Wikipedia:Reference desk/Archives/Science/2013 January 15

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January 15[edit]

Piggyback IC picture?[edit]

Could anyone photograph a piggyback circuit like MK38P70 with a suitable commons license? Electron9 (talk) 00:46, 15 January 2013 (UTC)

I perused the archives but . . . anal sex question[edit]

Within the porn industry, there is an increasing amount of (unprotected) anal sex. In reading the wikipedia artical on anal sex and reviewing quite a few archive responses, I am still unsure of something (or a few things).

As I understand the wiki artical, one of the problems is a lack of sufficient lubrication in the anal area that can cause pain and increases the risks of harm. With this in mind, how do porn actresses manage to perform so "vigoriously?" Some of the participants seem to be going at it quite roughly. While I am sure that there is lubricant being used, of course the application of such is not shown. So, how does it get applied and to whom? How can the actresses perform with such "enthusiasum?" Do they mentally block out the pain? How do they reduce the potential harm/injury their "enthusiasm" may cause?

Another related question is how the actors/actresses keep mthemselves safe. The vast majority of scenes do not show the use of condoms. Also, there are many scenes where the penis is removed and the female performs oral sex (sometimes the penis was in her own anus while at other times it was in another woman's anus). So, how do they keep themselves safe?

My apologies for so many queries in one post; I know this is poor form. (talk) 01:16, 15 January 2013 (UTC)

For your first question, they edit out the application of the lube. Which probably causes some people to try it, find it unpleasant and wonder how the actors could do it so easily. The actresses (speaking from a hetero viewpoint, insert various genders as you see fit) who perform so, as you say, vigorously not only have the aforementioned lube but are also often used to performing the act in their own private lives or on camera previously. They're also more comfortable in front of the camera than many people trying it for the first time at home would be. The relaxation helps the men penetrate and keeps the women from feeling (as much) pain. To reduce the potential harm, the actress can have fingers or a toy slide in to again increase the amount of relaxation and start things a bit more slowly. As to whether this is included in the final film is up to the director.
As far as keeping themselves safe from infections and such, some states require porn actors to be tested for STDs every so often. I don't know the specifics but California has laws on the books for such things. Also, the more reputable production companies will encourage testing since it keeps their actors safe and keeps the money flowing in. And as for the Ass to mouth, before doing an anal scene, most if not all actresses perform a enema on themselves to clean out their rectum. Dismas|(talk) 02:21, 15 January 2013 (UTC)
Stoya did an AMA on Reddit about eight months ago and was asked a question by someone "sorta curious about how anal sex works in porn". Her response mostly had to do with cleanliness/prep so I don't know if it really answers your question, but it's all I got. Braincricket (talk) 02:52, 15 January 2013 (UTC)

iPhone 5 Vibration in Response to Rubbing[edit]

When my iPhone 5 is resting on a flat hard surface (a wooden desk), and I rub my finger across the top silver-colored metal edge of the phone (just above the ear speaker), I feel a very faint vibration in response. For comparison it reminds me of the vibrations felt from singing bowels bowls. It does not vibrate if I do the same thing while holding it in my hand other hand, nor if I use my other hand to hold the phone in place on the desk. While it seems to be easiest to elicit this vibration from the top silver edge, I've also gotten it from the right edge too indicating to me it might be possible to do this on every edge (though I have been unsuccessful in my attempts to do so). My question is, what is responsible for the vibration? I originally thought it must be a part or parts within the phone vibrating, perhaps even the mechanism that causes vibration during text messages and other alerts. Then I thought it might simply be a reaction between the surface of the metal and my finger. Any help in solving this mystery will be appreciated! Lord Arador (talk) 03:46, 15 January 2013 (UTC)

See sympathetic vibration. μηδείς (talk) 03:50, 15 January 2013 (UTC)
Thanks, that clears the basics up for me. I'm still wondering though, why certain surfaces or objects (like my phone) will vibrate in response to rubbing while others do not seem to. What differentiates objects on their ability to vibrate so? The references weren't particularly helpful. Lord Arador (talk) 04:14, 15 January 2013 (UTC)
It's not really possible to give a specific answer without physical specifics. I can tell you I have had phones that have and have had phones that have not vibrated when rubbed. But I never got to the point of dissecting one. (Old rotary phones, which I did disect, actually had bells inside!) The relevant fundamental is that these phones are meant to vibrate, so its not surprising that they do. There is probably some tech type here who will tell you there's an internal vibrating plate. I'll retire at this point. μηδείς (talk) 04:26, 15 January 2013 (UTC)

