Wikipedia:Reference desk/Archives/Science/2010 March 9

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March 9

Yellow hands

A young girl I know has a peculiar yellow tint to her hands, and I'm wondering what it could be. She is east Asian, but there is a distinct almost "stained-yellow" color to her hands, as if she was soaking them in a brown ink every day. She is healthy, I was thinking it might just be increased carotene? Any ideas? 210.153.207.42 (talk) 00:58, 9 March 2010 (UTC)

I should note that only her hands are visibly colored. 210.153.207.42 (talk) 01:00, 9 March 2010 (UTC)

Saffron is that color, but I'm not aware of anyone dying their hands with it intentionally, although I suppose it could bleed into their hands from preparing foods with saffron that require lots of hand manipulation. StuRat (talk) 01:58, 9 March 2010 (UTC)

It's possible, though her hands have been like that (as far as my noticing goes) for at least a year. Maybe she really likes paella. 210.153.207.42 (talk) 02:43, 9 March 2010 (UTC)

The color you describe sounds a little like Henna. Paul Stansifer 03:14, 9 March 2010 (UTC)

Yes, to be honest I thought the same thing, but again I don't understand why it would last so long, nor why she would be continuously using henna! I was actually under the impression that it was likely to be an internal thing, which is why I mentioned carotene. It does look like the skin itself is colored, though I can't tell why it would only coloring the hands. 210.153.207.42 (talk) 03:58, 9 March 2010 (UTC)

There's certainly precedent for people having very yellow skin as a side-effect of eating much too much carotene, so that's a reasonable thought - but it still seems odd for it to be restricted only to the hands. ~ mazca ^talk 09:05, 9 March 2010 (UTC)

Mind you, it's not like I've seen her whole body. Her legs and face aren't yellow though. 210.254.117.185 (talk) 10:31, 9 March 2010 (UTC)

Turmeric is a pretty good yellow dye. It's dyed several of my pots and utensils and cups. It's common in SE Asian cooking, and is reputedly good for your skin. Indeterminate (talk) 05:21, 9 March 2010 (UTC)

Tobacco can stain fingers yellow, but that wouldn't usually be the whole hands. --Tango (talk) 05:38, 9 March 2010 (UTC)

I now have a great mental image of a small girl chain-smoking huge cigars held in her fist. ~ mazca ^talk 09:05, 9 March 2010 (UTC)

Localized jaundice. I have this, on my face and hands. —Preceding unsigned comment added by Fire2010 (talk • contribs) 19:50, 9 March 2010 (UTC)

Handling nitroglycerine or cordite? —Preceding unsigned comment added by 79.76.188.14 (talk) 23:17, 9 March 2010 (UTC)

How young is the girl? I've seen it more then a couple of times when girls have strangely yellowed hands and it was my fiancé's younger sister who gave me the answer. She was only 15 and started using this "sun cream" which was not only sun block but also "fake tan" in one bottle. Since you use your hands to apply it, your hands soak up a lion's share of the ointment, if you don't wash them immediately, which girls never do since girls never read instructions, especially 15 year old ones. ;) I'm not guaranteeing this is the case here, but everything you've said so far seems to fit with this theory.Vespine (talk) 00:46, 10 March 2010 (UTC)

The OP says she's been like this for a year. She'd have to be a rather 'slow learner' for something like that to continue for so long. Either that or this fake tan stuff is a lot nastier then I thought if it lasted that long from one or two instances Nil Einne (talk) 03:51, 10 March 2010 (UTC)

Well my fiancé's sister is 17 and she still uses the stuff. Apparently yellow hands are a small price to pay for vanity.. Actually my fiancé teases her because even I agree the entire "fake tan" effect is a ridiculous orange and blotchy, especially around her face! But the younger's sister wants to do what she wants to do and no one can tell her otherwise.. Vespine (talk) 04:18, 10 March 2010 (UTC)

I'm not surprised she still uses it. I am surprised she hasn't yet learnt to wash her hands immediately after application... The word I said earlier does seem to apply. Nil Einne (talk) 15:52, 11 March 2010 (UTC)

Having read this post a few days ago, I could not help but think of it when I heard a quickly-read side effect of Cymbalta on a television commerical: "yellowing of the skin." AlexHOUSE (talk) 23:16, 11 March 2010 (UTC)

I guess the obvious answer is there are probably plenty of reasons, we'll never know which. If the OP is genuinely interested, they could befriend this person and ask them at some stage in the future when it doesn't seem inappropriate (obviously don't do this if you're going to completely forget about the person once you know). You can even come back months or whatever from now when you know and tell us if the person consents Nil Einne (talk)

plastic? it breaks weird

is the window in this

http://www.youtube.com/watch?v=PH5OMyuAppg

plastic? it breaks weird —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 01:09, 9 March 2010 (UTC)

