Wikipedia:Reference desk/Archives/Science/2015 October 4

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October 4

Boiling uncovered

Why does the packaging of my dried beans advise boiling uncovered? Does this serve a purpose other than creating additional steam? Also fix your mobile/Android question submission page so it doesn't keep putting submissions at the top of the page. Doesn't anyone test these things? — Preceding unsigned comment added by 78.148.105.223 (talk) 21:46, 8 October 2015 (UTC)

W Thomson / Lord Kelvin paper on "image effect" in electrostatics.

In W Schottky's 1914 paper on electron emission of metals, he starts with what he calls "Thomson's image force" and derives an equation for the saturation current of vacuum tube diodes. It is possible that he was refering to something like the "method of images" - a standard method of analysing the forces on charged particles etc near conductive surfaces. Schottky gives no reference and seems to assume the reader is fully familiar with it.

I would like to read Thomson's paper.

Problems: I consulted textbooks I have on electrostatics and others that cover the method of images - none tell where this method came from. I googled papers written by W Thomson and none appeared by their title to be relavent.

Do you have any clue what paper or journal letter it might be? Citation? 121.221.120.212 (talk) 13:27, 4 October 2015 (UTC)

You're either talking about the method of images, or the method of image charges; and in addition to W. Thomson, there is also the similarly named physicist J. J. Thomson. I don't know what paper specifically first introduced the technique. I doubt it was first used by either Thomson, but I bet he wrote a lot on it and developed it conceptually. I do know it's covered extensively in a lot of books, most famously in Jackson's Classical Electrodynamics.

If I had to hazard a guess, the method was probably used earlier by mathematicians like Dirichlet, Poisson, and Laplace - even though their work predated the formalization of electrostatics in physics, they formally solved the same equations that would show up in physics a century later. On that note, it would not surprise me if Gauss and Euler both used the method, because if you learn anything about mathematics, it's that Gauss and Euler almost always did it two hundred years before anyone realized it was important.

On some further reading, through a lot of archives, I found an 1848 paper: Thompson, W.: (Lord Kelvin), 1848, Note on the integration of the equations of equilibrium of an elastic solid. (Cambridge Dublin Mathematics Journal, Volume 3, pages 87–89), which is sometimes cited as the "oldest" Kelvin paper in the history of the method. That paper is only about a page long, and it was available online. Though it focuses on elastic equations for stress, it contains some discussion about applications of symmetry to simplify boundary conditions in similar equations in electrostatics... but it's hardly a textbook example of the method we know today.

Nimur (talk) 13:47, 4 October 2015 (UTC)

Nimur, thanks for your prompt reply. Schottky refers in one place to the guy as "Sir W Thomson". However, I wouldn't rule out it being J J Thomson. I had a look at the Cambridge Dublin Mathematics Journal article. I don't think that's the one. I was already aware of the method of images. But I would like to read the actual Thomson paper, to find out 1) just what Schottky meant by "Thomson's image force" and 2) its applicability. 121.221.120.212 (talk) 16:38, 4 October 2015 (UTC)

Schottky may have been referring to Kelvin transform. In this book it is stated that "Thomson originally called it the principle of (electrical) images". Apparently this method was first described by Thomson in 1845/6 in three letters he wrote to Joseph Liouville, though I don't know if they are available somewhere online. - Lindert (talk) 22:38, 4 October 2015 (UTC)

Thanks. Looks promising. According to the book you linked, Thomson's letters were published in Liouville's journal. A little frustrating, because Google books won't let me see the citation numbers (1845b, 1847a)in the list of references. However, I found that Liouville's Journal is available online for free from Galica. The Journal is in French, which I have no knowlege of, so it will take me some considerable time to sus it out.

I should have mentioned that Schottky refers to "Thomson's image force" when discussing electrons that leave a metal surface & enter a surrounding vacuum. Schottky seems to have thought there is an "image" opposite charge behind the surface (like a visual reflection in a mirror) for each individual electron, holding it back within distances < 10^4 mm, not to be confused with the space charge (a macro effect). It is difficult if not impossible to verify the consequences (derived by Schottky) of this in the lab, as so many other factors affect electron movement.

