Wikipedia:Reference desk/Archives/Science/2014 July 18

Science desk
< July 17	<< Jun | July | Aug >>	July 19 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

July 18

Electron = black hole?

The electron is assumed to be a dimensionless point particle since the electric repulsion between the parts of a finite-sized electron is supposed to be so strong that it would disintegrate. If so, then the electron is a tiny black hole: how long does it take for such electron-black-hole to evaporate due to Hawking radiation ? Antonquery (talk) 02:03, 18 July 2014 (UTC)

There's an article on this, black hole electron, but it's rather awful at the moment so don't read it.

Black holes in GR must satisfy q² + a² ≤ m², where q is the electric charge, a is the angular momentum, and m is the mass (all in natural units). Electrons violate this inequality by a factor of (from memory) about 10²¹. Therefore either they are naked singularities (no event horizon) or the GR calculation is wrong somehow. The simplest way it could be wrong is if there are large extra dimensions, but the LHC hasn't found any evidence for that.

Black hole evaporation conserves mass-energy and electric charge. There are (for unknown reasons) no charged particles lighter than the electron. Therefore electrons can't decay by Hawking radiation even if they are black holes.

It's not impossible for the electron to be a composite particle; it could be made of preons bound by a force like the strong force. It's hard to understand why its mass is so low in that case, but that's hard to understand anyway. Many preon models have been proposed over the years, but there's no experimental support for any of them. Elementary particles are not pointlike in string theory either. -- BenRG (talk) 02:54, 18 July 2014 (UTC)

An electron is not really a point particle. It's not really a finite-sized particle either. It does not necessarily have a precisely defined position in space, or size. You can describe an electron as a particle and use that model to talk about some aspects of its behavior. You can also just as well describe it as a wave and describe some of its properties that way. Both models are fully correct and equivalent. See Wave-particle duality.--Srleffler (talk) 16:16, 18 July 2014 (UTC)

Thank you for your answers, Antonquery (talk) 10:16, 20 July 2014 (UTC)

Experimental evidence for muscle microtrauma in exercise?

I've been hearing for a few decades that the reason muscle strengthening exercise works is that it causes small tears in muscles, and the resulting healed muscles are stronger than the original (roughly speaking). Has anyone actually observed these tears in exercised muscles and counted more tears than exist in unexercised muscles? Failing that, what other experimental evidence exists?--Wikimedes (talk) 03:59, 18 July 2014 (UTC)

DOMS is a good place to start. 86.164.27.197 (talk) 12:30, 18 July 2014 (UTC)

Evidence for myofibril remodeling as opposed to myofibril damage in human muscles with DOMS: an ultrastructural and immunoelectron microscopic study. suggests some of the physical evidence that is typically considered. 86.164.27.197 (talk) 15:13, 18 July 2014 (UTC)

Thanks for the reference. It's good to know that the hypothesis is being tested.--Wikimedes (talk) 01:09, 20 July 2014 (UTC)

Were ancient oceans orange ?

As I understand it, before there was oxygen in the air, micro-organisms released oxygen into the oceans, which reacted with iron which was then dissolved in large quantities in the water, to form rust (iron oxide), which then precipitated out. So, did this happen at a fast enough rate to visibly make the oceans rust-colored, if anyone had been around to see them ? StuRat (talk) 04:36, 18 July 2014 (UTC)

At modern rates of net primary productivity there would have been more than enough rust created to make the ocean surface appear visibly discolored. However, I don't think we can make anything other than wild ass guesses about what the rate of oxygen formation was during that early epoch. Dragons flight (talk) 10:42, 18 July 2014 (UTC)

I should think we could get a good estimate, based on the rate of iron oxide deposition on the sea floor, which can determined by taking core samples. StuRat (talk) 15:36, 18 July 2014 (UTC)

I thought that too, and immediately thought of banded iron formations, but our article states that it is unknown if the bands are from seasonal variation or some other process. That means we don't know how much time is represented by each band of iron, so I suspect it makes it hard to precisely estimate the iron concentration in the water that led to the formation. I think we need to attempt to track down references on estimated iron concentrations, then find information on what concentrations would cause noticable changes in water color. Other questions such as if the surface layers of the ocean had as much concentration as lower ones may be much, much harder to find information on. Katie R (talk) 19:09, 18 July 2014 (UTC)

Still, even if we can't find the deposition rate for individual years, if we find the total amount of deposition, then divide by the total number of years over which deposition was likely to have occurred, we can get a good average rate, right ? StuRat (talk) 15:38, 23 July 2014 (UTC)

The idea that electromagnetic radiations in the wavelength range 590-620 nm should be distinguished from other wavelengths by the colour name "orange" is a perception that humans owe to the long evolution of the colour-discriminating eye and early implementations of colour signaling by interacting organisms; for example, the orange of Agelas clathrodes elephant ear sponge signals its bitter taste to predators.

