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December 3

Has the density of the Universe ever been greater than 1.0?

In Planck units, how could you ever have a Planck density greater than 1.0?

That completely fills the Holographic principle leaving no room for any other information. Any history before that moment would be crowded out.

Ergo the Universe didn't start with infinite density, just density 1.0 or less. Hcobb (talk) 00:16, 3 December 2015 (UTC)

Our article on this is Planck epoch. Graeme Bartlett (talk) 21:55, 3 December 2015 (UTC)

Gay Bomb

Gay_bomb page has some abuse on it. Im very poor at wikipedia, can someone try to fix the page. --84.248.87.146 (talk) 09:42, 3 December 2015 (UTC)

I've reverted some recent vandalism. Clarityfiend (talk) 10:12, 3 December 2015 (UTC)

Masturbation for Astronaughts

I'm not going to to lie, but every man I've ever known (including myself) really needs to ejaculate at least once or twice a week. Trying to hold back the urge for more than two weeks is a nightmare. And with most missions lasting months, what are astronaughts meant to do about it? Is there any sort of training their given. Anti-libido pills? Some kind of sock? I mean, in low gravity, the stuff would go everywhere especially if you've got a crew of many men. The risks would be immense but you can't ignore natures call?? — Preceding unsigned comment added by 210.216.57.223 (talk) 15:21, 3 December 2015 (UTC)

I want to answer this, but I keep giggling to the tune of On the Beautiful Blue Danube and trying to work out the zero-gee mechanics... give me a minute. Wnt (talk) 15:30, 3 December 2015 (UTC)

I'm not sure this is a legit reference, but it's a start... Wnt (talk) 15:33, 3 December 2015 (UTC)

your wish is my command
The following discussion has been closed. Please do not modify it.
Just waiting for the defacto RD police "M + BB" to shut this question down and cry "troll". — Preceding unsigned comment added by 92.241.130.120 (talk) 15:39, 3 December 2015 (UTC)

Nay, you should research and post something relevant if you find it. "Enjoy yourselves. Tomorrow it'll be a ruin." Wnt (talk) 15:49, 3 December 2015 (UTC)

See Wikipedia:Reference desk/Archives/Science/2012 December 11#Astronaut Lifestyle - it didn't end well, but the question has been addressed before. "Astronaut", from the Latin nauta, incidentally. Tevildo (talk) 20:37, 3 December 2015 (UTC)

Astronaut says: The term derives from the Greek words ástron (ἄστρον), meaning "star", and nautes (ναύτης), meaning "sailor". But no human has ever been anywhere near a star, or has ever even tried. Maybe they should be called lunonauts, selenonauts, or planetonauts. -- Jack of Oz ^{[pleasantries]} 04:19, 4 December 2015 (UTC)

Maybe the OP is thinking of "astronaughty bits". ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:02, 4 December 2015 (UTC)

By the way, the Apollo 12 flight journal linked from that old posting would now be here. Well, I was curious. --76.69.45.64 (talk) 17:27, 4 December 2015 (UTC)

Survival trumps frivolity. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:17, 4 December 2015 (UTC)

• Here is a link to masturbation for editorial convenience. μηδείς (talk) 23:11, 4 December 2015 (UTC)

Stages of non-grief emotions

Is there any counterpart to the Kübler-Ross model for emotions other than grief, that would analyze them in specific stages?

I'm specifically curious because I feel like stages of, I dunno, "suspicion" seem closely allied to the scientific method. For example, suppose you think you hear a funny noise from the furnace. Well, first you just make a note of it in case it happens again ... then you're listening for it intently ... then you start hypothesizing about what is wrong ... then testing if it is in fact not working. Or some such thing. It seems like that's not that different from some of the stages of grief like denial and bargaining, and of course the furnace problem can have some anger, resignation, even fear involved also. But if that were true, it would mean the scientific method is instinct, something bred into the limbic system, rather than a technological achievement at any time in recent history. Anyway ... has such a generalization ever been attempted? Wnt (talk) 15:56, 3 December 2015 (UTC)

I'd just like to note that this is a very interesting question. I realize that although I do this all the time, I have never thought of it as a thing. Thanks User:Wnt. μηδείς (talk) 01:29, 4 December 2015 (UTC)

Have a look at abductive reasoning, and this paper [1], particularly the bits (p.378) where they cite Charles Sanders Peirce as well as some work from this century. The Carruthers (2002) paper I think will be worth a look regarding the potential for an innate/instinctual human tendency that is rather similar to the scientific method. SemanticMantis (talk) 19:26, 3 December 2015 (UTC)

I found that here, but ... well, at least at first glance I'm having a hard time doing anything with it. He's looking at it from a different perspective, or maybe I'm just not giving him a chance.

For one thing, I'm thinking at the moment of something much more general. For example, some dating service used to advertise with "First Comes Like", capitalizing on the notion that people accept that love goes through a series of stages which, again, don't seem all that dissimilar from those of grief or scientific method in concept. Fear on the other hand is maybe a bit of an outlier in that it tends to go straight to full mast, but even it can start slowly under the right circumstance ... though maybe it can be regarded a stage of something else, like fight-or-flight? I feel like there ought to be some kind of unifying architecture underlying all emotions, of which scientific curiosity is one. Wnt (talk) 20:04, 3 December 2015 (UTC)

For what it's worth, I should note it is possible to look up a great number of articles that talk about stages of falling in love. Since grief and love are practically the same emotion anyway, save for circumstance, trying to place a chart from this beginning may help to clarify my thoughts. Though what they have in common is (not so surprisingly) limited, there are some commonalities we might expect: people are infatuated at the beginning, make decisions in the middle, and become more comfortable or habituated later on. (quoted terms are from [2]):

Emotion	Background resistance	Affect	Data gathering	Judgment call	Renormalization	Acquiescence
Grief	Denial	Anger	Bargaining		Depression	Acceptance
Falling in love	[some might be oblivious or hard to get]	"Infatuation", 'chemistry'	Learning and sharing personal detail	"Accommodation", deciding about the relationship	"Burying", day-to-day collaboration	Confidence/Comfort in the relationship
Scientific method	Skepticism of novel phenomena	Interest in the phenomenon	Collecting data to induct from	Formulating a hypothesis	Checking ongoing observations for consistency	Confidence in the theory

Something that pops out as I try to draw up the chart is that I'd think the "bargaining" stage might have two substages - one in which a person tries to find out as much as possible about the disease, and another where they say I hope it's only that, maybe I can stop it here etc. I wonder if there's anything in favor of that. Wnt (talk) 04:19, 6 December 2015 (UTC)

Are Modal Realism and the Mathematical Universe Hypothesis the same thing?

Hi,

I mean ontologically: obviously the two ideas are motivated very differently and purport to explain extremely different phenomena, but they seem to be in very much the same ballpark in the kinds of things they describe as existing. To put the question another way, are there possible worlds which a modal realist believes in but not a MUH-er, or vice versa?

Thanks much in advance, helpful internet people :) Dan Hartas (talk) 17:13, 3 December 2015 (UTC)

I think you're on to something. Tegmark's key paper is here [3], and he says that his intent is to

“ cast... the so-called modal realism theory of David Lewis in mathematical terms, akin to what Barrow refers to as “π in the sky” ”

The sentence contains inline citations that I've omitted for clarity, but they will probably help anyone who doesn't know what Barrow is was talking about. The full context is on p. 16 and the first hit for "modal" in the article. That being said, I suppose it's possible that some adherent of modal realism (person A) disagrees that Tegmark has succeeded in his self-claimed goal, and A may well believe in some possible world that Tegmark does not. Possible world semantics are, as you likely know, a bit of a pain :) SemanticMantis (talk) 18:40, 3 December 2015 (UTC)

Fake snow that feels liquidy but no apparent moisture on your hand?

Is there a type of fake snow that feels liquidy but leaves no apparent moisture or wetness on your hand? Also, it does not melt on your hand. Natural snow feels icy cold and uncomfortable, but this unknown material feels like some kind of liquidy, moist, cool substance. 140.254.136.161 (talk) 19:27, 3 December 2015 (UTC)

Whatever it is, is this thing even biodegradable? What happens if birds accidentally eat this stuff? Will they be poisoned? Will they choke? 140.254.136.161 (talk) 19:28, 3 December 2015 (UTC)

Dry ice works this way - I suppose if powdered "just the right way", you might compensate for the increased surface area (which tends to freeze you quickly) with a general "fluffiness", which would be more insulating. But when dry ice I've seen seems snowiest I think you've just let it get moisture into it, and that bit is wet on evaporating. Are there other non-toxic gases that freeze at a higher temperature and have no liquid phase at standard pressure? Wnt (talk) 20:08, 3 December 2015 (UTC)

However, dry ice sublimes at −78.5 °C (−109.3 °F) - this is cold enough to cause nasty frostbite burns. You don't want to get that one your hand! Smurrayinchester 22:26, 3 December 2015 (UTC)

@Smurrayinchester: I've held enough of that in my hand not to be excessively concerned... it can be colder if powdered - the thing is, usually powdering it makes it like sand. If there were a way to powder it into "fluffy clumps", some kind of filaments of dry ice on the microscopic level I suppose, it might not seem very cold at all. (I don't know, would be interesting to see) It only really gets nasty if you wet it with ethanol or something. By and large the exposed metal in a -80 C freezer is worse, and who really wears gloves to reach into one of those? (Unless it's to protect their precious RNA samples, that is) Wnt (talk) 16:04, 4 December 2015 (UTC)

Our article on triple point lists acetylene as another with triple point above 1 atm, but it freezes actually at a lower temperature than CO2. I looked for some other alkynes but it looks like they get alkane-like, with low BPs and a liquid phase. I'm not really sure how to hunt through data for all known chemicals to find one with a triple point around 300 K and >1 atm. Wnt (talk) 20:22, 3 December 2015 (UTC)

• You're probably thinking of Sodium polyacrylate - a common chemical for artificial snow that holds water very effectively so it feels cold and wet, but doesn't leave any noticeable liquid behind. Smurrayinchester 22:26, 3 December 2015 (UTC)

Why do real flowers feel so soft on the fingers?

Fake flowers feel stiff and papery. Real flowers feel so soft and smooth, and when you rub on the petals or the leaves, they feel moist. 140.254.136.161 (talk) 19:31, 3 December 2015 (UTC)

Expensive fake flowers are made of silk, cheap fake flowers made of polyester. More info at Artificial_flower. Both of those are rather different from the living cells that make up a flower petal. The gross surface structure is called the Plant_cuticle, and it can vary quite a bit across different flower types. Petals are really just specialized leaves, and the soft, velvety texture of e.g. a rose petal is in part due to its roughness at a very fine scale. This is the same reason that velvet feels softer than paper. This roughness makes the petal hydrophobic, and helps keeps the petals clear of dust and debris (so as to remain most visible to pollinators). Some info on this can be seen at Wetting#.22Petal_effect.22_vs._.22lotus_effect.22.5B21.5D. The Lotus_effect is a bit different, but related, and that article is much better. Here's some recent popsci coverage [4] as well. SemanticMantis (talk) 19:46, 3 December 2015 (UTC)

Some real flowers don't feel stiff and papery. Try Dipsacus or Xerochrysum bracteatum. Similarly some leaves of flowers don't feel soft and smooth, try Symphytum or Stinging nettle if you have those plants in your part of Ohio. Richard Avery (talk) 07:59, 4 December 2015 (UTC)

I think you meant some real flowers do feel stiff and papery, and that's a good point too. SemanticMantis (talk) 14:32, 4 December 2015 (UTC)

Will water-based personal lubricants work for non-sexual purposes?

