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March 15

Does it matter which way you apply a Nyloc nut?

When fastening a Nyloc nut on a screw, does it matter whether the nylon side points forward or backwards? — Sebastian 02:27, 15 March 2015 (UTC)[reply]

The nylon is not threaded. Unless the Nyloc nut was reused, which is not recommended, I think one would have difficulty getting the Nyloc nut started onto the bolt. This is just a guess. I hope someone familiar with the product weighs in. Bus stop (talk) 02:52, 15 March 2015 (UTC)[reply]

Yes, the nylon portion is not pre-threaded. Sebastian, are you proposing to run a bolt through from the "proper" end to cut or press correctly aligned threads into the nylon, and then to attempt to engage these threads to run the bolt in from the other direction? If successful, you are facing some reuse safety issues on your first use.

Also, the end away from the nylon has the better seating / bearing surface. -- ToE 03:04, 15 March 2015 (UTC)[reply]

Sorry about being unclear. I think your answers already give me the answer I was looking for: The metal side is the "proper" side; I agree that it's harder to put the nylon side on a bolt first, presumably because it has no precise guidance for the thread. And no, I wasn't proposing a two-stage process as in ToE's first paragraph. Thanks! — Sebastian 03:38, 15 March 2015 (UTC)[reply]

numbers that stands for part of sublevels in electron configuration

What is the explanation for the negative numbers that stands for part of sublevels in electron configuration? (-2,-1,0,1,2)5.28.179.219 (talk) 07:48, 15 March 2015 (UTC)[reply]

That isn't a standard notation for Electron configuration - a typical example is 1s²2s²2p⁶3s¹, the ground state of the sodium atom. Where did you see the notation in your question? Tevildo (talk) 09:31, 15 March 2015 (UTC)[reply]

These numbers look to be the magnetic quantum number. It describes the space quantization of the angular momentum of the orbiting electron. The + number means that the angular momentum vector is closest in direction to the field direction, and a negative means it is pointing in the maximum backwards direction. 0 is perpendicular. Graeme Bartlett (talk) 11:32, 15 March 2015 (UTC)[reply]
Another possibility that these are valences, or oxidation states, see e.g. List of oxidation states of the elements -- 87.151.33.39 (talk) 12:26, 15 March 2015 (UTC)[reply]

I think that they refer to valencies, -1 refers to a lack of an electron that would make up the full outer shell, 0 would mean that the atom has the full complement for its outer shell, while +2 means that there is an excess of electrons. DISCLAIMER..Chemistry is not my strength. I'd go with Tevildo's answerRead-write-services (talk) 04:15, 16 March 2015 (UTC)[reply]

Given electrons have negative charge, it's not common to say that having excess electrons would be a positive-sign electronic situation (compare to 87.151.33.39's answer that is standard for concepts of atomic charge). But given the question is about identifying sublevels, Graeme is right on with explanation and links for this standard meaning. DMacks (talk) 04:25, 16 March 2015 (UTC)[reply]

The OP is talking about the magnetic quantum number for the l=2 (i.e. d sublevel) state. Without going to deep into the mathematics, (most of which I forget anyways), the quantum numbers are solutions to the Schrödinger equation that produce the various quantized energy states an electron can exist in. To simplify the equation, the quantum numbers are always integers, and they follow a rather simple set of rules. For example, n must be a positive integer, while the l = 0 --> -n for each value of n (thus, at n = 1, l = 1, at n = 2, l = 0 or 1, at n = 3, l = 0 or 1 or 2). The m values (the third quantum number) can equal -l --> +l for any value of l, so if l = 1, m = -1, 0 , +1. Two of the quantum numbers, the n (energy level) and l (energy sublevel) are of different energy (thus a 1st level electron has less energy than a second level electron, while a 2p electron has more energy than a 2s electron). However, all of the m values for any given l are equal in energy, so the designation of a particular orbital as m = -2 or m = -1 is arbitrary. There's some conventions that say define the orientation of a specific orbital with a specific m values, but these conventions require one to pick an arbitrary direction to define the alignment of the orbitals to. The - has no physical meaning per se, except as a sign convention for directionality. --Jayron 32 05:13, 16 March 2015 (UTC)[reply]

Could hydrogen and oxygen form a ring molecule?

Could a molecule be something like H-O-H-O-...-connect to the first H atom? Would this molecule be stable? Llaanngg (talk) 16:31, 15 March 2015 (UTC)[reply]

The ring that you describe appears to have the hydrogen exhibiting a valence of 2, and hydrogen only has one native electron, and doesn't have a valence, in the usual sense, of 2, so that, no, the molecule wouldn't be stable, and wouldn't exist as a molecule at all. If, on the other hand, you are asking whether the hydrogen atoms could be attracted to nearby oxygen atoms by hydrogen bonding, then that is one of the characteristics of water, which isn't a ring molecule, but consists of H2O molecules bound to each other (weakly compared to the strength of the internal bonds). Robert McClenon (talk) 16:45, 15 March 2015 (UTC)[reply]

Such a configuration would be an electron deficient cycle of Three-center two-electron bonds, whereby each hydrogen will have two electrons, and each oxygen will have seven electrons. It would also be a polyradical, with each oxygen having an unpaired electron. This would mean that the molecule is extremely reactive and unstable with respect to rearrangement, or decomposition. Plasmic Physics (talk) 06:49, 16 March 2015 (UTC)[reply]

You may be interested in water dimer. Graeme Bartlett (talk) 09:45, 16 March 2015 (UTC)[reply]

The structure of ordinary ice has loops like this ... but the hydrogens always prefer a position closer to one oxygen, further from the other. What's interesting though is that you could take those structures and reverse them, i.e. there must be some absolutely stupendous information storage capacity in ice if you could read and write bits of data by moving the hydrogens around the ring. I think. Wnt (talk) 13:57, 16 March 2015 (UTC)[reply]

Basic species question

Suppose a group of organisms, a "species", can interbreed with each other to produce fertile offspring. Is it generally supposed that the group should be able to reproduce and produce fertile offspring with the group's most recent common ancestor?--Leon (talk) 18:36, 15 March 2015 (UTC)[reply]

That isn't an easy question. See species problem to see the complexity of what is considered a species. Part of the question would be how long ago the group had a single common ancestor. Thousands of years ago? Tens of thousands of years? Hundreds of thousands of years? Has the species been under selective pressure since it began radiating from a common ancestor, so that all of its modern members differ from the common ancestor? Sometimes it isn't even easy to define a "common ancestor", as the discussion of mitochondrial Eve and Y-chromosomal Adam should indicate. Questions involving what is a species are often more complicated than one might think. Robert McClenon (talk) 18:52, 15 March 2015 (UTC)[reply]

I think the answer is not necesarily. Try ring species perhaps mightbe relavant? Vespine (talk) 23:10, 15 March 2015 (UTC)[reply]

Actually i'm going to change my answer to "this is a malformed question". Have you read Most recent common ancestor? It took me several goes around before I started understanding it. Neither "species" nor MRCA hass a very "fixed" definition. Most recent common ancestor of a single species, could by definition be of that species, so would be able to breed with the species. BUT on the other hand, a single isolated population of a species COULD undergo a speciation event (that's how "it" happens after all), then the population that was isolated would have a common ancestor that could no longer breed with the "new" species, but then is the MRCA of the new species, the same as the MRCA of the "old" isolated species, or is there a "new" MRCA from when the speciation event occurred? Vespine (talk) 21:59, 16 March 2015 (UTC)[reply]

I'm not sure how to answer your last question. But my gut says surely that the new species has a new MRCA. How could it not be? Where am I going wrong?--Leon (talk) 13:16, 17 March 2015 (UTC)[reply]

The other thing to think about is simple timing. If I have a set of N individuals (not necessarily a species), then as N gets larger, the MRCA becomes almost certainly dead - so no breeding is possible without a time machine. I'm not sure, but I suspect sympatric speciation could lead to a situation where the MRCA of species A could not make viable offspring with species A, even if we had a time machine. Island biogeography may well have some examples of this. SemanticMantis (talk) 14:41, 17 March 2015 (UTC)[reply]

I assumed the OP meant with access to a time machine. I doubt there are any species (beyond bacteria perhaps) where the MCRA is still "alive". In any case, i think the OP has more of a problem with semantics than genetics. I would recommend the OP read The Ancestor's Tale, I think it explains certain concepts about evolution very well, specifically concepts relating to common ancestry. Vespine (talk) 22:10, 17 March 2015 (UTC)[reply]

March 16

Why do I get all sweaty when I pull an all-nighter?

Just last night I stayed up all night to get some work done. Shower in the morning so I'm nice and clean, get changed into new clothes, then not ninety minutes later I'm sweating like a pig. Staying up all night isn't something I do super-frequently, but getting all sweaty happens every time I do. --2404:2000:2000:5:0:0:0:C2 (talk) 00:55, 16 March 2015 (UTC)[reply]

We can't answer medical questions. If you think your body is misbehaving, either on its own or because you did something to it unwisely, you should seek the advice of someone with proper training. --Jayron 32 01:43, 16 March 2015 (UTC)[reply]

That is called a night sweat and it can mean many things. Bubba73 ^{You talkin' to me?} 02:01, 16 March 2015 (UTC)[reply]

Night sweat is not relevant, and User:Kainaw/Kainaw's criterion applies, the OP has asked for a personal diagnosis. μηδείς (talk) 03:04, 16 March 2015 (UTC)[reply]

I disagree, the question closest in format to mine is the "white painful bumps" one. Please interpret my question in the light of that:

I sometimes get white painful bumps on my tongue. Is that a side-effect of tooth whitening toothpaste?

It is apparent that the questioner is asking if his or her white bumps are caused by the toothpaste, but that is not the literal question. The literal question is asking if the toothpaste has been known to have a side-effect of causing white bumps. This may be answered as long as care is taken not to diagnose what the questioner's white bumps are.

--2404:2000:2000:5:0:0:0:C2 (talk) 03:11, 16 March 2015 (UTC)[reply]

I don't know the answer to your question, but I can confirm that you are not alone in this experience. If I am working overnight, I find that there are moments at which I get extremely sweaty (and feel surprisingly hot, given that it's the middle of the night and the central heating is turned off), and once or twice this has carried over into the following morning. I'd be interested to know what causes this. RomanSpa (talk) 04:07, 16 March 2015 (UTC)[reply]

One possible reason is just that your antiperspirant has worn off. This doesn't have anything to do with the time of day, other than, if you apply antiperspirant in the morning as most people do, then late at night is when it is likely to wear off.

Also, do you use caffeine to stay awake ? This can cause sweating: [1]. StuRat (talk) 05:30, 16 March 2015 (UTC)[reply]

Personally I agree with μηδείς/Jayron32. But anyway some people seem to have failed to read the question. The OP didn't say anything clearly about sweating at night when you stay up late. They said they sweated a lot the morning after they stayed up late. The question is somewhat ambigious, it's possible they also sweat a lot while staying up, but this wasn't clearly stated. Nil Einne (talk) 07:30, 16 March 2015 (UTC)[reply]

What is clear is that the IP is wikilawyering (Every single clause has the word I in it, it's not a general question) and those offering answers haven't comprehended the question as stated. This should be shut down, since we have no idea, maybe the OP is diabetic, or has a heart condition. If it's serious enough to need answering it's serious enough to take to his gen prac. μηδείς (talk) 22:20, 16 March 2015 (UTC)[reply]

Thawing a solution/emulsion and homogeneity

If I thaw a solution (maybe containing reagents) or milk, am I right in thinking that I need to wait for the whole lot to melt and then mix to ensure that I remove a proper (i.e. containing the correct ratios of constituents) aliquot? I imagine it might depend on the precise contents. I'm interested in reagents (used in life sciences) in general and milk specifically (which I sometimes freeze domestically for convenience). --92.6.114.195 (talk) 08:43, 16 March 2015 (UTC)[reply]

Correct, you should always thaw the whole solution to ensure homogeneity. If not, you may suffer from the reverse of fractional freezing or temperature dependant solubility issues. 131.251.254.154 (talk) 09:38, 16 March 2015 (UTC)[reply]

In the case of milk, freezing can cause lipids to clump together, so you get "cream on the top". Rehomogenization would then be required to get it back to the original mixed state. StuRat (talk) 16:51, 16 March 2015 (UTC)[reply]

The worlds of nature which was building on superconductivity

1) Did micro-nano worlds build on superconductivity?

2) Did a world of biological cells build on the superconductivity?--85.141.236.250 (talk) 13:45, 16 March 2015 (UTC)[reply]

I'm not sure what the OP means but I interpret as a question that I've wondered about for a while. Do individual molecules exhibit superconductivity at higher temperatures? For example, if you knock an electron out of a benzene ring or larger aromatic system and use some applied field to start the hole moving around the ring with a measurable speed (because of resonance I'm not sure you can actually do this, but then again, I'm not sure you can't provided you can measure the momentum to narrow the range of available states...), will it maintain that speed under another force is applied? Wnt (talk) 14:04, 16 March 2015 (UTC)[reply]

To my knowledge superconductors have never existed on Earth, until humans made some, relatively recently. So "no" to both of your questions. Covellite is often suggested as a "naturally occurring superconductor", but I don't think it would act as a super conductor under any Earth-normal conditions. SemanticMantis (talk) 14:13, 16 March 2015 (UTC)[reply]

B-birds

Hi everyone, I'm looking for help identifying these birds. Although they were at the zoo, they were not in individual enclosures and thus not identified. — Crisco 1492 (talk) 15:44, 16 March 2015 (UTC)[reply]

Species found in Gembira Loka
Crested serpent eagle
Black lory
A female eclectus parrot
Dusky lory

The red and blue one looks a lot like a female eclectus parrot. By the way, I just used google's reverse image search, and clicked through a few similar examples until I found one that seemed to be the same bird and have a good description. It's a fun game; no bird expertise needed to at least suggest candidates. SemanticMantis (talk) 18:41, 16 March 2015 (UTC)[reply]

The bird is most definitely a female eclectus. My friend owns one that looks exactly like this one, and she loves to be rubbed and handled by me. :-) --Modocc (talk) 18:57, 16 March 2015 (UTC)[reply]

Does the parrot get jealous of you rubbing and handling your friend? :) μηδείς (talk) 22:13, 16 March 2015 (UTC)[reply]

The last one could be Dusky lory. The geography, beak/eyes/legs colors match; plumage is close. Your bird looks thinner/bigger to me, but that could be just a matter of perspective. Abecedare (talk) 21:58, 16 March 2015 (UTC)[reply]

And the pair in the second photograph is likely to be that of Black lories (see similar photo here, and description here). The bird in the first photograph will be difficult to identify given the tight view, but may be someone more knowledgeable will pipe in. Abecedare (talk) 22:35, 16 March 2015 (UTC)[reply]

Thanks, everyone! I'll update the image pages on Commons. My apologies for regularly (well, irregularly) asking here, but I know that there are people who know birds well and would have a much easier time getting the right species than me and Google. — Crisco 1492 (talk) 23:50, 16 March 2015 (UTC)[reply]

Your questions are well-directed at the ref-desk, since one of its purpose is to help improve wikipedia content, which your photographs combined with species identification certainly do. Plus they are fun to sleuth... so keep them coming. Cheers. Abecedare (talk) 00:46, 17 March 2015 (UTC)[reply]

Bird number 1 appears to be the crested serpent eagle, Spilornis cheela. μηδείς (talk) 01:24, 17 March 2015 (UTC)[reply]

- I think I remember seeing such a label around this one. Thanks! — Crisco 1492 (talk) 01:33, 17 March 2015 (UTC)[reply]

Nice find, Medeis. Abecedare (talk) 01:54, 17 March 2015 (UTC)[reply]

I used the same reverse-image method (which I have used before, but not exclusively) and the picture I found was a few page scrolls down. Taxonomy has always been a hobby of mine, and it was easy to quickly rule out most of the other pictures. The difficult part is that the crested serpent eagle is highly variable. μηδείς (talk) 16:54, 17 March 2015 (UTC)[reply]

I agree with Abecedare, Crisco 1492, please post more, this is both beautiful and fun. μηδείς (talk) 17:19, 19 March 2015 (UTC)[reply]

- I'll see what I can find on my next photography trip! Shame I lack the equipment for most wild birds. — Crisco 1492 (talk) 23:08, 19 March 2015 (UTC)[reply]

One can find a lot of wild birds in singles' bars, but the environs are not well lit, and photography may be discouraged. In any case, with a little knowledge of taxonomy and google images, it's amazing what you can do. Back in the early years BS (Before Simpsons) none of this was imaginable. μηδείς (talk) 05:38, 20 March 2015 (UTC)[reply]

How was the speed of quantum entanglement measured?

