Wikipedia:Reference desk/Archives/Science/2013 July 2

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July 2[edit]

Mars will definitely survive or it is possible to get eaten by sun[edit]

I am trying to find an outside source say Mars may get swallowed up by sun in 6-7 billion years [1] I can't remember every source I visited in the history stating Mars may even get eaten up by sun. Is the best answer to state Mars will definitely not get eaten by sun in 6-7 billion years or best answer is since Mars is further away from sun than Earth is it stands at better chance surviving than Earth? I don't know who said sun's expansion can reach 2 AU. Maybe our diagram is somebody made mistake, because I can't find other source said 2 AU?I am guessing somebody on Wikipedia made mistake-- (talk) 02:04, 2 July 2013 (UTC)

This is what Wikipedia has to say on the subject. There is always a bit of fuzziness as to predictions and models of future events, in terms of what will happen to the sun and how large it will get at its maximum extent. There are some educated guesses as to how big it is likely to get, but we can't predict it down to the inch. There are going to be some significant differences from one model to the next. --Jayron32 02:23, 2 July 2013 (UTC)
That diagram shows the sun at Earth's orbit - 1 AU radius or 2 AU diameter. Not out past Mars. Rmhermen (talk) 18:35, 2 July 2013 (UTC)
"Through the Wormhole" Season 4 Episode 3 agrees that the sun going supernova will not swallow Mars. Sandman30s (talk) 20:08, 2 July 2013 (UTC)
Not while Mars is where it is, anyway. Entirely possible it may be knocked closer by some huge asteroid within the next several billion years. Or something else happens that scientists don't yet think can happen. Long time to go. InedibleHulk (talk) 02:13, July 3, 2013 (UTC)

What's pictured in this astronomical photo?[edit]

A photo of the Andromeda Galaxy.

Is there somewhere that will tell me what the other objects in this file are? I just have a curiosity about what the big blue object is to the lower left of Andromeda is or what the wide yellow object is in the lower center of the image. Once I was curious about those, I looked more and kept asking "I wonder what that is too!" about various other points of light. So, maybe if there was a site where I could click and zoom around from the Earth's point of view, that would answer all my questions. Is there such a site? Thanks, Dismas|(talk) 05:00, 2 July 2013 (UTC)

Stellarium has a very complete catalog of stellar and deep sky objects, and its interface is suitable for beginners as well as expert users. It is free software but it is not web based. I also like the user interface in KStars. If you want a very complete catalog of astronomical objects, suitable for professional use, I'm sure we can point you to some more thorough catalogs, but these tend to require a lot more effort to use. Nimur (talk) 05:19, 2 July 2013 (UTC)
(For example, once you know the object's coordinate, you can use, e.g. Hubble's digital sky survey catalog, and and just type in coordinates. Most users probably want something a little easier). Also keep in mind that just because something appears point-like and distinct in one image product, that does not mean that it's a distinct astronomical object. So what you see in false color - your photo is mostly composited from invisible ultraviolet light! - gets rendered as a "bright blue point-like star" - but the same area shows as a continuous and nondescript piece of blurry gas in visible light in Hubble's catalog survey. Many very dramatic astronomical photographs are generated using equal parts image-processing science and artistic license to manipulate the input image data. Astrophysicists pore over the spectral data trying to deduce what structure might actually exist in these distant objects. Nimur (talk) 05:31, 2 July 2013 (UTC)
I've found the site Atlas of the Universe to be a fascinating place to visit over the years. --TammyMoet (talk) 11:22, 2 July 2013 (UTC)
Google Earth now has a Google Sky star field in it; I've found it very easy to use, already being familiar with the GE navigation. You can apparently view "Sky" through a browser, but I haven't tried that. Matt Deres (talk) 11:28, 2 July 2013 (UTC)
Google Sky made it impossible for me to ever view our planet as important again. But yeah, that doesn't cancel out the coolness of it. Adds to it, really. InedibleHulk (talk) 02:23, July 3, 2013 (UTC)