I found water-based personal lubricants at home. I know some people use them for sex. But will they work for non-sexual purposes too? Can I use it to clean the table? Will it work? 140.254.136.161 (talk) 19:40, 3 December 2015 (UTC)

It's a lubricant, not a soap or detergent. I don't know that it would clean your table so much as make it kind of greasy feeling. Many water-based lubricants become tacky as they dry out. --Jayron32 19:51, 3 December 2015 (UTC)

What do you mean by "tacky"? 140.254.136.161 (talk) 20:02, 3 December 2015 (UTC)

Definition 1 here. --Jayron32 20:17, 3 December 2015 (UTC)

Wouldn't #2 do nicely also? :) Bottom line though ... give us the ingredients or at least the brand name, otherwise it's pointless to guess. Wnt (talk) 20:24, 3 December 2015 (UTC)

The major brands and generics of such personal lubricants have roughly the same ingredients, in subtly different proportions. The main ingredients are usually polyols of some sort (glycerin or propylene glycol or sorbitol or xylitol) which provides the lubrication, and the "jelly" forms also have thickeners such as alkoxy-cellulose. The viscosity is controlled by the amount of water in the system; and as they dry, they become more viscous. --Jayron32 20:34, 3 December 2015 (UTC)

I'm still struggling with why you'd want to use lube of any kind to clean your table. There are oils that get used for furniture polish, but they're not there to clean and they're not really lubricants (or at least would rarely get used as such). Generally speaking you need to be careful when switching lubricants of any kind as there are many different kinds with a wide variety of appropriate uses (a famous example is that many petroleum based ones degrade latex, so are unsafe for people using condoms) . Our article at lubricant gives an idea of the complexity, but could really use some work. 64.235.97.146 (talk) 21:00, 3 December 2015 (UTC)

Part of the confusion may be because the only real difference between, say, liquid hand soap and KY Jelly is a detergent or soap compound like sodium stearate. In other words, if you take KY Jelly and mix in sodium stearate, you basically create liquid hand soap. They often feel the same to ones hands (which aren't terribly sensitive), and people may wonder why liquid hand soap cleans, why KY Jelly does not. The difference is in the sodium stearate, which is the soap part. --Jayron32 21:04, 3 December 2015 (UTC)

Furniture "cleaner" may work on different principles than soap... people use all sorts of furniture polish. Someone online promotes using a mix of oil, vinegar, and glycerin [5] and from the comment above this might (or might not) contain glycerin. This is art not science - I assume you're balancing what it does to clean, how glossy it looks, how stable it is over time, if it attracts dust, how it smells, God knows what. Maybe someone is thinking of how it might feel on a certain person's bare bottom... :) I don't know. But what I do know is that we're not giving professional advice here, or any sort of advice, and if you mess up a $3000 table our liability is still limited to $0.000000000000001 or less. Also, all legal actions should be settled by a private arbitration action before the Caliph Abu Bakr al-Baghdadi; the party suing should travel to him first to lay out the case; we should be along in a week or two afterward to hear the verdict. :) (This is actually a totally legal term of service to include in a product insert in the U.S., AFAIK!) Wnt (talk) 22:18, 3 December 2015 (UTC)

The vinegar in that case is the key ingredient; while many cleaners and the like are based on base chemistry (see saponification for all the gory details), acid-based cleaners are also well known, classically Pine Sol is based on a phenol-based solution, which provides acid, rather than base, chemistry for the cleaning. Vinegar (acid) generally works about as well as ammonia (base) as a cleaner as well. The glycerin in these cases is almost always there as a humectant, that is it is used as a treatment to keep the wood moist. Glycerin, like many polyols, is hygroscopic. In the case of your furniture polish the vinegar cleans, the glycerin retains moisture, and the oil seals the surface. --Jayron32 02:42, 4 December 2015 (UTC)

See Preston v. Ferrer and AT&T Mobility LLC v. Concepcion. Not that _this_ should be constituted legal advice, either. Tevildo (talk) 22:44, 3 December 2015 (UTC)

Disasters / International space station

Is there any procedure in place for the crew of the ISS if matters took a turn for the worse here on earth. Say, a full scale nuclear exchange resulting in the destruction of any sort of civilization. Let alone the means to rescue the Soyuz capsule.

I mean, what would they do. Cyanide pills? Sit it out and starve / run out of oxygen? — Preceding unsigned comment added by 213.202.212.178 (talk) 22:53, 3 December 2015 (UTC)

At any time, the ISS has Soyuz capsules already attached with enough capacity (and comfy personalised moulded seat linings) to return the entire crew to Earth without outside intervention. A Soyuz can have a rather bumpy landing (sometimes very bumpy) and usually landing crews wait inside the capsule for the ground folks to show up to help them. But it's always been considered possible that, in some exigent circumstance, they might end up having to leave the capsule unaided and fend for themselves in the central asian wilds (see TP-82, and this article). -- Finlay McWalterᚠTalk 23:02, 3 December 2015 (UTC)

Without assistance from earth, ISS is doomed. If there is a full scale nuclear exchange resulting in the destruction of any sort of civilization on earth then ISS is doomed. The best option for crew of ISS to survive long term is to escape down to earth and play real life Fallout 4. 175.45.116.61 (talk) 00:49, 4 December 2015 (UTC)

Excuse my cynicism but if there was a full scale nuclear exchange which destroyed any sort of civilisation on earth why would the members of the ISS attract any special consideration above the rest of humankind. Richard Avery (talk) 07:45, 4 December 2015 (UTC)

I'm really amazed to hear about the guns, but I still think cyanide pills would be a really unlikely idea. I mean, think about how liquids act in zero G, worming their way into things... and what potassium cyanide does when it touches water. Hard to open a window to fan out the fumes! Wnt (talk) 18:56, 4 December 2015 (UTC)

And as long as we're being morbid, cyanide poisoning is a painful and terrifying way to die. It isn't pretty. If the crew wanted to commit suicide easily and painlessly, they'd just vent the station. Hypoxia is painless. Air hunger is caused not by lack of oxygen, but high blood levels of carbon dioxide. --71.119.131.184 (talk) 21:55, 4 December 2015 (UTC)

There was a story on the radio recently about a situation where a bad software patch was sent to the ISS and crashed their computers. It also took out almost all communications with the ground. The comment they made on this was that the lack of ground communication was deeply concerning because any fault conditions that crop up on the ISS have to be fixed in consultation with the ground crew. So I think the ISS would only survive until the next significant equipment failure. Even if they had spare parts on hand, all of the expertise needed to diagnose the fault and relay instructions on how to fix the problem lies in the hands of the ground crew. Failures of one system or another are fairly common up there - so I think their lives aboard would be pretty short. When this problem occurred with the computers - the first instruction was "go find the emergency backup radios and ask for help". Since other "failure modes" are largely handled on the ground - it's rather unlikely that this one extreme situation would be provided for in flight crew training. Besides, there are multiple ground stations - and it's hard to come up with ANY scenarios where life on earth would be wiped out so rapidly that instructions could not be radioed to the ISS to tell them what (if anything) they should do. SteveBaker (talk) 20:15, 4 December 2015 (UTC)

It's my understanding that, if they really have to, the ISS crew can operate it autonomously, but (because it's arguably the most expensive self-contained object ever made by mankind) they're loath to do so without many terrestrial boffins to check the maths. The limits to the ISS' untended endurance are twofold - consumables for the crew and kinetic energy. The longest the ISS has gone without a resupply is about 120 days; maybe with eating through the emergency rations and stuff they can eke it out to 180 days. Secondly is KE - the ISS is gradually slowed down by the drag of the thermosphere on it, causing it to lose altitude all the time (graph). In normal operation it receives a periodic reboost from the visiting Progress craft; absent them, the Zvezda module has 2 altitude thrusters and a reasonable supply of fuel (860 kg of unsymmetrical dimethylhydrazine and its hypergolic oxidiser nitrogen tetroxide), which can reboost for a while (I don't know whether the ISS usually has a radar altimeter necessary to know quite how high they are - but I guess with a stopwatch and sextant, and some identifiable marks on the ground, the crew can figure that out for themselves). That 180 days or so gives them time to select a landing area (they're going to want to aim for the centre of a continent) and maybe wait for the wait for the weather there to be okay (it'd be tough to survive unsupported on the Kazakh steppe in February), and if the calamity is nuclear or biological then it may be wise to try to wait out the worse short-lived radioisotopes or the peak of the plague. If they landed in western Kazakhstan in May, with the Soyuz packed with tools and supplies (rather than the usual science experiments and bags of poo it usually carries back from space) 180 days after Judgement Day, they'd probably be much better off than all of us. -- Finlay McWalterᚠTalk 01:02, 5 December 2015 (UTC)

December 4

Humans without junk DNA

Yes, I know that the question of whether apparently useless DNA has in fact some purpose is a controversial one, but it still seems strange that some organisms are virtually free of non-coding DNA while others, including our own, have genomes which are more than 97% junk. If junk DNA does have some purpose, why this disparity? And, following on from this, we would now have the capacity to delete all such DNA from a genome. Would a human be in any way different if they had no such DNA in their genome? Myles325a (talk) 04:35, 4 December 2015 (UTC)

These categorizations are controversial, because they often work from different definitions. When one decides that DNA is "junk" DNA (formally noncoding DNA, there are many ways one can define the terms. Strictly speaking, noncoding DNA is merely DNA which does not directly translate to a protein's amino acid sequence. Claims of "97% junk DNA" generally work from this most restrictive application, while lower estimates (including the low value of 20% junk DNA) are based on notions that DNA have other important biological function aside from merely being a code to create proteins. When you have reliable, scientific bodies varying in estimates as wide ranging as 20%-97%, it's quite clear there's major definitional problems that need to be solved before one can even start to approach to answer the question of "why", the why question is irrelevent until we get an agreed upon answer to the "what" question, and "what" is all over the map. --Jayron32 04:43, 4 December 2015 (UTC)

OP myles325a back live. See, this is what really gets me down on the floor and dragging up carpet tacks wid my teeth while making noises like a Tasmanian Devil on crack. I ask a perfectly sensible question which would be comprehensible to 99.0% of WP readers and I get a brusque note from a trophy polisher basically telling me nothing except that I am an ignoramus and a dickhead. Your answer is nought but garrulous and pompous evasiveness. I note that you make no attempt to say what the “useful” component of non-coding DNA actually does. In any case, even if you knew, my question would still stand. Is that component of DNA which does not “merely” code for proteins necessary for life, and what would happen if you deleted it? I’m a plain-speaking Australian, who has asked an honest and sensible question. It is your answer which is “irrelevent” (sic). Myles325a (talk) 02:44, 7 December 2015 (UTC)

To answer the second question, a human embryo with all noncoding DNA removed would just die. We know that at least some of noncoding DNA is essential to life; one example is telomeres in eukaryotic cells. This is largely why scientists don't like the term "junk DNA", because it has misleading connotations. --71.119.131.184 (talk) 05:18, 4 December 2015 (UTC)

OP myles325a back live. Waaahh, pooor bubba. However, I am supposing that telomere length in a new cell IS determined by DNA coding, else male sperm cells produced by a 60 year old man would inherit the truncated version, and this would be passed down to his progeny. So bubbs lives after all. Not too sure about this, but in any case, one instance can hardly champion the 97% of DNA which does not code. Myles325a (talk) 02:54, 7 December 2015 (UTC)

Coding DNA determines which proteins the body can make, but it says nothing about where and when they should be made, or in what quantity. That information is contained in the noncoding DNA, encoded by a variety of mechanisms. Also, as the answer above points out, noncoding DNA serves several mechanical functions. Looie496 (talk) 13:37, 4 December 2015 (UTC)

So you're saying that non-coding DNA is involved in gene expression, right? That article mentions non-protein coding DNA, and also non-coding DNA, and non-coding RNA, and a few other categories that seem hard to keep straight. Non-coding DNA can also affect mechanical properties of DNA, such as DNA supercoiling, and that can also affect gene expression in some organisms. SemanticMantis (talk) 14:11, 4 December 2015 (UTC)

