Wikipedia:Reference desk/Archives/Science/2017 January 12

= January 12 =

Zeroth
I heard he had sa law, but who was Zeroth?--86.187.171.92 (talk) 00:42, 12 January 2017 (UTC)
 * It is "0th" -- referencing thermal equilibrium in zeroth law of thermodynamics. --2606:A000:4C0C:E200:C03A:9D20:31EF:82F7 (talk) 01:02, 12 January 2017 (UTC)

...Actually, it precedes the first law of thermodynamics. --2606:A000:4C0C:E200:C03A:9D20:31EF:82F7 (talk) 02:01, 12 January 2017 (UTC)


 * Well, we were going to call it the Noughtth law but the spellchecker wouldn't let us. It is a bit of a conceit, basically the First Law was well known and then some smarty realised that there was a more fundamental law that needed to be established first. So it got named the First-1 law, ie Zeroth Law. Greglocock (talk) 05:24, 12 January 2017 (UTC)


 * When they come up with the "negative oneth law", it will be even sillier. StuRat (talk) 16:17, 12 January 2017 (UTC)


 * I can't imagine saying "negative oneth"; to me it has to be "negative first". This seems to hold only for pure numbers, because I would say "n-plus-oneth" instead of "n-plus-first". Double sharp (talk) 07:04, 15 January 2017 (UTC)


 * That could be confused with the "bad" meaning of negative, as if there are some good (positive) laws and some bad (negative) laws. StuRat (talk) 19:22, 16 January 2017 (UTC)


 * Am I missing something? How do we know OP is talking about thermodynamics? Maybe they are asking about the zeroth law of robotics or the the laws of zeroth order logic? Those are both mentioned at the 0th page. SemanticMantis (talk) 16:29, 12 January 2017 (UTC)


 * Also used in chemical kinetics, i.e. zeroth order. -- Jayron 32 16:44, 12 January 2017 (UTC)


 * That Zeroth is a real Renaissance man. ;) --2606:A000:4C0C:E200:C03A:9D20:31EF:82F7 (talk) 17:07, 12 January 2017 (UTC)


 * Are you thinking about Zeno of Elea and Zeno's paradoxes? Graeme Bartlett (talk) 22:53, 13 January 2017 (UTC)

Extra credit
If somebody came up with a law more fundamental than the 'Zeroth Law', what would they call it? --2606:A000:4C0C:E200:C03A:9D20:31EF:82F7 (talk) 18:18, 12 January 2017 (UTC)


 * Whatever they chose to. Like if Joe Green came up with it, they might call it Joe Green's Law. ←Baseball Bugs What's up, Doc? carrots→ 18:26, 12 January 2017 (UTC)
 * Leonard Susskind proposed a "Minus First Law" (since he considered it more fundamental than the zeroth law) which is "Bits cannot be destroyed". Some consider it a corollary of the second law, and not a proper law of its own.  A few sources use "Negative First Law", but Susskind used "Minus First Law".  See here for Susskind's own formulation.  -- Jayron 32 18:34, 12 January 2017 (UTC)


 * Wire gauges went from 0 to 00 to 000 to 0000. Negative numbers are also possible.  Or, at some point one needs to just abandon the system and come up with a new one.  Switching to A, B, C, ... would avoid confusion with the old numbering system. But, personally, I don't think numbering laws is a good idea.  We should refer to them by names instead, so laymen have a clue what we're talking about.  Which makes more sense, "Einstein's law of general relativity", or "physics law #28" (if it were called that) ? StuRat (talk) 18:39, 12 January 2017 (UTC)


 * A, B, C only works until they have to switch to "before A", and then eventually they drop classifications other than the multiple A's, i.e. minor league baseball. -- Jayron 32 21:09, 12 January 2017 (UTC)


 * This happened with US household battery sizes, too. Yet another reason not to assign numbers or letters to such laws at all. StuRat (talk) 03:49, 13 January 2017 (UTC)


 * I think "minus first" is adequate and amusingly expresses how fundamental it would be. Anything beyond that would stop being funny, but to be honest if you need to go beyond −1, your "first law" was probably not fundamental enough and would not have been accepted as the "first law". Double sharp (talk) 07:02, 15 January 2017 (UTC)

Bird hipped and reptile hipped
My son and I are reading a National Geographic book. In the section on dinos, there is reference to bird hipped and reptile hipped dinos. The artical then goes on to say that modern birds are more closely related to the reptile hipped dinos than the bird hipped. 1) in what way is this so? 2) if birds are more closely related to the reptile hipped dinos, how can they have evolved from bird hipped dinos? — Preceding unsigned comment added by 76.71.158.242 (talk) 02:21, 12 January 2017 (UTC)


