Wikipedia:Reference desk/Archives/Science/2008 October 27

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Science desk
< October 26 << Sep | October | Nov >> October 28 >
Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

October 27[edit]

Indoor marijuana cultivation retardant[edit]

I heard of a chemical that can be put into a house's air ducts that will hamper marijuana growth by I think preventing pollination or something. I've read the mj cultivation and indoor cultivation articles and looked on google - does anyone know? —Preceding unsigned comment added by (talk) 02:16, 27 October 2008 (UTC)

Preventing pollination is often considered a good thing, so that's probably not it. —Tamfang (talk) 02:58, 27 October 2008 (UTC)
Narking on the cultivator would be a more efficient solution to the problem of having someone in the household cultivating marijuana, of course with its own risks. Edison (talk) 03:06, 27 October 2008 (UTC)
No, preventing cultivation in the first place is the more efficient solution. Turning in a grower does nothing to prevent the property damage or protect the property owner from legal and property seizure ramifications of owning a marijuana house. Telling potential renters that dope wouldn't grow because of the retardant DOES.
Putting a chemical into a house's air ducts could be a health and safety hazard, and your tenant might have a claim against you in law. There is only a remote chance that a particular tenant would be intending to grow marijuana. Depending on the jurisdiction it would be better to build into the tenancy agreement a right for the landlord to inspect the property at regular intervals, and a heavy financial penalty if they were found to be engaging in an illegal activity. Itsmejudith (talk) 20:35, 27 October 2008 (UTC)
None of which prevents the landlord from TELLING his tenants that he did this in order to discourage them from undesirable behaviors. Not everyone is smart enough to think these things through to their logical conclusions. SteveBaker (talk) 05:16, 28 October 2008 (UTC)
Obviously nobody's actually heard of the chemical, because it's safe, it's approved for use, and it's on the market right now. I just can't remember the name of it, and frankly nobody who's felt the need to contribute to this thread has been the remotest bit helpful. Please credit people with a modicum of sense? We're not all looking for a bunch of uninformed or general opinions. Some of us actually know our stuff, we just need a little nudge in the right direction. Don't anyone bother actually answering this question, I won't be back to this page again. —Preceding unsigned comment added by (talk) 13:30, 29 October 2008 (UTC)
I was just about to answer the question, but since the questioner won't be back, I guess there's no point. -- kainaw 13:39, 29 October 2008 (UTC)


I haven't read Flatland in years, so maybe this is answered there, but anyway: An object in a 2-dimensional land such as flatland would appear from inside the land as a line segment, possibly changing length is the object turned. Except -- the only way it would be visible is if there was some non-zero third dimension ("height") to this figure; otherwise, there would be nothing to see. (Similarly if in the real world you drew a line segment with zero thickness, you wouldn't see anything.) So this implies that there must be a non-zero infinitesimal third dimension. This would then imply that a 3-dimensional world must have an non-zero fourth dimension to be able to actually perceive anything (aside from time: time would apply in the 2-dimensional land as well), and that the fourth dimension world would have a non-zero fifth dimension, and so on. Therefore, the universe has infinite dimensions.

What's wrong with how I'm thinking? zafiroblue05 | Talk 03:07, 27 October 2008 (UTC)

By "see", you are referring to a light particle bouncing/reflecting/emitting from a surface and hitting a sensory organ in some sort of eye. Light particles may be defined as having width, but it is just as easy to define them as a zero-size wave of energy. So, it is not necessary for the surface to have height since the wave of energy coming from it doesn't have to have height. Also, the point of flatland isn't that there isn't height, it is only that the beings living in flatland cannot comprehend or sense height. So, flatland doesn't say there isn't height. In fact, it uses a demonstration of height - shoving your finger through flatland. The beings there will see a weird object that changes shape as your finger moves through and they see it slice by slice. -- kainaw 03:59, 27 October 2008 (UTC)
Why shouldn't a Flatlander's eye have a one-dimensional retina that sees one-dimensional images? Consider the cross-sectional diagrams you've seen of light entering an eye and forming an image; now take that diagram literally. In our world something with no thickness has no substance, but Flatland is not our world. A four-dimensional observer might make the same comment about our vision that you make about Flatland vision. —Tamfang (talk) 05:29, 27 October 2008 (UTC)
(I think?) that's what I'm saying - that we shouldn't be able to see each other unless there is another physical dimension in which we are "thick," just as flatlander wouldn't be able to see each other if they really had no height. And that by induction this would continue to an infinite amount of dimensions. But Kainaw's explanation that we don't have to be "thick" in another dimension because light can be a zero-seze wave (that can be absorbed and therefore processed and seen) seems to work for me. zafiroblue05 | Talk 05:59, 27 October 2008 (UTC)
Well, I see two problems in your reasoning. First off, the flatland example only suggests that you need N+1 dimensions to be able to perceive in N dimensions. Once N dimensions are present, perception in N-1 dimensions becomes possible. Nowhere in this argument is an N+2 dimension necessary unless there are beings that percieve in N+1, and so on.
The other problem I see in your reasoning is that your premises are about the nature of perception, but you draw conclusions about the nature of the universe. Our perceptions are structured from sense data we receive from our body and are structured into experience by the mind. How we understand the universe through our perceptions does not need to match up with reality as long as our perceptions remain consistent. Mathematically, we could actually live in a 2D holographic universe, and we wouldn't even know it because our experience is 3D! It's even possible that we don't have accurate access to the content of our minds (a very wierd but fun idea). In the very least, you must concede that the fact that you can watch TV and see more than flashing lights is testament to the fact that our brains perceive depth in our world in ways that at least aren't always accurate. --Shaggorama (talk) 07:21, 27 October 2008 (UTC)

