Wikipedia:Reference desk/Archives/Science/2018 September 28

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September 28

Flexible tubing resistant to ~350 C (660 F)

There's a desoldering tool whose main feature seems to be a piece of silicone tubing which the manufacturer claims can be in contact with the soldering iron. A typical soldering iron temperature is 350-370 °C (~660-700 °F). I figured I could buy some silicone tubing and put it on my cheap desoldering tool but I can't find any that is good up to 350 °C. Is it actually possible? If so, does anyone know how I might find it or alternatively some other small-diameter tubing that's as flexible and heat-resistant? 185.230.100.66 (talk) 03:01, 28 September 2018 (UTC)

Your google fu is weak https://core-electronics.com.au/replacement-tubes-for-professional-silicone-tip-solder-sucker-ss-02.html Greglocock (talk) 04:36, 28 September 2018 (UTC)

Thanks! — Preceding unsigned comment added by 185.230.100.66 (talk) 05:45, 28 September 2018 (UTC)

Solder sucker tips are usually made of PTFE (Teflon) that melts at 327°C. Although our article about Silicone rubber quotes an upper use temperature of 300°C (and an O-ring manufacturer quotes a limit at 450°F=232°C[1]) the "fancy" transparent silicone tube for solder sucking is claimed[2] to be heat resistant to 350°C. The term silicone can cover a large group of Elastomers in which vinyl-methyl-silicone is the central ingredient, with chemical inertness and high temperature resistance attributable to the stability of their Si-O-Si atomic backbone. DroneB (talk) 15:03, 28 September 2018 (UTC)

• There are several factors to take into account, because heating an object has a lot more involved than just temperature. There are also things like thermal conductivity, thermal diffusion, and heat capacity to consider, to name a few. Temperature, for example, you can think of as being a surface quality, because you can only measure it at the surface or extract energy from it at the interface of a surface.

Most polymers (plastics) have low melting temperatures. As far as common polymers go, Teflon, is the highest, although some exotic polymers do exist that reach temps up to 850 degrees F, these are mostly used in the aerospace industry. However, if your polymer is a thermoplastic and not a thermoset, it will melt, but it will melt like glass rather than a crystalline like ice or metal. Before it melts it crosses through the glass transition (T_g), and starts to be come pliable and rubbery. The more you heat the softer it gets, until it crosses the glass melting temperature (T_m). A thermoplastic's damage threshold is often (but not always) lower than the glass transition and much, much lower than the glass-melting temp. Teflon, being a semi-crystalline, is one of those exceptions. It's T_m is 626 degrees F (330 C) while its T_g is -166 F (-110 C). (This is what gives it its combination of rigidity and pliability.) However, above 527 F (275 C) the material begins to lose that rigidity sharply, thus the damage threshold is kept 50--100 degrees lower as a safety margin.

Elastomers (elastic polymers) like silicone are different, because these are usually thermosets, and thus will not melt. Instead, above their damage-threshold safety margin, they begin to burn instead. For high-temp silicone, this will be at around 500 F (260 C), which is the highest temp you can find in a common elastomer. (Although there are some exotic ones like Kalrez that can go higher.) For much higher temps you may need to use a fabric, or even a glass fabric that can get you up over 1000 F (540 C).

Fortunately, this really only applies if you're holding it at that temp for extended periods of time, such as in an oven. In a solder sucker, the plastic only contacts the molten metal for a short time. Because the plastic has poor conductivity and high capacity, it doesn't absorb this heat very fast, so it never actually reaches the temp of the molten metal. (This also keeps the metal from cooling too quickly and hardening on first contact.) So, for intermittent use like this, a plastic or polymer with a lower melting point than the metal can work just fine. Zaereth (talk) 19:34, 28 September 2018 (UTC)

The OP whose IP address is located in the UK posed a question with temperatures primarily in degrees Celsius, the unit used by all countries except the United States, the Bahamas, Belize, the Cayman Islands and Liberia. It would be a courtesy to give answers in the same units rather than imposing a superfluous conversion from a unit of local use in the United States, the Bahamas, Belize, the Cayman Islands and Liberia. DroneB (talk) 22:13, 28 September 2018 (UTC)

Sorry, I will keep that in mind. The OP asked using both, and for that reason it didn't occur to me to convert from the numbers I know by heart. Zaereth (talk) 23:08, 28 September 2018 (UTC)

Courteous behavior is what you do and not just something you think about doing some time in the future. Do you wish anyone to help edit your post with appropriate units? DroneB (talk) 23:59, 28 September 2018 (UTC)

If you wanted me to change my post all you had to do was ask. My time is very limited, but I thank you for the lesson in courtesy and how to deliver it with condescension and equivocation. (Suddenly, I remember why I don't respond here.)Zaereth (talk) 06:05, 29 September 2018 (UTC)

Ref. desk rules differ from Wikipedia mainspace in that I am not allowed to change what another has posted, so I only suggested how and why your post might be edited. Thank you for acting on my suggestion and for all your work here. DroneB (talk) 14:47, 29 September 2018 (UTC)

Actually, here in the U K we are familiar with both scales. The papers will say that temperatures will reach 95° and we all know what that means. If they said they were expected to reach 35° we would have to think about it. — Preceding unsigned comment added by 86.131.233.235 (talk) 19:03, 29 September 2018 (UTC)

