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November 26

'Writing about Vampires' seeks Comprehensive list of Disease Involving Sunlight

I'm a writer who is currently writing somewhat about vampires but what I really need is a comprehensive list of diseases involving sunlight to help with my current research needs. Thanks in advance. —Preceding unsigned comment added by 70.238.136.205 (talk) 01:24, 26 November 2008 (UTC)

This isn't bad: make sure you click the link to see the table. - Nunh-huh 01:29, 26 November 2008 (UTC)

For some people, going into bright sunlight triggers sneezing. See Photic sneeze reflex. I'm pretty sure this is not classified as a "disease" but it might be of interest anyway. CBHA (talk) 04:05, 26 November 2008 (UTC)

A disease you might want to check out that I remember being characterized as particularly vampiric is porphyria, which messes with the enzyme pathway that makes hemoglobin. Photodermatitis is sometimes a symptom. --Shaggorama (talk) 16:14, 26 November 2008 (UTC)

Tuberculosis sufferers were once thought to be vampires. See Tuberculosis#Folklore. - Draeco (talk) 05:19, 27 November 2008 (UTC)

Seasonal Affective Disorder (SAD) sufferers experience depression and other mood changes in the winter. Seasonal Affective Disorder is believed to be related to the much lower levels of sunlight in winter. CBHA (talk) 05:58, 27 November 2008 (UTC)

Xeroderma pigmentosum is a classic example of such a disorder. – ClockworkSoul 08:03, 29 November 2008 (UTC)

Black holes

Hi, A thought just occured to me while i was brushing my teath; what would happen if a human being was situated next to a black hole and stretched out their arm so that only their arm fell beyond the black hole's event horizon. Would they lose their arm? or would the black hole suck them in completely? 79.75.254.37 (talk) 01:27, 26 November 2008 (UTC)

The black hole gravity will pull hard on the arm, so if it is big enough to pull more than a few millimeters, the arm will drag the rest of the human in as well. However the tidal force and gravity would be expected to be huge as well, so even in an orbit around the hole you can expect to be spagettified. Graeme Bartlett (talk) 01:39, 26 November 2008 (UTC)

Being within armsreach of a sizeable black hole's event horizon is not a really comfortable situation! Between the spaghettification and being cooked by the gamma rays being emitted by stuff entering the hole...then the severe time, space and mass dilation effects of moving so rapidly...the fate of your arm is really the very least of your problems! SteveBaker (talk) 01:45, 26 November 2008 (UTC)

I saw a documentary about it... DMacks (talk) 02:11, 26 November 2008 (UTC)

An event horizon is not a magical shell where you don't feel the black hole's gravity outside of it, but you do feel it inside of it; F = mg still applies. For a small black hole with a high gravity gradient, see Steve Baker's answer. For a large one, the event horizon will be very large (such as the size of Pluto's orbit), and you won't feel much when you stick your arm in, but even if you then had your arm amputated, your space ship will require nearly infinite energy to escape the hole's gravity. If you find yourself in this situation, it's probably best to just keep your arm on so that you can carry out your final activities intact. --Sean 15:35, 26 November 2008 (UTC)

What does "nearly infinite" mean? — DanielLC 16:01, 26 November 2008 (UTC)

If we assume that the black hole is large, and thus the tidal forces are small, and that there isn't enough other matter falling into the black hole in order to harm you, and that you are magically (or otherwise) hovering above the event horizon, then you would actually never experience your arm passing the event horizon because this event is at t = ∞ in your reference frame! That can be seen from the Schwarzschild metric. As your arm moves closer to the event horizon, the time dilation in your arm compared to the rest of your body will certainly cause strange effects.

Note that the situation is quite different for falling observers.

Icek (talk) 15:32, 26 November 2008 (UTC)

But the problem with that explanation is this 'magical hovering' bit - we simply can't let you get away with that - even in a thought-experiment. Once you stick your arm through the event horizon - you can't have it back because in order to escape the black hole, it would have to be moving faster than the speed of light relative to the black hole. You may not see anything different when you do that - but we know that light from your arm can't get back either - so if you didn't notice an abrupt change when you stuck it in there (which I agree, you don't) then it must be that there was only just BARELY any light coming from your arm BEFORE you stuck it into the event horizon. So there must be something very odd happening to you BEFORE you stick your arm across the event horizon in order for that not to be very noticable.

But remember - in the absence of 'magic' - in order to avoid the rest of your body getting stuck in the hole too - when you're just a foot or two outside the event horizon - you have to be moving at 99.9999999% of the speed of light relative to the black hole! The event horizon is just the place where you can't escape even by moving at the speed of light. In the region close to the event horizon, you can only avoid falling in if you're going 99.9999999% of the speed of light...sure, it's possible to escape falling in theory - but severely difficult in practice!

So we can deduce that you are orbiting the black hole just the slightest smidgeon below lightspeed (relative to the black hole itself). That is insanely fast! At those speeds (and - inevitably - in a circular or elliptical orbit) you only have to glimpse a particle of matter falling into the hole to be completely cooked by the resulting high energy gamma radiation. This really isn't a good way to run your life!

SteveBaker (talk) 20:02, 26 November 2008 (UTC)

Unfortunately, such a kind of orbit is not possible; at 1.5 Schwarzschild radii the orbital speed already reaches the speed of light, and no closer free-falling orbits are possible! (the time dilation factor for circular orbits in the Schwarzschild metric is ${\sqrt {1-{\frac {3\;r_{s}}{2\;r}}}}$) Icek (talk) 22:46, 26 November 2008 (UTC)

Are CD jewel cases recyclable?

I'm moving all my CDs to flip albums and I have sacks of discarded jewel cases. Just curious if CD jewel cases are recyclable? The clear plastic is obviously different from the gray Cd holder part. But I don't see any plastic classification symbols anywhere. --68.88.175.36 (talk) 03:21, 26 November 2008 (UTC)

These cases are probably polycarbonate, this is one of the plastics that are not recycled much. However there would be other people who would like to use the cases as they are to store CDs, so I think you will be able to give them away easily. Graeme Bartlett (talk) 10:17, 26 November 2008 (UTC)

Are you sure of that? I know the CDs and DVDs are polycarbonate but I'm not so sure about the jewel cases. From the examples given in the linked article and the properties, it seems a bit odd to me they would use something like polycarbonate for jewel cases which are meant to be cheap, not especially hardy and mostly disposable. I've comes across various people suggesting they are type 6 (polystyrene) or one person suggested type 5 (polypropylene) which seems more likely to me. Specifically this [1] which means one of the slim line cases having a type 6 code and says it's confirmed from a government website. This website about manufacturing them [2] also suggests they're polystyrene. The (usually black) insert may be different from the clear/jewel part though, not sure (however there are those with transparent/clear inserts which I presume are the same at least Nil Einne (talk) 13:01, 26 November 2008 (UTC)

The best idea as others have said is to give them to somebody that can reuse them - libraries are often after jewel cases as people borrow their discs and bring the cases back broken. However, they definitely can be recycled - at least here in the UK. The company I work for sends all its scrap CDs and any excess jewel cases (including the paper inlays and black plastic parts) to a company on merseyside who recycles the lot - see this website: http://www.polymerrecycling.co.uk/cd.html I think they take them for free as well although you would have to pay to ship them there.62.25.96.244 (talk) 13:24, 26 November 2008 (UTC)

Lights

If two identical spotlights shining on the floor overlap, the intensity of the overlapping region doubles. If light is a wave, whhy would this happen? Wouldn't the light interfere with itself? —Preceding unsigned comment added by 76.68.247.230 (talk) 04:12, 26 November 2008 (UTC)

Because spotlights aren't coherent light. Unless the two beams of light are of the same wavelength, they won't interfere with each other. Spotlights feature a wide spectrum of wavelengths, and these don't interfere any more than a room full of musical instruments all playing at the same time (i.e. an orchestra) would interfere... --Jayron32.talk.contribs 04:40, 26 November 2008 (UTC)

It's not just the variety of wavelengths. Even a pair of Sodium lamps (which basically emit only two frequencies) don't interfere. The real reason is that the light isn't 'coherent'. Imagine a good old fashioned tungsten filament lamp - or a florescent tube maybe...each little part of the filament or of the glowing surface is giving off a little bit of light...right down to the individual atoms - each one is emitting light. But nothing is keeping the lightwaves they produce in synchronism - so at any given instant, some of the tiny light emitters that make up one 'lamp' are at the crest of their waves while others are in the trough and others are at the halfway point. Nothing forces them to stay together. Even if they were 'together' at the start, the shape of the filament/tube is such that the sources of all of these lightwaves are starting out at different places and radiating outwards in all directions...so they might interfere constructively here - and destructively there. As Jayron says - in the case of a white lamp - the light is coming out at all different frequencies too - and that complicates matters still further.

So the light that comes out of such a crude device is a horrible mixture of interfering lightwaves...it's a complete mess. But on the average of quadrillions (at least) of individual glowing atoms - there is light. OK - now add a second lamp...now you're averaging over two quadrillions instead of one quadrillion...but the results are much the same...except that there is now twice as much light energy. But even a pair or completely monochromatic light sources don't form interference patterns unless the light is 'coherent'.

To get some nice interference going, you need something like a laser - which (by devious means) produces 'coherent' light - where all the waves are in perfect synchronism and all at one very specific frequency. Laser light does indeed interfere in situations like your thought experiment - and if you could hold the lasers still enough and peer at the ground with a microscope - you'd see tiny interference patterns.

SteveBaker (talk) 19:46, 26 November 2008 (UTC)

Fuel consumption with a cold engine.

My car (a turbo-charged MINI Cooper) manages about 40mpg (US gallons) when I drive it carefully. I'm aware that car engines use more gas when they are cold - but today I found out how much more...and I'm astounded!

The car has a miles-per-gallon gizmo - but it's basically useless because it either averages over the entire life of the car - or it swings wildly moment by moment and tells you nothing useful. So I've always known my average MPG - but didn't get a good feel for how it varied over a journey.

Well, this morning, I was kinda low on gas - so I switched the car computer over to tell me "available range" (really: "miles remaining until you're out of gas"). It's not a mode I use much...but it turns out to give you a much better idea of what's going on. It's a 17 mile trip to work - and when I left home, it said I had 77 miles worth of gas in the tank. After just about 8 miles, I glanced at the gauge and noticed to my horror that it had dropped to 55 miles(!)...22miles off of my 'available range' but only 8 miles travelled!!

By the time I got to work (about 9 miles further) the gauge showed 50 miles left - so the first 8 miles of my trip used four and a half times more gas than the second half! Almost the entire trip is on freeways and I leave early enough to miss all the traffic.

Having an enquiring mind - instead of filling up the tank - I repeated the experiment on my drive home - and got very similar results. But it was astounding how fast the 'available range' dropped in the first mile alone. This was a good test because I was doing the trip in the reverse direction so the first half of the first trip was the second half of the second trip.

Tomorrow I'm going to make a note every mile...graphs need to be plotted! The world needs to know!

So here is the question...what the heck makes a cold engine use FOUR TIMES as much gas as a warm one?!? I can think of a few small things (like the engine oil isn't as runny) but that doesn't seem enough to account for the difference!

SteveBaker (talk) 05:37, 26 November 2008 (UTC)

Perhaps your gizmo got some glitches. I think you need an alternative way of measuring your fuel consumption (If you have the time to find one, sorry I have no idea what would that be) to compare with the data your gizmo provides.--Lenticel ^(talk) 05:50, 26 November 2008 (UTC)

If your car is new enough, you can get an aftermarket MPG display. I've been thinking about getting one, just for kicks. But the ones I've seen are a bit pricey. Doesn't answer the original question though. APL (talk) 14:12, 26 November 2008 (UTC)

The cheapest solution might be to write it up as a nice idea for Mythbusters -- they've done the small-quantity fuel efficiency sort of thing a few times before, as I recall (maybe suggesting that cold weather has an abnormally large effect can even call those previous experiments into question, too!) — Lomn 14:26, 26 November 2008 (UTC)

About the only way the engine could actually be burning that much more fuel is if the cylinders are missing (a lot). If that was the case the vehicle would be running very roughly and stalling. So, it must be the inaccuracy of the device. I'd compare this to the "time remaining" bar during a download. At the beginning, it tends to be highly inaccurate, but it gets more accurate the longer the download runs, as it's able to average info over a longer period to more accurately figure the current download rate. StuRat (talk) 14:53, 26 November 2008 (UTC)

Without knowing the details of how your car's "miles remaining" calculation works it's impossible for me to be certain, but I can think of at least a couple of confounding factors here which might explain your readings. When you turn your car on, it may be using the average fuel efficiency for your previous trip to calculate its "miles remaining". (Alternatively, it may use a factory-set 'default' value.) Once the car starts moving, the efficiency measurement is reset, and new calcuations are based on the current trip's data. Early in your trip, you will accumulate a lot of low-efficiency time: starting the car, stopping and starting at intersections, hard acceleration to get on the freeway and merge. By the time you reach the end of your journey, most of your time and miles are under efficient constant-speed conditions. Even counting the little bit of city driving at the end, the overall average efficiency for the mostly-highway trip will be good. You will see a similar effect on your journey home.

This is not to say that most automobile engines aren't appreciably less efficient when cold. Particularly in winter conditions, engine oil is quite a bit more viscous than it is at normal operating temperatures, and the engine has to work hard against that sticky, sludgy goo. But it generally takes very little time for a car to warm up when it is being driven. TenOfAllTrades(talk) 16:01, 26 November 2008 (UTC)

Answers above question the accuracy of the "miles remaining" information. Comparing that gauge information to when you have to fill the tank should give you a very good sense of how reliable the information is, IMO.

When I used to keep careful records of gas mileage, I was surprised at the dramatic difference between summer and winter gas consumption. It seemed too drastic to make sense - after all, so I thought, once the car has warmed up in the first part of a trip summer versus winter should not make a "lot" of difference. Parhaps my mistake was in underestimating just how much fuel was used in the warmup period. Unfortunately I did not have a "miles remaining" feature. CBHA (talk) 19:15, 26 November 2008 (UTC)

I think the way to discover whether there is something odd about the gauge (which is certainly possible) would be to drive the car from cold - then stop, turn off the engine, wait a minute - then jump back in and drive the exact same route again - but with the engine hot at the outset. If I'm right and it really is a cold versus hot engine situation - then the second time around would show normal consumption rates throughout the trip. I'll give it a try over the weekend.

But I do know that cold engines use more gas - that's a fact for sure - but what surprises me is the magnitude of that effect.

SteveBaker (talk) 19:30, 26 November 2008 (UTC)

Are you factoring in the gas used by starting the engine? --Carnildo (talk) 22:59, 26 November 2008 (UTC)

I didn't look at the 'miles to go' gauge until after I'd started the engine (because that's when it tells you you're low on gas) - so the cost of starting the engine was not a factor. SteveBaker (talk) 14:51, 29 November 2008 (UTC)

Though there are a number of salient difference, a internal combustion engine is still basically a heat engine so an appeal to the Carnot efficiency can be illustrative (if not entirely accurate).

Carnot: $E=1-{T_{Low} \over T_{High}}$

In this case, T_Low is roughly the temperature of the air-fuel mixture prior to ignition, and T_High is the temperatures of the vented exhaust after it has finished all delivering all the useful work it can. For T_Low lets take something around room temperature, say 300 K (27 C). I don't know, T_High, i.e. the gas temperature, but I do know one doesn't want the engine block as a whole to go much above 100 C (373 K), so maybe the gas exits at around 400 K (127 C)? That would give a thermodynamic efficiency of 25%. Now suppose we lowered these values to simulate starting on a cold day. If you take -13 C (260 K) and 50 C (327 K), that gives a thermodynamic efficiency of 20%, or in practical terms it might take about 1.25 times as much fuel to deliver the same amount of useful work. Of course cold also adds other variables like more viscosity engine oil, but ultimately, I think this is the right order of magnitude. I would guess an engine that is warming up probably uses 15-50% more fuel than a warm engine and not the 300% more fuel that your experiment suggested. Dragons flight (talk) 23:29, 26 November 2008 (UTC)

(The reason you don't want the engine block going over 100C is that it's water cooled. If the water gets even close to 100C, tiny steam bubbles form in the hotter regions of the engine block (close to the cylinders, presumably). Those bubbles are excellent insulators - so they greatly inhibit further heat from being transferred from that spot on the block to the water - that local hot-spot distorts the metal and is the major cause of a cracked block...which is generally totally terminal for your engine! So the 100C operating limit (it's generally more like 85C) is not an efficiency thing - it's a not-destroying-your-engine thing! SteveBaker (talk) 14:51, 29 November 2008 (UTC)

Yes, I know the limit exists because the engine is water cooled, but it is still an efficiency thing. IF the components of your engine were capable of running hotter, then the fuel would be used more efficiently. Dragons flight (talk) 22:46, 29 November 2008 (UTC)

I guess this is OR (if educated guessing is research) but the computer knows to a high degree of precision (a fraction of a spritz) your fuel consumption but is not so good on your remaining fuel volume. And the fuel management box could be fast-warming your engine/exhaust system. In the old days that was done by leaning the mixture. That would lead to inefficiencies, too.

An alternative testing method is switch to instantaneous-fuel-use mode and get to max BMEP (~3000 rpm. Best fuel economy, fast enough for drag effects to show but still a safe, cold-engine speed) for long enough for the mpg reading to stabilize (very steady on the throttle). Do this at the beginning and end of your trip. Compare and discuss :-) Saintrain (talk) 01:48, 28 November 2008 (UTC)

Modern fuel-injected engines deliberately run "rich" for the first few minutes in order to "light off"/"light up" the catalytic converter. That is, by running rich, unburned fuel makes it as far as the catalytic converter and burns there, rapidly warming up the catalyst to proper operating temperature. You, of course, see this as really poor fuel economy for a few miles.

Atlant (talk) 23:53, 30 November 2008 (UTC)

Endorphins and interest in sports

Does lack of interest in a sport lead to a failure of the body to produce endorphins while playing when they would normally be expected? Vice-versa? (As a child, I noticed that I was not only the least interested in sports of anyone in any of my gym classes, but also the least able to cope with pain from an injury.) NeonMerlin 07:54, 26 November 2008 (UTC)

An interesting theory. As for myself, I might be interested in playing a sport, but find watching strangers play sports to be as dull as watching paint dry; I simply can't make myself care who gets which ball into which basket/hole/crevice. StuRat (talk) 14:45, 26 November 2008 (UTC)

I saw a good discovery channel show on a phenomenon that equated competitive desire within sport to testosterone levels (in both men and women). It discussed a correlation between testosterone and overall desire to "compete" (in any area). Other than a means of keeping the body fit, sport is primarily an outlet for these competitive desires, especially in a decidedly VERY uncompetitive youth that most western societies establish. In a sport like American (or in my case, Canadian) football, some degree of injury (usually just soft tissue; the type of thing that won't be life-long) tends to occur in every outing, for example. From experience, I could always tell who would be most successful as being those that were most willing to "play through" those non-life-long injuries (not display any of the behavioural indications that an injury has been sustained, like holding an injured area or limping), not because of peer pressure or social expectation or rational reward, but rather just because of that internal competitive desire.NByz (talk) 20:50, 26 November 2008 (UTC)

It's been shown that athletes have higher basal endorphin levels and response (Inder et al, "Elevated basal adrenocorticotropin and evidence for increased central opioid tone in highly trained male athletes." The Journal Of Clinical Endocrinology And Metabolism [J Clin Endocrinol Metab] 1995 Jan; Vol. 80 (1), pp. 244-8.), so lack of playing could definitely decrease your central opioid tone. If you're asking whether a "naturally" decreased endorphin tone causes decreased sports interest, that's tough. I don't know of any studies that approach the question in that way, most likely because you would have to study children from early in development all the way to adulthood...a very ambitious undertaking. - Draeco (talk) 23:22, 26 November 2008 (UTC)

Boundries of longitude and latitude for western europe 1955-1990

I wanted to know what the boundries for Western Europe would be as far as latitude and longitude? I am needing these to know what a person would meet criteria for a US Military medal criteria. Many medals have a boundry criteria for an award of a medal in a theater of operations. Like the European-African-Middle Eastern campaign Medal, they have a boundry. I need to know the exact latitude and longitude of Western Europe from the above time periods —Preceding unsigned comment added by 70.212.140.156 (talk) 08:09, 26 November 2008 (UTC)

It probably depends a LOT on who is doing the defining. I would say that before 1989 or so, the eastern boundary of Western Europe was the eastern boundary of West Germany; eastern and southern boundaries of Austria, and eastern boundary of Italy. The question is whether to include such countries as the Scandanavian countries (politically yes; geograpically probably considered "Northern Europe"). Our article on Western Europe includes a half-dozen or so maps that define it in slightly different ways. --Jayron32.talk.contribs 11:38, 26 November 2008 (UTC)

4d rotation of 3d objects

Last year I've read the novella 'Flatland' by Abbott. Then I came along another website telling stories in a way similar to Flatland, e.g. 3d beings messing with 2d ones and 4d beings with 3d ones. In one section, a 3d human lifts a 2d book out of the plane where 2d beings live, flips it over (rotates it 180 degrees in 3d space) and puts it back. The book is reversed/mirrored. 2d beings are confused as no rotation in a 2d plane can make this happen. Similarly, the 4d being does the same to a 3d book and upon inspection we find that the book was mirrored. Unfortunately I can't recall that website but I hope you get the idea.