I think the problem is that you're not seeing things from a truly 2D viewpoint. There is no reason why truly 2D photons coming from a 2D light source should not bounce off a 2D object, be focussed through a 2D lens and land on the viewer's (presumably) 1D retina - thereby forming a 1D image. There is no need for any extra dimensions to make this work. Hence your extrapolation (which in itself is a bit 'iffy') is entirely invalid. Incidentally - the book 'Flatland' was written in 1884 and it's basically crap. You won't learn anything about the nature of a 2D world from it. It's mostly a diatribe about class distinctions and politics - it's sexist as all hell (quite an embarrassment to read, actually) and its ideas about a 2D world are poorly thought out from any kind of scientific perspective. If you want a truly great book on the subject, I strongly recommend "The Planiverse" by A.K.Dewdney. It's by far the best book to cover the idea of a 2D world and it has a really careful treatment of what it would mean to live in two dimensions - the world is fleshed out in great detail with lots of interesting diagrams (you can easily spend 20 minutes looking at the 2D steam engine or the structure of a 2D 'house' or a fishing boat. The appendices to the book cover some serious scientific issues that probably mean that a 2D world with the kind of richness needed to form stars, planets and creatures could probably not exist at all. For example, it's believe that 2D atoms would be unable to form chemical bonds at all. But the book also has a great plot and I recommend it to anyone with an enquiring mind (which means everyone here at the science ref desk!) - read it to your kids too. SteveBaker (talk) 13:34, 27 October 2008 (UTC)

I think Flatland was being satirical about the sexism thing. Also, who is to say that light and sight work the same in flatland, IIRC, gravity pulls consistently southward, and gets less potent toward the northern latitudes, and rain always "falls" in the same direction. Sliver Slave (talk) 22:43, 28 October 2008 (UTC)

Urgent need to pee[edit]

Suppose someone really really really goes to go but they don't want to because it would be embarrassing (eg, marching in a parade) or very messy to clean up (eg, driving a car) or very both (eg, riding in the boss's car.)

Can a person hurt themself by trying to hold it till they get to an "appropriate" place? Or is it safe to hold on as long as they can?

Second part of the question -- are there any strategies to help people "hold on"? (Please, no suggestions to carry clothespins at all times.)

CBHA (talk) 03:23, 27 October 2008 (UTC)

PS: Just on the off-chance that anyone wants it, I irrevocably agree to release this contribution under the terms of the GFDL. CBHA (talk) 03:26, 27 October 2008 (UTC)

Spontaneous rupture of the bladder is very rare, but does occur. To quote a case study, one scenario is: "The pathogenesis involves bladder overdistension and thinning of the dome from diuresis. The patient ignores natural cues to void due to alcoholic stupor. Thereafter even trivial increase in intra abdominal pressure like coughing can rupture the bladder." - Nunh-huh 03:52, 27 October 2008 (UTC)
See Tycho Brahe#Death for a well-known case where someone was claimed to have killed himself in this way, although not with a rupture. --Anon, 05:53 UTC, October 27, 2008.
BTW, there is no need to include a statement licensing your contribution under the GFDL. By posting any text to wikipedia, you've already agreed to release your contribution under the terms of the GFDL, without exception. And it is not as odd as it may seem since there are many wikipedia mirrors who mirror our content completely legally. And we archive all reference desk questions so who knows, maybe some day someone will want to publish a book or CD or whatever 09:45, 27 October 2008 (UTC)
I need to go to the toilet now.I bet that was your suggestion. There's probably a word for that like one yawn making everyone else yawn but it 'scapes me now - gotta go :) Dmcq (talk) 16:34, 27 October 2008 (UTC)
Contagiousness. PrimeHunter (talk) 18:08, 27 October 2008 (UTC)
or suggestion. --Tango (talk) 23:36, 27 October 2008 (UTC)
I've heard your kidneys just stop producing urine after a while. If that's correct, you could probably get kind of sick if you let the toxins in your bloodstream build up long enough. I'd consider that hurting yourself. — DanielLC 23:42, 27 October 2008 (UTC)
As a practical matter, wouldn't bladder control give out long before the kidneys ceased to operate (leaving aside the case of someone with kidney disease)? CBHA (talk) 04:45, 28 October 2008 (UTC)
not too risky as one episode, but doing this as a habit can cause the bladder to stretch, and that makes it weaker. (as the radius of a sphere increases, the projection of the tension of the wall in the radial direction becomes less, until of course at infinite radius the two are perpendicular and the inward pressure is zero no matter how high the tension of the wall) Gzuckier (talk) 06:06, 1 November 2008 (UTC)


Can objects stuffed up the eye go down the optic nerve? February 15, 2009 (talk) 04:18, 27 October 2008 (UTC)

