Wikipedia:Reference desk/Archives/Science/2014 December 26

= December 26 =

Can anyone name any documentaries specially about the Narwhal?
I know I asked this question a few years ago but I'm really looking for documentaries about this fascinating animal Merry Christmas and thank you! Venustar84 (talk) 04:24, 26 December 2014 (UTC)
 * There are many, mostly short, videos and other items including narwhals not as the main subject. Google "narwhal" then click on "videos" at the top when you get results, and scroll down.  There is a 1hr talk at https://www.youtube.com/watch?v=6fkn09vkZYs μηδείς (talk) 04:30, 26 December 2014 (UTC)
 * Well a 1 hour talk is boring. I would like to see a documentary that at least includes them. Venustar84 (talk) 04:51, 26 December 2014 (UTC)
 * Some content about narwhals in BBC documentaries here, but you may not be able to view the clips if you are outside the UK. The BBC have uploaded one of the clips to YouTube here and I found some other clips by National Geographic here and here. Best I could do I'm afraid. Alansplodge (talk) 22:37, 27 December 2014 (UTC)

is Turritopsis_dohrnii immortal? why isn't anything?
is Turritopsis dohrnii immortal? can examples have survived since the age of dinosaurs, for example in some cave?

why isn't anything immortal - one could easily imagine a mutation that allows a particular organism to just not die if it has access to nutrients, and also it's easy to imagine some indisturbed source of nutrients that has been extant for three hundred million years. 212.96.61.236 (talk) 06:03, 26 December 2014 (UTC)


 * Evolution.
 * An "immortal" lifeform can't evolve. When the environment changes, it's stuck in a rut.  Lifeforms with short lifespans can change to fit changing conditions relatively easily.  Longlived organisms are stuck with the hand they were dealt at birth...no matter how badly it fits a changing world. SteveBaker (talk) 14:42, 26 December 2014 (UTC)


 * Plenty of organisms don't age, but they still need to reproduce, because at some point even un-aging individuals will be killed by a predator, disease, or the environment (forest fire, landslide, etc.). μηδείς (talk) 12:19 pm, Today (UTC−5)


 * I would take claims of immortality with a full shaker of salt. One would assume, for example, that single celled organisms that continually divide must be immortal.  Yet budding yeast is in fact not immortal - you can track the lifespan of the mama yeasts and show it is finite; they are replaced by the baby buds!  With other single celled organisms you can't always tell which cell is the 'parent' as with yeast, but that doesn't necessarily mean they are all the same and immortal.


 * In the case of Turritopsis, it is said to be theoretically immortal as it could (it is said) repeatedly revert to larval stages.  However, biology doesn't actually understand theory.  It certainly could be, but until someone actually shows that he has de-differentiated the cells of a single medusa/polyp a hundred times in a row, I don't regard it as proven.  And even if he did I'd be suspicious that the organism would turn out to be clonal from some recent 'generation' of dedifferentiation, coming out of a germ cell lineage, rather than representing the full set of cells that the first medusa had to begin with.  (Since cells of an organism are supposed to be clonal to begin with, that's a picayune distinction, but the point is, if the cells are clonal from a germ cell they have had less chance to accumulate somatic mutations/cancer, but also, if the cells were able to store memories somehow then all those memories would be erased just as with a new individual) Wnt (talk) 17:51, 26 December 2014 (UTC)


 * See also Senescence, Evolution of ageing, and Genetics of aging.-- O BSIDIAN  †  S OUL  00:20, 27 December 2014 (UTC)

Is it possible to buy large and affordable (artificial) gemstones like rubies, emeralds and sapphires?
I'm thinking of starting a bit of a gem collection of crystal-y gemstones like amethysts, rubies, etc but the prices for a good sized one is ridiculous... RuneScape seems to have tricked me. I read on Wikipedia that artificial ones are a fraction of the price but the only websites for them seem to be direct from a factory in China and there's almost no pictures of the stones. Is there a place where I can buy those polished, cut, crystal-y gemstones for less than 50 pounds, that are also bigger than my thumb? 2.102.184.78 (talk) 06:48, 26 December 2014 (UTC)


 * Lab grown sapphires, rubies, amethysts, and emeralds can be made to almost arbitrarily large sizes relatively easily. Here are some examples of low-cost large-ish stones.  I suspect googling "synthetic sapphire" and similar terms will find other moderate cost examples for these.   Dragons flight (talk) 08:06, 26 December 2014 (UTC)


