Wikipedia:Reference desk/Archives/Science/2013 October 11

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October 11

Have people really fused with their own sofas?

It always sounded like an urban legend to me, but it has been reported (a couple of times, that I can recall over the years) in the mainstream media that people have actually sat on their sofas for so long that their flesh had actually grown into and fused with the fabric. Now, it wouldn't be the first time that some random piece of bullshit that circulated on the internet was picked up and reported as news in one of the less reliable newspapers - but seriously, is there even any way that this could even work in reality?

If you were literally never moving from your sofa for 'x' number of years (that always seems to be a common element in these stories) and therefore inevitably pissing and shitting all over yourself where you were, then surely you'd die of an infection or get eaten by bugs long before you could actually grow into your seat - and your home would become so much of a biohazard that the local authorities wouldn't stand for it? --Kurt Shaped Box (talk) 01:12, 11 October 2013 (UTC)

I think more realistically that someone with an open sore, such as a bedsore, could have the clot/discharge stuck to the fabric in a way that made it painful or perhaps even damaging to move him without considering the issue. Wnt (talk) 02:45, 11 October 2013 (UTC)

Googling "skin fused to couch dies" gets you a lot of hits, although some seem to be recycled stories. Google news gets no hits. This detailed story was published in the Mail. Obviously the skin is not going to grow blood vessels into the couch. But a several year old callous would be pretty thick and not easy to remove in place. We're not really in a place to question the sources. μηδείς (talk) 02:56, 11 October 2013 (UTC)

Common mistake: callous is an adjective. What we need here is the noun callus. -- Jack of Oz ^{[pleasantries]} 12:46, 11 October 2013 (UTC)

I knew something looked off. μηδείς (talk) 16:36, 11 October 2013 (UTC)

Always trust your gut. What you have left of it, anyway.  :) -- Jack of Oz ^{[pleasantries]} 18:30, 11 October 2013 (UTC)

I happened upon Nip/Tuck while channel surfing one night, and saw an episode about a woman who was so impossibly, grossly, disgustingly, insanely obese that she had lost the ability to move and had totally merged with her sofa, where she had remained for some years. Still mentally alert and talking volubly. Still eating (she had a helper) and eliminating waste products (the helper didn't go there). The smell was apparently indescribable. The plastic surgeon's job was to somehow separate her from the sofa. After they achieved this, the house had to be demolished. How true to actual real life this dramatisation was, I cannot say, but I really hope it was uber-exaggerated. -- Jack of Oz ^{[pleasantries]} 03:13, 11 October 2013 (UTC)

The adjective you are looking for is "extremely" obese. Compulsive overeating is a common psychological condition, so common that most of suffer from it in a mild form. Please don't blame the victim. There but for the grace of God... Itsmejudith (talk) 20:50, 11 October 2013 (UTC)

OK, I accept that. I know about weight issues and eating disorders, having lived with both of them for a very long time, and I have experienced many cruel barbs from others, so I would never blame the victims and I certainly wasn't doing so above. It's just that, saying "extremely obese" would in no way have given you an impression of how monstrously enormous this person was. Obviously it was all, or mostly, artificially added to her real body, because I don't believe any human could possibly be that big. Think of Mr Creosote from Monty Python's The Meaning of Life and you're getting towards the ballpark. -- Jack of Oz ^{[pleasantries]} 05:05, 12 October 2013 (UTC)

Thanks for your thoughtful response. It seems that the main thing to be angry about is that the lady had so little support until it was too late. Also, perhaps, that the TV show was sensationalising in pursuit of ratings rather than bringing a complex topic to public attention. From what you've said, "extreme" is the precise word in this case, i.e. it was at the far end of what is physically possible. Itsmejudith (talk) 22:42, 13 October 2013 (UTC)

Well, so long as we're citing fiction, here's the pièce de résistance of all skin fusing. μηδείς (talk) 03:33, 11 October 2013 (UTC)

This Tetsuo also has fusion problems. Akira's way better though. Effovex (talk) 04:18, 11 October 2013 (UTC)

• It happens. The Associated Press/Yahoo News (normally reliable sources) has an article here about a woman from Missouri who had fused to her vinyl recliner. Here is a similar story from a TV station in Florida about a woman fused to her couch after 6 years. --Jayron32 12:11, 11 October 2013 (UTC)

Why do light rays bend while passing from one medium to another (during refraction)?

