale -- so I think I should be OK, as long as the dust doesn't get inside. 67.164.54.236 (talk) 00:51, 24 June 2016 (UTC)

Just out of curiosity ... couldn't you measure refractive index directly by firing a pulsed laser at a sample and measuring the time delay for the first light to pass through the sample, even if it were nearly opaque? Wnt (talk) 19:15, 23 June 2016 (UTC)

Yes in principle. But a pulsed laser has a broad wavelength spectrum that will suffer Dispersion which reduces measurement accuracy. See Dispersion#Dispersion in gemology. The same problem arises in measuring emission times of pulsars. AllBestFaith (talk) 21:36, 23 June 2016 (UTC)

MOSFET driving several LEDs simultaneously

I'm trying to use a MOSFET to turn on/off several LEDs simultaneously like so[8] (only two LEDs shown). Do I need a resistor in series with the drain of Q1? Or the source of Q1? Or would that be extraneous?

I will be driving the MOSFET with the 3.3v GPIO of a microcontroller. Do I need a small resistor in front of Q1's gate to protect it? Johnson&Johnson&Son (talk) 04:48, 22 June 2016 (UTC)

The devices shown are two opto-couplers driven by a MOSFET. So long as the values for R3 and R1 are appropriate, the MOSFET will not be damaged, since its drain current will be limited by those resistors. So you do not need a resistor in series with the drain. A series resistor in the gate lead would be wise, since current will flow in the gate-source circuit when the drive voltage is made positive. This resistor will also act as a stopper for RF energy picked up from say, a nearby radio transmitter or internet router. It should be connected directly at the gate terminal and a suitable value might be 47K. On the other side of that resistor (the GPIO side), you should connect a resistor of say 4.7K to ground, so that if the triggering voltage becomes indeterminate due to disconnection of the GPIO terminal, the gate is pulled down to ground and the LEDs stay off instead of perhaps flickering. Akld guy (talk) 08:18, 22 June 2016 (UTC)

See Your µCPU what is the low output voltage? Tie the gate of the MOSFET to GND using a resistor located next to the MOSFET. Keep the gate wire as short as possible. You are using opto-couplers? Make sure there's no solder flux or dirt under the coupler device. Clean before operate on hazardous voltage. --Hans Haase (有问题吗) 11:38, 22 June 2016 (UTC)

Intestinal gas exchange

Recently, while experiencing a bit of bloat, I was wondering: Do gases in the intestine enter the blood stream to any measurable degree? I would think that if nutrients and water can cross over, then at least some amount of gas would also find its way across. On the other hand, there can't be too much gas exchange otherwise gas buildup wouldn't tend to be much of a problem. If there is some gas exchange, does that cause any problems with blood chemistry and the like? Dragons flight (talk) 07:24, 22 June 2016 (UTC)

Many of these gases dissolve freely into the bloodstream, but they also dissolve freely out of it, making it possible to test them on the breath, etc. [9][10]. The second source seems to suggest that swallowed nitrogen is more persistent than oxygen, which is absorbed; meanwhile carbon dioxide can enter. Only 1/3 of people have the secret mutant power to generate methane; the rest have to content themselves with farting hydrogen and CO2. But I feel like I don't really have the answer, because I'd want to see rates of production and diffusion to get a full picture - I'm assuming it's all a matter of kinetics. Wnt (talk) 12:08, 22 June 2016 (UTC)

Finasteride and fertility.

Does Finasteride decrease the sperm count and thereby making one impotent ? — Preceding unsigned comment added by 182.18.177.78 (talk) 08:02, 22 June 2016 (UTC)

Physicians use Finasteride primarily to treat BPH, informally known as an enlarged prostate, and the FDA approved label reports cases of diminished libido or erectile dysfunction. Finasteride partially inhibits 5α-reductase with side effects that include reduced Epididymis (outlet tube from testicle) and decreased sperm motility. Suspected Male impotence connected with BPH treatment can have many causes which will not be diagnosed on this ref. desk and should be resolved in consultation with a urologist who may prescribe any of a number of medications with different side effects. For example, Dutasteride is an alternative 5α-reductase inhibitor to Finasteride, with a different risk profile. AllBestFaith (talk) 11:46, 22 June 2016 (UTC)

Note that decreased sperm count doesn't directly lead to impotence - lots of guys are shooting blanks and never know it until they start wondering why no babies are coming out! Wnt (talk) 12:10, 22 June 2016 (UTC)

We may suppose that infertility is an undesirable side effect of BPH medication. However Silodosin in contrast to other α₁ blockers has shown promise as both a BPH medication and as a chemical contraceptive for men, see Silodosin#Pharmacology. AllBestFaith (talk) 18:23, 23 June 2016 (UTC)

Seeing a rocket go up

If a Long March 7 rocket launches at sunset 19:30, 2016 06 25 around 126 degrees to the southeast, around 100 km away, will we see it go up from the top of a building in Haikou? Anna Frodesiak (talk) 10:36, 22 June 2016 (UTC)

The human eye should certainly be able to see that amount of light at that distance - experiments showed that the eye can actually see a candle flame at 30 miles! However - it will rather depend on the weather! http://www.livescience.com/33895-human-eye.html Wymspen (talk) 11:49, 22 June 2016 (UTC)

And you'll see it when it's just less than 1km from the ground, fwiw, based on a quick scan of this table --Tagishsimon (talk) 11:59, 22 June 2016 (UTC)

Thank you, Wymspen and Tagishsimon! Anna Frodesiak (talk) 21:14, 22 June 2016 (UTC)

Magnetic field influence in neutron

Does the applying of a magnetic field influence the average lifetime of a neutron by increasing or decreasing from the value of approximately 15 minutes in absence of field?--82.137.9.64 (talk) 12:23, 22 June 2016 (UTC)

Possibly, but by only an infinitesimally small amount. Ruslik_Zero 14:22, 22 June 2016 (UTC)

Neutron half life is unaffected by magnetic field strength in ordinary contexts. It is suspected to decrease, however, in magnetic fields stronger than 10⁸ tesla. Magnetic fields as this strength would only be found at the surface of a magnetar or possibly inside a star that is in the process of collapsing into a black hole. However, a magnetar will still contain neutrons since neutron half life is increased by matter density in a way that more than cancels out its dependence on magnetic field strength http://journals.aps.org/pr/pdf/10.1103/PhysRev.187.2141]. Someguy1221 (talk) 04:41, 23 June 2016 (UTC)

Which tetrapod group could evolve into a new class?

I wonder whether exists a tetrapod group which can evolve in a reasonable amount of time (ten-twenty million years?) into a new class of organisms as different as are mammals or birds.--Carnby (talk) 13:57, 22 June 2016 (UTC)

My WP:CRYSTAL is cloudy, cannot read. You may be interested in exaptation, mutation rate, rate of evolution, and Error_catastrophe. Also this [11] article on a rapidly evolving group of fish looks interesting. SemanticMantis (talk) 15:15, 22 June 2016 (UTC)

Agree with the above, but see also species problem. The concept of species is fraught with exceptions and hard-cases and it's much more easily defined than "class" or "family". A new class could be created at any time by deciding to organize phylogeny slightly differently. Matt Deres (talk) 16:16, 22 June 2016 (UTC)

Organizing phylogeny differently, a ready-made new class could be Chelonia, couldn't it?--Carnby (talk) 16:40, 22 June 2016 (UTC)

You would want to look for the current classes which already show great diversity between different sub-groups. Possibly bony v cartilaginous fish, turtles/tortoises v snakes v lizards/crocodilians, penguins v flying birds? Wymspen (talk) 17:59, 22 June 2016 (UTC)

That would be true if we were fine with arbitrary classification, but the goal is to support these things with scientific evidence. We do get new evidence and shuffle things around quite a bit, but not classes. If you're doing modern systematics (largely via Computational_phylogenetics), classes are actually often easier and less subjective to separate than species are. Families are pretty tough. Given the species problem and the three-domain system, taxonomy gets more anchored and stable at the top and bottom, and it's the middle-to low taxonomic ranks like family that are most arbitrary. Consider that bird taxonomy has shuffled things quite a bit in recent decades, but class Aves has remained unchanged for quite a while. According to Tetrapod#History_of_classification, no tetrapod classes have changed since the reptiles and amphibians were split in 1804. SemanticMantis (talk) 18:40, 22 June 2016 (UTC)

My point was not about re-classifying existing species. If you are considering where evolution might lead to such a high variance that it was no longer possible to consider all the species involved to belong to the same class, the logical starting point seems to be those classes where a very high level of variance has evolved already. I didn't suggest such a process for an mammalian groups, because the class is more recent, and probably shows less variance than the older ones (though the cetaceans may well be on their way). Wymspen (talk) 20:02, 22 June 2016 (UTC)

Yes, I took your point, it was fine. I was replying to Matt Deres' comments on creating new classes of extant species, per WP:INDENT style. SemanticMantis (talk) 20:21, 22 June 2016 (UTC)

• The biggest problem with the question as such is that "class" is an artifact of our evolving understanding of evolution and cladistics. That being said, birds and mammals probably would not have become considered new classes, except for extinction events. Given the widespread prevalence and small size of songbirds, rodents, and microchiroptera, my guess is they would probably survive another K/T type event, and speciate quite rapidly.

