Wikipedia:Reference desk/Archives/Science/2011 December 14

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December 14

Earth with Rings?

Say that one day, possibly 3 billion years ago, a massive rocky object, maybe a rogue planet or giant meteor, hit the Moon (without hitting the Earth), with enough force to destroy it and break it into thousands if not millions of pieces. Would these pieces eventually circle around the Earth and create a ring system? If not, what is likely to happen to the shattered moon? 64.229.180.189 (talk) 01:22, 14 December 2011 (UTC)

I would say it would form a ring, but the ring wouldn't last, with parts of it falling to Earth, other parts escaping the Earth's orbit, and possibly the rest reforming a new moon. I'm not certain what forces cause this, but it is noted that no terrestrial planets in our solar system have rings while all the Jovian plants do have rings, so the planet's size seems critical in ring stability. StuRat (talk) 03:38, 14 December 2011 (UTC)

What is needed is gravitational pulling and pushing to keep the ring from reforming into a moon. Mars and Venus don't provide much gravitational disturbance on Earth. Jupiter doesn't either. So, it would have to come from a moon around Earth. Around Saturn (and the other ringed planets, but mainly Saturn), the moons push and pull on one another with great force. They nearly rip each other apart. For the rings, they keep them from reforming. -- kainaw™ 03:49, 14 December 2011 (UTC)

It is theorised that the Moon was formed by a large body (roughly Mars sized) hitting the Earth and causing a large amount of debris to get thrown up into orbit. That debris formed a ring, which then coalesced into the Moon. (See Theia (planet).) If you destroyed the Moon, some of the debris would fall to Earth, some would escape and some would form a ring again. Given enough time, that ring would re-coalesce into a new (smaller) moon. As Kainaw says, the rings around gas giants can only stay around for a long time because the moons of those planets stop them coalescing. --Tango (talk) 04:02, 14 December 2011 (UTC)

If the presence of a moon or moons is all that is needed for ring stability, then shouldn't the Earth and Pluto, with large relative moons (and a couple extra small moons, for Pluto), and Mars, with two small moons, have rings ? (Perhaps Pluto does have rings, which we can't see.) StuRat (talk) 04:25, 14 December 2011 (UTC)

All the Jovian planets have rings, Uranus, Jupiter and Neptune. They are just less obvious then Saturn's. So my guess is that it's something to do with the fact they are Gas giants, rather then anything to do with moons. I don't doubt they play a role, they may be a necessary condition, but not a sufficient one. Vespine (talk) 04:36, 14 December 2011 (UTC)

Yes, all the planets with rings (Jupiter, Saturn, Uranus and Neptune) are gas giants, but they also have 64, 62, 27 and 13 moons respectively. The moons are important. You can get a ring whenever you have matter orbiting within the Roche limit (which is quite small for small planets, so the mass of the planet is a contributing factor) however it wouldn't form the kind of stable, distinct, clearly defined rings we see around the gas giants (and particularly Saturn) without moons to "shepherd" them. You can read more about it at planetary ring. --Tango (talk) 05:01, 14 December 2011 (UTC)

You might enjoy looking at that. Dauto (talk) 05:09, 14 December 2011 (UTC)

It would be handy to have such a clearly visible indicator for compass directions and latitude. Still no easy way to determine longitude though. APL (talk) 03:04, 15 December 2011 (UTC)

One thing that seemed to be missing from that video was the Earth's shadow on the rings, as viewed from Earth. The rings also looked a bit too bright, during the day. StuRat (talk) 03:29, 16 December 2011 (UTC)

Appearance of Moon - geographic variations

Following is a quote from the article Day of Ashura.

"While Ashura is always on the same day of the Islamic calendar, the date on the Gregorian calendar varies from year to year due to differences between the two calendars, since the Islamic calendar is a lunar calendar and the Gregorian calendar is a solar calendar. Furthermore, the crescent appearance to determine when each Islamic month begins varies from country to country due to obvious geographical reasons."