In some experiment, the speed of the effects of quantum entanglement was estimated to be $10000c+$ . How was this accomplished if no information can be transmitted at a speed faster than light? — Melab±1 ☎ 16:20, 16 March 2015 (UTC)[reply]

Is your question "how was it measured?" or "how does a faster-than-light effect work?" If it's the former, that's simple: you compare clocks after the fact, which does not rely on real-time data transmission and so doesn't care about the speed of light. If it's the latter, then the answer is far more complicated, but quantum entanglement, the no-communication theorem, and the EPR paradox (a famous objection to entanglement) may provide a good start. The short version is that events can propagate FTL without usable information being transmitted with them (or without even the capability for information transfer existing). — Lomn 17:29, 16 March 2015 (UTC)[reply]

The paper is arXiv:1303.0614. I guess the idea is that if you generate a Bell pair and send the halves in opposite directions to detectors a distance d apart, and in front of the detectors are polarizers that rotate randomly at a time scale comparable to d/10000c, and you observe a violation of Bell's inequality in that experiment, then you've established a lower bound of around 10000c on some quantity. Calling that quantity the "speed of entanglement" is misleading since entanglement doesn't and couldn't have a speed. What they're really bounding is the signaling speed of some unspecified classical hidden-variable theory that uses superluminal signaling to (imprecisely) simulate entanglement. -- BenRG (talk) 00:19, 17 March 2015 (UTC)[reply]

light move back and forverd in time , in high dimension , so its transfer statistic information in this dimension that can be seen from entanglement , thanks water nosfim — Preceding unsigned comment added by 192.116.142.154 (talk) 10:58, 17 March 2015 (UTC)[reply]

Is it possible computer’s programming of the biological cells (gene or genome)?

Is it possible to over completed the biological (natural) program code of the biological cells (gene or genome) by computer’s logical software code? I saw some interesting films in which it is been done.--83.237.194.120 (talk) 16:33, 16 March 2015 (UTC)[reply]

Yes, it doesn't seem all that complicated, once we know exactly what each gene does, to figure out which combo will do what. This doesn't even really require a computer. The tricky part is figuring out exactly what each gene does in the first place. Then actually changing the genes isn't that easy either, requiring "programming" a virus to inject it. Having them remove existing genes is trickier still.

Where computers do seem to be critical is reading DNA. The most productive approach seems to be to read many small, overlapping fragments of DNA, then use computers to find the overlaps and piece it all together to find the entire genome of the individual. StuRat (talk) 16:47, 16 March 2015 (UTC)[reply]

Much Thanks! I suppose that it is possible to done the magnetization of biological cell so, that in the biological cell been done existence the computer’s software code, is it right?--83.237.194.120 (talk) 16:57, 16 March 2015 (UTC)[reply]

We have articles on this topic, including biocomputer and DNA computing. Looie496 (talk) 17:26, 16 March 2015 (UTC)[reply]

Thanks! I’m Looked’s through. So, meaning it is possible bit’s of DNA!--83.237.195.135 (talk) 18:02, 16 March 2015 (UTC)[reply]

What is a mutation from the point of vision of IT computer’s technologies (computer’s software)?--83.237.223.251 (talk) 19:25, 16 March 2015 (UTC)[reply]

Well, a disk error can cause a bit or series of bits to be reversed. Just like in biology, I would mostly expect this not to matter or to be bad, but occasionally (one in a million ?) you could get one that's actually helpful. However, since there is no mechanism to reproduce this single bit error, it wouldn't propagate. StuRat (talk) 23:20, 16 March 2015 (UTC)[reply]

Thank you! I assume that the mutation is always evolutionary jump (shift).--83.237.203.145 (talk) 05:43, 17 March 2015 (UTC)[reply]

Could evolution be in searching of the formerly losted (dismissed) evolutionary chain – bit’s?--83.237.203.145 (talk) 05:58, 17 March 2015 (UTC)[reply]

(Fairy funny joke - Could science exactly answer to the question whether been the first human on planet Earth a Cro-Magnon Teuton?)--83.237.197.10 (talk) 06:32, 17 March 2015 (UTC)[reply]

Did the computer is able to recover a losted source (initial) information complementing her by skipped (dismissed) logicality?--83.237.197.10 (talk) 07:31, 17 March 2015 (UTC)[reply]

Maybe evolution is always facing to backwards?--83.237.198.193 (talk) 09:11, 17 March 2015 (UTC)[reply]

Maybe the perfecting nature is constantly striving to recover the losted (dismissed) better perfect (sustainable) biological species?--83.237.218.251 (talk) 10:47, 17 March 2015 (UTC)[reply]

Your questions imply that you are under the impression that evolution has a goal and, possibly, some sort of plan. Evolution is a term used to describe a system in which things change over time. Commonly, when referring to animals, evolution is simply a term used to describe how a species changes over time to better fit the environment. The specific process is commonly referred to as "survival of the fittest." In the end, evolution isn't looking towards any goal. It is not intelligent and does not have a plan. It is merely a word used to state "things change." 209.149.114.176 (talk) 12:20, 17 March 2015 (UTC)[reply]

Thanks, for a fairy tale joke - The nature of Orthodoxes is always been consisted in the suppression of (struggle against to) the variability of biological species!--83.237.195.169 (talk) 13:23, 17 March 2015 (UTC)[reply]

Why is it believed dark-matter particles do not self-annihilate?

From e.g. Berlin et al. (2014) Simplified Dark Matter Models for the Galactic Center Gamma-Ray Excess, it seems to be the prevailing assumption that dark matter spontaneously decays into normal matter (quarks or leptons). I don't understand why this needs to be the case. Couldn't DM particles be their own antiparticles, and self-annihilate directly into gamma rays? — kwami (talk) 17:54, 16 March 2015 (UTC)[reply]

We don't know what we don't know about Dark matter, even if it exists. But when your fudge factor is 95% of your total, you start to wonder about the validity of your model. Rmhermen (talk) 18:56, 16 March 2015 (UTC)[reply]

(edit conflict) Then we would probably expect to see gamma rays, or similar high-energy electromagnetic radiation... and we don't! SLAC has some very nice archived public lectures on this topic: Deep Science: Mining for Dark Matter (2011) and The Dark Universe Through Einstein's Lens (2013) were both very interesting.

My take-away is that cold hydrogen gas provides a surprisingly consistent explanation for everything we observe about the "missing mass" problem, but a lot of observational astronomers (and a lot more of the popular science publications) are fixating on the exotic matter simply because it's more interesting. After all, what is the point of studying the parts of space that we already understand?

Nimur (talk) 18:58, 16 March 2015 (UTC)[reply]

We've been through this before. There is simply no way that hydrogen can explain dark matter, because its behavior is completely different. For one thing, the latest CMB data shows in section 3.3 that all baryonic matter in the universe make up only 4.8% of its energy density, compared to a dark matter density of 26%. Even your own link makes the point that dark matter cannot be made of atoms: "To account for the structure of galaxies and clusters of galaxies, the universe must contain six times more dark matter than ordinary atomic matter." Finally, the OP's paper is precisely about the "gamma rays, or similar high-energy electromagnetic radiation" that is consistent with dark matter self-annihilation in the galactic center. Its title is "Simplified Dark Matter Models for the Galactic Center Gamma-Ray Excess" (!!) --Bowlhover (talk) 19:48, 16 March 2015 (UTC)[reply]

That is the opposite of the prevailing assumption. From the abstract of the Berlin et al. paper:

"Taking a model-independent approach, we consider an exhaustive list of tree-level diagrams for dark matter annihilation, and determine which could account for the observed gamma-ray emission while simultaneously predicting a thermal relic abundance equal to the measured cosmological dark matter density."

"Dark matter annihilation" means self-annihilation. Self-annihilation does produce gamma rays, but it also produces other particle-antiparticle pairs, which the paper lists. --Bowlhover (talk) 19:13, 16 March 2015 (UTC)[reply]

Thank you! — kwami (talk) 20:35, 16 March 2015 (UTC)[reply]

Also note that in WIMP dark matter scenarios, self-annihilation is the usual mechanism that gets you to the right dark matter density in the early universe. The idea is that WIMPs were in equilibrium with photons above some temperature, and then "froze out" as the temperature decreased. They could still annihilate until the expansion of the universe made it unlikely for any two WIMPs to find each other. If the WIMPs have interactions on the scale of the weak force, this mechanism gives about the right density. --Amble (talk) 00:05, 17 March 2015 (UTC)[reply]

Electric clocks

I was reading a shopping catalogue which advised not plugging in an electric clock into an extension cable, especially if the extension is used to power a high load appliance, such as a heater, as it will cause the clock to gain time. Googling didn't lead me anywhere, except that electric clocks use the mains frequency to govern the timekeeping, and that high loads at the generating plant can lead to a reduction in the frequency - which would surely slow a clock, not make it run fast, and I can't believe one heater would affect the mains frequency. What am I missing? (edited)BbBrock (talk) 22:43, 16 March 2015 (UTC)[reply]

That advice seems wrong to me. I would expect a high local load to reduce the voltage available, not the frequency. StuRat (talk) 23:15, 16 March 2015 (UTC)[reply]

Wow, I think this may refer to (as stated above) the voltage, due to loading may drop-however slightly, but the mains frequency-increasing? I doubt it. Mains frequency is REALLY stable- I can't imagine that you plugging in your heater would affect it. there is a thing called power factor correction-referring to inductive/capacitive loads...mmm. which the heater is...*thinking* We need an electrician to answer this. Also, If the mains frequency changed-the utility company would be in REAL trouble!Read-write-services (talk) 23:34, 16 March 2015 (UTC)[reply]

Sounds dubious to me too. The speed of a synchronous motor (used in Synchrnous electric clocks), depends upon the frequency, and not the voltage, of the AC power supply; and this frequency is very carefully controlled (it is varied a bit for load sharing purposes between different power generators, but its average value is very stable). Abecedare (talk) 23:52, 16 March 2015 (UTC)[reply]

Are we asking about old-fashioned electric clocks, or modern electric clocks? Very few electric clocks in this century use synchronous motors that rely on frequency and display the time in analog fashion. Most modern (twenty-first century) electric clocks display the time in some digital fashion, usually with LEDs, and it is my understanding that most of them rely on a quartz crystal. A quartz crystal has an inherent resonant frequency and so should be extremely accurate anywhere in its proper operating range. I may be mistaken, having not done extensive research on the subject, but it isn't obvious to me what change in either voltage or frequency would change the resonance of a quartz crystal. Robert McClenon (talk) 01:53, 17 March 2015 (UTC)[reply]

See quartz clock for a discussion of the accuracy of quartz clocks. That article does not refer to any sensitivity to the voltage or frequency, but does note that nearly all modern electric clocks do use the quartz crystal technology. I think that the concern about dependency of the clock on the electrical input is exaggerated. Robert McClenon (talk) 01:58, 17 March 2015 (UTC)[reply]

Well, when unplugged and running on batteries, they do indeed keep abysmal time. However, there should be no timing signal in the electricity coming from the battery at all, so it must use quartz crystals there, but that doesn't explain why they keep time so poorly when on batteries. StuRat (talk) 02:01, 17 March 2015 (UTC)[reply]

^{[citation needed]}. You sound very confident, but my impression is that the ubiquitous cheap plug-in alarm clocks in the US are still primarily synchronous clocks tuned to mains frequency. As, I believe, are the clocks in most of the appliances where the clock is only a minor feature, like in a microwave, stove, coffeemaker, or DVD player. Such clocks are nonetheless pure digital, but there is no big electronic difference between tuning to a quartz oscillator and tuning to the mains oscillation, and using no quartz element saves money. Dragons flight (talk) 02:10, 17 March 2015 (UTC)[reply]

Such clocks will tend to exist within a DC circuit, and so their use of the AC oscillations sounds dubious and v.more expensive than using a quartz oscillator. Colour me unpersuaded. --Tagishsimon (talk) 02:49, 17 March 2015 (UTC)[reply]

Without saying exactly how common such clocks are, here is a news story discussing concerns about US clock instability tied to fluctuating mains frequency [2]. Here is a spec sheet for a digital alarm clock IC that uses mains frequency to keep time [3]. In that case, you have to tell the IC whether it is plugged into 50 Hz source or 60 Hz source. Dragons flight (talk) 03:07, 17 March 2015 (UTC)[reply]

WP:OR: I used to spend a lot of time listening to mains hum. In fact, my user page has a photograph of me on a government grant to listen for it. The power spectrum of commerically-delivered AC electricity is surprisingly broad-band. Look at the frequency spectrum in our article on mains hum. Look at this "Low Frequency Sounds" presentation which includes real measurements and includes the concise but very applicable statement, "Amplitude, phase, and instantaneous frequency are highly variable." Anybody who sets their clock by the power line - on the mistaken belief that the power line 60Hz frequency is very stable or very accurate - has not been measuring the frequency-stability of their clocks or their power-lines. The frequency of the power varies because the power station dynamo is non-ideal; and the aggregate electrical load is non-ideal; and the transmission line is non-ideal. This problem gets worse with complex interconnected electrical grids. Even if the power station had elaborate control systems to ensure that their AC power came out at 60.0000000 Hz, dispersion from the imperfect transmission would cause that signal to broaden. Phase noise - which is mathematically equivalent to frequency instability - is a natural consequence of the constantly-varying load as consumers of electric power increase and decrease their usage.

