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January 28

Trash dumping into the ocean

Are there still governments that dump trash into the sea as a way of getting rid of it? You know, like with barges and such? Anna Frodesiak (talk) 08:00, 28 January 2018 (UTC)[reply]

Some dumping still occurs - see Toxic waste dumping by the 'Ndrangheta. But whether the 'Ndrangheta or Kenyan rebels or the Somalian subunits, etc. count as governments is a philosophical question I'll leave to you. Wnt (talk) 14:55, 28 January 2018 (UTC)[reply]

A lot of other waste is finding its way to the sea. For example see Brussels goes to war against plastic garbage, The Commission also focused on seas, where each year between 150,000 and 500,000 tons of plastic waste enters the oceans. The strategy calls marine litter — debris from items such as plastic products and abandoned fishing gear — a “visible and alarming” sign of the problem of waste.. Presumably it depends upon individual government regulation and enforcement, as it is probably one of the cheaper ways of dealing with waste. --Jules (Mrjulesd) 17:36, 28 January 2018 (UTC)[reply]

See also Marine debris: 8.8 million metric tons of plastic waste are dumped in the world's oceans each year. Asia was the leading source of mismanaged plastic waste, with China alone accounting for 2.4 million metric tons.. --Jules (Mrjulesd) 17:47, 28 January 2018 (UTC)[reply]

Mrjulesd, the thing is, that's an awful lot of plastic for just nets and gear and bottles from storm drains, don't you think? It just doesn't seem like that much could accidentally end up there without large-scale dumping. Anna Frodesiak (talk) 10:20, 29 January 2018 (UTC)[reply]

I share your skepticism. Some "marine debris" is clearly accidental - lost fishing nets, and debris from spilled "nurdles", but the marine debris article gives an amazing claim that 80% is "blown off of landfills", a phrase that sounds like a direct quote from the Mafia types who usually run them. I mean, you'd think that if that much material was blowing off landfills all the way to the ocean you'd hear more frustrated beachfront property owners volubly complaining, wouldn't you? Wnt (talk) 11:49, 29 January 2018 (UTC)[reply]

Anna Frodesiak absolutely, there is industrial scale dumping taking place. Most of it decomposes, but the exception is plastics, so they pose the greatest problem. Actual waste disposal in seas is probably in the tens of millions of tonnes per year. --Jules (Mrjulesd) 13:52, 29 January 2018 (UTC)[reply]

Thank you, Wnt and Mrjulesd. Yes, my guess is that there are communities that routinely drive the garbage truck to the sea and dump their trash into it. Humans! Anna Frodesiak (talk) 22:09, 29 January 2018 (UTC)[reply]

Thank you, Wnt. Anna Frodesiak (talk) 10:20, 29 January 2018 (UTC)[reply]

Most plastics are estimated to decompose after 50-1000 years. Till 1993 14 states dumped their nuclear waste into the ocean. Japan actually does again today since the coastal Fukishima nuclear plant's cooling water is also led out (leaked/ deposed on purpose) to the sea [1]. Its likely that nature or science will develop new microorganisms in the near future to use the accumulated masses of plastics in the "foodchain". Most likely some new Marine fungi, as they are natures best decomposition specialists already. That will not happen to nuclear waste however. Everything nuclear leaking out somewhere will slowly spread around the whole world. --Kharon (talk) 07:17, 30 January 2018 (UTC)[reply]

A group of humans?

According to the List of English terms of venery, by animal, depending on species, a group of animals is called a(n)...

colony of ants
troop of apes
family of beavers

... et cetera ...
swarm of bees flock of birds herd of elephants army of frogs gaggle of geese cackle of hyenas swarm of insects fluther of jellyfish mob of kangaroos leap of leopards barrel of monkeys watch of nightingales parliament of owls colony of penguins bevy of quail mischief of rats pod of seals hover of trout committee of vultures pack of wolves

dazzle of zebras
______ of humans?

What about humans?

Is there a generic term for a group of humans?

Or is "group" the generic term?

Is there a definitive article or list on collective nouns for humans? So far, I've found:

Are there others?

I look forward to your replies. The Transhumanist 12:59, 28 January 2018 (UTC)[reply]
P.S.: please {{ping}} me if you respond. -TT

@The Transhumanist: Term of venery doesn't apply to humans (relates to hunting & eating). The collective noun for humans is people, and the collective noun for groups of humans depends on what "group"; e.g.: a troupe of artists, a panel of experts, etc... See an interesting list here: "≡ List of Collective Nouns for People + Groups of Humans + Professions". Adducation. —2606:A000:4C0C:E200:5816:CC2:4ADE:73A0 (talk) 13:24, 28 January 2018 (UTC)[reply]

Then there's a list of ersatz collective nouns related to computers: a bleat or jury of users; an absence of engineers; a trough of salespersons, etc. from a book called The Computer Contradictionary.[2] ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:29, 28 January 2018 (UTC)[reply]

The first thing I thought of was mob which led me Crowd. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 13:12, 29 January 2018 (UTC)[reply]

We don't only organize physically. A social group is a term that I think is particularly applicable. We can be scattered over great distances and still be tied together. Even time doesn't separate us, as it might other species. We see that in the history of any socially-tied group of people, as long as their history remains reasonably intact. Bus stop (talk) 13:21, 29 January 2018 (UTC)[reply]

