Wikipedia:Reference desk/Archives/Science/2011 September 20

= September 20 =

Dynamics of hypercanes
There is a theory (hypothesis) that exists which states that water temperatures around or above 120°F would result in hypercanes, which would taller, faster, and more compact than normal hurricanes. Obviously at this point the dynamics of the hypercane would be different than that of a hurricane, but how would they be different (the plume of water vapor penetrates the stratosphere, different patterns of air currents form, etc.)? --Melab±1 &#9742; 02:22, 20 September 2011 (UTC)


 * The dynamics of ordinary hurricanes aren't understood well enough to simulate their interiors and eyewalls yet, so probably nobody can say. 208.54.38.175 (talk) 04:53, 20 September 2011 (UTC)


 * I don't think they would penetrate the stratosphere -- the tropopause is essentially a very strong inversion layer, and any weatherman knows how tough it is for air currents to penetrate those. FWiW 67.169.177.176 (talk) 04:59, 20 September 2011 (UTC)


 * Our article says "A hypercane's clouds would reach 30 km (19 mi) into the stratosphere". StuRat (talk) 05:09, 20 September 2011 (UTC)

Gallium arsenide
If taking the MO diagram into consideration, is it correct to say that for the monomer of gallium arsenide has a bond order of four, and that the resulting molecule is a zwitterion?

There is one sigma bonding orbital, and three degenerate pi bonding bonds, gallium only contributes by one third to the pi orbitals, not by half. As is my understanding, electrons are indistinguishable and there is no way to tell which electrons in the pi orbital associates with which atom. However, since a bond order of four means that gallium has an excess of electron density around it, and arsenic has a defficiancy around it. Meaning that, there is a unit charge of 1- on gallium and 1+ on arsenic. Note that the bond order is an integer, meaning that the charge difference must also be an integer. Plasmic Physics (talk) 02:36, 20 September 2011 (UTC)
 * Not sure where you get GaAs has a bond order of 4 via the MO diagram. It isn't an "expanded octet" molecule, so you should be able to work out an MO using just the valence level s and p orbitals, I get the resulting monomer to have the following MO configuration:


 * σ(4s) = 2
 * σ*(4s) = 2
 * σ(4p) = 2
 * π(4p) = 2
 * π*(4p) = 0
 * σ*(4p) = 0
 * That's 6 bonding electron, 2 antibonding electrons, and that give me a net of 4 electrons, or a bond order of 2. So Gallium Arsenide is predicted by M.O. theory to have a double bond, not a quadruple bond.  When I work out the formal charge on said molecule, I do get formal charge of -1 on the gallium and +1 on the arsenic, however.  The whole "quadruple bond" thing does exist, but not in compounds like this.  In this case, the only way a quadruple bond gets predicted is by "lewis theory" or valence bond theory; since you only have 8 valence electrons to play with, the only way to "complete the octet" is to have 4 shared pairs of electrons; but what you see here is an example of where lewis theory falls short compared to MO theory.  Actual quadruple bonds require participation of d-orbitals, and I don't see anywhere that this molecule would have d electrons which participate in the bonding.  Even if you involve the d-electrons from the nearest d-orbitals in an expanded MO diagram, all of the bonding and antibonding electrons from that contribution should cancel.  -- Jayron  32  17:06, 20 September 2011 (UTC)

Well, I'm looking at the valence MO diagram as given in a lecture slide. It gives the following configuration: In this diagram, there are no antibonding orbitals. Plasmic Physics (talk) 00:16, 21 September 2011 (UTC)
 * s2 (sigma)
 * px2 (sigma)
 * py2 (pi)
 * pz2 (pi)
 * s*0 (sigma*)

It shows that the sigma* is higher in energy than the p orbitals. Plasmic Physics (talk) 00:24, 21 September 2011 (UTC)


 * I'm not sure that make sense, unless there is significant overlap between the bonding energies of the s and p orbitals. In nearly all MO diagrams I know of, the order for the valence level MO has the sσ followed by the sσ* before any of the p-orbital contributions.  Some molecules have some difference between how the p-orbital MOs order (some go σ - π - π* - σ* and others go  π - σ - π* - σ* (see Molecular orbital diagram).  I am not ruling out the unusual MO diagram you show above, I suppose it is possible, just not an organization I have ever seen.  I would check with your professor after class, and ask them personally to explain the slide.  -- Jayron  32  00:29, 21 September 2011 (UTC)

The gallium arsenide MO diagram is used to describe the formation of exitons in semiconductors. It calls the two degenerate pi-type HOMOs, the valence band; and the antisigma-type LUMO, the conduction band. Plasmic Physics (talk) 00:57, 21 September 2011 (UTC)
 * Ah. If you are dealing with conduction/valence bands, you have steped outside of molecular bonding into the world of metallic bonding and Network covalent bonding.  See Electronic band structure for an overview.  Band theory has its own quirks and rules which may not directly corrolate to expectations of discrete molecules as described by standard MO theory, since they have different applications: MO theory is designed for discrete molecules, while band theory is designed for network and metallic solids.  There's probably ways to make the theories work together somewhat, but basically it's  "Different game, different rules".  So go with what your professor says.  My band theory is a little rusty.  -- Jayron  32  02:41, 21 September 2011 (UTC)

