Wikipedia:Reference desk/Archives/Science/2013 January 1

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January 1[edit]

Industrial Revolution and Coal[edit]

The Industrial Revolution used and began our use of coal. But won't coal be used up? What is the answer of the people who originally began, invented, and developed the Industrial Revolution?

Republicanism (talk) 00:37, 1 January 2013 (UTC)

Of course sooner or later it will be used up -- but it will not happen for at least 400 years, so this is not an urgent issue at this time. 24.23.196.85 (talk) 00:49, 1 January 2013 (UTC)
It's unlikely that we could actually consume the remaining coal before we make the planet virtually unlivable...hence we won't run out of coal. If we have sense, we'll stop using it long before it actually runs out. The people who started the industrial revolution were (at the outset) using so little coal, that the issue of if/when we'd ever run out was simply not a problem. It's only as that use accelerated through the next century that the possibility of running out might be considered. SteveBaker (talk) 00:56, 1 January 2013 (UTC)
[citation needed] "Virtually unlivable" in what way? If you mean smog or acid rain, this can easily be mitigated by scrubbing the sulfur out of the smoke, as is universally done today. 24.23.196.85 (talk) 01:42, 1 January 2013 (UTC)
I imagine he meant global climate change due to increased atmospheric carbon dioxide. I certainly hope we will have better energy options than coal, before that happens. StuRat (talk) 03:41, 1 January 2013 (UTC)
[citation needed] The notion that CO2 is responsible for climate change is disputed -- there are many other factors at work here, including an increase in solar radiation, and/or the action of trace gases (especially glyoxal and its derivatives). Also, climate change will not make the planet "virtually unlivable" -- in fact, it can actually benefit the civilized countries (especially Europe and Canada) by increasing agricultural productivity. 24.23.196.85 (talk) 04:05, 1 January 2013 (UTC)
Sweet racism bro. Those uncivilized brutes in Africa totally deserve what climate change will bring. 24.255.30.187 (talk) 06:33, 1 January 2013 (UTC)
So you want all of us Americans to cripple our own energy sector and set our economy and culture back by maybe two centuries just because of the off chance that some Stone-age troglodytes might get their land flooded if we don't? What kind of crazy, self-hating thinking is this? 24.23.196.85 (talk) 00:50, 2 January 2013 (UTC)
At this point, the only ones who deny that CO2 causes climate change are right-wing politicians and any "scientists" on their payroll. StuRat (talk) 06:38, 1 January 2013 (UTC)
Even among those people, very few deny that CO2 causes warming, since the physical fact that CO2 is a greenhouse gas is indisputable. They just deny that warming has in fact happened on Earth, or if it has, that it's anthropogenic. --99.227.0.168 (talk) 16:58, 1 January 2013 (UTC)
It is worth noting that with carbon sequestration we might be able to use up all the coal, oil shale, and assorted such goodies without getting overheated - if we are clever enough to do it but not clever enough to outsmart ourselves, that is. (I am primarily thinking of the carbonate formation under "chemical processes" in that article) Wnt (talk) 13:23, 1 January 2013 (UTC)
Being one of "those people" I think it is clear that the extra CO2 humans do contribute to the atmosphere does contribute to increased warming, but that other factors obviously hugely drown out that signal (look at the warmth of the late middle ages and the Roman era), and that a massive socialist redistribution scheme is not the answer to any problem if an anthropogenic one is ever conclusively demonstrated. I am also hugely in favor of nuclear power, a consumption (i.e., carbon and other materials) tax, and encouraging the development of fusion via tax and patent incentives. That actually seems like a rather sober and objective viewpoint if you ask me. μηδείς (talk) 21:29, 1 January 2013 (UTC)
Except for the part about fusion power, it is. Fusion is at least fifty years away from being commercially viable; nuclear fission, on the other hand, is not only viable but is actually cost-competitive with coal and natural gas, and is also very safe for the most part (especially with the new generation of super-safe nuclear reactor designs in development right now, like the lead-bismuth-cooled fast-breeder, or the General Atomics graphite-helium reactor). 24.23.196.85 (talk) 01:01, 2 January 2013 (UTC)
I don't have an educated opinion as to how far distant viable fusion power is (and 50 years is soon) but I am in favor of granting a fifty year patent on it and waving all tax on profits associated with it for that period. That should incentivize it like you can't imagine. μηδείς (talk) 02:46, 2 January 2013 (UTC)
(ec) And I'm a socialist, so we could squabble all day. Instead, since this is the science reference desk, I'll provide a scientific reference, because there's an overwhelming consensus among climate scientists against your unsupported assertion that "other factors obviously hugely drown out that signal". From the Medieval Warm Period article: "globally the Medieval Warm Period was cooler than recent global temperatures" (with a citation). From the graph in that article, the temperature peak representing the MWP is 0.1-0.2 C in height and a few hundred years in width, whereas the global temperature has risen 0.8C since the beginning of the 20th century. I could not find any temperature estimates of the Roman Warm Period. --99.227.0.168 (talk) 01:05, 2 January 2013 (UTC)
Your "overwhelming consensus" is that of politically motivated liars who've been caught out over and over. There's no suitable long term sample, just recent flawed cheerleading models for the refuted hockeystick. But do cite away til you feel warm and cozy. μηδείς (talk) 02:42, 2 January 2013 (UTC)
Even if this is true, this does not prove that CO2 is responsible for the warming trend -- there's a lot of other crap being released into the atmosphere that didn't used to be back then, like methane, nitrogen oxides, all sorts of halogenated hydrocarbons, and the above-mentioned glyoxal derivatives, ALL of which are considered to be much more potent "greenhouse gases" than CO2. Add to that the concurrent increase in solar radiation (which is right now the only plausible explanation for the warming trend currently observed on Mars), and then anyone can see that CO2 is by far NOT the only factor at play here, nor is it even necessarily the biggest. Correlation does not imply causation! 24.23.196.85 (talk) 01:23, 2 January 2013 (UTC)
If you are asking historically — e.g. what did the people who started the Industrial Revolution think — it's worth pointing out that 1. nobody really consciously started the Industrial Revolution, and 2. the amount of coal is quite vast, even today, and was considered essentially limitless at the time of the Industrial Revolution. So I doubt they worried much about it running out in the short term. --Mr.98 (talk) 03:29, 2 January 2013 (UTC)
Agreed; there's still a huge reserve of coal under the UK (where the industrial revolution began),[1] it's just a whole lot cheaper to import it from open cast mines abroad. Alansplodge (talk) 18:37, 2 January 2013 (UTC)

