Wikipedia:Reference desk/Archives/Science/2008 April 6

= April 6 =

How to make a flaming drink
I am in a play "The Farmer's Daughter." In the show, a girl makes a drink called Glug. Before giving it to me she pulls a fireplace poker out of the fireplace, and puts it in the drink.

In the movie, the drink flames and goes out. That would be a pretty neat trick. Does anyone know how we could pull this off? Keep in mind there is no fire in the stage fireplace and I have to be able to drink this beverage.

If you'd like to see the flaming drink in the movie trailer, it shown on the bottom of the page I have for the show.

http://wonderley.com/shows/2008/FarmersDaughter

--Wonderley (talk) 01:48, 6 April 2008 (UTC)


 * For the drink, water with a little bit of pure (or 80%) ethyl alcohol very carefully poured on top might do it. If the alcohol is warmer, it might lie on top of the water for a while before mixing. To get the fire, hide an electric sparker in the tip of the poker and a trigger in the handle of the poker. Have a stagehand with fire extinguisher ready and waiting if you try this live or in rehearsal and make sure your costume isn't flammable. Franamax (talk) 02:09, 6 April 2008 (UTC)


 * Flaming liquids sound rather dangerous to me, both to the actors and the audience if it starts a general fire. Perhaps some type of lighter, set on high, hidden on the far side of the glass, could create enough of a flame without being so risky. StuRat (talk) 02:23, 6 April 2008 (UTC)


 * Flash paper in the glass and a burning incense or punk stick on the far side of the poker should do it. --hydnjo talk 03:01, 6 April 2008 (UTC)


 * Whatever you do, the key word here is safety, safety, safety. Applause happens once, burn scars are forever, fire deaths last longer. From the video clip (which we all assume you obtained copyright release for): watch the actress hand, her grip is curious; she dips deliberately into the cup as if to contact something, then pulls back a little, then removes the poker; the cup is opaque; the scene ends, as all movie scenes do. No way to tell what happened there, I'd guess a pilot light in the cup, she pushed a trigger to open the main gas line, then the key grip guy shut the gas off. Did the drinker actually drink anything? Did the cup get subbed in for the next take? There could be a whole lot missing where the entire set went up in flames. Safety, safety, safety. Franamax (talk) 07:26, 6 April 2008 (UTC)


 * Not wishing to pour water on your special effects but are your insurance company happy with this? Richard Avery (talk) 10:17, 6 April 2008 (UTC)

Any "high-proof" liquor will burn (because of the included ethanol). The problem is that the alcohol fire is practically invisible under the stage lights. You might find that doping the drink with table salt (sodium chloride) will produce visible flames. That's basically what I did once when a production needed two flaming brazier-style lights (although nobody was going to drink from the braziers so I used straight alcohol, probably (poisonous!) methanol). Today, though, I'd probably fake it with streamers, fans, and lights (for reasons of safety). Heck, if it only has to flame for a few seconds, you could probably design that same streamers/lights/fan mechanism into a cup and power it with NiCd batteries; LEDs can be very bright with very little power and a brushless DC computer fan draws almost no power either.

Atlant (talk) 15:41, 6 April 2008 (UTC) (revised 15:50, 7 April 2008 (UTC))


 * !!If you are going to drink it, DO NOT use methanol (or anything else with a skull on the bottle). Franamax (talk) 19:44, 6 April 2008 (UTC)

It should be clear by now that this was not an appropriate question for the Reference Desk: if you're going to have a fire on the stage, you'll need a professional stage effects person, and not advice from random people at Wikipedia. --Anonymous, 20:56 UTC, April 6, 2008.


 * Anonymous, if I got bad advice, I wouldn't use it. Flaming drinks and food are not uncommon.  I was just getting ideas that maybe I had not thought of for the drink and the ignition source.  Suggestions like adding table salt to make the flame more visible makes the stunt safer.  Not drinking beverages with a skull on the bottle's a pretty good idea too. ;-)  So, it seems pretty appropriate to me.  But thanks for your concern.