So, the MO diagram is not correct in this demostration? I'm confused. Plasmic Physics (talk) 03:57, 21 September 2011 (UTC)
 * No, let me reiterate what I said a few posts ago: it may very well be, but what you need to do is ask him personally to explain it to you to your satisfaction. The MO diagram you described is not one of the "standard" MO diagram orders I am used to (not that it is wrong, just not a standard order) and that may (or may not) be because we're dealing with a different type of bonding, since gallium arsenide is a network solid (and does not exist as discrete molecules, normally) then the band model may be more useful in understanding its electronic structure than the MO model (since MO deals with molecules).  I assume that your professor was attempting to demonstrate some connection between the MO model (homo-lumo) and the band model (valence band-conductance band) as there is a connection between them; so you'll have to ask him about the particulars of why he uses that specific MO diagram (or an MO diagram at all, since gallium arsenide is not normally a molecular substance).  -- Jayron  32  04:02, 21 September 2011 (UTC)

Oh. However, the diagram has the title of MO diagram of GaAs monomer. Plasmic Physics (talk) 04:59, 21 September 2011 (UTC)


 * That's why I said talk to the guy who made the diagram. He would know.  -- Jayron  32  15:18, 21 September 2011 (UTC)

OK, I'll do that. Thanks. Plasmic Physics (talk) 23:18, 21 September 2011 (UTC)

sweet potato flavor
The flavor of sweet potatoes seems to be effected by boiling too long but not by removing sprouts or rotten spots and then boiling for no more than 5 hours. The inside of a sweet potato that has grown sprouts, however, seems to have cavities surrounded by root like projections from the stem inside the potato. Are these cavities just the result of the spouts taking energy and nutrients from the sweet potato itself? --DeeperQA (talk) 03:33, 20 September 2011 (UTC)


 * I would think so, but mostly the result of taking water out, which is most of the mass. StuRat (talk) 05:04, 20 September 2011 (UTC)


 * No more than 5 hours? Don't you mean minutes? --TammyMoet (talk) 08:10, 20 September 2011 (UTC)


 * Boiling for five hours? You have to be British. I've cooked thousands upon thousands of sweet potatoes in my life, and I've never boiled one. Baking is best. As for the cavities, enzymes break down the starch in the sweet potatoes into sugar, which is then absorbed and transported by the root-like projections to the growing sprouts. The loss of mass represents the mass of the sugar transported along with the water it is disolved in. Dominus Vobisdu (talk) 10:21, 20 September 2011 (UTC)


 * Not neccesarily british. I boil sweet potatoes. I peel and cut them into thin slices, add salt and boil for 20 min (or until soft,) mash the sweet potatoe, add milk or cream, cinnamon, and sugar. Then heat the mixture until it is no longer flows as a liquid, avoid burning by stirring.


 * I admit, sweet potatoes are take longer to boil, but it can be sped up by using smaller chunks. Plasmic Physics (talk) 12:14, 20 September 2011 (UTC)


 * We both boil and bake sweet potatoes. And fry em, caramelize them, and mash em, and eat young leaves in salads besides. And @Tammy, they take ages to cook, not like actual potatoes, sweet potatoes are generally massive tubers with thick skin.--  Obsidi ♠ n   Soul   15:31, 20 September 2011 (UTC)


 * Are you sure you don't mean yams ? They are massive, while a sweet potato is close in size to an russet potato. StuRat (talk) 17:56, 20 September 2011 (UTC)


 * Sweet potatoes do tend to be slightly larger than regular potatoes and certainly have tougher skin. --Tango (talk) 19:10, 20 September 2011 (UTC)


 * You can get both very large and fairly small sweet potatoes. E.g. I currently have one that is over 850g and it's far from the largest one I've ever had. It also depends somewhat on the variety. They do tend to be a different shape from potatoes. Nil Einne (talk) 23:31, 20 September 2011 (UTC)


 * It's also probably a difference in harvesting time. Sweet potatoes are not cultivated extensively here as they can survive pretty easily without human intervention when planted along otherwise unarable land. They are harvested from feral plants, so they've usually been growing for quite a while. More like New Zealand kumara sweet potatoes (which is confusingly called 'yam' in the US), but not quite as large (by far) as true yams of course. I also suspect that smaller sizes are a result of market homogenization, as they are easier to handle and cook at those sizes. Potatoes here on the other hand, are tiny, averaging at only 3 in in diameter. ;) -  Obsidi ♠ n   Soul   02:19, 21 September 2011 (UTC)


 * I'm British. I usually bake or roast sweet potato, although I do sometimes boil and mash them (usually mixed with something else). Baking and roasting are a much better use of them, though. They certainly don't need to be boiled for 5 hours, though (and 5 minutes wouldn't be long enough, so I'm sure what the OP means...). --Tango (talk) 19:10, 20 September 2011 (UTC)


 * I boil them, along with many other items, as part of a perpetual stew, in winter. Thus, they may be boiled many times over many hours before finally eaten, but they seem to hold up fairly well (although the skin falls off). StuRat (talk) 19:15, 20 September 2011 (UTC)


 * I prefer nuking the small-to-medium sized ones whole in the microwave for about five to seven minutes, flipping them over about midway though the cycle to redistribute the heat. --Modocc (talk) 21:43, 20 September 2011 (UTC)


 * You use a nuclear weapon to cook potatoes?! 67.169.177.176 (talk) 05:03, 21 September 2011 (UTC)
 * In the USA, at least, to "nuke" is slang for using the microwave. ←Baseball Bugs What's up, Doc? carrots→ 06:17, 21 September 2011 (UTC)
 * Now added at List of words having different meanings in British and American English: M–Z :-) Ghmyrtle (talk) 08:25, 21 September 2011 (UTC)
 * "Nuke" is also used in American English the way it's used in British English. The microwave stuff is an additional slang usage in American English. It's also worth pointing out that "nuke" has also been used (at least in America) as a slang term for a nuclear power plant. (See No Nukes) ←Baseball Bugs What's up, Doc? carrots→ 14:08, 21 September 2011 (UTC)