Question: Isn't barrel of monkeys incorrect? (I realize it is sourced at List of English terms of venery, by animal.) Bus stop (talk) 13:47, 29 January 2018 (UTC)[reply]

Humans that lived together in the wild as a group, like the above animals do, when a (pre-)historian refers to them, are usually called a "tribe". --Lgriot (talk) 15:02, 29 January 2018 (UTC)[reply]

Yes, tribe describes a group of humans too. I think there is no shortage of words for humans related in some way. Clan is used. Family is also used, especially when loosely defined. Bus stop (talk) 15:42, 29 January 2018 (UTC)[reply]

I suspect it's because we humans organise ourselves in numerous different ways, depending on the enterprise at hand, unlike say, rooks or elephants which habitually use a single group structure. Compare a drinking party in a pub with an infantry battalion on parade for instance. Alansplodge (talk) 09:15, 2 February 2018 (UTC)[reply]

Three legged folding chair with a back

See this.

Could one be made with two legs longer than the other one? The two legs stick up to make a back support. The triangular fabric is then an isosceles triangle rather than equilateral. Would the sitter get thrust forward into the third leg? Could such a chair be made. Someone would be eternally grateful if this could be made. Anna Frodesiak (talk) 14:09, 28 January 2018 (UTC)[reply]

Hacksaw.

I don't think you can turn this from a stool into a chair (with a back). You'd need a bit more rigidity for that, also a curve to the two rear legs. Andy Dingley (talk) 14:58, 28 January 2018 (UTC)[reply]

Your link [3] actually includes several images of three-legged folding chairs with backs - just scroll down the page a few rows. Wymspen (talk) 17:27, 28 January 2018 (UTC)[reply]

Thank you, Andy. Darn.

Thank you, Wymspen. I forgot to mention that I am specifically interested in one with a triangle, fabric seat. Anna Frodesiak (talk) 00:39, 29 January 2018 (UTC)[reply]

There are at least two fitting that description among the images in the link - fourth row. [4] and [5] link to them individually. Wymspen (talk) 11:03, 29 January 2018 (UTC)[reply]

Ah, yes. Thank you, Wymspen. Anna Frodesiak (talk) 22:13, 29 January 2018 (UTC)[reply]

Electric Universe concept removed from Wikipedia.

Hello,

http://neutrinodreaming.blogspot.com/2011/09/electric-universe-theory-debunked.html

The above article claims that the entery for the Electric Universe concept was removed due to illegimate citations and a lack of publications.

Is that true? Is there a reference I could look at?

However, if you search for Electric Universe on the wiki, you are shuntted over to Plasma Cosmology which is unrelated, i.e., Plasma Cosmology is a legitimate hypothesis back by peer review and computer models while the Electric Universe concept has no peer reviewed papers nor any formalized logic to support it. Confusingly, this could give someone the impression that the Electric Universe concept is synonymous with Plasma Cosmology.

Thanks in advance for any clarification you could offer.— Preceding unsigned comment added by 74.72.174.10 (talk) 20:05, 28 January 2018‎ (UTC)[reply]

Plasma Cosmology is a legitimate hypothesis it is also fringe, but notable enough to have its article. —Paleo Neonate – 20:07, 28 January 2018 (UTC)[reply]

Please read Wikipedia:Articles for deletion/Electric Universe model. Cullen³²⁸ Let's discuss it 20:15, 28 January 2018 (UTC)[reply]

It eventually crossed an event horizon at Wikipedia:Articles for deletion/Electric universe (concept). Thincat (talk) 21:31, 28 January 2018 (UTC)[reply]

January 29

Electron affinities of the superheavy elements

Have there been any published predictions of EA values for elements with Z > 103 beyond the few (Nh, Mc, Ts, Og, elements 119 and 121) listed at Electron affinity (data page)? Double sharp (talk) 09:54, 29 January 2018 (UTC)[reply]

Google Scholar search for predicted electron affinity superheavy gave a bunch of useful-looking refs, including:

Eliav, Ephraim; Fritzsche, Stephan; Kaldor, Uzi (2015). "Electronic structure theory of the superheavy elements". Nuclear Physics A. 944: 518–550, December 2015, Pages 518-550. doi:10.1016/j.nuclphysa.2015.06.017. Abstract: High-accuracy calculations of atomic properties of the superheavy elements (SHE) up to element 122 are reviewed. The properties discussed include ionization potentials, electron affinities and excitation energies...
Fricke, Burkhard (1975). "Superheavy elements a prediction of their chemical and physical properties". Recent Impact of Physics on Inorganic Chemistry. Structure and Bonding. Vol. 21. Springer. pp. 89–144. doi:10.1007/BFb0116498. ISBN 978-3-540-37395-7. Discusses elements Z=104–172 and also Z=184 (but I can't access enough to know what properties are covered).