On wikipedia, you can just write {{convert|95|°F|°C}} or {{convert|35|°C|°F}}, which will display as "95 °F (35 °C)" or "35 °C (95 °F)" respectively. You state what you have, and the template converts it to the other one automatically. Then we can spend our time more productively, arguing about which to should be the main vs parenthesized units. DMacks (talk) 04:14, 30 September 2018 (UTC)

For what it is worth, I gathered everything I have that is made of silicone -- around a dozen different items. I then applied my soldering iron. At 350/375/400 °C (my normal soldering temperatures) the silicone laughed at me. At 450 °C I was able to make a mark on a cheap scrubbie ( https://www.amazon.com/gp/product/B01MREBZ2V/ ) but not on any of the other items. --Guy Macon (talk) 11:12, 30 September 2018 (UTC)

Yesterday I had a bunch of soldering to do, so I decided to use one of the cheap scrubbies I mentioned above (flat side up) as a soldering mat. I usually solder at 375°C, switching to 350°C for heat sensitive components and 400°C for soldering to heavy ground planes. It worked great. I put a blob of solder on it and heated it to 400°C. When it cooled off it fell right off, and didn't even leave any flux residue. The pad looks like it did when it was new. --Guy Macon (talk) 17:22, 1 October 2018 (UTC)

Antimatter

In space, are there naturally occurring accumulations of antimatter in significant amounts (say, 300 lbs. or more)? 2601:646:8A00:A0B3:19E8:E4E1:14EA:832C (talk) 06:18, 28 September 2018 (UTC)

As far as we know, the answer is no. If they do exist, they must be quite rare. If there were large clumps of antimatter in our universe, these would be expected to sometimes encounter ordinary matter, which would result in colossal explosions. The fact that we haven't seen the signs of large matter-antimatter explosions indicates (at the very least) that any macroscopic accumulations of antimatter must be extremely rare. Dragons flight (talk) 07:15, 28 September 2018 (UTC)

I'm not an expert, but from the sort of explanation given in Chronology of the universe, it is believed that all of space was filled with a nearly homogeneous plasma for quite some time. As such, it is difficult to imagine that nucleosynthesis or subsequent processes would have permitted the assembly of 300-pound lumps of antimatter in the middle of space at random; they should have been annihilated. Every once in a while I read about people hunting for antimatter islands in the cosmos, but my understanding has been they are looking for very large regions (very, very far away) which might be indicative of how the overall asymmetry got started. That said, then there's stuff like this. Dragons flight was correct to take the empirical approach, but I just wanted to heads-up a little on the theoretical aspects. Wnt (talk) 19:24, 28 September 2018 (UTC)

In the very beginning of the Big Bang there was neither matter nor antimatter, but the primordial ingredients for both. It is really a mystery as to why one formed but not the other, but it could have been as simple as the grain of rice that tips the scales. What we do know, and most people don't consider, is that space is not a total vacuum, but is filled with dust and gases; in some places at extremely low pressures and others extremely high. In fact, our local region of space, through which the heliosphere travels, is one of those extremely low-pressure areas compared to the surround galaxy. Even so, far greater vacuums have been created here on Earth than are found in space. According to Chakrabarti, the closest thing you can find to a total vacuum is near the event horizon of a black hole, where matter enters with the speed of light. Thus, it is highly unlikely that any quantities of antimatter exist, and if they do, it would most likely be extragalactic. Zaereth (talk) 22:43, 28 September 2018 (UTC)

Oh yes, by "very, very far" I meant "large Hubble constant". Even so, that antimatter-detecting instrument on the ISS at least seems to be finding something. I think your description of the heliosphere and outer space in general is inaccurate but I don't have the figures to argue it. The asymmetry has something to do with the failure of CT symmetry, so it's probably not just random. Wnt (talk) 23:51, 28 September 2018 (UTC)

Average density in the area of Earth is around 0.25 particles per square centimeter, which is a mixture of neutral atoms (mostly hydrogen and helium) and ions traveling outward from the sun at supersonic speeds. However, at that distance, the gas pressure is not nearly as high as the ram pressure (the inelastic, supersonic column of pressure described a few sections above), which is roughly equivalent to the magnetic or radiation pressure. The pressure gets very high as the flow goes from supersonic to subsonic, forming a shockwave we observe as the bubble of the heliosphere. The shock dissipates the energy until the pressure in the shockwave reaches an equilibrium with the surrounding local interstellar medium (LISM), which has a density of about 0.07 to 0.015 particles per square centimeter, although this tends to be lower than the density in the surrounding local interstellar cloud.

I think it's likely antimatter exists out there, but find it doubtful it does in large quantities within the interstellar medium. (There is an interesting theory that the accelerating expansion of the universe may be powered by a pressure differential between it and the total vacuum that may be outside the universe (where laws like the speed of light may not even apply). It may be entirely possible that gas densities between galaxies are even higher than in certain areas within them, like water whirlpooling around a drain or air in the capture-zone of a fan. Or they may be lower. These are all just hypotheses at this point.) The problem is that the original question is one of cosmology, thus all we have are best guesses. Zaereth (talk) 01:29, 29 September 2018 (UTC)

Our article Local Bubble is somewhat relevant. Long story short: the Solar system and a few nearby stellar systems sit within an irregular bubble whose interstellar medium of gas and dust has around 1/10th of our galaxy's average, caused by one or more nearby supernovas within the last 20 million years. As a formerly active astronomer and science textbooks editor, I concur with Zaereth's initial and subsequent descriptions, which perhaps Wnt initially misread. {The poster formerly known as 87.81.230.195} 90.217.102.65 (talk) 10:11, 29 September 2018 (UTC)

There's a Larry Niven story Flatlander about a planet made of antimatter. Spoiler:

It was as if he'd screamed. I could hear that word echoing from side to side in my skull.