I question the last sentence. Are there "country to country" differences in the appearance of the moon within a 24 hour period? Thanks, Wanderer57 (talk) 06:32, 14 December 2011 (UTC)

It depends on how well the observers can see. So at some point in time the crescent moon will be visible. And different people with different visual acuity will see it at different times, as it gets bigger and bigger. Graeme Bartlett (talk) 08:29, 14 December 2011 (UTC)

There is a different depending on the local time. The new crescent might show too late to count in a given location while that will be early enough elsewhere. Dauto (talk) 08:42, 14 December 2011 (UTC)

Thanks. To see if I have this clear, is the key difference in the hour at which the moon becomes visible to people in different places or in the "shape" of the crescent as seen on the same night by people in different places? Wanderer57 (talk) 16:48, 14 December 2011 (UTC)

The former. The latter also has an effect but it will be much smaller. Dauto (talk) 17:12, 14 December 2011 (UTC)

Groung water tannins

Hello-

I have tannins in my groundwater. We just built our house 1 year ago. We had the water tested, no iron, no magnesium, no bacteria .....many minerals/organisms that cause problems. We cut our own wood up on our 13 acres for our wood stove for winter. I sometimes notice a horrible oil smell when I burn some of our wood. I have had psoriasis since age 3 and the smell reminds me of coal tar. Is it the tannins? Thank you, Hallie Cornell — Preceding unsigned comment added by Halliekoss (talk • contribs) 06:59, 14 December 2011 (UTC)

Surface water often contains tannins due to plant matter. It makes the water brown, like tea. The ground water could easily come from this brown surface water. The smell of burning wood has nothing to do with the water. Graeme Bartlett (talk) 08:18, 14 December 2011 (UTC)

(edit conflict)No, the tannins in the water, I would guess, come from the leaf cover of the ground. I'm guessing your well is shallow and is basically leaf tea. It might be good for you, if there aren't any sprays or poisons in the area. The smell of the wood in a stove will vary with the temperature of the fire. I'm guessing you are burning pine wood or another wood with lots of pitch. If it's oak or other hardwood, I don't know what's happening. A very pitchy piece of wood which is burning hot will smell like oil, and it's not nice. If you burn it cooler, it might smell nicer, but you will build up creosote in your chimney and all that nice-smelling smoke could have been heating your house. Go for a balance between having a cool smokey fire and letting the heat go up the chimney by regulating the damper. This is all from personal experience, you might ask an expert. B^e——C_ritical 08:23, 14 December 2011 (UTC)

What psoriasis question is that Graeme? Hallie was explaining why she knows the coal tar smell. I agree with Critical. Caesar's Daddy (talk) 08:33, 14 December 2011 (UTC)

Yeah OK, I have removed that comment as you are right there is no question about it there. Graeme Bartlett (talk) 12:02, 14 December 2011 (UTC)

Sounds like your not leaving it enough time to properly dry before burning. Here are some tips. [1]. The tannin in wood should not effect the burning quality... it just burns and thus decomposes.--Aspro (talk) 16:30, 14 December 2011 (UTC)

Insistently, you can save even more money and save the Earth at the same time by using the wood ash as a source of lye. Also, you can recycle all that applejack you hillbillies drink by saving your urine. Follow these instructions and be no more need to keep rushing down to Walmart for another bottle of laundry room essentials. --Aspro (talk) 16:47, 14 December 2011 (UTC)

I'm not sure if your question was misinterpreted. It sounds like you think the ground water tannins could affect how wood cut from the area smells when it burns? But tannins are present at quite high levels in wood by its nature - the tree doesn't concentrate them out of the groundwater. I think that even cut wood can produce more tannins when it discolors during storage or drying, though apparently more often it is breakdown or alteration of the tannins it has previously produced.^[2] Wnt (talk) 20:02, 14 December 2011 (UTC)

bonferroni correction

Is that like bonferroni corrections are done only for p values that are statistically significant? Research articles with tables show many p values and some of them are marked with asterick, mentioning it to be statistically significant and corrected by bonferroni. What does this mean? were they already significant and then corrected by bonferroni or every p value (significant of not) is corrected by bonferroni? — Preceding unsigned comment added by 199.224.149.10 (talk) 08:35, 14 December 2011 (UTC)

Bonferroni correction is one of a number of methods for addressing the problem of multiple comparisons in statistics. When you see jargon like, "statistically significant and corrected by bonferroni", that means that rejection of the null hypothesis was supported by the statistical test used even after correction for multiple comparisons using the Bonferroni method. In a situation like that, it would be unusual to report other un-corrected p values when such correction would be appropriate. I presume that in the situation you describe, the alternative would be that the null hypothesis was not rejected. -- Scray (talk) 12:19, 14 December 2011 (UTC)

Thanks friend. — Preceding unsigned comment added by 199.224.149.10 (talk) 04:42, 15 December 2011 (UTC)

Boulder clay?

