Wikipedia:Reference desk/Archives/Science/2016 October 16

= October 16 =

Radioactivity sucker
Is there such a device that can suck all the radioactivity out of something radio active. I just saw it on a science film?--86.187.171.5 (talk) 01:25, 16 October 2016 (UTC)
 * What was the name of the film? Ian.thomson (talk) 01:27, 16 October 2016 (UTC)


 * Usually you would have to do something like isotope separation. The time when you might be able to "suck" is when you remove radon, which is a gas. See radon mitigation. Nuclear reprocessing can be used if the radioactive substance is a different chemical element. Graeme Bartlett (talk) 02:01, 16 October 2016 (UTC)
 * Are you by any chance talking about X the Unknown, the article of which you edited prior to posting this question? If so, well, it's a science fiction film. There's a reason it's called that. --47.138.165.200 (talk) 03:58, 16 October 2016 (UTC)
 * Please keep in mind that not everything in a work of science-fiction is necessarily fiction, so it's legitimate to ask the question. However, I think Graeme has answered it already: basically, no, there isn't. --69.159.61.230 (talk) 06:47, 16 October 2016 (UTC)


 * No.  But most bulky things aren't themselves radioactive, they're contaminated with particles of something else that is. For soil around large nuclear accidents in particular, there has been success with methods as simple as cabbage growing. These absorb the contaminant metals and grow radioactive brassicas, which contain more of the contaminant (as a ratio) than the soil did, thus help to reduce the contamination in the soil.  The vegetables can be picked and disposed of in one place.
 * If the base material is a liquid, with a contaminant dispersed in it, then separation techniques like chelation can help in a similar way. Andy Dingley (talk) 08:58, 16 October 2016 (UTC)


 * The sizes of hot particles encountered will vary by means of distribution (and with distance from the source). Particles from a fire, such as that at Chernobyl, entering the global environment, are of the order of 1 μm (ref), which is the same range as ordinary combustion-product contaminants (see the chart in the particulates article). Concomitantly the number of such particles will be in the billions, and only some wholesale process like Andy's brassicas (yay, another reason not to eat cauliflower) will address the issue. But where the particles are large (and distributed by a means like water, or just being ejected by an event like an explosion) there may be few enough (and each particle large enough) to make individual detection and removal practical. This is the case for the effluent from the Dounreay facility in Scotland. It may have shed 5,000 particles, each the size of a grain of sand, into the local marine environment(ref). Those particles, hundreds of times bigger than the aerosolised contaminants from Chernobyl or Fukushima, seem to be staying mostly in the environs of the Dounreay plant. SEPA routinely searches the local beaches for particles, and if it finds one it individually removes it - they've done this about 200 times so far.  I imagine (but I can't find sources) that the areas around major disasters like Chernobyl will have a ring of such particles - outside the visible debris area, but with larger (and thus much more dangerous) particles than the airborne ones - and presumably watercourses will have carried these kind of particles away, better than the wind could have done. -- Finlay McWalter··–·Talk 12:55, 16 October 2016 (UTC)
 * Radioactivity is the continuous process of atoms emitting particles and energy as they decay, see Radioactive decay. It is impossible to predict when a particular atom will decay. One can only characterize a material by its Half-life which is the time for 50% of any large number of its atoms to decay. Materials are known with half-lives ranging from years to fractions of a second for unstable isotopes made in the laboratory, but there is no device that can change the half-life of a given material. An important use of a known half-life is in dating once-living carbon-containing remains by their relative content of carbon-14 whose half-life is 5,730 years. The answer to the OP is that there is no such device for a given material, but there are many ways and devices to carry out Decontamination which includes the physical removal of radioactive substance(s) by methods and devices as basic as a Vacuum cleaner. AllBestFaith (talk) 13:25, 16 October 2016 (UTC)
 * Isn't it possible to increase the radioactivity of a given sample of radioactive material e.g. by subjecting it to a neutron source or, with some materials, a Neutron moderator? Fission rate is controlled and adjusted in nuclear power plants and bombs.  Could an object be made less radioactive in the future by encouraging fission in it now?  Preferably so we don't create transuranics or other nastiness.
 * There is a fictional thing called nuclear damper but that is science fiction. 91.155.195.247 (talk) 14:27, 16 October 2016 (UTC)
 * See Nuclear_transmutation. Fgf10 (talk) 16:22, 16 October 2016 (UTC)
 * Hmmm, this gives me an idea... Wnt (talk) 14:54, 19 October 2016 (UTC)
 * With Po-210, even the meekest guy can be an alpha male. DMacks (talk) 15:07, 19 October 2016 (UTC)
 * Join the UPPU Club today! (See p. 126). Double sharp (talk) 15:34, 19 October 2016 (UTC)