Eliptical Machines[edit]

I am using an eliptical machine as a cross training activity for long distance running. I find something about them strange. Why do I not feel sore at all the day after a strenous workout on an eliptical machine (eg doing fast paced intervals or going for a long period of time), but feel sore the next day after a equally strenous run or weight lifting workout? I know they are supposed to be low-impact, but I would expect to feel some muscle soreness. Same thing with swimming. -anon

I'm guessing you're in good shape, so the exercise doesn't overtax your muscles and cause soreness that way. Thus, the only soreness you normally feel is from microscopic injuries caused by impacts. You might want to increase your resistance/weight/reps/time to make it more of a challenge. StuRat (talk) 03:35, 1 January 2013 (UTC)
Stu's on the right track. It probably also means that you have a good elliptical, or at least one that suits you well. I've used at least three different styles of elliptical and had different experiences with each regarding muscle tiredness, joint sensitivity, and so on. Matt Deres (talk) 04:40, 1 January 2013 (UTC)
My experiences and opinions. I think elliptical machines are very low impact. Your feet are on the paddles ALL THE TIME. And your muscles are working nearly ALL THE TIME. The machine is quite friendly to your legs. You can you your arms if you really want to. I can usually "run" maybe 1.5 times of distance on a elliptical machine than actually jogging.
This may not be a fair comparison because we have air conditioning in a gym. This is not fair. It can be very hot outdoors. I also drink less when I am jogging. You always have water in a gym.
I think treadmills are friendlier than jogging and elliptical machines are even more friendlier than treadmills. However, jogging outdoors can be much more fun. I just hate to jog in summer. -- Toytoy (talk) 16:05, 1 January 2013 (UTC)

Did any of you use an eliptical at any point? What is a suggestion as to how much I should increase the duration of my workouts every sesson? Is increasing the duration of my workouts by 2 minutes each sesson reasonable? — Preceding unsigned comment added by 99.146.124.35 (talk) 23:14, 1 January 2013 (UTC)

We can't give that sort of advice for practical and legal reasons, but you may have a personal trainer or other professional available at your gym who can--do ask them. μηδείς (talk) 02:37, 2 January 2013 (UTC)
The advice I was given was to slowly increase the workout until I do get sore, or at least feel muscle fatigue. This is basically the "no pain no gain" advice, although I think "pain" is a bit strong. You should feel it, but not be in agony. You might also want to strap weights on your legs or otherwise increase the difficulty level. StuRat (talk) 03:21, 2 January 2013 (UTC)
Retaining a personal trainer for even a few sessions can really help. I don't think exercise advice is quite at the level of medical advice (which we're not allowed to give), but it's simply common sense: a good personal trainer can watch what you're doing and give you instant feedback about what you're doing right and wrong - and tips for the future. Matt Deres (talk) 23:25, 2 January 2013 (UTC)

Alexander graham bell[edit]

complaint over priority referred to article talk page
The following discussion has been closed. Please do not modify it.

Alexander graham bell did not invent the telephone, that went to an inventor a few years earlier. Putting a sentence saying he invented a working telephone, insults all pioneers and their inventions. You should change the reference to include the Alexander Graham was created the first telephone the concept and design for which was invented by.... I cant recall the person who actually invented the phone. — Preceding unsigned comment added by 124.148.227.176 (talk) 03:35, 1 January 2013 (UTC)

This belongs on that talk page. However, Leonardo da Vinci had diagrams of helicopters [2], but his designs wouldn't fly, so should he be credited with their invention ? StuRat (talk) 03:38, 1 January 2013 (UTC)
Bell's article says he is credited with inventing the first practical telephone, a big difference from what you're complaining about. Invention of the telephone lists various candidates for the telephone's daddy. Clarityfiend (talk) 05:29, 1 January 2013 (UTC)

Closing--OP has been refererred to article talk page. μηδείς (talk) 16:35, 1 January 2013 (UTC)

Lizzie Velazquez - A Rare Condition[edit]

Speaking in a strictly academic capacity with perfect propriety, my first question is what actually is the name of the rare condition Lizzie Velazques has? I can't seem to find anything on wikipedia. I don't think she has a page. All the articles, everything I see on google/youtube, no one actually mentions the name of the condition. They just keep saying that it is such a rare condition that only 2 or 3 people in the world are known to have it. Any useful informative references on the disease will be useful. Second question, from what I understand, she weighs just 60 pounds and has no adipose tissue, and cannot create muscle, store energy, or gain weight. She has no body fat or muscle tissue but then how come her mammary glands are so swollen? Maybe it is my ignorance of human physiology but I thought that subcutaneous adipose tissue (according to wikipedia anyway) gives breasts its shape and size. So if she's not supposed to have any fat or muscle in her body, then how come her breasts are so big and shapely? At least to me they look unusual compared with the rest of her stature. Is it known if she ever got artificial enhancements/supplements or if the condition takes away fat/muscle from certain parts of the body and leaves the rest alone? Thanks! - Looking for Wisdom and Insight! (talk) 10:49, 1 January 2013 (UTC)