Bats and whales are diverse enough that were all other mammals to go extinct, there'd be little sense in keeping them closer than turtles an birds. And I agree with the above statement that if you want to go with existing tetrapods, separating off the turtles and crocodiles from the lepidosauria would make the most sense. This is all my POV, of course. μηδείς (talk) 00:44, 23 June 2016 (UTC)

Yes, there's a lot of philosophy in this question. Cetaceans are indeed even-toed ungulates - zero is even, after all. :) - but cetaceans aren't a class, not even an order (though they were considered such at one time). But surely a bird and a bat are more similar than a whale and a mouse deer? Only with great effort does the taxonomist know what to look for to (rather absurdly, you'd think) dispute this claim.

For everything that's not a bird: note the fur and mammary glands. Note the lack of hollow bones. Note the uterus and lack of cloaca. That the bat is more closely related to the mouse deer and the whale than the crow should be obvious to anyone who's dissected all four. You're right that the number of taxonomic ranks and their names are a bit arbitrary, but the distinction between tetrapod classes is far brighter and more easily supported than e.g. chimps vs. bonobos or any ring species. Class disctinctions are less artificial than species or genera, not more. Another way of saying it: the deeper the cut between two clades, the less debate is possible. SemanticMantis (talk) 20:04, 23 June 2016 (UTC)

Oh, I'm definitely not denying that the clade distinction is most fundamental and important. But determining the relative importance of characters is not easy; it's only in hindsight we know to look for hairs and to distinguish them from feathers. So to say "a class of organisms as different as mammals or birds" is actually a tautology - whatever makes that group a class will be an important difference from a cladistic point of view, no matter how small and subtle that feature may be. But to the eyes of the layman, it may look like a big nothing, or more closely related species (humans and chimps, say) may seem much more different than the classes as a whole. Wnt (talk) 23:35, 23 June 2016 (UTC)

It would seem in "true" taxonomy the status of class therefore is not earned by morphological difference, though morphological difference may be its expression ... sort of like grace and good works in theology, perhaps. The penchant of taxonomists seems to be to add superphylum and taxonomic domain near the top of the list, so my guess would be as time goes by, categories ideally would simply work their way up the ranks. The exception being species, with its unique definition, versus genus. But if many species become genera, then genera become families, families become orders, orders become classes. And so any order today has a roughly equal chance, depending on its recent fortunes and changing ecology, of becoming a class. All others need not apply, unless of course they happen to be things that ought to be orders now. Now could there be an event in the next ten million years that is drastic enough that species radiate out into genera? Well, a mass extinction clearing out most existing lifeforms would do the trick, and happy chance, we're in the middle of one. So the odds, I'd say, are looking good. Wnt (talk) 16:43, 23 June 2016 (UTC)

June 23

Naegleriasis cause of death

Is the ultimate cause of death in cases of naegleriasis damage from the pathogen itself, such as from necrosis or bleeding? Or is the cause of death related to inflammation of the brain? Does the human body mount a significant immune response to the parasite? Someguy1221 (talk) 04:42, 23 June 2016 (UTC)

From this paper [12]:

Basically, "yes". N. fowleri...deeply penetrates the cortex to the periventricular system, and incites meningoencephalitis with rapid cerebral edema, resulting in cerebellar herniation. The olfactory bulbs and orbitofrontal cortices are necrotic and haemorrhagic. Histology has shown acute inflammatory reaction, mainly composed by neutrophils with extensive areas of lytic necrosis with the presence of several trophozoites.... Increased intracranial pressure and herniation are usually the cause of death. Opabinia regalis (talk) 05:47, 23 June 2016 (UTC)

So yes, there is a significant immune response, and yes the cause of death is inflammation, not really the necrosis or direct impact of the pathogen. SemanticMantis (talk) 13:40, 23 June 2016 (UTC)

Well.... technically, according to that source, the increased ICP caused by the inflammation is the cause of death, not the inflammation itself. Nitpicking, I know, but it's a causal sequence, infection causes neuroinflammation, which causes oedema, which causes raised ICP, which causes death. The inflammation is only halfway through the process. Fgf10 (talk) 22:49, 23 June 2016 (UTC)

Fair enough. I think the important thing is that the causal chain is long. At some point, the amoeba is responsible as an ultimate cause, but it's not really "trying" to kill you, the way many/most other diseases are (please excuse the teleological shorthand and consequent scare quotes). SemanticMantis (talk) 16:21, 24 June 2016 (UTC)

I'll forgive the shorthand, but I'm unsure about the "many/most" comment. Surely almost every microbe simply "wants" to survive and multiply. Our deaths do almost nothing to help that, so my guess is that it would actually be quite rare for a microbe to intentionally bump us off. I'm no epidemiologist, but I can't think of a single one where our death would provide a benefit to them. Matt Deres (talk) 18:21, 25 June 2016 (UTC)

Necrosis itself also can cause edema, causing raised ICP...etc., though I don't know how much that contributes in this particular sequence of events. Opabinia regalis (talk) 23:08, 23 June 2016 (UTC)

Slow-moving water

What's the difference between a bayou and a slough, at least in its North American use? I understand that the former term is more common in the southern USA than elsewhere, but one can find bayous and sloughs together in the same areas farther north, and the definition in the latter article does a good job of defining places that are typically named "bayou", whether today or in 1820 (both links address the same location), as well as defining places such as Levy Slough at 37°51′5″N 88°0′19″W. I'm not clear if the terms are generally used as synonyms (e.g. "creek" and "brook") or if there's some distinction between them. Nyttend (talk) 14:36, 23 June 2016 (UTC)

Mostly synonymous, as per our articles and the dictionaries I just checked. My NOAD says bayou: (in the southern US) a marshy outlet of a lake or river. from Louisiana French, from Choctaw 'bayuk'. Slough:a swamp, a muddy side channel or inlet. That bayou definition is a bit narrower, and I prefer the broader sense given in our article (what does Oxford really know about Louisiana French anyway - though it does clarify that nobody really talks about bayous much outside of the southern USA)

There are perhaps some differences in denotation, but then we get into regionalisms and personal preferences. E.g. some people do think there's a difference between a brook and a creek (and a rivulet and a stream, etc.), but it's not really correct to say those are well-supported distinctions. Anyway, if you want subjective denotations: Bayous often have cypress knees, sloughs don't. Slough gets used sometimes for human-engineered backwaters/drainage things, bayou doesn't. Bayou is usually reserved for something rather larger, sloughs can be pretty small. SemanticMantis (talk) 17:45, 23 June 2016 (UTC)

Thanks for the checking. I've always lived in hillier areas nearer headwaters (the only river city in which I've lived sits half on a bluff and half on a narrow plain along a somewhat entrenched river), so I've only known either bayous or sloughs as a visiting outsider. I should have made it more clear that I was indeed looking for solid, well-agreed-upon distinctions, because indeed I wasn't interested in personal preferences or individual distinctions. Nyttend (talk) 18:54, 23 June 2016 (UTC)