Hello, is it fair to say that this term, Boulder clay, is obsolete? See articles such as clay, till (espec.), and soil. I was going to rewrite the current article until I noticed it was an orphan based solely of an early 20th c. open content encyclopaedia. Now, when I search boulder clay on the internet there are *some relevant* hits, so I will probably just leave it for an expert but will just ask in case we've any experts floating about here... ~ R.T.G 12:47, 14 December 2011 (UTC)

I very much doubt that the term boulder clay is obsolete. It's a sort of thing of much interest, I'd have thought, to civil engineers who have to be concerned about the strata on which they build buildings. I think its orphan status probably says more about our poor coverage of specialised civil engineering and geology concepts than it says about the term. --Tagishsimon (talk) 13:00, 14 December 2011 (UTC)

I understand the subject being interesting but see also till and other articles vastly better improved which seem to cover most or all of the same, is it fair to say boulder clay is a specialised topic or is it just an obsolete term? It seemss pretty much the same subjects to me only that boudler clay has a different name.. ~ R.T.G 13:13, 14 December 2011 (UTC)

Till is a much wider term for "stuff which used to be under a glacier". Boulder clay is a specific stuff which, in part, used to be beneath a glacier. IMO boulder clay is a notable specialised term and, having played on google a bit, certainly not obsolete. Neither is the overlap between boulder clay and till, soil, etc, enought that we should ever contemplate merging it into another article. Don't let the EB1911 source convince you otherwise. --Tagishsimon (talk) 13:19, 14 December 2011 (UTC)

I agree with Tagishsimon. My soil mechanics lecturer regaled us with stories about it. It's the curse of pile drivers and tunnellers, because initial soil sampling can easily miss the fact that you might have a 2-tonne boulder in your path. It would be better to add some links from related articles, such as clay. That might encourage more editors to do some work on the article.--Shantavira|^{feed me} 15:53, 14 December 2011 (UTC)

The British Geological Survey define Boulder Clay as "Clay and silty clay, commonly pebbly and sandy, reddish brown, stiff, possibly interbedded with sand and gravel-rich lenses and rare peat" here, so certainly not obsolete, but I note that the term is not used on any of their 1:50,000 maps, suggesting that it is not the preferred name for such deposits. To me it's just an informal name for till, but it may have a more defined usage than I'm aware of. I'll see what else I can dig out. Mikenorton (talk) 22:13, 15 December 2011 (UTC)

This report from 2004 uses the term in parentheses "thick till (boulder clay) deposits". Mikenorton (talk) 22:30, 15 December 2011 (UTC)

The terms have apparently been regarded as synonyms since 1863 "These terms are used interchangeably in this paper" according to Archibald Geikie[3]. Mikenorton (talk) 22:43, 15 December 2011 (UTC)

And finally from 2009, "The term till is used in preference to the more commonly used term 'boulder clay' to which it is synonymous. Boulder clay is a generic term rather than a lithological description, but it is generally misunderstood by engineers who may complain with justification that the material described as boulder clay on the map has neither boulders no clay as constituents."[4]. Mikenorton (talk) 22:53, 15 December 2011 (UTC)

Good stuff Mike. ~ R.T.G 23:17, 17 December 2011 (UTC)

