Wikipedia:Reference desk/Archives/Science/2010 August 24

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August 24

What kind of lizard is this?

Unidentified lizard

I found this little guy last Friday while looking at ghost towns in Juab County, Utah. Its environment is desert, if that helps any. I saw the same species of lizard on Antelope Island last May. The Raptor ^{You rang?}/_{My mistakes; I mean, er, contributions} 00:14, 24 August 2010 (UTC)

My guess is the Lesser Earless Lizard (Holbrookia maculata) who lost part of its tail. ---Sluzzelin talk 00:19, 24 August 2010 (UTC)

Completing my physics education

I'm enrolled in a physics undergrad program program in a Quebec university, which means that my program is three years instead of four years. The reason is that we have a CEGEP-system; that is, high school ends a year earlier and university starts a year later, with a two-year CEGEP thing in the middle. Now, normally this wouldn't be a problem, except that I took a total of three physics courses during my stint at CEGEP. And they were baby courses to begin with (classical mechanics without calculus, waves without the wave equation, etc.) I'm a little worried about the quality of my education, and that I will be behind those students who've had a four year education, so I've decided that I'll do some self-study to fill in the gaps. Here's my program schedule:

U1 Required Courses

(27 credits)

MATH 247 (3) Honours Applied Linear Algebra

MATH 248 (3) Honours Advanced Calculus

MATH 249 (3) Honours Complex Variables

MATH 325 (3) Honours Ordinary Differential Equations

PHYS 241 (3) Signal Processing

PHYS 251 (3) Honours Classical Mechanics 1

PHYS 257 (3) Experimental Methods 1

PHYS 258 (3) Experimental Methods 2

PHYS 260 (3) Modern Physics and Relativity

U2 Required Courses

(24 credits)

MATH 375 (3) Honours Partial Differential Equations

PHYS 253 (3) Thermal Physics

PHYS 350 (3) Honours Electricity and Magnetism

PHYS 357 (3) Honours Quantum Physics 1

PHYS 359 (3) Honours Laboratory in Modern Physics 1

PHYS 362 (3) Statistical Mechanics

PHYS 451 (3) Honours Classical Mechanics 2

PHYS 457 (3) Honours Quantum Physics 2

U3 Required Courses

(6 credits)

PHYS 551 (3) Quantum Theory

PHYS 352 (3) Honours Electromagnetic Waves

U3 Complementary Courses

(21 credits)

6 credits selected from:

PHYS 459D1 (3) Honours Research Thesis

and PHYS 459D2 (3) Honours Research Thesis

PHYS 469 (3) Honours Laboratory in Modern Physics 2

PHYS 479 (3) Honours Research Project

15 credits selected from:

PHYS 332 (3) Physics of Fluids

PHYS 434 (3) Optics

PHYS 479 (3) Honours Research Project

PHYS 514 (3) General Relativity

PHYS 521 (3) Astrophysics

PHYS 557 (3) Nuclear Physics

PHYS 558 (3) Solid State Physics

PHYS 559 (3) Advanced Statistical Mechanics

PHYS 562 (3) Electromagnetic Theory

PHYS 567 (3) Particle Physics

PHYS 580 (3) Introduction to String Theory

What texts would you recommend I look into? Thanks. (And if you're really generous, what complementary courses should I take in the third year?)76.68.247.183 (talk) 00:25, 24 August 2010 (UTC)

I'm somewhat unclear on what the question is. Are you currently starting the programs of courses outlined above and looking for advice on how to further supplement that on your own? Dragons flight (talk) 00:37, 24 August 2010 (UTC)

Yes exactly, sorry for being unclear. 76.68.247.183 (talk) 01:05, 24 August 2010 (UTC)

I would definitely call up the university and see if they can put you in touch with one of their advisors. What you are asking is very detailed and depends on a detailed knowledge of the unusual course you've done and the precise syllabus are pre-reqs of one you are going into - and the odds are slim that we'll be able to get you an answer that's any better than guessing. SteveBaker (talk) 00:43, 24 August 2010 (UTC)

That's too bad, but thanks anyhow. 76.68.247.183 (talk) 01:05, 24 August 2010 (UTC)

My advice, if you have time to spare for something like this, is to contact a lab that does something you are interested in and see if you can volunteer, or even get hired, as an undergraduate assistant. Practical research experience is worth ten times as much as studying. Looie496 (talk) 00:54, 24 August 2010 (UTC)

Thanks for the suggestion, I'll look into it. 76.68.247.183 (talk) 01:05, 24 August 2010 (UTC)

In reply to Dragons field, I parse the situation to be that the OP is about to start this year's Honours Physics program at McGill. I think in the OP's position, I'd be concentrating all of my efforts on getting through the first year, about half of which is mathematics. Lack of prior physics tuition looks only to be a problem from year 2 onwards. Only the OP will know his or her areas of mathematical weakness, but for instance, right now, a decent book on calculus might be indicated. --Tagishsimon (talk) 00:56, 24 August 2010 (UTC)

I think my math is fine (Cals 1 through 3, linear algebra, and even an intro to differential equations). My general misgiving not that I am improperly prepared, but rather that I'll miss out on some of the physics that, although interesting, isn't absolutely necessary for, say, grad school (which is what this program is preparing for). 76.68.247.183 (talk) 01:13, 24 August 2010 (UTC)

(ec) That's not really the way it works. In a three year course in any of the sciences, the first two years try to cover the material which ever practitioner in that science (here, every physicist) should know: in the final year, you get to drop some of the bits you don't like and specialize a little bit (but nowhere near as much as you specialize in grad school). By the time you get to the third year, there will be some of those optional courses that you just don't want to take because the subject matter doesn't interest you – it's pointless asking yourself which ones at the moment, because you haven't yet been exposed to the physics at university level so you don't really know what's going to interest you in two year's time or not.

In my own case (I'm a chemist, but the principles are similar), I was certain (and my grades backed me up) that I didn't want to be an organic chemist, so I specialised in my final year in inorganic and theoretical chemistry, not in organic or physical chemistry: I then did my PhD in inorganic chemistry. That doesn't stop me editing organic chemistry articles on Wikipedia, because I know the basics, I'm just not a specialist in that field: I have to look things up that a specialist would know almost instinctively, but at least I understand them when I look them up! Physchim62 (talk) 14:59, 24 August 2010 (UTC)

I don't see anything significant missing from the physics coverage compared to what is typical at other grad school preparatory programs. I will note that Solid State is often a required course, and some grad schools assume you've taken it, so that is probably a good choice under the optional work. I do notice that there doesn't seem to be any requirement for statistics or computer programming, both of which are skills that are very valuable to many practicing physicists. For some specialties (e.g. particle physics, string theory, general relativity) it would also be useful to take additional math courses (e.g. Group Theory, Differential Geometry, etc.). If you goal is to learn practical everyday physics, then I would suggest that Fluids is quite valuable (as well as being useful for some experimentalists). However, people focusing on nuclear and particle physics do often skip Fluids with no real detriment. Personally, I like Astrophysics for its breadth and ability to consider a wide variety of unusual problems. On the other hand, I've seen people who consider Particle Physics to be a critical bit that every physicist should know even though most will never use it for anything. Ultimately, I'd suggest you base those U3 choices on what interests you at the time. This is especially true if you are thinking about grad school at that point and want to try out a topic area you are thinking of specializing in.