I still can't find any authority attempting to carefully formalize a definition for either. This is the stuff of folk taxonomy, methinks. Anyway, neither word appears in this fairly comprehensive glossary of hydrology [13]. Neither word appears in our Glossary_of_geography_terms. They have brief and ever-so-slightly different definitions in this National Geographic glossary [14]. SemanticMantis (talk) 19:46, 23 June 2016 (UTC)

In England, a "slough" is only to be found in the pages of The Pilgrim's Progress (the "Slough of Despond"), unless you count Slough of course. Alansplodge (talk) 20:52, 23 June 2016 (UTC)

There is a nature reserve in Coventry called Wyken Slough though. --TammyMoet (talk) 11:23, 24 June 2016 (UTC)

English also has [15] slough n. an outer covering that can be shed such as the cast-off skin of a snake, and slough v. to cast off (hair, skin, horn or feathers), from 1720. AllBestFaith (talk) 21:19, 23 June 2016 (UTC)

According to our articles and to [16] a Bayou has slow moving or stagnant water and a slough is only sporadically filled with water[17]. What I find interesting is that in British English we don't use it as a noun in that sense any more, although, as Alansplodge says, we have the town of Slough - pronounced "slau". However in BE we have "plough" - which is now spelled "plow" in American English, but for some reason slough has kept its old spelling in AE. Incidentally, when the word is used as a verb in BE i.e. to "slough off", it is pronounced "sluff" like the word "clough" - which is a wooded valley in Northern England - or "enough". Complicated or what? According to the Oxford dictionary definition given above the difference in pronunciation is because the noun derives from middle english and the verb from low German. Richerman (talk) 23:30, 23 June 2016 (UTC)

"Slough" doens't rhyme with "plow" in American English so why should it be spelled the same. "Slough" rhymes with "slew". Rmhermen (talk) 18:15, 24 June 2016 (UTC)

As does "through". ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:53, 24 June 2016 (UTC)

According to Merriam Webster it can be pronounced either slau or slew in AE - it probably depends where you come from. Richerman (talk) 19:13, 25 June 2016 (UTC)

I remember seeing a claim that American English is actually less altered from ancient usage than British English; presumably the dispersal of colonists and the relative paucity of culture slowed down linguistic innovation for a bit? But that's a topic for a different question... in any case, "slough" is specifically mentioned in the American English article, alas with 'citation needed' beside it. Wnt (talk) 23:43, 23 June 2016 (UTC)

This discussion has been closed. Please do not modify it.
The following discussion has been closed. Please do not modify it.
So does "slough" in AE not rhyme with "plow"? In Britain, if anyone talked of a caterpillar "sluffing" off its old skin they would be laughed out of the office. 92.23.53.54 (talk) 18:38, 25 June 2016 (UTC) Then I suggest you look at the pronunciation in wiktionary and the OED [18]. Richerman (talk) 19:17, 25 June 2016 (UTC) That one word "slough" comes from different roots with different meanings, which could help explain the different pronunciations.[19] ←Baseball Bugs What's up, Doc? carrots→ 18:42, 25 June 2016 (UTC) Er, yes, I think I explained that above. Richerman (talk) 19:13, 25 June 2016 (UTC)

Big Rip, black holes

If and when a big rip occurs, will black holes be ripped apart also?144.35.45.67 (talk) 19:33, 23 June 2016 (UTC)

They gradually lose mass due to accretion of phantom energy, see here for details. Count Iblis (talk) 20:38, 23 June 2016 (UTC)

The Big Rip hypothesis assumes that the Speed of gravity is finite such that in a continually accelerating expanding universe all matter eventually becomes unbound by gravity. There could then be no Event horizon boundary between the inside and outside of a Black hole. AllBestFaith (talk) 21:07, 23 June 2016 (UTC)

Fear of heights totally absent on a ship, why?

Being on the fifth story of an appartment building I feel less than perfect. However, being up much heigher on a cruiseship I feel totally comfortable. Looking down from a balcony: zero problem even when the ship is docked and I'm looking down at the dock. Why is that? Joepnl (talk) 20:56, 23 June 2016 (UTC)

Handrail. AllBestFaith (talk) 21:22, 23 June 2016 (UTC)

Nope Joepnl (talk) 21:26, 23 June 2016 (UTC)

Think this is simply different mental reference points of fearful situations. Unease in building is possibly an implicit memory formed years ago (with the original experience that formed it forgotten). Some people can't bring themselves to climb to the top of a three extension ladder but thoroughly enjoy their vocation jet leaving the runway. It is all to do with context. You may have become older-and-wiser by the time you first experienced a cruse ship and thus your implicit memory didn’t trigger due to the different context, which was not down to hight itself but the situation, but cruse ships were not part of the experience, when your naïve implicit memory formed. So, being on a cruse ship doesn’t trigger anything from the past. There is a technique called 'search back', where by think back to the time when the unease was first noticed – a re-examination of the event can nullify the unease. --Aspro (talk) 22:13, 23 June 2016 (UTC)

There's maritime law and the law of gravity, but no maritime law of gravity. So nothing to fear. InedibleHulk (talk) 22:59, June 23, 2016 (UTC)

A very interesting post. Anna Frodesiak (talk) 23:02, 23 June 2016 (UTC)

Seriously though, it might have to do with solid straight lines. If they converge, as in the side of a building against a street, that can give you a different perspective from the wavy, curvy lines. A bit easier to discern how far you'd fall, I find. InedibleHulk (talk) 23:05, June 23, 2016 (UTC)

Can you even see the side of a ship from a railing at all? If not, and you're ever close beside something your own height, try scanning to the bottom of that thing instead. I'll bet you'd feel at least a bit sweatier. InedibleHulk (talk) 23:37, June 23, 2016 (UTC)

I'm not so sure the OP wants tips on how to increase his anxiety level. :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:06, 24 June 2016 (UTC)

I don't mind an experiment for science :)

@InedibleHulk Yes you can and still no problem. But you are right, I have no fear of heights at all in an airplane. It's also not that the ship is made of "safe" metal compared to "unsafe" bricks or concrete. The Eiffel Tower is terrible as well :) But thinking of a floating Eiffel Tower, I think I'd have no problem climbing it! It really is strange. Joepnl (talk) 00:34, 24 June 2016 (UTC)

Also strange is how pictures can have the same effect, despite the viewer knowing damn well they're perfectly safe. Spiderman 2 messes me up worse than any "more realistic" game I've seen since. And Turok: Dinosaur Hunter still makes me carsick, while cars don't. InedibleHulk (talk) 13:56, June 24, 2016 (UTC)

Pictures like that make my hands sweaty, knowing that not only the building is perfectly safe, but that I'm just looking at a picture of it as well :) Joepnl (talk) 13:52, 25 June 2016 (UTC)

I'm pleased that xxx is enquiring enough to asked this question, because the contradictions (in feelings) can appear baffling to one's own logical side of the brain. So, sure the the OP is looking for an answer -so would I in his situation if I didn't I know the answer already (don't all you jump on me together for RS proof - just pointing it out). One's own instincts are a wonderful thing. When one is young and can't intellectualize a potential danger, instincts are your friend -they protect you from harm. As young ones, we get bombarded from every-side, with advice from adults saying such things as don't stand too close to the edge, you may fall etc. Up a three-extension-ladder they might say be very careful. Again these comments reinforce unease. Yet, get onto a holiday jet that has to wait 20 minutes from push back to finally getting to take off and everyone on board is jubilant. They have paid good money to the airline who has (one hopes) employed and air crew that takes on the responsibility for ones safety. So, no trigger. One does not have to 'take care' of oneself as it is being done by others -the air crew. Note too. The OP mentions that if the Eiffel Tower was floating they would have no trouble. Is this not a bit like sky-divers who when early on exiting a planes feel great trepidation -like walking off a edge of a cliff... When they progress to doing free-fall at much higher altitudes, their minds become so focused on free-fall techniques that they can step out of the plane without using will-power to over come their initial instinctive fears. Think about it. Face it: One has to be completely nuts to exit an aircraft with just a main and secondary cute to prevent you from becoming strawberry jam when you hit the ground. But with experience, one over comes those instinctive fears. Lets take this to the extreme - for added emphasis. Bet the last thing on the astronauts mind that do EVA's on the ISS is getting splattered on a side-walk 200 hundred miles below. The context is so much different. I mention Reachback earlier and now you have the link. Do it and you will not only be able to look over the edge of the Eiffel Tower but come to the UK and experience the "Walk of Faith" and enjoy the experience. This is no more than just a glass floor on Blackpool Tower to stop one plummeting down to the side walk below. What is the difference between a concrete floor or a glass floor? (Imagination, that's all). Blackpool Tower Eye (Glass Floor Walk, Lift and Ballroom)--Aspro (talk) 15:01, 24 June 2016 (UTC)