Geodesic for thrown body

How can one draw the geodesic for a body thrown straight up from the surface of the earth? The rubber-sheet interpretation of general relativity won't give anything that makes sense (the geodesic on a rubber sheet stretches out to infinity, so a body thrown up will always never come back). My understanding of general relativity is that a massive body curves space into the time direction (and vice versa). Basically, when the 'rock' (massive body) is placed on the sheet, the rock bends the rubber sheet into the time direction. So, when a body is thrown up, it goes partially against the 'flow of time', and slows down; and if its velocity is not too lagre, it will stop and reverse its velocity. This seems to explain the body being thrown up (though I am not sure if this explanation is correct, please let me know if it isn't), but I have no way of figuring out the geodesic for a thrown body that is consistent with reality. A straight line going up and then suddenly doesn't look right, as geodesics are usually smooth curves, not pointy things. I suspect it also has a component in the time direction that makes sense, but I'm not sure. So how does the geodesic look? And why is the space-component of the geodesic pointy? Thanks, ManishEarth^{Talk • Stalk} 13:01, 14 December 2011 (UTC)

You're quite right that it has a component in time; it has to, because I can throw two objects along the same initial direction at different speeds and they trace out very different geodesics despite being initially tangent in the spatial dimensions. The body's world line initially points away from the earth (to the right, say), then turns smoothly through the vertical back to the left. Why it should curve is the interesting bit: it might help to draw a different kind of rubber sheet, one with one space and one time dimension, with the usual grid drawn on it to represent the coordinates of a distant observer. The planet's mass distorts the sheet so that the horizontal lines (those that correspond to a particular constant time) converge a bit as you move to the left (gravitational time dilation). Then it only makes sense that the geodesics on such a surface should also act like there is some sort of center of rotation to the left, and they curve towards it. --Tardis (talk) 14:07, 14 December 2011 (UTC)

Thanks, I think I got it... Just one thing: On a distorted 2D space time diagram, like the one you described, how does one draw the geodesic/path for a particle at a certain point, when the particle has a certain direction? For example, do we say that the particle is 'accelerated' along the angle bisector of the space and time lines in the diagram? Or, another way of looking at it is that the paper you are drawing the lines on is the xy plane, the space lines are a vector field S, and the time lines are T. At a point x,y, given the directions of S and T, and the direction of the particle's motion, what will the direction of the geodesic be? Thanks, ManishEarth^{Talk • Stalk} 15:12, 14 December 2011 (UTC)

If you include the time dimension then the path of the rock in spacetime is a parabola (think of a graph plotting the rocks height on a vertical against time on a horizontal) so it is indeed a smooth curve. If you collapse the time axis to a single pont, the parabola becaomes a line segment - this is an example of what mathematicians call "projection". This is fine - there is no reason why the projection of a smooth curve has to remain smooth.

I think you need to be careful about taking the "rubber sheet" analogy too literally. Although the rock does bend spacetime a little, the reason why it travels in a parabola rather than in a straight line is because the Earth (which is much more massive than the rock) bends spacetime in its vicinity - this bending of spacetime is what we perceive as gravity. Gandalf61 (talk) 15:15, 14 December 2011 (UTC)

Whoops, in my second comment for some reason I used the word geodesic in place of World line everywhere.. ManishEarth^{Talk • Stalk}

@Gandalf:When I used the term 'rock' in the rubbersheet analogy, it corresponded to the Earth (or whatever massive body is creating the bending). I just used the term as it's fairly common. Sorry if it caused any confusion.. ManishEarth^{Talk • Stalk} 15:21, 14 December 2011 (UTC)

How do photons know the type of charge they are interacting with?

When two particles interact via the electro(magnetic/weak) force, they exchange a photon. Repulsive force is when the one particle emits a photon towards the other, and is absorbs. The recoil/push from this exchange result in bothe particles moving away. Fine. Attraction is when a particle emits a photon in the opposite direction, and the photon hits the other particle anyways, due to the fact that the photon is a spread out wavefunction and can have any position immediately after emission. (Another interpretation that i've seen is that the photon is emitted "backwards in time", thout I think that these two interpretations are the same thing) Also fine. Now, my issue is, how does the photon 'know' which mechanism to use? It probably has to do with the momentum/space wavefunction of the photon, which (i think) is the only thing that can depend on the type of charge (as spin, speed, etc are not dependant), and thus 'encode' the charge that sent it. But the wavefunction should be radially symmetric, and for the attractive/repulsive forces, the wavefunctions should differ along the common axis. Basically, if I have a positive charge, it will emit the same photon regardless of the type of charge sitting next to it. So, both positive and negative charges will experience equal attractive and repulsive forces as they have equal probability of being hit by an 'attractive' or 'repulsive' photon. There must be some quality of the interaction of the photon with the second charge that collapses the photon's wavefunction into a predominantly attractive of repulsive position/direction. What is it? How does this mechanism exactly work? Note:I understand what wavefunctions and all are (and how to deal with complex valued wavefunctions), but not stuff like Hamiltonian operators, and the mathematics of wavefunctions (why one needs to multiply this wavefunction with that one, etc). So layman's terms are not required, but if there is any mathematics involved, please explain why a certain thing needs to be done (if its not too complicated). Thanks, ManishEarth^{Talk • Stalk} 13:34, 14 December 2011 (UTC)