Sorry, but your question isn't clear. If you're asking for medical advice (For example, if you've crammed something into your eye.) then we can't give medical advice but if you're worried then you should probably get to an emergency room.
If you're just curious, you might be thinking of an ice pick lobotomy. I don't think that actually touches the optic nerve, but it's a path from the eye-socket to the brain. APL (talk) 05:01, 27 October 2008 (UTC)
Sorry OP, APL seems to have confused a question about human anatomy with a request for medical advice. Objects don't really travel down nerves, just chemicals. But, the optic nerve passes through the a hole in the orbit called the optic canal, which does go directly to the brain. A quick browse around google gives the canal a diameter of 4-6mm in adults, so some objects (such as icepicks, as APL gruesomely suggested) can pass through the without damaging the bone. But please, do not stuff anything into your or anyone elses eyes. —Preceding unsigned comment added by (talk) 07:02, 27 October 2008 (UTC)
I did not entirely assume it was a request for medical advice as you're suggesting. My first sentence was a statement that I didn't find the question clear. The second was an answer for if it was medical advice, and my third and fourth sentences was an attempt to offer an informative link about my best guess of what they were asking about.
However, I had assumed that the article on ice pick lobotomies would at least briefly discuss the route from the eye-socket to the brain. Looking more closely, I see that isn't the case. APL (talk) 07:23, 27 October 2008 (UTC)
The questioner did not present any intent to either put in or pull out something out of his optic nerve. Sounds unlike medical advice to me. Mac Davis (talk) 19:00, 27 October 2008 (UTC)

Solar-To-Electric Efficiency (STEE)[edit]

In Wiki–page vide- numerous method of harnessing solar energy is explained. But only under sub section- "solar pond" I came across this parameter "Solar-To-Electric Efficiency"(the S-pond has STEE 2%).Whilst under section Photo Voltaics therein, I read

"converted less than 1% of incident light into electricity".

Is the same STEE intended therein? What about Concentrating solar power? Under its main article vide I read

"Parabolic dish systems display the highest solar-to-electric efficiency among CSP"

without any mentioning of any percentage under the same sub-section. Apart from these, there are numerous methods of harnessing solar power. It would be delighting to compile a short article of STEEs of different methods, history, development, breakthroughs, etc.

Would this be a valid contribution (by anyone)? "Solar-to-electric efficiency of different methods".

By a reader of Wikipedia (talk) 12:32, 27 October 2008 (UTC)

Yes - anything we can add to the encyclopedia in these areas of increasing importance is worth doing. I would only caution you though that we require our contributors to supply 'references' for every significant fact they provide - so you'd need to come up with reliable references to books, scientific journals, trade magazines and things of that kind to back up most of what you say. Also, if you happen to work for a company that makes or sells those things (so that there might be a conflict of interest) - then you should probably NOT write the article yourself - but rather use the article's Talk: page to pass on information and references to the people who are actually doing the writing. But aside from those two concerns - YES! PLEASE! SteveBaker (talk) 13:18, 27 October 2008 (UTC)
It's worth noting that the "less than 1%" figure applied to the very first solar cells, which were little more than a nineteenth-century curiosity. Silicon solar cells, developed in the 1950s, started out at roughly 5% efficient. Widely-deployed photovoltaic panels today run from about 12 to 24% efficiency. Costly special-purpose panels (primarily used aboard spacecraft) are better than 30% efficient, while experimental cells have exceeded 40% efficiency in the lab. TenOfAllTrades(talk) 14:15, 27 October 2008 (UTC)
You also need to be aware that terrestrial and space solar cells efficiencies are computed with a different standards so they cannot be simply compared. The standard for space-faring solar cells includes UV intensities that are not seen on Earth because of atmospheric blocking. Rmhermen (talk) 20:12, 27 October 2008 (UTC)
We would be really glad to see you (and anyone who has contributed to this) on Talk:Solar energy, as there are lots of improvements to the article that we are currently discussing there. Itsmejudith (talk) 20:30, 27 October 2008 (UTC)


I came across Thixotropy which suggests ketchup shows thixotropy. I'm not however certain if this is true (or for that matter, any of the other examples are correct). I believe it is definitely Shear thinning (from a NASA article) but both wikipedia articles note there is a distinction and the terms are often confused (although I presume itcould be both). Searching didn't help because there are far too many references which treat the two as the same thing. I had the same issue previously with with silly putty where there was confusion over whether it showed dilatant or rheopecty (it appears it is a dilatant but the article had inaccurate information for a long while) Nil Einne (talk) 14:12, 27 October 2008 (UTC)

Ketchup seems thixotropic to me. exactly the way toothpaste is. Mac Davis (talk) 18:57, 27 October 2008 (UTC)
There are a lot of Non-Newtonian fluids out there - and the precise classification of which is of which type is a bit tricky. Fortunately, our article on the subject specifically names Ketchup as a non-newtonian fluid and labels it as being Thixotropic. SteveBaker (talk) 23:14, 27 October 2008 (UTC)
Should it also mention it's shear thinning? Nil Einne (talk) 10:46, 29 October 2008 (UTC)

How is the phase between electric and magnetic waves in a lightwave determined?[edit]


Consider this image of a lightwave.
What I want to know is how is the phase relationship between E (electric force) and B (magnetic force) determined?
How is it measured? I mean, how do we know the phase is 0° and not, say, 90°?