Thanks for the links, everyone. I tried Google Sky but it doesn't name every, or even most, object(s). Dismas|(talk) 23:56, 2 July 2013 (UTC)

There's a list of hierarchial checkboxes of things to label in the left-hand pane. Many are unchecked by default. You may want to fiddle with that, if you haven't. InedibleHulk (talk) 02:26, July 3, 2013 (UTC)
The photo is taken in ultraviolet light. The view in visible light is slightly different (and strangely Commons doesn't seem to have a normal visible light image at a high resolution). The "big blue object is to the lower left" is one of the stars in our own galaxy, the Milky Way. It shows up well in the ultraviolet image, but that star is actually pretty faint, so it isn't listed in List of stars in Andromeda. However a search on Google Sky to get the coordinates and a search on SIMBAD identifies the star as HD3431 (see this page). Other data on SIMBAD suggests the star has a magnitude of 6.86, a spectral type of A0 and is ~615 light years away. The "wide yellow object ... in the lower center" is another galaxy, called the Triangulum Galaxy. Astronaut (talk) 19:46, 4 July 2013 (UTC)

admission for engineering[edit]

hey people I have got into institute if chemical technology for btech oils for first year engineering. wats d opportunity for campus placements? nd does it make a gud branch? — Preceding unsigned comment added by (talkcontribs) Looie496 (talk) 06:41, 2 July 2013 (UTC)

Presumably that's the Indian Institute of Chemical Technology. On Wikipedia our convention is to spell out words, not write them in text-speak. Looie496 (talk) 06:46, 2 July 2013 (UTC)

I've got this song stuck in my head...[edit]

...and I'd be too embarrassed to tell you what it is. Fortunately, I know from experience it'll be a different song tomorrow. But seriously, it seems it happens to a lot of us. Has any serious research been done on it? How much of the population does it happen to? Does it vary between cultural groups? I sometimes wake up with a song going round in my head that I haven't heard or thought about in years. Is that common? What's really going on with this? HiLo48 (talk) 07:42, 2 July 2013 (UTC)

Our article on earworms says that "according to research by James Kellaris, 98% of individuals experience earworms". There are a while bunch of references in that article that might tell you more. Gandalf61 (talk) 07:49, 2 July 2013 (UTC)
Thanks. I'll have a look at that. But the name. Earworms? Never heard of it. No wonder I couldn't find that article. (I did look for one.) The article doesn't have an etymology section. Where did that name come from? (Yeah, I know, it's probably in the sources, but is that name really common?) HiLo48 (talk) 09:06, 2 July 2013 (UTC)
There's an interesting discussion at Talk:Earworm#Requested move. It's apparently a translation of the German Ohrwurm, but I've seen the English word mentioned frequently in books and articles on popular culture. Ghmyrtle (talk) 09:18, 2 July 2013 (UTC)
Sounds like a metaphorical equivalent to Earwig. The TV show Brain Games talked about this phenomenon, and if you google the subject [tune stuck in head], there are endless references. It is thought to have some connection to survival instincts. ←Baseball Bugs What's up, Doc? carrots→ 10:30, 2 July 2013 (UTC)
Oh so there is such a term! Hehe, remember watching a good ol' SpongeBob SquarePants episode titled Earworm... It really was a worm. :P ☯ Bonkers The Clown \(^_^)/ Nonsensical Babble ☯ 13:09, 2 July 2013 (UTC)
Earworm is a calque from the German Ohrwurm. Aaadddaaammm (talk) 06:01, 3 July 2013 (UTC)
There's more discussion on the word here. I've now added it at List of calques. Ghmyrtle (talk) 07:52, 3 July 2013 (UTC)

Dark matter/energy[edit]

Hi I've been listening to a few lectures and debates by Professor Lawrence Krauss and find him a fascinating and progressive champion of science. Is he highly regarded as a scientist (possible Nobel material) or does he fall into the category of celebrity scientists? In more than one of his lectures, he mentioned that ordinary matter comprises only 1% of the universe with everything else comprised of about 30% dark matter and about 70% dark energy. He proudly calls us cosmic pollution and says repeatedly that we are more insignificant than we think! Now, the dark matter article disagrees and says that ordinary matter is 4.9%. Who is correct? Is there more than one school of thought in how the mass-energy of the universe is measured? Sandman30s (talk) 07:51, 2 July 2013 (UTC)

