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June 28

Power Press

I want to know the type of air compressor used in the Pneumatic power generator in a Power Press Machine.I will be very grateful to any one who can give me an actual working method of a Power Press Machine....I would like to have the description of all the components in the machinery which drives the Power Press. —Preceding unsigned comment added by 121.246.174.130 (talk) 02:54, 28 June 2009 (UTC)

There are lots of power press machines. This lists some of them and their manufacturers, who have the information you want. Cuddlyable3 (talk) 13:08, 28 June 2009 (UTC)

they dont give me the working...only the information about its material is given —Preceding unsigned comment added by 121.246.174.130 (talk) 17:07, 28 June 2009 (UTC)

What in the world is this creature?

http://www.youtube.com/watch?v=Bv6cqUpqelc&feature=related

^ I'm referring to the gigantic crustacean depicted in the above film. It looks to be some sort of lobster, but it might be a crayfish, or something else, for all I know. I'm really curious, this thing is HUGE. —Preceding unsigned comment added by 75.148.127.194 (talk) 03:30, 28 June 2009 (UTC)

There are literally hundreds of species of lobster in the world; judging by the lack of large claws, this may be a variety of Spiny lobster or "Rock lobster", of which, according to our article, there are at least 45 different species. Our article mentions a 3-foot, 26-pound rock lobster as the record, so this wouldn't even be close to that. My guess is this is an 8- or 9- pounder, certainly large but no where near unheard of... --Jayron32.talk.contribs 04:00, 28 June 2009 (UTC)

Actually, looking at the video again, it may be a species of true lobster rather than spiny or rock lobsters. Reviewing our articles, true lobsters are distinguished by the having claws on the first three sets of walking legs; while rock lobsters do not have these. This appears to be a species of true lobster based on that, however our article list 48 known species of true lobster; there are only articles on a dozen or so of these, and only pictures of 3-4. It's certainly not a "Maine lobster" or other American or European lobster, but I can't narrow it down more than that. --Jayron32.talk.contribs 04:10, 28 June 2009 (UTC)

Looks like a Rock lobster, Panulirus ornatus to be specific.[1] Richard Avery (talk) 07:42, 28 June 2009 (UTC)

Well, there ya go... --Jayron32.talk.contribs 12:24, 28 June 2009 (UTC)

If you're into large crustaceans - check out the largest...one of my favorite animals - the Coconut crab. SteveBaker (talk) 00:29, 29 June 2009 (UTC)

Virtual Gravity

I'd like to live comfortably aboard a space station for the remaining 60 or so years of my life. The space station I imagine is a very long cylindrical rod rotating about its central axis to achieve that biologically-approved 9.8 m/s/s constant acceleration. The human cargo would be on the lowest level of the spinning rod where the gravity is virtually earth-like. My question is: how long does that rod of a space station have to be so that the entire height of a 6' human would be subjected to within 1% of 1g gravity? Follow-up question: is a differential of 1% of 1g over a human body acceptable for human biology to thrive very long-term? (This is not a homework assignment, I promise. I'm watching 2010 and the spinny thing they have going on their craft is so short it would seem to only achieve a gravitational nightmare.) Sappysap (talk) 04:39, 28 June 2009 (UTC)

The artificial gravity effect is proportional to the radius of rotation, so a 600' long rod should do. I think the human body would do just fine with a differential much higher than 1%. Dauto (talk) 05:41, 28 June 2009 (UTC)

A quick googling landed me on this page which suggests you may want a rotation period of 30 seconds or more (2 rpm) or you have a good chance of getting dizzy. The page has a link to a handy calculator for space station designers. A radius of 225 meters gives 1 g at 2 rpm. 62.78.198.48 (talk) 09:57, 28 June 2009 (UTC)

You are describing an O'Neill cylinder, I believe. (WP:WHAAOE) --Tango (talk) 17:37, 28 June 2009 (UTC)

From your description, the length is irrelevant. A shape like a bicycle wheel like 1940's science fiction space stations makes far more sense, or two or more habitats connected by long cables to a central hub about which they rotate. The radius or distance from the axis and the rotation rate creates the virtual gravitation. I believe that a gravitational differential between head and toe would create vertigo if you sat down or bent over. The rotation period would be unrelated to dizziness unless you were looking outside a window, since you would otherwise be unaware of it. Edison (talk) 03:18, 29 June 2009 (UTC)

The question was a bit unclear. Sappy first said the rod was rotating "around its central axis", which would mean spinning like an axle or drive shaft; in that case the radius or diameter of the cylindrical rod would be the relevant dimension. But then he or she asked how long it would have to be; that would be the relevant dimension if it was spinning end-over-end like a propeller blade, and I'm guessing that this is what he or she had in mind. (Of course, the bicycle-wheel space station includes the end-over-end rod as a component, and gives a much larger area at full "weight", i.e. the full perimeter of the wheel, than the rod alone)

If the 1% g variation that Sappy requested is taken as definitive rather than the estimated rotation speed posted by 62, then Dauto's logic in calculating a length of 6/1% = 600 feet is correct, but it applies to the radius of the circle of rotation, not the diameter. So a rod-shaped station rotating end-over-end would have to be 1200 feet long if built symmetrically. It could be made shorter by building it with a large mass at one end, so the center of mass would be closer to that end. For a bicycle-wheel design, you want a diameter of 1200 feet.

It's also possible that the negative effects of dizziness would disappear after some time spent in the facility. When astronauts first enter free-fall, they get that horrible sensation of falling - they feel sick - all sorts of bizarre sensations afflict them - but after a few days, they get over it and it all seems perfectly natural. It's possible that the dizziness due to coriolis in an overly small spinning craft would subside after a few days and you'd learn to expect things not to fall in a straight line, etc. SteveBaker (talk) 04:36, 29 June 2009 (UTC)

A Science Channel series, something like "Escape from Earth" discussed such artificial gravity for a very long distance space trip, like th Gliese 581c, and showed a centrifuge on Earth as a prototype. Strangely, the person's head was at about the pivot point, and only at the feet was normal gravity. This did not cause any strange feeling in the person, but moving his head around caused vertigo. I would strongly vote for 2 or more capsules a long distance apart, twirling about the central axis. An elevator could allow visiting back and forth. Edison (talk) 03:19, 30 June 2009 (UTC)

Yes - I agree. You stick all of the motors and fuel tanks and other stuff you don't need during the trip into one 'pod' and the people and their food and recycling stuff in another - set them spinning using a counter-rotating flywheel in the "hub" of the machine and then let centrifugal force unwind a pair of long cables between the two. You can power the flywheel electrically from solar panels - so it's easy to alter the spin rate and the diameter of the rotation of the crew quarters at any time during the mission without consuming valuable reaction mass. The cable only has to be strong enough to support the weight of the spacecraft under 1g of normal earth gravity - so a fairly slim steel cable ought to suffice. A small, motorized cable climber would allow astronauts and other items to travel between crew quarters, hub and propulsion pod - or you could use a soft, inflatable tube to connect the two pods and stick a rope ladder inside to allow people to move between the two pods. When you need to accelerate the spacecraft - or to keep it from spinning while (say) the earth-to-orbit shuttle docks with you, you use the energy stored in the flywheel to slow the rotation rate as you reel the cables back into the hub - then you only have to endure zero-g while the craft accelerates or as you take on supplies. You can scale the system up or down by connecting multiple such systems together by attaching them at their hubs. Flimsy structures such as solar panels, zero-g experiments, telescopes and communications gear that needs a stable platform can be attached to the hub and kept from spinning with a second flywheel. This seems like a relatively simple prospect - and I'm a little surprised that we aren't already doing this kind of thing - given the health risks to astronauts who man the ISS in free-fall over long periods. SteveBaker (talk) 12:43, 1 July 2009 (UTC)

UFOs in my bathroom

Every evening, I have lots of small insects in my bathroom: they're unidentified and flying, so I'd like help with identifying these UFOs in my bathroom. Their feet grip very well — they can hang onto a vertical mirror without problem — and when they're on the mirror it's plain that they're insects. They're shaped somewhat like grasshoppers, and they can jump very suddenly: in a fraction of a second, one jumped from one side of the sink to the other, before I could even realise what was going on. Colour is a pale green; size is quite small, with the largest ones being perhaps 5mm and the typical one being perhaps 2mm. They appear to be interested in the flourescent bathroom light (in the same fashion as moths are). My location is in western Ohio; any ideas what this species/these species are called? Nyttend (talk) 04:47, 28 June 2009 (UTC)

• I couldn't tell you the species from your description. Your easiest bet would be to catch a few and take them to your local university. Alternately get a camera with a macro lens and take a few photos. Yesterdays POTD (a scorpion) was found in the shower. Noodle snacks (talk) 06:06, 28 June 2009 (UTC)

Katydids maybe? Nymphs can look like miniature versions of adults in some species.[2]- 71.236.26.74 (talk) 07:22, 28 June 2009 (UTC)

check out leafhopper --Digrpat (talk) 11:39, 28 June 2009 (UTC)

I think that they're some sort of leafhopper: I couldn't find anything there that looks like them exactly, but the general body shape and description fits quite well. Definitely not katydids, and sadly there are no universities or other scholarly things around here. Nyttend (talk) 13:30, 28 June 2009 (UTC)

Wonderful section heading, by the way (in large part because it is quite appropriate to the question). Hard to skip reading at least a little... Chapeau! --Scray (talk) 19:41, 28 June 2009 (UTC)

Digital cameras - more pixels useless due to camera shake?

It is now possible to buy a camera giving a 5 megapixels photo for £25 or $41 (compare with the reconditioned 1.3MP camera I paid £80 $132 for from a discount retailer four or five years ago). 1) Does camera shake mean it is pointless having so many pixels? 2) In other words, are they just a sales gimmick? 3) And might they just be software-interpolated from the true hardware resolution? Camera shake will be even worse as many cameras no longer have an optical viewfinder and are thus held far less stabily. 4) Do these cheap cameras tend to have wider-angle lenses than similar cameras a few years ago? Thanks. 78.147.242.96 (talk) 11:24, 28 June 2009 (UTC)

Actually, most cameras now have stabilizers which hold the image steady even if your camera shakes a little bit. --Jayron32.talk.contribs 12:22, 28 June 2009 (UTC)

1) The extra pixels are not pointless unless your camera shake is always so violent that the resolution within every frame is degraded in every direction to the 1.3MP level or less. Camera shake correction aims at recovering the full resolution. 2) Caveat emptor. The extra pixels are real but you are getting just under 2x increase in linear resolution. Enlarged prints will look slightly better. 3) Digital cameras with optical viewfinders are readily available. Many people prefer to use the LCD viewfinder that can also show menus, camera status and previously taken pictures, and they do not necessarily hold the camera less steadily in that viewing mode. Disadvantages of LCD displays are that they add to battery drain and they may not be easy to see under bright light or for long-sighted users. 4) Most cheap digital cameras now have 3x ratio zoom lenses. I think they tend to have narrower-angle views because A) the digital image sensors are smaller than typical film sizes such as 35mm, and B) it is relatively expensive to build a good wide-angle lens but very cheap to obtain a reduced-resolution telephoto effect by in-camera digital processing. Cuddlyable3 (talk) 12:43, 28 June 2009 (UTC)

To your question 1, the answer is "no", because camera shake can be prevented or reduced by using a tripod and/or increasing the shutter speed (where possible). To your question 2, the answer is "to a degree". In order to have a high pixel count camera, you need to have good enough optics to match the imager resolution, and you cannot compress the output image too heavily. I don't know if the situation has changed recently, but I've looked at pictures (5 to 7 megapixels) taken with cheap cameras several years ago, and was quite disappointed. When you enlarge the pictures enough to be able to see individual pixels, you'll see very noticeable fuzziness and annoying artifacts. Basically, the picture quality does not commensurate with the pixel count. --173.49.12.134 (talk) 15:28, 28 June 2009 (UTC)

You can solve the camera shake problem with a tripod or other camera-stabilizer, but the lens is also very important, and there is no good way to compensate for a low-quality lens. Looie496 (talk) 16:25, 28 June 2009 (UTC)

A major problem is that for the small CCD sensors of most consumer cameras, adding resolution also adds more random noise, or, to be more precise, the smaller and smaller areas dedicated to each pixel become more and more sensitive to the (basically) constant noise floor. I've seen reviewers that put the best trade-off between resolution and noise for current compact cameras (with 4.5 by 3.5 mm CCDs) somewhere between 5 and 6 megapixels, and who claim a noticable degradation for larger resolutions. --Stephan Schulz (talk) 22:14, 28 June 2009 (UTC)

When viewed 1:1 full sized photo from these high-resolution point-and-shoots is just disgusting, all the details smoothed to lumps of colours. --antilived^{T | C | G} 01:00, 29 June 2009 (UTC)

Well, to be fair "1:1" would be 4.5*3.5 mm (or, if you are generous, 36*24 mm ;-). --Stephan Schulz (talk) 10:27, 29 June 2009 (UTC)

Not true. The pixels on my LCD monitor are bigger than the pixels on my digital camera. --203.129.49.222 (talk) 12:38, 29 June 2009 (UTC)

I have a 12MP pocket camera and I very rarely take purely hand held shots unless the light is very good. I always try to brace myself when taking a photo, most of the time I put my camera against a light or sign post, fence, corner of a building, anything. If there is nothing around you can squat down and put your elbow on your knee. If you absolutely must take a hand held shot not squatting down, instead of extending your arms out, press them tightly against your body, you don't have to look into the view finder once you get the hang of point and shoot and with digital you can check as soon as you've taken the shot to make sure you framed well. Vespine (talk) 23:47, 28 June 2009 (UTC)

In an emergency, you can reduce camera shake simply by holding something heavy in the same hand as the camera. But the amount of blur that camera shake causes depends a lot on shutter speed. For short shutter times (in bright light), shake is much less critical. So finding a camera with a more sensitive detector array and a bigger lens (which allows more light in) will all help to make those extra pixels earn their keep. SteveBaker (talk) 00:22, 29 June 2009 (UTC)

Bracing your elbows against your chest can help steady the camera while still allowing you to see the LCD screen (you may have difficulty if you want a use a viewfinder, though). --Tango (talk) 00:50, 29 June 2009 (UTC)

In short, no - because in direct sunlight and other bright settings, the shutter speed is so fast that the camera shake is negligible, even handheld at 10 or 20 megapixel resolution. So it's useful. As for upscaling, I would consider that false advertising of the worst kind and I would hope no one would stand for it - the camera ought to advertise its actual sensor resolution. I don't know much about the typical angle-of-view of cheap lenses, but I'd expect a 35mm-equivalent focal length of about 50mm, which is the typical "as people see" focal length. Dcoetzee 04:33, 30 June 2009 (UTC)

In bright conditions, without any zoom whatsoever, it's usually OK. A lot of photos are taken in conditions that don't satisfy those two requirements though. Tiny, dense, high megapixel sensors also tend to suffer from extreme noise at higher ISO speeds or over long exposures, so again they're less useful in lower light / faster motion situations. And as mentioned above, at a point you can't really gain any extra resolution out of it (or at least not enough to justify the pixel increase), just more noise which smooths out in a larger view but up close is completely useless. -- Consumed Crustacean (talk) 04:51, 30 June 2009 (UTC)

In the next part of this comprehensive tutorial on the art of photography our resident team will address composition techniques, lens cleaning and how to identify the exposure button on your camera. Links will be provided to every one of each poster's holiday snapshots since this is relevant to the OP's question. Cuddlyable3 (talk) 10:41, 29 June 2009 (UTC)

Why do some people appear to age less than others?

Cher for example still looks much younger than the typical 63 year old, both in face and body. What are the actual ressons for this in practice? Regarding her face - I expect she's had a facelift, has dyed hair and/or a wig. But regarding her body - does staying slim and exercising really make you age less than others? 78.147.242.96 (talk) 12:15, 28 June 2009 (UTC)

Genetics + LOTS of plastic surgery + money + fitness = Cher. --Jayron32.talk.contribs 12:21, 28 June 2009 (UTC)

http://www.officialcherfanclub.com/ invites one to send a message of up to 600 characters about "just about anything" to Cher. I stay slim and exercise but I am nothing like Cher. Thank you for your interest. Cuddlyable3 (talk) 12:55, 28 June 2009 (UTC)

I do not imagine that La Cher is an expert on Gerontology. 78.149.197.193 (talk) 15:06, 28 June 2009 (UTC)

When your career rides on you being in shape and looking good, you tend to stay in shape and look good. It's not like she has worked in a cubicle her whole life and tries to exercise on the weekends.

In any case, YES, exercising regularly and avoiding excess pounds does make you look a LOT younger than your contemporaries who do not. (It doesn't mean you will necessarily live longer or be healthier, mind you, but in terms of looks, definitely a factor.) You can see this rather dramatically in class reunion photos when people get to be around 40 — those who really take care of themselves on a regular basis (regular exercise multiple times a week, no obesity) easily look a decade younger than their peers who do not. In my experience. --98.217.14.211 (talk) 19:51, 28 June 2009 (UTC)

On another hand, when my dad lost a lot of weight, at age 63 (when I hadn't seen him in a couple of years) he "suddenly" looked much older – because he was no longer baby-faced. —Tamfang (talk) 09:53, 22 July 2009 (UTC)

Additionally make-up, a with-the-current-style hair-cut and wardrobe can help reduce ones apparent age enormously. ny156uk (talk) 22:02, 28 June 2009 (UTC)

1) Makeup. Did you ever see photos on the cover of tabloids of celebrities as they look when they walk out of the house in the morning to pick up the newspaper, compared to how they look with the lip gloss, concealer, and eye shadow? 2) Photoshop. They remove blemishes and wrinkles, and trim the tummy and tush, and remove wattles from the neck. Edison (talk) 03:13, 29 June 2009 (UTC)

I would add Diet and General Lifestyle as two important factors. Eating McDonalds 5 times a week or going to a quality grocer will no doubt influence the ageing process. A simple thing like sleeping with a window open would also help reduce the toll of decades, I should imagine. Vranak (talk) 19:02, 30 June 2009 (UTC)

Halogen

why iodine posess a very high electroposetive character though other halogen are highly electronegetive?Supriyochowdhury (talk) 15:56, 28 June 2009 (UTC)

According to our electronegativity article, Iodine has a Pauling electronegativity of 2.66, which is higher than carbon (2.55) and hydrogen (2.2), so I wouldn't say it was electropositive. The validity of those values might be questionable though, as I've been told that hydrogen and carbon have electronegativity values so close that it's unsure which is more electronegative than the other. (reference: someone with a PhD in organic chemistry) --Mark PEA (talk) 16:04, 28 June 2009 (UTC)

After looking at the article futher, it appears by the Allen scale that iodine is less electronegative than carbon (but still higher than hydrogen). Although chlorine is only a tiny bit more electronegative than carbon, so you can't say "all other halogens are highly electronegative". --Mark PEA (talk) 16:05, 28 June 2009 (UTC)

I'm not sure what you're asking. Iodine is fairly electronegative. Among the halogens, it's less electronegative than Bromine, but more so than Astatine, which is what you would expect. This can be attributed to the larger atomic radius. --Pykk (talk) 08:04, 29 June 2009 (UTC)

The reason why iodine is less electronegative than the other halogens is because its atomic radius is bigger and it has more electron shells between its nucleus and valence shell (which cause electrostatic shielding), so there's less electrostatic attraction between the nucleus and valence electrons. Hope this answers your question. Clear skies to you! 76.21.37.87 (talk) 01:28, 30 June 2009 (UTC)

Toyota High Performance Engines.

a While ago I stumbeled onto a web page that had a picture history of High performance and multi-valve Toyota engines. They ranged from 4 to 12 cylinders I think it was. All shapes and sizes. For the life of me I cannot find it again. I have looked everywhere on the net but to no avail. Can you maybe assist?

Regards, B —Preceding unsigned comment added by Benniebarnard (talk • contribs) 15:59, 28 June 2009 (UTC)

Wikipedia has a great history of Toyota, ranging from the Toyota AA to the Prius. Most of the articles actually have pretty good descriptions of the mechanical and engine particulars. Nimur (talk) 01:43, 29 June 2009 (UTC)

Is this site what you're looking for? http://www.geocities.com/MotorCity/Pit/9975/dataBySubject/EnginePix.html SteveBaker (talk) 02:10, 29 June 2009 (UTC)

Nope, not this one, it had HD pictures with exelent detail. If my memory serves, it was a simular list and had more competition type engines.196.25.43.75 (talk) 05:53, 29 June 2009 (UTC)

Plenty of Toyota engines here and here. - KoolerStill (talk) 09:59, 29 June 2009 (UTC)

Some nice ones here!!! The articla I saw had quite a number of wide head multivalve headed motors and manny of them had more than one sparkplug per cylinder. This made me think that they must have been for the motorsport market. Injected, sidies, downies,,,the lot!196.25.43.75 (talk) 05:05, 30 June 2009 (UTC)

Need help identifying an animal skull from northern Alberta

unidentified skull from northern Alberta

The skull shown in the image below was found in the boreal forest of northern Alberta, Canada. A local informant suggested it might be a fox and a search of images for the red fox (Vulpes vulpes) seems to confirm this identification except for one feature: the teeth. It looks more like a juvenile deer to me -- mule deer (Odocoileus hemionus) are fairly common in the area, white tailed deer (O. virginianus) less so.

If anyone here can help identify this skull that will be appreciated. Eco ant (talk) 17:00, 28 June 2009 (UTC)

It is almost certainly a deer skull. The dentition is that of a herbivore and the zygomatic arch is indicative of a ruminant. However, telling the exact species is tricky at best and impossible at worst. Have a look at some skulls here; many are simply identical. Fribbler (talk) 17:44, 28 June 2009 (UTC)

Thanks Fribbler. I'll consider it a species of deer. The external site you give is quite interesting. Eco ant (talk) 19:53, 28 June 2009 (UTC)

Fribbler probably right, not a fox, and its a herbivore.Polypipe Wrangler (talk) 14:01, 4 July 2009 (UTC)

Mini hang glider

Would a hang glider measuring approximately 580mm x 420mm, be able to carry a 500 gram mass across a distance of about 20 metres? If so, how high up would it need to be launched from? 86.166.46.34 (talk) 17:01, 28 June 2009 (UTC)

Is this a homework question? TastyCakes (talk) 17:47, 28 June 2009 (UTC)

It doesn't look like a homework question. For one thing, the problem is too underspecified for the second part to be answered precisely. --173.49.12.134 (talk) 19:22, 28 June 2009 (UTC)

Are you assuming still air? Thermals make a big difference for full size hang gliders. Widn would make a difference. RJFJR (talk) 19:21, 28 June 2009 (UTC)

The shape of the glider, as well as any initial momentum (if allowable), would also make a difference. I think the answer to the first question is obviously yes. If not, any glider that fits the description will come down almost vertically when launched from the outer edge of the atmosphere. And that's just most counterintuitive. --173.49.12.134 (talk) 19:29, 28 June 2009 (UTC)

We have to be a bit careful here. Small details of the rules matter! I recall that my son won a paper airplane "distance" contest at our company picnic some years ago by (in the first round) folding the paper so many times that he made a solid needle-like structure with zero lift but very little drag...but won the finals by taking the sheet of paper and scrunching it up into a tight ball which "flew" a lot further than the competition simply because he could throw it harder and it had a lot less drag than the competition. (The rules changed the following year!)

So - if you start at the top of a tall enough structure and throw the thing hard enough - your 500g mass will certainly travel 20m with no "glider" at all. No matter the design of your glider, it's always going to be possible to provide a high enough launch speed to make the mass travel the desired distance...especially if the launch height can be arbitarily high.

Hence, the answer (within the limits of what you ask) is "Yes". But since I strongly suspect that's not what you really want to know - we have to ask: "At what speed can the glider be launched?" - are you going to toss it by hand? Could you rig up a high speed bungee-cord launcher?

May I recommend this web page: [3] - which discusses the critical matters of "wing loading" and "span loading". These equations allow you to calculate a lot of the parameters of your design. As a short-cut, we could look at our Wing loading article which indicates that a typical "hang glider" has a wing loading of around 6.3 kg/m² - meaning that to support 500g with that kind of a design, you might need 0.5/6.3=0.08 m² of wing area...and you have 580mm x 420mm = 0.24 m²...so your wing loading is around 2.1 kg/m² - which seems pretty good. However, airspeed also has a big impact on lift...your model hang glider will probably fly a lot slower than the real thing - so it needs a lower wing loading. Again, check the equations in Wing loading...if this is a school project - then there is much to learn there - and I probably shouldn't do that for you.