Yes - it certainly looks like plastic of some kind. When you hit a piece of glass, it's so brittle that cracks propagate outwards to the edges of the pane. But plastic can bend enough to stop cracks from propagating - so you get those kind of rounded chunks falling out. Also, you can see the intact panes bending in the wind. It's hard to be sure though. SteveBaker (talk) 02:26, 9 March 2010 (UTC)

They look like storm windows to me. They are commonly plastic on the outside and (usually) placed over glass on the inside. If there was glass on the inside, you wouldn't see it after the axe went through. Some people put up storm windows without real windows behind them. So that could be the case here. -- kainaw™ 06:25, 9 March 2010 (UTC)

Comments on YouTube suggest the window material is Plexiglass (Poly(methyl methacrylate)) but from its apparent flexibility I expect it is vinyl. Cuddlyable3 (talk) 21:52, 9 March 2010 (UTC)

Cover slips are often made from glass but break like plastic. ~AH1^(TCU) 01:47, 14 March 2010 (UTC)

plant growing

A technical? question about growing large plants. I assume that while more sunlight = more energy for the plants, and thus a brighter area can support a larger number of (non-shady) plants, too much sunlight evaporates too much water and thus there is a balance between the amount of sunlight a plant can get vs. the available water. If extra sunlight was redirected towards (not focused at) a large garden area, and care is taken to keep the ground cool/moist (the redirected light could be aimed parallel to the ground so as not to heat it directly), would this make the area more fertile? Am I thinking in the wrong direction? A large greenhouse isn't really feasible, and this can't really be a big expensive/mechanical operation. 210.153.207.42 (talk) 04:10, 9 March 2010 (UTC)

Sorry, but that just wouldn't work. The reason is is that the sun produces infrared waves (heat) along with the visible light. So even if the light is not focused, wherever you can see the sun's light, there will be heat. However, I believe the best thing to do would be to redirect the light at the plant's leaves, but not the ground. This way, the plant would take energy from the sun, but it would not dry up the soil. Hope this helps, --The High Fin Sperm Whale 04:20, 9 March 2010 (UTC)

Yeah, that's exactly what I was proposing, by aiming the reflected light parallel to the ground, rather than at the ground. 210.153.207.42 (talk) 05:06, 9 March 2010 (UTC)

Whether it will result in better plant growth will depend on whether it was sunlight that was the limiting factor before. It could be that they have plenty of sun and actually need more water, or more nutrients in the soil, or more physical space, etc. If one of those things is limiting the plants' growth then more sunlight won't help. --Tango (talk) 05:42, 9 March 2010 (UTC)

Thanks! What about in a more complex forest, with large tree growth, and smaller ferns and bushes underneath? I've seen a lot of Canadian shield forest (and badly planted artificial forest) where tall trees block out the sunlight leaving almost none for the undergrowth, so I'm thinking of a way to promote more plant variety. 210.153.207.42 (talk) 05:51, 9 March 2010 (UTC)

And also, what is the limiting factor for space? If there is plenty of sunlight/nutrients won't plants be able to grow around each other? 210.153.207.42 (talk) 05:55, 9 March 2010 (UTC)

If there is room to grow around things, then there isn't really limited space. A plant that is growing between two large rocks may not be able to grow as big as it would otherwise do, simply because there is nowhere for it to grow into. It is quite unusual for space to be the limiting factor, I think, but it isn't impossible. --Tango (talk) 23:06, 10 March 2010 (UTC)

You may be interested in Forest gardening. In biological systems, something may be held back by a limiting factor, but once that limiting factor is overcome then another limiting factor is in control. Difficult to know what the limiting factor may be, it could easily not be lack of sunlight. I take it you are in a hot dry area. You could consider trickle or Drip irrigation or mulching to conserve water. It may be simply that there is not enough diversity of seeds for what you want, or they are dormant for lack of water, or that fertilizer would help. I would consider scattering a variety of seeds, possibly with fertilizer, and supplying water. Too much sunlight may scorch the plants. Many plants seem to like moist warmth, but what is best will vary from species to species. You could consider a polytunnel, perhaps home-made, but perhaps your plants will wilt in the heat. For large plants it is better and quicker but more expensive to buy them already grown from nurseries. The polytunnel article only mentions small ones, but I was thinking of ones seven or eight feet in diameter, which are quite common where I am. 78.146.202.143 (talk) 19:59, 9 March 2010 (UTC)

It is more likely, from what you have described, that the plants are being held back by lack of water rather than lack of sunlight. Even in Britain, which is as far north as Newfoundland and hence has less intense sunlight, plants which have access to water such as being by a stream are especially lush. 92.26.160.145 (talk) 20:51, 10 March 2010 (UTC)

I haven't built anything yet, I'm in the planning stages, and I'm just wondering how to obtain the most fertility (self-sufficient, within a restricted area) without relying on fertilizers/overly mechanical irrigation techniques. I'm actually in a fairly moist cool area, near Vancouver, though my goal is to promote as much variety and "lush" as possible, so I figured with my relatively high latitude, sunlight was likely to be a limiting factor. It's apparent that there are likely to be many other limiting factors, dependant on soil type, so I'll keep that in mind too! I will definitely consider having some kind of underground water "polytunnel", as well, if I can easily borrow from a nearby stream (without harming the stream). Thanks for the info! 210.254.117.185 (talk) 05:56, 11 March 2010 (UTC)