Onde electromagnetique.svg

Thanks! —Preceding unsigned comment added by InverseSubstance (talkcontribs) 17:55, 27 October 2008 (UTC)

Maxwells equations can explain this, these are from Faraday's law of induction and Ampère's circuital law with Maxwell's correction. To understand the 90° angle between the magnetic field, read Curl (mathematics). When you look at the equations you can see that E and B are related by differentiating twice (in a linear material), so that a sine turns into a -sine with a 180 degree shift. Graeme Bartlett (talk) 20:44, 27 October 2008 (UTC)

That's not what I'm asking. I'm trying to understand why it is that the electric force E and the magnetic force B are synchronized. I'm wondering how we know that when E is at maximum, B is at maximum too. I mean, is it possible for E to be to a maximum, and B to be at zero? So this question is about the phase in time, not in space. —Preceding unsigned comment added by InverseSubstance (talkcontribs) 23:14, 27 October 2008 (UTC)

OK if you look at Sinusoidal plane-wave solutions of the electromagnetic wave equation the equations have a solution. The derivative of the Electric field with respect to z the distance along the travel direction is proportional to the derivative of the magnetic field with respect to time. When you consider the wave is traveling, then z is equivalent to time, and then derivative of E is proportional to derivative of B, ie they are in phase. Do you need a more symbolic expression of this? Graeme Bartlett (talk) 05:46, 28 October 2008 (UTC)

Very good!
It looks like the E and B forces can in fact be out of phase, which makes the light have an elliptical form.
Thanks, -- (talk) 06:28, 28 October 2008 (UTC)

I Think you will find in normal space or materials that the fields will still be in-phase, for circular or elliptical polarization. The E and B vectors will spin around around the axis of propagation but still be in phase with the other field at 90 degrees in space with it. Graeme Bartlett (talk) 00:51, 29 October 2008 (UTC)

Why do Budgerigars have such crappy night vision when compared to humans?[edit]

Question as topic. From my experience with my own birds, it seems that they are unable to see objects in the dark until they are mere inches away (at which point, the budgie freaks out). If a budgie has a 'nightmare' (or a night fright, or whatever) and falls off its perch, it seems to be completely unable to find it again will flap around wildly and screech until the light is turned on. --Kurt Shaped Box (talk) 18:47, 27 October 2008 (UTC)

Well, they're not nocturnal birds so the obvious feature (specially adapted eyes) aren't present. In the article under vision here[1] their vision is maybe more strictly designed for full spectrum sunlight. Compare this with human adaptation, making our sight more versatile (sunlight, twilight and night). It'd be interesting to look at a budgie's eyes in terms of size ratio and compare that with human eyes ratio to body size as well. Julia Rossi (talk) 21:43, 27 October 2008 (UTC)
(after edit conflict)You'd think that a bird as low down in the food chain as the Budgerigar is would at least be physically capable of keeping something of a look out for nocturnal predators when roosting though, wouldn't you? If they are unable to spot a human at a distance of six feet in a room with the lights turned off, what chance would they have in the wild against an owl? --Kurt Shaped Box (talk) 23:13, 27 October 2008 (UTC)
Humans have about 7 million 'cone' cells that are responsible for daylight, color vision - and between 75 and 150 million 'rod' cells that are there for low light level monochromatic vision. If we didn't need to see in poor lighting conditions, we could either have eyes that were 10 to 20 times smaller (and therefore require less energy and less weight) - or we could have daytime vision that would be 10 to 20 times sharper. So we pay a LARGE price for our night vision. A creature such as a non-nocturnal bird might well do much better without reasonable night vision. SteveBaker (talk) 23:10, 27 October 2008 (UTC)
Wait, "we could [...] have eyes that were 10 to 20 times smaller"? Surely the area of the retina matters to the quality of our vision? We couldn't just have the same number of cone cells on a smaller retina and expect the same results, could we? Or would a different lens solve this? (talk) 21:44, 30 October 2008 (UTC)
in fact, the cone cells are concentrated in a very small part of the retina, the fovea. the result of this is the continual movement of the eye to see more than one little area at a time (saccade). this also means that rod cells, spread all over the retina, are responsible for not only night vision, but also the "seeing out of the corner of your eye" thing.Gzuckier (talk) 06:11, 1 November 2008 (UTC)

Harmonic Vibration[edit]

Two part question

1 - Is Sympathetic resonance the same concept as Harmonic vibration - i.e. a sound vibrating an object at a frequency that can eventually cause an object to shatter?

2 - Is it possible to weaponise this concept for use against humans? Could we induce SR/HV in the human skeleton, causing someones bones to shatter into powder?

Exxolon (talk) 19:21, 27 October 2008 (UTC)

Vibrations can only be sustained or built up if the Q factor is high. Bones and humans do not have such a response to vibration, so you need to put in very high power. The target will probably be affected less than the shooter. Graeme Bartlett (talk) 20:50, 27 October 2008 (UTC)
although there is a persistent urban legend about the military developing a weapon to excite specific resonances of the gastric tract to incapacitate the opposition nonlethally. i don't know if that's true, but can personally vouch for having my guts uncomfortably scrambled following the first time my buddy's dad left us alone at home with his macintosh stereo and wharfdale speakers for a few hours. Gzuckier (talk) 06:16, 1 November 2008 (UTC)

Staying underweight by thinking?[edit]

I was reading the article of L (Death Note), and noticed that one line read, "he remains underweight because the brain uses the most calories of any organ in the body." First of all, how much of this is true or false? Like for instance, if one were a deep thinker, would they be able to keep their weight down? What other metabolic functions are involved in this as well? Thanks, Valens Impérial Császár 93 20:09, 27 October 2008 (UTC)