Well, after that I read in a short story (by Asimov, if I remember correctly) that such a rotation would mirror the molecules and if a man were to undergo that procedure, his amino acids would turn from L to D and sugar molecules D to L and in the end he may be starved.

Yet in another message board(!) I read that such a rotation would not only mirror the molecules but also turn every particle into its antiparticle thus upon returning to the 3d world the object would be annihilated into gamma rays.

Sorry for the lenghty intro but visualising these is really hard for me. So,

1- Does such a rotation mirror the molecules forming the rotated object?

2- Does it also turn the particles into antiparticles?

3- Could a 4d being watching us from "above" interact with our 3d universe to accomplish such tricks?

4- Are the questions already moot as the electromagnetic interactions essential for seeing, touching and rotating matter are confined to our 3d universe so there is no way a 4d being could watch us or interact with our objects?

5- Also invalid as such feats would violate conservation of energy?

5- Or not moot at all because there may be 4d photons, other 4d force carriers, etc for the 4d being to observe and interact with our universe? 3d beings may or may not observe those forces directly but they would observe the effects and not finding a cause, maybe they'd call it "dark energy"? .. Ok that one was pure speculation, but I couldn't help writing!

Thank you!! 78.176.16.183 (talk) 12:10, 26 November 2008 (UTC)—Preceding unsigned comment added by 78.176.16.183 (talk) 12:08, 26 November 2008 (UTC)

I think the answers to 1 and 2 would be yes. For 3 the answer would also be yes, but it could also be done in three dimensions with a non-orientable wormhole. Jkasd 13:42, 26 November 2008 (UTC)

The answer for (1) is yes, for (2) it's no (see Parity (physics)), the other points are moot because we don't know 4d beings or the hypothetical space they inhabit. The conservation of energy shouldn't be violated by mere mirroring. Icek (talk) 15:05, 26 November 2008 (UTC)

Addendum: You might also be interested in reading C-symmetry, T-symmetry and CPT symmetry. Icek (talk) 15:07, 26 November 2008 (UTC)

Just as a footnote - Abbots flatland really sucks - and I think I know the other book you're talking about...and it sucks too. Go out and grab a copy of "The Planiverse"...it's a MUCH better description of a 2D world. I absolutely guarantee it'll bend your mind! You can easily spend a half hour looking at each of the many illustrations - trying to figure out how (for example) the 2D steam engine works - or why the 2D house is built the way it is. Abbot's book is just awful by comparison. SteveBaker (talk) 18:42, 26 November 2008 (UTC)

Flatland's not bad, it's just not much good as a description of a 2d world. As a satire of Victorian society (the main point), it's ok. Algebraist 19:04, 26 November 2008 (UTC)

Um...it's kinda sexist...actually, outrageously, PAINFULLY sexist. It's embarrasing to read...you just want to grab the author by the throat and tighten your grip until he goes limp and finally quits this talk! His view of the 2D world is wrong in many regards (think about his descriptions of houses with doors and windows)...he kinda flips back and forth between a top-down 2D world and a side-on 2D world without proper consideration of what this actually MEANS. I dislike it greatly. Get a copy of Planiverse and you'll immediately see what I mean. SteveBaker (talk) 19:23, 26 November 2008 (UTC)

I haven't read the book for a while, but my recollection is that while the narrator (being a victorian gentleman) is outrageously sexist, the book itself is not. Algebraist 19:25, 26 November 2008 (UTC)

The narrator actually struck me as a little more progressive than his Flatland society, reflecting Abbott's own views on Victorian treatment of women(and the "criminal classes" represented by irregular polygons). Back to the general subject, the idea of a fourth spatial dimension large enough for rotation of objects is pretty speculative in itself, but another work I might recommend on the subject is The Annotated Alice by Martin Gardner, which discusses varying interpretations of what "looking-glass" matter(either antimatter or oppositely-chiral molecules) would do when in contact with "normal" matter. 69.224.113.5 (talk) 21:10, 26 November 2008 (UTC)

By the way, the "Asimov" story mentioned above is actually Technical Error, also published under the title The Reversed Man, by Arthur C. Clarke. --Anonymous, 02:15 UTC, December 3, 2008.

"Brain Balance" autism treatment

I can't seem to find much about this (http://www.brainbalancecenters.com/) treatment regime, except for posts on autism activism sites. Would this approach be described as 'evidence-based' or 'alternative'? Messiahxi (talk) 18:37, 26 November 2008 (UTC)

If you can't find much, especially on sites like PubMed, that's a very good clue that it's more to the alternative part of the spectrum. -- Aeluwas (talk) 18:40, 26 November 2008 (UTC)

indeed... as is the fact that it was founded by Dr. Robert Melillo, who is apparently a Chiropractic Neurologist. I was just wondering if anyone had specifically heard of this program. Messiahxi (talk) 18:56, 26 November 2008 (UTC)

A quick flip through the site reveals absolutely nothing about what, specifically, they actually DO. For people at the autistic end of the spectrum, some kind of treatment that actually works would be a truly wonderful thing - and clearly the parent of an Autistic kid needs to explore all of the options to help the child out.

But at the more 'normal' end, "curing" Asperger's syndrome is considered by most people who have it (me included) to be a REALLY BAD IDEA. Almost every adult who is at the more mild end of the spectrum will tell you that as bad as the downsides are - they are easily outweighed by the up-sides. If there were a magic pill that would cure my Asperger's - I wouldn't even consider taking it...not for one moment! So I get a little upset when people talk about "curing" children of the syndrome...aside from the fact that this site doesn't look too convincing to me, I worry that they may actually be destroying the potential that Aspergers offers. Aspergers (and Autism) is an actual difference in the structure of the brain - you can't simply use therapy and nutrition and whatever else they do to "fix" that. What you can do is to cause the child to suppress the beneficial things in order to "fit in" - which is a terrible, awful thing to do.

What us Aspies REALLY need is a comprehensive testing program so that "sufferers" can be identified earlier in life - and placed on the appropriate slot in the spectrum (Normal...Mild Aspergers...Severe Aspergers...Autism...Profound Autism). I didn't find out why life seemed so difficult until I was nearly 50 years old! What a SPECTACULAR difference it would have made if I'd known when I was in my early teens...I can't tell you the number of things I screwed up in interpersonal relations simply because I didn't know. Now I do - I positively cringe at some of the things I did that I now know to avoid. Once identified, we need to be taught the set of social skills and body language that everyone else takes for granted (most are mere 'conventions' that are quite teachable to someone with the intense ability to focus that characterises an Aspie). I've been through a 1 week course - and it's INCREDIBLE how much that helped. They didn't try to cure anything - just to tell me what other people know instinctually and apply automatically that I have to learn explicitly and think about consciously. That's why knowing is a HUGE part of what an Aspie needs on a day-to-day basis.

Case in point from yesterday. My kid (who is in college) phones me up at work (which is unusual) and tells me all about some text book that he needs and why he needs it and how he's going to pick it up - and oh, by the way, since we recently moved house, is the billing address on his credit card OK? So I listen carefully, answer the questions he asked, say goodbye and put the phone down. Then - my "training" kicks in. Why on earth did my kid ask me all of that crap? I don't need to know it. Then the alarm bell goes off..."Hold on - this must be one of those 'hidden agenda' things that I'm so useless at spotting!"...so I think hard about what OTHER message was buried in the phone call - and BINGO!...he wants me to offer to pay for the book. The point being that I totally lack that part of the brain that tells me what the other person might be thinking (I've heard this area of the brain called "the mirror neurons" because they function as a copy of the other person's thought processes. I simply don't have the ability to put myself in my son's position of needing to ask for a favor and not wanting to come right out and demand money. (Which is unfortunate - because an Aspie needs to be told exactly what you want because he/she can't know any other way!) But - because I've had the training - I know that when a conversation goes oddly, then there is something I'm missing about how the other person is thinking...and sometimes I can work out what it is and fix it. But when I didn't KNOW I had this problem (or, more exactly - when I didn't know that everyone else DIDN'T have this problem) - I'd never have thought to call my son back and ask if I could pay for the book.

(Of course, from my perspective - I'm just wondering why the heck there has to be all of this machiavellian double-talk going on in the world. If you want me to do something - JUST SAY SO FOR CHRISSAKES!)

SteveBaker (talk) 19:12, 26 November 2008 (UTC)

If it helps you at all, Steve, I'll tell you right now that every time a kid calls home from college, he's looking for you to pay for something, so you may as well just begin your conversation with "how much and how soon?" Matt Deres (talk) 21:26, 26 November 2008 (UTC)

Also, doesn't it seem strange that your son hasn't yet figured out how to get what he wants from you? Even if he wasn't aware of the Asperger's, you'd think (or at least I would) that he would intuitively have figured out what he needed to do? My daughter figured out how to wrap me around her finger in pretty short order. Matt Deres (talk) 21:31, 26 November 2008 (UTC)

Perhaps he has. He did, after all, get his dad to buy the book. APL (talk) 21:43, 26 November 2008 (UTC)

I can’t tell you how many times I’ve wished that people would just say what they mean, and I don’t have Aspergers as far as I know! (the mores the pity) --S.dedalus (talk) 21:37, 26 November 2008 (UTC)

I've wished the same thing, and I have been tested for Aspergers and found not to have it. I have no problem playing the game, but I really wish I didn't have to... --Tango (talk) 21:44, 26 November 2008 (UTC)

Firemaking in the 1700's.

Hello, I was wondering how fires were started and candles were lit in the 18th century. I searched for matches but found they were invented in the 19th century. I have asked a few people and they didn't know but guessed at flint or two sticks, however,I thought this was quite primitive for the 18th century and would like a certain answer to how fires were produced. Thank you. 82.27.54.8 (talk) 19:16, 26 November 2008 (UTC)

They used a tinderbox. —Jeremy (talk) 19:18, 26 November 2008 (UTC)

This was discussed here circa May 19 2008. Link? Edison (talk) 03:43, 27 November 2008 (UTC)

An easy and once common way to light candles, fires, etc, was to use an already lit candle, fire, coals, etc. The question is how did one start a fire when there wasn't a flame or smoldering embers somewhere around already. A minor point, sure, but the most common way to light a candle in the 18th century was probably to use a flame or embers already handy (depending on location and circumstance of course). In earlier times than the 19th century, when starting a fire was more difficult, it was common to "borrow" fire from your neighbor/friend/kith. Making fire might be of interest. Pfly (talk) 06:40, 27 November 2008 (UTC)

Good point. My grandmother lived as a girl in a house where there was no electricity. A collection of rolled up pieces of scrap paper she called " tapers" was kept near the fireplace, and one could be lit from the remaining coals in the fireplace to light a kerosene lamp or a pipe. I supposed this saved the cost of a match. Edison (talk) 17:20, 28 November 2008 (UTC)

November 27

Chicken head stabilization

I just thought this gizmodo story [3] is very cool and was surprised I can't really find more information on this behavior. Can anyone confirm that this is not an elaborate hoax and maybe offer some more videos/info on the subject?

I've handled chicken before but don't recall them doing that, but then, i wasn't paying much attention. Thanks. —Preceding unsigned comment added by 70.79.159.37 (talk) 06:45, 27 November 2008 (UTC)

That's regular chicken behaviour. The chicken is clearly used to being handled which accounts for the calm display of head stability. If you've ever had a chicken travel in a car with you it works even better. The possible reason for the head stabilising behaviour has, I think, been answered in a previous question somewhere. Richard Avery (talk) 08:31, 27 November 2008 (UTC)

Is that behaviour unique to chickens, as a matter of interest? --Kurt Shaped Box (talk) 10:43, 27 November 2008 (UTC)

Here's the same guy demonstrating the phenomenon with a non-chicken. [4]

Part of me wonders if that is real. There's something a little unnatural about the way these birds look and move and I'm not just talking about the heads. There's something computer generated looking about their heads and bodies. Maybe I'm just being paranoid. But the shapes and movement seem wrong, and the depth of field seems wrong. --98.217.8.46 (talk) 07:10, 28 November 2008 (UTC)

Why are limes seedless?

A bartender told me that all the limes she has seen are seedless while lemons contain seeds. Why is that? Did seedless limes arise naturally or were they bred for that trait, and if the latter, why not breed seedless lemons also? --Mathew5000 (talk) 10:00, 27 November 2008 (UTC)

Seedless lemons are rare but do exist: new varieties were reported recently[5][6], although the NYT shows up a 1911 reference to a seedless variety which I imagine did not catch on for some reason.[7]. The most common variety of (largely) seedless lime is the Persian lime, which is believed to be a hybrid[8], and which is propagated by grafting. The first article I linked mentions that one problem with seedless fruit is that it is difficult, requiring many years of breeding, to ensure that it really is seedless and not just rarely seeded. It takes a long time to selectively breed trees in general due to the time it takes before they are able to fruit; limes are a lucky hybrid. —Preceding unsigned comment added by 193.172.19.20 (talk) 11:04, 27 November 2008 (UTC)

Another thought. Is there much of a demand for seedless lemons? AFAIK, people don't generally eat them 'straight' (do they?)... --Kurt Shaped Box (talk) 11:10, 27 November 2008 (UTC)

I do. I'll eat a few slices after dinner to "cleanse the palate". StuRat (talk) 14:57, 27 November 2008 (UTC)

Any citrus works well for that. I use oranges. -- kainaw™ 19:01, 27 November 2008 (UTC)

However, restaurants don't usually give me orange slices for that purpose, but the lemon wedges in my drink work well. StuRat (talk) 06:13, 28 November 2008 (UTC)

Hooray for kumquats! bibliomaniac15 20:57, 27 November 2008 (UTC)

Also after poetry, especially Keats.

I'm inspired:

"Have a citrus slice, after eats,
 and also have one, after Keats." StuRat (talk) 14:39, 29 November 2008 (UTC)

Lots of people like lemon wedges in their iced tea or other drinks, and for squeezing over their fish, mozzarella in carozza, etc. And the seeds must bother at least a fair number of these people, or high-end joints wouldn't serve said wedges in a prophylactic cheesecloth that keep the lemon seeds out of the drink/main course. - Nunh-huh 03:55, 28 November 2008 (UTC)

Well, never underestimate the importance of pointless doohickeys that are meant to project high-class... I doubt people care all that much about the seeds. The cheesecloth just makes us feel fancy and justified in paying that much for our lobster... --07:02, 28 November 2008 (UTC) —Preceding unsigned comment added by 98.217.8.46 (talk)

Thanks for the answer, 193.172.19.20! --Mathew5000 (talk) 23:49, 27 November 2008 (UTC)

Bromelain from Pineapples

Hey all, For my A-level Biology coursework, I've got a task about the effect of bromelain on Jelly. I've read that there are two types of bromelain (stem and fruit), but am unclear on the difference between the two, other than where they're found. Can anyone help? Many hugs, Amzi (Talk To Me) 10:08, 27 November 2008 (UTC)

Trying to make jelly with raw pineapple pieces is doomed to failure in my experience! It liquefies around the fruit. Graeme Bartlett (talk) 11:28, 27 November 2008 (UTC)

Turns out that pineapple has enzymes (oh yeah, that'd be bromelain) that destroy the gelatine (not surprising given that gelatine is primarily protein, and bromelain is a protease). If you want to make pineapple jelly you have two options: use a gelling agent unrelated to gelatine; or (better) use something that prevents the enzyme from wrecking the gelatine - if you heat your jelly mix with some pieces of a bell pepper you can then gel it with gelatine. I doubt it helps Amzi though. --121.127.209.126 (talk) 12:02, 27 November 2008 (UTC)

The coursework involves heating it to a high enough temperature to denature the enzyme - I think about 75 degrees Celsius is about the temperature you need to heat it to - so the jelly will set after all. 86.128.107.146 (talk) 17:01, 27 November 2008 (UTC)

if you read the bromelain article it explains the difference between stem and fruit enzyme. Graeme Bartlett (talk) 05:36, 28 November 2008 (UTC)

is this for real??? -- Bruce Lee plays ping pong with nunchuck

Is this video for real?? How could they fake it:

http://uk.youtube.com/watch?v=9QHslHpK4-Q

Thanks! —Preceding unsigned comment added by 86.217.99.209 (talk) 10:36, 27 November 2008 (UTC)

I'm not convinced it's really Bruce Lee -- the video is so small, it could be a look-alike in a track suit. Remember Forrest Gump? Tom Hanks really wasn't a ping pong champion. And the fact that its a commercial really makes me believe it was faked. --70.130.54.91 (talk) 15:02, 27 November 2008 (UTC)

I don't know about Bruce Lee, but legendary cricketer Donald Bradman honed his skills using a cricket stump to hit a golf ball repeatedly against the curved surface of the family's water tank when he was growing up. So it might be possible to use a nunchuck for ping pong but whether it's Bruce Lee for real is hard to tell. Julia Rossi (talk) 05:20, 30 November 2008 (UTC)

Note that the Bruce character is filmed from a rear angle, his face is rarely shown close up and hardly ever frontal, unlike the opponent(s). You can get a glimpse of his facial features around 00:35 and 00:52, and he doesn't look like Bruce Lee. Some of the ball movements don't look quite natural, "Bruce" doesn't even follow the ball's movements with his eyes, sometimes looking 90 degrees away, and it's a commercial. I don't know how they "faked" it, but one likely scenario is having the Nunchaku-Ka and ping pong player mime their motions without a ball at all. Air ping pong, if you like. Maybe they improvised, maybe someone was shouting instructions while filming, maybe it was thoroughly choreographed. The ball could have then been added later by some variety of computer animation. ---Sluzzelin talk 06:19, 30 November 2008 (UTC)

The mystery of illusion is a bit more transparent in this clip, by the way. Enjoy! ---Sluzzelin talk 06:37, 30 November 2008 (UTC)

It's probably faked the same way they faked the tennis matches in the movie Wimbledon (see the special features on the DVD). Watch the video closely and you'll see two high, bouncing shots on "Lee's" side of the table that look a little unnatural. The scene is choreographed and the actors go through all the motions without a ping-pong ball. The ball is then added in using CGI. This works great until you need a slow-moving ball, where it becomes difficult to get the motion right. --Sub-nav5019 (talk) 18:42, 1 January 2009 (UTC)

Why would any of you doubt Bruce Lee's powers and abilities?

Ok, to clear the air. I led the team that created this viral campaign at JWT Beijing. This was a viral campaign to promote the Limited Edition Bruce Lee N96 for Nokia.

The person is not Bruce Lee but a chinese national who has won multiple Bruce Lee lookalike contests in China. He is also a student of Jeet Kune Do.

The video was shot using a background sound of people playing ping pong so that “Bruce” and the ping pong player / players know when to “hit” the ball.

The ball was later superimposed into the video + sound and all.

Hope this clears the air. I glad that you enjoy it. We had lots of fun making it.