DMacks (talk) 14:15, 29 January 2018 (UTC)[reply]

Both papers are very interesting (and I've seen the latter before), but it looks like the only new value given is the EA for Rg (Z = 111, eka-Au) in the first paper. But thank you very much for this help! Double sharp (talk) 06:17, 30 January 2018 (UTC)[reply]

@DMacks: I've added the Rg value to the data page; unfortunately no others are given in either article (except for element 171 in the second paper, eka-tennessine, but that is so very far away from what is currently known that even the author only dares to say that his calculations would likely be not "too far away from reality" up to eka-radium, element 120). Double sharp (talk) 14:37, 30 January 2018 (UTC)[reply]

Oh, and I found a paper (10.1103/PhysRevA.91.020501) with values for Mc, Lv, and Ts as well. I also see the values for Cn and Fl are predicted to be negative, but I can't find anything saying how negative they ought to be. Double sharp (talk) 15:03, 30 January 2018 (UTC)[reply]

Reactivity of ytterbium

With the exception of Yb, the reactivities of the lanthanides increase with size; for example, Eu has the largest metallic radius and corrodes most quickly, followed by La, Ce, Pr, and Nd in about that order (since metallic Eu and Yb have two electrons delocalised per atom while the other lanthanides have three). So why is Yb such a glaring exception? Double sharp (talk) 10:07, 29 January 2018 (UTC)[reply]

Ytterbium has a 4f14 6s2 electron configuration; having two complete orbitals is particularly stable and results in low reactivity; this is sometimes called "pseudo-noble-gas configuration" as it is not a true s2 p6 configuration, but it does lead to lower reactivities for elements with it. --Jayron 32 13:05, 29 January 2018 (UTC)[reply]

The ytterbium article explains metallic radius in terms of having only two delocalized electrons. I would suppose this may be related to the third ionization energies listed in lanthanide (Yb and Eu are particularly high, hence the +2 states). Yb also has a different lattice, though I'm not sure if this matters to the corrosion process. Wnt (talk) 02:50, 30 January 2018 (UTC)[reply]

Is there such a thing as "clean" (non-pathogenic) particulate matter?

Greetings!

I've been studying the health effects of particulate matter and am curious about whether some of it may not be harmful; viz., can one engineer microscopic particles that—when inhaled—do not adversely affect people?

Imagine a 100 gram mass of "clean dirt" (for want of a more proper term) evenly ranging in diameter from 400 nanometers at the smallest to 700 nanometers at the largest, thus blocking out visible light rays when scattered in the air. Can such a substance—that would occult visible light and also remain harmless to human physiology—be produced with existing materials science?

Also, assuming that such a substance exists, can it be made to adhere to a magnet (like iron or nickel filings, but non-pathogenic)?

Thank you. Pine (talk) 10:50, 29 January 2018 (UTC)[reply]

Probably not. Most particulate pollution affects the lungs based on the size of the particles rather than their composition, i.e. otherwise inert compounds still cause harm due to just being in the lung. Particulate matter as a pollutant is generally classified by particle size alone, without regard for composition of those particles. See here "The size of particles is directly linked to their potential for causing health problems. " --Jayron 32 16:41, 29 January 2018 (UTC)[reply]

Tell that to the people using them as a drug delivery mechanism. Fgf10 (talk) 19:28, 29 January 2018 (UTC)[reply]

~~Those are 50 nm particles. If you read the article I linked, it notes that <2.5 nm particles are the sizes where it starts to get bad. --Jayron 32 20:12, 29 January 2018 (UTC)~~[reply]

Correct, hence your "Probably not" was entirely incorrect. Accuracy and phrasing matter. Also, it's nanometre, not nanomolar Fgf10 (talk) 21:52, 29 January 2018 (UTC)[reply]

Point taken. Thanks for clarifying. It also helps to explain, in detail, what the specific error a person makes is, while you are correcting them, so that they know and can correct it. --Jayron 32 22:30, 29 January 2018 (UTC)[reply]

Just to clarify, one defines PM_2.5 as particulates that are less than 2.5 μm (2,500 nm) in diameter. My question relates to particles evenly ranging in size from 400 nm to 700 nm. Since certain 50 nm particles can be benign—or even beneficial—to people, does that mean that particles large enough to block visible light may also be?

Pine (talk) 08:23, 30 January 2018 (UTC)[reply]

It may not be that simple. Ruslik_Zero 20:34, 29 January 2018 (UTC)[reply]

There is one common class of particulate matter where the current evidence is fairly ambiguous about whether or not it is harmful. That is sea salt particles. Fine particles of sea salt dissolve in the moisture of the body, but one is unlikely to breathe enough mass to meaningfully change the body's total salt composition. Hence, it is plausible that sea salt particles may be pretty benign. That could be an avenue to consider for your question. If you were thinking about other options, then it pretty much needs to have similar qualities. A substance that easily decomposes into essentially harmless material after it enters the lungs. Dragons flight (talk) 20:31, 30 January 2018 (UTC)[reply]

It seems like you're trying to reinvent smoke or even fog. It looks like marijuana can readily be put to the use of producing particles with a median size of 380 nanometers. [6] You could use something else for this application, but ... why? ;) Wnt (talk) 00:18, 1 February 2018 (UTC)[reply]

January 31

Speaking tubes

Why is the whistle of a speaking tube at the receiving end and not the transmitting end? Having it at the receiving end leads to the possibility of it not being replaced after a conversation, and thus leaving the chap at the other end not being able to give the chap at the other end a tinkle. DuncanHill (talk) 21:50, 31 January 2018 (UTC)[reply]

The article you linked says "...with whistles at either end" (whistle tubes). 2606:A000:4C0C:E200:855B:A505:748:9655 (talk) 23:36, 31 January 2018 (UTC)[reply]

The article I linked says "Later designs of the voicepipe inserted a removable cork-mounted whistle, which could be sounded by blowing into the tube from the other end. On naval vessels, this created a distinctive sound associated with urgent intra-ship communication on old warships. The sound of the whistle would summon the listener, who would remove the whistle and answer the call." DuncanHill (talk) 00:09, 1 February 2018 (UTC)[reply]

