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May 15

H2CL2

Why does this here [1] is 2HCL but not H2CL2 ? --Ip80.123 (talk) 01:02, 15 May 2016 (UTC)

It is dichloromethane, there is a "C" (carbon), that is not labeled, in the center of this skeletal diagram. And it's completely not true that the two H are "across" from each other or at right angles to the two Cl and vice versa. Our article has some nice 3D diagrams of the shape of this chemical, a detail that is easy to mis-understand in the image you found. DMacks (talk) 02:14, 15 May 2016 (UTC)

The Implicit carbon and hydrogen atoms section of the above article is the most important. LongHairedFop (talk) 16:54, 15 May 2016 (UTC)

Where are Salmonella bacteria are founded in the eggs?

Sometimes I hear about the risk to consume eggs in some places in the world since they contains a high level of salmonella. Where are Salmonella bacteria are founded or located in the eggs, are they founded on the shell from outside or into the eggs or maybe both places? (it matters for example, for case that we can wash well the eggs with soap)93.126.95.68 (talk) 06:18, 15 May 2016 (UTC)

See Salmonellosis#Causes, which says that an infected hen can transmit the bacteria to eggs she produces, or bacteria can enter the egg through the shell. Egg shells contain small pores to allow in air for the embryo to "breathe". --71.110.8.102 (talk) 06:59, 15 May 2016 (UTC)

The U.S., Japan and a few other countries do wash them for that reason but then you need to keep them refrigerated.[2] Rmhermen (talk) 12:52, 15 May 2016 (UTC)

If you wash an egg with soap then the soap can get inside... The Quixotic Potato (talk) 13:13, 15 May 2016 (UTC)

In Israel it's forbidden to wash eggs in water according to the health minister (this is for public places) and for the citizens it's not recommended, because the bacteria can get inside through the shell. I would like to know about other countries. 93.126.95.68 (talk) 03:23, 16 May 2016 (UTC)

Same here, in the Netherlands, it is not recommended (but I don't know if its forbidden in public places). Washing eggs is a bad idea. My brother has pet chickens. If you google "wash eggs" you will find many sites that all say something similar to this: "Eggs are laid with a natural coating on the shell that is applied as the last step in the laying process called the "bloom" or sometimes the "cuticle". This coating is the first line of defense in keeping air and bacteria out of the egg. Since eggshells are porous, if you wash your eggs as soon as you collect them, you are removing that natural barrier." [3] The Quixotic Potato (talk) 12:01, 16 May 2016 (UTC)

This PDF says: Current European Union legislation prohibits the washing of Class A eggs. The Quixotic Potato (talk) 12:09, 16 May 2016 (UTC)

Here are the recommendations from the Food Standard Agency in Ireland regarding egg washing.[4] DrChrissy ^(talk) 16:03, 16 May 2016 (UTC)

This is a rather informative, non-technical account of the pros and cons of egg washing.[5] DrChrissy ^(talk) 16:07, 16 May 2016 (UTC)

Looking for the Full List

Over ten years ago, I read a tract in which the Author spoke of seven, what I believed he called, principles of engineering, or principles of mechanics, and named them as the cog, hinge, lever, pulley, screw, spring and wedge. I think what we was saying was that these were the seven foundations of mechanical movement, and I wonder, whether there were more, and also, if anyone else has heard of such a list, and what it was called. I could think also of the wheel, the ball, a ball and socket joint, although that could kind of be thought of as some specialised kind of hinge, bearings, couplings, nails, chains, among other things. But perhaps the list was about such things at their most basic level, where these become the basic parts to more complicated machines. I suspect also that the rubber band is seen as a kind of spring, at least in a more basic sense. If anyone has any other information on this, that would be good. Thank You. Chris the Russian Christopher Lilly 06:34, 15 May 2016 (UTC)

Simple machines. Sagittarian Milky Way (talk) 06:39, 15 May 2016 (UTC)

Thank You for that.Chris the Russian Christopher Lilly 00:39, 16 May 2016 (UTC)

Nostrils--- one or two?

Both my nostrils have been clear for the last couple of months. ie I can breathe thro both of them at the same time. Is this normal? I seem to remember reain on a WP page that nostreils alternate in being clear for operation. Is that statement false? — Preceding unsigned comment added by 178.106.99.31 (talk) 17:44, 15 May 2016 (UTC)

Yes sorry I forgot to sign.,--178.106.99.31 (talk) 17:46, 15 May 2016 (UTC)

See Nasal cycle. However, although there is a regular alternation, most people are not acutely aware of one nostril being blocked and the other open. If you feel that one nostril is blocked for a longish period, you have a problem. 81.132.106.10 (talk) 17:55, 15 May 2016 (UTC)

Both my nostrils have been clear for a few months. Is that usual?--178.106.99.31 (talk) 17:57, 15 May 2016 (UTC)

It's unclear whether asking why no one has punched you lately or telling you to read our guideline against medical advice would be more helpful. μηδείς (talk) 19:03, 15 May 2016 (UTC)

I dont think my inferior turbinates are undergoing alternating complete turgescence as far as I can tell at the moment. Am I fooling myself,or is it that I am in the 20% of the population that does not exhibit alternating turgesence? Or is it possible that I only experience partial turgesence in either nostril?--178.106.99.31 (talk) 22:56, 16 May 2016 (UTC)

Gas analysis

Can it be told what is wrong with a persons body by analising the anal gas emanations?--178.106.99.31 (talk) 17:57, 15 May 2016 (UTC)

Possibly not what you are asking, but my sister-in-law who is a nurse has told me that they can tell what the difference is between a Clostridium infection, C.diff and gastro-enteritis simply by the smell of the stools. The human nose is, as always, a far superior organ to any artificial nose. --TammyMoet (talk) 18:45, 15 May 2016 (UTC)

I'm impressed that she can tell Clostridium from Clostridium difficile! —Tamfang (talk) 08:37, 17 May 2016 (UTC)

As for now, you mean. Robotic noses are surveillance technology, and nothing is being funded and developed so much as surveillance technology. Wnt (talk) 16:18, 17 May 2016 (UTC)

You can detect some diseases by analysing exhaled gases, which is close to the OP's question. [6]. LongHairedFop (talk) 21:03, 15 May 2016 (UTC)

Analyzing gases from breath and skin is well known and can be refined. Tuberculosis makes skin smells like bread, some myocardial infarctions make skin smell burned or like smoke. Some blood suggar problems make breath smell like aceton or paint thinner. --Hans Haase (有问题吗) 09:19, 16 May 2016 (UTC)

Animals have amazingly developed senses of smell. See [7] and Canine cancer detection. 5.150.93.133 (talk) 09:49, 16 May 2016 (UTC)

There was a larger studie on flatulence gas mixture analysis a read a few years ago (I thought about how the collection was done) and there a peolple with hydrogen as a main compound while others have methane as a main compound, most of it is carbon dioxide any way. But the studie did not mention the trace gases which could indicate the mixture of microorganisms in the digestive tract.--Stone (talk) 10:06, 16 May 2016 (UTC)

Flatus can be collected in a "flatal bag" and then analyzed, but this doesn't seem to happen much, presumably because there are more accurate ways to evaluate digestive system problems, such as a stool analysis, where the collection method is simpler. However, a sudden change in flatulence, without any obvious cause like a change in diet, might be reason to see a doctor. StuRat (talk) 16:08, 16 May 2016 (UTC)

The methane test is quite entertaining! ;)--178.106.99.31 (talk) 20:43, 17 May 2016 (UTC)

"Flatus bag" being the more standard name (as usual, WP articles tell us things). DMacks (talk) 03:52, 18 May 2016 (UTC)

Well, strike a light.--178.106.99.31 (talk) 23:27, 18 May 2016 (UTC)

its all about light

from where does the light gets its speed111111111us (talk) 18:19, 15 May 2016 (UTC)

The speed of light in a vacuum appears to be a universal physical constant of the universe. No practical answer to "why is it that way?" exists for such constants except for "because that's the way it is". — Lomn 18:46, 15 May 2016 (UTC)

Exactly. The speed at which light propagates can be decomposed into vacuum permittivity and vacuum permeability, which are fundamental constants that represent electric- and magnetic- components. Some physics books consider these properties to be even more fundamental constants than c (which can be derived from these other constants, based on our understanding of the way electric- and magnetic- fields interact). At the end of the day, they're still just constants that never seem to change, no matter how we measure them - and although we can study them from lots of perspectives, we don't actually have any specific explanation for why they take any particular value.