Perturbation theory in quantum mechanics

I have a question about perturbation theory. If we expand the exact state as

$|n\rangle =|n^{(0)}\rangle +\lambda |n^{(1)}\rangle +\lambda ^{2}|n^{(2)}\rangle +\cdots \ ,$

with |n⁽⁰⁾> the eigenfunction of the unperturbed H₀. Normalizing the exact state gives to first order in λ (supposing |n⁽⁰⁾> was normalized):

$\langle n^{(0)}|n^{(1)}\rangle +\langle n^{(0)}|n^{(1)}\rangle =0\ .$

The usual reasoning goes on saying that, "since the overall phase is not determined in quantum mechanics, without loss of generality, we may assume <n⁽⁰⁾|n> is purely real." But with "overall phase" only the phase of |n> is meant, isn't it? Changing its phase would change the phase of |n⁽⁰⁾> with the same amount, so that their inproduct remains unchanged. This would mean that it is not in general possible to assume that <n⁽⁰⁾|n> is purely real. What am I missing? MuDavid 12:55, 27 November 2008 (UTC)

The problem has been solved. The "overall phase" may be a function of λ (which seems pretty crucial, so maybe our article should be changed to reflect this), and by choosing this function the right way, <n⁽⁰⁾|n> can be made purely real. Bransden and Joachain explicitly say the phase may be a function of λ, but they do not stress that's what makes the argument. MuDavid 13:54, 27 November 2008 (UTC)

Natural selection in humans

If, due to some freak tectonic shift, the entire Eurasian and African continents shifted overnight so that Sub-Saharan Africa was located where Northern Europe is now, and vice versa, how long would it take before natural selection made the two populations physiologically resemble what the other one formerly was? (i.e., how long before most of the Africans now living in a cold climate had white skin, and the Europeans now living in a very hot climate had black skin) 69.177.191.60 (talk) 16:55, 27 November 2008 (UTC)

It probably wouldn't happen. We would just use sunscreen and vitamin supplements to negate the effects of having the wrong colour skin for your climate (in fact, with a decent diet, the vitamin supplements probably aren't even required). --Tango (talk) 17:01, 27 November 2008 (UTC)

I've read that the genetic shift from dark skin to light is estimated to take ~10000 years. Of course, as Tango says, that was before the advent of modern technological and medical advances. Dragons flight (talk) 05:58, 28 November 2008 (UTC)

And involved much smaller populations. With small populations you have things like founder's effect and etc. With very large populations you get regression to the mean. --98.217.8.46 (talk) 06:53, 28 November 2008 (UTC)

For natural selection to operate, people would have to die as a result of their skin color. We have ways to prevent that now. Of course, a small portion of the people would likely ignore all the medical warnings and go without vitamins or sunscreen, and die as a result. So, we might eventually get changes in skin color, but only if this effect was quicker than natural genetic drift and the effects of intermarriage. StuRat (talk) 06:09, 28 November 2008 (UTC)

Well, technically they wouldn't have to die, they'd just have to not reproduce, and others would have to out-breed them. But yeah, same difference, not gonna happen in today's world, population is too big and we don't tolerate that sort of thing. --98.217.8.46 (talk) 06:52, 28 November 2008 (UTC)

If the freak tectonic shift also ended technological civilization, there would certainly be selection for dark skin in the new Africa, but I don't think the population of the new Europe would necessarily evolve to "white" skin. The Indians of Canada and Alaska have been there for over 10,000 years and they don't have white skin. —JerryFriedman (Talk) 23:06, 3 December 2008 (UTC)

dissassociation of salts

Do salts necessarily disassociate completely when dissolved in water? Our article does not say. Or is there an equivalent of pKa for salts to describe their tendency to disassociate? ike9898 (talk) 17:13, 27 November 2008 (UTC)

They don't necessarily dissociate completely. And there absolutely an equivalent of pKa, and it's calculated the same way. It's usually called the solubility product constant. See solubility equilibrium. --Bennybp (talk) 17:37, 27 November 2008 (UTC)

Salt solubility in non-aqueous solvents

Is there any freely accessible information anywhere on the solubility of common salts in non-aqueous polar solvents (e.g. alcohols, ethers)? 69.177.191.60 (talk) 17:19, 27 November 2008 (UTC)

Our article, Sodium chloride includes a table of its solubility in various liquids. I expect out articles on other salts will have similar data. --Tango (talk) 17:36, 27 November 2008 (UTC)

I believe the CRC Handbook of Chemistry and Physics has that information. I guess that's "freely available" if you check your local library - typically the reference section. It can be a bit hard to find the information though. --Bennybp (talk) 17:42, 27 November 2008 (UT

Engineering handbook in English, German and Japanese

I would like to find three general handbooks in these three languages. What are the most common works?--Mr.K. (talk) 18:17, 27 November 2008 (UTC)

You don't say which kind of engineering you have in mind? I'm not an engineer, but in the field of mechanical engineering I sometimes turn to the Mechanical Engineers' Handbook, which is in a library near me. Engineering is such a vast subject that for any particular topic a general handbook is likely to point you somewhere else. Xn4 (talk) 03:13, 28 November 2008 (UTC)

In the meantime I found two German general engineering handbooks. There are this and this one. Engineering is surely a very vast field. However, there is plenty of common stuff. Physics', mathematics', material science's books for engineering are not uncommon. I need handbooks that unite all this common ground. Mr.K. (talk) 16:17, 28 November 2008 (UTC)

Jacuzzi Question

When I'm sitting in the jacuzzi with a cigarette, the water start to bubble when I blow out the smoke. Does anyone know why this happens? Thanks in advance. 99.230.51.61 (talk) 23:11, 27 November 2008 (UTC) —Preceding unsigned comment added by 99.230.51.61 (talk) 23:10, 27 November 2008 (UTC)

Are you sure you're not passing gas? —Cyclonenim (talk · contribs · email) 23:11, 27 November 2008 (UTC)

The water bubbles whenever the bubbles are switched on, it has nothing at all to do with your cigarette. See confirmation bias. --Tango (talk) 23:12, 27 November 2008 (UTC)

Sorry, I said what I meant wrong. When I blow the smoke over the jacuzzi I hear the bubbles a lot louder. Why? 99.230.51.61 (talk) 23:39, 27 November 2008 (UTC)

The ears and mouth are connected, so it's possible to act of blowing somehow affects your hearing. Try doing it without the smoke, just blow, and see what happens. --Tango (talk) 23:54, 27 November 2008 (UTC)

I've done that. Also, the sound gets quite a lot louder. 99.230.51.61 (talk) 00:01, 28 November 2008 (UTC)

All sounds rather dubious to me. The smoke is not going to be in a large enough amounts to affect the bubbles or things like air pressure, and it will be rapidly rising away from them at that. My humble suggestion is some sort of placebo effect and confirmation bias. --98.217.8.46 (talk) 06:46, 28 November 2008 (UTC)

Do you mean the sound gets louder when you blow without smoke? If not, then it's probably just your imagination playing tricks on you (combined with confirmation bias). If it does get louder without smoke, then it could be a genuine effect on your hearing (it won't have any effect on the actual volume of the sound, though). --Tango (talk) 13:31, 28 November 2008 (UTC)

November 28

Chemistry 1310

When 3.77 g of compound A (molar mass = 121.0 g) reacts with a few grams of compound B (molar mass unknown), 6.98 g of product C is produced. Analysis shows that C is actually a simple addition compound (that is, AB) and that the yield of product was 76.3% based on A. If A is the limiting reagent, what is the least amount of B that must be used to prepare the maximum amount of C obtainable from 3.77 g of compound A? —Preceding unsigned comment added by 128.61.26.178 (talk) 00:45, 28 November 2008 (UTC)

Do your own homework. Then you will learn somethng. —Preceding unsigned comment added by 98.16.67.220 (talk) 01:35, 28 November 2008 (UTC)

Or at least show us your attempt to solve it, if you want our help. StuRat (talk) 06:03, 28 November 2008 (UTC)

A psychology question - when do we feel we've "seen all the examples"

Suppose I have a collection of items, say N of them. The objects might be episodes of a TV show, collectible figurines, whatever. (In my case, they are snippets of information I show on a website - a different one each day or week).

Suppose I present them one by one to a subject, who doesn't know how big N is.

My basic questions are :

• How soon will the subject begin to feel that they've seen all the objects, and lose interest?
• How can I order the presentation to hold the subject's interest for as long as possible?

Any ideas, even partial, even "this is called 'Phenomenon X' so look it up yourself" would be welcome! mike40033 (talk) 03:44, 28 November 2008 (UTC)

I think you may have a bad assumption there, that people will only lose interest after they feel they've seen all the objects. While that may be true for some, others may lose interest the first time they see a repeat, or even before that. For an example, when I checked out my friend's cable TV, which has just about every channel there is, I only flipped through the channels until I felt I had a good sample of what was out there, then lost interest.

As for holding interest, you want each object to be more interesting than the last. As an example, let's try a joke:

"My garage is so big I can fit a boat in there, or even a yacht. I have a Nimitz class aircraft carrier in there at the moment." - Stays interesting because successively more absurd items are listed.

"My garage is so big I can fit a Nimitz class aircraft carrier in there, or a yacht. I have a boat in there at the moment." - Starts out interesting, but quickly gets dull.

There is an interesting problem with trying to make each object more interesting than the last, however. It's something I like to call Fantasy Island syndrome. That TV show started out to be quite reasonable. For example, they would bring a couple of separated High School sweethearts together again, and maybe there would be a romance. However, the network felt the need to have each episode trump the previous, so that they became more and more absurd. Toward the end Mr. Roarke had apparently become God instead of the original owner of a quirky resort. Then the show was canceled. So, beware that you can only outdo the previous object so many times, before you hit a wall. StuRat (talk) 05:40, 28 November 2008 (UTC)

Related point, from a statistical perspective. If your subject has seen n of the N objects, his maximum likelihood estimate for N will be n, although some authors have argued for a point estimate of 2n. HTH, Robinh 08:04, 28 November 2008 (UTC)

I believe that quite a lot of research work has been done on this. The makers of collectible card games (Pokemon, etc) have to solve this problem. They want to keep people looking out for 'new' cards - but they don't want to have to design and print too many different designs. So they have to introduce new es once in a while. But it's not enough to simply add a new card at full production run once in a while - it's necessary to have a new card that only shows up very rarely - that you'll only ever see once. That leads you to think that some cards must be very rare indeed (because you've seen some that are fairly rare) - and therefore, if you wait long enough, there may be an even rarer one coming along. This kind of trick is also used in computer games to keep things seeming new...if you get waves and waves of the same enemy coming at you time after time, it gets boring fast - but introducing a rare 'new' thing (and then not bringing it up again) makes you want to keep playing in order to see the next rare thing.

So I'm pretty sure there is some science behind this - I don't know (in detail) how they plan this stuff out - but I believe there is (somewhere) a comprehensive answer.

20:16, 28 November 2008 (UTC)

Is that anything to do with a law of intermittent returns that keeps people say, watching test cricket? There's also another "law" operating built into that one which means that the minute the fan is distracted, something exciting happens and they miss it. Incentive has a useful intro and maybe anything to do with reward anticipation, Julia Rossi (talk) 21:49, 28 November 2008 (UTC)

Are you impuning test cricket? Gadzooks!

I recall reading somewhere about the question of how often a slot machine has to pay to keep gamblers interested. This is probably well-researched. Whether much of the research is published is another matter. CBHA (talk) 22:34, 28 November 2008 (UTC)

Neva CBHA, not moi, but since you mentioned it's allure (more or less) it would be an interesting study to find stats of the efforts televised cricket must make to keep people glued to the screen: replays, minute detail of technicalities according to the bowling style,, new/old ball, batting stance/angle/averages, stump tweaks, slip and field positions and their rationale, dropped catch/great catch, wind direction, crowd behaviour, the finer points of lbw, including all those diagrams of field arrangements and runups, and findings of a player's state of mind, form, god it goes on and on. Not to mention the romance of the game. This kind of open-endedness means people simply must stick around to find some kind of closure or decide on balance it's going one way or the other, and opt for a conversation with the person next to them. Now there's a study in delayed gratification. Julia Rossi (talk) 07:27, 29 November 2008 (UTC)

Great article, Julia, I only wish I'd created it myself [9]. :-) StuRat (talk) 18:48, 29 November 2008 (UTC)

PS, puts a new spin on the idea of "test" cricket, non? Julia Rossi (talk) 07:34, 29 November 2008 (UTC)

To an American, a "test cricket" is a grasshopper used in an experiment. StuRat (talk) 18:48, 29 November 2008 (UTC)

Overlap of electron orbitals in violation of Pauli Exclusion Principle?

Electron orbitals (s,p,d, etc.), visualised in the conventional way as probability distributions centred on the nucleus, are frequently shown SEPARATELY in textbooks as spheres, dumbells, etc. Many diagrams appear to indicate that the probability function reaches inwards fairly close to the nucleus in all cases (I realise there is a finite probability of 'finding' any 'orbital' electron in almost ANY position). If this is taken at face value, then does this not mean that for atoms with several orbitals (more than one s-orbital, or an s- and a p-orbital, for example), the orbitals OVERLAP, and therefore, for example, a p-electron could be found in the space that could also be occupied at another time by an s-electron? To make myself completely clear, I am imagining an atom with dumbell-shaped p-orbitals and a spherical s-orbital, and cannot think how to draw the two orbitals without them passing through one another. Bearing in mind the restriction on electron numbers in an orbital set by the Pauli Exclusion Principle (2), this indicates my visualisation is wrong, but I don't know what the correct visualisation is. Is it perhaps the case that the orbital diagrams are completely hypothetical , being merely solutions to the Schrodinger equation, and that no atoms (other than Hydrogen?) actually have anything like these textbook distributions I have referred to, the truth being that the orbitals hybridise in some complex way? If so, do the conventional diagrams have any value? I asked a University chemistry lecturer this question 40 years ago, but he was unable to answer it. It has been nagging me ever since, and this forum is the first real opportunity I have had to obtain a solution. Pigmailion (talk) 10:41, 28 November 2008 (UTC)

Your visualisation is correct, the orbitals do overlap (indeed each electron has a positive probability density at almost every point of space), and the Pauli principle is not violated. All the Pauli principle says here is that no two electrons can have exactly the same quantum numbers; it says nothing about how the position-distributions are related. Algebraist 13:43, 28 November 2008 (UTC)

Thank you. Would this imply that I need to free myself of the concept of electron energy levels being rigidly related to distance of the electron from the nucleus? It seems that a 'valence' electron could spend some of its time closer to the nucleus than what I would call an 'inner-shell' electron. Although, as I understand it, one free electron in space is physically indistinguishable from any other, does a particular single electron in a given atom preserve its quantum identity indefinitely in the absence of external stimuli, or is there the possibility of two electrons spontaneously exchanging quantum states (leaving the atom overall unchanged)?Pigmailion (talk) 15:23, 28 November 2008 (UTC)

I think your mistake is that you're thinking of the wave function of a two-particle system as two one-particle wave functions superimposed on one another in some sense. That's not how it works at all. Wave functions (unlike every other kind of wave found in physics) live in the configuration space of the system, not in physical space. When your system consists of a single particle whose internal state (like spin) can be neglected, there's a one-to-one correspondence between points in space and (a particular orthogonal decomposition of) states of the system, so you can think of the wave function as living in space and draw it as such. But in a two-particle system the configuration space is six-dimensional.

To be a little more concrete, let me work this out for the much simpler problem of noninteracting spin-0 fermions in a one-dimensional infinite square well. (Spin-0 fermions are impossible in relativistic QFT but perfectly fine in nonrelativistic traditional QM.) In the one-particle case the Schrödinger equation is

$\partial _{t}\Psi (x,t)=-ik\partial _{x}^{2}\Psi (x,t)$

with the side condition that $\Psi =0$ at the boundaries of the box, which I'll take to be at $x=0$ and $x=\pi$. The solutions are then normalized linear combinations of

$\Psi _{n}(x,t)=e^{ikn^{2}t}\sin nx$

where n ranges over the positive integers. In the two-particle case the Schrödinger equation is

$\partial _{t}\Psi (x_{1},x_{2},t)=-i(k_{1}\partial _{x_{1}}^{2}+k_{2}\partial _{x_{2}}^{2})\Psi (x_{1},x_{2},t)$.

If the particles are distinguishable then the solutions are linear combinations of

${\begin{array}{ll}\Psi (x_{1},x_{2},t)&=(e^{ik_{1}n_{1}^{2}t}\sin n_{1}x_{1})(e^{ik_{2}n_{2}^{2}t}\sin n_{2}x_{2})\\&=e^{i(k_{1}n_{1}^{2}+k_{2}n_{2}^{2})t}\sin n_{1}x_{1}\sin n_{2}x_{2}\end{array}}$.

But if the particles are indistinguishable fermions then we have the side condition that $\Psi (x_{1},x_{2},t)=-\Psi (x_{2},x_{1},t)$, and in order to satisfy that we have to limit our solutions to antisymmetric combinations of the above, i.e. to

$\Psi (x_{1},x_{2},t)=e^{ik(n_{a}^{2}+n_{b}^{2})t}(\sin n_{a}x_{1}\sin n_{b}x_{2}-\sin n_{b}x_{1}\sin n_{a}x_{2})$.

Note that we no longer have solutions with $n_{a}=n_{b}$. The lowest energy state is the one with $\{n_{a},n_{b}\}=\{1,2\}$. Do the wave functions of the two particles overlap? It's a meaningless question because the particles don't have individual wave functions. There's just one wave function and it's defined over a two-dimensional configuration space, even though the physical space of the problem is still one-dimensional. The exclusion principle is manifested in the fact that the wave function is zero along a "diagonal" line in the configuration space, which has no analogue in physical space. Note also that the single-particle wave functions overlap completely in this example and can't be classified according to their distance from any particular location. -- BenRG (talk) 17:21, 28 November 2008 (UTC)

A less technical explanation is that "two orbitals overlap" means their associated electrons can be in the same place. That doesn't require that they are there at the same time. More importantly, the possibility of being in the same place doesn't require that they have the same angular momentum and energy (comparable to "velocity and direction" in more conventional object motion) when they are there. DMacks (talk) 03:06, 29 November 2008 (UTC)

Possibility of life on another planet which does not Evolve

Given that one assumes the appearance on another planet (in another solar system) of an initial single 'living' organism, can we question the NECESSITY of some ubiquitous features we find on planet earth? For example, is there an inevitability that more than one living organism exists on this other planet?
Is it conceivable that the control mechanisms for building the body of the first-appearing organism do not have, or need, to provide reproductive abilities? I am imagining a stable environment in which the sole (very simple?) organism on the planet metabolises, grows, maybe repairs or discards damaged parts (having a fairly uniform internal structure), and lives for a considerable time. Maybe there would be some difficulty in this case of deciding whether the organism was alive! Is the answer to this question linked to the necessity of supposing that more than one organism would be expected to appear on a planet where life develops?
Secondly, can we imagine another planet whose environment is very uniform and very stable over a long period, such that, given some initial period of evolution of (a number of) organisms, natural selection operates in such a way as to eliminate all significant deviations from the existing population structures caused by mutation and genetic drift. Would this not result in a planet with species that changed very little over large timescales? Or is the very nature of interaction between species chaotic, regardless of environmental stability? Does the huge number of species that have existed on this planet(most of which are extinct) result mainly from the instability of this earth's environment, and is not therefore something we should necessarily expect to find elsewhere in the cosmos, or is it an inevitable consequence of life's chemistry? Pigmailion (talk) 11:42, 28 November 2008 (UTC)

• I recommend reading Solaris, it discusses a situation not unlike what you have just described. --131.188.3.21 (talk) 12:52, 28 November 2008 (UTC)

Reproduction has been part of every definition of life that I've seen (it's a very difficult thing to define, but the definitions have certain things in common). As for life without evolution, it is certainly possible for a species to stay essentially unchanged for millions of years, there are examples on Earth. For an entire ecosystem to be unchanged seems unlikely (although presumably not impossible). Natural selection only affects characteristics that improve or hinder an organism's chance of reproducing, a lot of characteristics don't do that so aren't affected. Those characteristics would be susceptible to genetic drift, so there would be some changes going on over long enough time scales. Interactions between species could also be relevant (you can get "arms races" between species, eg. a plant develops harder and harder flesh so an animal develops harder and harder teeth). Earth's environment probably isn't any less stable or uniform than that of other planets capable of supporting life as we know it, so I expect most ecosystems would include evolution on a similar scale to that seen on Earth. --Tango (talk) 13:06, 28 November 2008 (UTC)