Oxygen began to outgas from the oceans 3–2.7 billion years ago, leading to the Great Oxygenation Event (an extinction event for anaerobic organisms) around 2.3 billion years ago. Thus the OP asks about the colour of oceans that neither eyes, nor Arthropods to have them, had yet evolved to see, existing under an unbreathable atmosphere of (probably) nitrogen, carbon dioxide, methane and (in a hypothesis about early greenhouse effect) Carbonyl sulfide and illuminated by the relatively weak young Sun. The question is moot. 84.209.89.214 (talk) 18:32, 18 July 2014 (UTC)

Not moot at all. Part 2 of my question would be if we can detect orange (water) oceans on exoplanets, and use that to infer that those oceans contain micro-organisms giving off oxygen, along with dissolved iron. The idea being to supplement looking for free oxygen in the atmosphere as a sign of life. The orange-ocean method would presumably work for earlier life forms than the free oxygen in the atmosphere method. StuRat (talk) 19:25, 18 July 2014 (UTC)

Well, usually the exoplanet hunters are trying to look for absorption in the atmosphere. Trying to detect the components in the oceans... well, the exoplanet transiting its star is essentially in a state of solar eclipse to us. There must be some light that reflects off the ocean on the near side and scatters in the atmosphere to us, but ... well, I've learned by experience not to say what's impossible for exoplanet hunters any more, but they will sure impress the hell out of me if they can do that one! Wnt (talk) 21:47, 18 July 2014 (UTC)

From an older source (in exoplanet search, that was around 2010 or 11), I remember they picked up on a planetary atmosphere of a hot gas giant (the easy-to-find kind of planet), identifying one atmospheric gas by spectroscopy.

The "bad" news was that that gas was nickel. - ¡Ouch! (^{hurt me} / _{more pain}) 06:27, 22 July 2014 (UTC)

Jupiter-sized F-bomb inside — deploy at your own risk, esp. on hand-held devices!
The following discussion has been closed. Please do not modify it.
My Google-fu is lacking again. While it seems to confirm that 51 Pegasi is the planet in question, Amazon keeps offering exoplanets (including delivery — are you fucking kidding me???) on the same page! - ¡Ouch! (hurt me / more pain) 06:27, 22 July 2014 (UTC) Too tangential. Hatted — the more important bit is still outside. - ¡Ouch! (hurt me / more pain) 13:17, 22 July 2014 (UTC)

Part 2 of the question is expressed as a condition "if we can" rather than "can we?". Supposing that we can, and do, detect a WOE (wet orange exoplanet), these sobering expositions may cause SETI devotees to restrain their celebrations.

• Inferences from the prehistorical terrestrial biosphere only make sense if taken in full. So a WOE is a Waste Of Expectation unless it lies within Goldilock's orbital zone.
• The status of Drake's equation for the number N of civilizations in our galaxy who might have radio communication

$N=R_{\ast }\cdot f_{p}\cdot n_{e}\cdot f_{\ell }\cdot f_{i}\cdot f_{c}\cdot L$

as far as we know is still

$0=$ ∏ wild guesses

The WOE gives a little magnitude to the factor f_l (planets that actually develop life) but does nothing to f_i (life that develops intelligence).

• Anthropocentric loyalty requires us to shun contact with WOEs at distances 0 to 4 and >10 billion light-years which are Waste Of Energy distances, due to the alien intelligence not having had time to evolve yet or having had enough time to evolve, make guns and blow themselves up before Earth missionaries arrive. 84.209.89.214 (talk) 15:47, 19 July 2014 (UTC)

Check out Blood falls from the Taylor Glacier. Id. be inclined to say that if we can see it now, it was probably more widespread earlier. --DHeyward (talk) 07:38, 21 July 2014 (UTC)

Yep, good find. My ego and superego tend to agree. :-) StuRat (talk) 15:38, 23 July 2014 (UTC)

"Eupleridae", meaning

I want to know what that word means. It doesn't say. 174.22.238.66 (talk) 07:56, 18 July 2014 (UTC)