"Singing bowels"? like this guy? Mingmingla (talk) 05:53, 15 January 2013 (UTC)

Wow, although that's surprisingly somewhat relevant, I of course meant singing bowls. Lord Arador (talk) 06:43, 15 January 2013 (UTC)
You might also want to check out friction idiophones, such as Ben Franklin's armonica. ~E: 07:02, 15 January 2013 (UTC):modified: (talk) 09:12, 15 January 2013 (UTC)

Evolution (type)[edit]

 Scientists believe that these two species evolved from a common ancestor which was forced to North America's southeastern and southwestern corners by advancing glaciers.
 Separated for centuries by vast ice sheets, the survivors evolved into two species which are still separated by a wide gap across the continent's midsection.

From the Chimney swift article →

Which would best describe this as an example?

  1. Common descent
  2. Adaptive radiation
  3. Evolutionary radiation
  4. Divergent evolution
  5. Other?

(Note: the above articles should do a better job explaining distinctions and commonalities.)
~Thanks, ~Eric (talk) 03:58, 15 January 2013 (UTC)

Is this homework? Whoop whoop pull up Bitching Betty | Averted crashes 04:22, 15 January 2013 (UTC)
Actually, I'm assisting with editing the Chimney swift article, and was thinking about clarifying, or at least linking to the proper place. ~E: (talk) 05:03, 15 January 2013 (UTC)
(EC with all prior below) I'm still somewhat unclear what you want to do. Common descent will obviously describe the relationship between these two species but it also describes the relationship between you, me and the two chimney swift species as well as with all those and the human and chimney swift microbiome. Since we're only describing two species and from the information provided I don't know that Evolutionary radiation or Adaptive radiation are great descriptors of what happened (which is not to say they're wrong presuming the changes are adaptive, simply that AFAIK they normally primarily used for larger scale speciations). Without reading the article, there's a fair chance Divergent evolution as I suspect Allopatric speciation can be said to be involved, and a bunch of other things besides. A lot depends on how similar the species even are, it may be that the amount of change is actually limited anyway (are we sure the changes are even primarily adaptations as opposed to genetic drift?) if the environments were similar and these species haven't actually seemed to diverge that far despite the separation for a long time in which case for some of these terms, while they are not necessarily wrong, may not be great descriptors. In other words, while I appreciate your desire to help, I'm not sure just throwing in a bunch of key words to every article in which they apply is really necessary (is this the norm in FAs?). But if you really want to put something, probably just mention Allopatric speciation if it's correct and leave it at that. Nil Einne (talk) 05:47, 15 January 2013 (UTC)
Y'know, the way you placed this really makes my (prior) suggestion seem redundant. You could've just placed your addition in temporal order, like the rest of us do (ec's are common for us all). -- Scray (talk) 07:04, 15 January 2013 (UTC)
How about Allopatric speciation? -- Scray (talk) 05:18, 15 January 2013 (UTC)
Sounds like an effect of isolation, like with Galapagos tortoises, due to biological dispersal to the various islands. StuRat (talk) 05:23, 15 January 2013 (UTC)
The similarity between the two species is a result of common descent; the differences between them are a result of allopatric speciation, which is a type of divergent evolution as well as a type of evolutionary radiation, and may be a type of adaptive radiation as well (if the differences are adaptive rather than merely random). Looie496 (talk) 05:43, 15 January 2013 (UTC)
That sounds about right. May I quote you on that?   ;)   An {{efn}} might be the best option for this, since it is tangential to the article, and a bit more complex than expected. Btw: "A picture is worth [several] words."
~Thanks again, ~Eric F (talk) 05:59, 15 January 2013 (UTC)
...or, how about simply linking:   ...[evolved into two species] → [Allopatric speciation] ? ~E74.60.29.141 (talk) 06:13, 15 January 2013 (UTC)
Made the link for you -- check it out! :-) (talk) 06:26, 15 January 2013 (UTC)
That does the trick! ~E: (talk) 06:52, 15 January 2013 (UTC)

Chimney cleaning[edit]