Nimur (talk) 20:42, 15 May 2016 (UTC)

The article Electromagnetic radiation also sheds some light on the subject. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:53, 15 May 2016 (UTC)

Surprisingly, the answer to scientific questions is sometimes "philosophy or religion". The science don't know. (besides "whatever it is, the current speed of light will not be one of the values that makes your species impossible"). Sagittarian Milky Way (talk) 20:51, 15 May 2016 (UTC)

I agree it's philosophy but i'm not sure why anyone would call it "religion", it has very little in common with religion. In fact, one of the major philosophical shifts of the scientific revolution was to stop trying to explain the world with answers to "WHY?" questions, using agency and motivation to explain natural phenomena, and instead explain it with answers to "HOW?" questions using mathematics and models. In this case, it's not that "science doesn't know 'why' light travels that fast", it's because that question does not have a useful answer. Of course we can scientifically answer a "why" question like "why does a ball drop when you let it go", but you can't "why?" all the way down, the buck HAS to stop somewhere, and with science, the buck stops at the natural explanan it, because Gravity IS that way, or light IS that way. Religion would always take it one step further and say because god MADE it that way, but that extra step doesn't actually ADD any explanatory power so science dropped it. Vespine (talk) 01:18, 16 May 2016 (UTC)

See also Non-overlapping magisteria for one viewpoint on this. --Jayron32 02:04, 16 May 2016 (UTC)

It's only religion for some people. Sagittarian Milky Way (talk) 03:09, 16 May 2016 (UTC)

It depends on what "God" means. If you equate "God" to "Nature", then "God made it that way" is totally valid. But as you say, it doesn't really add any new information. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:40, 16 May 2016 (UTC)

It's rather nonintuitive, but light doesn't seem to accelerate or decelerate, it just always goes the same speed (in a given medium), similar to how electrons jump from one energy level to another, without seemingly ever having been in-between. The proverbial "quantum leap". StuRat (talk) 21:56, 15 May 2016 (UTC)

There is mention of nanoseconds there, isn't this rather slow in consideration with light ? So you say that the electrons jump ( in a few nanoseconds ), generating light in the process - which does not accelerate but is a full c speed right from the beginning. Is it that the famous quantum leap ? --Askedonty (talk) 11:17, 16 May 2016 (UTC)

Yep. StuRat (talk) 04:11, 18 May 2016 (UTC)

Watch this video: [8] --71.110.8.102 (talk) 08:32, 16 May 2016 (UTC)

May 16

.1 (leading 0 is implicit)

Is .1 (leading 0 is implicit) always the same as 0.1? And even if mathematically they are the same, could a manual of style advise editors not to use the one or the other?--Llaanngg (talk) 01:37, 16 May 2016 (UTC)

yes and yes, seems obvious..is there a specific context for asking this?68.48.241.158 (talk) 01:44, 16 May 2016 (UTC)

It may not be the same if the "." in .1 is actually a blemish on the paper. Note that there could be infinite leading zeros, as there is no unit, no ten, no hundred etc.... Our style guide should have something to say on the matter. Graeme Bartlett (talk) 01:46, 16 May 2016 (UTC)

The style manual says to use the leading 0:Wikipedia:Manual of Style/Dates and numbers#Decimals. Graeme Bartlett (talk) 01:59, 16 May 2016 (UTC)

Indeed the mathematics and interpretation of .1 is the same as 0.1 - and style determines which to use. The leading '0' is a huge aid to readability - especially when you consider that there are parts of the world where the role of '.' and ',' are interchanged in their meaning within numbers. SteveBaker (talk) 02:17, 16 May 2016 (UTC)

I think Steve should have stopped before "especially". In areas where "," is the decimal point and "." is the thousands separator, neither ".123" nor "0.123" is a possible number; instead we would be talking about ",123" and "0,123", neither of which is a possible number where we live. --69.159.60.83 (talk) 05:51, 16 May 2016 (UTC)

The problem comes in when it is used cross-culturally. For example, if we wrote "Color was blue,and the quantity measured,123", that might be taken to mean 0.123 in a place where a decimal comma is used. Adding a space after each comma helps reduce this type of error. StuRat (talk) 16:30, 16 May 2016 (UTC)

Why is this question on the Science Desk? Joseph A. Spadaro (talk) 04:21, 16 May 2016 (UTC)

Species of deer fly

A deer fly with a centimeter scale

Can anyone identify the species of this deer fly (from near the Atlantic coast of Georgia)? Bubba73 ^{You talkin' to me?} 03:25, 16 May 2016 (UTC)

Not a very clear image - but it could be Chrysops vittatus (full description here - http://animaldiversity.org/accounts/Chrysops_vittatus/ ) 81.132.106.10 (talk) 20:44, 16 May 2016 (UTC)

Thanks. It is hard to take a photo of things that small. Here is another one. Bubba73 ^{You talkin' to me?} 02:54, 17 May 2016 (UTC)

Another view

Follow-up question

Why do the eyes change from one photo to the other? (It is the same deer fly.) Bubba73 ^{You talkin' to me?} 03:36, 18 May 2016 (UTC)

It's a still dead no eyed deer fly. Vespine (talk) 06:28, 16 May 2016 (UTC)

Not sure if it's the same as for fish, but their eyes cloud up after death, so you want clear eyes to get fresh fish. StuRat (talk) 15:06, 18 May 2016 (UTC)

That is probably it. The first photo was taken shortly after death - the other was several hours later. Bubba73 ^{You talkin' to me?} 22:31, 18 May 2016 (UTC)

User:Bubba73 That might be part of it, but it's not the only factor, nor even necessarily the dominant factor. When you take a photo of an insect's compound eye, it's sort of like taking a photo of a sphere composed of cylindrical straws - so very slight changes in angle can change the apparent darkness of one tiny lens. Look at the photo of Arthropod_eyes, and you'll see lots of refractive shimmering colors, like an oil slick. So even if the two photos were taken within seconds, you'd expect rather different-looking eyes. In this case, there may be some effects of dessication, but flies are rather robust to water loss. 65.111.115.16 (talk) 15:19, 19 May 2016 (UTC)

Can a pregnant woman become pregnant again while still pregnant?

Can a pregnant woman become pregnant again while still pregnant? Just curious about that odd situation. If this were the case, the woman might give birth to a baby. And then, say, 4 months later, give birth to a second baby. Is this possible? Has this ever happened? Does this have a name? Thanks. Joseph A. Spadaro (talk) 04:23, 16 May 2016 (UTC)

Superfetation which has happened with human children conceived two months apart. This was very easy to find with google. μηδείς (talk) 04:59, 16 May 2016 (UTC)

It's possible, as noted, but very rare and abnormal in humans. Normally in humans, ovulation is suppressed during pregnancy by high levels of progesterone. Most hormonal contraceptives work the same way, by containing a progestin that has the same effects. --71.110.8.102 (talk) 06:30, 16 May 2016 (UTC)

It is worth noting that although there are a few recorded cases of a second conception (though only during the early stage of the first pregnancy - two months seems to be the longest recorded gap) the births in each case have been simultaneous. It seems extremely improbable that the first conceived child could be delivered, while the second one then continued to develop in the womb for a significant period. 81.132.106.10 (talk) 08:21, 16 May 2016 (UTC)

However, there are cases where twins are born some months apart because of danger to one of the babies. Do a Google search on "twins born some months apart" for examples. --TammyMoet (talk) 10:06, 16 May 2016 (UTC)

I believe these two cases can be reconciled by stating that it normally requires medical intervention to deliver only one of the babies without the other(s) being born soon after. A C-section, presumably, is the normal medical intervention. Not sure if this would be possible with identical twins, which share the same amniotic sac (could it be cauterized/sutured ?). StuRat (talk) 16:18, 16 May 2016 (UTC)

No, StuRat; monoamniotic twins are extremely rare. DMacks (talk) 16:37, 16 May 2016 (UTC)

Not that rare, "about 1% of twin pregnancies", according to our article. StuRat (talk) 17:17, 16 May 2016 (UTC)

No Stu. 0.00285714285714% to 0.0016666666666667% of pregnancies is extremely rare!--TMCk (talk) 17:41, 16 May 2016 (UTC)

I don't think it is. We wouldn't call a disease that was that common "extremely rare", as then up to 200,000 people worldwide would have it. But, again, you are taking the percentage of the entire population, while I was only talking about identical twins. StuRat (talk) 17:47, 16 May 2016 (UTC)

Sure. That's why you removed the inconvenient part of your post. Full of it as always.--TMCk (talk) 17:55, 16 May 2016 (UTC)

I didn't notice that they had stated the odds directly in the article the first time, and removed my math and replaced it with a direct quote as soon as I did. And keep the attitude off the Ref Desk, please. StuRat (talk) 22:52, 16 May 2016 (UTC)

While it isn't a "disease", the accepted medical definition of "rare" is covered at Rare disease, with definitions ranging from 1/1000 of 1/200,000 as being "rare". .002% is 1 out of 50,000 pregnancies. --Jayron32 17:57, 16 May 2016 (UTC)

Do they define "Extremely rare" ? StuRat (talk) 22:52, 16 May 2016 (UTC)

That would be rarer than rare. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:19, 19 May 2016 (UTC)

I actually believed something similar. But I also did what TammyMoet recommended. From there I read sources like [9] which suggest this can occur without apparent significant medical intervention medical intervention. In fact [10] suggests medical intervention in the opposite direction i.e. ensuring the second twin was delivered at the same time used to be more common.

Note also that the original discussion was about pregnancies with conception happening at different times. Monoamniotic twins are already rare enough. Monoamniotic non identical twins with conception happening at different times is probably as close to impossible as we get in biology.

Perhaps of more relevance to the original question is that in rare cases a women with double uterus have had successful pregnancies in both uterus simultaneously. StraighDope mention a few, another slightly more recent one is here [11]. Possibly conception happening at different times is more likely in these cases than in a more "normal" case although since there are so few of them, conceptions happening at different times would be more likely in more "normal" cases. (To be clear, I'm not saying conception at different times is likely if a woman has a double uterus, but rather the probability of it happening, low that it is, may be higher.)