Eupleridae means a family of carnivorans endemic to Madagascar. If you are asking about the etymology, I suggest you visit the Language Desk--Shantavira|^{feed me} 12:07, 18 July 2014 (UTC)

Google scholar has references about Eupleridae and you may read the Wikipedia article. Eupleridae is also an entry in Wikispecies and is a family of carnivorans endemic to Madagascar and comprising 10 known living species in seven genera. 84.209.89.214 (talk) 12:10, 18 July 2014 (UTC)

(edit conflict) Well, I'd say that the name is pretty transparently from Greek εὖ ("well") and πλήρης ("full" or "filled up"). It's based on Eupleres, the genus name of the falanouc, which is just the two Greek words stuck together. I'm not, however, finding any indication of why the falanouc was considered "well filled" by some taxonomist (maybe he saw a particulary fat one?). Perhaps someone here can turn up the scientific paper in which the species was originally described. Deor (talk) 12:09, 18 July 2014 (UTC)

Whoah, wrong track! See wikt:eu- - the first part generally means "true" in taxonomies, as opposed to say "pseudo". To begin with, here's a reference to the creation of the name from Eupleres in 2005.^[1] Hmmm, except actually the word "Eupleridae" at least (no idea if it's a similar grouping) apparently dates to 1850. The name Eupleres was nonetheless first (as you'd expect) from Doyère, 1835.^[2] That's Louis Michel Français Doyère. From [3] I came to [4] which at least might be the actual source text, but in classic early 1800s style I'm not finding table of contents and it's all in... French. At this point I may take a break in hope that beneficent fairy folk will stop by and wave a magic healing wand at it to make it something other than... French. :) Wnt (talk) 12:57, 18 July 2014 (UTC)

In French books, tables of contents most often appear at the end, Wnt (at least nowadays; I'm not sure about the early 19th century). In this instance, there's a "Table Méthodique" back there, but I'm not seeing any mention of Eupleres in it, nor does the name seem to be mentioned in the book's section on viverrids (p. 183 ff.), where one might expect to find it. In any case, that book's just an overview of mammalian systematics that lacks any etymological information at all, from what I can see. The initial description of Eupleres must lie elsewhere. Deor (talk) 14:45, 18 July 2014 (UTC)

According to eol.org, the original description is in Doyère, P. 1835. Description d'un nouveau genre de mammifières carnassiers. Bulletin de la Société des Sciences Naturelles, 3: 45. That doesn't appear to be online. However, there is also myetymology.com, which claims (without sources) that the word is from eu (no meaning given) and pleres meaning "replete, or covered over; by analogy, complete". So Eupleres might mean 'completely covered'. I found some fairly convincing confirmation of this on Google Books in The American Journal of Science and Arts (1836), which contains this on p.192: "A new genus of Mammalia has been found ... which M. Doyère ... proposes to call Eupleres ... the sole of the foot being the only part free from hair." --Heron (talk) 21:20, 18 July 2014 (UTC)

I corrected a spelling in your post for clarity, Heron. The website says pleres, not pleures, referring to the same Greek word I cited above. (Pleur- would have something to do with the flanks or the ribs.) Deor (talk) 22:54, 18 July 2014 (UTC)

You're quite right, Deor. I didn't mean to disagree with you; it was just a typo. My fingers decided to auto-correct the unfamiliar pler- to the more familiar pleur-. --Heron (talk) 11:21, 19 July 2014 (UTC)

Good job, Heron! And no less than I deserved for suggesting someone else was on the wrong track without completing my own. Deor was actually not far off the mark; "completely covered" with hair then. If there's one thing I ought to know from biology it's that there are no laws. Wnt (talk) 21:42, 18 July 2014 (UTC)

Yes, Wnt, the only law is that the names have to be unique within a kingdom; otherwise, they are at the whim of the discoverer. Even jokes are allowed. --Heron (talk) 11:40, 19 July 2014 (UTC)

excellent. never would've guessed. thx. 174.22.238.66 (talk) 22:17, 18 July 2014 (UTC)

Help identifying a feather

I recently found this feather in a wooded area of southeastern Pennsylvania. I am unable to identify the bird that it comes from. The feather is a very bright yellow (more so than the photo may suggest) and is about 6 inches long. I am not aware of any yellow birds in the area that are large enough to have such a feather. (Though the bird may not appear as yellow as some parts of the feather itself, because it is the underside that is the yellowest, and the presumably more exposed top side has more brown.) Can anyone help identify this? Thank you. 108.52.245.122 (talk) 12:03, 18 July 2014 (UTC)