While the brain does consume quite a fair share of the body's energy intake, the largest amount of the brain's function is not necessarily consumed by conscious thinking. Large areas of your brain are devoted to lots of unconscious processes, such as regulating all the processes that simply keep you alive. Also, there is no reason to assume that a person who spends more time in "deep thought" (i.e. thinking about really important or difficult problems) exhibits more brain activity than people who spend their time thinking lots about boobies and brands of beer. Also, what is "deep" for one person is not "deep" for another. Bill Belichick likely spends lots of time thinking about different things than does Stephen Hawking, yet each is as likely to spend as much brain activity in his own field. As a last thought, should not spend too much time looking for logical consistency or scientific stringency out of anime. Most of the time, people who write fiction just make stuff up. 20:28, 27 October 2008 (UTC)
Maybe you could try some of these deep thoughts. --S.dedalus (talk) 22:37, 27 October 2008 (UTC)
<Anecdotal evidence warning> I remember ending up with terrible headaches after study sprees, exams that (mostly due to lack of preparation) needed a lot of improvisation and after endless hours of chess games. Something that definitely didn't happen after equally long hours of day-dreaming during boring trips. --Taraborn (talk) 22:39, 27 October 2008 (UTC)
<Not medical advice however much it may look like it warning ;)> My guess would be that you were focusing close up for long periods of time - it's your eyes that caused the headaches, not your brain. You should take regular breaks from close up work and allow your eyes to focus on something in the distance. If you get such headaches regularly, then see a doctor or optician, of course (I did and it worked for me!). --Tango (talk) 23:32, 27 October 2008 (UTC)
Just because your brain uses more calories than the rest of your body - doesn't mean that you can make it use yet more by doing something differently. SteveBaker (talk) 23:04, 27 October 2008 (UTC)
Actually, despite a lot of the anecdotal pessimism in the answers so far, the brain actually does consume a huge amount of energy and what you are doing with it does affect how many calories it consumes. "Even at rest, the brain consumes 20% of the body's energy."[2] "During periods of peak performance, adults increase that energy consumption by up to 50%."[3] Thinking "deep thoughts" is probably not enough—doing challenging mental work, though, is more on par. Speculating about whether there is a God by itself is probably not deep enough—trying to rigorously prove it one way or another, working your way through all of the logical ends, probably is. Many "deep thoughts" are pretty cognitively empty unless you back them up with rigor.
Could you keep thin through mental activity? Potentially. It would depend on your overall calorie consumption, size of brain, amount of mental activity, etc. There are also basic metabolic issues that differ from person to person. Clearly just engaging in regular mental activity is not enough for some people—think of Herman Kahn, for example, who was an active thinker by any definition, but he was a complete sybarite and probably far out-consumed any calories burned by thinking (and probably did do enough walking in any case—cutting out normal calorie-burning activities like walking is pretty much the equivalent of chowing down on cake). -- (talk) 01:14, 28 October 2008 (UTC)
Studies at MUSC (shown on Mythbusters) use brain activity (which may possibly relate to calorie usage) to identify if a person is telling the truth or not. As shown in the episode, when a person lies, it takes more effort and shows up as more brain activity. So, you could stretch this all very thin and make an unscientific claim that telling nothing but lies will cause the brain to burn more calories. Of course, everyone here should know at least one person who constantly lies without apparently burning many calories. -- kainaw 01:19, 28 October 2008 (UTC)
"Hi Honey...sorry I lied to you - but I'm on a diet." Hmmm - well it's worth a try. SteveBaker (talk) 05:10, 28 October 2008 (UTC)
Offhand can't think of any obese fiction writers. Anyone? Julia Rossi (talk) 06:33, 28 October 2008 (UTC)
Depending on your definition of fat, Victor Hugo, Alexandre Dumas, père & Alexandre Dumas, fils, George Sand, Chaucer? - Nunh-huh 07:48, 28 October 2008 (UTC)
Thanks for that, I guess I was thinking of when fat was not so cool, more like now. Also, maybe successful writers can afford more nutrition so it's not about thinking or lying that loses weight but good ol' eating or not. Julia Rossi (talk) 00:18, 31 October 2008 (UTC)
also: the brain runs on glucose only, and i don't believe there's any pathway to convert fat to glucose, so you could think yourself into starvation but still not lose any fat weight. Gzuckier (talk) 06:17, 1 November 2008 (UTC)

Analyze a liquid[edit]

I currently pay a lot of money for a certain commercially sold product (a special type of cleaning solution, no ingredients listed on the label) and wanted to explore the possibility of creating my own at lower cost. How do I go about reverse-engineering a liquid? Do I lookup "labs" in the Yellow Pages and ask them how much it would cost to come up with the recipe? If yes, how much would such a venture typically cost?

I would assume that the solution is patented, and so I don't know if it would be illegal to produce this yourself. I guess it would probably be OK if you are only using it for yourself.
If I were you, I would look for a cheaper alternative. If you have already searched, and one doesn't exist or it doesn't live up to the standards you expect then I would take further action.
You could ask the company for the ingredients, and I am under the belief that they have to give it to you (I may be wrong) - obviously if you were to do this, make up a lie such as "Could you please provide me with a list of the ingredients that go into your Product XXX. I need this because I clean very sensitive substances that can't come into contact with many commercial cleaning products, and I need to check if your product can be used with these substances." That is a pretty poor lie so don't use it, but I'm sure you can come up with something better.
If they don't tell you, you could get a lab to find out the ingredients. The cost of this could be anything, it depends on how long it would take them to work out the ingredients, which depends on the complexity of the recipe.
Even if you do get the list of ingredients, how do you expect to manufacture it? The ingredients might be impossible for you do get hold of - simply because of the danger. Even if you do get hold of ALL of them, you might need a lot of equipment to manufacture it, including safety equipment. As you would be making this on a small scale this would probably be false economy. Even if we ignore all of these things, the ingredients might not just have to be mixed together, but to go through various processes, for example, heat Ingredient 1 for 5 minutes, then add Ingredient 2 and allow to react for 10 minutes when you will then add Ingredient 3. You would probably not be able to work out what these processes are.
I think your safest bet is to try and find a similar product. W.i.k.i.p.e.d.i.a - Reference desk guy (talk) 22:27, 27 October 2008 (UTC)
Making it yourself is almost certain to be more expensive. Just go to the supermarket and buy the cheapest cleaner that says it does what you want and try it out, if it doesn't work, buy a more expensive one and work your way up the market until you find something suitable. --Tango (talk) 22:40, 27 October 2008 (UTC)
Blindly figuring out what is in a liquid could be difficult, especially if the mixture is complex. What is more reasonable would be figuring out the concentrations of the various components based on an ingredients list, which some products do provide. This is what an analytical chemist can do. Alternatively, if the product is patented, you could try searching for the patent information. It might be difficult to read and won't contain everything, but it is a start. What product is it that you are using? --Russoc4 (talk) 22:49, 27 October 2008 (UTC)