You can't hear a speaking tube unless you put your ear to it. You can hear one at the whistle end, if it's blown. Andy Dingley (talk) 00:18, 1 February 2018 (UTC)[reply]

Even a loud whistle from the other end? Does anyone have a speaking tube I can experiment on? DuncanHill (talk) 00:29, 1 February 2018 (UTC)[reply]

In a quiet environment, you would hear a loud whistle from the other end, especially if the receiving end gradually increases in size like a horn speaker to allow the sound out into the space, but a local whistle will be much easier to hear. Try it! A length of garden hose might suffice for the experiment. Dbfirs 08:34, 1 February 2018 (UTC)[reply]

The single tube is a two way system, so can't simultaneously taper both ways! For a whistle to be blown at the caller's end (which might be either actual end), the tube would initially have to be open at both ends; the caller would then have to insert a whistle, then blow it, then remove it and listen for a reply, then repeat the whole process if the callee didn't hear the first whistle. The caller would also have to remember to re-stow the whistle at some location close to the tube, from where it might be dislodged and lost.

If the whistle is to sound at the callee's end, each end is by default plugged by its whistle; the caller removes the whistle at his end, blows, and listens, the callee removes his end's whistle and replies, and at the end of the conversation both whistles are replaced in their ends of the tube. This process is simpler and makes the misplacement of either whistle less likely, as the default has the whistle stowed on/in the tube. As Andy Dingley and Dbfirs have already indicated, this also means that the whistle will be considerably easier for the callee to hear, as a naval ship in operation is generally far from being a silent environment.

A further advantage is that keeping both ends whistle-plugged by default lessens the likelihood of getting a mouthful of spider! {The poster formerly known as 87.81.230.195} 2.221.83.136 (talk) 10:46, 1 February 2018 (UTC)[reply]

A single narrow tube can have an open tapered horn at each end (see Impedance matching#Acoustics), and this would work 2-way in a quiet environment, but otherwise I agree 100% with what you write above. Dbfirs 11:12, 1 February 2018 (UTC)[reply]

Royal Navy whistles were retained on a bit of chain like this so that they didn't get lost. Alansplodge (talk) 17:55, 1 February 2018 (UTC)[reply]

Thank you all. I'd still like to test this properly, if anyone has a spare destroyer they could lend me One can avoid spiders by remembering not to suck. DuncanHill (talk) 18:40, 2 February 2018 (UTC)[reply]

February 1

"Weak Filling Condition" - What does it mean?

I'm trying to understand the following phrase and I can't. This phrase describes a product (pulse-oximeter) on Ebay and it states: "Measurement Performance in Weak Filling Condition: SpO2 and pulse rate can be shown correctly when pulse-filling ratio is 0.4%. SpO2 error is ±4%, pulse rate error is ±2 bpm or ±2%, whichever is greater." What does it mean "weak filling condition"? What does it mean "pulse filling ratio". I understand basic science but I felt to understand these things after trying many times. (I thought maybe it should be "weak feeling condition" where the pulse oximeter can't feel the pulse. But I'm not sure) — Preceding unsigned comment added by 185.191.178.183 (talk) 17:16, 1 February 2018 (UTC)[reply]

No idea if this helps: See our article on symplectic filling, which states: A weak symplectic filling of a contact manifold (X,ξ) is a symplectic manifold (W,ω) with ∂\partial W = X such that ω|ξ>0. --Cookatoo.ergo.ZooM (talk) 17:37, 1 February 2018 (UTC)[reply]

Yeah, that's obvious [tongue-in-cheek]. Evidently, its a real thing, not a poor translation, or mistake. E.g.:[7] My vague understanding is that it is a form of interpolation (?). 107.15.152.93 (talk) 18:02, 1 February 2018 (UTC)[reply]

According to pulse oximeter#Function, the actual measurement is of the amount of HbO2 and Hb change--the difference between minimum and maximum as the blood pulses--not the absolute amount in the light path. If there is a weak pulse, poor circulation, etc, the amount of change is smaller so the relative error in its measurement is greater. DMacks (talk) 18:34, 1 February 2018 (UTC)[reply]

I believe it relates to "filling in the (data) blanks"; relating to error minimization; i.e.: interpolation.2606:A000:4C0C:E200:211C:FF2A:3329:F571 (talk) 21:37, 2 February 2018 (UTC)[reply]

Breaking an opponents neck

It has been seen many times in movies, on TV and in other media where two people are fighting and one "breaks" the other's neck by twisting hard and resulting in immediate death. Is this accurate or even possible? Could even a trained (soldier, warrior, martial artist or whomever)kill an opponent in this manner? I have no doubt about serious injury (up to an including paralysis), but immediate death? If it is possible, what are the mechanics of it? 76.71.157.121 (talk) 22:11, 1 February 2018 (UTC)[reply]

A buddy of mine (who was giddy as a child about the detonation cord he got for Christmas, if that tells you anything) had a copy some hand-to-hand combat handbook for the US Marines. Can't guarantee that that move was or was not in there, but I'd be willing to bet $40 that it was followed with a stomp on the opponent's head to make sure they stayed down (as that's now almost every maneuver ended, even ones you'd figure would've killed the target five times over). I don't know whether that indicates that it's actually really hard to kill someone by breaking their neck, because, again, this was a USMC handbook. Ian.thomson (talk) 22:27, 1 February 2018 (UTC)[reply]