OP myles325a back live. See, SOMEONE thinks that I am asking a reasonable question. We know that the genome has vast real estate of evolutionary dead ends and meaningless repetitions. (I believe that about 3% of DNA comprise these repetitive strings, so we have as much DNA devoted to accidental repetition as we have to the coding DNA. It is interesting to think that the long stretches of DNA deriving from now non-functional phenomes is necessary for proper genome and phenome expression today. But what then about the organisms, like puffer fish, who have next to no non-coding DNA. And why would organisms like wheat need so much of it. Myles325a (talk) 03:14, 7 December 2015 (UTC)

That's why "junk" DNA is misleading, and also why placing such an emphasis on "noncoding DNA" vs. "coding DNA" is also misleading. The fact that some string of DNA doesn't directly code for a protein sequence doesn't mean it isn't necessary, or that you could remove it with no harm. --Jayron32 14:19, 4 December 2015 (UTC)

OP myles325a back live. Groan, the trophy polishing hair splitter is back. The reason we would place such an emphasis on DNA which "merely" codes, is that just about all we know about the makeup of an organism comes from there. You seem sure that non-coding DNA is important, but you provide no clue as to why it is. And yes, as you say, the fact that "some string of DNA doesn't directly code for a protein sequence doesn't mean it isn't necessary". Agree, but it also does not, ipso facto, guarantee that it IS necessary. The SCIENTIFIC way to ascertain the truth in such circumstances, is to do as I have suggested and delete the non-coding DNA of an neonate. If doing this to a human embryo is considered unethical, we could use a hamster or a rat or a pig or such. Myles325a (talk) 03:14, 7 December 2015 (UTC)

If there's selective pressure to reduce DNA length, this can be done, but normally I think it takes a long time. Some of the deletions could turn out to be deleterious after all, and then the organism needs a way to compensate for them. Doing it as an engineering project requires absolute confidence in one's knowledge of what every base-pair is for, and we don't have that.

OP myles325a back live. Hmmm Wnt, I appreciate your thoughts, but in the above you seem to have segued between deletion via natural selection and deletion by geneticists. Luckily, the quality improves after this initial blooper. Myles325a (talk) 03:21, 7 December 2015 (UTC)

A specific role of the junk DNA is in posttranscriptional regulation. Something like an Alu element can occur in a sense or antisense configuration in an mRNA. If so, that mRNA becomes subject to a network of sense-antisense interactions that may affect where it goes in the nucleus and how active its translation will be.

OP myles325a back live. Ok, Wnt, but while I understand but little of the page you refer to, it DOES seem to be devoted to the special role of RNA on posttranscription processes. That means there are certain changes which are not the result of DNA coding, but there is nothing there, as I read it, relating to the usefulness of stretches of non-coding "junk" DNA. Myles325a (talk) 03:33, 7 December 2015 (UTC)

In the longer term, purging genomes of junk DNA could be a bad thing. The junk elements have a tendency to sit down in introns, because otherwise they disrupt genes - they sort of "press" on the genome with a constant stream of deleterious mutations, which might seem good to get rid of.... but later on, homologous recombination can create what you might call "Hopeful Monster" genes, some exons of this spliced onto some exons of that, in a way that random breakage or less specific homologous recombination would rarely manage (i.e. with many fewer translatable genes produced per mutation, and therefore, with a much higher cost for the same amount of evolutionary experimentation). So it's possible you might purge these genes and a hundred million years out the species hasn't had the opportunity to change as much as another. But here I'm just guessing, because how do you test that? It's really, really hard to predict what messing with biology in a new way will do, that's all. Wnt (talk) 15:54, 4 December 2015 (UTC)

OP myles325a back live. This is a beautiful concept. Much of evolution proceeds via random mutations, and if there was a storehouse of abandoned genome sequences, and even sequences from other organisms, held in escrow in the genome, then there might be a rich treasure house of genomic sequences which could be recombined and brought back from the wings to centre stage again (to mix a metaphor in a context which invites such). Thus, the happy monster. I did have an idea earlier that such a treasure house could be opened by excessive radiation, which accelerates mutation rates. Thus, a dystopia occurring after a nuclear war, when new phenotypes are needed, might trigger the reactivation of ancient phenotypes like body hair. As the dying sun expands and solar radiation begins to strip away the atmosphere, high radiation rates might foster de-evolution, reintroducing hardy organisms which can withstand such ferocious conditions. Then again, evolutionary processes are not teleological (end-directed) so it is hard to see how they could be favored by natural selection on a generation by generation level. But I digress.....Myles325a (talk) 04:04, 7 December 2015 (UTC)

(ec)If we assume (keeping in mind it's a controversial assumption) that "junk DNA" is unnecessary for humans to function, the question naturally arises of why it's kept around. (For the persnickety pedants, treat this as a Gedankenexperiment.) But one possible explanation that doesn't necessitate function is similar to that for neutral drift. The extra DNA may be kept around because there's no strong selective pressure to remove it. Humans have several years to replicate our germline cells. Even our somatic cells are able to be somewhat leisurely in replicating - normally taking several hours for each doubling. There's plenty of time to replicate all of that DNA. Material costs aren't really limiting either - if humans were resource starved, it's easier to remove whole cells (e.g. not grow as big) than try to trim fractions of a percent of the metabolic cost by reducing the amount of DNA. Contrast this to organisms which are lean, mean, "junk DNA"-free machines. These are normally bacteria and viruses who take the tactic of replicating fast and reproducing as much as possible as quickly as possible. For them, every second they don't have to spend synthesizing DNA is one second faster on the replication cycle, and by reducing the amount of DNA, you can possible squeak out an extra generation or two in a resource poor environment. Also, with a quick reproductive cycle and a boom-and-bust population dynamic, there's many more opportunities for small selective pressures to act on the population. (Remember, there's no junk DNA specific cleaner. Excess DNA has to be removed via random deletions, which are as apt to remove a stretch of DNA with a necessary function as to remove a stretch which is superfluous. This means that insertions can be less disruptive than deletions, leading in an asymmetry in the unselected DNA growing/shrinking balance.) Finally, even if portions of the "junk DNA" are doing things like serving regulatory or structural functions, those quickly-reproducing organisms have an incentive to find alternative mechanisms for those functions, ones which are less time and resource intensive. Humans don't necessarily have the same selective pressure to the same extent. - So in addition to "Why don't humans get rid of junk DNA?", it might be helpful to consider "Why would they?" -- 160.129.138.186 (talk) 16:19, 4 December 2015 (UTC)

Nature is doing try and error. Some of the junk DNA might still have an epigenetic background. Some of it makes its owner resistent to several unknown conditions. Influenca can kill people never came in touch with its successors. Corn has no brain but several times the amounth of DNA as human have. As the decoded the chapters of the DNA, we still can not read it. We can identify the letters, but we do not understand the information, expressed by the DNA code. --Hans Haase (有问题吗) 11:27, 5 December 2015 (UTC)

Endogenous retrovirus makes good reading. Still, the example of Takifugu rubripes tells us that organisms can purge most "junk" without obvious ill effect, at least in the short term. Wnt (talk) 16:07, 5 December 2015 (UTC)

Alcohol rubs when drawing blood

Why is it that some places use alcohol wipes on your skin before drawing blood and others don't. 2A02:C7D:B901:CC00:CCA2:261C:1C78:FFEE (talk) 14:10, 4 December 2015 (UTC)

It may have to do with whether or not the alcohol wipes are adjudged by the organization to be effective or not in disinfecting the injection site. There are some studies on the use of such wipes and their effectiveness; like many such practices there's some information out there to indicate that it isn't all that effective in preventing infection. So depending on which studies the organization is reading up on, may determine the policies of said organization. Some such studies include [6], [7], and there are many more out there. I did also find this forum discussion which cites some more studies. The literature is decidedly mixed. --Jayron32 14:18, 4 December 2015 (UTC)

Better safe than sorry. If someone is intending to draw blood or otherwise insert a needle in you, and they don't wear fresh rubber gloves and/or they don't swab the spot they're sticking the needle in, you had best get up and leave ASAP, and find another clinic. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:15, 4 December 2015 (UTC)

Unless, let's say, that the swab only killed the harmless bacteria that were competing the harmful bacteria at bay, and keeping them from making you sick. If your swab kills the wrong bacteria, you're going to be quite unsafe, and equally as sorry. That's why some antibiotics mess up your gut flora. --Jayron32 19:04, 4 December 2015 (UTC)

And a respondent here telling someone to leave a medical clinic due to lack of alcohol swabbing seems rather close to medical advice, and specifically it seems like medical advice that is contrary to that clinic's professional practice. SemanticMantis (talk) 19:38, 4 December 2015 (UTC)

Also against the reliable references I provided. But Bugs just writing whatever he feels without regards to what reliable experts have already written about the subject is expected behavior based on past performance. --Jayron32 20:04, 4 December 2015 (UTC)

It should be pointed out that some people getting their blood drawn have filthy skin, and an alcohol wipe is an inoffensive way of cleaning that skin. - Nunh-huh 05:29, 5 December 2015 (UTC)

I thought most people naturally have a "filthy" skin as far as it being a nice place for bacteria to live. I'm not sure whether someone whose beliefs or lifestyle include avoiding alcohol would consider this inoffensive, if that's what you meant. Bazza (talk) 11:04, 5 December 2015 (UTC)

No, I meant filthy as in "covered in dirt". Using an alcohol wipe or two is an inoffensive way of cleaning that up without them feeling judged. - Nunh-huh 13:57, 5 December 2015 (UTC)

Some of this stuff is creeping toward medical advice, and I'm skeptical of some of it. Particularly, I doubt it matters whether you kill "good" bacteria on a small patch of skin before a needle pierce - the wound will clot soon afterward, and if there's a kind of bacteria that are demonstrably good to rub into an open wound in order to antidote the bad ones I don't know about it, though I couldn't actually rule it out. By definition, whatever a significant proportion of doctors routinely do is accepted medical practice. Wnt (talk) 15:42, 5 December 2015 (UTC)

Table 3

I believe the underlying question is the efficacy of the alcohol wipe. It is well accepted that alcohol kills a large amount of pathogens, but why are we now seeing the alcohol rub skipped altogether? The answer is that while it is a statistically significant amount of pathogens killed at the injection site, this isn't practically significant enough to show infection. This article referenced a World Health Organization bulletin , which I read and found Table 3 to be extremely useful.

Even with this bulletin released, which was for muscular shots and not blood draws, the WHO still recommends an alcohol wipe, but honestly I couldn't find a decent reason for this. Jasonmfisher (talk) 15:06, 6 December 2015 (UTC)

References

Holographic universe and Simulation hypothesis

This article:

http://news.sciencemag.org/2015/12/controversial-experiment-sees-no-evidence-universe-hologram

Basically says that the "holographic universe" hypothesis has just been effectively disproved. I know the results of the experiment are controversial - and might be wrong. But if it has indeed proved that there is no fine-scale jitter in the positions of objects, does that also disprove my favorite hypothesis - the Simulation hypothesis? Seems like if objects can be positioned without jitter then the amount of data to completely describe that position must be infinite - which means that the universe can't possibly be a giant computer simulation like The Matrix.

But I'm not entirely sure I understand the holographic universe hypothesis - so it's not clear that this approach to disproving it also disproves the simulation hypothesis too.