SteveBaker (talk) 00:11, 29 June 2009 (UTC)

Evolution of desperation

What makes people react negatively to a display of one's desperation? It seems that even though desperation is the last attempt at correcting something (and I suppose it's natural) people would rather not 'rectify' it (someone else's desperation, of course). Does this follow the pattern that the 'weakest become weaker' and so desperation must be annulled? 94.196.190.79 (talk) 18:45, 28 June 2009 (UTC)

Are you sure that all people react in this way? This could easily just be a cultural thing—whereby desperation is associated with weakness, and weakness is shameful. There's no reason to necessarily assume that evolution has shaped this response (would it have had a differential effect on reproduction rates? probably not). --98.217.14.211 (talk) 20:57, 28 June 2009 (UTC)

People learn from experience that getting involved with people who are desperate often means giving a lot and getting nothing in return except trouble. If people were capable of offering an equivalent return for meeting their needs, they wouldn't be desperate. Looie496 (talk) 21:04, 28 June 2009 (UTC)

Fresh milk

What are the risks of drinking milk straight from the cow (directly from the udders) in comparison to drinking it unpasteurised after it's been milked and stored for a day or so (in a fridge)? Vimescarrot (talk) 19:13, 28 June 2009 (UTC)

Not many nowadays probably - see pasteurised. It does sound a bit kinky and you might get kicked though. Dmcq (talk) 19:32, 28 June 2009 (UTC)

Well, i dare say that depends a lot on what cow we are talking about. If you mean a cow raised on an organic farm then probably not much, but I don't think you could pay me enough to drink milk straight from the udder of a cow raised on RBGH. Wow!!! I just had a look at that article for the 1st time in a few years and it looks like all the bovine growth hormone stuff is on the way out! Last time I read about it, it looked like monstanto was winning with all the litigation against organic farmers and stuff. Well done, that's fantastic.. Vespine (talk) 23:57, 28 June 2009 (UTC)

Tuberculosis has been transmitted by raw milk [4]. Edison (talk) 03:10, 29 June 2009 (UTC)

Interesting. Thank you. Vimescarrot (talk) 18:40, 29 June 2009 (UTC)

I grew up on a farm. As a child, this was common practice.Either squirting it from the udder into our mouths or from the Milking bucket, steaming like smoke on water! These cows grazed the open fields though!! The only hormones they got was their own !!196.25.43.75 (talk) 15:08, 30 June 2009 (UTC)

Abraham Lincoln's mom died from fresh milk, though she would not have been saved by refrigerating it for a day. The cow had eaten White Snakeroot and she got milk sickness. --Sean 21:42, 30 June 2009 (UTC)

A small chance of brucellosis too. Catching tuberculosis used to be mostly from just being around the cows, you dont have to drink the milk. Whole dairying families used to have TB. Leptospirosis is a possibility too. Polypipe Wrangler (talk) 14:18, 4 July 2009 (UTC)

Calories in a pound of fat

If I want to lose a pound of weight I need to have a caloric deficit equal to the energy content of a pound of my fat. How many (kilo)calories is that? RJFJR (talk) 19:18, 28 June 2009 (UTC)

Fatty tissue does also contain other things than fat, and storing and releasing fat will also cost some energy, so weight to calories is not one to one, but for the question see food energy. If you want to lose your pounds easily, why not go to London stock exchange? 93.132.184.56 (talk) 19:26, 28 June 2009 (UTC)

Fatty tissue as mentioned contains a lot of water. The guide often used is 3000 calories will give about a pound in body weight (but far less weight of actual fat) however I cannot find a particularly reliable source for it. --BozMo talk 20:01, 28 June 2009 (UTC)

Had a look at food energy which says 3500 but the references are very weak (mainly websites selling diet products which should not make WP:RS) --BozMo talk 20:09, 28 June 2009 (UTC)

The standard value I've seen is 4000 KCal per pound of pure fat, but I don't have a ref at hand. Looie496 (talk) 20:56, 28 June 2009 (UTC)

One of the references is Health Candada which I don't think they are selling diet products. See page 45. 93.132.184.56 (talk) 21:00, 28 June 2009 (UTC)

The kcal/g listed in the Health Canada document is for dietary fats such as vegetable oil. The calories in a pound of body fat is less, since adipose tissue doesn’t consist of pure fat. Red Act (talk) 21:32, 28 June 2009 (UTC)

The American Dietetic Association counts as reliable source that doesn’t sell diet products. And the “American Dietetic Association complete food and nutrition guide” lists the 3500 calorie figure.[5] Red Act (talk) 21:22, 28 June 2009 (UTC)

Cellular respiration produces 2880 kJ per mole of C₆H₁₂O₆ (i.e. glucose, not fat). That translates to 1730 Calories / pound of glucose. As noted above, fat is a higher density storage medium, so there will be somewhat more Calories per pound of dry fat. Dragons flight (talk) 21:05, 28 June 2009 (UTC)

The 3500 kilocalorie figure has come from a variety of reliable sources over several decades. Others may be original research. Edison (talk) 03:08, 29 June 2009 (UTC)

However, eating 3500 kilocalories less (over whatever period) does not guarantee you will lose any weight at all. Most diets of any kind will give you a loss of 1 to 2.5 lbs in the first week just in water loss. The fat already on you needs to be broken down and used as energy, which is not likely to happen from eating 3500 Kcal less in one week. - KoolerStill (talk) 10:14, 29 June 2009 (UTC)

Are you sure? Not true. Sensible weight lose diets suggest resticting ones diet to 500 Calories less per day (compared to typical needs) is the best way to permenantly lose weight, and this gives the 3500 in a pound of fat per week. In fact such a diet in an overweight person is likely to cause much more weight loss! A 500 calorie restriction not only causes weight loss, it is used as a "control" diet in scientific papers to compare the result of restricting different food groups or adding suplements [6], [7]YobMod 12:01, 29 June 2009 (UTC)

RJFJR, you might like to download the book The Hacker's Diet. It has a lot of stuff like that in it. There should be a download url in the article. 208.70.31.206 (talk) 05:41, 3 July 2009 (UTC)

Tiredness after a meal

What are the physiological and biochemical mechanisms that make us tired after a meal? This happens to quite a lot healthy people, I'm not looking for medical advice. I'm not satisfied with the "all blood is in the belly" stuff because when you do exercises a lot of blood is in your muscles and when you do, err, something else, a lot of blood is in some other body part without you feeling tired at all. 93.132.184.56 (talk) 19:20, 28 June 2009 (UTC)

I feel tired when I exercise... --Tango (talk) 20:57, 28 June 2009 (UTC)

I don't. I sometimes feel tired afterwards but it's different tiredness from what I experiences after a heavy meal. Especially, the brain isn't tired after exercises. 93.132.184.56 (talk) 21:05, 28 June 2009 (UTC)

If you feel tired when you exercise, you are not exercising enough.174.3.103.39 (talk) 08:57, 30 June 2009 (UTC)

It could be that 'lack of alertness' is being interpreted as 'tiredness'. A fairly reductionistic view would be that the parasympathetic nervous system is fully active whilst the sympathetic nervous system is pretty much fully inactive. In my opinion I'm not tired after a meal, only very heavy ones (like at Christmas or when going to a restaurant which serves huge portions and one forces oneself to eat it all since one paid money for it). --Mark PEA (talk) 21:39, 28 June 2009 (UTC)

Yes, that's it. It's just a different mode of operation. There is a long forgotten time where I was more acquainted with these things, I'll have to have a new look on these. Thanks a lot! 93.132.184.56 (talk) 22:06, 28 June 2009 (UTC)

You should get your food packed. Ask for a box. Don't get the servers to pack it for you. Their hands are dirty, and most of them leave out a lot of food.174.3.103.39 (talk) 08:59, 30 June 2009 (UTC)

As a side note, it’s perfectly OK on Wikipedia to say “having sex” instead of “err, something else”, and “penis” instead of “some other body part”. Wikipedia has a “no censorship” policy, and has articles like vulva that go way beyond avoiding euphemisms. Red Act (talk) 21:54, 28 June 2009 (UTC)

Yeah, but euphemisms are funny :)

Ben (talk) 22:01, 28 June 2009 (UTC)

You were a little faster than me. Thats what I think. 93.132.184.56 (talk) 22:06, 28 June 2009 (UTC)

A large meal, high in carbohydrates, can cause a rise in blood sugar, especially in diabetics or those who have impaired glucose tolerance. Very high blood sugar can cause drowsiness. I've also read that some chemical in turkeys ("tryptophan?") an cause drowsiness. Edison (talk) 03:04, 29 June 2009 (UTC)

Actually, turkey isn't that high in tryptophan, as this BMJ article notes. The consumption of any heavy meal can cause drowsiness due to the reduction of blood flow/oxygenation to the brain, as that article also notes (although its references are missing). Gwinva (talk) 05:03, 29 June 2009 (UTC)

The "turkey-tryptophan-tiredness" link is typical cargo cult pharmacology. The logic goes along the lines of: Melatonin = sleepy chemical. Melatonin is synthesized from serotonin, which is synthesized from 5-HTP, which is synthesized from tryptophan. Turkey contains tryptophan, therefore, the drowsiness after Thanksgiving/Christmas must be due to tryptophan. Unfortunately this doesn't take into account: the bioavailability of tryptophan when eaten as a constituent of turkey, the time it would take for the tryptophan to reach the brain, the time it would take for the tryptophan to be converted to 5-HTP then 5-HT, the fact that melatonin is only synthesized when certain frequencies of light are not hitting the retina, and probably some other things (enzyme/transporter competition, plasma protein binding, etc).

Alternative medicine has exploited this and marketed 5-HTP and melatonin as natural sedatives. I haven't read much into it but it appears melatonin may have some efficacy in age-related insomnia (which is supposedly caused by decreased synthesis in later life [8][9]) --Mark PEA (talk) 11:48, 29 June 2009 (UTC)

Ooohh! "Cargo cult pharmacology" - I love that phrase! I will be stealing it in the future! SteveBaker (talk) 12:48, 29 June 2009 (UTC)

So if I s build a simulated pharmacy counter in my basement, will a Walgreen's truck driven by John Frum deliver a load of drugs? That is what Cargo cult pharmacology would be about. The sleepiness after Thanksgiving dinner probably has much more to do with a carbohydrate overload raising bloodsugar, than with turkey tryptophans, agreed, Edison (talk) 03:10, 30 June 2009 (UTC)

I completly agree with Mark PEA about not making such biochemical guesses as biological systems don't react simply nor linearly. It is similar to most of the science behind vitamin supplementing "We need tiny amounts of vitamin X to live --> eating huge amounts of vitamin X will give extended-life/super-powers", which is clearly non-scientific, but such claims are everywhere.

5-HTP definitely has some effect - more like being mildly stoned rather than a sedative imo - but this does not mean tryptophan would do anything similar (large amounts could inhibit the enzyme, shunting tryptphan into deamination, for example).YobMod 09:31, 30 June 2009 (UTC)

Can anybody identify this beetle?

Hi. Just wondered if anybody could identify this beetle, please? It fell down my chimney tonight, flew around the room a bit, and then just sat on the floor. It was generally very lethargic. I am in London, UK. Thanks Chalk House (talk) 21:18, 28 June 2009 (UTC)

Thought of a cockchafer first but then found Amphimallon solstitialis. 93.132.184.56 (talk) 21:28, 28 June 2009 (UTC)

Thanks. It certainly looks very similar to a Cockchafer, I wonder if the head of the Amphimallon solstitialis might be a bit too hairy. I uploaded a couple more pics that might be helpful [10] [11]. Thanks again Chalk House (talk) 22:13, 28 June 2009 (UTC)

There are more species like that but wikipedia is a bit short in articles and pictures on that. Btw, we are not to give legal advice but, the animal on the last two pictures doesn't look very healthy. If I were you I would not show that lest you'll get sued by some PETA activists. 93.132.184.56 (talk) 22:37, 28 June 2009 (UTC)

Thanks. Are there any other internet resources you know about that I could search? Don't worry about the beetle (whatever it is) it was just very lethargic, as I said, hardly moving for long periods of time. When I released it, it wandered off very slowly. Not sure if the fall down the chimney did it some harm though. Chalk House (talk) 01:06, 29 June 2009 (UTC)

You might like to try here, [12] Richard Avery (talk) 06:59, 29 June 2009 (UTC)

I can tell you that in German a cockchafer is called a May Bug (Maikäfer literally), while Amphimallon solstitialis is called a June Bug. Both for good reasons. So, I guess you've got an Amphimallon. Of course they might occur in the UK at different times than on the continent. Amphimallons are also quite a bit smaller than Cockchafers. 195.128.250.104 (talk) 23:23, 30 June 2009 (UTC)

Can a chimpanzee really commit suicide?

Our article on Michael Jackson's pet chimpanzee, Bubbles, claims that this chimpanzee attempted suicide but was rushed to the hospital and saved. The cited sources are this and this. Can a chimpanzee really commit suicide? If yes, how exactly would a chimpanzee make such an attempt? A Quest For Knowledge (talk) 22:15, 28 June 2009 (UTC)

By making a noose out of his tyre swing? Just a thought. --Kurt Shaped Box (talk) 22:38, 28 June 2009 (UTC)

We don't describe chimpanzee suicide methods on the Ref Desk, sorry. Impressionable young chimpanzees could be reading. --98.217.14.211 (talk) 22:55, 28 June 2009 (UTC)

That is probably a result of lazy journalism. Notice that the Telegraph prefaces it with "according to reports..." which is is a large red flag when considering reliability of a statement. There is a lot of utter nonsense written about Michael Jackson, and this sounds like utter nonsense to me.

As to whether a chimp could commit suicide or not, depends very much on how you define "suicide". It could certainly kill itself, but its unlikely it could do so with the premeditated intention of ending its life. That would demonstrate an awareness generally thought to be beyond hon-human animals, even chimps. Thats not to say that animals do not regularly kill themselves in what we might consider "suicidal missions" (think bee or worker ants defending their queen), but those are not really suicide because the intent is not death, instead death is just the inevitable consequence. If Bubbles really did almost take his own life, then it was almost certainly without intent. Rockpocket 23:10, 28 June 2009 (UTC)

For the purposes of my question, let's define suicide as intentionally killing itself for the goal of ending its life. A Quest For Knowledge (talk) 01:35, 29 June 2009 (UTC)

I'll have to think more about this "intent", i mostly agree with the above, but, i don't know, we've seen primates exhibit a lot of behaviour that was previously thought to be purely human, altruism is one that comes to mind.. As far as pure method goes, the easiest way for a monkey would surely be to just climb to a high place and jump. Vespine (talk) 00:03, 29 June 2009 (UTC)

I'm not sure suicide is beyond non-humans. My understanding is that dolphins are considered to be a species that occasionally commits purposeful suicide. --98.217.14.211 (talk) 01:13, 29 June 2009 (UTC)

Depression is a well documented problem in pets. In extreme cases loss of appetite can lead to the animal becoming too weak and dying of related causes. e.g. [13]71.236.26.74 (talk) 02:38, 29 June 2009 (UTC)

Dolphins and whales have been known to intentionally beach themselves, and in some cases even re-beach themselves after "helpful" humans returned them to the water. Death is an inevitable consequence of doing that (barring intervention) but it is unclear how much awareness and intent the animal may have. I would note that some animals that do this do seem to be ones that were recently abandoned or dealing with the grief of a lost mate, etc., and to the extent human analogies makes sense could easily be considered depressed. Dragons flight (talk) 06:40, 29 June 2009 (UTC)

Suicide would require a concept of self commonly called metacognition. Whether or not non-human animals have this concept of self is debatable... --Jayron32.talk.contribs 03:03, 29 June 2009 (UTC)

My opinion is that the article is not remotely true. What is a hospital going to do with a chimp? The staff is not equipped or knowledgeable in the area of treating a chimp. 65.121.141.34 (talk) 13:18, 29 June 2009 (UTC)

Given the context, "hospital" could easily mean veterinary hospital. Dragons flight (talk) 15:56, 29 June 2009 (UTC)

It would have to be seriously specialized. Maybe a zoo would have the stuff. 65.121.141.34 (talk) 19:23, 30 June 2009 (UTC)

Naturism

Are there any known health issues or studies with naturism apart from extra exposure to sunlight? (not looking advice) ~ R.T.G 22:20, 28 June 2009 (UTC)

At least you don't have to fear pickpocketing. 93.132.184.56 (talk) 23:10, 28 June 2009 (UTC)

It's gonna depend dramatically on where you're doing it. Naturism in the antarctic is certainly going to come with health issues! SteveBaker (talk) 23:45, 28 June 2009 (UTC)

Indeed. I think most problems are going to be down to the fact that you are extremely exposed. What you are exposed to (sun, heat, cold, wind, sand, etc.) will depend on where you are. --Tango (talk) 23:48, 28 June 2009 (UTC)

It can be very unhealthy for men who are geese herders. The birds tend to snap at things. Edison (talk) 03:01, 29 June 2009 (UTC)

I'm never going to be able to look a geese the same way again... --Tango (talk) 05:56, 29 June 2009 (UTC)

Well now, woo, we get Mediterreanean sun in winter and hailstones in summer, occasionally (Irish south Atlantic) but nothing is found in this case about normal room temperature except - extra sun exposure = Vitamin D. ~ R.T.G 06:17, 29 June 2009 (UTC)

If you live in an area with Gnats or Mosquitoes you'd offer oh so much more opportunity for them to shout "lunch". Encountering a patch of Stinging nettle, Poison oak or Poison ivy may also put a significant damper on things. 71.236.26.74 (talk) 08:58, 29 June 2009 (UTC)

The OP is owed an apology for the nervous jokes that their question has evoked instead of rational answers.

See Naturism#Criticism and Issues in social nudity for some issues. Typical issues concern hygiene precautions for sitting on shared towels, and debate on whether naturist venues should have rules to keep an even male-to-female balance.

Clearly there are studies because the search keywords naturism survey study got 44 500 hits. Examples:

• Mark Storey 'Children, Social Nudity and Academic Research' Nude & Natural magazine, 23.4 Summer 2004; Children, Social Nudity and Scholarly Study has copious references.
• Political activist Nikki Craft researched child molestation within the movement. A critical website.
• Heliotherapy - Research News and Information

Cuddlyable3 (talk) 10:22, 29 June 2009 (UTC)

It's something you wouldn't think of so easy. ~ R.T.G 22:21, 29 June 2009 (UTC)

Rechargeable batteries with no shelf life?

Are there any rechargeable batteries that have no shelf life, meaning they will never die out and you can keep using them indefinitely? ScienceApe (talk) 23:50, 28 June 2009 (UTC)

No battery will work indefinitely. Rechargeable battery has a nice list of technologies with expected cycle and shelf life. Vespine (talk) 00:12, 29 June 2009 (UTC)

Old-fashioned Lead/Acid car batteries that had to be topped up with acid once in a while as a part of routine maintenance could be drained dry and stored for very long periods. People who maintain ancient antique cars in factory condition rely on this fact - and some of them have batteries that go back to the very early days of motoring. However, the need to refill them in order to use them - and drain them again for long-term storage may not be the kind of thing our OP is thinking of. In terms of buying rechargable batteries for your camera or whatever - I don't think there are any technologies out there that give you what you'd like to have. SteveBaker (talk) 01:55, 29 June 2009 (UTC)

In my experience they were topped off with water, not acid. As for long term storage, there were "dry charged" batteries which sprang to life in a charged condition when the battery (with no liquid inside") initially had the sulfuric acid solution added to it. Batteries I am familiar with only have a few hundred charge/discharge cycles in their life under ideal conditions. Deep discharge decreases the life of some. Discharge or charge at too high a rate decreases the life of some. Always leaving on trickle charge and never discharging lowers the amp hours of nicad batteries. Failure modes differ among different battery chemistries.Edison (talk) 03:00, 29 June 2009 (UTC)

Modern drivers have no clue how much hassle owning a car before the 1970's really was! The idea of maintaining (or ever repairing) a car battery is completely alien to us these days!

The battery contains lead plates and sulphuric acid - but in the age before sealed batteries - they were vented to allow hydrogen gas to escape (if the vents got blocked - the battery would explode - or crack, spilling concentrated acid everywhere). Unfortunately, those vents also allowed the liquid in the battery to evaporate. It was important to keep the acid concentration within some range in order to get enough power from the battery. So as the liquid evaporated, you'd initially be able to do a top-up with distilled water and keep the thing working - but if you did that enough times, the pH of the liquid would gradually increase and the battery would get weaker and weaker. Hence, at longer service intervals, you'd stick a hydrometer into each cell in turn and adjust the acid levels to get them back to the correct value.

Handling that concentrated acid wasn't something you'd be expected to do on your own - so you'd generally rely on a garage to do that for you on your regular service/oil-changes - which is probably where you got the idea that you only needed to add water. The owner's manual for my 1963 Austin Mini says that you have to top up the battery with distilled water on a WEEKLY basis (!!!) - and measure the specific gravity and adjust acid levels according to specific chart every 6,000 miles. It also talks about flushing out the battery and replacing all of the fluids "as needed". I just looked this up in the (rather quaint) 'schedule of charges' book for my 1963 Mini. It says that the dealership will charge you 4 shillings for doing a hydrometer test and topping the cells off with distilled water but the cost would rise to 5 shillings and 4 pence if it was necessary to add acid - I didn't see a price for a complete battery flush. Needless to say, my '63 Mini has a modern sealed-for-life battery...I'm not messing around with concentrated sulphuric acid! SteveBaker (talk) 04:10, 29 June 2009 (UTC)

As someone who has messed around with concentrated sulfuric acid (in a lab setting), why not? I have a distinct memory of trying to move a few milliliters in a syringe, only to discover it it had reacted strongly and eaten into the syringe during the few moments during which I was trying to do the transfer. Also the very high heat of dilution could be a serious nuisance. Wow! That's a red link?!? Dragons flight (talk) 06:51, 29 June 2009 (UTC)

Mostly along the lines of rechargeable batteries for electronic devices like laptops, handheld games, and such. The chart is interesting. Looks like Lithium-titanate battery is promising. Has a shelf life of 20 years if that chart is correct. I'm not really sure what those categories mean though. What category determines how long the battery will last on a full charge? ScienceApe (talk) 03:01, 29 June 2009 (UTC)

I just got my first ever sealed battery this year; the early ones were reputed to have high danger of exploding.(But a conventional one did explode on me. The acid must have been fairly dilute, because, while it burned holes in my clothing, there was only minor damage to exposed skin. Handling the acid is only a problem when topping it up).

Dragons flight, redlinks are links to articles that don't exist. You were looking for exothermic reaction. - KoolerStill (talk) 10:52, 29 June 2009 (UTC)

No, we ought to have a specific article discussing the heat of dilution (also called the enthalpy of dilution) for various substances and its physical origins similar to heat of formation, heat of combustion, heat of vaporization... A one line comment in exothermic reaction isn't even a suitable redirect target. How many other concepts in physical chemistry are not yet documented I wonder? Dragons flight (talk) 15:51, 29 June 2009 (UTC)

This question needs a link to low self-discharge NiMH battery. These don't last for ever but at least they are an improvement on standard NiMH. --Heron (talk) 20:47, 29 June 2009 (UTC)

"As someone who has messed around with concentrated sulfuric acid (in a lab setting), why not?" -- I handle concentrated sulfuric acid on a regular basis, and I can tell y'all, it's something that really requires special training and lots of experience. That stuff is so corrosive that if you get just a little bit of it on your skin, it can burn your skin to a crisp (and I mean completely blackened like an overdone hamburger) within seconds! And if it splashes into your eyes, well, that will surely ruin your eyesight for life. Plus, it quickly dissolves almost all metals (including your car's bodywork, engine block, anything like that). And to top off the list of hazards, its dilution is extremely exothermic, so the only way to dilute it is to very slowly add the concentrated acid to the water, with vigorous stirring; if, by terrible mistake, you add the water to the acid (and that includes if you've spilled some of the acid and try to wash it away with water), it starts bubbling and splashing all over the place and might even burst the container! No, handling concentrated sulfuric acid is definitely not something that the average person can do without endangering himself/herself and anyone else who might be standing too close. 76.21.37.87 (talk) 02:15, 30 June 2009 (UTC)

Lead acid batteries use dilute sulfuric acid as electrolyte. It is not all that concentrated, although I would not care to have it on my skin or clothing. The adding of acid or the "flushing" with fresh acid solution is not something I have heard of as part of the maintenance of substation battery banks or car batteries, From cradle to grave, distilled water was the only fluid generally added. When that no longer sufficed, it was time to buy a new battery (or cell). What was the supposed mechanism for sulfuric acid escaping the battery, so that more acid needed to be added? Only if you have turned over the battery and accidentally spilled out the electrolyte would there be occasion to add more acid [14]. Edison (talk) 03:04, 30 June 2009 (UTC)

That's certainly most people's experience - you'd top up the battery with water (every week!!) and when you put your car in for a service, they'd add acid if necessary - so it's perfectly possible that most people didn't realise that this was a part of the service. But the 1963 Mini Owner's Manual - and the "Scedule of charges" for their car dealerships doesn't lie. You're supposed to check the specific gravity in each cell every 6,000 miles - and add acid if necessary. Failure to do that would mean that you were probably tossing out a perfectly good battery. But as I said, in the 1950's and early 1960's, people would still repair faulty batteries - you could even replace the lead plates in them (they are listed in the 1963 Mini's spare parts catalog) - so there was really never a reason to completely throw one away - although doubtless many people did. Some of the more fanatical classic car owners out there still use the original battery that came with the car as further proof that their car is in factory condition. SteveBaker (talk) 13:20, 30 June 2009 (UTC)

You have a good ref for that being part of the maintenance for that car's battery, but it seems to be the exception. Water is lost from electrolysis at the end of the charge cycle, or from evaporation. Acid and lead remain in the battery. Unless acid somehow leaves the battery, no acid needs to be added. Was the acid in that battery absorbed into the structure somehow, or was the goal to remedy sulphation of the lead plates? Only water needs to be replaced, absent spillage. Like the older source I cited above, a Google search shows numerous sites over several pages saying "Never add acid" to a lead acid battery [15]. One site discusses remanufacturing a cell, and replacing the chemistry as part of that process[16]. Remanufacturing, maybe. Maintenance, definitely no. Edison (talk) 14:15, 30 June 2009 (UTC)

June 29

God Delusion question: Infinite regress of multiverses

In The God Delusion, Richard Dawkins suggests that this universe is just one of many in a multiverse, chosen from among them by the anthropic principle. If this is true, don't we need to explain how the multiverse came into existence, and possibly how it became finely tuned to produce universes? Won't this ultimately lead to a multi-multiverse and an infinite regress? And couldn't the same infinite regress also serve to explain the existence of a God, with each god having been created by an older and more complex God? NeonMerlin 02:43, 29 June 2009 (UTC)

That multiverse theory isn't meant to explain the existence of the universe, just the fact that it is so remarkably fine-tuned to support life, so the reason for the existence of the universe/multiverse is still an open question. I'm not sure in what way a multiverse would need to be fine-tuned, though. Fine-tuning refers to the physical constants being just right for life as we know it to evolve. I'm not sure the multiverse would have any such constants - everything can vary from one universe to another. --Tango (talk) 02:48, 29 June 2009 (UTC)

The argument you propose NeonMerlin is an old one. See Cosmological argument. Dawson's book has two flaws; one it ignores the role of pure faith in people's understanding of God. Second, it confuses people's understanding of creation with the creation itself. If we accept God as axiomatic (that is, we take his existance on pure faith) than our changing understanding of creation does not reduce or minimize his role in our lives, as many claim is happening. God is unchanging, creation always happened the same way. All that changes is our more and more finely tuned understanding of it. --Jayron32.talk.contribs 03:01, 29 June 2009 (UTC)

Dawkins' book does indeed address the issue of "pure faith" (I have no idea about "Dawson" however! :-) - you should probably go back and re-read it.

If you insert the god hypothesis as an axiom - then of course it doesn't change the result - which is the universe we can see and measure today. If adding that axiom did make a difference - then we'd have proof that god exists. Since we don't have that proof, inserting that unnecessary axiom is kinda pointless. It's like taking the beauty of euclidean geometry and adding "Banana's are Yellow" as an additional axiom ("All right angles are equal", "You can extend a straight line"..."Bananas are yellow")...it's true - but it's unnecessary. Basing a theory of everything on the circular argument "I believe it because I believe it" (aka "faith") really doesn't help - and the beliefs of some subset of one kind of organism is truly irrelevant compared to the universe as a whole. There are an infinite number of theories like that - but none of them is any better than any other - so we have to fall back on Occams' razor and pick the simplest. If it turns out that we NEED to add some other fundamental thing in order to explain everything - then we're not precluded from doing that (we're adding dark matter and dark energy, for example...we NEED them in order to explain certain observations). But we have no need to add one or more gods in order to explain everything we see...no more than we have a need to add "Bananas are Yellow" into our fundamental laws of geometry in order to understand triangles and circles and such. SteveBaker (talk) 03:34, 29 June 2009 (UTC)

Exactly; which is why we don't really spend much time dealing with God as a scientific construct. He cannot be proven or disproven using the tools of science, and yet the human experience is not all science. Art, music, beauty, and yes, faith, make up a significant portion of the human experience; all of which are really quite untouchable by scientific inquiry. It doesn't make science less powerful, or them less important. Its just the matter of recognizing that people's lives aren't merely made up of a neverending quest to describe the details of the mechanisms of the universe. Certainly, that is an important part of life, but not the totality of it. See Stephen J. Gould, esp. Rocks of Ages, which I found more satisfying that Dawkins... --Jayron32.talk.contribs 02:12, 30 June 2009 (UTC)

You are confusing what humans do with what humans can study using the tools available. I'd certainly agree with the bare statement that: "the human experience is not all science" - after all, most people are not experiencing the practice or findings of science most of the time - sometimes they're vegged-out in front of the TV watching mindless soap-operas for example. But that doesn't mean that I accept what you're trying to say: That human experience cannot be studied and understood scientifically - it most certainly can - there are very few "No Go" areas for science - and those that do exist are of our own discovery (eg you can't know what happens inside the event horizon of a black hole). But we are actually starting to have a pretty good handle on art, music and beauty - and are making inroads in the study of faith too.