You can measure this yourself: you can build a home-brew VLF receiver using widely available hobbyist parts and you can hook it up to a computer's audio card and you can analyze the frequency spectrum of the electric power delivered to your own house. If you see a perfect spectral peak and no harmonics, your home receives 60.00000000 Hz with perfect frequency stability. If you live on Earth, that is not what you will measure. Nimur (talk) 03:46, 17 March 2015 (UTC)[reply]

Not sure how relevant the mains hum phenomenon is, since the power spectrum of the induced sound is not the same as the power spectrum of the electric signal. Since you have research experience in the area, do you have any plot the latter handy. I'd be interested in knowing what the main-lobe width is (the harmonics are of course irrelevant to the accuracy of a properly designed electric clock). Abecedare (talk) 04:08, 17 March 2015 (UTC)[reply]

To be more clear: the "hum" is a radio emission, and directly corresponds to the power spectrum of the, um, power. It is called hum because that's exactly what it sounds like if you connect a radio receiver to a speaker. (If you play in a rock band and your guitar doesn't have a humbucker, your guitar is a radio receiver ... and so are the wire leads that go into your amplifier, and so you may also hear that humming called "power line hum"). In supplement to this RF hum, you might also actually hear acoustic hum from a high-power electrical line; that can be caused by many factors, including thermal expansion and electroacoustic coupling. This direct conversion of electric power to acoustic energy is a lot messier, because it's almost definitionally caused by a nonlinear effect.

There are loads of spectrograms from worldwide collections hosted on the Stanford Very Low Frequency Research website. Those are power spectrums of (mostly natural) radio phenomena, and power line hum is almost always visible... even when the site is in a very remote location. Nimur (talk) 04:18, 17 March 2015 (UTC)[reply]

(edit conflict) OK, found this real-time display of power-line frequencies at various locations in US. Simply eye-balling the numbers the instantaneous frequency seems to be vary about +/- 0.02Hz, which if sustained would result in an accumulated time error of about 30s in a day! However, according to this North American Energy Standards Board document utilities apply a frequency correction once these clock timing errors exceed ~10 seconds, so that such errors don't continually add up (Aside: Ironically, such frequency corrections, would broaden the main-lobe of the power spectrum of the electric signal, but yet result in reduced timing error!). Abecedare (talk) 04:27, 17 March 2015 (UTC)[reply]

Indeed. A cheap quartz oscillator in a digital watch might have a Q factor of 10⁷ which would be some million times more stable than the AC mains. If you're still interested in worldwide data, here's the new spectrogram archive. If you look for ELF broadband spectra, you'll see the 60Hz lines with enough resolution to gauge their bandwidth. Nimur (talk) 04:32, 17 March 2015 (UTC)[reply]

Yes, the active adjustments to control the long-term average are discussed some in utility frequency stability. Dragons flight (talk) 04:36, 17 March 2015 (UTC)[reply]

Without going into rigorous mathematical gymnastics, the key takeaway is that it doesn't matter if the frequency is stable "on average" when you're using it to drive a clock. That's mathematically equivalent to saying that the "dc" component of the ac frequency is perfect! We don't really care if it "averages out" to being correct! We care about its instantaneous accuracy and its maximal deviation - in other words, at any particular time during the day, is the clock correct? Precisely, how wide is the frequency spread? This is its q factor, or bandwidth. Nimur (talk) 04:45, 17 March 2015 (UTC)[reply]

Here's an example from the Netherlands [4] that shows that a clock tied to the mains frequency as measured at a home wall outlet making an error of -10 to +50 seconds compared to a true clock over 70 days of sampling. A similar test in the US [5], where the average frequency is more tightly regulated, found an error of -5 to +10 seconds over 45 days. Either tolerance is presumably fine for most home application where you don't care about a high level of precision. Dragons flight (talk) 05:11, 17 March 2015 (UTC)[reply]

And for completeness (although I realize we have drifted - ha!- away from the original query): Here is a fun paper measuring the accuracy of 4 (inexpensive) quartz watches, to be 0.07 to 0.6 seconds a day (ie, since its drift is bounded, a mains-clock in US can be expected to be more accurate than a quartz watch after running 0.5-5 months). Btw, the measurement methods/watch analyzer sections of the paper reminded me of the torque calibration scene from My Cousin Vinny. :-) Abecedare (talk) 05:31, 17 March 2015 (UTC)[reply]

Many thanks to everyone who took the time to research and answer my question. I was skeptical of the claim, and I haven't read anything to make me change my mind on that. Thanks again everyone BbBrock (talk) 12:44, 17 March 2015 (UTC)[reply]

Ahah. Don't drop this so quick. This calls for you to email this shopping catalogue (pro bono) for a fuller explanation. You can point out that as Wikipedia Ref Desk drew a blank, then they may have miscarried and confused the manufacturers advice. Thus, misinforming their shoppers. The may have a technical enquires department (PR departs understand nothing -don't waste your time with them). Email them with the WP link - >https://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Science#Electric_clocks< and ask... “explain!” They will no doubt pride themselves, on giving good information to their customers, so they should have no problem with sorting out what the manufacture meant. The manufacturer may be in a place where English is not their first language and so tech things can easily get garbled. The shopping catalogue will ( I hope) realize, that as consumers we have a right to know and any delay in replying will look bad on them .Post those replies, back here, on a new section please.--Aspro (talk) 20:37, 17 March 2015 (UTC)[reply]

Aspro, I think I will do just that. This wasn't in some cheap tat catalogue, but one for a national health charity which specialises in environmental equipment for their clientele, and does pride itself on its good advice. Whilst this "pro tip" obviously won't negatively impact on anyone's health, I'm sure they won't want unsubstantiated information in their catalogue. I'll let you know BbBrock (talk) 22:12, 17 March 2015 (UTC)[reply]

I still don't understand why anyone at all uses a clock with a cord. They are inaccurate, constantly prone to power outages that means they are unreliable, consume absurd amounts of energy, and are no cheaper than LCD clocks that can run well over five years on a single AA battery, which are capable of quite a loud alarm. The bizarre part is that it is harder to find the good clocks than the insane ones at the market, a pathology of commerce I cannot understand. Wnt (talk) 03:28, 18 March 2015 (UTC)[reply]

It may be a clock for people that suffer from seasonal affective disorder in which case it may well have a 20 watt incandescent bulb. An AA battery is just not a solution for all clock applications.--Aspro (talk) 17:19, 18 March 2015 (UTC)[reply]

March 17

Gender detection via pulse checking

In the Korean drama Sungkyunkwan Scandal, there is one scene (albeit dreamed up & not part of the actual plot) where the female main character, while disguised as a male, faked an illness in order to avoid following the monarch's orders, which caused the monarch to summon a doctor; the doctor then checked "his" pulse near the wrist and immediately realized that "he" was female. Is this realistic in real life - in other words, are trained traditional Asian medical practitioners really able to detect a patient's true gender simply by checking their pulse without taking off the patient's clothing? 98.116.73.98 (talk) 05:26, 17 March 2015 (UTC)[reply]

No. Or I highly doubt it in any case. But someone familiar with anatomy might see other subtle clues from which they could fairly reliably guess the gender: How hairy their arms are, whether they have an adam's apple, the length and shape of fingers, etc. Alone, those things fall within a range, where a female with above average hairy arms would have hairier arms than a male with below average hairy arms, but taken together, barring "outliers" like very effeminate males, I think a doctor probably could tell an average female trying to disguise themselves as a male just by looking at them fully clothed. Vespine (talk) 05:42, 17 March 2015 (UTC)[reply]

As seen in this doc an average 18 yo female has a resting heart rate almost 10 beats/min higher than a male of the same age. This, combined with the factors Vespine mentioned, would at least allow one to guess the gender of the patient, although the test's error rate will be pretty high (esp. considering that the doctor was measuring the pulse of a supposedly ill person, which would provide an alternate explanation for the presumably higher heart rate). Abecedare (talk) 05:48, 17 March 2015 (UTC)[reply]

Fitness has even more effect on resting heart rate. This page (granted not as "scientific as the above) has the male vs female difference not as high, it says average 18 year old male is 70-73 and average female is 74-78, a "below average" male is 74-81 and an above average female is 70-73, and "above average" isn't a "great" difference, there are then still: good, excellent and "athelete" categories which are even lower for females. Vespine (talk) 23:25, 17 March 2015 (UTC)[reply]

It also depends on the fitness level expected of the male and female elite. The males may be expected to have martial prowess, whereas females might be trained in more sedate activities. LongHairedFop (talk) 14:39, 18 March 2015 (UTC)[reply]

Frostbite

I was just looking at Facebook and noticed that someone was asking about what sort of lotion or cream was good for frostbite. They got replies such as Aveeno, Vaseline, Nivea cream, Penaten and make a hole in a Vitamin E capsule and pour it on the affected area. I looked on Google but very few of those seem reliable. This seems OK and says don't put any on it. I also thought that the University of Maryland Medical Center would have been OK until I saw the "Complementary and Alternative Therapies" and then realised that it was part of their Complementary and Alternative Medicine Guide. What I am wondering is if any of the things mentioned on the FB would be of any use? I've had frostbite several times on my face in the last 40 years but I've never actually put anything on it. The only reason I could think to do would be after several days, when the dead skin had dried up and was peeling. By the way this is not a request for medical advice. It's just curiosity and I have no intention of telling them what they should be doing. Also I just noticed the Maryland link says that depression will put you at risk for frostbite, why though? CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 09:59, 17 March 2015 (UTC)[reply]

The more serious versions would require medical treatment, but the least serious result of exposure to cold might just be drying and cracking of the skin, which can be treated with a moisturizer. A thick moisturizer, like Vaseline or Bag Balm, would require fewer applications.

As for depression, if the person isn't in a mood to do much of anything, then doing the things it takes to prevent frostbite might fall into that category. StuRat (talk) 11:07, 17 March 2015 (UTC)[reply]

True frostbite is were the skin/muscle has been frozen long enough for it cells to die (as opposed to getting a few little white points of skin through carelessly handling dry ice etc.). If the cells are dead then there is no point in applying anything to make it better. However, a prophylactic treatment to prevent complications like a bacterial infection setting in may be in order – especially if it is serious. Applied creams may stop the dead stuff desiccating and leave one with the equivalent of Petri dish on your face, feet or wherever -ugh! Most of are alive today because even peeling skin still acts a a good bacterial barrier. In addition to StuRat comment about depression, exhaustion can also lead to periods of self-neglect too. So the OP could do well to ask his medical practitioner on how to treat frostbit in all its degrees, because this is often one of those injuries, where when it happens there is not doctor around for miles and miles. We don't give medical advice here but he can ask his GP if it is a good idea to carry around something like Dettol.--Aspro (talk) 14:28, 17 March 2015 (UTC)[reply]

Thanks. I don't really need to see a doctor as the main thing is to not get frostbitten at all. Over the years I've frozen my ears, nose and cheeks several times. It can be quite painful as they thaw out. Nowadays I'm usually more careful. I've also frozen my fingers a few times and that's caused nerve damage. It was just that I'd never really seen anyone wanting to put anything on it. Of course there is always the possibility of gangrene which will require a doctor. Oh yes Dettol isn't available here plus it would probably freeze unless carried on you rather than in your grub box. CambridgeBayWeather (mobile) (talk) 21:52, 17 March 2015 (UTC)[reply]

Measuring g with a pendulum

It's clearly easy enough to measure $g$ with a pendulum as the frequency depends on the length of the pendulum and $g$ . My question: why bother doing it for different pendulum lengths? Why not just use one length? I'm helping someone with a report on this very point, but I don't see any merit in using different lengths of pendulum.--Leon (talk) 13:19, 17 March 2015 (UTC)[reply]

The problem is which length does everybody agree should be the standard length. In other words: does one decide upon a yard, meter or a length that give a period in seconds. And how did one accurately define a second before the acceptance of the caesium standard anyhow(?) since the speed of the Earths rotation changes whereas the yard and meter should not (in an ideal world). Having said that however, by using pendulums of a different length it proves the theory that pendulums can agree on a reliable and repeatable way to measuring

g

. --Aspro (talk) 13:52, 17 March 2015 (UTC)[reply]

Second#History explains a bit about how seconds were measured prior to the 1997 adoption of the caesium standard. (Also has some good info and links related to the OP's question) Short answer - first subdivision of days, then non-pendulum clocks, then pendulum clocks. I've heard that one's own heart rate/pulse was often used by researches in the Age of Reason - Huygens was contemporary, but his clocks probably had low market penetration for the first few decades. SemanticMantis (talk) 14:34, 17 March 2015 (UTC)[reply]

Also, did the OP google Wikipedia pendulum length first? That has more info too...Pendulum#Standard_of_length. --Aspro (talk) 14:50, 17 March 2015 (UTC)[reply]

Well, the other reason for doing multiple pendulum lengths is in good experimental design. How does one know that the relationship between frequency and length is linear? You'd need multiple data points to determine that. --Jayron 32 14:57, 17 March 2015 (UTC)[reply]

reincarnation

Hello, now, is there someone who reincarnates? 雞雞 (talk) 14:17, 17 March 2015 (UTC)[reply]

Reincarnation will tell you you a decent amount about the topic. SemanticMantis (talk) 14:35, 17 March 2015 (UTC)[reply]

It may be worth considering that while reincarnation with paranormal recall of events from specific past lives is an unscientific idea, I am not aware of any scientific argument to distinguish the qualia experienced by one individual from those experienced by another. For example, there is no scientific determination of whether a person who has the corpus callosum cut has "two souls" or one; nor whether the bridging of the gap between brains via other nerves in conjoined twins or via some other means would make them "the same person" or not. Science can measure only the ability to communicate and recall information, which is a distinct ability since of course we all may fail to recall even what "we ourselves" have seen. Wnt (talk) 03:35, 18 March 2015 (UTC)[reply]

How much tar does the food contain?

