Wikipedia:Reference desk/Archives/Science/2014 July 5

= July 5 =

Name that beetle
Can anybody ID this beetle. I found it in Cambridge Bay on Victoria Island (Canada) so it is obviously an Arctic dweller. It does not appear to be either Upis ceramboides or Cucujidae. While I forgot to measure it I would estimate that it was about 1 cm long. Thanks. CBWeather, Talk, Seal meat for supper? 03:50, 5 July 2014 (UTC)


 * There are a lot of beetles out there. However, it does look like a Harpalus (genus), and several species are recorded from Northwest Territories as shown here. Mikenorton (talk) 09:45, 5 July 2014 (UTC)


 * I was thinking it looked like it could be a species of the genus Eleodes (unfortunately our coverage of this genus is poor, with a particular species at the genus article location, for some reason, but a common search engine image search will turn up many of the variants), but looking at Harpalus, it seems to share the rather distinctive morphology of the lower abdomen found in CB's specimen, so I think Mike is on the right track. Anisodactylus is another possibility.  Certainly it seems to be a member of Carabidae/Harpalinae.  S n o w  talk 10:10, 5 July 2014 (UTC)


 * Thanks. When I posted it I didn't realise just how many different types there were. CBWeather, Talk, Seal meat for supper? 18:39, 5 July 2014 (UTC)
 * If it's any consolation, very good pics, nice focus and detail! SemanticMantis (talk) 16:31, 6 July 2014 (UTC)
 * Thanks but I think that was more luck. First one I found in the house and was able to get it into a plastic tub. CBWeather, Talk, Seal meat for supper? 01:27, 7 July 2014 (UTC)

Keratometers
How accurate are keratometers in diagnosing astigmatism? Can it sometimes think someone with no astigmatism has astigmatism? For example, can dry eyes or even incorrect use of the machine cause this? 90.192.110.77 (talk) 11:44, 5 July 2014 (UTC)
 * See Keratometer, Astigmatism, and Javal's Rule. The keratometer measures the physical dimensions of the cornea, so won't be affected by dryness.  On the other hand, any sort of measuring equipment will give incorrect readings if it's used incorrectly.  If you're worried about your eyesight, you should contact an optician.  If you're worried about the competence of your optician, you should seek a second opinion. Tevildo (talk) 12:08, 5 July 2014 (UTC)

Scheiner disc?
Our article Keratometer (see previous question) refers to "Scheiner's rule" and a "Scheiner disc". Julius, or Cristoph, or some other scientist? There are several references to the device out there in optometric contexts, but something definitive about its history would be a useful addition to the appropriate article. Tevildo (talk) 12:13, 5 July 2014 (UTC)


 * This book gives two possible Scheiners in different chapters, either Christopher or Thomas, with the date given as 1619 in both cases. After checking with more sources, it seems that it was Christoph in his work Oculus, hoc est: fundamentum opticum, published in either 1619 or 1620, according to what shows up in this google book search. Mikenorton (talk) 12:44, 5 July 2014 (UTC)
 * And here's a quote (translated) from that work, describing the principle of the disc. Mikenorton (talk) 13:58, 5 July 2014 (UTC)
 * Thanks very much! This is Scheiner's original text, and this is a useful paper on the subject.  Now, to Scheiner's Rule.  I'm sure (a) it's the same Scheiner, and (b) tracking it down won't be too difficult. Tevildo (talk) 14:31, 5 July 2014 (UTC)
 * OK, "Scheiner's rule" is just "if you can see two images, your eye is out of focus." Now, where's the best place to put this?  Should we have a new article on Scheiner disc, or should information on it go into another optometry article (Autorefractor, perhaps)?  I don't think Christoph Scheiner itself is the _ideal_ location, but it's a possibility.  Tevildo (talk) 10:33, 6 July 2014 (UTC)

Largest research centers in the world
What are the largest --employee-number-wise-- research hubs in the world? Thanks. --Schweinchen (talk) 12:30, 5 July 2014 (UTC)


 * Clarification of your question will help get better answers. Do you mean an organization, or a place, or both? It's an important clarification, because e.g. NASA and the CDC have many many researchers employed, but they are split across many different locations. Even large research universities often have several campuses, e.g. University of Texas and Ohio State University. Also keep in mind that a lot of scientists work at CERN, even though they have "home" institutions at some other place, and may not be technically considered employees. SemanticMantis (talk) 15:35, 5 July 2014 (UTC)


 * Many large research centres are part of military structures. You won't find very good public details about them. HiLo48 (talk) 22:30, 5 July 2014 (UTC)


 * I think that this answers my question. --Schweinchen (talk) 11:16, 6 July 2014 (UTC)
 * National Institute of Informatics is the largest? What is it/how big? (And I looked at our article.) 75.41.109.190 (talk) 13:14, 6 July 2014 (UTC)