This URL contains a pretty good explanation: http://math.ucr.edu/home/baez/physics/Quantum/virtual_particles.html. Excerpt: 'The important point is that the photon doesn't "know" that it's going to hit a particle of the same charge as the one that emitted it, or of the opposite charge. The distinction between attraction and repulsion actually arises when the effect of the virtual photon interferes with the unperturbed wave function! In general, the distinction comes from interference between the contributions from odd and even numbers of virtual photons traveling from one particle to the other.' Truthforitsownsake (talk) 13:54, 14 December 2011 (UTC)

Thanks, i understood everything except:

• Why is the momentum wavefunction of the emitted photon in the imaginary plane?
• Why ido we multipy the wf of the photon by i and the reciever particle charge? The i multiplication probably has the same reason as my above point, but what does the particles charge have to do with it? I'm referring to this section:

 The effect of a virtual photon hit on the charged particle's momentum-space wave function is, then, quite simple.  The photon has a certain probability amplitude of knocking the charged particle to the left and a certain amplitude of knocking it to the right.  The probability amplitude for each possibility is just proportional to i times the charge of the particle times the photon wave function times the time!

Basically, I want to know the aspect of the interaction that makes the charge of the particle part of the wavefunction.

Thanks, ManishEarth^{Talk • Stalk} 14:53, 14 December 2011 (UTC)

I believe he is illustrating the momentum-space representation of the photon wavefunction (which is a complex function) in the imaginary plane for clarity to show the feature he wants. This feature is that "the wave function is a function proportional to the electric charge of the emitting particle (in a sense this defines what electric charge is)". In other words, the charge determines whether the photon wavefunction is "up" or "down" in the imaginary plane. When the photon interacts with the particle, we are really multiplying two complex functions, which is why the two magnitudes end up being multiplied by i to get the true value. Truthforitsownsake (talk) 15:32, 14 December 2011 (UTC)

My question was more of "why is the momentum function complex" or "why is the momentum function the shape that it is"? I understood why they were multiplied by i, but not why they had to be complex in the first place.. But after thinking a bit, it seems that it comes directly from certain equations, the likes of which I'd rather not go into.. Thanks, ManishEarth^{Talk • Stalk} 15:47, 14 December 2011 (UTC)

All wavefunctions are complex by definition. "Why" this is I don't think anyone knows, but the world would certainly be a much different place if they weren't. Truthforitsownsake (talk) 15:51, 14 December 2011 (UTC)

Standard gravity and huge objects

In the formula for calculating Standard gravity, there is no mentioning of the object that is 'free falling' to earth. What happens if an object with a huge mass, say mass of Jupiter - but with a small radius, 'falls' onto earth?. Will it still fall with an acceleration of g? Gil_mo (talk) 14:13, 14 December 2011 (UTC)

It won't: the Earth will fall to it. Well, technically, they will both fall towards their common barycentre, but to a first approximation the relative movements of two mutually gravitating objects depend only on their masses, not their densities and hence sizes: hence, for example, a planet will orbit in exactly the same way around a physically tiny black hole as it will around a much larger star of the same mass. "Free-falling" in a straight line is merely a particular case of an orbit, one with an eccentricity of ∞.