I would also like to second the comment by Looie. If you think you might want to go to grad school some day, then getting involved with research (even as only a part-time volunteer) is probably the best thing you can do for yourself. Physics is a rich discipline, and undergrad programs often tend to try to cover all of physics, but in doing so it is easy to miss skills that are important in the day to day life of many researchers. For example, computer programming, statistics, electrical / circuit engineering, etc. Working in a lab can help you learn the mindset of a scientist and pick up some of those skills that may not be part of the curriculum. If you are interested in grad school, then getting involved in research as an undergrad is probably the single best thing you could do improve your chances with top schools. Of course, some areas of research will only be accessible to advanced students (string theory, particle physics, etc.), but many of the experimental projects have work that even early undergrads can be trained to do. Depending on your preferences (and other workload) it may make sense to wait till U2 before looking for a place to volunteer, so that you'll have a better foundation in physics, but I would encourage you to get involved in research no later than that if you do want go to a top school afterward. It is also not uncommon to see undergrads who volunteer a little bit during the school year but also work full-time (for pay) in a lab during the summers, so that is something to consider. A lot of potential opportunities aren't advertised, so it makes sense to learn the research interests of the various faculty and reach out to them directly. Dragons flight (talk) 14:48, 24 August 2010 (UTC)

You want http://www.oercommons.org/courses/collection/light-and-matter-physics-and-astronomy-resources -- start with the "Simple Nature" title to get an overview. For your third year, go with Fluids, Nuclear, Solid State, Advanced Statistical Mechanics, and Electromagnetic Theory to avoid the unapplied fluff. Ginger Conspiracy (talk) 22:56, 24 August 2010 (UTC)

Coral identification (from the Great Barrier Reef)

I'd appreciate any help you can give in the identification of these two corals. I've tried a fair bit myself, but didn't come up with much. Thanks. 99of9 (talk) 01:11, 24 August 2010 (UTC)

The spherical one is probably a porites, no idea which variety. Mikenorton (talk) 11:56, 24 August 2010 (UTC)

I'm not even convinced by that, it doesn't have "finger like" structure... --99of9 (talk) 21:42, 24 August 2010 (UTC)

There are many different types of Porites, not all of which have finger-like structure, see here for example, - that's particularly a reference to Porites porites I think. Mikenorton (talk) 22:05, 24 August 2010 (UTC)

Ok, so even the one sentence lead in the stub on porites is deficient! Our coverage of stony corals is surprisingly deficient compared to most other orders of animals I've seen. Thanks. I'd love to hear other opinions too. --99of9 (talk) 04:08, 25 August 2010 (UTC)

How would those dents in the top originate — damage, or does it naturally grow that way? Nyttend (talk) 11:59, 24 August 2010 (UTC)

They're certainly not recent damage, but perhaps some early damage has been grown over and left the dimples in the surface. --99of9 (talk) 21:42, 24 August 2010 (UTC)

What is Galactic Alignment?

Kindly enlighten me with a word i have come across Galactic Alignment.What would be its effect on earth. —Preceding unsigned comment added by 59.182.236.67 (talk) 07:25, 24 August 2010 (UTC)

Often, this sort of term ("galactic alignment", "celestial alignment", and so on), is used in a pseudoscientific way. In actual fact, astronomical alignments can and do occur, but they have little or no effect on Earth or any events here. A lot of mysticism and mythology has been concocted to conjure up "important effects", but in reality, any such alignment passes without really affecting anything. It's "neat" for people who like observing planets and stars. "Galactic" alignment is a pretty loose term - what, exactly, in the galaxy is aligning? Galaxies move very slowly; any "aligning" that they do with respect to anything else, especially as viewed from Earth, would occur over the course of millions of years. Nimur (talk) 07:53, 24 August 2010 (UTC)

The article covers this topic rather well. Bear in mind:

• the zodiac is a circle around the Earth, and the Milky Way is (in appearance) a circle around the Earth, so the two have to intersect, in fact twice. (Though since the center of the Galaxy is in Sagittarius, it is arguably the better of two choices)
• the Earth intersects as a function of precession, but when it intersects depends on what time of the year you look, since the Sun goes all the way around the Zodiac every year. So the choice of "winter solstice" for the alignment is one of four options for traditional solstices and equinoxes. (Even so, that's once every 26,000/4 = 8500 years
• the exact timing of the intersection depends on the exact middle plane of the Galaxy meeting the exact center of the Sun. But there's a huge amount of wiggle room there for the idea to be pounded around to meet the facts, because the Galaxy is a fuzzy object. I can't say exactly how much this blurs the time frame

In conclusion, it is not entirely a bogus concept - it does have a certain logic as a way to derive an astronomical Year Zero - but the 2012 thing is not an astronomical coincidence, so to speak. Wnt (talk) 15:01, 24 August 2010 (UTC)

Take a look at 2012 phenomenon for the interested. ~AH1^(TCU) 19:23, 26 August 2010 (UTC)

Histrionic Personality Disorder

Do people who have histrionic personality disorder cheat more often than other people? Have there been any studies done on this? I couldn't find any —Preceding unsigned comment added by 76.169.33.234 (talk) 07:59, 24 August 2010 (UTC)

See histrionic personality disorder. ~AH1^(TCU) 19:22, 26 August 2010 (UTC)

Already did, I asked only because there was no information about it. What would be the purpose of me seeing the article? It doesn't have the answer to my question. Not trying to be rude, but don't just answer to answer. Only answer with a useful answer. —Preceding unsigned comment added by 76.173.106.64 (talk) 03:23, 27 August 2010 (UTC)

Body Fat Level

Why is it that two people that are equally active and eat the same number of calories can weight different amounts? I know that their thyroid hormone levels can be different, but I can't see this making that much of a difference. Shouldn't they be both burning the same amount of calories? Can your genes make so much of a difference that one person will be overweight and the other very skinny? —Preceding unsigned comment added by 76.169.33.234 (talk) 08:02, 24 August 2010 (UTC)

See our article on Basal metabolic rate, which might vary widely between the two and is "usually by far the largest component of total caloric expenditure." Gabbe (talk) 11:23, 24 August 2010 (UTC)

Unfortunately, this article is not very complete - it gives simple formulae for BMR which do not admit easy change, and thus are not very satisfying for our purposes. See [1] for a study in which BMR (also caloric intake) was rapidly altered in experimental subjects. Wnt (talk) 14:45, 24 August 2010 (UTC)

According to a study for the BBC's Horizon, Jan 2009, there seems to be pre-set fatness level for everyone, presumably genetically predetermined. They took otherwise healthy volunteers and fed them twice their normal calorie intake, whilst reducing the amount of exercise they took. The volunteers' weights did rise, but some of them only slightly. The BBC article is a bit light on the details, and doesn't have a decent cite, but it might be a useful area to start websearching from. CS Miller (talk) 15:08, 24 August 2010 (UTC)