 * Nah, it's current slang in the UK too. We all have slang terms we don't recognise: doesn't make it an international difference. And you should have a reliable source to reference the difference before you add it to an article. 86.164.60.149 (talk) 17:54, 21 September 2011 (UTC)
 * If you look, there doesn't seem to be a reliable reference in the entire list. Googlemeister (talk) 21:02, 21 September 2011 (UTC)
 * Yes, it does look like junk. Anyone up for finding references, and cleaning out the nonsense? It shouldn't be too hard, given how popular the topic is. I guess I could go through it at the weekend, but that shouldn't stop someone else who's looking for something to do (I do hate formatting proper inline references). 86.164.60.149 (talk) 22:10, 21 September 2011 (UTC)


 * To me, to "nuke" a foodstuff, is too charr it beyond recognition, unintentionally of course. Plasmic Physics (talk) 10:36, 21 September 2011 (UTC)


 * Yes, that would be another meaning "to get rid of or destroy". StuRat (talk) 23:09, 21 September 2011 (UTC)

Eyelids twitch when scratching toes
When I scratch my toes (and sometimes other body parts) the scratching sensation somehow transmits and reaches my eyelids, and they begin to twitch. I think this is common to all people. What is this phenomenon? Gil_mo (talk) 06:26, 20 September 2011 (UTC)


 * It's not universal. I would guess the nerves have some "cross-talk" in your brain, a form of synesthesia, similar to grapheme-color synesthesia, where numbers and colors are linked. StuRat (talk) 06:32, 20 September 2011 (UTC)


 * It's not common to me either. I can sometimes smell my own nose, strange... Plasmic Physics (talk) 07:00, 20 September 2011 (UTC)


 * hmmm, puzzling  Sean.hoyland  - talk 07:35, 20 September 2011 (UTC)

I was referring to scratching a very itchy toe (or between toes), not just anytime. Gil_mo (talk) 07:51, 20 September 2011 (UTC)
 * What happens when you have very itchy eyelid and scratch it ? Also, since you say it's sometimes other body parts too that trigger the eyelid, perhaps it's the finger that you use for scratching that's wired to your eyelids...  Sean.hoyland  - talk 08:35, 20 September 2011 (UTC)

hall effect
can a simple hall effect circuit test magnetic fields of the order of picotesla .even a true/false judgement i.e. if the field is present or not judgement would help??can any one help. if the input is provided to a pc could we get some better analysis ..if yes please guide.? 203.197.246.3 (talk) —Preceding undated comment added 09:52, 20 September 2011 (UTC).
 * I really don't think so.. The potential generated by even the best designed hall probe is going to be very small in a picotesla field - this will have to be amplified - but there is a limited to how much amplification is possible -eg limited by thermal noise etc. Here http://cat.inist.fr/?aModele=afficheN&cpsidt=15394074 they get the sensitivity down to microtesla.. ie ~0.2V per T - that would have you measuring 0.2 picovolts very small)
 * I would guess that there might be a way to get it to work - but - it would require a specially designed sensor - or some elaborate microscopic construct using the hall effect in a more complex system (integrated circuit integrated with hall effect sensor?? + low temperatures?) Imgaril (talk) 10:12, 20 September 2011 (UTC)
 * I note that http://www.tristantech.com/prod_lab_meas.html (which uses a SQUID to detect magnetic fields) mentions a Picovolt Measuring System which is cryogenic - this suggests that a the measurement of the ~pV level signals from a hall effect sensor are within the bounds of possibility - but it would need to be very cold.Imgaril (talk) 11:58, 20 September 2011 (UTC)