In such a case as you posit, the Standard gravity formula is inapplicable, because the mass of the other object is not negligible. You will need instead a more general formula that takes both masses into account. {The poster formerly known as 87.81.230.195} 90.193.78.30 (talk) 14:41, 14 December 2011 (UTC)

To a distant third observer, the Jupiter-mass black hole will still be attracted towards Earth with an acceleration of g -- but Earth will be attracted towards the JMBH at an additional substantial acceleration (much higher than g). From the perspective of an Earth-bound observer, the JMBH will be falling much faster than g. Newton's law of universal gravitation holds for all two-mass scenarios (handwaving over relativistic effects and such). — Lomn 14:43, 14 December 2011 (UTC)

If so, the formula mentioned in Standard gravity is an approximation for small objects? What would be the corrected formula taking into account the second mass? Gil_mo (talk) 14:47, 14 December 2011 (UTC)

The acceleration is the same (neglecting deformation of the Earth's shape due to strong tidal forces which would definitely happen). The apparent acceleration (as seen by someone standing on the Earth) is going to be proportional to the total mass of the system (as opposed to being proportional to the Earth's mass alone). Dauto (talk) 15:02, 14 December 2011 (UTC)

The formula in standard gravity is exactly correct for all objects at the surface of the Earth (note that it's not correct for objects falling from height). However, the Earth also falls towards all objects. For conventional small-mass problems, that attraction is so small as to be functionally zero and so we ignore it. If you don't want to ignore it, though, you use the same equations that you would for Earth, except with parameters from the other body. Newton's law is a good way to do the calculation. Once force is found, force over mass yields the acceleration. — Lomn 15:05, 14 December 2011 (UTC)

See Gravitational acceleration which says:

The relative acceleration of two objects in the reference frame of either object or the center of mass is:

$\mathbf {\hat {g}} =-{G(M+m) \over r^{2}}\mathbf {\hat {r}}$

The standard gravity is g₀ = G×M/r² ~ 9.8 m/s², where M and r is the mass and radius of Earth.

If the other object has n times the mass of Earth then the total mass is 1+n times Earth and they accelerate towards eachother with (1+n)×g₀. PrimeHunter (talk) 15:57, 14 December 2011 (UTC)

Rage-induced blackout

Hi everyone, I was wondering what the technical term for a rage-induced blackout is? What I'm describing is like an alcohol-induced blackout, but the subject is not under the influence of drugs at the time: the trigger is an event that makes them very angry. Someone told me the term was Redout, but our article on that term refers to G-forces (and video games). Our article on Anterograde amnesia doesn't mention rage and our article on Intermittent explosive disorder doesn't mention memory, is this something that has been studied by scientists/doctors? (I hope this doesn't fall afoul of the proscription of medical advice, I have not experienced this and am not seeking advice on treatment.) Mark Arsten (talk) 17:25, 14 December 2011 (UTC)

Scanning some psychiatric journals, I quickly found a few that dealt with extreme anger and referred to the amnesia as "redout". Our article is a stub, so omissions of anger shouldn't lead to the assumption that anger does not cause redout. -- kainaw™ 17:34, 14 December 2011 (UTC)

Comment - in aviation physiology, redout is the term for a very specific, different condition. It's the antithesis to a blackout, is purely physiological in nature, and has nothing to do with emotional state. Nimur (talk) 19:10, 14 December 2011 (UTC)

According to a few psychology articles I read, redout is used because those who experience it say they feel like everything turns red ("I was drowning in a red tide" was one quote). -- kainaw™ 19:14, 14 December 2011 (UTC)

The basic problem here is that it is essentially impossible to generate a rage-induced blackout experimentally, and even if it was possible it would probably be unethical. So everything that is written about this is anecdotal, and for many of the anecdotes one has to wonder whether there was really a blackout or whether it was invented as an excuse to avoid having to explain a violent act. Looie496 (talk) 18:12, 14 December 2011 (UTC)

The obvious solution to this problem is to find other animals which suffer from the problem, too. Perhaps animals subject to uncontrollable rages ? Bulls come to mind, but also some primates, like chimps and baboons. As for the mechanism, the higher blood pressure which accompanies rage might cause a stroke, embolism, or aneurysm, but I'd expect more serious and long-lasting problems if any of these had occurred. Perhaps the increase in adrenaline causes a reaction in some people ? StuRat (talk) 21:36, 14 December 2011 (UTC)

