Wikipedia:Reference desk/Archives/Science/2011 September 25

= September 25 =

How do slot machines "decide" when to pay out jackpots and other large winnings?
What kinds of variables, factors, formulas, etc. do they use? Thanks. --70.179.163.168 (talk) 01:42, 25 September 2011 (UTC)


 * Have you read Slot_machine? --Mr.98 (talk) 01:47, 25 September 2011 (UTC)


 * I have every once in a blue moon read some intriguing news snippet about people prosecuted for using "an electronic device" to influence the odds of slot payouts. I assume that the organized crime syndicates that set up the casinos must have ways to make it as easy for someone to win big as it is for someone delivering a payment to arrange to lose everything; otherwise it wouldn't be a very effective way to tracelessly launder money.  Though apparently lower-tech methods work pretty well. Wnt (talk) 03:55, 25 September 2011 (UTC)


 * Looks like someone might have been watching too many James Bond movies... ;-) 67.169.177.176 (talk) 04:21, 25 September 2011 (UTC)

Frozen milk
Why is it that when you defrost a bottle of frozen milk, that the liquid milk is initially richer in lactose, making it digustingly sweet? Only once the milk is completely defrosted, does the lactose concentration return to normal. Plasmic Physics (talk) 06:27, 25 September 2011 (UTC)


 * Ice formation means that the water is all tied up, so anything in the rest of the milk is more concentrated, basically fractional freezing. SDY (talk) 06:43, 25 September 2011 (UTC)

Oh. That reminds me, can you filter out the additives from denatured ethanol using fractional distallation? Add water to denatured ethanol, and partially freeze it so that it forms a crust of ethanol/water. Collect the crust, and repeat after adding more water. Melt all the crusts back down into a ethanol solution. Keep adding anhydrous magnesium sulfate untill anhydrous ethanol is obtained. Will the crusts be free of additives? Plasmic Physics (talk) 09:13, 25 September 2011 (UTC)
 * I don't think so - fractional freezing will enrich the liquid portion in the lower freezing part of the mixture -eg alcohol - but it will not remove methanol from the alchohol mixture - this remains in the alcohol part not the frozen water part.Imgaril (talk) 11:03, 25 September 2011 (UTC)

I don't have to worry about methanol - in modern times, methanol is banned in many countries, from being added as a denaturant. According to the article, the frozen component contains ethanol, that is what I am taking advantage of. Plasmic Physics (talk) 11:23, 25 September 2011 (UTC)
 * Do you have a reference for that? My understanding is that methanol is still the most common additive used to denature ethanol. That's what our article on denatured alcohol seems to say. The whole point of denaturing it is to make it undrinkable, so that methanol is highly toxic is hardly a reason not to use it. --Tango (talk) 15:31, 25 September 2011 (UTC)
 * Denatured alcohol may or may not contain methanol; what it does usually contain are isopropanol (gives you a tummyache like you wouldn't believe), denatonium and various ketones (taste awful) and also pyridine (makes you throw up). Note that the additives are purposely chosen so that they cannot be easily removed from the alcohol. 67.169.177.176 (talk) 02:25, 26 September 2011 (UTC)


 * The way fractional freezing/freeze distillation works is that when water (or any other substance) freezes, it wants to form a regular crystalline lattice, as that's the most energetically favorable way of forming a solid (especially for water, which has all those hydrogen bonds to form). Any impurity would disrupt that crystal lattice, so the substance tries to exclude it from the lattice when possible (but if you freeze something long enough or fast enough, the impurities will get trapped in the solid eventually). Therefore anything that's not what's crystallizing gets concentrated in the still-liquid portion. -- 174.24.217.108 (talk) 18:01, 25 September 2011 (UTC)

I had a second look at the references, they seem to contradict each other, so I retract the statement on methanol. What about the remaining additives? Can the alcohol be removed using the above technique? Plasmic Physics (talk) 22:29, 25 September 2011 (UTC)


 * As for freezing to make the solution denser, it works with artificial tear eye drops: DO NOT apply eye drops you have just taken out from the freezer, wait till it melts instead. &#x2013; b_jonas 20:54, 28 September 2011 (UTC)