What is a chest node?
A kind editor has added the information that the famous operatic tenor Jonas Kaufmann has, as the source puts it, "recovered from surgery to remove a chest node". I would like to wikify this, but when I looked at Node I got rather lost. Any guidance please?  almost - instinct 12:14, 20 September 2011 (UTC)
 * Presumably nodule (medicine) is meant. A vocal fold nodule is a common singing injury. It might be something else, though. This news item with the words "vical nodules" in the URL and the comment "A node in the chest has nothing to do with vocal nodules" doesn't make things much clearer. Sounds like it's one of those probably-not-cancerous lumps people sometimes randomly get. (To be less vague, I was thinking of a benign tumor.)  Card Zero  (talk) 12:21, 20 September 2011 (UTC)
 * Thank you very much. I've found this from an open letter JK wrote to apologise for pulling out of a tour: "The fact is that I need to have an operation to remove a node in my thoracic area". Does that help?  almost - instinct 12:42, 20 September 2011 (UTC)
 * That letter is also on the page I linked to: it looks like it originates from a Japanese tour promoter's site, and is the official piece of information on the matter. Even Jonas Kaufmann himself might not know what he means by "node". Googling "chest node" brings up some breast cancer forums, though. Perhaps it was even malignant: whatever it was, it's gone now. Tumor seems the best article to link "node" to (unless somebody else knows better). Oh wait! I think it means Lymphoma, possibly, where the node in question is a lymph node?  Card Zero  (talk) 12:49, 20 September 2011 (UTC)
 * Since all JK has said on the subject is "node in the chest" -("I’m pleased to say that the operation to remove a node from my chest that I had to undertake earlier this month went very well and that the recovery is making good progress") - and there's ambiguity I had best not link either to benign tumour or lymphoma. If people want to be vague about their medical state, that's their perogative I suppose. Thank you for your help: hopefully it'll be useful if more detailed information comes out  almost - instinct 13:03, 20 September 2011 (UTC)
 * Yes, just link to "tumor", it covers all the bases. I searched for Jonas Kaufmann "lymph node", and found a half-visible Google cache of a Twitter comment by one naomip86, which says that JK confirms in a comment left somewhere, written in Japanese, that the node is indeed a lymph node; but I have a feeling this might not qualify as a reliable source. Card Zero  (talk) 13:15, 20 September 2011 (UTC)
 * Congratulations on getting so close to Absolute Zero on the Reliability Index ;-) Yes, I'll do that, thanks.  almost - instinct 13:21, 20 September 2011 (UTC)
 * Maybe, though, that refers to the original letter, which is written first in Japanese, here and I think it has the Japanese for "lymph node" in it. Somebody here (Kagetora?) can do a reliable translation of that.  Card Zero  (talk) 13:24, 20 September 2011 (UTC)
 * Oh yes! Google translate gives it "must undergo surgery for resection of lymph nodes in the chest". I shall await (semi)patiently  almost - instinct 13:28, 20 September 2011 (UTC)
 * I'm a native ja speaker. Yes, it's "lymph nodes" in the letter in ja. The ja word is リンパ節.  Oda Mari (talk) 15:07, 20 September 2011 (UTC)
 * For reference, here is what Eijiro says.  KägeTorä - (影虎)  ( TALK )  16:02, 20 September 2011 (UTC)
 * Thanks, you two. Sorry for suggesting "tumor", which Almost-instinct added to the article and then had immediately reverted by somebody else. I've changed it to "lymph node" now, let's see how that goes down. Card Zero  (talk) 16:52, 20 September 2011 (UTC)
 * Thank you everyone, its all settled and accepted now :-)  almost - instinct 21:34, 20 September 2011 (UTC)

dry versus disolved borax powder in air
I am careful not to breathe the dust when adding the powder to laundry but can find no caution about spraying a dissolved solution of borax in water. Is spraying this solution dangerous and if so what kind of respirator mask should be used? --DeeperQA (talk) 17:31, 20 September 2011 (UTC)


 * A respirator seems like overkill, but do leave the laundry area after spraying and ventilate the area (with an open window). StuRat (talk) 17:58, 20 September 2011 (UTC)
 * Here's a MSDS http://www.anvilfire.com/21centbs/material/33850-usborax-borax.pdf - generally little threat to you. Don't drink it. It's also alkaline so if you get a lot on your skin it may eventually burn/sting/itch. Washing with water will remove contamination.
 * Here's a MSDS for a 1% solution - http://www.sciencelab.com/msds.php?msdsId=9925661 - I really couldn't decribe it as dangerous - but don't breath in the spray (this applies to just about every spray you can name - starch, furniture polish, etc - most of which are of greater hazard)
 * If you are concerned about this sort of thing wearing a cheap dust mask will stop you breathing in any mist. If you are using a lot or use it everyday in a job (like these guys who use to treat timber ) then I'd recommend wearing a dust mask, and the gloves. Imgaril (talk) 20:33, 20 September 2011 (UTC)
 * Yes, thanks. This is just the information I need since the sprayer being used was a paint sprayer and one person had already noticed a reaction like a cold with mucus production but an ironically with an increased ability to breath like he had used an antihistamine. The key was that when he tried to treat a slight sour throat with vinegar it stung well beyond anything he had ever experienced. --DeeperQA (talk) 21:44, 20 September 2011 (UTC)


 * Just FYI: Breath is a noun, breathe is a verb. --Trovatore (talk) 21:48, 20 September 2011 (UTC)


 * Anyone who doesn't know that must be a blond (or blonde). StuRat (talk) 02:51, 21 September 2011 (UTC)


 * I will reprogram my grammar/spell checker. --DeeperQA (talk) 22:12, 20 September 2011 (UTC)


 * BTW, what's a "sour throat"? Methinks treating it with vinegar would only make the problem worse... 67.169.177.176 (talk) 04:02, 21 September 2011 (UTC)


 * We can't give you medical advice concerning whether your application of borax is safe for you. In general, borax is something that exists in the environment, in evaporite deposits, and has been dug up and traded for 4000 years.  It is true that in high doses it has health effects, including harmful reproductive effects, but I would think that the wind blowing in a place like Boron, California can't be that tremendously terrible.  I'd think a person can get over passing, casual exposure to the compound without the need to take extraordinary precautions. Wnt (talk) 01:57, 21 September 2011 (UTC)

I used a saturated solution (versus 1% as above) for about three of four hours of paint sprayer (blowout orifice) distribution in a light wind outdoors. The next morning I noticed I had a very open and unrestricted airway and lungs like with antihistamines. Mucus and sore throat were present like with a cold. Vinegar caused a very painful stinging sensation in back of throat. The Borax solution is alkaline. It took until now for the airway condition to tapper off but not fully go away. There was no sensation while spraying but slight smell like concrete blocks. I'll use the dusk masks when I fully recover. --DeeperQA (talk) 07:05, 23 September 2011 (UTC) Many days now after the incident, I am quickly out of breath when riding my bike. I am fatigued very easily and sluggish and my muscles ache. A dust mask if not a respirator may have prevented these problems. --DeeperQA (talk) 16:12, 24 September 2011 (UTC)

