Wikipedia:Reference desk/Archives/Science/2008 December 16

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December 16

Density (follow on from the above)

So say i made something out of this Osmium stuff, how much more would it weigh than say some tin, or some plastic, or iron, or other stuff. I mean to say...if I had say a chunk the size of a golf-ball would I be able to pick it up? I know that's a bit of a simple question but i'm not sure what 22.6 g/cm³ is like in comparison to say everyday option (essentially i'm looking for a weight-based equivilent of those "this ship could fit 5 empire state buildings end-to-end in its hull" style claims). 194.221.133.226 (talk) 13:19, 16 December 2008 (UTC)

According to density#Densities of various materials, that's about twice as heavy as lead. Pretty heavy, but you could certainly pick up a golf ball of it. Algebraist 13:42, 16 December 2008 (UTC)

EC:Well, lead, as in bullets, has a density of 11.34 g/cm³, or about half that of osmium. StuRat (talk) 13:42, 16 December 2008 (UTC)

A sphere the size of a golf ball would have a volume of 40.67cm³. So, that'd work out to about 919.1g so, about two pounds. About twenty normal golf balls.

(For comparison, a lead golf ball would only weigh as much as ten normal golf balls.) APL (talk) 13:45, 16 December 2008 (UTC)

To put it in terms more illustrative to a drunkard like me: a fifth of bourbon weighs 750 grams (1.6 lbs), while a fifth of osmium would weigh 17,000 grams (37 lbs)! --Sean 14:14, 16 December 2008 (UTC)

Quite the heavy drinker, eh? What mixer would one use? DMacks (talk) 14:42, 16 December 2008 (UTC)

My official unit of weight is a 1l Tetra Brick of milk, which is close enough to 1kg or 2lb for getting an intuitive grasp. Quite by coincident, its about the same weight as the Osmium golf ball. If you prefer soft drinks, 2 golf balls is a 2l bottle of coke.... --Stephan Schulz (talk) 15:32, 16 December 2008 (UTC)

I had touble visualising a pound (I've always wallowed in the metric system) - so I went around the house weighing things. My sneaker weighs exactly a pound. SteveBaker (talk) 02:31, 17 December 2008 (UTC)

There's the answer then : A Osmium golf ball would weigh as much as both of SteveBaker's shoes. APL (talk) 04:57, 17 December 2008 (UTC)

Visualising weights and densities requires a bit of mental preparation. The metric system is a HUGE help in that regard. The way to think about metric weights is that a 10 cm x 10 cm x 10 cm cube of water is 1 liter (an alternative name for a liter is a cubic-decimeter) - and one liter of water weighs a kilogram. That's why 1 liter of milk weighs 1kg and 2 liters of coke weighs 2kg - because milk, coke and water are pretty much the same density. The density of water is 1kg/liter - but handily, a 'cc' (cubic centimeter) is 1/1000th of a liter and a gram is 1/1000th of a kilogram. So 1g/cc and 1kg/liter are the same density. You can go up a step and visualise that too - a metric ton (tonne) is 1000kg or 1 megagram - that is the weight of a 100cm x 100cm x 100cm cube of water - a 1m x 1m x 1m cube. So a 1 meter ice cube would weigh a tonne. So now you can think 1g/cc, 1kg/liter and 1tonne/cubic-meter are all the same density - and now you can visualise the gram, kilogram and tonne as 1cm, 10cm and 100cm cubes of water - roughly, something the size of a sugar cube, a tetrapack of milk or a large refigerator (to stick with a 'kitcheny' theme!). So Osmium is 22g/cc, 22kg/liter or 22tonnes/cubicmeter - lead is 11g/cc, 11kg/liter or 11tonnes/cubicmeter, iron is 6g/cc, 6kg/liter or 6tonnes/cubicmeter. Gasses are harder to visualise. Air is just 0.0012g/cc which is impossible to visualise - but we can go with 1.2g/liter, 1.2kg/cubicmeter and mentally compare the weight of a tetrapack of water to the weight of the air inside a large, empty refrigerator and be roughly right. SteveBaker (talk) 18:43, 16 December 2008 (UTC)

Steve, Steve, Steve... did you just say that ice has the same density as water? A m³ of ice will weigh less than a m³ of liquid water. I'm so shocked that I'm not even going to get on your back about kilograms not being a measure of weight! Matt Deres (talk) 17:43, 17 December 2008 (UTC)

