Wikipedia:Reference desk/Archives/Science/2016 May 21

= May 21 =

What form can "HCO" can have?
49.135.2.215 (talk) 01:01, 21 May 2016 (UTC)Like sushi
 * What context? What do you mean by HCO?  -- Jayron 32 01:03, 21 May 2016 (UTC)
 * Assuming it's a chemical formula, HCO doesn't exist. H2CO is formaldehyde.  See HCO (disambiguation) for other possible meanings. Tevildo (talk) 12:22, 21 May 2016 (UTC)
 * There is no stable molecular or ionic configuration of one hydrogen, one carbon and one oxygen atom. Roger (Dodger67) (talk) 15:17, 21 May 2016 (UTC)
 * HCO (the formyl radical) and HCO+ have both been detected in the interstellar medium. --Wrongfilter (talk) 19:02, 21 May 2016 (UTC)
 * Do you have a reference for this? It would be a useful addition to our Aldehyde article. Tevildo (talk) 23:14, 21 May 2016 (UTC)
 * Not at all my field of expertise, but here is a random one (HCO mapping of the horsehead nebula). A long list with "HCO" in the title can be obtained like this. --Wrongfilter (talk) 17:32, 22 May 2016 (UTC)
 * The formyl radical and isoformyl are noted in list of interstellar and circumstellar molecules. Formyl redirects to aldehyde. Sagittarian Milky Way (talk) 19:49, 22 May 2016 (UTC)

Hydrogen inbetween Lithium films? Helium inbetween carbon films? Spherical spaces in carbon, silicon, or "sulfer glass"?
(I would not surely be back)

49.135.2.215 (talk) 01:31, 21 May 2016 (UTC)Like sushi
 * You've been back several times despite promises to never return. Since you keep coming back, can you elaborate on your questions.  Your questions are hard to understand because you rarely explain exactly what you are looking for.  -- Jayron 32 03:29, 21 May 2016 (UTC)


 * I'd say these questions are difficult to understand because they have no verbs? He could well mean: " Hydrogen inbetween Lithium films".--Llaanngg (talk) 20:49, 21 May 2016 (UTC)


 * You may wish to look at helium compounds where one or two helium atoms can be trapped inside a spherical carbon ball called a buckyball. Also at helium compounds, under high pressure (1.7Gpa) helium can be compressed so that it "dissolves" into silica. I don't know about helium with graphite or lithium or sulfur though. Graeme Bartlett (talk) 06:32, 25 May 2016 (UTC)


 * For helium on graphite sheets, look at http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.58.2680 where they also claim that helium can tunnel through as well as stick to sheets. In http://www.sciencedirect.com/science/article/pii/002231159190067H another group claim a few ppm of helium on graphite, but only testing at ambient pressures. These people only claim movement across surfaces and via pores, not tunneling! They were trying to make a container for a fusion reactor. Helium in metals is energetically unfavourable as a helium atom has to push aside metal in the crystal lattice to make space for itself, so you are lucky to get one part in a billion of helium in a metal. For hydrogen it will depend on bonding with the metal also. Graeme Bartlett (talk) 07:39, 25 May 2016 (UTC)

500 tons of TNT
In this YouTube video (which is likely from the Discovery Channel or the History Channel), the narrator says that 500 tons of TNT is capable of leveling a "small city". I'm having trouble imagining a non-nuclear weapon that could destroy a city. Is that accurate? — Melab±1 &#9742; 02:44, 21 May 2016 (UTC)


 * The Wikipedia article titled TNT equivalent may help you in you research. It is worth noting that energy is energy; nuclear bombs are not magic destruction spells.  The Hiroshima bomb was only about 30x as powerful as that (15000 tons of TNT), and it was leveled; Hiroshima is a fairly large city.  It would of course depend on how you define a "small city".  The Halifax explosion was 6x the size of that, was amazingly destructive, it destroyed everything in a 2.6 km radius.  -- Jayron 32 03:27, 21 May 2016 (UTC)


 * See also Largest artificial non-nuclear explosions, which has a list of large explosions, and gives the destruction caused by some. Note that air bursts tend to be more destructive that ground-level blasts. LongHairedFop (talk) 09:32, 21 May 2016 (UTC)
 * (Fixed your link.) --69.159.60.83 (talk) 09:43, 21 May 2016 (UTC)
 * (Fixed your link.) too. --Llaanngg (talk) 14:52, 21 May 2016 (UTC)