WTC escape solution
Several people scaled the WTC towers using a camming device and the window washer apparatus channels or rails. Is there any type of descent system using the channels or rails (versus a parachute stored in your cubicle) to get you from high up in a building to the ground without killing you? --DeeperQA (talk) 22:10, 20 September 2011 (UTC)
 * I wouldn't try to slide down the face of a high-rise building if I was you -- the risk of slipping and falling to your death is just too great. (You have to remember that the people scaling the towers were trained professionals, as are the window washers.)  That said, it's often possible to climb to the roof of a burning building, from where you could be rescued by a helicopter.  I wonder why they didn't try this on 9/11... 67.169.177.176 (talk) 04:10, 21 September 2011 (UTC)
 * There probably wasn't time to get such a rescue operation going. While only the first one was burning, they could have tried the Phillipe Petit approach. ←Baseball Bugs What's up, Doc? carrots→ 06:16, 21 September 2011 (UTC)
 * Also, a fire of that type would be extremely problematic for a helicopter. The large amount of smoke would have visibility be almost 0, there were those tall spires on top were a hazard, and a fire like that also creates nasty wind conditions above it.   I would expect that only military chopper pilots have been trained for that kind of a rescue, unless the NYFD has helicopters of their own for that sort of thing.  Googlemeister (talk) 13:49, 21 September 2011 (UTC)
 * In the 1993 WTC bombing,elevators were stopped and stairways were filled with smoke. Police helicopter did rescue a number of people from the roofs of the two buildings,despite heavy smoke, although that was never part of the official emergency plan. Several groups of people were lifted from the roof of the South Tower. Emergency Services personnel were lowered and sawed off any projections which were in the way of the chopper. One person was similarly rescued by rope from the roof of the North tower. This annoyed the Fire Department, who insists on the right to "rescue" people, so very strong doors with a remote operated lock were installed to prevent a repeat rescue by the police chopper. Unfortunately, the office which could have remotely unlocked the door was destroyed by the plane impacts on 9/11, so there was no roof access for the people trapped in the restaurant. Edison (talk) 18:39, 21 September 2011 (UTC)
 * And that was the NYFD's doing, you say? If that's true, then whoever ordered this is a mass murderer and deserves to be burned at the stake! 67.169.177.176 (talk) 22:46, 21 September 2011 (UTC)
 * What??? First murder is an intentional act, unintentional acts are manslaughter at worst, which is not a capital offense. Second, burning at the stake is not a legal method of execution in any of the 50 US states, most likely disqualified by the 8th amendment to the US Constitution.  Googlemeister (talk) 13:32, 22 September 2011 (UTC)
 * The hell you say -- if what Edison said is true, this amounts to INTENTIONALLY impeding a rescue operation resulting in a massive loss of life, and therefore is MASS MURDER! This falls under the same laws/precedents by which causing a fatal plane crash by stealing equipment or siphoning fuel from the plane in question constitutes murder regardless of the culprit's actual intentions!  Your so-called "logic" is the same that allowed the owners of the Triangle Shirtwaist Factory to get away with incinerating almost their entire work force!  And if burning at the stake is unconstitutional, then the electric chair is the only other fitting punishment for that NYFD official who doomed hundreds of people to a fiery death!  67.169.177.176 (talk) 00:44, 23 September 2011 (UTC)
 * A long enough rappelling rope could be tied inside the building, but nobody expected to need such a rope, and breaking the window from the inside might have been difficult. Dualus (talk) 06:41, 21 September 2011 (UTC)
 * And I don't think rappelling past a part of the building that is burning is going to work either from smoke inhalation or the heat. Googlemeister (talk)
 * There were some sides of the building that weren't spewing flames, and unless the heat melts the rope, it's probably easy enough to slide past 10 floors fast enough to survive. As for breaking the windows, plenty of victims contacted by cellphone before the collapse said that they had been able to break open windows. 70.91.171.54 (talk) 18:59, 21 September 2011 (UTC)
 * It is very rare for a highrise fire to start out with flames coming out all sides of the building., There is typically a long time during which there is intense fire on one side, with some sides cool enough for a person to be lowered. This is why fire escapes outside buildings were traditionally there: builders and fire safety officials did not dismiss the ability to walk down the north side when there was a fire on the south side. I worked in a high rise building which had an employee who could not walk working in an office several floors up. The boss bought a rescue harness and a l-o-o-ng rope to lower the employee to the ground from a window in the event of elevators being unusable in a fire. The employee and coworkers agreed that the employee would instead be carried down the stairs, either seated in an office chair or over a shoulder in a fireman's carry, rather than having a team of people lower the employee via a rope. But it was feasible, and was tested by lowering an equivalent weight. I've always thought a personal lowering device for a highrise would be easy to build. A long wire cable on a reel, a centrifugal brake to control the unreeling speed to a safe one, and a bosun's chair. Trapped people could be lowered one at a time, and the seat could be cranked back up after each use. Nothing innovative or high tech required. A metal eyebolt could be installed above a window on each side of the building to allow using the noninvolved side.  It might even be possible to insert rescuers into a burning highrise at a floor above the fire, to install such several such devices and supervise the lowering of trapped people. One could go fancy and wear fireresistant garb, helmet, gas mask, etc, or just rely on the rapid descent speed to get past any hot or smoky area and get people out faster. Edison (talk) 19:08, 21 September 2011 (UTC)
 * Are you seriously thinking that hundreds of people rappelling 1000 feet to the ground from a burning building is remotely feasible? Googlemeister (talk) 20:55, 21 September 2011 (UTC)
 * Yeah, much more sensible to ensure the doom of each and every one of them by a lack of planning, and by ignoring simple means of leaving a high place without going thud. Rarely are the trapped people 1000 feet above the ground, and it rarely is the case that hundreds of people are trapped. The people who survived because of a communal or personal descent rig would be quite happy not to have been incinerated or asphyxiated. Edison (talk) 23:44, 21 September 2011 (UTC)
 * True, but a system that relies on rappelling 1000 feet down the face of a building would not have been practical, since it can only be used by highly skilled mountaineers. On the other hand, some kind of "communal descent rig" (I'm thinking of something along the lines of an external, rope-suspended elevator) might well have been a practical idea for an emergency escape system. 67.169.177.176 (talk) 01:13, 22 September 2011 (UTC)
 * Edison, that's easy for you to say. You know that the buildings were going to burn and collapse. But an equally likely outcome was that these risky rescue ideas would be installed, and a lot of people would have died using them in a fire that would otherwise be survivable. It's far more likely that your rescue equipment will be used when it's not needed, then it is that a jet-liner will crash into your building. APL (talk) 08:16, 22 September 2011 (UTC)
 * Exactly. This is similar logic as to why passenger airliners do not have parachutes on hand.  Googlemeister (talk) 13:33, 22 September 2011 (UTC)
 * Besides, the building DID have a fire escape stairwell in its central core. The building designers could not have anticipated that part of the stairwell would collapse as it did on 9/11, or that the escape doors to the roof would be locked with no way to open them except remotely (according to Edison, but AFAIR corroborated by at least one other source).  To them this kind of scenario was simply inconceivable. 67.169.177.176 (talk) 00:49, 23 September 2011 (UTC)