Interesting observations, I looked again and was able to find a couple of articles to peruse (such as [5]). Thanks, Mark Arsten (talk) 18:54, 14 December 2011 (UTC)

A common phrase for this in the UK is "red mist", as in "The red mist came down and I lost my temper". I wonder if searching using that phrase would elicit any other results? --TammyMoet (talk) 22:19, 14 December 2011 (UTC) I wonder if there is anything in Anger#Physiology about this? --TammyMoet (talk) 22:22, 14 December 2011 (UTC)

Common Method Variance

I'm a psychology student and I've come across "common method variance" in several articles that I've been using in a related project. Could someone please explain as simply (but thoroughly) as possible what CMV is? I can't seem to get the gist of it. Lord Arador (talk) 18:21, 14 December 2011 (UTC)

NOTE: After typing the comment below, it was brought to my attention that the definition of CMV is different in different fields of science. My comment is based on how I've used it in health informatics. -- kainaw™ 19:37, 14 December 2011 (UTC)

CMV is a correlation between two things being measured that is inflated (or, sometimes deflated) due to the use of the same method being used to measure each one. I saw a lot of examples that are hard to grasp, but there's an easy one I read about a long time ago. When measuring depth the ocean floor, a trawler would use GPS to travel in as a straight a line as possible for a few miles. It would turn and go back along a parallel line. Then, it would turn around and go back along another parallel line. It went back and forth, mapping out the depth to the ocean floor in about a 3 mile by 3 mile square. When the results were put in a computer, they were amazed to find that the ocean floor had been carved into very straight stair steps. These were long steps that spanned the length of the survey. Further, they were very straight - something that had to be man-made. So, they found, deep under the ocean, evidence of what must be the stairs leading into a huge city (Atlantis?). Then, someone ruined it all by bringing up CMV. They used the same method to measure the distance to the ocean floor on each trip back and forth and didn't take anything else into account - like the tide. So, on each trip, as tide went out, they were closer to the rather flat ocean floor. Putting that anecdote into a more complicated scenario... Consider you stop 100 people walking out of McDonalds and ask them if they like fast food. Then, you stop 100 people walking out of McDonalds and ask them if they have hypertension. You can easily have a CMV increased correlation between fast food and hypertension here because you used the exact same method of measure for both of the variables. You didn't account for anything else, such as the possibility that people walking out of McDonalds may prefer fast food or that they may be prone to hypertension after dealing with the fast-food staff. -- kainaw™ 19:13, 14 December 2011 (UTC)

feynman

Do/did Japanese people ever dislike Feynman for his role in Manhattan project?--Irrational number (talk) 19:51, 14 December 2011 (UTC)

Feynman's memoir Surely You're Joking, Mr. Feynman! contains a section where he talks about visiting Japan in the 50s, and the topic never comes up. I'm sure some Japanese people quite possibly disliked him, but it certainly wasn't widespread enough that Feynman - and other American physicists - weren't invited to visit the universities. Smurrayinchester 21:25, 14 December 2011 (UTC)

Even Oppenheimer was invited to visit Japan, and he had a much more crucial role (both in the making and the decision to use the bomb) than Feynman did (Feynman had zero input into the latter). He was not treated poorly by the Japanese to my knowledge. It would be interesting to contrast the treatment of Japanese physicists/biologists by Americans and American physicists by Japanese, with the treatment of German physicists by the British and Americans, in the postwar period. It would be a nice little undergraduate research paper, anyway. The German physicists got treated the worst out of the bunch, I believe. --Mr.98 (talk) 21:38, 14 December 2011 (UTC)

They got treated the worst? Both the US and the USSR scrambled to get German rocket scientists working for them. Von Braun, the leader of the Saturn V project, is just one example. Space exploration wouldn't have been possible for a long time without enlisting their help. --140.180.15.97 (talk) 23:09, 14 December 2011 (UTC)

Maybe mistreated just by satirists like Tom Lehrer: "...the widows and cripples of old London town / Who owe their large pensions to Wernher Von Braun." ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:15, 15 December 2011 (UTC)