A polytunnel is above ground. The ones I am familiar with are more than big enough to stand up in. They are in the shape of half a cylinder, and are formed of a very large sheet of clear polythene stretched over very long rods bent into a U-shape and stuck into the ground. Trickle pipes are usually just left on the surface. You could try building a pond. 89.243.212.29 (talk) 14:58, 11 March 2010 (UTC)

price wiki

Is there a wiki where one can enter the price, date, store location and UPC or PLC of the item and that tracks price changes and/or differences over time and location? 71.100.11.118 (talk) 05:57, 9 March 2010 (UTC)

I don't know about a Wiki, but there are many price comparison websites on the net. —Preceding unsigned comment added by Fire2010 (talk • contribs) 19:48, 9 March 2010 (UTC)

You may be able to find or create one at Wikia. ~AH1^(TCU) 01:44, 14 March 2010 (UTC)

Name of an "larva"

Resolved

Hi, about six or seven years ago my sister received a present that was like an aquarium for insects. Basically, it was like a plastic pool that you filled with water and then there was a packet of dried "insects" that, when applied to water, would "hatch" and eventually start swimming around. I remember the box saying that those "insects" (or "larvae" or whatever) were "millions of years old" but that could've been an exaggeration to boost sales. From my memory, the older ones had tails. Does anyone know the name of the insect/amphibian? 144.124.16.28 (talk) 07:47, 9 March 2010 (UTC)

Sea monkeys. Stupid me. Thanks anyways. 144.124.16.28 (talk) 07:53, 9 March 2010 (UTC)

That's the marketing name. They are typically really brine shrimp. I will mark this Q as resolved. StuRat (talk) 15:00, 9 March 2010 (UTC)

Mobile phones on airplanes

I have to turn off my mobile phone when on an airplane because it intefers with the plane's navigation system - But while it's turned off, I can receive SMS and also calls to my mailbox - why don't these signals cause problems for the airplane too? Thanks for info, --AlexSuricata (talk) 12:50, 9 March 2010 (UTC)

They do cause the same issues (to the extent that there are any real issues of concern - entirely another debate). What sort of phone do you have that when turned off, it is still on? Mine, fwiw, is very much off when it is off. --Tagishsimon (talk) 12:57, 9 March 2010 (UTC)

(ec) I'm pretty sure that, when your phone is off, it doesn't receive anything; messages get queued up by the phone company for delivery when you first turn it on. This is why there's some delay between turning the phone on and getting messages. Paul Stansifer 12:59, 9 March 2010 (UTC)

And as for the voicemail messages, those are not stored on your phone at all - if you do not answer your phone, the call gets directed to your mailbox in your cellular carrier's system. When you turn your phone back on, you're simply receiving the notification that there are more messages in said mailbox than there were before. Text messages (SMS) are stored on your phone itself, but they queue in your carrier's SMS delivery system while your phone is not connected to the network, such as when it is off or in an area with no service. They are released when your phone next makes contact with the network. Coreycubed (talk) 14:48, 9 March 2010 (UTC)

I've always suspected that the ban on cell phones in the plane was more about not annoying other passengers than safety. However, people are less likely to violate the ban if they think the plane will crash in flames when they turn it on. StuRat (talk) 14:56, 9 March 2010 (UTC)

I did not turn my phone off the last time I was flying, and noticed the battery drains really fast. Is that because the phone is moving to a different cell tower every 30 seconds? Googlemeister (talk) 15:06, 9 March 2010 (UTC)

It's for the same reason that it drains faster out in the middle of nowhere...it has to struggle to find reception...weak reception/searching for service kills phone batteries, and there's not much service 40,000 feet (12,000 m) in the air. Ks0stm ^(T•C•G) 15:13, 9 March 2010 (UTC)

Obligatory WP:WHAAOE link: Mobile phones on aircraft -- Coneslayer (talk) 15:19, 9 March 2010 (UTC)

And since we unsuccessfully avoided Tasishsimon's "entirely another debate" statement, the real reason we aren't supposed to use portable electronic devices on aircraft is because they emit harmful pilot killer rays! Coreycubed (talk) 17:04, 9 March 2010 (UTC)

Half life zpe device for book

Hi guys

What would be a good alternative that is more realistic ( i say more, but still) way of acheiving the effects of the zpe gun in Halflife 2? A machine that if it existed would be Like mechanical telekinesis. I know this is not possible with technology ( at least not at the moment) but what forces would you need in real life to acheive this kind of thing. would electron manipulation work? I ask this because In real life even if you could manipulate zero point energy or vacuum energy it wouldnt be strong enough?

So are there any Ideas ?