Hello all, I've been meaning to ask this question for some time now: When cleaning chimneys, how exactly can the sweep tell if substantially all the soot and creosote has been removed? In the article Chimney sweep, it says that back when they used climbing boys, they would determine by feel whether the chimney walls were smooth (which meant that the chimney was clean) -- but how did they know when to stop cleaning after this practice was (rightly) outlawed and they changed over to using a telescopic brush? Also, while it's pretty easy to remove loose soot and creosote, how did they manage to remove baked-on gunk without anyone actually going inside the chimney? (talk) 06:23, 15 January 2013 (UTC)

It's a rather gnarly wire brush, capable of scraping it off. StuRat (talk) 16:17, 15 January 2013 (UTC)
Thanks! So one pass through the chimney is all it takes to get all the gunk out? (talk) 00:45, 16 January 2013 (UTC)
I suppose multiple passes are better. Here are some pics of the brushes: [1]. BTW, are you familiar with the creosote sweeping log: [2] ? Using that first would make the creosote more brittle, and thus easier to remove (they claim it will fall off all by itself, but that might be a bit overly optimistic). StuRat (talk) 02:26, 16 January 2013 (UTC)
When I had my chimney inspected last year, creosote and soot buildup was checked simply by shining a rather bright flashlight up the chimney and seeing what the sides looked like. --Carnildo (talk) 02:18, 16 January 2013 (UTC)
With coal fires, as far as I know, you don't get the creosote deposits that you get with burning conifer logs. When I was a child in 1960s London, my memory of the chimney sweep (who used to arrive on a bicycle equipped with a large box to carry the soot away with) was that he used to run the brush up and down the flue until the soot stopped falling out. I remember being asked to stand in the back garden and yell when the brush appeared out of the chimney pot. Those who didn't employ a sweep would have to call out the London Fire Brigade when the accumulated soot in their chimneys caught fire, a fairly regular occurrence. The firemen would use a stirrup pump to squirt water into the flue, making a terrible mess in the process. Alansplodge (talk) 15:15, 16 January 2013 (UTC)
Thanks for the info, everyone! You see, I'm writing a military thriller that takes place during World War 2, and one of the important characters has a day job/cover job as a chimney sweep (whereas his work in the Maquis is as a demolitionist and a spotter) -- so naturally I'm trying to find out as much as I can about that trade.  :-) (talk) 01:04, 17 January 2013 (UTC)
You're welcome. May we mark this Q resolved ? StuRat (talk) 17:46, 18 January 2013 (UTC)
If you want -- but if anyone else wants to chime in, they're welcome to do so. (talk) 02:47, 19 January 2013 (UTC)

Gender differences in autism spectrum disorders[edit]

Why are autism spectrum disorders so much more common in males than females? -- (talk) 06:57, 15 January 2013 (UTC)

"This could be because of genetic differences between the sexes, or that the criteria used to diagnose autism are based on the characteristics of male behaviour. However, our understanding is far from complete, and this will remain the case until we know more about the causes of autism."[1]


  1. ^ "Autism: why do more boys than girls develop it?". Gender and autism. The National Autistic Society. Retrieved 15 January 2013. 

~E: (talk) 07:20, 15 January 2013 (UTC)