Second Google hit references [3] which says neonatal progeroid syndrome is the current best guess (we only have progeria written so far); during her childhood de Barsy syndrome had been suspected, but she didn't have learning difficulties. It says she is currently being studied by Professor Abhimanyu Garg, MD, at the University of Texas Southwestern Medical Center in Dallas, who came up with the NPS diagnosis. Wnt (talk) 13:17, 1 January 2013 (UTC)
Perhaps they are just falsies or implants, allowing her to look normal in at least one respect. StuRat (talk) 03:17, 2 January 2013 (UTC)

Air refueling stealth fighters[edit]

F-22s and F-35s are capable of air refueling.

Why do they need air refueling? Certainly, they need extra fuel to extend their ranges.

But unlike many other airplanes, these airplanes do not have hardpoints, as a result, they can always add a central hardpoint for an external fuel tank.

I know that external fuel tanks are radar reflectors.

But air refueling also gives away a stealth fighter's position. The tanker airplane is a much larger radar reflector and air refueling is slow.

On the other hand, external fuel tanks are lighter, more efficient and they can be dropped.

Why don't stealth fighters use external tanks? -- Toytoy (talk) 15:54, 1 January 2013 (UTC)

From Wikipedia's article on the F-22: "the wings include four hardpoints, each rated to handle 5,000 lb (2,300 kg). Each hardpoint has a pylon that can carry a detachable 600 gallon fuel tank or a launcher holding two air-air missiles."
Our article on the F-35 don't mention it, but this link seems to point ot at least two of the hardpoints being plumbed for droptanks. Since the F35 is still years away from being in service, take any information regarding it with a grain of salt though.
WegianWarrior (talk) 16:18, 1 January 2013 (UTC)
You can carry more weapons without a heavy external fuel tank. And carrying an external fuel tank for the home trip into a combat zone makes you slower and less maneuverable. Air refueling is usually done in an area considered relatively safe from enemy attack. (Have planes ever been attacked during the procedure?) See more in Aerial refueling. PrimeHunter (talk) 16:45, 1 January 2013 (UTC)
And using a safe area for refuelling (which is necessary mostly because the tankers are vulnerable) means that if the enemy does realise the fighter's presence, they'll likely lose track of it once it detaches from the tanker and moves into the hot zone. With the exception of a tiny handful of convert assassination and first-strike operations, the purpose of stealth isn't to conceal the presence of the aircraft, but to prevent enemy missiles from successfully engaging it. The air defence system around Baghdad in 1991 was perfectly well aware that there were F117s around (once stuff started exploding) but they couldn't get their radar-guided weapons to acquire a lock on them. I guess there may be some interest in a stealthy refuelling system, to support the tiny number of cloak-and-dagger strikes, and perhaps to maintain stealthy drones. -- Finlay McWalterTalk 17:09, 1 January 2013 (UTC)
Is there any reason why there couldn't be a stealth refueling plane, or why refueling itself couldn't be stealthy? I mean, stealth doesn't require a plane to perform like a fighter, does it? I imagine they don't tell us everything they waste money on... Wnt (talk) 19:13, 1 January 2013 (UTC)
It seems that it could in principle be done, but there's not a lot of good reason to do it. (Note that even very 'stealthy' aircraft would be vulnerable during midair refuelling; the aircraft performing such a manoeuvre are necessarily flying relatively slowly, carefully maintaining constant speed and altitude. I also don't know what wrinkles might occur in developing a stealthy fuelling boom.) Consider the biggest 'stealth' aircraft ever built, the Northrop Grumman B-2 Spirit 'stealth bomber'. Normally, it carries up to 76 metric tons of fuel, and up to 23 tons of ordnance; it has an operational range of a whopping 11,100 km. Conceptually, there's no serious difficulty with stripping out the bomb racks and replacing them with another 23 tons of internal fuel storage, deliverable up to a third of the way around the world. I suspect that if you cut into the B-2's own existing tanks to trade range for deliverable capacity, you'd probably get close to the same fuelling capabilities as a KC-135.
For reference, the McDonnell Douglas KC-10 Extender carries a maximum fuel load of 160 tons and has an operational range of 7,000 km; its still-in-service predecessor the Boeing KC-135 Stratotanker carries up to 91 tons and has a range of 2,400 km. (The actual amount available for refuelling other aircraft depends on how far the tanker has to fly and how long it has to loiter; our articles don't break out the specific amount of fuel available for transfer from these tankers versus the amount required for their own use.) Our hypothetical B-2 Stratotanker costs about $800 million (plus development costs for the midair fuelling variant), whereas a KC-135 costs about $40 million. TenOfAllTrades(talk) 21:35, 1 January 2013 (UTC)
Our article on the F22 says: "Range: >1,600 nmi (1,840 mi, 2,960 km) with 2 external fuel tanks" - so it does indeed have the capability to extend it's range in that way. Furthermore: "Fuel Capacity: 18,000 lb (8,200 kg) internally, or 26,000 lb (11,900 kg) with two external fuel tanks"...and that's the problem. With in-flight refuelling, you can almost double your range - with external tanks you gain at most maybe 40% more range. (Also, those tanks cause drag and extra weight - which means that the aircraft is less fuel-efficient when carrying them - so they clearly don't extend range by as much as you'd expect from the raw numbers). Furthermore, you can (and routinely would) refuel on the way out to the target and on the way home - which triples your range. SteveBaker (talk) 02:08, 2 January 2013 (UTC)
I noticed that F-22's long flights over the Pacific Ocean require external tanks. I still think that carrying multiple external tanks are more reasonable than air refueling.
You just drop the tanks and then you're OK. -- Toytoy (talk) 03:40, 2 January 2013 (UTC)
About vulnerable stratotankers, it might be less of a vulnerability than you think, with all those fighters moving back and forth. It could be an issue if there was another (non-US) power using stealth aircraft, trying a sneak attack on the refueling fighters and the KC herself, but as of now, non-stealth fighters are detected from 100's of miles away, and refueling doesn't last that long. They could intercept any non-stealth intruder without penalties to their weight/drag/stealth.
Keep in mind that applying a layer of stealth skin to a drop tank is not an option. You don't want to give away stealth technology, lest the enemy copy or defeat them.
About stealth refuelers, some jets including the Tornado GR.4 have been converted to tankers in small numbers, so it is likely that some stealth planes have been converted, too. - ¡Ouch! (hurt me / more pain) 08:33, 2 January 2013 (UTC)
Ahem, Panavia Tornado. - ¡Ouch! (hurt me / more pain) 08:57, 2 January 2013 (UTC)
Of course we're missing another use of inflight refuelling - which has little to do with extending range. When you want to carry the maximum possible amount of munitions. The maximum weight that the aircraft can take off with is considerably less than the amount it can fly straight and level with. So one trick is to take off with a minimal fuel load (thereby allowing more payload to be carried) and to almost immediately refuel when at altitude. Once at altitude, the total of fuel plus payload can safely exceed the maximum take-off weight. SteveBaker (talk) 15:27, 2 January 2013 (UTC)
And there may be a day when you need to attack a target that's more than 920 miles away. The RAF's 1982 Operation Black Buck raids involved a round trip of 8,000 nautical miles, each bomber requiring 11 tanker aircraft. In the Gulf War, "on 16 January 1991, a flight of B-52Gs flew from Barksdale AFB, Louisiana, refueled in the air en route, struck targets in Iraq, and returned home – a journey of 35 hours and 14,000 miles round trip". Alansplodge (talk) 18:32, 2 January 2013 (UTC)