Nil Einne (talk) 18:23, 16 May 2016 (UTC)

Would that be "double uteri" ? StuRat (talk) 22:56, 16 May 2016 (UTC)

Thanks. Let me follow up with a question of semantics. Let's look at two possible scenarios. Scenario "A": Two babies are conceived at different times, but both are born at the same time. For example, the first conceived is delivered normally today, but the second conceived is delivered early (prematurely), also today. Scenario "B": Both babies are conceived at the same time. One is delivered today, and the other is delivered some time down the road, maybe a month later (for whatever medical reasons). Are the babies in Scenario "A" properly called "twins"? And how about Scenario "B"? Thanks. Joseph A. Spadaro (talk) 03:56, 17 May 2016 (UTC)

(sorry, just an opinion, but I can't help myself): I think that if a woman spends a day with two babies (well, fetuses or embryos) inside her, she is carrying twins. And once a twin, always a twin. So I'd say A and B. Requiring the same moment for conception or parturition doesn't make sense because babies are rarely conceived nor born at precisely the same moment. (Well, identical twins are conceived at once, or fertilization might truly simultaneous, and maybe they can be "born" the same moment by Caesarian, but that's kind of stretching it) A consequence of this logic is that in theory baby 1 can be a twin of baby 2, and baby 2 of baby 3, but not baby 1 of baby 3. If someday that happens, I can live with that semantics. Oh, also I see the source used above actually uses "twins" to refer to staggered pregnancies two months apart in two uteri. Wnt (talk) 09:50, 17 May 2016 (UTC)

May 17

Parachuting

What special precautions (if any) must be taken when parachuting into a heavily forested area? 2601:646:8E01:515D:F88D:DE34:7772:8E5B (talk) 01:49, 17 May 2016 (UTC)

https://en.wikipedia.org/wiki/D._B._Cooper68.48.241.158 (talk) 02:30, 17 May 2016 (UTC)

That should be avoided if at all possible. The parachutist is likely to get hung up in a tree and need rescuing, so communication equipment and GPS would be needed, and water to drink until the rescuers arrive. Diapers might be a good idea, too. StuRat (talk) 02:34, 17 May 2016 (UTC)

Also, try to avoid carrying large satchels of money, as D.B. Cooper did. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:44, 17 May 2016 (UTC)

I wonder if a specially designed parachute could be made that would allow the occupant to lower themself down on a rope to the ground. Depending on the height of the trees, it could be hundreds of feet down. Of course, there would still be the risk that they would hit a branch and be killed or incapacitated. StuRat (talk) 02:47, 17 May 2016 (UTC)

Aside from pre-planning as you're suggesting, the best advice would be, "When parachuting into a forest, try to avoid trees." ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:49, 17 May 2016 (UTC)

That might not be as silly as it sounds. Obviously, where you have complete tree cover, avoidance isn't possible. But if aiming for a clearing in the middle of forested area, a stunt parachute may help to steer it into the clearing. StuRat (talk) 15:17, 18 May 2016 (UTC)

For unintentional tree landings in sport parachuting, see the "Trees" subsection of 5-1F (General Recommendations / Skydiving Emergencies / Landing emergencies) of the USPA Skydiver's Information Manual. -- ToE 03:20, 17 May 2016 (UTC)

For paratroopers intentionally targeting forested areas, see Treejumping. -- ToE 03:31, 17 May 2016 (UTC)

For forestry personal, I would have expected us to have something under Fire jumper, but alas that link is currently red. see Smokejumper -- ToE 03:36, 17 May 2016 (UTC)

I created redirects from Fire jumper and Firejumper to Smokejumper. --Guy Macon (talk) 10:24, 17 May 2016 (UTC)

Here's a publication from the FAA that includes both regulatory and advisory details on parachute landing areas (e.g., information about mandatory rules and optional decisions): from their advisory circular database, Report DOT/FAA/AR-11/30, Criteria for Parachute Landing Areas on Airports. In their section on hazards, they describe trees, and recommend sizes of areas at specific distances from dense trees. There are a lot of useful diagrams. More complex operations need more obstacle-clearance. The publication also references several Army sources for paradrop operations; if you actually do decide to go parachuting, those field manuals are sort of the "canonical" source of math and equations. For example, the FAA cites FM 3.21 Pathfinder Operations for equations on landing drop zone sizes. Obviously, consult your dive-master or parachute jump coordinator for more specific, current, local information.

More good reading: Advisory Circular 105-2D, Sport Parachuting; this government publication advises about hazard and obstacle avoidance, and references several other publications of the U.S. Parachuting Association as further reading. For example, here's the Skydiver's Information Manual, a lengthy 270-page book that includes the BSRs (Basic Safety Requirements). These are advisory rules - the Government doesn't enforce them, but FAA encourages you to learn from a reputable instructor, especially one affiliated with USPA, and to adhere to their safety rules. Per Federal Aviation Regulations parts 91.15, 105.21, 105.23, and 105.25, the Government doesn't really care what happens to you if you fall out of an airplane - as long as the pilot takes "reasonable precaution," and provided that you don't land on an airport, a congested area, or special use airspace. You can land on those things too, provided that you carefully comply with the rules. But if you splat on a tree, that's sort of on you; or, rather, you are on it.

Part 105 of the Federal Aviation Regulations does specify actual federal laws that pertain to parachute operations ("skydiving").

Nimur (talk) 04:26, 17 May 2016 (UTC)

Thanks, all! ToE was especially helpful. Now, a follow-up question: Does Baseball Bugs's advice about large satchels of money also apply to carrying weapons and ammo? 2601:646:8E01:515D:F88D:DE34:7772:8E5B (talk) 11:29, 17 May 2016 (UTC)

Well, the more weight you carry the larger the parachute would need to be to support that weight. At some point it would no longer fit in a backpack, but then an alternative deployment system can be used. Alternatively, ammo and supplies can be sent down on their own parachute. Not so good when there's just one jumper, because if he doesn't find and retrieve his supplies he is in rough shape. But with many jumpers, they will find at least some of the supplies and ammo. I wonder if a timed system could then be used to lower the supplies and ammo on a line after they hit the trees. (Some would get hung up, but not all.) StuRat (talk) 13:39, 17 May 2016 (UTC)

Good -- that's just what I needed to know! 2601:646:8E01:515D:F88D:DE34:7772:8E5B (talk) 04:38, 18 May 2016 (UTC)

Maybe read through the U.S. Army's Airborne School description. The life of an airborne infantryman is not an easy one. Before they let you jump at all, you have to be pretty prepared. Before they let you do a tactical jump with full equipment, there are a handful of requirements, including completion of Basic Combat Training (described in detail at the Army recruiting page). Weapons, ammunition, and jumping out of airplanes are each uniquely dangerous; there's a lot of prerequisite training to prepare yourself physically and mentally.

Nimur (talk) 14:02, 17 May 2016 (UTC)

“have to be pretty prepared.” Brain washed more like it! Here on Wikipedia many editors take exception to 'fringe science' . This is a good example of a 'so called' intervention that has not under gone any – repeat- any scientific randomised trials. Read: Parachute approach to evidence based medicine. So it also needs hating as we don't give answers to anything remotely medical in nature.--Aspro (talk) 19:30, 18 May 2016 (UTC)

Nazi Luftwaffe parachute troops had it even tougher, hence carried less; see Fallschirmjäger#Uniforms_and_equipment Jim.henderson (talk) 22:59, 18 May 2016 (UTC)

This is a very strange "dig" to add to this specific question, I really can't figure out how it is at all relevant. It sounds like you've just been waiting for an opportunity to link this parachute paper you found somewhere. The fact is Randomized controlled trial are the gold standard, but of COURSE science recognizes that it is not always possible to test everything in a randomized controlled fashion. I know this article you linked is trying to be facetious but in my opinion it's crossing the line of disingenuous. Just because its not possible to test some things in a randomized fashion, does not mean we should accept a lower standard of evidence from other interventions that could be tested but haven't. you know there have even been medicines that were so effective that the trials were discontinued, since it was deemed unethical to not give the medicine to the placebo group. Vespine (talk) 23:16, 18 May 2016 (UTC)

The parachute paper is a famous piece of satire that was written by some highly-qualified medical researchers in order to present a point by way of a humorous counter-example. Deeply interested readers can research its authors for context on why they wrote it, and why the editors of a prestigious journal decided to publish it. From the "rapid responses" (electronic letters to the editors), you can get a quick feel for the spirit of the paper.

I really try not to use appeal-to-authority, but in this case... when you're the department head for a major research hospital, you're allowed to write a little bit of satire, even a piece as blunt as the parachute paper. I somewhat suspect that the contributor who reposted that journal paper here on the reference desk does not carry any equivalent such credential, so when he posts the same joke, the irony is completely lost.

In case any of our readers actually really don't understand, the paper is not advocating against the use of parachutes, nor is it making a sincere plea for any research related to parachute aeronautics of any kind. It is a paper whose thesis is a rhetorical question on the topic of how medical journals (and other peer-reviewed scientific journals) ought to set their editorial standards, as they pertain to the burden of proof.

Nimur (talk) 02:09, 19 May 2016 (UTC)

Wait a minute, how did we jump from parachuting to medical research all of a sudden??? 2601:646:8E01:515D:F88D:DE34:7772:8E5B (talk) 02:41, 19 May 2016 (UTC)

Another editor posted this comment. Nimur (talk) 03:25, 19 May 2016 (UTC)

Related:if you are reading historic or foreign sources, bear in mind that "forest" may not mean what you assume. Some have no trees, for example, and so would pose little difficulty to parachutists. From our article: "Although forest is a term of common parlance, there is no universally recognised precise definition, with more than 800 definitions of forest used around the world. Although a forest is usually defined by the presence of trees, under many definitions an area completely lacking trees may still be considered a forest if it grew trees in the past, will grow trees in the future, or was legally designated as a forest regardless of vegetation type."

Carbon Caryatid (talk) 10:00, 19 May 2016 (UTC)

References

bioengineering a space telescope lens

Could it be feasable or beneficial to develop a space telescope that incorporates biological material? For instance, using elecrowetting with synthetic electrolytes in order to create a superfluidic lens that can be spun in zero-G to generate a concave lense shape. Would this have an advantage over traditional designs (ie, self-repair in case of micrometeor strikes, curvature adjustability)?