A glass floor is also much more pleasant to fall through, since concrete doesn't fall around you. Still no picnic, though, warning signs or no. And imagining you'll be fine is pretty useless. That said, everyone should see the CN Tower before they die. InedibleHulk (talk) 15:47, June 24, 2016 (UTC)

But never ever reach back like this. InedibleHulk (talk) 15:56, June 24, 2016 (UTC)

@Aspro, while as I child I didn't experience fear of heights, I'm quite sure it's not related to an incident (that I might have forgotten). It feels totally normal to be afraid of potential dangers, and looking down from a cliff is certainly a danger. Other people are terrified by spiders and while my brain doesn't mind them I don't think it's absurd. There is a certain evolutionary advantage to having phobias. A text written in red will have drawn your attention, and you cannot "unlearn" that red texts are more important than black ones. So, I'm totally OK with my fear of heights and it's not something I have to "deal with". Last time I enjoyed a beer when my friends climb the Eiffel Tower. However, the lack of the same fear of heights in planes or on ships is IMHO interesting. I wonder if other people have that experience as well and what could be an explanation that makes sense. I think it's very well possible that small adjustments to the design of high buildings (fountains? moving art? wood? Suggesting that the building actually is a ship?) could completely undo fear of heights. One of the most common phobias must have more research than Acrophobia has. Joepnl (talk) 22:41, 24 June 2016 (UTC)

You seem to have painted yourself into a corner, which stops you standing back and looking at that -which will solve your puzzling. I stated that instincts are good and so I agree that it is not something you have to "deal with". Just pointing it that the unease can be dissolved -if you so wish. Just a 'quick think' will not do it, because if the causative events come to mind that quickly you would have already realign your mind-view of the early perceived danger; that you once or twice sensed long, long ago. Should you take the time to dissolve the unease you will thereby answer your own query by seeing how it originally took hold. P.S. Next time you’re considering climbing the Eiffel Tower, consider taking the lift instead. That option may offer more drinking time but not for beer, rather try Absinthe. A few goblets of that and you'll end up abseiling back down without ropes.--Aspro (talk) 00:21, 25 June 2016 (UTC)

I had a very unpleasant meeting with a cat as a child, but I'm not afraid of cats. I don't think the millions of people who fear heights all had some bad experience they cannot remember. Surely, I would remember "my experience" right away because it should include at least a concussion or a fracture to make heights a special thing. Anyway, I didn't come here for medical advice. I really couldn't care less about "suffering" from acrophobia. My question is just: what's so special about a floating structure that, for me at least, it removes fear of heights. I think that's really strange and worthy of more research, which I was hoping had already been done. Joepnl (talk) 13:52, 25 June 2016 (UTC)

June 24

Drinking sub-zero alcohol

I've heard that strong brandy won't freeze even at -20°C. If I were to keep a bottle at say -5 or -10°C would my mouth and throat start to freeze when drinking it considering we're mostly made of water? 78.0.252.164 (talk) 13:07, 24 June 2016 (UTC)

Frostbite of the tongue would give you a hint to stop your experiment. AllBestFaith (talk) 13:35, 24 June 2016 (UTC)

Your drink might not be cold enough to cause serious damage - but there have been serious consequences from a Liquid nitrogen cocktail Wymspen (talk) 14:02, 24 June 2016 (UTC)

Hehe, should've remembered to ask Russians :D 78.0.252.164 (talk) 21:02, 24 June 2016 (UTC)

Why do you want to drink it so cold? You will not experience the bouquet (the whole point of a snifter is to warm the liquor in ones own hands to release the bouquet ) If you want to drink sprites very cold, then go for low quality spirits like American Bourbons. Made very cheaply from maize (the US call it Corn -but the results are the same). --Aspro (talk) 15:28, 24 June 2016 (UTC)

Sounds like someone has not had much exposure to Bourbon, or at least not the right kinds. Anyway, vodka is the spirit that is commonly served ultra-cold. SemanticMantis (talk) 16:16, 24 June 2016 (UTC)

Depends on the liquor definitely. I find that whiskey is best drunk cold, except maybe for Jim Beam and similar. But then again I don't like Jim Beam much 78.0.252.164 (talk) 21:02, 24 June 2016 (UTC)

http://msgboard.snopes.com/message/ultimatebb.php?/ubb/get_topic/f/108/t/000648.html --Guy Macon (talk) 17:39, 24 June 2016 (UTC)

Probably one key reminder from that discussion is that freezers are often -15°C or lower, so anything store in them for long periods, like ice cream, sorbets, ice blocks and ice cubes are likely to be at those temperatures. Yes they're solid so won't make so good contact with the lower part of the mouth (although probably better with the upper part). And even for those which are normally eaten frozen like ice blocks, ice cream and sorbets it's normal to let them warm up slightly and eat them slowly. Still I'm sure many people even here have experience eating at least one straight from the freezer and gulping it down. As for ice cubes, I'm sure some people here have putten an ice cube straight from the freezer into their mouth, some have even accidently or intentionally swallowed one. The biggest danger would likely be choking. Heat capacity and quantities are relevant, I'm sure you could cause some injury due to the cold if you tried hard enough but generally there's no reason to think the drinks are going to be generally different. (The earlier points along with heat transfer don't seem to have been considered in the discussion about air temperatures on Snopes.) Notably, even if the alcoholic drink did freeze you could always make an ice cube or block out of that just like with water, in other words there's even less reason to think of the non freezing drink as special. Perhaps if you had something which froze at exactly -15°C (or whatever) then enthalpy of fusion would be relevant but that doesn't seem to be what was referred to and I don't think alcoholic drinks are likely to freeze or melt in a simple way anyway. P.S. It's possible Leidenfrost effect would make some difference, or there would be some effect of an insulating layer, but I don't think it's clear that will be significant for water or water mixtures or ice cream at the temperatures involved. Nil Einne (talk) 19:19, 24 June 2016 (UTC)

Thanks guys. FWIW ice cubes are fine with me even straight out of the freezer, the worst that can happen is tongue getting stuck anyway, I was more worried about cold liquid coating and freezing the whole mouth, but yeah I suppose it's not a danger at these quantities and temperatures especially with the summer heat here.78.0.252.164 (talk) 21:02, 24 June 2016 (UTC)

Very cold beverages can actually cause a burn in the mouth or throat. And such burns can lead to cancer, according to the WHO. See here. Akld guy (talk) 00:14, 25 June 2016 (UTC)

Number of leads for a segmented LCD display

For 1/2 duty 1/2 bias segmented LCD displays:

1. 14 segments requires 9 pins

2. 18 segments requires 10 pins

What's the formula here?

My best guess so far is ceiling( # of segments / 2 ) + 2. Not sure if that's right or not. Johnson&Johnson&Son (talk) 15:06, 24 June 2016 (UTC)

TI's datasheet: http://www.ti.com/sc/docs/products/micro/msp430/userguid/ag_14.pdf

You need to loook for "2MUX", also "3MUX" and "4MUX". Note that this is LCDs, not LEDs. Andy Dingley (talk) 18:59, 24 June 2016 (UTC)

Thanks!