Continental drift seems unusual, and serves to change the environment considerably, including climate and the level of isolation of land species. The sometimes cloudy/sometimes clear nature of the sky on Earth also seems unusual. Most other planets either always have clear skies or always have a thick cloud cover. This means that long term changes in the cloudiness of the sky (due to volcanoes, meteors, etc.) can affect evolution in ways it can't on other planets. StuRat (talk) 14:21, 28 November 2008 (UTC)

It's unusual in our solar system, but then so are planets capable of supporting life as we know it. Planets capable of supporting such life are likely to be more Earth-like than other planets in our solar system. --Tango (talk) 15:11, 28 November 2008 (UTC)

I had a similar thought to the one organism concept. However, I thought it more plausible that one colony of single celled organisms, like coral, could exist where the individual cells do evolve, but any cells that split off from the colony are unable to survive on their own. This could eventually lead to one colony spread around the planet. StuRat (talk) 14:28, 28 November 2008 (UTC)

There would be strong evolutionary pressure for cells to become independent because doing so would reduce competition for resources. Even if the situation you describe can develop, I don't think it can be stable. --Bowlhover (talk) 06:06, 30 November 2008 (UTC)

Here's an example: Picture a colony of single celled organisms that develops sexual reproduction, yet is incapable of motion, and requires that two cells be adjacent, so the genetic material can be exchanged through the cell walls. Any cell that split off from the colony would be incapable of reproducing. StuRat (talk) 18:12, 30 November 2008 (UTC)

Disease transmission from old books (and other artefacts)

I'm a collector of old books, residing in England. Some of my books are 300 years old. At that time, and much later on, I guess there were a number of fairly common disease organisms around, which are now much rarer, that could have been transmitted via contact with a book that had been in contact with an infected owner. Does anyone know of a modern case of infection (by a nowadays rare organism) from an old book? I could also extend my question to ask whether there is any evidence of disease transmission through books and other secondhand items (computers, toasters, cars, etc. etc.) that change ownership today. It strikes me that, if hospitals have to go to great lengths to sterilise equipment, that organisms can readily be transmitted in this way. I'm not a hypochondriac, just curious about the survival times of various disease-causing organisms in the normal human environment. Pigmailion (talk) 13:54, 28 November 2008 (UTC)

Most disease organisms can't survive for more than a few hours outside the body. I would think the longest lasting organisms would be eggs of a parasite, that, when ingested, might hatch. However, I doubt if even they would last 300 years. StuRat (talk) 14:08, 28 November 2008 (UTC)

Most ... but not all. See endospore. Gandalf61 (talk) 14:26, 28 November 2008 (UTC)

Golden staph is considered a big bogey in hospitals where human to human contact is what it requires. It's considered "an incredibly hardy bacterium, as was shown in a study where it survived on a piece of polyester [hospital curtain] for just under three months." Science fiction and mummy's curses account for other misinformation, though the section Possible causes] lists some moulds. Julia Rossi (talk) 21:38, 28 November 2008 (UTC)

Anthrax spores, according to the article can last for many decades and possibly centuries. Richard Avery (talk) 08:11, 29 November 2008 (UTC)

Single or multiple breasts

Are there any validated examples of women "born with" (i.e. later developing) either just one or more than two (natural) breasts? If so, why would this be? —Preceding unsigned comment added by 209.161.213.199 (talk) 14:03, 28 November 2008 (UTC)

Extra nipples (supernumerary nipples) are quite common in both men and women. Extra breasts (including nipple, areola, and fat) are rather more rare, but so-called accessory breasts are not unheard of. (The term for the condition is polymastia.) TenOfAllTrades(talk) 14:45, 28 November 2008 (UTC)

erath gravity

what is the power needed to escape the erath atmosphere by considering the efect of hight on gravity bat not the airodinamic? --אזרח תמים (talk) 14:37, 28 November 2008 (UTC)

I think you're talking about gravitational potential energy. The formula for it is $U=-G{\frac {m_{1}m_{2}}{R}}$ (it's negative because you need to add more energy in order to get free). If we plug in the mass and the radius of the Earth, the energy (in Joules) required to get an object from the surface of the Earth to infinite distance is 62.5 million times the mass of the object (in kilograms). If the object is, say, a person weighing 70kg, the energy required is about 4 gigajoules (equivalent to about a tonne of TNT). If you don't want to get all the way away from the Earth but just high enough that you are out of most of the atmosphere, it's significantly less. Low Earth orbit starts at about 200km above the surface (that's roughly where it becomes possible to have reasonably stable orbits without the atmosphere being a problem - orbits do still decay, just fairly slowly), the energy required to get an object to LEO is the energy required to get it from the surface to infinity, minus the energy required to get it from LEO to infinity. The energy required to get it from LEO to infinity is the same formula as above, but with R replaced by R+200km, so for the 70kg person we get the difference as 133 megajoules, or about 33kg of TNT. --Tango (talk) 15:10, 28 November 2008 (UTC)

tanks--אזרח תמים (talk) 16:04, 28 November 2008 (UTC)

You're welcome. --Tango (talk) 16:58, 28 November 2008 (UTC)

How much additional energy would be needed to add orbital velocity to the person, besides getting him to the specified altitude of 200 km, from which he would fall back down? Edison (talk) 17:15, 28 November 2008 (UTC)

Excellent point, I forgot to mention that! Orbital speed at 200km is about 7.8 km/s, plug that into E=1/2 mv² gives (for the 70kg person above), an additional energy requirement of about 2 GJ, or half a tonne of TNT. When you factor in things like gravity drag (essentially the energy required to maintain your current altitude while you're climbing) and atmospheric drag, the actual amount of energy required to get from the surface to orbit is going to be greater than the sum of those values. You'll notice that the energy to get into orbit is nearly 20 times greater than the energy required just to get to the right altitude - that's why sub-orbital flight is so much easier than orbital flight (and hence why companies like Virgin Galactic are just doing straight up and straight down flights for the public with about 6 minutes in space rather than actually taking them into orbit). --Tango (talk) 17:41, 28 November 2008 (UTC)

What you are calculating is the potential and kinetic energies a mass would have once it reaches orbit or escape velocity. The actual energy expended when using, for instance, a rocket to reach required velocities will be much greater. Remember, you are lifting and accelerating a large amount of fuel in order to propel a much smaller mass, and the potential and kinetic energies of that fuel needs to be taken into account. Probably the easiest way to approach the problem, is to find the required Delta-v, then use Tsiolkovsky's rocket equation to calculate the total energy required.—eric 22:17, 28 November 2008 (UTC)

Indeed, I'm assuming some form of 100% efficient propulsion, a (ideal) space elevator, say. Rockets require far more energy than the naive calculations I have presented would suggest. --Tango (talk) 22:30, 28 November 2008 (UTC)

PCR Primers

If I ran a PCR reaction and one of my primers was not working, for whatever reason, is there any possibility to have no bands appear under UV light after gel electrophoresis? Donek (talk) 17:21, 28 November 2008 (UTC)

Usually you'll see your primers at the bottom of the lane, but (for example) they can be obscured by loading dye. It also depends on what you're using to visual nucleic acid (ethidium bromide, SYBR green, etc), and how you visualize your gel (exposure time, etc). --Scray (talk) 17:38, 28 November 2008 (UTC)

I'm using dntp's as well as the dye. Might either obscure this? I'm using ethidium bromide to visualise and only exposing the gel for a moment's glance and throwing it away as not getting results. How do I test if a tube labelled as containing a certain primer actually contains a primer at all? Donek (talk) 18:15, 28 November 2008 (UTC)

You should always have a positive control, and having multiple controls will allow you to know which of your reaction components is working properly. In addition, your gel imaging station should support integration (prolonged exposure) because you might miss your result otherwise. --Scray (talk) 18:25, 28 November 2008 (UTC)

I have been getting positive results for all other reactions except one. This outcome occurs in a repetitive fashion. I use positive and negative controls and I am using bromo-blue as the loading dye. I have suggested to other students (one phD) and two lecturers that there may be a problem with the primer but they have said that there would have been evidence of this, maybe what you initially suggested. I'm going to go in to test it anyway tomorrow but I don't know how likely I am to be right. I don't understand why it would work for all other reactions but not one in particular, especially in a repeating pattern. I can only think it could be the primers at fault. Donek (talk) 20:54, 28 November 2008 (UTC)

I would think hard about every single thing that is different between your positive controls and your experimental reaction. Additionally, I would search for a PCR troubleshooting page, just to explore ideas, e.g.: [10]. Hope this helps! --Scray (talk) 00:48, 29 November 2008 (UTC)

That's a great link, thanks. One more question. What would be observed under UV light if only one primer was added to the mix? Donek (talk) 14:00, 29 November 2008 (UTC)

There would be very little if any signal. You're staining with ethidium bromide, which intercalates between the bases in double-stranded nucleic acids. Unless the primers form primer-dimers, they wouldn't stain incredibly efficiently. Perhaps more importantly, however, if only one primer, rather than a primer pair, was added to the PCR mix, the resulting amplification would be linear (1, 2, 3, 4, 5, ..., N) rather than exponential (1, 2, 4, 8, 16, ..., 2^N) leaving you with very little amplification product and lots of unused primers in the end. – ClockworkSoul 18:08, 29 November 2008 (UTC)

November 29

caffiene

can caffiene be smoked? —Preceding unsigned comment added by 76.14.124.175 (talk) 02:23, 29 November 2008 (UTC)

In the world of shisha there are ads for blends of caffeinated tobacco. I don't know anything about the actual dosage or effect. ---Sluzzelin talk 06:10, 29 November 2008 (UTC)

I can think of at least three other alkaloids – nicotine, morphine (as opium), and cocaine – that are smokable, which suggests that it's possible, but I know of no instances where caffeine is subjected to the same process. I would strongly advise against attempting it, however. Seriously. Caffeine overdoses can be fatal. – ClockworkSoul 08:18, 29 November 2008 (UTC)

I agree, we should be looking for ways to make smoked drugs into something edible, like coffee, instead, as smoking anything causes lung cancer. Pass the special brownies and grow those tomacco plants, please. StuRat (talk) 14:33, 29 November 2008 (UTC)

It is not true that “smoking anything causes lung cancer”. --Mathew5000 (talk) 15:23, 29 November 2008 (UTC)

Well, whilst I don't agree with the certainty with which StuRat stated it, it's kind of true that smoking (not inhaling) anything can cause cancer. When you smoke, you burn something, almost always inefficiently. When you do this, you produce carcinogens. Carcinogens cause cancer. —Cyclonenim (talk · contribs · email) 16:25, 29 November 2008 (UTC)

(ec) It's a pretty good approximation to 'true', however. Burning just about any organic material at low temperatures generates a number of carcinogenic products of incomplete combustion; this includes nasty polycyclic aromatic hydrocarbons like benzo[a]pyrene. I suppose that for some smoked products the user does not typically inhale particularly deeply, providing a modest amount of protection to the lungs; in those cases carcinogens would be largely deposited in the nose, mouth, lips, and throat, leading to oral and nasopharyngeal cancers. TenOfAllTrades(talk) 16:40, 29 November 2008 (UTC)

You are arguing that smoking anything should cause cancer, theoretically. But empirical data refute the claim; a 2006 study found no statistical association between smoking marijuana and lung, head, or neck cancer.[11][12] --Mathew5000 (talk) 19:16, 29 November 2008 (UTC)

It's rather dangerous to rely on a single study to draw a conclusion. Your remark could just as easily have said – correctly – that "a 2006 study found a statistically-significant association between smoking marijuana and lung cancer": PMID 18238947. Looking at PubMed, the best I can say is there's not a good scientific consensus one way or another. I don't see any clear-cut results from the last couple of year's publications, and there's a review in Arch. Intern. Med. that summarizes the data up to 2006 pretty well: PMID 16832000. Essentially, there's good data to support the conclusion that heavy marijuana smoking is linked to a number of clinical and histopathological markers of premalignancy, but the step to a demonstrated increase in lung cancer (or not) isn't there yet. Most of the studies I've looked at today don't seem to be sufficiently large or well-controlled. My two cents. TenOfAllTrades(talk) 20:14, 29 November 2008 (UTC)

I think it's also fair to compare the level of exposure that a "heavy" marijuana smoker gets to the amount that a "heavy" cigarette smoker when considering carcinogenic effect. I've known plenty of people who smoke 40 cigarettes a day (2 packs), but I've never met anyone who smokes 40 joints per day. --Sean 20:42, 29 November 2008 (UTC)

Agreed. While I stick by my claim that all smoking causes cancer, most pot-heads may be lucky enough to be below the exposure level which would cause a statistically-significant effect that can be easily measured. StuRat (talk) 18:03, 30 November 2008 (UTC)

It's also possible that smoking tobacco exposes a person to more or more powerful carcinogens then smoking marijuana dosage being equal. This doesn't imply that all smoking causes cancer is wrong Nil Einne (talk) 11:43, 1 December 2008 (UTC)

Cannabis & lung cancer

This case-control study suggests a link between the two. There are many potential reasons why this link might be less obvious than the tobacco–cancer link:-

• Cannabis smoke has less carcinogenic effect than tobacco smoke. This article indicates reasons for this. Interestingly, cannabis smoke contains anti-carcinogenic chemicals
• Cannabis users smoke comparatively less cannabis than tobacco smokers smoke tobacco
• Cannabis smoke inhalation is less deep than tobacco smoke inhalation, so carcinogen exposure is reduced
• Cannabis smokers tend to be younger, at an age when the risk for tobacco smokers is also low
• Many cannabis smokers also smoke tobacco. Thus the effect of cannabis is partially masked by that of tobacco
• In many countries, smoking cannabis recreationally is illegal. As a result:-

  cannabis users may be more reluctant to volunteer for studies, hence smaller studies

  cannabis smokers may not be truthful about the quantity used

• Systematic bias, including recall bias

Axl ¤ [Talk] 10:28, 2 December 2008 (UTC)

Cost of an additional degree of heating

Let's say the average temperature outside is 30 °F. Now, let's say that someone can tolerate an indoor temperature of 70 °F but feels better with, say, 71 °F, and would feel even more comfortable with 72 °F or 73 °F. For a single-room studio apartment, how much more will it cost to heat that additional one degree over a month? Just a little bit, or a lot? What about an additional, say, two degrees? Or three? Basically, I'm trying to figure out whether it's worth it to turn up the thermostat or just keep shivering or wearing uncomfortably bulky clothing to save on heating costs. —Lowellian (reply) 04:28, 29 November 2008 (UTC)

The monetary answer depends strongly on how well insulated the apartment is. In general, conductive heat loss is directly proportional to the temperature difference, so if you have a 40° F difference between inside and outside then increasing it by 1° F will make you lose heat 41/40 = 1.025 times as fast. Which means using ~1.025 times as much heating and increasing your bill ~2.5% from what it otherwise would be. Most other factors (such as convective heat losses if you have a draft, or secondary sources of heating) will tend to imply this a lower limit, and the actual cost increment could be higher. Dragons flight (talk) 05:49, 29 November 2008 (UTC)

Please ignore Dragons flight's answer. It's completely incorrect. Heat loss isn't "directly proportional to the temperature difference"...Heat loss increases as the SQUARE of the temperature difference (per Newton's law) - which is why turning your thermostat down by a small amount produces much bigger gains than you'd expect. So going from 40 to 41 is a 5% increase in cost - not 2.5%. Read what I wrote below. SteveBaker (talk) 14:36, 29 November 2008 (UTC)

Steve, are you sure it's the square and not, as User:Dragons flight says, "directly proportional"? According to Wikipedia's article on heat transfer, "Newton's law of cooling, states that the rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings, or environment." —Lowellian (reply) 19:17, 29 November 2008 (UTC)

Not an answer but a tip: if you sit still for a longer period of time, instead of warming the whole apartment you could buy an electrical foot warmer. I use one and I find that with warm feet, my whole body stays warmer. Lova Falk (talk) 09:17, 29 November 2008 (UTC)

Counter-tip: wool socks aka "boot socks". I keep a pair laying by the couch, if I'm feeling cold I put them on. You're absolutely right that keeping the feet warm is a big part of the puzzle. Franamax (talk) 12:02, 29 November 2008 (UTC)

The thing is, once my feet are cold, no socks can make them warm again. It rather feels as if the socks insulate the icy skin of my feet. I've heard that alternating foot baths (that is, alternating hot and cold water) do wonders for cold feet, but it is way too much hassle. Lova Falk (talk) 15:56, 29 November 2008 (UTC)

Because we don't know how efficient your heater is - or how well your house is insulated - or how much electricity/gas costs where you live - we can't answer the question as a direct amount of money. What we can do is tell you how much your electricity/gas bill will increase as a percentage of whatever you're paying now. Newton's law of cooling says that the rate at which heat is lost increases as the square of the difference in temperature between the inside of your house and the outside air. That fact is true regardless of the amount of insulation you have - or how your heating system works. So when the temperature outside is (say) ten degrees below what it is inside - then you are losing ten-squared=100 "units" of heat - which your heater has to replace using 100 "units" power you have to pay for (I'm being deliberately vague about what a "unit" is because that depends on all of those things that we don't know). If you increase the thermostat setting by just one degree then the difference is 11 degrees and you'll lose eleven-squared=121 units of heat. So the cost of increasing by one degree in a 10 degree temperature difference is to add 21% to your heating bill! However, if the weather outside is just one degree below your thermostat setting (1x1=1 unit of heat loss) - and you increase the thermostat by 1 degree then your (very small) 1 unit heating bill will go up to 2x2=4 units! Your heating bill will quadruple in a 1 degree temperature difference. (But then it was such a small bill in the first place - you may never notice).

As the temperature difference between inside and outside get bigger (eg because the weather got colder) then the cost of adding one degree gets smaller. If you live in deepest Alaska and the outside temperature is zero degF and you keep your home at a toasty 70 degF then you are already using 70x70=4,900 'units' of heat...if you wind the thermostat up one degree in that situation then you'll be using 71x71=5041 'units' - which is only about a 3% increase in your heating bill.

Insulation and having an efficient heater are vitally important because they reduce the cost to you (and to the environment) of adding one 'unit' of heat to your house.

The same rules apply when airconditioning a house too.