I'd endorse that reference strongly. It's not at all clear that the large gender imbalance in cases of autism is not an observational artefact. AlexTiefling (talk) 11:08, 15 January 2013 (UTC)
There is some suggestion that autistic females exhibit different symptoms (such as Anorexia nervosa...see especially: Anorexia_nervosa#Relationship_to_autism) than autistic males who have the same underlying disorder. If anorexia and autism are merely different sides of the same coin then perhaps there is no gender disparity in the underlying disorder at all - but rather in the way those symptoms are presented and the outcome of the resulting diagnosis. It doesn't help that autism is a "spectrum" disorder with victims going all the way from near normality to people who are totally cut off from humanity - and even people who are nominally at the same point in the spectrum often have wildly different symptoms. That fact might be a reflection of there being multiple underlying disorders with similar outcomes that science has bundled under the "autism" term - or it might reflect any number of other environmental, developmental or genetic differences amongst victims that might change the way the disorder presents itself - which would lend credibility to the anorexia nervosa connection in females.
That said, the research work surrounding autism is very difficult and solid results are hard to come by.
This might be a time when the best answer for our OP is "Nobody knows".
SteveBaker (talk) 15:37, 15 January 2013 (UTC)
Our article Autism mentions the "extreme male brain theory", but I'll decline to say much about it because of my skepticism of such a simplistic idea. I think of it more as a question of whether genes on the sex chromosomes could be involved (see [3] for example). Though one can argue that this is sort of the same concept, the point is, a few genes being in a more extreme form - even SRY - are not I would think of as "hyper-maleness", plus, the fact that autism is seen more often in males means that genes which make someone male should naturally turn up as involved, so there's something a little circular about it. Still... trace that linkage back far enough, and it's got to be connected to something. Wnt (talk) 16:49, 15 January 2013 (UTC)
There are lots of other odd gender-linked conditions surrounding this. For example consider that:
  1. Left-handed people are more often autistic than right-handed people (or to put it the other way around, autistic people are more often left-handed than the general population).
  2. Dyslexia is a common co-morbid condition of Autism - ie more people have both conditions than statistically likely if they are completely unrelated.
  3. Dyslexia is much more common in left handers.
  4. Males are more often left-handed than females are.
  5. Males are also more often dyslexic than females.
...and so, again, we see a gender-related difference. Is this because left-handedness and dyslexia are caused by mild forms of autism - or because autism, dyslexia and left-handedness are all separately related to maleness and therefore there will be a statistical correlation between them even though they don't share a common cause?
Which is cause and which is effect? This is truly insufficiently well studied.
SteveBaker (talk) 17:23, 15 January 2013 (UTC)
Perhaps the strangest sex-linked trait is sexual orientation. That is, a disproportionate number of males seem to be sexually attracted to females. :-) StuRat (talk) 01:08, 17 January 2013 (UTC)

K in KCl[edit]

How much (in gram) elemental potassium is there in 1 gram of potassium chloride? --PlanetEditor (talk) 07:17, 15 January 2013 (UTC)

Sounds like homework. What are the proportions (as percentage of total, based on atomic weight) of potassium and chloride in KCl? -- Scray (talk) 07:48, 15 January 2013 (UTC)
74.55g of KCl contain 39.10g of potassium and 35.45g of chlorine. I hope I did it right.--Stone (talk) 09:07, 15 January 2013 (UTC)
Ok, thanks. --PlanetEditor (talk) 14:16, 15 January 2013 (UTC)

Acceleration of acceleration[edit]

Student me, please help. How do we find the d covered if we have acceleration of acceleration rate. For eg: A train starts from rest, and starts acceleration. Each second the acceleration rate goes up by 1m. What will the distance covered and velocity after 10 secs? How will we dot it? [Not a homework, please tell me, its just intuition of an 11 year boy.]— Preceding unsigned comment added by (talk) 11:05, 15 January 2013 (UTC)

The rate of change of acceleration is called Jerk (physics). They even have to consider the change of jerk when designing roller coasters. Dmcq (talk) 12:01, 15 January 2013 (UTC)
First get a formula for the acceleration. From what you describe it sounds like a(t) = t, where t is seconds. Then take the antiderivative (twice) which is quite easy for a function like this, in order to get the velocity and displacement. See Polynomial#Elementary_properties_of_polynomials for the antiderivative of a polynomial. Staecker (talk) 12:47, 15 January 2013 (UTC)
The answers can be obtained using the algebraic equations for uniform jerk given in the article which Dmcq linked to, in the section here: Jerk_(physics)#Equations Modocc (talk) 13:15, 15 January 2013 (UTC)

How can we derive the formula? (talk) 14:07, 15 January 2013 (UTC)

By definition, , so
and likewise, , so
And , so
If , then we can start solving the integrals, using the rule .
We get , so
And finally,
And this is essentially the formula that you wanted to derive. - Lindert (talk) 15:05, 15 January 2013 (UTC)


I have purchased a potassium citrus tablet. In the ingredients section the following is written:

  • "Potassium Citrate IP 1000 mg (10 meq potassium per tablet)"

So how much elemental potassium is there in 1000 mg potassium citrate? How could I convert meq into mg? --PlanetEditor (talk) 14:20, 15 January 2013 (UTC)