120.145.155.42 (talk) 01:53, 5 October 2015 (UTC)

Here is a reprint of papers on electrostatics and magnetism / by sir William Thomson, 1872. Electric Images, two letters to Liouville. From Liouville's journal de Mathématiques 1847: Page 161 (Table of contents says 208) Ssscienccce (talk) 03:49, 5 October 2015 (UTC)

Hmmm... Begins page 144 in the version I downloaded from Hathi Trust. Reproduced in French - ugh! 60.228.210.220 (talk) 16:08, 5 October 2015 (UTC)

Written in French, I think. He learned French in his teens and went to work in a lab in Paris for a while. The gallica version seems corrupted, doesn't load page 151, nor the next ones.... Ssscienccce (talk) 00:58, 6 October 2015 (UTC)

I've completed translating the first letter (October 1845)and it seems to be not the one. It is about more complex applications of the image theory, and was written on the basis that the image theory was already known to both parties. 60.228.100.2 (talk) 10:21, 8 October 2015 (UTC)

Transport professional bodies

What is the difference between the Chartered Institute of Logistics and Transport and Chartered Institution of Highways and Transportation. Both seem to be professional institutions for transport. — Preceding unsigned comment added by 2A02:C7D:B91D:2200:D9CB:BE48:2957:D624 (talk) 15:00, 4 October 2015 (UTC)

The CILT is concerned with "transport" as a verb - with Logistics. It deals with trucks, warehouses, containers, etc. The CIHT is concerned with "transport" as a noun - with Traffic. It deals with roads, bridges, car parks, etc. Tevildo (talk) 15:13, 4 October 2015 (UTC)

I see, so is there a separate one for rail and air or does CIHT cover those too? 2A02:C7D:B91D:2200:D9CB:BE48:2957:D624 (talk) 16:01, 4 October 2015 (UTC)

As far as I can tell, there isn't an institution specifically dedicated to rail infrastructure in the UK - see Category:Railway associations, Community of European Railway and Infrastructure Companies and Institution of Mechanical Engineers for some potentially useful links. Airport infrastructure comes under the auspices of IATA, but (again) there doesn't seem to be a dedicated UK professional body. Tevildo (talk) 17:09, 4 October 2015 (UTC)

Perhaps CIHT tries to cover them too? The article claims that CIHT was originally called the institute of highways engineers so perhaps by including transportation in the name they wanted to expand to cover rail and air too? 2A02:C7D:B91D:2200:D9CB:BE48:2957:D624 (talk) 21:39, 4 October 2015 (UTC)

Gravity-trigerred nuclear fission

Can an extremely strong black hole-like gravitation overcome nuclear binding energy and pull atomic nuclei apart, initiating nuclear fission and subsequent nuclear explosion of an object? Judging by gravity fields of black holes, it can't, but is there a theoretical magnitude capable to do that? 93.174.25.12 (talk) 15:52, 4 October 2015 (UTC)

The bigger the black hole, the weaker the tides at the event horizon. So it's actually small holes you want. Which are subject to Hawking radiation, which is sometimes described in terms of virtual particles that get separated (though perhaps less due to tidal force than simple chance? I don't know) A very small black hole in concept might be capable of emitting large amounts of energy while being fed matter to make up for it, and thus 'catalyze' the conversion of mass to energy ... but since that involves the net conversion of matter to antimatter, it is a remarkable idea; in any case we have not tested any small black holes to find out what happens. I also don't know if the alleged correlations of Hawking radiation that bring information back out of the hole would impact that in any way. Wnt (talk) 16:01, 4 October 2015 (UTC)

In stellar evolution there are end products like dwarf stars, neutron stars and black holes (the later usually after a supernova). So, when it ends as a black hole, the fusion is all over and done, and the former star collapses to a rather unrecoverable state. So I don't think that for a black hole we could speak of nuclei any longer, basically all that's inside is gone to Neverland. Tgeorgescu (talk) 17:05, 4 October 2015 (UTC)