 * But do note that everyone will have a huge precious stone soon, reducing the coolness of it. Smartphones are moving to replacing their screen's glass with colorless sapphire starting with the next iPhone. Sapphire is harder to crack than Gorilla Glass and can only be scratched by diamond and other sapphires (and a few man-made substances (and rubies, but those are red sapphires)). Sagittarian Milky Way (talk) 08:28, 26 December 2014 (UTC)


 * Sapphire is more scratch resistant than Gorilla Glass sure. I don't think it's clear it's harder to crack, since it depends what you mean. While alot of the sourcing here comes from self interested manufacturers particularly on the Gorilla Glass side (in particular, I don't think it helps that the primary proponent of sapphire seems to be fairly silent perhaps because they don't really seem to have a suitable mass market product yet), quite a few sources do suggest pristine Gorilla Glass is harder to crack in some circumstances than sapphire  . However, as the latest source in particular emphasises, it is complicated since scratches (which may occur during a drop) can make a crack more likely. Ultimately, the idea that sapphire is harder to crack seems at the very least a big caveat. As for the next iPhone, well people were saying the same thing about the 6 or 6 Plus and look where we are now? Or to put it a different way, there are rumours all the time and there's a good reason why wikipedia shouldn't deal with them Nil Einne (talk) 13:43, 26 December 2014 (UTC)
 * Didn't Apple buy a sapphire factory in Arizona? I read the idea is that the price only becomes low enough when you run the sapphire making machine round the clock and reach levels of sapphire production never seen before, which would happen when make tens of millions of sapphire phones a year. Why the heck else would Apple buy a sapphire factory? But that's why it didn't happen yet. Samsung or something said it's not economical enough yet for them. And come to think of it, they may have qualified it with the same caveat that you gave. Anyway, Gorilla Glass isn't that strong. It's probably silly strong for glass (I think stronger than tempered) but it's very thin. I bought a Lumia 635 for £20 and tried opening it with a knife to the opening slot but some glass suddenly failed and flicked at my eye. I'm really surprised my eye closed faster than a piece of glass can be flicked a yard at 50 km/h. (one piece stuck into the epidermis for the curious) The only way to safely unbrick it is to pry the knife under the very well-glued glass and peel it off without crack-folding it too hard. (it's very flexible) You can now cover the LCD with the page of glass to know where to click and then turn the glass page to see. So if you put the battery & SIM in yourself follow the instructions and pry, just squeeze the sides of the super rigid plastic first. And no tools. Sagittarian Milky Way (talk) 06:08, 27 December 2014 (UTC)