 * Franamax, I didn't exactly obtain a copyright release, but the trailer on the TCM web site has a "Embed this video on your site" button, so I assumed it was OK.--Wonderley (talk) 23:33, 6 April 2008 (UTC)
 * As far as I'm aware, 'embed this video on your site' usually refers to code which allows you to embed the hosted video on your website. It should not be taken as allowing you to redistribute the content by hosting it on your own website. You may very well be allowed to redistribute the trailer but the information at hand isn't enough to say you are Nil Einne (talk) 15:46, 7 April 2008 (UTC)


 * Yeah, Einne. "Embed this video on your site" usually refers to code which allows you to embed the hosted video on your website.  And, that's what I did. I don't know why you might even think otherwise.--Wonderley (talk) 18:58, 7 April 2008 (UTC)


 * I didn't actually check out your site, but was going from what I read by you and Franamax which made it sound like you thought it was okay to host video on your site because there was an 'embed this video' link on the original site. I apologise for any confusion Nil Einne (talk) 12:43, 8 April 2008 (UTC)

The wag in willy wagtail
The article wagtail doesn't explain the mechanics of the little bird's movement style. What makes it wag when it moves? Julia Rossi (talk) 03:16, 6 April 2008 (UTC)
 * It's voluntary, the way a dog wagging its tail is voluntary, though for a different purpose. kwami (talk) 03:35, 6 April 2008 (UTC)
 * Is it a space or warning thing? Like to make the little bird seem bigger to intruders? Julia Rossi (talk) 04:15, 6 April 2008 (UTC)
 * I don't know, but it seems to me that for the East African sp. it is some kind of communication. They do it with each other, and they do it when not on their home territory. kwami (talk) 04:43, 6 April 2008 (UTC)
 * Thank you Kwami, it makes sense - just that it's seems unusual for a bird to flutter and wag constantly, though it is low-key. And strange that the article doesn't comment on it's namesake feature. Julia Rossi (talk) 08:56, 6 April 2008 (UTC)
 * The reasons for the behaviour are actually slightly unclear although a recent study suggests that it signals vigilance to potential predators. I have updated the article and linked to the study. As for the article not having it before, well, there are lots of birds and I assure you WP:BIRD is flat out trying to improve them! Sabine's Sunbird  talk  02:38, 10 April 2008 (UTC)

mental capacity
Is there a test which rates mental capacity on the basis of reducing to minimum form a logical equation having a certain number variables and states? 71.100.173.69 (talk) 06:54, 6 April 2008 (UTC)


 * No. Tests for mental capacity are designed so that they can filter out something like "innate capabilities" from "learned abilities". In your example, a genius who has never taken algebra would probably rate as a dullard based on lack of experience with the formalities alone. --Captain Ref Desk (talk) 14:30, 6 April 2008 (UTC)


 * I'm talking about intuitive, rather than formal reduction. Did you go to school? 71.100.173.69 (talk) 17:01, 8 April 2008 (UTC) —Preceding unsigned comment added by 71.100.160.37 (talk)

Hair
What are the usual age ranges for men and women to begin a) getting grey hair? b) losing their hair? Thanks 92.5.114.92 (talk) 10:06, 6 April 2008 (UTC)
 * See a) Effects of aging on hair color and b) baldness D0762 (talk) 15:43, 6 April 2008 (UTC)

Where does the fat from skimmed milk and low-fat yogurt or cheese go?
There must be lots of it, how is it then used please? I cannot believe it is just dumped somewhere. Thanks 80.0.106.237 (talk) 19:41, 6 April 2008 (UTC)


 * cream, butter, ghee are all possible uses. Graeme Bartlett (talk) 21:21, 6 April 2008 (UTC)


 * The cream (fat) is actually more valuable than milk. Cream normally comes in smaller containers, but you might find some overlap, like a 1 quart container, so you can compare prices in the store.  You'll also notice that skim milk is often a bit cheaper than whole milk. StuRat (talk) 02:41, 7 April 2008 (UTC)


 * Ice cream! Many processed foods include some sort of fat; you don't see butterfat too often, partly because it is relatively expensive. The expense suggests to me that there is no great surplus of butterfat.  ike9898 (talk) 19:29, 7 April 2008 (UTC)

Future costs of photoelectric cells?
Will photoelectric cells become cheap enough to cover the walls and roof of my house with, or will the price always be high because they contain some rare element? 80.0.106.237 (talk) 19:44, 6 April 2008 (UTC)


 * They don't contain any 'rare' elements, per se... the silicon that is used in the majority of terrestrial solar panels can be found in sand. However, there are huge energy and cost barriers needed for processing pure silicon and making solar panels.  The energy cost takes about twelve years of average use to recoup.  As for cost, I estimated that it would take me ~30 years to recover the costs of installing solar panels on the roof of my house.  This may be different depending on where you live (I'm from Rhode Island... sun can be limited in the winter).  I know that in California they are topping a lot of department stores with panels to combat peak energy-use times (such as the summer).  I also think the technology is improving every day, so solar panel housing may not be far off! --138.29.50.28 (talk) 23:25, 6 April 2008 (UTC)