Elephant's booming voice was curiously soft. «Antimatter?»

«Of course. We have no excuse, of course, but you should have realized it at once. Interstellar gas of normal matter had polished the planet's surface with minuscule explosions, had raised the temperature of the protosun beyond any rational estimate, and was causing a truly incredible radiation hazard. Did you not even wonder about these things? You knew that the system was from beyond the galaxy. Humans are supposed to be highly curious, are they not?»

173.228.123.166 (talk) 02:58, 29 September 2018 (UTC)

Hawking radiation

How big must a black hole be in order for its evaporation to create a 20-kiloton explosion? 2601:646:8A00:A0B3:19E8:E4E1:14EA:832C (talk) 06:20, 28 September 2018 (UTC)

Since the blackhole's entire rest mass is released as energy as it evaporates, the mass of the black hole that causes a release of 20kT($8.37\times 10^{13}J$) will be given by $m={\frac {E}{c^{2}}}$ i.e. $9.298\times 10^{-4}kg$. Then we can use the relationship between the Schwartzschild radius and the mass ($r_{s}={\frac {2GM}{c^{2}}}$ where G = 6.674×10⁻¹¹ N·kg^–2·m²) to determine that such a black hole would have a Schwartzschild radius of $1.38\times 10^{-30}m$. 202.155.85.18 (talk) 08:55, 28 September 2018 (UTC)

Thanks! Would it be possible to create such a black hole artificially (e.g. in a particle accelerator), or would the energy requirement be prohibitive? 2601:646:8A00:A0B3:D843:FF23:EE04:4F41 (talk) 11:25, 28 September 2018 (UTC)

Today I learned the largest fossil fuel power plants burn a Hiroshima of energy each in ~2 hours. No wonder there's global warming. Sagittarian Milky Way (talk) 18:45, 28 September 2018 (UTC)

I wasn't talking about the biggest power plant, but about the biggest particle accelerator (or whatever other means there might be of creating black holes artificially). The reason is, there's been a scare a few years back about the possibility the Large Hadron Collider might create a black hole which would then suck in the whole Earth -- which is an impossibility given that small black holes evaporate so fast, but I thought that maybe such a scenario could create the hazard of a nuclear explosion instead? 2601:646:8A00:A0B3:D843:FF23:EE04:4F41 (talk) 09:30, 29 September 2018 (UTC)

If a micro-black hole was created in a particle accelerator, there is no guarentee that it would evaporate, since Hawking radiation is postulated, but not proven. On the other hand, it's totally impossible for a micro-black hole to "suck in the whole Earth". A micro-black hole of a given mass doesn't have any more gravitational pull than any other object of the same mass. In other words, a ~1g micro-black hole such as the one that would give a 20kT blast if it does in fact evaporate, would exert no more gravitational pull on the matter around it than a 5 carat diamond. 2400:D400:9:1268:306:200:0:10B0 (talk) 09:58, 29 September 2018 (UTC)

True, but my question is, would it even be possible to create a 1g black hole in the first place, or would the amount of energy required be too out of this world? 2601:646:8A00:A0B3:D843:FF23:EE04:4F41 (talk) 10:40, 29 September 2018 (UTC)

That's really difficult to say with any degree of accuracy, but we can make a ballpark guess. The compressibility of nuclear matter is very roughly 300MeV based on theoretical calculations [3]. If we wanted to compress a proton into a space smaller than its Schwartzschild radius, we'd be reducing its volume by 38 orders of magnitude. To a first order approximation (and assuming this type of classical mechanical calculation is even valid for this quantum system) that would take around 337 Joules. That's not a prohibitive amount of energy for us to come up with, but it's probably very difficult for us to focus that amount of energy as a compressive force on a single proton. Since the Large Hadron Collider is not some kind of quantum scale diamond vice, it's hard to imagine a situation where a micro-black hole would be created. Maybe where the forces of acceleration on a given particle are so great that it experiences enormous compression on a time scale too short for it to relax through expansion in the dimensions perpendicular to the acceleration. Though when day dreaming about what fantastical properties a subatomic scale black hole might have, it's good to keep in mind that electrons already display many of the properties of a micro-black hole.139.194.67.236 (talk) 12:29, 29 September 2018 (UTC)

My impression is that the black hole electron idea involves a mass and singularity that doesn't fit within the Schwartzschild radius (the position is simply too uncertain!). Yet if it doesn't ... how is it a black hole? Hmmm. I wonder if anyone has tried to model a super-extremal fuzzball (string theory)?? Our article says those have a volume equal to black holes, but are made up of strings, which are quarks. I'm not clear on whether each of the six types of quark has a volume in string form that is proportional... the part about them getting less dense the more they are is also curious ... but if you can take those quarks and somehow shave them down to something with a -1 charge and a mass much less than that of a quark, that would take the game, set and match! Wnt (talk) 00:28, 30 September 2018 (UTC)

Electric-field equivalent of Lenz's law?