We have discovered that (for example) the perceived beauty of a human face depends on how close it is to the average of all human faces...and that in all likelyhood, the reason for that is that the less 'average' a face is, the more likely it is that the person is somehow sick or possesses some kind of genetic problem that makes them less desirable as a mate. It follows that the experience of beauty is quite possibly a very simple evolved behavior. A beautiful plant is one that's more likely to be useful to us - a butterfly is beautiful but a housefly isn't - because the former is harmless and the latter carries diseases. "Cute" animals have eye-to-head-size ratio's that are closest to human babies. We are discovering LOTS of things about the human experience of "beauty".

These things are not some wonderous mystery that science is somehow locked out of - they are simply harder to study than some other subjects given the tools that we've had at hand throughout most of the history of science. But now that we have things like PET scanners that can see what parts of the brain light up when art/music/beauty/faith are contemplated, you can bet that it won't be long before we start to understand and explain those things. Check out the book: "Why we believe what we believe" by Andrew Newberg for an example of work going on in this area of scientific enquiry. Human brains and thought processes are hard to study - but that doesn't mean we can't do it. SteveBaker (talk) 13:06, 30 June 2009 (UTC)

Well, you are still making the assumption that faith is somehow an invalid or unneccessary aspect of the human experience merely because its effect on human physiology can be described by science. No matter how much detail one can ascribe to a phenomenon, one cannot neccessarily equate that detail with purpose. That we have religious faith, and that we can describe how that religious faith affects the brain does not mean that somehow that religious faith is less "real" or an "invalid" way of experiencing the world. That we can show how ones relationship with God affects the body does not mean that that relationship does not exist. --Jayron32.talk.contribs 14:43, 30 June 2009 (UTC)

Not at all - but I am saying that (perhaps) in a few years time - we might show that a particular brain chemical in a particular place causes faith. Would you be so convinced of the importance of this emotion if we were able to turn it on and off with a little pink pill? You take the pink pill - you are immediately flooded with this profound feeling of religious joy. You take the yellow pill and it goes completely away - god feels about as real and as relevent to you as the tooth fairy. That's a possible result of current studies - would that mean that faith is not something that some supreme deity projects onto us - but instead just the consequence of some unpronouncable protein? If this seems fanciful - check out psilocybin - which produces an effect not dissimilar to the pink pill. SteveBaker (talk) 00:47, 1 July 2009 (UTC)

There are other reasons to consider the multiverse idea - it provides an elegant explanation for some of the wierder aspects of quantum theory (see: Many worlds hypothesis) - but Dawkin's idea is not much more than a means to avoid having to invoke the anthropic principle - which says that the universe isn't the way it is because of the need to support life - but life is here because the universe happens to be the way it is. If it were some other way then there would be no creatures like us to remark on the fact. In most versions of the many-worlds/multiverse hypothesis, they all start at the same instant with the same big-bang and the same exact initial configuration - only becoming different as random quantum events happen differently in each 'copy'. Hence, no special new science would be required to explain the multiverse than to explain a single universe. No god or gods are required in any event. For an interesting alternative way to think about multiverses, I recommend Neil Stephenson's (fictional) book "Anathem". Our article about the book does a poor job of explaining the idea of configuration space/phase space/state space upon which the book ultimately hinges. Basically, he's saying that every possible state of the universe (of which time is a property) simultaneously exists - making our progression through time an essentially illusory property of the instant of time we're in. This includes states that are "unreachable".

At any rate - while most of these ideas allow for the possibility of a god or gods, none of them require such a thing. As such, gods are no more necessary than pink piano-playing aardvarks on the far side of the moon...no more necessary than an infinite number of other things that might be true. Occam's razor tells us to pick the simplest answer - and that says "no gods" - and arguably "no multiverse" either. SteveBaker (talk) 03:17, 29 June 2009 (UTC)

(ec)The logic behind the anthropic principle is that every planet or universe where intelligent life arises must be conducive to intelligent life, so the fact that our universe is just right to support life is a logical necessity and not a sign of God. However, how the fine-tuning was done is not yet known. There are a few possibilities:

1. An all-powerful God did it.
2. Our universe is one of many multiverses.
3. Something else entirely. Perhaps a talking teapot made the universe 200 years ago and erased all evidence of it?

None of these possibilities have any supporting evidence, so scientifically, none of them are more plausible than the others. Philosophically, the second possibility is more satisfying because it proposes a Big-Bang-like beginning for the multiverses, and this beginning has almost no complexity. The first possibility, on the other hand, would require a complicated intelligence to exist at the very beginning of the universe. However, this is philosophy, and philosophy is useless for just about everything. All three possibilities are unproven; until somebody comes up with experimental evidence, all three are rubbish.

Jayron: Does Dawkins ignore the role of faith? I would have thought that the whole book's point is to address the stupidity of believing in God with no evidence whatsoever. --Bowlhover (talk) 03:47, 29 June 2009 (UTC)

So the problem is - why do the values for certain fundamental constants appear to have exactly the values that are needed for life to exist - if they had different values, then there would be no life. Well, there are lots of possibilities:

• That there is a true, underlying reason why those numbers have to be like that - a reason we have yet to discover.
• That all possible values for these constants show up in an infinity of universes - allowing the weak anthropic principle to explain why we are living in the good universe.
• That the values were randomly determined at the instant of the big bang - and we just got lucky.
• That we are incorrect in assuming that no life is possible with other values for these constants. Do we really understand ALL of the implications for a 10% larger charge on the electron? We haven't studied that scenario in any great detail - there are a few brief dismissals of the possibility of atoms forming - but maybe something else forms instead - and life appears from the something else? Is it possible that life of other kinds are possible in these very strange universes? If so, it might mean that intelligent life (although not "as we know it") appears in almost all configurations of the universe - and no "coincidence" is required.
• ...Or some supernatural entity made the universe especially for us.

The last of these is unsatisfying on many levels: How did the creator get created? Why does the place where the creator exists have exactly the right parameters for the creator to exist? This isn't any kind of an answer at all - it's just regressing the question back one more step for no particularly good reason. SteveBaker (talk) 04:28, 29 June 2009 (UTC)

There are different types of multiverse theory. The many-worlds interpretation of quantum mechanics is independent of the kind of multiverse Dawkins is talking about. You may want to read up on the distinction between the strong and weak anthropic principles. Multiverse theory allows us to do away with the strong version (which is very difficult to justify) and means we can just use the weak one (which doesn't need justifying at all, common sense is sufficient). --Tango (talk) 04:05, 29 June 2009 (UTC)

Seashells (Clam/Giant Clam) that have morphed

I live on a Pacific island and make jewelry from things that I find on the beach: shells, coral, sea glass etc. (no live animals taken). I have found whole, half and pieces of bi-valves that seem to have morphed into what looks like Marble. They are beautiful and the pieces that have rolled around in the surf are absolutely stunning! My theory is that the shells have been buried under extreme pressure in the sea bed and have morphed into Marble. If this is indeed correct I would like to share it with my customers who buy my creations but I don't have any proof. Can anyone provide me with the answer?Billyabston (talk) 02:52, 29 June 2009 (UTC)

I don't think that's how they are formed - shells under extreme pressure turn into limestone - and under even more extreme circumstances, limestone turns into marble - so the chemical composition of marble may not be all that different from your shells - which may explain the similarities in appearance that you're seeing. But after all of those extreme circumstances, there would be nothing left of the original shape of the material - it wouldn't look like a shell fragment anymore. SteveBaker (talk) 03:40, 29 June 2009 (UTC)

To go from the original aragonite of the mollusc shell to calcite doesn't take much burial but to completely recrystallise the calcite to make a marble requires quite high temperatures (rather than pressure) and by then it's going to be part of a rock. Although the original fossil shapes can be preserved in a marble, they normally get destroyed by ductile deformation, as calcite is a relatively weak mineral at elevated temperatures. As to what the OP found, I'm with Dauto below. Mikenorton (talk) 07:30, 30 June 2009 (UTC)

Are you talking about mother of pearl? Dauto (talk) 06:15, 29 June 2009 (UTC)

The shape of the mollusk survives. The walls of the shells have thickened and the weight has increased ten fold. The now morphed material has layers ranging from stark white to light gray. We have giant clam shells that have not changed into this material that I am speaking about and they are much lighter weight and have not thickened. Not Mother of Pearl either. Billyabston 20;57 30 June 2009 —Preceding unsigned comment added by Billyabston (talk • contribs) 09:00, 30 June 2009 (UTC)

Effects of higher gravity

Some works of fiction have adopted a theory that a human body forced to develop under greater weight will be much stronger than average if returned to a normal Earth environment. This is accomplished either by the use of weighted clothing (e.g. weight belts, wrist bands, leg weights, etc.), or by allowing the person to develop on planets with intrinsically higher gravity. Quite contrary to the fictional stories, I've heard comments that the prolonged use of external weights can actually damage ligaments and things, but I don't know how reliable those reports are.

I'm curious, have there been any studies (either theoretical or practical) on how terrestrial physiology would respond to a higher gravity environment? And would that response impart heightened strength and other benefits to a person then returned to normal gravity as imagined in those fictional works? My initial guess is that human physiology, having known only life on Earth, would be largely maladaptive under high gravity.

I also have this fanciful imaginary image of a rodent colony forced to live their entire lives in a 2g centrifuge. Has anyone ever done any real experiments like that? Dragons flight (talk) 07:26, 29 June 2009 (UTC)

There is a centrifuge being advertised for experimenters, and there was a centrifuge experiment in 1995 concentrating on the effect on rat temperature and mating. Many other experiments have been to determine changes in muscles, the liver, membrane integrity etc. Centrifuge experiments were also conducted on rats on the Russian satellites Cosmos 936 and Cosmos 1129. Our articles on these flights are single sentences which barely qualify even as stubs. - KoolerStill (talk) 12:00, 29 June 2009 (UTC)

I have seen archeologists report in National Geographic Magazine skeletons whose bones show enlarged muscle attachment points that they think are caused by the occupational stresses on galley slaves and bowmen. Sorry no references. Cuddlyable3 (talk) 13:23, 29 June 2009 (UTC)

Cool! My crazy rat experiment really gets done in real life. Dragons flight (talk) 02:08, 30 June 2009 (UTC)

Masturbation

How much calorie is lost during male masturbation (if the total time including erection and ejaculation is 6 min)? KnowledgeAbound (talk) 12:23, 29 June 2009 (UTC)

While you will burn calories, just as you would by sleeping, the amount you burn is negligible. A calorie is a big unit. For reference, there is a chart in the rehab room at our hospital that shows calorie burn per exercise. An average person doing a vigorous workout on the treadmill for 10 minutes will burn around 100 calories. So, compare that to about half the time while exerting far less effort. -- kainaw™ 12:33, 29 June 2009 (UTC)

If you did it with weights attatched to your wrist, what do you reckon about building up large muscles....Alaphent (talk) 12:36, 29 June 2009 (UTC)

You can do it while running on a treadmill. The question is limited to masturbation. It is not "What can I do while masturbating to maximize calorie burn?" -- kainaw™ 12:53, 29 June 2009 (UTC)

I was just interested after reading this in the possibility of masturbation as a form of excersise. Not interested in it as anything more than a curiosity though, mind Alaphent (talk) 13:05, 29 June 2009 (UTC)

Swimming consumes calories. Sperm swim. There are lots of sperm. Has anyone a figure for the calories ejaculated? Cuddlyable3 (talk) 13:08, 29 June 2009 (UTC)

According to Cecil Adams it's pretty small figure. [17] APL (talk) 15:45, 29 June 2009 (UTC)

It really depends on how you engage in it. Some people move a lot during masturbation, using their back, leg, and gluteal muscles, raising their heart rate, and breathing heavily. Others lie relatively still and mainly move just their hand. Some people may find it helpful that masturbation tends to cause the rapid release of endorphins, which reduces perception of muscle pain (this is why people often notice a sudden muscle soreness after sex). The ultimate limiting factor though is the duration - even running for 6 minutes just won't burn a lot of calories. You'd have to get the duration up to have a more significant effect (which you can do - masturbation for extended periods is possible). Even if you did this, though, it would make uneven use of your muscle groups, so it would be an incomplete workout for muscular strength, and it would be difficult to maintain an intensity suitable for cardiovascular exercise. Dcoetzee 04:22, 30 June 2009 (UTC)

Surely there's energy needed to produce sperm? And surely new sperm must be produced after masturbating? —Preceding unsigned comment added by 81.11.170.162 (talk) 09:05, 30 June 2009 (UTC)

Not particularly, no. First of all, sperm constitute only a very tiny percentage of the volume of semen - mostly it's water. Also, sperm are continuously produced and reabsorbed. They don't really live long enough to just hang around waiting forever. Dcoetzee 20:05, 30 June 2009 (UTC)

Esterification Mechanism

In an esterification reaction between a carboxylic acid and an alcohol (I know they are normally carried out with acyl chlorides) the mechanism I have shows an electron pair moving from the carboxylic acid OH to the carbonyl carbon, and then an electron pair from the carbonyl double bond (NOT the O) moving to generate a bond with a H⁺ catalyst. This protonation forms a more reactive electrophile for the alcohol to attack. It looks like a carboxylic acid group with a H attatched to a positivly charged O. I am fine with this, however my question is why doesn't the carbonyl O use a lone pair to form a bond with the H⁺? As this would give exactly the same intermediate. This movement is possible, and is neccessary for the acid catalysed formation of hydrates/acetals/hemiacetals etc....basically any nucleophilic carbonyl reaction that requires a stronger carbon electrophile. Alaphent (talk) 12:35, 29 June 2009 (UTC)

EDIT - The wikipedia on Fischer-Speier esterification shows the second mechanism I proposed. Now I am really confused....Alaphent (talk) 12:43, 29 June 2009 (UTC)

A carboxylic acid group is stabilized by resonance: "an electron pair moving from the carboxylic acid OH to the carbonyl carbon" (and back again, switching between those two forms) happens at all times whether or not H+ (or anything else) is present. Well technically, it doesn't actually happen at all, "reality" is some single average/intermediate structure looking sort-of like both cases:) Because both forms are already present, you can draw either one as the reactant in the protonation step. In one sense, it's more likely the O- form that reacts ("the most negative thing is most likely to be protonated" and "less stable/charged form more likely to react than totally neutral form"). But the neutral form is more stable and a better representation of the starting structure, so some prefer to use that as the reacting form directly or via explicit resonance. And it totally doesn't matter which mechanism you use, because the result is the same. The protonated form is also involved in resonance via the same first step you described. DMacks (talk) 17:01, 29 June 2009 (UTC)

The lewis-electron-pushing-arrows mechanism does not really capture how the electrons flow , but rather show a sort of "shortest path" from the starting and ending state. In reality, the electron density probably moves from between the carbon-oxygen atoms to between the oxygen-hydrogen atoms as described, but rather than attacking from that location, the electrons probably flow around the oxygen atom to form the new bond to hydrogen. If you could find an electron-density-flow animation of some sort, it would make more sense than the simple lewis arrow diagrams, which are an approximation of reality meant to simplfy stuff for people working with pencils and paper to model the processes, and not the sort of advanced computer modeling we can do today... --Jayron32.talk.contribs 02:07, 30 June 2009 (UTC)

Cities on the Moon

Assume in the future there are large cities on the moon (approximately the population and size of the Eastern Seabord of the US). During a new moon (also assume these cities are on the side facing us) would a person be able to see city lights with an unaided eye?

Also, how small of a lightsource could it be before you wouldn't be able to see it? Assuming cities there are similar to those on Earth (in terms of density, light output per capita)what population size would be required before you could see it?

Finally, what about Mars (I imagine you'd need a telescope but even than what would it take to be visible)? TheFutureAwaits (talk) 15:04, 29 June 2009 (UTC)

A city on the moon would be several arcseconds in angular diameter from Earth, so would appear as a point source of light with the naked eye (you could probably resolve a few details with decent binoculars). Unfortunately, I can't find any details about the amount the minimum brightness required to be visible to the naked eye (it's about magnitude 6, but I can't find a way to convert that to luminosity - anyone?). As for Mars, I don't think you would be able to see much. Since Mars is further away from the Sun than us it doesn't have phases, the side facing us is always lit. There might be a dark bit on one edge depending on the relative positions of the Earth and Mars, so I guess with a decent telescope you might be able to see some lights there, but they would only be visible for a short amount of time. Just like Venus is only visible from Earth for either a short time after sunset or a short time before sunrise, the same is true of Earth from Mars, and it's only during that time that you would be able to see the light from a given Martian city. --Tango (talk) 15:52, 29 June 2009 (UTC)

While hardly definitive, The Straight Dope quotes Apollo 12 astronaut Alan Bean as saying:

"The only thing you can see from the moon is a beautiful sphere, mostly white [clouds], some blue [ocean], patches of yellow [deserts], and every once in a while some green vegetation. No man-made object is visible on this scale. In fact, when first leaving earth's orbit and only a few thousand miles away, no man-made object is visible at that point either."

— Alan Bean

I'm assuming that we'd have similar luck, or lack thereof, resolving lunar human details from Earth. If nothing else, there's a good chance that Earthshine will wash out detail. As our article notes, it's at its strongest near the new moon, counterbalancing much of the benefit of a generally darker moon. I don't see a specific reference for the equivalent magnitude, but it's certainly higher than mag 6, since it's easily visible in my generally urban area. This photo provides a good comparison and this paper suggests that its magnitude may be on par with the brightest stars in the sky. — Lomn 18:03, 29 June 2009 (UTC)

At new moon, the Sun, Moon, and Earth are almost in a perfect line. It's absolutely impossible to see cities on the Moon at this time; in fact, the Moon itself is impossible to see since it would be within a few degrees of the Sun. The "newest" moon that has been sighted was 12 hours old [18], but that sighting was only possible with a telescope and lots of amateur astronomy experience. For the few days following or preceding new moon, the Moon can be seen but it stays close to the Sun; seeking out dim lights on the dark side would be very difficult.

Several days before or after, it would be possible to see the Moon when the Sun is well below the horizon, but ask an amateur astronomer and they'd tell you dim stars are easily washed out by the Moon if the Moon is anywhere in the sky at all. Since the cities to be looked for are on the dark portion of the moon, and that's less than half a degree from the lit portion, the limiting magnitude would probably be very low; based on personal experience, I'd be surprised if it were higher than 2 without optical aid. With a 6-inch telescope, though, even 8th magnitude shouldn't be a problem.

For something on the Moon to appear to be 6th magnitude, it'd have to put out 15 GW (back of the envelope calculation)--about 70 times higher than the total wattage of artificial light that the entire UK sends skywards. Even 8th mag would require 2 GW, which is lower but still much too high. Add to this the fact that electrical power on the Moon will presumably be scarce, so the lunar colonizers will make sure they don't waste as much energy sending light upwards as Earthlings do light polluting their skies, and you get an idea of how dim lunar cities will be.

So sadly, it probably won't be possible to see city lights on the moon without a very powerful telescope; they're just too dim. However, if a large portion of the lunar landscape is reworked--"large" meaning more than a few arcseconds--and the reworked area is much more colorful, reflective, or otherwise distinctive than the asphalt-like moon rock, it might be possible to see this area using a telescope while it's on the lit portion of the moon. --Bowlhover (talk) 20:22, 29 June 2009 (UTC)

I have changed your ref-tag into an external link since we do not have a References Section on the Science Desk. Nimur (talk) 13:18, 30 June 2009 (UTC)

Thanks Bowlhover, that was a very interesting read! Quick question, do you know how this would work in reverse (ie can you see the cities on Earth from the Moon?) TheFutureAwaits (talk) 20:42, 29 June 2009 (UTC)

Yes, that shouldn't be a problem. The interesting thing about the Moon is that it's tidally locked to the Earth, so to an observer on the Moon, the Earth would always be in the same position. While the Sun and the other stars move slowly across the sky due to the Moon's rotation, Earth would go through its phases once a month but always remain at the same altitude and azimuth. That's great for lunar telescope users because the telescopes don't have to be tracked; they can remain absolutely stationary and still never lose sight of Earth. This is actually not absolutely true due to libration, but unless someone is planning to stare at Earth for days on end, it's a good enough approximation.

The Moon also doesn't have an atmosphere, which means there is no scattering of sunlight or Earthlight. As a result, no matter where the Sun happens to be, the surrounding sky is always pitch black. As long as the Sun, the Earth's lit portion, and any objects illuminated by them are kept out of your eyes' field of view, your eyes will eventually dark adapt to the point of being able to see dim stars.

Based on the figures for U.K. light pollution, a city like Las Vegas should be magnitude 11-12 at nighttime. Since cities are typically several arcseconds across when viewed from the Moon, Las Vegas's size and brightness would be similar to that of a dim galaxy. A 6-inch telescope could probably pick up downtown, and with larger telescopes it would be possible to see some of the suburbs. Very little detail is visible with objects this dim, however, and seeing color would certainly be impossible because the cone cells require a lot of light to activate. Las Vegas would look like a dim, virtually featureless patch of light that's barely distinguishable from the surroundings.

Viewing Earth's cities is a bit easier if those cities are in daylight. In that case, they would stand out as grey patches in the surrounding green forests or blue lakes/oceans. Because you'd be looking through Earth's atmosphere, astronomical seeing is just as much of a concern as it is for astronomers on Earth, and seeing typically limits a telescope's resolution to 2 arcseconds. That corresponds to 3 km on Earth's surface. To get an idea of what Earth would look like, see these Blue Marble images. Click on an 8 km/pixel image and zoom in on your browser. Do the same for an 2 km/pixel image. The size and detail of what you see approximately matches the size and detail a lunar observer can expect with an amateur telescope and 140x magnification. --Bowlhover (talk) 10:10, 30 June 2009 (UTC)

The perfect viewing time would be a total eclipse of the moon during midnight. —Preceding unsigned comment added by 84.187.70.226 (talk) 20:44, 29 June 2009 (UTC)

Ah, crap, I didn't know that. The atmosphere refracts too much light around the earth. —Preceding unsigned comment added by 84.187.70.226 (talk) 20:51, 29 June 2009 (UTC)

No, you're correct -- a total lunar eclipse is the best time to see this sort of phenomenon. It's just that even then it's still a long shot (the paper above estimates that the lunar surface remains roughly magnitude 0; only 4 stars in the night sky are brighter. — Lomn 21:03, 29 June 2009 (UTC)

Hmm. On one hand, the Moon is much brighter during a lunar eclipse than the dark, Earthshine-lit portion of the Moon is during other phases. On the other hand, during an eclipse there is no bright sunlit Moon to light-pollute the sky. I don't know which effect dominates, but if I had to guess I'd a lunar eclipse would indeed be the best time to see lunar cities.

Some food for thought: maybe a solar eclipse would work as well? --Bowlhover (talk) 10:10, 30 June 2009 (UTC)

No, the moon is darker during a lunar eclipse than is the Earthshine portion normally. A solar eclipse would still be dominated by solar phenomena. — Lomn 12:14, 30 June 2009 (UTC)

Not in my experience. Lunar eclipses vary widely depending on atmospheric conditions, but most I've seen have been pretty bright. Earthshine is very dim indeed. --Tango (talk) 03:02, 1 July 2009 (UTC)

Quoting from the source linked above, "...indicates that earthshine on the Moon is several times brighter than the totally eclipsed Moon and should easily be visible except for the fact that it may be overwhelmed by the brightness of the sunlit Moon", which noted earlier in the source, is some 100 times brighter. — Lomn 13:02, 1 July 2009 (UTC)

Ah, that's a good point - a totally eclipsed moon will be in a dark sky, an Earth-lit moon is always right next to a Sun-lit moon. That probably explains why my naked eye observations differ from the actual numbers. --Tango (talk) 01:52, 2 July 2009 (UTC)

Interesting. I have photos of two lunar eclipses, along with the EXIF data and the camera I took them with, so I'll try photographing earthshine with the same settings and see what I get. --Bowlhover (talk) 03:37, 2 July 2009 (UTC)

wind turbine numbers

How many wind turbines have been installed in the US in the past year that are 1MW or larger? 65.121.141.34 (talk) 15:41, 29 June 2009 (UTC)

[19] (page 14) shows the number of windmills installed in 2008 and the total MW for each windmill producer. But it doesn't breakdown which ones are more than 1 MW. 5105 windmills larger than 100kW were installed last year for 8554 MW total, or 1.69 MW average. Rmhermen (talk) 19:01, 29 June 2009 (UTC)

Page 19 of that document has a graph of installed sizes but you can't get exact numbers from it either. Rmhermen (talk) 19:35, 29 June 2009 (UTC)

Ethanol molecule structure

There is a picture in Ethanol article that shows the hydrogen bonding: File:Ethanol-xtal-1976-3D-balls.png. It can be seen that in some molecules the hydrogen atom near the oxygen is located symmetrically, and in others it is rotated. Does it mean that these are different isomeres of ethanol? Or may be this angle isn't strictly defined and the hydrogen atom can rotate rather freely around the oxygen? Btw, on Wikimedia Commons there is an entire category with ethanol molecule representations, which also locate that hydrogen atom differently.--Ring0 (talk) 21:21, 29 June 2009 (UTC)

All of the bonds in an ethanol molecule can freely rotate. See: conformational isomers. --Mark PEA (talk) 22:14, 29 June 2009 (UTC)

Punching completely through someone

In various comics I've perused over the years, sometimes obstensibly human characters have literally punched straight through human opponents. While this obviously isn't supposed to be realistic, what sort of level of force would be required to do this? Is it feasible for even the strongest human to punch clean through someone else?