Why do farms have soil?
So I've been reading the article on hydroponics, and it occurs to me that if it is a method which is cheaper due to various efficiencies savings, and reliable, it is in the main simply better. In particular, better for industrial growing because the disadvantages can be dealt with by using good precautions. But latifundia of farms don't use hydroponics, almost all fruit and veg is still grown in all countries using traditional fields. Why is this, surely a hydroponic farm would be cheaper and therefore 'better' for the farmers? Prokhorovka (talk) 11:29, 25 September 2011 (UTC)


 * "Using good precautions" certainly costs money. And soil is getting cheaper and cheaper. The same applies to the logistics, which enables you to trade products across the globe, and therefore, from places with even cheaper soil. Quest09 (talk) 12:02, 25 September 2011 (UTC)


 * Cheaper in the long run and in bulk amounts. It requires a substantial amount of capital and know-how to start up. Something inaccessible to most people.--  Obsidi ♠ n   Soul   12:34, 25 September 2011 (UTC)

So it's soil economics and capital costs in the main? Many thanks. Prokhorovka (talk) 17:01, 25 September 2011 (UTC)


 * Add to it the risk of epidemics. Hydroponics are also an excellent for the cultivation of bacteria. Quest09 (talk) 19:02, 25 September 2011 (UTC)


 * Can you imagine the sheer complexity of having millions of hectares of hydroponics? How would you mechanically harvest a field of wheat or maize (let alone potatoes) without destroying the equipment? For veg it is already a reality (so long as 90 hectares is a latifundia) - check out Thanet Earth. SmartSE (talk) 22:20, 25 September 2011 (UTC)

Moon escape away from Earth
If the Moon were able to escape from its current orbit to a far enough point where no more Earth-Moon tides would be significant, would this affect Earth's day and by how amount approximately?--Almuhammedi (talk) 14:21, 25 September 2011 (UTC)
 * The answer to this type of physics question always depends: how would the moon "escape" from its orbit? If you can specify that, we can follow through with the consequences by solving the equations of motion for the Earth-Moon system.
 * For example, if you hypothesize that a giant comet large and fast enough to change the moon's orbit were to impact the moon, .... well, we would need to calculate the effect that such a large comet has on the orbits of Earth and everything else in the solar system, too. We could solve that problem by setting up an n-body problem to model the solar system, including Earth, Moon, Sun, and other planets; and we would use perturbation theory to study how sensitively the system reacts when we add in a new comet on a course to impact the moon.  The results are difficult to compute, but this can be done in a reasonable amount of time with a reasonable amount of effort.
 * Our article on tidal locking has some mathematics, including this equation, but it's lacking the context you would need to apply it in our hypothetical case. (The equation depends on some assumptions, e.g., that the moon is smaller than the earth, and so on - and the question is about Earth's day - so we need to reformulate that equation to solve for Earth as the object that will become tidally locked... which is just a little messy mathematical manipulation).  Suffice to say: the timescales for tidal locking (i.e., engaging an orbital/rotational resonance) depend very strongly on the distance between the Earth and the Moon.  By being farther away, the moon has a much smaller effect on Earth's rate of rotation.  This effect (semimajor axis to the sixth power) almost always will overpower any other effect, including a change in the Moon's mass, angular momentum, etc., due to inelastic collision with a comet.
 * On the other hand, if you just want to make something up, "just imagine" that the moon magically changes its orbit, all bets are off. We can't meaningfully speculate what consequences follow when one law of physics breaks "because of magic."  Anything could happen.  Everything we know about the way the Moon's orbit couples into the Earth's rotation depends on the rules of physics as we currently understand them.  Nimur (talk) 15:16, 25 September 2011 (UTC)


 * I'm afraid I was trying to just imagine that Moon has dropped suddenly from the 3 body or 2 body problem and I wasn't paying attention to other effects that will definitely take place. I was just interested in Earth's spin because I though it would be if affected the most significant thing we would realize (tides for example won't make things worse as I expect).--Almuhammedi (talk) 15:52, 25 September 2011 (UTC)