Very speculative, but note yellow-shafted Northern flicker. Wnt (talk) 13:06, 18 July 2014 (UTC)

I think you might be right. They live in this area, they are about the right size, and a Google images search finds plenty of pictures of the undersides of their wings which look bright yellow. Thanks. 108.52.245.122 (talk) 14:43, 18 July 2014 (UTC)

Disabling MANPADS

Since some countries cannot keep track of all their MANPADS (MAN Portable Air Defense Systems, i.e. Stinger missiles), I am wondering if they could be made with an expiration date, much like landmines. However, since some will no doubt be stored along with other equipment or munitions, it would not be a good idea to simply detonate the warhead when the expiration date arrives. So I'm wondering if there is some chemical reaction that would render the explosive part of the warhead inert without causing an explosion or starting a fire. Yes, I know, there is a huge amount of energy stored in the warhead, but to me chemistry is mostly black magic, so maybe there is a way to do this. — Preceding unsigned comment added by 50.43.11.252 (talk) 16:13, 18 July 2014 (UTC)

Another approach would be to make the electronics fail after some period of time. A timer could go off after the designated time period, and detonate a micro-charge that would be just enough to burn through some wires or critical electronic components. Of course, the terrorists might be able to repair this or remove the charge before it detonates, if they are sophisticated enough. Using components that just naturally fail with age is another approach, and would be more difficult to prevent or repair, but there the timing would be less exact. In any case, the explosives and fuel could still be removed and used for some nefarious purpose, but probably won't kill as many people as if a plane is shot down.

I believe there is a great need for this, for example in Syria, where any weapons given to the rebels may well end up being used against civilians. StuRat (talk) 16:24, 18 July 2014 (UTC)

When components fail, it's not all that hard to simply replace them with newer (and more reliable) ones. A better (if expensive) solution would be to equip civilian aircraft with infrared jammers (what the hell, no article?!) to prevent the missile from guiding properly. 24.5.122.13 (talk) 19:57, 19 July 2014 (UTC)

Terrorists aren't likely to have the spare parts and the knowledge to replace damaged components. Or, for those who do have those things, they could probably build their own surface-to-air missiles anyway. StuRat (talk) 15:49, 23 July 2014 (UTC)

These missiles are made to take down military planes. I am therefore more than a little skeptical about the claim you could harden civilian planes to resist anything but the most utterly obsolete weapons. Wnt (talk) 21:00, 19 July 2014 (UTC)

We have an article infrared countermeasure which mentions Israel is attempting to develop a laser based system for civilian aircraft to help defend against MANPADs which is what the question was about. MANPADs are of course mostly a threat on take off/landing and not when overflying, Nil Einne (talk) 21:12, 19 July 2014 (UTC)

Given that ALL aircraft have to take off and land somewhere, and that many civilian airports are both extremely busy in terms of traffic and inadequately guarded, a threat to civilian aircraft at takeoff and landing is definitely to be taken seriously. What if, for example, terrorists from Al-Qaida stake out the departure paths from several major civilian airports (JFK, LAX, Chicago O'Hare, Sea-Tac, etc.) and use Stinger missiles (plentiful from old Afghan stocks) to simultaneously shoot down several jumbo jets right after takeoff?! 24.5.122.13 (talk) 23:03, 20 July 2014 (UTC)

Maybe, but the fact remains the evidence is that those who are looking in to this seem to be those who believe there is an active treat. Not everyone else. It could be that the possible cost is seen as not worth it cconsidering the possible risk and the many other likely avenues of attack compared to the alternatives to deal with such risks particular if the systems may post their own risks (see e.g. Flight Guard and perhaps Civil Aircraft Missile Protection System). The RD is not the place to speculate on what should happen. Nil Einne (talk) 13:14, 22 July 2014 (UTC)

The fact remains that there IS an active threat (as shown, e.g., by the 2003 Baghdad DHL shootdown incident), and that the "everyone else" who refuse to believe this or to act upon it are WILLFULLY BLIND to this fact. Enough said! 24.5.122.13 (talk) 00:13, 23 July 2014 (UTC)

No chemical solution for this problem?