I'd imagine part of the issue would relate to where the punch was aimed (easier to punch through soft abdominal tissues than the sternum or skull) and the physical condition/size of the punchee (smaller/weaker target easier to punch through)

We have the additional problem of whether if such a punch due to Newton's third law would cause serious injury to the puncher. Any ideas anyone? Exxolon (talk) 22:41, 29 June 2009 (UTC)

Sorry. I remove my comment. (In response to below.) Bus stop (talk) 00:19, 30 June 2009 (UTC)

I'm not sure if that answer belongs on this page, it was neither helpful or humorous. This person clearly has a reasonable level of understanding of physics, and your answer just takes the mickey to be honest. Alaphent (talk) 23:24, 29 June 2009 (UTC)

No worries mate, I'll leave the above to stand though if that's ok? Alaphent (talk) 00:33, 30 June 2009 (UTC)

Sounds OK to me, mate. Bus stop (talk) 00:39, 30 June 2009 (UTC)

There would have to be something holding the person being punched still, otherwise they would just be thrown backwards. --Tango (talk) 00:27, 30 June 2009 (UTC)

I seem to remember reading somewhere (no source, sorry - may have been here) that human flesh takes on similar characteristics to rubber when struck hard and fast. I'd say that trying to punch straight through a person would be much like trying to punch straight through one of those thick rubber gym mats. I have seen football (soccer) injuries where someone's foot has been driven straight through someone else's leg (not just at the joint either), leaving the thing dangling there by a thread - but that's a rather different situation. --Kurt Shaped Box (talk) 00:32, 30 June 2009 (UTC)

I guess that's more ripping off than ripping through, so is quite different. --Tango (talk) 00:48, 30 June 2009 (UTC)

Expansion - I imagine part to the fundamental physics is that it's much easier to push a small, hard and sharp object through someone that a large, soft and blunt one. The concentration of force at a point is the key. For instance a moderately strong person could lunge with a rapier and pierce completly through a human body, assuming they missed the bones - the question is can it be done with the fist, a much larger, softer (relatively) and blunter instrument? Exxolon (talk) 00:56, 30 June 2009 (UTC)

I don't think that even the strongest punch could go completely through someone, because the force is not strong enough and because it's spread over the area of the puncher's fist. A karate kick, though, might go through soft tissue or even through bone, provided that the entire force is concentrated at the kicker's heel and applied at a right angle to the target (I've seen someone in my team get his head busted open in just this way -- OUCH!), but that's a whole different situation too. 76.21.37.87 (talk) 01:57, 30 June 2009 (UTC)

If it's just a matter of pressure - then we can look at the cross-sectional area of a rapier (maybe 20mm²?) and the cross section of a fist (maybe 5000mm²) and say that it takes 250 times as much force? But I strongly suspect that's an under-estimate. The rapier can slide off and slip between bones - the fist really can't do that. It's clearly impossible. But even if some super muscle-bound freak could apply that much force - you'd have to expect the damage to his fist and arm to be comparable to that of the victim. SteveBaker (talk) 02:03, 30 June 2009 (UTC)

I have this mental image of the MythBusters, their chicken gun, and the inevitable pig carcass... 62.78.198.48 (talk) 04:03, 30 June 2009 (UTC)

So that raises the obvious question: if a mere human could not punch through a person without significant harm to themselves, what about a Terminator-style humanoid made entirely out of steel or some other hard metal? Could they pull it off, or would some other unexpected result occur? Dcoetzee 04:13, 30 June 2009 (UTC)

Mythbusters shot canon balls through human analogs at 300 or 400 mph. The canon ball was probably of similar size to a fist, so if you could get a metal fist going that fast, I'm sure it is possible. Engineering a robot capable of getting that much power in it's punch would be very challenging though, and the fist would need to be quite solid to avoid also breaking it in the process. Dragons flight (talk) 06:54, 30 June 2009 (UTC)

If a barracuda 4 feet long can impale a human, and a 13 year old can impale himself on the bicycle handlebar under his own power, without a fall from a height or a car crash then a human should be able to impale a human. I think it is plausible that extended fingers might penetrate the front of an unmuscular abdomen if there was a full force strike. Sharp fingernails would doubtless aid the initial penetration. It would be hard to make it all the way out the back. The striking area would be far smaller than the typical cannonball so the force of the blow would be more concentrated. There would certainly be a chance of finger breakage. Google news archive has a horrible collection of impalement stories. Typically someone falls onto a fence or is thrown against a post, pipe, or railing in a train, car, or horse riding accident. (Iron spiked fences have caused countless unnecessary deaths.) If someone in the 1930's in Germany had fallen from an airplane and landed on Hitler's upraised arm, how far would the penetration be? Edison (talk) 23:20, 30 June 2009 (UTC)

I have been informed that the first person to refer to Hitler in a debate, loses, so I concede. As a consolation prize, I imagine it to be Hermann Göring that falls out of the airplane. Coincidentally, one of the Google News archive results for "impalement" was "BULLFIGHTER RECOVERING FROM GORING. Edison (talk) 05:41, 1 July 2009 (UTC)

June 30

How to estimate calories required daily?

I want to create a gradual weight loss by reducing my calorie intake slightly below the amount of calories that would make me neither fatter or thinner. How can I estimate this amount? It must be related to body size etc. 92.27.159.22 (talk) 01:46, 30 June 2009 (UTC)

That would be the Harris-Benedict equation. SteveBaker (talk) 01:56, 30 June 2009 (UTC)

Also, there are websites that will take a lot of info from you (what kind of exercise you do, how far you walk per day, etc.) and tell you exactly what the additional caloric burning/cutback you'd need to burn a pound a week or something along those lines. Obviously they are not precise but they give an estimate. Doing that made it clear to met that switching to diet soft drinks (if soft drinks must be drunk) would make sure things seriously, seriously easier! An extra few thousand calories out of one's weekly intake makes quite a difference, and it's an incredibly easy way to do it... --98.217.14.211 (talk) 03:01, 30 June 2009 (UTC)

I don't think this approach will work. It's almost impossible to estimate either your caloric intake or caloric output with an accuracy better than 10% -- even 20% is very hard -- hell, even 30% is hard. If you get it wrong, it will take weeks before you get enough feedback to tell you so. The only workable way to lose weight by dieting, I believe, is to cut your calorie intake to 3/4 or less of what you estimate you are expending.

I agree, it also seems that even with accurate inputs, there is generally a more than 10% error on this: "A review of the data reveals that the methods and conclusions of Harris and Benedict appear valid and reasonable, albeit not error free. All of the variables used in the equations have sound physiologic basis for use in predicting BEE," from [20] but also "Harris-Benedict equation overestimated basal energy requirements by 10 to 15% in 201 studies of healthy men and women. These results raise questions regarding the accuracy of predicting an individual's energy requirements." from [21] and "overestimation of 10% to 15% is normally found" from [22], and "Calculated resting metabolic rate was more than 10% different in 33%" from http://linkinghub.elsevier.com/retrieve/pii/S0002822303009829. Basically even the most complicated equations and perfect input of caloric intake and excercise only give a rough estimate.YobMod 17:28, 30 June 2009 (UTC)

Thanks. I had in the past tried a harsh diet of 2000c during weekdays and 2500c at the weekend that dropped my weight in a few weeks. But, like most dieters, as soon as you stop the diet, your weight soon returns to what it was previously. Currently I am on a milder diet of 2500c per day, which is undoubtedly less than what I ate before when unrestrained, since normal processed foods have too many calories in them to be eaten except as rare treats. I have been eating lots of vegetables and fruit and so far have not felt particularly hungary except mildly late in the evenings. 89.240.105.155 (talk) 19:47, 30 June 2009 (UTC)

You might like the online book The Hacker's Diet. 208.70.31.206 (talk) 07:37, 2 July 2009 (UTC)

simulating finger prints

How might I fabricate a material that could simulate human finger prints, i.e. very small grooves on the surface of a smooth rubbery? skin-like surface. Obviously you can't really replicate real fingers 100%, but what might be a reasonable material to simulate the skin? And how might I get the fingerprint "grooves"? I'm thinking some sort of rubber that I can harden into a cast after imprinting my own finger prints, and then use that mold to create the outer skin layer which I will cover the replica fingers with. Any idea what sort of rubber I could use to do this? Or does anyone know of a better way? Thanks! 124.154.253.146 (talk) 02:53, 30 June 2009 (UTC)

That sounds like a difficult problem. But I wouldn't be surprised if there were answers out there. My mind immediately turns to gloves -- made of vinyl, latex, or nitrile. See the work of Duane Hanson, not that I know how he made his wonderful sculptures. Finally, if you can get your hands on the DVD for the movie Click (film), there happens to be an amazing segment on that DVD, not part of the movie, which describes and shows how some of the body transformative makeup is produced and applied. (It won't really answer your question, but it shows the amazing things that can be done in the general realm of transforming the face and body.) The people working in that field (Make-up artists) would seem to be the most knowledgeable people I can imagine for coming up with a solution to the problem you pose. Bus stop (talk) 03:10, 30 June 2009 (UTC)

It's possible that a process used in make-up art will suffice, but since I'm more looking for functional similarity than visual similarity, I'm not sure if that's the right direction to go look. Wax sculptures, after all, can be frighteningly real, but they serve no real scientific purpose. Then again, functionality is sometimes an issue when making movies (the actors after all, sometimes have to use their hands, even if they're latex), so I could be wrong. 124.154.253.146 (talk) 03:37, 30 June 2009 (UTC)

In an episode of Mythbusters they were able to fool a fingerprint sensor with just a piece of ballistic gelatin which had been chemically etched with a scan of a fingerprint, though fooling a forensic scientist may be a bit more difficult.-RunningOnBrains^{(talk page)} 04:01, 30 June 2009 (UTC)

Notably, if you actually want to leave fingerprints on surfaces, your fake finger has to have oil on it, like the kind emitted by human skin. Dcoetzee 04:09, 30 June 2009 (UTC)

I guess I should have mentioned that the point is to simulate the amount of grip fingerprints add (or don't) to your finger. 124.154.253.146 (talk) 06:01, 30 June 2009 (UTC)

It may be tough to find a material that mimics skin well enough to make that direct comparison. However, you could probably get some idea whether you're on the right track or not by comparing smooth gelatin against gelatin with a fingerprint pattern. http://www.antionline.com/archive/index.php/t-241708.html describes how to make a gelatin fingerprint. See also: http://www.realtechnews.com/posts/3129 SteveBaker (talk) 16:09, 30 June 2009 (UTC)

This recent study asserts that fingerprints do not improve grip. --Sean 13:15, 1 July 2009 (UTC)

I believe the current theory is that it improves our sensitivity to subtle surface textures. As your finger moves over a bump or an edge, the tiny ridges in the fingerprint briefly lock onto it and the skin is deflected to a larger degree than smooth skin would be - this provides a bigger signal to the nerve endings in the fingertip. The fact that someone already did the 'grip' experiment should in no way deter our OP - for science to proceed, many people have to repeat an experiment before the results of it will be widely accepted as "the truth". SteveBaker (talk) 11:33, 2 July 2009 (UTC)

It really Works !!!

Remember I had asked a question a few days back, here. Well what do you know, It really works !! It responds to light just fine on the breadboard, and it is as sensitive as it can get... I think there must be something in IR emitters after all which would enable them to detect light, and do it quite well... But thanks for helping out, guys...Rkr1991 (talk) 08:12, 30 June 2009 (UTC)

Thanks very much for testing that out, and good luck with the rest of the project. Any special trick you can see used to get it to work like putting a bias voltage onto it? I though there was a good chance of success but when I tried a red LEDs with an ohmmeter I couldn't get anything when going out in the sun. Are you sure it is the IR emitter? If so I'll be able to blow a raspberry to a very valued contributor ;-) Dmcq (talk) 08:57, 30 June 2009 (UTC)

Yep, you bet, it's the IR emitter all right. There is in fact a line in the book which I used, which I am quoting : We can't use the detectors, they're too weak. And we don't want our device to be too mousey. I didn't know what to understand from that statement. If the detectors were too weak, I suspected the emitters would be even weaker, which is why I asked the question. And its not clear what he means by too mousey. But who cares about all that, all that matters is that it works ! In fact, the detectors are even more sensitive. And yes, I did reverse bias the emitters. That was given in the book, I'm not very good in the logic part yet, we're just beginners... But overall, I guess that the fact that the emitters work would be saying something to our expert here.. Rkr1991 (talk) 11:06, 30 June 2009 (UTC)

I would guess mousey = "like a mouse". So you don't want it to be only as sensitive as a computer mouse, which needs high proximity or even contact to detect.YobMod 16:04, 30 June 2009 (UTC)

So may I just say neah-neah-ne-neah-neah to

“ There is no way a light emitter can be used as a detector. Your book is wrong. If it's not a misprint then the author is an idiot...which is actually possible - many of these books are written by enthusiastic amateurs who are sloppy with scientific terms ”

:-P Dmcq (talk) 21:22, 30 June 2009 (UTC)

I'm surprised nobody has found this article yet: LED as light sensor. "A LED is simply a diode that has been doped specifically for efficient light emission and has been packaged in a transparent case. Therefore, if inserted into a circuit in the same way as a photodiode, which is essentially the same thing, the LED will perform the same function."

Even more interestingly: "LEDs can be used as both emitters and detectors of light, which means that a device having only a single LED can be used to achieve bidirectional communications with another device meeting these requirements. Using this technology, any of the ubiquitous LEDs connected to household appliances, computers and other electronic devices can be used as a bidirectional communications port." --Bowlhover (talk) 00:13, 1 July 2009 (UTC)

No, User 76.11.230.33 in fact pointed out this article to Steve saying it disagreed with him. But Steve's point was that why use the emitters to detect when you've already got two very specialized detectors, which still remains fuzzy... Maybe the detectors would make it too sensitive... Rkr1991 (talk) 04:52, 1 July 2009 (UTC)

Where is Steve hiding, by the way ? He did contribute at 17:30 June 30th at the Miscellaneous desk.. Rkr1991 (talk) 04:57, 1 July 2009 (UTC)

And on July 1st at 12:22... Rkr1991 (talk) 15:14, 1 July 2009 (UTC)

thermodynamics equilibrium constant

the equilibrium constant of a reaction depended only on temperature . At what condition equilibrium constant not change with temperature?Rikichowdhury (talk) 09:01, 30 June 2009 (UTC)

From the Vant Hoff equation, if ΔH for the reaction is zero, then the equilibrium constant is independent of temperature. Rkr1991 (talk) 11:09, 30 June 2009 (UTC)

In fact, our article on Equilibrium constant gives the link. Please do try to read the relevant articles. Rkr1991 (talk) 11:10, 30 June 2009 (UTC)

Hypotension

Can low blood pressure cause cold hands or cold extremeties? How does it cause that? --Mudupie (talk) 13:45, 30 June 2009 (UTC)

It is not a cause. There may be a correlation. However, I've never seen a study on hypotension and cold extremities. I've only seen studies on the correlation between hypertension and cold extremities. Many find a stronger correlation between use of beta blockers and cold extremities. -- kainaw™ 13:50, 30 June 2009 (UTC)

See vasoconstriction, vasodilation, and total peripheral resistance for articles on how the peripheral vasculature (not the big arteries of the body) can affect blood pressure and perception of "cold" or "warm" extremities. The perception of "cold extremities" is generally due to vasoconstriction of the peripheral blood vessels, which could be due to the body trying to preserve the core body temperature and prevent hypothermia, or could be due to the body trying to preserve blood flow to critical organs (i.e. prevent hypotension) in a state of dehydration, hypovolemia, or blood loss.

As Kainaw said, it isn't really a cause-effect relationship, although one could imagine a situation in which acute hypotension led to peripheral vasoconstriction (and the accompanying perception of cold extremities). One could also imagine the reverse situation, in which there was acute vasodilation (accompanied by a sensation of "warmth" or "flushing") with resulting hypotension due to decreased peripheral resistence. So not a direct cause or effect, but a correlation. --- Medical geneticist (talk) 15:10, 30 June 2009 (UTC)

To Mudupie: yes. See "Shock (circulatory)". Hypovolemic shock, cardiogenic shock and obstructive shock will all lead to cool peripheries. Distributive shock leads to warm peripheries. Axl ¤ [Talk] 17:00, 1 July 2009 (UTC)

Nitrogen enhanced gasoline

I have been reading up a bit on the new Sell gasoline that is nitrogen enhanced. I find a lot of controversy and contradiction re: the legitimacy of this enhanement. So, can anyone shed some light on whether or not nitrogen enhanced gasoline really is beneficial and if so in what way? —Preceding unsigned comment added by 209.161.211.158 (talk) 14:11, 30 June 2009 (UTC)

I have always been suspicious of this claim. The addition of nitrogen-containing compounds MAY have some effect on altering the octane rating of the gasoline, and thus improve performance. It also may reduce the incomplete combustion of the gasoline, which would reduce the accumulation of soot along vital engine parts. However, enhancing the nitrogen content of gasoline can ONLY lead to increased nitrogen oxides production, and nitrogen oxides are universally recognized as a serious contributor to air pollution, especially smog. So what you are probably getting is a cleaner burning fuel, from your engine's point of view, but this is at the cost of increasing polutant levels in the air. Presumably, the gasoline still meets federal clean-air requirements in the U.S., but I cannot see how it does not increase polution over non-enhanced gasoline. --Jayron32.talk.contribs 14:37, 30 June 2009 (UTC)

It's probably beneficial in that it has cleaning additives. However, there are a couple of key points that don't get mentioned. One, most major gas brands have some form of cleaning additive. One-A, you don't need the cleaning additives every single time you fill up. Most people, without ever thinking about it, have sufficiently clean valves and the like. Two, it has no impact on the gasoline itself. Your fuel economy filling at one reputable gas station will not meaningfully differ from your fuel economy filling at another. — Lomn 14:39, 30 June 2009 (UTC)

Nitrogen compounds as cleaning additives?! Come on people, get real! I've done some research on shale oil (which has LOTS of nitrogen compounds in it), and I know for a fact that those compounds are definitely harmful to fuel quality: they have a strong tendency to spontaneously polymerize and form huge amounts of disgusting sticky black sludge that clogs engine components in no time flat! In fact, in the case of shale oil, nitrogen compounds must be completely removed from the fuel, and to the best of my knowledge, they must also be removed from conventional petroleum that happens for some reason to have too much nitrogen in it. Sounds to me like Shell is trying to charge extra for low-quality gasoline by trying to market it as something good for your car, when really it's nothing of the kind. FWiW 76.21.37.87 (talk) 06:50, 1 July 2009 (UTC)

Have you considered the thought that Nitrogen forms more than one compound? It is entirely possible, even likely, that some compounds are harmful while other are beneficial.APL (talk) 22:38, 1 July 2009 (UTC)

APL -- I am perfectly aware of that; however, I know for a fact that most amines and nitrogen-containing heterocyclic compounds such as pyridines and pyrroles are harmful to fuel quality. Furthermore, to the best of my knowledge, it is precisely the compounds listed above that are most likely to be found in Shell "nitrogen-enhanced" gasoline, because most other nitrogen compounds are rarely, if ever, found in petroleum and petroleum products. I also reiterate that from what I know about petroleum refining (which is quite a lot), high nitrogen levels in petroleum are in general undesirable and are (if excessive) lowered by hydroprocessing. Therefore, I stand by my position that "nitrogen-enhanced" gasoline is of a lower quality than conventional gasoline. FWIW 76.21.37.87 (talk) 04:19, 2 July 2009 (UTC)

Chai - laxative qualities?

My local bagel shop serves a chai latte'. I'm not a tea drinker but this stuff is outstanding! A couple other people and I have noticed that we have to defecate soon after drinking it. So, we're wondering, does whatever version of chai that this most likely is have any laxative qualities? Note: I am not seeking medical advice. We have just noticed this pattern in three non-genetically related people. Again, this is not a request for medical advice. Dismas|^(talk) 14:46, 30 June 2009 (UTC)

I think the general answer is no. Chai latte that i've had (Starbucks?) is just chai-style tea made with the latte milk steaming machine. There is nothing in this combination that would be any more laxitive than the two things alone. But as chai usually have a secret mix of spices in, it is possible that this one example does have an unknown ingredient with this effect (if so, it should occur without the Latte).YobMod 15:25, 30 June 2009 (UTC)

By the way, the three people that have noticed this live in two separate households, in two different states, and have noticed this from different bagel shops. Dismas|^(talk) 17:01, 30 June 2009 (UTC)

Perhaps a Pavlovian response. 65.121.141.34 (talk) 18:07, 30 June 2009 (UTC)

Could just be the caffeine, though our tea article says there's much more caffeine in a cup of coffee. Tempshill (talk) 18:49, 30 June 2009 (UTC)

Since caffeine is a diuretic, shouldn't it have the opposite effect and cause constipation due to lost water? 213.122.68.63 (talk) 14:54, 1 July 2009 (UTC)

Caffeine is actually not a significant diuretic except in very special circumstances (this topic has been discussed ad nauseum at Talk:caffeine), but tea -- ordinary tea -- is a pretty strong diuretic. Looie496 (talk) 01:22, 2 July 2009 (UTC)

I've noticed from personal experience that tea in general is a laxative. 89.240.105.155 (talk) 19:35, 30 June 2009 (UTC)

Yeah? Try some native teas boys. There's one for every purpose. Take the time to learn them from an elder and you would be surprised by the results! Me??? I'm fond of spotted joe pyeweed tea or comfrey tea. Tastes horrible, hard on the taste buds and the liver but good for the brain! Experiment but BE CAREFUL! B.T.W. J-weed ...stay away from it, Salvia likewise. 67.193.179.241 (talk) 21:08, 30 June 2009 (UTC)Rana sylvatica

Strange plant in northeast Kansas.

I was hacking down plants with a machete in my brothers backyard today and I came across a very tall, non-woody-stemmed plant (about the size of a small tree). It has a reddish-purple stem and huge, long, pointed ovoid leaves. The stem is very thick (two or three inches at the base)and when I hack it open, the pith inside is divided into little segments all the way up by little white membranes. The tiny, white flowers near the top have five petals and seem to be in the process of turning into little green berries. I don't have the slightest clue what this plant might be and I'd really like to find out. Any help would be appreciated. 76.250.254.192 (talk) 17:11, 30 June 2009 (UTC)

Sounds like something in buckwheat genus, Fagopyrum; or related. Still, very hard to tell without a picture. --Dr Dima (talk) 18:54, 30 June 2009 (UTC)

When in doubt, suggest it's Phytolacca americana, the American Pokeweed. Seems to be the most commonly asked after plant this time of year. The description sounds accurate. Not sure about the stem section, though. --Rkitko ^(talk) 18:58, 30 June 2009 (UTC)

Yes, that's a good call. American Pokeweed is posionous, so caution should be exercised when dealing with it. --Dr Dima (talk) 19:57, 30 June 2009 (UTC)

I concurr, but when young, the plant is not toxic. "pokeweed salad" anyone? 67.193.179.241 (talk) 21:12, 30 June 2009 (UTC)Rana sylvatica

It's still toxic unless properly prepared, and it's a little bit toxic even then. See Poke salad. -Arch dude (talk) 02:25, 1 July 2009 (UTC)

My first guess based on the text description was pokeweed as well. It is somewhat poisonous if directly consumed, but you should be fine to touch it; its not like poison ivy or anything. The most annoying thing is the purple berries it puts out which stain your clothes. When in doubt, call Annie. She'll know what to do with it. --Jayron32.talk.contribs 03:53, 1 July 2009 (UTC)

OP here, posting from a different IP address. I just wanted to confirm that what I found was indeed Pokeweed. Thanks a lot for the help! 63.245.144.68 (talk) 22:18, 1 July 2009 (UTC)

Thanks for the confirmation post. Glad we could help! :-) Rkitko ^(talk) 02:21, 3 July 2009 (UTC)

Diffraction of sound over a wall

You have a solid heavy wall which is two metres high. 50 metres away from the wall is a point source of noise of n decibels. Although practically none of this noise gets through the wall itself, the noise will diffract over the top of the wall. Is there any way to estimate what the decibels of noise will be at various positions (x,y) on the quiet side of the wall? This is not a homework question, but I'm just trying to estimate to what extent building a walled enclosure in my garden would reduce traffic noise. Thanks. 89.240.105.155 (talk) 20:05, 30 June 2009 (UTC)

Have you read about diffraction? It will depend on the wavelength of the sound. Since traffic noise covers a wide range of wavelengths, different regions (close to the wall, far from the wall), will have varying degrees of damping for different tones. Also, you should reconsider whether the wall will completely block transmitted sound - in reality, it will reflect much energy and attenuate much energy, but some energy will pass through as well. A non-negligible quantity of sound energy can also be transmitted underground. Nimur (talk) 21:01, 30 June 2009 (UTC)

A number of companies sell sound wall caps designed to alter the diffraction of road sound over roadway noise barriers; these vary in construction from simple concrete I-caps to complex arrangements of horizontal vanes. Which is suitable depends on the traffic (particularly its speed) and the relative locations; this maker of soundwalls recommends an acoustic engineer be consulted. 87.115.68.24 (talk) 00:02, 1 July 2009 (UTC)

Would a row of tall, evergreen bushes be effective? Perhaps two rows would be better, with the bushes staggered from the bushes in the other row. I think the leaves would vibrate slightly from the sound and convert it to a small amount of heat. - GlowWorm. —Preceding unsigned comment added by 98.17.43.38 (talk) 00:53, 1 July 2009 (UTC)

I wouldn't think that it would overcome the fact that more sound would travel through the bushes than a solid wall. —Akrabbim^talk 19:41, 1 July 2009 (UTC)

Blue giant

Is blue giant a main sequence star, or blue giant is not entirely dissimilar from blue supergiant. What is a yellow supergiant. Does yellow supergiant evolve from blue or white supergiant. Then what blue type is main seqeunce, is it blue dwarf or blue ginat?--69.229.111.118 (talk) 21:21, 30 June 2009 (UTC)

These sound a lot like homework questions. They can all be answered by reading the main sequence, yellow supergiant, and supergiant articles. Red Act (talk) 22:21, 30 June 2009 (UTC)

Antartica shifting away from South Pole?

After continous moving of plate tectonics, is Antartica suppose to move away from South Pole one day. Is Australia suppose to collide with Asia one day? I thought Africa just continues to drift north. Alot of diagram shos in 200 million years Kenya will lie to like 35 degrees North liatitude, and North Africa suppose to be more or less to Artic Circle.--69.229.111.118 (talk) 21:26, 30 June 2009 (UTC)

This is a pretty cool animation if you have a fast enough connection to view it. Looie496 (talk) 03:09, 1 July 2009 (UTC)

Does anyone else find it ironic that you need a fast connection to view a process that ordinarily takes 200 million years to unfold!?! SteveBaker (talk) 12:25, 1 July 2009 (UTC)

Any guess as to how that video justifies that the movement of the plates will instantly go into reverse at some point in the future? -- kainaw™ 15:43, 1 July 2009 (UTC)

That's the Pangaea Ultima scenario. It assumes that the Atlantic oceanic crust at the margin of the North American plate eventually ruptures and becomes a subduction zone that then consumes the Atlantic. It's not entirely crazy since this is among the oldest oceanic crust in the world; however, other people suggest the Amasia scenario (without that reversal) is more likely. Dragons flight (talk) 17:37, 1 July 2009 (UTC)

July 1

Cyan stays behind

Why does the cyan pigment in various colored posters get retained rather than the other ones? I've seen posters and other materials exposed to the sun and/or rain having only a faded cyan colored image.--Lenticel ^(talk) 01:30, 1 July 2009 (UTC)

Perhaps because the cyan dyes are less susceptible to photodegradation (breaking down due to light exposure)? --Jayron32.talk.contribs 03:49, 1 July 2009 (UTC)

Different pigments have different lightfastness, and the difference in the lightfastness isn’t due just to the color of the pigment per se. For example, the Monastral Blue cyan pigment has better lightfastness than the Tartrazine Yellow Lake yellow pigment, but the Hansa Yellow G yellow pigment has better lightfastness than the Peacock Blue (erioglaucine) cyan pigment. The reason the cyan pigment in multiple posters appears to have the best lightfastness of the pigments used is because in any part of the world, certain pigments tend to be the most commonly used there, due to economic and other factors. For example, in Europe, the Univit Blue Primaire and Major Blue Primaire cyan pigments are popular, which both have a lightfastness of 8, and the Major Yellow Solid and Major Yellow Primaire yellow pigments are popular, which have a lightfastness of 5 and 3, respectively.[23] Red Act (talk) 04:00, 1 July 2009 (UTC)

Is this genetically possible?