No neck grabs were part of the Marine Corps handbook as of 1990 (that is the date of mine). There are a few trip and take-down maneuvers. There is an arm-lock followed by a take-down. There is the standard "2 down low" followed by a take-down. All of the take-downs end with a head stomp. That is really only effective with the arm lock because it separates the shoulder. If done properly, the person will have a dislocated elbow and shoulder, making him unlikely to continue trying to fight. Of note, the purpose of hand-to-hand combat in the Marines is to get the opponent on the ground and incapacitated as quickly as possible. It isn't anything like boxing or MMA. You aren't scoring points or trying to pull cool moves. You just want to cause severe pain, very quickly, and move on to the next opponent. 209.149.113.5 (talk) 15:08, 2 February 2018 (UTC)[reply]

It involves very much the same mechanics as How to Dispatch a Chicken. It is a bit difficult to practice on humans in order to get the technic right. Not going to describe how the military are taught, because some twit reading this, may try it out in jest – and whoops – finds it works. It snaps the spinal cord, resulting in immediate paralysis and any attempts to resuscitate prove futile. Aspro (talk) 22:36, 1 February 2018 (UTC)[reply]

Cerebral hemorrhage is also likely with enough trauma to the upper spine with an elevated risk of instant coma or death. As a taekwondo practitioner, I've unfortunately witnessed an accidental death immediately after a kick behind the neck, death was almost instantaneous with visible bleeding from the eyes. There's also a popular video of a similar incident during a live wrestling show. This was not exactly spine twisting trauma, however. —Paleo Neonate – 00:10, 2 February 2018 (UTC)[reply]

This is basically the same thing as the effect of "long drop" (warning, some unpleasant pictures in article) hanging: massive trauma to the brain stem. Such an injury usually causes rapid loss of consciousness. "Instant death" in complex animals only really happens with total disintegration, like having a nuclear weapon detonate directly on top of you. Otherwise, it takes at least a measurable amount of time for cardiopulmonary arrest to occur. (And the less complex the animal, the harder it is to get it to stay dead. Cut a flatworm in half, and now you just have two flatworms.) It should go without saying that most works of fiction are going to involve some artistic license. See for instance the Instant Death Bullet that live-action entertainment is fond of. --47.157.122.192 (talk) 04:10, 2 February 2018 (UTC)[reply]

It's dangerous to mess with the neck, even when you're not trying to kill or injure someone [8], [9]. In an American case, an unqualified trainer manipulated a man's neck in the bedroom vigorously and walked out of the house after the session. The terrified man shouted down to his wife "I can't move!" and died shortly thereafter. 86.176.18.217 (talk) 13:28, 2 February 2018 (UTC)[reply]

Thank you for that comment user:86.176.18.217. Although it can't be performed as as depicted in the movies (where the actors don't want to kill each other for real). Knowing how to use mechanical advantage takes little strength to sever the spinal cord. Not much use in hand-to-hand combat. There, a striated blade plunged into the belly, turned and withdrawn causes so much pain that one's opponent is incapacitated and is so much quicker. A blade also avoid the emotional effect of touching ones opponent. Aspro (talk) 15:44, 2 February 2018 (UTC)[reply]

Thanks everyone. I have been a martial artist for over 30 years (karate, tae kwon do, aikido) and various instructors have "demonstrated" techniques that cause "instant death." I have never used any of these "techniques," of course but suspect that the effectiveness of them are more in the realm of myth or urban legend . . . and more likely to cause serious harm than actual death. Movies and television always tends to err on the side of the dramatic and artistic license than reality. 76.71.157.121 (talk) 23:24, 2 February 2018 (UTC)[reply]

I agree that there's a lot of mythology and pseudoscience in relation to martial arts. —Paleo Neonate – 19:20, 3 February 2018 (UTC)[reply]

One thing about TV and movies is time constraints. They can't spend a long time trying to show reality. They have to do the entire show to fit a one or two hour time slot. Hence other fanciful stuff, like getting DNA test results in like five minutes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:21, 3 February 2018 (UTC)[reply]

February 2

Equation for Period of Orbit

A link to the appropriate Wikipedia article will be fine if it answers my question. What is the equation, assuming a circular orbit, that gives the period (time) of an orbit if the mass of the primary is known, the radius of the orbit is known, and the gravitational constant G is known (which of course it is)? That is, please provide the equation with the result being the period (in time units). Alternatively, given the orbital period in time units and the mass of the primary, what is the equation that will specify the radius of the orbit?

Thanks. Robert McClenon (talk) 04:23, 2 February 2018 (UTC)[reply]

See Orbital period#Small body orbiting a central body. Explanation: if the orbit is circular, then the centrifugal (from motion) and centripetal (from gravity) forces must be in balance. Therefore

GMm / r² = mv² / r

GM / r = v²

v = √GM / r

On the other hand, the period T can be calculated from the orbital speed and circumference

T = 2r

π

/ v

T = 2r

π

/ √GM / r = 2r

π

√r / √GM

T = 2r^3/2

π

/ √GM

You can then turn this around to get the answer to your last question:

r = (T²GM / 4

π

²)^1/3

An interesting consequence: the orbital speed and period do not depend on the mass of the orbiting body (m). Hence, the orbited body's mass can be estimated by observing the radius and revolution period.