I see this bird in Catford

 * Does anyone know what species this bird is? Sorry if it's grainy, but hopefully you can identify it as that's the only photo of that bird I have on my computer._ CyanoTex (talk) 12:02, 16 October 2016 (UTC)


 * RSPB bird identifier suggests (with me guessing some of the info) a Wryneck, but with other possibilities including a starling. -- Finlay McWalter··–·Talk 12:28, 16 October 2016 (UTC)


 * *| Hmm. I'll see if I can get a more polished picture when the weekend's over. Description: Small bird when next to a pigeon. Black and yellow (more like a golden shade) color scheme. Beak looks more or less medium sized and perhaps of medium thickness._ CyanoTex (talk) 13:35, 16 October 2016 (UTC)
 * Almost certainly a Common starling (the wryneck is much smaller than a pigeon). See, in particular File:Sturnus vulgaris no.JPG. Tevildo (talk) 14:09, 16 October 2016 (UTC)
 * I do a bit of bird watching here in the UK. I think it is either a Song thrush or a Mistle thrush.  Note the breast patterning. DrChrissy (talk) 15:18, 16 October 2016 (UTC)
 * I still think a starling is more likely - the thrush has a pale breast with dark spots, while a starling (and the OP's bird) has a dark breast with pale spots. A photo of the bird's head would probably be decisive. Tevildo (talk) 15:47, 16 October 2016 (UTC)
 * The OP describes it as "black and yellow" - that would be a very unusual starling as they are black, sometimes with spots (hence the name "starling"). DrChrissy (talk) 16:08, 16 October 2016 (UTC)
 * I concur that a Common starling is quite likely. At this time of year they are moulting (I was greatly puzzled when I first saw one close up in this state), and additionally the juveniles look somewhat different to the adults – see the first photo in the Description section of the article (already linked above), bearing in mind that there can be some individual variation. {the poster formerly known as 87.81.230.195} 90.197.27.88 (talk) 17:10, 16 October 2016 (UTC)
 * I doubt it is a wryneck - according to our article, their toes are in the manner of woodpeckers', with two pointing backwards. Common starling is possible, but most are darker and shinier than that. Matt Deres (talk) 13:21, 16 October 2016 (UTC) (restoring comment deleted by CyanoTex). Matt Deres (talk) 19:13, 16 October 2016 (UTC)
 * * | It is a common starling! Huh. Thanks, Reference Desk._ CyanoTex (talk) 20:51, 16 October 2016 (UTC)


 * In October? It's a starling. Andy Dingley (talk) 02:35, 17 October 2016 (UTC)


 * I'd like to see a bit of explanation there. I mean, I think of starlings as glossy, scruffy, purplish or greenish even, while this seems softer.  Its underside is practically a zebra stripe, as much white as black, and it even seems like there's a sort of a whitish band across the back.  I understand an immature starling is browner, but usually very visibly speckled white on black though yes some are lighter.  Can people comment on subspecies or point to some similar images for reference? Wnt (talk) 11:08, 17 October 2016 (UTC)
 * Cf. this one. N.b. the brown-edged, black secondaries. "There is more genetic variation between common starling populations than between nominate common starling and spotless starling". As explained at common starling, there is *tons* of genetic variation here, and subspecies are far from being unequivocally defined. Keep in mind we're not only talking juvenile/mature changes and subspecies changes in plumage, we're also right in the middle of molting time, and that creates a lot of varied looks too. Sure, it could in principle perhaps be a funny-looking example of some other bird. But OP shows us a photo that looks much like one of the most common urban birds in the world, and it's probably that. SemanticMantis (talk) 15:12, 17 October 2016 (UTC)
 * Perhaps it is a leucistic individual. That could explain the white band on the neck. DrChrissy (talk) 17:29, 17 October 2016 (UTC)
 * The image is blurry, but from what I can make out, there appears simply to be three exposed white feathers, with black ones underneath these, because this bird's head feathers are raised on account of it preening feathers on its chest. --Modocc (talk) 17:50, 17 October 2016 (UTC)

What are the grid fins on Shenzhou for?
These photos: https://twitter.com/AJ_FI/status/787725451238207488

seem to show Grid fin not covered in the Shenzhou (spacecraft) articles.