Is it genetically possible for a black man and a white woman to produce children that appear to be completely white?[24] —Preceding unsigned comment added by 67.184.14.87 (talk) 02:57, 1 July 2009 (UTC)

You would have to give a precise definition of "black man", "white woman", and "completely white" for that question to be answerable. None of these are scientifically defined concepts. If the real question is whether Michael Jackson could have fathered Michael Jackson's children, the answer is that I don't know. Looie496 (talk) 03:12, 1 July 2009 (UTC)

based on Mendelian inheritance probably not. But human skin color is not simply due to the interactions of a dominant black gene and a recessive white gene like the classic black mouse x white mouse experiment. In fact, we still don't know much behind the genetics of skin color. So it is possible but we just don't completely understand the genetics. --Lenticel ^(talk) 03:30, 1 July 2009 (UTC)

I'd say "yes". If the black man was actually mixed race (one black parent, one white parent) then they could, theoretically, give all the skin colour determining genes from the white parent to their child, resulting in a white child. Plenty of people of mixed heritage look plenty black enough to be called a "black man". I don't know what the odds of it happening are, though - the genes determining skin colour are rather complicated and I don't begin to understand them (I'm not sure anyone does). --Tango (talk) 03:50, 1 July 2009 (UTC)

The genetics of skin color is complicated and not completely understood, but a fair amount is known. Red Act (talk) 05:52, 1 July 2009 (UTC)

Statistically, it depends on whether the white-determining part of the gene is recessive or dominant. In all the attention that has been paid to race, has this ever been investigated? - GlowWorm. —Preceding unsigned comment added by 98.17.43.38 (talk) 04:36, 1 July 2009 (UTC)

It isn't determined by a single gene, so the concept of dominance doesn't really apply. --Tango (talk) 04:48, 1 July 2009 (UTC)

As Looie496 points out, this isn’t really a science question, since “black man”, “white woman”, and “completely white” are all subjective, unscientific terms. However, in my subjective opinion, Vin Diesel looks “completely white” in most photos I’ve seen of him, even though one of his two parents is African-American. Also, Wentworth Miller definitely looks “completely white” to me, even though his father would count as a “black man” at least according to the one-drop rule. Red Act (talk) 04:47, 1 July 2009 (UTC)

It's debatable as to whether the term “race” is biologically meaningful. For example, according to the race article, in a survey taken in 1999, 69% of the physical anthropologists and 80% of the cultural anthropologists surveyed disagreed with the statement "There are biological races in the species Homo sapiens." Increasingly, in scientific circles, concepts such as “population” and “clinal gradation” are used, instead of trying to divide people into “races”. Red Act (talk) 05:12, 1 July 2009 (UTC)

Lamarckism (once popular, but more recently said to be discredited) says that acquired characteristics, such as a black man managing to turn his skin white, could be passed on to his children. Edison (talk) 05:33, 1 July 2009 (UTC)

It's not just said to be discredited, it is discredited. We not only have enormous amounts of evidence for Mendelian inheritance but we have a considerable understanding of the mechanism behind it. --Tango (talk) 05:49, 1 July 2009 (UTC)

To answer the OP's question: If, by "black" and "white", he/she means "pure black" (i.e. with only black ancestors and no white ancestors) and "pure white" (i.e. with only white ancestors and no black ancestors), then, IMHO, the children would probably look like light-skinned black children (I think "mulatto" is what they used to be called, but I'm not sure); if, however, either parent had even a slightly mixed ancestry, then a wide range of appearances would be possible, from white with a somewhat tan complexion to a fairly dark black. So my own answer to the OP's question would be "probably yes", but that's just my own unscientific opinion. FWiW 76.21.37.87 (talk) 07:09, 1 July 2009 (UTC)

It is genetically possible, see albinism and Leucism. Single genes that can result in hypopigmentation, include tyrosinase, CD117 and microphthalmia-associated transcription factor Rockpocket 07:28, 1 July 2009 (UTC)

But then who do you count as a “black” ancestor or a “white” ancestor? Median skin color, for example, varies in a fairly gradual cline as you consider a series of populations along a path from sub-Saharan Africa, through northern Africa and the Mediterranean area, and up to northern Europe. See this map of skin colors. At what point along that path do you consider the gradually changing median skin color to no longer be “black” and start to be “white”?

You’d also need to define how far back you’re looking when you’re considering who an “ancestor” is. According to the Environmental factors section of the human skin color article, it only takes about 500 to 1000 years for the average skin color of even a fairly isolated migrating population to adapt to be what’s ideal for the amount of UV light that the sun shines on a given latitude.

And what all phenotypes do you consider when you’re categorizing an ancestor as “black” or “white”? Presumably more than just skin color? But if you look at all the world’s populations, the other phenotypes that you might use to distinguish “black” and “white” don’t necessarily vary in sync with skin color, since the sun exposure that creates an evolutive pressure on skin color is different from the other environmental factors that create evolutive pressures on other phenotypes. Red Act (talk) 08:08, 1 July 2009 (UTC)

People seem to think this is a purely theoretical question and we don't really know. Well, look, here. Yes it is possible, yes it happens, and yes very few people (if any) have no ancestors of a different 'race' if you go back 20 or 30 generations. 89.168.19.118 (talk) 10:10, 1 July 2009 (UTC)

What is this thing? Strange life form?

Please see this video of some form of life(?) in a drain: http://www.liveleak.com/view?i=890_1246374233 The sites comments are all stupid, but I was wondering what it actually is? The only sensible suggestion seems to be that they are some form of Bryozoan but that doesnt seem to fit either.--58.111.133.169 (talk) 09:28, 1 July 2009 (UTC)

I'm a bit suspicious because: The water's very clean, the lighting is ok, the camera work is kind of ok (not too jerky when walking, focus changes a bit strange), the pulses the thing does look quite destructive - if they do that too much, they look like they'll fall off the wall. I'm no expert in sewer lifeforms or film-making, so I'm very ready to be corrected in everything I said. Aaadddaaammm (talk) 10:18, 1 July 2009 (UTC)

Apparently they are fairly well known in the industry

http://www.kdvr.com/kdvr-prehistoricsewermonstercaug-5439314,0,673974.story —Preceding unsigned comment added by 58.111.133.169 (talk) 12:08, 1 July 2009 (UTC)

That story says "in 20 years of sewer work, they had never seen anything like it before." - that doesn't sound like "fairly well known in the industry" to me! The first video makes it look like these things are pretty big - but that's a robotic camera in a fairly narrow tube - so they could be as small as a centimeter or so. I agree that this appears to be something like a bryozoan - and our article says that there are 8,000 species of them to choose from, so it would take an extensive and difficult search to rule out that possibility. SteveBaker (talk) 12:22, 1 July 2009 (UTC)

---

http://www.youtube.com/watch?v=TcKpx2DxGwY

The video claims it's from a sewer, but I don't buy it. It looks like the camera is zoomed in on something else, indicating that everything in this video is tiny. The water seems to be behaving like it's just a small quantity of water as opposed to how water would behave in a normal sewer... So what the heck is it? ScienceApe (talk) 19:00, 1 July 2009 (UTC)

I don't know what the "creature" is, but it looks like a pretty normal sewer pipe to me (a small one, but they come in all sorts of sizes). --Tango (talk) 19:02, 1 July 2009 (UTC)

Oh ok. I kinda figured by "sewer" they meant the ones you can walk through. ScienceApe (talk) 19:07, 1 July 2009 (UTC)

My guess would be internal medical imagery, probably during some surgery, perhaps with some type of artificial irrigation. Bus stop (talk) 19:05, 1 July 2009 (UTC)

But the water wouldn't be on the ground like that if it was something inside of a body right? ScienceApe (talk) 19:07, 1 July 2009 (UTC)

It looks just like a ceramic pipe to me... --Tango (talk) 19:47, 1 July 2009 (UTC)

---

The above content has been moved here from a section below. Abecedare (talk) 19:10, 1 July 2009 (UTC)

The video is legitimate. According to Raleigh city officials:

... staff biologists have confirmed that the "creature" is actually a colony of tubifex worms. The colonies attach themselves to roots that gradually work themselves into weak points in the pipes. "They seem to respond to the light from the camera," Buchan said. "That light is pretty hot." The worms naturally occur in sewage and pond sediment and are actually sold both live and dried as fish food in pet stores.

See more details in this news report. Abecedare (talk) 19:58, 1 July 2009 (UTC)

(EC), I think the same result as Abecadare: [25]. Aaadddaaammm (talk) 20:05, 1 July 2009 (UTC)

about gills the shark has

Generally, the shark has 5 gills, but i heard there is a kind of shark which has 6 gills. Is it true? How does it look like? —Preceding unsigned comment added by Patrickyu (talk • contribs) 09:49, 1 July 2009 (UTC)

Hexanchiformes have six or seven pairs of gill slits. Within this order members of the genus hexanchus, which includes the bluntnose sixgill shark, have six pairs of gill slits. Gandalf61 (talk) 10:14, 1 July 2009 (UTC)

There's also the sixgill sawshark, in the Pristiophoriformes order. Red Act (talk) 10:20, 1 July 2009 (UTC)

Counting of visible gill slits has to be repeated on the other side of the shark. Cuddlyable3 (talk) 22:32, 4 July 2009 (UTC)

Gravitation and Electromagnetism

Suppose the sun explodes at this moment and separates into two halves traveling in opposite directions at high velocities. The sun's gravitational field will change immediately and affect the Earth's orbit instantly (slightly at first). But it will take about 8 minutes for the electromagnetic radiation from the exploded sun to reach Earth. Why does gravitation have an immediate effect on distant objects, but the effects of electromagnetism are delayed? If gravitons exist, they must travel faster than the speed on light. How is this possible? David 70.55.183.195 (talk) 13:06, 1 July 2009 (UTC)

Actually, the gravitational effect would also take ~8 minutes to get to us, since it too travels at the speed of light in a vacuum. See Speed of gravity for more info. - Akamad (talk) 13:09, 1 July 2009 (UTC)

Gravity chat

If the speed of gravity was in fact infinite, would it be possible/practical to build a gravity-based telecommunications medium with enough bandwidth to, say, have a chat session with someone on Mars? Let's say 10 bytes per second. For the transmitter I'm thinking something like an array of heavy objects on maglev tracks that you scoot back and forth to indicate on and off bits, and a LIGO-type rig for the receiver. --Sean 13:29, 1 July 2009 (UTC)

As was stated above, the speed of gravity equals the speed of light, so it is not infinite. Discussing what would be possible if it was infinite is not scientific and cannot be answered by scientific means, which means it is out of scope of this reference desk. --TheMaster17 (talk) 13:52, 1 July 2009 (UTC)

Given fallibility, is there really such a thing as an unscientific discussion about imaginary physics? The discussion could be outside of any existing body of knowledge, and futile, but that's not the same as unscientific. 213.122.68.63 (talk) 15:37, 1 July 2009 (UTC)

Science has to be falsifiable. If I theorise that "If the speed of gravity were infinite real time communication with Mars would be possible" then that isn't falsifiable since there is no experiment that can show it to be true or false since the premise is false. Obviously it is possible that our understanding of gravity is flawed and it does travel at infinite speed, but that makes the question unanswerable since the premise would mean we have no real understanding of gravity on which to base an answer. --Tango (talk) 17:28, 1 July 2009 (UTC)

Right. We could similarly note that if the speed of light were infinite, LEDs could allow real-time conversations with Mars, or that if the speed of pigeons were infinite, RFC 1149 would finally be worth implementing. — Lomn 14:00, 1 July 2009 (UTC)

I do agree that just asking how the relevant equations would change if one of the constants was different is not "unscientific" at all. There have been many instances where measured or theoretically derived constants were incorrect, and the last time I checked questions about the propagation of gravitational waves were still considered active research. There is nothing wrong in a little careful speculation, and it does not make it "unscientific" (it is not asserting a non-falsifiable theory or anything like that). --98.217.14.211 (talk) 20:23, 1 July 2009 (UTC)

I don't think making the speed of gravity infinite can be considered as just changing the value of a constant. "Infinity" is not a real number so all the equations that are based on the speed being a real number (ie. any equation in which the constant appears) will cease to work. --Tango (talk) 20:36, 1 July 2009 (UTC)

The OP never said the transmitter must be located on Earth. Cuddlyable3 (talk) 22:21, 4 July 2009 (UTC)

Amended question

Since the responses to my first run at this question focused on the science rather than the engineering, I'll try again: would it be possible to build a reasonably fast machine for moving mass around on Earth that could be detected on Mars (after a suitable delay!). --Sean 19:19, 1 July 2009 (UTC)

I think your question was perfectly reasonable. We have a theory of infinite-speed gravity, namely Newton's, and wireless gravitational communication is possible in Newton's theory. To communicate wirelessly you only need a change in the charge distribution in one place to affect the field in another. It doesn't matter how long it takes for it to happen.

Take a generic 1/r² force law (instantaneous or retarded, doesn't matter). I'll write it as $F=\pm {\tfrac {GMm}{r^{2}}}{\hat {r}}$, though M and m might be electric charge and G might be the Coulomb force constant. Let the emitting and receiving stations be separated by a distance D. Suppose the emitting station consists of a charge M moving in a circle of radius d at a frequency ω in the plane perpendicular to the line between emitter and receiver. It's easy to see that the force at the receiving station will "precess" around a central value at the frequency ω. Because the force is aligned with the source, the slope of the force vector relative to the emitter-receiver line is d/D, so the amplitude of the circular component is about d/D times the absolute value of the force, or ${\tfrac {GMmd}{D^{3}}}$. Of course, this force has to be added to the influence of every other object in the universe, but the time-varying component will still be there and you will probably still be able to detect it, as long as relatively few nearby objects are rotating at that exact frequency. That's how radio communication works, roughly. However, this doesn't work for gravity, because there's no way to detect the force! The only way to detect force is by the associated acceleration, and the only way to detect acceleration is by comparing to a nearby inertial object, but there are no such objects in this case because gravity acts on everything equally. All you can detect is the local variation in the force, i.e. the first derivative. The first derivative will look like a spring force law, ΔF = k Δx, but with three different constants k along three perpendicular axes of symmetry. In this case the symmetry axes are obvious: the line between emitter and receiver, the (time-varying) direction between the object and the center of rotation, and the direction perpendicular to those. The force constants along those three axes are, respectively, $\left(2-\left({\tfrac {d}{D}}\right)^{2}\right){\tfrac {GMm}{D^{3}}}$, $\left(2\left({\tfrac {d}{D}}\right)^{2}-1\right){\tfrac {GMm}{D^{3}}}$, and $-{\tfrac {GMm}{D^{3}}}$. The first of these doesn't help much because it's constant. But the other two axes rotate into each other over time, so we will see a sinusoidal variation in the force constant in that plane with an amplitude of $\left({\tfrac {d}{D}}\right)^{2}{\tfrac {GMm}{D^{3}}}$ and a frequency of 2ω. This will lead to a sinusoidal oscillation in the distance between two test particles. The amplitude of that oscillation is proportional to the distance, and the (unitless) proportionality constant is ${\tfrac {GMd^{2}}{(2\omega )^{2}D^{5}}}$. And that, at long last, is what LIGO measures. According to online sources it's most sensitive at around 200 Hz, where its design detection threshold is about 10⁻²³. So let's plug in some values. Take M = 10 kg, d = 10 m, 2ω = 2π × 200Hz, and D = 56 million km (the closest approach between Earth and Mars). And the result is... about 10⁻⁶⁷. So the answer is: not a chance in hell. Note that that's just to unambiguously detect the existence of the carrier signal—never mind modulating it, and never mind doing so fast enough to communicate at 80 bps. -- BenRG (talk) 19:37, 1 July 2009 (UTC)

Hmm, I think there's something wrong with my brilliant argument because it makes orbiting pulsars very undetectable too. Better ignore it for the time being. -- BenRG (talk) 20:02, 1 July 2009 (UTC)

Why do you have the tidal forces following a sping-like law? I thought they followed an inverse cube law. --Tango (talk) 20:37, 1 July 2009 (UTC)

Possible? Eh, maybe, sorta, kinda, in a hideously expensive utterly impractical sort of way, if we worked out all the necessary science and engineering first. Our gravitational wave article covers the underlying principles of such a system. Or we could use perfectly good electromagnetic methods of communication. — Lomn 19:42, 1 July 2009 (UTC)

Note: part of the reason we're unlikely to ever care about this, as a practical matter, is that gravity is 10³⁶ times weaker than EM radiation. It's very difficult to construct a scenario in which perceived advantages of gravitational communication outweigh this massive roadblock. — Lomn 19:45, 1 July 2009 (UTC)

I think that's why he originally asked the question about a universe where gravity moves faster than EM radiation. -- BenRG (talk) 20:02, 1 July 2009 (UTC)

Question regarding dBm

In a book I've been reading, I found the following statement (among other similar statements):

200 mW –3dBm = 100 mW

Is this correct? Why is the result 100 mW and not 198 mW? If it is, what's the explanation for it?

Thanks. 93.108.139.109 (talk) 16:22, 1 July 2009 (UTC)

It is correct, but in perhaps a dfficult form for beginners to understand. See dBm. dBm is logarithmic unit of power, so it is non-linear. Power in dBm is defined as 10 * log (P / 1 mW), where P is a power in mW. Using the properties of logarithms, adding and subtraction in logs is equivalent to multiplying and dividing. So since the inverse log of 3 dBm is 2, -3dBm is the same as saying divide by 2. Usually people wouldn't mix units of mW and dBm in the same equation, but the author probably thought it would be okay since -3dBm is very easily recognized as being one half. —Akrabbim^talk 16:32, 1 July 2009 (UTC)

It's still wrong though. dBm is an absolute unit, so 3 dBm is close to (note, not exactly) 2 mW under all circumstances, just as -3 dBm is about 0.5 mW. In no case can "-3 dBm" mean divide by 2. Only "-3 dB" can mean that. So the OP's expression, if it means anything at all, must mean ~198 mW. If the writer intended it to mean 200 mW / 2, then he should have written 200 mW x (- 3 dB), although that's still an incorrect use of the terminology. --Heron (talk) 17:08, 1 July 2009 (UTC)

The equation seems poorly stated, since -3dBm could mean subtraction of 3dBm, or it could mean divide by 2. Edison (talk) 18:18, 1 July 2009 (UTC)

You're right, it really is the question's fault. What I explained in my first answer, is if 200 mW is converted into dBm (23 dBm), and then 3 dBm is subtracted, then the answer is 20 dBm, or 100 mW. Or, if we wanted to convert the second term into mW, we wouldn't know if we were adding .5 mW or subtracting 2 mW from 200 mW. Now that I think about it, adding or subtracting dBm from mW is very ambiguous, and meaningless in equation form. —Akrabbim^talk 19:37, 1 July 2009 (UTC)

You should never add (or subtract) things that are measured in different units, so the equation is clearly nonsense. It could work as an abuse of notation, but, as you say, it is rather ambiguous as to what the abuse is meant to mean. --Tango (talk) 01:48, 2 July 2009 (UTC)

With respect the first response contains errors. -3dB is the same as saying divide power by 2 (more exactly by 10^.3 = 1.99526...). That is a dimensionless ratio. The little "m" in -3dBm means 1mW divided by 2 which is 0.5mW. That is a power. What the OP read in an unspecified book is flat wrong and the author should have written

200 mW -3 dB = 100 mW

or

200 mW - (-3 dBm) = 199.5 mW

Cuddlyable3 (talk) 22:00, 4 July 2009 (UTC)

humane meat harvesting

Florida stone crabs are said to be one of two animals whose meat can be harvested without killing it. What is the other animal?

Some species of lizards drop their tails when they are grabbed. That is a potential for some meat without harming the lizard. Best that I can come up with. 65.121.141.34 (talk) 18:12, 1 July 2009 (UTC)

Autotomy appears to be the relevant concept here, and there are more than two species that could conceivably have meat harvested in this fashion. Additionally, I would submit that severing an animal's appendages is not inherently "humane" if you're examining the moral issues of eating meat. — Lomn 19:04, 1 July 2009 (UTC)

A traditional food of the Maasai people is a blood porridge of some kind, the blood having been harvested from cattle that they keep around for that purpose. Blood isn't meat, I suppose, but I don't think too many vegetarians drink it. --Sean 20:06, 1 July 2009 (UTC)

This question would be much more interesting minus one "e" ;-) --Stephan Schulz (talk) 20:08, 1 July 2009 (UTC)

What? We don't need to be humane for mat harvesting ;)--Lenticel ^(talk) 00:23, 2 July 2009 (UTC)

Leaving them alive but less able to survive? what's humane about that? - KoolerStill (talk) 08:41, 2 July 2009 (UTC)

Pregnancy in Space

Is there any evidence people could not conceive, gestate, and give birth to children in space? I'm curious if there has been any multi-generational studies of animals in space and how that data would correlate with people. Would the fetus develop properly in the absence of gravity? TheFutureAwaits (talk) 17:44, 1 July 2009 (UTC)

[26] from 1995 describes some experiments with pregnant rats in space for part of the gestation, and says that multigenerational animal experiments were planned for the International Space Station. A 2002 NASA report [27] says on page 32 that they still would like to do multigeneration studies on primates in space, but offers no hint that any multigeneration studies had been done by then. If you email NASA they might be able to search their database and provide a more definitive answer. Edison (talk) 17:50, 1 July 2009 (UTC)

Animals in space lists the longest animal flight as 90 days - unfortunately the tortoises involved didn't quite have enough time to make multiple generations. Other shorter lived animals have flown though. Rmhermen (talk) 22:18, 1 July 2009 (UTC)

I assume you mean "in zero gravity". It's possible to closely simulate terrestial conditions in space, in which case I can't imagine any reason why pregnancy would not proceed as usual. Dcoetzee 01:37, 2 July 2009 (UTC)

As we have even less experience with living beings in "artificial gravity" than we do with "zero g", I would be hesitant to say that there would be no effect. Rmhermen (talk) 02:54, 2 July 2009 (UTC)

My Astronomy professor said that there seems to be some problem with pregnancy in space, in that it seems to cause miscarraiges in animals. If it is the same for humans—and it very well may be—then on long voyages, women may have to spend nine months in a rotating chamber that simulates gravity. —Pie4all88 ^{T C} 03:11, 2 July 2009 (UTC)

As has been pointed out, it is not yet verifiable whether a rotating chamber inducing a gravity-like force is "identical" to terrestrial conditions. There are a lot of confounding factors beyond the first-order net "downward" force that is felt inside a rotating chamber. Nimur (talk) 03:17, 2 July 2009 (UTC)

I see there's another thread about artificial gravity, so I'll read through it when I get a chance. Thanks for the info! —Pie4all88 ^{T C} 07:19, 2 July 2009 (UTC)

See reproduction and pregnancy in speculative fiction. Robinh (talk) 07:41, 2 July 2009 (UTC)

Ungrounded alternator

I'm curious to know the potential difference between one of a single-phase alternator's lines and the ground when this alternator has its neutral not connected to the earth? --Email4mobile (talk) 17:47, 1 July 2009 (UTC)

Good question. It is undefined, since you have specified no neutral to ground connection. The voltage in practice might be anywhere from zero to the output voltage from either conductor to ground, since there will be leakage current and capacitive coupling to ground. In practice, if there were a voltmeter from each output line to ground, the measurement circuitry would constitute a high impedance ground connection and would determine the voltage measured. If only one voltmeter were connected to one line at a time, it would pull the measured line down and force the unmeasured line higher. Three phase equipment in factories is sometimes designed to be operated ungrounded, because the first unintentional ground does not cause fault current. Ground indicator lights or equivalent relays are used to detect such a ground, and it can be found and fixed without necessarily having an emergency shutdown, There, similarly, the ungrounded phases rise to a high potential to ground while the grounded phase goes to a low or zero potential to ground. Edison (talk) 18:13, 1 July 2009 (UTC)

Thank you very much indeed. I've tried to find an explanation for that problem once, and assumed the capacitive effects. However when I started simulating that measured voltage via mathematical equations I was stuck by the equivalent circuit to be analyzed due to my insufficient knowledge in this subject and poor imagination of capacitance and impedance patterns. It would be more helpful if you know a reference which details this problem (and have a good day/night. I'm going to bed).--Email4mobile (talk) 18:52, 1 July 2009 (UTC)

An alternator with its neutral not connected to ground? Wouldn't that be extremely dangerous?! 76.21.37.87 (talk) 04:27, 2 July 2009 (UTC)

Is the alternator in your car connected to earth ground? Do you feel yourself to be indanger in the car because there is no wire from the neutral terminal to earth ground? How about in an airplane? How about in the International Space Station or the Space Shuttle? There is a neutral but it is not connected to earth ground. How about on a ship? In the early days of marine elecrical systems, some countries used the phase and neutral isolated from the ship hull, and others used the hull as a ground to which the neutral was connected. It is possible that a load element or the alternator winding itself might have graded insulation, with a lower insulation level near the terminal that is supposed to be at earth potential, like the frame of the alternator, particularly if it has a very high voltage output. In such a case, the case of the alternator might be at a dangerously high voltage, or the insulation might fail. A low voltage alternator is likely to have the same insulation level at all points on the winding, and the neutral and phase wires are likely to be of the same insulation rating. In that case the alternator, switch, fuse, wires, and load would probably work with or without the grounding of the neutral. It is basically a safety measure, so that there is less risk of a dangerous voltage on the neutral or frame, or on unswitched and unfused conductors. It also allows fuses or circuit breakers to operate if the phase or intended hot wire becomes accidentally grounded through a break in the insulation. Edison (talk) 00:05, 3 July 2009 (UTC)

Regarding the car/plane/ship alternators: although they are not connected to earth ground, they are connected to the bodywork/airframe/hull instead, so technically they are still grounded, even though there's no connection to earth ground. Note also that in all these cases, the bodywork/airframe/hull would act as a Faraday cage and thus protect the occupants from getting zapped even if the insulation fails on the alternator. What I meant was that an alternator with its neutral not connected to anything at all would likely be dangerous, especially if it operates at a high voltage. 76.21.37.87 (talk) 03:48, 4 July 2009 (UTC)

Position basis of a wave function

In literature I'm reading about intro quantum mechanics talking about single particle wave functions, they often discuss them in terms of the position basis (including here: wave function) and other continuous bases like the momentum basis. I was under the impression that wave functions as functions over the points in space lived in L²(C), since they use that inner product and norm. But the position basis (or any other uncountable set) isn't a basis of L² and similarly Dirac delta functions aren't in L² since functions that are equal a.e. are put in the same equivalence class. If not L²(C), then what Hilbert space are wave functions supposed to live in? What's going on here? —Preceding unsigned comment added by Rckrone (talk • contribs) 18:40, 1 July 2009 (UTC)

If it is a good book, this should be declared in some kind of intro section. Ah, and if you really have a good book on quantum mechanics, please tell me, for I don't know any. Sorry if this isn't helpfull. Hoping there will be better responses. I would like to know the answer myself, too. 93.132.130.9 (talk) 20:04, 1 July 2009 (UTC)

The Dirac delta "function" is not a function at all, not even in ${\mathbb {R} _{\infty }}^{\mathbb {R} }$. There's no way you could arrange for its integral to be 1. Expressions involving the delta function are really implicit limits of expressions involving normalized Gaussians or suchlike as the width goes to zero. The delta function by itself wouldn't make sense but an expression incorporating it is legitimate as long as the limit of the whole expression exists. Likewise the position "basis" is really a limit of fuzzy Gaussian-like distributions of position, and one requires (or at least hopes) that expressions that define quantities of physical interest converge sensibly in the limit. That's how I think of it, anyway. -- BenRG (talk) 22:00, 1 July 2009 (UTC)

One does not have to pretend that statements involving deltas are just shorthands for statements about limits. The dirac delta function is a perfectly good mathematical object, it's just not a bona fide function on the reals. It's a measure or a distribution or something (depending on your point of view). Algebraist 22:04, 1 July 2009 (UTC)

It's a functional rather than a function. Looie496 (talk) 01:11, 2 July 2009 (UTC)

But Dirac delta functions aren't in the dual of L² either. δ_x would the functional that maps f to f(x), but an element of L² is an equivalence class of functions that are equal a.e., so they're free to differ at x. On the other hand thinking of it as an idealized limiting case definitely clears some things up, but I'm still not satisfied with the idea of the position "basis." It's certainly not the limit of some sequence of bases. It has the wrong cardinality among other problems. Rckrone (talk) 04:00, 2 July 2009 (UTC)

The delta function, as a functional, is not quite the mapping from f to f(x); that's a simplified definition. See Dirac delta function#The delta function as a distribution for more info. Looie496 (talk) 15:52, 2 July 2009 (UTC)

What the heck is this?

