Wikipedia:Reference desk/Archives/Science/2013 September 7

= September 7 =

Largest volcano on earth discovered?
Re: Tamu Massif, as mentioned on the main page - how exactly could scientists not have known for decades that something of that size was down there? I mean, finding a 260,000 square kilometre volcano... it's not like finding a set of car keys, is it? Did they just miss it? I'm confused. --46.208.75.245 (talk) 00:26, 7 September 2013 (UTC)


 * It doesn't have an obvious caldera, and it's over a mile down, and 145 million years old. They determined it is just one volcano by studying the lava flows, which all originate from one center.  That's not an easy feat given the physical and time depth and erosion and deformation over that period. μηδείς (talk) 00:31, 7 September 2013 (UTC)


 * For decades they had assumed that Tamu Massif was formed from several volcanoes that had grown together. Think of the Hawaiian islands for comparison.  Each island is a separate eruption center, and hence those islands were formed from a group of related volcanoes.  The surprise with Tamu Massif is that the entire feature now appears to have been created by a single volcano.  Dragons flight (talk) 01:24, 7 September 2013 (UTC)

Light emitting black hole
As we know black hole emit a Hawking radiation and the smaller the black hole, the more powerful the radiation. Is it possible that there is a sweet spot for a black hole size so its emitted radiation is in the visible light spectrum not just in usual gamma ray? 140.0.229.26 (talk) 01:07, 7 September 2013 (UTC)


 * As explained in the article, the temperature of black hole Hawking radiation is inversely proportional to mass. To get a sun-like spectrum (e.g. 5000 K), you'd need a mass of about 2 kg (about twice the mass of Ceres), which implies a event horizon radius of about 30 nanometers.  Dragons flight (talk) 01:34, 7 September 2013 (UTC)


 * Note the evaporation rate according to the article is 3.562 x 1032 W / M2 (with M in kg); for the mass given above it should be 8.9 x 10-7 W. I think that if magnified under a microscope about 4000x it should seem like an incandescent bulb in brightness, but with an arc just (under the scope, appearing to be) 0.12 mm in size the filament would seem a little thin and bright by comparison. Wnt (talk) 06:17, 7 September 2013 (UTC)

Yellow–brown stains on marble
Is this true? Thanks, 84.109.248.221 (talk) 17:08, 7 September 2013 (UTC)
 * It certainly looks like it. You can see similar stains on the arms - but not on other protruding parts. This source says that oils leave a dark brown stain on marble - and that's what we're seeing here.  It's hard to imagine any other source of oil being selectively deposited there. The image at right here shows similar staining on places where people's hands are most likely have reached. SteveBaker (talk) 20:06, 7 September 2013 (UTC)
 * Also, this blog shows a photograph of a bronze sculpture where the breasts were worn shiney bright while the rest was a more typical tarnish. SteveBaker (talk) 20:16, 7 September 2013 (UTC)


 * I'm not saying it's not true, but there is in fact at least one imaginable other source of oil being selectively deposited there: A combination of linseed oil and beeswax that used to be "applied as a polish, permeating the structure and, over time, forming an oxalate skin which invariably discolours the crystalline structure. Oxalate skins are complex and almost impossible to remove." ("Cleaning Marble", Victoria and Albert Museum). ---Sluzzelin talk  20:28, 7 September 2013 (UTC)
 * OK - but why would someone use the wrong kind of polish for cleaning marble...and do it selectively only on that specific part of the statue - and not at all on the male statue standing right next to it? I have presented evidence that other statues have their boobs groped on a regular and selective basis - how could that not be the case here? SteveBaker (talk) 00:15, 8 September 2013 (UTC)
 * Apparently, some owners or their employees did use to apply this kind of polish, maybe out of ignorance, I don't know. Yeah, I have no good explanation for the selectiveness, except that those surfaces might have looked more smudged, or that some caretakers perhaps polished these surfaces more vigourously, but I'll gladly concede that point. I just wanted to make sure no one came to believe that yellow stains on marble in general always came from human oils. ---Sluzzelin talk  19:37, 9 September 2013 (UTC)
 * See also this photo of the bronze boar outside the Deutsches Jagd- und Fischereimuseum in Munich. Note which parts are highly polished... Tevildo (talk) 00:14, 8 September 2013 (UTC)