Gravitational and magnetic force[edit]

why we can't relate gravitational force with magnetic force? since most of the living and non living things contains elements that can be attracted by magnetic force. 116.202.68.193 (talk) 16:31, 1 January 2013 (UTC)

I would attempt an answer to that question if only it made any sense... Dauto (talk) 17:58, 1 January 2013 (UTC)
I'm guessing they mean "replace it" as in artificial gravity in a space station.--Gilderien Chat|List of good deeds 18:39, 1 January 2013 (UTC)
They are similar in some ways, but not similar enough. For starters, everything accelerates exactly the same under gravity (this has been tested to one part in ten trillion), but some magnets are much stronger than others. Plus, magnetism can't explain the bending of starlight or the anomalous precession of Mercury's orbit. -- BenRG (talk) 18:40, 1 January 2013 (UTC)
Ben, I'm not sure I understand what you mean by "everything accelerates exactly the same under gravity" - are you referring to Galileo's experiment showing that different masses accelerate at the same rate (and thus fall at the same rate) due to gravity? Because if so the obvious rebuff is, just as some magnets are much stronger than others, some masses are much more, er, massive than others... (so the distance between two 1-kg masses finitely far apart in a vacuum with no other forces decreases faster than that between a 1-kg mass and a 1-g mass in the same situation, for example).
@OP: I'm surprised no one's mentioned this, but there is the fact that magnets have poles, and we have never discovered a magnetic monopole (this not to say they don't exist, of course), and precisely the opposite, gravity is only ever attractive so far as we can observe, there is no "negative mass" that repels the mass we observe (even antimatter attracts matter via gravity, likewise darkmatter). Even if there were, it wouldn't line up with how we observe like charges and magnets to repel, because it would have to be opposites that repel and likes that attract (to see why this is, consider the sun, the earth, and the moon. They all attract each other, so they are likes, because if they were opposites this couldn't be the case) 72.128.82.131 (talk) 04:20, 2 January 2013 (UTC)
General relativity and electromagnetism do fit together rather nicely, in the form of Kaluza–Klein theory. There's also gravitoelectromagnetism, although that's just an analogy that only works in an approximate sense under certain conditions. Red Act (talk) 22:54, 1 January 2013 (UTC)

Any studies on whether whale strandings may have analogue in human stampedes?[edit]

67.243.3.6 (talk) 17:09, 1 January 2013 (UTC)