I believe the derivation for an elliptic orbit shouldn't be much harder, but as I haven't done physics beyond high school, I won't chance it. 93.136.124.10 (talk) 05:36, 2 February 2018 (UTC)[reply]

93.136 says that "the orbital speed and period do not depend on the mass of the orbiting body". But those equations are for a small orbiting body, meaning one whose mass is negligible compared with the central body. In fact, if the smaller body is not that small, you just have to substitute the total mass of the two bodies for M in the final equations. See Orbital period#Two bodies orbiting each other. --70.29.13.251 (talk) 02:35, 3 February 2018 (UTC)[reply]

An elliptic orbit has the same period as a circular orbit with the same long diameter (one of Kepler's big three observations), but I can't prove it. —Tamfang (talk) 00:22, 3 February 2018 (UTC)[reply]

The orbital period which comes out of these equations is a mean, i.e. you are starting with the assumption that the body moves in a circle at constant velocity. That is the essential feature of the "mean longitude" argument in the tables. In The History of the Tropical Year celestial mechanics experts Jean Meeus and Denis Savoie give average intervals between vernal equinoxes at various dates but they describe them as "mean" intervals although the lengths vary widely in Ephemeris Time (which is constant). In Ephemeris Time the mean interval between vernal equinoxes is 365d 05h 48m 45s and always has been. The authors give no explanation of how they calculated their figures and, despite extensive investigation, nobody else has been able to find out either. Should information which cannot be verified be allowed to remain in the article? 2A00:23C1:E083:8201:9875:F878:985D:A2C7 (talk) 05:25, 3 February 2018 (UTC)[reply]

We're getting off topic, but Wikipedia's role as an encyclopedia isn't to verify that this is absolutely, truly, "the real number" -- only to tell readers that a book by Meeus and Savoie said it is the real number. If you can find more, better sources you might be able to push that one out, though truly, a good encyclopedia would never discard a valid source from consideration entirely. Wnt (talk) 12:37, 3 February 2018 (UTC)[reply]

Your own calculation of the average over 2000 years verified the Meeus figure (though you deliberately got it wrong). Dbfirs 19:06, 3 February 2018 (UTC)[reply]

References

Meeus, J.; Savoie, D. (1992). "The history of the tropical year". Journal of the British Astronomical Association. 102 (1): 40–42. {{cite journal}}: Invalid |ref=harv (help)

Thank you. I know that the orbital period does not depend on the mass of the satellite. It is interesting that, to determine the mass of a light object, you have to use a heavy object; and to determine the mass of a heavy object, you have to use a light object. A light object is one like a grain of salt, a breadbox, a human, a truck, a fully loaded 747, or an artificial satellite, whose gravitational field is negligible for other purposes. A heavy object is one like Luna, or Mars, or Sol, whose gravitational field is non-trivial. To determine the mass of a grain of salt or a 747, you measure its weight on the Earth, and weight is a function of mass and of planetary gravity. (This makes it hard to determine the mass of a piece of debris in space, because weight is measured by resistance, not by observing an orbit.) To determine the mass of a heavy object, you have to observe something orbiting it. The mass of Mars was much better known in 1878 than in 1876; the masses of Deimos and Phobos were and are still just estimated, but the mass of Mars can be determined by their orbital parameters. Robert McClenon (talk) 22:00, 3 February 2018 (UTC)[reply]

Omega 3

I read that omega 3 can help dry eyes, which I have, especially the omega 3 fatty acids DHA and EPA. Since I hate fish which is the only real source of DHA and EPA, I was reading up on this. There are other supplements of DHA but not alot for EPA, and on wikipedia it appears to say that EPA is converted to DHA, so does this mean EPA is not needed? But it also says that ALA another omega 3 fatty acid is converted to EPA and DHA, so I am confused as to if EPA itself is necessary as a nutrient.--User777123 (talk) 05:23, 2 February 2018 (UTC)[reply]

Have you asked your eye doctor? ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:16, 2 February 2018 (UTC)[reply]

I found one clinical study supporting this as treating for dry eye disease.[10] Krill oil was mentioned as a new thing multiple times in media lately. Cod liver oil also contains omega 3 fat (20%) and has a long history as medicine. I guess that counts as "fish oil". To be fair most medicines tastes awful too. I know cod liver oil is sold in tasteless capsules you can swallow so you dont get to taste it unless you bite one open. --Kharon (talk) 06:31, 2 February 2018 (UTC)[reply]

I can't swallow pills, I have tried chewing up fish and krill oil pills and it is terrible.--User777123 (talk) 07:12, 2 February 2018 (UTC)[reply]

We can't give you advice for your dry eyes (after all, we've not seen them), but eicosapentaenoic acid is generally reckoned as a precursor to docosahexaenoic acid. See [11] To be sure, that doesn't mean that taking DHA can't have an indirect effect on its level; I can't say in which direction at the moment. Alpha-linolenic acid is a precursor to both, apparently not that effective though. I mostly think of that one in terms of breast cancer chemoprevention, though I once saw something about decreased mouse mammary gland development during embryogenesis that struck me as potentially lamentable. Scratching my memory about hemp oil I found this hopeful missive about stearidonic acid in hemp potentially being a closer precursor to EPA. I haven't really chased that rabbit far - the last time I played with hemp oil was around 1990, when it was a fairly nasty way to try to cook spaghetti, and I don't know how good a source it really is. I see there are pure EPA supplements online, and if cost is less concern than pill-swallowing I suppose you could buy them and try to mix the oil into something or other. Use your imagination, but not high heat. Wnt (talk) 13:11, 2 February 2018 (UTC)[reply]