We're looking for ROUGH ways to visualise weight - not PRECISE ways to measure it - the difference between the density of ice and water is well within my error bars here! A liter of liquid water doesn't weigh a kilogram either - it depends on temperature and in any case, the standard definition of a kilogram is the mass of some block of metal in a museum someplace. Also, (rightly or wrongly) we all describe the weight of things in kilograms all the time - if you don't believe that, you're going to have a very hard time making your way in the world! There is a time to be pedantic and a time to help the OP...this is the latter. SteveBaker (talk) 19:50, 17 December 2008 (UTC)

Dude, you're talking to him about g/cc densities and megagrams, but I'm being pedantic? ;-) You're 2.54 centimetering into hypocrisy on that one. And if there's one thing that gets 5.44N'ed into you on these desks, it's that you can always make room for pedantry! Matt Deres (talk) 20:55, 17 December 2008 (UTC)

How is measuring densities in g/cc pedantic? How would you measure them? --Tango (talk) 21:26, 17 December 2008 (UTC)

It would depend on what it was. I don't think of cc being used anywhere outside of the medical and auto spheres, which is probably why Steve is familiar with it. I've been raised in metric, and I use litres (and mL) for all general volume uses of that kind of scale. Obviously, there's nothing wrong with it (I was more interested in giving Steve a hard time than anything, after all), but it's not a unit I would tend to use. If I say something like "Gimme 100 cc's of chocolate milk!" surely that brings up an image of getting an intravenous injection even without the "Stat!" at the end? Matt Deres (talk) 22:44, 17 December 2008 (UTC)

Either that or the name of an especially pathetic motorbike (cf "Gimme 800cc of Harley between my legs!") The reason I used 'cc' was because cm³ (or worse: 10^-6[[meter|m]]³) is harder to type. Also, in my defense, I was educated right at the start of the time when kids were taught the metric system in British schools - and the precise details of whether you should say 'cc' or 'cm³' or 'ml' were still being thought through. It wasn't "SI-units" or "mks" (meter-kilogram-second) - it was some fuzzy idea of "The Metric System" or perhaps "cgs" (centimeter-gram-second) - none of which are exactly the same thing! It's taken me ages to stop thinking about "dynes" and "ergs" - but "cc" does creep in once in a while! But (as I said before) the meaning is clear and in informal prose such as the RD, it really is OK to use them interchangeably. At least we don't have to worry about pounds and ounces and fluid ounces(British) versus fluid ounces(US)...yuck! SteveBaker (talk) 21:07, 18 December 2008 (UTC)

• Anyway, one easy one to remember is that "a pint of water weighs a pound-and-a-quarter". In the United Kingdom - American water does not conform to this DuncanHill (talk) 21:14, 18 December 2008 (UTC)

• • Fortunately, in America "A pint's a pound the world around" works (in American standard units, 1 pint of water weighs exactly 1 pound, as standardized). Given that Imperial volume units are 25% larger than American Standard units, its an easy conversion to make. --Jayron32.talk.contribs 21:50, 18 December 2008 (UTC)

    "The whole world round" meaning "in the United States of America" :) DuncanHill (talk) 12:51, 19 December 2008 (UTC)

A critical dictionary of psychology?

Looking through the APA Dictionary of Psychology (first=latest edition, 2006, ISBN 1-59147-380-2), I see that it treats psychoanalysis, analytic psychology, "neuro-linguistic programming", and even scientology in all seriousness. I mean, these are treated as living subfields of psychology/psychotherapy/etc, not as well-intentioned historical missteps (or worse). While the entry for "pseudoscience" does give scientology as an example, it doesn't give any of the others, and the entry for "scientology" doesn't link to pseudoscience. All of this strikes me as an extraordinary -- but no, I mustn't speechify. There are of course plenty of books that debunk this or that pseudoscience or pseudotherapy, but is there a fairly up-to-date general-purpose dictionary of the putative science of psychology that's discerning (whether by evaluation or selectivity) and recommendable? Tama1988 (talk) 11:09, 16 December 2008 (UTC)

But what about Scientology and psychiatry? Scientologists are strongly opposed to psychology/iatry.-- MacAddct1984 ^{(talk • contribs)} 15:12, 16 December 2008 (UTC)

All definitions seem just like something you'd expect in a dictionary. They aren't treated as living subfields of psychology. They are merely described. This dictionary also does not take a stance towards animism, sociobiology, Christian science, or evolutionary psychology. The only entry that I have found that explicitly takes a stance is social Darwinism.--droptone (talk) 16:03, 16 December 2008 (UTC)