This question gets asked at least 1000 times a day in doctors offices around the world. Yes, it is quite obvious that two persons of similar size may have dramatically different calorie needs and that one may lose and the other gain on the same calorie intake. This inherent rate of calorie expenditure for basically staying alive is referred to as the basal metabolic rate. There are genetic components, with genome wide array studies discovering increasing numbers of genes associate with differences; these are unchangeable. There are probably early life programming factors that are not easily changed at an older age. There are likely ongoing factors that can gradually change the BMR of adults, such as activity level, diet composition or pattern, stress, illness, etc. The BMR is at least partly controlled by a hypothalamic mechanism that functions as a "set point thermostat", shifting energy expenditure mechanisms when weight exceeds or falls below the set point. It is a safe bet that a hundred pharmaceutical companies have lab scientists hard at work at finding ways to safely manipulate your BMR and when someone has an effective, safe product, it will be marketed to you every 15 minutes on every website, spam email, or television channel and will be more famous than Viagra. I long ago lost count of the number of times I have answered this question for overweight people or their relatives. Pass it around. 159.14.241.253 (talk) 16:39, 24 August 2010 (UTC)

That argument applies only to products that are patented and sold under monopoly - there is no special funding for other aspects of diet and lifestyle that might affect weight, including herbal supplements such as guggul (as well as related Commiphora described by Dioscorides). Once a weight loss product is developed and marketed, as a rule, it causes sudden death in large numbers, e.g. 2,4-dinitrophenol, amphetamines, fen-phen, and ECA stack supplements. This is one issue on which people definitely need to do their own research, and not rely on the regulatory system to support or protect them. Wnt (talk) 17:34, 24 August 2010 (UTC)

The idea that people can "do their own research" about something like this is idiotic. There is less safety and efficacy information available about anything sold as a "dietary supplement" than about anything FDA-regulated. The whole point of the "dietary supplement" status in the US is to avoid the onerous rules that attempt to provide at least some degree of assurance of safety and efficacy. For things sold as dietary supplements, "do your own research" is a mendacious delusion. Thanks but no thanks. 159.14.241.230 (talk) 17:13, 25 August 2010 (UTC)

A lack of regulation doesn't mean a lack of information. And the rules aren't always really about safety. The meadow saffron described in the Ebers papyrus for use against pains in the lower extremities, and denounced as poisonous by critics from Dioscorides to the present day, is exactly the same drug as the Colcrys sold for fifty times the price of previous colchicine on account of FDA approval and FDA monopoly in the U.S. Because the dosage of colchicine has traditionally been pretty much "use as you feel like", the control over concentration (which predates the FDA-approved version) really isn't such a large advance. Likewise, consider aspirin, which causes gastrointestinal bleeding, not caused by the more advanced preparation of willow bark extract found on a clay tablet from the city of Ur, several centuries before the birth of Abraham. Wnt (talk) 14:35, 26 August 2010 (UTC)

Nonsense; fuzzy stories for the ignorant, but completely untrue. The whole reason for formation of the FDA was to provide standardization of preparations and laws against adulteration. When people know no one is checking and there are no penalties for fraud they will sell you anything, like the melamine in the chinese baby formulas. Those who know no history peddle bullshit and are ripe for the latest incarnation of the eternal political and medical cons. 76.117.81.78 (talk) 23:26, 28 August 2010 (UTC)

See Somatotype and constitutional psychology. Most people have a given body mass range set by their bone structure. ~AH1^(TCU) 19:21, 26 August 2010 (UTC)

This was a respectable theory back in the 1920s and it is maybe sorta kinda a little bit true that BMR and living conditions being equal, there is a relationship between skeletal build and body fat. The point the questioner was asking about however is that BMR still varies among people of roughly the same size, so this is not a very helpful answer. 76.117.81.78 (talk) 23:26, 28 August 2010 (UTC)

Need help understanding some poorly written chemistry info...

From the writings of a colleague: In high temperature, sodalite would transform to cancrinite of which twelve-ring channels cage prefer bigger cation. So when Ca2+ exists in solution, it prefer occupying the cage to instead of two Na+s, forming Na6[Al6Si6O24]•2CaCO3•nH2O.

My attempt at rephrasing: Sodalite transforms into cancrinite when exposed to high temperature. Cancrinite's twelve-ring channel cage prefers larger cations and thus preferentially selects Ca2+ over two Na+s when the former is present in solution. The final product in this case is Na6[Al6Si6O24]•2CaCO3•nH2O.

Does that make sense?

First, my chemistry knowledge is next to nothing - for example, I have no idea what a twelve-ring channel cage is. Second, while this is a language question, I figure the technical ability on the Science RD would be more valuable than the language parsing ability on the LRD. Third, thank you for any writing assistance you can provide! 61.189.63.185 (talk) 12:30, 24 August 2010 (UTC)

I would say "the pseudo-twelve-coordinate site in cancrinite". Cancrinite certainly has a pseudo-12C site (see here, and click on "Large pop-up" to see it more clearly), and Ca²⁺ would be a better fit than Na⁺. Physchim62 (talk) 16:06, 24 August 2010 (UTC)

Drunk

Can you get drunk from alcohol on tongue? Like if you just dipped your tongue into a cup of vodka but didn't drink. Would it diffuse into you? —Preceding unsigned comment added by Prize Winning Tomato (talk • contribs) 15:52, 24 August 2010 (UTC)

It would certainly diffuse into you. Whether it would do so faster than your body can process it (thus eventually rendering you drunk), I'm not sure. — Lomn 16:03, 24 August 2010 (UTC)

Maybe. This might be a fun experiment: hold a mouthful of ethanol-based (20 proof? 40 proof?) mouthwash in your mouth for a minute, rinse thoroughly, and then measure your blood alcohol content with those test strips or a breathalyser if you have access to one. I wonder if the uptake rate would vary much between individuals. Ginger Conspiracy (talk) 23:55, 24 August 2010 (UTC)

I don't think you can absorb much through the tongue, but you certainly can from under it, see: Sublingual administration. Ariel. (talk) 06:24, 25 August 2010 (UTC)

I think mythbusters did a show where they used mouthwash and then took a breathalyzer test and the BAC that the test showed would have been lethal to a human. Even after waiting for a significant period of time it was still showing highly elevated levels. Googlemeister (talk) 13:28, 25 August 2010 (UTC)

A breath-based alcohol measurement is likely to be very unreliable under those conditions. See Breathalyzer#Mouth alcohol, Breathalyzer#Products that interfere with testing. Trace amounts of alcohol residue in the oral cavity will badly skew the apparent alcohol content of breath. TenOfAllTrades(talk) 13:50, 25 August 2010 (UTC)

Light

Is light from a light bulb the same as natural sunlight? Or are there different types of light? Because well watered plants indoors with no sunlight tend to die —Preceding unsigned comment added by Prize Winning Tomato (talk • contribs) 15:54, 24 August 2010 (UTC)

You may be over-watering them - that makes the roots rot. The pot they are in needs to have drainage. There are many plants successfully grown as houseplants, so I am surprised, unless you truely mean zero natural light. Houseplants tend to get put next to windows. If over-watering is not the problem, then you could try plants that are adapted to deep shade, such as ferns. 92.15.13.237 (talk) 10:09, 26 August 2010 (UTC)

Light is made up of a spectrum of colours. Light from the sun will tend to have a different spectrum (that is, a different mix) of colours, than light from a bulb. Reading Grow light might be helpful - these are bulbs designed to produce a spectrum which is suited to nurturing plants. --Tagishsimon (talk) 16:01, 24 August 2010 (UTC)

