Wikipedia:Reference desk/Archives/Science/2011 August 10

= August 10 =

particle trails
Did I understand correctly that the shortest possible time interval between the dots of a particle trail stemming from the collision of two protons in the large Hadron Super Collider is one nanosecond? --DeeperQA (talk) 00:59, 10 August 2011 (UTC)
 * Which instrument are you asking about? The Large Hadron Collider is the parent-project, sort of an umbrella for many different measurement apparatuses.  The ATLAS produces ~ 100 terabytes of data per second; you can read more about its data acquisition system.  ATLAS produces more complicated data than a simple x,y,z,t particle trajectory, so it's invalid to try to reduce it to a "sampling rate" for an individual particle trail.  Nimur (talk) 01:11, 10 August 2011 (UTC)


 * No, it would be fairly typical for the readout rate to be of order a nanosecond (or somewhat faster), so that each detector element was queried for hit / no hit every nanosecond. But during that nanosecond refresh cycle, dozens (or hundreds or thousands) of detector elements may have been triggered by the reaction products flying through the detector.  Dragons flight (talk) 02:13, 10 August 2011 (UTC)
 * The time resolution of the wire chamber depends on the spacing of its parallel wires. Other gaseous ionisation detectors such as the cloud chamber and spark chamber do not work in real time and have different resolution limits. Cuddlyable3 (talk) 11:15, 10 August 2011 (UTC)

So then the way around a limit of say a nanosecond data acquisition rate is to start adding detectors such that each captures data at different starting points in the nanosecond time frame or are you saying that other detectors can be setup to capture data in longer (or smaller) time frames so the data can be captured at intervals of time made possible by using a vernier time scale? --DeeperQA (talk) 17:14, 10 August 2011 (UTC)
 * Start by reading Sampling (signal processing). Next, read interferometry.  You are essentially suggesting time-domain interferometry, which is a known technique.  Finally, read the technical documentation I linked above, explaining the ATLAS data acquisition system.  The electronic design of an experimental physics program is very complicated; there are some prerequisite concepts you need to understand before you can make sense of the specific details of the LHC experimental setups.  In the case of ATLAS, for example, a high-resolution multi-instrument sample is triggered by a low-resolution trigger-system.  Particle trajectories are derived from massive quantities of data using very elaborate software post-processing.  If you are curious how this is done, here is the list of publications that explain the process.  Nimur (talk) 18:39, 10 August 2011 (UTC)


 * In general, one gets more detail by using the spatial distribution rather than finer timing. In 1 ns, particles can travel 30 cm.  In the most detailed sensors, sensor distribution can be less than 1 mm allowing hundreds or thousands of sensors to be tripped each ns.  The next nanosecond, the particle goes further and get more detail on the same track.  Knowing where the track began and ended during each nanosecond helps one to infer more precise timing.  Dragons flight (talk) 19:49, 10 August 2011 (UTC)

Mold on bread
I've been buying a 100% whole wheat (sprouted wheat) bread that does not carry a manufacture or fresh-by date on the otherwise professionally designed packaging. There is a bit of molasses (2% DV of sugar), no salt. The last bag I placed in the fridge as soon as I got home. With half of it left, I noticed mold on some of the slices, so I trashed it. No doubt I had eaten a few spores before I'd done so.

Knowing next to nothing about breadmaking, I'm guessing that the mold came from the yeast used to rise the bread, so it should be less harmful than one would otherwise suppose, right? Imagine Reason (talk) 02:42, 10 August 2011 (UTC)