On the subject of patents: To obtain a patent, the patent-holder must specify in detail how to create the patented product. For a liquid, this means specifying precisely what they put into the liquid and in what proportions, and how it was treated if applicable. If he hasn't done this, then there is no patent, and it is perfectly legal to recreate. In that case, it is likely a trade secret, so reverse-engineer to your heart's content if you can find a way to do it ;-) Someguy1221 (talk) 23:01, 27 October 2008 (UTC)

In many countries, manufacturers and most retailers are required by law to provide you with an MSDS sheet for chemical products. You can also look them up online (just type the product name in full with MSDS in Google). The MSDS will tell you the active ingredients in the product. If I was a gambler, I would bet decent money that the actual cleanser is no different than a dozen others on the shelf. Matt Deres (talk) 23:06, 27 October 2008 (UTC)

I'm reluctant to divulge precisely which liquid I'm referring to, but it is a unique product and nothing else like it is available. The reason I think I can do this myself cheaper is because after some discussion with the manufacturer (a small family-centered operation) I got the feeling that this is something they mix together themselves in their basement. But it does work as advertised and I'd like to replicate it if possible. —Preceding unsigned comment added by (talk) 14:03, 28 October 2008 (UTC)

In the U.S. a company has to provide info for the Material Safety Data Sheets which many companies, schools, hospitals, etc have to keep on premises. So if "Farmer Joe's Secret Formula Triple X Lingerie Wash and Engine Degreaser" lists no ingredients, what would a poison control center do if a child drank some and they got a call? There should be a contact for ingredient information, or a MSDS should be available. Edison (talk) 14:40, 28 October 2008 (UTC)

Uranus disc color[edit]

Though Uranus looks pale blue most of the time, could it look bluish-purple sometimes? Since methan gas could make the planet look purple sometimes depend on the sunlight.--Freewayguy 22:46, 27 October 2008 (UTC)

I would think that the colour would depend on the angle of the sunlight on Uranus, and maybe even where Uranus is in relation to the Earth.W.i.k.i.p.e.d.i.a - Reference desk guy (talk) 23:03, 27 October 2008 (UTC)