I note that the article on Lenz's law states that "the direction of the current induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes the initial changing magnetic field". This is useful heuristic for getting the sign on the magnetic field right on boundary condition. Is there a corresponding law for electric fields? If so, what is it called? If not, why not? I admit that I might be missing some understanding, here, so comments/help are welcome. Attic Salt (talk) 17:25, 28 September 2018 (UTC)

As there are no magnetic charges and therefore "magnetic" conductors, there is no "Lenz's" law analog for electric field. Ruslik_Zero 18:30, 28 September 2018 (UTC)

Hmm, I guess I was thinking of something different from that. Insofar as magnetic discontinuities are supported by current sheets, for example, at surfaces, I would think that a (possible) electric Lenz's law would involve surface charge -- something consistent with Maxwell's equations and Ohm's law. I just don't quite know how to phrase it or if someone has it named after him/her. Attic Salt (talk) 18:57, 28 September 2018 (UTC)

Two urine streams from pressure

I get the experience when I often lay belly down on the floor or bed and putting pressure on my urethra, it seems that is cause me whenever I pee it usually comes out in two streams or one wide stream rather than one thin stream. Other times when I get away from home and not laying on the floor for hours, I usually pee it out in one solid stream afterwards. Is it true that pressing urethra on the floor or bed causes it to pee it out in two streams? PlanetStar 22:19, 28 September 2018 (UTC)

You should see a doctor. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:31, 28 September 2018 (UTC)

LOL, this is a deep male secret that no woman should be permitted to learn, so here goes. ;) Humans do not form vaginal plugs, but wankage is not always entirely traceless. Wnt (talk) 23:54, 28 September 2018 (UTC)

Not funny. Meatal stenosis or narrowing of the opening of the urethra that causes abnormal direction of the urinary stream is commoner among circumcised males due to lack of a protective foreskin. A urologist (whom the OP should consult) may carry out a Voiding cystourethrography (VCUG) test if a physical exam, e.g. using ultrasound, indicates an incorrect urine flow or Urinary tract infection that could put the bladder or kidneys at risk. DroneB (talk) 00:30, 29 September 2018 (UTC)

Semen does get sticky when it congeals, no? Anyway, what you describe sounds like a long-term/medical situation, but what I'm suggesting is an issue that, once understood, is readily attributable, and in any case (dis)solves itself. Wnt (talk) 01:30, 29 September 2018 (UTC)

See Nozzle. Bus stop (talk) 01:13, 29 September 2018 (UTC)

The one reference source more comprehensive than Wikipedia has an article about this.[4] 173.228.123.166 (talk) 04:25, 29 September 2018 (UTC)

Despite the fact that I have pointed out on multiple occasions that no Wikipedia policy or guideline exists against giving medical advice except in the fevered imagination of a few people who do not understand the concept of "disclaimer" -- and that only an idiot pays any attention to medical advice from random strangers on the Internet -- this is a situation where I really think that User:PlanetStar should see a doctor. It doesn't happen to me when I lay down the same way, nobody here has come out and said that it happens to them, and it just might be either [A] something minor but still worth asking a doctor about, or [B] something serious that is just starting to show the first symptoms. (Medical disclaimer.) --Guy Macon (talk) 04:29, 29 September 2018 (UTC)