 * Tidal acceleration explains the effect of the Moon on day lengthening. Removing it would stop the change in day length, but the Earth needs no outside power source to keep turning.  Simple conservation of momentum keeps it spinning. Wnt (talk) 16:48, 25 September 2011 (UTC)
 * The tidal interaction between the Earth and Moon is causing the Moon to slowly move further away from the Earth and for the Earth to slow down in its rotation (lengthening the day). Removing the moon would stop that and the length of the day would become pretty much constant. There is a theory that the presence of the Moon has helped keep the orientation of the Earth's axis stable, so that orientation may start moving around more if the Moon disappeared. See What If the Moon Didn't Exist for a description of some work that was done trying to work out what the Earth would be like if the Moon had never existed (that's a little different to the moon disappearing now, but still interesting). --Tango (talk) 17:04, 25 September 2011 (UTC)
 * There's also a Discovery channel documentary called If We Had No Moon that's very informative. It may be available online. --George100 (talk) 14:43, 29 September 2011 (UTC)

Neutrinos speed at OPERA
What was the speed of alleged superluminous neutrinos in OPERA experiment? Our article doesn't specify it.--178.181.211.251 (talk) 18:19, 25 September 2011 (UTC)


 * From OPERA experiment: (1.0000228 ± 0.0000028statistical ± 0.0000030systematic) times the speed of light. Dragons flight (talk) 18:26, 25 September 2011 (UTC)
 * Which is what in km/h? 178.181.144.239 (talk) 19:15, 25 September 2011 (UTC)


 * 1,079,277,460 km/h Dragons flight (talk) 19:18, 25 September 2011 (UTC)

The implication that communication may travel backwards in time if neutrinos go faster than the speed of light is still nullified by the fact that neutrinos nor light can travel into the past by going more fast from point A to point B than in zero time. Going back in time requires time reversal and not just exceeding the speed of light. Try unburning a candle first. --DeeperQA (talk) 20:42, 25 September 2011 (UTC)
 * DeeperQA, who are you replying to? No one in this conversation mentioned sending messages back in time. APL (talk) 20:54, 25 September 2011 (UTC)


 * but since you mention it, I feel compelled to reply because what you said isn't correct. It would be correct if we lived in a Euclidean space. But Physicists know that this is not the case. That's been known for over a century now. This is a relativistic effect. Faster than light travel (FTLT) does indeed allow for messages to be sent backwards in time and that's why FTLT is believed by most physicists to be impossible. Dauto (talk) 23:16, 25 September 2011 (UTC)
 * Well I mentioned it because its usually the next thing to come. Lets say there is an electromagnetic wave that can travel in empty space but at slower speed due to a hiccup in its electromagnetic interaction. If you send info via that wave it will get there after the same info sent by light. You can send info by light versus by "slower" wave traveling back in time but it is not the same as time reversal except perhaps for using the speed of "slower" wave as your reference. My reference, however, is zero time in which it is not possible to travel at all. A candle will not burn in zero time and you can not unburn it if you started at a later time and tried to get time to go in reverse. --DeeperQA (talk) 01:14, 26 September 2011 (UTC)


 * See tachyonic antitelephone. If anything can travel faster than light, then it is always possible in principle to construct a system that allows information to be sent back in time.  If your tachyon is only slightly faster than light (as per the neutrino claim), then one half of your system must be moving just slower than the speed of light in order for it to work, but such things are always possible in principle.  Dragons flight (talk) 01:40, 26 September 2011 (UTC)
 * But either end could be the moving end, right? Maybe Wikimedia should build a stationary receiving end now, in case the Wikimedia foundation at some point in the future builds the 99.99+% speed-of-light spaceship needed to form the transmitting end. Imagine the advantages of letting editors from the future edit the encyclopedia. APL (talk) 02:00, 26 September 2011 (UTC)


 * Dauto and Dragons flight, the standard argument that FTL communication is always possible with tachyons makes very little sense, as I said in the thread. It depends on the weird quasi-Newtonian assumption that the causal "future" for an emitted tachyon consists of later coordinate times in the rest frame of the emitter. This is all kinds of crazy. First, I can't imagine why anyone would expect it to be true in the first place, post-1905; it's comparable to emission theories of light. Second, both ends of a tachyon worldline, or neither, can be "the emitter" by this definition, so it isn't even logically coherent. Third, what exactly is "the rest frame of the emitter" in quantum field theory? Fourth, wouldn't "the emitter" here be a muon traveling toward the detector at much more than (1 − .0000228) c wrt the ground? Because if so, and you believe this silly rule, then the emitted tachyon would have to be going at much less than (1 + .0000228) c. -- BenRG (talk) 02:22, 26 September 2011 (UTC)
 * I like the idea of recording something now and preserving it for the future so that it can be edited later on. It is the sending the edit back in time that I do not think will work. --DeeperQA (talk) 02:27, 26 September 2011 (UTC)