It's hard to say exactly - but it seems that Krauss is one of a fairly typical group of older scientists who have passed their prime years of doing cutting edge research work and are motivated to move towards "popular science" - explaining this often confusing world to the general public. That's actually not such a terrible thing, we need people who actually understand this stuff to pass it on in a more digestible form! But that likely indicates that he won't be doing work at the Nobel Prize level anymore. That said, there is often a long delay between some great contribution and the recognition of a Nobel - and his early promotion of the idea of dark matter/energy could become sufficiently notable if/when we finally understand what all of that stuff actually is. So while I think it's unlikely, the Nobel committee can be capricious and nothing is impossible.
As for the percentages of dark matter/energy versus regular matter/energy - this is a field of rapid change, and accurate observations are difficult - so we shouldn't be surprised at seeing differences like this. The overwhelming message that "dark" stuff by far outweighs the matter and energy that we're familiar with is unchanged - so rather than ask why there is such a large disparity between 1% and 4.9% of ordinary matter - consider the fairly firm agreement that 95 to 99% of everything isn't ordinary stuff! SteveBaker (talk) 14:18, 2 July 2013 (UTC)
Thanks! This insignificant clump of stardust thinks that that is a good point... Sandman30s (talk) 19:56, 2 July 2013 (UTC)
Actually, accurate observations are not difficult, now that Planck (satellite) has mapped out the entire CMB. The fraction that ordinary (baryonic) matter takes up out of the universe's energy density is known as the baryon density, which, according to this article, is 4.56% with an uncertainty of 0.16%. That figure is from WMAP, which launched over 12 years ago. The newer Planck data gives around 4.9%. If Krauss really did say 1% (I've never heard him make such a claim), and you're sure he was referring to the baryon density, his claim is wildly inaccurate. --Bowlhover (talk) 23:28, 3 July 2013 (UTC)
It will take some effort to find the youtube links and exact times within them, but I can do so if you're interested. He never mentioned the word baryon as far as I can remember, but mentioned 'all stuff that you can see, including you and me and the earth and moon and stars etc.' - so very layman words implying that everything observable by us amounts to only 1%. I thought I was mistaken until I heard the figure twice. Sandman30s (talk) 12:22, 4 July 2013 (UTC)

citation counts: most cited people[edit]

Do we have somewhere a list of people ordered by the number of citations they draw (I mean "cites" that other people use when writing articles / books)? I am wondering if anyone keeps counts, at least for the ~10 most respected scientific publications (but to be honest I would be interested in any study provided they explain what counts and what doesn't. --Lgriot (talk) 08:50, 2 July 2013 (UTC)

I don't know if Wikipedia has a list, but you'll find plenty of sources online with opinions. How you count citations can make a difference. But in general the most cited scientists are those who developed widely used methods. It's easier to measure the citations to a single paper, and for some authors the number is simply staggering. Protein measurement with the Folin phenol reagent by Oliver H. Lowry has been cited about a quarter of million times, making this paper probably the most cited scientific work ever. You can see a few more examples at this article. That's from the 80s, so the numbers have drifted quite a bit since them, but those papers are still getting thousands of new citations every year, and I suspect they remain the most cited scientific works ever. Someguy1221 (talk) 08:59, 2 July 2013 (UTC)
Is there like a re-count every year by some organisation? And posted on the web for everyone to see? Googling "citation count" takes you google scholar citations gadget, but they say on that page it currently doesn't work, and I agree, I typed "Dawkins" in the author and got 0 citations as a result. --Lgriot (talk) 09:20, 2 July 2013 (UTC)
For scientific citations, Google Scholar does indeed work (although Google has a fairly expanded view of what counts as a scientific citation). For authors, check the "Author Search" feature. Dawkins is here, with a bit over 40000 citations. This only seems to work for authors that have some kind of profile, however. Noam Chomsky beats Dawkins hands down only counting the first page of results, but he has no author profile. Stephen Hawking is covered, with ~810000 citations. --Stephan Schulz (talk) 09:42, 2 July 2013 (UTC)
Thanks a lot, Mr Schulz, I was using it wrongly.--Lgriot (talk) 13:41, 2 July 2013 (UTC)
Resources described here may be helpful, too. -- Scray (talk) 14:56, 2 July 2013 (UTC)