Yet another off-topic attempt to enforce an imaginary rule that does not appear in any Wikipedia policy or guideline. --Guy Macon (talk) 02:18, 1 October 2018 (UTC)
The following discussion has been closed. Please do not modify it.
Wikipedia:Medical disclaimer is the policy or guideline. ←Baseball Bugs What's up, Doc? carrots→ 08:47, 29 September 2018 (UTC) Even if I accept your dubious claim that a disclaimer is a policy, that page would be a "policy" that utterly fails to say that we cannot give medical advice. The lawyers who wrote the disclaimer were invited to set a policy (which they are allowed to do; see Wikipedia:Office actions) that we are not allowed to give medical advice. They declined to do so. Wikipedia:Medical disclaimer says that when we give medical advice, no warranty is made that the advice is accurate, true, correct, precise, or up-to-date. It doesn't say that we can't give medical advice. It says that when we give medical advice, our advice cannot substitute for the advice of a medical professional. It doesn't say that we can't give medical advice. It says that when we give medical advice, even if our advice is accurate, it may not apply to you or your symptoms. It doesn't say that we can't give medical advice. It says that when we give medical advice, we do not take any responsibility for the results or consequences of any attempt to follow our advice. It doesn't say that we can't give medical advice. It says that when we give medical advice, it should not be construed as an attempt to engage in the practice of medicine. It doesn't say that we can't give medical advice. All of which is lawyer talk saying the same thing I said in plain English above: only an idiot pays any attention to medical advice from random strangers on the Internet. Baseball Bugs, please stop citing imaginary policies. For the pedantic who really want to know what the rules are: some medical advice is forbidden under the general rule prohibiting disruptive comments, but not all medical advice. For example, the following medical advice is allowed: Don't do crystal meth. It will screw up your health. Don't bother asking a doctor if crystal meth is good for you. It isn't. There. I just provided medical advice, and while I did make a point, I did so without being disruptive. There are some who believe that Wikipedia has a policy against giving medical, legal, and business advice, but no such policy or guideline exists except in the fevered imagination of a few people who do not understand the concept of "disclaimer" (If you are about to cite the reference desk guidelines, please read WP:LOCALCON and then show me where the Wikipedia community approved them). Feel free to report my behavior at WP:ANI if you believe that I have violated any Wikipedia policy or guideline. Did I mention that Wikipedia:Medical disclaimer doesn't say that we can't give medical advice? Because it doesn't. --Guy Macon (talk) 09:52, 29 September 2018 (UTC) Advising someone to obey the law does not constitute professional advice. ←Baseball Bugs What's up, Doc? carrots→ 12:31, 29 September 2018 (UTC) Actually, In my comment above I gave medical advice. To expand on my medical advice (which I remind you, I advise you to ignore because I am unqualified to give medical advice), don't become a meth addict even if the Libertarians win enough seats to control congress and legalize meth, heroin, etc. It will still be bad for your health. --Guy Macon (talk) 06:29, 30 September 2018 (UTC) Recommending not ingesting illegal drugs does not qualify as medical advice. ←Baseball Bugs What's up, Doc? carrots→ 09:44, 30 September 2018 (UTC) Also, since you've stated this same hypothesis a number of times, have you run it by the WMF to get the opinion of the owners of this website? ←Baseball Bugs What's up, Doc? carrots→ 12:46, 29 September 2018 (UTC) By my count, five individuals have asked WMF legal to issue a ruling that says that we are not allowed to give medical advice such as "don't do meth". WMF legal has declined to do that. Feel free to do your own asking. I am not going to ask because the WMF medical disclaimer (which, I remind you, does not say that we can't give medical advice) seems clear to me. --Guy Macon (talk) 06:29, 30 September 2018 (UTC) User Guy Macon pastes yet again his purported "allowed medical advice" in what looks like an opportunistic attempt to filibuster and provoke. The last time he did it [5] I pointed out[6] the error in his advice about crystal meth (which is Methamphetamine and is sometimes a legitimate medical prescription). Guy Macon defies suggestion that his rhetoric amounts to soapboxing[7] while he much more credibly admits ""When it comes to medical topics, an electronics engineer like myself is pretty much lost" [8]. I wish to distance myself from, and to reject as unacceptable and dangerous any medical advice like Guy Macon's that contains the phrase Don't bother asking a doctor.... DroneB (talk) 17:10, 29 September 2018 (UTC) ...Which, of course, you are free to do. In fact, I highly recommend ignoring (as opposed to rejecting; that would lead you to taking crystal meth) my medical advice, and doing your own research if you are considering taking crystal meth. I would even advise (which you should ignore) that if you are so dimwitted that you can't figure out that becoming a meth addict is bad for you without a M.D. telling you, then go ahead and waste your doctor's valuable time asking him whether to take crystal meth, and while you are at it, have him check your cognitive abilities, based upon your inability to figure it out without him. Please do ignore any medical advice I give you. Please do not make claims about imaginary "policies" that do not exist. Please do report me at WP:ANI if you honestly believe that my repeatedly correcting editors who fabricate imaginary policies and guidelines is disruptive. --Guy Macon (talk) 06:29, 30 September 2018 (UTC) Please see Wikipedia:Reference desk/Guidelines/Medical advice "Any question that solicits a diagnosis, a prognosis, or a suggested treatment, or any answer that provides them, is considered inappropriate for the reference desk." Dmcq (talk) 10:22, 29 September 2018 (UTC) Please show me where the Wikipedia community demonstrated a consensus for the above "policy". Until you do, per WP:LOCALCON (which is a WP:POLICY), the refdesk guidelines "have not formally been approved by the community through the policy and guideline proposal process, [and] thus have no more status than an essay". --Guy Macon (talk) 06:29, 30 September 2018 (UTC) (...sound of crickets...) --Guy Macon (talk) 02:36, 1 October 2018 (UTC) The disclaimer presumably gets the WMF off the hook legally. But does it get YOU off the hook legally? If you post medical advice, someone takes it, and something bad happens, might YOU be sued? That's the question to ask the WMF. ←Baseball Bugs What's up, Doc? carrots→ 09:41, 30 September 2018 (UTC) Go ahead and ask it. They will either ignore you or tell you that it is the WMF's job to insure that the WMF won't be sued, not to insure that I personally won't be sued. And it shouldn't be your concern either -- especially while you are in the process of evading any discussion about the established fact that you keep making up fake Wikipedia policies. I would really, really enjoy having someone try to sue me for telling people that crystal meth is bad for them. --Guy Macon (talk) 02:36, 1 October 2018 (UTC) That's not medical advice. ←Baseball Bugs What's up, Doc? carrots→ 03:50, 1 October 2018 (UTC)

Double streaming may be caused by a strand of hair across the orifice. This has no medical significance. Whether this is a problem for the circumcised but not the uncircumcised I am not in a position to say. 86.152.81.16 (talk) 12:03, 29 September 2018 (UTC)

It might be, or it might not be. Only a doctor can tell the OP. No one here is qualified to. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:29, 29 September 2018 (UTC)