No, yes. See colour temperature. 92.15.15.228 (talk) 18:04, 24 August 2010 (UTC)

Even if the spectrum (color temperature) of light is the same, the intensity is vastly different. Direct sunlight is about 100,000 lux, and a sunny day in the shade is over 10,000 lux. Even an overcast day is around 1,000 lux. In contrast, a typical living room is only 50 lux. That's over 1000 times dimmer than direct sunlight. We tend not to realize this because our eyes are so efficient at adapting to a wide range of light intensities. -- 140.142.20.229 (talk) 19:19, 24 August 2010 (UTC)

The comment above is correct, but as additional info, the light from an incandescent bulb is quite a bit redder than natural sunlight. However chlorophyll absorbs best in the red-yellow part of the spectrum, so the spectral difference wouldn't be harmful. It's the intensity that makes the difference. Looie496 (talk) 03:09, 25 August 2010 (UTC)

Light from a typical incandescent light bulb is more yellow, and at a lower color temperature, than sunlight, which is judged to be "white" light. You can purchase "daylight" bulbs, which have a blue filter coating more nearly approximating sunlight, though at a reduced efficiency. Light bulbs, whether yellow or daylight, incandescent or compact fluorescent or LED, emit electromagnetic radiation in the visible range, as does the sun, with varying efficacy. Edison (talk) 03:46, 25 August 2010 (UTC)

Try looking at your bulb (incandescent or compact fluorescent?) through a spectrometer. ~AH1^(TCU) 19:19, 26 August 2010 (UTC)

Milky Way Galaxy

What is the Milky Way galaxy made of?165.212.189.187 (talk) 15:58, 24 August 2010 (UTC)

Galaxies are made of stars and stellar byproducts, dust, and (probably) dark matter. Dark energy, as I understand it, is generally pervasive rather than clumped in galaxies. — Lomn 16:02, 24 August 2010 (UTC)

See also Milky Way#Composition and structure --Tagishsimon (talk) 16:04, 24 August 2010 (UTC)

There is a lot of speculation about dark matter these days; but it may turn out to be "uninteresting" cold hydrogen gas that just isn't warm enough to be incandescent. It may also turn out to be some form of exotic matter. Unfortunately (because it is dark and far away) we have few tools to study it directly. Nimur (talk) 19:56, 24 August 2010 (UTC)

Galaxies are made of "everything". A few hundred billion stars, a honking great black hole in the middle - and the dust, gas, moons, planets, asteroids and comets - but also people, trees, fish, elephants... When you come right down to it - it's hard to think of anything that a galaxy ISN'T made of! SteveBaker (talk) 23:37, 24 August 2010 (UTC)

... agreed, but galaxies contain only some (what proportion?) of the dark matter in the universe, and only a very small proportion of the dark energy (assuming that it exists). Dbfirs 08:20, 25 August 2010 (UTC)

Exactly my point, Steve. The Eentropy of Mixing is alive and well in all galaxies. —Preceding unsigned comment added by 165.212.189.187 (talk) 13:02, 25 August 2010 (UTC)

Don't forget about the nebulae and supermassive black hole. ~AH1^(TCU) 19:17, 26 August 2010 (UTC)

Why did some prick throw a brick into this washing machine?

What did he hope to accomplish? To solve? Why did this prick want to commit harm to it when he could've done good (or at least harm to something else) instead?

(And why was the washing machine smoking in the first place?)

http://www.youtube.com/watch?v=364dzVsBs2o

--70.179.165.170 (talk) 15:31, 24 August 2010 (UTC)

Are you seeking to accomplish or establish something by the repeated use of the idiom "prick"? To be honest, it merely rebounds onto you, leaving us to think that you may in fact be one. Why, for instance, could you not have "done good" and avoided the aggresive and unhelpful language. --Tagishsimon (talk) 16:22, 24 August 2010 (UTC)

A trip to your local dump / civic-amenity / recycling centre will reveal a horrid truth about modern society : we throw away a huge collection of manufactured goods that are defective but repairable, but that are nevertheless beyond economic repair. It's likely that this machine had such a defect - a bad controller card, a bad pump assembly, an agonisingly worn main bearing. If a new machine would be cheaper than the repair (which is very often the case) or the parts just aren't made (which seems to be very common indeed for machines older than a decade) then you end up having to chuck out something that otherwise still works. I'm guessing that's the case here (and may well explain the smoking). -- Finlay McWalter ☻ Talk 16:24, 24 August 2010 (UTC)

Concur. I was unable to get an old but high quality TV repaired simply because parts were no longer available. I was forced to take it to the local recycling centre. Exxolon (talk) 16:47, 24 August 2010 (UTC)

A friend at work had his 2 year old flat-screen TV start acting up. When he took it to get it repaired, the cost estimate was 70% of the original cost of the TV, and because flat screen TV's have gotten cheaper since then, that was about the same as the cost of a replacement (which had more features - better quality, etc). In light of that, it's not surprising that he was going to chuck it out. However, by searching for the model number and the fault condition online, I discovered that the problem was 90% certain to be one of the capacitors in the power supply. Within 10 minutes with nothing more than a torx-wrench and a soldering iron (and a bunch of generic capacitors that I had in my junk bin, probably recycled from something else that I'd pulled apart), I had the TV working again and saved the guy several hundred bucks - cost $0. Sadly, there doesn't seem to be a way out of this noose for the majority of the population. Even if you know it's a 10 cent part - very few people know how to use a soldering iron - and for some reason they don't realize that there a bajillion websites that explain how to use one. Whatever happened to "You aren't a 'real man' unless you have a garage full of tools and know how to use them"? SteveBaker (talk) 23:27, 24 August 2010 (UTC)

Was this yet another victim of the capacitor plague? It's surprising that the Taiwanese capacitor industry was penalized so greatly for doing something that made the manufacturers so much money... Wnt (talk) 22:54, 27 August 2010 (UTC)

To see what happens. Vimescarrot (talk) 16:29, 24 August 2010 (UTC)

Perhaps for entertainment. Lot's of people have spent a good deal more than the price of a used washing machine to make an entertaining youtube video.

There is no law that says that a person must devote every penny's worth of property they own to the betterment of mankind.

Craigslist tells me that the price of a damaged (notice that it's smoking) washing machine is about $100. Are you really berating this person for wasting the equivalent of two video game's worth of stuff? You've never spent $100 or more on entertainment?