Moved question and responses to an earlier section where the same question is posed. Abecedare (talk) 19:08, 1 July 2009 (UTC)

Plain water

For some reason drinking plain water makes me feel sick, but I can consume any other drink just fine, even flavoured water, which doesn't seem like it would be different enough to... be different. What's the deal? Vitriol (talk) 22:39, 1 July 2009 (UTC)

Is it any plain water or just the plain water from a certain area? What about bottled water? There are places which have tap water I find very unpleasant, possibly even to the point of making me feel unwell. It's just the taste, as far as I know. --Tango (talk) 22:37, 1 July 2009 (UTC)

I dunno if water from the ice dispenser and the tap would be different, but if it is then both make me wanna barf. And it's definitely not the taste. Vitriol (talk) 22:39, 1 July 2009 (UTC)

Presumably the ice dispenser gets its water from the tap? When you say "flavoured water", do you mean water that is bought with flavouring or tap water with orange squash or similar added? If its the latter, then it must be the taste, that's the only thing that is different. --Tango (talk) 23:27, 1 July 2009 (UTC)

My understanding is that fluids with low osmolarity (concentration of dissolved substances) are hard for the stomach to absorb, and that almost any dissolved substance will help. Looie496 (talk) 01:07, 2 July 2009 (UTC)

You'll have to be clearer what you mean by plain water. If you're drinking distilled water, the sort used for scientific experiments, that's going to taste bad and cause the problems described by Looie496. But tap water usually contains a variety of dissolved impurities. If your tap water makes you feel sick, it's probably something in the water, perhaps some kind of allergy (since it's evidently not making everyone sick). Dcoetzee 01:41, 2 July 2009 (UTC)

It can't be something in the water if other drinks made from that water are fine, though... --Tango (talk) 01:44, 2 July 2009 (UTC)

If the same water which makes you sick when plain does not make you sick when something is added to it, the cause of the illness is probably psychosomatic; there is no allergan or pathogen in the water, but for some reason the thought of drinking plain water sickens you... --Jayron32.talk.contribs 03:52, 2 July 2009 (UTC)

I concur. Richard Avery (talk) 07:43, 2 July 2009 (UTC)

Yeah, I have a similar problem and I strongly suspect it's psychosomatic. If I drink any plain water within an hour or two of waking up, I generally feel rather sick - but I can drink tea, or orange juice or whatever and feel fine. I can also drink plain water later in the day and feel fine. I can't think of a good scientific reason for this, so I assume it's just my brain playing with me - or just the fact that the tap water here tastes a little horrible and I'm more delicate in the morning! ~ mazca ^talk 08:35, 2 July 2009 (UTC)

Water memory? ;-) Axl ¤ [Talk] 06:23, 2 July 2009 (UTC)

It may not be psychosomatic. It's possible that the water that's been sitting in your household plumbing all night has picked up some dissolved chemicals - and that the oxygen dissolved in it has dispersed - making it taste 'flat'. Later in the day - when everyone in your neighborhood is using lots of water - and the stuff that's been in your pipes all night has been flushed or showered - you should be getting more aerated water that hasn't been soaking up who-knows-what from your pipes all night. Ergo: Either run water to waste for a few minutes before drinking any - or perhaps shake the stuff up vigorously with air to aerate it. SteveBaker (talk) 11:26, 2 July 2009 (UTC)

Try half-filling a bottle with the water, closing it, and shaking it pretty hard for a little while, to dissolve some air into the water. That may make it more palatable to you. Or, add a few drops of lemon juice. 208.70.31.206 (talk) 07:42, 2 July 2009 (UTC)

I get this too, i always thought it was to do with stomach chemistry, drinking plain cold water would be a shock to your system and dilute your pre breakfast stomach juices. I think even adding a spoon of sugar in tea or orange drink or whatever you put in the water would give the empty stomach something to do, so to speak, rather then just diluting it. Mind you, the first thing I usually drink is a hot black coffee with no sugar, so maybe the temperature has something to do with it? There are some chinese people at my work that drink plain hot water from the urn, they believe it's better for you then cold water. Vespine (talk) 00:06, 3 July 2009 (UTC)

The article Water purification describes the wide range of methods and chemicals used in municipal water purications, which may leave traces that the OP finds unpalatable. Cuddlyable3 (talk) 15:39, 4 July 2009 (UTC)

'Karl Malden nose'

What is the proper name for the nose condition sometimes colloquially called 'Karl Malden nose' (where the person's nose is all bulbous and has a strange texture to the skin)? Note, I don't know if KM actually had this - but his death today reminded me of the subject. --90.240.60.140 (talk) 23:01, 1 July 2009 (UTC)

Not being familiar with Malden, I can only suggest Rosacea. Nanonic (talk) 23:12, 1 July 2009 (UTC)

Possibly rhinophyma? Ginogrz (talk) 23:17, 1 July 2009 (UTC)

Rosacea of the nose, as seen in people like Karl Malden and W.C. Fields was commonly called "gin blossom", as alcohol-thinned blood tended to make the thin blood vessels in that part of the nose rupture it used to be assumed (incorrectly) that alcohol caused the problem ed note: changed due to valid point made by Richard Avery below ; the swollen nose is similar to cauliflower ear. See also the description of the origin of the band name of the Gin Blossoms, who took their name from the phenomenon. --Jayron32.talk.contribs 03:48, 2 July 2009 (UTC)

"alcohol thinned blood tended to make the thin blood vessels in that part of the nose rupture". Do you have a citation for that Jayron? The scientific cause of rhinophyma [[28]], [[29]], [[30]]appears to be unknown at present although there are a number of associated signs that can predict its occurrence. Richard Avery (talk) 07:41, 2 July 2009 (UTC)

So fixed... --Jayron32.talk.contribs 12:33, 2 July 2009 (UTC)

July 2

Acceptability of wave function

How I mathematicaly prove e^ -|x| is acceptable function .plese give a example .Supriyochowdhury (talk) 01:22, 2 July 2009 (UTC)

First you need to define "acceptable" - this term does not have a specific meaning in mathematics. Do you mean "finite-valued," "bijective," or some other description of a function? Acceptable redirects to Proper, which does have several mathematical meanings - but out of context, I think it's too vague to pick which meaning is intended. You mentioned wave-functions, so do you intend to show that the integral of e^ -|x| is integrable and that the probability function integrates to 1? If that is your intent, you should perform the integral and check whether it is suitable for your problem. Nimur (talk) 03:34, 2 July 2009 (UTC)

I am assuming the domain is Quantum Mechanics...I don't think it needs to Integrate out to 1, if it doesn't, you can always normalize it..The important thing is, it must be finite. So, I think being continuous and well defined in the whole region from minus infinity to infinity would do... So now you can see it is satisfies both conditions... I'll leave it for the experts to explain more... Rkr1991 (talk) 05:27, 2 July 2009 (UTC)

Yes. Simply prove that the integral of abs(exp(-abs(x)))^2 over all x (from -infinity through + infinity) is finite —Preceding unsigned comment added by 81.11.170.162 (talk) 07:14, 2 July 2009 (UTC)

Solution to biting insects?

Having been bitten (by midges, I suspect) no less than 10 times in the past two days, I've declared a state of emergency and am searching for a way to combat this continued assault. I would like something cost-effective and long-term and low-maintenance.

• I've heard that moving-air is a deterent.
• I've been told that barbed-wire wont help.
• I've read that cheap consumer units for electric-based destruction are ineffective (insects not attracted to blue ("UV") light) - I have first-hand experience of this, from a couple of years ago
• I'm considering deet but it may dissolve my mosquito net (which I suspect is made out of some plastic polymer) and needs to be replaced every day.

I'm a student, living in a single room, so I don't have a large area to cover but I don't think my windows are amenable to nets due to their manner of opening, besides which insects can invade via housemates's rooms.

I'm living in NL. ----Seans Potato Business 01:40, 2 July 2009 (UTC)

Where exactly is NL? Nimur (talk) 03:36, 2 July 2009 (UTC)

That refers to .nl surely. 208.70.31.206 (talk) 07:45, 2 July 2009 (UTC)

• I've had problems with flies in the past. Sticky fly paper is the way to go - just hang up a bunch of them. It works, and you can see it work. Also make sure you don't leave wet trash out - that's where flies breed. Don't trust in ultrasonic deterrents. You can also look at some of the heavy duty systems used in horse stables - you can read more for example here. Actually fly zappers do work, but this can depend on the particular type of fly. Dcoetzee 01:48, 2 July 2009 (UTC)

I've had some success with insect repellent candles, particularly if you are sat out on a balcony in the evening, or something. --Tango (talk) 01:56, 2 July 2009 (UTC)

I've heard that Citronella and lemon grass are plants which can act as a deterant to many biting insects. --Jayron32.talk.contribs 03:44, 2 July 2009 (UTC)

Citronella and lemon-grass plants are an interesting idea! Citronella oil is the active ingredient in insect repellent candles. DMacks (talk) 05:56, 2 July 2009 (UTC)

The bug patch is the latest thing and has been recommended to me. You stick it on your skin. Get it on the net or in camping stores.--Shantavira|^{feed me} 07:35, 2 July 2009 (UTC)

If the bugs are only bothering you at night, try sleeping under a mosquito net. 208.70.31.206 (talk) 07:45, 2 July 2009 (UTC)

You might be able to find Neem oil at a local health food store, herbalist or flea-market nl:Azadirachta indica. Try a bit on a paper towel first, some people find the smell hard to bear, others hardly notice. (OR To me it sort of smells like cold vegetable soup.)71.236.26.74 (talk) 09:14, 2 July 2009 (UTC)

It's claimed that biting insects are attracted to carbon dioxide (that's how they find living, breathing things) - there are several CO2 generators out there that claim to be able to rid you of mosquitoes "naturally". Sadly though, this may not help our OP - you wouldn't want to use one of those indoors for obvious reasons. SteveBaker (talk) 11:19, 2 July 2009 (UTC)

Try any of the artemsia plants, especially southern wood. Unfortunately the fly family, Tabanidae (horseflies & deerflies) find you using visual cues. 67.193.179.241 (talk) 14:39, 2 July 2009 (UTC) Rana sylvatica.

I removed the leading space from your answer 67.193, so that it didn't extend further that the width of the page. Hope you don't mind! --Kateshortforbob 15:46, 2 July 2009 (UTC)

The best insecticide/repellent I have ever used is a pyrethrin-based aerosol. Gets rid of all flies, mosquitoes, midges, cockroaches... Have a google search for pyrethrin-based products available in your part of the world. Gwinva (talk) 04:19, 3 July 2009 (UTC)

Who has a "blood-brain barrier"?

Obviously, humans do. Animal experiments are mentioned, so perhaps all mammals have the blood-brain barrier; is this true? What about other animals which have brains; do they all have a blood-brain barrier, or ??? Thank you. - Hordaland (talk) 05:06, 2 July 2009 (UTC)

(Whoever has the answer, please improve the cited article. Good catch, Hordaland.) Tempshill (talk) 06:30, 2 July 2009 (UTC)

This is an excellent question indeed. I know mammals have a BBB as adults, but usually do not have a functional BBB when very young. I also know that birds (or at least some birds) have a BBB. As for other vertebrates - I don't know, and I could not find anything useful in Google Scholar. I know frogs have a functional choroid plexus, though, so they may have a BBB as well. I'll do a more thorough search tomorrow. I don't know if arthropods have anything homologous to a BBB, either. Of course arthropods can not have a proper BBB, as they do not possess a closed circulatory system to begin with; however, they may still have some sort of an epithelial barrier preventing at least some parts of their nervous system from the direct contact with the haemolymph. Anyway, great question. I'll fix the article, but I need to do some reading first :) --Dr Dima (talk) 07:15, 2 July 2009 (UTC)

All vertebrates have a BBB that consists of epithelial cells. Some invertebrates have an analogous system (insects for example), that consists of glial cells that surround blood vessels. Some sources taken out of the german wikipedia article (which is much more scientific and complete than the english one): [31], [32], [33] --TheMaster17 (talk) 09:31, 2 July 2009 (UTC)

Crayfish and fruit flies, even. The one paper speaks of "CNS barrier systems", plural. Thanks, all (so far)! - Hordaland (talk) 16:26, 2 July 2009 (UTC)

Ether Physics

Due to the limit of speed for the propagation of waves being based on the characteristics of the medium through which the wave travels, what would be the characteristics of the medium (Ether) through which light and gravity travel in the absence of transparent materials like glass such as the vacuum of space?

7 August 06

Summary: The forces of magnetism, electricity, and gravity are simply different types of perturbations in a single field that permeates the universe and comprises the fabric of existence. “Everything is flux” – Heraclitus -- Taxa (talk) 05:46, 2 July 2009 (UTC)

Joking, of course. To the OP: Have you read our speed of light article? Tempshill (talk) 06:36, 2 July 2009 (UTC)

I do not recall a reason being given in the article why the speed of light has a limit in a vacuum. -- Taxa (talk) 09:15, 2 July 2009 (UTC)

It doesn't have a limit, it has a fixed speed. --Tango (talk) 17:33, 2 July 2009 (UTC)

Does not light travel slower through glass than through a vacumn? -- Taxa (talk) 04:32, 3 July 2009 (UTC)

See our article on luminiferous aether. Gandalf61 (talk) 10:12, 2 July 2009 (UTC)

Our electromagnetic wave equation article may be of use to you. The equation, derived from the Maxwell equations describes the propagation of electromagnetic fields through a medium. It turs out the speed of propagation is dependent on the electric permittivity and magnetic permeability properties of the medium. For a vacuum, these are known universal constants (see vacuum permittivity and vacuum permeability). OP, did this answer your question? I couldn't tell if you were actually asking about the obsolete luminiferous aether theory, annd the last bit of your final question was worded oddly to me. —Akrabbim^talk 10:32, 2 July 2009 (UTC)

Our OP seems a little confused - so let me try to spell it out more simply.

When we talk about the speed that electromagnetic and gravitational waves are moving - we have to be extremely careful. Light does "slow down" when it moves through air or glass or something (that's why lenses and prisms work - and why diamonds are so sparkly). But then we're talking then of the "group velocity" of the waves (the speed at which information carried by the wave travels) - not the "phase velocity" (the speed that the actual waves move)...it gets a bit technical/mathematical and it's hard to explain in words without getting into deep waters! This image may help though:

• The red dot moves at the "phase velocity" - a speed which represents 'c' - "the speed of light in a vacuum" - the thing that is the cosmic speed limit. This speed never changes - no matter what the medium is.
• The green dots are moving at the "group velocity" - the speed at which a change in the size or frequency of the waves can be propagated. This speed is slower than the phase velocity in air, water, etc - but happens to be the same as the phase velocity in a vacuum. When you hear of scientists "slowing down" or even "stopping" light - they are talking about the group velocity.

In a true vacuum, the two speeds are exactly the same. Unfortunately, when we use the term "the speed of light" - we tend to get slightly fuzzy about which speed we're talking about. For all of the exciting relativity kinds of thing - we're talking about the phase velocity - and we should strictly be saying: "the speed of light in a vacuum" or "the phase velocity of light" - and not just "the speed of light" because that is confusing. For measuring the speed of light in (for example) air and glass so that we can calculate the refractive index and make the right kind of lenses for your spectacles - we're talking about the group velocity - and we should say so - but we usually don't.

'Ether' - in this context - is correctly spelled 'aether' (and often expanded to luminiferous aether) because there is a chemical called 'ether' that is an entirely different thing! The idea that there is an 'aether' through which the waves travel is a seriously outmoded concept - the utter failure of the many efforts to detect the presence of the aether is the reason that Einstein discovered relativity in the first place.

As for "reasons"...these are always difficult for physics. We mostly deal in the "what" - not the "why" of nature. We can measure what it does - but not why it does that. So I don't think we know of a reason why there is a cosmic speed limit. If we had to say anything, it would probably be that he nature of relativity is that there is a cosmic speed limit built into the laws of nature - you can see it clearly in the equations. Light and gravity travel at that speed. We call it "the speed of light" mostly for historical reasons. In the case of light, photons (having zero rest-mass) can't help but travel that fast - if they were (hypothetically) ever to travel any slower then even an infinitesimal force would impart an infinite accelleration (because F=ma - so a=F/m - and if 'm' approaches zero and 'F' is finite - then 'a' approaches infinity). That infinite acceleration would instantly push the photon them up to the cosmic speed limit. Now - as to why there is a cosmic speed limit...that's something we don't know the answer to.

SteveBaker (talk) 11:06, 2 July 2009 (UTC)

Wow Steve, that was incredibly informative. My knowledge of the subject seems to me much less definitive than I had thought. Your response leaves me wondering, though, are photons always traveling at the phase velocity? Or are they tied into the group velocity? —Akrabbim^talk 12:11, 2 July 2009 (UTC)

Steve, if a change in size or frequency of light can only pass through air, water etc. at less than 'c' how can one prove that any higher velocity exists in the medium ? Cuddlyable3 (talk) 12:28, 2 July 2009 (UTC)

See Cherenkov radiation. --Tardis (talk) 16:22, 2 July 2009 (UTC)

Steve, your response was pretty inaccurate. The phase velocity of light is not generally equal to c (the vacuum speed of light). It can be smaller or larger. It's effectively infinite for a standing wave, even in vacuum. For light in glass it's roughly the same as the group velocity (that animated image shows a gravity wave, not light, and as an illustration of group velocity it's kind of dubious anyway since there's no real wave packet). It's the phase velocity that's defined to be c/n in a refractive medium and that figures into Snell's law and lensing (see the animated image at the top of refractive index). The group velocity can also exceed c and is not the speed at which information is communicated in general. This Java applet shows how group velocity can be larger than c or negative (that is, opposite the direction of information propagation). The relationship between phase velocity, group velocity and "actual information propagation velocity" is subtle, and I think it may even be an open question. See the last part of this page, starting from "How about using tachyons to transmit information faster than the speed of light..." -- BenRG (talk) 00:52, 3 July 2009 (UTC)

The OP's post is confusing because of the lengthy indented quotation and the mysterious date "7 August 06" in the middle. Cuddlyable3 (talk) 12:12, 2 July 2009 (UTC)

Apologies: I had added the indent when I responded. Because of the date in the middle, I mistakenly thought Taxa was responding to an unsigned OP. Indent removed. Tempshill (talk) 19:27, 2 July 2009 (UTC)

A minor nitpick to Steve's answer. The phase velocity does not have to exactly equal c (the universal constant). There are plenty of materials (optical prism?) where both phase velocity and group velocity are non-constant or vary with frequency. Nimur (talk) 16:33, 2 July 2009 (UTC)

I too am wowed by Steve's answer, whether it is right or wrong. Steve's answer is still extremely informative as to how one might go about answering the question. Most important is his introduction of the relationship between force, mass and acceleration and ultimately energy, which should properly be responsible for a speed limit. The problem I have with group versus phase velocity is that if you can clip the intensity and in effect use it to propagate information then group velocity would always equal phase velocity if such a clipping could be done. Another response that comes to mind is that the limit may be simply be the limit that a magnetic field can generate an electrostatic field and vice versa as the means of propagation. This process must be very efficient and use up very little energy which may or may not support the idea of the existence of a luminiferous aether]]. -- Taxa (talk) 05:02, 3 July 2009 (UTC)

As a side note, see this. It's an issue of a webcomic -- in this case atypical in comic content for this comic, but typical for interesting commentary, in this case on Maxwell's equations. -203.129.49.222 (talk) 11:32, 3 July 2009 (UTC)

Oh yeah. That fully explains it. I suppose that at some point in the transition of magnetic to electric field light would take on characteristics of a particle while in the opposite phase the characteristics of a wave? -- Taxa (talk) 13:43, 3 July 2009 (UTC)

Second Generation Growth

First generation crystal right, second generation left

The owner of this crystal tells me that the first generation crystal (right) formed first. Then the second generation solution came in and formed the crystal on the left. Does wikipedia have an article on second generation crystal growth, or can anyone find a reference? This would be be a perfect illustration if I could find the article. Noodle snacks (talk) 09:38, 2 July 2009 (UTC)

I notice the OP uploaded the image of calcite (?) today and it is not used in any article yet. Cuddlyable3 (talk) 11:50, 2 July 2009 (UTC)

The OP did, but the OP is looking for what is described above to add the image there too. Noodle snacks (talk) 11:54, 2 July 2009 (UTC)

Hydrogen atom

defination of Degeneracy.Supriyochowdhury (talk) 11:12, 2 July 2009 (UTC)

Your quesstion seems to be a homework question, as do the ones below. This desk is not answering such questions per policy. Some answers might be found at Hydrogen,degeneracy, Ion, potential as well as other related Wikipedia articles. As aditional advice: The utilization of socks is frowned upon. Try to aviod making the same spelling mistake all over your questions. Its a deat giveaway. --91.6.12.225 (talk) 11:50, 2 July 2009 (UTC)

Running around acting wild and paying no heed to the expectations and norms of society. Like a semiconductor, a human can be doped into total degeneracy. Edison (talk) 23:55, 2 July 2009 (UTC)

Haha, Edison -- good one! 76.21.37.87 (talk) 04:04, 4 July 2009 (UTC)

quantum mechanics

defination of simple harmonic motion.Supriyochowdhury (talk) 11:14, 2 July 2009 (UTC)

Simple harmonic motion. No quantum mechanics is involved in the definition (correctly spelled). Cuddlyable3 (talk) 11:55, 2 July 2009 (UTC)

Note that a quantum-mechanical treatment of a simple harmonic oscillator is not the same as a classical physics treatment. This example is commonly the first example worked in a quantum physics text-book. Nimur (talk) 16:35, 2 July 2009 (UTC)

Quantum harmonic oscillator. Algebraist 16:36, 2 July 2009 (UTC)

conductivity of electrolites

define ionic mobility.Rikichowdhury (talk) 11:24, 2 July 2009 (UTC)

We have a relevant page: Conductivity (electrolytic). --Scray (talk) 12:14, 2 July 2009 (UTC)

thermodynamics

defination of chemical potential.Rikichowdhury (talk) 11:28, 2 July 2009 (UTC)

We have a page for this, too! Chemical potential --Scray (talk) 12:15, 2 July 2009 (UTC)

conductance

defination of molar conductance.Rikichowdhury (talk) 11:31, 2 July 2009 (UTC)

I think this is described here as well: Conductivity (electrolytic) Before asking for things that could easily be found by searching, please search Wikipedia and other sources a bit, as suggested at the top of this page. If you need to ask, please keep in mind that we are all human beings, here to enjoy interaction, not automatons waiting for your command. --Scray (talk) 12:21, 2 July 2009 (UTC)

That latter statement is untrue. I am waiting for his command, as are others like me. Tempshill (talk) 19:23, 2 July 2009 (UTC)

fingers and toes

Is there a scientific reason why humans normally have 5 fingers and five toes on each limb? Why not 4 or 6? Why is 5 the magic number? 65.121.141.34 (talk) 16:29, 2 July 2009 (UTC)

Depends on what you mean by "reason." The simplest answer is that we have five digits because our ancestors had five digits (pentadactyly). Someone else might be aware of research showing why 5 is more adaptive than 4 or 6, but I wouldn't be surprised if there's no such research. Many traits are not adaptive. Adaptive or not, an expert in ontogeny could probably give you another kind of "reason," that is, exactly how our genes encode for various proteins that lead a fetus to develop five digits.

This probably doesn't answer your question, but hopefully it's something to think about pending a more complete answer from someone with more expertise. --Allen (talk) 16:57, 2 July 2009 (UTC)

Increasing or decreasing the number of digits presumably would make the overall body function less effectively. Bus stop (talk) 17:12, 2 July 2009 (UTC)

Not necessarily. We can presume that it wouldn't make the body function more effectively, but that is all. --Tango (talk) 17:18, 2 July 2009 (UTC)

Why one presumption over the other? To me they both seem equally likely presumptions. Bus stop (talk) 17:25, 2 July 2009 (UTC)

They can't be equally likely since one includes the other (unless it is impossible for 5 and 6 fingers to be equally effective and there is no reason to assume that). If 5 fingers was worse than 6 fingers then we would expect natural selection to select people with 6 fingers and by now we would all have 6 fingers, but if 5 and 6 fingers are equally effective then there is no selection pressure and it just gets chosen at random. So we can presume that 5 is either better than 6 or as good as 6, but we can't tell which without more research. --Tango (talk) 17:31, 2 July 2009 (UTC)

I think we are comparing 5 to any other number. Isn't that what we are really comparing? The questioner mentions both four (a lesser number) and six (a greater number). Bus stop (talk) 17:33, 2 July 2009 (UTC)

Tango, you say, "If 5 fingers was worse than 6 fingers then we would expect natural selection to select people with 6 fingers and by now we would all have 6 fingers". I don't think that's true. It might be that 6 fingers confer a very slight advantage, and that there has not been sufficient environmental pressure to make that advantage play much role in determining reproductive success. -GTBacchus^(talk) 17:44, 2 July 2009 (UTC)

I am pretty sure Tango misread my statement. This is getting hideously confused. Bus stop (talk) 18:04, 2 July 2009 (UTC)

If only I had a couple of extra digits, I could probably sort it out, and then get on with my reproductive goals... -GTBacchus^(talk) 18:19, 2 July 2009 (UTC)

lol Bus stop (talk) 18:27, 2 July 2009 (UTC)

Our ancestors have had 5 fingers for a long time, all primates have 5 fingers/toes so that means it happened at least 10s of millions of years ago. Polydactyly is fairly common (and can be inherited and, as far as I know, isn't associated with any other negative conditions), so there has been plenty of opportunity for us to evolve to have a different number of fingers. It wouldn't need to be a very large advantage to it to have happened. --Tango (talk) 21:55, 2 July 2009 (UTC)

Ok, so we're saying the same thing, for different values of the phrase "very large". :-) -GTBacchus^(talk) 01:15, 3 July 2009 (UTC)

I was using 6 as an example, replace 6 with any other number at it is still true. --Tango (talk) 21:55, 2 July 2009 (UTC)

I don't have time to do a search, so I can just try to piece together fragments from an old memory... In genetic research, the gene group that is responsible for creation of the digits (fingers and toes) are also responsible for creation of the reproductive organs. So, if there is a genetic abnormality that causes more or less digits, it is highly likely that reproduction will be hindered. Therefore, the ability to stray from five digits is limited by the ability to reproduce. What comes to mind is something like HAX or HEX or HOX. I don't actually work in genetic research. I read this while researching genetic information on the four-toed hedgehog. Does this nonsense ring a bell for anyone who actually knows about genetics? -- kainaw™ 18:29, 2 July 2009 (UTC)

I just googled for "genetics h.x" and got a lot of hits for Hox genes. -- kainaw™ 18:30, 2 July 2009 (UTC)

HOX is short for homeobox and they determine all sorts of things about the arrangement of the body (eg. that your face is on the front, not the back). It wouldn't surprise me if HOX genes were responsible for the number of fingers, however I've never heard of people with Polydactyly being infertile. --Tango (talk) 22:01, 2 July 2009 (UTC)

Not the scientific answer you're looking for, I know, but I like to attack the questioner's frame of mind, not the question itself:

If we had 4 or 6, you would just as soon ask, "why not 5?". There's 5 because evidently, that's what works best. Trying to break down that 'why' into some bio-mechanical or socio-evolutionary explanation would be so lengthy and obscure that it wouldn't be worth the effort – in my opinion. Vranak (talk) 19:09, 2 July 2009 (UTC)

Fingers started as stiffeners for fish fins. The practicality of mittens shows that the number of human fingers doesn't matter much. The evolutionary step that did matter was when a primate gained an opposable thumb. Hands would no more be just for walking on, now they could be used to fruitpicking, hitchhiking and typing the spaces in Wikipedia. Cuddlyable3 (talk) 22:34, 2 July 2009 (UTC)

The number of digits is (partly) mediated via CRABP-II. Axl ¤ [Talk] 20:02, 3 July 2009 (UTC)

Could you give a few more examples of what else CRABP-II mediates besides the number of digits? I'm not a geneticist, but I'd like to know if a modified CRABP-II gene is likely to be maladaptive. 76.21.37.87 (talk) 04:12, 4 July 2009 (UTC)

In Mutants (ISBN 0006531644), Armand Marie Leroi points out that until recently all known tetrapods (i.e. land vertebrates) had no more than five digits, and those with fewer than five always had ancestors with five digits: the normal conclusion was that the common tetrapod ancestor was pentadactyl, and all subsequent tetrapods had inherited this trait, though in some cases subsequently lost digits. But the discovery of Acanthostega, Turlepreton and Ichthyostega has changed this, and it now looks as though there was considerable variation in the dactyly of early tetrapods before pentadactyly became universal.