R —Preceding unsigned comment added by 79.67.141.98 (talk) 14:26, 9 March 2010 (UTC)

For those not familiar with Half-life, perhaps you might summarize what the thing does? Here's what I'm reading into it: you point the gun at something -- say, a crate 100 feet away. The crate glows with cool blue light, and then by swiveling the gun, the crate moves, staying in line with the barrel. Then you release the trigger and the crate falls. Good enough? So, with that sort of thing, you've got to cancel mass. That's the simplest (in terms of linguistic expression) means of lifting the crate and moving it around on the end of a really long arm. And it can't be done. There's no "mostly realistic" or "more realistic" about it. Worse, it's the sort of tech that absolutely breaks a story unless you can set hard limits on it (F=ma has just become absurd, and that's pretty core to how everything works). So if you want to use it, fine, any technobabble will do. Oh, and it needs a power source. I recommend tritanium batteries. They're rechargeable, you know. — Lomn 14:39, 9 March 2010 (UTC)

Oh, and to borrow from Baseball Bugs' recent comment on a related subject, if the writer is smart, he won't waste much time explaining the weird tech, as explanations often do little but further open the door to rebuttal. I'd say the key exception is where the explanation reveals a plot point and/or closes a plot hole. For example, in The Mote in God's Eye Niven and Pournelle spend a fair bit of time on the theory behind the Alderson drive because limiting FTL travel is essential both to their presentation of how the universe is explored and to keeping the "sci" in "sci-fi" from floating straight out the airlock. — Lomn 14:52, 9 March 2010 (UTC)

There is no possibility of creating a real gravity gun -- it violates the principle of conservation of momentum. Looie496 (talk) 20:39, 9 March 2010 (UTC)

Not necessarily. Perhaps it transfers momentum to the ground. — DanielLC 21:32, 9 March 2010 (UTC)

This is clearly not a possible device - but for a sci-fi story, stick to the rules:

1. There shall not be more than one or at most two impossible technologies.
2. All impossible technologies must have limitations that are commensurate to their power.
3. Make up a name and handwave the explanation for how it works.

SteveBaker (talk) 04:46, 10 March 2010 (UTC)

nuclear power station sites

Since it will take at least 10 times the number of nuclear power stations the US now has to displace the current usage of fossil fuel how many sites have been evaluated and/or selected to become nuclear power stations since George W Bush told the American Congress that the US was addicted to oil? 71.100.11.118 (talk) 16:15, 9 March 2010 (UTC)

Nuclear_power_in_the_United_States#Resurgence may help to answer your factual questions. Please note that the Reference Desk is not the place to start a debate or advance a particular position. -- Coneslayer (talk) 16:25, 9 March 2010 (UTC)

Please note that I can not prevent the news media from reporting that Barack Obama was taking another look at nuclear energy or that George W Bush told the American Congress that America is addicted to oil, both of which are facts I could care less about debating but merely want to know in which what, if anything is being done in accordance with pub.ic statements made by American Presidents. You on the other hand might want to start an argument over what you have been told you can and can not do as a good little Wikipedia boy or girl while I could care less. 71.100.11.118 (talk) 16:42, 9 March 2010 (UTC)

"pub.ic statements made by American Presidents" ? Are we talking Bush ? StuRat (talk) 05:00, 10 March 2010 (UTC)

You're welcome for the help. -- Coneslayer (talk) 16:45, 9 March 2010 (UTC)

The question in its distilled form is "How many sites have been evaluated to become nuclear power stations?" The answer is found in the article linked above; 26 applications received, 7 more expected. Six reactors have been ordered. We currently have 104 nuclear power plants. By your own math, we would need an additional thousand. No need for anything other than AGF here; myself, I could not care less. Coreycubed (talk) 16:51, 9 March 2010 (UTC)

I seem to remember hearing that "could care less" has been misused enough to now be a synonym for its opposite. But I couldn't care less, so I'm not going to follow it up with a question to the language desk... or a check of a dictionary --Polysylabic Pseudonym (talk) 03:11, 12 March 2010 (UTC)