SteveBaker (talk) 14:31, 29 November 2008 (UTC)

Newton's law of cooling is linear not quadratic. Please ignore Steve's answer. It's completely incorrect. Dragons flight (talk) 22:02, 29 November 2008 (UTC)

From Physical Calculations (J.J.Tuma, c.1983), Sec. 6(6) Overall Heat Transfer, (a) Wall Transfer: quantity of heat Q transferred in the interval t through three stages is Q = A(T_a - T_b)t divided by (rec(h₁) + rec(k) + rec(h₂)) where A = transfer area, T_a, T_b are internal and external temperature, h₁ and h₂ are convection coefficients (air space) and k is thermal conductivity of the wall. (Sorry I haven't figured out <math> yet, also rec(x)=1/x) This implies a linear relationship (T_a - T_b), but then we need to examine k. My impression was always that thermal conduction varied with e ^(-kT), so I'd be interested in a resolution here. Franamax (talk) 01:58, 30 November 2008 (UTC)

And I might be wrong on the minus, and it should be a delta-T that I'm completely wrong on - so you can understand my complete confusion on this. :) Franamax (talk) 02:10, 30 November 2008 (UTC)

The rate of cooling, dT/dt, is indeed proportional to the temperature difference:

dT/dt = -k(T-T0), where the negative sign indicates temperature is decreasing

e^(-kt) can easily be found by rearranging the equation and integrating to solve for T:

dT/(T-T0)=-k dt

ln (T-T0)=-kt + C

T = (Ta-T0)e^(-kt) + T0, where Ta is the initial temperature of the cooling object

It is the temperature of an object left to cool that obeys this equation, not the rate of heat exchange. Since this rate is what matters in the case of a room being maintained at a constant temperature, the power spent by the heating unit should be linear, not exponential. --Bowlhover (talk) 05:35, 30 November 2008 (UTC)

I've been away from the Reference Desk for awhile, and when I return, I'm disappointed to see it devolve into this. "...please ignore the previous answer"... "...complete and utter nonsense..."... Reference Desk regulars, let's keep in mind that this is the Science Desk. There is no reason to ignore anything - incorrect or inaccurate discussion can still be educational - if nothing else, it shows that smart people can disagree about precise factual claims; more precision leads to more squabbling over the details. Let's not forget that Newton's Law of Cooling, like all other laws of Science, are mathematical generalizations based on empircal data. Models are not always correct; and they are very often inapplicable. Before throwing the differential equations around, it would be more productive to consider this situation qualitatively. Raising the thermostat will cause the furnace to turn on more often. How much more often? It will depend on the rate of cooling, and it will also depend on the differential rate of efficiency of the furnace to re-heat the room. (I suspect that turning on the furnace entails "overhead" - so heating from 70 to 71 degrees may actually take negligibly less energy than heating from 65 to 71). The consequence of this result is that the range of the thermostat's dead-zone has a bigger impact to the heating budget than small variations on the temperature setting. The total on-time of the furnace (and hence, the bill) might not change much for a single-degree change on the thermostat dial. Nimur (talk) 02:53, 1 December 2008 (UTC)

THC absorption (repost)

Reposting removed question (see Wikipedia talk:Reference desk#Removed medical advice (THC absorption)). Zain Ebrahim (talk) 11:43, 29 November 2008 (UTC)
Ages ago, I learned (from somewhere, heck if I can remember) that when smoking marijuana, it is more effective to "hold it in" for as long as possible after inhaling to maximize the amount of THC taken in. Now... is this tactic effective? Does holding it in increase the amount of THC intake versus a quick inhaling followed quickly exhaling (as in "regular" breathing)? I guess an effective way to test this would to smoke same amounts of the same strain of marijuana with the same method of delivery over an identical period of time in each test on different days... except, there are other variables involved (food in the system, surroundings and comfort, mood, etc) and it may prove difficult to properly record or quantify any results (it's a lot of work for a part-time stoner to try and process with any consistency while under the influence). --Abin Sur (talk) 17:32, 24 November 2008 (UTC)

From the literature circulated in my church group, something like 90% of cannabinoids are absorbed immediately in the inhalation process. Brief holding-in would increase the absorption to some degree. Holding your breath for any amount of time will tend to reduce your blood oxygen, which could enhance the effect - however holding in the smoke is mostly part of the ritual, since it proves you're not being greedy and over-toking. Anyway, that's what I've heard at my church group, I never touch the stuff myself :) Franamax (talk) 11:54, 29 November 2008 (UTC)

According to "Cannabis in medical practice" [13], holding your breath for up to ten seconds increases absorbed THC, but not any longer than that. Also, holding your breath for longer increases exposure to tar and carbon monoxide. Fribbler (talk) 15:07, 29 November 2008 (UTC)

You're right, Abin Sur, your query did not run afoul of any applicable guidelines; its removal was unwarranted. If I recall correctly what I've read, THC absorption drops off sharply after five seconds or so. There are some high-quality references in Volcano Vaporizer, some of which address this what you're curious about. —Scheinwerfermann ^T·_C17:49, 29 November 2008 (UTC)

Hydrogen peroxide and yeast

When mixed together do they react or is the hydrogen peroxide a catalyst for the yeast? —Preceding unsigned comment added by 89.241.68.206 (talk) 15:15, 29 November 2008 (UTC)

Oxygen is released because of the yeast's catalase enzyme. Catalase breaks the peroxide into hydrogen and oxygen. Fribbler (talk) 17:41, 29 November 2008 (UTC)

While true, there won't be a great deal of catalase in the yeast medium. Peroxides, including hydrogen peroxide, are actually somewhat toxic at the cellular level, and won't be very good for yeast cells. – ClockworkSoul 18:00, 29 November 2008 (UTC)

Food Safety

This question relates to a prior discussion, now archived. Wikipedia:Reference desk/Science#Why is refrigeration of tin a bad idea?

Are food cans sealed with solder that contains lead? I understand from our article that they once were. Are they still?

Thanks. CBHA (talk) 17:37, 29 November 2008 (UTC)

No, they aren't soldered at all any more. StuRat (talk) 18:39, 29 November 2008 (UTC)

Plant Propagation

What factors (physical, biological, genetic) affect the ability of a plant cutting placed in water to grow roots.

Soft-tissue plants such as Saintpaulia, Coleus root very readily. What are the issues with tougher plants, and can they be overcome?

Just for example, I'm trying to root Schefflera cuttings (not because I need another Schefflera, just to see if it can be done.) After about five months, they still look healthy but there is no sign of growth. Ficus cuttings, put in water at the same time, have small roots.

Thanks, CBHA (talk) 18:43, 29 November 2008 (UTC)

Have you used that hormonal rooting powder? SteveBaker (talk) 20:32, 29 November 2008 (UTC)

Yes, it was used on the Schefflera and the Ficus. CBHA (talk) 20:35, 29 November 2008 (UTC)

Thanks for your responses. I guess I did not make my question clear. What was revolutionary with the surgery she performed was not that she did it from a remote location or even the technology that made that possible. Instead, what was revolutionary was the innovative nature of a surgical technique she devised to conduct the surgery. It's a technique that she apparently perfected and which is not on record as having been performed before anywhere in the world.

PlatoSelfstarterone (talk) 19:40, 1 December 2008 (UTC)

Ground-breaking Cardiac Surgery Technique.....

A female doctor from Michigan devised a new heart repair surgical procedure. She remotely (from her home), led and directed a team of other surgeons at a San Diego hospital, to perform the surgery on a 26 year old male patient. The surgery was performed sometime in November 2007. It was even rumored that the new procedure might be named after her. Does anyone out there know the name of this doctor and the name and/or type of procedure she performed?

PlatoSelfstarterone (talk) 19:12, 29 November 2008 (UTC)

2007 seems a bit late for that to be terribly ground-breaking (unless the innovation was that she did it over dial-up :) ). See Remote surgery. --Sean 20:45, 29 November 2008 (UTC)

The technology used is shown here. http://www.mybuzza.co.za/ It is revolutionary. ;o) CBHA (talk) 20:59, 29 November 2008 (UTC)

Feeding the seagulls

I was throwing bits of stale bagguette to a seagull this afternoon. I suppose that they were too hard or rough for him to swallow because every time I threw him a chunk, he'd pick it up, take it over to a puddle, swish it around in the water a bit until it was all soggy and soft and then swallow it and come back for more.

Has anyone else seen seagulls do this, or is this something that this one seagull has figured out on his own, do you think? --84.68.183.229 (talk) 19:32, 29 November 2008 (UTC)

I've seen ducks do the same thing. --Tango (talk) 19:34, 29 November 2008 (UTC)

I can't answer your question but I'm surprised by it. My experience is that if I feed one seagull, approximately 83 others appear. CBHA (talk) 19:38, 29 November 2008 (UTC)

This one was already pecking around in my garden for worms or something before I fed him. I don't think that the other gulls saw him eating the bread. --84.68.183.229 (talk) 19:48, 29 November 2008 (UTC)

Psychoneuroimmunology

Is there an easy way to find out which universities offer a degree in Psychoneuroimmunology? Also when such degrees first became available?

Would such a degree be a Doctor of Medicine degree or a Doctor of Philosophy?

Thanks, CBHA (talk) 19:42, 29 November 2008 (UTC)

I believe such specialism is only possible after studying a medical degree such as an MD, MBBS etc. I don't think there is a specific degree in psychoneuroimmunology but rather you train to become a psychoneuroimmunologist, like an immunologist or neurologist. Therefore, you would be a Doctor of Medicine. The specialism has existed for around 40 years. —Cyclonenim (talk · contribs · email) 20:06, 29 November 2008 (UTC)

While there will be doctors specialising in it, there will probably also be researchers with PhD's working in the field too having done their first degrees in pharmacology, (bio)chemistry, psychology, etc. (and then specialising for their PhD and subsequent work). It's also not uncommon for people to have both an MD (or equivalent for their country) and a PhD if they are involved in medical research. --Tango (talk) 22:54, 29 November 2008 (UTC)

Please Be Patient And I Thank You For Your Time

Awhile back, I believe some people did not take this seriously, so I am hoping everyone will taking this 'question' seriously (this time around).

I also want to give notice to this because this was some new information that had not be included. I humbly thank you.96.53.149.117 (talk) 22:18, 29 November 2008 (UTC)

We attempted to give you a serious answer and you refused to accept it. Our answer isn't going to be any different this time - chest hair is perfectly normal and there is absolutely no reason to believe it is a recent phenomenon. --Tango (talk) 23:01, 29 November 2008 (UTC)

I see absolutely no reason to suspect that any hair on your chest is unique to you or unique to the last 100 years. --98.217.8.46 (talk) 01:10, 30 November 2008 (UTC)

As before and before that... If you believe you have some sort of physical problem, this is a medical issue. See a doctor. If this is not important enough to you to see a doctor, you must not consider it truly unique or special - so why should we? -- kainaw™ 01:17, 30 November 2008 (UTC)

Yes, such hair is absolutely normal. When you get old, you can also look forward to hair growing out of your ears and eyebrows that never stops, too. It seems this hair was put there primarily for God's amusement. StuRat (talk) 02:37, 30 November 2008 (UTC)

Evidence that not all hair is entirely useful: [14]. Sometimes, hair just gets in the way. --Jayron32.talk.contribs 03:42, 30 November 2008 (UTC)

. . .indeed it does [15]

I think I finally understand what the questioner is trying to ask, but has failed to do so properly. He appears to be under the impression that he has some special kind of pubic hairs on his chest. Also, he appears to be under the impression that chest hair in general is a recent step along the evolutionary ladder. So, since short chest hairs are recent and he now has big chest hairs, he must be one step past the rest of the world on the evolutionary ladder. In fact, he is no longer a simply homo sapien. He is a completely new species, perhaps a homo pubicium. -- kainaw™ 14:05, 1 December 2008 (UTC)

Pubic hairs do often follow shortly after walking erect. :-) StuRat (talk) 00:51, 2 December 2008 (UTC)

What does "higher mammal" mean?

Is it related to their ability to think or some other classification? Can you point out a sample list of these animals? Thank you =) Louis Waweru  Talk  22:59, 29 November 2008 (UTC)

I've never heard of a strict definition of the phrase, it's usually used quite loosely. I think it usually refers to intelligence, at least partially - humans and primates would almost certainly be included. Intelligence is very difficult to define, though, which makes such a classification pretty much useless for any serious work. --Tango (talk) 00:05, 30 November 2008 (UTC)

It could also mean placental mammals, as opposed to marsupials and monotremes. StuRat (talk) 02:32, 30 November 2008 (UTC)

It is usually used to refer to the most intelligent mammals: apes. Axl ¤ [Talk] 10:05, 2 December 2008 (UTC)

Heheh, okay. I get the idea[s]. Louis Waweru  Talk  18:28, 2 December 2008 (UTC)

Accession number needed for BLAST

I would like to compare the gene sequences of PCAF and GCN5 (Homo sapiens, both) using BLAST. BLAST requests accession numbers. Here is the page of the NCBI entry for PCAF: [16] - it gives the number 8850. When I use this number in NCBI BLAST, it using a different gene sequence (something unrelated to PCAF. Why is this? Where is the correct accession number? --Seans Potato Business 08:00, 30 November 2008 (UTC)

When I click on the link, I see a page for KAT2B, which I see is also known as PCAF. Is that not what you get?CalamusFortis 01:33, 30 November 2008 (UTC)

Also, here is the data for GCN5, also known as KAT2A. [17] CalamusFortis 01:38, 30 November 2008 (UTC)

Well thanks; that's fine and dandy, but I need accession numbers that I can put into NCBI BLAST. I don't see them on those pages. --Seans Potato Business 08:00, 30 November 2008 (UTC)

I think I may have found what you need. At the very bottom of the page for the genes, there is a number associated with the nucleotide sequence. For PCAF, it's AC099057. For GCN5, it's AC105024.8. Could that be what you need?CalamusFortis 15:30, 30 November 2008 (UTC)

Lipid and Phosphate Granules

On your diagram of a section through a yeast cell on the yeast article, within the cell are two granules, on lipid and one phosphate. What do these granules do and is there any significance to the phosphate granule being within the vacuole.

Thanks in advance 84.13.17.47 (talk) 23:42, 29 November 2008 (UTC)

If nobody here rises to the occasion with an answer, you may want to post this Q on the yeast talk page, instead. StuRat (talk) 02:29, 30 November 2008 (UTC)

November 30

Shooting the ISS out of the sky

Just a goofy question I had. What would be the minimum technology necessary to shoot the International Space Station out of the sky? (I've no interest in doing so, personally.) It looks like a rather fragile thing up there, though I suspect its great height and relatively fast speed would mean you'd require some sort of fairly sophisticated anti-satellite weapon to do so. But it is pretty large compared to most satellites, so maybe it would be an easier target? Or maybe you could shoot a missile somewhere into its path that would just shoot out a lot of debris? I'm sure some of you mad scientists out there have even better ideas... --98.217.8.46 (talk) 01:16, 30 November 2008 (UTC)

The ISS is in a fairly low orbit, which is why it moves so fast. USA 193 was destroyed at a similar altitude (and therefore similar velocity), so such technology does exist - that's just one example, though, so there's no way to know how reliable it is. The ISS being so big would make it an easier target compared to other satellites in a similar orbit. --Tango (talk) 01:43, 30 November 2008 (UTC)

If don't want to develop a real anti-satellite weapon, any ICBM can reach the ISS altitude, and I'd imagine that with a nuclear warhead you'd only have to get close so steering and guidance would matter less. Dragons flight (talk) 04:01, 30 November 2008 (UTC)

You would have to get closer than you might expect - without an atmosphere you don't get the same blast wave doing damage over a wide area. --Tango (talk) 13:29, 30 November 2008 (UTC)

Though the EMP would fry the ISS's electronics and cause it to drop out of orbit fairly quickly (because there'd be no way of making course corrections - assuming that there's no 'fire booster rockets manually' lever behind a break glass somewhere), wouldn't it? --Kurt Shaped Box (talk) 15:38, 30 November 2008 (UTC)

You don't need to make course corrections to stay in orbit, once you're in orbit your momentum keeps you there. You might hit space debris which could do damage, though (I'm not sure how much debris there is that intersects the ISS orbit). Eventually it would de-orbit due to atmospheric drag since the loss of attitude control would make it impossible for craft to dock and use their rockets to boost the orbit (which is done periodically), but that would take months at least, probably years (they boost every few months, but I'm sure they don't leave it to the last minute). They may even be able to use gyroscopes to maintain basic attitude control without electronics, I don't know. --Tango (talk) 16:04, 30 November 2008 (UTC)

Well, I was hoping for the most low-tech solution. A nuclear ICBM ain't that! My thought was, what if you had some very primitive sounding rocket, could you get it high enough and have it create some sort of debris field that the ISS would be forced to go through, or something like that. --98.217.8.46 (talk) 16:29, 30 November 2008 (UTC)

Our article on sounding rockets says they can easily get high enough, and there's no reason you couldn't put an explosive charge in one to create debris. I'm not sure you would get enough debris to reliably cause an impact, though - it's going to spread out pretty quickly and then fall down (since it isn't in orbit), so you need to get the timing very precise. I'm not sure sounding rockets are that accurate. --Tango (talk) 16:36, 30 November 2008 (UTC)

See, that's what I want to hear about. ;-) --98.217.8.46 (talk) 16:51, 30 November 2008 (UTC)

What do you mean shoot it "out of the sky"? There was some controversy a while ago when Russia blew up one of their satellites, but the problem was that it was still in the sky, and had created a lot of dangerous debris. — DanielLC 16:54, 30 November 2008 (UTC)

Are you sure you're not thinking of 2007 Chinese anti-satellite missile test? While both Russia (well actually the USSR) and the US have blown up their satellites with missiles before it appears to be the most recent case I'm aware of involving a destruction using missiles for demonstration/testing purposes. See Anti-satellite weapon. The only other recent case is USA 193 although officially that was because of the risk the satellite may pose. There was this [18] but if the destruction was intentionally (which we don't know) it was designed to be able to self-destruct and definitely wasn't shot by a missile Nil Einne (talk) 11:35, 1 December 2008 (UTC)

2012

What are the governments saying about it?

What governments? What topics? There are millions of people working for governments around the world and they may be saying billions (if not trillions) of things about 2012. You must limit your question to something that can be answered within the confines of a reference desk. -- kainaw™ 01:22, 30 November 2008 (UTC)

I assume you're talking about 2012 (film). Those hollywood people love disaster movies, no matter how far-fetched. -- JSBillings 01:37, 30 November 2008 (UTC)

i meant, what is the US gov. saying about 2012 if anything at all...ok i know wikipedia is known for saying 2012 is just hype and paranoia...but guys,... it's scary how all those calendars from dif. cultures coicide on the date and also that strange galactic occurrence... if there is such a hype, why doesn't NASA educate the public? i mean...they don't say anything....thats kinda weird, right? —Preceding unsigned comment added by 75.68.165.235 (talk) 02:25, 30 November 2008 (UTC)

What galactic occurrence? Dragons flight (talk) 02:45, 30 November 2008 (UTC)ou her

Didn't you hear this? We will be passing through the exact, perfectly defined and perfectly known geometric plane of the milky way on April 1st 2012, exactly at 11:11 (a.m.). --Stephan Schulz (talk) 09:14, 30 November 2008 (UTC)

What time zone? --128.97.245.27 (talk) 04:41, 1 December 2008 (UTC)

On April 1st, 11:11 occurs simultaneously in all time zones. --Stephan Schulz (talk) 10:04, 1 December 2008 (UTC)

There is none, but there certainly are a fair number of conspiracy theories that predict the date 2012 as the end of the world, or Armageddon, or whatever. Their proponents allege various cultures/mavens/seers all agree; you can choose from the Mayans, Edgar Cayce, Native American myth, Our Lady of Fatima, Nostradamus, Medjugorie, etc., etc., etc. Suffice it to say that, to the extent that governments are rational, they have nothing to say about it, and that the question belongs on the pseudoscience desk, not the science desk. I believe the NASA component of the conspiracy alleges they've discovered "Planet X" that is due to collide with Earth in 2012... -Nunh-huh 02:52, 30 November 2008 (UTC)

See ZetaTalk on that one. Algebraist 02:55, 30 November 2008 (UTC)

It's important to note that there are LITERALLY a million or so distinct belief systems and religions out there; and a significant number of these have specific dates for the end of the world. Every decade or so a new one comes up. This is just the next one on the docket. It will pass, like the hundreds of predictions before this, without event, and we will promptly forget it and move on to the next one. If anyone wants to read more about the end of the world, Eschatology is as good of a Wikipedia article as any on this. --Jayron32.talk.contribs 03:37, 30 November 2008 (UTC)

ZetaTalk lady is, without a doubt, not of sound mind. And I'm not intending that as an insult, it is completely serious. It's actually somewhat sad to hear her on the radio, as well as frightening (not for fear of doomsday, of course). -- Consumed Crustacean (talk) 09:53, 30 November 2008 (UTC)

People have been predicting that the world would end in their lifetimes for thousands of years. You might enjoy this list of failed end-of-the-world predictions. (Well, the ones in the past have failed; the ones in the future will fail in a few years.) -- BenRG (talk) 13:36, 30 November 2008 (UTC)

And on April 1st no less :) -hydnjo talk 14:47, 30 November 2008 (UTC)

Wouldn't you be MORE worried if your government, which is supposed to be focused on the 10 million ACTUAL problems in the world today, like the totally failing economy, terrorism overseas, multiple wars, genocide, ecological disasters, YOU NAME IT, was instead wasting its time, and YOUR MONEY, looking into whether the coincidence of multiple religions allegedly having similar dates that their calendars loop over was somehow a national security threat? How would they even evaluate that? What would you be expecting them to do? Stock up on shamans? Now take a look at the people who are saying it will be the end of the world. Are they reputable? Are they recognized experts anywhere except for rather crackpot places? Do you really want an acidhead like Daniel Pinchbeck taking government money and directing government policy? (Here's a nice article on him and his ilk if you have the time.]) The government has got limited time and limited money. They use things like "actual science" as a way of determining which of the million potential issues they should be spending it on. Science itself purposefully limits the sorts of things it can worry about to those which have a hope of being reliably determined, because it too has limited attention and limited resources. The 2012 thing, even if you imagine it to be some sort of real thing, is not a great thing for the government to be wasting its limited resources on, especially at a trying time like this. The people who are promoting the idea that there is some sort of disaster are people who all directly profit from people being scared of it. Be wary. --98.217.8.46 (talk) 16:32, 30 November 2008 (UTC)

but guys, isn't our solar system supposed (scientifically) to be in a special place and alignment that day? (21, dec.?) i mean...it's not just religions...what do reputable scientistssay about the alignment , pole shift , photon belt and stuff?I read that it's supressed scientific knowledge...