I do wonder if you're working homework here, in which case it is useful to realize that we have an article milliequivalent which explains the relationship with millimolar (Note K+ and H+ carry the same charge, but there's more than one K+ in the formula of potassium citrate). We also have an article on potassium citrate in which the molecular weight can be looked up. (For serious homework you should double check our figures in case someone's having a prank...) You may find it easiest to determine how many moles of potassium citrate are in 1000 mg, then how much that many moles of potassium weighs, but you could also figure out the ratio first by the ratio of weights if that's what you prefer. Wnt (talk) 16:40, 15 January 2013 (UTC)

Pluto and Neptune collision[edit]

From the images below and since Neptune and Pluto cross paths about every 200+ years, is it likely the two will ever collide? Are there any theories on this? Thanks Jenova20 (email) 14:31, 15 January 2013 (UTC)

Pluto's orbit and the ecliptic.
Orbit of Pluto—ecliptic view. This 'side view' of Pluto's orbit (in red) shows its large inclination to Earth's ecliptic orbital plane.
Their paths do not cross. They path of Pluto at times takes it closer to the sun than Neptune, but it does so without ever crossing the path that Neptune takes in its orbit. --Jayron32 14:34, 15 January 2013 (UTC)
This animation shows the relationship of the orbits of Neptune and Pluto over time. It's plotted relative to Neptune, which makes it (the blue blob) stationary in this view. Note the loops of the orbit of Pluto, where it dips closer to the Sun than Neptune. But the resonant character of their orbits means the two aren't ever very close. I can't find an estimation based on modern data, but a 1965 paper "Libration of the close approaches of Pluto to Neptune" by Cohen & Hubbard puts the closest approach at a massive 18AU.[4] -- Finlay McWalterTalk 15:43, 15 January 2013 (UTC)
Ahhh...very interesting. Thank you very much for that. I suppose if they could collide on their paths then they would have done it by now anyway. Thanks again guys Jenova20 (email) 16:13, 15 January 2013 (UTC)
See Stability of the Solar System#Neptune–Pluto resonance says "Although the resonance itself will remain stable in the short term, it becomes impossible to predict the position of Pluto with any degree of accuracy more than 10–20 million years (the Lyapunov time) into the future" -- Finlay McWalterTalk 16:19, 15 January 2013 (UTC)
I'm rather confused watching the simulations on Pluto. It looks to me like it hits the little blue dot, which I assume to be Neptune, both on the top and side views, at the same time. It doesn't look like it is "furthest" from Neptune in the plane of the ecliptic at that time, but like that's when it is crossing the ecliptic. Is there an error in the graphic or am I just somehow looking at it wrong? Wnt (talk) 16:26, 15 January 2013 (UTC)
Pluto Orbit (Not Animated).png
I agree that those two animations don't help much! At right, I've uploaded the last frame of the top-view animation for clarity (it's still not a great diagram - but it'll have to do!). The problem is that you need to visualize the two orbits in three dimensions. Look carefully at the top-view diagram. The red line showing the path of Pluto is "beneath" the white grid lines (ie, the white lines block your view of the red line) when the planet is below the plane of the ecliptic (on the left side of the diagram) and "above" those white lines when the planet is above that plane (on the right side). From that, you can tell that the point where Pluto crosses upwards through the plane of the ecliptic (and the red line switches from being drawn below the white lines to being drawn above them) is at about 6 o'clock on the diagram. and goes back down again somewhere around 12 o'clock on the diagram. Now look at the dark blue dot, representing Neptune and the circle representing that orbit. At 6 o'clock, it's about two grid lines inside the orbit of Pluto - and at 12 o'clock, it's about one grid line outside of the orbit of Pluto. So at the two points where Pluto is at the same "height" as Neptune, it's far away "horizontally". So it doesn't matter where the two planets are along their orbits - they still cannot possibly collide because one orbit never comes remotely close to touching the other. SteveBaker (talk) 16:59, 15 January 2013 (UTC)
So if we said the universe was a flat plate, then Pluto is usually above or below Neptune in height because it orbits the sun at a different degree right? Thanks Jenova20 (email) 17:11, 15 January 2013 (UTC)
Yes, exactly. (Well..."If the universe solar system was a flat plate...". The universe is far from flat!) And more importantly, the two places where pluto's tilted orbit passes through that "flat plate" are nowhere near where neptune orbits. FYI: That "flat plate" is called "The Plane Of The Ecliptic" - and most of the moons, planets, asteroids and such like orbit more or less exactly in that flat disk. That's because Jupiter's giant gravity tends to pull orbits into that nice, flat, organized disk. The reason why Pluto's orbit is so whacky is a subject of considerable debate. SteveBaker (talk) 17:57, 15 January 2013 (UTC)
No,no, Jupiter didn't create the ecliptic and it doesn't force other objects into the ecliptic. In fact Jupiter interactions with other planets over time - noticeably Saturn - has driven their orbits away from the ecliptic. The ecliptic exists because the planets were formed from a disk of gas and dust that formed around the young sun. Pluto has a different origin. Dauto (talk) 00:37, 16 January 2013 (UTC)
Also see Pluto#Relationship_with_Neptune. StuRat (talk) 17:48, 15 January 2013 (UTC)
You've answered all the questions i had on the subject. Thank you very much Jenova20 (email) 11:24, 16 January 2013 (UTC)
Ah, one more. Everything just repeats every 3 Neptune years, about 5 centuries. They only pass each other once (at least in this eon), at almost the furthest possible point. Sagittarian Milky Way (talk) 21:45, 16 January 2013 (UTC)