How much tar does 1 cup of black tea drink contain? How much tar does 1 cup of coffee contain? How much tar does 1 cup of milk contain? How much tar does 100 grams of meat contain? How much tar does 1 medium egg contain? How much tar do the vegetables contain? How much tar do the fruits contain? — Preceding unsigned comment added by 88.235.209.56 (talk) 15:36, 17 March 2015 (UTC)[reply]

How do you know any of these items contain tar? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:02, 17 March 2015 (UTC)[reply]

As our article on tar explains, it is a mixture of hydrocarbons and carbon produced by heating certain types of plant matter. Untreated plants don't contain tar. In cigarettes the tar is produced by the process of smoking it. Looie496 (talk) 17:03, 17 March 2015 (UTC)[reply]

So it's at least conceivable coffee might have trace amounts of tar, since the roasting of beans could achieve some destructive distillation to make tar compounds. Other things that people commonly eat that might have tar: maybe molasses or soy sauce? What about roasted vegetables? Couldn't they have traces of carbon/hydrocarbons brought out by heat? I don't know enough food science/chemistry to understand if enough pyrolysis occurs during processing to make tar in those foods, but it seems reasonable... this [6] is not terribly reliable, but it does claim that coffee, roasted grains, and some roasted vegetables can contain tar. SemanticMantis (talk) 18:21, 17 March 2015 (UTC)[reply]

I had the exact same thought about coffee potentially containing tar due to the roasting process, but searching around I didn't find any source that says that this is an actual concern. According to Cofee:Physiology (page 351), while coffee heated to 350°C was shown, back in 1938, to produce "coffee tar" containing harmful 3,4-benzpyrene, regular coffee roasting doesn't go beyond 200-220°C and the 1938 experiment is thus, "of interest from a historical and academic perspective view [sic?], but has no practical validity". The chapter has much more details on later experiments, with the bottom line being that brewed coffee has 3,4-benzpyrene conc. of < 1 ng/kg, which is not considered undue. For comparison, an average person ingests 250 ng of benzpyrene per day, mainly through oils, fats, and cereal ie equivalent of 2000+ cups of coffee!.

Side note: the work linked previously, which SemanticMantis also tags as "not terribly reliable", is by Herbert M. Shelton and is particularly untrustworthy. Abecedare (talk) 17:41, 18 March 2015 (UTC)[reply]

Skin disinfection prior to needle insertion

When my blood was sampled recently, the nurse did not disinfect the skin first as I recall being done when I was much younger. I'm pretty sure this has happened before in the recent past as well. Has this disinfection step (using an alcohol wipe in the past, IIRC) been done away with at some point? Country of residence is the United Kingdom. --92.6.114.195 (talk) 17:56, 17 March 2015 (UTC)[reply]

I take it you understand if you have specific concerns about your treatment, you should contact your health care professional or other relevant contact point. In terms of general recommendations in the UK, this vaccine green book on the UK government website recommends that visible dirty skin be cleaned with soap and water, but that it's otherwise not necessary to clean the skin [7]. This patient.co.uk guideline [8] specifically recommends against using alcohol swabs, or really any swabs, although one of the reasons isn't relevant for non vaccines. This [9] suggests the actual policy depends on the specific NHS Trust. While these all relate to injections, I'm not sure it's any different for blood samples. For example, not an RS but [10] includes comments relating to the UK where it's suggested cleaning of some sort may be recommended in for cannulation (although I'm not sure there's even agreement on that) or for glucose tests, but not for general simple in and out needle insertions. Nil Einne (talk) 19:09, 17 March 2015 (UTC)[reply]

If someone failed to swab my skin before bringing the needle forward, I would get up and leave. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:53, 17 March 2015 (UTC)[reply]

And what is your evidence source that cleansing is necessary Bugs. Richard Avery (talk) 08:10, 18 March 2015 (UTC)[reply]

Common sense. Better safe than sorry. And standard practice in American medicine. You can't know what microbes might be lurking on your skin, eager to enter an open wound. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:19, 18 March 2015 (UTC)[reply]

Apparently, it's not that obvious whether to swab or not to swab. "Both disinfection prior to skin injections and omission of disinfection were followed by (almost) no infections" in [11]. The Straight Dope provides a further rationale for swabbing, explaining why previously to lethal injection the arm still gets swabbed: "Apart from its usefulness as an antiseptic, alcohol causes blood vessels to rise to the surface, making it easier to insert the needle. More important, there's a chance the prisoner's sentence might be delayed or commuted at the last minute." [12] --Noopolo (talk) 13:07, 18 March 2015 (UTC)[reply]

I take an injection of Gila monster-venom once weekly. The nurse who told me how to inject it told me to wipe the injection spot off with alcohol, then to wipe off the alcohol so the injection doesn't sting as much! I think the main concern is probably with things like Staphylococcus aureus which are very common on the skin and in the mucosa, but which wreak havoc if they reach the bloodstream. μηδείς (talk) 18:09, 18 March 2015 (UTC)[reply]

Soul and neuron action potentials -- A follow-up

In regards to the recently archived thread on Soul and neuron action potentials begun by Brandmeister, in the headlines today was an article summarizing a report in Cell: "Even worms have free will. If offered a delicious smell, for example, a roundworm will usually stop its wandering to investigate the source, but sometimes it won’t. Just as with humans, the same stimulus does not always provoke the same response, even from the same individual."

From Cell: "We found that the collective state of the three neurons at the exact moment an odor arrives determines the likelihood that the worm will move toward the smell. So, in essence, what the worm is thinking about at the time determines how it responds.... It goes to show that nervous systems aren't passively waiting for signals from outside, they have their own internal patterns of activity that are as important as any external signal when it comes to generating a behavior."

μηδείς (talk) 20:06, 17 March 2015 (UTC)[reply]

What's the question? Vespine (talk) 23:17, 17 March 2015 (UTC)[reply]

Read the entire header beyond the first five words and the first sentence, including the link. I have emphasized them for your ease. μηδείς (talk) 00:44, 18 March 2015 (UTC)[reply]

There was no question, or indeed a point. The quoted has nothing to do with the fictional concept of a 'soul' 131.251.254.154 (talk) 13:22, 18 March 2015 (UTC)[reply]

I am not about to quote the entire past thread or to modify the archives. The OP asked how neurons could act spontaneously, rather than being governed solely by their inputs from other cells. If you are not interested, fine, you don't need to comment. But If you are interested, just reading the headlines won't help, go back and read the thread that was archived on the 15th. μηδείς (talk) 17:57, 18 March 2015 (UTC)[reply]

Studying souls in worms sounds like a job for a Jainist. If I program a robot to turn toward the smell of gasoline 70% of the time, does that mean it has a soul? Free will is, like qualia, like the soul in general, a paranormal phenomenon. You cannot measure whether someone has free will. No matter whether random or deterministic, mechanical systems do not create free will. IMHO (and no other, to my knowledge, and despite/because of the paradox implied) the capacity for free will, like other paranormal phenomena, depends on precognition of the fixed and unchangeable future. Wnt (talk) 14:19, 18 March 2015 (UTC)[reply]

I have no interest in arguing this, ("soul" was the OP's word, not mine) but animals do have volition, the ability to act without or despite external stimuli. That's why Buridan's ass doesn't starve. That's what the worm article is about. (The use of "free will" is a little bit sloppy from a philosophical standpoint.) And calling it "free" will is simply the recognition that we hold healthy adults responsible for their uncoerced volitional actions. Volition is a biological phenomenon, free will is a moral and legal concept. Neither has to do with metaphysics. μηδείς (talk) 17:57, 18 March 2015 (UTC)[reply]

The worm has no free will. Higher animals do. Free will, it is when a living creature creates a sequence of images, models in his mind/brain with a few possible outcomes and chooses one of them depending on circumstances. And still there are situations when the brain snaps and takes a route that according to calculations was not optimal. All decisions including primitive ones in the worm nervous system with three neurons are done on quantum level and quantum operations have intrinsic property to be unpredictable. This unpredictability may be low and the chance that the worm will turn away from the food source/smell may be very small but such things do happen. --AboutFace 22 (talk) 23:22, 18 March 2015 (UTC)[reply]

Free will was the term used by the reporter analyzing the actual paper in my link. The paper says, "in essence" the action is determined by what the worm is "thinking about". The Caenorhabditis elegans brain has some 302 neurons and 7000 synapses, but is the nonlinear (my word) interaction of these three neurons which determines whether the animal will veer towards the smell of isoamyl alcohol.

I agree with your point that speaking of free will is at best metaphorical on this level, but again, mere volition and the uncoerced morally responsible choice of experienced adults are two different things. The worm does indeed have a rudimentary form of volition. I agree quantum mechanics has its effects, but even if we just treat this system classically, it will develop chaotic behavior. But I think it's only the dualist notion of the mind-body dichotomy that makes us attempt to attribute free will to mysterious forces. μηδείς (talk) 00:39, 19 March 2015 (UTC)[reply]

The totality of all living tissues is inanimate in the same way as individual organs and tissues are, like neurons or blood vessels. If you had all organs and tissues assembled together to form that roundworm (or any other organism), it still wouldn't live. The nervous system which controls movements in most animals is also inanimate, which implies the existence of an external input to produce volition signals for it. In that sense, the organism acts rather as a medium for processing such volition neuron potentials, not as their origin. Brandmeister^talk 10:15, 19 March 2015 (UTC)[reply]

That's simply not true. All cells are alive until they senesce. There is no point at which the egg and sperm, fertilized egg, fetus, child or adult is an inanimate lump of dead flesh, although some outer layers like skin and hair are composed of once-living but now dead cells. See cell theory. I despair of trying to teach you biology 101 on line, but I posted this link to show you that the internal states of cells are just as important as externally generated action potentials. You seem to be channeling Aquinas and his idea that ensoulment begins with quickening (i.e., that the baby first kicks once it gets a soul). That might be relevant in a debate on abortion, but at no point is there an animated thing which becomes animated. μηδείς (talk) 17:16, 19 March 2015 (UTC)[reply]

The cells are alive as long as they are supplied with energy. You can isolate one cell, but it will live as long as you take care of it. Even non-cellular life in the form of viruses requires a more complex host to thrive. A single cell isn't the same as the simplest living being. In most animals the sustainability of cells requires neuron potentials which trigger the necessary movements for energy resupply (feeding and drinking). As you know, humans and some other animals can voluntarily starve themselves to death (hunger strikes, etc), ignoring related internal stimuli and as such not producing the required neuron potentials. Where do such volitions come from? Obviously, not from cells, despite being mediated by them. Brandmeister^talk 20:04, 19 March 2015 (UTC)[reply]

You seem to be taking a snapshot in time, ignoring the past and the context, and providing borderline cases. Yes, someone can choose to self-immolate or starve. But they have to get to that point due to prior experiences and choices. A woman I use to know by the name "Cat" used to say, between stimulus and response lies choice. In any case, the heart begins to beat spontaneously, and the entire development of an embryo is effected by the migration of cells and their electrochemical interactions. There is never any point at which the body is dead, and a soul is needed as a Re-Animator. μηδείς (talk) 05:31, 20 March 2015 (UTC)[reply]

Yes, but the point is that who or what makes the choice? During a knee reflex, for instance, your organism makes the choice, not you. During a hunger strike, for instance, you make the choice, not your organism. In other words, a healthy person can distinguish between the neuron potentials triggered by his/her organism and the neuron potentials triggered directly by him/her (an external input, not coming from the organism itself). Brandmeister^talk 11:06, 20 March 2015 (UTC)[reply]

Labia Human only?

The Wikipedia article on the Labia seems to make the presumption that this anatomical feature is only something that occurs in humans, is this correct?Naraht (talk) 20:14, 17 March 2015 (UTC)[reply]

I suspect the (fallible) contributors to the article unconsciously assumed that no-one would be interested in nonhuman labia. I'm not going to web-search this topic on a work computer, and being still at work can't check the authors and title of a book I have at home, but it's a detailed and scholarly work about Orangutans, which includes photos of genitalia, so I can give you only an an unreferenced assurance that, yes, they at least do have them (if female). Perhaps someone else can contribute online references. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 20:24, 17 March 2015 (UTC)[reply]

WP:SOFIXIT. If Wikipedia is missing some knowledge, and that is something that bothers you, you're not only allowed, but politely requested, to fix the problem. --Jayron 32 20:34, 17 March 2015 (UTC)[reply]

If I had the information I would do so, however I asked here because I don't have the information.Naraht (talk) 20:51, 17 March 2015 (UTC)[reply]

If you don't have an answer Jayron, why reply? If the OP knew the answer, they would probably have added it already. They don't, so they very reasonably ask here. Naraht, although vaginal anatomy varies between species, most mammals have a labia-like structure. As for the human bias in the article, this is disappointingly common, almost all anatomical and biochemical articles are almost exclusively human focussed. I would be a mammoth task to bring some balance to them. Fgf10 (talk) 07:37, 18 March 2015 (UTC)[reply]

Of course, you're correct with that. I apologize sincerely to the OP and to any other readers for my uncalled for rudeness. It is unacceptable, and you all deserved better. --Jayron 32 12:47, 18 March 2015 (UTC)[reply]

Development of the labia is deeply intertwined with development of the scrotum and glans penis, since these are dual-use tissue progenitors. I know for example spotted hyena have labia and have a surprisingly male-like development, essentially a female scrotum and penis (which of course is not the case in related species). So the structure's evolution goes pretty far back, but right now I'm drawing a blank on exactly when. Wnt (talk) 03:21, 18 March 2015 (UTC)[reply]

March 18

wilmshurst machine application!

i want to make generator by using wilmshurst machine. Wlimshurst machine uses the static energy but we don't know how to storage the static electrocity. I know the leyden jar but is there anything I can alternate? And Wilmshurst makes the high voltage and little current, but I want to boost the current so I can use for any charger. Please help me — Preceding unsigned comment added by 1.211.74.81 (talk) 02:55, 18 March 2015 (UTC)[reply]

What's a Wilmshurst machine? --Jayron 32 03:35, 18 March 2015 (UTC)[reply]

Wimshurst machine. The rest of the question is non trivial. I suspect you could charge a capacitor which you could then discharge into something else, that would be far from "easy", you could just use a dynamo to do the same thing but much simpler. I understand if the "challange" of it is to use a wilmshurst machine instead, but if no one else has done it before you (cursory google search doesn't show anything obvious), you have some real "figuring it out" ahead of you. Vespine (talk) 03:56, 18 March 2015 (UTC)[reply]

Polar Clock - article needed

I came across some fancy android app about Polar Clock. It’s a clock with concentric circles which shows second, minute, hour, date and month. See this Google images search result for better understanding of what I mean. Seems that there are also wrist watches based on this. Searching for it in Wikipedia I came across something of same name at http://en.wikipedia.org/wiki/Charles_Wheatstone#Measuring_time. I am not sure if both of these are same, or are based on similar principles. Maybe Wikipedia should have an article on both of these. 14.141.141.26 (talk) 06:41, 18 March 2015 (UTC)[reply]

Sphere spin problem

Suppose I drop a rough but perfectly rigid sphere on a rough horizontal plane and the sphere is spinning about a vertical axis. If it is rotating clockwise when viewed from above, does it spin clockwise or anticlockwise after the bounce? I can imagine it doing either. Is there a rotational equivalent of Newton's experimental law of restitution? Thanks, Robinh (talk) 07:28, 18 March 2015 (UTC)[reply]

The bounce affects only the linear motion, so the rotation will not, in an ideal bounce, be affected at all. In practice, there will be some deformation, and therefore a small torque about the spin axis during the time in contact, so there will be a slight slowing of the spin.