 * No, the mold would not be yeast growing out of control, but rather another micro-organism either introduced when it was made and packaged or subsequently when you handled it. However, bread molds don't seem to be all that harmful, and some bread molds are actually beneficial, like penicillin.  Still, I wouldn't eat any if it can be avoided, because there are a few nasties, like ergot.  I suggest you freeze this bread, if you buy it again, to keep it from spoiling.  StuRat (talk) 02:57, 10 August 2011 (UTC)
 * The rule I learned from my mother (so it may be totally off, but I follow it to this day) is that mold on bread is bad; if you see the slightest bit of mold on your bread you have to throw the whole loaf away. Mold on cheese, on the other hand, is not so bad; you can just cut off the moldy part and eat the rest of the cheese. (Referring to unintentional mold on cheese of course: if you're eating bleu cheese, you're supposed to eat the mold together with the cheese.) For products other than bread and cheese, you're on your own. Pais (talk) 08:04, 10 August 2011 (UTC)
 * I think your mother may have been a little over-cautious, but that was her prerogative, being rresponsible for others' health as well as her own. Being poor, I can't afford to throw away food unnecessarily, and whenever possible buy bread (and other foodstuffs) reduced in price having reached its "sell-by" date. Not infrequently the later-consumed portions of a loaf, packet of rolls or whatever have developed a few surface spots of mould by the time I reach them (and which I am usually able to detect by smell even before spotting them visually): I simply remove them and a small area around/under their position. However, more extensive surface mould spots/patches, or any mould actually within the body of the loaf, etc, would cause me to discard the item. In several decades I have never suffered any ill-effects as a result, but while I'm prepared to chance my own health (not in any case being particularly delicate in constitution, perhaps because such practices keep my immune system well-exercised), it's not something I'd risk with anything someone else was going to eat. {The poster formerly known as 87.81.230.195} 90.201.110.129 (talk) 10:07, 10 August 2011 (UTC)
 * The USDA advises discarding moldy bread but says you can use moldy hard cheese if you cut off an inch around the mold. Their factsheet has information on food mold in general and what to do with various types of moldy food. --Colapeninsula (talk) 11:27, 10 August 2011 (UTC)
 * I doubt you really know if you've suffered any ill effects. It's possible you've increased your chance of getting cancer by 0.5% for example but there is no real way you'd know that. Nil Einne (talk) 15:52, 10 August 2011 (UTC)


 * General advice: bread goes moldy fairly quickly if kept moist by sealing it in plastic. If stored in paper, or loose in a non-airtight breadbin, or out on a bread board (perhaps covered with a teatowel to keep flies off) it will go stale, but it won't generally go mouldy in a normal timeframe. So if you're prepared for the bread to get tougher and staler over the days it takes to eat, you can avoid mould by allowing it to slowly dry out. Stale bread still makes fine toast, as well as chewy/crunchy sandwiches, and can be used to make croutons and eggy-bread and bread and butter pudding, as well as summer pudding. Stale breadcrumbs can be used to thicken soups or make bread sauce or treacle tart. If you're looking to save money, people have developed all sorts of uses for stale bread over the centuries, so it can continue to be food. Mouldy bread is worthless. 82.24.248.137 (talk) 13:31, 10 August 2011 (UTC)


 * Also (unrelated to the mold question), don't put bread in the refrigerator. It makes it go stale very quickly. You can freeze bread, but you cannot refrigerate it. If you don't eat your bread quickly, put half the loaf in the freezer and put the other half in a closed container in a (hopefully) cool dry location (like a pantry). -- k a i n a w &trade; 13:51, 10 August 2011 (UTC)

Keep in mind that the problem with mold on food is not that it is a germ which can infect you from one invisible cell but has potentially released toxins which could make you ill if eaten in large quantity. You certainly don't need to cut away a whole inch from mold on hard cheese. Any toxins will stay close to the visible colored fruiting bodies. Removing all the affected surfaces down to an eighth of an inch will work just fine. As for a sliced loaf of bread, if you are sure you don't see any growth on a particular slice it is fine--there wouldn't be enough toxin to make you ill if there is not enough mold to be visible. μηδείς (talk) 16:52, 10 August 2011 (UTC)


 * Why would putting bread in the refrigerator make it go stale quickly? Bus stop (talk) 18:35, 10 August 2011 (UTC)


 * Bread goes stale because of a breakdown in the starches. There are many ways in which the starches can go stale. One is by crystallization, which happens just above freezing (refrigerator temperatures). So, keeping bread in a refrigerator increases the staling process (see the link in case it has better information). -- k a i n a w &trade; 19:21, 10 August 2011 (UTC)


 * Thanks, Kainaw. That Staling article does confirm the "just above freezing" factor. Bread is a pretty delicate thing, it seems. It is composed of a lot of air spaces. I wonder if there could be a high-tech storage container that exchanged the air for some particular gas chosen for its non-staling effect on bread. Even if possible, it would be more expensive than buying another loaf of bread, but I wonder if some gasses are non-staling. Bus stop (talk) 14:42, 11 August 2011 (UTC)


 * See this book if you want more information than any normal person would want to know. -- k a i n a w &trade; 14:52, 11 August 2011 (UTC)