Yes, celestial bodies with such strong gravity do exist. For instance, neutron stars, in which all nucleus have split. However, it does not cause any explosion. Ruslik_Zero 20:30, 4 October 2015 (UTC)

And I believe that's because a star only ever has a tiny portion of radioactive elements, such as uranium. So, the energy released when they break up is minuscule, on the scale of a star. (Stable elements can also be broken up, but I believe it takes more energy to break them up than you get from it.) StuRat (talk) 22:10, 4 October 2015 (UTC)

Not for all stable elements. Rather, it's any element before nickel-62 on the nuclear binding energy curve. And in reply to Ruslik, nuclei still exist in the surface layers of neutron stars; see Neutron star#Structure. --71.119.131.184 (talk) 12:57, 6 October 2015 (UTC)

Also, the fission of lithium actually releases energy, as both natural Li isotopes have lower binding energies per nucleon than neighbouring elements He and Be. Double sharp (talk) 03:42, 7 October 2015 (UTC)

So does proton-boron fusion (why this isn't called "fission" isn't immediately clear) - the boron-11 nucleus splits into three alpha particles, giving off energy as well. loupgarous (talk) 06:41, 8 October 2015 (UTC)

Earth's layers 'air' and 'water'

Do we have an article(s) stating all about the atmosphere of the 'earth' including the atmosphere of the ocean? -- Space Ghost (talk) 19:02, 4 October 2015 (UTC)

Biosphere is probably what you're looking for. Tevildo (talk) 19:26, 4 October 2015 (UTC)

Something like the way it shows the Van Allen radiation belt. All in one for 'air' and all in one for 'water'. -- Space Ghost (talk) 19:31, 4 October 2015 (UTC)

Earth's atmosphere? Ocean? Not really sure what you are looking for. Dragons flight (talk) 20:28, 4 October 2015 (UTC)

If you look at the end of the first article you stated, there is a blue box, it will show all the 'spheres', 'pauses' and 'layers' when you click the 'show' link. Current illustration in the article only shows 8 or 9 or so. I'm searching for an illustration with all the 'spheres', 'pauses' and 'layers' in it, along with 'miles' starting from the sea level if possible. A similar thing for ocean too because I heard once (either from T.V or from a hearsay) that people can't go below 1000 metres or so. -- Space Ghost (talk) 21:44, 4 October 2015 (UTC)

This illustration in the article shows all of the atmosphere's layers except the exosphere. It stops at the exosphere because it's to scale, and the exosphere doesn't really have a definite point at which it ends. It just gradually merges into interplanetary space. Remember, all of these layers and boundaries are human classifications and are to some degree arbitrary. Moving on, "atmosphere of the ocean" is a phrase no native speaker would use, so that's probably what's confusing people. I think you mean the layers of the ocean? The ocean article has a diagram. You should be able to find plenty of other images with a little Web searching. Regarding diving, the limit for human diving appears to be even less than that: see deep diving. --71.119.131.184 (talk) 07:33, 5 October 2015 (UTC)

I viewed of all before user 'Dragons flight' stated, I thought we would have something better. Also, if you look at the 'Deep diving' article, it states about the Atmospheric Diving System (ADS) suit. This is the reason why I was using the word atmosphere on both places... Thank you anyway for the clarification though, I needed a second confirmation/clarification... -- Space Ghost (talk) 03:29, 6 October 2015 (UTC)

Your "this illustration" is obviously flawed. The various language variants are different. The weather balloon at 40km is below the Troposphere at 12km. They need some work by someone who knows. -- SGBailey (talk) 10:27, 5 October 2015 (UTC)

I believe the illustration in question is correct, but uses a confusing, artistic "three-dimensional" effect to magnify the lowest layers of the atmosphere in a way that can easily be misunderstood. The weather balloon is meant to be "in front" of the troposphere - rather, at the 40-kilometer altitude, but projected outwards, rather than projected on the backplane. In other words, the vertical axis of this chart does not monotonically map to altitude. Nimur (talk) 15:02, 5 October 2015 (UTC)