Charles Murray's Human Accomplishment addresses this topic on a worldwide basis, giving statistics for work done up to 1950. I am fairly certain Newton comes in first place. μηδείς (talk) 22:05, 2 July 2013 (UTC)

"Physical" dark matter chunks near Earth?[edit]

There's been discussion of dark matter around here for some time [2] ; meanwhile, more "dark matter galaxies" are being announced or suspected: [3] [4]

Now, I understand there are many models of dark matter which represent it as hot, fast-moving, even non-self-interacting, so that it doesn't form physical "chunks". Still, I thought I should ask: how much can we currently restrict that model based on what has been observed? I assume we can't absolutely rule it out (assuming more than one kind of dark matter may exist) but we could limit the amount that is possible?

In other words, I suppose if you had a "dark matter planet" that went through or even near the Earth, we'd really find out about it due to tidal effects. If a "dark matter asteroid" is possible it would presumably make anomalies in satellite motion. And "dark matter stars" ought to leave other suns circling without a visible reason. I assume someone has looked for the limits of such evidences?

A particular scenario that appeals to me is a supernova remnant, which is often asymmetrical, shooting a remnant off into space at high speed. Presumably any dark matter that it gobbled up during life should remain gravitationally bound at the point of origin, right? So... does anything turn out to be perturbing the gas remaining at that point? Wnt (talk) 15:35, 2 July 2013 (UTC)

The strongest limits on this come from gravitational lensing, see e.g. here. Count Iblis (talk) 16:49, 2 July 2013 (UTC)
To form small clumps you'd really need the dark matter to interact with itself or ordinary matter so it could be slowed down. Otherwise a particle just speeds up towards a centre of mass, then goes round and away again like a comet. Random whizzing around can clump under gravitation to give a cloud but it won't lead to small chunks like stars (well not unless it is dense enough to start forming black holes). Dmcq (talk) 08:52, 3 July 2013 (UTC)
There is no scientific evidence for "dark matter". --Kharon (talk) 21:14, 3 July 2013 (UTC)
Well, the reason why I mentioned the supernova was that I figured, even if dark matter doesn't self-interact under any circumstance but gravity, it should still sink to the core of the supernova and then remain gravitationally bound after it blows apart. Unless the stuff is so "hot" (?) that it "evaporates" right out of the gravity well anyway?
(to clarify, I'm not so clear on this: even if the dark matter collides with nothing, including itself, shouldn't the orbital mechanics of the matter eventually lead to some particles being flung out to infinity while others lose speed and remain permanently within the growing star during the billions of years leading up to the supernova?) Wnt (talk) 22:14, 3 July 2013 (UTC)
There are no orbital mechanics left in the common inbetween dimensions of astronomical distances between stars and Star systems. If one would calculate the Relation between space "filled" by matter and space containing nothing you would find some very oddly tiny result. Same with distance. Pluto is ~4 Light Hours away from our Sun. The next star Alpha Centauri is around 35 000 Light Hours away (and astronomical concidered "near"). --Kharon (talk) 00:14, 4 July 2013 (UTC)
Interaction should in principle lead to kinetic energy redistribution in terms of a thermal model, though the time scale might be huge, especially if the interaction is weak. The average kinetic energy of the chunks relative to some gravitational picture would probably be key. In effect, small particles should behave as a gas, and if the initial average temperature is more than a few K, unless there is a mechanism (e.g. radiative) extracting energy from them collectively, they would presumably never coalesce into anything more dense than "clouds" – in the case of primordial hydrogen, electromagnetic radiation must have been crucial in the formation into galaxies and stars. Weak interaction with normal matter at the atomic level might lead to some extraction of energy, and to reduction of the local temperature, and hence some clumping. One supposition/model I've seen (a public lecture by an astrophysicist) gives local dark matter density going by a simple power law around centres (i.e. not within a star, but inside and extending out from it, like an atomic 1s orbital), but it was not clear what the minimum size was – a star? a galaxy? In any event, such cooled clumps of gravitationally bound dark matter seem to be a serious consideration, but if significant clumping occurred at the level of stars, we should have had abundant evidence of it from planetary orbital observations. — Quondum 11:12, 4 July 2013 (UTC)