 * You are thinking of GT Advanced Technologies which partnered with Apple in an attempt to supply sapphire screens, but ultimately failed to deliver a usable and affordable product in the quantities Apple needed. Leading the company to file bankruptcy  and Apple to write-off some $400 million they had invested in the effort.  GTAT did make sapphire blocks weighing nearly 600 pounds though.  Dragons flight (talk) 06:41, 27 December 2014 (UTC)
 * Yeah this was slightly covered in the links above although I wasn't keeping up and didn't know they'd actually filed for bankruptcy. The links said the company and their relationship with Apple imploded but I didn't know how far and didn't bother to look in to the details. It seems it was quite far indeed with various accusations now known . It seems unlikely this is going to be sorted out before the next iPhone, and I don't think anyone else has reached that level of capability so another nail in the idea the next iPhone will have sapphire. Nil Einne (talk) 12:22, 27 December 2014 (UTC)
 * I never said Gorilla Glass is "that strong" whatever you mean by that. I said it is stronger than sapphire in certain cases (mostly when it is unscratched), since you implied sapphire is always strong than Gorilla Glass when there's strong evidence it isn't. Or to put it a different way if Gorilla Glass isn't "that strong" nor is sapphire. I don't get the relevance of thickness. I'm fairly sure Gorilla Glass can be made in a variety of thicknesses, probably more easily than sapphire in fact and in more thickness than 0.55-2 mm list in the data sheets if you're willing to other large enough quantities. The precise thickness used in any specific application would depend on the requirements and expectations for that device, however whether sapphire or Gorilla Glass would likely tend to the thinner side for mobile phones considering the current push towards thinner devices etc. Nil Einne (talk) 12:22, 27 December 2014 (UTC)
 * I just wanted to say that Gorilla Glass isn't that strong when used at the thinnesses of smartphones. Mainly cause of what I read when I first learned of Gorilla Glass (that it was invented in 1960 but was so strong no one could think of an application for it until someone realized in the late 2000s that (paraphrase) if they made it way thinner like 1 mm it'd still be very strong and allow a thinner phone), rather than because of anything you said. (they used some undue weight/dramatic license to make a better story). I guess I forgot the part about scratches seeding cracks. And yes GG is a bit ludicrously strong by glass standards, I've never seen glass bend so much before cracking (now that was some strong glue). But it's still only 1 mm thick which means that people with slightly slower reflexes thinking they wouldn't put the slot there if the glass would break first will have glass hit their globe. That's the only way to change the SIM, by squeezing the hard back very hard and leveraging it off with a fingernail. Since chisels are equally scratchable as glass, diamonds are the most rigid Earthly substance known, but diamonds have been shattered by hammers I'm really curious to know how hard you could slam a sapphire phone onto a chisel in a vise and still use it (uncracked). Or use a carpentry hammer on it. I really have no idea if it'd be weak like glass or need a blow similar to genuine hammer use. If it's hard enough though that would be awesome. Sagittarian Milky Way (talk) 19:05, 27 December 2014 (UTC)
 * Don't know why you'd want to use a chisel on your phone and not completely sure it's a useful test, it doesn't sound like the sort of thing likely to stimulate much common real world damage. But in terms of less real world usage tests, as I already said, there is testing out there of sapphire vs Gorilla Glass in various ways including videos e.g. / (same video comparing, this tends to be the most common by far) or and . We don't know for sure how an iPhone with Sapphire from GT Advanced would have performed but all these videos and commentary support the idea that Sapphire isn't necessarilty better, and could easily be worse than Gorilla Glass when it comes to stuff besides scratching, so I still don't understand why you're treating this like some super mystery. Also, while I've never used a Lumia 635, this link  does not recommend you use any tools to open it or to remove the SIM. To be frank, it sounds to me a lot like you're doing something wrong, or there was a defect with your phone or SIM card. Nil Einne (talk) 13:27, 28 December 2014 (UTC)
 * I wouldn't risk my iPhone 7 for a party trick, well maybe if it was verifiably invulnerable at the force I was going to hit it but apparently that's not going to be the case. A chisel or hammer test is not a meant to be a real-world simulation, it's like the Will It Blend videos where they used the world's most powerful blender to blend things that are much harder than food. Like blending a load of marbles until a cloud of glass dust rose from the coarser stuff when the contents were poured out. Or blending a load of three feature phones or a large remote control. Sure the cut might've been many minutes but one thing's for sure, if it can do that then it's going to blend food very rapidly and no food will make it overheat.
 * See diamond anvils are used to make the pressure of the center of the Earth and when I was young and impressionable there was a TV ad that bragged that this watch had a sapphire face allowing it to withstand 800 (400?) pounds of unadulterated pressure. So you can see why I might think sapphires are amazing. And as for the Nokia, this picture should tell you much. Now I remember why I didn't want to open the back without removing the glass first. You have to squeeze the back of the phone, not the side, the screen was already cracked from trying the tab in the front. I didn't think they would be so stupid to put a slot there if the glass could shatter before the back opened. I've never had a phone who's back was so hard to remove much less break if you did it wrong and you need to do it if you declined getting the battery and SIM installed at the store. Broken Lumia mobile phone.jpg
 * Synthetics may be a fraction of the price for natural stones of good quality and free from intrusions. Yet those natural stones are  very  expensive. So for you to  hope that you can find a gemstone the size of your thumb on  your paupers budget is like wishing on a star. --Aspro (talk) 15:45, 26 December 2014 (UTC)