It's always a very tricky matter to talk about absolute color for things like far distant planets. What you'd probably want to know is what color the planet would appear if you were in orbit around it looking down. But sadly, there is VERY little sunlight out that far - and the planet would be exceedingly dim - almost black. So with your dark-adjusted eyes, things would look more blue than they usually do - but pretty much monochromatic. Well, that's not really the answer most people actually DO want - so when NASA shows pictures of these things, they boost the brightness and juice-up the color to show the details...but it's very rare that the pictures were taken with electronics that have similar properties to human eyes - they are often looking in the infra-red or the ultra-violet - or in colors other than the red, green and blue that our eyes can detect. The cameras may not actually have captured any significant reflected light in red, green or blue. So you see a wide variety of 'interpretations' of remote imagery. It's tough to say what's "right" because nothing is really "right". SteveBaker (talk) 01:11, 28 October 2008 (UTC)
  • Isn't Saturn very far from the sun too. The photos Voyager taken can be closely right or little off. Well, some iamge from Voyager finds Uranus green or blue-green, Uranus from space may look blue-purple, I was told to be pale blue. For Saturn I was told if blue-silver color, it may be yellow or gold sometimes, this all depends on sunlight and chemical. Neputne looks usually dull blue from Voyager 2, sometimes neptune is VERY blue, maybe a little purple dye sometimes.--Freewayguy 02:44, 28 October 2008 (UTC)
My understanding is that the Voyager crafts use a Vidicon camera - black and white. They put color filters, such as orange and violet, in front of the camera. Then, NASA combines snapshots taken through different filters and apply color "correction" to make the image appear pleasing. It is not a true color of the objects being photographed. -- kainaw 02:51, 28 October 2008 (UTC)
  • From this view Neptune's color is blue but duller. This all matters on chemicals, and depends on cluds. For instant Venus may be very yellow sometimes sometimes Venus is white. All spacecraft going through distant palents colors goes in differ color. Jupiter is a distant planet too, sometimes it have black, white, gray, yellow stripes too maybe blue and green.--Freewayguy 02:55, 28 October 2008 (UTC)
  • What about Jupiter and Saturn. Cassini, pioneer, and Galileo gone through those planets. You said Jupiter and Saturn may not be a true color is it right. Do pineer, Cassini, and Galileo use black-and white cameras like Voyagers, then put into orange-violet filters for NASAS photos. Which spacecraft of Jupiter and Saturn is true colors?--Freewayguy 02:55, 28 October 2008 (UTC)
  • is tan or gray for Mercury a true color, or all spacecrafts use black-and white for all panets. Mercury is only visit by one spacecraft so far, is those photos true colors for Mercury?--Freewayguy 02:59, 28 October 2008 (UTC)
Mercury has been visited by two spacecraft. See Exploration of Mercury. Rmhermen (talk) 03:39, 28 October 2008 (UTC)
  • My question is is almost all the planet in fake color, when spacecraft visit it. Jupiter and Saturn have been visit by at least 5 spacecrafts. If I go orbiting it truly in space will disc be blue, white? Jupiter looks orange through spacecraft Pioneer, Galileo too, or those is not true color either. Do most spacecraft work same way as Voyagers?--Freewayguy 03:52, 28 October 2008 (UTC)
  • Can you answer this quickly. You seem to lose me a little bit. Gas giant interior is white-hot and generate off mor heat than it gets from the sun, menas it's interior is white, very white, then at each cloud layer they scatter numerous of light waves. The atmospheric layer is thick, menas every point of layers have differ colors. uranus and neptune have methane, I doubt the true color will be black, but maybe not blue. Methane usually makes things look purple, amybe around blue-purple colors to both planets (Uranus maybe a little lighter, Neptune maybe a little darker). jupiter and Saturn is mostly hydrogen gases, and it have a very light interior, part of sky may have white, gray, light brown colors, the disc colro might vary green, orange, yellow paly through every single color. Venus may be perfectly white, all CO2-brightest planet. For Titan may be like burnt orange.--Freewayguy 04:34, 28 October 2008 (UTC)
The gas giant's core produces heat but no light. So that's an irrelevence. It doesn't affect the color. The gas giants don't "glow" - they reflect light just like the rocky planets do. Since they don't glow with their own light - the remainder of your statements are unimportant. SteveBaker (talk) 05:04, 28 October 2008 (UTC)
  • Just answer quickly, you seem to be confusing me. I doubt gas giant's sky is black. Which planet have absolute true color or none of them do?--Freewayguy 04:41, 28 October 2008 (UTC)
No - the sky isn't black until you get VERY deep into the atmosphere. Just like here on earth, the materials that make up their atmospheres will scatter sunlight via the Raleigh and Mei scattering mechanisms - so their sky's will appear colored from moderately shallow distances into the clouds up to the outer reaches of the atmosphere when the sky doesn't scatter enough light and it appears black...just like here on earth. But that doesn't affect what I've been telling you. The AMOUNT of sunlight out at Uranus is not enough for humans to see colors. So if you were near Uranus - it would be a very dim, dark swirling mass below your feet. The sun would look like a candle flame 50 or 100 feet away - hardly enough to cast any light on the subject. At those low light levels, we humans don't see colors - just shades of blueish grey...irrespective of the "true" color of the object. We can produce fake color pictures using the various sensors on the spacecraft but to answer the question "what color would it look like"...the answer is more or less "Black". SteveBaker (talk) 05:04, 28 October 2008 (UTC)

Mercury, Venus, Mars, Jupiter and Saturn are all VASTLY closer than Uranus. You can see them all with small telescopes or binoculars and they are quite bright. Jupiter is five times further from the Sun than we are - sunlight there is 25 times dimmer than here on earth - pretty much the same as the sunlight we get here on Earth on a very cloudy day - so it's obvious that you'd be able to see Jupiter very clearly if you were in orbit above it. Saturn is about ten times further from the sun than we are - so the light there is 100 times dimmer than on earth - but that's still enough to see quite clearly and in full color. The lighting inside your house at night is probably around 100 times dimmer than the sun. But Uranus is twice as far away as Saturn - that's 400 times less sunlight than here on Earth. The sun is only as bright as a candle flame halfway down my wouldn't see Uranus at all well until your eyes got dark-adapted - and that means no color vision. Spacecraft use peculiar colored filters so that they can maximise the scientific value of the images they produce. They don't often carry a set of red/green/blue filters in order to produce 'natural-looking' photographs for the benefit of human vision. SteveBaker (talk) 04:55, 28 October 2008 (UTC)