 * When I have baked bread and left it on the counter in a plastic bag, it has stayed for a couple of weeks without any mold appearing, even though it stayed moist, and even without all the preservatives in commercial bread. On the other hand, I have seen expensive bread baked in the bakery department of a gourmet grocery store get moldy in 3 days. A training course for bakers which I once studied said there are many kinds of mold found in bakeries and other places which store lots of bread. According to "Food and beverage mycology,(1987)" by Larry Beuchat, besides the penicillium mold, there are many kinds of "bread mold:" "Black bread mold" from R. nigracans, "red bread mold" from Neurospora intermedia. Bacillus mesentericus causes "ropy mold."  Serratia macescens causes "bloody bread." There are two yeasts, not the type used to make bread rise, which cause "chalky mold."   Commercial bakeries use trucks which take new bread to the stores, and which bring back stale "returned" bread which is near the end of shelf-life, either to the bakery, to charities or some place which converts it into some other product. I suspect that mold from old scraps of bread in a bakery, or from trucks, could get on newly baked bread, while it is in a cooling rack after the baking, or while it is being sliced, or from packaging machinery. The home kitchen might not have not have the inventory of bread mold spores drifting around in the air that a commercial operation has. One practice in commercial bakeries which fosters growth of mold is packaging it while it is still too warm, causing condensation of moisture, per "Modern food microbiology,(2005)" by Monroe et al. pp 203-204. "Baking Techmology" (1922) pages 338-339, described how just bringing one loaf of moldy bread into a room filled the air with spores of aspergillus niger, which causes black mold.  Some unscrupulous bakers mixed old baked goods  back in the dough and sold as a portion of the newly baked goods, vastly increasing the likelihood of contamination. Edison (talk) 19:02, 10 August 2011 (UTC)

sc
do homes in Charleston, sc have insulation  — Preceding unsigned comment added by Von1235 (talk • contribs) 10:52, 10 August 2011 (UTC)
 * They have insulation.  Ebe 123  talkContribs 12:04, 10 August 2011 (UTC)


 * This question appears to be based on two types of houses available in Charleston:
 * First, there is the carriage house. Originally, these were garages. We park cars in our garage, but they used to park carriages in them. Many houses have large carriage houses next to them that are rented or sold as housing. A carriage house listed as utility doesn't have to be insulated, but when it is listed as residence, it must be insulated to meet code.
 * Second, the old slave houses were not insulated. But, to be fair, insulation was very rare at that time. So, no houses were insulated. After the Civil War, what little was left of the plantation housing (most was burned) was used by the ex-slaves. As insulation became popular, they did not insulate their homes. Further, they continued building their own houses in the same style. You can still find many "raised shotguns" along the sea islands. It is a long, narrow house raised about 3 or 4 feet off the ground. The short end points towards the ocean so the sea breeze will blow under the whole length of the house and cool it down. Those houses do not meet code - but out on the sea islands, there is very little inspection of homes. It is important to note that the sea islands are not part of the city of Charleston, but some are in the county of Charleston. Further, they are being heavily developed, which is driving the Gullah (the people who lived there) out of the islands and removing their old homes. -- k a i n a w &trade; 12:57, 10 August 2011 (UTC)

How to get rid of mice
Hello. I'm trying to get rid of mice at home. I've tried snap traps, bucket traps, humane traps, ammonia and filling in every hole I can see. But I've been unable to catch any mice at all. The only three things I can think of are:

1) Getting a cat (but I don't want a cat) 2) Using rat poison (but in addition to causing a very gruesome death, there's the danger that mice die in some hard-to-acess place and start rotting away) 3) Using glue boards (but these are also very gruesome and I don't know whether they're legal in my country).

Does anyone have other ideas? Thanks! Leptictidium (mt) 13:48, 10 August 2011 (UTC)


 * Snap traps have worked for me in the past, but you have to make sure the mice can only access the trap from the front. If they take the bait from the side, they won't get caught. If you put the trap in a corner, so that two sides of it are blocked off, and then block off the third side with a piece of wood or a bottle or something, then the mouse can only approach the trap from the front and will get caught. Pais (talk) 14:15, 10 August 2011 (UTC)
 * Ditto. Snap traps positioned on the floor against a wall (mice are great wall followers) and bated with peanut butter, which invites repeat trips. IMO cats are useless; they're more likely to bring mice in from outside & release them. I've never had to block the sides of the trap. --Tagishsimon (talk) 14:20, 10 August 2011 (UTC)
 * Worst case, you could hire an exterminator. Googlemeister (talk) 14:28, 10 August 2011 (UTC)


 * (Ec) I'm rather surprised that you've been unable to catch any mice with snap traps. Are the traps being triggered without catching any mice, or are the mice ignoring the traps?  (Or are the traps failing to trip even when a mouse is present?)  In my experience, the plastic snap traps with the semi-circular jaw have a wider 'working angle' than the older wood-and-metal bar traps; they also seem to have a more sensitive trip (which can be a bit of a nuisance when setting them).  I've also found that peanut butter is an extremely effective bait.  Place traps in areas where you've seen mice (or signs of mice: mouse poop and chewed-up stuff).  Locations along walls are good; mice don't like to be out in the open, and you don't want to step on traps.
 * Try to be extra-fastidious about food spills and crumbs for a few weeks, too&mdash;hungry mice may be encouraged to seek out easier pickings in your neighbor's house. While plugging obvious holes won't hurt, the truth is that mice can squeeze through a 6 mm (quarter inch) gap, and it's virtually impossible to get every single one of those.  TenOfAllTrades(talk) 14:34, 10 August 2011 (UTC)