This is the crucial difference between a DICTIONARY and an ENCYCLOPEDIA. A dictionary defines what the word means - an encyclopedia provides facts and explanation relating to that meaning. Hence, here at WikiPEDIA, we talk about Astrology and explain that it's a pseudoscience - but over at WikTIONARY we simply say that it's "The study of the movements and relative positions of celestial bodies and their supposed influence on human affairs.". Dictionaries are not there to explain - merely to define. You shouldn't read any kind of acceptance of these ridiculous thing into their presence in the dictionary. SteveBaker (talk) 18:06, 16 December 2008 (UTC)

Then why would they call social Darwinism "a discredited theory ..."?--droptone (talk) 21:40, 16 December 2008 (UTC)

It's a good question, actually. Social Darwinism can mean many, many things, some of which are discredited, some of which are just seen as not in vogue, some of which are considered pretty standard. Much the same can be said about psychoanalysis. What do they say about, say, "eugenics"? --98.217.8.46 (talk) 01:46, 17 December 2008 (UTC)

"a social and political philosophy, based loosely on the evolutionary theory of Charles Darwin...The eugenic position is groundless and scientifically naive, in that many conditions associated with disability or disorder, such as syndromes that increase risk of mental retardation, are inherited recessively and occur unpredictably". It defines g as hypothetical, they raise objections in the definition of IQ but dismisses them, chi is defined without objections, acupuncture is defined while saying that scientists are unable to explain how it works (with the presumption that it does), homeopathy is defined without objection, reflexology is also defined without objection, as is reiki.--droptone (talk) 13:23, 17 December 2008 (UTC)

Thank you for your responses and my apologies for my absence.

The APA Dictionary announces that it represents a snapshot of the lexicon of psychology as it exists at the beginning of the 21st century. [...] Although selective in scope, it seeks not to limit the vocabulary but, rather, to delineate the current and evolving understanding of the language used within the field. That last sentence seems bizarre, implying as it does that language has been used "within the field" with a limited understanding of what that language meant; I'll guess at some copyediting error here. Surely this is the language that is used (and perhaps also obsolete language that is still quoted and discussed) for the current and evolving understanding of the field. There's no hint that it's also a dictionary of what I imagine would be called ethnopsychology, vernacular understandings and misunderstandings of the area treated by psychology.

The only comparable book that I possess is Stuart Sutherland's International Dictionary of Psychology (2nd ed., 1995), which I inexpertly think is very good but which is showing its age. This doesn't bother with "neuro-linguistic programming" or "scientology", or with any that I bothered to look up of the depressing list (homeopathy, reflexology, etc.) that Droptone gives above. It does cover the wobbly Freudian and Jungian edifices, and it does so politely; but Sutherland discreetly inserts such phrases as "said to be" in these contexts, so the reader isn't lulled too easily into taking it all too seriously. As for seriousness, Sutherland is a witty writer where he can be (the two prefaces make me laugh), but the comments on this book at amazon.com unfairly highlight the Johnsonian joke entry for "Love", which is very atypical.

I suppose what I'm looking for is something like an updated and expanded 3rd ed. of The International Dictionary of Psychology. Tama1988 (talk) 02:40, 18 December 2008 (UTC)

the method to reduce alcohol or menthol scent

I need to know, How to reduce alcohol or menthol scent but still keep the cool function?

may answer to my e-mail ***@*** —Preceding unsigned comment added by Pattytai (talk • contribs) 14:55, 16 December 2008 (UTC)

E-mail address removed, as per ref desk rules (see the top of this page). Mostly to protect you from spam etc. Aeluwas (talk) 15:13, 16 December 2008 (UTC)

Alcohol, when applied to the skin, cools via evaporation: the same mechanism that allows sweating to cool the body. I am guessing alcohol feels cooler because it vaporizes much quicker taking heat away at a higher rate even at room temperature. Menthol creates a cooling sensation via a different mechanism; it binds to receptors on the skin which fools the brain into thinking that patch of skin is cool (like inverse capsaicin). Alcohol must evaporate in order to cool, so the only way to reduce the smell is to mask it with other, nicer smells. Menthol on the other hand just needs to be in contact with the skin so preventing it from evaporating (i.e. becoming smellable) is one solution, along with masking it with other smells. Mixing the menthol with wax or petroleum jelly may help a little... but it will still be smellable anyway. 152.16.15.23 (talk) 16:19, 16 December 2008 (UTC)

Flat screen moving volumetric display with full vertical and horizontal parallax?