 * Energy returned on energy invested (EROEI) is poor only for monocrystalline and polycrystalline silicon solar cells.  For amorphous silicon or thin film solar cells EROEI looks much more promising. Keep a eye open - they are going to hit the mass market in the next few years.  Cambrasa  18:40, 11 April 2008 (UTC)


 * Current solar cells also suffer from the problem that they only use a small portion of sunlight's frequencies. We need solar cells that convert the entire optical range (and infrared and ultraviolet light) into electricity.  This will hopefully allow the energy used to produce them to be more quickly recouped. StuRat (talk) 02:45, 7 April 2008 (UTC)


 * A search using "production doubles price photovoltaic" gives opinions that when the production of solar cells doubles, cost drops 18-30%. The source I listen to uses 20-30%.Polypipe Wrangler (talk) 10:21, 7 April 2008 (UTC)


 * When I did a research project on silicon solar cells, I remember reading somewhere that they have followed Moore's Law just like CPUs for the last 30 years, except that the time it takes to halve the price per unit of power generation is much longer - namely 8 years instead of 18 months. I think yes, solar cells will probably one day be cheap enough to compete with electricity generated from power plants. But it might take another couple of decades.


 * The rare element issue isn't always the bottleneck - exotic elements used as dopants and transparent conductors are only needed in tiny quantities. And even non-silicon cells such as CdTe cells can be easily recycled.  Cambrasa  18:46, 11 April 2008 (UTC)

How small can computers get in the future?
I've decided to ask this here rather on the Computing Desk as it is more about physics than software. Soon, I hope, computers will be able to use human speech as their input and output, doing away with keyboards and screens for some applications. Will it then ever be possible to have computers, with the equivalent power of a laptop, that are small enough to fit on a keyring? And how small could the talking thinking computers of SF films be in actuality in the future? I'm thinking about the limits to the smallness of microchips, and would quantum computing be smaller? Thanks 80.0.106.237 (talk) 20:02, 6 April 2008 (UTC)

-Arch dude (talk) 22:28, 6 April 2008 (UTC)
 * We can already make a computer that is as capable as a laptop but that will fit on a keyring. (cell phone)
 * We have had competent speech recognition on home computers for fifteen years
 * We have had speech output for longer that that
 * The theoretical limit on information storage is the Bekenstein bound. We are many orders of magnitude away from it
 * The "practical limit" of achievable size reduction and speed increase is ten years in the future, or appoximately a 32-fold improvement from our existing capability. This has been true since 1950. In 1950, the limit was to be reached in 1960. In 2008 the limit is to be reached in 2018.... See technological singularity.


 * I have to disagree on us having had competent speech recognition for 15 years. I would define "competent" as being as good as the average human.  I don't know of any speech recognition software that can understand a 100,000 word vocabulary, in a nosiy room, without first being trained to an indivual's voice.  When they can do that, I'll call them competent. StuRat (talk) 02:36, 7 April 2008 (UTC)


 * I think I'll stay with the keyboard regardless. It's a faster way to input (when you know how to type) than speech, and nobody has to know what I'm doing. And it's bad enough that people blab on and on to their cell phones in coffee shops—imagine if they were all blabbing to their computers (and their computers blabbed back)!
 * In any case, note that you don't necessarily need to miniaturize everything. If you came up with fast, secure, and cheap wireless interfaces, you could have a tiny thing in your ear that just interfaced with the central computer. It becomes a communications issue, not a processing one. This is featured in many SF movies and books, too (the second book of the Ender's Game series comes to mind). --Captain Ref Desk (talk) 23:53, 6 April 2008 (UTC)
 * I agree, the noise pollution is bad enough without banality pollution as well. Julia Rossi (talk) 01:22, 7 April 2008 (UTC)


 * Computers will get smaller, faster, and more capable as they become more refined to specific purposes. Similar to object-oriented software design, computers will begin to take on specific tasks while communicating with one another.  Why have a clock in your cell phone when your watch does that job just as well?  Why have a camera lens in your phone when it can be in your glasses, already pointed at what you want to photograph?  Why have a phone in your pocket and a earbud on your ear when the earbud can handle all the call-placing tasks itself?  In the future, we'll wear a network of mini-computers without thinking of them as anything more than helpful gadgets.  The idea of a computer that does a million different tasks will be abandoned for the average person.  In fact, many people don't like them already. --  k a i n a w &trade; 01:45, 7 April 2008 (UTC)