(P.S. My favorite video of this kind is this one. Mostly because I wish I owned a hat like that.) APL (talk) 18:47, 24 August 2010 (UTC)

I agree: entertainment, curiosity, and the lurking lust for destruction. This is a good way of living it out. Not prickishness. There are also people who satisfy these needs by experimenting with or destroying what belongs to others (not just primitive vandalism of private or public property, also reckless experiments on college campus, for example). I agree with APL (though I admit I have my own personal limits of sensitivity toward destroying inanimate objects for show when it comes to food or musical instruments). In any event, it is likely that the smoking washing machine wasn't in mint condition, and even if it wasn't beyond repair, at least this was a creative and entertaining form of wastefulness. Didn't Letterman drop things from buildings for a while? ---Sluzzelin talk 19:00, 24 August 2010 (UTC)

How about asking the uploader? You might want to avoid calling them a prick though if you want an answer. Interestingly, that looks to be the same washing machine that I have. It's only a yearish old and it had a five year parts guarantee which does kinda make me wonder why they did it too. Smartse (talk) 13:54, 25 August 2010 (UTC)

Oh and this video is so much better and reinforced Vimescarrot's point. Smartse (talk) 13:58, 25 August 2010 (UTC)

"Will it Blend" are paid advertisements for blenders. So they don't really demonstrate honest curiosity. APL (talk) 14:50, 25 August 2010 (UTC)

I feel sorry for it :( 82.44.54.25 (talk) 14:09, 25 August 2010 (UTC)

The difference between sacrifice and blasphemy (picture and video) ? Cuddlyable3 (talk) 19:08, 26 August 2010 (UTC)

7 degrees of separation

Most people know the old adage, "You're only 7 people away from knowing everyone in the world?" What is the etiology of this? Have there ever been any well-controlled studies about it? Are the scholars (philosophers, sociologists etc.) who've focused a great deal of time looking into it's supposed validity? Are there any good books about it? Buddpaul (talk) 17:48, 24 August 2010 (UTC)

Six degrees of separation has a lot of information. -- Finlay McWalter ☻ Talk 17:54, 24 August 2010 (UTC)

It's certainly not a cast iron RULE. There are undoubtedly people who can't be reached in so few steps. But it is an exceedingly solid average. There was a rather good Discovery channel documentary on this - which they tested by picking a bunch of people around the world and asked them to get a message to a specific US researcher by passing it on to someone they knew - amazingly, they all managed to get the message to it's destination - and in each case, within the six degrees. There is a significant body of mathematics that show why this is true - and it has applicability to all sorts of systems. For example, you can almost always get from your computer to any other on the Internet by routing the message through about six other computers.

The game "Six degrees of Kevin Bacon" requires you to find a chain of actors, producers or directors who are linked to Kevin Bacon by participating in movies that link them along the way. (eg Elvis Presley was in Change of Habit (1969) with Edward Asner who was in JFK (1991) with Kevin Bacon) - someone who studied the Internet Movie Database (IMDB) discovered that of the 1.6 million people listed there, only 150 of them could not be connected to Kevin Bacon in 6 steps or less. However, we're restricting them to being connected only by movies they've participated in - if we were allowed to connect them by friends, aquaintances, neighbors, co-workers, etc - I'm sure the paths would be much shorter.

An experiment on Facebook connects friends of friends of friends...it finds that the average number of friend links to get from anyone to anyone else is 5.7...again, less than 6 degrees. There have even been experiments right here in Wikipedia to see what the fewest number of links you have to click on to get from any article to any other...and again, the answer is less than 6.

The result is so ubiquitous across so many fields that it starts to seem like a rather fundamental result.

SteveBaker (talk) 22:43, 24 August 2010 (UTC)

Wow, I had no idea there was an Erdős–Bacon number, let alone an article on it! ---Sluzzelin talk 04:17, 25 August 2010 (UTC)

Has there been any research done on this subject in the context of sexual partners? For instance HIV/AIDS presumably started with one individual and has now spread to very large numbers worldwide, implying that there is a very large network of people linked by sexual contact. I wonder how many links there would be on this network between random people. The network is of course much larger than the HIV/AIDS numbers by themselves suggest, given that the probability of catching it from an infected person is well less than 1. --rossb (talk) 14:11, 25 August 2010 (UTC)

The experiment on Facebook showed that the largest separation number among participants was 12, although a user could easily have friends they don't know or not have someone on Facebook who they do know. ~AH1^(TCU) 19:16, 26 August 2010 (UTC)

Common Descent

What are the odds that we are actually descended from the particular, specific fossils we've found in Africa like Lucy? What if she had no children herself? Is there any way to prove we're directly descended from a fossil and not one of their siblings? TheFutureAwaits (talk) 19:00, 24 August 2010 (UTC)

The only way to do that would be by means of archaeogenetics. The "Ancient DNA" article only mentions this technique having been applied as far back as eg. "Ötzi the Iceman" and the Ancient Egyptian mummies -- ie., maybe five or six thousand years, nowhere near the 3 or so million years ago for the "Lucy" remains!

So much for "proof." As to odds, those will depend on things like the population size and distribution, etc., of contemporary Australopithecus afarensis and I will leave it for others to try to estimate those if they can... Wikiscient (talk) 19:19, 24 August 2010 (UTC)

You might also want to consider the information in the Mitochondrial Eve article, though I'm not sure this is going to address the specific question you seem to be asking. Wikiscient (talk) 19:23, 24 August 2010 (UTC)

If you are asking about the probability of a specific early fossil being an ancestor of you, personally - then the odds are surprisingly high. Someone who lived just 30 generations ago (600 years - in about the 1400's) would by now have over a billion descendants. Several estimates say that someone who lived in the 6th century BC could easily be the ancestor of everyone alive today - other estimates put it MUCH more recently than that (unless you happen to be a native of the Amazon basin or something equally out of the way). The most recent ancestor of all people of European descent probably lived less than 1000 years ago.

Our Most recent common ancestor article is worth reading.

The most likely chance for a fossil (rather than just a rather old skeleton) would be a fossil from about 70,000 years ago when human population crashed (according to the Toba catastrophe theory) to less than 10,000 individuals - perhaps only 1,000 breeding pairs. The La Ferrassie 1 fossil is about that old - and is highly likely to be your ancestor.

Back at 1.2 million years ago, there were around 26,000 people in the world - and that number is probably fairly constant all the way back to the time of Lucy (3.2 million years ago).

The difficulty is that beyond a few thousand years ago, the issue isn't so much whether you, personally, are descended from a particular individual - the question is whether ANY of that person's offspring survived. If they had a blood line continuing for more than a handful of generations, then the odds are extremely high that you are a descendent - but obviously if that person had no children, or those children all died before child-bearing age - then the odds are zero.

That means that the odds are all about the number of surviving children from each generation that made it through to child-bearing age back at the time of the fossil you're thinking about. I don't think we have a clue about how many children a Lucy-era Australopithecus would have had - let alone how many would have survived - so it's tough to know whether we are all likely to be ancestors of Lucy or not...maybe she died childless...maybe she bore a dozen healthy kids who all gave her a bunch of grandchildren - if that's what happened, then she is an ancestor of all of us.