Why do light rays bend while passing from one medium to another (during refraction)? Scientist456 (talk) 04:04, 11 October 2013 (UTC)

See Refraction#Explanation. Bubba73 ^{You talkin' to me?} 05:00, 11 October 2013 (UTC)

This article does not explain the bending of light deeply. Scientist456 (talk) 06:16, 11 October 2013 (UTC)

Per Lagrangian mechanics and Hamiltonian mechanics, the path taken by a particle is such that the action (the difference between the particle's kinetic energy and its potential energy, integrated over the path) is stationary (which usually means it's a minimum), i.e. the first-order variation of the action is zero. In layman's terms, you could say the path taken is the most efficient one. The analogy my professor used is this: imagine you're on the beach, and someone is drowning. To get to them, you have to run across the beach for some distance (easy) and swim some distance (harder by a factor n). The extreme paths are one where you minimise the swimming part but have to run a lot, and the one where you minimise the running but have to swim a lot further. As it turns out, the quickest way to get to the drowning person is the path where $\sin \theta _{1}=n\sin \theta _{2}$ -- i.e., it is given by Snell's law. If you recall that the refractive index n is the factor by which light in a medium travels slower than c, that means light bends simply because it's the quickest path. See also: Hamiltonian optics. --Link ^(t•c•m) 09:18, 11 October 2013 (UTC)

diffrent matiryals transfer light in diffrent speed , ray of light moves forwerd and backwerd many time in time and stabilize on the fastest way , that way the light bend . thanks Water Nosfim — Preceding unsigned comment added by 81.218.91.170 (talk) 12:08, 11 October 2013 (UTC)

The thing is , To get to know the fastest way, you have to return from it with knowledge of its speed, ie to return from her back in time , Water Nosfim — Preceding unsigned comment added by 81.218.91.170 (talk) 12:56, 11 October 2013 (UTC)

I don't pretend to understand it, but try the last paragraph of this: http://www.sparknotes.com/physics/optics/light/section3.rhtml — PhilHibbs | talk 15:03, 11 October 2013 (UTC)

Metal used in hard disk drive chassis?

What kind of metal alloy is used in a hard disk drive chassis? any sources? Electron9 (talk) 04:10, 11 October 2013 (UTC)

I'm almost certain it is just aluminum. But I'm not having luck finding a good source. 203.110.235.8 (talk) 05:39, 11 October 2013 (UTC)

I can't see why aluminium would be used. All the HDD's I have examined have a diecast chassis. Diecasting is (at high production volumes) cheap, and produces a strong accurate product with a vety good finish. The HDD's I have examined have the typical light grey finish of diecasting in alloys that are mainly zinc. Not that it is common for lay men to mistake zinc diecastings for aluminium. 121.221.33.239 (talk) 11:12, 11 October 2013 (UTC)

I recently had to destroy a hard drive of a computer I was discarding, to prevent data theft, and finally chose to drill through it to destroy the memory platter since it could not be easily smashed with a hammer or hatchet. The metal case seemed far harder than aluminum or zinc. Odd little fasteners were used to assemble it which I did not have in my set of screwdrivers and bits. I don't see why it would need to be armored since it is normally inside the computer case. Steel would provide some protection against external magnetism which might affect the stored data. Edison (talk) 14:47, 11 October 2013 (UTC)

What is the material in the top lid ..? Electron9 (talk) 21:49, 11 October 2013 (UTC)

Looking at an old Seagate HDD before me, it is (speaking as an engineer) a Magnesium alloy. Can't give any ref other than this. [1] The molding, tolerances, stiffness, economics, etc., can only be matched this alloy (unless you go to very exotic materials -in which case it would appear very different from the thing before me). --Aspro (talk) 21:55, 11 October 2013 (UTC)