119.171.79.241 (talk) 05:08, 17 May 2016 (UTC)

I'm not sure if it's me or you but I think you are mixing up some concepts which are not necessarily related. We have an article about Liquid mirror telescope which is directly related to what you are asking, but it does not seem like you need to involve biology, electrowetting or superfluidity. Unless you think somehow those factors would counteract the fact that I'm not sure simple spinning would stop the fluid from just floating off in zero G. Vespine (talk) 05:33, 17 May 2016 (UTC)

Aaand we also have this artcile Liquid mirror space telescope. Vespine (talk) 05:36, 17 May 2016 (UTC)

There is high energy radiation in space that even has an aging impact on tough construction materials. Any biological material would either have to be very tough in multiple senses or its simply put in a very wrong place. --Kharon (talk) 02:49, 18 May 2016 (UTC)

• Space telescopes need phenomenally precise lenses – the Hubble Space Telescope was very nearly ruined by just a 10 nanometer error in the mirror grinding stage – and I doubt you could get practically achieve that precision with biological growth (you'd basically need every cell to be in exactly the right place). A non-biological liquid mirror telescope is already adjustable and (since it's just liquid) largely self-repairing. Smurrayinchester 08:30, 18 May 2016 (UTC)

If you read that link more carefully, the 10 nm tolerance was fine, and the mirror met that tolerance. The problem was not the tolerance; it was the shape, which was off by more than 200 times the tolerance at the edge. --Trovatore (talk) 20:07, 18 May 2016 (UTC)

I read it as a cumulative error (a 10 nm misalignment that built up towards the edge of the mirror), but I could be misreading it. If anyone knows better, please fix the article. Smurrayinchester 08:42, 19 May 2016 (UTC)

Go/no go thread gauge

When you have a pair of Go/no go thread gauges, is the go male thread gauge supposed to screw freely into the go female thread gauge?

There are 4 possible combinations:

1. go male + go female

2. go male + no go female

3. no go male + go female

4. no go male + no go female

Which of the four is supposed to screw freely into the other? Johnson&Johnson&Son (talk) 06:35, 17 May 2016 (UTC)

Yes. A "go" is essentially the "correct" version of the thread, so a go male will fit into a go female (case 1). A "no go" is the other test, it is NOT SUPPOSED to fit into the go thread, so case 2 and 3 should fail, (NOT fit more than 3 turns). Whether it is possible for a no go to fit into a no go is undefined to the test and i am not familiar enough with it to say if there is a 'common' or 'standard' resolution, i.e. if they "usually" do fit or usually do not fit, but it does not matter to their actual purpose. Vespine (talk) 06:47, 17 May 2016 (UTC)

• No it's not supposed to screw anywhere! They're both precise and hardened. Screwing gauges together like this is a route to damaging them. Especially when people "store" them screwed together like this (avoid all contact on the gauging faces in storage anyway).

The "go" gauge is intended to fit a workably sized thread. So the male go gauge should fit the female go gauge. The other combinations should not fit. The no go / no go combination won't work because the male is oversize and the female undersized, so it won't fit by two tolerances, not just one.

Note that it's not practical to use this sort of simple go/no go gauging to detect a faulty undersized male thread, or an oversized female. It is rarely seen that a "must not fit" gauge is produced where "no go" is then correct behaviour (ie an undersized female gauge used for detecting undersized male threads). These are rare though, as they create endless confusion with unfamiliar operators. Andy Dingley (talk) 10:32, 17 May 2016 (UTC)

Thanks, you two. @Andy I know they're not supposed to be screwed against each other, but I need a way to check that I've been given properly tools and haven't been scammed, so this is a one-time emergency measure.

Since my go male + go female gauge won't screw into each other, there must be something wrong with at least one set of them. I called the seller about it for a replacement and he told me that they're designed not to fit into each other like that, since the male is "M27x0.75 6H" thread, and the female is a "M27x0.75 6g" thread and thus incompatible. Is this true？ How do I verify this? What he says does make sense, but then again he does have a financial incentive to mislead me. Johnson&Johnson&Son (talk) 11:01, 20 May 2016 (UTC)

Free gases

Are there any free gases floating about in the solar system between the planets?--178.106.99.31 (talk) 21:13, 17 May 2016 (UTC)

See Interplanetary medium. CodeTalker (talk) 21:16, 17 May 2016 (UTC)

(ec) sure, there is. See interplanetary medium. On the outskirts of the Solar System it transitions, via a heliopause region, into interstellar medium. All along, it's a mixture of dust, neutral and ionized gas, with varying composition. You may also want to read plasma (physics) article,. --Dr Dima (talk) 21:25, 17 May 2016 (UTC)

So are the gases differnt depending on which planet you are near?--178.106.99.31 (talk) 21:54, 17 May 2016 (UTC)

Yes. see Solar wind#Solar System effects. The solar wind interacts with the top layers of the planet's atmosphere, so that there is a persistent flux of matter from the planet's atmosphere into the interplanetary medium. The amount and composition of atmospheric material being stripped by the solar wind depends on the planet's mass, radius, orbit, atmosphere composition density and temperature profile, strength of the planet's magnetic field, and so on. Mars lost most of its atmosphere this way, while Venus, Earth, and the gas giants still have substantial atmospheres. I don't remember the Earth rate of atmospheric loss, but I'll add it here when I find it. --Dr Dima (talk) 22:57, 17 May 2016 (UTC)

Here you go: Atmospheric escape. You may also want to read Atmosphere of Earth#Evolution of Earth's atmosphere. --Dr Dima (talk) 22:59, 17 May 2016 (UTC)

"Gas" is a mass of elemental molecules and most common Gases build pairs among their Particles/Atoms (Hydrogen=H₂=two Hydrogen atoms,O₂). But Atoms are far to scattered in Space to refere to them as a mass of elements or even Molecule. Outer Space Vacuum is "space void of matter" and thus the complete opposite. There are just a few atoms per cubic meter and that is commonly refered to as "particles" per Volume of space. So there is no "Gas" in Space at all. --Kharon (talk) 22:59, 18 May 2016 (UTC)

May 18

Polypropelyne capacitor marking

I have some PP capacitors marked with the letters MKT. What do these letters mean?--178.106.99.31 (talk) 14:10, 18 May 2016 (UTC)

It's a code for the type of capacitor construction. As noted at the Wikipedia article film capacitor and at this table here, MKT is code for "metallized polyester foil". I don't know that the letters directly stand for anything. --Jayron32 14:21, 18 May 2016 (UTC)

Thanks. Couldnt find it in the article before, but found it now. So my capacitors are polyester not polypropylene. It seems the M stands for metal, the T is from polyester and the K means?? So polyprop would be marked MKP. :)--178.106.99.31 (talk) 14:31, 18 May 2016 (UTC)

These codes were the German ISO 41379 ; (declared obsolete, [12]). See altungen this(de) document: the 'K' would be Kondensator (probably not 'Keramik'). See also in: [13] (by TDK), as you want to cross-check your deductions. --Askedonty (talk) 15:51, 18 May 2016 (UTC)

• MKT "Metallisierte Kunststofffolie aus Polyester (Polyethylenterephthalat) als Dielektrikum"
• MKP "Metallisierte Kunststofffolie aus Polypropylen als Dielektrik"

Guess as last letter was already occupied for Polypropylen they picked T for Terephthalat. --Kharon (talk) 22:31, 18 May 2016 (UTC)

Ah! Sehr gut mein Herr. Danke schoen.--178.106.99.31 (talk) 23:10, 18 May 2016 (UTC)

Yes. 'Kunststoff folie' seems to translate from German as 'plastic film' (or foil). So the K stands for....you guessed it. The WP page on film capacitors in the German edition seems to have more detail than english edition. But I cant read German to that level.--178.106.99.31 (talk) 15:52, 19 May 2016 (UTC)

Seeking a Reference

Can I have some free links to references on continuous and descrete spectra (Quantum mechanics)?Sayan19ghosh99 (talk) 17:04, 18 May 2016 (UTC)

Can you be more specific? I'm not sure there's anything in quantum mechanics that wouldn't count as continuous or discrete spectra (of operators). -- BenRG (talk) 19:40, 18 May 2016 (UTC)

Spectral line will talk a bit about discrete spectrum. Hydrogen spectral series gives a specific example of discrete. The Continuous spectrum usually happens because of the present of free electrons which can have arbitrary energy. Graeme Bartlett (talk) 08:15, 19 May 2016 (UTC)

Blackbody radiation may also be of interest here. --Jayron32 13:04, 19 May 2016 (UTC)

Acctim radio controlled clock module

Does anyone know how to access the 60kHz signal that these clocks operate on? --178.106.99.31 (talk) 21:59, 18 May 2016 (UTC)

See Radio clock. It's just a CW signal, any radio receiver tunable to that frequency can pick it up. Tevildo (talk) 01:32, 19 May 2016 (UTC)

This is the detailed specification from NIST for the WWVB signal. Tevildo (talk) 01:51, 19 May 2016 (UTC)

You will actually need a specialised receiver, such as a communications receiver. Most receivers will not support frequencies that low, even radios designed for the long wave band. Graeme Bartlett (talk) 08:03, 19 May 2016 (UTC)

Cat in a new home

Hi everybody, I have recently adopted an indoor cat from a lady who has had to return home to China. I was wondering what period of adjustment I should allow for the cat to get used to his new home and people, and if it would possible for him to be tempted to venture outdoors. I live in a fairly quiet part of the countryside in the UK, where it's normal for cats to go outdoors, and would like to give him the benefit of a natural cat lifestyle. Also, any advise on helping him to settle in would be appreciated. He is neutrered, microchipped, vaccinated and 9 months old. Thanks in advance --Andrew 22:16, 18 May 2016 (UTC)

He'll go out if he wants to, and vice versa. Fit a cat flap.--178.106.99.31 (talk) 22:44, 18 May 2016 (UTC)

If he's a totally indoors cat, letting up go outside could prove fatal. And if not, he could bring fleas into the house. But that's up to you. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:17, 19 May 2016 (UTC)

Yes, the benefit of a cat going outside is pretty much early death. As for getting used to new circumstances, cats can take months to make that sort of adjustment. - Nunh-huh 00:27, 19 May 2016 (UTC)

• I guess if your speaking as Americans, it's a cultural norm for cats to be kept indoors, across the pond. Here in Britain we see things differently, and you're in the minority if you own an indoor cat. Given that I live in a rural part of the country, I don't see any risks with his wellbeing, and see the benefits of him going out and being able to exhibit his natural behaviours. To me, there's nothing more unusual than seeing a cat on a leash, they love to be free to roam outdoors --Andrew 01:43, 19 May 2016 (UTC)

I'm not talking about cultural norms, I'm talking about an actually shortened life. Average lifespan of an indoor cat is 12-15 years. Average lifespan of an outdoor cat is 2 to 3 years less. You could Google "Indoor and Outdoor Cat Life Expectancy Differences" to see if there's anything magical about being in the UK that reverses that. - Nunh-huh 04:17, 19 May 2016 (UTC)

• Are you doing this for the cat, or for you? Are there any roads near your place? Any large dogs? Any wild animals like foxes or coyotes? Are you OK with the fact your cat could be dead within days or even hours? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:07, 19 May 2016 (UTC)

I think that might be a little backwards. Cats really want to go outdoors. If you keep them indoors long enough, they sometimes forget there's such a thing as the outdoors, but they'll mourn heartbreakingly for a while until that happens. I wouldn't want to be kept prisoner just because I'm safer that way — why would I expect my cat to?