Oddly enough, its true that the theory of relativity is not a Euclidean model of space, and yet still, it has resulted in a century's worth of complex and useful modeling. Nevertheless, that has not stopped me from trying to sort this mess out for my own peace-of-mind, thus I should be blogging my Euclidean toy model in the near future, as it might help us to incorporate a recently discovered quantum mechanics analog, as well the new neutrino data, if necessary... such that we can perhaps ditch a load of metrics. Modocc (talk) 04:35, 26 September 2011 (UTC)

entry and exit door lock logic
Some front door locks have a small chisel edge knob in the center of the door knob that turns to lock or unlock the door. For some doors the chisel knob position controls both exit and entry. On other doors the chisel knob position does not effect exit but only entry. Where can I find a table or diagram for all types of entry and exit door lock logic? --DeeperQA (talk) 18:53, 25 September 2011 (UTC)
 * I believe that it's called a "Snib" if it helps. Alansplodge (talk) 21:45, 25 September 2011 (UTC)
 * ...humm, that introduces another level of logic where you can block use of a key. The entry logic would then have three states:
 * door unlocked
 * door locked requiring a key to open
 * door locked

--DeeperQA (talk) 01:27, 26 September 2011 (UTC)

Living on Mount Everest
Does anything live on the top of Mount Everest? Whoop whoop pull up Bitching Betty 19:16, 25 September 2011 (UTC)


 * No. Please stop asking all these frivolous questions. We have an article on Mt. Everest you know, perhaps you should try reading it. Beeblebrox (talk) 19:21, 25 September 2011 (UTC)


 * The article only says what lives on the mountain (all elevations,) not if anything lives on the TOP (summit) of Everest. And I do not believe i have asked many frivolous questions >:-( (two is not a lot.) Whoop whoop pull up Bitching Betty 19:26, 25 September 2011 (UTC)


 * Ok, let's try it another way. The top of the mountain is referred to as the death zone. What do you think might live in the death zone, where it is extremely cold and the air is so thin you have to bring your own oxygen? Beeblebrox (talk) 19:36, 25 September 2011 (UTC)


 * Well, come on, humans have to bring their own oxygen. Doesn't follow that everything does.  I don't know whether there's any life that can survive in that environment (some sort of plant or cyanobacterium with some serious antifreeze in its tissues?) but the question is not absurd on its face. --Trovatore (talk) 19:47, 25 September 2011 (UTC)

i have the same question in my mind, but im glad someone else asked it looking at the response it gets — Preceding unsigned comment added by 203.112.82.128 (talk) 19:48, 25 September 2011 (UTC)


 * Well, others have asked too. This astronaught chap went all the way to the summit in May 2009 to find out: "Searching for signs of life on Mount Everest could provide a window into the extreme environments that organisms might inhabit elsewhere in the universe. So, former astronaut Scott Parazynski will set up instruments to hunt down elusive evidence of life at the top of the world when he attempts to summit Everest Wednesday." Watch this space while I try to find out what happened. Alansplodge (talk) 20:18, 25 September 2011 (UTC)


 * More about Scott Parazynski's search here; apparently NASA were hoping to find some Endoliths. Alansplodge (talk) 20:29, 25 September 2011 (UTC)


 * According to our article, tardigrades have been found at altitudes of over 20,000 ft in the Himalayas, and they have survived exposure to the vacuum of space, so I imagine they could live at the top of Everest. Gandalf61 (talk) 20:44, 25 September 2011 (UTC)


 * This article states: "Pressure decreases with increasing altitude, such that at 10 kilometers (6.2 miles) above the Earth's surface, the pressure is only about one-fourth that at sea level. Organisms have been discovered growing on the top of Mount Everest, the highest point on the Earth's surface (more than 8.8 kilometers [5.4 miles])." Frustratingly there are no more details, but there is a list of sources at the end. Alansplodge (talk) 20:47, 25 September 2011 (UTC)