It is amazing how much alloying can change a metal's properties. Pure aluminium is soft and ductile, whereas when alloyed with a little copper, becomes tough and rigid. One should not assume what the dominant metal component material is from the apparent properties. I can imagine that rigidity and low cost would be the primary criteria for a HDD chassis. Magnetic shielding is unlikely to be a consideration, since stray magnetic fields will be too weak to have a significant effect on modern magnetic recording media. — Quondum 20:07, 12 October 2013 (UTC)

Being die cast does not exclude aluminum as a possible candidate. Here is one website (blocked link, google ehow "What Are Computer Hard Disk Drives Made Of?") which supports my original answer. The housing is very rigid and is usually made of thick aluminum. Vespine (talk) 00:45, 14 October 2013 (UTC)

Duralumin is not used in diecasting, (re Quondum's link). Note that adding copper to aluminium does NOT make duralumin. While copper is the next largest fraction after aluminium, it is the other elements added (principally manganeses) that make it duralumin. If other elements are not added in significant fractions, or other elements are added, it becomes aluminium bronze with a nice gold colour and completely different mechanical properties, or nordic gold, used for coining, for instance.

However, you are certainly correct in saying the alloyed elements can make a big difference in properties, which is why zinc alloys used in diecasting are not soft like pure zinc. 121.221.33.239 (talk) 00:56, 14 October 2013 (UTC)

What kind of spider is this?

I saw this at Hayes & Harlington Station in west London.

https://dl.dropboxusercontent.com/u/8129635/Photo%2016-08-2013%2016%2019%2053.jpg

— PhilHibbs | talk 14:52, 11 October 2013 (UTC)

The distinctive markings on the back suggest that it's a Steatoda nobilis or False Widow spider. They have become more common in the UK kn recent years, and have been the subject of some alarming, but possibly overstated or hoaxy, stories - see e.g. this one (warning: alarming image) which came up on my Facebook feed today. 16:39, 11 October 2013 (UTC)

Some more from the reliable folks at the BBC, which I saw a few days ago on the telly: False widow spider sightings in the UK on the rise. Alansplodge (talk) 18:38, 11 October 2013 (UTC)

Happens in the US too; just today the paper had an article about a man who had vanished and was declared dead 30 years ago, but showed up alive (and not a zombie) recently, much to the surprise of his remarried widow. Gzuckier (talk) 04:07, 13 October 2013 (UTC)

Looks more like a Steatoda grossa to me. — PhilHibbs | talk 14:41, 5 November 2013 (UTC)

Say WHAT? Nostril specific sniffing test for Alzheimers

Can someone cast suitable aspersions on the credibility of this? [2] [3] (original report: [4]) I know nothing is impossible in biology, but......... this really puts that to the test! (I don't have access to the journal, never heard of it, and it's from the University of Florida... still...) Wnt (talk) 16:22, 11 October 2013 (UTC)

There's nothing about it that strikes me as outright impossible, but it's a small-scale pilot study with loose methodology, and those sorts of things often don't hold up when done on a larger scale with more careful methodology. In short, good enough to justify a more thorough investigation; not good enough to take seriously as a diagnostic tool yet. (I don't have access to the journal either; I'm judging by the abstract.) Looie496 (talk) 16:43, 11 October 2013 (UTC)

I do have access, and a quick scan of the paper doesn't reveal anything strikingly bad about it. They're just measuring olfactory discrimination type responses, as they say in the paper, it is known that the olfactory cortex is an early victim of AD (loss of smell is well described). So not too shocked there. Whether it will translate into a clinically relevant test, time will tell. As far as the journal goes, I'd never heard of it either, and I work as a neuroscience researcher, and have published in the Journal of Neuroscience amongst others. It seems to be a genuine journal though, if not a very impressive one, with only an impact factor of 2.4. EDIT: Forgot to address the nostril specific effect, yes that's a bit odd, but possibly one hemisphere is affected earlier in the disease process than the other? Not sure. Fgf10 (talk) 17:12, 11 October 2013 (UTC)

(ec) Not crazy at all. (Argument from incredulity isn't generally a helpful analysis technique.)