 * Have you read our article on Moore's Law, and its section on the limits? You're right to think about limits in the size of semiconductor microchips. At a lecture I attended on quantum computing, it was suggested that technology is approaching the size where quantum tunnelling of electrons will become an issue. As for quantum computers, it's hard to say as no-one has come up with a way to do everything a computer needs to do. The first steps which are being taken are pretty big though, as they often need lots of vacuum and/or optical equipment. AlmostReadytoFly (talk) 08:54, 7 April 2008 (UTC)


 * You need to solve the battery-life problem first. Lithium ion batteries are good, I'll give you that, but you can't get fingertip-size batteries that can power laptops for 24 hours yet. 68.101.123.219 (talk) 03:18, 8 April 2008 (UTC)

Helium filled football
I am doing a science project about whether a helium filled football or an air filled football can be thrown further. Do you know how or where I can go to get helium inside of a football?70.18.162.125 (talk) 20:22, 6 April 2008 (UTC)CD


 * I'd start with party-supplies places. If they can inflate a balloon with helium, they may be willing and able to inflate a football.  I say "may be able" because I don't know if there will be problems connecting a football to the tank.


 * Some issues:
 * The gas used in party supplies may not be pure helium. It only has to be light enough to make a balloon rise, and diluting it with a heavier gas light nitrogen may make it cheaper.
 * Helium leaks out of things faster than air does, because the atoms are so small. So you'll want to take the football directly from the place where you get it filled to the place where you want to throw it.
 * I would expect the difference will be too small to be meaningful. (Even if so, that doesn't mean the project is a bad idea!  If you prove there's no significant difference, you've still proved something.)  A well-designed experiment would involve plenty of throws with each ball, and statistical analysis such as a chi-squared test to determine whether the differences are significant.
 * If the same person is throwing the ball several times, they will get tired, or they will first get more warmed up, and then get tired. So you don't want to do something like 5 throws with air followed by 5 with helium.  Use an alternating pattern or something like ((air, helium, helium, air), repeat as many times as desired).
 * For the same sort of reasons, if different people are throwing the ball, have half of them do air first and half do helium first.


 * Have fun. --Anonymous, breathing air, 21:11 UTC, April 6, 2008.


 * I would suggest that you will not notice the difference. The air in the ball will only weigh about a gram. Graeme Bartlett (talk) 21:25, 6 April 2008 (UTC)


 * I agree with the above comments, but also suggest that you not tell the person throwing the football which version he has, as that may affect his throw. StuRat (talk) 02:29, 7 April 2008 (UTC)


 * If you can find it online or on DVD, there was a Mythbusters episode (Episode 47: Helium Football) that dealt with helium-filled American footballs. A couple of websites cover the episode, like this one. &mdash; Scientizzle 02:35, 7 April 2008 (UTC)
 * Ahem, Wikipedia covers it too, at MythBusters (season 4). --Kjoonlee 13:10, 7 April 2008 (UTC)

Limb regeneration in Humans
Are there any documented cases of people regenerating limbs (or digits) that they've lost? I know that this is generally impossible, but my impression (IANAD) is that medically impossible things do happen sometimes, and our species certainly has a long history with amputation. 71.239.209.220 (talk) 20:36, 6 April 2008 (UTC)


 * Our article on Regeneration (biology) has some (imperfect) sections on regeration of human organs and fingertips, the only extremeties observed to regrow. It says what is basically true, that there is evidence children have the capacity to regrow lost fingertips, although there is more or less anecdotal evidence this can occur in adults as well . Someguy1221 (talk) 22:36, 6 April 2008 (UTC)

Homemade Water Filtration?
How can I filter blue food colouring out of water using a homemade filter? I do not have access to activiated charcoal. Are there other materials that are as effective at cleansing water? Thanks, Perfect Proposal  Speak Out!  21:22, 6 April 2008 (UTC)


 * Can you make charcoal by burning wood or toast. If so you can make activated charcoal.  Another way to do it is by fading.  Intense focussed sunlight will bleach your blue colour. I am assuming that your blue will not be easy to chemically alter to a clear substance.  Indigo can be reduced to white.  Some you can bleach with chlorine bleach. Graeme Bartlett (talk) 21:29, 6 April 2008 (UTC)


