Wikipedia:Reference desk/Archives/Science/2011 October 21

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October 21

Spider ID

Heteropoda maxima

Could someone please identify the huge spider I've seen today on the outside of my window? (Sorry, no picture, but I didn't have time to get my camera out -- the critter was letting itself down too fast.) Description is as follows:

-It is the biggest spider I've ever seen so far other than in a zoo exhibit -- my rough estimate of its body length (without legs) is 1 to 1.5 inches, maybe even bigger; legs are very long, at least 3 to 4 inches;
-Abdomen is almost perfectly spherical, not oblong as in most common (non-venomous) spiders, and is of proportionate size to the rest of the body (not oversized as in many species of the widow family);
-The critter is brightly colored: body is mottled red/black/white, legs are striped red/white (this in particular has me concerned: in nature, the general rule is that bright colors = venomous);
-I did NOT notice any kind of hourglass, but CANNOT be certain of its absence.

In any case, whatever this critter might be, I'm certain that it's definitely NOT a brown recluse, nor any of the most common widow spiders (those tend to have oversized abdomens and dark coloration). However, I still don't know if it's something harmless (some kind of mutant house spider or something like that), or some exotic and venomous critter like a redback widow or even an Australian funnel spider (this last possibility is very unlikely where I live, but cannot be ruled out entirely). So I'd really like to know what it is, and especially whether it's venomous. Pictures of similar-looking species would be great, too -- if there are several different look-alike species, I could probably identify it from the photos. Thanks in advance! 67.169.177.176 (talk) 06:30, 21 October 2011 (UTC)

What part of the world are you in? HiLo48 (talk) 07:26, 21 October 2011 (UTC)

Need more information than that. And yes, the most important: where are you from?

Did it resemble any common spiders you know of? Huntsman spiders, tarantulas, Araneus, Nephila, Argiope, jumping spiders, bolas spiders, etc.? What other characteristics can you describe? Anything would help. How large was its eyes, how fast was it, how did it walk, was it crawling or descending by a thread, did it have a web and what is it shaped like if it does, etc.

However, wild guess: it's a huntsman spider, possibly from the genus Heteropoda which vaguely resemble your descriptions and are quite huge.-- Obsidi♠n Soul 07:37, 21 October 2011 (UTC)

Another possibility may be a species of Wolf spider; there are some pictures there which may match his discription. Heteropoda seem restricted to Southeast Asia; the OP has not stated where they are from, but if they aren't from there the wide ranging Wolf spiders may be a better match. And some of them can get pretty large. --Jayron32 11:59, 21 October 2011 (UTC)

Heteropoda is a pantropical genus as are other huntsman spiders (family Sparassidae). Hence my earlier mistake at assuming the spider in the picture, the species H. maxima (which is the largest spider by leg span) were Australian, nevertheless there are members of Heteropoda in Australia that resemble the Laotian H. maxima in the picture and are also very large. This is, of course, assuming that the OP is Australian (given the time of his post). If the OP is not, however, there are more widespread species like Heteropoda venatoria or the Hollywood-famous but relatively harmless Delena cancerides. But yeah, wolf spiders are another possibility with an even wider global distribution.-- Obsidi♠n Soul 12:35, 21 October 2011 (UTC)

The OP geolocates to California. Mikenorton (talk) 12:44, 21 October 2011 (UTC)

Here is a link [1] to pictures of spiders seen commonly around where people live (synanthropic if you prefer) in California. Mikenorton (talk) 12:51, 21 October 2011 (UTC)

And here's another. Also spiders from California.-- Obsidi♠n Soul 13:25, 21 October 2011 (UTC)

Given the geolocation to San Jose, my guess is a California Orb Spider, which grows to the right size, lives in that area, and has basically the right coloration. Unfortunately we don't have a picture of one, but here is a link to a picture on Flickr. Looie496 (talk) 21:32, 21 October 2011 (UTC)

OK, more info: the spider was descending by a thread at a rather rapid rate, so I did not get a good look at it (I estimate only 5-7 seconds between when I first saw it about 1/3 of the way down the pane and when it reached the lower frame and went out of sight). Therefore I don't know what its eyes looked like. Also, I didn't notice any web on or above the window, although there do seem to be some irregular spider threads above the window frame. And yes, I live in California at this time. That said, after examining the photos, I can tell you that it was definitely not a California orb spider -- the coloration is all wrong (the one I'm describing has more of a stippled pattern of very small spots), and so is the size of the abdomen (orb spiders in general have oversized abdomens, while my critter has a more proportionate one). In fact, I didn't see any exact matches, but the Heteropoda seems to be the closest match as far as coloration (darned if I know where it blew in from, though...) Thanks for the photos! 67.169.177.176 (talk) 02:44, 22 October 2011 (UTC)