Thanks for the links dragons flight, but those are too small. I'm after at least 5 cm in length. I've been on lots of websites and they only seem to offer small gemstones to be put in jewellery. :( 2.102.184.78 (talk) 04:40, 28 December 2014 (UTC)
 * I could be wrong but I suspect given your fairly small budget and the fact you're asking for something which I don't think is in very high demand, you'll probably need to deal direct the factories or other sellers in China in whatever. I don't really understand why you dismissed this earlier but in a case like this, it's probably your best hope, particularly since your demands are as you've said fairly unusual. If it's a manufacturer or someone close to one, you could likely ask and see if they have or can make something that meets your requirements. Similarly if you want photos (although that would require they actually already have something). Your budget is fairly small, but still large enough that someone in a developing country like China may be willing to give some degree of personal service (and frankly I've had decent info from Chinese sellers on AliExpress etc for smaller amounts in other cases). You will ultimately need to rely on some degree of trust, although there may be AliExpress Escrow or whatever depending on where you buy it from and what the seller is willing to do. I am presuming you mean GBP50 for one gemstone not multiple and it'll probably be better to start with one and see how it goes. Nil Einne (talk) 13:44, 28 December 2014 (UTC)
 * Okay, I'll try that then. I even saw one factory offering gems up to 20cm in length, so this might be the best option. 2.102.184.78 (talk) 14:18, 29 December 2014 (UTC)

Excess of Nitrogen in the blood
Hypercapnia is an excess of carbon dioxide, hyperoxia is an excess of oxygen. What is the term for an excess of Nitrogen? --2A01:E34:EF5E:4640:F164:A688:6426:94E (talk) 10:10, 26 December 2014 (UTC)


 * To the best of my knowledge, there is no common-usage clinical term utilized, in an analogous manner similar to the other physiological terms you mention, for excessive free nitrogen.  However, blood urea nitrogen (BUN), nitrogen balance, hyperuricemia and hyperammonemia may be of interest to you.  As a general rule, context for non-ideal concentrations of nitrogen are likely to involve the catabolic pathways and kidney function.  If a more general physiological term for excessive nitrogen did exist and was consistent with standard naming conventions/morphological transitions for other terms in the context, it would be most likely to take the form of "hypernitrogenia" or possibly "hyperazotia".  S n o w  talk 11:58, 26 December 2014 (UTC)
 * Thanks. I'd already seen the urea- and ammonia- related terms, but what I'm looking for is excessive disolved Nitrogen (where 'excessive' is a partial pressure greater than about 3.4 bars). Hyperazotia sounds like it might fit the bill though. --2A01:E34:EF5E:4640:F164:A688:6426:94E (talk) 13:57, 26 December 2014 (UTC)


 * For dissolved N2 gas in blood and other tissues, an excess (caused by exposer to higher partial pressure of N2 followed by reduction in pressure at too rapid a rate to allow for sufficient offgassing) can lead to decompression sickness. (See also decompression practice.)  Breathing N2 at partial pressures greater than 4 atm (such as when breathing air at more than 5 atm absolute, corresponding to a diving depth of greater than 40 m sea water) can cause nitrogen narcosis, an intoxicating effect which is quickly reversed upon returning to shallower water.  While there may be more technical terms used in some medical literature, I have only heard "excess dissolved nitrogen" for the former and "excess partial pressure of nitrogen (pN2)" for the latter. - ToE 13:53, 26 December 2014 (UTC)
 * You hit the nail right on the Head. My question is directly related to nitrogen narcosis. --2A01:E34:EF5E:4640:F164:A688:6426:94E (talk) 13:57, 26 December 2014 (UTC)
 * Hopefully someone else here can come up with the term, but barring that, I'd suggest looking though some medical research papers on nitrogen narcosis to see what terms they use. Please let us know if you come up with something that way.  Good luck! -- ToE 15:05, 26 December 2014 (UTC)

A google search of excess blood nitrogen -urea -ammonia brings up only the bends and nitrogen narcosis as mentioned above. Since under normal circumstance nitrogen is inert, it wouldn't be surprising if there's no one-word term for it. μηδείς (talk) 19:36, 26 December 2014 (UTC)

Road surfaces
What are the main surface materials used in urban roads, rural roads and freeways? Do all use asphalt now? — Preceding unsigned comment added by 94.14.212.193 (talk) 17:32, 26 December 2014 (UTC)
 * We have an article unsuprisingly called (you'd at least expect a redirect) road surface which gives other types. Nil Einne (talk) 17:50, 26 December 2014 (UTC)


 * I don't know about in the UK, but in America most of the "superhighways" tend to use concrete, while more conventional roads tend to use asphalt. There aren't all that many gravel or dirt roads nowadays, except in fairly remote or less-traveled areas, side roads, etc. Paving brick was once a common surface in cities, but is now almost entirely a thing of the past. ←Baseball Bugs What's up, Doc? carrots→ 18:14, 26 December 2014 (UTC)