 * Steel wool is good for plugging small gaps - the mice can't chew through it, although you have to be careful not to leave small holes as TenOfAllTrades said. 15:15, 10 August 2011 (UTC)
 * I'd suggest bronze wool instead old boy - steel has a dashed nasty habit of rusting when it gets wet which can cause beastly unpleasant stains and odours. Quintessential British Gentleman (talk) 16:33, 10 August 2011 (UTC)
 * I have had the same problem with snap traps. They catch a mouse once in a while but most of the mice just ignore them, even when baited with peanut butter. thx1138 (talk) 15:46, 10 August 2011 (UTC)


 * Not sure whether this is true, but I've heard that snap-trapped mice (killing is rarely instant) leave a tell-tale pheromone in their pee so that other mice avoid the trap. They are very clever and very wary. They also have a homing instinct which means that even if you humanely trap them and release them outdoors they will find their way back, and they won't be caught twice.--Shantavira|feed me 16:16, 10 August 2011 (UTC)


 * My experience is that this isn't true. With occasional mouse plagues I have had to revert to using traps. I reuse the same traps multiple times. Have found no diminished effectiveness in the reused traps - actually, from a totally anecdotal observation, if anything once a trap has caught one mouse it seems to have have greater likelihood of catching more. --jjron (talk) 08:30, 11 August 2011 (UTC)


 * Glue traps are not painful. Check them daily and then put the trap in a small bag and dispatch any trapped mouse with a mercifully quick blow to the head from a can of Goya Black-Bean Soup or any Goya canned product you prefer.  μηδείς (talk) 16:33, 10 August 2011 (UTC)


 * Not painful ? I saw a mouse rip half it's face off trying to get away. StuRat (talk) 16:44, 10 August 2011 (UTC)


 * I'm with you on that old boy - glue traps are really not cricket. If you must use deadly force against the blighters use snap traps - instant death. Quintessential British Gentleman (talk) 16:50, 10 August 2011 (UTC)


 * Or better yet, drown them in a spot of tea. What could be more civilized ? StuRat (talk) 17:24, 10 August 2011 (UTC)


 * No, drowning is slow torture, a womanly act of cowardice from a ponce afraid to deal the coup de grace with swift manly grace. μηδείς (talk) 18:17, 10 August 2011 (UTC)


 * They die in seconds when submerged, so I don't see how it could be "slow torture." "Fast torture," maybe. But "lethal injection" of tranquilizers, followed by a general anesthetic to produce unconsciousness, followed by a drug to stop the heart, seems ridiculous for mass numbers of vermin. My gold standard for getting rid of a large number of mice is the http://www.google.com/products/catalog?q=mouse+trap&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&tbm=shop&cid=3401823187228338771&sa=X&ei=ktFCTvuvH4qGsgLUybDnCQ&ved=0CHMQ8gIwAQ Victor M260 Multi-Kill Electronic Mouse Trap.]. Bait it with a dab of peanut butter. Then it electronically detects the presence of a mouse inside the trap, electrocutes it within 5 seconds with high voltage, and dumps the carcass into a holding chamber. It can accommodate 10 mice, one after the other. 4 C batteries can kill 150 mice. It is pricey, costing from $72 to $99 depending on where you shop. I suggest emptying it every couple of days to avoid stink. For regular snap traps, I also recommend baiting with peanut butter, and placing the trap so its long axis is nest to the wall or baseboard, since mice tend to creep along next to the wall. Edison (talk) 18:49, 10 August 2011 (UTC)


 * Nonsense. I have tried drowning mice.  It takes more than "seconds"--assuming you mean by that less than ten.  I repeat, drowning them is for womanly ponces more concerned with handwashing than mercy--cruelty born of cowardice.  Crushing their skulls with a can of beans kills them quickly enough that they die without suffering. μηδείς (talk) 18:59, 10 August 2011 (UTC)
 * Remind me never to eat canned beans at your house. Edison (talk) 20:18, 11 August 2011 (UTC)
 * It seems to take about 12 seconds for them to drown. I'd much prefer that to having blood splattered about. StuRat (talk) 19:29, 11 August 2011 (UTC)
 * I did say put the trapped mouse in a small shopping bag before administering the coup de goya, did I not? μηδείς (talk) 19:21, 12 August 2011 (UTC)