  • The dynamics are unsimilar, whales are not crowded onto the beach or crushed or trampled by other whales. (My personal bet is that there is a microorganism to blame which spends part of its life cycle on the beach, similar to other parasites which drive their hosts to odd behaviors like rabies or fungi that cause snails and ants to climb to high locations in order to be eaten or to spread spores in the wind.) μηδείς (talk) 21:18, 1 January 2013 (UTC)
"Citation needed". :) Though it is a creative idea, and could be true. I would suspect that there could be a common basis - stranding of whales and dolphins are widely though not unanimously blamed on loud sonar arrays (see whale beaching), and I suspect that loud noise contributes greatly to the confusion in some human stampedes. But I can't find a reference for that, either... Wnt (talk) 02:03, 2 January 2013 (UTC)
If you are asking me regarding my personal guess, I already quoted myself. Do you want me to put it on my talk page so someone else can quote me here? μηδείς (talk) 02:29, 2 January 2013 (UTC)
Meideis' ridiculous speculation aside, see beached whale#Causes for more credible explanations. Beaching of single whales is much more common than beachings of multiple whales, and is usually caused by injury or disease. Multiple-whale beachings are sometimes caused by strong social cohesion--one whale sends out a distress call while close to the shore, and other whales follow. By contrast, human stampedes are caused by panic or disasters, and death is usually by asphyxiation. If you've been to any major event, like Toronto's New Year countdown, you know how easy it is for the crowd to squish you when lots of people are pushing. I don't see any obvious connection between the two, but if the OP wants to point out what kind of similarities he's thinking of, he might receive a better answer. --99.227.0.168 (talk) 05:41, 2 January 2013 (UTC)
Hiding behind an IP does not give you any special privilege to ridicule the posts of others here. ←Baseball Bugs What's up, Doc? carrots→ 06:26, 2 January 2013 (UTC)
This is a reference desk, not a "make up your own theories and post them" desk. I see no rule that says IP users cannot correct non-IP users when the non-IP user posts no references and the IP user does. --99.227.0.168 (talk) 07:07, 2 January 2013 (UTC)
Your term "ridiculous speculation" does not belong here. ←Baseball Bugs What's up, Doc? carrots→ 07:15, 2 January 2013 (UTC)
Well, editors really ought to be providing referenced facts rather than "personal bets". However, "It is by politeness, etiquette and charity that society is saved from falling into a heap of savagery". Alansplodge (talk) 17:53, 2 January 2013 (UTC)

Anyhow, back to the point. I've had a fairly good trawl through Google and found Keeping Together in Time, or the Natural History of Social Cohesion. A Critical Evaluation of W.H. McNeill's New Book (1995) is an article that seeks to compare a new work on human social cohesion with mammalian behaviour. The Google search result for the page says "It (presumably group behaviour) may take precedence over all other forms of behaviour, as for instance in lemming migrations or mass stranding» of whales; but much more often it is integrated with other modes of social interaction." You can't view the article without subscription. Sorry, that was all I could find. Alansplodge (talk) 18:17, 2 January 2013 (UTC)

Thanks. It should be noted that lemmings behavior has been greatly exaggerated. 67.243.3.6 (talk) 14:17, 3 January 2013 (UTC)

Understanding the EPR paradox[edit]

In the article on the EPR paradox an explanation is given on how the experiment was or can be performed. The part about this experiment I'm trying to get is not the faster-than-light aspect, but rather the certainty or not of a state.

I'm very familiar with 3D vector math, so the part that puzzles me is when they talk about the spin that can be seen as "a superposition of two states". I view the spin as an "axis" (about which the electron "spins"). Surely this must lead to an infinite number of possible states, corresponding to directions. Is the article saying that the experiment can be set up in such a way that only those two states are possible?

And then, when the measurements along a particular axis is made, are we talking about projections (like dot product) or is there some quantum effect that causes the vectors to become 100% parallel to the measured axes? Or is some quantum effect simply making all measurements binary (with no possibility of zero or small values) along all possible axes? 105.236.57.198 (talk) 19:03, 1 January 2013 (UTC) Eon

This is a basic fact of spin (quantum mechanics). Spin can be along any axis, but when measured, it always has one of a few discrete values according to which way you looked. As I understand, remeasuring it from another angle has a chance of getting the other value, depending how wide the angle - and if you remeasure again from the first angle, it could then be different from what it was the first time! So defining the axis is ... difficult. Most of the physics types will say don't even think about it in classical terms, it's just a number, but we find this ... unsatisfying. Not when it still sorta kinda is like something you can picture. Note that the general idea that angular momentum is quantized is absolutely fundamental to quantum mechanics - people might talk about how, say, an electron has quantized "energy", but really, it has equally spaced increments of angular momentum that determine its energy because if it had any more or less with a given angular momentum it wouldn't be in orbit. Every photon carries the exact same angular momentum, the reduced Planck constant, and that is what an electron changes by when it flips from one spin state to the other, just as when it goes up a level in energy. Wnt (talk) 19:16, 1 January 2013 (UTC)
Thanks for an excellent summary. Actually, I couldn't figure it out from that description because it doesn't go all the way. I found this article by a user here that continues the explanation to the point that I fully understand the weirdness of entanglement. It doesn't appear to be an official article, but I think it would be great if that was included. The official article merely "tells" one how it works. That explanation convinces one by tracing the path to the conclusion. 105.236.57.198 (talk) 20:10, 1 January 2013 (UTC) Eon
I used this question as an excuse to revamp something I wrote ages ago. It's now at User:BenRG/Bell's theorem as a game show. Let me know if it's helpful. -- BenRG (talk) 06:53, 3 January 2013 (UTC)
By the way, the 99%/98%/96% argument in the actual article is wrong. I'll mention it on the talk page.It's okay. There are classical counterexamples to the claim "if A and B measured on two particles are 99% correlated, and likewise B and C, then A and C are at least 98% correlated". But there are no counterexamples if you also require that A and A, B and B, and C and C are 100% correlated. -- BenRG (talk) 06:54, 3 January 2013 (UTC)

Astronomical naming conventions[edit]

I get a bit confused over the names of some things. Our star, and its planets, are collectively known as the "solar system", but "solar" comes from Sol, the name of our star. What, then is the general name of such a system called? Star system apparently refers to systems of multiple stars, while planetary system seems to exclucde the star (the article specifically mentions The Sun and its planetary system).