Okay, I like the centrifuge governing descent idea. That could really work especially if the window washer channels were toothed on on side - an idea that might accommodate several other speed governing methods. Outside exposed to the elements is not the best way down but in a dire emergency if a controlled "down" is the only solution I'd choose a Mountain Banshee over free fall. --DeeperQA (talk) 04:33, 23 September 2011 (UTC)
 * Yes, some kind of platform with safety railings all around and a reel with some kind of (FAIL-SAFE!!!) speed governor may well work for high-rise emergency escape. This should preferably accomodate a group of people, so as to expedite descent for all who might be trapped on the upper floors. 67.169.177.176 (talk) 06:05, 23 September 2011 (UTC)
 * Realize any such system is for dire emergency only after all other options except jumping have failed. Its got to be limited to multiple sets of one or two persons to accommodate carabine latch and swing out. Time is of essence not user comfort. Jam proof design to allow for slower descent below. Think of a rail of reusable devices to accommodate an unlimited number of people in succession. Think mountain climbing not penthouse elevator. --DeeperQA (talk) 07:27, 23 September 2011 (UTC)
 * I'd think a zipline would work fairly well, and the tourists would either love it or not return their customer satisfaction form. Wnt (talk) 17:49, 23 September 2011 (UTC)
 * That's a joke, right? 67.169.177.176 (talk) 19:57, 23 September 2011 (UTC)
 * Well, admittedly, given the height of the towers it would need to be a pretty long zipline ... you might need carbon nanotubes or other advanced materials to make it work. But it would provide quite a tour of the city. ;) Wnt (talk) 03:39, 24 September 2011 (UTC)
 * With building code to match - multiple ziplines could be fired from one building to another at angles of no greater than 13.5 degrees during an emergency like hooking up two ships for transport of personnel or supplies. Unfortunately the design of the new towers may not permit this. --DeeperQA (talk) 16:06, 24 September 2011 (UTC)

Plane crash on Mount Everest
What would happen if a plane crashed near the top of Mount Everest? Whoop whoop pull up Bitching Betty 22:26, 20 September 2011 (UTC)
 * The plane remains would be there for ever as a monument to human endeavor/stupidity. Dauto (talk) 23:03, 20 September 2011 (UTC)
 * Depends on the type of plane, the speed it was traveling at, the weather,etc. At that altitude it is likely everyone on board would die, as they would not be prepared for the extreme cold and thin air, presuming they survived the impact in the first place. Specialized high-altitude helicopters can indeed reach such an altitude to perform rescues, as documented at Mt. Everest but as I said the survivability of such a crash would be near zero. Also, I'm fairly certain air traffic is re-routed specifically to avoid such a thing. Alaskans know to stay away from Denali in the air because it is so massive it creates its own weather. Beeblebrox (talk) 23:22, 20 September 2011 (UTC)
 * Something I read in a book about Everest once. "There is no 'trapped on Everest' - only 'dead on Everest'", or something along those lines. If you're up there somewhere and any potential rescue isn't immediately at hand, then you might as well be on the moon for your chances of survival. --Kurt Shaped Box (talk) 00:58, 21 September 2011 (UTC)
 * In general, mountain peaks above the 8000-meter line are referred to as "the death zone" -- a person who finds himself unexpectedly trapped in that zone would certainly perish. 67.169.177.176 (talk) 04:47, 21 September 2011 (UTC)
 * Time for a very ignorant question: Suppose a large jet with a large amount of fuel crashed right at the summit. Might the resultant explosion be strong enough to blow away part of the summit, thus shortening the mountain's height? ←Baseball Bugs What's up, Doc? carrots→ 06:02, 21 September 2011 (UTC)
 * ABSOLUTELY NOT! To do this would require a multi-megaton atom bomb at the VERY LEAST! 67.169.177.176 (talk) 06:25, 21 September 2011 (UTC)