SteveBaker (talk) 22:18, 24 August 2010 (UTC)

There is only one way, in principle, to prove descent from a specific individual from long ago -- that's if the individual had a novel genetic mutation that was not present in either parent, and is present in you. The odds of ever being able to prove that for an ancient individual are extremely slim, with emphasis on extremely. Looie496 (talk) 03:03, 25 August 2010 (UTC)

Add to the above the (slim, but nonzero) probability that the specific fossilized individual was a part of a monozygotic multiple birth, and it becomes impossible to prove that they were your direct ancestor. -- Scray (talk) 04:38, 25 August 2010 (UTC)

Searching for fossils by radar

How come this hasn't taken off? It sure seems easier than digging blind! http://www.americanscientist.org/issues/pub/2001/1/fossil-hunting-by-radar TheFutureAwaits (talk) 19:05, 24 August 2010 (UTC)

Radar has limited penetration through rock or soil except where conductivity is low - dry sand is ideal, anywhere that is wet (particularly if at all saline) or consists of mainly clay for instance would yield far less useful data. I don't suppose that this sort of thing comes cheap either, any group would need to be well-funded. I see that the article linked to is nine years old, maybe they couldn't either raise the funding or the results of the pilot project were not that good. Mikenorton (talk) 19:24, 24 August 2010 (UTC)

Geophysical survey (archaeology) has some nice links and photos. For archaeology, the advantage is that human artifacts tend to be near the surface (not very deep) and are often metal or highly contrasting material to the surrounding overburden. With more ancient fossils (like dinosaur bones, for example), RADAR penetration and reflectivity contrast is not very good. Nimur (talk) 20:10, 24 August 2010 (UTC)

I would expect the main problem is false positives. You're going to get hugely noisy signals. Looking at something comparable, take a look at the kinds of things you get from side scan sonar. For every photo like this, where you can tell pretty well what it is, you get millions like this, or this, or this, or this. (And THOSE are probably chosen as the most illustrative of their own surveys!) Now imagine that instead of just going sideways in the ocean looking for solid structures on the surface, you are actually looking down into the rock and so on of the last few thousand (if not millions) years of history. You get images like this. What is that? It turns out it is a cemetery. (Using Ground-penetrating radar.) Is getting a survey like that likely to be useful, or is it going to send you off on a thousand false positives, thinking you've found a cemetery (or dinosaur, or whatever), and instead finding a bunch of buried parts from an industrial factory, or some odd shaped rocks, or whatever else is underground? This is just my hunch but I'd think that such a thing would be a pretty difficult endeavor. --Mr.98 (talk) 00:37, 25 August 2010 (UTC)

Mineralization converts fossils to the same material as the surrounding rock, more or less; more often no sign of their presence remains at all. I think even fresh biological materials buried in rock would be very difficult to find by ground penetrating radar, even before being tightly compressed, unless quite large voids are present. Wnt (talk) 04:40, 25 August 2010 (UTC)

motors

Are electric motors and dynamos the same thing? So for example I could take the motor from a fan and put it on my bicycle and it'd power the light? Or are they different —Preceding unsigned comment added by Prize Winning Tomato (talk • contribs) 20:04, 24 August 2010 (UTC)

DC motors containing a permanent magnet can generate electricity when rotated, just like a dynamo. Electric motors not containing a permanent magnet need a more complicated mechanism to produce electricity. Dynamos are specialized for their use though, so they probably generate a higher voltage than electric motors would. --Chemicalinterest (talk) 20:24, 24 August 2010 (UTC)

Talking of motors, I too raise my hand. I have a DC motor with permanent magnet. It works well on 3 volts, but does not work on 9 volts DC or more. why ?  Jon Ascton  (talk) 01:10, 25 August 2010 (UTC)

Back in the 1860's they realized that generators and motors were basically the same things. But if you take a motor from a fan, and it was previously powered by 120 v AC (US) or 240 v AV (most of the rest of the world) it will not generate appreciable voltage when you spin the rotor,unless the stator is energized at the correct voltage and phase. If you devise and implement a way to have the field (stator) energized correctly while you cause the rotor to spin, you could use the motor as a generator. Direct current machinery is probably easier to use in this way than alternating current machinery. Edison (talk) 03:40, 25 August 2010 (UTC)

One cool demo I do a lot for people is to take a couple of simple DC motors (two Lego Technics motors work well because they have internal reduction gearing) and connect them together - no batteries, no switches, nothing but a couple of feet of wire. It is really spooky that you can turn one motor (thereby making it be a 'generator') and see the other precisely mimic its motion (well, precisely - minus a bit of inefficiency along the way...but remarkably little) - even though they are a couple of feet apart. You turn one a quarter turn, the other one turns a quarter turn...you turn the second one a quarter turn back to where it was - and the first one obediently mimics it. Even when you know what's going on, it's really quite freaky! SteveBaker (talk) 04:48, 25 August 2010 (UTC)

Thanks for that. I once saw that demo performed but I thought the two devices must be specially constructed for the purpose. I didn't realise it would happen with any old pair of DC motors! Dolphin (t) 08:23, 25 August 2010 (UTC)

I think it may be important to a really convincing demo that the motors have internal gearing - you have to generate enough current in the 'dynamo' motor to overcome stiction in the other or it won't move at all. If the motor isn't geared then you might have to spin the shaft more rapidly than you can easily do with your fingers to generate enough current. The Lego motors that I use have a 16:1 reduction gear inside - so by gently rotating the output shaft, you're spinning the actual motor 16 times faster. Having said that, I managed to get the effect to work well enough with two of the tiny motors they use to make cellphones vibrate...so it may not be so difficult without gearing. SteveBaker (talk) 15:47, 25 August 2010 (UTC)

One of the simplest physical principles that I've never understood is the idea of self-excitation of a dynamo such as those invented by Ányos Jedlik. I just don't understand how the current gets started. But I suppose such a device must be as reversible as any other motor. Wnt (talk) 13:59, 25 August 2010 (UTC)

It might be noted that on many railways the fact that the same device can be a motor and a generator is used in an important way. See dynamic braking for diesel-electric trains, and regenerative braking for electric ones, where slowing down one train can help power another (or even help power things off the railway). --Anonymous, 22:26 UTC, August 27, 2010.

Human IQ

a) How long ago was it when the IQ of human ancestors was equal to the IQ of contemporary chimps? b) Why do humans have so much surplus IQ? Surely evolutionary speaking we just need enough IQ to feed and reproduce, but not to deduce that E=mc^2? How or why did this surplus IQ evolve? c) If in a population the less intelligent parents have more children that average, could this reduce the average IQ of the population? How many generations would it take? Is there any indication that this may be happening currently? Thanks 92.15.3.135 (talk) 20:10, 24 August 2010 (UTC)

I really don't know how applicable IQ tests are to animals. There is a fair amount of bias in IQ tests between human cultures, let alone non-humans. Googlemeister (talk) 20:18, 24 August 2010 (UTC)

(ec) There is not an easy answer to any of these questions. You can start by reading Evolution of human intelligence and theories of human intelligence. It is not even clear how to measure and compare "average" intelligence between different people in the same era, let alone through multiple decades, centuries, or so distant into the past that evolutionary biology becomes the dominant factor. It will be hard to give an exact historic timeframe for when we became "smarter" than chimpanzee, but human evolution discusses this well. Sapiens, or "wise human", is the name commonly given to those first fossil hominids that we identify as "modern" and "intelligent" - and they appeared around a half-million years ago - but understand that this transition toward "intelligence" occurred over a wide swath of the timeline and our best fossil evidence is "size of skull" as an indicator of intellect. Other evidence, such as behavior, lifestyle, toolmaking, and so on (things we would consider the hallmarks of "intelligence") are largely inferred from indirect evidence as we go deep into prehistory hundreds of thousands of years back - so exact dates are impossible to proscribe. Regarding the evolution of additional intelligence, beyond the basic need for survival - I would call this a sort of "evolutionary inertia." We may have evolved "merely to survive," but as a side effect, we proliferated and thrived - because conditions were good enough, and we became the apex predator. Intelligence has helped humans to maintain their position as apex predator, and the rise of civilization throws much complexity into the simplistic view of straightforward natural selection. The definition of "fit enough to survive and reproduce" significantly changed as humans began to make easy work out of "basic survival." In light of this, even your last question is not easy to answer; you might also want to consider the nature versus nurture debate. Modern intelligence is a plethora of different skills - innate and learned - so it is not even safe to say with certainty that "dim" parents will produce "dim" progeny. Nimur (talk) 20:26, 24 August 2010 (UTC)

a) I think you mean "intelligence" here much more informally than its rigorous definition according to "IQ". You can't give an IQ test to a chimp. So the answer is that humans started developing "human intelligence" as soon as human ancestors and chimp ancestors parted ways evolutionarily (which was as long ago as maybe 15 million years depending on how you look at it).