On second thought, the coloration also seems to match the description of the Hogna helluo wolf spider. (Not that the difference is all that important -- neither of these is aggressive or especially venomous.) Once again, thanks for the info! 67.169.177.176 (talk) 03:42, 22 October 2011 (UTC)

They are quite similar, one way to tell the difference between the two is the way their legs are held in relation to the body. In huntsman spiders the legs curve forward and inward, similar to crab spiders, and are very long. In wolf spiders the legs are spread straight out away from the body.-- Obsidi♠n Soul 13:40, 23 October 2011 (UTC)

AFAIR this spider's legs did not curve forward and inward, so it's more likely to have been a wolf spider (most likely H. helluo, maybe another Hogna species). Thanks! 67.169.177.176 (talk) 20:29, 23 October 2011 (UTC)

does an equivalent of a SOFAR channel in the sun exist?

Does one exist? I imagine there's a strong density gradient, and at the frequencies of light involved, wouldn't there be a portion of the sun that acted as a waveguide for certain frequencies? I do remember that light often takes thousands of years to escape the sun... elle _{vécut heureuse} ^{à jamais} (be free) 13:10, 21 October 2011 (UTC)

Sound propagates through a medium, light doesn't. I can't see how a SOFAR channel for light would work. The sun is essentially opaque beneath the photosphere. In the photosphere, light at certain frequencies is absorbed, creating black lines in the sun's spectrum (see Fraunhofer lines). --Tango (talk) 13:41, 22 October 2011 (UTC)

Light propagates through different indexes of refraction. That's how fiber-optic cables work, I thought? elle _{vécut heureuse} ^{à jamais} (be free) 05:05, 24 October 2011 (UTC)

Radio waves? ~AH1 ^(discuss!) 15:10, 24 October 2011 (UTC)

Compatibility between GPS and Galileo

Will GPS devices be able to use the Galileo network? Oct21 (talk) 13:47, 21 October 2011 (UTC)

Somewhere between highly and completely unlikely. Current GPS devices have no expectation of Galileo, are not listening out for it and in any event do not talk its language. Later we might see devices capable of talking both to Galileo and the American GPS satellite network. And indeed, maybe the Russian network. --Tagishsimon (talk) 14:12, 21 October 2011 (UTC)

There are already commercially-available devices (both for civilian use and for military and scientific applications) which are capable of receiving and interpreting both GPS and GLONASS (Russian) signals. Heck, our article on GLONASS has pictures of more than one. While the Galileo constellation isn't yet active (initial service is anticipated for 2014), the specifications for the system are widely available to hardware manufacturers, and Galileo compatibility can be built in to systems in anticipation of the network's activation. Here's just one example from all the way back in 2007 of a receiver chip that can interpret GPS, GLONASS, and Galileo signals. Here's a manufacturer announcing products that support all of GPS, GLONASS, Galileo, and the Chinese Compass system. TenOfAllTrades(talk) 14:28, 21 October 2011 (UTC)

(ec)Existing ones probably not. Galileo operates on a different frequency, and probably uses different protocols. However, dual-band receivers are expected to become available essentially immediately. Google Scholar has papers on approaches to mass-market dual-band receivers here, dating back to 2008. As GPS is upgraded, it will also be modified to allow interaction with Galileo, to support applications that use satellites from different systems for improved precision (or at least that is the unsourced claim at Galileo_(satellite_navigation)#GPS_and_Galileo. --Stephan Schulz (talk) 14:42, 21 October 2011 (UTC)

A related question: can you calculate your location from a mix of satellites? For example, could you get a position fix when all you can see is a pair of GPS satellites, a GLONASS satellite, and a Galileo satellite? --Carnildo (talk) 00:06, 22 October 2011 (UTC)

Yes. Each satellite is a clock, and it sends its signal by radio. Theoretically, a device using more than one satellite positioning network will be far more accurate than a device using only one. Dualus (talk) 08:03, 22 October 2011 (UTC)

Technically, two satellites are insufficient to get a fix, but this might be possible if some assumptions are made based on previous position and altitude. Dbfirs 14:58, 23 October 2011 (UTC)

Crohn's disease.