From the time the first electric power central station went in service in 1882 until the 1970's, utilities had to scramble to add an average of 7% more generation each year, which means doubling it every 10 years (varying with the economy and local conditions). This was due at first to more and more homes and business getting wired for electricity, then with its increased use for more purposes. Saturation eventually occurred, and efficiency /conservation efforts helped to limit growth. Transmission lines were planned and generation sites were selected and purchased years decades ahead to allow for this growth. Larger and larger generator were installed until they were over 1000 megawatts each. When the growth of demand for electricity fell off in the 1970s, the new generations sites were deferred and ultimately many were cancelled. A utility might have planned for ultimately 4 1000 megawatt nuclear units at a site, but cut it back to 2, while some other 4 unit site was cancelled entirely. Where you see a 2 unit nuclear plant, the ultimate may have provided for 4 units. The cancelled sites are likely just rented out as farmland at present, but transmission lines rights of way may have been purchased years ago which provide for the lines to crisscross nearby to allow for a variety of outlets for the power. "Ultimate" or "many years in the future" future system plans are still in drawers at the electric utilities, which could provide for much more nuclear generation than was ever built, perhaps double the existing number of nukes at a given nuclear utility. Load flow studies were done which modelled loads several times as great as present, noting what generating and transmission would be needed. Present nukes are designed to operate without trying to follow the daily peaks and troughs of demand, but rather as "base load" units ideally running night and day at a constant output. Smaller fossil units and peakers accomodate the peak loads and can cycle up and down. Better, cheaper and higher capacity energy storage would let the base load units do their constant output thing while storage near the load centers helped accomodate peaks without overtaxing transmission lines or running fossil units. Certainly the public would yell "Not in my backyard," as they always did, if utilities announced plans to build 346 and 765 KV AC and 500 KV DC transmission lines and nuke stations with cooling lakes or cooling towers near their communities. The upside of a nuke plant is that the property taxes enrich the local schools and municipalities. The downside could be more Chernobyls if design and operation are not adequate. Edison (talk) 17:22, 9 March 2010 (UTC)

That leads to my conclusion that, due to real threats (like terrorism) and perceived threats (like The China Syndrome), we need to build nuclear plants more defensively. They could be constructed in old mines, far from population centers, in areas with stable geology, with the cooling towers up above. Hopefully, then, even if there was an explosion, the radiation would be confined to the mine. Another advantage would be that spent fuel could just be left in the mine, not hauled cross-country to a disposal site. You would, however, still have the risk of delivery of the nuclear material, unless it could also be processed from low-grade ore at the reactor site. It would be necessary to build more transmission lines, due to the remote nature of such a set-up, and they should be buried, for several reasons: 1) aesthetics, 2) to make attacks by terrorists more difficult, 3) to limit electromagnetic interference with nearby electrical equipment, 4) so they don't "spook" people who are afraid of medical side-effects. StuRat (talk) 14:32, 10 March 2010 (UTC)

The increase of cost of doing something like that would make them even more infeasible and economically draining than they already are (the capital costs are already basically prohibitive for major nuclear expansion without major government financing). A more serious goal would be to engineer the containment building to withstand a direct and purposeful crash with a 747 (they can already withstand a lot, but I'm not sure about that), to the degree that it wouldn't release significant nuclear material. Anything more than that is probably overkill (if someone is literally dropping bunker busters or nukes on your reactor, you have other problems). Note that at the moment we have zero evidence of terrorists doing any kind of successful attack on reactors whatsoever, and it would take a very non-trivial effort (e.g. a crashing 747) to do serious harm to the reactor vessel (they are very rugged). A more serious terrorist threat would be the spent fuel that is kept on site. The clever terrorist is going to attack "softer" targets (some of which—like chemical storage platforms—could do as much or maybe even more damage than a reactor). (And, arguably, the concern with terrorism is a bit overblown here, as far as threats go.) --Mr.98 (talk) 15:16, 10 March 2010 (UTC)

I am not sure on the containment building taking a hit from a 747, but It is a fairly rugged building. According to our containment building article, one location tested a containment building by hitting it with a jet at 450+ mph and it basically only scratched the outer concrete layer. Googlemeister (talk) 15:40, 10 March 2010 (UTC)

But what you're missing is that, no matter how safe it actually is, the perception of danger and corresponding public opposition will lead to delays and cost overruns or even the cancellation of the project. And I have to think that building in an abandoned mine would have to be cheaper than the massive containment building needed to protect it from a 747. StuRat (talk) 17:38, 10 March 2010 (UTC)

I strongly endorse the idea of building the plants at a site which is easily protected and using high capacity transmission lines to carry it to the load center, coupled with local energy storage at the load center. Human frailty, unforeseen multiple failures, or terrorism could breach any containment than has been built. In the worst case, people many miles downwind would have to evacuate in a very short time, and I have severe doubts about how successful such an evacuation of Chicago, or New York City would be, given the Hurricane Katrina fiasco in New Orleans. If a terrorist had control of one plane with one large conventional bomb, or an ANFO bomb in a large truck, attacking a chemical storage facility, a nuke plant, fuel storage pools, or perhaps a dam could cause a multiplicative effect of damage compared to just dropping the bomb on a target city. No dam, chemical plant or nuclear plant has security guards on site prepared to fend off a very large force of well armed and well trained suicidal attackers. Edison (talk) 18:10, 10 March 2010 (UTC)

But putting it in a mine is not necessarily going to fix those issues. In fact, waste disposal in mines has indeed been tried, and run into massive public opposition. One of the first attempts in the US to find a permanent disposal site involved an abandoned salt mine in Lyons, Kansas (Project Salt Vault)... it ran into massive problems. In part because mines have complicated geology once you really start looking at them. Yucca Mountain is in an abstract way an ideal site—middle of nowhere, under a mountain, nobody lives on it, government owns all the land already. Yet it has hardly been controversy-free, or problem-free. Anyway, I'm honestly not sure one is going to overcome public fears by technical means, however ingenious. As for the containment v. mine costs—I don't know. The nice thing about a containment building is that you don't have to contain the whole plant; only the core is important, and that is relatively small compared to the rest of the plant. --Mr.98 (talk) 00:13, 11 March 2010 (UTC)