Of course you could use this fact to argue for an adaptive advantage in no more than five digits, but I think such an argument would be weak ;) --ColinFine (talk) 16:18, 4 July 2009 (UTC)

Try this article (although it's a little old). CRABP-II is involved in neural crest development. "CRABP-II mRNA have been shown to increase in tissues and cell lines of various origins, including F9 teratocarcinoma cells, P19 embryonal carcinoma cells, adult human skin, skin fibroblasts, and lesional hyperplastic psoriatic skin following treatment with retinoic acid." Axl ¤ [Talk] 19:57, 4 July 2009 (UTC)

Light speed clarification

To me I'm still confused. I haven't got the chance to study about special and general relativity in the university. I tried to read some books and visit such web pages as Relativity of simultaneity to understand some more. Now I need to distinguish the following: 1- Light speed is absolute: What can prove this other than Maxwell's equations? 2- Assuming 1 holds true; what makes us assume that the observer in moving frame of reference will find that light in that frame passes both (front and back) directions and reaches equal distances at the same time (So far we shouldn't conclude that time is relative till both 1 and 2 postulations are verified)?--Email4mobile (talk) 17:55, 2 July 2009 (UTC)

That the Speed of light as an absolute and unchanging quantity, independent of the speed of the observer has actually been proven experimentally, and not just via deduction. Consider the seminal work of people like the 17th century Ole Rømer. Of course, the definitive works is the Michelson–Morley experiment, which essentially disproved the idea of 'aether', and the Ives–Stilwell experiment, which showed that redshift could be accounted for only if the observed speed of light is identical looking forwards and backwards. Also see History of special relativity which explains the development of all of these ideas and more. --Jayron32.talk.contribs 18:10, 2 July 2009 (UTC)

I've read about Ole Rømer and Michelson–Morley experiment but non of them explained that light is absolute nor is simultaneity observer's dependent. I'd like to know more about experiments done to realize or prove the 2 points in question before Albert Einstein or his followers formulated the time dilation equation.--Email4mobile (talk) 08:58, 3 July 2009 (UTC)

Did you read the other articles, or folow any links in the see-also sections of any of those articles? The information is here for you to find; the History of special relativity has lots of details and lots of links; also the Ives–Stilwell experiment which also explains your direct question regarding perceptions of the speed of light in a moving observer. --Jayron32.talk.contribs 20:32, 3 July 2009 (UTC)

Solar Panels

If I have a solar panel operating at a certain voltage and current, and I cover part of it, what will decrease, the voltage, the current, or both? Not homework, just curious. 149.169.104.64 (talk) 18:02, 2 July 2009 (UTC)

Assuming it is a photovoltaic panel, I would think that it would directly reduce the voltage output. Depending on the load network that the panel is attached to (I have no idea how they are integrated into power grids), the current would probably be reduced as well. —Akrabbim^talk 19:19, 2 July 2009 (UTC)

It's going to depend on what else is on the circuit. I don't know a whole lot about electronics, but if we assume a simple case where whatever you're powering has constant resistance R no matter what, then the voltage and current are going to stay in the ratio V/I = R. So cutting the power by half, and using P = IV, the voltage and current would both be reduced by sqrt(2). Maybe someone who knows more about this can comment on how likely that assumption is. Rckrone (talk) 23:36, 2 July 2009 (UTC)

Actually looking at Electromotive_force#Solar_cell it looks like it's a bit more complicated than I thought. The current and voltage will stay proportional for a fixed resistance, but the power isn't determined only by how much light is hitting the solar panels like I was assuming, it depends on the current, so instead of using the equation P = IV you would have to use the one listed there to figure out exactly by what factor the current and voltage would both drop. Rckrone (talk) 00:04, 3 July 2009 (UTC)

Voltage and current both reduce (and the covered part of the panel gets hotter). Polypipe Wrangler (talk) 14:41, 4 July 2009 (UTC)

Green stars?

Most stars are colored red, or yellow or white because of their temperature. Are there any known green colored stars? Say one that has a lot of chlorine or copper in it? Is such a star theoretically possible, even if we don't know of a current example? 65.121.141.34 (talk) 18:16, 2 July 2009 (UTC)

I wish I could back this up better, but the gist of it is this: stars output their light in a curve, so to speak. Bright, blue stars output most of their light in the blue wavelengths, whereas red stars output most of their light in redder wavelengths. Now, a star with a peak in the green won't appear green for reasons I don't quite remember, but it had something to do with the other (bluer, IIRC) wavelengths drowning it out. So yes, there *are* green stars, but the human eye won't ever perceive them as green. Actually, here is a reference, and here's another one. I left my old text since I think it's mostly correct. ;) -- Aeluwas (talk) 19:10, 2 July 2009 (UTC)

That's a pity. The green stars I see in Freelancer are particularly nice-looking. —Akrabbim^talk 19:21, 2 July 2009 (UTC)

Human color perception is a strange thing in many ways. Consider that there are actual two different "yellow" colors, which are VERY different, but which our minds cannot distinguish between. One is a single wavelength color consiting of pure yellow light, and the other is a mixture of two wavelengths of light, one red and one green. The human mind only sees these as the same color, though one is clearly a primary color, and one is a secondary color. There are LOTS of colors that work this way. See Color vision for more on how we perceive color. --Jayron32.talk.contribs 20:52, 2 July 2009 (UTC)

How do you define the colour of a star apart from what colour it appears to humans? Those are the only real definitions of colours we have (except for monochromatic colours that can be defined by their wavelengths). --Tango (talk) 21:46, 2 July 2009 (UTC)

Except for absorption lines whose effect is relatively minor, stars emit blackbody radiation, which is spread over a quite broad range of wavelengths. For cooler stars, most of their output is in the infrared region, so we can only see the top of their spectrum which is red; for hottes stars, it's mostly ultraviolet, so we can only see the blue part. Stars with intermediate temperature emit over the whole visible spectrum, so they are white. Black bodies can only have colors on the Planckian locus; so there can be no green or purple star. --A. di M. (formerly Army1987) — Deeds, not words. 21:42, 2 July 2009 (UTC)

Interesting fact: our Sun is a "green" star because its spectrum peaks in the green, or at least very close to it. Not surprisingly, the human eye's sensitivity peaks around the same wavelength, but why leaves reflect green light most strongly is a bit harder to explain. --Bowlhover (talk) 23:31, 2 July 2009 (UTC)

Insect identification

This morning I found these on my front gate; I've never seen anything like them before, and was wondering if anyone could identify? I'm assuming they're moths, and they're mating (?), but beyond that I'm lost. I'm in Belfast, Northern Ireland where I found these guys about 8am. Unfortunately I wasn't able to line anything up for size comparison, but the body length was approx 1.5 inches and 2 inches from wingtip to wingtip. Are they mating? They don't exactly look like the same species - are males and females often significantly different in appearance? Thanks --Kateshortforbob 22:14, 2 July 2009 (UTC)

I think the species is Poplar hawk-moth, Laothoe populi. So, yes, they are moths; and yes, they are mating. Regarding the appearance - I need to look it up. I've seen both grey and brown form in the photographs, but I do not remember if it is sexual dimorphism or just different color forms. --Dr Dima (talk) 22:24, 2 July 2009 (UTC)

Oops, I gave our article less credit than is due. It explains the colors. --Dr Dima (talk) 22:26, 2 July 2009 (UTC)

You should replace the current 'mating' photo with this one and explain the color difference in the caption. It's a prettier photo than the current one. Tempshill (talk) 23:15, 2 July 2009 (UTC)

That might be a good pic for the main Mating article too... --Kurt Shaped Box (talk) 00:16, 3 July 2009 (UTC)

Cool! Moth-porn. SteveBaker (talk) 14:27, 3 July 2009 (UTC)

Disgusting! Will no one think of the larva? Dragons flight (talk) 19:55, 3 July 2009 (UTC)

I boldly added this excellent pic to both articles. --Jayron32.talk.contribs 00:45, 4 July 2009 (UTC)

Thanks Dr Dima, for the identification - I will update the description page accordingly. Thanks also, Jayron32, for adding the picture to those articles - I suspect I would have committed some embarrassing captioning error if I did it myself! --Kateshortforbob 10:28, 4 July 2009 (UTC)

July 3

Nose-picking in nonhumans

Do all animals that have a nose and the physical capability to pick a nose, in fact pick their noses? YouTube says that parrots do. Just got me wondering... --Kurt Shaped Box (talk) 00:14, 3 July 2009 (UTC)

Many animals, such as cows, have a long tongue which is easy for them to stick up into the nostrils for cleaning purposes. It would be difficult for a cow to pick her nose with her hoof. Edison (talk) 02:27, 3 July 2009 (UTC)

My dogs don't. A Quest For Knowledge (talk) 03:12, 3 July 2009 (UTC)

Animals like people don't get to pick their noses and they have to work with the nose they are given like you know who. Cuddlyable3 (talk) 12:53, 3 July 2009 (UTC)_{Yah! mean cheap shot.}

I've seen chimps and gorillas doing it - and it has been observed (sorry - I can't locate the link) that in many (if not all) primates, the nostrils are the exact same diameter as the index finger. This is unlikely to be an accident. SteveBaker (talk) 14:26, 3 July 2009 (UTC)

Well, Darwin would say it's an accident. Tempshill (talk) 17:37, 3 July 2009 (UTC)

@Tempshill: I don't think that's correct, if you're using "Darwin" as a representative of adherents to evolutionary theory. Just to reduce the risk of confusion, I'm going to hazard a guess: "accident" is being used here (by both SteveBaker and Tempshill) to mean "coincidence" or random chance. Though evolution depends on random variation to generate diversity, it is selection that drives adaptation to specific function (which I think was the point SteveBaker was making). --Scray (talk) 19:49, 3 July 2009 (UTC)

I think SteveBaker used "accident" in the latter sense, and I was using it in the former sense. I don't know that I'd subscribe to the theory that human finger diameter and human nostril diameter have been selected to match each other. Tempshill (talk) 20:39, 3 July 2009 (UTC)

cortisone

What does it mean to get a cortisone shot? —Preceding unsigned comment added by 76.171.21.74 (talk) 01:52, 3 July 2009 (UTC)

It means an injection of cortisone, which is a steroid. --Allen (talk) 03:58, 3 July 2009 (UTC)

What sort of math is being used?

I don't understand how this works or how to stump it? Ideas? --Reticuli88 (talk) 03:57, 3 July 2009 (UTC)

There's nothing very mysterious about it. If we ignore the obfuscating steps that don't involve your number at all, and rearrange the initial grid a bit, then it boils down to being given a 5x5 grid of numbers, choosing one of them, telling someone which row and which column your number is in, and them then working out your number. Algebraist 04:01, 3 July 2009 (UTC)

It looks very simple once you take away all the pointless stuff. First, it asks you the color. That narrows it down to only 4 or 5 numbers. Then, on the step with the houses, the numbers for the colors are split up so that each house contains only one number of each color. Knowing the color from before, that leaves only one possible number. Ta da! --Bennybp (talk) 04:51, 3 July 2009 (UTC)

light propogaton versus particle stability

Is perhaps the only difference between light (as a particle) and other particles is that light is self propagating perhaps due to an inability to become a stable particle whereas other particles are either stable or their instability does not cause self-propagation but self-inhalation instead? -- Taxa (talk) 05:18, 3 July 2009 (UTC)

I would advise you to read the article photon. Photons are pretty stable, you can see them around everywhere. I don't understand what you mean by "self-inhalation", or how you propose that a particle can "self-propagate" if it is unstable. Maybe you mean "annihilation" but that requires two particles - one matter and one which is antimatter. Rkr1991 (talk) 06:36, 3 July 2009 (UTC)

pocket desert

What is a pocket desert? —Preceding unsigned comment added by 89.247.57.20 (talk) 08:07, 3 July 2009 (UTC)

Based on Pocket park and Pocket beach I suspect it is an informal name for a small desert that is surrounded by otherwise non-desert geography. 194.221.133.226 (talk) 09:22, 3 July 2009 (UTC)

Some context would be useful. It could mean someone with empty pockets?! You might like to try the Language desk.--Shantavira|^{feed me} 09:53, 3 July 2009 (UTC)

Typing "pocket desert" into Google turns up articles about a specific place near Oliver, British Columbia. Our article describes it as having a 'pocket desert' nearby. This has more information, as does this. So the term seems to be a generic one for multiple 'pocket deserts' - yet only this specific one ever shows up as an example of such a thing. Perhaps the term is used only in Canada with some other terminology being used elsewhere? SteveBaker (talk) 14:22, 3 July 2009 (UTC)

Searching on "desert pocket", found quite a lot of examples describing areas of local desert conditions as suggested by 194, mainly from the US but also from New Zealand and the Himalayas (cold desert in that case). Mikenorton (talk) 15:32, 3 July 2009 (UTC)

I'm aware of small areas of desert near Lillooet, British Columbia, could it be the same "pocket desert" Steve found on Google?

76.21.37.87 (talk) 04:22, 4 July 2009 (UTC)

What are the strongest and weakest points of gravity on earth?

I'm aware that a number of 'gravitational maps' exist, however, I have heard, in the past, of a place where the phenomena of gravity is noticeably at variance with that of other parts of the world. Where are these places and what, if any, explanation exists for the variance? —Preceding unsigned comment added by 24.234.123.169 (talk) 16:53, 3 July 2009 (UTC)

Our article Gravity anomaly gives the facts, in a sketchy way. It's possible that you're thinking of stories about places like Confusion Hill in northern California, where the layout of the landscape creates an illusion that objects roll uphill. Looie496 (talk) 17:05, 3 July 2009 (UTC)

Due to the shape of the earth, gravity will tend to be strongest at the north and south poles - and weakest around the equator (the earth isn't a perfect sphere). However, you don't feel that difference because the centrifugal forces are zero at the poles and higher at the equator...which is why the earth is that shape to start with and gravity-centrifugal force is pretty much constant everywhere. Aside from that, differences in mineral composition and therefore density can make a tiny difference from place to place - also the presence of mountains or deep valleys. This map [34] gives you a better way to visualise it. ~~

Actually, the effects of oblateness and rotation act in the same direction, both reducing the effective acceleration due to gravity at the equator as compared to at the poles. The difference is about 0.35%, of which about 2/3 is due to the rotation of the Earth and 1/3 is due to the oblateness of the Earth. Definitely a noticeable effect - a pendulum clock on the equator loses about 2.5 minutes a day compared to an identical clock at the poles. See Equatorial bulge#Differences in gravitational acceleration. Gandalf61 (talk) 19:38, 3 July 2009 (UTC)

The story that I heard, was that there was a place where gravity or some other phenomena affected the surface of a lake in Africa. The phenomena supposedly caused the surface to have a noticeable curvature. However, I suppose that this is a legend or myth of some sort.

As an aside, is it possible to obtain the data-set used to generate the map show in [35] ? —Preceding unsigned comment added by 24.234.123.169 (talk) 17:20, 3 July 2009 (UTC)

At what speed do galaxies travel through the universe/space?

At what speed do galaxies such as the Milky Way and Andromeda travel through space? As a follow-up, what are the speeds of the solar system and earth as well? How are these measured? How does this affect our measurements such as the speed of light, radio waves, etc. Is there a point where the speed of a mass shall decline to 'absolute 0'? Theoretically, is there a way to 'see' a mass traveling faster than the speed of light? —Preceding unsigned comment added by 24.234.123.169 (talk) 17:38, 3 July 2009 (UTC)

As it turns out, the speed of light relative to you will be equal regardless of how fast you're moving. Check out Special_relativity#Lack_of_an_absolute_reference_frame and also Introduction to special relativity. As a result, measurement of the speed of light is not affected by how the earth or the galaxy are moving, and an object can never be observed to travel faster than light. In addition, objects don't have a meaningful absolute velocity since there's no single "preferred" reference frame in which light behave properly; you can only talk about objects' velocities relative to other objects. Here's some info on the Milky Way: Milky_way#Velocity. Rckrone (talk) 18:34, 3 July 2009 (UTC)

The orbital speeds of the planets relative to the Sun are listed in our articles for each of the planets. For example, Earth's is just under 30 km/s. ~AH1^(TCU) 19:12, 3 July 2009 (UTC)

Neoprene wetsuit in chlorinated water

Hi everyone I recently bought a wetsuit made of neoprene and on the label it says do not use in chlorinated water. I intended to use it in chlorinated water. I am wondering if I do go in chlorinated water in this suit will it affect the insulating properties of the material? If chlorine only acts to discolourise/stain the material I don't much care but I want to make sure that going in chlorinated water won't stop the suit doing its job if you know what I mean. Any help would be much appreiciated. Thanks RichYPE (talk) 17:53, 3 July 2009 (UTC)

I was taught, vaguely, that chlorine would somehow destroy the wetsuit. Googling "neoprene chlorine", this result from the first page of results claims that "Neoprene ... contain[s] carbon-carbon double bonds as an essential part of their polymer chains. These bonds are susceptible to oxidative damage from species such as ozone and chlorine." As a layman I'm not exactly sure what "oxidative damage" means, but it sounds like it'd be worse than just staining. Tempshill (talk) 20:10, 3 July 2009 (UTC)

See Halogen addition reaction and ozonolysis for the chemistry behind the reactions you drescribe. --Jayron32.talk.contribs 20:25, 3 July 2009 (UTC)

Thanks for your help but chlorinated water is usually in the form of sodium hypochlorite rather than just actual chlorine. I wonder if this makes a difference and whether or not this would react with the neoprene... RichYPE (talk) 22:17, 3 July 2009 (UTC)

Actually, read the article Bleach. Hypochlorite is really a dynamic equilibrium with chlorine and water, as described here:

Cl₂ + H₂O $\rightleftharpoons$ H⁺ + Cl^- + HClO

With low pH favoring the backwards reaction and high pH favoring the forwards reaction. Still, even under roughly neutral conditions, there may very well be enough Cl₂ present to react with any double bonds via alkene halogenation mechanisms; even if its only a trace amount, Le Chatelier's principle tells us that since the reaction removes chlorine from the system, the hypochlorite-chlorine equilibrium will just generate more chlorine on demand to meet the need. I did some looking, and there does not appear to be any common hypochlorite-alkene reactions directly; however the chlorine is clearly the reactive species here. --Jayron32.talk.contribs 00:39, 4 July 2009 (UTC)

As far as I'm aware, the chlorine addition reaction will not destroy neoprene rubber, but is likely to cause embrittlement over an extended period of time. So, if you frequently use the wetsuit in chlorinated water, it won't come apart the first few times, but you should definitely expect it to wear out sooner than normal. 76.21.37.87 (talk) 04:29, 4 July 2009 (UTC)

Apparently there is an Italian made polyester wetsuit fabric that is chlorine resistant. But as you've already bought your suit, you could try this Wetsuit Shampoo that supposedly removes chlorine. - KoolerStill (talk) 12:00, 4 July 2009 (UTC)

Hi thanks for the posts guys. What I will do is get a refund on my suit (still have receipt) and buy one which is chlorine resistant. Cheers RichYPE (talk) 19:05, 4 July 2009 (UTC)

Minimum Sample Size for a Correlation Study

I know of a formular for determining the minimum sample size for a prevalence study, which most research studies use. Is there any formular to determine minimum sample size for a correlation study, like a correlation between birth weight and fetal cord leptin concentration-a research?Tunmisadej (talk) 19:54, 3 July 2009 (UTC)

I'm not sure there is a general answer to this. For a specified minimum confidence level and correlation value, one can determine the number of samples needed, but since it depends on the strength of the correlation one may not have a good estimate in advance. For example, a perfect correlation can be statistically significant with only a small number of samples. By contrast, a weak correlation (which is much more common in practice), may require a quite large sample to confidently document. Dragons flight (talk) 20:11, 3 July 2009 (UTC)

This is the most common reason for doing power calculations, and our article covers the considerations pretty well. --Scray (talk) 04:47, 4 July 2009 (UTC)

I am sorry, I still find the reference above not clear to answer the question. The one that was mostly discussed was sample size for determining proportion study. If I have correlation coefficients from prevoius research studies, I would like to know if this can help in determining minimum sample size using any formula or otherwiseTunmisadej (talk) 11:30, 4 July 2009 (UTC).

I had a similar question once and although I never really solved it. This may help, but I'm not sure since I haven't formally taken any statistics. Sifaka ^talk 20:40, 4 July 2009 (UTC)

Blood pressure in cats

Our vet always quotes our cat's blood pressure as a single number whereas human blood pressure is always quoted as two numbers, the systolic and diastolic pressures. Why is only one quoted for cats and which one is it (or is it some other number entirely)? Thanks. --Tango (talk) 22:27, 3 July 2009 (UTC)

The information on this site (http://www.pets.ca/encyclopedia/hypertension_cats.htm) has some details under the 'diagnosis' section and seems to suggest both types of numbers being run against cats. Are these measured separately or together? If they are separate then maybe it is to minimize stress on the animal and perhaps the single piece of information is usually enough. All speculation though, sorry. ny156uk (talk) 23:12, 3 July 2009 (UTC)

I think you have to ask your vet on this one: it's certainly possible to obtain the usual systolic/diastolic readings in cats (normal is ~124/82) using a machine (I think the cat's rapid heartbeat might make it difficult to do by ear). But whether your particular vet is quoting systolic, diastolic, or mean arterial pressure is something only he or she can say. - Nunh-huh 23:16, 3 July 2009 (UTC)

July 4

what sort of atomic radius is this?