Letting a cat out is hard on the owners, though, when the cat doesn't come back at the time expected. If you have an indoor/outdoor cat, expect to have to worry sometimes. --Trovatore (talk) 02:45, 19 May 2016 (UTC)

In my experience, cats who have spent time outdoors want to be outdoors, and they'll pester you to let them out. Cats who have spent their entire lives indoors don't. They are not interested in the outdoors except to observe it through the windows. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:31, 19 May 2016 (UTC)

• There are compromises between inside and outdoors cats. You can have a fenced-in yard, and a cat door, so they can escape into the house if anything attacks. Being neutered keeps them from wandering quite so much. You can also sit in the yard with them, as they explore. Or, for the most paranoid, keep them inside, just open the window, but keep the screen in, so they get a good sniff. That does wonders for their mood with very little danger. StuRat (talk) 02:27, 19 May 2016 (UTC)

That's pretty funny Nunh-huh. My cats are happy outside and acclimatise to new things, such as moving house, within days. Obviously you have very special cats. Greglocock (talk) 02:38, 19 May 2016 (UTC)

Yes, well I guess you have genius cats and mine are a bit slow. Their inability to adjust to change may or may not be related. - Nunh-huh 04:17, 19 May 2016 (UTC)

As for how long it takes to adjust, it depends on the personality of the cat. I've had them take over a year to do so. Expect them to spend most of their time hiding until then. They might become comfortable with one person but not the rest of the family, first. I'd avoid letting them out then, as they might "go home" to their old house. StuRat (talk) 02:33, 19 May 2016 (UTC)

• Guys, cats are dumb animals and they're not all the same. I'm saying that as a cat person. My cat back home thought that the house was "outside," and thought that outside was Unknown Kadath. The one time I brought her outside (for all of five seconds at night), she buried herself to my chest nervously for the first three seconds, and upon seeing a tree taller than our house, clawed over my shoulder (only time she ever did that) to run back into the house. Once inside, she bolted to the end of the house furthest from the door and hid, coming out an hour later still shaky with a puffy tail and back hair. The few times she tried to explore outside before that, she saw the bright South Carolina sunlight and decided "screw that, I'll just sleep in Ian's lap for another hour."

That said, yes, cats were bred to live outdoors and get all sorts of endorphins killing local wildlife (they're hunters, deal with it). The difference, from the cat's perspective, is pretty much "would you rather spend your nights carousing with friends or staying home and planning a responsible diet?" The difference for the owners is really "do I want to put more work into their emotional well being or their physical well being?" Emotional? Indoor. Physical? Outdoor. No work? Don't get a pet.

As for OP's question, nine months old is basically a teenager. Yeah, sure, their entire world has been replaced, but they're still at an age to get used to it. Heck, my cat (14 years old, pushing 15) completely adjusted to my granddad's house after about a week. Ian.thomson (talk) 05:11, 19 May 2016 (UTC)

I react the same way when forced outside (except for sleeping in Ian's lap, that is). StuRat (talk) 05:28, 19 May 2016 (UTC)

Best you provide food at an specific time and place each day and not to much. After a few weeks your cat will tune in and unpaiciently expect to be fed in sense of comming to and walking around you at that time. I guess then you are pretty save your cat has accepted his/her new home. --Kharon (talk) 06:43, 19 May 2016 (UTC)

Most cats don't seem to overeat, especially if given dry food. (If I had to eat that, I wouldn't overeat either.)StuRat (talk) 15:52, 19 May 2016 (UTC)

My last six cats quickly made themselves at home, at ages ranging from three months to eight years. (The youngest was a bit feral and took a week or so, iirc.) The present pair are my first indoor-only cats; once in a while (including today, as it happens) they get out but quickly return when they find the Big Room to be chilly and strange. —Tamfang (talk) 09:28, 19 May 2016 (UTC

There is some advice on the subject here. Perhaps respondents to this thread should read this discussion about the pros and cons of the indoor/outdoor lifestyle and the difference in attitude in the UK and US or Australia. Richerman (talk) 09:37, 19 May 2016 (UTC)

Agree with Richerman. Here in the UK we usually advise to keep them in for a period of time - maybe 6 weeks - until the cat is used to their new surroundings and to you as well. Then maybe let the cat out. Make sure the cat is microchipped - and if she already is, update the details on the chip record. Your vet will be able to do this for you. --TammyMoet (talk) 12:20, 19 May 2016 (UTC)

A cat's instinctive priority is to remain close to a 'reliable' food source. That is how cats domesticated man. When our forbears became farmers and stored cereal grain that attracted rodents -the cats moved in and have been with us ever since. Three weeks should be more than sufficient to establish the notion that you are providing such a reliable food source. Then, during the times when one is at home, leave the doors open. By then it will have become accustomed to your voice calling it for meals (I take it that you call its name when your ready to feed it). Once cat is back inside again one can close the doors. If you do not want to fit a cat-flap make sure there is a way for the cat to get on to a window ledge or someway that it can look through a window and attract you attention when it wants to be let in again. Foxes are on the increase in many parts of Britain so whether or not you fit a cat flap, look around to see if the cat has somewhere to climb to. If the house cat become secure in the feeling that it always has a safe refuge there is no reason why it should suffer acrophobia. Let the cat expand its horizons naturally. Also, a cats natural diet and metabolism requires meat protean. Not this modern pet food stuff that contains more than 50% vegetable protean with added vitamins. Per 100 grams it is cheaper to go to the supermarkets and buy a cheap frozen bulk bags of coley and beef mince (and don't forget kitchen scraps). The cat will appreciate it more and it will keep him healthier. Cat don't like very cold food though. So, deforest to room temperature and pussy will come back for more. At nine month old it will naturally start to forage due to instincts. It may soon be bring home the odd rat, half as big as himself and dump it on the kitchen door step. Praise such an instance. It is his way of showing that he is now able to contribute to the family that feeds him. As I said, cat domesticated man. So for a happy symbiotic relationship – don't use brain- allow the cat to guide you as to how to satisfy its needs and desires. It really is that simple when it comes to caring for cats.--Aspro (talk) 14:11, 19 May 2016 (UTC)

Re: "deforest to room temperature", won't this deforestation deny them the trees they need for emergency escapes ? :-) StuRat (talk) 15:56, 19 May 2016 (UTC)

Nice to no, that that you have tooken the bother two reed wot eye have rote :¬)--Aspro (talk) 12:57, 20 May 2016 (UTC)

It's very rare for urban foxes to kill cats [14] - they mostly ignore each other and, although they do occasionally fight, the fox often comes off worst. Cats do not have any other predators in the UK (and no, there are no coyotes). Richerman (talk) 17:01, 19 May 2016 (UTC)

True, but I have witnessed cats spooked by the presence of foxes and they avoid confrontation. That is probable why the statistics show that “fox attacks on cats are exceptionally rare”. I would also agree with your source written by Dr Pete Wedderburn BVM&S CertVR MRCVS that “Foxes are generally shy creatures that do their best to avoid contact with humans” but round my way they aren’t. This File:The_thirsty_fox.jpg is a photo of one of the foxes that drinks at my local pub. Give him a few years and I wouldn’t be surprised to find him standing beside me at the bar winking at all the barmaids. Just because someone has letters after his name doesn’t mean his utterances are to be taken as dependable guidance (after all he is a vet) – as it is promoting the fallacy argumentum ad verecundiam . One's cat 'needs' some where to take refuge and avoid confrontation.--Aspro (talk) 12:57, 20 May 2016 (UTC)

@Aspro, why is the fox anonomised in your photo - did he refuse to sign the model's waiver rights release form?  ;-) DrChrissy ^(talk) 16:47, 20 May 2016 (UTC)

There are cars, which run over animals all the time. Also, outdoors cats are more likely to be attacked by fleas and diseases. If the OP doesn't care what happens to his cat, then so be it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:04, 19 May 2016 (UTC)

Don't forget dogs, and other cats, as in the case of intact males fighting. StuRat (talk) 03:43, 20 May 2016 (UTC)

Bugs, you do your reputation and argument no good by continually bickering from a point of obvious ignorance and lack of experience. Many (if not almost all) cats in the UK wear 'flea collars' to avoid infestation and cats are more likely to get fleas from other cats and not the outdoors per se. It is very rare to see or hear of a cat killed by a vehicle in the UK, other animals, predominantly in rural areas, are killed more frequently but that is irrelevant to this argument. I am unclear what you mean by "other diseases". Your final sentence with its inflammatory emotional claim is crude and unhelpful. Richard Avery (talk) 06:41, 20 May 2016 (UTC)