Not only do you have to define "small city", you have to define "destroy". Would it turn a small city into a crater? No, not unless your city is like, one building. Could it render every building uninhabitable? Maybe. From playing with various blast-radius calculators on the internet, it seems like a 500 ton air burst could theoretically damage every structure in a half a kilometer radius. There are "cities" smaller than that, though they may be cities in name only. Someguy1221 (talk) 10:52, 21 May 2016 (UTC)


 * Also, it depends very much on how you distribute the TNT. A lot of small explosions will be a lot more destructive than one big explosion. I've tried to google how much explosives are used to demolish a skyscraper, but most hits lead to 9/11 truther sites. But the original WW2 blockbuster bombs weighed 4000lbs, about 3000lbs or 1.35 tons of which where explosives. These were supposed to be enough to to level one city block. --Stephan Schulz (talk) 17:35, 21 May 2016 (UTC)


 * Agreed. You also want to avoid explosions in open air, where the force mostly dissipates into compressing and heating the air.  Yes, with enough force, like a nuclear weapon, it can still be massively destructive when this is taken into effect.  Of note is that destroying some types of bridges from aerial bombing is extraordinarily difficult because of how the force of the explosions mostly dissipates in air.  On the other hand, a demolition team can easily bring the bridge down with far fewer explosives, say by drilling holes in the supports and placing charges there. StuRat (talk) 18:30, 21 May 2016 (UTC)


 * Our Building implosion article is pretty thin on cites and has no information on how much explosive is used for modern techniques. DMacks (talk) 19:16, 21 May 2016 (UTC)
 * People who do explosive demolition for a living pride themselves on how little explosive they can use. They find the key structural members, sever those with carefully shaped and placed charges, and then let gravity do the rest.  Inexperienced demolitionists who use lots of explosives to just "blow it up" are derisively referred to by their more-sophisticated peers as having "launched the building".
 * My point is that if you want to figure out how much damage a single randomly-placed bomb is going to do, you're not going to learn much of anything by comparing to multiple carefully-placed demolition charges. —Steve Summit (talk) 11:23, 22 May 2016 (UTC)
 * Sometimes a little too little . P.S. To be clear this is a joke, I have no idea of the actually reason. Nil Einne (talk) 20:18, 22 May 2016 (UTC)
 * Wow! Leveling cities!  That's heavy stuff.  It can be pretty hard to imagine, if you've never seen it.  I happened to have been reading about clearing terrain this week, so I have a few thoughts and can share some of my reading material.
 * In actual fact, it's much easier and cheaper to level a city with thousands of tiny deployments of explosive than to use one giant blast. Quoting this reference that I regrettably drag out of my archive once again... if your enemy wanted to obliterate and level your city, "...the first thing that's going to hit you is the Soviet artillery, and that artillery is going to come into your area at about 1,200 rounds per square kilometer in the first forty-five minutes."  (U.S. Army General Sunell, on his Experience and Visions...)
 * Here's what a tiny barrage - little itty-bitty- man-portable mortars - did to a formerly very-nice building in Golan Heights. They save the big guns for further targets.  Have you ever seen a whole city after an artillery shelling?  Here's the August 1982 cover of Time Magazine.  Post-artillery-barrage cities look remarkably unlike civilization.  Decades later, you could find leveled buildings on every street in the city.  But for a real taste of the terrifying power of artillery, read about the Battle of Berlin.  Two weeks of Soviet shelling - with conventional munitions - are estimated to have killed more people than the atomic bombing at Hiroshima - even if we count deaths due to adverse health effects of nuclear radiation.  Nuclear war is bad and its destruction can be devastating, but conventional weapons of war make devastation and destruction cheap and easy.  That might actually be a worse problem.
 * Last week, while reading about parachute drop zones, I came across Field Manual 5-164 Tactical Land Clearing (an obsoleted manual available from Archive.org). It contains, in chapter 4, both qualitative and quantitative discussions of land clearing operations for engineers employing large munitions (e.g. an M121 T56E4 10,000 pound munition).  That munition - about 5 tons of high explosive - seems to level all vegetation within a five meter radius, and clears some vegetation within a 25 meter radius.  While nearly instantaneous, this method of land clearing is difficult, dangerous, and expensive; and it usually requires follow-up operations by a bunch of combat engineers armed with chainsaws.
 * The point is, there are lots of ways to level terrain, using conventional methods.
 * The manual also contains some photographs - mostly of combat engineering operations in Army test facilities - but if you go searching around, you can find other spectacular, awe-inspiring, and terrifying photographs of wartime combat engineering operations. When it comes to levelling terrain, there are none better at it than the construction battalions - the combat engineers whose irregular unit evolved in to what we now call Navy SEALs.
 * At one point in history, the United States evaluated using nuclear explosions for such construction purposes, too. Notably, we created the Sedan crater in Nevada; and there was a serious investigation into creating an artificial harbor for Alaska's North Slope oilfields.  You can take a look at photos and diagrams of those experiments to see how they would have worked.
 * Generally, at this time, most informed people concur that we ought not use nuclear detonation at all.
 * At least one very well-informed individual who knew a little about the topic also seemed to think we all ought to use less conventional detonation, too.
 * Nimur (talk) 19:40, 21 May 2016 (UTC)