Has anyone ever invented or have a design for a "perfect" large, high definition, (nearly) flat screen volumetric display with 180 degree vertical and horizontal parallax, and proper occlusion of overlapping light and dark areas? And if no one has, what would be the best way for a lone inventor to exploit or promote the design? —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 15:18, 16 December 2008 (UTC)

I think the article Volumetric display and its links gives an account of the state of the art. Can't say I've heard about anything resembling what you describe, but holograms do it well for static pictures in black and white. If you have a design that you want to promote, this is probably not the right place to ask. But there are forums on the net as well as personal accounts by inventors that discuss how to proceed from an idea to a finished product. EverGreg (talk) 15:36, 16 December 2008 (UTC)

You might try building a working prototype and using it as a demo to get investors and form your own business selling volumetric displays. I'm sure this isn't easy, but it probably has the highest potential pay-off for inventors. APL (talk) 17:25, 16 December 2008 (UTC)

There are three additional criteria to specify:

1. Can you view it without any kind of special eyewear or headwear?
2. Is it capable of supporting multiple simultaneous viewers?
3. Can it do appropriate hidden surface occlusion?

If the answer to any of those three questions is "No" then there are several solutions. The only systems that I'm aware of that can cope with multiple viewers and does not require special user-mounted equipment and can do hidden surfaces - are holograms. Contrary to what EverGreg says - I've seen (with my own eyes) moving, interactive, color holograms generated by computer. The system was a half million dollars worth of Silicon Graphics workstation with some very custom hardware involving ultrasonics and all sorts of other mysterious things - but it could display a small (like 5 centimeter) low resolution color hologram of a cube that was spinning - being updated a couple of times a second. I suspect that it only had horizontal parallax - but in most applications, that's good enough.

So in answer to whether a "perfect" solution exists - certainly not. Nor do I expect we'll ever see one that isn't a hologram simply because if you don't know where your viewers are and they don't have some kind of modified vision or are in some other manner restricted - then your display has to generate the complete waveform of the light that would come from a real object - and that's a hologram.

Not one of the systems out there (including the hologram) is able to exclude light coming from behind the object - so at best, you get the R2D2 "Help me Obi-Wan Kinobi you're my only hope" type of translucent hologram - not the StarTrek "Holodeck" kind that look 100% real. It's really hard to imagine how a system could do that...even in principle.

I agree that if you can build a working prototype (and get your patent registered) that would be the ideal first step. Once you have those two things - just announce it in as many places as you can think of (Slashdot and Digg would be good places!) and the news will spread like wildfire. If it really does work as you seem to be implying - there will be no shortage of people beating a path to your door. However, you must forgive me for being skeptical - there have been VERY many attempts at solving this in the past and I doubt very much that you've cracked it either. If you have not built a working prototype then I'm afraid that it's overwhelmingly likely that there is something that you have not thought about.

SteveBaker (talk) 17:53, 16 December 2008 (UTC)

Lenticular displays are making progress, and they meet Steve's three bullet points, but they only have parallax in one dimension, so they don't answer the question either. APL (talk) 19:32, 16 December 2008 (UTC)

Lenticular displays are a great theoretical solution - but building them with enough resolution to give you stereopsis and arbitary view direction requires insanely high-res displays. In the limit, they ARE holograms because if you can get the resolution up high enough to do arbitary viewer smoothely, you have enough resolution to render a hologram directly and you can dump the lenticular lens layer. SteveBaker (talk) 19:55, 16 December 2008 (UTC)

Incidentally, haven't you already invented a 'Retrocausal information transfer' device? You could probably use that to make money on the stock market, then use those earnings to finance your 3d display company.

See you at SIGGRAPH! APL (talk) 19:43, 16 December 2008 (UTC)

Ah - thanks for the reminder...OK - nothing to see here - move along! SteveBaker (talk) 19:55, 16 December 2008 (UTC)

My idea meets all three criteria. As for retrocausal data transfer, I can now predict (0-3) decimal at a couple of percent above expectations, instead of just one bit at fractions of a percent greater than chance, so I could finance it, but getting a team together to sort out the practicalities is more of a challenge. I will send Steve Baker (who seems to know more about optics than me) an avi video of my design to see if it is practical and completely original-or so expensive or open to challenge that I may as well give the idea away on this forum, bearing in mind the legal minefield the patent process is for even a well financed private individual these days.Trevor Loughlin (talk) 05:49, 17 December 2008 (UTC)

No - please don't send it to me. I also invent things - I have patents on display technologies - and I don't want you claiming that I stole something from you. First patent - THEN show to people. SteveBaker (talk) 19:42, 17 December 2008 (UTC)