Surely you solve a NIMBY issue by moving the reactors out of people's back yards, right ? StuRat (talk) 06:25, 11 March 2010 (UTC)

As a matter of interest, here is a video of the plane crash test that Googlemeister mentioned. 131.111.248.99 (talk) 20:37, 10 March 2010 (UTC)

So then it is fair to say that without military dictatorship to order construction of 1,000 more nuclear plants in the next 3 years that we remain pretty much permanently dependent on foreign oil? 71.100.11.118 (talk) 02:12, 12 March 2010 (UTC)

It certainly would be much better if the US could have an alternative energy infrastructure up and running when the oil runs out, but it doesn't look like that's going to happen, due to a lack of political will to do what it would take (such as heavy taxes on oil and subsidies on alternative energy). So, failing that, oil prices will skyrocket and then there will be a huge surge in alternative energy production, with years of blackouts and brownouts before they get up and running. I'd also expect people to start producing their own power, with windmills and solar panels, as power from the grid will be unreliable for many years. So, while pure capitalism does ultimately fix such problems, there can be huge disruptions before the "balance is restored". StuRat (talk) 13:26, 12 March 2010 (UTC)

The US would not have electrical interruption on the scale you describe. In 2008, only 1.1% of the US electricity was petroleum (http://www.eia.doe.gov/cneaf/electricity/epm/table1_1.html). What would be the big problem would be how to run the millions of cars and trucks we have. Googlemeister (talk) 16:32, 12 March 2010 (UTC)

What's the average amount of caffeine in a single medium roasted coffee bean?

From what I know, the amount of caffeine is actually reduced when brewing and roasting a bean, but how much is the amount left in a single roasted bean before brewing? IllusionalForce (talk) 17:50, 9 March 2010 (UTC)

There is lots of data about mass of caffeine per serving and mass-fraction of caffine in a bean. Either of those would allow you to calculate it, all you need to know (and I don't know it) is the typical mass of a coffee bean. DMacks (talk) 18:59, 9 March 2010 (UTC)

Do you mean Arabica coffee beans or Robusta coffee beans. There are two different species of coffee plant typically used in making coffee; Robusta has more caffeine per bean (according to our article, about twice the caffeine) but has a less desirable flavor profile. So, you'd of course first have to know WHICH coffee bean you are working with. --Jayron32 04:42, 10 March 2010 (UTC)

Convert to mhtml

Moved to WP:RD/C.

Black is black?

Black is black because it reflects nothing - right? So how come I can see a sheen of reflected light from some black painted objects? —Preceding unsigned comment added by 79.76.188.14 (talk) 21:12, 9 March 2010 (UTC)

Because it's not quite black. — DanielLC 21:26, 9 March 2010 (UTC)

See the article on Specular reflection. It is quite difficult to get a truly black non-reflective surface but a school's black Chalkboard is close. If you paint it with a transparent shiny varnish it becomes shiny black which is still 'black' but specular reflections. Cuddlyable3 (talk) 21:30, 9 March 2010 (UTC)

Black is black because of a low level of diffuse reflection, not because of a low level of specular reflection -- in other words, it's quite possible to be shiny and still be black. The level is never zero, though, it's just a matter of degree. Most things that we call black emit more light if placed in bright sunlight than a white object will if placed in a dim room, in fact. Looie496 (talk) 21:43, 9 March 2010 (UTC)

Above are good answers. Also consider that black is sometimes used in a relative sense. "Black" on your computer monitor is where no energy is intentionally spent illuminating it. It's still not black, but rather "as dark as it gets". 03:35, 10 March 2010 (UTC)

When we talk about "color" we're using a very minimal short-hand for the complexity of what's really going on. Humans generally use "color" to talk about the light that is scattered off more or less equally in all directions from the surface ("diffuse" or "lambertian" reflection). We do that because for most materials, the light that's "specularly" reflected (like a mirror - angle of incidence equals angle of reflection...roughly) takes on the color of the light source and has more or less nothing much to do with properties of the object. Shine a red light onto a shiney black surface and the specular reflections are red - shine a green light on it and it reflects green. But diffuse reflection is modified by the spectral characteristics of the material. The properties of the material are evident in the diffusely reflected light - but not so much so in the specularly reflected light. So if you want to talk about the nature of the object and not the nature of the light source - then you have to talk about the diffuse reflectivity - which is what we (mostly) do. Hence, there are 'flat' black objects and shiny black objects and really good mirrors that are also technically "black" because they don't scatter light in a lambertian manner at all. Our failure to have a consistent name for the color of a mirror (most people say "silver"...which isn't a color at all!) is a measure of the incompleteness of the way we name things. Materials like polished copper that specularly reflect in unusual ways almost defy description - we say "coppery" which really is a failure of linguistics! SteveBaker (talk) 04:06, 10 March 2010 (UTC)