There's a lot of literature out there that report microsmia(diminished sense of smell) and anosmia (loss of sense of smell) as symptoms associated often associated with Alzheimer's disease. AD patients often have trouble sensing and identifying particular odors, even at very early stages and while having very mild cognitive impairments. For an overview, try Rahayel et al. (2012) "The effect of Alzheimer's disease and Parkinson's disease on olfaction: a meta-analysis" Behav. Brain Res. 231(1):60-74. It is also known that there tends to be left-right asymmetry in the loss of gray matter in Alzheimer's patients (the refs are in the paper), so it's not unreasonable to hypothesize there might be an associated asymmetry in sense of smell.

Thanks for pointing this out - I should have thought to look at the reference list. [5] looks useful. Wnt (talk) 17:49, 11 October 2013 (UTC)

As Looie496 says, it's a single small study at a single clinic. There are the usual concerns and caveats about the robustness and reproducibility of such studies in general, but I didn't see any obvious red flags, and it suggests an area for further research. TenOfAllTrades(talk) 17:13, 11 October 2013 (UTC)

Ethics in scientific research

Why is that in the 19th century and early 20th century people could do whatever they wanted in science without any limitations of ethical standards? I learned that cars were invented prior to mandating that you can't drink and drive at the same time! In science, you hear stories about unethical well-known experiments that were carried out, like that experiment where Clark Hull trained Ernest Hilgard to blink in anticipation of a slap to the face. Fortunately, the slaps did not dissuade Hilgard from going on further into research. 164.107.102.72 (talk) 16:37, 11 October 2013 (UTC)

This actually seems more like a Humanities question - you should get better answers there. I can't think of a good scientific source that could explain it, though obviously we can reference developments like the Nuremberg Code without a deep understanding of the cause and effect involved. But at a time where slaves could be whipped with impunity, or later on, where "free" blacks and the poor were routinely exploited under Jim Crow, I can hardly imagine a code of ethics would be more than rudimentary, except within isolated subcultures. Wnt (talk) 16:41, 11 October 2013 (UTC)

It's certainly true that ethical standards have become stronger over time, but it's not true that people were ever able to do whatever they wanted with no limitations. For example, in the 19th century and earlier, people who studied human anatomy often had to obtain material by illegal means, and were subject to very severe penalties if they were caught. Looie496 (talk) 16:49, 11 October 2013 (UTC)

The ethical values have evolved over time. Also, we now have a more formal system of approving research proposals, testing whether ethical guidelines are satisfied is a standard part here. But you can't blame previous generations for not having our ethical norms, as they are subjective to some degree. E.g. the limit on your blood alcohol level for diving is rather arbitrary, and there is no limit on many other prescription drugs that will also affect driving abilities. Another example is that we have rules of pollution, but air pollution isn't taken very serious. Euthanasia is illegal in many countries because of opposition from religious organizations. That's arguably a severe human rights violation of those terminally ill people who are now deprived of making the choice to end their lives. In the grander scheme of things, the way we treat the environment is so bad that if ET were to arrive here on Earth he would probably decide to exterminate the entire human race.

So, my point is basically that most people will tend to support whatever the ethical values of the society he lives in are, and will view the ethical values of other societies as being "wrong". Count Iblis (talk) 16:55, 11 October 2013 (UTC)

Um... I think Clark and Ernest are both white. And none of you have mentioned ethics in animal research. 164.107.102.72 (talk) 17:09, 11 October 2013 (UTC)

• Ethics in specific fields tend to evolve over time and only after the field itself develops. The rules of the road in driving such as highway passing rules didn't develop until after driving was around for a while. Horse whispering and other non-coercive methods of "breaking" horses have only developed in the last century, while horses have been ridden since 4000 BC. The notion that infants didn't really feel or suffer from pain ended only in our lifetimes. Educated Romans often had very admirable ethical codes, such as Stoicism, but there is a reason people of the countryside were called villains and pagans. Progress isn't unidirectional--the British Empire ended slavery and high-seas piracy, both of which have made striking comebacks. Historically speaking, animal research is a very recent phenomenon. See also Steven Pinker's The Better Angels of Our Nature. μηδείς (talk) 00:25, 12 October 2013 (UTC)

Medeis, I think you better read slavery as the British Empire did not end it. Saudi Arabia didn't abolish slavery until 1962 and they still had about 300,000 slaves in 1963. I doubt too that the BE was able to eradicate piracy. CambridgeBayWeather (talk) 05:16, 12 October 2013 (UTC)