The rotational equivalent of a "bounce" would be the situation where opposite projections on the sphere come into contact with rigid stops. In theory, given perfect elasticity between the projections and the stops, the resulting couple will reverse the direction of spin. This perfect reversal would be difficult to achieve in practice, and a couple of springs at the stops would probably be better at absorbing the rotational energy and reversing it, just as in the case of the vertical bounce. Newton's law of restitution applies to the forces at the stops (equal and opposite), and hence to the rotational motion. Dbfirs 08:30, 18 March 2015 (UTC)[reply]

(OP) thanks Dbfirs. I've just tried it with a football and depending on the details of the surface (carpet, grass, concrete) the spin can be zero, clockwise, or anticlockwise. So the answer is "it depends", I guess. So I'm going to need a coefficient to describe this. Best wishes, Robinh (talk) 21:47, 18 March 2015 (UTC)[reply]

Yes, you can get some very interesting effects with a football which is far from the rigid sphere that you specified. I'd be surprised if you can reverse a fast spin with a bounce because I can't see where a large couple could be produced, but certainly carpet and grass can produce non-symmetrical forces during the deformation of the football as it bounces. No simple coefficient can describe the rotational changes because they depend on irregularities in the surface. Of course, if the football has some forward motion as it bounces, then forward spin and back spin and side spin will affect how it rebounds because of the extra frictional forces as it deforms. Dbfirs 22:15, 18 March 2015 (UTC)[reply]

Reminder: if you're going to talk about footballs, please clarify which sport is called football where you live. The shapes are rather different. --65.94.50.15 (talk) 03:33, 19 March 2015 (UTC)[reply]

I think we were both assuming the round-ball game here, but the shapes used for Rugby football and American football behave even more strangely when bounced.

(thanks!) agreed, except for the bit about "no simple coefficient". Sure, it might not be possible to get anything exact, but I don't see why something along the lines of equations 1 and 2 of http://arxiv.org/pdf/cond-mat/9708093v3.pdf , but specific to the relative angular velocities of the surfaces at the contact point couldn't be useful as an approximation. I guess I was asking whether there is a name for such a coefficient. Best wishes, Robinh (talk) 23:14, 18 March 2015 (UTC)[reply]

Yes, the coefficient of tangential friction determines the tangential force that has a moment about the centre of mass of the sphere, and this moment (integrated over the time of contact) determines the change in angular momentum of the sphere. This applies to your football with a forward motion, or to two colliding footballs, but not to your original perfectly rigid sphere since, in that idealised case, no force has a moment about the spin axis. Dbfirs 00:18, 19 March 2015 (UTC)[reply]

OTOH a perfectly rigid sphere wouldn't bounce on a perfectly rigid plane either. Maybe it would shatter. I guess "perfectly rigid" isn't quite as, er, rigid an assumption as we might like! Robinh (talk) 00:53, 19 March 2015 (UTC)[reply]

water displacement ballast propereties

How fast will an object rise in water if it displaces more water than its weight. Also does the speed accelerate if it displace 10 time its weight. object is 55 gallon drum with tapered nose. it is released from 100 ft. below the surface. The water is salt water common in any ocean. Also what is the terminal velocity? — Preceding unsigned comment added by 71.10.122.228 (talk) 02:11, 20 March 2015 (UTC) Please give answer in feet per second. — Preceding unsigned comment added by 71.10.122.228 (talk) 09:00, 18 March 2015 (UTC)[reply]

The speed will accelerate, self-evidently, as the object is released under water from zero speed, and if it is then moving, it had to accelerate to get there. It will accelerate until it reaches terminal velocity in the water, or until it reaches neutral buoyancy, whichever is first. It's speed at any given point in time cannot be determined by a single number from the information you've given, but will depend on a number of factors, including the depth the object is released from, the density of the object in question, its shape, the drag it creates in the water, etc. You've not given nearly enough information to even start to solve the problem. this page discusses some of the complexity and gives you the equations necessary to make the calculations you want to make. --Jayron 32 12:42, 18 March 2015 (UTC)[reply]

Agreed. Also note that it's not as simple as the object accelerating at a constant speed until it reaches terminal velocity in water. The density of water varies at different depths, so the drag will vary with that as well as with the speed. And, once the surface of the water is breached, the buoyancy will change as the object rises, and thus displaces less water. If it leaves the water completely, then it would presumably slow and drop back down to the surface, unless the object is also lighter than air. StuRat (talk) 04:49, 19 March 2015 (UTC)[reply]

Physical representation of a memorized image

Was there any research about the possibility of physical representation (either via displaying on screen or even by printing) of a memorized image through head-attached electrodes or some other mediating device? AFAIK, current devices are able to at least pinpoint an area in the brain working when a particular memory is recalled (and the majority of people can retain a photographic memorized visualization of a given image). Brandmeister^talk 10:03, 18 March 2015 (UTC)[reply]

Have a look at this for example [13]. With better training for the person and using a larger part of the brain it might be possible to get something better, but for instance for me if the image isn't just purely visual you might get 3D or some other kind of relationship structure without a viewpoint though it would be interesting to automatically turn it into a 2D picture with colors for feelings for instance. Dmcq (talk) 11:56, 18 March 2015 (UTC)[reply]

That's interesting, but not really a memorized image. Rather, that's the brain processing an incoming image. Images really aren't stored as bitmaps in the brain, but more as concepts. For example, if there was a person sitting in a chair, the "person" and "chair" concepts would be stored, with some attributes stored for each like the age, gender, and other descriptions of the person, or the name, if known, and the type of chair. Other info stored in a pic would be lost, like the position of freckles on the person's face, unless that was somehow significant (if they had a particularly large freckle, for example). And some random writing in the background might not be stored either, again unless significant. StuRat (talk) 05:00, 19 March 2015 (UTC)[reply]

Condom protection against hiv

Why are condoms only 85 percent effective at preventing hiv/AIDS when used consistently and correctly if it's almost impossible for the virus to pass through a condom? — Preceding unsigned comment added by Roger adams49 (talk • contribs) 10:41, 18 March 2015 (UTC)[reply]

Who says they are? ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:20, 18 March 2015 (UTC)[reply]

Well, our own article says that, for one. And the source for that comment verifies it. Dismas|^(talk) 11:42, 18 March 2015 (UTC)[reply]

Our article did but I removed it. I can't see where the source supports the claim, perhaps provide a quote? It mentions correct and consistent usage in several places in relation to other STIs and in general, but only mentions consistent usage for HIV. Nil Einne (talk) 12:05, 18 March 2015 (UTC)[reply]

It's at the top of page 14. Dismas|^(talk) 12:08, 18 March 2015 (UTC)[reply]

Where? That only mentions "Condom usage was classified into the following three categories: always (100% use), sometimes, and never" and "Among participants who reported always using condoms" and "consistent condom use decreased". As I said, I don't see anywhere correct usage is mentioned in the HIV section. Only consistent usage. Correct and consistent is mentioned in a few other places, but not in relation to HIV. Our article mentioned corrrect and consistent until I removed it [14], as did the OP, but I can't see where the source supports the claim of correct usage. Nil Einne (talk) 12:11, 18 March 2015 (UTC)[reply]

(EC) I take it you are referring to our condom article? If so, the claim the 85% was referring to correct and consistent usage wasn't actually in the source as far as I can tell, so I removed it [15].

Other sources also don't mention correct usage e.g. [16] says condoms "provide protection of about 80 to 85% against HIV" with 100% consistent usage. But it also makes clear it's not talking about perfect use, it includes usual rates of breakage, slippage etc.

Note that the wording in the second source is perhaps a litte confusing unless you read the later clarification "In other words for every 100 cases of HIV infection that would happen without condom use, about 15 (range: seven to 24) would happen when condoms are used consistently." Our article which I presume you read says the same thing but in less words. The 85% is the reduction compared to no condom usage.

The seroconversion rate is "0.9 per 100 person-years with condom". This [17] gives "1.14 per 100 person-years". In either case, this seems to be referring to cases involving "discordant couples (i.e. couples in which one of the partners is HIV-positive and the other free from HIV)". That source also provides a few reasons why the 85% or actually 80% for their case reduction compared to no condom usage may not be entirely correct.

BTW, once again may I suggest you read the sources in our article if you are confused about the details? Also if you do have to ask here, do link to whatever you referring to so people know what it is.

Nil Einne (talk) 12:04, 18 March 2015 (UTC)[reply]

BTW, I'm not entirely certain how correct usage is defined (I have an idea but lazy to confirm it). However I suspect correct usage doesn't prevent breakage and slippage. In fact the NIH report also includes several mentions of "correct use without breakage or slippage", which I take to mean the without bit is in addition. (These are generally mentioned when the authors are trying to explain for certain STIs this still won't prevent some transmission since unprotected areas of skin will also transmit the STI.) Nil Einne (talk) 12:32, 18 March 2015 (UTC)[reply]

Why do young birds reach full size quicker than mammals?

It's not always the case, but it seems that a lot of birds tend to be roughly the same size and shape as their parents by the time they are able to safely leave the nest, although they may still behave like 'babies' and be dependent on their parents for months (even years in the case of parrots) afterwards. Mammals, OTOH seem to have pronounced 'childhoods', where they're clearly much smaller and of a different body shape to their parents. Why does this happen? --Kurt Shaped Box (talk) 13:48, 18 March 2015 (UTC)[reply]

Very good question. As you acknowledge, quick maturation of birds is not a general rule, but it does seem to be a trend. Consider that a mouse will be roughly full size and reach sexual maturity in a few months max [18]. Consider that an ostrich only weighs about 100 lbs after their first year, and can take up to 3 years to reach maturity in captivity [19].

The general topic here is known as Life history theory in evolution/ecology. Several factors will affect a species' life history traits. If you have a lot of babies, you can't invest much time in caring for each one, and many will die. If you have only a few babies, the will get more resources from parents, but the total fecundity is lower. This is known as a "tradeoff", and when specifically thinking in terms of clutch size, this is known as r-k selection.

Age to maturity is not the same as clutch size, but there are similar tradeoffs. Also age to maturity is not the same age to max weight, but for many species they are closely related. Here's a paper that discusses how predators can affect age to maturity in prey [20], and here's one that relates age to maturity to life span [21].

As you know, some birds are very long lived, and they have a lot of variety in clutch sizes as well. The one fairly general pressure on flighted birds is that non-flying juveniles are extremely vulnerable, so that puts a strong selective pressure on fledging as fast as possible. That part is the basic intuition, but I can't easily find a ref that clearly states that. Here's a paper that discusses body size and time to maturity (from viruses to whales!) [22]. If we think only about flying birds, then they have strong restrictions on max weight, and that will also lead to faster times to maturity.

Here's a study of how time of fledging and weight at fledging affect one bird species [23], and here is a more general survey of growth rates in birds [24], which says "It is concluded that most species grow at some physiologically maximum rate."

So, this question taps in to a large amount of evolutionary theory, and you can get lost down that rabbit hole, but the basic idea I think comes down to the fact that no bird can hatch ready to fly, but some mammals can pop out ready for running and pronking - [25] (~4:30 or so for the good part). Hope that helps, SemanticMantis (talk) 14:18, 18 March 2015 (UTC)[reply]

(nb. many of the scientific articles I linked are behind paywalls, if anyone would like a copy for WP purpose they can contact me or ask at WP:REX SemanticMantis (talk) 14:25, 18 March 2015 (UTC))[reply]

Note that juvenile birds often appear larger than their parents, for a couple reasons, both ultimately due to them not flying yet:

1) Since they don't fly yet, they can pack on the pounds, which would be a disadvantage when flying, but a distinct advantage when just staying in the nest.

2) They can also have juvenile feathers, not designed for flight, but rather to keep them warm. Instead of the slick flight feathers, these juvenile feathers tend to be rather fluffy, and hence make them look bigger than they are. StuRat (talk) 17:28, 18 March 2015 (UTC)[reply]

The needs of flight and migration are crucial. Waterfowl have huge clutches due to their very high infant mortality, with small chicks leaving the nest upon hatching. There's a minimum muscle mass necessary for flight, and it is an advantage to reach that quickly. Also, birds that migrate seasonally simply have no choice but to reach adult mass before the advent of the first migration. See also altricial versus precocial species. μηδείς (talk) 17:44, 18 March 2015 (UTC)[reply]

"Huge" ? Isn't it around a half dozen ? StuRat (talk) 05:02, 19 March 2015 (UTC):[reply]

No. Merely checking the most obvious example that sprang to mind, Mallard, one finds "The clutch is 8–13 eggs", which from my half-remembered ornithological interests in former years I recall as being fairly typical for British ducks. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 14:28, 19 March 2015 (UTC)[reply]

Yep, and wood duck can go up to 16 eggs per clutch [26]. Of course "Huge" is very relative - both those ducks have small clutches compared to the mola mola, which can release ~ 300 million eggs at once. Further illustrations of r-k selection :) SemanticMantis (talk) 14:59, 19 March 2015 (UTC)[reply]

Thanks for all the answers so far, folks. I have just been thinking today - does anyone know of a flying bird species that is fully capable of flight before it reaches adult size/shape (ornamental plumage excluded)? Because I don't. AFAIK, you never see young birds that're something like 2/3 the size of their parents on the wing, despite what cartoons may tell us. --Kurt Shaped Box (talk) 16:30, 19 March 2015 (UTC)[reply]

I make no apologies for the use of the word huge! Lol. The "fowl" or Galloanserae (relatives of the chickens, ducks, and their ancient, separate lineage) are characterized by large clutches and precocial chicks. They don't feed their offspring, the offspring imprint on the mother, and follow her on the day they are born to begin feeding at a location she leads them to. The Neoaves which includes all birds that are not ratites (like the Ostrich and Kiwi) and are not land or water fowl tend to have much smaller clutches, songbirds often have four, and raptors and seabirds one or two, the second often not surviving. But the birds are fed in the nest until they grow large enough to fly and fend for themselves. μηδείς (talk) 17:06, 19 March 2015 (UTC)[reply]

In a bird context, I think it's fair to say 16 eggs is a huge clutch. Most waterfowl will indeed have larger clutches than e.g. passerines, for the reasons you mentioned. I looked around a bit, and couldn't find any other wild bird with a larger clutch size than the wood duck (domestic fowl are another matter entirely). SemanticMantis (talk) 18:10, 19 March 2015 (UTC)[reply]

This book chapter has a table of fledging times for grassland birds (Table 4.3 [27]), they range from 8.7 to 10 day means. Now that doesn't really tell us what you want to know, which is "percent of adult weight (or volume, length etc.) at time of fledging" - but it does make you wonder if a sparrow can really reach e.g. 90% max weight after just 8 days. I think you're right that in general most birds will reach a large percentage of their adult weight before they can fly, but also I think it would be hard to tell if a newly fledged sparrow only weighed 66% as much as their parents... Anyway, I think this is beyond our abilities to answer rigorously without a large amount of sorting through the scientific literature. AFAIK we have no actual ornithologist regular participants here. But, you can contact the ornithologists at one of the world's best labs here [28]. Note that they do not guarantee a response at all, and it might take a long time. One other thing you could do is bypass the front door and find a grad student who is studying something about bird nesting, incubation, or fledging, and ask them directly. Most grad students I've known would be flattered that you found them and asked. The Cornell lab directory [29] has a few grad students, research assistants, and postdocs that you could email, or you could look for a similar ornithology group based at a university in your area. SemanticMantis (talk) 18:07, 19 March 2015 (UTC)[reply]

I can tell you that a fledging sparrow is indeed lighter than and adult. We had a nest once in a birdhouse, and the last chick did not leave with the other chicks. After two days, I went to the nest, and found the chick's leg had been caught by a string in the nesting material. The chick was trapped and the leg was dead, so I amputated it at the knee. It probably weighed about half of the adult mass of a house finch, which I used to catch by hand when they flew into my window frame through a slit in the screen, but could not escape.