 * No, not according to their "methods" page:
 * "Size (S). Number of pages recovered from four engines: Google, Yahoo, Live Search and Exalead. For each engine, results are log-normalised to 1 for the highest value."
 * -- so your link is reporting that NII of Japan has the largest 'size' in terms of number of web pages-- that doesn't have much of anything to do with employment figures. SemanticMantis (talk) 16:30, 6 July 2014 (UTC)

Witches and stakes...
So in the UK, we are old that in "the olden days" witches were burnt at the stake. Has anyone ever found the body of a witch who was burned at the stake? --TammyMoet (talk) 17:57, 5 July 2014 (UTC)
 * Hmm. The physical remains of cremation don't really constitute a "body", so the answer to your question is probably "no".  See Witch trials in the early modern period for our article.  The last person to be burnt as a witch in the UK was Janet Horne in 1727. Tevildo (talk) 18:24, 5 July 2014 (UTC)
 * (ec) I remember hearing on QI (not always the most reliable source) that witches were more likely to be hanged than burned, and List of people executed for witchcraft seems to bear this out, as far as it goes. Burning was more commonly used to punish heresy, and for (non-noble) women convicted of treason (because the male sentence of being hanged, drawn and quartered would have been "unseemly" for women). As for finding the body of a specific victim, I have no idea. AndrewWTaylor (talk) 18:30, 5 July 2014 (UTC)


 * I refer you to Burning of women in England and Witch trials in the early modern period; the latter says "In England, witches were usually hanged before having their bodies burned and their ashes scattered. In Scotland, the witches were usually strangled at the stake before having their bodies burned — though there are several instances where they were burned alive". Alansplodge (talk) 20:02, 5 July 2014 (UTC)


 * The question doesn't necessarily ask whether witches were burned in the UK - it says "in the UK we are told that...". For a general account of witches burned at the stake see Death by burning. Richerman    (talk) 21:49, 5 July 2014 (UTC)


 * In British North America, in the Salem witch trials, those who were convicted (or pleaded guilty) were hanged. (One defendant who refused to plead was pressed to death.)  Robert McClenon (talk) 22:04, 5 July 2014 (UTC)


 * Cremation may involve higher sustained temperatures than mere "burning" over a stack of wood. Is there evidence of any requirement that the fire at a witch burning be continued hot enough and long enough to reduce all bones and teeth to unrecognizable ashes? Isn't it likely that when the condemned was clearly dead they just buried or scattered the bones and teeth? Is there any historical report of the executioners building a new stack of wood, placing the remains on it, and continuing he process after the fire had burned down and perhaps the stake had burned and fallen over??  It would seem possible that someone might have collected and buried bones of some burned witch after the excitement was over and the crowd had gone home. Edison (talk) 02:16, 6 July 2014 (UTC)
 * Thanks for this thought Edison. I actually posted after reading that the Palestinian boy had been burned to death and they had discovered this after an autopsy, which implies that there was an intact body with internal organs. One thought led to another, and that's why I posted the OP. --TammyMoet (talk) 18:43, 6 July 2014 (UTC)


 * It's possible to do post-mortems on even cremated remains, though it takes an expert such as William R. Maples to do it. Even the tiny chunks of bone left over are enough for identification. Matt Deres (talk) 14:39, 7 July 2014 (UTC)
 * Why would we find bodies or bits of bodies? A simple Flame-Freezing Charm would render the flames harmless.  Nyttend (talk) 22:47, 7 July 2014 (UTC)

Rocket launch sequence
In footage I've seen, they first start the rocket engines, then disconnect from the tower, then launch.

1) I wonder why the don't disconnect from the tower first.

2) If they aren't able to successfully disconnect, can they stop the engines, to abort the launch ?

3) Also, once they disconnect, I imagine that reconnecting would be difficult, but not impossible. Is this correct ?

StuRat (talk) 21:21, 5 July 2014 (UTC)


 * The answer to this question will depend on the type of rocket, but that sequence isn't correct for the Saturn V - on that spacecraft, the sequence was Start Engines > Launch > Disconnect Tower. The disconnection sequence was triggered by the movement of the rocket off the pad. This is just speculation, but I imagine that's to reduce the risk of a premature disconnection - if the disconnection signal was electrical rather than mechanical, it might be triggered accidentally.  On the Saturn V (and even more so on the Space Shuttle, with solid-fuel motors), the main engines couldn't be (quickly) shut down once they'd started - in this case, the LES tower motor would be fired to remove the command module from the stack, and the Range Safety Officer would then initiate destruction of the rest of the vehicle.  The Shuttle didn't have such an abort mode, which is why the Challenger disaster resulted in fatalities.  The disconnection was done with guillotines, so it wouldn't be possible to reconnect (and I don't really see why you'd want to). Tevildo (talk) 22:06, 5 July 2014 (UTC)


 * If they disconnect first, then tried to start the engines, but there was a total ignition failure, then they might want to reconnect. StuRat (talk) 03:41, 6 July 2014 (UTC)