I am aware of such continued local slavery and piracy, but didn't think it necessary to mention there were pockets of such barbarity. μηδείς (talk) 05:50, 12 October 2013 (UTC)

• In the UK the Anatomy Act 1832 was passed to prevent the illegal trade in corpses mentioned above and the Cruelty to Animals Act 1876 set strict limitations on scientific experiments on animals calculated to cause pain. The Cruelty to Animals Act had developed from earlier Acts put in place to protect animals. See also: History of animal testing#Early debate. Richerman (talk) 23:20, 12 October 2013 (UTC)

• The claim that people "could do whatever they wanted" is simply false. The legal system has always regulated what people can do vis-a-vis each other, that is, for as long as it has existed. Before there were laws, there were other means, such as, if someone slapped someone on the face, they could slap them back. Ethics committees and similar review bodies did not invent the idea of social control. From the pdf found by googling "clark hull ernest hilgard slap", see here, there is nothing suggesting how hard the slap in the face was, so any claims about the ethical standards are open to debate. The history of the modern ethics process begins with Karen Ann Quinlan, and is something of a response to specific circumstances. You may like to look into the history a little further. IBE (talk) 03:39, 13 October 2013 (UTC)

There are many possible answers to your question, but I'll give three:

1. Professional science has only existed since the mid-19th century, and modern medicine is later still. It takes a while for consensus to form. Even today, there is no consensus among the scientific community about the morality of stem cell or animal research.

2. There were early regulations, but they weren't as extensive or protective as today's. Richerman gave two good examples.

2. Isaac Newton said "If I have seen further, it is by standing on the shoulders of giants." He was talking of science, but the same is true of morality. You have all of mankind's knowledge at your fingertips, searchable with a speed unimaginable even 50 years ago. The world has gathered 150 years of experience in professional science, experimented with every conceivable form of moral code, seen horrors like the Holocaust or Unit 731, and done away with war or even borders on an entire continent. Looking back at someone from 1800 and asking how he could be so immoral is like berating Ptolemy for not landing a rover on Mars. For all you know, future generations might look upon today's slaughterhouses and animal research labs in the same way we look upon the Holocaust. --Bowlhover (talk) 06:13, 13 October 2013 (UTC)

Digital clock speeding up.

Hi.

I've had this clock for about twenty years. It's a Cosmo Time, model #E517A. In the last two days, it's been counting fast (about 22 seconds per "minute"). Any ideas what's going on here? InedibleHulk (talk) 17:15, 11 October 2013 (UTC)

See if the clock has a 50/60 Hz mains frequency switch that your cat has bumped to the wrong position. Other random possibilities: it's running on battery instead mains (uses wonky internal crystal instead of mains frequency), dirt or moisture got inside it, broken electronics, your utility company has switched to remotely readable electric meters and the clock is confused by their control signals. 88.112.41.6 (talk) 17:37, 11 October 2013 (UTC)

That last one seems possible. I'll have to look into it. Maybe the dirt thing, too (I'm a heavy smoker, but have been the whole time). Thanks for the tips. InedibleHulk (talk) 17:56, 11 October 2013 (UTC)

Check for the Hz switch though, or 110/220 volt switch. Because if you live in 50 Hz world and your clock is configured to 60 Hz, that's *exactly* 22 seconds per minute overclocked. 88.112.41.6 (talk) 18:10, 11 October 2013 (UTC)

I don't see a switch, and think I live in 60Hz land (Ontario). But I'll look harder (at my clock and recent Hydro news). When I unplugged the clock, I noticed the 12:00 flashed much faster than normal. In 15 minutes, it's already 4 minutes ahead. Just another reason to hate smart meters, I guess. InedibleHulk (talk) 18:19, 11 October 2013 (UTC)

Back of the clock says "AC/CA 120V 60 Hz 5W". InedibleHulk (talk) 18:21, 11 October 2013 (UTC)

Not necesarrily a smart meter issue. Google suggests that it has a 9V battery backup, which means everything probably runs off DC internally. I would guess something has failed in the oscillator circuit that it uses to keep time. Running it off battery would let you know if the problem is in the clock or in the incoming power. Katie R (talk) 18:47, 11 October 2013 (UTC)