SteveBaker (talk) 20:06, 4 December 2015 (UTC)

Holometer is the article (and I guess it needs an update). The whole thing looks iffy to me. This blog post quotes Raphael Bousso and Leonard Susskind as saying that the experiment is useless (long before the results came in), which is pretty bad since they're two of the biggest proponents of gravitational holography. Sabine Hossenfelder and Luboš Motl also seemed to be suspicious of it. The experiment seems like a pet project of Hogan's, albeit one that he got $2.5 million in funding for. -- BenRG (talk) 23:00, 4 December 2015 (UTC)

Great answer - I should just point out that blog post leads on to [8], which is far, far more than I'm ready to digest currently. Wnt (talk) 05:36, 5 December 2015 (UTC)

I don't see how you can draw any conclusions about simulation, based on physics known inside the presumed simulation. Why should the simulators' physics look anything like ours? Maybe they're simulating some entirely counterfactual physics.

In other news, physicalism, materialism, and naturalism may all be false. --Trovatore (talk) 23:18, 5 December 2015 (UTC)

You might also enjoy these: http://www.smbc-comics.com/?id=2535, http://www.smbc-comics.com/?id=2824 (very mildly NSFW), http://smbc-comics.com/index.php?db=comics&id=2055 --Trovatore (talk) 23:53, 5 December 2015 (UTC)

December 5

What's the cheapest fully automatic car that has a clutchless manual mode?

Sagittarian Milky Way (talk) 00:28, 5 December 2015 (UTC)

It's difficult to know whether there is an even cheaper car, but Ford Fiesta, at $17,500 including the clutchless option, might be one candidate. It has a standard 6-speed manual, with the option of a "PowerShift", which is a clutchless manual. --Denidi (talk) 01:27, 5 December 2015 (UTC)

@Denidi: That's a manual with a clutchless option. Our OP is asking for an automatic with a clutchless manual.

From what I've seen, a bunch of full automatics have the option to push the stick off to the side and force the computer to shift up or down - which is essentially a "clutchless manual" - or an "overridable automatic" - depending mostly on how your mind works! Some go so far as to add paddle-shifters to the steering column. My wife's bottom-of-the-range Kia Soul had that - and the 2015 Soul starts at just $15,190.

With any car where there is a computer controlling the automatic shifter - it's just a matter of adding a couple of $1 switches and a $0.10 spring to the shifter mechanism to add this capability - so I'd expect even the cheaper automatics to include it - so this may boil down to "what is the cheapest automatic?"

Personally, nothing short of a full manual will do - so I may be missing something here. SteveBaker (talk) 03:10, 5 December 2015 (UTC)

How would I know that you could override the shifting computer?, I don't drive. I thought they just went PRNDL. They go PRN1234L, too? Was it always like that? As for why everyone doesn't use a manual, there's too much stuff to do. Pay attention to the engine sound/foot off gas/press clutch/move stick/ease off clutch slowly/wait for the right engine sound/foot off gas/press clutch/move stick/remove clutch slowly/listen for rpm signal/foot off gas/press clutch/move stick/remove clutch slowly/gas pedal just to get on the freeway? And I might even die if I screw up cause the engine stalled or I broke gears? I'm sure it's more fun than a semi-manual if you rented a racetrack or have zero traffic but I'd probably hit a car far frequenter than in an automatic cause I'm trying to not press the clutch too long or do a step 0.1 seconds too soon. Sagittarian Milky Way (talk) 03:57, 5 December 2015 (UTC)

The cars I've seen have PRND - maybe PRND1 - but also a way to push the shifter sideways from the 'D' position where there is a "+" and a "-" position marked next to the shifter. Nudging the stick forward causes it to up-shift by one gear and nudging it back causes it to down-shift. Multiple nudges get you multiple shifts. It's kinda like a manual - but without having a clutch - but the computer will still take over and override your gear selection if it thinks you'll overrev the engine or cause it to stall...so you don't quite have the same level of control as with a true manual. The lack of a clutch still removes some degree of control - and because you can't feel what gear you're in from the position of the shifter, you either have to remember or glance down at the instruments (which generally show which gear you're in)...that wouldn't be so bad if the computer didn't ever override you - but I find it all to easy to get flustered and not know which gear I have selected. Hence I never really use the manual override on my wife's automatic - even though I prefer driving a manual transmission car. SteveBaker (talk) 04:42, 6 December 2015 (UTC)

Why would I ever want to breach the redline or stall the engine though? If it automatically upshifts at redline then I guess there might be times where one would rather have it keep it at redline with the throttle but redline is less efficient (both mpg and thermodynamic % and auto parts life) so one might want a higher gear then anyway. So the overrevving/stall override part doesn't seem that bad to me. Sagittarian Milky Way (talk) 01:52, 7 December 2015 (UTC)

It's not really much different from riding a bicycle - it becomes second-nature very quickly. The quickest way to screw up is to actually think about what you're doing. Bazza (talk) 11:00, 5 December 2015 (UTC)

I don't know how to ride a bike either. Sagittarian Milky Way (talk) 01:52, 7 December 2015 (UTC)

And in Europe, the large majority of people do use a manual (see Manual Transmission: Section 9). As a driver, I regard it as much easier than riding a bicycle (see also Section 8.1), but that's because I never learned the latter :-). {The poster formerly known as 87.81.230.195} 94.11.50.58 (talk) 23:32, 5 December 2015 (UTC)

I'm with Steve — I prefer a full manual, because it makes you feel in control, and there's a special satisfaction in physically moving the gearbox around, not just touching a paddle on the steering wheel. That said, it's a satisfaction that wears a bit thin in stop-and-go traffic, especially on hills. --Trovatore (talk) 23:43, 5 December 2015 (UTC)

Absolutely - a manual gearbox is a pain in stop/go traffic. The problems on hills has largely been fixed in my car where the computer holds the footbrake on for 5 seconds after you take your foot off the pedal or until you move the gas pedal (whichever happens first)...but in slow traffic, it's a real pain. The inability to control engine-braking in an automatic is what bothers me - also that no matter how clever the computer is, it can't know that I want to down-shift to get more RPM's to spin up the turbo prior to accelerating hard...it can only react to a command I've already given. I feel very "out of control" when I'm forced to drive an automatic transmission car. That said - automatics are getting better every year - and here in the USA, it's getting harder to find cars with a manual transmission option. SteveBaker (talk) 04:42, 6 December 2015 (UTC)

Making human males female

Can we make human males female by adding and deleting DNAs and making Y chromosome X, and extending the effects to all the body?, for example, making original sperm (I don't know the words for it) ovum, making body cells female-wise, letting metabolize, originating vargo from original cells (I don't know the words for it either)? --Like sushi49.135.2.215 (talk) 01:39, 5 December 2015 (UTC)

Even if that might work, removing an entire chromosome in every single cell of the body and replacing it with another one is far *FAR* beyond what science can currently do. If you could somehow do that, you'd be replacing a large percentage of the person's DNA - so the question of whether this would really remain the same person would be kinda tricky. If you duplicated the existing X and deleted the Y, you'd end up with someone with two identical X chromosomes - and that could easily result in some dangerous genetic diseases cropping up. If you added an X from someone else and deleted the Y then you'd have added a ton of new genetic material - possibly changing the person in many more ways than just altering their gender.

But this is all very hypothetical. Once large-scale body structures are in place, simply switching chromosomes wouldn't immediately create a complete gender change in that sense. When gender reassignment is done right now, merely changing the hormone balance doesn't do all the work - and surgery is needed. Even after that, there are residual effects that don't change - one example being the vocal chords - transgender people often have trouble sounding like their new gender.

SteveBaker (talk) 03:28, 5 December 2015 (UTC)

I don't see how it could work, unless such a switch were made immediately after the egg was fertilized and before it divided. And such experiments might well be illegal anyway, never mind unethical. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:51, 5 December 2015 (UTC)

We could inactivate SRY throughout the body by some means or other, or at least knockdown (though this would be a technical masterpiece slightly beyond our current competence). But this approach would have most of the limitations of ordinary transgender hormone treatment, chemical castration or whatever - it wouldn't erase an Adam's apple or broaden the pelvis or change the bones of the face, etc. Neither would a more thorough chromosomal replacement. The body doesn't have any Doctor Who style regenerations built in - it came to be what it is by gradual development over time, with a cumulative result.

The main use of chromosomal manipulation would be to make eggs for reproductive purposes - this is reasonably feasible by stem cell transplantation into someone else's ovary, with the added convenience of a bona fide womb close at hand. There was a paper about it (in mice) something like a decade ago ... I could go hunt if you're interested. Wnt (talk) 05:12, 5 December 2015 (UTC)

Imagine the psychological aspect. As somebody was born as male and the society does not respect him as male and having him (ab)used for his work power only, it might be discriminating. The issue was asked as a biological question changes to a political one. A scrotum or uterus has never been created by surgery, but an uterus has been transplanted from woman to woman, sometimes form mother to daughter due cancer or similar issues. In some countries on this planet, parents killed their female babies to have their families a better financial condition. As more families did it the same way there were no women for the men. Today, those men say "thank you" to their parents an their governments who a trying to solve their tolerated crime by war, gender politic or prostitution. --Hans Haase (有问题吗) 11:06, 5 December 2015 (UTC)

Well, now you're getting into social issues of gender, which is a great mystery. I mean, [9] When I was a kid, it was embarrassing for a boy to get an erection in the boy's locker room. today it would be embarrassing for a girl to get an erection in the girl's locker room. Wnt (talk) 11:18, 5 December 2015 (UTC)

As the human brain is doing much by learning and even more people expect. It is still not completely discovered. But some theories are made around it. The scientific way would be find or causes an interactions that made the things like they are. Sometimes we will find ourselves in a small bubble, looking for a truth inside it but still forgot what outside the bubble is. Before focussing on an aspect, see its dependencies to have an answer that covers all occurring conditions and also faces the point where its not applicable. --Hans Haase (有问题吗) 11:59, 5 December 2015 (UTC)

• It wouldn't be possible to do that to an adult, because most of the effects of sex chromosomes play out during development, especially childhood and puberty. There is no way to undo those processes in an adult. It would be possible, in principle, to do that in a single-celled embryo, but there is an easier method than replacing the Y chromosome with an X. All you would need to do is remove or otherwise inactivate the Y chromosome. In a normal human female one of the two X chromosomes is inactivated anyway, so the result should develop just like a normal female. Looie496 (talk) 14:34, 5 December 2015 (UTC)

That's a horrible idea, it leads to Turner syndrome which means a whole list of mental and physical impairments, including sterility, deformities of the neck and jaw, a lack of breast development, and being prone to loss of sight and hearing. Even though one X chromosome is deactivated per cell in XX females, which X chromosome is deactivated is random for each cell. Hence if a vital gene is missing in one X, at least half the body is still producing the necessary protein. μηδείς (talk) 21:17, 5 December 2015 (UTC)

Oh well, you learn something new every day :-(. Looie496 (talk) 22:33, 5 December 2015 (UTC)

Guy on earth looking at a camera inside a spaceship.