We can not give medical advice here, however, if you can't stand seafood (you may be histamine sensitive), Evening primrose oil is a very good precursor. One's mitochondria can easily convert that into the oils you need. You can get it in gelatin capsules to swallow. Then migrate slowly to cheaper flaxseed and hemp and see how you get on. Also, your home may be very dry. A relative humidity at or below 40% will aggravate dry eyes – so get a meter and measure it. Aspro (talk) 16:24, 2 February 2018 (UTC)[reply]

nurse watches, lapel watches

When did those watches (upside down and worn pinned to the lapel or apron) appear with nurses in (a) the UK and (b) the US? Could there be another country, where these types of watches were "invented"? THX! GEEZER^{nil nisi bene} 15:41, 2 February 2018 (UTC)[reply]

According to this, lapel pin watches came into vogue in the late 19th and early 20th century, they have an example there from 1901. --Jayron 32 15:44, 2 February 2018 (UTC)[reply]

This forum post discusses the history. It may lead you somewhere interesting. --Jayron 32 15:46, 2 February 2018 (UTC)[reply]

Thanks! Hopping on from there I found this. Case closed! GEEZER^{nil nisi bene} 12:00, 4 February 2018 (UTC)[reply]

February 3

Cat claws in a fight

Do cats use their claws to scratch each other when fighting? I haven't seen such instances. Thanks. 77.254.12.184 (talk) 15:31, 3 February 2018 (UTC)[reply]

Are Your Cats Playing Or Fighting?. Alansplodge (talk) 15:52, 3 February 2018 (UTC)[reply]

This suggests they do, and as they use their claws very freely on humans when they try to restrain them I can't think of a good reason why they wouldn't. I've certainly seen a cat using it claws on a dog that brought into our house - the poor dog wondered what hit it when she clung to his face for a few seconds scratching it with her back claws and then disappeared. After a real cat fight they often end up with bits of fur and ears missing, I'm sure no animal would allow that to happen without using all the weapons at its disposal. Richerman (talk) 22:28, 3 February 2018 (UTC)[reply]

For what little it's worth: I've known many cats, but only one who used his claws during play. He was a bony kitten when we found him and I suspect that he was separated too early from his siblings, else they'd have taught him courtesy. –Tamfang (talk) 02:37, 4 February 2018 (UTC)[reply]

Kittens learn to control their claws very fast - in their first month. Cats have a natural urge to sharpen/use their claws so they have plenty of training and full control when they are grown up. Then its simply a question of character and their local cat society's Code of conduct. Normal housecats are likely rather peaceful. My aunt once had a cat she claimed grew up wild, which always seem very serious, unforgiving and unapproachable. Since i used to play with every cat i encountered (i just love them) i got some very painful lessons from my aunt's cat for not waiting for an explicit invitation. So cats use their claws very flexible, as they see fit. --Kharon (talk) 05:43, 4 February 2018 (UTC)[reply]

Concentrated Sodium cloride

I take table salt, drop it in a glass full of water and stir carefully. I wait until the excess of salt settles to the bottom. Now there is equilibrium. What is the concentration of sodium chloride in the water above the sediment? Thanks, - AboutFace 22 (talk) 21:58, 3 February 2018 (UTC)[reply]

It depends on the temperature of the water see Solubility table but at room temperature it should be somewhere between 35% and 36% assuming it's pure salt, however, table salt may be fortified or may contain anti-caking agents. Richerman (talk) 22:16, 3 February 2018 (UTC)[reply]

The Solubility table lists grams of sodium chloride per 100 ml of water, with results between 35 and 38 depending on temperature. I don't know how to express this as a percentage or if there is some different formal way to express a concentration. -Arch dude (talk) 01:23, 4 February 2018 (UTC)[reply]

3.5 to 3.8%, or 5.6 to 6.5 molar. Fgf10 (talk) 09:30, 4 February 2018 (UTC)[reply]

@Richerman & @Arch dude, thank you. AboutFace 22 (talk) 01:32, 4 February 2018 (UTC)[reply]

Environmental science question.

How much food in kg does the average human adult need to eat to give the dunny a good filling at least twice a day?149.254.234.82 (talk) 22:58, 3 February 2018 (UTC)[reply]

(Dunny: Australian slang for outhouse.) Looie496 (talk) 23:13, 3 February 2018 (UTC)[reply]

Well actually no, it's Australian slang for a shithouse. Richerman (talk) 23:53, 3 February 2018 (UTC)[reply]

Depends how much Dietary fiber or Prebiotic (nutrition) your food contains. If your Defecation happens three times in one day you likely have Diarrhea. I am not a medical expert but i doubt defecting twice a day is regarded normal. I also doubt you can enforce defecation that far by eating as much food as you can manage. --Kharon (talk) 05:21, 4 February 2018 (UTC)[reply]

Defacation twice a day is perfectly normal (just Google it) for me, and I certainly don't overeat.--Shantavira|^{feed me} 09:18, 4 February 2018 (UTC)[reply]

Oh, one can easily force defecation to twice a day by overeating. Abductive (reasoning) 07:39, 4 February 2018 (UTC)[reply]