We took he chick to an animal sanctuary in a shoebox. The little bugger flew off once we cracked the lid of the box to show the caretaker. (She said not to worry, there was plenty of water and there were feeders behind the shelter.) I suspect the bird had lost weight due to starvation and dehydration over two days. It was the length of an adult, but not of the same mass. In any case, it had no trouble flying and perching. μηδείς (talk) 18:27, 19 March 2015 (UTC)[reply]

Earth's magnetic field

From North Magnetic Pole:

The North Magnetic Pole is the point on the surface of Earth's Northern Hemisphere at which the planet's magnetic field points vertically downwards (in other words, if a magnetic compass needle is allowed to rotate about a horizontal axis, it will point straight down). There is only one location where this occurs, ...

Is "There is only one location where this occurs" a physical certainty, or is it just based on the fact that only one pole has ever been observed, to the accuracy with which such measurements have been made? I obviously understand that a simple bar magent has only one north pole, but images of the magnetic field around, for example, the Sun, appear to show a tangle incorporating numerous smaller local poles. Could such a thing happen, in a less intense way, on Earth? 109.153.227.129 (talk) 14:25, 18 March 2015 (UTC)[reply]

See Dynamo theory for starters. SemanticMantis (talk) 14:30, 18 March 2015 (UTC)[reply]

I should explain in slightly more detail what I am envisaging. I am not envisaging a hitherto undetected pole in the middle of the Pacific Ocean, or anything like that; I am wondering whether within a few miles or tens of miles of "the" magnetic pole, the angle of the field lines could fluctuate around 90 degrees, such that several (or numerous) poles could exist within the vicinity. 109.153.227.129 (talk) 14:40, 18 March 2015 (UTC)[reply]

The International Geomagnetic Reference Field is the most widely respected model of Earth's non-ideal magnetic field. It is updated every few years based on high-accuracy, high-resolution measurements. This field is used by navigators, researchers, and other people who have stake in accurate measurement of the imperfect deviations from a simple dipole.

A pure dipole field would have exactly one point satisfying the OP's conditions. In actual fact, the Earth is very dipole-like. It would be a difficult numerical problem, however, to show whether the IGRF model predicts any other purely-vertical field lines pointing toward the Earth's barycenter (or, normal to the Earth's surface, a different but equally-interesting problem that would require very high-resolution topography data, like the SRTM dataset). The limitation, of course, is the resolution of the model. It is very plausible that as you get incredibly close to the "dipole" pole that minuscule deviations at very tiny length scales - say, meters or even millimeters - might satisfy the conditions. These types of details →are really just mathematical curiousities: in practice, we don't have models that make meaningful predictions of Earth's geomagnetic field with resolutions in the millimeter-scale.

Nimur (talk) 15:38, 18 March 2015 (UTC)[reply]

Full disclosure: I know many expert researchers who use the Dipole model of the Earth's magnetic field - and not the IGRF - because in their applications, the numerical differences are so small as to be negligible.

I even know aviators who even ignore the magnetic declination (the error between true north and the direction that the compass points) - either because they fly using GPS, or because they fly in Chicago, or because they fly in windy parts of California and just don't concern themselves with a constant course error of only 14-degrees while navigating visually. These guys would be lost, though, if they ever got chased into the clouds by the Luftwaffe.

And remember, as AOPA Magazine reminds you in Wind Directions: True or Magnetic?: surface winds reported by METAR are true direction; surface winds reported by ATIS are magnetic direction: unless the ATIS is digital, in which case they are true direction; winds aloft are true direction, unless they come from a PIREP, in which case you have to guess...

This might give you some perspective on how nearly perfect our simple magnetic field models are.

Nimur (talk) 15:54, 18 March 2015 (UTC)[reply]

IGRF is a 13th degree spherical harmonic solution, which implies the natural feature size in that model is still hundreds of kilometers. If there were multiple points of vertical inclination separated by even 100 km you wouldn't expect IGRF to reconstruct that faithfully. (For scale, the magnetic North pole is presently about 400 km from true North). Hence the global field models probably aren't the best tool for looking for duplicate poles. That said, I don't think a scientific expedition in the Arctic would miss a duplicate pole feature if the separation was anywhere as large as 100 km. Dragons flight (talk) 18:02, 18 March 2015 (UTC)[reply]

I generally agree that the resolution is quite low... but that's the best resolution available!

I found this posting in Dispatches from Antarctica, published as part of the official Department of Defense Science Blog, in which Lt. Col. Ed Vaughan wrote:

“

What are isogonic lines and how do they influence magnetic compass readings? Most modern airplanes have both magnetic compasses and gyroscopic compasses of some sort. Given the relationship between the Geographic South Pole and the Magnetic South Pole, and especially the density of isogonic lines in the region, which describes the rate of change of magnetic variation, magnetic compasses are next to useless here for flying.

”

In other words, if I may paraphrase... people who specifically study this problem and work near the poles just ignore the local magnetic field variations!

Here's a really cool data-book, published by the Government of Austrialia's Geosciences program: Isogonic Map of Austrailia (1965). The isogonic lines on the map just stop at the 41st parallel of latitude! A more recent map, in digital form, is available from NOAA: Historical Magnetic Declination. These charts are computed from IGRF, and it is the exact same source-data that official navigation charts are made from... I don't think anything higher resolution exists! If you zoom really close into the magnetic poles, you'll see rendering artifacts - in fact, some of the polygonal lines cross each other. Those would be places where the IGRF provides an inaccurate model compared to ground-truth, and those are the spots where you might expect to find it difficult to disentangle "duplicate poles." Some of these artifacts are surely rendering artifacts exacerbated by the choice of map projection and the specific method used to draw these lines programmatically; but others may be actually representative of model effects.

Nimur (talk) 19:51, 18 March 2015 (UTC)[reply]

When the poles flip they don't just turn upside down, the magna's circulation breaks up and forms new cells. The dipole is the net effect of all those cells, hence the new field may be stronger or weaker than the original. i hazard a guess that during the chaotic bit between stable solutions there would be more than one area where the field lines were vertical. Greglocock (talk) 21:30, 18 March 2015 (UTC)[reply]

I am not sure anyone answered the OP's questions. The article to look at is Magnetic dip. At the North Magnetic Pole it is straight down 90 degrees from level and it is close to level (0 degrees) near the equator. I suppose there could be more then one place near the North Magnetic Pole where this happens, just because of iron deposits messing with the compass. Keep in mind the North Magnetic Pole moves around. Here is a picture of a dip needle to measure this sort of thing. Richard-of-Earth (talk) 09:28, 19 March 2015 (UTC)[reply]

The trouble is that no great maps of isoclinic lines - lines of constant geomagnetic inclination - not many people need that. You can create your own map from the same model or from the dataset. However, there are plenty of maps of the isogonic lines - and you can approximately infer the inclination by assuming the simplification that isoclines run parallel to the gradient of isogonic lines. The same problem exists as above: no dataset or model provides sufficient spatial resolution near the poles, which are the region of interest here. Nimur (talk) 13:19, 19 March 2015 (UTC)[reply]

Thanks for the replies. 109.153.236.190 (talk) 12:12, 20 March 2015 (UTC)[reply]

Automated cell counting on microscope slides

Is there anything that I can buy to automate counting of cells across an entire microscope slide? It's not practical to do it manually 194.66.246.62 (talk) 16:48, 18 March 2015 (UTC)[reply]

I imagine counting the total number of objects could be automated, but recognizing which objects are cells and which are other things could be rather tricky. As far as doing it manually, why not use a smaller sample you can count, and then extrapolate to estimate the total ? StuRat (talk) 17:21, 18 March 2015 (UTC)[reply]

I might be missing something but why do you want to count across the 'entire' slide? What is to stop you using a hemocytometer and doing the math?--Aspro (talk) 17:29, 18 March 2015 (UTC)[reply]

This is commonly done with the free software ImageJ. It would require you to photograph each slide, with a decent camera and decent light. People in my old lab used it to count pollen, but little blobs are little blobs as far as image processing software is concerned... it can distinguish dust specks from cells, and also distinguish hairs or leaves from pollen. This google scholar search for /count imageJ/ [30] will show you many papers that use that software to count cells and other things. With a little more searching, you might even find a paper that hosts the specific code they used in an online repository. SemanticMantis (talk) 17:42, 18 March 2015 (UTC)[reply]

.....which is just ImageJ (Fiji Is Just ImageJ), sorry couldn't resist.. OP, you'll have to tell us a bit more about exactly what you want to do. There are hardware and software solutions for these kinds of problems. Fgf10 (talk) 21:49, 18 March 2015 (UTC)[reply]

Sun's radiation

As time passes, is the sun radiating less heat and light, more, or is it constant? --Llaanngg (talk) 18:30, 18 March 2015 (UTC)[reply]

Solar luminosity, Stellar evolution, Faint young sun paradox. Stellar evolution models estimate that 4 billion years ago the sun would have been only about 70% as bright as it is today, and that it will continue brightening at a rate of about 1% per 100 million years for the next several billion years. Dragons flight (talk) 19:06, 18 March 2015 (UTC)[reply]

Main sequence stars, as noted, very gradually increase in luminosity as long as they stay in the main sequence. At some time in the distant future, the Earth will become too hot for human habitation, and we will all have to move to Mars unless in the meantime we develop a technology for moving planets themselves. Robert McClenon (talk) 21:16, 18 March 2015 (UTC)[reply]

Question about genealogy/evolution

I hope this question is not taken as racist, because this is only because of scientific curiosity.

If a European white couple were to move to central Africa and have a baby, the baby would turn out white as well, right? But if their bloodline stayed in central Africa for many generations and only interacted with other bloodlines of European descent, surely their babies couldn't stay white forever?

I mean, something must have happened in human history that caused different skin colours to develop in the first place. Will the surroundings eventually affect the babies' skin colours? I understand this would take millennia at the least. JIP | Talk 20:12, 18 March 2015 (UTC)[reply]

See Lamarckism for some interesting reading. Human_skin_color#Genetics_of_skin_color_variation may also help you in your research. --Jayron 32 20:17, 18 March 2015 (UTC)[reply]

JIP's claim that light-skinned people could eventually have dark-skinned descendents doesn't depend on Lamarckism, I don't think. I'll simplify the scenario and assume that a few light-skinned Europeans start a clan in Africa, which has no other people. After the population has grown, there will be some natural variation in skin tone, and it may indeed be the case that fair skinned descendents have less offspring than their darker cousins, leading to a selective pressure for darker skin, and perhaps even gene fixation. I'm not saying this would definitely be the case, just that it could be, without appealing to (mostly wrong) Lamarckian concepts. SemanticMantis (talk) 20:52, 18 March 2015 (UTC)[reply]

If a fair-skinned European (or northeast Asian) couple were to have a baby in Africa, of course the baby would have their genes for skin color, yes. Dark skin is an adaptation to the African tropical sun, and fair skin is an adaptation to the mid-latitude sun of Europe or eastern Asia. Presumably there would be some selective pressure for darker skin in Africa. As the OP noted, any re-darkening would be on a time scale of millennia. I agree that the question isn't about Lamarckian evolution, but about Darwinian evolution. I think that the question is more or less answered as yes, that there would be a very slow selective pressure toward darker skin. (In the short run of one-and-one-half centuries, all that happens to Anglo-Celtic Australians is that they, unlike aboriginal Australians, get skin cancer.) Robert McClenon (talk) 21:14, 18 March 2015 (UTC)[reply]

I think the answer is possibly but not necesarily! Many evolutionary processes appear not to be easily "reversible". For example, it seems that it didn't take fish very long to evolve air breathing lungs, once they started down the land dwelling road, BUT no animal in histrory has ever gone BACK to water breathing gills (or any organ), even thugh several animals went back to the water long ago and have made other extraoirdinary adaptations for aquatic life. Vespine (talk) 21:59, 18 March 2015 (UTC)[reply]

Just to correct the "didn't take very long" bit, the first fish appeared during the Ordovician period, 480,000,000 years ago or so. The first fish-amphibian hybrids crawled onto land during the Devonian, about 120,000,000 years later. That's a pretty long time. But, you are correct, in the intervening 365,000,000 years, none of the animals that went back to the ocean evolved gills back again. Evolution is not likely a reversible process. Also, it seems unlikely that modern humans face the evolutionary pressures that humans did thousands of years ago. --Jayron 32 23:18, 18 March 2015 (UTC)[reply]

