Wikipedia:Reference desk/Archives/Science/2010 May 29

= May 29 =

Sun Distance
How much closer would the sun have to be before we'd all die? I will also accept the scenario where we have to stay inside specially built igloo houses, for fear of death in the outside world.74.104.107.137 (talk) 02:24, 29 May 2010 (UTC)
 * Half the present distance would be fatal for sure, as all the water would evaporate and we'd all die from thirst. FWiW 67.170.215.166 (talk) 02:41, 29 May 2010 (UTC)
 * Habitable zone has a table showing what various scientists think is the closest safe distance (0.75-0.96 astronomical units). Note that this does not apply to Chuck Norris. Clarityfiend (talk) 04:09, 29 May 2010 (UTC)


 * If we're considering "specially built igloo houses" (ie technologically sophisticated living quarters) then we could survive much closer to the sun. We could imagine solar-powered refrigeration units keeping us cool - perhaps in some underground situation.  With such technology, we could live much closer to the sun than halfway.  Also, consider some place like Mercury: The sunny side gets up to about 500C and would be utterly unlivable - even with high tech habitation.  But the 'dark side' is at -170C - which is way too cold.  Someplace between those two extremes, there ought to be a place on the boundary between the sunlit and dark sides of the planet where there would be perpetual twilight and we could live - albeit with some fancy technology.  Since Mercury is the closest body to the sun, that is the limit.  Of course if we're talking about stars in general - then I'm sure there are other stars with planets even closer in than Mercury that could sustain sufficiently high-tech humans.  Another problem with living close to a star would be radiation - but again, if you have an entire planet between you and the star, you'll be reasonably well protected. SteveBaker (talk) 17:59, 29 May 2010 (UTC)
 * Mercury doesn't have twilight. You need an atmosphere for that. Twilight is defined as the time between sunset and it getting dark (for a given definition of dark, which depends on what you are doing). If there is no atmosphere, then it will get completely dark as soon as the sun sets (well, a mountain just on the other side of the terminator might reflect some light, I suppose, but it's unlikely to be enough to be considered twilight). A habitable ring near the terminator of a tidally locked planet (you seem to be assuming a tidally locked planet) is a feature of sci-fi and could happen, but it requires an atmosphere to moderate the temperature gradients. --Tango (talk) 20:54, 29 May 2010 (UTC)


 * That's true. But without an atmosphere, you're obviously not going to be wandering around on the surface without a lot of technology.  Assuming you're living in a well-engineered habitat, the important thing is that you're able to control the temperature cheaply and easily.  If you live close to the terminator - you could run pipes with water or some other liquid flowing through them out onto the sunny side and the dark side of a small hill - and by controlling the flow rates get water at any desired temperature.  The other nice thing about a tidally locked planet is that you can erect solar panels that are at the perfect angle to collect sunlight without having to make them turn to face the sun - and you don't need backup batteries because there is never any cloud cover and it's never nighttime.  With a perpetual/limitless 600 degC temperature differential, you could also use steam engines to generate power.  With ample electricity and no problems with heating or refrigeration, it's actually not such a terrible place to set up home.  But if you are close to the terminator, any object with even a modest albedo that's sticking up into the sunlight would provide ample illumination into the areas in shadow.  But given the level of radiation coming from the sun and a planet with no magnetic field to deflect it - you're not going to be going out onto the surface anywhere near the terminator! SteveBaker (talk) 23:45, 29 May 2010 (UTC)
 * One problem with a tidally locked planet that has an atmosphere, though, is that the temperature gradient would create hurricane-force winds that would blow you away before you could say "convection". Looks like Tango completely forgot about that :-) 67.170.215.166 (talk) 02:53, 30 May 2010 (UTC)


 * On second thoughts, you don't need an atmosphere to moderate the temperatures - the ground will do that. You just have a build your settlement underground. The surface will have a sudden 600 degree temperature jump, but the temperature a few metres underground will be gradual. I'm starting to like your idea! A venue for Wikimania 2100, perhaps? --Tango (talk) 23:56, 29 May 2010 (UTC)


 * Sponsored by Google ? ( how already have plans for a Martian Data center allegedly) XD Sfan00 IMG (talk) 13:39, 2 June 2010 (UTC)


 * The greenhouse effect of a planet will play a major role in whether it is habitable. See also Goldilocks planet. ~ A H  1 (TCU) 18:25, 30 May 2010 (UTC)

Maximum/Minimum Irradiance for "Human habitable" planet temperatures?
(Third time's a charm)

I keep trying to create a simple model for anyone who wants to speculate on a planet having habitable temperatures for people (not extremophiles) based on Irradiance.