 * The glue itself is not painful--mice will try to escape any type of trap--that's why I said check them daily--and snap traps, which are less successful than glue traps, are always painful when not instantly fatal. μηδείς (talk) 17:16, 10 August 2011 (UTC)


 * You will hear them writhing in pain before you go around to check. StuRat (talk) 17:25, 10 August 2011 (UTC)

Wrap your house in a big piece of airtight plastic and pump chlorine gas in it. Count Iblis (talk) 17:41, 10 August 2011 (UTC)
 * Most people with mouse problems live in apartment buildings. μηδείς (talk) 18:18, 10 August 2011 (UTC)


 * No, you will not necessarily hear them first--although I would say you hear the initial squeak of surprise maybe 30% of the time assuming you are on the same floor. I am philosophically opposed to killing most organisms, including spiders and stink bugs and other harmless invaders.  I consider life sacred--and since I myself am alive I also consider self defense perfectly valid.  I don't even pull weeds or throw acorns in the trash--I liberate them in a nearby wooded area to sprout or serve as squirrel fodder rather than sending them to the dump in the trash.  But like roaches and bedbugs, mice and rats are deliberate parasites and invaders, which I will kill as effectively as possible, as I would a dose of the clap.  My experience is that glue traps are the best at catching mice, and that the mice can be killed with a mercifully quick head crushing blow, assuming you have the balls to dispatch them yourself.  Yes, I did once find a mouse with half its face pulled off as well.  But that is the way such things go.  μηδείς (talk) 18:07, 10 August 2011 (UTC)


 * Oh, and we are not "deliberate parasites and invaders" when we invade another creature's habitat, capture them, subjugate them, breed them, and slaughter them—and serve them on a bun with fries and a large Sprite? And how about collecting their milk and their eggs (two separate animals)? As if that isn't parasitic. : ) Bus stop (talk) 19:07, 10 August 2011 (UTC)


 * You so crazeh. Have at it then.  Let the cows and chickens like yourself who resent being born and dying on farms rather than in the wild attack.  I dare you. μηδείς (talk) 21:40, 10 August 2011 (UTC)


 * Farming for milk and eggs definitely seems symbiotic, rather than parasitic, as the livestock gets lots in return, like food, water, and shelter, and hence are able to maintain a much larger population. The same could also be argued about animals killed for food, although there they might decide they would rather go free, if they could understand that staying means certain death. StuRat (talk) 19:27, 11 August 2011 (UTC)


 * "... mice and rats are deliberate parasites and invaders, which I will kill ... as I would a dose of the clap." That explains the crushing blow from a can of Goya Black-Bean Soup. -- 110.49.234.50 (talk) 07:59, 12 August 2011 (UTC).
 * Today we have less painful treatments for a dose of Gonorrhea though the soup would be nice too. Cuddlyable3 (talk) 10:37, 12 August 2011 (UTC)


 * Lol, literally. μηδείς (talk) 19:21, 12 August 2011 (UTC)

I have seen some dogs - terriers and beagles - do very quick and effective mouse elimination. You may be able to borrow one. HiLo48 (talk) 22:32, 10 August 2011 (UTC)


 * I recommend snap traps against the wall + mouse poison. Kittybrewster  &#9742;  14:04, 11 August 2011 (UTC)


 * I've had bad experiences with poison. Poisoned mice aren't able to hide like normal mice, so might stagger across the floor in the middle of your dinner party.  Also, if they do die in some inaccessible space, you not only get the decomposition smell, but they also give off the smell of the poison, which I found even more noxious (perhaps it had been metabolized into something like formaldehyde).  And, of course, poison is out if you have pets or small children.  StuRat (talk) 19:22, 11 August 2011 (UTC)


 * I know you said you don't want a cat, but if you know anyone with a Maine Coon or a Norwegian Forest Cat you could borrow it for a few days. They are both good mouser breeds. Beeblebrox (talk) 15:57, 11 August 2011 (UTC)


 * I would think the size of a Maine Coon cat would prevent it from getting at mice in the small places they like to hide. StuRat (talk) 19:14, 11 August 2011 (UTC)


 * Get a seagull, preferably a great big, burly one. If you've ever seen a v.large gull catching mice, you'll know that they don't mess around at all in terms of catching and killing - and have a huge appetite. --Kurt Shaped Box (talk) 21:53, 11 August 2011 (UTC)