I have worked in the veterinary profession for 20+ years, I lecture vet students on animal behaviour, and I am a cat owner living in rural UK (North Somerset, so plenty of dangerous foxes and badgers and drop bears). I believe the main concern about moving a cat to a new area and letting it out, is injuries caused by other cats. Cats have a great way of time-sharing their territories. They can determine how long it is since a previous cat was in the territory by sniffing the pheromones in each others urine. They avoid visiting the place too soon after another cat has been there, and so generally do not meet. However, if they do meet, they may fight. Cats are extremely dangerous when riled (they have 5 sets of weapons whereas dogs have only 1). The most likely wound that your cat might experience is a cat bite abscess. These usually occur on the cat's cheeks or the flank. Inspecting your cat or noting any tenderness when stroked will reveal an abscess early in development and you must seek veterinary advice immediately for antibiotics, otherwise this can become deeply infected and very expensive! Regarding the time taken to let the cat outdoors, this will depend a lot on his experience. If the cat is used to change and stimulation, he will be rather plastic (flexible) in his behaviour and will quickly adapt to his new environment; if he has had a less stimulating history it may be more fearful and unwilling to go out. In your favour is that he is still young and therefore naturally more inquisitive. Get a cat flap -- and give the cat the choice about inddors or outdoors. Don't let him out for the first 2 weeks, but establish where he gets his food. Then, take the plunge and open the cat flap. By the way, I have a male neutered cat who eats only dry food and is now so fat he can't get out the cat flap! - Very handy! Best of luck. DrChrissy ^(talk) 16:41, 20 May 2016 (UTC)

In that case, why don't you restrict his food supply and/or use diet food ? StuRat (talk) 16:48, 20 May 2016 (UTC)

May 19

Human height data

Can someone tell me where to find data about the distribution of human heights? More specifically, for adults in North America, or the USA, or Canada?

Thanks, CBHA (talk) 04:39, 19 May 2016 (UTC)

Our article on Human height, has US specific age x growth and age x height graphs for males and females. Vespine (talk) 06:49, 19 May 2016 (UTC)

Why do women prefer tall men (besides these reasons)....

there are exceptions of course, but women on the whole prefer taller men as mates. If you asked a woman who feels this way why she feels this way, she might say something about tall men being stronger, making her feel safe, etc.. And while all height might be *loosely* correlated with physical strength, we all know plenty of short people who are strong as oxen as well as many tall, skinny weaklings. Also, if you asked a woman who she found more attractive: a competitive strongman who was five-foot-2 or a man of slightly below average strength who was six foot two, and they were equal in all other ways, many woman would choose the tall guy.

So if we assume, for the sake of argument, that height is NOT a reliable proxy for physical strength, what are the other reasons for preferring tall partners? Is it considered a proxy for good physical health (related to strength, but not the same thing), or is it just some kind of inexplicable evolutionary behavior of which the woman herself is unconscious?--Captain Breakfast (talk) 07:15, 19 May 2016 (UTC)

There may be some opportunistic motivations such as you are describing ( if accurate however that there exists such thing as an homogeneous set of the "women" the way you are classifying them ). But if we are considering sets, there may be also a question of an image (resulting from the pattern and used in that hypothetical pattern of an element of one set considering those of an other set ). Selecting randomly one of the cloud links in the article image could lead you to the article microscope. If you were a woman you probably would not want to carry the device around, so there is some chance that too tall works too. My opinion is that the view you're exposing is probably accurate only as long as the market can absorb and afford to further increase the size of our SUV's, after this will become too expensive and the market crashes there is some chance we might come to observing the opposing trend. --Askedonty (talk) 07:51, 19 May 2016 (UTC)

• There are lots of studies – this gives a good overview. When done properly, evolutionary psychology (and other evolutionary studies) doesn't say "This trait evolved because it had this advantage" but rather "This trait evolved because it improved survival or reproductive for this reason" (see misconceptions about evolution). Evolution doesn't have a plan - it doesn't know that tall men are stronger - it's just a process of random mutations that have no real goal. So - assuming it's evolved and not cultural - women didn't evolve to prefer tall men because they're stronger, but maybe because the children of women who preferred tall men were more likely to survive to adulthood, or perhaps because tall men were able to defend and care for the woman better so she lived longer and had more children. Smurrayinchester 08:54, 19 May 2016 (UTC)

(Jayron32's answer to the question below reminds me that sexual selection may also play a role here - in theory, if tall men dominate in the population, women who are attracted to tall men have an advantage since they have more partners to chose from.) Smurrayinchester 14:19, 19 May 2016 (UTC)

• The "height is NOT a reliable proxy for physical strength" claim caught my eye. Assuming that this is an evolutionary trait (it may be cultural - it would be interesting to see any studies from Asian regions where humans are, on the average, shorter), evolutionary preferences do not have to be reliable. They just have to be right slightly more often than wrong. --Guy Macon (talk) 09:50, 19 May 2016 (UTC)

It exists at the least. I always wondered why my short Asian mom hoped I'd grow till 6 feet. Sheesh. That is not realistic when her husband's 5'8" and her family's way shorter than 5'9" (my actual height). Sagittarian Milky Way (talk) 14:49, 19 May 2016 (UTC)

A couple possibilities come to mind:

1) Age marker. If a male is tall, there's was good chance they were an adult, or at least old enough to father and hopefully care for children.

2) Health marker. Poor health, and in particular a protein-poor diet, can result in short height. So, a tall man is more likely to be healthy and have access to good food. StuRat (talk) 16:02, 19 May 2016 (UTC)

Two words: Stiller... and Meara. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:34, 19 May 2016 (UTC)

Evolutionary body hair reduction in females

Both female and male apes, including chimps who are regarded as the closest relatives of humans, are fairly hirsute. Human females, however, became less hirsute during evolution, losing facial and most of body hair, compared to males. Why is that?--93.174.25.12 (talk) 09:33, 19 May 2016 (UTC)

Who says so? ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:44, 19 May 2016 (UTC)

Excuse my learned colleague, he always answers a question with another one. There doesn't seem to be one accepted hypothesis, but Evolution and Prehistory: The Human Challenge by William A. Haviland, Dana Walrath et al (p. 158) presents the argument that the human body hair pattern is the result of a large brain and a bipedal gait; the "Wheeler" mentioned seems to be Professor Peter Wheeler. There's also the now largely discredited Aquatic ape hypothesis, which puts our hair pattern down to spending a lot of time up to our necks in water at an early stage of our evolution. Alansplodge (talk) 12:45, 19 May 2016 (UTC)

Not always, just when an OP's premise is based on facts not in evidence. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:33, 19 May 2016 (UTC)

What? Are you asking for a citation for the statement that most women don't have beards? CodeTalker (talk) 20:20, 19 May 2016 (UTC)

Many men have sparse facial hair and/or body hair. And many women have some facial hair and certainly leg and underarm hair. The OP's premise is flawed. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:51, 19 May 2016 (UTC)

There is also the general concept of sexual selection; traits desirable for mating get passed on to future generations. Those traits don't have to be "advantageous", they just need to make one's mate horny. --Jayron32 13:02, 19 May 2016 (UTC)

Sexual selection is the only theory thus far that explains the sexual dimorphism seen in the hair patterns of men and women. Halting of hair development at the juvenile stage or Vellus hair is consistent with men preferring juvenile characteristics in a breeding partner, evident today in the near total removal of pubic hair in pornography for male consumption. A rationalisation that body hair might conceal the female's state of health can be related to medieval witch-hunts when an alleged witch would be shaved to discover the so-called Witches' mark on her body. AllBestFaith (talk) 13:18, 19 May 2016 (UTC)

A twist on the sexual selection theme is the suggestion in Evolution and Human Sexual Behavior by Peter B. Gray, that body hair is associated with sebaceous glands and apocrine glands which make men smell stronger than women; women also have a better sense of smell than men, which "fluctuates across the ovulatory cycle" making women "more aware of male scents at times when it may matter most". Alansplodge (talk) 16:08, 19 May 2016 (UTC)

Yes, not a better sense of smell, a differently selective one. Counting everything, they may have a number of sensitive advantages which, those amongst them using male distraction as a useful extension to their own set of camouflage, allows them to point smarter. --Askedonty (talk) 22:25, 19 May 2016 (UTC)

Clothing (wearing furs, initially) is likely a factor in both reduction of thickness in hair in males and females (and even more so in children). That is, one of the main advantages of a thick coat of hair, keeping warm when it's cold out, was no longer an issue. The advantages of less hair include increased effectiveness in cooling by sweating, which would be important where humans first evolved, in Africa. Other benefits include fewer skin parasites, like fleas and lice. This doesn't directly address the Q of why there would be a differences between males and females, but once there was a mix of genes for "less hair" and "more hair", this allowed sexual selection to occur. StuRat (talk) 16:09, 19 May 2016 (UTC)

A reference for StuRat's post above. Alansplodge (talk) 16:13, 19 May 2016 (UTC)

Was the African savannah ever cold? Sagittarian Milky Way (talk) 16:47, 19 May 2016 (UTC)

Currently it's "consistently cool to cold at night" [15] although that's relative - 15 degrees Celsius. Still a bit chilly if you're naked I should think. Alansplodge (talk) 17:27, 19 May 2016 (UTC)

I guess the savannah's pretty high and/or dry then. York, Nebraska is a grassland 41° from the equator, 0.5km above sea level, has hardly any heat island and averages 17.6°C lows in mid-summer. Singapore#Climate's record low is only 19.4°C! Sagittarian Milky Way (talk) 18:44, 19 May 2016 (UTC)

Naked and possibly wet, if it just rained, and children would be particularly vulnerable to losing body heat, especially when windy. But with some nice furs to wrap around the kids, they should stay warm even in a storm. StuRat (talk) 03:38, 20 May 2016 (UTC)

Where in a plasmid map is 0 bp?