What's the sourest object in the known universe?[edit]

Any ideas? Just a question that occurred to me when eating one of those super-sour Toxic Waste sweets recently. I do seem to recall that something was once announced as the most foul-smelling object in the known universe... --Kurt Shaped Box (talk) 20:53, 2 July 2013 (UTC)

If sourness is the sensation of acidity, fluoroantimonic acid is at the top of superacids. Theoretically if you could eat a spoonful of protons those would be the most acidic thing there can be. Sorry for how the dull the answer is... (talk) 21:08, 2 July 2013 (UTC)
If sourness is ability to donate protons then you probably can't go past ionized hydrogen, and there is plenty of that in the universe. Graeme Bartlett (talk) 21:18, 2 July 2013 (UTC)
I started wondering what would happen if you had pure protons at an everyday life density. Say a spoonful of water and instantaneously remove all the oxygen nuclei and electrons. Those protons wouldn't like to be close to each other due to electrical repulsion, would they? Would that be minor heating of the spoon or a big-hole-in-the-ground event? (talk) 21:58, 2 July 2013 (UTC)
It is impractical to remove the electrons - the coulomb force is amazingly strong, and you'd have to expend a lot of work to separate the electric charges. So, in your scenario, a necessary condition is an input of a huge amount of energy to dissociate (and then separate) the ions and electrons. As a result, you'd have a very hot ionized mass of hydrogen. You can easily calculate how hot you need to get to ionize the hydrogen: it's the ionization energy divided by the heat capacity. (!!). Accounting for adiabatic expansion which is reasonable when you compare the time-constant of the expansion to the effective rate of heat exchange with the outside air, I think you'll find it hard to keep the resulting explosion contained in a spoon-heap-sized volume! Nimur (talk) 22:30, 2 July 2013 (UTC)
An Assistant-Principal at a school I once taught at was a really sour old b.... HiLo48 (talk) 23:34, 2 July 2013 (UTC)
Perhaps, you mean "sourest non-toxic substance"? Plasmic Physics (talk) 02:29, 3 July 2013 (UTC)
Don't think that really helps. Vinegar isn't considered toxic but glacial acetic acid is. (talk) 05:01, 5 July 2013 (UTC)

One should take care that one is dealing with the correct concept. "Sourness" might relate to hydronium concentration rather than proton donation. — Quondum 03:03, 3 July 2013 (UTC)

Something is wrong with the magnetic induction " B" ![edit]

When we analize the interaction between two current carying conductors we first represent the magnetic induction "B" following the right hand rule. But, if you look back at the origine of this representation you can find that it comes from Faraday and the orientation of the magnetic induction "B" was based on the pattern of iron filings formed around a magnet bar which resemble to " field of lines" conneting the two poles. If you look closer the iron piling particles also can be considered tini magnets and their orientation will always be that their internal atomic currents that creates their magnetic field will be aligned with the internal atomic currents of the large permanent magnet bar so they will tend to have the same direction ! The independent "lines" are formed because the adjacent particles of iron will align their internal currents with the stronger current of the large permanent magnet bar while between the "lines" there will be repulsion, also particle of iron from a "line" will form chains with the top and the bottom particle so that their internal currents will be aligned too. So now from the two parallel electric current situation we arrive to another two parallel electric current situation! And the real magnetic field looks more like "something" that is allong the lenght of the conductor. Think about two ships on water that moves parallel to each other in the same direction. Because of Bernoulli effect the ships will be drawn together, but if they move in opposite directions they will be pushed away from each other...The same it seems to be with the magnetic field too. There is no such a thing like magnetic induction "B" that is tangent to the conductors or circle the conductor...its just an illusion ! Can you see the error? — Preceding unsigned comment added by (talkcontribs)