Scroll down the image page and compare the English and Spanish versions. The English is obviously wrong. -- SGBailey (talk) 22:09, 5 October 2015 (UTC)

You're right; the cloud part... -- Space Ghost (talk) 03:29, 6 October 2015 (UTC)

Friends, thank you all for your clarifications. I guess this has to do. Regards -- Space Ghost (talk) 03:29, 6 October 2015 (UTC)

Guys, I can't find a suitable illustration for the Earths's atmosphere. -- Space Ghost (talk) 20:24, 6 October 2015 (UTC)

An Electric plug

Friends, I was just going through my 'treasure box' and I found a 'universal plug' which is 250V~3AMP. Currently I'm using 250V~10AMP. What do you guys suggest I should use? -- Space Ghost (talk) 21:52, 4 October 2015 (UTC)

What's your goal/situation? DMacks (talk) 21:54, 4 October 2015 (UTC)

I forgot that I bought one in Canada and now I found it. I'm currently in a third world country using the 10AMP; I do not plug anything to it whilist charging my PC which is made in UK, but do put everything else altogether possible whilist not charging my PC, e.g., phone, shaver, music player... -- Space Ghost (talk) 22:04, 4 October 2015 (UTC)

The Refdesk isn't supposed to give advice. If you fry your computer or start a fire, nobody here is gonna pay for it. If you have a question about something factual, please clarify what it is. Wnt (talk) 22:09, 4 October 2015 (UTC)

Sorry, you guys are all I have... I do know, forgot, I'll recall the 'factual' part hopefully from next time onward. -- Space Ghost (talk) 22:32, 4 October 2015 (UTC)

Well, let's see. I believe the rated wattage is the voltage times the rated amperage. So, 3×250 = 750 watts and 10×250 = 2500 watts. Generally, an appliance that changes the temperature will use over 750 watts, so things like hair dryers, space heaters, microwave ovens, and air conditioners should use the 10 AMP rating, while most small appliances can use the 3 AMP rating. And, of course, if it gets hot, then that's too much for it. StuRat (talk) 22:14, 4 October 2015 (UTC)

Love you Stu! -- Space Ghost (talk) 22:32, 4 October 2015 (UTC)

If you are already using the 10Amp, there's no reason to switch to the 3A. The other advice Stu gives above is generally sound. If you ever need to use both, use the 10A one for the device(s) that uses more power. Vespine (talk) 22:19, 4 October 2015 (UTC)

Okay! Thanks. -- Space Ghost (talk) 22:32, 4 October 2015 (UTC)

Yes, Stu's statement was enough for me to analyse what to do here with the plugs. I'm saying the following just in case you guys don't know, it states on the plug that you intend to insert into the universal plug. -- Space Ghost (talk) 22:32, 4 October 2015 (UTC)

Thanks all! -- Space Ghost (talk) 22:47, 4 October 2015 (UTC)

High mass star

There are three arrows specified in this illustration, I understand the black hole and the neutron star part. what's the third one? Does it mean that after a supernova there won't be any star remnant? No bones in other words? Leaves just a nebula after a supernova? -- Space Ghost (talk) 22:49, 4 October 2015 (UTC)

There are more than three arrows, but you must mean the ones coming from the supernova explosion on the right. The diagram comes originally from a NASA educational page now located here. The text on that page says that "If the remnant of the explosion is 1.4 to about 3 times as massive as our Sun, it will become a neutron star" and if it's larger than that range then it becomes a black hole. But it says nothing about remnants smaller than that range.