 * You could filter it through hundreds of coffee filters. I imagine each pass would remove a small amount of dye. StuRat (talk) 02:25, 7 April 2008 (UTC)
 * You might end up with a big pile of soggy blue paper and no liquid! Graeme Bartlett (talk). In the natural world water is purified by bacteria, and other living things consuming the organic matter.  Distillation will do a pretty good job too. 05:42, 7 April 2008 (UTC)
 * Some manner of solar still might be the easiest solution. It is a bit slow, however, so may be impractical if you've got large amount of blue water you need to process. There are ideas on that and a few other homemade filters in the Steampunks' Guide to the Apocalypse, I don't have a huge amount of faith in that source, but if you're just looking for ideas, it's worth a look. APL (talk) 14:13, 7 April 2008 (UTC)


 * In case you didn't know, it is really easy these days to get activated charcoal. Most pet stores will carry it in the fish section (used for treating aquarium tank water) - although I wouldn't recommend using it for food use. Alternatively, you can probably find some in camping/outdoor supply stores. However the easiest method is to just buy a Brita style water filtration cartridge from your local grocery store. Most of the drinking water filters use activated charcoal to remove impurities. -- 128.104.112.85 (talk) 20:24, 8 April 2008 (UTC)

If the challenge is to do it without activated charcoal, one strategy we use in the lab to soak up stains doing gel electrophoresis is to use a wadded-up tissue placed in the corner of a soaking tray. The tray is slowly rocked back and forth, and in an hour or so the tissue soaks up a considerable amount of the blue dye. Jeff Dahl (Talk • contribs) 23:24, 8 April 2008 (UTC)


 * That is indeed the case. I could do it with activiated charcoal, but I'm in the hypothetical situation where I can't access any. Thanks Perfect Proposal  Speak Out!  00:22, 9 April 2008 (UTC)

electromagnetics
A uniform surface charge density of 20nC/m2 is present on the spherical surface r=0.6 cm in free space. a) Find the absolute potential at P(r=1cm, θ=25°, φ=50°). b) Find VA-B (potential difference between point A and point B) given points A(r=2cm, θ=30°, φ=60°) and B(r=3cm, θ=45°, φ=90°). —Preceding unsigned comment added by Yabadapado (talk • contribs) 22:21, 6 April 2008 (UTC)


 * Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt to solve the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Thank you. Someguy1221 (talk) 22:30, 6 April 2008 (UTC)
 * One way to approach this is to work out capacitance of the sphere and then calculate the voltage on the surface for the chargd. There would be other more direct ways to work it out however. Graeme Bartlett (talk) 05:50, 7 April 2008 (UTC)
 * One way to approach this is to work out capacitance of the sphere and then calculate the voltage on the surface for the chargd. There would be other more direct ways to work it out however. Graeme Bartlett (talk) 05:50, 7 April 2008 (UTC)


 * I'd suggest you consider the symmetry of the problem and make use of Gauss' Law. There may be some superfluous information in the problem statement that could lead to confusion. ;-)  --Prestidigitator (talk) 18:31, 8 April 2008 (UTC)

Plants with not much light
Are there any indoor plants that do well in inner spaces without much light ? (like halls that are a bit dark and gloomy with no window). Thanks for any info. --AlexSuricata (talk) 22:42, 6 April 2008 (UTC)


 * Depends on the wavelength of the light mostly - This link might be helpful .  Wisdom89  ( T |undefined /  C ) 23:14, 6 April 2008 (UTC)
 * It's in the link above, but the Aspidistra was a universal parlour and hallway plant in the Victorian era and Edwardian times and possibly the Georgian era before, in very gloomy conditions like terrace housing, so tested, yep. Julia Rossi (talk) 01:13, 7 April 2008 (UTC)
 * Aspidistra still grows in dim places this century too! Graeme Bartlett (talk) 05:49, 7 April 2008 (UTC)


 * You might like to think about some ferns which tolerate low light levels. But bear in mind that even the good old aspidistra and ferns need a minimum level of light to survive healthily. Richard Avery (talk) 07:41, 7 April 2008 (UTC)


 * Ferns are probably not a good idea, because they need more humidity than is usually found in homes. Other good low-light house plants include philodendron (many types, trailing and bushy), spathiphyllum (peace lilies), aglaonema (Chinese evergreens), dracaena (many types), sansevieria (snake plant), polyscias, Kentia palm (Howea forsteriana), parlor palm (Chamaedorea elegans). I agree, however, that if there are no windows at all, you can't grow anything. I suggest that you buy at least two plants of the same type and then rotate them from dark to semi-dark locations. I would switch them around at least once a week, preferably every few days. That way you can have lush plants everywhere in your house. This is something I have done successfully for years.--Eriastrum (talk) 20:19, 8 April 2008 (UTC)

That's fantastic, thank you very much indeed! --AlexSuricata (talk) 12:52, 9 April 2008 (UTC)