Similarly, what would a "solar flare" on any other star be called? A stellar flare? 90.193.232.232 (talk) 19:24, 1 January 2013 (UTC)

  • The expected term would be stellar system, but you don't often find it, most people being ignorant of Latin and etymology in general nowadays. You do hear "planetary system". μηδείς (talk) 19:53, 1 January 2013 (UTC)
Basic commutativity. If the sun is a star, then a star is a sun, right? Poetically I've heard of the "children of other suns". I would say that there are many solar systems but only one Solar system. The same astronomers probably have a pet "Dog" :) But I'm not an astronomer, sorry. Wnt (talk) 20:01, 1 January 2013 (UTC)
This seems to me just like first having the Moon, and then finding out that there are other natural planetary satellites and calling them moons. There are lots of moons but only one Moon. I've often heard of other stars referred to as other suns, although there is only one Sun. So the analogy would be that there are many solar systems but only one Solar System. Words' meanings evolve as semantic needs evolve. Duoduoduo (talk) 22:25, 1 January 2013 (UTC)
We have adequate terminology now, if only I we were able to force convince people to use it. In the long term, better usage will evolve. Then people will move to other stars and the provincials will start talking about earthquakes on their new planet and sunstorms on their new star. Depressing. μηδείς (talk) 02:27, 2 January 2013 (UTC)
An earthquake is when the earth shakes, not when the Earth shakes, so "earthquake" is fine on Mars, when the good red Martian earth starts quaking beneath your pressure-suited feet. --Trovatore (talk) 05:39, 2 January 2013 (UTC)
As noted below, Moonquakes and Marsquakes and even Sunquakes are attested. μηδείς (talk) 17:18, 2 January 2013 (UTC)
The terms earth, moon, planet and sun are all carryovers from the assumption that we are the center of the universe... which, for most practical purposes, we are. The earth is the ground we stand on, the "moon" is cognate with the "month", the sun is cognate with words that mean "shine". Medeis is right that if and when we migrate to other planets and stars, terms will evolve. If you're on Mars, there's a reasonable chance you'd call it a "Marsquake", but if we establish a civilization there, in some future generation they might come up with different names, as the notion of it being the realm of the god of war would seem silly. ←Baseball Bugs What's up, Doc? carrots→ 06:23, 2 January 2013 (UTC)
No, earth meaning dirt is the older usage. The planet is named after the dirt. There's nothing wrong with talking about an earthquake on Mars, as it is indeed a quaking of the earth that's there. (Not sure Mars actually has tectonics at all, but that's a side issue.) --Trovatore (talk) 07:48, 2 January 2013 (UTC)
Sure, and that's where the planet's name came from. At that time, no one knew there was soil on other planets (not for sure, anyway). You may find Quake (natural phenomenon) of some interest. ←Baseball Bugs What's up, Doc? carrots→ 07:56, 2 January 2013 (UTC)
You're missing the point, and at this point I have to suspect you're being deliberately dense. It's not called an Earthquake, meaning the planet shakes. It's called an earthquake, meaning the dirt shakes. Mars has earth too. --Trovatore (talk) 08:20, 2 January 2013 (UTC)
Well, who should I believe, you or the wikipedia article? ←Baseball Bugs What's up, Doc? carrots→ 08:23, 2 January 2013 (UTC)
The article does seem to source "moonquakes" and such, but surely those words were chosen a little facetiously. If not, it's just dumb. --Trovatore (talk) 08:25, 2 January 2013 (UTC)
I've certainly heard the term "moonquake" before. I can't vouch for the others as such. Maybe you would call it a Marsquake if you were observing from earth, and an earthquake if you were actually standing on Mars, or maybe just a "quake". Mars certainly has solid ground and some kind of soil or ground (let's not say "dirt"), but there's no guarantee that citizens of Mars would use the term "earth" to indicate the surface, at least not right away. ←Baseball Bugs What's up, Doc? carrots→ 08:41, 2 January 2013 (UTC)
It's interesting that the Latin terra is likewise used for both the land and for the planet.[4] The two concepts are closely linked. ←Baseball Bugs What's up, Doc? carrots→ 08:43, 2 January 2013 (UTC)
'Marsquake', How Earthquakes On Mars Could Sustain Alien Life is a Huffpost Tech article dated Feb 24, 2012 that is based on an interview with a NASA-affiliated scientist. Others based on the same report and with the same approximate date are [5] and [6]. Duoduoduo (talk) 13:42, 2 January 2013 (UTC)
However, the abstract and title of the study that those news articles are reporting on refer to "paleomarsquakes" and "marsquakes". Duoduoduo (talk) 13:58, 2 January 2013 (UTC)

Geology of Mars. Duoduoduo (talk) 12:54, 2 January 2013 (UTC)