Los Bravos discussed "black is black" in 1967. Edison (talk) 17:50, 10 March 2010 (UTC)

magnetic field

How strong of a magnetic field would be needed to rip the iron out of a human's blood a'la X men 2? Googlemeister (talk) 21:32, 9 March 2010 (UTC)

If it can be done at all (and I'm rather skeptical), it would take a stronger field than humans have ever been able to generate. Iron in blood is paramagnetic (weakly) and not ferromagnetic like bulk iron. Dragons flight (talk) 22:35, 9 March 2010 (UTC)

A magnetar's magnetic field would be able to kill at 1000km by tearing water out of tissues. No idea if that's the first thing that the magnetism would do to kill you, though. Paul Stansifer 05:57, 10 March 2010 (UTC)

Frogs start flying due to diamagnetic effects well before the iron is ripped out of their blood. http://en.wikipedia.org/wiki/Diamagnetism#Diamagnetic_levitation . 157.193.173.205 (talk) 08:13, 10 March 2010 (UTC)

I should point out that in X-men 2, Magneto isn't ripping out hemoglobin. Mystique injected some sort of liquid metal, presumably ferrous, into the guard's body. So removing it from his body should require a far less powerful magnetic field than that required to affect hemoglobin; an MRI is capable of pulling ferromagnetic metal implants from your body. —ShadowRanger ^(talk|stalk) 21:15, 10 March 2010 (UTC)

Reaction type

What type of reaction is 2Na₂O₂ + 2H₂O -> 4NaOH + O₂ ? --70.250.214.164 (talk) 21:34, 9 March 2010 (UTC)

I believe that would be a displacement reaction. --The High Fin Sperm Whale 22:18, 9 March 2010 (UTC)

(Edit conflict with below) Or more generally, an Oxidation-Reduction reaction. The oxygen in the sodium peroxide has an oxidation state of -1. Some of it is oxidized to the 0 state in O₂, while some of it is reduced to a -2 state in the hydroxide. I'm not sure I'd call this a displacement reaction at all, really. Buddy431 (talk) 22:48, 9 March 2010 (UTC)

Lorentz dilation?

Suppose a rod is moving at a speed v relative to an observer, with the rod oriented towards the direction of motion. In the observer's reference frame, the length of the rod can be determined by measuring the time Δt it takes for the rod to pass the observer. Then, L=vΔt. In the rod's reference frame, the time it takes for the observer to pass the rod, Δt₀, can also be measured. Likewise, the length of the rod can be calculated by L₀=vΔt₀. We then have L₀/Δt₀=L/Δt. Substituting Δt=γΔt₀, we arrive at the equation L=γL₀. However, it should be L=(1/γ)L₀. What have I done wrong? 173.179.59.66 (talk) 21:41, 9 March 2010 (UTC)

Wait, I think I got it: It should be Δt₀=γΔt, right? 173.179.59.66 (talk) 22:17, 9 March 2010 (UTC)

Yes, right. It is Δt₀=γΔt. Dauto (talk) 03:50, 10 March 2010 (UTC)

When you write L=γL₀, it means that Δt₀=0, which means that you are considering two measurement events occuring at the same time in the (x₀,t₀) system, which means that the rod is moving in that system, which means that it is at rest in the (x,t) system, which is not the case.

So you should have L₀=γL (and thus L=(1/γ)L₀), with Δt=0, so the rod is indeed moving in the (x,t) system.

Now you take this equation Δt=γΔt0. This is valid for two measurement events satisfying Δx₀=0, i.o.w. occuring at the same place in the (x₀,t₀) system, but you said that the rod is passing the (x,t) observer. That means that you need two events satisfying Δx=0, for which the transformation indeed produces Δt₀=γΔt. DVdm (talk) 22:52, 9 March 2010 (UTC)

Nomogram construction

I have a nomogram of height & weight = body area. The scales are arranged in three vertical columns, the idea being that one takes the known value of height on the far left, aligns a straight edge to the weight on the far right, and the central point on the straight edge is the surface area on the central column.

What I am trying to do is rearrange the whole nomogram to a different layout - ideally a circular one, something with turning discs maybe, but I'm damned if I can come up with a way of working it and I've about decided that it's impossible. But I'd thought I'd ask you clever chaps...? FreeMorpheme (talk) 22:25, 9 March 2010 (UTC)

I'm not sure I get what you mean by a circular layout, but it seems like you basically want something like a circular slide rule -- since area equals length times width, you need a mechanical way of doing multiplication; a slide rule does that by adding logarithms. Looie496 (talk) 23:40, 9 March 2010 (UTC)

What equation are you using to relate height & weight to body area? SteveBaker (talk) 03:34, 10 March 2010 (UTC)