Imagine there is a guy X on earth, now imagine ther is a spaceship travelling near the speed of light.
This spaceship has a camera inside it that record what is happening inside the ship, this image is them shown on a monitor that guy X is looking at.
The question is, what would this guy X see
— Preceding unsigned comment added by 201.79.59.44 (talk) 10:28, 5 December 2015 (UTC)

Guy X would not see a thing, as in a millisecond, the screen would be 300km away. Can you see a screen that far away? If the camera is transmitting a signal to a screen stationary with respect to X, there would be a very serious Doppler effect. The video would be nowhere near standard and the screen would likely not sync to it. If it did, the image would appear to be in slow motion, matching the time dilation observed. Note that even trying to transmit a video to or from an aeroplane give synchronisation problems. Graeme Bartlett (talk) 12:36, 5 December 2015 (UTC)

The video might be faster or slower depending on whether the ship is receding from Earth or approaching it. The speedup/slowdown is given by the Doppler shift formula, not the time dilation formula. It's the same if the screen is on the spaceship and the guy on Earth is looking at it from there (ignoring the practical difficulties of doing that). -- BenRG (talk) 17:23, 5 December 2015 (UTC)

Hang on, is the monitor on the spaceship or is the monitor on earth? 110.22.20.252 (talk) 12:49, 5 December 2015 (UTC)

Originally on Earth, but Ben was pointing out that exactly the same speed effect would be visible if X was somehow able to view a monitor on the spaceship (super-telescope, and for a tiny fraction of a second as the ship passes Earth?). Ben will no doubt correct me if I am wrong, but I think there will be a difference -- an additional (blue or red) colour shift if the monitor on the spaceship is viewed from earth (because for a monitor on Earth the true colour will be re-created from the signal in coded form, with synchronisation corrections, of course). Our article on Doppler effect gives the formula only for sound. For the correct formula to use for light and radio (monitor) signals, see Doppler radar or Relativistic Doppler effect. Dbfirs 22:11, 5 December 2015 (UTC)

I understood the question as being about the camera inside the spaceship, transmitting to a monitor on Earth. None of the answers so far seem responsive on that point. I guess the Doppler shift implies that the Earth-based equipment would have to do some juggling merely to render the signal at all (as the carrier frequency would be constantly changing), and at that point, who knows; it depends on the corrections applied by the Earth-based system.

I thought we were all replying about that scenario, except for commenting on the difference. The Doppler formula for light determines the speed change in the video, assuming that the equipment can cope with the synchronisation problems. Dbfirs 23:03, 5 December 2015 (UTC)

I don't think that's clear at all. Let's say the camera records 60 frames/second, and spits them out in a transmission. The Earth-based receiver is able to follow the changing carrier frequencies and reconstruct the frames. Then what do you see? That depends entirely on how the receiver chooses to render the frames. To me, the most natural-seeming possibility is that it would render them at 60 frames/second. Then the viewer would see nothing particularly unusual (well, except insofar as the inside of a relativistic spaceship is unusual). However, it might have to do some caching to be able to do that. --Trovatore (talk) 23:09, 5 December 2015 (UTC)

Oh, I'd assumed that the camera was transmitting live, so each frame would be delayed by the Doppler effect if the ship were moving away. I agree that there are some complications, and if a recording were being transmitted then the receiving equipment might well be adjusted to show the film at normal speed be delaying early frames. Dbfirs 23:15, 5 December 2015 (UTC)

Also, the inside of a relativistic spaceship is entirely normal. These is no distortion "caused" by speed. Dbfirs 23:17, 5 December 2015 (UTC)

I wasn't talking about distortion caused by speed. I just imagine that the interior of a relativistic spaceship is probably unusual, given that I do not usually encounter relativistic spaceships. Maybe they have seventies-style black velvet paintings and lava lamps. That would be unusual. --Trovatore (talk) 23:23, 5 December 2015 (UTC)

I thought it had just left Earth, but yes, I see what you mean. Dbfirs 23:27, 5 December 2015 (UTC)

Not responsive to the original question, but possibly interesting to people thinking about this stuff: The Visual Appearance of Rapidly Moving Objects. Do we have an article that discusses these effects? --Trovatore (talk) 22:46, 5 December 2015 (UTC)

Ignore where the monitor is. If it is on Earth, the receding space ship needs to transmit the image to the monitor. The transmission happens at light speed, making it equivalent to the monitor being on the ship.

The original question is equivalent to asking "what do you see if you look at a mirror receding at near light speed?" My intuition is you see a normal image of yourself, but intuition can easily fail here. Anyone? 91.155.193.199 (talk) 23:16, 5 December 2015 (UTC)

Intuition isn't always reliable when the speed of light has to be taken into account. If you are talking into your mirror mounted on a moving vehicle on Earth, will you expect to hear the echo of your voice at normal frequency and speed? Dbfirs 23:24, 5 December 2015 (UTC)

Yes, I think I would expect reflection of sound and light to be unaltered, on basis of conservation of momentum. Or would the reflection speed up or slow down the receding reflector? Sourced scholarly discussion of this would be welcome of course. 91.155.193.199 (talk) 06:06, 6 December 2015 (UTC)

You are correct that the reflected sound will travel at the same speed in the opposite direction, but the fact that the reflector is moving away will increase the wavelength (and thus reduce the frequency) of the reflected sound. See our article Doppler effect for details. The same applies to light and all electromagnetic radiation, as illustrated by a Radar gun. Dbfirs 07:49, 6 December 2015 (UTC)

If you're talking about sound reflecting off a wall that's at a constant distance from you, you will hear no Doppler shift. The reflected sound can't be faster because it would eventually overtake your voice, and it can't be slower because there would have to be an ever-larger region of space to buffer the sound that hadn't gotten back to you yet (or a changing speed of sound, which could happen if there was an ever-increasing wind, I suppose). -- BenRG (talk) 20:13, 6 December 2015 (UTC)

Looking at the ship (or a video feed from the ship) and looking at yourself in a mirror on the ship are not quite the same. In the latter case you get a double Doppler shift (the square of the Doppler shift factor). -- BenRG (talk) 20:13, 6 December 2015 (UTC)

transistor as a switch/oscillation

in the common emitter configuration, if I connect the collector to the base (negative feedback), why doesn't the circuit oscillate? In my (undoubtly simplistic) mental model, the collector resistor and the transistor form a voltage divider. Initially, the transistor is open. The supply voltage drops across the open transistor, the base is pulled high, the transistor closes, the base is pulled to ground, the transistor opens, repeat. A similar circuit with a reed relay would oscillate, shouldn't this one, too? Is this because of inertia (in the relay)? Asmrulz (talk) 10:29, 5 December 2015 (UTC)

Beginning work with electronic essentials, an amplifier always becomes an oscillator and an oscillator never oscillates. Similar to mechanic assembly it is to install a spring between two parts. If there's no change, it returns to a condition where it is being forced to. There are many oscillator circuits and You need make Your circuit amplifing the change to make it oscillating. Also see the bikicle, stepping on the pedats the right time an position, makes You ride faster. When stepping the wrong way or time or not releasing the foot when the pedal returns, You need to ride down a hill or stop riding it when the hill ends in the bottom of a valley. In Your case, the capacitor only variates the transistors behaviour on a change in the operating voltage or the base input. When charged in the new condition, it will remain there. --Hans Haase (有问题吗) 10:48, 5 December 2015 (UTC)

As a relay completely turns off and has mechanical inertial mass that shifts the delay for oscillating. A transistor, see its meaning as transfer resistor, can be used as a switch but, it is also working analog as a the volume control on Your stereo. This makes the transistor stay in a definend condition like a voltage regulator. Transistors had a long time the problem not to reach the low resistor value of a switch or relay when turned on. But that is history. --Hans Haase (有问题吗) 11:45, 5 December 2015 (UTC)

See Electronic oscillator for our general article, and Barkhausen criterion and Nyquist criterion for some more mathematical details. As well as providing positive feedback, a working circuit needs to ensure that the overall gain is (exactly) 1, otherwise the output will just drive to the maximum or minimum DC value, and that this gain occurs at a particular frequency, otherwise the circuit will just generate noise. Tevildo (talk) 11:58, 5 December 2015 (UTC)

I just thought that as a relay can be made to oscillate by having it pinch off its own supply current, the same could be done with a transistor. In the classic discrete multivibrator, two transistors pinch off one another in turns Asmrulz (talk) 14:40, 5 December 2015 (UTC)

Yes, that's how a blocking oscillator works. The important thing is the feedback path must contain some components to determine the frequency - it won't operate with just a resistor. Tevildo (talk) 15:19, 5 December 2015 (UTC)

The transistor is not a Schmitt trigger. As the relay turns on and of, by the mass of its lever, the Schmitt trigger is triggeres by the charge level of a capacitor when used as oscillator. --Hans Haase (有问题吗) 12:09, 5 December 2015 (UTC)

Will a schmitt inverter oscillate if I short the output to the input? I know non-schmitt inverters (74HC04) just settle at roughly half the supply voltage Asmrulz (talk) 13:22, 5 December 2015 (UTC)

I googled and it seems, it will Asmrulz (talk) 14:18, 5 December 2015 (UTC)

Based on an Operational amplifier its output has a rise time. It will only run between its trigger voltages. It might be possible to use the next faster operational amplifier in comperator mode to change it to a square voltage. Feeding the inverted schmitt trigger over and resistor to capacitor on ints input, You have a simple RC-Oscillator, higher resistor or capacitor lower its frequency. Smaller values rise the frequency. --Hans Haase (有问题吗) 15:48, 5 December 2015 (UTC)

I'm coming to the discussion late because the question and answers were posted while I was asleep overnight. Are you sure that the circuit does not oscillate? According to theory, it should, but the fact may not be readily apparent. When power is applied, current is initially not flowing in the collector-emitter path, but current that flows via the collector resistor into the base-emitter junction causes heavy collector current to flow, pulling down the collector voltage to about 0.6 volts in the case of a silicon transistor. That voltage is not sufficient to keep the base current flowing, so the transistor begins to turn off, whereupon the collector voltage starts to rise again. The process repeats in the same manner. So the OP is correct in assuming that the circuit should oscillate. The problem is that because of the high gain (presuming a silicon device), only a minute rise and fall in base voltage is sufficient to turn the transistor on and off (respectively). It is therefore oscillating at the millivolt level or less, and perhaps OP hasn't noticed that it's doing so. It might appear to him to be in a steady state condition with collector voltage at less than supply voltage (Vcc). Also, because there are no timing components (eg. capacitor and resistor) in the circuit, oscillation will take place at a very high frequency, probably hundreds of MHz, limited only by stray circuit capacitance and the transistor's Hfe versus frequency limit. A DC voltmeter will not show the presence of oscillation at such frequencies. Akld guy (talk) 19:27, 5 December 2015 (UTC)

It seems You created a blocking oscillator. When adding the coils, You might have it operating better or oscillating in an predictable frequency range. The parasitive inductivity of the capacitor You used might have completed the blocking oscillator. See also: de:Kategorie:Elektrischer Oszillator contains more articles as the Category:Oscillators. --Hans Haase (有问题吗) 22:02, 5 December 2015 (UTC)

Exaggerated colour in old movies

I've noticed that the colours in old movies on tv look unnaturally intense. It seems to be particularly noticable in movies from the 1950-60s era. Is this phenomenon related to film chemistry, the age of the film, or perhaps the process of converting to video? I've just looked at "Raintree County" and "Meet Me in St. Louis" that just happened to be on my satellite service right now and the over-intense colour is very noticable in both. Others that show the phenomenon clearly are "Seven Brides for Seven Brothers" and in the case of "Brigadoon" it's so intense that it almost looks like cartoon colouring. Roger (Dodger67) (talk) 10:48, 5 December 2015 (UTC)

I took the liberty of Wikilinking those... the first two mention Technicolor in the articles. Wnt (talk) 11:15, 5 December 2015 (UTC)

I think that Technicolor is the answer. Bubba73 ^{You talkin' to me?} 00:47, 6 December 2015 (UTC)

Companies like Kodak and Agfa rised their business with chemical solutions for color films. But if You are seeing movies from Video, note NTSC and SECAM have no color carrier signal correction. PAL has it by frequently shifting the color carrier signal by 180 degrees. This also causes effects like brown and yellow washed pictures. As old movies are reworked by removing sand and noise, some also have been recolored. It might be done with less manual interaction when understanding how noise is being removed from pictures and 100 Hz oder 120 Hz television is working. It deinterlaces and interpolates the missing information from the previous pictures. It is an industry to rework old movies. --Hans Haase (有问题吗) 11:16, 5 December 2015 (UTC)

Sorry User:Hans Haase, your post is completely incoherent, I'm afraid your English is not fluent enough to help here. Roger (Dodger67) (talk) 11:21, 5 December 2015 (UTC)