If we ever got to live on a planet orbiting another star, I'm pretty sure we'd still say things like "What a pretty sunset!" and "Oh, look! A full moon. How romantic!" - and not get into tangled new vocabulary like "Alpha-Centauri-rise" or "A full Triton". It seems that when uncapitalized, "sun" and "moon" refer to whichever star and moon you happen to be nearest to and when capitalized "Sun" and "Moon" refer to the Earth's sun and moon. It's only in the last hundred years that it's mattered - and even then, not to many people and not in most conversations. But capitalization would rapidly get confusing in speech - so "Sol" and "Luna" are probably words we might take up if we lived elsewhere than on Earth and we needed to talk specifically about the Earth's sun and moon. In places like NASA, "earth" (as in dirt) is carefully called "regolith" in cases where ambiguity might result - and the Mars missions talk about "sols" instead of "days" to avoid confusion. Our language adapts as need arises. Words like "earthquake" are corner cases - but using terms like "moonquake" and "marsquake" makes it difficult to write sentences like "The comparative study of earthquakes on different celestial bodies is a branch of seismology." - you can't say "The study of quakes..." because the word "quake" can mean ground shaking other than of a geological origin (see Wiktionary). SteveBaker (talk) 15:14, 2 January 2013 (UTC)
  • Interestingly enough, the word terra originally meant "dry (they are cognates from PIE) and the term terra firma didn't mean firm terra so much as the dry firmament. The Spanish for earthquake is terremoto, which literally means the dry heaves. μηδείς (talk) 03:37, 3 January 2013 (UTC)
    • The firmaments,[7] as described in the book of Genesis. That word terremoto comes directly from the Latin terraemōtus, which I take to essentially mean "land motion". ←Baseball Bugs What's up, Doc? carrots→ 11:32, 3 January 2013 (UTC)

Rydberg molecular hydrogen[edit]

A few more questions about Rydberg atoms forming Rydberg matter. (I also list some assumptions in case they're wrong...) Feel free to answer any part independently.

1. I assume it is possible for two Rydberg atoms of hydrogen to interact in such a way that they are not immediately disrupted, to form a Rydberg molecule of hydrogen with two protons and two electrons. ([8] describes one with three hydrogens, which I shall not even try to figure out.)

2. My recollection is that Rydberg atoms of hydrogen have something like n=20, maybe 50, and the electron can - somehow - be visualized as an isolated blob of negative charge revolving around a distant nucleus in a Keplerian orbit.

3. Suppose a Rydberg atom has a perfectly circular orbit, and does not emit a photon while being observed. Or suppose it has a perfectly linear orbit, with the electron falling straight through the photon on every oscillation. Can you call one a "50s orbital"? The other a "50p orbital"?

4. Suppose two Rydberg atoms are collided so that two electrons are somehow orbiting two protons in a stable configuration. What would that look like?

5. Is the bond qualitatively different if you have one electron with "n=49" and another with "n=50", as opposed to two with 50? Can you visualize the Pauli exclusion principle somehow because the spins have to be opposite for them to fall in the same orbital? Or is there a way to write a molecular orbital formula for the two electrons so that they sail neatly one after the other along the same course?

6. Is the angular momentum of each electron quantized in relation to each of the two protons? In relation to the other electron? In relation to the whole system? Do these conflicting demands for simultaneous quantization force them out of a perfectly elliptical orbit as measured?

Wnt (talk) 19:57, 1 January 2013 (UTC)

A Rydberg atom is just an ion and an extra electron that's bound to it (i.e. has negative total energy) but isn't as close as the other electrons. You can certainly form bound states of two ions, and you can always in principle introduce another particle whose kinetic energy is small enough that it's bound to the ions, and I suppose that would be a Rydberg molecule, if you want to call it that.
The electron orbitals that you see in textbooks are not the only possible orbitals. They're simply a basis for the possible orbit(al)s, i.e. for the possible wave functions of bound electrons. If an electron is bound to a nucleus then (in a suitable approximation) you can always express its motion as a sum of basis orbitals, even if the electron is localized and following a quasiclassical orbit. Quasiclassical orbits don't have a single letter or number; they're some complicated sum (superposition) of infinitely many orbitals with many different values of n and ℓ. But you don't have to use that basis; you can just think of them as quasiclassical orbits, which is mathematically equivalent and probably more sensible in this case. In general these systems are going to look (for a brief time) sort of like a classical gravitational system.
The quasiclassical electron will be spread out in orbital-angular-momentum space in accordance with the uncertainty principle. But the orbital angular momentum space is discrete/quantized (since it's compact) so it's actually spread out over a bunch of discrete momenta. If you measured its orbital angular momentum (which is not really possible but is theoretically possible) you would force it into an orbit of fixed angular momentum, which would be spread all around the atom in position space and hence nonclassical.
Incidentally "nonclassical" here really refers to classical particle theory. A lot of what I said above still holds in classical wave theory. You can still do the decomposition into basis orbitals, there's still an uncertainty relation, the angular frequency is still quantized, etc. -- BenRG (talk) 05:52, 3 January 2013 (UTC)
Thanks for setting me straight. I suppose that if you could make the measurement, and thereby disperse an electron into a symmetric shell, this would be the most iconic illustration of the Heisenberg uncertainty principle that I can think of. Wnt (talk) 15:06, 4 January 2013 (UTC)

Brain question[edit]

I was wondering, since the brain is mostly controlled via electrical impulses, and you can mess with peoples heads by shocking parts of the brain (I think?), what would happen if you were to open up a persons skull and pour something like saline solution, or some sort of liquid that conducted electricity onto it? Would the brain short circuit? What if it were just dribbled instead of coating the whole of the surface? Gunrun (talk) 23:36, 1 January 2013 (UTC)