b) Again I think you are wondering about surplus "intelligence" and not "IQ" per se. One thing to consider is that this intelligence, informally speaking, is in large part due to cultural development. Einstein could derive "E=mc²" only because he lived at a time when the math and physics he used to do so had been sufficiently developed. As the theory goes, he could have been born a million years earlier and still have been as "capable" of developing his theories as he was a hundred years ago -- had he simply had the same cultural tools available to him a million years ago. (For more on how this could be, see eg. "exaptation" (= "using a trait for some purpose other than that for which it evolved") and "positive feedback loops" and etc.)

c) According to the Fertility and intelligence article, there are indeed indications that "this" may be happening currently in some ways. But I expect it would take much, much longer than that trend is likely to last (even if that turns out to be hundreds or even thousands of years) for Homo sapiens to evolve a "genetically" "lower IQ."

Wikiscient (talk) 21:10, 24 August 2010 (UTC)

You may enjoy the novel Galapagos, by Kurt Vonnegut, which is told from a viewpoint a million years in the future, and which postulates that the big brains of today's humans has been one big evolutionary mistake; humans end up evolving into creatures with much smaller brains, able to swim in the water and catch fish as seals do, but without the predilection or even the capacity to create nations or war or mass environmental destruction. Comet Tuttle (talk) 21:31, 24 August 2010 (UTC)

I don't think that the assumption that "we have IQ to spare" makes a lot of sense. We (more or less) agree that IQ isn't about memory capacity - in computer terms, it's more like "CPU speed" than "RAM size". That being the case, you don't "run out of IQ" like you might run out of memory. You might need a certain amount of brain power to conceive of the shape of a stone arrowhead and to figure out how to knap that from a large flint rock - or to figure out how deer behave when you encircle them in a particular way at a particular time of day when they are not near a water supply and have calves with them at the time. That's probably not much different from the amount of "CPU power" it takes to figure out E=mc². When people are thinking hard about problems like that, they tend to need quiet, no distractions, not to be doing anything else at the time - which suggests that we're using close to the full amount of CPU power that we have available.

There just isn't any evidence that we're smarter than our homo-sapiens ancestors. Einstein didn't come up with E=mc² just from nothing - he needed the results of experiments - the benefits of prior thinking from the likes of Newton. He needed writing and printing and mass-production and the ability to have a job that allowed him to spend long periods without distraction without having to (say) search for drinking water or make a fire or...whatever. We can do what we do because our brains aren't being used for a whole bunch of other things that we'd be using it for if we didn't have all of the benefits of modern civilisation...not because we're smarter than the cavemen. Obviously, there was a time when we weren't this smart - and looking back at fossil hominid skulls would probably allow us to guess when our brain size started to get bigger than that of modern chimpanzees. So we have obviously been getting smarter - but never smarter than was necessary in order to thrive in the environment of the time.

SteveBaker (talk) 21:36, 24 August 2010 (UTC)

Re. your first paragraph: this is basically what I'm saying about "exaptation" above.

For example: consider alexia, the neurological condition of having very specifically lost the ability to read only (ie., no other visual impairment, etc) due to damage to specific parts of the occipitoparietal region of the brain. So reading (an aspect of "intelligence" as the term is being used informally here) is a specialized, hard-wired, phenotypical trait of the human brain.

Reading has been around for a few thousand years. Have our brains evolved such a complex ability that quickly? No. Then why have we been carrying around a "reading gene" without using it for a million years or so?

As Oliver Sacks wrote a couple of months ago:

"Writing, a cultural tool, has evolved to make use of the inferotemporal neurons’ preference for certain shapes. The origin of writing and reading cannot be understood as a direct evolutionary adaptation. It is dependent on the plasticity of the brain, and on the fact that experience is as powerful an agent of change as natural selection. We are literate not by virtue of a divine intervention but through a cultural invention and a cultural selection that make a creative new use of a preëxisting neural proclivity."

"Intelliegence" is all like that! :) Wikiscient (talk) 22:25, 24 August 2010 (UTC)

The question (which I doubt has been researched) is whether someone with alexia is still able to understand the meaning of cave paintings - and track animals by 'reading' their footprints. I very much doubt that such a study has been done - but I'd bet good money that they'd find other somewhat-related abilities were also lacking. The difficulty in doing such a study is that not many humans still have the ability to "read" cave paintings or footprints (or whatever it is that this part of the brain actually evolved for doing) - so the probability of someone with one of those abilities also contracting alexia and being studied in great detail afterwards is vanishingly small. SteveBaker (talk) 04:39, 25 August 2010 (UTC)

Nobody knows what IQ even measures.--92.251.132.249 (talk) 22:30, 24 August 2010 (UTC)

Well, that's not really very true. There are entire disciplines of psychology dedicated to the study of intelligence quotient and standardized testing - the people who design and analyze these tests are very sure they know what they are measuring. And though individual performance may vary due to statistical outliers, there is absolutely no doubt at all that when measured across large populations, IQ strongly correlates to things like salary, mortality-rate, performance on Army rifle-range scores, dental hygiene, and so on - the number of things that IQ positively correlates to is actually quite striking. Correlation does not imply causation. But standardized tests definitely measure things like the ability to focus; the ability to think clearly; and the ability to reason through difficult problems. Modern tests also go to great lengths to eliminate cultural, language, and educational background biases. So, while it may be fair to claim that "many people do not know how to properly interpret the meaning of an IQ or other standardized intelligence metric," it is completely incorrect to say that "nobody knows what IQ measures." Nimur (talk) 23:37, 24 August 2010 (UTC)

Getting off-topic, but see also: What is Intelligence? Wikiscient (talk) 00:20, 25 August 2010 (UTC)

You're making a number of presumptuous assumptions. First off, you would have to define exactly what it is your measuring in your IQ test. The you would have to balance the test, which across species would lead to an inherent bias due to a lack of understanding/misinterpretation. See Stanford-Binet Intelligence Scales.Smallman12q (talk) 01:40, 25 August 2010 (UTC)

I always thought that human intellingence resulted from sexual selection, but I don't have any reference. --Lgriot (talk) 13:46, 25 August 2010 (UTC)

Perhaps in our early ancestors sadly there was a lot of fighting and manipulation over mates, so to reproduce you needed to be smarter and stronger than your rivals. This might explain gender dimorphism. 92.15.13.237 (talk) 10:16, 26 August 2010 (UTC)