If I take a mole of some element, measure its volume, then divide by 6.024 * 10^23, and then find the radius of the sphere with that volume, what am I measuring? Van der waals radius? —Preceding unsigned comment added by Em3ryguy (talk • contribs) 01:16, 4 July 2009 (UTC)

I'm not sure you are measuring anything useful. Any substance is going to have a space between its atoms in any phase of matter; your calculation includes this extra-atomic space as part of the radius of the atom itself. Even assuming you had a perfect crystal at absolute zero (which is an impossible to reach state), you still have to consider packing efficiency. In any real solid, the atoms are going to still obey kinetic molecular theory in that they will vibrate in place; and this motion will also add volume to the theoretical perfect packing required for your calculation to work. See Van der Waals radius#Methods of determination for real experiments used to calculate the Van der Waals radius. I am pretty certain that most modern chemists would use X-ray crystallography to find such values today. Also, the Van der Waals radius is something of a meaningless curiosity. It supposes that atoms are hard spheres; they are not, and do not behave as such under any conditions where their radius is likely to be important. --Jayron32.talk.contribs 01:28, 4 July 2009 (UTC)

Useful or not, though, there is a technical term for this radius: mean interatomic spacing, or crystal lattice atomic spacing (depending on the type of matter, you might or might not have a crystal lattice). Take a look at this material science textbook, for example. Nimur (talk) 04:00, 4 July 2009 (UTC)

The real reason the most shell fish should be kept live until cooking

I'd like to read a accurate and somewhat scientific description of the reason that most shellfish are kept alive until cooking. I haven't been able to find much on or off Wikipedia. ike9898 (talk) 01:26, 4 July 2009 (UTC)

Live lobsters do not generally rot. Dead ones might, if improperly stored. Edison (talk) 03:39, 4 July 2009 (UTC)

No, it's a good question from the OP because other dead animals we eat aren't kept alive until throwing them into the cooking pot. Tempshill (talk) 04:27, 4 July 2009 (UTC)

Only because it's impractical to do so. When kept alive, shellfish are far less likely to escape than other animals.--Shantavira|^{feed me} 04:45, 4 July 2009 (UTC)

Shellfish are kept alive until cooking because there is often no way to distinguish between a recently dead shellfish and a long-dead shellfish. This is especially true of true shellfish like clams and oysters; you generally only can tell if its good to eat if it hasn't rotted, and the only way to tell if it hasn't rotted is to ensure its still alive when you cook it. Most live shellfish ship pretty well on ice, which is why you can get live clams pretty much anywhere (for the right price). Heck, I've seen them in seafood markets in Chicago, which is 1000 miles from an ocean. Crustaceans, which often get classed as shellfish, (though they really aren't), like shrimp, prawn, lobster, and crab are probably safe to eat if frozen alive; in fact lots of shrimp is handled that way. Lobster, on the other hand, is not generally cheaper to ship frozen than alive; unlike shrimp, lobster can survive for a long time out of water, and can survive in a "dormant" state if kept on ice, like dry ice, which is why live lobsters can be shipped to many parts of the country. Crabs are usually cooked and packaged on the boat, in the case of snow crabs or king crabs, which are the kinds of crab you get when you get those crab legs on the chinese buffet. Other types of crab, such as dungeness crab or blue crab are usually only availible dockside. Live crabs are cooked to consume at the restaurant, or cooked and picked and shipped in the form of "lump crabmeat". Unless you are at the shore, you are not going to be able to get raw or fresh crab to cook. --Jayron32.talk.contribs 18:13, 4 July 2009 (UTC)

Dumping

Why do I always need to take a dump about half to one hour after a meal? Do most people do this? —Preceding unsigned comment added by 79.75.91.172 (talk) 02:47, 4 July 2009 (UTC)

It happened to me at one era in my life right after breakfast, otherwise not for many years. It was as automatic as putting a coin in a gumball machine. Edison (talk) 03:38, 4 July 2009 (UTC)

The gumball machine operator may be liable under product description regulations. Cuddlyable3 (talk) 15:11, 4 July 2009 (UTC)

The first half of your question is requesting a medical diagnosis. Please see Wikipedia:Reference desk/Guidelines/Medical advice and User:Kainaw/Kainaw's criterion. The second part of the question can be answered by directing you to a study on defecation frequency. 152.16.59.190 (talk) 03:54, 4 July 2009 (UTC)

Is enquiring about trends in normal bodily functions seeking a medical dignosis? Do most people dump shortly after a meal? Thats all I want to know. Its not medical its statistical. —Preceding unsigned comment added by 79.75.91.172 (talk) 09:57, 4 July 2009 (UTC)

Seeking a medical diagnosis for a perfectly normal and widespread phenomenon? Have you looked at Gastrocolic reflex it should answer your question and confirm the normality of the action. It happens to a lot of people, particularly after the first meal of the day. Richard Avery (talk) 10:01, 4 July 2009 (UTC)

Well thats exactly the answer I was looking for. Thanks Richard. —Preceding unsigned comment added by 79.75.91.172 (talk) 12:52, 4 July 2009 (UTC)

Maybe a link to this could be added to the article on defecation —Preceding unsigned comment added by 79.75.115.133 (talk) 22:41, 4 July 2009 (UTC)

X-ray background

From Wikipedia, the free encyclopedia, quote: "The X-ray background is occulted by the dark side of the Moon." Is this true? How could it be? Please explain. And, please do make sure, when you replying, you actually do understand that "dark side of the Moon" do not actually refer to the "far side of the Moon". Another quotation: "The far side [of the Moon] should not be confused with the "dark side" (the hemisphere that is not illuminated by the Sun at a given point in time), as the two are the same only during a full moon. ". Vitall (talk) 03:14, 4 July 2009 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. — Preceding unsigned comment added by SteveBaker (talk • contribs)

What lead you to believe that question asking if Wikipedia article statement is true/correct could be homework question??? And, that is unrelated, but where in the world topic of X-ray background radiation are taught in schools? Vitall (talk) 03:58, 4 July 2009 (UTC)

An edit earlier today changed the link in the article so that it pointed to Far side of the moon, which created an incorrect statement. I've reverted that edit. For an explanation of how the dark (unlit) side of the moon appears to occult the background radiation, see the description for File:Moon in x-rays.gif. Actually, the entire Moon occults the x-ray background, but in that image x-rays generated by the sun are reflected from the lit portion of the Moon's surface. 152.16.59.190 (talk) 03:37, 4 July 2009 (UTC)

the entire Moon occults the x-ray background <--- I fully agree with THAT statement. Sort of obvious. So do Sun, Mercury, Venus etc. occults the x-ray background radiation. And, so there is absolutely no need to keep designated Moon statement in X-ray astronomy and X-ray background articles??? And no need to emphasize dark side of the Moon? Vitall (talk) 04:08, 4 July 2009 (UTC)

Point taken. Sentence removed. By the way, Wikipedia is the encyclopedia that anyone can edit. Be bold when you see something that needs to be changed. 152.16.59.190 (talk) 06:32, 4 July 2009 (UTC)

Ohh. Please also check this edit. Should be OK I guess. Vitall (talk) 06:45, 4 July 2009 (UTC)

Now what in the world does X-ray background have to do with the occult? ;-) 76.21.37.87 (talk) 04:35, 4 July 2009 (UTC)

That was also part of the question. When I was reading X-ray astronomy, I came across statement that "observed X-ray background is occulted by the dark side of the Moon." It sort of throw me away - in what sense? "Occulted" just like "covered", "hid"? Or Wikipedia meant something different? And why only dark side? And if that radiation is observed, how could it be "occulted", etc. Vitall (talk) 04:46, 4 July 2009 (UTC)

"Occult" means hidden. Astronomers use the term "occlusion" to denote the covering, or hiding, of one phenomenon by another. So to say that the moon occults the X-ray background is technically correct, although it differs from popular usage of the term. Maybe a better term to use in this case would be "occluded" rather than "occulted".--TammyMoet (talk) 08:44, 4 July 2009 (UTC)

OCCULT verb: become concealed or hidden from view or have its light extinguished, cause an eclipse of (a celestial body) by intervention[36]. Etymology: From 1533, "secret, not divulged," from Latin occultus "hidden, concealed, secret," past participle of occulere "cover over, conceal," from ob "over" + a verb related to celare "to hide," from Proto-Indo-European base *kel- (see cell). Meaning "not apprehended by the mind, beyond the range of understanding" is from 1545. The association with the supernatural sciences (magic, alchemy, astrology, etc.) dates from 1633[37] a century later. Cuddlyable3 (talk) 15:03, 4 July 2009 (UTC)

Food questions

If cooking kills bacteria and fungi, then why not just cook spoiled food instead of throwing it away? —Lowellian (reply) 03:53, 4 July 2009 (UTC)

Spoiled food is not only unhealthy because of the presence of bacteria or other microorganisms. These organisms have chemically changed the food (e.g. by breaking down proteins; consuming starches and sugars; potentially producing waste toxins, etc.). Nimur (talk) 04:08, 4 July 2009 (UTC)

If fungi like mushrooms are used for food (and thus presumably nutritious), then why isn't fungi like mold also nutritious? —Lowellian (reply) 08:11, 4 July 2009 (UTC)

Some bacteria and fungi produce toxins as a byproduct of metabolism Even if you kill the pathogen later by cooking, the toxin is still there. See botulism as an example. Our article on Foodborne illness describes this quite well. For your second question, remember the fungi are as different from each other as plants are. Some are beneficial, some are innocous, and some are deadly. -Arch dude (talk) 12:24, 4 July 2009 (UTC)

Also, what food group do mushrooms fit under? They're fungi, so they're not fat/oil, fruit/vegetable, wheat/grain/bread, dairy, or meat/poultry, so what are they? —Lowellian (reply) 08:11, 4 July 2009 (UTC)

Mushrooms are the fruiting body of the mycelium, so they are fruit.--TammyMoet (talk) 08:40, 4 July 2009 (UTC)

TammyMoet, mushrooms are indeed known as "fruiting bodies". However it is an unusual stretch to extrapolate this to describe mushrooms as "fruits". The United States Department of Agriculture classifies mushrooms as "vegetables and vegetable products". Axl ¤ [Talk] 11:00, 4 July 2009 (UTC)

To expand on Axl and the U.S. government; fruits and vegetables are not culinarily exclusive categories; there is some overlap. Botanically speaking, a fruit is any seed-bearing body in a plant. Culinarily speaking, a vegetable is any part of a plant which is used in cooking for savory applications. Thus, there are lots of fruits which are used as vegetables. Consider not only tomatos, but also the entire family of squash and eggplants and cucumber and lots of other fruits which are used in savory cooking applications. There are even a few plants which, while techinically not "fruit", take on fruit-like applications in cooking, such as rhubarb. --Jayron32.talk.contribs 12:40, 4 July 2009 (UTC)

The reason I had my doubts about classification of mushrooms as vegetables is that my understanding is that vegetables are defined as plants that aren't fruits or seeds, but mushrooms aren't plants, so doesn't that contradict the definition? —Lowellian (reply) 18:28, 4 July 2009 (UTC)

Well, except that chefs and taxonomists don't necessarily consult each other when working these things out. From a culinary point of view, something you eat is either a "Plant" or an "Animal". That's it. That Linnean taxonomy has changed over the past 100 years to remove fungi from the "plant" kingdom where they were formerly classified, and moved them to their own kingdom on co-equal footing with plants doesn't matter much to cooks. They still use mushrooms in the same manner in cooking as they always have. And they are used as vegetables. --Jayron32.talk.contribs 19:22, 4 July 2009 (UTC)

If mushrooms are vegetables, does that mean that one could survive on a diet in which one consumes only mushrooms in place of other fruits and vegetables? (That is, you would still be eating stuff like bread, milk, meat, etc., but no other fruit or vegetables like carrots, lettuce, bananas, spinach, etc.) —Lowellian (reply) 18:28, 4 July 2009 (UTC)

All these words are informal. Biologically, mushrooms are not even plants -- they are thought to be more closely related to animals, in fact. Looie496 (talk) 18:37, 4 July 2009 (UTC)

To answer Lowellian: Since humans can survive on a diet that contains very little if any plants (as e.g. in the original life style of Inuit or Mongols), I don't think adding mushrooms will hurt. Fruit and vegetables are a very good and convenient source for many nutrients, but not the only one. --Stephan Schulz (talk) 19:02, 4 July 2009 (UTC)

Viewing solar eclipse

With a solar eclipse coming on the 22nd of this month I wanted to ask what precautions I must take while viewing the eclipse (i.e. wear sunglasses etc.). And will it be visible here in Pakistan? Thanks. —Preceding unsigned comment added by 116.71.61.65 (talk) 06:06, 4 July 2009 (UTC)

See Solar eclipse of July 22, 2009 and Solar eclipse#Viewing. By far the safest way to view a solar eclipse is by projecting the eclipse onto a flat surface and viewing the projection. NASA has a web site dedicated to eye safety during solar eclipses. 152.16.59.190 (talk) 06:41, 4 July 2009 (UTC)

See same question (Archives June 26 "Solar eclipse") > no. 14 welder's glass/goggles are safe and should be available in Pakistan. Don't use any lower grade though. 71.236.26.74 (talk) 15:26, 4 July 2009 (UTC)

Physics questions

My science textbook sucks, and I have some questions about motion (Note: please don't oversimplify anything):

1. When I lift an object, I'm converting some form of energy inside me into kinetic energy (to lift the object) and then to gravitational potential energy. When I drop the object, the energy is converted back into kinetic energy. Once the object hits the ground, where has the energy gone? There's no kinetic energy.
2. My textbook states "... when he [a weightlifter] holds the barbell above his head, no work is being done on the barbell. The weightlifter is applying an upward force equal to the weight of the barbell, but there is no movement in the direction of the upward force." This doesn't sound right - surely work is being done to counteract gravity and prevent the barbell from falling?
3. If I hit a very small brick with a very large force (sideways, so the brick may move), my hand will hurt because of Newton's 3rd law. If I hit a brick wall (made of the same material) with the same force, will my hand hurt the same amount?
4. $E=mc^{2}$ states that objects at rest have energy. The Energy article states that energy is "the amount of work that can be performed by a force", but the energy of an object at rest can't be used by any force, can it?

Thanks in advance. --wj32 ^t/c 07:51, 4 July 2009 (UTC)

A1. The answer is that when you drop the object down, either it bounces back up again if its something like a ball, or it makes a big sound. It scatters all the air and dust particles in the area and slightly heats up the ground. The energy is dissipated in doing all these small small tings.

But most of the energy ends up as heat, both in the object and in whatever it hits. -Arch dude (talk) 11:33, 4 July 2009 (UTC)

A2. Somebody owes Steve a dollar. Well, you're confusing force with energy. The weightlifter needs to keep supplying force in order to counter gravity, but he does no work, and ideally, spends no energy, keeping it up. Work is force times displacement. Since he just has to hold the weight in place, he doesn't do any work.

Give the poor sweating weightlifter a rest and replace him with a six-foot-tall rack to hold the barbell. Does the rack doo work? No. -Arch dude (talk) 12:12, 4 July 2009 (UTC)

A3. Yes, your hand will hurt the same amount. The thing is, it is easy for us to give more force to a stationary brick wall than a movable brick, because it just, well, moves away. However, for equal impulsive forces, you will hurt the same.

The physics of injury is complicated, so we cannot give a real-world answer. But a simplified answer is that hitting the wall will hurt more, because the "hurt" depends on how much ofhe energy of teh blow is absorbed by the hand. when the brick can move, much of he energey is converted into kinetic energy in the brick, while the rest is absorbed as pressure waves in the hand and the brik, withthe pressure waves eventually dissipating as heat. With the wall, none of he energy is converted to kinetic energy, so more of it is availble to hurt your hand. -Arch dude (talk) 12:12, 4 July 2009 (UTC)

A4. Read Nuclear Energy. That is the very same energy which can be used to blow up a city.

E=MC² operates when mass is converted to energy, typically in a nuclear reaction. This is separate from any kinetic energy or gravitational potential energy. However, there is no feasible way to convert ordinary mass conpletely into energy. We know how to convert a tiny percentage of some kinds of mass into energy, as in a nuclear reactor or a thermonuclear detonation. -Arch dude (talk) 12:12, 4 July 2009 (UTC)

Happy to help... Rkr1991 (talk) 08:37, 4 July 2009 (UTC)

"there is no feasible way to convert ordinary mass completely into energy"... what about matter-antimatter collisions? It's feasible (though fortunately not easy, given the relative lack of abundance of antimatter). --98.217.14.211 (talk) 13:03, 4 July 2009 (UTC)

Thanks for the answers. I'm still confused about No. 2. Doesn't the weightlifter use energy to exert a force? After all, if I push against a wall I'm using energy to exert a force against the wall even though it's not moving... Where does that energy go? --wj32 ^t/c 08:48, 4 July 2009 (UTC)

Exerting a stationary force does not use energy, and a stationary force does no work. The barbell could be supported at the same height on a pillar or by hanging it from the roof - no energy is used by the pillar or the cable. You could lean a heavy object against the wall - again, stationary force, no work done on the wall, no energy being used. Your body uses energy all the time, to keep your heart beating, your lungs breathing and to keep you warm. Sometimes some of this energy might do external work - when you are lifting a weight, or pushing a moving object, for example. But all the energy used by the stationary weightlifter or the stationary wall pusher is wasted as heat - none of it does external work.

For extra credits, analyse the energy and work in a frame of reference in which the weightlifter or wallpusher are not stationary - put the weightlifter in a lift moving vertically at constant speed, and put the wall and wallpusher on a train travelling on a straight track at a constant speed. Gandalf61 (talk) 09:07, 4 July 2009 (UTC)

Just to add to what Gandalf said, when a weightlifter holds a dumbbell in the air, he is not doing work in the scientific sense of the term. It may look as if he is, with all the sweating and gurning, but muscular effort is not the same as work. Muscles are designed to be most efficient for running and throwing, and other dynamic activities. Under those conditions, the force they exert is cyclic, so they get a chance to recover between contractions. They are not designed for exerting large forces over long periods of time. From what I can gather from a quick look at muscular contraction, a muscle fibre contracts when it receives a command, and then starts to relax whether you want it to or not. The biochemistry of muscle fibres means that they cannot stay contracted indefinitely. If you tell a muscle to exert a constant force, what actually happens is your nervous system triggers one bunch of muscle fibres; and then, when they get tired, it triggers another bunch. Eventually it runs out of fresh fibres and has to start re-using the first bunch again. This is why muscles twitch under these conditions. The muscle is thus consuming chemical energy all the time just to stay in one place. --Heron (talk) 10:13, 4 July 2009 (UTC)

Thanks for all of your responses! I think I understand it now... --wj32 ^t/c 10:23, 4 July 2009 (UTC)

I disagree with Rkr1991's answer to question three. Try punching a punching bag as hard as you can. Your hand might sting a little. Now try punching a brick wall as hard as you can. [Medical advice: don't actually try that.] In both cases, the change in momentum (impulse) is the same. The movement of the punching bag allows the impulse to be applied over a longer period of time, which means that the maximum force applied is lower. It's the maximum force that determines the pain (and severity of injury). In your scenario where the small brick moves, the impulse is applied over a longer time period. Axl ¤ [Talk] 11:32, 4 July 2009 (UTC)

By impulsive force, I mean a large force applied over a very short period of time. Punching the punching bag increases the time of application of force, because it deforms, or as I said, moves away. So, it doesn't hurt as much. I stand by my statement. Rkr1991 (talk) 12:42, 4 July 2009 (UTC)

A soft hand is incapable of delivering a mathematical impulse function. Cuddlyable3 (talk) 14:46, 4 July 2009 (UTC)

Since your question is now answered you might find this article [38] on hitting bricks interesting. 71.236.26.74 (talk) 15:51, 4 July 2009 (UTC)

Black or white parasol?

If you are given only the color of parasols, which is more likely to keep you cooler, black or white one? I think black color absorb more light (at least in the range of visible frequency), so it tends to keep you less cool than white one. Like sushi (talk) 07:53, 4 July 2009 (UTC)

Depends on the infra red transmission of the material. Visible light is not infra red and therefore does not warm you. —Preceding unsigned comment added by 79.75.91.172 (talk) 10:00, 4 July 2009 (UTC)

No, this is wrong. Visible light will indeed warm you unless you are a perfect mirror. Where else would the energy go? Or why would a monochromatic laser in the visible be able to burn holes through some material (including "you" ;-)? --Stephan Schulz (talk) 11:38, 4 July 2009 (UTC)

The human body preferentially absorbs infra red. It penetrates to a couple of inches into the body. Other wavelengths do not penetrate and therefore are not absorbed. —Preceding unsigned comment added by 79.75.115.133 (talk) 22:37, 4 July 2009 (UTC)

It's correct that infrared is absorbed quite well. But it is not correct that other wavelength "do not penetrate" and therefore "are not absorbed". Hold a strongish flashlight up against your hand in the dark to see visible light partially penetrating through a part of your body. And even if a given wavelength is only absorbed on the surface, it will still heat the body. Light does not penetrate most metals (due to the electrons ability to interact with nearly all photons), but an iron skillet in the sun will still heat up. --Stephan Schulz (talk) 23:09, 4 July 2009 (UTC)

As far as I understand it, light colours reflect more light and tend to keep you cooler if you are wearing them? The opacity of the material may also be a factor. Exxolon (talk) 12:23, 4 July 2009 (UTC)

Would a two-tone parasol that is white (or even better: aluminised shiny) on the top and black on the inside surface keep one coolest? It could be made reversible for use as a warming umbrella in Winter. Cuddlyable3 (talk) 14:30, 4 July 2009 (UTC)

This general question came up some time ago, in the guise of whether light or dark clothing keeps you cooler. As I recall, there were arguments in both directions, and it was never really solidly resolved. Looie496 (talk) 16:44, 4 July 2009 (UTC)

I think black on the bottom has pros and cons. On the one hand radiation reflecting up against the bottom won't reflect back down and hit you, but it's not as if that energy just disappears. The parasol will convert it to heat, some of which will reach you anyway by conduction through the air and radiation. Rckrone (talk) 18:05, 4 July 2009 (UTC)

Thats a new twist to the discussion. —Preceding unsigned comment added by 79.75.115.133 (talk) 22:23, 4 July 2009 (UTC)

Work of objects in inertial motion

I asked here some time ago (in fact, on may 20) about the definition of "work", and have come to know that the same amount of force applied for the same time could mean different work done.

I was browsing today's questions and noticed something.

As the work is defined as Force*Displacement, (although I don't know much about what displacement is), it seems that objects exerting some force, but stationary in a reference frame are doing some work for an observer in a diferent reference frame. As any two parts comprising an object are attracted to each other through gravity, and if the object does not change shape, there is a force to cancel out the effect of gravity, and as the object is displaced (right?), objects in an inertial motion seem to do work. Is it right for objects not changing velocity to be doing work?

Like sushi (talk) 13:11, 4 July 2009 (UTC)

It's not possible for objects to exert a force on each other while remaining stationary. If you push against a wall you will accelerate away from it unless you brace yourself against something that's ultimately attached to the wall, like the floor, in which case the sum of the forces against the wall and floor will be zero. There's no net work being done with respect to any reference frame. Objects do self-gravitate and there is a force opposing that, but the sum of the gravitational and opposing forces is zero. -- BenRG (talk) 13:44, 4 July 2009 (UTC)

(ec) Let us first see what Displacement is. It is a vector, having direction pointing to the direction of the overall motion, and magnitude the length of the shortest line joining the initial and final points. Please read the relevant the relevant article for further clarifications.
We need to get one more point clear. Say I push you (literally). The force is applied by me and you move. The product of my force and your displacement is work. So Work done by an object A on another object B is the force applied by A to push B multiplied by the displacement moved by B. I have to say, it should be a dot product, but never mind.
it seems that objects exerting some force, but stationary in a reference frame are doing some work for an observer in a different reference frame. Yes, that's right. Work is dependent on reference frame, that is, it depends on how you look at it.
As any two parts comprising an object are attracted to each other through gravity, and if the object does not change shape, there is a force to cancel out the effect of gravity, and as the object is displaced (right?), objects in an inertial motion seem to do work. I think you are a little confused. Objects push other objects to do (mechanical) work, not themselves. However, you can say gravity (earth) does work on these objects.
Is it right for objects not changing velocity to be doing work? The fact that whether the object that is doing the work is moving or not is irrelevant. What matters is the force applied by the object and the displacement on the object on which work is done. Rkr1991 (talk) 13:50, 4 July 2009 (UTC)

Basically if a moving object isn't accelerating, it must be that the net force on it is zero. So while it's possible for something else to be exerting a force on it in the direction of motion and therefore doing work to it, some other force either from the same source or from somewhere else must be canceling it out and therefore doing the same negative work to it, which is why the kinetic energy of the object stays constant. Rckrone (talk) 19:00, 4 July 2009 (UTC)

Need help identifying this... thing

Anybody have any idea what this is? I think it might be some kind of fungus, but I don't know the first thing about biology. Thanks, –Juliancolton | ^Talk 16:36, 4 July 2009 (UTC)

Looks to me like a bunch of insect pupae where somebody has cut through the cocoons. Hard to make out, though. Looie496 (talk) 16:41, 4 July 2009 (UTC)

It looks like they've removed something flat that was laying on top and thus exposed the puppae. -- Brangifer (talk) 16:46, 4 July 2009 (UTC)

Ah, that makes sense! Indeed, there had been a tablecloth on top of it all winter long. –Juliancolton | ^Talk 17:48, 4 July 2009 (UTC)

Definitely insect pupae, the question that now remains: pupae of what? Could be some sort of potter wasp or mud dauber. The only way to be sure (or at least have a better id chance) is to take some pupae and put them in a container to allow them to hatch and attempt to id the imagos. We'll await a further post. Richard Avery (talk) 17:40, 4 July 2009 (UTC)

I'll try that. –Juliancolton | ^Talk 17:48, 4 July 2009 (UTC)

Can't get a clear image, but you might want to have a look at Lichen particularly the Xanthoparmelia picture. It's not exactly that, but maybe similar.71.236.26.74 (talk) 18:17, 4 July 2009 (UTC)

What term would describe this

In a medical article Im working on, I need a term to describe the coining of new syndromes... This has to do with Rumination syndrome, where a recent paper proposes the characteristics, diagnosis criteria, causes, and potential outcomes of the disorder in adults (Where the syndrome until now was considered a disorder of infancy).

Is there a term to describe this process of formally and medically assigning the symptoms and causes of a disorder/disease? -- ʄɭoʏɗiaɲ ^τ _¢ 17:47, 4 July 2009 (UTC)

These phrases begin as neologisms. After publication, the phrase gradually pervades the medical literature and comes into general use. Axl ¤ [Talk] 19:15, 4 July 2009 (UTC)

Rogue pulsar

I am reading a science fiction book and the "antagonist" is a "rogue pulsar." In the story, there is a rogue pulsar travelling through a solar system and it threatens to destroy a planet and it's civilization on its way by. Is this possible? Can pulsars travel through space? —Preceding unsigned comment added by 216.154.19.192 (talk) 19:07, 4 July 2009 (UTC)

Well, pulsars are just rotating neutron stars, and should have a similar distribution of position and velocity as their progenitor stars. That means that yes, they travel through space and might come close to other stars and solar systems. But they are not traveling in some kind of controlled manner, and the chances of an encounter with any given star systems are miniscule. Also see this article. What is the title of the book in question? --Stephan Schulz (talk) 19:18, 4 July 2009 (UTC)

Is there a term for this psychological phenomenon?:

Let's say you're feeling angry or depressed about something which you know, rationally, is petty, selfish, insignificant, and just not worth that kind of emotional reaction(like a comment on the Internet denouncing your favorite books, or being denied a small treat you weren't really entitled to). But rather than admit to yourself that you're getting worked up over that, you tell yourself that your negative feelings are actually caused by something else-- perhaps something(like, say, governmental corruption) of greater significance to the world but with less personal import than the aforementioned petty thing. Has this form of self-deception been documented and named? If so, is it common? 69.224.113.202 (talk) 19:08, 4 July 2009 (UTC)

Some form of rationalization I guess, but there may be a more specific term. Abecedare (talk) 19:14, 4 July 2009 (UTC)

Sounds more like Transference, which is about changing the locus of negative feelings to reduce psychic tension. --Jayron32.talk.contribs 19:16, 4 July 2009 (UTC)

That's close, but the technical term is displacement. Unfortunately that article is only a stub, but there's a lot of literature about this phenomenon. Looie496 (talk) 19:48, 4 July 2009 (UTC)

It seems to me that displacement is concerned with changing the target of your anger (or other negative emotion), while rationalization is changing the supposed reason for the anger. So the OP's query could go either way, depending upon whether he says, "I am not angry at the parking meter that ate my quarter; but at the town mayor for his incompetence" (displacement) or "I am not angry because of the loss of 25 cents, but because it represent governmental incompetence" (rationalization). Of course, ill-feelings are more diffuse than such linguistic analysis, so the distinction in this instance may be somewhat pedantic. May be relevant, though, if one is writing a novel and needs to use the exact term to prevent those &%@$*# reviewers (who never could write anything worthwhile themselves) from nitpicking it apart. :-) Abecedare (talk) 21:03, 4 July 2009 (UTC)

Could what I describe be classified, then, as a kind of rationalization through (attempts at) displacement? 69.224.113.202 (talk) 22:12, 4 July 2009 (UTC)

Also, just a small clarification: what I had in mind is that the real and presumed reasons for negative emotions may be completely unrelated-- as I tried to convey with the examples of (possibly imagined) personal slights and government corruption. 69.224.113.202 (talk) 23:23, 4 July 2009 (UTC)

A question of comfort

When I leave the shower cubicle for the cooler bathroom, immediately I feel cold across the arms and whole upper body. Though it takes only a few minutes to towel the upper half completely dry, whereupon the discomfort disappears, the way of doing this makes a subjective difference. I find it better to remove all of the water from one part before dealing with another, as opposed to quickly towelling most of the surface water from the whole area then dealing with the residual dampness a part at a time. I know that the water is conducting my body heat to the surrounding air - is this exactly the same as heating the water to evaporate it? In terms of overall heat loss, will it make any difference what towelling procedure is adopted, assuming water is being removed at a constant rate? I'm assuming that any model of the physics involved should ignore body heat generated by towelling effort, including local frictional heating.≥86.146.175.89 (talk) 19:40, 4 July 2009 (UTC)

Your trunk may tend to be more sensitive than your extremities with regards to heat changes; for good reason. Since all of your vital organs are there, your body would probably react more negatively to even slight temperature changes than would your arms and legs, which while important, from a survival point of view, are more expendable than say your heart or lungs. --Jayron32.talk.contribs 19:45, 4 July 2009 (UTC)

Not sure about the answer but if you wipe yourself down before leaving the shower-cubicle you'll drive off quicker with less wetness for the towel to pick up. A few 'swipes' of your hands down your arms, legs and front (back is a bit tough!) gets rid of a lot of the water and makes it quicker to get dried in my experience. ny156uk (talk)

I'm not sure it matters how much volume of water is on your body so much as how much surface area of your body is wet. In other words a thin film of water after a quick pass may have nearly the same cooling effect as the large drops before any toweling. So being thorough might be the most efficient in terms of losing the least heat. Rckrone (talk) 20:30, 4 July 2009 (UTC)