 * The articles are at Ornithischia and Saurischia. Sagittarian Milky Way (talk) 02:58, 12 January 2017 (UTC)


 * Ichthyornis is one of the closest animals to full bird. It too evolved from lizard-hipped dinosaurs. (not a bird ancestor, just a cousin) Sagittarian Milky Way (talk) 03:57, 12 January 2017 (UTC)




 * To answer the question, see convergent evolution. That two different, unrelated groups develop similar structures through evolution is well documented.  I.E., whales and fish have both evolved fins, but whales did not get those fins because they evolved directly from fish.  Similar things happened between birds and ornithischia; the hip structure in birds evolved independently, but along similar patterns, as did that of the ornithischians.  -- Jayron 32 13:31, 12 January 2017 (UTC)


 * For point 2) it is not correct to say that birds evolved from bird-hipped dinos. Origin_of_birds explains that modern birds are a group of theropod dinosaurs. All theropods are part of the Saurischia group linked above. So it is not correct to say that birds evolved from bird-hipped dinos. It is correct to say that birds are theropods, and evolved from earlier lizard-hipped (i.e. Saurischia) dinosaurs. The book is trying to explain that just because the bird-hipped dinos are called "bird-hipped", we should not assume that modern birds are descended from or most closely related to them. Hope that helps, SemanticMantis (talk) 15:18, 12 January 2017 (UTC)
 * The "bird hipped" description of the Ornithischia is an old one (1880s), from visual observation of similarities in shape. Although it's later than the discovery of Archaeopteryx (1860s), it also pre-dates the notion that birds evolved from dinosaurs at all. At the time, Archaeopteryx was described (by Darwin) as a "strange bird" and was seen as an ancient bird of unknown origin, not as an evolution from the dinosaurs.
 * Later work, based on far more specimens and better techniques, such as cladistics, for recognising lineage of evolution showed that the birds are now thought to have arisen from the sauropod dinosaurs (i.e. lizard-hipped), not the bird-hipped. Convergent evolution gives a similar shape in later generations. To further confuse it, we also see early bird-hipped dinosaurs like Psittacosaurus (it even means "parrot lizard") which are now thought to have been partially covered with bristles, a structure resembling feathers  (despite being far older than Archaeopteryx and having no relation). Andy Dingley (talk) 17:46, 12 January 2017 (UTC)
 * Saurischia (and more specifically therapoda, not sauropod. Sauropods are the long/neck tail dinosaurs like Brontosaurus. 86.177.146.201 (talk) 22:13, 13 January 2017 (UTC)

Thank everyone. Just a wee point of clarification: the reason I referred to birds evolving from "bird-hipped" dinos was because in the National Geographic book my son and I are reading is the graphic "family tree" of both branches and the birds were included in the "bird-hipped" branch with a * noting that birds are more closely related to "reptile-hipped" than "bird-hipped." No idea why they didn't include the birds in the other branch with an explanation. Thanks again 76.71.158.242 (talk) 00:49, 14 January 2017 (UTC)

Why do nurses remove bubbles from syringe before injection to IM?
Why do nurses remove bubbles from syringe before injection to IM (intra-muscular)? I do understand why they do that before injection to IV or Intra-artery, because it can cause to air embolism but I don't understand what can be in case of injection to IM.93.126.88.30 (talk) 04:06, 12 January 2017 (UTC)
 * Same reason -- air bubbles anywhere within a person's body can cause an air embolism! 2601:646:8E01:7E0B:6CD5:FDD3:C2B8:18E8 (talk) 04:16, 12 January 2017 (UTC)


 * Oh nonsenese. if you have been on IV for any number of days you'll have lots of little bubbles injected into you. Greglocock (talk) 05:26, 12 January 2017 (UTC)


 * 1) Habit. 2) As part of measuring the correct dose (if there is a bubble in the syringe, then the markings on the syringe barrel will overstate the volume of medication).
 * That said, for some intramuscular injections, a small amount of air – after the medication – is sometimes deliberately injected to help trap the medication in the tissue:.
 * As an aside, it's actually relatively difficult to cause a fatal air embolism by intravenous injection. While not recommended, tiny bubbles injected IV will almost always be trapped in the lungs (and fairly rapidly dissipate).  (Our article on air embolism mentions this.) TenOfAllTrades(talk) 04:37, 12 January 2017 (UTC)
 * How long does the air stay there? Does it dissolve in the capillary blood and go out the lung? Sagittarian Milky Way (talk) 01:31, 13 January 2017 (UTC)
 * then the OP's answer is incorrect ("Same reason -- air bubbles anywhere within a person's body can cause an air embolism!"). Is it right? 93.126.88.30 (talk) 04:50, 12 January 2017 (UTC)
 * [Point of clarification: you, 93.126.88.30, are the OP (Original Poster), while 2601:646:8E01:7E0B:6CD5:FDD3:C2B8:18E8 is an IP poster.] {The poster formerly known as 87.81.230.195) 2.122.62.241 (talk) 10:38, 12 January 2017 (UTC)