February 4

3 butterfly species

Hello all, I've been meaning to ask this question for quite a while: I'd like to know 3 rather prolific (as in, literally dozens of them flying around everywhere) species of butterflies I saw in August in and around Nashville, TN -- (1) a small, rather cute one which has similar black markings to the large white, but smaller and is colored a pale yellow-green, like an unripe lemon; (2) also a small one (about 2 inches in wingspan) which is a solid golden-yellow or canary-yellow color with no markings whatsoever, is trapezoidal in shape, and tends to congregate into large groups; and (3) a medium-large black one, similar in coloration and size (slightly bigger than) the mourning cloak, but with disproportionately long forewings (proportions are about the same as for the monarch, but overall size is much smaller), and lacking the distinctive white band around the edges. (I will clarify right now that (3) is not a swallowtail, since it lacks the spurs on the hind wings, and is far too small, and also the tips of the forewings are rounded rather than pointed.) 2601:646:8E01:7E0B:61B1:2817:FCB1:9B27 (talk) 05:38, 4 February 2018 (UTC)[reply]

Anyway, these are all just guesses from doing Google and Yahoo image searches for 'butterflies of Tennessee'. If you find that I was wrong, please tell me the correct species. Abductive (reasoning) 07:37, 4 February 2018 (UTC)[reply]

Well, you got at least 2 of the 3 right -- #2 is definitely right, and #3 is probably right (the shape is right, and the coloration I observed was intermediate between the 2 at the top of the page). I have my doubts about #1, though -- the shape is right, but the ones I saw were more vividly yellow-green, and the black markings were darker (maybe the local variety is more vividly colored?) Anyway, I'm not an expert on this subject, and I don't want to search the images myself because I would inevitably come across images of swallowtail butterflies (as like as not on high magnification, too), and I don't want to traumatize myself in this way (I'm OK with many butterfly species including all of the above 3, but swallowtails creep me out!) Thanks! 2601:646:8E01:7E0B:61B1:2817:FCB1:9B27 (talk) 09:50, 4 February 2018 (UTC)[reply]

Oh, BTW, on second thought, could #1 have been Statira sulphurs? Or are they not found in the Nashville area? (Of course, the ones shown at the top of the page are too brightly yellow, whereas the ones I saw were paler and with a more greenish hue, but the markings are just about right.) 2601:646:8E01:7E0B:61B1:2817:FCB1:9B27 (talk) 09:55, 4 February 2018 (UTC)[reply]

What's the highest voltage a closed circuit of D or 9 volt batteries in series could cause for ≥1 second?

Doesn't have to be exact, even an order of magnitude or lower or upper bound is still better than nothing. What would happen to the system? (i.e. terminals heating to X Kelvin, thousands of batteries exploding..) Sagittarian Milky Way (talk) 06:53, 4 February 2018 (UTC)[reply]

Are you connecting cells in series to create a high voltage, or are you asking about the highest current? The latter depends on the internal resistance of the cells, and a modern Lithium-ion battery can acieve hundreds of amps. Dbfirs 07:38, 4 February 2018 (UTC)[reply]

In https://www.youtube.com/watch?v=8hwLHdBTQ7s they got 2000V. I would not recommend the safety precautions seen there, as a current from a 9V battery is enough to kill a person. In another similar video, the spark melted the wire they used. If even more were put in series a spark break down, or corona discharge becomes much more likely. Graeme Bartlett (talk) 10:51, 4 February 2018 (UTC)[reply]

Impossible to say without more details. The internal EMF of each battery is 9V, same as ever. The voltage at the terminals depends on the potential divider effect of the battery's internal resistance and the outside load. This will be less than the EMF, and if the battery is depleted its internal resistance increases so that less will appear across the load (this is why dry cell batteries "lose their voltage" when flattened).

If you series connect a hundred of these, you get 9V × 100 of EMF, somewhat less as voltage (you're probably using second-hand half-flat batteries anyway). The current will be identical to the current of a single shorted 9V battery. For a PP3, this isn't much - the PP3 design is not a high current battery. The power is high, because it will be the product of I × V and however many batteries you have. If you short the terminals of your kilovolt battery, there will be arcing and heated wire. However each individual battery will barely be affected - no more than if it were shorted individually. So no, the batteries (PP3s anyway) wouldn't "explode". D cells? Bit more. NiMH or LiPo? I'd want a blast shield and wouldn't have my hands anywhere near it.

The Zamboni pile, used for early electrical experiments, the Oxford bell and 1940s IR night-vision goggles, was a similar battery. Lots of cells. Lots of voltage, very little current. Andy Dingley (talk) 11:19, 4 February 2018 (UTC)[reply]

Does soapy water kill my silverfish?

I sometimes find dead silverfish in the kitchen sink after I've washed my hands with a pretty mild kind of soap actually (Marseille soap). I would like to avoid killing my pet silverfish as I find those little guys cute and harmless. So could it be soapy water? It doesn't happen very often, though. But I'd like to avoid it happening at all. Thanks. Basemetal 08:35, 4 February 2018 (UTC)[reply]

Aren't they simply drowning in the water? (They are of course insects, not fish.) Silverfish are considered household pests, due to their consumption and destruction of property [sic], and contamination of food.--Shantavira|^{feed me} 09:24, 4 February 2018 (UTC)[reply]

They're probably drowning. Adding soap lowers the surface tension of the water, making it more dangerous to small creatures. PiusImpavidus (talk) 09:36, 4 February 2018 (UTC)[reply]