 * The Silvertown explosion in London in 1917 was caused by 50 tonnes of TNT - it destroyed 900 houses and damaged 70,000 more. The quote in the original question is about an explosion from ten times that much explosive. Alansplodge (talk) 17:50, 25 May 2016 (UTC)

Does a pin get blunter without being used?
Imagine a perfectly sharp steel pin, never having been used, put inside a vacuum sealed container, and that container being surrounded by a metre of lead and then a 3 metres of bronze, and the whole kept at a low temperature. If a million years were to pass, would that needle be as sharp as the day it was put away? How about a billion years? I am thinking about the possibility of random quantum effects gradually making the point less sharp. Would a higher temperature make the process of blunting the needle faster? Given enough time, say quadrillions of years, would the needle become a shapeless mass, even though no force other than quantum effects came into play. Myles325a (talk) 07:06, 21 May 2016 (UTC)


 * Theoretically in 1065 years, all solid matter will have been rearranged into spheres through quantum effects. See Timeline of the far future for some more bizarre but plausible predictions about what might happen. Someguy1221 (talk) 11:00, 21 May 2016 (UTC)


 * I'm just wondering who's going to pay the electric bill to run the refrigerator during those quadrillion years. ←Baseball Bugs What's up, Doc? carrots→ 12:08, 21 May 2016 (UTC)
 * Interplanetary space is quite cold. No bills ones placed in the correct position. Bytesock (talk) 20:12, 22 May 2016 (UTC)


 * Yes, "solid" molecules move around all on their own, but rather slowly. Cold welding may be of interest.  So, if two pins were in contact, they would weld together (just on the nano scale, at first, then on the macro scale, as time goes by).  And yes, I do expect heat to speed up the process.  Even at absolute zero, though, there's still radioactivity within the pin itself (such as from carbon-14), to provide the energy, and your precautions won't keep neutrinos out. StuRat (talk) 18:11, 21 May 2016 (UTC)


 * A "pin" will be unchanged by anything less than rusting or other bulk chemical processes. They're just not that sharp, to this sort of scale.
 * Back in the '70s (maybe 1955 from the WP article, but that's news to me) the first imaging at the atomic level was done by a field ion microscope. This uses an incredibly sharp point (neat piles of individual atoms). Now for that, a per-atom change could be said to blunt the tip. Even then though, what's causing it?  Metal atoms are bound into the lattice by fairly strong forces. Quantum effects bend these bonds (and we now make use of such effects every day) and change their energy, but they don't break the bonds or free atoms.  It's the difference between twanging a spring and snapping it.
 * It's all probabilistic, of course, so these effects can shift an atom, but rarely. Yet you're asking two things here: to have a rare event happen, and to have it happen to one of a small number of specific atoms (there are only a few atoms on your pinpoint). The ratio between those chances involves Avogadro's number: 6×10^23. The chances are so vanishingly small that this is thus unlikely: also a million or a billion years isn't that long.  It is more likely (at these scales) for such an event to happen to "an atom on the surface of a macroscopic pin" (there are more than billions of these) than it is to happen to one of a small number of atoms on the pinpoint in the billion years. Andy Dingley (talk) 09:49, 22 May 2016 (UTC)