Someone keeps changing Crohn's disease page to an autoimmune disease when it is an infection and inflammation, with a phase 2 immune disorder, this is not autoimmune. It's completely irresponsible of this person to do this and lives are in danger for putting such horribly wrong info out there. — Preceding unsigned comment added by 81.164.180.114 (talk) 14:16, 21 October 2011 (UTC)

As stated you need to provide review articles. A few already support the fact that it is seen as an autoimmune disease.Doc James (talk · contribs · email) 14:39, 21 October 2011 (UTC)

Besides that we strongly discourage people from relying on wikipedia for medical advice, and for several good reasons. To be frank, there's something seriously wrong outside wikipedia if someone's life is in danger because of something on wikipedia, even more if it is supported by multiple review articles. If someone is relying on wikipedia for medical advice, there's no guarantee they're not going to read it when it says 'Crohn's disease is a harmless disease. The medical consensus is it's not worth worrying about, and a colonoscopy is a waste of time, although some doctors encourage them for financial reasons. People with it or suspected of having it should drink plenty of milk and smoke as it may reduce symptoms.' due to vandalism. Nil Einne (talk) 15:56, 21 October 2011 (UTC)

The right place to discuss contentious changes to the article is at Talk:Crohn's disease. --Sean 18:01, 24 October 2011 (UTC)

Sky box uk

Why do we need two coaxes from dish to box?--CubicleMonkey (talk) 14:49, 21 October 2011 (UTC)

I assume you mean a Sky+ box. They have two cables so they can receive two channels at once. That is necessary if you want to record one channel while watching another, or record two channels at once. --Tango (talk) 17:18, 21 October 2011 (UTC)

... and, of course, a Sky box works perfectly with just one co-ax. It just won't do the "+" functions mentioned by Tango above. Dbfirs 07:16, 23 October 2011 (UTC)

Why human body gets heat up and cools in fever...?

Why human body gets heat up and cools in fever...? is there any thermodynamics behind this.? — Preceding unsigned comment added by 220.225.96.217 (talk) 16:15, 21 October 2011 (UTC)

Have you read our fever article? The body releases chemicals that effectively change the body's 'thermostat', raising the temperature. There are reasons to believe that this helps the body fight infection, but quite how that works or whether fever is generally a good thing remain controversial. Mikenorton (talk) 16:28, 21 October 2011 (UTC)

Some good reading might also be on the articles titled Homeostasis and Thermoregulation. Of course, thermodynamics is involved, thermodynamics is an inescapable fundemental process of the universe. There is thermodynamics involved continuously in all of existance. --Jayron32 17:00, 21 October 2011 (UTC)

How Phone Companies Restrict Access To Paying Customers

While keeping the technical depth to as minimal a degree as possible, I would like to know how telephone companies ensure that only phones connected to paying accounts are able to access and use their network to make calls. I'm interested in the cell phone network as well as the PSTN. 20.137.18.53 (talk) 17:10, 21 October 2011 (UTC)

Each cell phone has a ID number encoded into it, called either a mobile equipment identifier or electronic serial number. When a cell makes contact with a cell phone, the phone identifies itself using its ID number. The transmission is encrypted so that anybody who might be listening is unable to decode the number. The cell phone also transmits its phone number, so that the cell system can look up its account information. Looie496 (talk) 17:30, 21 October 2011 (UTC)

In addition, mobile telephony technology relies on public key cryptography to ensure that the software remains secure; and it relies on carefully regulated export control policy (among other things, ITAR) to make sure that the electronics and radio hardware remain uncompromised. In other words: for you to spoof on a modern telephone network, you would need to break secure software algorithms (a mathematically-infeasible task with today's technology); and you would also need access to specific types of radio and electronics hardware that you can not buy at any ordinary store. I have often wondered whether there exists a black-market for mobile telephony hardware; but I believe the answer is "not currently, in any great degree," because otherwise, I would expect to see lots of spammy services advertising ways to get free mobile-telephone service. (Contrast this to satellite television: we do see spammy advertisements for ways to get free access to subscription-satellite-television-channels; satellite communication technology similarly relied on careful control of required software and hardware to ensure the system remained "un-cracked," but evidently there was a leak). Nimur (talk) 17:56, 21 October 2011 (UTC)

Wired phones are simpler: the phone company has a pair of wires running from the switchboard to your house, which then branch out to all the phones in your house. If you haven't paid for phone service, the switchboard computer reject any non-emergency calls from that pair of wires. --Carnildo (talk) 00:21, 22 October 2011 (UTC)

What is this please?

[2] ? Kittybrewster ☎ 21:53, 21 October 2011 (UTC)

I have read some strange questions posted here but what have you been smoking? --Aspro (talk) 22:00, 21 October 2011 (UTC)

What has a.n.other been smoking? Kittybrewster ☎ 22:01, 21 October 2011 (UTC)

At this end, its a rather nice French Château --Aspro (talk) 22:08, 21 October 2011 (UTC)

Maybe that green plant material you're trying to have identified? Clarityfiend (talk) 22:04, 21 October 2011 (UTC)

It appears to be a collection of short pieces of branches and possibly flowers, strewn on a white surface. I do not know more specifically. (I would have liked to know beforehand that the JPEG image would measure 4,000 by 3,000 pixels.)