I meant the nuclear physicists, not the rocket engineers (totally different types of scientists there, totally different outcomes — don't confuse the physicists with the engineers!!). And what I meant specifically was things like not being invited to conferences, spurned by their colleagues, and so on, for a number of years. People took the whole "worked on an atomic bomb for Hitler" thing fairly hard. --Mr.98 (talk) 12:56, 15 December 2011 (UTC)

Generally speaking, once a war has been over for awhile, the once-opposing warriors often get along well. They understand that each was just doing his duty. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:16, 15 December 2011 (UTC)

Additionally, many physicist who were involved in the project Manhattan became outspoken critics of nuclear weapons. 88.8.78.13 (talk) 16:06, 15 December 2011 (UTC)

I wonder how many Japanese even knew he worked on the project. Clarityfiend (talk) 21:48, 15 December 2011 (UTC)

Strange animal behaviour

Hi. In recent years, especially around November and December of 2009 and this December of 2011, I've seen flocks of geese flying north (or other atypical directions such as west) when they normally would have migrated south weeks ago. I'm in Southern Ontario, north of Lake Ontario. What does this unusual behaviour signify? Thanks. ~AH1 ^(discuss!) 21:51, 14 December 2011 (UTC)

Perhaps it's based on temperature. That is, when it gets cold, they head south, and when it warms back up, they head back north. This sounds inefficient due to excess travel, but if they can get more food out of an area that has warmed up again, it might be worth it. StuRat (talk) 00:11, 15 December 2011 (UTC)

So how sure are you that this is not simply an observational error? I don't mean that you don't know which direction is which, but simply that you've just started noticing something that has always been happening. That is, you expect the birds to be migrating south but you now notice them heading other directions. But what we don't know is how long have you been observing birds in this location and how familiar you are with their historical behaviour. While their general migratory direction might be south at this time of year, in any given location it would not necessarily be the case, for example they may divert short distances to access feeding sites say in other directions. In your particular location this may appear to be a north or west migration, but their overall direction remains south. If you are quite near the lake I would suspect this would increase the chances of apparently odd migration directions. In terms of later migration than you expect this may be a response to climate change; I have heard reputable scientific sources in recent times reporting changing migration patterns such as this. Many species are quite sensitive to even minor temperature variations. Just a possibility; there's not that much info to go on. --jjron (talk) 14:28, 15 December 2011 (UTC)

Generally speaking, the reason birds migrate is to find food. Some birds will stick around in a wintry climate if there's a food source. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:09, 16 December 2011 (UTC)

The geese in the Scottish Highlands are currently flying south by west in the evenings. 85.211.148.143 (talk) 19:20, 17 December 2011 (UTC)

USS Constitution commander glass rooms

Resolved

 – – Kerαunoςcopia^◁_galaxies 02:46, 15 December 2011 (UTC)

I'm extremely curious about the glass rooms connected to two of the officers' berths on the USS Constitution. They stick out on each side of the ship and would allow someone to sit and watch the ship from "outside" of the ship while it's traveling. What are these rooms called? Are they typical of ships of the time, or is this a one time situation? My understanding is that one of the gun deck crew members (or boys) would stick their heads out of a porthole during battle and watch for damage in the side of the ship; I'm assuming this glass room could've been used for the same purpose, but because it's connected to an officer's room, it probably wasn't. And finally, were these glass rooms added during one of the later restorations, or was it always part of the original design? It just seems a bit on the luxurious side to me for a ship of war. – Kerαunoςcopia^◁_galaxies 22:00, 14 December 2011 (UTC)

That would be excessive luxury today, yes, but back then admirals and generals felt entitled to certain luxuries. And perhaps it could be justified as an "observation room". StuRat (talk) 00:09, 15 December 2011 (UTC)

They're called quarter galleries. By the 19th century they were relatively vestigial, and served principally to house the captain's and sometimes the senior officer's head and washing facilities. They were designed into the ship and were standard equipment in naval architecture, which was heavily ruled by very conservative tradition in design practices.I agree with StuRat that they were, in part, symbols of privilege. They began to disappear a couple of decades after the Constitution was built. The quarter galleries on the USS Constellation (1854) are quite attenuated. Acroterion (talk) 02:23, 15 December 2011 (UTC)

Thank you both so much, that's wonderful! – Kerαunoςcopia^◁_galaxies 02:46, 15 December 2011 (UTC)