Yes, your error is that you are confusing magnetic field with magnetic induction. These terms refer to distinct physical entities. If you use terminology differently from everyone else, you won't be able to understand the commonplace explanations. Magnetism obeys simple rules that have been experimentally tested and verified with increasing accuracy for around two centuries; if something was catastrophically wrong with our understanding, we would all have noticed! Nimur (talk) 21:17, 2 July 2013 (UTC)

I think that you are confusing "magnetic induction B" which is also called "magnetic field" (read wikipedia :) with "electromagnetic induction" ... Saying that " magnetism obeys simple rules" its a very superficial statement, anyway.

I noticed our disambiguation page - I read Wikipedia - and many other things - quite extensively! I'll go out on a limb here and say "usage of the term 'magnetic induction' to refer to the magnetic field is incorrect and should be eliminated from the disambiguation page." I had no prior recollection of ever hearing the term "magnetic induction" abused this way. In deference to my limited knowledge, I referenced two university-level textbooks on electrodynamics that I keep handy next to my bed for just such situations. Tipler's Physics for Scientists and Engineers gives a great description of the history of the magnetic field, and carries a full chapter titled "magnetic induction." Magnetic induction is defined as the process by which "emfs and currents are caused by changing magnetic fields..." Nowhere in the chapter, nor in the convenient glossary, does this text use the term "induction" to refer to the field.
David J. Griffiths' "Introduction to Electrodynamics", §6.3, has a special note on the topic, while discussing fields in materials, and I quote: “Many authors call H, not B, the "magnetic field." Then they have to invent a new word for B: the "flux density," or magnetic "induction" (an absurd choice, since that term already has at least two other meanings in electrodynamics). Anyway, B is indisputably the fundamental quantity, so (Griffiths) shall continue to call it the "magnetic field," as everyone does in the spoken language.” I guess this scores a point for the OP - the term is used somewhere. But not in modern textbook-definition usage. A further note, in my edition: “For those who disagree, (Griffiths) quotes A. Sommerfeld's Electrodynamics (1952)... "The unhappy term 'magnetic field' for H should be avoided as far as possible. It seems to us that this term has led into error none less than Maxwell himself" ...“
I was willing to entertain the notion that the terminology is a foreign-ism, or archaic (... it would not be the first time I encounter unfamiliar physics lingo, only to discover that all students in, say, Ghana or India use different terminology than I do). So I went straight to my digital copy of "Experimental Researches in Electricity," (which is available free online) to refresh my memory - I never recalled its author using the term "magnetic induction" incorrectly! Michael Faraday uses terminology in a way I would agree with; "magnetic induction" is described as the process of inducing a current using a changing magnetic field, and never to refer to the magnetic field itself. So, I know of no historical or archaic usage, but this was arguably a very short literature survey. Based on Sommerfeld's comments, Maxwell may be the source of the original terminology confusion; I'll probably dig up some Maxwell writings for my own entertainment, but I don't usually find those very enjoyable to read, because his writing style is confusing.
I hope if nothing else comes from these references, you'll have some good reading suggestions to help clarify the topic. Griffiths' chapter on magnetism and its interaction with magnetized materials is excellent and may clear up your original question. If nothing else, it may dispel any rumors that I make flippant or superficial contributions! Nimur (talk) 11:24, 3 July 2013 (UTC)
For anyone who is still waiting on the edge of their seat for the startling conclusion: it was in fact Maxwell who first used the term 'induction' in this way, in A Treatise on Electricity and Magnetism, Part 3, Chapter 2, Magnetic Force and Magnetic Induction. I will not be the first, nor the last, physicist to say that Maxwell's writing-style and choice of terminology was not very clear, and it certainly deviates from modern terminology. Nimur (talk) 18:07, 4 July 2013 (UTC)