Gaining or losing lungs or gills is quite a major change, and would require all the intermediate stages to be useful. In contrast, everyone (apart from albinos) have some melanine in their skin, and evolving a darker or lighter skin would just be a matter of changing how much is produced, an so presumably much easier. Also, bear in mind there's no such thing as a "pure" race, so this transplanted "white" population may well have had some recent "black" ancestors, and still have their genes in the genepool. As the genes get shuffled over the generations, some of their children might inheret more "black" genes - and if this is enough to provide an evolutionary advantage, then that lineage will produce more and healthier descendents, and the population as a whole will become darker. 62.172.108.24 (talk) 16:32, 19 March 2015 (UTC)[reply]

The reason dark skin developed in tropical areas is that the greater amount of sunlight there makes sunburn and skin cancer more likely, unless the UV light is blocked by greater amounts of melanin. However, we now have sunscreen, protective clothing, etc., so this can take the place of melanin. Actually, sunscreen, etc., seems like it might be a superior solution, because dark skin can also lead to overheating, which is a real problem in Africa. Thus, it may no longer be advantageous to have dark skin in Africa. StuRat (talk) 05:10, 19 March 2015 (UTC)[reply]

It should be noted that dark skin did not develop as an adaptation for pale skinned humans. They were already dark skinned, and already in Africa. Humans who moved to other areas developed lighter skin, not the other way around. See Recent African origin of modern humans. --Jayron 32 14:49, 19 March 2015 (UTC)[reply]

True, but whether there has been much redarkening is I think still somewhat unclear. Our Human skin colour seems to suggest there hasn't. "Investigations into dark skinned populations in South Asia and Melanesia indicate that skin pigmentation in these populations is due to the preservation of this ancestral state and not due to new variations on a previously lightened population." Our dark skin, however says "According to Nina Jablonski, darkly pigmented modern populations in South India and Sri Lanka are an example of this, having redarkened after their ancestors migrated down from areas much farther north." One thing that is clear I think is that some populations have a darker average than surrounding and this is likely a later adaptation (i.e. there definitely has been some darkening). It is perhaps also worth mentioning that dark skin is an adaptation in itself, just one that began earlier in human evolution, around the time we lost body hair. Nil Einne (talk) 01:44, 20 March 2015 (UTC)[reply]

JIP's scenario would only work if the babies born with slightly darker skin tended to produce more children, while the lighter skinned babies produced fewer (by dying or being sick, etc.) If they all wore sunscreen and there was no differential reproduction there'd be no evolution toward dark skinnededness. μηδείς (talk) 16:55, 19 March 2015 (UTC)[reply]

Sewing machine oil vs turpentine substitute

My sewing machine instruction manual advises the application of kerosene to the oiling points after the machine has been idle for "some time" in cases where it does not "run smoothly". After applying kerosene to the oiling points the machine is to be a run quickly for one minute after which the oiling points are wiped off and oil applied. How does kerosene compare chemically to sewing machine oil? Wiping the oiling points will not remove all of the kerosene. Will the rest evaporate? Does the sewing machine oil turn rancid over time like cooking oil? --Seans Potato Business 21:27, 18 March 2015 (UTC)[reply]

Kerosene is a better solvent, so it will help to dissolve any gum from dried out oil. But, it is not a very good lubricant, so it will wear out your machine more quickly than oil.Any residual kero will dilute your oil a bit, if you are worried by this oil it, run it, wipe it clean, oil it again. Kero will evaporate very slowly, but any gum dissolved in it will then redepositGreglocock (talk) 21:38, 18 March 2015 (UTC)[reply]

Yes kerosene will evaporate. Think though, that the term 'polymerization' is more fitting than 'rancid' as the latter refers to taste. In resent years, cheaper lubricating oils have been used which in time polymerize (i.e., thicken). More tradition (and expensive) lubricants like 'porpoise jaw oil' lasted for years and didn't leave deposits. These days it is hard to find. However, a good clock maker may be able to get you some (by clock maker, I mean a proper horologist, not a purveyor of modern plastic round things controlled by a quartz oscillator). --Aspro (talk) 22:38, 18 March 2015 (UTC)[reply]

For the latter part, see rancidification and I think Hydroxylation. My WP:OR and previous reading suggests that mineral oils are far more stable than animal oils, and that plant oils (most cooking oils) go rancid/break down the fastest, at least generally speaking. I'm not sure what type of oil is sold as "sewing machine oil" (Lubricant#Base_oil_groups?), but I suspect it will not go rancid before it wears away, and the kerosene will help remove any residues. SemanticMantis (talk) 23:15, 18 March 2015 (UTC)[reply]

? I intermatted above that 'rancid' is not a good term. Stability, is the oils ability to resist cross-linking (get gummy). Mineral oil fractions can do this too. The origin of the lubricant does not matter as much as the the characteristics of the monocular chain. Nye Lubricants - 170 years of History--Aspro (talk) 00:02, 19 March 2015 (UTC)[reply]

Sure, you said that stuff, but you didn't include any refs or even wikilinks. I pointed out rancidification because OP asked about it, and it tells us "Akin to rancidification, oxidative degradation also occurs in other hydrocarbons, e.g. lubricating oils, fuels, and mechanical cutting fluids" - and that's what led me to hydroxylation. I admit I can't follow the details of the chemistry, but it seems that the degradation of plant oils and mineral oils is at least somewhat analogous. SemanticMantis (talk) 14:52, 19 March 2015 (UTC)[reply]

OK. Polymerization.--Aspro (talk) 20:02, 19 March 2015 (UTC)[reply]

My understanding is that the chemistry is pretty simple really. Drying oils from unsaturated fats that have often multiple double bonds that allow them to undergo reactions quite readily, whereas those that do not react are saturated hydrocarbons. With enough double bonds, oils can "dry" i.e. react with oxygen so quickly that they cause spontaneous combustion. It is very useful for one's sense of paranoia to understand this difference so you don't have to look at every oily piece of cloth the same way, but can... prioritize. Wnt (talk) 23:45, 19 March 2015 (UTC)[reply]

Hello, the kero would be used to remove the "gum" or "varnish" (for all the names given as stated above) sewing machine oil is a mineral oil, however just like petorleum fuels used in engines, it eventually deposits some gum onto working parts if they have not moved for some time, or become overheated, this is why you are meant to lubricate with new oil often. as a sidenote, but related, One of the most common problems with small gas engines is that the fuel goes "stale", and leaves varnish on the jets of the carburetor etc. therefore new fuel is the first remedy.Read-write-services (talk) 22:50, 19 March 2015 (UTC)[reply]

March 19

Hydrogen peroxide and oxygen

How can I tell the difference between hydrogen peroxide and water without any materials or scientific tools? — Preceding unsigned comment added by 67.83.184.207 (talk) 00:29, 19 March 2015 (UTC)[reply]

Catalase. It's an enzyme in your skin that will break down 2 H2O2 -> 2 H2O + O2. So if you touch H2O2 to your skin, it will bubble, but water won't. Caveat: I'm speaking of over-the-counter hydrogen peroxide solution certified for use on human skin - you would not like the outcome of the experiment with the pure compound! Wnt (talk) 00:57, 19 March 2015 (UTC)[reply]

Taste it. If its strenght is something like 40 volumes you should dilute it down first – read the label.--Aspro (talk) 01:18, 19 March 2015 (UTC)[reply]

How about if I can't taste or touch it because it's too strong? — Preceding unsigned comment added by 67.83.184.207 (talk) 02:01, 19 March 2015 (UTC)[reply]

What can you do? If all you have is a glass of (by eye) clear, colorless liquid and you can't use any other items or devices, and you can't taste or touch it, seems like all you have are smell, hearing, and sight. Strong peroxide does have a smell compared to water (smells "clean" but not quite "chlorine-like cleaner", maybe reminds me of doctor's office disinfection or other disinfectants originally, but I've used it enough I just recognize it). Are you allowed to use and touch it with anything at all (i.e., colored paper/fabric, a rusty nail, mix it with actual water)? DMacks (talk) 02:36, 19 March 2015 (UTC)[reply]

Hydrogen peroxide will bubble a bit on it's own, but adding nucleation sites, like some sugar crystals, should get it going faster. Or you could just shake it. StuRat (talk) 05:14, 19 March 2015 (UTC)[reply]

Pure hydrogen peroxide's density is 1.450 g/cm3 and water's is 1 g/cm3. Get an equivalent quantity of water in an equivalent container and compare the two. Even of the hydrogen peroxide is diluted it will weigh more. I suppose the problem is a scale might be considered a scientific tool, so you would have to come up with weighing tricks like floating them in a tub of water and see which one goes deeper into the water or sealing them and seeing which one sinks faster in a tub of water. Of course, if it is a large enough amount, you could just feel the difference, especially if it is a high concentration. Richard-of-Earth (talk) 08:31, 19 March 2015 (UTC)[reply]

Darn, I just re-read the question and getting an equivalent amount of water would be using materials. Stu's last answer is best. Richard-of-Earth (talk) 08:41, 19 March 2015 (UTC)[reply]

Evolution

Are there any animals in the world that do not follow the "eyes and mouth at the top in the head and excretion from the bottom" design? My Little Question Can't be This Interesting (talk) 13:12, 19 March 2015 (UTC)[reply]

Cnidarians! Poriferans! Nimur (talk) 13:21, 19 March 2015 (UTC)[reply]

Sea_anemone, octopus? 217.158.236.14 (talk) 13:22, 19 March 2015 (UTC)[reply]

To go even further, there are plenty of groups of animals that don't even have separate mouths and anuses. 131.251.254.154 (talk) 13:31, 19 March 2015 (UTC)[reply]

Not meaning to invalidate the excellent examples supplied above, but bear in mind also that designation of what constitute anterior and posterior portions of an organism, considered across the wide array of life which exists (let alone has existed), is highly contextual -- and in some cases, the very features you've listed are criteria by which those orientations are defined. The only useful and concise answer to your question that I can think of is that for any major organ group you can think of, you can find an organism that put it just about anywhere in relation to other major anatomical features. In the context of terrestrial species, the eyes are overwhelmingly affixed to the conceptual "front" of the body, on the head. Sea life is much more variable in this regard; if you're using the broad critera of an eye being any photoreceptive organ attached to a central nervous, there's an astounding variety in where the photoreceptors are found along the body, especially in those exotic species found at intense depths. Likewise, marine life also has a larger variety in the anatomical placement of features of the gastrointestinal tract and similar systems. Snow ^{I take all complaints in the form of epic rap battles} 13:57, 19 March 2015 (UTC)[reply]

Riftia spp. have no mouths nor anuses of any sort! They don't eat or excrete anything in the traditional sense. SemanticMantis (talk) 15:02, 19 March 2015 (UTC)[reply]
Echinoderms typically have the mouth at the bottom, the anus at the top, and (in the case of starfish) eyes on their "arms" 62.172.108.24 (talk) 16:40, 19 March 2015 (UTC)[reply]

Animals that move forward linearly tend to have a "head" which includes Planaria but the cephalopods get their odd design from the fact that they sued to be encased in shells, as the Nautilus still is. This recent at the BBC is cute, but not very technical. But it does show a flatworm whose mouth is on the belly, and its multiple anuses are on the top. μηδείς (talk) 16:51, 19 March 2015 (UTC)[reply]

Anatomists usually use "top" and "bottom" to mean the dorsal-ventral axis, which points from the back to the belly. The axis that the question is asking about is called rostral-caudal (head to tail). The basic answer is that the rostral end is defined as the end that contains the head and eyes; the caudal end is defined as the end that contains the anus. As a matter of fact, bilateria, meaning all animals that have approximate left-right symmetry (these make up the vast majority of animal species), divide mainly into two groups called protostomes and deuterostomes. Protostomes consist of arthropods, molluscs, and other phyla; deuterostomes consist of vertebrates, echinoderms, and other phyla. The two groups are defined on the basis of the fate of a feature of the very early embryo called the blastopore. In protostomes the blastopore develops into the mouth; in deuterostomes it develops into the anus. So it would not be totally unreasonable to say that the head-to-tail axis is reversed between the two groups. However, the gene expression patterns that define levels on the rostral-caudal axis are not reversed, as I understand it. Looie496 (talk) 17:49, 19 March 2015 (UTC)[reply]

Schrodinger's cat video

I was having a debate with a friend recently, who argued that he had good reason to believe (based on scientific principles) that our reality is caused by conscious observation. He then showed me this video, concerning the Schrodinger's cat thought experiment. The video explains that, according to quantum mechanics, a cat in a bunker with gunpowder (or, a box with a vile of poison) can be thought of as both alive and dead until one observes the cat; "the act of looking forces nature's decision."

However, based on what I know about quantum mechanics, this sounds a bit philosophical. The observer effect article states, "[the observer effect] is often the result of instruments that, by necessity, alter the state of what they measure in some manner." Certainly, when quantum physicists are doing experiments on a subatomic level, they cannot simply "look" at a particle and have its wave function collapse; they must be altering it in some way. So my question is, does the video have any basis in science? Does quantum physics account for the effect of "observation" on a macroscopic scale? Thanks for your input. 70.54.113.221 (talk) 16:40, 19 March 2015 (UTC)[reply]

Can you apply the scientific method to answer this question? Can you create a testable hypothesis and run controlled experiments to validate the hypothesis? If not, this isn't science as practiced by scientists: it's metaphysics as described by lay-philosophers.

If you'd like to read what professional philosophers have written on this topic, the Plato Stanford Encyclopedia of Philosophy has a good review article: Measurement in Quantum Theory.

Nimur (talk) 17:11, 19 March 2015 (UTC)[reply]

Well, per quantum immortality, the cat always thinks it's alive... so you can wait a while... Wnt (talk) 17:12, 19 March 2015 (UTC)[reply]

Interpretations of quantum mechanics has a dozen or more answers to your question. Take your pick. Gandalf61 (talk) 17:28, 19 March 2015 (UTC)[reply]

Although I don't see an article on it, it seems to me your friend is talking about what's called a "reality construct." There is only one reality, but that doesn't mean we can know what it is or that we will necessarily agree on what it is. The statement "the act of looking forces nature's decision" is extraordinarily egotistical. Nature couldn't care less whether we're looking or not - and the cat will either be dead or alive, we just don't know which. The fact that we don't know has nothing to do with the actual condition of the cat. In short, it's an amusing but weak attempt to explain atomic-level behavior. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:01, 19 March 2015 (UTC)[reply]

sorry there more then one reality , there many worlds , and only when you satabilize , on dead or alive reality , it becume yours whis yours aye .thanks water nosfim.

A random Youtube video, even/especially one with 4 million views, is not a great authority, but since your friend cited it I suppose it's worth pointing out that it actually disagrees with his position: it says "we're just like the cat", implying that there's nothing special about our conscious experience.