Neurons, including those in the brain, do indeed work on electric pulses, but they are not like currents flowing through a conductor: the ions are "pumped" chemically not electrically. So concepts like "circuit" in the electrical sense (and a fortiori "short circuit") simply do not apply. --ColinFine (talk) 00:14, 2 January 2013 (UTC)
However, it is possible to "mess with peoples heads by shocking parts of the brain" - see Electroconvulsive therapy. Don't try this at home. Alansplodge (talk) 00:56, 2 January 2013 (UTC)
A less-dramatic approach is transcranial magnetic stimulation. --Mr.98 (talk) 03:25, 2 January 2013 (UTC)
The brain is already immersed in saline solution, and it works just fine (in most people, anyway) -- so just on the face of it, the OP's suggestion won't work. 24.23.196.85 (talk) 01:07, 2 January 2013 (UTC)
Presumably the balance of the various ions that the brain uses would be kinda critical - so while dumping extra saline in there wouldn't short anything out - it would screw up all of the concentrations - and that might well be fatal. SteveBaker (talk) 01:45, 2 January 2013 (UTC)
The answer to this is complex. The conductance of the extracellular medium could vary, and would affect neural signalling. action potentials cross the membrane; even so, the voltage, and also specific ions that have to move, affect the opening of more channels up and down the axons and dendrites. Much of this happens inside the neuron where the change in medium might not affect it (depending on what exactly you did to it). See [9] for some basic biophysics of this - but I won't claim to have gone through it all. Wnt (talk) 01:51, 2 January 2013 (UTC)
Given the sophistication of the question, I think the prior answers (no, nerves and the brain don't work that way) are sufficient. The OP should read brain, neuron, and action potential, and then come back and ask for help if he wants it at that point. μηδείς (talk) 02:24, 2 January 2013 (UTC)
Replacing the CSF with saline would kill you, as Steve said. It doesn't have the calcium that is absolutely required for neuronal activity (and indeed for survival of all other cells. Cells are pretty good at concentration calcium, but stores would be depleted over time as they migrate across the concentration gradient. Fgf10 (talk) 11:45, 2 January 2013 (UTC)

Thanks for the answers and links and stuff guys, time to do some reading! Gunrun (talk) 23:04, 2 January 2013 (UTC)

CO2 laser - output power versus input.[edit]

I have a CO2 laser (100 Watt) which is rated for 23mA of power at the power supply. The power supply was shipped with the current limiter set somewhere down around 8mA...so the laser wasn't performing very well. So now I've adjusted the limiter to provide the 23mA required - and I'm definitely getting more "oomph" out of the laser now - although the only measure I have of that is how well it cuts holes in things - and that's not linear with the laser energy anyway.

The question is: Is the amount of output laser power directly proportional to the input - or is there something more complicated going on?

Another issue is that these lasers degrade slowly over time (I believe the seals are imperfect so you get impurities leaching into the CO2 gas - which reduces the power you get out of the machine). Would it be reasonable to assume that the current consumed by the laser would be a reasonable measure of that deterioration - or does it consume just as much input current but produce less laser energy?

If it helps, this is a water-cooled device.

TIA SteveBaker (talk) 23:52, 1 January 2013 (UTC)

To the first question, no. The maximum power output is at the point where internal resistance of the power supply is equal to load. --Gilderien Chat|List of good deeds 02:16, 2 January 2013 (UTC)
That would be the maximum power output of the power supply - that's not what I'm asking. The power output of the laser is my concern. Not all of the electrical energy going into the thing emerges as useful light - much is wasted in heating the thing up (hence the need to water cool it). I'm interested in the relationship between the current going into the tube and the light energy coming out of it. SteveBaker (talk) 14:53, 2 January 2013 (UTC)
It's impossible to answer this question without details of the laser construction and its cooling. Why don't you perform an experiment to see how much it heats up identical volumes of infrared-opaque fluid (or just water) for the same duration at different power input levels? 70.59.14.20 (talk) 18:26, 2 January 2013 (UTC)
It's not exactly a trivial experiment for someone who doesn't have access to a fully equipped lab! It's also tough to do - glass is opaque to the IR light coming from the laser and is etched by it - and you can't risk stray reflections from things in the path of the laser because they tend to set light to things on the other side of the room! I rather hoped someone might know the general form of the relation between input power and light output. SteveBaker (talk) 22:09, 2 January 2013 (UTC)
Fire the laser downward into water in a metal dewar flask for a second, then put a thermometer in it? 70.59.14.20 (talk) 01:21, 4 January 2013 (UTC)
For an ideal laser, there is a "threshold" input power, below which the laser won't lase. Once the input power is above threshold, the laser output should ideally rise linearly with the input power. In practice, the output rises linearly with input for a while and then rolls over due to heating of the gas and other effects that reduce efficiency.
Degradation in performance over time may be due to erosion of the electrodes rather than contamination of the gas. This might cause the voltage required to get a given current to increase. Changes in the electric field distribution due to the wear on the electrodes would probably cause the laser to produce less power at a given current over time.
Make sure you wear proper laser safety goggles while operating the laser. Even a tiny fraction of a 100 W beam can blind you.--Srleffler (talk) 17:49, 4 January 2013 (UTC)
Ah! That's what I needed. So it's linear with the input power once it's lasing and then up to some point where overheating takes over (which should be well-controlled with the chilled water supply)? That's exactly what I needed to know! Thanks!
(And, yes - when the case of the machine is open, we wear special polycarbonate safety goggles that are specifically designed to filter out light at the frequency of the laser. When the machine is running (it's a laser cutter BTW), the case is light-tight except for a dark-tinted polycarbonate lid - which, again, is specifically designed to filter out the harmful light. Even the reflection of a reflection of the beam is enough to cause eye damage! This thing can happily slice through a half inch of solid wood! SteveBaker (talk) 17:54, 4 January 2013 (UTC)