 * Apparently Everest's height is measured to an accuracy of ±0.21 m. It may not be unreasonable that a major crash could make a measurable difference. A plane crashing with a near-full fuel tank has been known to make quite an impact. Mitch Ames (talk) 12:16, 21 September 2011 (UTC)
 * You could knock off the snow on top which is a few feet if I recall. Not enough to help anyone.  Googlemeister (talk) 12:59, 21 September 2011 (UTC)
 * If you dropped a bomb on it, you could probably take a few metres off the top (basically, the same amount as the depth of the crater you would create if you dropped it on flat ground, give or take). Near-full fuel tanks don't really explode, though, they just burn. Empty fuel-tanks explode because they are full of fuel vapour, which is explosive. Liquid fuel isn't. If the tanks were empty, though, the amount of fuel vapour wouldn't be enough to cause any but a small explosion, not enough to significantly damage the mountain. --Tango (talk) 17:23, 21 September 2011 (UTC)
 * I didn't necessary expect significant damage, but I expected that something would happen. Obviously, it depends on the amount of force involved, and the precise angle and landing point. Looks like it would take a lot more than a conventional airplane to knock it down below the height of K2, which I think is about 800 feet shorter than Everest. The various answers provide a lot of insights. Thank you! Aside: Everest was photographed from the air long before it was climbed, but they kept a safe distance. It also occurs to me that if a plane is in that much trouble, it probably wouldn't even make it to Everest - it would probably crash on one of the somewhat-lower peaks in the vicinity. ←Baseball Bugs What's up, Doc? carrots→ 17:38, 21 September 2011 (UTC)
 * As for survivability, what if the plane fell or was knocked down the side of Everest, so that it ended up lower down on the mountain? Whoop whoop pull up Bitching Betty 22:58, 24 September 2011 (UTC)

Highest an aircraft can fly
What is the highest up an aircraft can fly (and I mean something like a jet plane, propliner, or helicopter, not something like Apollo 11 or the Space Shuttle)? Whoop whoop pull up Bitching Betty 22:35, 20 September 2011 (UTC)


 * About 100 km altitude. This is where the speed needed for the aerodynamic forces to overcome gravity becomes similar to the speed needed to stay in orbit. Count Iblis (talk) 22:51, 20 September 2011 (UTC)


 * The current record is less than half that, about 37.5k, set in 1977. See F%C3%A9d%C3%A9ration_A%C3%A9ronautique_Internationale.  SDY (talk) 22:52, 20 September 2011 (UTC)


 * An airplane can fly a LOT higher than 37,500 feet. And wouldn't the jet engines be starved of air long before the altitude reaches 100 kilometers? Whoop whoop pull up Bitching Betty 23:00, 20 September 2011 (UTC)


 * That's probably intended to mean 37.5 km, not kilo-feet. Yes, getting air-breathing engines up to 100 km would be quite a challenge. Even the MIG-25 record of 35+ km was done using a zoom climb, not sustained engine performance. But several experimental aircraft have been fitted with rocket boosters in addition to their normal jet engines. --Stephan Schulz (talk) 23:12, 20 September 2011 (UTC)


 * Yes, although the original statement may not have be entirely clear (although can be inferred in the context of the discussion), the article they linked to as their source unsurprisingly is clear. Nil Einne (talk) 23:25, 20 September 2011 (UTC)


 * As for the highest sustained flight: Lockheed_SR-71_Blackbird says "On 28 July 1976, SR-71 serial number 61-7962 broke the world record for its class: an 'absolute altitude record' of 85,069 feet (25,929 m)." That's 25.9 km. StuRat (talk) 03:05, 21 September 2011 (UTC)


 * Does the X-15 count? 67.169.177.176 (talk) 04:03, 21 September 2011 (UTC)


 * The X-15 was a rocket with wings. The Blackbird was a ramjet. So probably not. I do recall reading in The Right Stuff about Yeager taking I think his conventional plane so high that the sky turned black, which means you're pretty much in space. At that point the engine conked out and the plane went into a dive that destroyed it (it "augered in"), but Yeager bailed out successfully. (It's been a long time, I hope I haven't conflated 2 or more stories into 1.) ←Baseball Bugs What's up, Doc? carrots→ 06:10, 21 September 2011 (UTC)


 * If the plane in question was the Bell X-1 or any derivative thereof, then the engine was a liquid rocket -- which means that it conked out because of fuel exhaustion, not because of thin air. As for the dive, in this case it might have been caused not by the engine failure, but by inertial coupling. FWIW 67.169.177.176 (talk) 06:29, 21 September 2011 (UTC)
 * I didn't dream it after all. It was an F-104. The article discusses the Yeager mishap. ←Baseball Bugs What's up, Doc? carrots→ 06:47, 21 September 2011 (UTC)

For a standard fixed wing aircraft, a very high altitude requires a very high lift body with an extremely high stall angle, and/or a ridiculous amount of excess thrust (which would basically make it more of a rocket than a traditional airplane).  Lynch 7  17:37, 21 September 2011 (UTC)
 * As I recall from the last time I read about this in any detail, the ability of a plane to achieve a high altitude is dependent on its type of engine, as you're indicating. A standard prop plane can only go so high because it can only go so fast. A conventional jet can go higher because it can go faster. And a ramjet can go very high because it can go very fast. In fact, I think the way a ramjet works is that, "The faster and higher it goes, the faster and higher it can go. Up to a point, of course, as it still needs air. Rockets don't need air, as their fuel is self-contained. Obviously. :) ←Baseball Bugs What's up, Doc? carrots→ 17:43, 21 September 2011 (UTC)


 * The F-15 Eagle can reach 100,000 feet in a zoom climb. The SR-71 can reach even higher altitudes in sustained flight (or at least so they say). 67.169.177.176 (talk) 22:52, 21 September 2011 (UTC)