 * Regarding reason #2, only if the air-bubble is pushed out of the dead volume. Even if you push the plunger all the way into the barrel, there is some internal space remaining in the Luer taper or other plumbing and the needle itself. If the syringe were at volume-marking 0 and you pull up to 1 mL with the needle in a liquid, pushing the plunger back to 0 expells 1 mL no matter what the dead volume had been. But, if you hold the syringe at any angle other than needle-straight-down, the bubble that represents the original dead volume might get expelled instead of that equivalent volume of liquid. So if you make sure there are no bubbles, the angle does not matter (trade-off of wasting the dead-volume-worth of liquid). DMacks (talk) 04:45, 12 January 2017 (UTC)


 * Note that an injection intended to be intramuscular may accidentally hit a vein or artery. Not very likely, but it would be nice not to kill the patient when it happens. StuRat (talk) 16:20, 12 January 2017 (UTC)


 * If you hit a vein or artery when trying applying an intramuscular injection, you would cause a bruise if you retract it without injecting it. But if you do apply it anyway, a little air bubble is just a small problem compared to the fact that you are injecting a medication through the wrong route.Hofhof (talk) 17:52, 12 January 2017 (UTC)


 * That depends on the med. A local anesthetic could cause death if injected into the wrong vein or artery, but some other meds would just be ineffective if so injected. StuRat (talk) 18:29, 12 January 2017 (UTC)


 * The article air embolism in the relevant part of it, is with a lot of "citation needed", then it's very dificult to relay on it. 93.126.88.30 (talk) 20:55, 12 January 2017 (UTC)


 * But the key part mentioned by DF above which contradicts part of what StuRat has said is supported by this ref . This ref used to support the info on arterial embolisms also supports the info on veneous air embolisms. Nil Einne (talk) 01:55, 13 January 2017 (UTC)


 * Who is DF and what part contradicted what I said ? StuRat (talk) 03:52, 13 January 2017 (UTC)
 * Possible meanings for DF. ←Baseball Bugs What's up, Doc? carrots→ 03:58, 13 January 2017 (UTC)
 * Let's say that he meant to Dear Friends... anyway, these sources don't mention the entering of gas to the artery through the periphery (and that's what relevant to our discussion) but through central places. 93.126.88.30 (talk) 04:18, 13 January 2017 (UTC)
 * But I wasn't commenting on arterial air embolisms other than to say the source used does support the claim made in our article, and also supports the claim made about venous air embolisms. Nil Einne (talk) 12:23, 13 January 2017 (UTC)
 * BTW I came across which isn't an RS although it does link to a bunch of them. The author clearly doesn't agree with current practices and beliefs about the lack of harm from air in IV lines. But it's also clear that they're talking about significantly more air then the small bubbles that may be present in syringe used for intramuscular or IV injection (unless someone majorly screwed up) and even there the actual danger isn't so clear cut (i.e. it's not going to definitely cause death) hence why the author has to argue for changes to current practices of ignoring significantly more air in IV lines than what we're talking about. (Reading a bit more, possibly it's easier to get larger bubbles in syringes than I expected, so I've changed my reply, but this doesn't change the relatives difference between the amount of air in syringes and that is apparently accepted for IV lines.) Nil Einne (talk) 12:42, 13 January 2017 (UTC)
 * In case there's still doubt, some more discussion here from nurses suggesting that while practices vary, often up to 20ml of air is ignored. This is mostly with IV lines, discountinf the 1 odd case where a nurse injected 20 ml of air. Also perhaps,  and . As far as I can see, while it's still recommended to avoid air bubbles with IV injections both for dosage reasons and just because it's considered practice, the actual evidence it's likely to cause death unless you have massive bubbles isn't there. Nil Einne (talk) 13:44, 13 January 2017 (UTC)
 * Sorry I meant TOAT. For some reason I thought it was Dragonsflight who made the above comment. TenOfAllTrades specifically said "actually relatively difficult to cause a fatal air embolism by intravenous injection" before your reply, and this is indeed supported by the article TOAT linked to with references and contradicts your suggestion that the presence of small air bubbles in the syringe (if these are not pushed out) means there's a good chance of causing death if you nick a vein. Nil Einne (talk) 12:23, 13 January 2017 (UTC)


 * I didn't say "good chance". Even if the chance was only 1 in a million, if nurses stopped worrying about air in the syringe, that would still likely result in thousands of deaths a year, not to mention other lesser complications.  So, it's worth the effort to remove the bubbles. StuRat (talk) 21:11, 13 January 2017 (UTC)