In their formula, Integer [2 + (#-of-segments/2)], is Integer() rounding up or down? Johnson&Johnson&Son (talk) 02:42, 25 June 2016 (UTC)

It would be rounding up. You need the connection whether you have one or two segments connected to it. Andy Dingley (talk) 09:12, 25 June 2016 (UTC)

Energy efficiency and speed of submarines and ships

Which can be faster and are energetically more efficient? Ships or subs? That is, comparing two which can hold the same cargo, not directly two which have the same size. --Llaanngg (talk) 19:00, 24 June 2016 (UTC)

A hint from nature is that the whale, the greatest sea mammal, travels long distances underwater rather than on the surface. See Whale#Locomotion. AllBestFaith (talk) 19:51, 24 June 2016 (UTC)

Nice hint, but there might be other non-speed, non-efficiency related reason for this. The skin or eyes could be too sensitive to travel on the surface, more food could be available deeper in the ocean, navigation might be easier underwater. --Llaanngg (talk) 23:51, 24 June 2016 (UTC)

FWIW: asked & answered on 'Yahoo! Answers' → [20] --107.15.152.93 (talk) 23:12, 24 June 2016 (UTC)

I am trying to find more reliable sources than Yahoo Answers, but thanks anyway. --Llaanngg (talk) 23:51, 24 June 2016 (UTC)

Submarines, because much of the losses are in creating waves on the surface.

In the 1960s, giant cargo submarines were studied conceptually to exploit this. However a long-submerged submarine needs nuclear power and the fuel elements for a compact reactor are also a gift for weapons production. Such a cargo submarine might also make a viable missile carrier. So, no cargo submarines.

The closest we got, in a way, was the bulbous bow which is also quite an efficient way to make a hole in water. Andy Dingley (talk) 00:01, 25 June 2016 (UTC)

Surface ships spend about half of their power to create waves. A submarine makes no waves, provided it's at a large depth compared to its diameter. Skin friction is lower for a submarine too, as it has a smaller wet hull area for the same displacement, assuming a typical beam:draft ratio for the surface ship. So the submarine is more efficient. However, a ship's size is often limited by draft. Most cargo ships are designed with the largest possible draft that still allows them to go where they have to go. At a given draft, a submarine has, because of its cylindrical hull, much less displacement and therefore loading capacity than a surface ship, which makes it less efficient. Then there's the limited safety of submarines, the nuclear material and the difficulty of loading/unloading any type of cargo except fluids or granular material, which makes them only usable for time-insensitive bulk. Using a cheap and slow surface ship works better for bulk.

Submarines have been proposed for transporting crude oil out of the Arctic, where they have the advantage of being capable of diving under the ice. But by first consuming the oil from warmer areas of the planet we managed to meld the ice cap, so there is no longer a need for that. PiusImpavidus (talk) 08:41, 25 June 2016 (UTC)

Portion size of food and nutrients

Recently, I watched Sugar Coated (2015) documentary. It was about the excessive use of sugar in the food industry to make food taste better and to compensate for the decrease in fat in order to increase sales. One man says that one piece of the fruity candy thingy has as much sugar as a candy bar or a bowl of strawberries, and argues that the vendor is marketing the candy as fruit. I paid attention to the bowl of strawberries part. I have personally eaten greater quantities of strawberries or grapes before. Counting by the amount of sugar consumed, is it possible to overdose on sugar by gorging on fruits while watching TV? 66.213.29.17 (talk) 19:41, 24 June 2016 (UTC)

Define "overdose on sugar". --Guy Macon (talk) 20:34, 24 June 2016 (UTC)

According to our article, the LD50 of sugar is 29.7 g/kg, so, a person weighing about 100 kg (rather above average for the general adult population), would need to eat three full 1 kg bags of sugar before it had immediate consequences - I doubt that's practically possible with pure sugar, let alone any sort of fruit. Of course, smaller amounts increase the risk of dental and medical problems, and the OP should see a doctor if they're worried about their health, but an actual acute overdose is unlikely. See Sugar#Sources for the numbers on various types of fruit. Tevildo (talk) 20:40, 24 June 2016 (UTC)

LD50s can vary quite a bit depending on the organism (as well as other factors about the population), I doubt we have an LD50 for sugar for humans. Maybe more important, remember LD50 is when half of the population is killed and there's pretty much nothing where half the population dies of only and precisely at a certain dose. So even if the LD50 for humans were as stated, many 100kg people are going to have immediate consequences before 3kg, including death. (Death isn't the only immediate consequence, you could have vomiting for example.) However empirical evidence would suggest if we ignore diabetics, the figure for immediate consequences would be quite high. Nil Einne (talk) 19:25, 25 June 2016 (UTC)

Hmmm... 64% of the carbohydrate calories in strawberries are sugars: fructose, glucose, and sucrose. But the glycemic index is 40, i.e. a low glycemic index food that is unlikely to cause blood sugar issues in diabetics. [21] There must be some crucial little detail here I'm not understanding... Wnt (talk) 20:46, 24 June 2016 (UTC)

If you're asking why the glycemic index is low, it's because fruit contains a buttload of fiber. --71.110.8.102 (talk) 00:13, 25 June 2016 (UTC)

And because strawberries consist of 91 percent water, meaning that there are little carbs in them. Sjö (talk) 06:45, 25 June 2016 (UTC)

Finding a cat in a big house

Hello all,

My wife and I are cat people. Currently we have one cat but she is young, small, spunky, rumbustious and very smart. We love her to death. Her objective is to get out of the house and roam outside but she is a house cat. Despite our best efforts she has managed to escape about a dozen times every time for a brief period except one, when we could not find her for about five hours. My wife went totally nuts, accusing me of neglect and threatening me with the hell's fire. Apparently she slipped between my feet when I was leaving home. It is not why I am posting though.

She has a habit of disappearing in the house for sleep. My wife sometimes spends an hour looking for her because she suspects that the cat might have escaped. I am worried also. Our house is not clattered by any means but it is impossible to find her. Then she would show up as nothing happened, almost smiling.

I know there are photo-cameras used to snap pictures of wild animals in nature during the night and I want to explore this option. I am thinking that if I install a couple of cameras like these I can eventually find out where she hides. I would appreciate any suggestions about the technology and how to use it. We simply want to have the ability to find her and make sure she is home. Thanks, ---AboutFace 22 (talk) 19:50, 24 June 2016 (UTC)

If you do a web search for [cat gps tracking], you'll find that there are collars and chip implants that might be what you need (I cannot attest to effectiveness, etc.). --107.15.152.93 (talk) 20:01, 24 June 2016 (UTC)

Before we go all New World Order here, surely it is not that hard to bell a cat (if you are not a mouse, that is). Wnt (talk) 20:49, 24 June 2016 (UTC)

Domestic cats have a habit of using one site to sleep in for a few days and then choosing another site for a while. This is presumably an adaptive strategy to avoid parasite re-infection. The reason I mention this is that if you set up camera-traps, you might find where she is sleeping at the moment, but she will move on when she feels the need and your worry will return. DrChrissy ^(talk) 20:55, 24 June 2016 (UTC)

Back in the Old World Order days, I tried a bell collar. It only encouraged the cat to move more stealthily (and of course, doesn't work when cat is asleep). --107.15.152.93 (talk) 21:35, 24 June 2016 (UTC)

I'd not go for cameras, but location devices. What's your budget? This [22] bluetooth thing might work well for in-house usage, it is designed to help you find your misplaced keys and such. If you scan around the house for a minute, it should be able to help you track the cat down. There are GPS widgets for pets e.g. [23], just google for others. You don't really need GPS to establish if the cat is in the house though, and it may be of limited value on such a small scale - the cat might be in the basement or under the couch and would look the same on GPS. On the other hand, full GPS would help you find the cat even if it left the house. Finally, in my experience, this hidey-cat behavior tends to get better with age. As the cat settles in and becomes more secure, it will probably have less need to hole up out of sight. SemanticMantis (talk) 22:20, 24 June 2016 (UTC)

Another possibility is to provide her with sleeping baskets/nests - plenty of commercial ones are available. Enclosed ones are probably the best. This might increase your chances of finding her, however, if she is like my cats, she will ignore the nests and sleep in the bloody box they came in!DrChrissy ^(talk) 22:57, 24 June 2016 (UTC)