The notion of a superposition of living and dead cat states has no operational meaning. The classical picture, that the cat is definitely alive or dead but we don't know which until we look, is consistent with every experiment that we could ever perform (if quantum mechanics is correct). The thought-experiment because famous because OMG DEAD CAT, not because it's intrinsically interesting. Even Schrödinger called it ganz burleske.

In situations where we can detect a measurement effect (by the vanishing of the interference pattern in a double-slit experiment, for example), consciousness plays no role. The interference pattern disappears when the particle's path is recorded by any device, whether or not a person ever learns the outcome of the measurement.

The measurement effect is a kind of interaction between the measurement device and the system, but it's definitely not an interaction in the conventional sense, involving contact forces or gravity or anything of that sort. This is most obvious in interaction-free measurement experiments. -- BenRG (talk) 19:59, 19 March 2015 (UTC)[reply]

If it is indeed the case that the cat is in an indeterminate state until the experimenter opens the box - then consider this extension to the original thought experiment: The laboratory containing the cat, the box and experimenter is also a closed system (to the extent that the box containing the cat and the poison gas contraption is also closed). It seems that the experimenter's wife happens to be the owner of the cat. She is very concerned about whether it lived or died and intends to phone her husband to find out what happened 30 minutes after he is scheduled to open the box.

OK - so the experimenter opens the box and now, as far as he is concerned, the cat is now very definitely either alive or dead. But from his wife's perspective, the cat's situation along with that of her husband is now entangled too. Until she observes the state of her husband, he is in a superposition of dreading her call because her cat is dead and a state of hoping she'll call soon so he can tell her the happy news.

There is no logical or physical basis to deny this - the quantum event that caused the cat to die (or not) used an intermediary system involving a particle detector and a poison gas cylinder - and that event didn't collapse until the experimenter opened the box. That same quantum event causes the experimenter to either regret performing the experiment or not - and his state of regret is just as entangled as that of the cat - and only collapses when the experimenters wife "opens the box ('lab')" by phoning him. Before that phone call is made, you can't reasonably say that the state of the cat has collapsed from the perspective of the wife because the state of her husband is determined by precisely the same quantum event and it's consequences as the death (or not) of the cat. But the state of the cat clearly did collapse from the perspective of the experimenter 30 minutes earlier when he opened the box - and the state of the poison gas contraption collapsed from the perspective of the cat some time even earlier than that.

You can extend this situation out further, to friends of these two people who live in remote cities...to aliens living 10 light years away. The collapse of the quantum state of that original particle ripples outwards into the universe - where it meets other entangled quantum events that may affect its consequences. (Imagine if our experimenter brought home a copy of the cat experiment, complete with poison gas despenser and accidentally left it under his wife's favorite chair with the lid open...now that second quantum event causes another superposition of dead or not-dead wife that interacts with the dead or not-dead cat. The universe in that locality now has a 4 way superposition.

Since quantum events of this nature must change reality in small ways all the time, the entire universe must be an insane superposition of an utterly ungodly number of states that have yet to collapse over the entire volume of space-time.

This brings you to the many-worlds hypothesis...and I think it's increasingly clear that this is the most reasonable explanation for all of this mess.

SteveBaker (talk) 21:03, 19 March 2015 (UTC)[reply]

The paradox of Schrodinger's cat is a crock, and is insulting to non-human animals. The idea that the cat is not resolved into alive or dead until a human observer opens the box is nonsense. The state of the cat has already been observed by the cat. Either the cat is alive, and knows that she is alive, or the cat is dead, and in that case the cat knew at least briefly that something was wrong. I don't deny that interpretations of quantum mechanics are weird, but this particular weirdness is a crock. I don't claim to have the answer to any question except that the paradox about the cat insults the cat. Robert McClenon (talk) 21:37, 19 March 2015 (UTC)[reply]

The thought experiment is still completely valid if you use a human. In that case, she (the human) will know if she's alive, but to outside observers, she's in a superposition between alive and dead. The OP's video makes this same point. --Bowlhover (talk) 22:52, 19 March 2015 (UTC)[reply]

You all do realize that Schrodinger's cat was satire, right? Schrodinger totally thought it was insane and stupid, which is why he created the thought experiment, to show how insane and stupid some of the interpretations of quantum mechanics were. --Jayron 32 23:21, 19 March 2015 (UTC)[reply]

Schrodinger intended it as satire, but that doesn't mean he thought the species of the animal inside the box made a difference. It doesn't. The thought experiment is equally valid or equally absurd whether the victim is a human or a cat. (It doesn't help Schrodinger's case that the other interpretations of quantum mechanics are equally or even more absurd, such as positing that an infinite number of universes are created every second.) --Bowlhover (talk) 00:04, 20 March 2015 (UTC)[reply]

The idea isn't that the universes are created - as in gazillions upon gazillions of tons of matter and energy just popping into existance. The idea is that this concept of quantum superposition - where a particle can be in multiple, quite different, states simultaneously - implies that the entire universe is in superposition of an almost infinite permutation and combination of superpositions. As humans, our brains are only able to perceive one out of that near infinite number of states - which we understand as "reality". We know that superposition exists - this is just an extension of that. SteveBaker (talk) 01:45, 20 March 2015 (UTC)[reply]

The concept here we are lacking is that of a sophist, someone who will teach you how to win either side of an argument. David Hume was a great modern example who ammased great prestige and fortune arguing that cause and effect was a dellusion and you could not be sure that an apple wouldn't turn into a blob of lava the very next second. He became famous off Descartes' dubito ergo sum. μηδείς (talk) 05:17, 20 March 2015 (UTC)[reply]

Plant question

Can a single leaf cell taken from a plant be placed into plant rooting hormones and grown into a full sized specimen of the donor plant? Would the resulting plant reproduce as normal or be sterile? My Little Question Can't be This Interesting (talk) 21:29, 19 March 2015 (UTC)[reply]

I doubt it, the cell would have been "established" i.e. it is not a stem cell- as a "leaf cell", unable to produce roots on its own, although, if it was placed into another plant, then that was dipped into hormone powder?, but this would not be the clone of the original cell, it would be a plant with one cell introduced into itself. The concept you are alluding to I think is very similar to a "cutting" but in the case of a leaf cutting, the original leaf attachment is able to sprout roots, the leaf attachment seems to have the capability of becoming rooted-this is a very good question. This is again, just my limited knowledge of cuttings and plant propagation with cuttings, in this case we need a plant scientist/botanist to give us the correct answer. Read-write-services (talk) 22:39, 19 March 2015 (UTC)[reply]

I think you have mostly the right reasoning, but I think the correct answer will depend on what we call a "leaf cell" and what type of plant. For instance, I'm pretty sure the apical meristem of oxypetalum is pluripotent - they can shoot out stems, leaves, and roots anywhere on the plant that seems like a good place to them, and the meristem is just the tip of the stem, which is poorly differentiated from the leaf. So I think it's reasonable that with careful laboratory-controlled conditions somebody could clone one of them from one stem cell. It would probably involve very careful manipulation of light, nutrients, and substrate. Rooting hormone would probably help, but might not even be strictly necessary, as plants make that themselves to varying degrees. I can't dig into the scientific literature now, but I probably will over the weekend if nobody else does :) SemanticMantis (talk) 23:12, 19 March 2015 (UTC)[reply]

For the second question: if this could be done, it would be a simple clone, and would be able to reproduce normally, both through vegetative reproduction and sexual reproduction - what you are suggesting isn't that different from the types of plant propagation that people do all the time - growing clones from cuttings (rhizomes, stolons, stems, etc.), air layering and a few other related techniques. This is just humans tinkering with and assisting what plants already do. If the parent was a sterile hybrid, then the "daughter" or clone would be too. Incidentally, all the named apple varieties that you can buy at the grocery store have been propagated exclusively via grafting - apples don't breed true, and if you plant an apple seed, the fruit of that tree will certainly be different than the parent, and likely not very good. So there is an original Honeycrisp apple tree, an original Granny smith, etc, and every apple we eat is a first generation offspring of the original. SemanticMantis (talk) 23:12, 19 March 2015 (UTC)[reply]

See plant tissue culture and micropropagation. This doesn't always refer to using a single cell but as our article mentions, it sometimes does. See also [31] [32] [33]. Note that a single cell will generally be used for the production of genetically modified plants, whether transgenic or cisgenic. Totipotency rather than simply pluripotency is normally what's needed. SemanticMantis is right in that it does depend on cell type and plant, although there is research in to how totipotency can be induced see [34] [35]. I would clarify one thing SM said. The plant will be able to reproduce normally, but won't necessarily be able to reproduce via sexual reproduction easily. One of the reasons why these techniques may be used is because some plants have difficult reproducing sexually at all (rather than simply not breeding true). E.g. most edible bananas are parthenocarpic, a number including those most commonly exported because they are triploid. While these can be reproduced via more normal vegetative means, plant tissue culture enables you to store a lot of different samples in plant tissue banks more easily (somewhat comparable to seedbanks). Of course these probably don't involve a single cell, although I think you may sometimes start with a single cell particularly if your trying to eliminate some disease. Producing disease free offspring is another reason plant tissue culture and microculture may generally be used. Actually you may sometimes be able to produce seeds which would otherwise be very difficult to do. To be clear, this doesn't mean that there's something unique about the plant you produce via cell culture techniques, but rather that reproducing normally for that plant may not include sexual reproduction. (If you're doing genetic work, you may intentionally induce sexual sterility for a variety of reasons, but in that case your offspring plant is obviously intentionally not the same as the plant the parent cell came from.) Nil Einne (talk) 00:01, 20 March 2015 (UTC)[reply]

Edit, I should clarify that while you may not always only use a single cell, the point isn't that the cells are different. Rather for convenience, safety, the difficulty obtaining a single cell, etc you may have tissue rather than a single cell. If you are able to propagate from plant tissue which would be of a single type, there's AFAIK no reason why a single cell wouldn't work. Nil Einne (talk) 00:24, 20 March 2015 (UTC)[reply]

Final clarification, while the distinction between pluripotency and totipotency is important, I'm not aware that it's actually that significant in plants. By which I mean I'm not sure that it's common that cells are pluripotent but not totipotent. See for example [36] [37] and also the earlier links. Nil Einne (talk) 04:10, 20 March 2015 (UTC)[reply]

This is a rather common phenomenon. Opuntia the prickly pear cactus sprouts from "leaves" but they are technically stems, the spines being the leaves. The wandering Jew bears baby plants on stalks, and there are plants from which a new plant will develop out of the middle of a leaf, but I can't remember a species off the top of my head. μηδείς (talk) 05:05, 20 March 2015 (UTC)[reply]

There are 9 plants called Wandering Jew, which one did you mean μηδείς ? ---- 62.56.48.4 (talk) 10:18, 20 March 2015 (UTC)[reply]

Is there another less arduous method to collect focus group discussion data without having to transcribe the entire discussion word for word?

Can the researcher only take notes of the high-points of the discussion instead of transcribing every words uttered by the participants? — Preceding unsigned comment added by Rja2015 (talk • contribs) 23:07, 19 March 2015 (UTC)[reply]

You can do whatever you want, surely? Why not record the session? Vespine (talk) 23:17, 19 March 2015 (UTC)[reply]

I disagree - the researcher might very well exhibit either conscious or unconscious bias in the words they choose to write down and those they choose to ignore. Without access to the ultimate source data - you have no idea whether you're just getting the opinions and biasses of a single researcher. 01:54, 20 March 2015 (UTC)

How about voice recognition software ? Certainly not perfect, but I doubt if it will choose to only transcribe positive reviews, for example, as a researcher might. StuRat (talk) 04:13, 20 March 2015 (UTC)[reply]

For at time, back when we paid for cable, rather than stealing everything off the internet, we watched Special Report with Brit Hume (they replaced him with a badger whose name I can't remember). In any case, they used those boxes you turn all the way to the right if you feel positive and all the way to thef left if you fell negative about what is being said. There was a line for conservatives, liberals, and independents, and it would fluctuate as people spoke.

The problem for the viewer was it was a distraction (one wanted to pay attention to the speaker, not what people though of the speaker) and there was a significant time lag, about 10-15 seconds, so you had to factor in that the response was to what the prior speaker had said 50 words ago. This is a less arduous means of gathering data, but a very imprecise one, since you mostly measure emotion, not thought, and there is only one dimension, when you know that people like myself would want at least three to feel comfortable. μηδείς (talk) 04:54, 20 March 2015 (UTC)[reply]

You seem to be thinking of some form of audience response measurement. For live TV, the result is commonly called "the worm" and is still sometimes used for election debates [38] [39] [40] although often with only a single worm (albeit I believe the data often does include different political groupings). Nil Einne (talk) 05:44, 20 March 2015 (UTC)[reply]

For clarity, are you asking about transcribing recordings? I.E. You will always have recordings of the sessions, you just want to know whether you need to transcribe the whole recording, or can take notes. If you aren't I agree with Vespire, the obvious question is why you can't record the sessions. If you are referring to transcribing recrods, I would suggest the answer depends significantly on what the purpose of the focus group is and how you plan to deal with the data. For example, if you're doing this for commercial purposes, and your client may want a transcription, then the answer is surely that you can't. If this is for academic research, and you're the only one likely to be analysing the data, and you won't actually be doing anything with transcriptions even if you make them, then perhaps it isn't necessary. (Usually you'd be expected to make the raw data available on resonable request, in such cases you can probably provide the recording.) There is perhaps some risk you'd more easily miss things, since reviewing audio recordings is probably going to be more difficult than reviewing transcriptions, so you'd need to take that in to account. Nil Einne (talk) 05:53, 20 March 2015 (UTC)[reply]

According to Qualitative Data Analysis from Start to Finish (pp.49-52) by Jamie Harding recording the video/audio of a focus group and later transcribing the proceedings is the standard practice. See the text for more details, exceptions, and recommendations; or, this short tutorial video on focus group data analysis, for why recording/transcription really seems unavoidable (as far as I can see). Now it is possible, that you have some other kind of focus group in mind than the one discussed by Harding (for example, along the lines μηδείς discussed; see also wikipedia article on focus groups), in which case you'll have to give us more specific details in order for us to be helpful. Abecedare (talk) 06:10, 20 March 2015 (UTC)[reply]

There is software used by stenographers for transcribing recordings e.g. depositions. Since it's used for something important, I assume it works a lot better than what YouTube uses for its hilarious machine-generated subtitles. Look into it and perhaps invest in a copy if you have the budget for it. I've transcribed (a small part of) a recording once--it was painful. I had to re-listen many parts multiple times to make sure that I heard every syllable right. It helps to an extent if you use a player that allows you to control the playback speed easily, so that you can re-play specific difficult parts at a lower speed. --173.49.16.112 (talk) 11:45, 20 March 2015 (UTC)[reply]

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