Wikipedia:Reference desk/Archives/Science/2016 December 10

= December 10 =

Men taking a pregnancy test
I read that if a man takes a pregnancy test and it tests positive (meaning pregnant) that the man very likely has early stages of testicular cancer. Is this well substantiated among medical science communities? 64.170.21.194 (talk) 01:10, 10 December 2016 (UTC)
 * . -- Jayron 32 01:36, 10 December 2016 (UTC)


 * In your link jayron it says "Primary pulmonary choriocarcinoma is an extremely rare tumor in men, with 13 cases reported in the literature." Does this mean that men using urine pregnancy tests can only test for this specific condition? there have only been 13 reported cases? 64.170.21.194 (talk) 01:41, 10 December 2016 (UTC)


 * I don't know what it means. -- Jayron 32 01:46, 10 December 2016 (UTC)

The positive result on the pregnancy test is caused by expression of human chorionic gonadotropin by some cancers of testicular origins, and this is frequently the hormone that pregnancy tests are reactive to. There is more than one type of testicular cancer, and the one that most commonly produces this hormone only does so in about half of cases ("mixed germ cell tumor"). Some types of testicular cancer appear to never produce this hormone. There are also several varieties of this hormone - a given pregnancy test may be sensitive to one, several, or none. HCG does have some predictive power in staging and prognosis of testicular cancer. Someguy1221 (talk) 01:51, 10 December 2016 (UTC)

Just a note: it's a bad idea to test something as serious as cancer using this route. You'd be giving the pregnancy test an off-label use, although there are specific test for it. Llaanngg (talk) 17:03, 11 December 2016 (UTC)


 * Agreed. A link to sensitivity and specificity might be in order. Men peeing on a pregnancy test stick would have an enormous number of false negatives, in large part due to the test not being designed for that purpose. Possibly false positives as well, but that's less clear to me. Matt Deres (talk) 17:31, 13 December 2016 (UTC)

In what way teachers in academy used to draw the signs of skeletal structures?
Many of the molecules in biochemistry (bio-molecules) have special signs such as: dashed lines, bold-wedged lines, solid lines, wavy lines, dotted lines or arrows - all of them about the 3D directions or the condition of the bindings. Anyway my question is if in academy teachers used to draw it (while drawing and explaining on blackboard) in way that we see on books & wikipedia illustrations (see here example of isoleucine with bold-line and wavy line) or there is another practical way to denote these things/symbols? (personally I didn't find it that easy to draw those signs when I have to draw man molecules, it takes a lot of time to deal with it and I suspect that normally teachers also don't do that, but maybe I'm mistaken) 93.126.88.30 (talk) 01:36, 10 December 2016 (UTC)
 * I (as a high school chemistry teacher) do, as does every instructor at every level I have ever known. You could also look at the Journal of Chemical Education, the primary peer-reviewed journal for chemistry education, which also uses it extensively.  -- Jayron 32 01:38, 10 December 2016 (UTC)
 * So when you use whiteboard do you draw these lines as the are drawn in the book? (what did you tell me to check in the link? I found that it's a name of printed journal, it's not handwriting if I'm not mistaken) 93.126.88.30 (talk) 02:23, 10 December 2016 (UTC)
 * Yes, I draw wedges and dashes and lines. It's really not that hard.  Also, you had a question about teaching chemistry.  This is the reference desk, so I provided you a reference to a reliable source on teaching chemistry.  -- Jayron 32 19:33, 10 December 2016 (UTC)
 * These diagrams are actually the most efficient way to convey the key facts of bonding and shape. With practice, it becomes second-nature. My handwriting looks like crap and my freehand diagrams are not perfectly aligned, but because the key details are only "line vs wedged vs dotted" and simple directional options such as "up, down, left, right, about halfway between up and left, mostly right but slightly down, etc", it's easy for me to draw something well enough that the basic details are obvious. Plus when I draw it and explain it while I'm drawing it, it's even easier to see which details are actually important for whatever point I'm trying to explain. It doesn't matter if the whole drawing is perfect or even completely clear, as long as it's clear enough for the detail of interest (I spend a few more seconds on a few of the bonds and atoms than on the rest). Think about how long it takes a child hand-write even a simple word, having to think about which letter comes next to spell it and then how to form each letter, vs you with years of experience can hand-write whole sentences without thinking about the mechanics of actually doing it. DMacks (talk) 05:06, 10 December 2016 (UTC)
 * Interesting. I found also this video (28:00) whose teacher indeed draws the dashed lines and bold wedges. 93.126.88.30 (talk) 05:53, 10 December 2016 (UTC)
 * It's not so hard to draw them, and you'll have to know how to do so almost from the beginning. I draw the outline of the wedge first and then fill it in, and I draw the wedges as a stack of lines decreasing in length, just as they appear in print. Double sharp (talk) 07:41, 10 December 2016 (UTC)
 * I'm afraid I'm not really grasping the difficulty here. There are a number of ways to do this, some as easy as anything else at a blackboard:  drawing a dashed line is a little annoying, but any blackboard lecturer can do it automatically, and the "wedge" is often done simply by drawing a narrow triangle.  The squiggly line for an indeterminate bond is not exactly complicated either.  I mean, using chalk to draw something that looks readable isn't trivial, but this doesn't seem to be any worse than that. Wnt (talk) 11:34, 10 December 2016 (UTC)