 * I've lived in two places with public olde paving within walking distance that are not next to historical buildings. One of them was several hundred yards away, though just the sidewalk and the other is a small part of the street grid where the asphalt suddenly turns into bricks (near where I live now). I'm sure this is more common in other Northeast cities where they are a little more old-timey. Sagittarian Milky Way (talk) 22:39, 27 December 2014 (UTC)


 * Concrete has been used on UK motorways in the past but it was considered to be noisy. I think it's being tried again with modern fast-setting concrete and a smoother finish, but it's not common on any British roads.  I've seen it most on farm tracks.  Asphalt is the norm for all British public roads.    D b f i r s   21:46, 26 December 2014 (UTC)

Please help me identify this anatomical feature
I have two slits/holes in the roof of my mouth towards the back, one on each side. I have had them for as long as I can remember. They seem to connect to my nose and I can suck snot from my nose down into my mouth through them. When I get a cold they become sore and painful because instead of blowing my nose I can just suck the snot out through them and swallow it, which is more convenient but seems to agitate them.

Is this normal? What are they called? I have searched online but all I can find are a few forums of other people saying they have something similar but also not being able to find any information on it. Whenever I talk to someone else about this IRL they are like "wtf are you talking about?" — Preceding unsigned comment added by Bculuper (talk • contribs) 18:56, 26 December 2014 (UTC)


 * We can't diagnose issues or give advice on the Refdesk; we can't say what is "normal" and "disease". But it is worth noting that clinically diagnosed cleft palate is quite common, affecting 1/700 infants, and wherever there is a clinical diagnosis there is a broad tail of situations that don't quite reach the point where they count for the diagnosis.  You might want to look into variations of the uvula and submucous clefts.  Wikimedia Commons would of course love uploads of the structures you describe, especially if you are able at some point to get a physician's description of what they are, and you might gradually see more description of the situation from articles that use them.  But don't count on us to answer "is it normal", because if we did you should distrust what we say! Wnt (talk) 21:11, 26 December 2014 (UTC)


 * What did your family doctor say when you asked him/her about these holes? Richard Avery (talk) 08:42, 27 December 2014 (UTC)

Is universe a isolated system?
Is universe a isolated system? — Preceding unsigned comment added by 106.215.155.253 (talk) 23:18, 26 December 2014 (UTC)


 * If by 'universe' one means everything that exists (the normal definition), clearly it is isolated in that nothing that exists is outside it. AndyTheGrump (talk) 23:21, 26 December 2014 (UTC)


 * Or it may be one of many universes in the multiverse - but the existence of the multiverse is only a hypothesis. Richerman    (talk) 01:19, 27 December 2014 (UTC)


 * But, we define "universe" to include everything that can possibly influence anything else...if there are "other" universes (we don't know) then - more or less by definition - they cannot have any possible influence on our universe - so we're still a closed system.


 * If we find ways in which "other universes" communicate information/mass/energy with us (we don't know) - then I think we'll have to redefine the meaning of "universe"...but that seems kinda unlikely.


 * So, I think that...by definition...the universe is a closed system.


 * That said, the universe might be infinite (we don't know)...and that makes the idea of "closed" kinda difficult. A closed system with infinite mass/energy in it is a bit tricky to deal with on any level.


 * SteveBaker (talk) 01:34, 27 December 2014 (UTC)