Toricelli-style barometer liquid height vs. basin area
With a barometer like the one Toricelli made consisting of just an inverted tube of mercury in a mercury-filled basin, would a larger basin area result in a higher column? It would seem to me that the same atmospheric pressure applied to a larger area would result in a larger amount of force available to push up the column, but I've seen many sources state that 1 atm. is roughly equivalent to 760 mm Hg without specifying any basin area. Is there a standard basin area in the definition of a Torr, or could someone explain how column height is invariant to basin area. Thanks. 20.137.18.50 (talk) 14:59, 10 August 2011 (UTC)
 * The surface area of the liquid in the basin makes no difference at all. This is because the additional "total" force added by having a larger surface area is exactly counterbalanced by the additional distances over which that force is dissipated.  Think about it: If the forces increased with surface area in the way you describe, wouldn't extremely large objects be subject to the real threat of being crushed due to the excessive forces?  How could you build something as large as a skyscraper, with its huge surface area, if we added up all of the pressure on its huge surface, wouldn't it just crush the building?  The fault in your thinking is that the extra "total" force can be directed at the submerged tube only.  It isn't, the applied force is equal in all directions, which means that changing the surface area or volume or anything else about the basin (or the tube for that matter) ends up having no effect on the height of the fluid in the tube.  There are some secondary effects when you play around with the sizes, like Capillary action effects, but these are so small as to be insignificant on most standard sized mercury barometers.  -- Jayron  32  15:10, 10 August 2011 (UTC)


 * (ec) Think about it this way. Across the exposed surface of the mercury pool, there is a uniform pressure exerted by the atmosphere (about 100 kPa, or 14.6 pounds per square inch, or 760 torr).  The units don't matter as long as they're units of pressure; don't forget that pressure is measured not as force alone, but as an amount of force per unit area.  Now consider the little patch of mercury that sits under the barometer tube.  If there's no mercury (and no air) in the tube, then that mercury under the tube feels no force from above and is pushed up by the mercury under (atmospheric) pressure around it.  The mercury column will continue to rise until the pressure on the mercury at its base exactly matches the pressure of the mercury around it.  Neither diameter of the tube nor surface area of the mercury pool matter, because pressure is based on force divided by area; as Jayron32 notes, the extra force on a broader pool will be divided by a proportionately larger area.  Every square inch of the pool supports 14.6 pounds of force, either from the open air, or from the weight of mercury in the column.
 * Note that this principle is used to great effect in hydraulic machinery, where small forces applied to small-diameter pistons can be used to generate large forces on large-diameter pistons. (The brakes in most automobiles rely on this effect.) TenOfAllTrades(talk) 15:28, 10 August 2011 (UTC)
 * So if I had a tube 761 mm tall and 1 mile in diameter sitting in a basin 1 mile and 1 mm in diameter, the mercury would still sit 760 mm tall? 20.137.18.50 (talk) 15:35, 10 August 2011 (UTC)
 * Ignoring the technical problem of generating a hard vacuum inside of a tube of that size, yes. -- Jayron  32  15:48, 10 August 2011 (UTC)
 * I just tried doing some calculations. The density of mercury is 15.534 g/cm^3. A mile is about 160,934.4 cm. The volume of a cylinder 160,934.4 cm in diameter and 760 mm tall is about 1.546*10^12 cm^3, which has a mass of about 2.401*10^10 kg, and a weight of 2.353*10^11 N. That's the downward force on the fat column due to gravity. The surface area of the thin ring of basin is the difference of the circle of diameter 1 mile + 1mm and the circle of diameter 1 mile, which is about 2.523 m^2. That multiplied by atmospheric pressure of 101325 N/m^2 equals 255,642.975 N. Note that I've made a mess of significant figures, but still, 2.353*10^11 N down by gravity on the giant column and 2.55642975*10^5 up from atmospheric pressure on the little ring. 20.137.18.50 (talk) 16:24, 10 August 2011 (UTC)
 * OK, so what? -- Jayron  32  16:31, 10 August 2011 (UTC)
 * So why wouldn't the greatly outweighing gravitational force easily push up the mercury in that thin ring? Remember, it's 2.353*10^11 N vs. ~2.556*10^5 N. 20.137.18.50 (talk) 16:32, 10 August 2011 (UTC)
 * No basin is actually necessary. If you made the bottom of that inverted tube of mercury out of a fine mesh so that little bubbles of air wouldn't easily enter due to surface tension, the mercury would stay up solely due to the air pressure beneath it. Wnt (talk) 16:48, 10 August 2011 (UTC)
 * Another way to look at it: it's not just the air that is under pressure - the mercury is under pressure. At the basin it's under 760 torr.  At the bottom of the tube, the same.  Higher up in the tube, less, until you get to zero where the top of the mercury is.  Now will mercury flow from a pressure of 760 torr to another pressure of 760 torr?  Not likely.  Like the Persians at Thermopylae, there's no motion at the front so there's none at the rear either. Wnt (talk) 16:52, 10 August 2011 (UTC)
 * OK, that explanation helped, Wnt. I calculated the weight of a cube of mercury one square meter in area and 760 mm tall and divided that by 1 m^2 and got pretty much 1 atm. in Pascals. 20.137.18.50 (talk) 17:08, 10 August 2011 (UTC)
 * Did that surprise you? Dauto (talk) 06:10, 13 August 2011 (UTC)