• Unless the OP lives in the middle of a free-way junction where she could get run over by just stepping out side – why try and force her into being a house cat? Being house-bound is not in their nature. Also, what’s wrong with her getting lost in the house. Cats like a bit of solitude from time to time. The OP states that he is a cat person -so how about showing the cat some respect and don't treat her as an item (like a fridge, TV or Barbie Doll). She is a sentient being, like you and I -with a mind of her own. --Aspro (talk) 00:59, 25 June 2016 (UTC)
  • We're supposed to be wiser, and care for our pets, who are often less wise. A cat who goes outside dies sooner than those who remain in the house. And that's a decision the human makes, not the cat. Cats are perfectly happy inside. A camera or Tile (bluetooth thing) on her collar sounds like it could help allay fears that she's gotten outside and killed without invading her space. -Nunh-huh 01:19, 25 June 2016 (UTC)

Even the smartest and strongest housecat rarely fares well against a cougar. Or a fisher. Eagles are a bit easier, but why risk the embarassment of losing her to a bird? Besides, it's not like she just wants out for an innocent stroll. If we're being empathetic here, imagine what a sentient chipmunk feels like being treated like a ball of yarn. Where's the love then? Those guys have hands, man! Plenty of animals are perfectly happy inside, and only risk the world beyond to eat, screw or crap. They indeed look at housecats with envy (and horror), not pity. InedibleHulk (talk) 04:06, June 25, 2016 (UTC)

Thank you very much for the multitude of suggestions. Yes, we want her to be an indoor cat but we live in a house with large windows and the cat begins to mew in the morning asking us to open the windows and doors for her. She understands what the freedom means. That's why we are so scared. Every time she disappears for 10 hours we think she's escaped. Yes, my wife will pay any money to be able to monitor her. We actually flew her from Europe with an escort when my brother died, she was his cat. Thanks --AboutFace 22 (talk) 02:47, 25 June 2016 (UTC)

Well, you've got more of a wife problem than a cat problem. I'm not being nasty, and in fact I sympathise with her, but cats are gonna do what cats want to do.http://pettrackingoz.com.au/products/petrek-lt-905g is the sort of gizmo I'd have liked for my most recent cat, who was easily capable of sleeping in any random spot for 12 hours at a time. Don't fret about the cat running away, unless someone offers her a better option she'll be back when she's hungry or bored. Greglocock (talk) 03:39, 25 June 2016 (UTC)

So the cat grew up in Europe and now no longer lives there? I don't know about your cat specifically, but most cats in Europe are free to go outside. She may be used to it. But maybe the outside world is more dangerous where she lives now than it was in Europe. PiusImpavidus (talk) 09:03, 25 June 2016 (UTC)

Cats are gods, it is both futile and sacrilege for their human servants to want to know too much about their nocturnal perambulations and other ritual activities. Your cat has chosen you to be its slave, it may not be challenged. Roger (Dodger67) (talk) 10:43, 25 June 2016 (UTC)

Couldn't agree more with Roger. Cats have needs. Just like Maslow's hierarchy of needs. Food, shelter and warmth are not enough. “Research shows that when people live lives that are different from their true nature and capabilities, they are less likely to be happy than those whose goals and lives match.”; same for cats – let her have a life. Then she will always return home to those that provide those right basic needs. 6 Pets that Traveled Long Distances to Get Home. You could instill in her paranoia by tracking her so that your always know where she is. This over-protection that your wife strive for, drives some teenagers to leave home and brake all contact with their parents. They become missing persons.--Aspro (talk) 15:13, 25 June 2016 (UTC)

People should be left alone too make their own decision on indoor vs. outdoor cats. They really don't need advice or opinions. Far better to talk about something that nobody has a strong opinion about, like the 2016 US presidential election, climate change, abortion, or gun control. :( --Guy Macon (talk) 16:49, 25 June 2016 (UTC)

The OP is asking for opinions though - in order to be better and more responsible cat owners to a cat that they cherish and feel fond of– and the majority consensus here, is that his wife is unwittingly standing on the wrong premise and so thwarting the cat's natural instincts. Relax – let the cat be a cat and stop trolling. --Aspro (talk) 17:39, 25 June 2016 (UTC)

Comment Readers of this thread may also be interested to read another thread about introducing a cat to a new home. Wikipedia:Reference desk/Archives/Science/2016 May 18#Cat in a new home DrChrissy ^(talk) 15:45, 25 June 2016 (UTC)

@DrChrissy, I am familiar with the post you are pointing to. It actually inspired my post here. It is amazing how many emotions the cats induce in us. That post especially, my daughter's advice to keep the cat indoors for her own good and longevity, as well and some observations in our neighbourhood which is partly rural have cemented our determination to keep our treasured animal indoors. I walk around on the weekends and see domestic outdoor cats roaming around and then you see a post somewhere, cat lost. We have coyotes, hawks, etc. She is a little animal. Still her attempts to get out after looking outside through our large glass panels is heartbreaking. It is mew after mew. We are in the United States but this cat in the old country was an indoor cat and she lived on the eighth floor of an apartment building. I really appreciate all opinions. Thank you --AboutFace 22 (talk) 18:06, 25 June 2016 (UTC)

Thanks for this. In my real life, I work on the science of animal welfare, particularly captive animals. A lot of discussion on animal welfare is about frustration of their motivations. However, we must not be anthropocentric about this. We do not have the same senses and motivations as cats. We are "locked in our own skin". Do you really know that she is mewing to get outside? When my cats see a bird through the window, they stay where they are and "chatter" at them through the glass, choosing not to go through my propped-open door which is only 3 metres away to chase them. Keeping your cat indoors to prevent her from being predated is certainly improving your cat's well-being, but animal welfare is widely considered these days to be about the animal's feelings. If your cat is not getting frustrated at being unable to get out, all is well. However, if your cat is frustrated, this could be having a negative effect on her welfare (please do not take this as an accusation whatsoever of wrong-doing on your part - I am simply putting forward an academic argument). DrChrissy ^(talk) 19:59, 25 June 2016 (UTC)

June 25

Having Only Bread and Water = Plugging Up Gastrointestinal Tract?

On an episode of NCIS, it was mentioned that an old naval punishment involved feeding offending sailors only bread and water for a week, in order to plug up their gastrointestinal tracts. In real life, will such a diet really have the aforementioned consequences? 173.68.173.114 (talk) 03:41, 25 June 2016 (UTC)

I'm not aware of any such effect, and don't see why it would be the case -- however, such a diet would lead to malnutrition over time. 2601:646:8E01:7E0B:BC8F:CE52:F743:E9A9 (talk) 04:31, 25 June 2016 (UTC)

Yeah, that seems like pretty typical bad fact-checking on an apocryphal tale. No basis in physiological reality whatsoever. Point in fact, the bread of the era being likely to be high in fiber, it is more likely to have pulled additional moisture into the bowel (leading to looser stools) when compared against much of the rest of the preserved fair that pre-modern navies depended upon. Quite the opposite to the scenario presented, it would be the withholding or limiting of water rations (rather than providing an excess of water and fiber) that would be most likely to induce constipation in that scenario. Certain varieties of bread might have had the desired effect, but the last thing a naval vessel would ever want was to punish through means that would then require additional and highly valuable quantities of water to reverse, especially when withholding those same rations from the start would be a more effective punishment (being at sea with minimal water borders on one of the most physically unpleasant states of being manageable for a human being).

Interestingly enough though, modern navies prefer to punish their malcontents by making them watch episodes of NCIS. ;) Snow ^{let's rap} 06:26, 25 June 2016 (UTC)

Bread and water punishment was available in the US Navy until 1995 - see Non-judicial punishment. I don't know how often it was used during the 20th century, though. Tevildo (talk) 11:07, 25 June 2016 (UTC)

Apparently resurrected for civilians in Maricopa County, Arizona in 2014, according to this news article. Alansplodge (talk) 11:44, 25 June 2016 (UTC)

Although it was removed as an authorized punishment by USN court-martial in 1995, confinement on diminished rations or bread and water for not more than 3 days is still an available non-judicial punishment which may be imposed on US sailors and Marines of rank E-3 and below who are attached to or embarked in a vessel. -- ToE 12:27, 25 June 2016 (UTC)

Yes, just so. Reduced rations, especially radically reduced rations at sea, are always bound to be a much more feared punishment than being given just water and bread, but plenty of it. Snow ^{let's rap} 14:02, 25 June 2016 (UTC)

Main Battle Tanks -T-14 Armata

I studied the design of T-14 and I found a problem , the designers made an unmanned turret so they put the commander`s position in the front , but I imagined a scenario as this : the tank`s panoramic sight is disabled , the driver`s rear camera is disabled , the crew can`t see what`s behind them , do you consider this a big problem ? 94.249.115.70 (talk) 10:39, 25 June 2016 (UTC)

See T-14 Armata for our article. Your concerns are mentioned (with references) under "Sensors and communication". Tevildo (talk) 10:42, 25 June 2016 (UTC)

The Armata is probably Israel's best design of MBT. The trouble is that it's Russian.