Look, let's make a bet. If you lose, come to my birthday party on Dec. 21, 2012 and bring me a gift. If you win, you would obviously not need to come.

Please point out specific claims made by specific authors and the Reference Desk will examine them. For an article on 2012, see http://www.universetoday.com/2008/05/19/no-doomsday-in-2012/. I suppose you already know that nearly every time the Reference Desk received a question like yours, I linked to all previous questions relating to 2012.

Reputable scientists are not likely to waste their time on crackpot theories, so I don't think you'll succeed in finding out their opinions. If you trust the people here, though, many (not including me) have considerable scientific knowledge and are qualified to comment on information you find, as long as you are specific. --Bowlhover (talk) 19:24, 30 November 2008 (UTC)

thank u guys...u r noble...I used to be a wikipedian...lol, this sounds like a tragic story...I even had a user page and stuff...i should use it again. so...is there NOT going to be a SPECIAL astronomicalevent going on on that date? I mean...doesn't mainstream science basically admit that that is a special date astronomicaly?

It's quite possible that something fairly interesting astronomical will happen around then, but not as interesting as the doomsayers are trying to make out. If this is the date I'm thinking of, the "planets will all align and cause massive gravitational effects like tides the size of mountains" is more like "roughly half of the planets will be kind of within a 90° wedge shape while the rest will be fairly randomly scattered, with a gravitational effect less than that of a full jumbo jet flying overhead". Confusing Manifestation(Say hi!) 22:33, 30 November 2008 (UTC)

thank u guys, I luv u and wikipedia! :) --Cosmic girl (talk) 00:22, 1 December 2008 (UTC)

Not quite a government, but some within the Republican Party are already considering Sarah Palin as a Presidential candidate for that year's election, so make of that what you will from an apocalyptic standpoint. 69.224.113.5 (talk) 00:46, 1 December 2008 (UTC)

And who knows, maybe Canada will have Stef Carse as PM by then. And the name of the President of France will be something easier to spell. Then they can go to war over who controls Montreal Nil Einne (talk) 11:10, 1 December 2008 (UTC)

Piperidine,

wat are the effects of absorbing(smoking,eating,ingecting) Piperidine into the blood? —Preceding unsigned comment added by 76.14.124.175 (talk) 02:29, 30 November 2008 (UTC)

Our article on Piperidine does not directly answer this question, but it is VERY well referenced. If you find and read those references, you could find more information. Alternately, here is an MSDS for Piperidine. Cheers! --Jayron32.talk.contribs 03:33, 30 November 2008 (UTC)

Why not freeze food twice?

Why aren't you supposed to freeze food twice? Here people argue that bacteria in thawed food procreate faster... which begs the question why that should be so. Shouldn't the cold temperature just after taking the food out of the freezer (and the first minutes after putting it back in) be even colder than regular storage temperature and, if anything, slow bacteria down? --Ibn Battuta (talk) 03:19, 30 November 2008 (UTC)

When you freeze food, you break cell walls/cell membranes in the cellular structure of the food. This causes 2 problems:

1. Freezing multiple times increases cellular damage, which produces mushier, less palatable food
2. Cellular membranes are actually pretty good barriers against bacteria. When these are broken, and their contents dumped out, it provides a more nutritious medium for bacterial growth. Thus, thawed food has a greater potential for bacterial growth than never frozen food.

Those are probably the best two reasons NOT to freeze multiple times. Fresh food is of course the best to eat; the closer to "alive" it is, the tastier AND safer it is... --Jayron32.talk.contribs 03:31, 30 November 2008 (UTC)

"the closer to 'alive' it is, the tastier AND safer it is..." - So I'm sure you eat all your meats raw and never touch baked goods like pastries and cakes? I find your generic platitude rather unhelpful and oversimplified. Dragons flight (talk) 03:50, 30 November 2008 (UTC)

If you take it to mean the time between the death of the animal or plant and the time to cook, all other things being equal, older food will tend to accumulate more bacteria. Of course, some foods (like Blue Cheese... yummmmmmmm) benefit from a healthy dose of microbes. But given a simple question of whether a slab of meat or an apple or some other unprocessed whole food is safest to eat, it is always safer to eat said food closest to when it is killed (for the animal) or picked (for the fruit). Over time, microbes will tend to accumulate on the food and, if uncontrolled, will tend to degrade the quality and safety of the food. --Jayron32.talk.contribs 20:03, 30 November 2008 (UTC)

Many people prefer aged beef, which is purposely allowed to go though some degradation. ike9898 (talk) 02:33, 1 December 2008 (UTC)

Other things aren't equal though. Cooking and processing food will kill and remove bacteria, which can dramatically improve food safety and longevity. For many foods, the result is safer than even if you ate the food as fresh as is possible. For safety, recently killed is usually far less important than how the food has been handled/preserved/cooked since it was killed. Dragons flight (talk) 20:59, 30 November 2008 (UTC)

You are 100% correct. --Jayron32.talk.contribs 02:18, 1 December 2008 (UTC)

There was a Straight Dope with a quite detailed explanation about this a couple of years ago, here's the link. Maelin (Talk | Contribs) 04:37, 30 November 2008 (UTC)

grant for study and visit st buddhist temples are over the world

i am interested to know and visit st buddhist temple,any agencies is ready to give grant to vist st buddhist temples?SAJITH 07:33, 30 November 2008 (UTC)

Why would someone give grants for that? --Mr.K. (talk) 18:02, 30 November 2008 (UTC)

What are st buddhist temples - it looks to me like you are calling Buddha a Saint. Although, I'm guessing English isn't your first language and you meant to type "visit at" when all you need is "visit."

As for grants, nobody's going to give you money just to visit. Are you in college? Perhaps you can devise some reason to study such temples, like for a Masters degree. (Or, even as an undergraduate project in some places. See College of Wooster and their Independent Study program, which gives such grants.) It has to be something that is seemed worthy to study. For instance, the architecture of them. Or, for sociology, peoples' habits upon entering. Things like that.

However, be forewarned, visiting "all over the world" will be seen as too broad by most, unless you really want to make it like a PhD. thing. Say, for instance, your professor in SOciology learns you want to study how people approach Buddha in different cultures. He or she will suggest something along the lines of people raised in the Orient versus Westerners who convert. And, he or she will expect you to have some hypothesis that you are trying to prove.

So, can you get grants to visit temples? Sure, but you're going to have to put a lot of work into it.Somebody or his brother (talk) 02:54, 1 December 2008 (UTC)

Publicly accessible free scientific lectures?

I saw on iTunes U, that I can download some to my ipod and found a couple of them INCREDIBLY interesting! Is there some free website where I can view/hear lectures by respectable scientists talking about new potential discoveries? Most of the ones on youtube are by fakes. I am interested in physics and biology, and am wondering if there are real lectures anymore? or if there is no real audience for that any more and there won't be any faraday lectures like the 1700s.

The only lectures so far which are plentiful and meet this criteria is global warming lectures, but I don't get enjoyment about hearing my 10th lecture on it. I like physics and biology personally, and no disrespect to climate scientists. 65.41.148.101 (talk) 07:53, 30 November 2008 (UTC)

Addendum I already know about OCW, and I love it! I am looking for an OCW style (in terms of quality and accuracy and no side-goal of trying to push a POV, but the only goal to educate), geared towards bright inquisitive minds who are temporarily under a 48 hour WoW ban, or similar. 65.41.148.101 (talk) 07:55, 30 November 2008 (UTC)

Here you can find some excellent neurobiology lectures. [19] Lova Falk (talk) 12:30, 30 November 2008 (UTC)

Ok, these aren't new but you might find these lectures by Richard Feynmann interesting: http://vega.org.uk/video/subseries/8 Jdrewitt (talk) 13:08, 30 November 2008 (UTC)

MIT offers many free online lectures from their courses in a wide variety of departments. Take a look: http://ocw.mit.edu/OcwWeb/web/courses/av/ – ClockworkSoul 07:51, 1 December 2008 (UTC)

Also CalTech and JPL have some very good streaming lectures but they don't look podable. Saintrain (talk) 00:05, 2 December 2008 (UTC)

I don't see why not. Just save the stream (both VLC and mplayer should be able to handle that although VLC at least won't be able to play the file, and also many more general purpose downloaders that support RTSP) and then convert it (you'd need something capableof support the RV40 codec obviously) to a format the iPod will accept (like MPEG-4 AAC). If the country you live doesn't allow format shifting this may be a violation of JPLs copyrights if they don't allow the practice but that's a different matter. Indeed for audio at least as far as I'm aware if your talking about portable level audio quality there's really no current way you can be stopped from format shifting becausde you can get decent enough quality by using the analog hole. With nearly all computers, this would simply be plugging the analog speaker out into the line in so the loss of quality is not likely to be noticable on a portable device except perhaps to someone with excellent hearing and ear phones. And indeed the vast majority of digital audio formats even those infested with DRM can usually be loselessly converted to an uncompressed wave with the right tools even I think on something like Vista Nil Einne (talk) 10:30, 2 December 2008 (UTC)

Water pressure

Why does water pressure increase with depth. I have the general idea: there's water above pressing down, an analogy with pressing on jello shows why there would be an increase in lateral pressure with depth. But where's the origin of the water pressure that's pushing up on an object in water?

See bouyancy. If that article doesn't float your boat, come back and ask a follow-up Q. StuRat (talk) 17:59, 30 November 2008 (UTC)

Well, I've read through the article, and I haven't seen anything that really answers my question. I know that bouyancy is caused by this pressure difference, and I know that this is in turn caused by the difference in the weight of water above a point, but I don't get why water pushing down on an object will cause an upward force.

At a lower depth, there is more water on top, pushing down. This causes pressure from the top, which in turn squishes the water molecules together, causing the water to be denser. Since the water is denser, it has more bouyancy ability, and thus it is able to float denser objects, as well as cause the water pressure to push on them from all sides, thus squishing them and causing it not to float. ~AH1^(TCU) 23:43, 30 November 2008 (UTC)

No. Water density doesn't change significantly with depth. You're thinking of a gas.

Try this: (as a thought experiment: don't actually do it.) line down on a partially-filled waterbed in its frame, place an empty waterbed mattress on top of yourself, well spread out. Now fill the top mattress with water to a depth of 10cm. do you think you will feel pressure? Why? how much? Why is this different than when the two mattresses contain air? Is the pressure different that what you would feel if you wer wrapped in a dry suit and held 10cm beneath the water surface? -Arch dude (talk) 01:14, 1 December 2008 (UTC)

As for why water pressure can push upwards, water resists the compression force exerted by the water above it, just as the ground exerts a normal force that prevents gravity from pulling objects through. The downwards force of gravity equals the upwards force because the water isn't moving; it is in mechanical equilibrium. --Bowlhover (talk) 04:50, 1 December 2008 (UTC)

I think I get it...now for a related question. If I were to construct a hut at the bottom of the ocean, would the water pressure in this hut be the same as the surrounding? Intuition says yes, but wouldn't there not be the weight of the water above pushing on it?

If the water can flow through it, then the pressure would be about the same throughout it. However, it would be slightly higher at the bottom of the hut than the top. StuRat (talk) 09:13, 1 December 2008 (UTC)

I'm saything that water can't flow through it.

OK, if you have a tank at the bottom of the ocean, which has been sealed since it was moved there from the surface, one of three things will happen:

1) The much greater pressure outside will cause the tank to collapse until the pressure is equalized.

2) The tank will collapse somewhat, and subsequently the pressure will increase a bit.

3) The tank is strong enough to resist any significant collapse. This would be easiest with thick metal and a spherical shape that distributes the forces evenly. In this case the pressure inside would be approximately the same as on the surface.

If you had constructed the tank at the bottom of the ocean, then the pressure inside would be the same as the outside, unless you pumped out some of the water inside to reduce the pressure. StuRat (talk) 13:59, 1 December 2008 (UTC)

If you constructed the tank at the bottom of the ocean, why would the pressure inside be the same as the pressure outside? Afterall, the weight of the water above no longer has an effect on the water inside the tank.

During the construction process the tank would be open, and the high pressure water would flow in. You would then need to remove most of it to lower the pressure to that at the surface. StuRat (talk) 00:45, 2 December 2008 (UTC)

(deindent) As StuRat said, the water is exerting significant pressure at any depth beyond a few feet. In fact, as all SCUBA divers learn, every 33 feet you end adding 1 more atmosphere's worth of pressure - 14.7psi. Lets say our hypothetical structure is at 66 feet under water. At this point the water is pressing in with 44 psi (2 atmospheres worth of water + 1 at sea level). If the internal pressure is equivalent to sea level then the net pressure is 29.4psi. You could deal with that pressure one of two ways - 1, increase your internal pressure until the net difference is 0 or 2, build your structure to handle that force. 29 pounds might not sound too bad, but that ends up being over two tons per square foot. It really is a huge amount of pressure. It can be done, (subs, for instance) but it has it's disadvantages. So why not increase the internal pressure? Well, that can be done but you end up introducing concerns with nitrogen narcosis and decompression sickness. Both can be dealt with (see underwater welding.) ---J.S (T/C/WRE) 22:01, 1 December 2008 (UTC)

See Caisson (engineering) - example of a pressurized underwater structure. -----J.S (T/C/WRE) 22:46, 1 December 2008 (UTC)

Thoughts, feelings and reality.

I'm not completely sure if this belongs in the science section, but nonetheless I'm looking for a scientific answer. I was just wondering, can thoughts influence or alter reality? For instance, let's say I'm going to do an exam and I think I will fail, will the probabilities of approving the exam change? Similarly, can feelings influence or alter reality? Note that I'm talking about reality, not the perception of reality. Thanks in advance. ― Ann _{( user | talk )} 12:09, 30 November 2008 (UTC)

Would self-fulfilling prophecy be an answer? And for an answer from me personally: yes, absolutely. Thinking you will fail an exam, can cause stress which leads to certain reactions in your body (and already on this level, thinking has changed reality, because the body now shows a number of physical reactions, such as a higher heart rate, muscular tension, faster respiration etc), which can influence how you perform on your exam. One of the results of stress mentioned in the article on stress is an inability to concentrate, and that would make it less probable that you pass the exam. Lova Falk (talk) 12:24, 30 November 2008 (UTC)

Thinking you will fail an exam can also cause learned helplessness, which in turn may lower the amount of effort you put into it. --82.21.25.219 (talk) 12:26, 30 November 2008 (UTC)

I see your point. Homever, those are reactions caused by the thoughts, not the thoughts themselves. Perhaps I phrased my question poorly, but I'm specifically asking about the thoughts. Let's suppose that I think I will fail such exam, but I don't feel stressed, my heart rate is fine, my respiration is normal, etc. Could reality be influenced or altered simply by mere thoughts? ― Ann _{( user | talk )} 13:59, 30 November 2008 (UTC)

In the sense that you're asking, no, science has no evidence to support telekinesis or other mind-alters-world phenomena. Absence of evidence is not evidence of absence and all that, but there have been plenty of opportunities to validate such claims and they've all struck out. — Lomn 14:21, 30 November 2008 (UTC)

Surely absence of evidence is evidence of absence. Maelin (Talk | Contribs) 14:30, 30 November 2008 (UTC)

No, it's not. We have an absence of evidence that there is extraterrestrial life elsewhere in the universe, but that's more a statement about the difficulties of collecting such evidence than it is that there isn't any out there. --98.217.8.46 (talk) 17:46, 30 November 2008 (UTC)

If you have an absense of evidence, then you have evidence of absense existing ;) —Cyclonenim (talk · contribs · email) 19:43, 30 November 2008 (UTC)

If you're referring to thoughts effecting anything other than the person with those thoughts, and not indirectly through said person, it's technically possible thanks to the butterfly effect, but what actually happens has no relation to what you were thinking. It will tend to be something equally unsurprising as what would have happened. By the way, conspicuous absence of evidence (i.e. absence of evidence when evidence would be expected) is evidence of absence. — DanielLC 16:43, 30 November 2008 (UTC)

This seems like an interesting answer. Now you have my curiosity sparked. Could you please explain this a little further, particularly regarding how it would work? ― Ann _{( user | talk )} 17:09, 30 November 2008 (UTC)

Also, if a tree falls in a forest... ~AH1^(TCU) 23:39, 30 November 2008 (UTC)

To me it seems confusing to separate thoughts and reality. Thoughts are real and have influences, causing an "alternate" reality compared to not having those particular thoughts. Exactly what effect they have is another question, and depends on many factors. But as to whether thoughts have an effect on reality--of course they do, they are part of reality. The question strikes me as a bit odd--doesn't reality include your thoughts, feelings, perceptions, and so on? Don't these influence your actions? Don't your actions influence the world around you? In short I don't understand the difference between the question "can thoughts influence or alter reality?" and the statement that some things, like stress, are reactions "caused by the thoughts, not the thoughts themselves." It sounds like you are asking whether thoughts can alter reality without causing any reaction to happen. How can there be an effect without a cause? Pfly (talk) 07:36, 1 December 2008 (UTC)

Instituto Conmemorativo Gorgas

How could I link Instituto Conmemorativo Gorgas to other pages like the one on William Crawford Gorgas and pages related to infectious diseases of the tropics, publica health and history of medicine?

Jorge Motta, MD, MPH

Like this: William C. Gorgas. --Cookatoo.ergo.ZooM (talk) 18:46, 30 November 2008 (UTC)

You need to go into "edit" to see what was done there, which is this: [[William C. Gorgas]], double square brackets surrounding the article name. SpinningSpark 18:56, 30 November 2008 (UTC)

Is it correct to say this (see below)?