Since a plasmid is circular, is there some convention for determining where it starts (like the origin of replication?) when producing a plasmid map with indicators regarding the map length (the ruler which marks every, say, 1000 bp)? --129.215.47.59 (talk) 12:38, 19 May 2016 (UTC)

See here. The covention is to start numbering base pairs at the point in the plasmid known as the ORI, or "Origin of Replication". The Wikipedia article titled Origin of replication also has some discussion of plasmids. --Jayron32 13:24, 19 May 2016 (UTC)

Can grape consumption kill true foxes?

--Romanophile (talk) 16:47, 19 May 2016 (UTC)

This PhD dissertation [16] says, with further citation, that foxes eat grapes sometimes. Remember the dose makes the poison, and this evidence of foxes eating grapes does not contraindicate toxicity (i.e. LD50) at high doses. SemanticMantis (talk) 17:24, 19 May 2016 (UTC)

I doubt anyone knows for sure. We don't really know what causes grape and raisin toxicity in dogs, and the phenomenon wasn't noticed until relatively recently. As many dogs have eaten grapes/raisins without any apparent symptoms, there have been suggestions that it might not be the grapes directly but rather something associated with them such as a pesticide or fungus that is actually the toxic agent, but at the moment we don't know what it is about grapes that sometimes makes some dogs sick. Out of an abundance of caution, vets generally advise both dogs and cats to avoid grapes (though cats are unlikely to eat grapes and have never been documented to have a bad reaction [17]). For what it is worth, thepetfox.net says that most foods that are bad for dogs are also bad for foxes and that foxes should not be allowed to eat grapes and raisins [18]. Dragons flight (talk) 17:40, 19 May 2016 (UTC)

Light trajectory inside a rocket at uniform speed

Hi, I'm starting to study General relativity and there is something that I can´t understand. If we are in a place without gravity inside a rocket with no movement and we turn on a flash light we will see the light trajectory as a straight line, for example, horizontal. If we accelerate the rocket up, so will see the light doing a curved trajectory as parable with inclination proportional to acceleration. In this explanation sometimes books give us example that the rocket moves faster each time interval and so the trajectory inside behaves as a parable. So my question is "Whats happen if the rocket is moving up at uniform speed and we turn on a flash light ? The trajectory of light will be a straight line horizontal or a straight line inclined down and with inclination proportional to speed ?" Suppose that my flash light is placed horizontal at left side at middle height of rocket.

If I think that the rocket at uniform speed has the same behave as a rocket with no movement, I will conclude that light trajectory will be a straight lin horizontal with no inclination. But if I think of explanation that while light is moving from one side to another, and during this time the rocket it´s also moving, I will conclude that light trajectory it should be a straight line with down inclination.

How can I explain and solve that ? — Preceding unsigned comment added by Futurengineer (talk • contribs) 18:05, 19 May 2016 (UTC)

You question really concerns the special relativity not general relativity since the speed is constant. You can also read aberration of light article. Ruslik_Zero 20:34, 19 May 2016 (UTC)

Since the motion is uniform, it's equivalent to view the rocket as moving past other objects, or as stationary while other objects move past it. In the frame of the rocket, it is stationary and the beam moves in a straight line horizontally. In the frame of an object which the rocket is traveling past, the rocket is moving at a constant speed and the light beam is moving at an angle (no longer horizontal) slanted in the direction of the rocket's movement, but still a straight line. CodeTalker (talk) 21:40, 19 May 2016 (UTC)

Chermetids

What are chermetids? Cave insect mentions these animals in the penultimate section of its intro, and unlike all other animals in that area, chermetids is a redlink. A Google search pointed me to [19], which says The false scorpions, Chermetidæ, may at once be recognized... (this is in the original printing, not an OCR error), but no such name appears at Pseudoscorpion, the target of the False scorpion redirect. Is this perhaps a typo for Chernetidae? Nyttend (talk) 19:06, 19 May 2016 (UTC)

It would seem also certainly to be a typo, since Chernetidae is a family of pseudoscorpions. Typing m for n would be easy to do. --Jayron32 19:15, 19 May 2016 (UTC)

If it is a typo, then it is both very old and very persisent: 120 google books [20], spanning at least 1886-1999. Here [21] are a few rather divergent bibliographic entries for the same work of Menge, who is the name authority for Chernetidae. It seems that he probably intended to give the family a name starting with "chern", but "Chernetiden" one spelling offered by google. Without seeing the original book (or perhaps Chamberlin (1931) or Beier (1932) as per [22]), it's hard to say for sure what happened.

Anyway, I agree that the words "chermetid" and "chermeditae" will almost surely refer to a family of psuedoscorpions also known as Chernetidae. I don't know what WP policy is when we cite a source that seems to have a mistaken spelling. Probably some big argument about truth vs. verifiability... I see now that someone has redirected chermetid to chernetidae, which either fixes the problem or exacerbates it, depending on your viewpoint and the value you place on adherence to proper taxonomic names ;) SemanticMantis (talk) 20:13, 19 May 2016 (UTC)

Just remember, "verifiable" means "able to be shown to be true". Verifiability not truth does not mean we are bound to repeat errors merely because they were recorded. --Jayron32 21:57, 19 May 2016 (UTC)

The distinction is apt, and relevant to WP in general as well as this matter in particular. In case it's not clear, I am well familiar with the dictionary definition of verifiability, and I thought I was making an obvious allusion to Wikipedia:Verifiability,_not_truth. I honestly cannot tell what the truth of the history is, or if perhaps ICZN views the names as synonymous in the limited sense of Synonym_(taxonomy). In this case, the name of the family is verifiably Chermiditae. It is also verifiably Chernitidae. If anyone thinks that is impossible, then I encourage them to practice belief in impossible things. Sometimes I've believed as many as six impossible things before breakfast [23] :)SemanticMantis (talk) 22:23, 19 May 2016 (UTC)

Regardless of sourcing, Wikipedia is not supposed to be in the business of posting information that is demonstrably false. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:04, 19 May 2016 (UTC)

The presence of multiple printed sources with the same misspelling is easily sufficient for creating a redirect for the wrong spelling; see {{R from misspelling}}, which I didn't use when creating the chermetid redirect. It's not fundamentally different from pages such as Threshhold and Millenium, which exist for the sake of people who misspell it themselves or people who might find the spelling error in print without knowing how properly to spell it. Nyttend (talk) 02:07, 20 May 2016 (UTC)

Lifeboats

Looking at http://www.usatoday.com/story/travel/cruises/2016/05/18/royal-caribbean-harmony-first-look/84437986/ ("Exclusive: Inside the largest cruise ship ever built") I am having a hard time believing that that many lifeboats could possibly hold "6,780 people, not including crew". Looking into it further, I found http://www.cruiselawnews.com/2013/01/articles/sinking/titanic-redux-can-royal-caribbean-safely-evacuate-8500-passengers-crew-from-the-oasis-of-the-seas/ ("Titanic Redux? Can Royal Caribbean Safely Evacuate 8,500 Passengers & Crew from the Oasis of the Seas?") But what if the ship lists before the evacuation starts? Will the lifeboats and rafts on the high side be usable? And how fast can that many people evacuate without trampling each other? --Guy Macon (talk) 21:11, 19 May 2016 (UTC)

There was "lifeboat sticking out technology" as early as the Britannic 1914. It would be stupid for the to regress. I believe they could even carry the lifeboat over the ship and launch from the other side if there was too much list. Not sure. Sagittarian Milky Way (talk) 21:55, 19 May 2016 (UTC)

"lifeboat sticking out technology". Davit. --Tagishsimon (talk) 21:57, 19 May 2016 (UTC)

That would not have helped Titanic, whose problem was the removal of lifeboats from the ship before it set sail. Which takes us back to the OP's question: Do these ginormous cruise ships have enough lifeboats, or are the operators gambling with their passengers' lives, as the operators of Titanic did? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:03, 19 May 2016 (UTC)

Our article MS Oasis of the Seas points to this short feature on the lifeboats, fwiw. --Tagishsimon (talk) 22:09, 19 May 2016 (UTC)

Nobody was gambling with passengers' lives. The British Board of Trade recognized a couple of decades before Titanic that the largest of ships were always travelling in shipping lanes and these lanes were now so heavily travelled that there would (or should) never be more than a few miles between ships. In an emergency, ships would be able to summon aid by firing rockets or signalling with semaphore light. The uptake of radio technology confirmed that aid could be summoned rapidly, and lifeboats were regarded as necessary only for transferring passengers to the rescue ship(s). Why go to the expense of providing lifeboats for everyone on board when the biggest and newest ships with watertight compartments could be expected to float for many hours and rescue would be close at hand. It was in fact a good decision, but everything went very wrong for the Titanic because the officers on the Californian failed to recognize her rockets as a sign of distress and their radio man was off duty, and more importantly, was not woken. Titanic actually carried four more lifeboats than required by the BOT. The findings by both the American and British inquiries that there had been not enough lifeboats was wrong and a cave-in to the desire to spread the blame as widely as possible so that no living person could be found to have been at fault. Captain Smith took part of the blame for travelling too fast, but the blame should almost entirely have gone to the officers and captain of the Californian. Justice is not just about the letter of the law. It's also about minimizing the guilt felt by those at fault who have to go on with their lives. Akld guy (talk) 04:49, 20 May 2016 (UTC)

Making the assumption that a nearby ship would rescue them is certainly a gamble. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:26, 20 May 2016 (UTC)

It would have been better if, when reducing the number of lifeboats, it had been made mandatory for ships' radios to be manned continuously. Also, many of the Titanic's lifeboats moved off with only a few people on board. 78.145.24.30 (talk) 11:19, 20 May 2016 (UTC)