 * If this is accurate at room temperature (a big if), then the equilibrium vapor pressure of iron at room temperature (300 K) is about 1 atom per cubic meter. At that level, we expect about ~3 atoms to evaporate off of your pin per square meter per hour.  If you continue to pull a vacuum, such atoms will be removed.  If not, then they will tend to be deposited somewhere randomly within the chamber.  If we assume your pin is 1 mm wide and 3 cm long, then it would have a surface area of about 1m2 and a mass of about 0.2 grams (~2 atoms).  So, we would expect the whole pin to evaporate at room temperature after roughly 8 years.  That's a fantastically long time (800,000 quadrillion years), but over time such things ought to happen if you can keep the experiment running and nothing else interferes.  Dragons flight (talk) 11:16, 22 May 2016 (UTC)
 * How do you know the rate of evaporation? ie 3 atoms/m²/hour. Bytesock (talk) 20:13, 22 May 2016 (UTC)
 * The rate of evaporation in a vacuum is $$\approx {P_{eq} \over \sqrt{2\pi \,m \, k \, T)} }$$, where Peq is the equilibrium partial pressure, m is the atomic mass, k is Boltzmann's constant, and T is the temperature. Dragons flight (talk) 20:20, 22 May 2016 (UTC)
 * Unit? N/(m^2.5*J^0.5) ? Bytesock (talk) 20:47, 22 May 2016 (UTC)
 * [Pa] / sqrt( [kg] [J] ) = ([kg] / [m] / [s]^2) / sqrt( [kg]^2 [m]^2 [s]^2] ) = 1 / [m]^2 / [s], which is implicitly atoms evaporated per m^2 per second. Dragons flight (talk) 21:17, 22 May 2016 (UTC)

'Hybrid' cells
What are these rechargeable 'hybrid' cell batteries they are selling noe in Maplin? Are they NiMH or alkaline or what? Searching the web does not find refs to 'hybrid' cells.--178.106.99.31 (talk) 17:27, 21 May 2016 (UTC)
 * You can read here. Ruslik_ Zero 18:03, 21 May 2016 (UTC)

Residual radioactivity after detonating a nuclear bomb
Couldn't a "no waste" nuclear bomb exist, which consumes all the fuel being used? --Llaanngg (talk) 21:28, 21 May 2016 (UTC)


 * It's too complicated to answer here, but some pointers:
 * This has been a goal since the 1950s. The key factor is to make the physics package work by nuclear fusion of hydrogen, rather than fission of plutonium. As is well-known, the H bomb is a couple of orders of magnitude more powerful than an A bomb, but it's also cleaner and (once designed) easier to make. In particular, it reduces the need to enrich uranium or to operate reactors to make plutonium. Fusion requires tritium, which also requires a reactor, but the bulk of it can be the rather simpler to produce lithium deuteride.
 * A second factor is to detonate a weapon as an air burst, rather than a ground burst. Much of the fallout produced by the blast is due to the irradiation of material from the ground and spreading this as a dust cloud. Andy Dingley (talk) 22:53, 21 May 2016 (UTC)
 * I'm slightly puzzled by the wording of your question. Are you asking "residual radioactivity" or "all fuel consumed"? "Fallout", as a general environmental problem, is created by the irradiation of ground material during the explosion, not by left-overs from a bomb's already radioactive fuel. They're a tiny fraction of what's produced.
 * For some exceptional designs, the cobalt bomb, or the "dirty bomb" form of the B41 Y1, the irradiation of a final fission stage would also produce considerable fallout (from the products of irradiation, not from the original fuel itself). These are unlikely to have ever been considered for use though, even by the Dr Strangeloves of RAND. Andy Dingley (talk) 09:52, 22 May 2016 (UTC)


 * In a word no (the gadget blows itself apart well before all the fuel is consumed) and the radiation will create other stuff like Cobalt-60 in ferrous metals.  Also, the workings of high efficiency nuclear devices are still classified. So you will not get an answer here in case Kim Jong-un's scientists are reading this Ref Desk.--Aspro (talk) 23:00, 21 May 2016 (UTC)


 * Also, a hydrogen bomb using a regular old dirty atomic bomb to set it off will have that as a source or radioactivity. But, if you could manage to set one off without that, and did so out in space so there was nothing around to transmute into radioactive elements, it should be pretty clean then, yes. StuRat (talk) 00:21, 22 May 2016 (UTC)


 * left over radiation from an air burst is almost a completely non-issue/non-existent..68.48.241.158 (talk) 01:15, 22 May 2016 (UTC)


 * I don't think anyone has linked to neutron bomb. μηδείς (talk) 03:16, 24 May 2016 (UTC)


 * I don't see why it's that relevant; a neutron bomb is intended to produce more ionizing radiation than a "conventional" nuclear weapon. --71.110.8.102 (talk) 09:22, 24 May 2016 (UTC)


 * Yes, but in the form of neutrons, which have a 15 minute half-life, and don't travel very far, as well as gamma-rays, which are photons. These may induce secondary radiation in their targets, such as tanks, but they don't produce much in the way of fallout of nucleotides directly. The article is well worth reading. μηδείς (talk) 22:04, 24 May 2016 (UTC)