Firstly, stinger missiles are only one model of MANPAD. There are others - see our article at man-portable air-defense systems. The article includes a brief section on countermeasures. You may find the links there to be useful. I don't see a "chemical" solution to the problem to be useful, but there may or may not be some sort of "component" solution, e.g. using hard-to-replace batteries. Of course, circumventing such a "solution" depends on the expertise of the insurgents. It reminds me of the minds put to use in bypassing Digital_rights_management, and the difficulty in implementing technologies which can't be bypassed. 110.149.148.134 (talk) 06:57, 21 July 2014 (UTC)

Identify a plant

Can anybody identify this plant, which is next to the hothouse in the Walled Kitchen Garden at Clumber Park? It is probably an exotic: the same bed contains specimens of Paulownia tomentosa and Echium wildpretii. I asked one of the gardeners (in another part of the garden, so it wasn't in sight at the time) and she thought it might be Tetrataxis, but she wasn't sure, and I haven't found a picture of that anywhere, so I don't know if that identification is even plausible.

Unknown plant

--ColinFine (talk) 16:16, 18 July 2014 (UTC)

A picture of Tetrataxis salicifolia which is listed as a critically endangered species shows a different leaf shape. 84.209.89.214 (talk) 17:16, 18 July 2014 (UTC)

I can't tell from the photo if the leaf margins and veination are right, but it reminds me of castor oil plant, see e.g. picture here [5]. Also I can't tell the context/ situation of the plant from the photo. Not sure why you think it's exotic, but the way it's poking out of the other hedge makes it seem like a weed to me... SemanticMantis (talk) 19:33, 18 July 2014 (UTC)

And in case of mispronunciation/transcription/slip-of-the-tongue errors, "Tetrataxis" could be confused for "Tetrapanax" (verbally, not botanically). See e.g. pictures at Tetrapanax papyrifer. It has a fairly similar leaf to your specimen, but I'm not sure that it would survive over winter in that location, even in a walled garden. It does apparently survuve in British Columbia, though... [6] SemanticMantis (talk) 20:30, 18 July 2014 (UTC)

Tetrapanax it is. Thank you, SemanticMantis. I actually thought she had said "Tetrapaxis" with a 'p', but I couldn't find that, and concluded it must have been "Tetrataxis". I actually thought it looked araliaceous, but didn't think of trying to look it up in Araliaceae. --ColinFine (talk) 23:23, 18 July 2014 (UTC)

thrombosis or sclerosis in the coronary veins

Can it be thrombosis or sclerosis in the coronary veins (usually they are only in the coronary artries)מוטיבציה (talk) 18:23, 18 July 2014 (UTC)

Yes, coronary venous thrombosis exists.[7] Red Act (talk) 18:34, 18 July 2014 (UTC)

Thank you מוטיבציה (talk) 01:05, 21 July 2014 (UTC)

"Do that thing with your eyes"

In Invasion of the Body Snatchers (1978 version), about 20 minutes in, Donald Sutherland asks Brooke Adams (actress) to "Do that thing with your eyes". She then wiggles the pupils back and forth rapidly. I can do the same thing. So:

1) What's this ability called ? It's similar to a saccade, but that's normally involuntary, and moves in all directions, not just horizontally.

2) How common is this ability ? StuRat (talk) 20:44, 18 July 2014 (UTC)

+1 here. I've seen others do it also; it's instinctive enough that I feel like it has to have something to do with the basic biology. Blatant speculation: It feels like there's some relationship with focusing nearer, crossing the eyes... I'm thinking somehow it's a set of saccades after a target that disagrees with itself due to the urge to cross the eyes; I think that because the disagreement is somehow tied to eye-crossing is why it is only left to right. Wnt (talk) 21:40, 18 July 2014 (UTC)

Yes, I find it much easier to do it when focusing both eyes on a finger placed just in front of my nose. StuRat (talk) 22:52, 18 July 2014 (UTC)

Over 30 years ago, 8% of "college age populations" could produce "voluntary nystagmus" according to Zahn JR (July 1978). "Incidence and characteristics of voluntary nystagmus" (J. Neurol. Neurosurg. Psychiatr. 41 (7): 617–23.) You can also find "voluntary flutter" or "voluntary ocular flutter". I guess you'd have to add "horizontal" to specify exactly what you're describing. (I can't do it, by the way, unless I'm looking straight out a train window). ---Sluzzelin talk 21:49, 18 July 2014 (UTC)

My optician used the term "voluntary nystagmus" when I inquired about it.--Gilderien Chat|List of good deeds 23:09, 18 July 2014 (UTC)