Yes. For White Star to have blamed others for the negligence of the Titanic operators is really cynical. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:49, 20 May 2016 (UTC)

Sense of smell

Do women haved a better sense of smell than men? My gf is always complaining of my smelly feet but I cant smell them at all.--178.106.99.31 (talk) 23:47, 19 May 2016 (UTC)

I've known women who had no sense of smell at all, and others whose sense of smell was very acute. It could also be that you're used to your own scents, so you don't notice. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:56, 19 May 2016 (UTC)

Here is a good start for your research. --Jayron32 03:04, 20 May 2016 (UTC)

To avoid smelly feet, take your shoes off when not walking. This lets heat and moisture out, and air in, which keeps the microbes from growing out of control. Shoes that allow for airflow are also a good idea, but I've never found any shoes, short of sandals, to provide sufficient airflow. StuRat (talk) 03:31, 20 May 2016 (UTC)

BB hit on two key points. Your sample size is apparently 2. You could just as well ask do people with red hair have a better sense of smell? Or, do people with green eyes have a better sense of smell? Or, do people from Irish descent have a better sense of smell? (I don't know if your girlfriend has red hair, green eyes or Irish descent and you don't, but you get the idea.) In other words, while any of these may or may not be true, there's no particular reason to think of them based on the data you've provided. We're only talking averages here and your girlfriend's suggested better sense of smell may just be because she's different from you and not any particular characteristic. Also olfactory fatigue or other factors related to the fact that it's your own odour may reduce your sensitivity to it. (Although I admit I couldn't actually find good sources discussion olfactory fatigue relating to body odour. There was only [24] where a group testing female responses to male body odour included a break due to the risk of olfactory fatigue/adaptation.) Nil Einne (talk) 12:43, 20 May 2016 (UTC)

May 20

Diamond in a rock tumbler

What if you put a big diamond in a rock tumbler? Anna Frodesiak (talk) 00:55, 20 May 2016 (UTC)

Define "big". ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:43, 20 May 2016 (UTC)

Like the size of a grape, but maybe the size wouldn't matter. Anna Frodesiak (talk) 01:46, 20 May 2016 (UTC)

The size might well matter, as more surface area could take longer to polish. The illustration doesn't have a scale, but some of the types of rocks suggest grape size or larger. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:51, 20 May 2016 (UTC)

But would it polish or just stay the same forever? Anna Frodesiak (talk) 01:59, 20 May 2016 (UTC)

If you're using standard polishing materials, it wouldn't polish as the prices relies on being able to scratch and smooth the surface. More likely the diamond would shatter or crack as they are brittle and easily chip along cleavages planes. You buffed with other diamonds, you could cut and polish it. EvergreenFir (talk) Please {{re}} 03:09, 20 May 2016 (UTC)

Rhenium diboride can be made harder than diamond, so you could polish diamonds with that. However, a polished diamond would just look like a glass marble. It's the facets that make them sparkle, and you get those by cleaving diamonds, not polishing them. StuRat (talk) 03:27, 20 May 2016 (UTC)

Very interesting. Thank you so much you two. Anna Frodesiak (talk) 05:37, 20 May 2016 (UTC)

It is a misunderstanding of hardness to assume that because diamond is harder than the other minerals involved, it will not be abraded at all. Diamond tipped drill bits do wear out, and have to be replaced - just not as often as other drill bits. When two minerals of differing hardness rub together, both are abraded - but the softer one is abraded much more quickly than the harder one. 86.141.19.154 (talk) 12:14, 20 May 2016 (UTC)

As an engineer who has done a lot of work with matterials rubbng and weraing, I can tell you that it is a well-known effect that the intuitive "the softer surface is abraded much more quickly than the harder surface" only hold true when both surfaces are harder than silicon dioxide (a major component of dust and dirt). If you have, say, teflon rubbing against stainless steel, the metal wears out. That's because little bits of dust get embedded in the soft plastic and act like a file to wear down the metal. --Guy Macon (talk) 15:59, 20 May 2016 (UTC)

• Hi User:Anna Frodesiak, interesting question as usual! If you'd like some scientific reference for rock tumbling: Here [25] is a whole study that gives empirical results on how size and shape of particles influence roundness, abrasion, and size reduction in the end product. Then they develop a theoretical model based on that that uses exponential functions to predict/relate how the various factors influence the tumbling process. A very nice little paper, IMO. While you could tumble larger diamonds in diamond dust, you could also tumble raisin-sized diamonds together and they would performs abrading action on themselves. Industrial diamonds are also sometimes prepared using a tumbling mill, see here [26] for a study involving that and a new way to impregnate diamonds in cutting tools. SemanticMantis (talk) 13:35, 20 May 2016 (UTC)

Dinosaur skeletons

Are most dinosaur skeletons found in pieces and not assembled together? 50.68.118.24 (talk) 04:02, 20 May 2016 (UTC)

Yes, in fact only a few bones may be found. A fully intact and articulated dinosaur skeleton is a rare find. But, since scientists can put them together in the proper order, and make fake bone to fill in for any missing pieces, it's not a problem. StuRat (talk) 04:11, 20 May 2016 (UTC)

Of course it's been a problem. See here, for example. Or for a less academic source, here. --69.159.60.83 (talk) 06:38, 20 May 2016 (UTC)

Leave it to Stu to reduce an entire scientific discipline (shaped over centuries, with many famous debates over validity of reconstructions) to "not a problem." :) SemanticMantis (talk) 13:47, 20 May 2016 (UTC)

Here [27] is a link to piece from the Smithsonian that describes how scientists attempt to correctly reconstruct dinosaur skeletons from partial finds, and here [28] is another discussion of the topic from Ohio University. Sometimes nearly a whole animal is fossilized, this is called a Lagerstätte. SemanticMantis (talk) 13:56, 20 May 2016 (UTC)

Equal distribution

If I roll infinite sided die with faces labelled from zero to one are the odds of it coming up higher than, say, 0.8 equal to it coming up lower than 0.8? I mean there as many numbers above 0.8 as there are below so it seems like it they should be. 88.164.119.137 (talk) 14:52, 20 May 2016 (UTC)

probably move to math...do you mean the die will have every real number between 0 and 1 (an infinite sum, I do believe)??..I'm curious how this will be answered..it's possible the question will be considered nonsensical..68.48.241.158 (talk) 15:16, 20 May 2016 (UTC)

The article almost surely almost surely provides some background to the problems when dealing with the intersection between infinite sets and finite sets. --Jayron32 15:19, 20 May 2016 (UTC)

It depends a bit on how you conceptualize this die. But the reasonable and naive thing to do is to identify it with the uniform distribution on [0,1]. That is analogous to the fair die in the case of finitely many sides. In that case rolling the die is the same as throwing a dart (whose tip is a point) at the unit interval. The probability of the dart hitting any given number is zero, and the probability of it hitting an interval is the size of that interval. So, for your example, the probability of getting a roll in (0.8,1] is 0.2, while P(x in [0,0.8))=0.8. The number of points in the interval is not as important as the size or measure of the interval. This is the distinction between cardinality of a set versus the measure of a set. So the measure of the set is the size of the event_(probability), and we use that to compute probabilities of given events. For intervals, the measure of the interval is just its length (l((a,b))=|b-a|), but for more complicated sets/events, you'd use tools form measure theory to compute the probabilities. SemanticMantis (talk) 15:43, 20 May 2016 (UTC)

op here. Thank-you for that clear and well sourced response. Does the same reasoning hold for a countably infinite sided die (faces labelled with, say, all the positive integers)? 92.90.17.111 (talk) 15:59, 20 May 2016 (UTC)

yes the cardinality couldn't matter...if infinite the chance of landing on a particular number would still have to be zero...and the discussion as far as measure would have to be same too...(it's possible there are fine points involved here that haven't been mentioned)..68.48.241.158 (talk) 16:10, 20 May 2016 (UTC)

or maybe I'm wrong as far as the measure as there's no defined interval like between 0 and 1...?? But I'm not sure this question is technically sensical..68.48.241.158 (talk) 16:17, 20 May 2016 (UTC)

I think the move from [0,1] to $\mathbb {N}$ is importantly different - the former accepts a uniform distribution while the latter does not. Never underestimate the weird things that can happen when switching back and forth between sets of countable and uncountable cardinality ;) SemanticMantis (talk) 16:39, 20 May 2016 (UTC)

You're welcome! For the follow up - No, I don't think so. What's the uniform distribution on the natural numbers? We can define it on an interval, but not on the whole line, and not on the positive integers. To put a probability distribution on a set we have to have an integrable function on it. For a discrete uniform distribution, we just set the probability at 1/n for n many choices. But there's no obvious way to extend that to all $\mathbb {N}$, because the infinite sum of a finite value will always be infinite. See here [29] [30] for some discussion of why we can't have uniform distributions on the whole line. It comes down to the axioms of probability. Improper priors are a way to look at things that are almost like probability distributions, but are not. Here [31] is a paper that examines things that are in some sense "almost uniform" distributions on the natural numbers. I haven't read that but it does look promising. Another thing to do would just be to have the die not be fair. Then you could put e.g. a Geometric_distribution on it. If you want more on this sub-question, I do recommend making a new post on the math desk, and including a link to this question if you do so. SemanticMantis (talk) 16:39, 20 May 2016 (UTC)

Capacitor information sought

I have found amongst my components what I think are polystyrene capacitors hermetically sealed in metal cans. The wires come out via glass to metal seals. The only printing on the cans is 'KS'at the top, then the value in pF (confirmed with a capacitance meter) and the voltage then a long number and finally at the bottom what appears to be a date code like 8/88 or 1/89. I have searched the web to find who might have made these units without avail. Can anyone tell me where to search to find details on these units?--178.106.99.31 (talk) 16:58, 20 May 2016 (UTC)