See Darwin Awards. Also the pressures of complex human society require intelligence to survive it, and it was especially needed after the move from hunter gatherer to agriculture. People who only recently by ancestry were hunter gatherers have problems with success in society and unrelated to IQ they also have problems with eating foods not of the paleolithic diet (e.g. cow milk, legumes, grains, etc.) Are you ready for IPv6? (talk) 01:55, 28 August 2010 (UTC)

Floating Metal Ships

Ships made of metal with a density greater than that of water float because they are not entirely made of that metal and much of the volume will be taken up by air, whose density is clearly less than that of water. I think this principle has a specific name but can't for the life of me remember. Anyone have any ideas? Thanks asyndeton talk 21:23, 24 August 2010 (UTC)

Are you just looking for the term "Buoyancy"? Wikiscient (talk) 21:27, 24 August 2010 (UTC)

Archimedes principle. Mikenorton (talk) 21:42, 24 August 2010 (UTC)

Have you thought about an airtight vessel made of metal with a density greater than that of water, but not full of air, infact it is full of nothingness, but still it will float ! What do you say to that ?  Jon Ascton  (talk) 00:31, 25 August 2010 (UTC)

$\rho _{metal+nothing}={\frac {m_{metal}+0}{V}}\ \approx \rho _{metal+air}$

Wikiscient (talk) 00:52, 25 August 2010 (UTC)

There is a classic schoolroom demonstration, in which a (lightly oiled) razor blade is floated on water, because the surface tension of the water prevents it from wetting the blade, which hence maintains the air needed for buoyancy above itself. Though I suppose a modern American school would expel anyone for attempting such a demonstration, lest they seize the blade and have a massacre. Wnt (talk) 04:33, 25 August 2010 (UTC)

Or you can avoid controversy, focus on the science, and float a paperclip. Nimur (talk) 19:25, 31 January 2011 (UTC)

Medical doctor specialties

Medical doctors often specialize ... for example, a cardiologist is a heart doctor and an oncologist is a cancer doctor (etc.). What type of doctor would I see if I were interested in weight loss? I don't mean as a morbidly obese person ... but just as a regular person trying to lose 10 or 20 pounds. Is there a medical specialty for weight loss? I'd rather not see a general practitioner, as they probably know no more than I do about weight loss ... or they can only tell me in general terms what I could probably find for myself in a book or on the internet. Thanks. (64.252.34.115 (talk) 21:34, 24 August 2010 (UTC))

Dietician? Clarityfiend (talk) 22:26, 24 August 2010 (UTC)

A nutritionist or a dietitian is a specialist, but not a doctor. Check carefully - these terms have significantly different meanings in different regions; in some places, there are no requirements, training, or licensing of any kind to be called a "nutritionist"; while in other regions, these terms are regulated and can only be used by trained professionals. It is rare to find a person of either specialty who is also a medical doctor, though. Nimur (talk) 22:28, 24 August 2010 (UTC)

Thanks. Then what type of medical doctor handles obesity? Thanks. (64.252.34.115 (talk) 03:34, 25 August 2010 (UTC))

In the USA, internists (those who have trained in Internal Medicine) have a strong interest in managing obesity. Their professional organization, the American College of Physicians (ACP) has a web page for patients and families about obesity, illustrating this interest. A similar role is embraced by family practitioners [2], gynecologists [3], and pediatricians [4]. Basically, primary care practitioners. -- Scray (talk) 04:31, 25 August 2010 (UTC)

Maybe a gastroenterologist? Especially if you're after gastric surgery. --TammyMoet (talk) 08:13, 25 August 2010 (UTC)

Also see weight loss and Obesity#Management.Though be aware Wikipedia doesn't give medical advice.Smallman12q (talk) 12:32, 25 August 2010 (UTC)

A bariatrician. --Sean 15:00, 25 August 2010 (UTC)

Unidentified moving blob in a sewer

http://www.youtube.com/watch?v=ELoqZiamr4E

what is that? Is it some kind of bacterial colony? Perhaps some kind of colony like a portugese man-o-war? Something fake?--92.251.132.249 (talk) 22:29, 24 August 2010 (UTC)

According to Dr. Timothy Wood, "They are clumps of annelid worms, almost certainly tubificids (Naididae, probably genus Tubifex). Normally these occur in soil and sediment, especially at the bottom and edges of polluted streams. In the photo they have apparently entered a pipeline somehow, and in the absence of soil they are coiling around each other. The contractions you see are the result of a single worm contracting and then stimulating all the others to do the same almost simultaneously, so it looks like a single big muscle contracting." This information is according to this article. — GorillaWarfare ^talk 22:42, 24 August 2010 (UTC)

See Tubifex tubifex. Ghmyrtle (talk) 22:46, 24 August 2010 (UTC)

This question has already been asked. ~AH1^(TCU) 19:12, 26 August 2010 (UTC)

Hah! As soon as I saw the title for this question, I knew it would be the same clip I'd asked about earlier. Matt Deres (talk) 18:19, 28 August 2010 (UTC)

Top soil and a layer of clay

I've been turning over the soil in the back yard a couple of days ago -- a fairly heavy clay-rich soil -- and the following has occurred to me. I always turn the soil about one spade deep; say, 10-15 inches. What then prevents the smallest mineral particles in the soil from being washed down and forming a watertight layer of clay at the depth of about 15 inches? Or does this really happen? I guess the earthworms can burrow deeper than that, so it's not completely watertight, but still, does this really happen? And is there something I'm supposed to do for this not to happen? --Dr Dima (talk) 22:30, 24 August 2010 (UTC)

Yes, if you get a hardpan clay subsoil layer that won't drain, you have a few options. You can plow it or otherwise mechanically mix in the soil or you can plant something with really aggressive roots at the layer involved (alfalfa?) or ideally both.

These kinds of agriculture questions depend heavily on your locale, geology, and climate. When I was a kid, whenever such questions would come on the USDA-run write-in radio program for farmers (why the heck was I listening to that? I must have been a really weird kid) the announcer would always say something like "consult your local university, college, or community college agriculture outreach program" which is probably pretty good advice for any gardeners who are facing those kind of problems. There might be some obscure plant that loves the kind of clay you get so much that just a little bit with a lot of water will tear it all up with roots and turn it into draining, fertile soil for tubers or whatever you want. Ginger Conspiracy (talk) 23:29, 24 August 2010 (UTC)

The problem certainly occurs at an agricultural scale, which is why clay rich soils need artificial drainage – in Holland, they even used windmills to pump the water out of the drainage ditches. At the back yard scale, there's little you can do in practice except to keep the top layer healthy, unless you have somewhere convenient to dump any excess water. Large plants with deep roots around the edge of the yard will help, but a lot depends on the size of the yard as well. Physchim62 (talk) 23:43, 24 August 2010 (UTC)

Pumps are needed in Holland becauise much of the land is below sea-level. Darwin studied how earthworms mix up the soil. See Earthworm#Locomotion_and_importance_to_soil and also the subsequent Benefits section. 92.24.186.119 (talk) 13:11, 25 August 2010 (UTC)

You might also be concerned about soil compaction. ~AH1^(TCU) 19:09, 26 August 2010 (UTC)