The equation is square root of (height x weight / 3600). I need to print this out and I would prefer to make some arrangement of discs, but I don't see a way unless the actual discs are geared, which is a bit much for cardboard 195.60.13.52 (talk) 15:36, 10 March 2010 (UTC)

In my original answer I somehow misread "weight" as "width", but even so, with the formula you are using, this is easy to do with a circular (or linear) slide rule -- they handle multiplication and square roots quite easily. Looie496 (talk) 17:10, 10 March 2010 (UTC)

I do not think you could do it with rotating discs of carboard, as the rotation of two of them would not determine the position of the third scale. But you could just have an ordinary graph with axis of height and weight, and the area being readable at their coordinates. With "contour lines" delineating the diferent areas, it could be interesting to look at. 78.151.126.97 (talk) 17:20, 10 March 2010 (UTC)

You can make a dense grid of 'body area' numbers indexed by height and weight and print it in concentric circles on a disk. You'd effectively be using polar coordinates such that the distance from the center of the disk is "height" and the angle around the circle is "weight" (or you could do it the other way around). Print the weights around the circumference of the disk. Now you need a second, rotating disk on top of that with a pointer on the outside and a radial slot cut into it. You'd rotate the disk until the pointer pointed to your weight - then look at a "height" scale printed next to the slot - and read out the number that's showing through the slot next to your height. This approach works for any function of two parameters. However, the precision of the result depends on how small you can print. But since the equation you're using to calculate body area is horrifically approximate anyway - this hardly matters.

If you want, you could use a third disk with a spiral slot cut into it and rotate that to select the appropriate number from the first disk by looking through the "window" formed by the intersection of the slots in the second and third disks. SteveBaker (talk) 14:06, 11 March 2010 (UTC)

Properties of metals

I noticed that, although many metals have useful properties, they are balanced out by severe disadvantages. For example, iron is extremely strong, but it corrodes easily and falls apart, lead is malleable, ductile, and corrosion-resistant, but highly toxic, etc. Why is it that every metal with any practical use is "balanced out" by having some significant flaw? --70.250.214.164 (talk) 22:49, 9 March 2010 (UTC)

What about Stainless steel or titanium or aluminium? —Preceding unsigned comment added by 79.76.188.14 (talk) 23:02, 9 March 2010 (UTC)

Everything in the universe can be described as having some good characteristics but lacking others. You are asking about an aspect of how our brains categorize things, not properties of metals. alteripse (talk) 23:08, 9 March 2010 (UTC)

But there's no pure metal which has good properties with no significant disadvantages. --70.250.214.164 (talk) 23:19, 9 March 2010 (UTC)

I think that's partially because alloys are, chemically, a significantly different thing than pure metals (on the other hand, aluminum and titanium are pure metals, as mentioned above, and they have few undesirable properties). And, in the other direction, plenty of materials are useless; you just don't hear about them because they're not useful. Paul Stansifer 04:31, 10 March 2010 (UTC)

God set it up that way in order to fool us into believing that He doesn't exist. Looie496 (talk) 23:35, 9 March 2010 (UTC)

Did you actually look up titanium? I cant find any disadvantages--79.76.188.14 (talk) 00:08, 10 March 2010 (UTC)

When powdered or shaved, titanium has a high chance of burning or exploding. --70.250.214.164 (talk) 00:13, 10 March 2010 (UTC)

So do most things —Preceding unsigned comment added by 79.76.188.14 (talk) 01:16, 10 March 2010 (UTC)

I think we can vindicate 70.250's view by acknowledging that many metals make useless insulators. --Tagishsimon (talk) 01:36, 10 March 2010 (UTC)

They're also pretty useless as thirst-quenchers. –RHolton≡– 19:07, 10 March 2010 (UTC)

I bet they are really great thirst quenchers! If a thirsty man were to drink 8 oz of molten lead, I bet he would no longer be thinking about thirst. Googlemeister (talk) 20:21, 10 March 2010 (UTC)

But he could still use a good quenching. -- Coneslayer (talk) 13:41, 11 March 2010 (UTC)

Expanding on comment by Alteripse: It's people that put an assessment on metals, they aren't good or bad, except in context. Gold is a great conductor. But in some situations, one does not *want* conductivity. Get one of the several hundred page books on materials, if your mind is wandering this direction. It's rather fascinating all the qualities metals have. Cheers, Piano non troppo (talk) 03:32, 10 March 2010 (UTC)

Indeed: gold and lead are malleable and ductile but not very hard. Their malleability and ductility (and general workability) are related to their softness. Being malleable and ductile is good if you want to make wire or jewellery but less good if you want to make cranes and bridges. Similarly, titanium has a very high melting point which is good if you want to use it at high temperature, but makes it hard to smelt, melt, and work with. Magnesium corrodes and is likely to catch fire, but that means you can use it for flares and in fireworks which is good. Lead is very heavy which is what you want for fishing weights and perhaps for roofing but rubbish for airplanes. --Normansmithy (talk) 13:21, 10 March 2010 (UTC)