The Armata concept is that of the Merkava, but even more so: the crew are the most valuable aspect so must be protected. It assumes the opposition are poorly supplied, few in number and easily discouraged. Yet Soviet tactics have always favoured the meatgrinder. Nor has Soviet ability to deliver a technical fix, and the untried Russian ability, ever been convincing.

In any combat, a working Armata wins the first round. But repeated attacks can attrite any such system of reactive armour. A rain of mortar shells will do it, so long as there are also enough mortarmen to deliver them. After a few rounds of such defence, the Armata is much less well protected.

There's also the question of whether an Armata can get to the battlefield and how much working electronics it brings along with it. You'll notice they've kept the glass viewing periscopes. Andy Dingley (talk) 11:35, 25 June 2016 (UTC)

So it`s an impractical tank as I supposed.94.249.115.70 (talk) 11:40, 25 June 2016 (UTC)

_If_ it works, it's great. Andy Dingley (talk) 14:45, 25 June 2016 (UTC)

That`s it .94.249.115.70 (talk) 20:58, 25 June 2016 (UTC)

Primitive semi-radius tachyons

As they almost said in The Matrix, for this mission we're going to need drugs... lots of drugs. Or science, if you're into the hard stuff. Pass those red pills and buckle up, cause Kansas is going bye-bye!

From "String Theory Co-Founder: Sub-Atomic Particles Are Evidence the Universe Was Created", CBS News:CNS News!

"Dr. Michio Kaku ... says theoretical particles known as “primitive semi-radius tachyons” are physical evidence that the universe was created by a higher intelligence."

After analyzing the behavior of these sub-atomic particles - which can move faster than the speed of light and have the ability to “unstick” space and matter – using technology created in 2005, Kaku concluded that the universe is a “Matrix” governed by laws and principles that could only have been designed by an intelligent being.

CBS refers me to a paper that I'm not getting in a readable form and this blog which makes its own curious claims like

Michio Kaku used a new technology created in 2005 that allowed him to analyze the behavior of matter at the subatomic scale, relying on a "primitive semi-tachyon radio." Tachyons ... are theoretical particles able to "take off" the matter of the universe or the vacuum contact with it, thus leaving the matter in its purest form, totally free from the influences of the world around them.

But what is this stuff? I mean, how are "primitive semi-radius tachyons" defined, what does that even mean? What is the new technology from 2005? What the hell is taking off? And so on... Wnt (talk) 14:42, 25 June 2016 (UTC)

Update: I have two sites [24] [25] which say that "primitive semi-radius tachyons" is a news garble that was never actually said - what was said is not so clear. But that doesn't take away from the weirdness of unsticking matter, matter in its purest form &c. Wnt (talk) 14:53, 25 June 2016 (UTC)

A Tachyon is a hypothetical particle that moves faster than light. Faster-than-light particles cannot exist because they violate the known laws of physics. AllBestFaith (talk) 14:57, 25 June 2016 (UTC)

It's plausible that Kaku would talk about tachyons. Tachyon condensation is real physics (it's part of the Higgs mechanism), and Kaku is fringy enough to believe in the faster-than-light kind of tachyons also. It's the "primitive semi-radius" part that makes no sense. -- BenRG (talk) 18:13, 25 June 2016 (UTC)

If tachyons do not interact in any way with normal matter or energy (and thus can never be detected or observed) they violate no laws of physics. Alas, the existence of such a tachyon can never be proven or disproven. --Guy Macon (talk) 18:18, 25 June 2016 (UTC)

I think this post by Franck Parra may be the origin of this. Here are some of his other posts, for comparison. It looks like "The Blog of Mystica" may have, for some reason, edited Parra's stream-of-consciousness writing into something more reminiscent of a press release, and republished it.

In any case, it is gibberish. Maybe it's vaguely related to something Kaku once said as filtered through the head of a crazy street person, but it's probably a waste of time to try to figure it out. -- BenRG (talk) 18:13, 25 June 2016 (UTC)

Wow. That 2013 posting definitely forms a clade with this news article, though the authors are not the same. I realize now this was CNS News - I hadn't looked closely before and for some reason I'd thought it was some local CBS affiliate. It is apparent that they are in serious need of scientific help. Wnt (talk) 20:11, 25 June 2016 (UTC)

I still suspect that Parra's post was the origin of this in English, but here's a version from November 2009 in Portuguese (which is probably Parra's native language). "Primitive semi-radius tachyons" has to be a garbled translation of "semi-raio primitivo de táquions". I don't know Portuguese (I do know some Spanish), but the only occurrence of "semi-raio" in the Portuguese Wikipedia is in Hilbert's axioms where the English article uses "ray" in its geometric meaning of a half line. I wonder if that Portuguese phrase is itself a garbled translation of something like "primordial ray of tachyons", which is a phrase that Michio Kaku might actually utter.

This version also says "the complete theory will be presented on January 9, 2010, at a conference in Switzerland", and credits the story to Scientific American. I doubt that Scientific American would publish anything resembling this story, and I can't find the conference. -- BenRG (talk) 00:34, 26 June 2016 (UTC)

Some Spanish-language sites, such as [26], attribute this story to "Jornal VDD", which is a fake-news publication from Brazil (it's mentioned in pt:Noticiário satírico). I bet that's the real origin. -- BenRG (talk) 01:50, 26 June 2016 (UTC)

NEMO as an illness

Trying to get data to fill out the description for File:North Livingston Baptist Church.jpg, I found their Facebook page, which had a request for people to be tested for a bone marrow donation. Part of that statement says This drive was set up for Mason, a local boy with NEMO, which is even more rare than HLH. HLH I suppose is Hemophagocytic lymphohistiocytosis, but what could NEMO be? NEMO lists a lot of things that aren't relevant; I suppose it could be a reference to a problem with IKBKG, but that seems a bit of a stretch. Nyttend (talk) 14:54, 25 June 2016 (UTC)

http://www.gosh.nhs.uk/medical-information-0/search-medical-conditions/nemo-deficiency-syndrome -- Finlay McWalter··–·Talk 15:02, 25 June 2016 (UTC)

I created a "stub" article based on that reference at NEMO deficiency syndrome and added a link in the disambiguation page for NEMO. Hopefully more information can be added there as it becomes available. One of the things that makes the ref desk useful is in finding gaps in Wikipedia's coverage - so this kind of question (and our response to it) is important to us. SteveBaker (talk) 17:33, 25 June 2016 (UTC)

Momentum conservation

[section header added:107.15.152.93 (talk) 18:41, 25 June 2016 (UTC)]

• • • If there are any mistakes in the following supplement for Momentum conservation, please correct them.

[The Supplement]

In a closed system (one that does not exchange any matter with its surroundings and is not acted on by external forces) the total momentum is constant.(the momentum conservation 1st law)

However, only in case of a physical system (called a newly semi or sub-closed system) that does allow certain types of transfers (such as transfer of mass and/or matter) inside the closed system,

the total momentum is "variable".(the momentum conservation 2nd law)

There are the following justifiable reasons.

In the first place, the law of momentum conservation has been implied by a principally action-reaction law as below.

[The mainly existing definition of the Newton’s third law]

~When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.~

However, the above law should be reformed (revised) as follows because it isn't so easy to distinguish the action-reaction forces from the equilibrium of forces in the above fixed definition.