Aren't we exaggerating the darkness for the outer planets here? Lux tells me there is about 32000 to 130000 lux (but why that range?) in direct sunlight on the Earth and 100 lux in an overcast day, or 50 in a living room. I can see colours in an overcast day, and also inside rooms. That's a factor of about 600 at best, so I would expect to see Uranus and Neptune's colours. If I read lux right, 100 lux would be one hundred candles just one metre away. That seems plenty bright. One candle a metre away (one lux, or the Sun on a planet 178 Astronomical units away) might be the threshold limit. -84user (talk) 21:56, 28 October 2008 (UTC)
Answering the questions about cameras... From what I've seen - and I am not an expert - all of the probes we've sent out have used black and white cameras. That is actually a bit vague. They can see more than visible light. They can take infrared and ultraviolet photos as well. Filters are used to limit the bandwidth of electromagnetic energy that is collected by the camera. With a set of photos from different filters, it is possible to create a true color photo of what something would look like if it had the same amount of light as we have here on Earth. That is not what normally is produced. Instead, a false-color photo is created. For example, there is a very famous photo of the Horsehead Nebula. Because so many people have seen it, they assume that the colors in that photo are the colors from the nebula. If memory serves, the colors in that photo were created by using one color for oxygen content, one color for hydrogen content, and one color for something else. But, the point of this is not to say that all those photos are fake. They are great photos for what the purpose they are created. Scientists don't care what shade of blue a certain ring around Saturn may be. They want detail about what is in the ring. A false color image created from infrared and filtered snapshots may produce the best visual representation for that purpose. -- kainaw 12:12, 28 October 2008 (UTC)
A color camera needs three sensors per pixel and a lens that is a compromise design that avoids chromatic aberration. Using a monochrome camera that's sensitive to a broad range of frequencies - with optical filters to narrow that range where required means that you can have a higher resolution, better-focussed, more sensitive AND more flexible design than if you have to compromise the design to be able to capture red, green and blue (or possibly, three different frequencies of infrared, five frequencies of visible light and two more of ultraviolet) simultaneously. A set of filters with a little motor to select which one is in front of the camera is a MUCH more effective design. The only reason you'd want to capture several frequencies at once (like a domestic digital camera) is to get a snapshot of a fast-moving target...but it's rare to need to do that on deep-space missions because everything happens so slowly. Furthermore, because the on-board storage capacity of the spacecraft's computers is limited and the rate that data can be sent back to Earth is HORRIBLY limited - you can't waste storage and bandwidth capturing data that isn't strictly required to meet the scientific goals of the mission. Routinely sending back red/green/blue data is wasteful. SteveBaker (talk) 13:19, 28 October 2008 (UTC)
Mine is a pinkish-brown color, but its really hard to see without a mirror, or a friend who I trust a WHOLE lot... oh, wait, you meant... OH, never mind... 12:32, 28 October 2008 (UTC)
Your license to tell jokes is hereby suspended. --Tango (talk) 17:53, 28 October 2008 (UTC)
By when i get deep into atmospheric layer, does this mean to interior or to space. You said for gas giants for Saturn, Uranus, and Neptune I will see it almost black until I get into atmospheric layer. The clouds scatter some light waves, same as Earth, I thought Earth would look dark blue until I get close to it it will lighten, if I get closer to Saturn, Uranus, and Neptune, by actually diving in atmospheric layer like I'm in their mesosperic layer will they have mix colors between blue, purple, and gray-is that the color of mehtane. Would true color for Mercury and Venus be almost white from space. Mars can look brownish orange sometimes, and the sky I will say close to brown since the atmospheric is much thinner.--Freewayguy 22:52, 28 October 2008 (UTC)
  • What you mean by low light, Saturn, URanus, and Neptune have a methane haze, though so the disc color would be like between blue, purple, and gray, and the sky close to it is something like this. Lower level, perhaps differ colors. I though sky don't blacken until we get to molecular interior, the next bound. What you mean by "Low light"--Freewayguy 22:55, 28 October 2008 (UTC)
  • You said low light, by what.Would Mercury and Venus look almost completely white when I orbit it?--Freewayguy 23:57, 28 October 2008 (UTC)
If I bring a flashlight would I see mix shade of blue, purple and gray color, becasue of it's gas. For Mars sky I beleive is closer to brown, sooner up it darkens and darken, until 100 m above it appears nearly black. Mars' atmosph is so thin, it won't be able to scatter as much light wave and Venus and Earth does. Would Venus sky be pale yellow seen from surface and the globe look almost white?--Freewayguy 00:01, 29 October 2008 (UTC)
  • Can you answer this quickly. Planet itself can't be black either, just loks black for few miles away. That's Pluto and Charon, 3 times further than Uranus. It's ground would look almost black--Freewayguy 00:43, 29 October 2008 (UTC)

Mistaking memory for reality - how?[edit]

A friend said recently his mother - who had Alzheimer's before she died - "thought it was her wedding day each day in her last months." A sweet way to go, to be sure.

In reading the Alzheimer's article I think I understand why - flashbulb memory connected with the fact emotions do seem to be recalled, even in the latter stages of Alzheimer's. My question is: 1. is minea correct presumption; and, 2. If so, how does this explain the person who thinks something more mundane is taking place. For instance, I have heard of non-Alzheimers patients who have thought they were in their home, when in fact they were in a nursing home thousands of miles away. (And, with no reminder of home, i.e.: an old picture that was always sitting out.) But, it is not as if anything special is "going on" for them at that moment. Or, could this be an entirely different part of the brain being triggered when that happens?Somebody or his brother (talk) 23:14, 27 October 2008 (UTC)

I think the only accurate response to your question is: "we don't know". Its a fair hypothesis though. When the neurons in the brain die during the progression of the disease, those that would normally wire together to form what we can consider to be a "memory unit" may become disrupted. But, as the Hebbian theory goes, "those that fire together, wire together". The neurons that are left are now misfiring, and they are likely to form synapses with other neurons. So neurons that, for example, "store" the memories of your wedding day could get wired up the the neurons that one uses to "store" short term memory. The result is that the person with dementia, almost literally, gets their wires crossed and recalls inappropriate memories in response to mundane cues. It seems intuitive that the "special" flashbulb memories would be the most persistent, and this is why they seem to survive until the end. But its also possible that there is some kind of recording bias. Memories that are meaningful to the caregiver are the most likely to be documented among the jumble of minor memories the person with dementia may recall each day. Its also comforting to think the sufferer is re-living happy times, and so there is a type of positive re-enforcement in the caregiver believing this. Either way, if significant memories really do persist more than other less significant memories, how and why is unknown. Rockpocket 08:06, 28 October 2008 (UTC)