There have been periods in Earth's history when the entire Earth was frozen solid, see Snowball Earth and Huronian glaciation. Count Iblis (talk) 21:58, 25 September 2011 (UTC)

According to Alpine_Chough, 'It has been observed following mountaineers ascending Mount Everest at an altitude of 8,200 m (26,900 ft)' (ref's from a book, so I can't check it myself). Not inconceivable that it might also make it up to summit or thereabouts for a scrat around sometimes. --Kurt Shaped Box (talk) 22:12, 25 September 2011 (UTC)


 * If there is something living on Everest it has not been found Yeti. Cuddlyable3 (talk) 22:36, 25 September 2011 (UTC)


 * The thing about the oxygen is, from what I understand, most of us have lungs far too small for such high altitudes to deal with the scarcity of oxygen. So, with people living at higher altitudes, natural selection would favour larger lungs, ya? Couldn't successive generations gradually moving up say 20 ft each generation maybe be able to adapt to permenant life on top of the mountain (not saying that the larger lung adaptation is given)? Provided they have some sort of food and water source as well as some bit of warmth. Sir William Matthew Flinders Petrie &#124; Say Shalom! 26 Elul 5771 22:47, 25 September 2011 (UTC)


 * You've hit upon the real issue, which is sustenance. If a tiny organism could survive the climate at the top of Everest, presumably it still has to eat something, unless it can somehow subsist on ice and snow. ←baseball Bugs What's up, Doc? carrots→ 23:31, 25 September 2011 (UTC)


 * Yea, except in a few rare, extraordinary cases, animal life follows plant life. Animals won't migrate to a place without plants. APL (talk) 23:37, 25 September 2011 (UTC)


 * Maybe, That'd be about a 10,000 year experiment. However, 10,000 years later you may find that your entire experimental tribe had dwindled to nothing and gone extinct.APL (talk) 23:37, 25 September 2011 (UTC)


 * (after ec) Human corpses? There's quite a few up there now. Too difficult/risky to get them down. Scavengers gonna scavenge. --Kurt Shaped Box (talk) 23:39, 25 September 2011 (UTC)


 * I'm not seeing it in the George Mallory article, so my memory may be faulty... but it seems to me I had read someplace that there was evidence of birds or other scavengers having fed on Mallory's body to some extent before he solidified. That wasn't at the summit, obviously. ←baseball Bugs What's up, Doc? carrots→ 00:21, 26 September 2011 (UTC)


 * Mount Everest mentions some birds being seen at fairly high elevations, and a spider that lives at about 22,000 ft, but that is still well below the summit. Up here in AK we have the highly improbable ice worm, which scientists currently have a very poor understanding of, but I've never heard of them living in the Himalayas. Beeblebrox (talk) 00:35, 26 September 2011 (UTC)


 * You learn something new every day here on wikipedia. Worms that are so well-adapted to the frigid that if it gets above 40 they disintegrate. Amazing. Like a worm form of Dracula. And they feed on algae, and the algae's presence there on glaciers has to be a story in itself. It would be interesting to take some of these worms and algae to the top of Everest and see how they would do. ←baseball Bugs What's up, Doc? carrots→ 00:43, 26 September 2011 (UTC)


 * Well plants only need CO2 and water and minerals they could get from under the ice on the surface of rock and light which they may need only 1/10th as much as full sunlight to grow. They produce oxygen and nutrients so animals could grow.--DeeperQA (talk) 01:38, 26 September 2011 (UTC)


 * "... if it gets above 40 they disintegrate." -- One presumes you mean 40 degrees Fahrenheit, not 40 Celcius. Mitch Ames (talk) 12:24, 26 September 2011 (UTC)
 * Yes, as per the ice worms article. ←Baseball Bugs What's up, Doc? carrots→ 01:58, 27 September 2011 (UTC)