 * That's why they start the engines first, then disconnect. (The other reason is that when the rocket is at the launch pad, the tower actually supports its weight -- not the rocket's tail.) 24.5.122.13 (talk) 04:10, 6 July 2014 (UTC)


 * Actually, that's another good point. Disconnecting the tower before starting the engines would introduce the risk of (a) the rocket falling over before the engines start, due to high winds, etc, and (b) the rocket falling over when the engines start, especially if one engine were to start early.  The risk of (b), in particular, is much higher and has much more serious consequences than flying the rocket with an arm still connected for the few seconds necessary to ensure a safe abort. Tevildo (talk) 10:48, 6 July 2014 (UTC)


 * Don't forget (c) the rocket falling over when the engines start, especially if one engine were late (or completely failed to start). Both b and c would result in dangerous thrust imbalance. - ¡Ouch! (hurt me / more pain) 08:19, 8 July 2014 (UTC)


 * I am willing to speculate that there is more than one connection to the tower. It would make sense to have two or even three steps to final disconnection. The first might be one that is connected manually when the vehicle is first brought into contact with the tower. It would be a robust system and could withstand fairly high winds. It would be disconnected manually, probably very early in the countdown sequence. There might be a secondary system that would be disconnected remotely but would be capable of being re-connected remotely if the launch were aborted. And finally there is the system that is disconnected remotely but cannot be re-connected. Such a cascade of connection systems would be consistent with the approach taken towards the engineering design of high-cost, high-risk, manned ventures. Dolphin  ( t ) 05:54, 6 July 2014 (UTC)


 * For the Apollo program, the "robust system" was the Mobile Service Structure, which was removed the day before the launch. See this article. Tevildo (talk) 09:51, 6 July 2014 (UTC)


 * Mercury-Redstone 1 sounds like the weight is supported by the rocket not the tower (and that at least the electrical connections are simple physical plug-in), and Mobile_Launcher_Platform clearly held the full Shuttle weight on the ends of the SRBs. DMacks (talk) 12:55, 8 July 2014 (UTC)


 * The weight of a launcher is not carried by the tower. Instead the launcher rests on a number of hard points around the skirt of the first stage, at the tail end. In most cases these are combined with a hold-down mechanism, which holds the launcher in place and stabilises it against sideways motion from wind. Crucially, these hold-downs remain while the (liquid-fuelled) motors are spinning up, and are only released when all the motors are running correctly; typically liquid engines are ignited a few seconds before T-0, and the release of the hold-downs marks the actual launch. This time window means it's possible to notice that the motors aren't running properly and shut them down, without the launcher starting to lift off the pad. A 2012 Falcon-9 launch aborted less than a second before launch, when automated systems detected one motor was out-of-spec and, rather than release the hold-downs, it killed the motors. Hold-downs come in two forms. The first is a system of clamps, which grab onto tabs on the rocket, and pull back to cut it loose. Pictures of the Saturn V hold downs (and the massive steel arms that held up the laden rocket) are here. Space-X uses a similar system. The second option is a fixed nut-and-bolt, where the hard points are bolted to the launch platform - releasing this hold-down scheme involves explosively severing the bolts or nuts. The Space Shuttle used the latter system, as discussed here, with four hold-down points on each SRB and frangible nuts. On the pad, the entirity of the STS system was carried by these 8 points - there was no hold-down on the orbiter or the external tank. The designers of the Space Launch System are concerned that these won't be sufficient to stabilise their rocket, and they're considering adding a vehicle stabilizer arm, which would allow the tower to prevent the launcher from swaying prior to launch; this would disengage at T-0.  A notable exception to this is the Soyuz launcher; the Soyuz doesn't have hold-downs and is serviced by a pair of boom arms (not really a tower) which retract just before launch. Instead of resting on its tail, the Soyuz hangs suspended over the pit on four angled gantries which fit around its midsection (it's a bit like holding your head up by putting your palms under your chin and your elbows on the desk).  When the Soyuz launches these arms fold back - they're counterweighted so they move out of the way when they're not holding the launcher's weight. -- Finlay McWalterᚠTalk 13:40, 8 July 2014 (UTC)


 * This is true not only of the Soyuz, but of ALL rockets in the R-7 family. 24.5.122.13 (talk) 06:25, 9 July 2014 (UTC)
 * I always thought it was interesting to see those giant arms rock back so gently during the launches. Thanks for explaining it! I don't see anything in R-7 (rocket family), and only minimally in Soyuz_(rocket_family) about the launchpad/support design. could you add some details there (or somewhere, and link)? DMacks (talk) 14:27, 9 July 2014 (UTC)


 * Thanks all, good info. I wonder if it's possible to have most of the connections held in place by gravity, such that the rocket launching will itself sever the connections. StuRat (talk) 14:27, 9 July 2014 (UTC)