Kidney transplant location
My grandmother had a kidney transplant (in the UK) around 1990. Mum says that her functional kidney is positioned over her stomach, at the front. Could this be correct or mum full of crap, as usual? --89.241.237.164 (talk) 18:09, 7 September 2013 (UTC)
 * See Kidney transplantation. According to the article, the new kidney is usually positioned in the iliac fossa (just above the top of your leg).  It wouldn't be near the actual _stomach_ (which is much further up your abdominal cavity), but using "stomach" as a general term for "abdomen", your mum is approximately right.  Mothers tend to be. Tevildo (talk) 19:22, 7 September 2013 (UTC)


 * A quick Google confirms that this is the case, although it may possibly have been different in 1990 (?). Alansplodge (talk) 14:28, 8 September 2013 (UTC)
 * My mother was frequently wrong before 1990... MChesterMC (talk) 08:31, 9 September 2013 (UTC)

Legality of spectrum analyzer use?
Is there any legal challenges to the use of a spectrum analyzer in the US ..? Electron9 (talk) 20:53, 7 September 2013 (UTC)
 * Are you sure you don't mean a radio scanner ? -- Jheald (talk) 21:15, 7 September 2013 (UTC)
 * A simple spectrum analyzer should be OK. There was a ban on scanners that could receive the analogue mobile phone system after some politician's phone call was publicized. If your spectrum analyzer can decode a signal into audio it may be subject to the same ban, and therefore have frequencies blocked. Usually equipment is made for an international market, so there will be a simple way to make it into a device suitable for a different country. Graeme Bartlett (talk) 21:48, 7 September 2013 (UTC)
 * Among the relevant places to check are the website of the Federal Communications Commission - http://FCC.gov - and Title 47 of the Code of Federal Regulations, e.g. 47 C.F.R. §18, regulating equipment for industrial and scientific use. I am not aware of any spectrum analyzer that requires operator licensing or regulation, (e.g., you do not need a HAM license to operate a radio receiver with spectrum analyzer attached), because most of them do not transmit any meaningful quantity of signal or interference.  On perusal of http://justice.gov, I found numerous court case dockets with the search term "spectrum analyzer," but almost all of these referred to allegations of intellectual property infringement; a few legal battles involved import and sale of spectrum analyzers and other equipment in violation of tax and import regulations.  Nimur (talk) 21:55, 7 September 2013 (UTC)


 * I saw this comment at slashdot:
 * ''strong cryptography on mobile phones (Score:1)
 * ''by fustakrakich (1673220) writes:


 * ''Shit, the FBI and NSA, et al put the kibosh on that before the damn things hit the streets. Instead they made a law that prohibits the sale of full spectrum scanners to the public, like was supposed to make them secure...




 * ''     Re: (Score:1)
 * ''     by Anonymous Coward writes:
 * ''     by Anonymous Coward writes:


 * ''     Instead they made a law that prohibits the sale of full spectrum scanners to the public


 * ''     Is that to outlaw bug sweepers and counterintelligence in general?


 * This in combination with TI:s sub 1 GHz spectrum analyzer MSP430 that covers 300-348, 383-464, 779-928 MHz made me wonder if there's something hiding in the open of the spectrum somehow. Electron9 (talk) 00:09, 8 September 2013 (UTC)


 * Some electronics test equipment is ITAR-restricted. That doesn't mean it's illegal; it just means that it's restricted.  Chances are very high that if you knew what to do with such equipment, you'd already be on your way to being well-paid and securely employed by a company or organization with access to that type of equipment.  Nimur (talk) 00:49, 8 September 2013 (UTC)


 * You'd have gotten a better answer at Humanities - off the top of my head, the problem was ECPA, which at the time stood out to me as the first case of banning a radio receiver in certain frequencies like in the Soviet Union. My impression is that the de facto outcome is that people import these products from other countries (I think it was Britain) instead of making them here.  In theory I think they might be subject to be stopped at Customs, or perhaps damaged by a meteorite impact during shipping... Wnt (talk) 05:26, 8 September 2013 (UTC)