 * You are equivocating between universe defined as all that exists and the visible universe. Neither is there any evidence the universe in either sense is infinite, nor any coherent way of describing an infinite universe.  To say the universe, how ever big it is, is bigger than it is, is a meaningless contradiction. μηδείς (talk) 02:23, 27 December 2014 (UTC)
 * No, I said nothing of the sort - I was not mentioning in any way the 'visible' universe - I was referring only to the entire universe. You're right that there is no evidence for an infinite universe - but there's none for a finite universe either.  That's why I said "(we don't know)".   Right now, that's an unsolved problem of cosmology - and since either seems equally possible - we have to hedge our answers accordingly. Incidentally, the visible universe is most certainly not a closed system.  Since it's defined relative to where we are observing it from, the parts of it out at the edges of our ability to see are clearly interacting with the parts beyond that reach.  Of course the effects of those interactions can never affect the observer - but it's clearly not a closed system from a thermodynamic perspective. SteveBaker (talk) 16:18, 27 December 2014 (UTC)
 * Medeis, you've said this before. It was wrong before and it's wrong now. "Infinite" does not mean "bigger than it is".  It means "bigger (whatever quantity you're measuring, volume for example) than any natural number".  It is perfectly possible to "describe" a universe that has that property.  Whether the actual universe has that property is an open question, and while it is unlikely to be settled in the near term or perhaps ever, it is not impossible to gather evidence one way or the other, and cosmologists do in fact do just that. --Trovatore (talk) 02:59, 27 December 2014 (UTC)
 * Yes, of course I have said it before. But there are no coherent theories of an infinite universe.  They all require that whatever size the universe is, it is actually bigger--that is, that the universe has no actual size, and therefore that existing things stand in no actual relationship to the size/mass/age of the universe.  Three things are needed.  The evidence.  The evidence is finite, but it has horizons, and we know there must be parts outside the universe that are not visible to us.  That still doesn't imply an infinite universe.  Second, a coherent theory.  Again, Aristotle covered this, and when Newton forgot it with his absolute space, Einstein came back and brought us back to curved, relative space.  Third, this is wikipedia.  The burden is on him who makes the assertion.  Those who claim the universe is bigger than it is need to prove that.  Those of us who claim the universe is definitely the size it is need make no further claim. μηδείς (talk) 05:06, 27 December 2014 (UTC)
 * See below. Your second and third sentences are flat wrong. As for burden of proof, I have not asserted that the universe is infinite, only that it is an open question.  I have explained in what way it is a coherent question, refuting your claim that it is not. --Trovatore (talk) 05:15, 27 December 2014 (UTC)
 * (By the way, please stop slipping the locution "bigger than it is" into the assertions you attribute to me. I have not said that the universe is infinite, but if I had said that, I still would not have said it was "bigger than it is".  It is certainly true that "bigger than it is" is incoherent.  But it is not what "infinite" means.) --Trovatore (talk) 05:20, 27 December 2014 (UTC)
 * To use your phrase "this is Wikipedia", feel free to read about the standard model of cosmology which is a widely used Einstein-based theory that describes an infinite universe. There are alternative theories that allow for a finite universe, but the contention that there is no "coherent theory" of an infinite universe is simply nonsense from the point of view of modern physics.  Dragons flight (talk) 06:02, 27 December 2014 (UTC)
 * Maybe the whole disconnect here with Medeis is just about definitions? If we say that X is Medeis-infinite if X is bigger than X is, then I'm perfectly happy to agree that the universe is not Medeis-inifinite, and indeed that Medeis-inifiniteness is an incoherent concept.  I generally respect Medeis and enjoy her contributions, so I'd like to think that.  Then we could agree to discuss a different notion of inifniteness, one that is not incoherent on its face, and maybe make some progress. --Trovatore (talk) 08:34, 27 December 2014 (UTC)
 * Mathematically speaking, it is not possible to have anything "bigger than any natural number". ←Baseball Bugs What's up, Doc? carrots→ 04:26, 27 December 2014 (UTC)
 * Yes it is. For example, consider the real line.  It is a mathematical object in which distances make sense, and yet its "length" is greater than any natural number &mdash; for any natural number N, there are two points on the real line such that the distance between them is greater than N.
 * Prior to Einstein, the usual picture of the universe was that it looked like R3; that is, three-dimensional Euclidean space. R3 has infinite volume in the same sense that R has infinite "length" (as I described above).
 * We now know that that picture is too simple &mdash; the universe does not look exactly like R3, not when you consider the metric, anyway. However it is still possible that the universe (meaning a three-dimensional spacelike submanifold of the four-dimensional universe) looks a lot like R3, albeit with some local bumpiness.  If so, then the universe is infinite.  This is an entirely "coherent" description, and gives one scenario in which it would be meaningful and correct to say the universe is infinite. --Trovatore (talk) 05:13, 27 December 2014 (UTC)
 * A 'universe' need not be isolated if used in the sense of an 'inter-universe' connection in Einstein-Rosen-Podolsky bridge; however, in addition to serious doubt about the viability of the bridge in general, this is something of an abuse of the word 'universe'. Wnt (talk) 03:11, 27 December 2014 (UTC)
 * "...for any natural number N, there are two points on the real line such that the distance between them is greater than N." Sure. For example, take the number 7. The distance between 8 and 16 is greater than 7. So? On the contrary, for any two points, there is a number N which is larger than the distance between those two points. ←Baseball Bugs What's up, Doc? carrots→ 15:11, 27 December 2014 (UTC)
 * Yes, you can keep leapfrogging like this for ever, yet Trovatore is still correct, because the length of the number line is not considered a natural (or real) number.   D b f i r s   16:12, 27 December 2014 (UTC)
 * The "length" of the number line is infinite, which means "never-ending". It has no "end", hence it has no definable "length". Infinity is not a number, it's a concept of boundless expansion. ←Baseball Bugs What's up, Doc? carrots→ 16:40, 27 December 2014 (UTC)
 * It's certainly true that it's unusual to speak of the "length" of the real line (that's why I put it in scare quotes from the start). If you want to say the real line doesn't have a "length", I'm OK with that.
 * However, the real line does have a one-dimensional Lebesgue measure, and the most natural short expression for "one-dimensional Lebesgue measure" is "length". The Lebesgue measure of the real line is &infin;. --Trovatore (talk) 18:09, 27 December 2014 (UTC)
 * The term "isolated" implies separation from something else. If there are multiple universes, then this one would appear to be "isolated". If there is only one universe, then "isolated" doesn't really mean anything. ←Baseball Bugs What's up, Doc? carrots→ 04:24, 27 December 2014 (UTC)