 * And I would still call the SR-71 an airplane, so I think it qualifies, ramjet or not. StuRat (talk) 23:05, 21 September 2011 (UTC)
 * Yes, absolutely, the Blackbird was/is an airplane. The X-15 was a "rocket plane". ←Baseball Bugs What's up, Doc? carrots→ 23:46, 21 September 2011 (UTC)

Unless I've missed something, nobody has provided a link to our Flight altitude record article. The answers that gives are: Jet plane: 37.65km (Mig 25), Piston prop plane: 20.43km (Boeing Condor UAV), Helicopter: 12.42km (Aérospatiale Lama), Glider: 15.45km. Alansplodge (talk) 23:34, 24 September 2011 (UTC)

Battery acid?
Ok, I've just returned from my yearly camping trip to Interior Alaska. We use a small battery powered fan most nights to supply a little breeze and some "white noise". One night the batteries began to fail while we slept, waking my wife, who replaced the batteries in the dark while half awake. When we woke in the morning the batteries seemed to be dying again already, and upon further inspection a thin, foamy liquid was seeping out of the battery door. It turned out three of the four D cells were in correctly, but one was backward. After discovering this I knocked the batteries into the trash and we cleaned the fan up. I got some of this liquid on my fingers. They seemed to tingle a bit but did not turn green, burn, or begin dissolving. Maybe I've seen too many cheap movies. So my question is: Was this substance battery acid? How corrosive is it? Why did the batteries still work at all when one was improperly installed? Can I guilt trip my wife for endangering my life or should I feel bad for not waking up and doing it myself? (that last one obviously not a scientific question but more of a domestic matter) Beeblebrox (talk) 23:36, 20 September 2011 (UTC)
 * See Alkaline battery and Carbon zinc battery Nil Einne (talk) 00:15, 21 September 2011 (UTC)
 * I'm surprised that the fan worked on half its normal voltage (the reversed cell would cancel out one third of the three correct cells), but it would be the reverse current that overcharged the reversed cell and caused the leakage because the hydrogen produced in attempting to charge the cell would force zinc chloride out of the cell (your description doesn't sound like potassium hydroxide from an alkaline cell). Zinc chloride is a skin and respiratory irritant, so I hope you washed your hands well, but I've had it on my hands many times without ill effect, so don't accuse your wife of attempted murder. The three cells that were not reversed probably needed only a good wash to be used again.    D b f i r s   00:45, 21 September 2011 (UTC)
 * Small DC motors can operate at various voltages, such that increasing or decreasing a voltage will increase/decrease a motor's torque and speed. The limiting factor is usually the excess heat that is produced in the motor's winding if one is operated too long above its rated voltage. --Modocc (talk) 01:36, 21 September 2011 (UTC)
 * Indeed it isn't uncommon (well more common in the past before the widespread availability of fan speed controllers) for someone to operate a 12V DC fan on 7V and occasionally even 5V in a computer. They don't always work, particularly at 5V but a fair few do. Nil Einne (talk) 05:31, 21 September 2011 (UTC)
 * The tingling you felt from the foamy liquid was potassium hydroxide which is not an acid but a base. It's very corrosive to metal, and if you rinsed your hands well, then no harm done.  Just be glad you didn't wipe your eyes after touching it, or you would have been in substantial pain and possibly at risk. Dualus (talk) 06:59, 21 September 2011 (UTC)
 * High-power alkaline batteries contain aqueous potassium hydroxide, but it doesn't normally leak as a liquid in my experience, which is why I thought that acidic zinc chloride from cheaper batteries was more likely, especially because of its deliqiescence. We agree that washing hands is important whichever it was.    D b f i r s   08:51, 21 September 2011 (UTC)
 * I've had one alkaline battery leak in decade.. However if the battery was reversed with a voltage of 4.5V across it the chemistry would change - possibly oxygen would be evolved (and maybe hydrogen at the other electrode - though this is supposed to be absorbed by the manganese dioxide) - if so this would cause an increase in pressure and break the safety seal - evolution of gas might also explain the foamy nature of the leak.
 * generally if it's an alkaline battery the electrolyte (liquid) feels very soapy - and also tends to sting on even the slightest skin cut (or skin damage - including tiny cuts you wouldn't have otherwise noticed) - if you didn't notice this (you have skin like a rhino or) it was a 'dry cell' - these also can produce gas if connected the wrong way round.Imgaril (talk) 11:11, 21 September 2011 (UTC)


 * Re: guilt tripping your wife - all modern batteries have a safety release valve - that breaks when pressure builds inside the battery - this makes the batteries safe - if they didn't have these than exploding batteries are a real possibility. However the evolved gas may be a mixture of hydrogen and oxygen - a real explosive mixture - it's unlikely to be enough to kill you (though the explosion might have deafened you and set fire to your tent in an extreme example) .. the rest is up to you.Imgaril (talk) 11:19, 21 September 2011 (UTC)


 * Regarding that battery type, they were non-rechargeable Duracell alkaline batteries. Anyhoo, my fingers didn't fall off, the fan still works, and my wife had to go back to work after our vacation 2 days before I did so I guess the guilt trip is cancelled as well. Thanks for the replies! Beeblebrox (talk) 23:45, 21 September 2011 (UTC)


 * In that case, Dualus was correct, it was potassium hydroxide (an alkaline), not the acidic zinc chloride in zinc-case batteries. I haven't seen Duracell batteries leak like that --  I'll have to try an experiment on reverse charging them.  Glad to hear that both your fingers and your wife are safe!   D b f i r s   12:52, 23 September 2011 (UTC)