 * Lichen might be a candidate for living atop Everest. StuRat (talk) 12:33, 26 September 2011 (UTC)
 * And what animals might live on Lichen? --DeeperQA (talk) 17:32, 26 September 2011 (UTC)
 * Caribou enjoy a nice lichen and are better suited for cold then most, but I don't think they could handle the lack of O2. Googlemeister (talk) 18:42, 26 September 2011 (UTC)
 * I'm thinking more on the order of tardigrades mentioned above. --DeeperQA (talk) 00:51, 27 September 2011 (UTC)


 * Snow fleas live on snow packs eating bacteria and algae and there is the glacier midge Diamesa sp.
 * Grylloblattidae is a family of extremophile and wingless insects that live in the cold on top of mountains.
 * μηδείς (talk) 01:27, 29 September 2011 (UTC)

Sanitary storage of cups and glasses
I keep coffee mugs, as well as other cups and glasses in a cupboard that has solid shelves. I've noticed that some people like to set receptacles in there upside-down, so they won't collect dust on the inside while waiting for use. Others like to place them right side-up, so the lip of the vessel won't be resting on the potentially dusty surface of the shelf. Is one method really more sanitary, or is this just down to personal preference? I apologize if this has been asked and answered before; my search of the archives didn't quickly reveal it. Thanks in advance for reasoned opinions. -GTBacchus(talk) 23:08, 25 September 2011 (UTC)


 * For the two options you gave, it is personal preference. The completely sanitary methods I've witnessed there are two more choices. Once is to place a saucer on the shelf and the cup upside down on the saucer. So, the saucer is clean and the cup is upside down on the clean surface. The other is to have cupholders so the cups hang and don't touch anything (except the handle where they hang). -- k a i n a w &trade; 23:21, 25 September 2011 (UTC)


 * ... and a further option that I thought Kainaw was going to suggest ... place the mugs right side up, but with a sheet of paper over the top so that dust doesn't fall in. Are we being paranoid about a bit of dust? -- we breathe it in all day!    D b f i r s   08:12, 26 September 2011 (UTC)
 * Paranoid? No. I don't care that I ingest dust. This question was asked out of academic interest. I'm not going to change the way I store cups, which seems to be about 50/50 between the two original methods asked about. -GTBacchus(talk) 15:34, 26 September 2011 (UTC)


 * I was once grossed out at my grandparents house, since they stored glasses on a high shelf, with the opening down. Since the shelf was high, and they were short, they couldn't see that he shelf had dead bugs on it.  Yuk !


 * Personally, I always rinse glasses after I remove them from the shelf, to get the dust and germs off them. Note that none of the methods listed so far prevent a spider from dragging it's pus-filled butt along the glass on the outside, where your lower lip goes when you drink. StuRat (talk) 12:25, 26 September 2011 (UTC)
 * Here's the solution to that Arachnid menace. Cuddlyable3 (talk) 13:24, 26 September 2011 (UTC)


 * I have taken to using the tops from Pringles tubes, and similar clear plastic tops from other similar food packaging (according to size requirements), to use as coasters on which to place upside-down drinking vessels, or as covers for ones displayed right-way-up (I collect branded beer glasses). {The poster formerly known as 87.91.230.195} 90.197.66.194 (talk) 15:21, 26 September 2011 (UTC)


 * Another variable: After washing, I have taken to stacking glasses and bowls irregularly such that they will be certain to dry out completely over a few hours.  When stacking plastic bowls in the normal fashion, a seal can be formed that traps the moisture currently on the bowls.  I have no proof that my method prevents explosive bacteria growth within the trapped water, but that's what I've been doing.  Comet Tuttle (talk) 19:28, 26 September 2011 (UTC)


 * Another option is to have one cup and one bowl. You want to use it. You wash it. You know it is always clean when you use it. -- k a i n a w &trade; 19:32, 26 September 2011 (UTC)
 * Now you're singing my tune! Get enough cups and bowls, and you start to think you need a washing machine! Something about simplicity... -GTBacchus(talk) 19:52, 26 September 2011 (UTC)

RhD reaction
What are RhD+, weak, and RhD- reactions?Markid1 (talk) 23:28, 25 September 2011 (UTC)
 * While there may be other reasonable interpretations, my guess is that this refers to the D antigen in the Rh blood group system. That page I linked should explain the reactivities pretty clearly.  -- Scray (talk) 02:18, 26 September 2011 (UTC)