~When one body (A) exerts an action force on a second body (B),

the second body (which does not exert an action force by itself) simultaneously exerts a reaction force equal in magnitude and opposite in direction on the first body.

And when A body’s action force interacts with B body’s action force, the equilibrium of forces between A & B are lost in case of (the initial) unbalanced momentums of the both bodies.

But, each body receives a reaction force equivalent to the action force by its body from the other body.~

Note : The force (F or -F)’s reference value for an equation of momentum conservation in a collision of two bodies is chiefly based on a measure of one body’s action force (F) or reaction force (-F).

That doesn’t indicate a pair (equal) of A body’s reaction force & B body’s action force in case of applying a pair (equal) of A body’s action force & B body’s reaction force as to F=-F.　

So, it is necessary to be careful of being in “uniform motion”, not “at rest” in the law of inertia for the united body in case of causing a perfectly inelastic collision by unbalanced action forces of the two bodies.

As for the above important matter, even a main (hollow) body in the sub-closed system (just like EmDriving machine)

that does allow certain types of transfers (such as transfer of mass and/or matter) in the same system under the momentum conservation law (which is similar to the law of inertia) could be applied.

That means one and the same body may move at a constant velocity, not remaining at rest, once it produces some internal pressure difference (unbalanced forces) inside (at both ends of) the hollow body.

• The movement has been already proved with the successful EmDrive tests by NASA etc. — Preceding unsigned comment added by More-kenlouise (talk • contribs) 18:15, 25 June 2016 (UTC)

Nonsense. See:

• NASA: Is Warp Drive Real?]
• You Still Shouldn't Believe in the emDrive
• Did NASA Validate an “Impossible” Space Drive? In a Word, No.
• No, NASA has not verified an impossible space drive!
• "The concept gained considerable press attention in 2015, after someone at NASA lab Eagleworks, which specialises in investigating almost-certainly-wrong Hail-Mary ideas on a 'what if' basis, tried out the idea and the press went nuts with the notion that this constituted NASA endorsing it."
• 4 Reasons Why The EM Drive is Probably Bullshit
• RF resonant cavity thruster#EmDrive

What? Nonsense!? What do you mean by...??

I (More-kenlouise) have asked about any mistakes in the above matter.

You cannot correct them at all???

selective amidation

Here's something I wasn't taught in chemistry class: I have a peptide containing serine, tyrosine and a C-terminal proline. I wish to amidate this proline residue with ethylamine (not necessarily directly), but without functionalizing the tyrosine and serine residues. Is this possible without use of expensive protecting groups? Yanping Nora Soong (talk) 18:16, 25 June 2016 (UTC)

GFCI mystery

I recently installed an electrical outlet on my outdoor deck. Naturally I used an outlet with an integral Ground Fault Circuit Interrupter. (110 VAC, North American practice.) It's a brand-new, commercial grade, heavy-duty, 20 amp, outdoor-rated outlet. I assume it has the latest and greatest circuitry, it even has a little LED indicator that glows green when it's working correctly. I installed it in a weatherproof outdoor box with a weatherproof outdoor cover, whole nine yards.

But the first time I tried to use my portable circular saw with it, it tripped immediately. This was 100% repeatable: every time I reset it and tried the saw again, it tripped again.

The saw works fine in a different GFCI outlet, and it's a double-insulated saw with a 2-wire plug, so it's unlikely to have a ground fault. I considered that I might have wired the outlet incorrectly (it's all too easy to wrongly connect the supply lines to the downstream load terminals), but I double checked, and it's fine.

I wondered if commutator noise from the saw's 15-amp motor might be tricking the GFCI's sensitive detection circuit into tripping. I grabbed a heavy-duty extension cord (12 gauge wire, 25 or so feet long) and plugged the saw into that and the cord into the outlet, imagining that perhaps the cord's inductance might be enough to filter out the noise and keep the GFCI from tripping.

It worked! I've been using the saw all afternoon, and the GFCI has only tripped once.

So my questions are, has anyone heard of this problem, is my diagnosis accurate, and is the extension cord's inductance likely to be helping? (Or is there something else completely different going on?) —Steve Summit (talk) 18:59, 25 June 2016 (UTC)

Did you put this outlet on a circuit that already has a GFCI at the panel? I've found this can cause problems. Shock Brigade Harvester Boris (talk) 19:02, 25 June 2016 (UTC)

I've been having troubles with GFCI's at my home - four of them (two in the kitchen, one in the garage and one in the bathroom) would trip all the time with a variety of different appliances - sometimes consistently, sometimes just at random. The others are in places where we rarely use them - so it's possibly that they have problems also.

I asked around about the problem - and was told by an "experienced electrician" over on Quora that very often the problem is when the GFCI has additional outlets attached "downstream" of it using the "LOAD" terminals. The explanation was not very coherent (the guy had evidently been taught that this isn't an ideal arrangement - but didn't seem to be able to explain why). He recommended replacing all of the outlets in places like workshops and kitchens with individual GFCI's rather than sharing a single GFCI among several outlets.

That seemed like a painful thing to have to do (we have ~100 outlets and GFCI's cost ~$10 each!) - and so I first tried replacing one of the troublesome GFCI's with a brand new one. Result: No more tripping out with any of the troublesome appliances. So then I replaced the other three problematic ones - and now I have no problem with those either. In the course of doing that, I found one that had been incorrectly installed ("LINE" and "LOAD" were swapped) - and one that had (worryingly) been wrapped around with half a dozen layers of painter's tape to prevent it from coming in contact with a grounded metal box in the wall that had evidently been bent during installation! (Yeah - not even electrical tape!)

However, I'm becoming convinced that either these things get worse with age (although my house is only 10 years old) - or that there are some cheap/nasty brands that should be avoided - so as I have time, I'm gradually replacing all of the GFCI's in my house with new ones...not least because I fear other "botched" installations.

What I imagine would be the best course of action for you would be to disconnect the "downstream" outlets from the GFCI and see if it'll still trip with your saw. To be honest, I prefer to have separate GFCI's on all outdoor outlets anyway and at $10 each, there isn't really a good reason not to do that.

Failing that, you could also try replacing the GFCI with one from a different brand.

SteveBaker (talk) 19:37, 25 June 2016 (UTC)

You may want to invest in some higher quality GFCIs rather than the cheap $10 units you are considering. In my professional opinion (I am an electrical engineer), the GFCIs listed here are the best available. --Guy Macon (talk) 20:02, 25 June 2016 (UTC)

You started an inductive load (a large motor), which is a recognised problem for use with GFCIs. Some ratings will be less sensitive to such inductive loads (there may be deliberate time delays etc.), but it's unlikely that a consumer grade socket will be doing this. Also it's a general rule for such things that the integral types are more cheaply made and less reliable than the better grades, which are only available as separates. Also outdoors is a poor environment for switchgear anyway, so installing the breaker indoors at the panel may be more reliable.

Also, even though double insulated, I'd PAT test the saw, specifically the insulation. Hand-held power tools get a hard life. Andy Dingley (talk) 20:12, 25 June 2016 (UTC)

I don't know this topic, but I'm suspicious the saw simply has very low resistance when the current first starts flowing (i.e. inductive load). If so, is it the added inductance of the electric cord that matters, or simply the resistance? For that matter, I wonder if you took some steel wool and burnished the plug on that cord until it looked like it was freshly bought, whether it would stop preventing the GFCI from going off. Not sure you want to try that :) Is there any little gizmo available that can be put on the end of a plug or into a light socketelectrical outlet that provides extra resistance for about one second only, then drops to near zero, specifically to stop such troubles? I'm thinking of something that would decrease in resistance drastically when heated for example, or it could be solid state. Wnt (talk) 21:37, 25 June 2016 (UTC)

This would be something like a Motor soft starter. The ones I'm familiar with are panel-type devices or are attached to the motor itself, not plug-in consumer-grade products. Shock Brigade Harvester Boris (talk) 22:11, 25 June 2016 (UTC)

See also: load controller (or not) ... Try a web search, I guess. This might be a solution, but I'm not an electrical engineer. --107.15.152.93 (talk) 00:42, 26 June 2016 (UTC)