is this correct?[edit]

I made what is my understanding based on what you've said so far for volume of gas/pressure stored inside a fixed-size container. Here: (note: feel free to inline it)

I would like to know if it's correct. Basically, as x goes to the right greater and greater amount of gas is put inside.

Thank you. (talk) 19:00, 15 January 2013 (UTC)

There are a few qualitative issues. Firstly, let us assume we choose a constant temperature that is below the critical temperature of the substance (i.e. a temperature at which it will liquify). As we add mass (taking away heat to keep the temperature constant), at fist the pressure rises close to linearly. As it starts to liquify, the graph then will go exactly horizontal, assuming that it is not supercooled (cooled below its condensation temperature without condensation occurring), where part of the contents of the container will be gas, part liquid. When we have added enough that it is all liquid, the pressure will rise very sharply, nearly vertical but not quite. At some pressure it will probably solidify, most likely creating a tiny horizontal plateau in the steep climb. Further transitions between different phases of solid may occur. Hydrogen, for example, may become metallic at sufficiently high pressures. Eventually, the primary source of pressure will be degeneracy pressure of the electrons, such as occurs in white dwarfs. As the pressure increases the electrons will combine with the protons to from neutrons (with the emission of electron neutrinos, which escape). This is the type of matter expected in the core of a neutron star. By this stage, the substance can not longer be considered to be hydrogen (or whatever we started with). Further compression may lead to a black hole, but that assumes that the substance in localized, so this should not be considered as part of the process without a clearer specification of the context. — Quondum 19:53, 15 January 2013 (UTC)
Thank you for taking the time to describe this curve to me. Is there any way you could draw it (even in paint), you can label the points 1 2 3 4 5 6 with the text tool and explain it here. I would be interested in the values (to rough orders of magnitude) of these things, if you could kind of demonstrate it for me. Thank you!!! (talk) 20:07, 15 January 2013 (UTC)
The science of hydrogen (and other substances) under extreme pressures is not exact, since there are limits to the pressures that can be reached experimentally. You can look at diagrams such as this, which gives density versus temperature but not pressure, or this, which gives pressure versus temperature. Answering your question semi-realistically would require a lot of hunting, reading and probably synthesis of results such as these, so the qualitative description will have to do unless someone else with more direct knowledge in this area can add to this. — Quondum 21:35, 15 January 2013 (UTC)
Note that adding material to a fixed-size container is (in the continuum approximation) equivalent to reducing the size of the container with a fixed amount of material. It is this latter process that is usually discussed, and quantities like specific volume are used that dispense with the irrelevant size of the container. For the vapor-liquid transition, I found an MIT resource with several related figures; many of the lines are exactly the path you're interested in (an isotherm, since you specify a constant temperature). We even have one neat 3D figure here at Saturation Dome. Quondum's description is quite good. If you're really interested, I have some of the appropriate simulation tools (at least for very simple materials). From memory, I've calculated hydrogen to achieve pressures upwards of a TPa at water density with a temperature of  K (which is not an unreasonable temperature if you compress it quickly rather than isothermally). --Tardis (talk) 03:05, 17 January 2013 (UTC)