RED RAIN
i recently read the article "red rain in kerala(India)".in that they mentioned a wide range of hypothesis for the phenomena but none of them made no sense.So could one point out the most authentic explanation for the phenomena.thanks.. — Preceding unsigned comment added by 175.110.242.217 (talk) 16:58, 10 August 2011 (UTC)
 * The article is Red rain in Kerala. I agree that there's a lot of weird stuff in that article, but the spore hypothesis is the one that makes the most sense to me. Looie496 (talk) 17:03, 10 August 2011 (UTC)
 * What about claims of extraterrestrial life? — Preceding unsigned comment added by 175.110.242.217 (talk) 17:06, 10 August 2011 (UTC)
 * Well, my personal opinion is that those claims are not plausible. Looie496 (talk) 17:09, 10 August 2011 (UTC)

Red rain can be caused by waterspouts and tornadoes sucking up red soil. μηδείς (talk) 18:09, 10 August 2011 (UTC)
 * We definitely get red rain in Australia when a dust storm encounters a thunderstorm. There is no need to postulate extraterrestrial life when there are several possible terrestrial explanations. HiLo48 (talk) 22:29, 10 August 2011 (UTC)
 * I'm persuaded that in this case the spore explanation is correct. See  (source 5 from the article).  Not merely were the spores (and not dust) found under a microscope, but they were actually cultured in agar medium, and special sporangia observed.  It may seem mysterious that lichens would produce so many spores in synchrony, which would go so far up in the air, but I would assume this has something to do with how the winds blow in the area - maybe the way the monsoon season works? Wnt (talk) 12:45, 11 August 2011 (UTC)


 * Barely mentioned in the article is the fact that the area being discussed has regularly had rain colored by spores in the past. Usually, it is green or black. This time, it was red. So, the real question shouldn't have ever been "what is it?" They knew it was spores. It should have been "why are the spores red this time?" -- k a i n a w &trade; 12:52, 11 August 2011 (UTC)

What are elementary particles, really?
And don't say preons, 'cause then the question is "what are preons." Are they just "crystallized" energy, so to speak? Energy fields? A truly solid sphere of "stuff"? --Goodbye Galaxy (talk) 18:54, 10 August 2011 (UTC)


 * All we can meaningfully say is, "we observe certain properties of the universe. Some of those properties appear to be localizable, so we can assign them a position coordinate.  We call those things particles."  It so happens that we observe sixteen types of such particles.  Nimur (talk) 19:03, 10 August 2011 (UTC)


 * There are several different ways to count elementary particles with different results. I can't think of a single one that gives 16 as a result. Dauto (talk) 20:36, 10 August 2011 (UTC)
 * Sorry. Standard Model; twelve elementary particles, plus four bosons.  My error.  And of course, as Dauto correctly points out, there are other classification schemes; and there are speculations about gravitons and Higgs bosons; and there are proposed unification theories that reduce the number of elementary particles, and so forth.  Nimur (talk) 20:44, 10 August 2011 (UTC)
 * Bosons are a type of elementary particle, so 16 is a good answer. It misses out all the anti-particles of those (some are their own anti-particles, so it's not going to be 32). --Tango (talk) 21:28, 10 August 2011 (UTC)


 * I guess there is a way to get 16 if one chooses to exclude unobserved particles such as the Higgs. Particle Physicists usually count different colors and different chiralities separately so you have 3 generations of 15 fermions plus 15 anti-fermions each for a total of 90 fermions plus 1 photon, two Ws, 1 Z, 8 gluons, and 1 Higgs. for a total of 13 bosons to which you may chose to add the Graviton. Then, there are even more speculative possibilities such as superparticles, axion, and more... Dauto (talk) 23:54, 10 August 2011 (UTC)

Particles are excited states of fields. Count Iblis (talk) 21:35, 10 August 2011 (UTC)
 * Could you elaborate on that a bit more? --Goodbye Galaxy (talk) 16:45, 11 August 2011 (UTC)
 * The best answer for a layperson to understand is probably Nimur's first answer. A particle is a set of properties confined to a set of localized coordinates in space-time.  That is, a particle is a particle because it exists in a specific place at a specific time.  Fields are properties that lack localization.  -- Jayron  32  17:08, 11 August 2011 (UTC)