I am with Bugs on this. Only a doctor can tell the OP. No one here is qualified to. All I can add is that it seems like the sort of thing one should see a doctor about. --Guy Macon (talk) 06:29, 30 September 2018 (UTC)

According to Pastry bag "Though a circular nozzle is quite useful for making round shapes and for filling pastries such as profiteroles, many differently shaped nozzles are commonly used to produce star, leaf, and flower-petal shapes." Bus stop (talk) 13:25, 29 September 2018 (UTC)

This is getting grosser by the minute. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:28, 29 September 2018 (UTC)

Might I suggest there are a couple of piss artists involved in the discussion. Dmcq (talk) 14:40, 29 September 2018 (UTC)

I don't know what that means, but it can't be good. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:47, 29 September 2018 (UTC)

See Wikt:piss artist. Alansplodge (talk) 17:22, 29 September 2018 (UTC)

Must be a British thing. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:37, 29 September 2018 (UTC)

I would be tempted to use the term wanker, but as you might infer from my non-medical explanation above, I'm in no position to talk, as such usage would formally make them wankers' wankers, which is to say not wankers at all. The drolls are calling and they want the Internet back - the bureaucrats have tried and tried, but they don't know how to wring any real pleasure from it! Wnt (talk) 23:49, 29 September 2018 (UTC)

Speaking of wankers, some Yankees haters call this team "Wankees". In the AL Wild Card Game to be played on Wednesday between A's and Yankees, some A's fans would call the opponent team Wankees. If Yankees win and play the Red Sox in the ALDS, some Red Sox fans would call them Wankees.

Two of the good places to post medical questions are Quora and Yahoo! Answers, which already have a lot of them. PlanetStar 19:44, 30 September 2018 (UTC)

If it is supposedly "unethical" to answer medical questions here, then it is sure as shit unethical to send poor bastards off to be diagnosed at Yahoo! Answers. Wnt (talk) 01:37, 4 October 2018 (UTC)

I see someone is asserting there is no consensus support for WP:Reference desk/Guidelines/Medical advice. This is untrue. At WT:Medical_disclaimer#RFC_for_deprecation_of_this_policy overwhelming support for the policy and guideline were shown. People should not go around saying a policy or guideline is not supported without raising the matter there or on WP:VPP first and getting the matter resolved, deliberately misquoting policy is a serious business. Dmcq (talk) 11:03, 1 October 2018 (UTC)

So, is it your claim that a consensus for retaining a disclaimer THAT DOES NOT SAY THAT WE ARE NOT ALLOWED TO GIVE MEDICAL ADVICE is somehow relevant to a false claim that Wikipedia has a policy or guideline that says that we are not allowed to give medical advice?

The RfC you cite showed a strong consensus that the disclaimer does not say that we cannot give medical advice:

"I've brought this up, and asked this, multiple times: how is a disclaimer related to policy? I am willing to admit I'm wrong if I am grossly misunderstanding the term "disclaimer", or misreading it, but the Medical Disclaimer does not, in any sense, appear to be saying "You may not give medical advice", but "Do not construe what you read as medical advice, we don't intend it to be, it is not such in any legally meaningfully way and, thus, you are in error, and at your risk, should you so take it."

"Note the language of the disclaimer, it is not aimed at people editing, it is aimed at people reading and seems, pretty clearly, a legal protection rather than a policy."

"A disclaimer, by its nature is not a policy, thus, has no place in this discussion of policy - in other words: we are citing the equivalent of a "Do Not Try This at Home" warning, why? We actually have policies, and other such, it would make a lot more sense to refine those and deal with those, as opposed to discussing and citing something that is not such."

"I am not sure that there is a medical advice policy. I am fairly sure that this template is not the "medical advice policy", so I think that this RfC is misplaced. Even if there were a medical advice policy, and it were deprecated, then this template and page might still be useful. Maybe Jayron32 as the proposer can write a medical advice policy so that people can comment on retaining or deprecating it, or maybe Wikipedia is better without a medical advice policy."

"The Reference Desk guideline which says that respondents may not provide medical advice has very little to do with this disclaimer, which says that nothing you read on Wikipedia should be construed as medical advice. (It's unfortunately true that these two concepts, though distinct, are popularly conflated.)"

"The disclaimer is an instruction to readers, not writers."

"Time for a snow close: I think this request was mistaken. The responses are overwhelmingly in favor of the status quo. I see from the request that some reference desk editors wish to provide medical information in response to a borderline request for advice, but I don't see that as disputing the disclaimer itself."

"This Medical disclaimer is entirely appropriate and is independent of the nominator's concerns of how this policy should be applied to questions on the Reference Desks which might be interpreted as requests for medical advice."

"Even if the discussion that sparked this RFC represented some kind of consensus to abandon the longstanding Reference Desk guideline against providing medical advice (which I do not believe that it does), that would have nothing to do with the Medical Disclaimer, which should clearly stay in any case.

"The reference desk guideline and the Kainaw criteria look fine too, if a little restrictive, and the template looks harmless. They are not related to the disclaimer."