—Wavelength (talk) 22:06, 21 October 2011 (UTC)

Apologies. Kittybrewster ☎ 22:16, 21 October 2011 (UTC)

I'd need to see a better picture (or sniff it) to be sure but it looks to me like a former acquaintance of mine. We aren't supposed to give legal advice, so I won't... AndyTheGrump (talk) 22:07, 21 October 2011 (UTC)

How do I send an electronic smell? Kittybrewster ☎ 22:29, 21 October 2011 (UTC)

Well, when I turned on my PC monitor this morning, there was a nasty smell of overheating electronics (I'm now using a spare monitor). But you're right, it is difficult to convey an aroma - even as pungent as the one concerned - via the internet. Suffice to say that when you've been introduced to Mary Jane, you'll know when she's around... AndyTheGrump (talk) 22:52, 21 October 2011 (UTC)

Yeah, same thought. Looie496 (talk) 22:09, 21 October 2011 (UTC)

Kine with not too much shwag. μηδείς (talk) 22:13, 21 October 2011 (UTC)

That's all Greek to me. Can you provide a translation? --Aspro (talk) 22:23, 21 October 2011 (UTC)

Thank you. It is doomed. Kittybrewster ☎ 22:15, 21 October 2011 (UTC)

"we're doomed!" I'll tell yah'... we're all doomed! --Aspro (talk) 22:23, 21 October 2011 (UTC)

I understand the best procedure is to incinerate it. Err, perhaps not... AndyTheGrump (talk) 22:17, 21 October 2011 (UTC)

That's not a problem! President Clinton explained that "not inhaling" is simply part of the Presidential candidates' fraternity.--Aspro (talk) 22:26, 21 October 2011 (UTC)

I'm not eligible to join that fraternity.Kittybrewster ☎ 22:31, 21 October 2011 (UTC)

Do you mean you did inhale?--Aspro (talk) 22:34, 21 October 2011 (UTC)

Both Kine (kind) and Shwag are defined at Urban Dictionary. See sense two for my meaning. μηδείς (talk) 22:33, 21 October 2011 (UTC)

I thought "kine" was a Middle English word -- and the sort of thing that would be rather exciting to try to smoke. --Carnildo (talk) 00:26, 22 October 2011 (UTC)

Low quality marijuana, usually very dry, full of stems and seeds and shit you don't want to inhale; Epitome of the phrase "quantity over quality"

what the fuck is this shwag doing in the bowl? shit man we might as well be smoking dirt. Kittybrewster ☎ 22:37, 21 October 2011 (UTC)

Oh Gosh, I did not know WP had such knowledgeable connoisseurs. Thank you, one learns something new every day.--Aspro (talk) 22:41, 21 October 2011 (UTC)

knowledgeable connoisseurs and eclectic linguists too apparently. Da kine is evidently Hawaiian Creole, but 'shwang' 'shwag'? Urban Dictionary defines it, but gives no hint to its etymology. It sounds vaguely Germanic (or possibly Yiddish), but that is pure guesswork. Perhaps I should ask at the language reference desk... AndyTheGrump (talk) 22:59, 21 October 2011 (UTC)

Shwag, no internal "n". μηδείς (talk) 23:51, 21 October 2011 (UTC)

Ooops! Yes, the 'n' was unnnecessary ;-) AndyTheGrump (talk) 23:58, 21 October 2011 (UTC)

I concur, it sure looks like weed. But it's been decades since I inhaled, so I'm not much of an expert anymore. College was a more interesting life than adulthood.Red Act (talk) 04:38, 22 October 2011 (UTC)

Check this sheit out. Dualus (talk) 08:06, 22 October 2011 (UTC)

flowering oregano

Sorry to be a downer, but it looks to me like it could easily be oregano- looks a lot like some mexican oregano that I cook with. I know- it's a lot less fun to talk about... Staecker (talk) 12:09, 22 October 2011 (UTC)

No, there is no question it is Cannabis. You can see the little flowers and the fibrous stem is what hemp fiber is made from. Oregano is just ground leaves. μηδείς (talk) 13:03, 22 October 2011 (UTC)

The oregano you get in the supermarket is just ground leaves, but if you grow it in your garden (I do) there are small flowers much like the ones in the picture.Sjö (talk) 14:18, 22 October 2011 (UTC)

Well, yes, there aren't many flowering plants that don't produce flowers, but the Cannabis flower is very distinct from the oregano more common-type flower with its showy petalled corolla. Cannabis lacks a corolla in the female flower but produces the feathery brown tufts you can see in this highly enlarged photo [3] and which are distinctly visible in the OP's photograph. Oregano also has a smooth stem, while the lengthwise grooves of the hemp stem are clearly visible in the OP's picture. There is no question whatsoever of the identification. μηδείς (talk) 17:14, 22 October 2011 (UTC)