1/6 mv^3
In all reactions mass is conserved, momentum is conserved, and energy is conserved. mass = m momentum = mv kinetic energy = 1/2 mv^2 Each term in this sequence is the integral of the previous one with respect to velocity. mv= ∫ m dv; 1/2 mv^2 = ∫ mv dv; etc. Does the series keep going? Since ∫ 1/2 mv^2 dv = 1/6 mv^3, is 1/6 mv^3 the basis for a conservation law? Why or why not? 98.116.111.230 (talk) 19:01, 10 August 2011 (UTC)
 * I have formatted your question with "pre" tags to preserve your linebreaks. Nimur (talk) 19:04, 10 August 2011 (UTC)
 * You can calculate the value of "1/6 m v^3," but it is not a conserved quantity. It just ... isn't.  Nobody knows why.  Something in our universe seems to have a preference for the second derivative.
 * Our article, Conservation law, outlines the quantities that we have determined (by careful experiment) that must be conserved in our universe. Why these, and not any others?  That's a very interesting question.  A lot of times, we can construct equations to describe symmetry; in other words, actually, only a subset of some properties are conserved, and they are generalizable under some symmetry transform to a unified property; but, despite the best efforts of many physicists, we have not yet come up with a satisfying simplification of this model.  Nimur (talk) 19:08, 10 August 2011 (UTC)
 * Thank you! That was very insightful! 98.116.111.230 (talk) 19:51, 10 August 2011 (UTC)

Note that mass is only conserved in the classical limit. You can then consider that limit and derive the classical conservation laws for mass end kinetic energy, as I did here. Count Iblis (talk) 19:57, 10 August 2011 (UTC)


 * ... and although mass/enerygy as a whole is conserved, kinetic energy by itself is often not conserved e.g. projectile motion; ball on an inclined plane; pendulum; mass on spring; charged particle in an electric field. Gandalf61 (talk) 11:46, 11 August 2011 (UTC)


 * The fact that they are integrals is something of a coincidence, hence the lack of physicality in your extrapolation. They are physically found by taking leading order expansions of the equivalent relativistic quantities (in the limit c->infinity). Where we find E^2=p^2+E_0^2 with E_0=mc^2. There is no obvious way of extracting any more quantities from this in the manner in which you did. — Preceding unsigned comment added by 129.67.37.188 (talk) 22:03, 11 August 2011 (UTC)

Orbital acceleration
Let's take an extreme case of an orbit in space: let's say an inordinately high amount of gravity, and thus an inordinately high required velocity relative to the radius of your orbit. Let's say values that if on an equivalent scale done with a human in an amusement park ride like the Rotor, one would be able to feel as they get pushed against the wall (the normal force of the wall being analogous to the gravitational force in the orbit). If a person was in an orbit around another object like this, would the person be able to "feel" the acceleration like they would in the amusement park ride? My intuition says no since there is nothing that is pushing against you, and every particle in your body is being accelerated towards the mass around which you are orbiting. If not, a further question would be what sort of an experiment could you do to confirm that you are in fact in an accelerated noninertial reference frame? 98.116.111.230 (talk) 19:50, 10 August 2011 (UTC)
 * You are correct, you would be in free-fall so would feel weightless. You could measure tidal forces (which are simply the difference between gravity at two different points, eg. one point nearer the central mass than the other). --Tango (talk) 21:31, 10 August 2011 (UTC)
 * How would you be able to measure the gravity at a given point if you can't perceive it since you're weightless? — Trevor K. —  01:11, 11 August 2011 (UTC)  — Preceding unsigned comment added by Yakeyglee (talk • contribs)
 * You can't measure gravity with a local experiment at a single point. You can however measure the difference between gravity at two different nearby points, for example by observing the behavior of two large masses connected by a spring of negligible mass.  For more realistic measurement of gravity's gradient, see gravity gradiometry.
 * In the right circumstances, it also works adequately to measure gravity in an absolute sense nonlocally, by using the light from a distant reference star, which is taken to not be accelerating. Gravity Probe B used a reference star like that.  Red Act (talk) 05:23, 11 August 2011 (UTC)
 * Larry Niven's short story "Neutron Star" has a very similar scenario (not an orbit but a flyby). Clarityfiend (talk) 22:21, 10 August 2011 (UTC)

Pharoh ants
Where can I obtain live pharaoh ants? As transparent as possible for trying ? 99.36.74.131 (talk) 23:52, 10 August 2011 (UTC)
 * From an ant shop? If they don't have what you want they may know a source. Richard Avery (talk) 06:28, 11 August 2011 (UTC)
 * I have a feeling in a few months he'll be back asking how to get rid of Pharaoh ants... ;) Wnt (talk) 12:48, 11 August 2011 (UTC)