Thanks, I have edited my answer above. --Hans Haase (有问题吗) 11:36, 5 December 2015 (UTC)

I still don't understand your post. The pieces of information appear not to be connected.Scicurious (talk) 13:35, 5 December 2015 (UTC)

It is not only caused by the photo chemicals. When receiving it over analog television, NTSC and SECAN also cause a lost of clear red and blue color. Click the links, I added. --Hans Haase (有问题吗) 15:35, 5 December 2015 (UTC)

• Unfortunately I don't know the answer in great detail, but it's basically a matter of technology. When those movies were made the photography industry had just begun to develop color film that responded fast enough for motion pictures, but just barely: it was necessary to use extremely bright light for color filming. The combination of crude chemistry and bright lighting led to substantial color distortion. Looie496 (talk) 14:26, 5 December 2015 (UTC)

Thanks, the Technicolor article Wnt linked contains some fairly good explanations - though the chronology is sometimes unclear. Roger (Dodger67) (talk) 14:46, 5 December 2015 (UTC)

I think User:Hans Haase's explanation may be at least as relevant - I don't know. To this day I still have no idea if Latin American soccer teams really play on yellowish-green grass, either. Haase's explanation above is not badly written as I'm reading it now (did miss "oder -> or", though). Also, according to IMDb "Seven Brides" was promoted as "In CinemaScope in blushing color". Incidentally, you may have encountered yet other films that were colorized, though this seems to be out of fashion lately. Wnt (talk) 15:35, 5 December 2015 (UTC)

Also Agfacolor appeard that way. Today digital video covers all that losts. But a damage causes loosing a number of frames or JPG «squares», the picture is split into. --Hans Haase (有问题吗) 15:38, 5 December 2015 (UTC)

• The high color saturation was a desired effect, not a mistake. They advertised that films would be in Technicolor. See the work of Frank Tashlin for example, and Pedro Almodovar's fascination with his color techniques. Full saturation went out of style in the 60's when realism replaced romanticism. But look at movies like The Fifth Element and What Dreams May Come as well as Amélie where color made a big comeback. μηδείς (talk) 00:13, 6 December 2015 (UTC)

Natalie Kalmus was color supervisor of virtually all Technicolor features made between 1934 and 1949. The article points out that she was in frequent heated disputes with the studios over the unnatural color intensity they insisted on using. The OP refers to the 1950s and 1960s when Kalmus no longer was color consultant, but the studios' desires to over-emphasize color may have persisted into those decades after her departure. Akld guy (talk) 04:01, 6 December 2015 (UTC) Edited for typo in date. Akld guy (talk) 04:16, 6 December 2015 (UTC)

Note that studios also intentionally picked colorful scenes to film in color, much like 3D movies tend to have lots of scenes with things flying "out of the screen". In the original Wizard of Oz, for example, there were ruby slippers, a yellow brick road, and the Emerald City, not all of which were specified to be so colorful in the book. On the other hand, in films where color wasn't seen as a selling point, they kept them in black and white rather than filming with subdued colors. See film noir, for example. StuRat (talk) 19:26, 6 December 2015 (UTC)

Routine blood test draw locations

Why is it that for most routine blood tests, they draw from the inner elbow? Why not go for the hand or another part of the arm? — Preceding unsigned comment added by 2A02:C7D:B901:CC00:193D:96FB:D0D4:9774 (talk) 20:30, 5 December 2015 (UTC)

They want an area with high bloodflow. The crux of the elbow has a large vein, and phlebotomists like the easily accessed vein in my right arm. They will indeed use the veins in the back of the hand, especially for IV drips, if they have to, but the hand is more sensitive, and the patient is more likely to jerk if pricked there. This is OR, but it comes from years of speaking with phlebotomists. μηδείς (talk) 21:08, 5 December 2015 (UTC)

To agree with Medeis, I will add that the hand has a lot of nerve endings, including pain nerves, reflecting the high utility of the hand for motor and sensory activity, and thus the need to protect it (with pain signals). The inner elbow doesn't have nearly as many pain nerves, and it has all of the blood flow of the hand, typically in one vein. Robert McClenon (talk) 21:22, 5 December 2015 (UTC)

Yes. It hurts more to have something inserted into the back of the hand than into the crook of the elbow. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:15, 5 December 2015 (UTC)

If one wants a spot with high blood flow then why not do what phebotomists do when confrounted by a DA. Blood gravitates downwards. Look your own ankles. The inner bony bit (medial malleolus ?) . The long saphenous vein is clearly visible there. One can't miss it -even if one is still hung over from drinking too much retsina the night before (thats providing it is possible to drink too much retsina, which is according to my OR is something I have not yet been able to ascertain – but I will go on trying).--Aspro (talk) 22:59, 5 December 2015 (UTC)

You are kind of going out of your way for no purpose. The phlebotomist doesn't want to get down on the floor, you don't want to get up on the table, then be stabbed in the ankle. Medicine is like cooking and engineering, it's an applied science with standard procedures that make sense because they have been shown to work for a long time. A doctor who needs to draw blood from an armless heroin addict might do all sorts of things, but the bottom line is that the crux of the armpit is convenient and reliable. μηδείς (talk) 00:07, 6 December 2015 (UTC)

An ionic bounding can occur between metals to metals or nonmetals to nonmetals?

An ionic bounding can occur between metals to metals or between nonmetals to nonmetals or it can occur between metals to nonmetals only? 92.249.70.153 (talk) 22:54, 5 December 2015 (UTC)

See below also regarding telling us your native language so we can direct you to a better place to answer your question. Again, as a "general rule", the kind one learns in a rudimentary chemistry class (usually at the middle or early high school level) one learns that ionic bonds are expected when one has simple binary compounds between metals and nonmetals, whereas covalent bonds are expected when one has simple binary compounds between two nonmetals. --Jayron32 23:19, 5 December 2015 (UTC)

I asked this question because I have read in the book "chemistry for dummies" the following sentence: "an ionic bond occurs between a metal and nonmetal" and it wasn't clear what about ionic bounds between metal to metals or nonmetals to nonmetals. Now I understand that indeed ionic bound occurs between metals to nonmetals only. Thank you. (By the way I'm not English native speaker but I'm learning in English books only)12:08, 6 December 2015 (UTC) — Preceding unsigned comment added by 92.249.70.153 (talk)

An ionic bond forming between a metal and a non-metal is, as Jayron said, a useful generalisation for when first learning chemistry, but it is not always true. Metal to metal ionic bonding is possible (eg caesium auride, CsAu) and ionic bonds do exist in compounds with only non-metals (like ammonium chloride, NH₄Cl, which has one NH₄⁺ cation for every Cl⁻ anion. Please do not mistake a general rule to use when starting as a statement that has no exceptions. A better statement might be something like: An ionic bond is formed by the attractions of opposite charges between a cation and an anion. The most common (simple) cations are metal cations like Na⁺, but there are also cations with multiple atoms which are all non-metals (ammonium above is likely the simplest example) and the hydrogen ion H⁺ is an important cation. The most commone (simple) anions are non-metal anions like Cl^{−, but there are also anions with multiple atoms like OH− and SO₄2− and some anions containing metals like [Fe(CN)₆]3−. The ratio in which the cation and anion are present in a compound is determined by their charges, as the overall compound will have zero net charge. So, the compound between K+ and [Fe(CN)₆]3− will be K₃[Fe(CN)₆] as 3 x 1+ charges are needed to balance 1 x 3− charge. EdChem (talk) 12:45, 6 December 2015 (UTC)}

Can it be an cation in the metals or an anion in the nonmetals?

92.249.70.153 (talk) 22:59, 5 December 2015 (UTC)

I'm not sure I follow your question. As a general rule of thumb, metals tend to form cations and nonmetals tend to form anions. So I think the answer to your question is "Yes". If your native language is not English, there is probably a Wikipedia in your native language; if you tell us what language you speak natively, we can direct you to the correct location where you can ask the question in your native language and get better answers. --Jayron32 23:15, 5 December 2015 (UTC)

As Jayron has said, metal cations and non-metal anions are common, a simple example being table salt, NaCl, with an Na⁺ cation and a Cl⁻ anion. There are, however, non-metal anions like ammonium, NH₄⁺ and metal containing anions. The page on potassium nonahydridorhenate mentions the formation of its tetraethylammonium salt [N(C₂H₅)₄]₂ReH₉ with the cation N(C₂H₅)₄⁺ and anion ReH₉²⁻. This compound was originally thought to contain the rhenide anion. Metal-containing anions like this are not unusual, the hexacyanoferrates like [Fe(CN)₆]³⁻ and [Fe(CN)₆]⁴⁻ are common examples. Compounds with uncoordinated metal anions are known - caesium auride, CsAu, is one example which has an Au⁻ anion, but these are comparatively rare. EdChem (talk) 06:03, 6 December 2015 (UTC)

I asked my question because that I saw in "chemistry for dummies - workbook" (p.194) the following sentence: "The metal is present as a cation (positive ion) and the nonmetal is present as an anion (negative ion)". 12:12, 6 December 2015 (UTC) — Preceding unsigned comment added by 92.249.70.153 (talk)

Ok, thanks for the clarification. As a general rule, compounds made up of one metal and one non-metal, like NaCl, CaO, PbCl₂ have a cation (positively charged species) and an anion (negatively charged species). The ratio in which the two species are present is determined by the charges (a compound will have no charge overall). Metals generally form cations and non-metals anions. So, sodium chloride has one positively-charge sodium cation (Na⁺) for every negatively charged chloride anion (Cl⁻). This 1:1 ratio is seen in the formula NaCl. Calcium oxide (CaO) also has a 1:1 ratio as the charges on the ions are again equal in magnitude but opposite in sign (Ca²⁺ and O²⁻). For a compound like lead(II) chloride, the anion Cl⁻ has only half of the charge of the Pb²⁺, and so two anions are needed for every cation to get a balanced compound, written as PbCl₂.

There are many ions which consist of multiple atoms and, as I described above, there are cases where anions may contain metals and cations non-metals, but as a general rule and a starting point for understanding ionic compounds, the sentence you quote is a reasonable start. Note that this is a generalisation and there are exceptions, in that there are compounds with metals and non-metals where there is little or no ionic bonding and an understanding of covalent bonding (like is present in water) is needed. For example, the anticancer drug cisplatin [Pt(NH₃)₂Cl₂] does not consist have a platinum cation but rather a platinum atom convalently bonded to the N and Cl atoms in the compound. EdChem (talk) 12:25, 6 December 2015 (UTC)

Kidney Stones / Hernia prior modern medicine

So whilst I was having a good play with myself, I had this disturbing thought.

Say I was a typical person in 7853 BC, and didn't have a car. I also happened to have Kidney Stones. Or a Hernia. Or pretty much anything that's extremely unpleasant and requires modern medical intervention to resolve. Am I screwed? Should I just find the nearest Dinosaur to kill me? It's both terrifying and morbidly intriguing. — Preceding unsigned comment added by 92.241.130.120 (talk) 23:55, 5 December 2015 (UTC)

While suspecting that this question is not being asked in 100% seriousness, see History of surgery, Lithotomy, and Truss (medicine). 7853 BC is going a bit too far back (you're still technically in the Neolithic at that point), but you'd have been (comparatively) OK in the Egyptian Old Kingdom, and other Bronze Age societies. Tevildo (talk) 00:41, 6 December 2015 (UTC)

There were no dinosaurs in 7853 BC. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:32, 6 December 2015 (UTC)

No non-avian dinosaurs. SteveBaker (talk) 04:22, 6 December 2015 (UTC)

IIRC, when Cleopatra needed a dinosaur by which to commit suicide, she exposed herself to a pai of venomous coconut swallows. μηδείς (talk) 16:46, 6 December 2015 (UTC)

If something "requires modern medical intervention" (bolding, mine), and you are not in the modern era, there is no possible solution. Untreated, an ailment can develop differently. However, according to History of alcoholic beverages, there are some indications that alcohol already existed back then in 7853 BC. So, they could hypothetical treat pain with it.--3dcaddy (talk) 02:43, 6 December 2015 (UTC)

You don't have to look back into pre-history for this. There are plenty of people in the world today who live out of reach of modern healthcare. The answer is that they suffer greatly and often die from easily treatable conditions. Even a relatively small injury can become infected - and without antibiotics, you can die. There are probably 'herbal remedies' that may or may not help much - possibly pain relievers of some degree of effectiveness - but generally not much that would come close to modern medicine. We know that Trepanning was a common practice in neolithic times - we know that "Out of 120 prehistoric skulls found at one burial site in France dated to 6500 BC, 40 had trepanation holes." - so if they were capable of such drastic surgical procedures - it's possible they could have tried other desperate measures in all manner of life-or-death situations. How successful this might have been is unclear - but it's unlikely such procedures would have been so common if they didn't work at least occasionally.