Now Wikipedia says at Supernova remnant that "there are three types of supernova remnant", but does not mention a black hole as a possibility. It talks about a "shell-like" remnant where the star is indeed blown into a nebula, and ones with a pulsar, and ones of "mixed morphology", but the description of the last one doesn't really make clear what happens to the ejecta to form that configuration. --174.88.134.156 (talk) 00:23, 5 October 2015 (UTC)

Stellar evolution and supernova may help. All supernova blow some material into a nebula. Depending on the size of the star before the supernova it can also create either a neutron star, a black hole, or no remnant at all. Type Ia supernova detonate in a way that only leaves a nebula behind with no additional remnant. Dragons flight (talk) 07:50, 5 October 2015 (UTC)

A type Ia supernova can completely unbind the star, therefore not leaving behind a neutron star or black hole. However, I think the arrow in the diagram is referring to something else. When the shock wave from a supernova hits a molecular cloud it compresses the gas and can trigger star formation. The supernova also enriches the molecular cloud with heavier elements, increasing the metallicity of the next generation of stars. In this sense it's not a different kind of remnant, but a different role (or two different roles) in the overall life cycle of stars. --Amble (talk) 16:26, 5 October 2015 (UTC)

• I heard or read within the last five years or so that, depending on the asymmetry of the explosion, some remnants can gain enough "sideways" momentum to be "ejected" from the nebula itself. I don't have a source, since this was either from a TV show or an article in a magazine borrowed from the library. μηδείς (talk) 16:15, 5 October 2015 (UTC)

174.88.134.156, Dragons flight, Amble, μηδείς: Thank you for pointing your statements out, I thought I was crazy; well I knew the articles were torturing me. Correcting me with the following if I'm wrong please.

Okay, so now, if only you guys say, than I'll believe in 5 types of 'supernova explosions', depending on its mass of course, i.e.

1. Leaving a shell-like remanant after ejecting everything in the nebula.
2. Black hole after ejecting everything in the nebula.
3. neutron star after ejecting everything in the nebula.
4. no remanant at all after ejecting everything in the nebula.
5. Pulsar?

Note: there is also 'a time may come' where the stars may decay - as defined in the ultimate fate of the universe article. Just a thought!.

Also, bulletins 2,3 4 above could occur before a supernova explosion (depending on the size or mass), but no supernova thereafter.

Have I got all this correctly now?

Space Ghost (talk) 03:08, 6 October 2015 (UTC)

Number 1 and number 4 are the same thing. The shell in #1 is just all the stuff that got ejected into the nebula. But the third arrow in the diagram, where material and shock waves hitting the molecular cloud contribute to the next round of star formation, isn't really a different type of remnant. It's just an additional effect that happens regardless of whether the supernova produces a black hole, neutron star, or complete disruption. --Amble (talk) 04:08, 6 October 2015 (UTC)

• Part of the confusion here is that the H II regions shown by the third arrow are, according to our article, produced from giant molecular clouds that are hit by shock waves from supernovae. See Eagle Nebula for the example given. Now the sources I saw seem remarkably unclear on where the original supernova was, and I think it's distinct from another one that is said to have destroyed the "Pillars of Creation" by "now". But the message I'm inferring is that you have a supernova remnant on one hand and the star-forming nebula on the other, but only if the supernova happens to be near that external fuel source when it goes off, and they potentially could then go separate ways. I think. Wnt (talk) 10:55, 6 October 2015 (UTC)

Points noted! Thanks. -- Space Ghost (talk) 20:14, 6 October 2015 (UTC)

Amble: The whole confusion was the words 'shell-like remanant'. I included the thought that if a supernova becomes a neutron star or a black hole than a shell-like remnant could mean 'a transparent ball'. Realistically, I was not in the wrong to think that. If it was clearly stated as e.g. the Type La supernova explosion is as similar as the primordial atom explosion, I would've clearly understood it. The diagram makes perfect sense now. Thank you

Space Ghost (talk) 20:14, 6 October 2015 (UTC)

User:Russell.mo: I can see how it could be confusing. A supernova may result in a new type of compact object like a neutron star or a black hole (or it may completely disrupt the star, without leaving any compact object at all). It also ejects a large part or all of the star's mass into the interstellar medium. A "supernova remnant" or "shell-like remnant" is a kind of nebula produced by the material that has been blown off. It's not a different type of compact object. --Amble (talk) 20:24, 6 October 2015 (UTC)

Thank you Words won't describe 'the amount of times I read all the articles containing a star's life cycle'... -- Space Ghost (talk) 20:31, 6 October 2015 (UTC)