 * According to BBBugs, infinity does not exist.


 * On the other hand, 0.9… periodic (ie an infinite series of 9s) = 1. There is 1 BBBug and this 1 BBBug is equal to 0.9… periodic BBBugs (note the depressing plural).  As a - negative - corollary:  Were there only 0.999…, a series of (∞ - 1) 9s, BBBugs, there would, mathematically, be <1 BBugs and BBBug would not exist.  BBBug himself is the proof of infinity.


 * QED


 * Any answer to the question “is BBBugs an isolated system?” constitutes medical advive.  --Cookatoo.ergo.ZooM (talk) 16:10, 27 December 2014 (UTC)
 * Infinity as a concept exists - the concept of limitless expansion. But there is no such "number" as "infinity". ←Baseball Bugs What's up, Doc? carrots→ 16:43, 27 December 2014 (UTC)
 * Whether "infinity" is or is not a "number" is more a semantic argument about the meaning of the word "number" than it is a math or science argument. For some applications (e.g. the extended real number line), mathematicians explicitly include infinity as an object on equal footing with more traditional numbers.  Similarly, "infinity" gets used in limit calculations and is the only proper answer to a variety of calculations (e.g. number of natural numbers).  I don't think mathematicians spend much time arguing whether infinity is a "number", because that is a argument with no practical consequence.  "Five" is a concept.  $$\sqrt{-1}$$ is a concept.  Hyperreals and quaternions and spin operators are concepts.  If the concepts are useful then they'll be used, but which ones are also called "numbers" probably isn't a useful discussion.  Dragons flight (talk) 18:05, 27 December 2014 (UTC)
 * Yes, nicely put. --Trovatore (talk) 18:36, 27 December 2014 (UTC)

Wow, there are at least three ways the discussion could go in response to Bugs here. Dragons flight already addressed one of them; the second would be to show that we can formulate the notion of "infinite universe" even within Bugs's paradigm. But I think I see a "teachable moment" here, so I'm going to go for the boldest, third option. What Bugs is saying &mdash; I think &mdash; is that he accepts potential infinity, but rejects completed infinity. In this, he would have been in total agreement with virtually all the greatest mathematical minds through the eighteenth century, and maybe a majority of them through most of the nineteenth. Gauss in particular is associated with this view, and he was certainly no slouch. Among non-mathematicians, Medeis has already brought up Aristotle, and we can add on Aquinas in perpetuating this seemingly very sober view. But they were all wrong. The paradigm started to show its age with the development of real analysis in the 19th century. Figures who started developing concepts in tension with it include Peano, Dedekind, Cauchy, Bolzano, and Weierstrass. But the real game-changer was the remarkable work of Georg Cantor. He was the first one to explicitly take the completed infinite seriously and show what could be done with it. This was an absolute revolution. Modern mathematics uses the completed infinite without embarrassment. There are still people who have trouble with it philosphically, and discuss it endlessly. But almost everyone is willing to use it, even if they may tell different stories about what they are "really" doing. You can criticize Cantor's viewpoint, if you like. But you first have to understand it. If you haven't absorbed and come to terms with the Cantorian revolution, you're just not addressing the issue when you talk about infinity. --Trovatore (talk) 18:50, 27 December 2014 (UTC)