Perhaps. If I find a 9-volt battery, I'll test that. Ten minutes off right now. InedibleHulk (talk) 18:50, 11 October 2013 (UTC)

Can't find a battery. But my "minute" was 45 seconds, at last check. Seems to be gradually speeding up, so I'd guess the 22-second connection to 50/60 was coincidence. My smart meter is consistently turning to a row of 8s every two seconds (for whatever that's worth). From what I've learned today of quartz timekeeping and the eastern power grid, I'm leaning toward blaming Hydro. I can't think of anything that would have damaged the crystal (before I checked for a switch, the clock hadn't moved for months).

I think I have enough of a start to try and solve this on my own now. Thanks, folks. I won't trouble the Science Desk with the question of whether to freeze or starve for time-of-use pricing this winter, which becomes the bigger issue, the more I Google. InedibleHulk (talk) 19:57, 11 October 2013 (UTC)

Amazingly, that kind of horrid inaccuracy is just what I expect from a Chinese digital clock running off the battery. But, clocks are cheap, so I'd just pitch it out and replace it. StuRat (talk) 00:56, 12 October 2013 (UTC)

Honestly, I firmly believe that any clock with a cord is a monument to stupidity that ranks right up there with the Pyramids of Egypt. The point of a clock is to be reliable; the nature of electricity not to be; and that's not even getting into the issue of a clock using so much power that its "emergency battery backup" that can keep it going for four hours contains sufficient energy to launch it halfway into space. I have an old digital alarm clock, no cord, that dates back to somewhere in the late 1980s, which I remember getting a single new 1.5V battery for perhaps twice, with a loud alarm and an easily readable display (though not illuminated). And I don't understand how things like yours are allowed to exist. Wnt (talk) 03:13, 12 October 2013 (UTC)

OK, I'll bite. Why are the Pyramids of Egypt "a monument to stupidity"? -- Jack of Oz ^{[pleasantries]} 04:53, 12 October 2013 (UTC)

Well, they were designed to protect the dead pharaoh and all his treasures, but were mostly robbed in short order. Later pharaohs realized that a pyramid is just like a giant "Rob me !" sign, and hid their tombs, instead. And, I suppose that wasting all those resources which could be better spent on roads, etc., could be viewed as stupidity, depending on your POV. StuRat (talk) 10:59, 12 October 2013 (UTC)

Pyramids and electric clocks and the Great Wall of China and eight-track tape players and that sort of thing all qualify as things that "seemed like a good idea at the time." ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:14, 12 October 2013 (UTC)

Meh. I live an unstructured life, so the time of day is mostly just a curiosity. And this clock answered that curiousity for decades. It's still somewhat aesthetically pleasing (compared to a pyramid), and I have other clocks, if I need to know. If a battery or cleaning can fix it, it's still a great clock. InedibleHulk (talk) 18:45, 12 October 2013 (UTC)

You sound like the guy in an old Cheech and Chong bit, where someone's trying to sell Chong a watch, and he says, "I'm not into time, man." ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:54, 12 October 2013 (UTC)

Makes sense. I also look like Chong. InedibleHulk (talk) 18:48, 13 October 2013 (UTC)

So Stu, I wonder why we don't just call them the Pharoahs' Tombs. -- Jack of Oz ^{[pleasantries]} 16:48, 13 October 2013 (UTC)

One possible cause of a digital clock losing its accuracy, from my experience: A couple of customers in the same neighborhood reported that after the power was off and restored, their digital thermostats ran fast. Investigation showed that a component in the clock (capacitor?) synchronized it to the mains frequency, and the spike from the interruption (lightning related) had burned out the coupling component, allowing them to run on their own frequency, which happened to be fast. Alternatively a spike or age related failure could have damaged or changed a component in the oscillator circuit of your clock, if it does not synchronize the the mains. Edison (talk) 19:32, 12 October 2013 (UTC)

The last outage was lightning-related (and almost fried me), but at least a month ago. Maybe it caused some damage, which gradually got worse. I can't see screws on the clock, so putting off opening it lest it doesn't fit back. But I'll definitely look for burns when I do.