Let's say that I want to know how to determine the gravitational force on the Earth due to another massive body. Isn't it then correct to say, "To weigh the earth, the gravitational force experienced by the Earth due to another massive body is measured"? 203.217.34.128 (talk) 16:28, 30 November 2008 (UTC)

To strictly describe the force attracting the Earth to the other body, yes. However, you would also want to determine the force attracting the other body to Earth, in order to determine the acceleration of the two bodies toward each each. StuRat (talk) 17:55, 30 November 2008 (UTC)

1. Newton's third law says the force attracting the other body to Earth is equal in magnitude and opposite in direction to the force attracting the Earth to the other body.
2. If you use the term "weight" to describe the attraction between the Earth and, for example, the Sun or the Moon, then I would say there is scope for much confusion here, as the Earth simultaneously has many different "weights". "Gravitational force" or "gravitational attraction" would be better terminology. Gandalf61 (talk) 19:58, 30 November 2008 (UTC)

Leaking batteries

What is the white crystalline stuff that leaking AA batteries sometimes leave behind and what is the best way to remove it from the appliance, e.g. is it okay to use a mild solvent?--Shantavira|^{feed me} 16:53, 30 November 2008 (UTC)

If it is regular alkaline batteries you are using, the electrolyte is potassium hydroxide and the white crystals are compounds that this alkaline chemical is forming with the metals (often copper) that it is attacking. I would recommend chipping off the larger pieces with a small screwdiriver or other tool and then polishing the battery contacts with a fine abrasive, I use a fibreglass pencil. You can use an electronics solvent such as Electrolube's ECSP to clean up any electrolyte on the circuit boards. If it is a bad attack there is a good chance that the corroded battery contacts disintegrate or break off while you are cleaning them and you will have to replace them. It is likely in any case that the protective plating on the contacts has been corroded away and they are more likely to oxidize and give you problems in the future (you will have to clean them now and then). A lot of Q&A sites, such as this one from Hewlett Packard recommend a 50:50 solution of water/white vinegar. This makes sense chemically as the acetic acid in the vinegar will tend to counter the alkaline electrolyte but I would not recommend it. Anything acidic being splashed around inside electronics is likely ot result in further damage if you do not take extreme care. SpinningSpark 18:38, 30 November 2008 (UTC)

Interesting. Thank you.--Shantavira|^{feed me} 08:57, 1 December 2008 (UTC)

Medical opinion (but not advice)

After seeing the picture below on the local news (in Spanish) about the burns of an Afghan girl, I was wondering: are this injuries recent or is the picture after a ´healing´? Is there any chance that this girl will have a somehow normal skin? (link: here, disturbing image!)--Mr.K. (talk) 18:23, 30 November 2008 (UTC)

I'd say those pics are after healing. It may be possible to restore an approximately normal appearance with a series of skin transplants, but this is well beyond the scope of what the average Afghan family can afford. StuRat (talk) 19:42, 30 November 2008 (UTC)

I'd say they're in the late stages of healing, judging by the fact there are still some scabs there. However, some of what appears to be scabbing may actually be an infection, hard to tell from the image. Anyway, StuRat has it about right. Skin grafts could reduce the image and help restore a normal look but it'd be difficult to make it anywhere near perfect, and Afghans cannot usually afford such operations. —Cyclonenim (talk · contribs · email) 20:19, 30 November 2008 (UTC)

Telling sunrise from sunset

Let's say I have a color photo where the sun is on or near the horizon, and I don't know anything about the time it was taken or the surrounding terrain which would allow me to tell if this is a sunrise or a sunset. Is there a way to discern which it is from the lighting or color of the sky alone? 69.224.113.5 (talk) 18:24, 30 November 2008 (UTC)

If all the people in the picture are still drinking then it is sunset. If they are laying unconcious on the beach or look like they have a hangover, then it is sunrise. For a serious answer, there is a daily change in the F layer but the change is only visible at radio wavelengths, as far as I know there is no effect on the visible spectrum. There might possibly be meteorological clues, but I leave that to a met expert to answer. SpinningSpark 18:53, 30 November 2008 (UTC)

According to sunset:

"The sunset is often more brightly colored than the sunrise,[citation needed] with the shades of red and orange being more vibrant. The atmosphere responds in a number of ways to exposure to the sun. In particular, there tends to be more dust in the lower atmosphere at the end of the day than at the beginning. During the day, the sun heats the surface of the Earth, lowering the relative humidity and increasing wind speed and turbulence, which serves to lift dust into the air. However, differences between sunrise and sunset may in some cases depend more on the particular geographical features of the location from which they are viewed. For example, on a west-facing coastline, sunset occurs over water while sunrise occurs over land."

Also see the previous discussions at [20] and [21]. Ignore the last answer in the first link; even the rising or setting Sun can completely overwhelm light pollution.

On a completely irrelevant answer, ignoring the color of the sky, if you used a digital camera to EXIF data can probably give you a 'time taken'. —Cyclonenim (talk · contribs · email) 20:16, 30 November 2008 (UTC)

One more difference: mirages of the Sun occur more frequently during sunrise than during sunset because they can only exist when the layer of air above the surface is hotter than the overlaying air. --Bowlhover (talk) 20:02, 30 November 2008 (UTC)

A similar question was once asked on Talk:Sunrise, but I'm not sure the responses there are much help. -- Coneslayer (talk) 17:10, 1 December 2008 (UTC)

If you can upload the picture somewhere we can take a look. Might be other clues in the picture. -----J.S (T/C/WRE) 21:02, 1 December 2008 (UTC)

There are a numer of ways that you may be able to discern north and hence use the fact that sun rises in the east and sets in the west. Firstly stars, if you can see an identifiable constellation. Prevailing winds have characteristic directions, which may provide other clues. Similarly, you can often discern the north side of hills (in the northern hemisphere) because they have more snow and/or less vegetation. Buildings are sometimes oriented south or north (to gather/avoid sun) depending on the location. If you know the date, you may also be able to use the presence of Venus or the moon in the sky near the sun and calculate its expected position, though I'm not sure about the mathematics. There are also other clues for time, e.g. plants which flower at particular times of day, signs of human activity, maybe animal behaviour. Individually, these may be comparatively rare things to see in photos, but I'm sure people can thing of other factors. --Maltelauridsbrigge (talk) 16:16, 2 December 2008 (UTC)

Where does today end and tonight begin ?

Weatherforecastwise, that is. 6 PM ? StuRat (talk) 20:43, 30 November 2008 (UTC)

I don't think there is a rule for this. 6pm is plasuible. Dusk is another good choice. I think it is just casual expression. -- SGBailey (talk) 22:35, 30 November 2008 (UTC)

Sunset would be a good guideline. Add 30 min fudge factor either way and you should be a-ok. -----J.S (T/C/WRE) 02:00, 1 December 2008 (UTC)

This is an unsupported personal understanding, but I always assumed that morning was 6:00 AM - 12:00 Noon; afternoon was 12:00 Noon - 6:00 PM, evening was 6:00 PM - 12:00 midnight, and overnight was 12:00 midnight - 6:00 AM. Day(morning + afternoon) is thus 6:00 AM - 6:00 PM and night(evening + overnight) is 6:00 PM - 6:00 AM. --Jayron32.talk.contribs 02:17, 1 December 2008 (UTC)

I have found myself saying "good evening" when at the start of an evening activity, even if it starts in what would be afternoon normally. (Say, a church service starting at 5 PM, saying it a few minutes before.) However, I think that's because it is unusual, to me at least, to say "good afternoon."

However, if you are looking at a technical definition, I would say dusk is the most likely, because unlike the definite AM and PM, evening is more of a state of mind. And, in the witner, at least to me, if it's 6:30 PM it can feel like 10:00 at night. Like Yogi Berra said once, "It gets late early out there." Just like, psychologicall, if a person has been up all night studying, there doesn't feel like there's been a break between night and the next day; they might say "good evening" to the guy delivering pizza at 1 AM even though, technically, it's "good morning."Somebody or his brother (talk) 02:45, 1 December 2008 (UTC)

I don't think I would usually describe 6pm as night unless it's rather dark. Perhaps it's because I grew up in Peninsular Malaysia which is in the UTC+7 timezone but uses UTC+8 so it isn't even close to being dark at 6pm and here in Auckland it seems to be getting dark way to early during winter. Agree dusk or around sunset time is a more likely definition although I guess that's somewhat problematic near to the poles where I think people would still consider there to be a night time and a day time even if it doesn't get dark or is forever dark Nil Einne (talk) 10:51, 1 December 2008 (UTC)

In calculations for working out the Jewish calendar, the day begins at 6.00 p.m. Simonschaim (talk) 09:26, 1 December 2008 (UTC)

In the UK all the newspapers used to publish daily "lighting up times", this used to be shown in calendars too. No one seems to bother any more but the Royal Observatory website still shows the details, basically half hour after sunset. SpinningSpark 11:44, 1 December 2008 (UTC)

There is also the definition of three different versions of twilight at the bottom of that page. SpinningSpark 11:47, 1 December 2008 (UTC)

I work at a television station in the US. When promoting our own programs, we use "today" for programs starting up to and including 5:30pm and "tonight" for those starting at 6:00pm or later. Thomprod (talk) 17:55, 2 December 2008 (UTC)

Distortions of sunrays and starlight by atmosphere: what can we conclude?

If Earth did not have an atmosphere surrounding it, the photons from the sun ("sunrays") and the stars could hit the ground unobstructed, traveling in a straight line from celestial light sources to Earth. However, the atmosphere is a mix of gases (oxygen, nitrogen, etc.). If I picture the atmosphere's molecules as tiny billard balls floating about in space and the photons as bullets mostly whizzing past the billard balls but sometimes getting absorbed by or ricocheting off them... what can I conclude about the density of the atmosphere. Most photons must be getting through unobstructed otherwise a glance at the sky would seem like seeing underwater with your eyes open or seeing nothing at all.

Does the degree of visual acuity, or lack of it, permit an extrapolation of the number of molecules in a given volume of air? Would that be easier to do in the daytime or at night, gauging the blurriness of stars? What data does one need to do the extrapolation -- for an example, is there such a thing as a cross-section of an O₂ molecule? Is it possible to conclude that out of 3x10⁶ photons, 2x10⁶ (grabbing a number out of thin air -- sorry for pun) will get through to my retina unimpeded?--Goodmorningworld (talk) 23:20, 30 November 2008 (UTC)

There are really two factors at play: Rayleigh scattering and astronomical seeing. The first covers most of what you are discussing and addresses in general the ability of molecules to scatter light. For example you could measure the ability of the atmosphere to scatter light by comparing the intensity of direct sunlight to the intensity of blue sky. That, plus some other assumptions could get you a density estimate. However that bulk scattering is not the principle source of the blur or twinkling in stars which arises mainly due to atmospheric turbulence. Dragons flight (talk) 00:22, 1 December 2008 (UTC)

Indeed there is an entire field, called aeronomy, which is the study of the atmosphere (and sometimes, the ionosphere, by proxy). The typical methods involve passive observation or active stimulation of the various layers of atmosphere (see ionosonde, LIDAR), seeking specific physical or chemical indications for various processes at a given layer of atmosphere. Not only can the density be calculated, but species can be determined (i.e. "How much Oxygen? How much O+ ion? How much Ozone?"). The standard techniques rely heavily on absorption spectrometry but the field is fairly mature and a lot of specific techniques have been explored. Nimur (talk) 21:34, 1 December 2008 (UTC)

Thank you, both of the respondents above, for the useful links. Is it possible for you to give me a ballpark figure as to what percentage of photons coming from the Sun travel in a straight line until they hit the ground (or my retina), conversely, what percentage get absorbed or refracted by the atmosphere?--Goodmorningworld (talk) 12:34, 2 December 2008 (UTC)

Cough-induced abdomenal reflex

During medical examinations, in addition to testing for the knee jerk reflex, sometimes they test for this thing where they ask you to cough, and listen with the stethoscope for some kind of reflex in your abdomen at the places where I imagine your ovaries would be (except I'm male, so I don't have any ovaries). What's this phenomenon called? Is there an article on it? Cough reflex doesn't talk about it; and none of the other ones on the list of reflexes seem to be relevant. Also, what is the place they are listening to called? --71.106.183.17 (talk) 22:46, 30 November 2008 (UTC)

I don't know of an exact match for what you describe. In examining a man for evidence of inguinal hernia, one can insert a digit into the inguinal canal and ask the patient to cough (or bear down - the goal is to increase intra-abdominal pressure). If one feels pressure at the fingertip, then a defect in the abdominal fascia may be suspected. If scrotal contents are enlarged and inguinal hernia is suspected, one may listen over the scrotum for bowel sounds (which should normally be absent).

Alternatively (no coughing involved in these) when renovascular hypertension, aka renal hypertension is suspected one may listen over the renal arteries for a vascular sound or bruit that would suggest renal artery stenosis (can you believe what a wiki-mess this is?). Similarly, one can listen for bruit over the inguinal ligaments when vascular disease of the iliac or femoral artery is suspected. --Scray (talk) 23:03, 30 November 2008 (UTC)

The inguinal canal seems to be totally internal to the body. How can you "insert a digit into the inguinal canal'? Or is "pressing on the skin near the inguinal canal" what is meant?

What diameter approximately is the inguinal canal?

Are new internal body parts still being discovered? When I went to school, there were heart, lungs, liver, kidneys, stomach, gall bladder, appendix, and tonsils. Some people had "intestines", but that was a lower class thing. And that was it. Now practically every time I read this Reference Desk, some other internal body part crops up. It's getting out of hand.

CBHA (talk) 06:46, 1 December 2008 (UTC)

(regarding the inguinal canal) In men, the scrotum provides loose skin and a path for a finger to reach the inguinal canal. The diameter is between 1 and 2 cm.

(regarding body parts) Just about everyone has intestines - even upper-class people. --Scray (talk) 12:21, 1 December 2008 (UTC)

Inserting a finger into the inguinal canal would be rather painful (for the recipient, and a rather tight squeeze for the probing finger). Axl ¤ [Talk] 10:46, 2 December 2008 (UTC)

It is not usually painful when done by a doctor, but can be uncomfortable. --Scray (talk) 12:21, 2 December 2008 (UTC)

radiant barrier

I read the wiki artical about radiant (attic) barriers and followed one of the suggested links (http://www.fsec.ucf.edu/en/publications/html/FSEC-EN-15/index.htm) but I was unable to find the answer I was looking for. Specifically, can one make their own rediant barrier for their attick by adhering aluminum foil (from the supermarket) to a backing (e.g. carbboard or kraft paper) and then securing this aluminum-side down to the roof trusses? If so, how efficient would this be? Is there something more efficient than aluminum foil?

Thanks

That article reads like an advertisement. You might like to look at Thermal insulation and go from there. Foil doesn't only reflect, it heats up, so layers and thicknesses come into it. If you want to improvise, there's Space blanket a kind of foiled sheet material available for people trekking in the wide outdoors and emergency insulation. Julia Rossi (talk) 01:12, 1 December 2008 (UTC)

On second thoughts, space blankets are aluminium on plastic and I'm not sure if they are durable or temporary. Your foil on cardboard sounds better than that. Julia Rossi (talk) 03:15, 1 December 2008 (UTC)

One thing to be aware of when insulating an attic is that you must not block air flow out of the attic, since this is needed to prevent moisture buildup. This moisture leads to all sorts of problems like mold, insects, and wood rot. StuRat (talk) 05:44, 1 December 2008 (UTC)

The advice in the article seems sound. I'd go for the stuff with a thin bit of insulation in between two reflective sheets which you can probably get in your local DIY store. Dmcq (talk) 16:49, 1 December 2008 (UTC)

December 1

Taste of Food Additives

I have a bottle of "lemon juice, made from concentrate". The complete ingredient list is water, lemon juice concentrate, sodium benzoate, sodium metabisulfite, and lemon oil. (Another brand lists water, lemon juice concentrate, sulfites, and lemon oil.)

I don't like to use this stuff to make lemonade because I don't like the taste of the resulting product.

The question is, do sodium benzoate and sodium metabisulfite give any taste to foods they are added to? The articles on these compounds have no mention of taste.

To put this another way, if sodium benzoate (or sodium metabisulfite) were added to water in the concentrations likely to be used in lemon juice, would the mixture have a taste different than water?

As a side issue, the article on sodium metabisulfite says that "when mixed with water, it releases sulfur dioxide (SO2), a pungent, unpleasant smelling gas that can also cause breathing difficulties in some people." Is a residue of this nasty stuff likely to remain in the reconstituted lemon juice?

CBHA (talk) 03:39, 1 December 2008 (UTC)

There are another three possibilities I can think of:

1) It's the lemon oil. This comes from the skin, which is also called lemon zest. It has a rather bitter taste (not sour, as in lemon juice). So, why do they include it ? Because it's cheaper to toss the whole lemons into the machine than peel them first.

2) It's the concentration process:

2a) The particular method of concentration may involve heating the juice to drive off water. This heating can cause the breakdown of some molecules in the juice and change it's flavor.

2b) The concentration itself, regardless of method, may also be a problem. Some of the molecules in lemon juice may be bound to water molecules, until the water is removed, and then may react with other molecules, as a result.

3) The water added during the reconstitution process may alter the flavor, based on minerals in the water, such as chlorine. StuRat (talk) 05:37, 1 December 2008 (UTC)

No idea regarding sodium metabisulfite but the taste do change when you add sodium benzoate to your fruit juice. I son't know how to describe the change in taste but it seems to be "less natural tasting". If you will consume the fruit juice within one day then you should not use these chemicals. However, if you plan to store it on two to three weeks then you should add the preservatives even though they compromise the taste --Lenticel ^(talk) 06:52, 1 December 2008 (UTC)

Also note that a lot of people (especially asthmatics) are allergic to sodium benzoate, so be careful when using bottled lemon juice for anything.--Shantavira|^{feed me} 09:06, 1 December 2008 (UTC)

Nova and Supernova

I'm trying to figure this out: If I'm calculating the distance to a nova in a far-away galaxy, but I mistake it for a supernova, will my incorrect calculations be shorter, the same, or longer than the actual distance? My guess is that it should be longer than the actual distance because supernovae come from stars that are more massive than those of novae, and it will be more luminous. Am I right? Thanks!--el Aprel (^facta-_facienda) 04:08, 1 December 2008 (UTC)

Yes. The typical maximum absolute magnitude for a nova is -8, while supernovas have brightnesses around magnitude -18. --Bowlhover (talk) 04:36, 1 December 2008 (UTC)

Motorcycle Dynamics

In scenes on TV and film of motorcycle riding, there is often a shot where the rider somehow tips back the cycle so that the front wheel is off the ground. I saw one of these tonight on the Compendium of Scientific Information (CSI), Miami division.

The implication is that the rider does this to go faster. Is there any real speed advantage in getting the front wheel off the ground, or is it just a cool trick to enliven a chase scene?

Is there a way to steer a cycle when the front wheel is up?

It seems to me it would take a lot more force to raise the front wheel from the ground to 30 degrees up than from 30 degrees to 60, or from 60 to 90 degrees. Do people trying to ride a motorcycle on the rear wheel risk tipping over backwards?

Thanks, CBHA (talk) 07:21, 1 December 2008 (UTC)

Well, in a perfectly abstract world, as soon as the front wheel comes of the ground, all the weight is on the rear wheel, thus increasing traction. So the motorbike can accelerate faster without slipping. In a non-perfectly abstract world, this a) increases aerodynamic drag, b) makes it nearly impossible to steer and 3) is a very unstable position, so you need to be very careful with the power control to void falling on your ass. In other words, I suspect it's purely for show. I've never seen this in real races, either. --Stephan Schulz (talk) 08:11, 1 December 2008 (UTC)

I don't see it as a method of achieving rapid acceleration but rather a result of rapid acceleration. In fast motorcycles and some race cars, the torque created about the rear wheels under full accel is enough to lift the front end off the ground. StuRat (talk) 09:09, 1 December 2008 (UTC)

See Wheelie. You may also find Bicycle and motorcycle dynamics interesting—it's a good, thorough article, even if it doesn't cover wheelies. -- Coneslayer (talk) 12:47, 1 December 2008 (UTC)

Time and causality

This is basically some daydreaming of mine, but I was wondering what seasoned theoretical physicists (and amateurs such as myself) thought of it.

The gist: we experience a global sense of linear (past->present->future) time and associated causality every day. But is there any reason, other than Occam's razor, to assume time is actually linear, even in the local sense? Supposing causality worked in any direction, including future->past, wouldn't we still experience causality in a linear fashion? If the future changed the past, we wouldn't know of a different past, and hence had no way to know a later event influenced an earlier one. From a purely theoretical point of view, is there anything prohibiting bidirectional time? And if there isn't, then wouldn't it also be safe to assume tachyons and related concepts could exist?

--Link ^(t•c•m) 10:47, 1 December 2008 (UTC)

There is an argument that the perception of time must, of necessity, be in the same direction that entropy is increasing. A laymans explanation of this can be found in Stephen Hawking's book A Brief History of Time. The argument goes something like this: to form a memory, a finite amount of energy must be stored in a structured way. But any local structuring of energy (decreasing entropy) must involve the transport of energy to form the structure, and globally (in the universe as a whole) entropy must be increased by the second law of thermodynamics. It is impossible to see into the future (remember the future) without breaking the second law. Since the second law is currently considered a fundamental law of nature that is ablsolutely true in all cases then the answer is that there can only be one path for time to take (for a given observer in a given frame). SpinningSpark 12:03, 1 December 2008 (UTC)

See also, arrow of time. There are a number of equations used in the sciences which are, as far as we know, unidirectional in time (cannot be reversed). --98.217.8.46 (talk) 14:54, 1 December 2008 (UTC)

Thanks for the replies. The entropy explanation seems valid. So basically, under the assumption that the second law of thermodynamics is true, it is impossible to change the local past in any way, provided that the universe is indeed a closed system (so no external "something" decreases entropy locally), right?

Still, the Second Law seems to be at least partly incompatible with the Poincaré recurrence theorem. I find this all quite mind-boggling, which is exactly why I love reading and thinking about it!