SteveBaker (talk) 04:22, 6 December 2015 (UTC)

Ancient medicine was a real phenomenon, and while modern treatments are usually better, on occasion the ancients had equivalent or even superior treatments. (For example, artemisinin was discovered by consulting an ancient Daoist text, or looking forward, I can't help but note that lanosterol, which has been reported as a method to clear cataracts once it is all duly developed, patented and monopolized, seems to be closely related to abundant triterpenes in cyclamens, the eye salve the Romans would have prescribed for the condition) In the case of kidney stones already causing pain, there are some things like chanca piedra that are alleged to help ease the passage of the stone ... but they're not really sufficiently studied. The literature is full of herbal remedies with one or two papers giving encouraging results that haven't been studied since. So it's hard to say that this or that would have saved you back when, but in aggregate, there would have been physicians who (as today) sometimes would help a little, sometimes a lot, often not at all. Even Neanderthals collected healing herbs, so I think even in Neolithic times you'd have had a chance, not necessarily a good one though. (note that long distance trade improves the power of herbalism ... even the separation of Europe from Middle East during the Crusades was sufficient to badly damage the utility of herbal medicine there) Wnt (talk) 11:24, 6 December 2015 (UTC)

I should also note that trepanation still works, and is still used on occasion ... the biggest difference is simply that people don't get their heads bashed with clubs and such as often. You don't need a trepan for a gunshot wound! The fact that physicians can see if there is a hematoma or not also, of course, greatly reduces the tendency for unnecessary procedures. Wnt (talk) 11:27, 6 December 2015 (UTC)

December 6

Does light accelerate?

When light goes through glass and air, does it accelerate and decelerate? Light speed is c / 1.5 (≈ 200000 km/s) in glass, and 299700 km/s in air.

If we could measure the speed of light at smaller and smaller distances, would we see light accelerating? Can we measure the speed of light at very short distances at all? Maybe it's just the case that light needs a really short distance to reach full speed.

All explanations I found so far about a hypothetical 'acceleration of light' were that it does not happen, because light has an absolute speed. This is kind of circular thinking to me --3dcaddy (talk) 02:33, 6 December 2015 (UTC)

It has an absolute speed in a vacuum but a different speed in a medium. Bubba73 ^{You talkin' to me?} 02:37, 6 December 2015 (UTC)

Yes, the question is what happens between those mediums. How can both options be tested? Does it accelerate to the higher speed or just jump to another speed without the intermediate speed? Intuitively, it's difficult to imagine that something has not to pass through the intermediate speeds.--3dcaddy (talk) 02:46, 6 December 2015 (UTC)

Well, electrons jump from one orbital to another without going in between. It seems to me that the same could happen to the speed of the photon. Bubba73 ^{You talkin' to me?} 03:35, 6 December 2015 (UTC)

For most 'normal' things, infinite acceleration is impossible because F=m.a - Force equals mass times acceleration. If acceleration is infinite and the object has any non-zero mass, then the force required would be infinite. But photons have zero rest-mass, so even the tiniest force could result in an infinite acceleration - so this kind of weirdness isn't impossible.

However, I think the mechanism that causes the change of speed is a lot more subtle than that...I believe it's easier to understand using the wave-aspect of light than the particle-like aspect. SteveBaker (talk) 04:04, 6 December 2015 (UTC)

See our article on the speed of light, which does not directly answer your question in the terms you've phrased it in, but should provide all of the necessary context for understanding the answer. In brief, no the light does not pass through intermediate speeds (unless it passes through multiple physical mediums sequentially). That is to say, as soon as the photon passes through the space occupied by the material in question, it instantaneously again achieves the speed of 299,792,458 m/s, a universal constant upon which many basic principles of the physical universe depend. As you note, this can seem counter-intuitive if you are expecting a photon to operate as would an object, but, as Steve notes, photons have zero intrinsic mass. Depending on the semantics you choose to apply to the verbs accelerate and decelerate (that is, whether it reflects a change in absolute speed or the process of achieving a given speed), you might say that light does not accelerate at all but rather moves at the constant c and at other constants when it must propagate through a material. That is, the very existence of the phenomena of acceleration as it acts upon any object (which must have a non-zero rest mass) is an artifact that results from the principal of mass-energy equivalence. Snow ^{let's rap} 06:24, 6 December 2015 (UTC)

One way to look at the answer is to say that light neither accelerates nor decelerates as it only ever travels at one speed - the speed of light. It just happens that that speed is different in different mediums. So, on passing from vacuum to air to plastic, the speed in each is different but it changes from the speed of light in a vacuum to the speed of light in air, etc, instantaneously on changing media. As noted above, it is like the situation with an electron being promoted to a different energy state, it ceases to exist in one and simultaneously starts existing in the other. This is intuitively bizarre when considered from a particulate point of view, but more comprehensible from a wave perspective. As an analogy, consider a graph of y = x on 0 ≤ x ≤ 1 and y = 2x − 1 on x > 1. The graph is continuous (like the path of light) but its gradient is discontinuous at x = 1 (like the speed of light at a boundary). We can say the graph has slope of 1 for x < 1 and slope of 2 for x > 1 but at x = 1 it is not sensible to say it increases from 1 to 2 going through slopes like 1.5; rather, it is one slope and then a different one. Snow Rise has offered another way of looking at the situation by noting the consequence of a lack of rest mass. That light has its own speed which is a constant but changes with medium is odd, I agree, but has profound consequences. EdChem (talk) 11:57, 6 December 2015 (UTC)

The OP has asked an excellent question. Can we be so sure light jumps from one speed to another at a boundary interface? I don't think so.

All real mediums have surfaces that at atomic-level distances are very rough, and surface roughness extends in size up to what can be seen in light microscopes. I find that the concept that a medium boundary is a straight line of perfect smoothness is a theoretical (you might say false) concept that can only be applied for electromagnetic energy (light is just EM energy at certain wavelengths) at very long wavelengths, such as applies with radio emission in the broadcast bands.

As actual medium boundaries are irregular on a scale that is comparable to at least the shorter wavelengths of light/EM radiation, they cannot necessarily be considered an abrupt transition, thus light does not, in general undergo an abrupt change in speed. If boundary roughness is multiples of the wavelength then the speed must change with some profile over that distance.

For very short wavelengths (beyond visible light, e.g, x-rays, gamma rays), the wavelenth may be comparable or long compared to inter-atomic spacing. Then the boundary certainly cannot be regarded as abrupt, even if the medium was a perfectly formed "straight sided" crystal.124.178.173.1 (talk) 16:47, 6 December 2015 (UTC)

I think you are confusing the issue. When the 'rays' strike the 'boundary' a new array of point sources are initiated, the combined wave front of which forms the light wavefront in the new material. By definition, the boundary is where the apparent acceleration occurs. It has a physical location, but may be either side of the local physical boundary between the two materials but will be within a wavelength of it. Greglocock (talk) 21:11, 6 December 2015 (UTC)

I may be confusing myself. But I think you have added to it. If you accept that the speed change boundary may be up to one wavelength away from the "physical boundary" (your "definition"), then you must also accept that the physical boundary is, on the wavelength scale, undefined. At wavelength scale, what we think of as a perfect plane surface may have hills and valleys multiple interatomic distances high. In fact there may be, at long light/EM wavelengths, hundreds or thousands of such hills and valleys.

At short wavelengths, multiple wavelengths may fit within adjacent atoms, so even with a "plane surface" there is no flat plane boundary. I'm not standing on a boundary if if there is nothing but an "atom" far to the left of me, and another far to my right, far below me, etc. So where is the step acceleration located, when the interatomic disance of the medium is of the same order or larger than a wavelength? I think there is no such location. At the very least, it is "undefined".

It is usually misleading to try to apply classical reasoning when you are working on the scale of interatomic distances. 60.228.161.183 (talk) 00:28, 7 December 2015 (UTC)

You should not confuse the phase speed of light with the speed of the actual photons. The former can change abruptly while the latter does not change at all. Ruslik_Zero 03:39, 7 December 2015 (UTC)

I recall a similar explanation...I'm sure this is the key here.

That said, it's always bothered me that the speed of light in air is not the same as the speed in vacuum - yet from the perspective of a photon, air is mostly vacuum, with an occasional molecule zipping past. Air molecules are (on average) about 4 nanometers apart - and the radius of a Nitrogen molecule is something around 0.1 nanometers (although the concept of "size" is a bit hard to define at the atomic level). It's like saying that a room containing 100 basketballs is full of basketballs. If the photon doesn't come close to any molecules - why should it travel at any speed other than 'c'? I don't get it.

But yes - phase speed and particle speed aren't the same thing. SteveBaker (talk) 03:50, 7 December 2015 (UTC)

What does the VIIA of periodic table stand for?

I would like to understand what the letter A stands for, in all these columns. 12:15, 6 December 2015 (UTC) — Preceding unsigned comment added by 92.249.70.153 (talk)

It doesn't stand for anything, but signifies that the column is on the left-hand side of the table. VIIB is on the right. Note that this labelling scheme is no longer recommended, with modern usage preferring a simple numbering from group 1 to group 18. You can read much more at Group (periodic table) article. Bazza (talk) 12:28, 6 December 2015 (UTC)

Thank you for your comment and for the beautiful article that you linked to. 92.249.70.153 (talk) 12:30, 6 December 2015 (UTC)

You can also look at Periodic table#group and History of the periodic table. The A/B originates back with Mendeleev's first periodic table. 'A' was used if the outermost electron in a group was in the 's' or 'p' orbitals, 'B' if it was in a 'd' orbital. EdChem (talk) 12:31, 6 December 2015 (UTC)

Also, unfortunately, the A/B designation differed depending on the source. Some periodic tables numbered the first 10 rows "IA-VIIIA" (the cobalt-nickle-iron triad was considered one "group") and then the next 8 rows "IB-VIIIB" starting with the Copper group through the noble gases.(former IUPAC system) Other systems did as you describe above: the "A" groups were the tall main group elements and the "B" groups as the transition elements.(CAS system) Eventually, the IUPAC said "screw it all" and just designated all groups from 1-18, with arabic rather than roman numerals (so as to avoid confusion with the two conflicting older systems). But you will still find modern periodic tables with all three systems, either alone or in some combination. This is all covered in the Group article cited above. I personally prefer the CAS system, because it separates the chemically distinct main group from transition elements, and the Roman numerals match many of the common valences of the elements.--Jayron32 21:37, 6 December 2015 (UTC)

Element can lose or gain more than three electrons?