What are they for? Hcobb (talk) 19:15, 16 October 2016 (UTC)


 * They've been a feature of Soyuz since the 1960s(?), although were covered by fairings until the mid 1970s (removed to lose unnecessary weight). They're part of the launch abort system. Andy Dingley (talk) 19:54, 16 October 2016 (UTC)

Are there more species which go on two legs permanently like human being?
I'm not talking about kenguru which is not really goes on two legs only as human being does. The same thing about bears. 93.126.88.30 (talk) 19:38, 16 October 2016 (UTC)
 * See our article on bipedalism. ---Sluzzelin talk  19:42, 16 October 2016 (UTC)
 * E/c Birds. We have an article on Bipedalism. DrChrissy (talk) 19:43, 16 October 2016 (UTC)


 * Sasquatch--Aspro (talk) 20:05, 16 October 2016 (UTC)


 * I'd like to know from the OP why they think Kangaroos do not move on two legs are you talking about the gait, i.e kangaroos hop whereas humans walk? DrChrissy (talk) 20:17, 16 October 2016 (UTC)
 * ok, actually I meant to ask about mammals rather than birds.  Kengero use a lot in their frontal legs. 176.100.5.242 (talk) 21:09, 16 October 2016 (UTC)
 * If you look at articles on kangaroos, they almost all classify them as bipedal. Don't forget, humans sometimes crawl using our front limbs, especially as children. DrChrissy (talk) 21:13, 16 October 2016 (UTC)
 * I believe the general view is that kangaroos are bipedal while moving fast (by hopping), but pentapedal when grazing or moving slow. See our articles (including Macropodidae and Tripod stance) and Nil Einne (talk) 01:55, 17 October 2016 (UTC)


 * That's got me thinking (and yes, before anybody else says it – I know I should refrain from this bad habit).  Apollo lunanoughts could put on foot in front of the other when walking slow but to move quickly, they found hopping was better -due to the inflexibility of an inflated space suit. Now: although they weighed only 1/6 of what they would have done on Earth, their 'mass' was the same and so was the mass of the very heavy life-support system which was on their backs. Look at the mass distribution on a 'roo and compare it with a lunanought. Looks to me about the same. Harrison Schmitt seemed to spend a lot of his time quadrupedal ( I am of that certain age when I was able to watch hours of telecasts live from de moon)  Apollo 17 EVAs 10 (Schmitt falls again). His actions are  more like a slow motion rendition, of a holiday-maker  in Cornwall, with a heavy backpack of tent and camping gear, looking for where he dropped his spectacles after drinking too much scrumpy. --Aspro (talk) 18:03, 17 October 2016 (UTC)


 * Hopping in low gravity gets around the problem of low friction between the bottom of the foot and the ground. It isn't simply due to the heavy and/or inflexible suit. You can think of walking in low gravity to be similar to walking on ice. Because you fall slowly, it is easier to hop, avoiding a slip, and then quickly adjust your stance when you land. I doubt that Kangaroos have any issues with ground friction. 209.149.113.4 (talk) 18:10, 17 October 2016 (UTC)


 * @ 209.149.113.4. I lived that era so don't try to kid me or anybody else. However, contrary to popular belief, the astronauts employed this form of movement not because of low lunar gravity, but because spacesuits of the era were not designed for walking. Moonwalking Astronauts Can Move Surprisingly Fast
 * --Aspro (talk) 19:11, 17 October 2016 (UTC)


 * Living in that era, you would have known about spacesuit design. You likely read "Have Spacesuit, Will Travel." Then, you would have knowledge that you did state above: the spacesuit weight is reduced, but the mass is not. Therefore, inertia is unchanged. The "heavy" suit is just as hard to start into motion as it is on Earth and just as hard to stop as it is on Earth. But, in less gravity, less weight, there is less friction on the ground. By pushing nearly directly down, friction is not an issue in starting momentum. By landing nearly directly down, friction is not an issue with stopping. The astronauts *did* try walking. They even tried running. It wasn't effective. Their feet simply slid out from beneath them. See Apollo 17 Jack Schmitt as he tries to pick up a sample bag. He steps to the side and leans. The foot with less weight on it slide out from under him and he falls down. Alan Bean became a lecturer and explained that you had to use your whole body to hop because you couldn't depend solely on the connection between your feet and the ground. It tended to slip. So, you had to use your arms to help direct your momentum upwards. While there are falls on record that clearly show that the astronaut lost balance, you can also find many falls on Youtube that clearly show the astronaut taking step and the slipping and falling. See this Youtube collection. The first one leans over, but as he tries to get upright you can see his feet slipping on the ground. Then, one falls over while hopping. You can see him try to push with one leg, but it just slides on the ground. Again, another foot slip. Then, one appears to be standing upright and his feet slide right out from underneath him. I believe that this is more than enough to back the statement that hopping is not used SOLELY because the space suits were bulky. It was also used to overcome the lack of ground friction. 209.149.113.4 (talk) 20:08, 17 October 2016 (UTC)