Well since you can get the finances I don't think assemblying a team will be a great challenge. Sure you may not be able to convince Nobel prize winners to join you or even the top students (well unless your evidence and ideas are very strong perhaps) but provided you have resonable evidence and theories and the cash to pay them, I'm sure you can easily entice some okay scientists, engineers and the like to join your team. Obviously they're only going to work for you if you can guarantee a resonable salary for the time they are employed, you can't expect them to work on the promise of future riches alone Nil Einne (talk) 12:47, 18 December 2008 (UTC)

Most powerful force on earth

What is it? —Preceding unsigned comment added by 79.67.56.238 (talk) 23:46, 16 December 2008 (UTC)

That's rather difficult to define, really. Do you want something sustainable, or is something that's extremely powerful for very short periods enough to qualify? Does an external force applied to the whole Earth qualify? If so, the Sun's gravity (ie. the Earth's weight) is almost certainly it at 3.5x10²²N, I can't think of anything else comparable. --Tango (talk) 23:56, 16 December 2008 (UTC)

Clarification: forces (transitory or continuous) created solely on and by the planet we call earth; and not due to any external solar system/universal effects. —Preceding unsigned comment added by 79.67.56.238 (talk) 00:05, 17 December 2008 (UTC)

Ok. There must be some pretty major forces at work during an earthquake - making large amounts of the Earth's crust move around would require a lot of force. That would be my guess. (Well, actually, your definition would allow the Earth's gravity on the Sun, which is exactly the same as the other way around, but I'm guessing you didn't mean to include that!) --Tango (talk) 00:17, 17 December 2008 (UTC)

Hmmm - F=Ma - so we either need a very big mass - or a very big accelleration. The earth/sun gravitational force involves some pretty spectacular masses - but the accelerations aren't that big. Maybe we should be looking at smaller masses with bigger accelerations. But whatever it is, it's not going to be able to knock the earth out of it's orbit - so it'll have to be a very brief acceleration. SteveBaker (talk) 02:26, 17 December 2008 (UTC)

UM, I call bullshit on "accelerations aren;t that big" in the Earth-Sun system. The Earth is turning around a huge circle at a fantastic rate of speed; curved motion represents an acceleration, so there are some rather profound accelerations in the system... --Jayron32.talk.contribs 05:55, 17 December 2008 (UTC)

Centripetal acceleration is $a=\omega ^{2}R=({\frac {2\pi }{T}})^{2}R$ For T=1 year and R=1 AU, google tells me that is 0.006 ms^-2. That's a pretty tiny acceleration. --Tango (talk) 13:16, 17 December 2008 (UTC)

Yup, I get the same. That's 0 to 60 mph in about 75 minutes. Gandalf61 (talk) 13:23, 17 December 2008 (UTC)

SteveBaker's F=ma is great - it mathematicizes the question. But the original poster asked about the most powerful force, so we might consider P = dW/dt (power is the rate of change of energy). So we might expand or restate the "big mass or big acceleration" to also include "lots of energy or very short amounts of time" - so, might the Strong Nuclear Force, with some of its transient interactions on the order of planck time scales, have extremely large bursts of momentary power? Nimur (talk) 15:35, 17 December 2008 (UTC)

What about what's going on in the core of the earth? Surely that's the answer?Rfwoolf (talk) 02:28, 17 December 2008 (UTC)

If you're okay with a very brief condition, I'd think that the detonation of a hydrogen bomb would create some pretty stupendous forces at its onset. As a side note, I know it isn't technically force, but Diamond anvil cells can achieve pressures more than one million times normal atmospheric pressure. -RunningOnBrains 06:14, 17 December 2008 (UTC)

Further clarification: I meant natural forces; not man or machine made ones.--GreenSpigot (talk) 14:58, 17 December 2008 (UTC)

The forces of flowing water: water tears down mountains to dust, over and over again. --VanBurenen (talk) 15:02, 17 December 2008 (UTC)

It's a nebulous question, so I'll throw in Krakatoa, wave power, and wind power, although the latter two are of course caused by extra-planetary forces. --Sean 15:25, 17 December 2008 (UTC)

The Strong Force! at about 10^39 times stronger than gravity, not to be dismissed. —Preceding unsigned comment added by 92.3.10.246 (talk) 00:59, 19 December 2008 (UTC)

probably not the answer you were looking for but: a good lie. "Not all the armies in all the world can stop an idea whose time has come..." —Preceding unsigned comment added by 94.27.221.237 (talk) 14:15, 19 December 2008 (UTC)

if $E=MC^{2}$so earth it self is the strongest force on earth--אזרח תמים (talk) 16:56, 22 December 2008 (UTC)

Newton's Third: What about the rest of the universe acting on earth?