"I Object to this RfC on procedural grounds. Firstly, it asks about a "policy" when the real targets are an editing guideline that only applies to the Reference Desks, an essay in userspace, and a template that cites no policies. Secondly, it only allows two choices -- deprecating or maintaining Wikipedia:Medical disclaimer -- and does not ask to, say, turn Wikipedia:Reference desk/Guidelines/Medical advice into a supplemental essay such as WP:BRD, WP:CHILD, WP:CREEP, or WP:BPCOI. Another option that was not presented for a !vote is to create an actual policy (policy, not disclaimer) on this that applies to all of Wikipedia."

If you want Wikipedia to have a real policy that says what your imaginary policy says, post an RfC. Because that is not the consensus of the the RfC you just cited. --Guy Macon (talk) 17:02, 1 October 2018 (UTC)

If the intention is to warn the reader, then anyone giving medical advice should post the disclaimer along with their response, so there's less chance the user will take such advice seriously. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:42, 1 October 2018 (UTC)

That's an idea that I can get behind. It isn't currently required, but maybe it should be. Of course you or anyone else could respond with the disclaimer to a question asking for medical advice or to any answer to that question. --Guy Macon (talk) 21:02, 1 October 2018 (UTC)

As I recall, I had tried doing that for a while, but it seemed like it was not well-received. The user Medeis was a lot more aggressive about this issue. But that's history, as it appears Medeis is deceased. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:44, 1 October 2018 (UTC)

The RfC summary says "This is a strange request. Legally, Wikipedia may not give medical advice. Anybody using Wikipedia in order to do so is skating on extremely thin ice, unless their advice is always, and only, to consult a registered medical practitioner. In as much as there is a status quo here, it is the Wikimedia Foundation's responsibility to assess it and change it if necessary. There is certainly no consensus here for any change to existing practice."

This states what the closer believed the result of the RfC and the status quo to be. As far as I can see it is a fair summary. The RfC was raised on the Medical disclaimer and the reference desk guideline and. The guideline is marked as an edit guideline and has stood the test of time. If somebody wants to argues that the guideline is not a summary of the status quo and is not a proper guideline then they should raise their own RfC rather than asserting the invalidity of the guideline and trying to get others to do their work for them. Dmcq (talk) 22:27, 1 October 2018 (UTC)

The disclaimer does nothing to prohibit people from providing information on biomedical topics, and providing information on biomedical topics has nothing to do with the disclaimer or its prohibition on medical advice, an article linked in that RfC closure. Read the fuckin' article:

Medical advice is the provision of a formal professional opinion regarding what a specific individual should or should not do to restore or preserve health.[1] Typically, medical advice involves giving a diagnosis and/or prescribing a treatment for medical condition.[2] Medical advice can be distinguished from medical information, which is the relation of facts. Discussing facts and information is considered a fundamental free speech right and is not considered medical advice.

That's not my text, but it certainly backs my point of view. The RFC declined to change Wikipedia's disclaimer that it is not providing formal professional opinions regarding what a specific individual should or should not do to restore or preserve health. Which is a no brainer. Wnt (talk) 01:46, 4 October 2018 (UTC)

Indeed it is. Alas, I have seen a question about the best method for cleaning and disinfecting a shower deleted as "medical advice", and multiple deskref regulars defending the removal. --Guy Macon (talk) 09:38, 4 October 2018 (UTC)

The RfC also declined to do anything about the reference desk guideline and accepted it as common practice. If you wish to change that then raise an RfC with your desired change and see if it passes. On Wikipedia arguments against what is documented are worthless on their own. Dmcq (talk) 12:23, 4 October 2018 (UTC)

Or at the very least do a bold edit to the guideline making it say the opposite of what it says and so start a proper discussion at the right place instead of pushing your opinions here as if they counted for anything when you have shown no consensus. Dmcq (talk) 12:28, 4 October 2018 (UTC)

User:Kainaw/Kainaw's criterion is I think a reasonable criterion on whether to answer medical questions. If you follow that then disinfecting a shower should I believe be okay by pointing at standard advice about it. It does not need diagnosis, prognosis or treatment advice for a person. Dmcq (talk) 13:37, 4 October 2018 (UTC)

Why does ocean water get colder as you go deeper

When you go deeper in soil/rock, you reach higher temperatures because you approach a strong source of heat (Earth's core). But if you go deeper in ocean, temperatures decrease. Obviously I'd expect upwelling of warm water to carry off some heat from the bottom layers and lessen the temperature gradient, but how can they become even colder than the top layers? How does this not violate the second law of thermodynamics? 93.136.121.252 (talk) 23:30, 28 September 2018 (UTC)

There's a flaw in your logic. Whether you're on the dry surface or at the bottom of the ocean, you're on the Crust (geology). As suggested in Thermocline, the surface of the ocean is heated by sunlight and air temperature, and is fairly active. The farther down you go, the less active it is, so the warmer water does not mix in. Generally, the bottom of the ocean is calm and cold, because there is almost nothing to heat it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:44, 28 September 2018 (UTC)

The OP has a decent argument, but has neglected that ocean currents travel vast distances over long periods between different climates. See thermohaline circulation. It is true that the ocean is heated from below to some degree, but the water is gradually replaced with new water from the poles. I don't have any idea whether it would be theoretically possible to maintain a cold layer at the bottom of an ocean in a completely homogeneous climate by periodic (nightly) cooling with downwellings from the surface layer; I'm skeptical, but I think relevant data might exist from smaller seas and lakes in the tropics. Wnt (talk) 01:57, 29 September 2018 (UTC)