Take for example HD 38801 b:

Star Radius = 2.53 sol

Star Te = 5222 K

Stefan–Boltzmann constant, σ = 5.67051E-8

Semi-major axis = d, in this case 1.7

Eccentricity = e, in this case 0

Emissivity = ε, (Earth=0.62009)

Albedo = A, (Earth=0.3)

=((((R^2)*σ*(Te^4)*(1-A))/(4*ε*(d±(d*e))^2))^0.25)-273.15

So I can get a global annual average temperature for a planet,

If I assume a global average albedo and a global average emissivity

Ignoring the perspective that single value Albedo and Emissivity are very

simplistic, since "Global Annual Average Temperature" is also but it exists:

A) at what levels of irradiance (max/min) does this become moot?

B) what combinations of Albedo & Emissivity are unrealistic or possible??

Thanks, 24.78.167.139 (talk) 06:35, 29 May 2010 (UTC)


 * Have you had a look at Atmosphere of Venus. Venus reflects two thirds of the light and yet its surface temperature is higher than that of Mercury. Even so there is a zone high up in its atmosphere which just might be okay for microbes. Dmcq (talk) 09:03, 29 May 2010 (UTC)
 * I was very clear that I was talking about people. The GAAT (14°C) is a surface temperature.24.78.167.139 (talk) 17:20, 30 May 2010 (UTC)

I came upon this chart in a search and realized this illustrates well the idea that there are a lot of possibilities but some are unrealistic. - 24.78.167.139 (talk) 17:36, 30 May 2010 (UTC)

Mercury battery illegal?
Are mercury batteries outlawed in the United States? Thank you. --Chemicalinterest (talk) 14:19, 29 May 2010 (UTC)


 * See Mercury-Containing and Rechargeable Battery Management Act. Gandalf61 (talk) 15:48, 29 May 2010 (UTC)


 * So the button cell I have must be a silver oxide or manganese dioxide cell with a tiny bit of mercury added to it. I was wondering if I could open it up and dissolve the mercury(II) oxide. But there isn't enough. --Chemicalinterest (talk) 16:26, 29 May 2010 (UTC)

If I might intercept the question - aren't those flashing LED shoes that kids used to wear back in the early 1990s using a liquid Hg amalgam to complete the circuit? Are those banned too? SamuelRiv (talk) 17:10, 29 May 2010 (UTC)

Cinnabar and Mercury switches also contain mercury.--Stone (talk) 17:35, 29 May 2010 (UTC)


 * Yeah that's what I meant. Now that I know the name of the switch, I have some good results: A thorough New York Times review, and a general mercury-containing-novelty-products page. The shoes were in fact banned in Minnesota, the company got Minnesota to pay for the shoes' recycling and then switched to a spring-trigger "inertia switch". Neat stuff. SamuelRiv (talk) 18:12, 29 May 2010 (UTC)


 * Yes my small brother used to have them and they had a spring trigger switch with a lithium primary cell in them. --Chemicalinterest (talk) 18:39, 29 May 2010 (UTC)

For my understanding the chemistry of mercury is interesting, but to use mercury cells as a source for experiments is not very good. Working with mercury is unpleasant and I would only do it in a lab with a fume hood. The chemistry of manganese and vanadium is similar interesting and both metals are by far less toxic!--Stone (talk) 22:04, 29 May 2010 (UTC)
 * How about zinc - excluding the absense of a +1 oxidation state much of the chemistry is 'similar' to mercury, it's not particularly toxic, and readily available. Yes I know zinc is boring - but it's not what you've got it's what you do with it...83.100.138.38 (talk) 14:15, 30 May 2010 (UTC)
 * Oh well so much for Hg. There isn't enough in one button cell anyway. --Chemicalinterest (talk) 23:17, 29 May 2010 (UTC)


 * I have an old mercury dial thermostat, if you really need some mercury..... Not sure it's safe to mail it though. Maybe offer to replace thermostats for people for free? But please do be careful. Ariel. (talk) 02:34, 30 May 2010 (UTC)
 * It's illegal to send mercury (or anything that contains mercury) by mail -- the reason is because mercury dissolves aluminum (including Boeings and Airbuses, and DC-3's too) -- so if the stuff leaks out, it could cause a nasty crash. Clear skies to you 67.170.215.166 (talk) 02:58, 30 May 2010 (UTC)
 * No I didn't ask for Hg metal, asked for HgO or mercury(II) compounds. Forget about Hg; NH2Cl and Cl2 are enough toxicity, not to mention Cr6+. --Chemicalinterest (talk) 19:43, 30 May 2010 (UTC)

Does Dracula exists?
Does Dracula exists? —Preceding unsigned comment added by 110.36.3.127 (talk) 17:26, 29 May 2010 (UTC)
 * He doesn't exist anymore. He died in 1476.