If failing after twenty years of satisfactory performance, you might consider replacing your watch with a radio-controlled watch. Whether your life is unstructured or not, it's nice to know that your watch is correct to the nearest second. You'll know if you actually need to run to catch the bus. Less stress. If you have the luxury of arriving late whenever you please for work or any other appointment, well good for you! Otherwise, the Casio ones (Waveceptor) are not very expensive. They function well in my experience, although I've had to manually adjust the time zone when traveling sometimes, if my hotel room has been in a city center, surrounded by tall buildings. --NorwegianBlue ^talk¨

It's an alarm clock with the problem. My watch is fine, though I rarely wear it. I mainly see buses, meetings, planes and hotels in movies. Not quite Cletus the Slack-Jawed Yokel, but closer to that end of the spectrum. InedibleHulk (talk) 18:48, 13 October 2013 (UTC)

I'm with you there. If you are constantly late for things, you don't need a better watch/alarm clock, you need to restructure your life so people stop expecting you to be places at specific times. :-) StuRat (talk) 21:52, 13 October 2013 (UTC)

As someone with a reliable watch that used to catch the bus into work, while the watch ma be acurate to the nearest second, the busses rarely are! MChesterMC (talk) 10:17, 14 October 2013 (UTC)

Photonic molecules

Can someone give a really dunce-level (and above all, long) explanation of photonic molecules? (Some of the results might be used to edit the article)

In particular:

• Why is there such a thing as a Rydberg blockade? What conditions prevent adjacent molecules from having the same excited state? What is the range of the effect, and what particle mediates it? Does it apply only to electrons, or would it also affect nuclear isomers? Can it be used for some kind of imaging akin to X-ray crystallography that maps the positions of pairs of excitable atoms? Etc. You don't have to answer some of these unless you really want :)

• How does a photon excite an atom while passing through it?

• What exactly is dispersive coupling?

• The photons exit the cloud as "normal photons (often entangled in pairs)". Does this mean that they are not photonic molecules at that point, but subject only to normal quantum entanglement?

• Does the photon "appearing to have mass" relate directly to the refractive index? Where does this mass come from? Does this work the same way as the Higgs boson gives mass to other particles? Does photon "mass" fold spacetime (ever so slightly) like Higg-derived mass?

Admitting utter confusion... Wnt (talk) 17:26, 11 October 2013 (UTC)

I suspect that you'll find few people who are less confused about this than you are. It takes specialized knowledge to be able to answer pretty much any of these questions. One could start to make guesses on some of these. What I say here should be treated as pure speculation; perhaps it will serve to trigger some responses and corrections from others.

• I'm skipping your first bullet.
• A Rydberg atom has an electron that is exited to nearly the point of ionization, where the energy levels are very close to each other. It seems likely that a low-energy photon will be able to easily excite it further during a normal photon absorption process, because of the availability of states with energy levels close to the level necessary. If the atom is in a suitably prepared superposition of Rydberg states, it seems reasonable that the incident photon would encode its quantum state (momentum, energy, polarization) on the excited electron, and that this could manifest as preferential emission of a photon with similar characteristics after some delay.
• Dispersive coupling probably relies on an interaction between dispersion and non-linearity in a medium. An example might be in Soliton (optics), where the effect occurs at high intensities and keeps a photon pulse very closely confined – either laterally or longitudinally. One might imagine a similar effect here, except that the number of photons is very small.
• I interpreted the photons to be normal photons upon exit, entangled as you suggest. It would only be within the medium that they could interact and form "molecules".
• A quantum field "appearing to have mass" would normally relate to how it propagates as wave. In the simplest case, this would lead to a propagation velocity that slows to zero as its energy drops to some critical value, its "rest mass". This occurs in superconductors, where photons below the critical energy only propagate into a superconductor as virtual particles: they "appear to have mass" inside the superconductor, which could be interpreted to lead to the Meissner effect. This would perhaps also be seen as a reducing refractive index (starting at ∞) at energies above the critical photon energy. The case here is likely to be more complicated.

So, now I'll wait for others to shoot all this down... — Quondum 19:39, 12 October 2013 (UTC)