Yes, ocean currents make sense, I forgot that they might replenish cold water faster than the hot crust/mantle can transfer heat. Thermocline says that in polar waters temperature often doesn't decrease with depth. If there's sea ice then the surface should actually be colder (<4C), so that's probably where the cold at the bottom of warm seas comes from. Still, I'm pretty amazed that oceans can cool the Earth so much. In a shallow lake the day/night cycle can be significant, but when you look at deep oceans, even the 0-30C difference pales in comparison with the temperature differential at equivalent continental crust depth. 93.136.121.252 (talk) 04:07, 29 September 2018 (UTC)

I have heard that the pressure at those depths made the water reach its maximum density, which occurs at 4 degrees C. So the temperature at the bottom of a very deep lake is supposed to be that. I'm not convinced though, and I've wondered about it. 173.228.123.166 (talk) 04:28, 29 September 2018 (UTC)

Nope. Nothing about the pressure cools the water. And if the water was completely still, the heating from the core would be greater than it it is in deep mineshafts, because the crust is thinner at the bottom of the sea. Wnt got it right. The water isn't still, and whenever there is a difference in temperature (such as near the poles) the colder water sinks and then spreads out when it hits the bottom. https://oceanservice.noaa.gov/facts/coldocean.html explains it all. --Guy Macon (talk) 10:01, 29 September 2018 (UTC)

That's not the point. But water at 4°C is at its densest, so that's what sinks to the very bottom. In lakes, where there's no sideways ocean current, this becomes a stable layer. Andy Dingley (talk) 12:11, 29 September 2018 (UTC)

The Wikipedia article I cited earlier states that while the crust at the bottom of the sea is vertically thinner, it's also more dense. And the other article says the bottom of the sea is calm. I wouldn't take that to mean there's no circulation at all, but much less than there is higher up. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:42, 29 September 2018 (UTC)

Not really the point, but it is worth noting that the 4 C density maximum only applies to fresh water. For typical ocean salinity, the maximum density of sea water actually occurs at its freezing point (approximately -2 C). Dragons flight (talk) 18:38, 29 September 2018 (UTC)

I was puzzling over that, since I always understood that the zero point on the Fahrenheit scale was the freezing point of brine. However, the article indicates that the "salt" referred to is actually ammonium chloride. 86.131.233.235 (talk) 19:16, 29 September 2018 (UTC)

Water actually has one of the highest thermal capacities of all substances. Also water has the highest "volumetric heat capacity". That means it can store allot of (heat) energy but also takes or gives allot of energy when changing 1°. It also has a very good thermal conductivity for fluids. So it needs a constant high energy input to stay at or around some heat level.

That is the main secret behind the seemingly paradox about deep sea cold streams. The heat input from the earth core is barely enough to keep the water from freezing while the sun, nomatter it "heats" only half the time, manages to even warm up the top sea streams so much that they start to vaporize considerably. --Kharon (talk) 20:35, 29 September 2018 (UTC)

it needs a constant high energy input to stay at or around some heat level. Sorry, what? The most reading I can make of the above is that because water has high conductivity it transfers heat faster to close areas, thus gets to equilibrium quicker, thus needs higher incoming flux to match the outgoing flux. However, it is wrong on multiple levels. One: the relevant variable would be thermal diffusivity which is actually fairly low for water (about 100 times less than air, for instance), precisely because the thermal capacity is so high. Two: in most fluids of large dimensions, the dominant phenomenon of heat transfer is not diffusivity but convection; maybe that is different at the bottom of the sea because of anomalous density effects, but you cannot just blather about conductivity effects without discussing that first. Oh, also, "heat level" is not a thing. Try temperature or maybe internal energy.

The second paragraph's mumbo-jumbo seems to imply that the lower sea bed is kept liquid by heat from the Earth's core. Let's say I would like to see a source for that. Tigraan^{Click here to contact me} 09:56, 1 October 2018 (UTC)

Google "ocean heat level". Its a thing. Even a global one. Also i already mentioned the "temperature or maybe internal energy" you are missing, in my first sentence. Its "a thing" called Thermal capacity. Also water has no high thermal conductivity! Its 0.591 "k" (W·m⁻¹·K⁻¹) and only high compared with other fluids. Copper is 400 k. So copper is 236 times as thermal conductive as water!! Graphene is even 5300k.

You have to read more precise and complete instead of "generous", which you also failed. I added all these links to give readers a chance to understand the "mumbo-jumbo" terms. They are actually Thermodynamics terms btw. --Kharon (talk) 15:53, 2 October 2018 (UTC)

You confuse thermal conductivity and thermal diffusivity despite me wikilinking the latter in my reply. For the benefit of whoever actually reads my posts, k is the symbol for conductivity, not its unit (we do not abbreviate m/s by v, or s^{-1} by f). Tigraan^{Click here to contact me} 11:29, 3 October 2018 (UTC)

"k" is just a variable(formularsign). Its noted as common formula sign for Thermal conductivity in the first sentence of its article. I start to wonder if you lake the basics of Algebra or you just troll me, with superior tendency to the later. --Kharon (talk) 21:50, 3 October 2018 (UTC)