 * I should explain some more! The famous fictional vampire is said to have been very loosely based on (and named after) the exceedingly nasty Vlad III the Impaler - who was arguably a much nastier person than the fictional Dracula.  The name "Count Dracula" is attributed to this guy - because: "His Romanian surname Dracula (also spelled "Draculea", "Drakulya"), by which Vlad was referred to in several documents, means "Son of the dragon" and points to his father, Vlad Dracul, who received that moniker from his subjects because he had joined the Order of the Dragon. Dracul, from the Latin word Draco, meaning "dragon", is derived from the Greek word Δράκων (Dracon), though in modern Romanian it means "devil".".  He was a Prince of Wallachia - not a "Count".


 * However, the whole vampire/undead thing and everything that goes along with it is purest fiction. SteveBaker (talk) 17:41, 29 May 2010 (UTC)


 * Of course, we must never forget that bloodsuckers still lurk among us. Like legends of yore, they will rise again. But seriously, the Vampire article is terrific, and the Vampire lifestyle briefly discusses and links to this unique teen subculture, though without a "Dracula"-like leadership. SamuelRiv (talk) 18:16, 29 May 2010 (UTC)


 * By the way, he has not much to do with Transylvania, which was then part of the Kingdom of Hungary. He was the ruler of Wallachia (a country roughly corresponding to today's Southern Romania), maybe the name "Transylvania" sounded more spooky to Bram Stoker and chose that instead. --131.188.3.20 (talk) 21:36, 29 May 2010 (UTC)


 * Notice that Transylvania is a real place, though, even if Vlad is from just South of there. (The word means "across the woods", and Vlad was just across the woods from there.)  Also note that vampire bats are real, and really do suck blood from the living, although humans are only rarely their target, and they are in the Americas, not anywhere near Romania. StuRat (talk) 01:38, 30 May 2010 (UTC)
 * There are much nastier vampires that actually prefer to suck human blood, though... 67.170.215.166 (talk) 03:03, 30 May 2010 (UTC)
 * Both mosquitoes and vampire bats  are attracted to people's feet, rather than their necks. Feet are easily located by smell, and aren't so sensitive. 81.131.17.60 (talk) 04:53, 30 May 2010 (UTC)
 * The Transylvania bit might come from a confusion with Elizabeth Báthory, another really nasty figure, whose father was a voivod of Transylvania. — Kpalion(talk) 16:38, 31 May 2010 (UTC)
 * Or maybe just cause the name sounds mysterious and kinda creepy. :-) 67.170.215.166 (talk) 05:20, 1 June 2010 (UTC)
 * Yeah, kinda like Pennsylvania. Much better than Siebenbürgen or Erdély in any case.

oral rehydration solution (ORS)
how can i get free oral rehydration solution (ORS) from WHO or UNICEF —Preceding unsigned comment added by Tom12350 (talk • contribs) 19:25, 29 May 2010 (UTC)
 * Sinebot didn't get the questioner, so I manually signed for them. Buddy431 (talk) 20:43, 29 May 2010 (UTC)
 * I wonder if all that reckless speeding on city streets at three in the morning left him critically dehydrated? ;-) 67.170.215.166 (talk) 04:58, 30 May 2010 (UTC)
 * I don't think the WHO or UNICEF manufacture them directly. Rather, they publish standards, and encourage individual nations to produce and distribute the solutions .  I don't know where you are, so I can't really help hook you up with free packets (if free packets are even available in your area).  Here's the WHO's recipe, if you wanted, you could make your own: .  Otherwise, there appear to be a number of commercial sellers online if you're not able to get free packets.  For more information on oral rehydration in general, see our article Oral rehydration therapy.  If you gave us more information on where you are, and what you need it for, we can probably help you better. Buddy431 (talk) 20:32, 29 May 2010 (UTC)
 * If you are in a disaster area, then aid agencies or the national authorities drop free ORS from planes and helicopters and set up distribution centres where you can queue for the stuff. If you aren't in a disaster area, then you might be able to get it free from health clinics, etc., but you probably have to buy it or make it yourself. --Tango (talk) 21:00, 29 May 2010 (UTC)