--Link ^(t•c•m) 15:51, 1 December 2008 (UTC)

The issue does not seem to be settled yet. See Retrocausality and John G. Cramer (there may be more physicists besides Cramer working on this.)--Goodmorningworld (talk) 12:31, 2 December 2008 (UTC)

Something SpinningSpark wrote caught my eye. It was the bit about memories being causally related to the ongoing march of entropy. It occurs to me that this sounds a lot like observation (in the quantum mechanics context) in that something that was once in disorder becomes more orderly. Of course I'm asserting that something in quantum superposition is less orderly than something having gone through wavefunction collapse. Is there any link in known science? --Rixxin 15:06, 2 December 2008 (UTC)

Strain Gauges

Could anyone step me in the right direction as to where a strain gauge would be used in Clinical Neurophysiology (eg EEG, EP, NCS, EMG) or the very least in neurology? Moffo (talk) 15:52, 1 December 2008 (UTC)

Looks like one type of strain gauge is used to measure blood flow and tissue swelling; see Strain gauge#Other gauge types. --—— Gadget850 (Ed) ^talk - 16:25, 1 December 2008 (UTC)

Might it be used to measure intracranial pressure on a continuous basis, as opposed to manometry via spinal tap? The pressure sensors sometimes inserted through the skull, for instance. (This certainly does not constitute medical advice!) Edison (talk) 21:08, 1 December 2008 (UTC)

Typical strain gauges that I work with are large compared to neurobiological sizes (typically measuring pounds of force or hundreds-of-pounds of force, e.g.). However, you might be interested to see optical tweezers, which can operate on microscopic objects such as cells or individual proteins; these have many published applications to neurobiology (see Exploring mechanochemical processes in the cell with optical tweezers, for example. Nimur (talk) 21:39, 1 December 2008 (UTC)

For discussion of strain gauges' usefulness in measuring intracranial presure, see [22] and other results from a Google search for this application [23]. Edison (talk) 14:57, 2 December 2008 (UTC)

Herpes research

There are a very large number of individuals infected with herpes in this country and I suppose throught the world. What are the chances of a cure in the near future(5 years)?— Preceding unsigned comment added by 129.112.109.252 (talk • contribs)

That's impossible to predict. It requires people to make predictions of future events, and until someone invents the time machine, or the crystal ball, or something like that, it would be difficult to determine. There are drugs like Valtrex that are known to effectively control the symptoms of herpes, and which also have been shown to reduce (but not eliminate) the transmission of herpes from infected persons. See our article on Herpes simplex for more info. --Jayron32.talk.contribs 18:10, 1 December 2008 (UTC)

Although there is no way to predict if we'll have a break through in the next five years, I find it unlikely that someone will come across a cure in that time. I believe that most hope lies in vaccination, which has already proved effective in several trials. —Cyclonenim (talk · contribs · email) 18:12, 1 December 2008 (UTC)

Viruses are almost never cured. As per Cyclonemin, our best hope is a vaccination and/or treatments that reduce it's contagiousness in individuals who have it. -----J.S (T/C/WRE) 20:55, 1 December 2008 (UTC)

Agreed, and I haven't heard of anyone nearing a vaccine for herpes simplex 1 or 2. A vaccine was recently developed for the related chicken pox virus, so maybe that bodes well for a simplex vaccine. But even if one were discovered/developed tomorrow, it would take several years to clear the FDA (at least in the USA). - Draeco (talk) 01:59, 2 December 2008 (UTC)

Herpevac is a potentially upcoming vaccine for HSV-1, but not currently very effective and not trialed extensively. —Matt (talk · contribs · email) 07:46, 2 December 2008 (UTC)

Less known cell line resources

Hello, all. I'm trying to locate a particular cell line that is commonly used in my area of research (HaCaT), but all the usual non- and for-profit resources don't seem to have it. This particular cell type is used fairly commonly in the existing literature, so I would really prefer to use it if possible. Before I go begging a possibly competing lab for a vial of some of theirs or seeking alternative lines, does anybody here have any suggestions regarding means that I hadn't considered? Cheers! – ClockworkSoul 19:42, 1 December 2008 (UTC)

Timespeed is increasing overtime

It seems that 2008 is the fastest year in human history! The timespeed, or how fast the time is going, is increasing overtime because knowledge, technologies, and busy-ness of people are increasing overtime. So up-to-date, 2008 has the most advanced knowledge, technologies, and people are the busiest of any previous years. To demonstrate how timespeed is increasing overtime is that because time contains hizo, a force that causes forward motion in time. The amount of hizo in time is increasing, because increases in knowledge, technologies, and busy-ness of people produce more hizoes, which in turn increases the timespeed. Are these statements true? BlueEarth (talk) 22:51, 1 December 2008 (UTC)

That's just a concoction of made up words - you can probably define those words in such a way as to make it true if you want. --Tango (talk) 22:58, 1 December 2008 (UTC)

First, you have to prove that there is such a thing as a hizo. It is pointless to make claims about what a hizo does if you have no proof that there is a hizo. -- kainaw™ 23:36, 1 December 2008 (UTC)

"Verb: hizo (infinitive: hacer) 1. Formal second-person singular (usted) preterite indicative form of hacer." - Ummm right.

In defense of the OP, ISTM they asked if the statements were true; they did not assert that there is such a thing as "hizo". Having said that, I have no ideas about the content of what they are talking about. Maybe this question needs the special touch of Mr. Baker? CBHA (talk) 00:06, 2 December 2008 (UTC)

I believe what you are talking about is the concept first presented in the book Future Shock, that, since future knowledge is based on current knowledge, the speed at which knowledge spreads and new inventions arrive is ever increasing, and this can even cause us psychological and societal problems if these changes occur too quickly for us to cope with. I don't agree with this, however, and would argue that changes occurred faster in the 1940s than they do today. With inventions like radar, jets, and nuclear weapons, and broad political changes from worldwide depression to fascism and the cold war, the 1940's were a time of global upheaval. I would posit that it only appears that change occurs more rapidly in the present than in the past when your only experience is with the present. Note that the book was written way back in 1970, so this isn't a new concept. I'd argue that there are also processes which retard innovation, such as patents and people being reluctant to change. Take Blu-Ray DVDs, for example. The players are vastly more expensive and the recorders aren't even really available. Under these circumstances the change from standard DVDs to Blu-Ray technology for a modest increase in screen resolution is, predictably, proceeding at a snail's pace. StuRat (talk) 00:33, 2 December 2008 (UTC)

It's worth remembering the same thing happened with DVDs even though these had far more advantages over video tapes Nil Einne (talk) 09:23, 2 December 2008 (UTC)

Are we busier than we were five years ago? Ten years ago? Twenty? Thirty? It's pretty hard to say. People weren't exactly just sitting around drinking sweet tea back then. People have been talking about how they've been busier than ever since, well, ever. Certain technologies have certainly changed the rate at which certain interactions have changed—for example, we communicate with others not in our immediate proximity much more rapidly than before—but that doesn't necessarily translate at all into doing more (or less, or whatever). People have been talking about how the busy-ness of modernity since the 19th century. The people then seemed to be just about as busy. Modernity is a condition of being busy. The technologies how we are busy, what we spend our time on, but they don't increase the number of hours in a day. --98.217.8.46 (talk) 02:19, 2 December 2008 (UTC)

People aren't busier in the modern world, they are more productive, and that's not the same thing. People used to spend 100 hours per week picking potatoes or pounding pieces of metal. Now we spend 40 hours a week checking email and punching numbers into computerized spreadsheets. You tell me who is busier? Because of technology, we have both increased the productivity per person AND decreased the amount of time spent at "work". 100 years ago it took 50 people all day to build a dozen cars. Now it takes 6 people working the controls of a few robots to build twice as many cars in half the time. Seems like we are a WHOLE lot less busy now than in the past. --Jayron32.talk.contribs 04:06, 2 December 2008 (UTC)

Yes, but work is only a portion of what makes us busy. While once kids would just play outside, now we feel the need to drive them to various sports around the town. While once we would go to our garden to get veggies or maybe walk to the corner store, now we must drive to a supermarket and wait in long lines. While once a vacation meant a trip to the nearby beach or "big city", now it may involve making lots of reservations, a flight around the world, renting a car, arriving on time for tours, etc. StuRat (talk) 04:47, 2 December 2008 (UTC)

Is it true? Well it is deployable. Please be patient with my impressionistic contribution here, but why do the terms, distraction, information overload and time saturation come to mind on this subject? Focus, localisation, centricity vs global village, media distraction, pluralities. People have so many options some of which they can't opt out of (thinking of you StuRat with your interactive type car – that's fairly time-consuming). Analog(ue) (finite mechanical mechanisms) vs digital (virtual, global, infinitely variable, storable and accessible). And to top it off, people now monitor each other and their children to the nth degree. Apart from the last thing, my post-modern mind loves it, but some of it needs to be allowed to flow past because getting caught up shrinks time even more. About hizo I know nussink. But give me a moment: aha, hizo (Spanish): it did; hacer (Spanish): to do. Maybe we could call it busy-ness, giving the illusion of time passing quickly. Someone else will say, Julia Rossi (talk) 07:21, 2 December 2008 (UTC)

I don't know whether a trip to the supermarket is necessarily costing more time then tradition. It depends a lot on the person and where they live I would suspect. For example, if you go to the supermarket about once a week and spend like 45 minutes in total (including travel time) you could easily spend less time then someone may have spent in the past when they would go to the corner stores 5 times a week and spend about 10 minutes in total (including travel time i.e. walking). Also going to your garden for veggies seems to miss the point that the veges don't get there by magic. It's easily possible you will spend more then 45 minutes peer week on average (obviously some weeks you may only spend 10 minutes, other weeks several hours) growing and collecting those vegetables which may include stuff like watering, weeding, collecting seed or bulbs, fertilising etc. Plus people nowadays may use snap frozen veges which can be used from the packet meaning far less time on preparing the veges. Yes there may be advantages to doing some of the stuff (like walking) and disadvantages to using frozen veges and the like but it doesn't change the fact people likely spent more time on it before. And a lot of people still spend vacations locally. Many children still play at home. They may also participate in sports in various places. One of the reasons why children probably participate in sports more commonly then they may have in the past is because both they and their parents have more time and greater mobility. If the kids have to help out around the farm (or whatever) they don't have time for 2 hours a day playing football or cricket or basketball or one of those odd American sports nor do their parents have the time to walk with them for 5 kilometres to get a place to play sport. In other words, a lot of what you are talking about are luxuries many people could ill afford in the past because they were more busy working or you could say less productive (in the sense that walking 5 kilometres is less productive then driving there if your only goal is to get from A to B). Having said that I would agree that we probably are busier in the more distant past, not because of a most of what has been said but because we don't have to stop everything when it gets too dark anymore Nil Einne (talk) 09:18, 2 December 2008 (UTC)

Since this is all about perception, the actual amount of time isn't the most important factor, but rather how hectic your day seems. Walking to the corner store or tending the garden isn't as frustrating as fighting traffic to get to the supermarket, then fighting crowds and lines once you get there. StuRat (talk) 14:39, 2 December 2008 (UTC)

Funny, I find sitting in my car, enjoyably listening to the radio to be far less frustrating than digging holes and pulling weeds all the time... --Jayron32.talk.contribs 17:29, 2 December 2008 (UTC)

December 2

If the universe is constantly expanding....

Then what is it expanding into? For example if you were able to freeze time, then you would be able to define a clear boundary of the universe, in which case what would be beoyond this boundary? Also what would the outer "walls" of the universe look like? I doubt anyone really has any conclusive theories about this, so conjecture is welcome also. Thanks. 79.75.225.71 (talk) 11:03, 2 December 2008 (UTC)

It's true that noone has conclusive theories, but Metric expansion of space sums up what we believe today. Some theories postulate an "outside" outside the known universe, notably those with extra dimensions and/or brane and string theory. EverGreg (talk) 11:40, 2 December 2008 (UTC)

Even in those theories, the universe isn't expanding into anything - the expansion is happening in out familiar 3 dimension, the "bulk" is outside out universe in terms of the extra dimensions. --Tango (talk) 14:13, 2 December 2008 (UTC)

It isn't expanding into anything, and there is no boundary. There are two possibilities, either the universe is already infinite so when it expands its size doesn't actually increase, things inside it just get further apart (not because they've moving apart, but rather because the space between them gets stretched), or the universe is finite in which case it will be shaped something like a sphere (actually, a 3 dimensional analogue of the usual 2 dimensional sphere). Imagine if the Earth were to expand - there wouldn't be an edge of the Earth that is moving outwards, it would be the whole thing expanding (yes, it would be expanding into empty space, but that's because the surface of the Earth is a 2D surface in a 3D world, you need to think of the universe as a 3D "surface" that isn't embedded in any larger space). --Tango (talk) 14:13, 2 December 2008 (UTC)

Tango has it. Basically the current theory postulates either an infinite universe (an "open" geometry) or a universe which has finite volume (a "closed" geometry). In both cases, there is no "boundary", any more than there is for a 2D ant crawling on an infinite sheet (an open 2D geometry) or the surface of a sphere (a closed 2D geometry). As a thought experiment, imagine a 2-D ant were crawling on the surface of a balloon that was being inflated - suppose that ant asked you how it was possible that his universe seemed to be expanding, and yet there was no boundary anywhere? What is his universe expanding "into"? If you can answer that 2-D ant, then you have your own answer too (just a little harder to picture in three dimensions). --Bmk (talk) 19:14, 2 December 2008 (UTC)

And since this is the refdesk, here is the wikipedia article about this subject - worth a look. --Bmk (talk) 19:15, 2 December 2008 (UTC)

Physics

Hi there.Please suggest me a link from where i can download free solution manual for the fourth edition of 'Physics for scientists and engineers' by Paul.A.Tipler.Loads of thanks!

Can we harness the power of tectonic plate movements?

How would that be done? I think that would solve a future energy crisis.

At present, no. In the future, who can say? I doubt there's much work being considered on a project of that scale, though -- there should be more than enough other ways to supply energy that are more reasonable engineering projects. — Lomn 14:12, 2 December 2008 (UTC)

I would think you could, by placing power generation stations on either side of fault lines with rods extended between them. During a quake the rods would be pushed one way or the other, and this motion could be used to generate power. However, the need to maintain the equipment for rare periods of power generation would make this not at all cost effective. A better approach would be to bypass the plates and go to the source, the Earth's geothermal energy. By drilling holes through the crust, we could fill such "wells" with water, then use the steam generated to power turbines continuously. StuRat (talk) 14:28, 2 December 2008 (UTC)

Big Bang in the USA

I have heard that a lot of people (especially in the USA) are not too keen on the Big Bang theory:
Christmas_tree#You_should_get_a_Christmas_tree
Is this true or just anti-American stereotyping?
--AlexSuricata (talk) 14:51, 2 December 2008 (UTC)

I have no idea what that link about Christmas trees is about, but it seems like you're talking about creationism. I don't have any statistics, but I think it is true that there are more creationists in the USA that other western countries (I have no idea about the rest of the world). --Tango (talk) 15:02, 2 December 2008 (UTC)

I would guess they're commenting on this diff. Nanonic (talk) 15:08, 2 December 2008 (UTC)

Yes, that would explain that, thanks! --Tango (talk) 16:09, 2 December 2008 (UTC)

Well of course there are more, the US is the largest western country by far. :-P I think what you meant to say is that there is a higher proportion of the population. From memory, some surveys have shown the only developed country with a higher proportion of people not believing in evolution then the US is Turkey. Ah here it is Level of support for evolution. Actually while it included Japan and 32 European countries including Turkey, it didn't include Taiwan, Singapore, South Korea, Australia, NZ or Canada. (N.B. Of course it's possible to believe in the big bang but not evolution or vice versa). Nil Einne (talk) 18:29, 2 December 2008 (UTC)

Solving Britain's housing crisis

Could massive land reclamation, for example extending the south west peninsula, cost effectively solve Britain's housing crisis?Trevor Loughlin (talk) 15:40, 2 December 2008 (UTC)

The depends on what the cause of the housing crisis is. I don't think it's a lack of land, it's a lack of building projects. There are plenty of brown field sites that could be built on, but no-one is building (especially now that the housing bubble has burst). --Tango (talk) 16:11, 2 December 2008 (UTC)

As noted, Britain is not a particularly densely populated nation. There's plenty of land to build upon; the issue of the housing crisis today is that the credit markets have dried up. There's plenty of places to build houses, and plenty of people wanting to buy, but there's no availible credit to loan to people to encourage the building of new houses. No money means no building. Heck, as recently as 40 years ago, Britain was busy creating new towns out of whole cloth, i.e. Milton Keynes. --Jayron32.talk.contribs 17:22, 2 December 2008 (UTC)

I don't know if this applies to the UK but in many countries although there's a lot of land available it's not necessrily where a lof of people want to live. For example many countries have rather dense populations around the cities (compares to the rest of the country). Part of the housing crisis is often that people want to live near the cities and not out in the wops, or even near the city but too far from the city centre. You can make new cities, but it's often not that easy to make a succesful city. You can also increase density in the existing cities but how acceptable this is to the populance varies Nil Einne (talk) 18:23, 2 December 2008 (UTC)

Acids taste sour...

why do bases not have a distinct taste? Or, do they act as "antisour"? Any thoughts on this important question? Thanks. Aaadddaaammm (talk) 16:12, 2 December 2008 (UTC)

Bases often taste bitter. DMacks (talk) 16:35, 2 December 2008 (UTC)

Bases DO have a distinctive taste. Take a bite of a bar of soap. That's pretty much what bases all taste like. Also, because of saponification (i.e. the ability of bases to turn material YOU are made of into soap), it is somewhat less wise to consume bases than to consume acids. Additionally, most nitrogenous bases (like ammonia and methylamine) are themselves quite toxic; acids such as acetic acid or even hydrochloric acid aren't all that toxic in-and-of-themselves... --Jayron32.talk.contribs 17:13, 2 December 2008 (UTC)

Limit to the number of discovered elements

How come it's so hard to synthesise more elements after say Roentgenium? If the ratio of neutrons increases with the number of protons, why can't we just increase the number of neutrons present to help space the positive charge? —Matt (talk · contribs · email) 17:51, 2 December 2008 (UTC)

While I don't know if it will answer your question, you may be interested in Island of stability and perhaps Transuranium element Nil Einne (talk) 18:16, 2 December 2008 (UTC)

I'm aware of the idea of the island of stability, and that elements have been synthesised higher than Rg, but I'm confused as to why we can't just keep increasing the number of neutrons to help spread out the positive charge so that we can form elements even higher. —Matt (talk · contribs · email) 18:27, 2 December 2008 (UTC)

It's frickin' hard to collect a bunch of protons and neutrons and squash them together close enough for them to stick and form a nucleus at all, let alone mix "just the right numbers" of each. DMacks (talk) 18:45, 2 December 2008 (UTC)

(EC) Nuclear physics is not my thing but I was under the impression too many neutrons is not a good thing either. At least thats's what the graph potrays to me Image:Island-of-Stability.png. As to why, I'm not sure but I was under the impression very large nuclei are not stable, and particularly if you just keep adding neutrons I don't see whats going to hold it together. Or are you talking about the practical side? If so the article says "Manufacturing nuclei in the island of stability may be very difficult, because the nuclei available would not deliver the necessary sum of neutrons. So for the synthesis of isotope 298 of element 114 by using plutonium and calcium, one would require an isotope of plutonium and one of calcium, which have together a sum of at least 298 nucleons (more is better, because at the nuclei reaction some neutrons are emitted). This would require for example in the case of synthesis of element 114 the usage of calcium-50 and plutonium-248. However these isotopes (and heavier calcium and plutonium isotopes) are not available in weighable quantities. This is also the case for other target/projectile-combinations." P.S. What DMacks said. You do realise of course that this isn't just a matter of typing into a computer I want an atom with 100 neutrons and 80 protons right? You actually have to come up with a way to sythesise it and AFAIK most/all? methods involve fusing nuclei together to get what you want. Even if you get an atom of element 114 I don't think you can just add neutrons to it particularly as it probably decays in milliseconds Nil Einne (talk) 18:51, 2 December 2008 (UTC)