I have a doubt, because I have read two things in the same book (chemistry for dummies) that look me as a paradox. 1) "but an element doesn't lose or gain more than three electrons" (p.56) 2) it's written in the same book in one of the tables there "Sn^4- so we see against the sentence that it could be that element will lose more that three electrons. Maybe I don't understand in the book or in chemistry? 12:28, 6 December 2015 (UTC) — Preceding unsigned comment added by 92.249.70.153 (talk)

I'd say the book is wrong. Titanium dioxide, TiO₂, is ionic and consists of Ti⁴⁺ cations, at least formally. It is trying to be simple but in this case is way too simple. EdChem (talk) 12:33, 6 December 2015 (UTC)

Could it be a typo? (I mean that instead of 4 it's written 3)? 92.249.70.153 (talk) 12:37, 6 December 2015 (UTC)

My opinion is that it is a statement made thinking about factors way beyond the level you are at and is more likely to cause confusion than to be helpful. I would ignore it. PS: I think you meant Sn⁴⁺ above, the tin(IV) cation is well known (it is the stablest of tin's ions) and the anion Sn⁴⁻ would be exceptionally unstable. EdChem (talk) 12:52, 6 December 2015 (UTC)

Oxidation state can run from -5 to +9 (at least according to the article, +10 remains hypothetical). However, it is such an approximation that it doesn't really mean that much. I have no idea how much positive or negative charge you can 'really' have on an atom in a stable compound, if you could somehow 'look' at it, and would welcome any insight! As for the book... without context I really don't know what they're suggesting. Wnt (talk) 13:26, 6 December 2015 (UTC)

@Wnt: the IP who asked the question has also asked about statements that ionic bonds form between metals and non-metals and that metals form cations and non-metals anions, so he is early in his chemistry studies and I doubt will have yet encountered oxidation state. Certainly my thinking was of cases like the chromate anion CrO₄²⁻ with a formal chromium(VI) centre actually having given up less than three electrons worth of density due to the covalency of the Cr=O interactions, which is why I said the statement is considering factors way beyond the IP's level. The other problem is that cations Mⁿ⁺ can be formed for high n in extreme circumstances - looking at the ionisation enthalpies, for instance - so the statement also runs into problems with over-generality (as have other statements the IP has quoted). If it is meant as an introductory text and restricted to the s and p blocks, then ±4 makes some sense as a limit, but I still think skipping over the statement is wisest. Does that make sense?

Oops... I forgot to sign this. EdChem (talk) 00:47, 7 December 2015 (UTC)

I never actually took a formal Inorganic Chemistry class, and I really don't know the usual order of instruction. But oxidation state is a really, really crude concept - simpler than VSEPR, let alone molecular orbitals or band theory - so I think it is as relevant to a beginning student as anyone else. It also tends to have a certain arbitrariness about it, special rules and "it can be viewed that way" answers. The article starts off saying it describes chemical compounds, rather than ions in vacuum, though it makes sense you can extend it to that, and if you do then yes, you should be able to have very high oxidation states. The system is defiantly contrafactual: as described at electronegativity, there really is no such thing as a pure ionic bond, and differences of about 1.7 correspond to 50% ionic character. So Ti-O or Cr-O bonds are slightly more than 50% ionic, in theory... I don't think it's quite that simple to come up with a result for the total charge on the metal though, since each partial positive charge will tend to repel the others. But it's definitely less than the formal charge. The main reason why I wanted to mention oxidation state at all is that it is one model in which atoms actually can lose electrons, per the OP's description. In reality I think there's always some kind of molecular orbital density around the electropositive atoms, and even a cesium bound to fluorine will get more time with its electron pair than an American family court would usually allot. Wnt (talk) 20:45, 6 December 2015 (UTC)

I am guessing the IP is at the mid-high school level of learning basic chemistry, which means (in Australia, at least) that oxidation state, crude a concept though it is, has yet to be covered. Like many concepts, oxidation state provides a useful tool but only when its limitations are recognized and respected, and I think it is ill-suited to a declarative statement as to a maximum number of transferrable electrons for some of the reasons Wnt mentions. EdChem (talk) 00:53, 7 December 2015 (UTC)

DIY fabrication of articles using resilient silicone material

I've seen ice cube trays and oven mitts made of some resilient silicone material. I wonder if it's feasible to make things with that type of material as a DIY project. I'm thinking about something like custom protective cases for electronics and custom grips for handles. The product needs to stand up to at least moderate use. If it's feasible DIY project, how do you do it? — Preceding unsigned comment added by 123.136.11.156 (talk) 18:51, 6 December 2015 (UTC)

See Silicone rubber and Injection molding of liquid silicone rubber. A Google search on "silicone rubber molding kit" might also be useful - there are plenty of firms out there who sell kits suitable for the hobbyist, although the process of designing the mould may not be trivial for complex shapes. Tevildo (talk) 21:50, 6 December 2015 (UTC)

I'm under the impression that the kind of kits you mentioned are for making molds that themselves will be used to reproduce solid shapes by casting. The silicone molds are typically the end products. Do you know how durable the material is? --123.136.11.157 (talk) 00:27, 7 December 2015 (UTC)

There is also this Sugru stuff that's quite popular, it is silicon based but it's more like modelling clay than rubber, so maybe not for protective cases or ice cube trays, but definitely for "solid" things like custom grip handles.. Vespine (talk) 21:53, 6 December 2015 (UTC)

Radios in trucks?

I'm currently writing a novel about a young woman running a farm in the American south in the early 1950s. I've been trying to be as authentic as possible where it comes to all the stuff about the geography of the area, farming methods used then, famous people of the period, etc. I'm having trouble with a scene where the main character is driving a new pickup truck home from a farm sale. I'd like to include them listening to the Grand Ole Opry on the radio (as sort of a tribute to a relative who lived then and loved Hank Williams), but I don't know if cars or trucks had radios back then. The truck manufacturer is not named but would probably be Ford or Chevrolet. So, did trucks come with radios back then? Thanks, White Arabian Filly (Neigh) 19:31, 6 December 2015 (UTC)

1950s? Yes, of course they did. I once owned a 1938 Ford V8 Deluxe, and found an original radio for it and fitted it. But even earlier cars than that had radios. Akld guy (talk) 19:50, 6 December 2015 (UTC)

I would say the average pickup truck came standard with no radio then, but that you could buy an AM radio as an option. An AM/FM radio might not have been available at that time, at least in a truck. (Note that trucks were considered to be strictly practical vehicles then, as this was before the days of Cadillac Escalades and their ilk. So, a radio for entertainment might not have been considered important, but AM radio was considered practical, for telling you about news and weather, for example. Also note that AM and FM were both strictly mono then.) StuRat (talk) 20:10, 6 December 2015 (UTC)

On the other hand, if you want an actual reference instead of what Stu would say, you might look (1) at advertisements of the period, or (2) at books about the trucks of the period. As to 1, some old advertisements (for example, in Life magazine) can be accessed through Google Books, but it's biased toward recent publications, so you have to find the hidden Advanced Search page in order to limit the search by publication date. I didn't find anything relevant but I didn't take much time trying it. As to 2, Google Books found Ford Pickup Trucks by Steve Statham, and showed me a snippet saying that on the 1948 models "an automatic push-button tuning AM radio was optional"; and it found Ford F-100/F-150 Pickup, 1953-1996 by Robert C. Ackerson, in which a table on page 12 says that "Radio (five-tube) with rectifier and single knob control" was an available accessory on the 1953 F-100. So apparently Stu's answer was right. --76.69.45.64 (talk) 21:29, 6 December 2015 (UTC)

It's important to note that any radio back then would be based on vacuum tubes - the transistor radio wasn't commercially available for automotive use until the late fifties (the Mopar model 914HR (1955), to be precise). A tube radio wouldn't really be very practical for a working farm truck, rather than one which would be driven entirely on paved roads - although, as noted above, they were available. Tevildo (talk) 21:57, 6 December 2015 (UTC)

Why do you say a tube radio wouldn't be very practical? If you mean it would be jolted around on rough roads...well, many roads of the day weren't paved, so family cars would have had the same problem and thus the radios were built for those conditions. With a great deal of experience in restoring WW2 military radios, I can say that (glass) tubes are far more rugged than latter day readers might think. Akld guy (talk) 22:18, 6 December 2015 (UTC)

In any case, vacuum tubes operate at lower temperatures and thus are more rugged than incandescent light globes. How often do you have to replace the various light globes in your truck? Not very often. 60.228.161.183 (talk) 00:55, 7 December 2015 (UTC)

The first commercial success of AM radios within in cars actually dates back to 1930 by Galvin Manufacturing (now known as Motorola). It was also came with a hefty price tag at the time being around $130. (ref 1) (ref 2) From that point on car radios become more and more common, still at a premium price though. In regards to your question, Chevy began offering radio as an advanced option in their trucks in 1947. (ref 3) So in summary, yes, there were AM radios in trucks in the early 1950. Aclark05 (talk) 22:44, 6 December 2015 (UTC)

Although not a farmer myself, I come from a farming family. Radios (AM band) have long been considered ESSENTIAL in all types of farm vehicles. Even closed cabin tractors have always had them. In rural areas, radio stations give information of keen interest to farmers - news, weather, fire information, sale yard prices, etc. But one thing that might be important. Farm trucks, especially in the 1950's were built well, but built down to a price. That meant they had higher cabin noise than sedans. And farmers travel outside towns, so their speeds are high ---> more noise. So if you were listening to a voice reading, fine, but for music it was a bit of a strain. Compressed rock and roll not so bad (we turned the volume to max), but any sort of music with dynamic range not good. Classical music in a 1950's farm truck was pretty hopeless. Note that car radios then had only 5 watt mono audio. Today's car radios may have 20 watts per channel or even more. That makes listening to music much less of a strain. 60.228.161.183 (talk) 00:55, 7 December 2015 (UTC)

Thanks to all. Most of the book has to do with horses and the fact that they were just then going big-time with most of the shows (improving the prize money to where you could make a good living training or riding because horses were about the hottest thing going, what with all the cowboy movies inspiring everyday people to get a horse and ride), but I want the non-horse stuff to be accurate as well. (I grew up on a farm, so I know horses and animals, and old tractors to some extent.) Thanks! White Arabian Filly (Neigh) 02:00, 7 December 2015 (UTC)

Aclark05, if you don't mind I changed your refs to inline links. Refs aren't constrained to the "section" so will remain on the very bottom of the reference desk page, making it appear like they belong to the bottom section, rather than this question. Vespine (talk) 02:58, 7 December 2015 (UTC)

As one data point, I tracked down the original purchase order for my 1962 Mini. It cost it's original owner 600 UK pounds. The AM radio was an optional extra and cost an additional 50 UK pounds. That's 1/12th the cost of the car! For comparison, seat belts were also an optional extra - also 50 pounds - and the owner didn't buy them. From this I deduce that the radio was a costly item, but considered sufficiently valuable as to outweigh having seatbelts.

Fast forward to today - my modern MINI cost me $21,000 - and the radio was (of course) standard equipment. But if it had been an optional extra costing 1/12th the price of the car ($1,750) I wouldn't have bought it! So, I think it's certain that a radio would be an optional extra in a truck of your era - I'm not sure how many people would have purchased it. Certainly it would be in the luxury category. SteveBaker (talk) 03:39, 7 December 2015 (UTC)

One of the prime functions of AM radio in rural areas in the 1950s and 1960s was to communicate farm commodity prices and to provide agricultural advice from the county extension agent. It would easily be reasonable for a farmer to have a radio in their truck to get the ag news. I remember substantial parts of the morning AM show in the 1960s devoted to agriculture. I would agree that a truck radio would have been optimized for voice, and that music would have sounded pretty tinny. Acroterion (talk) 03:49, 7 December 2015 (UTC)

But look at it this way, back then your 50 quid bought you the state of the art radio for the day right? I can't find the official prices, but according to this article "you can typically add £1,345 for navigation". That's including the MINIs that cost 11000 pounds. that's more than 1/10th the price of the car. Vespine (talk) 03:53, 7 December 2015 (UTC)

December 7