im in the usa can i get it?
 * Echoing Tango, I'd check any local health clinics. It seems doubtful to me that you'd be able to get it free in the US, but I don't really know.  You can also probably buy some at a local drug store (though it may be marketed specifically for infants, i.e. Pedialyte).  Sports drinks, such as Gatorade, are pretty good for this sort of thing as well (you won't get it free, but the prices aren't outrageous).  You can also make a pretty good substitute with just sugar and salt (13 g sugar, 3 g salt per liter of water, as per the WHO composition) (though having the potassium and citrate are of course preferable).  The question is, what's it for?  If you or your kid has diarrhea, you may want to talk to a doctor or other medical professional anyway.  They may be able to suggest the best solution. Buddy431 (talk) 22:40, 29 May 2010 (UTC)
 * I would be very surprised if you can't buy it in US drug stores. You certainly can in the UK (I think there are different versions for adults and children). --Tango (talk) 23:32, 29 May 2010 (UTC)
 * Yes and it tastes revolting! I'd much prefer to get a glass of diluted Ribena, add a pinch of salt, and drink it in one! --TammyMoet (talk) 07:30, 30 May 2010 (UTC)
 * If it tastes revolting, you don't need it. When you are dehydrated you lose the ability to taste salt and suddenly ORS starts to taste nice! I don't think there is enough sugar in Ribena for that recipe to match the WHO recipe - you need to add some extra sugar too. Otherwise, I can't see a problem with adding flavouring like Ribena to ORS. --Tango (talk) 15:01, 30 May 2010 (UTC)

what stores sell it? iv looked all over in the usa and cant find it —Preceding unsigned comment added by Tom12350 (talk • contribs) 22:48, 30 May 2010 (UTC)
 * Does that mean you've gone into local health clinics and local drug stores as suggested above, and asked? Did they not offer suggestions of where you might be able to get it? It also occured to me from the above posts that you may want to try some sort of travel/adventure/outdoor oriented store (a bit like Kathmandu (company) here in NZ). I presume if you've looked all over the USA you've already looked in places like Walmart. Nil Einne (talk) 09:11, 31 May 2010 (UTC)
 * Drug stores. --Tango (talk) 16:40, 31 May 2010 (UTC)

Crystal meth & the addicts body


I hope you can help me as I have had no luck in finding the answer to this question. If someone is addicted to & using crystal meth almost daily, can the meth get stored in fat cells, then later be released into the system when increased physical activity burns off fat? My son has been through rehab & swears he isn't useing and his moods & attitudes would seem to back up his words,  however, he recently started work with a landscaping company & it is very hard work. Suddenly his weekly UA tests are reading positive & he is steadfastly denying that he is useing again. Thanks for any possible help71.34.135.9 (talk) 20:41, 29 May 2010 (UTC)
 * That can certainly happen with some drugs and toxins. I have no idea about meth. --Tango (talk) 21:03, 29 May 2010 (UTC)
 * This happens with THC from cannabis and various other hallucinogens, so it wouldn't surprise me. Can't find a specific citation though. Regards, --— Cyclonenim | Chat 21:13, 29 May 2010 (UTC)
 * The Methamphetamine article says it's fat soluble, so it makes sense that it could happen. Ariel. (talk) 02:38, 30 May 2010 (UTC)


 * Gosh, best of luck to you and your son. I hope you can find a doctor to defend this concept, because coming off of something like that is so utterly important and it would be terrible if he lost his job and perhaps sink into a vulnerable state (especially since construction is great work). SamuelRiv (talk) 18:43, 30 May 2010 (UTC)

Salty Q
It's good to eat salt tablets when in the desert yet bad to drink saltwater when in a lifeboat. Why the diff ? StuRat (talk) 21:49, 29 May 2010 (UTC)
 * See Saline (medicine). Cuddlyable3 (talk) 22:16, 29 May 2010 (UTC)
 * See Seawater. Too much salt in the seawater (you need some salt to replace what you lose in sweat, but it must be accompanied a sufficient quantity of fresh water). Buddy431 (talk) 22:29, 29 May 2010 (UTC)
 * Precisely. Seawater is just too salty. You can drink it as a source of salt, but only if you drink enough fresh water with it (or, preferably, dilute it with fresh water). Likewise, you shouldn't eat salt tablets in the desert unless you have plenty of water with them. --Tango (talk) 23:14, 29 May 2010 (UTC)