Can norovirus be used as a non-lethal bioweapon for urban warfare?
Norovirus is highly contagious, the article says: "fewer than twenty virus particles can cause an infection[2] (some research suggests as few as five).[9] Transmission can be aerosolized when those stricken with the illness vomit, and can be aerosolized by a toilet flush when vomit or diarrhea is present; infection can follow eating food or breathing air near an episode of vomiting, even if cleaned up.[18] The viruses continue to be shed after symptoms have subsided and shedding can still be detected many weeks after infection.[19]"

Also:

"The norovirus can survive for long periods outside a human host depending on the surface and temperature conditions: it can stay for weeks on hard surfaces,[57] and up to twelve days on contaminated fabrics, and it can survive for months, maybe even years in contaminated still water.[58] A study done in 2006 found the virus still on several surfaces used for food preparation seven days after contamination.[59]"

This suggests that it could be the ideal bioweapon to eliminate an entrenched enemy like ISIS in Mosul. The question is then if it's possible to spray large areas with a norovirus spray such that you still have a large enough concentration of the virus surviving on the ground to cause a massive outbreak of illness, allowing soldiers to move in without facing significant resistance from the enemy. Count Iblis (talk) 02:46, 10 December 2016 (UTC)


 * Seems a bad idea to use any strategic weapon in an area where civilians outnumber enemy combatants 300 to 1, when the ostensible goal is to save life. I'd imagine the civilians would have a much higher death rate from normal due to the relative lack of food and medical care in such a war zone. Someguy1221 (talk) 02:59, 10 December 2016 (UTC)


 * Some thoughts: I've had this virus... under ideal circumstances, yes, there was a 24-hour period when it put me out of commission, and I was certainly weaker for days afterward.  Still, "spraying large areas" (like a city) is not trivial, and the military advantage of having some ISIS members out of commission briefly might not be as much as can be obtained by equal resources spent on bombs and bullets which put them out of commission for a more satisfactory period of time.  Once infected, a person is immune, so the reduction in fighting force is proportional to the number of people affected in one day of spraying, and only to the degree that their courses of infection are simultaneous, and it varies over a period of 48 hours or more.
 * Then there's the issue of civilian casualties. The civilians, unlike the fighters, have questionable access to water and food, and diarrhea without sufficient water and electrolytes can be deadly.
 * Beyond this, there's the problem that the enemy army doesn't know what it's been hit with. Even if you tell them you're going to spray norovirus (which would let them deploy some countermeasures, if only infecting some of their people in advance so they'd be immune when the attack came) ... would they believe you?  ISIS has shown a distinct lack of boundaries, but it still seems like it might be unwise to press them into active consideration of biowar possibilities.  The fixation of terrorists on a few weapons meant more to be targeted than to be deadly, like guns and IEDs, is not generally perceived as a blessing, but we could soon find out how much it was. Wnt (talk) 03:16, 10 December 2016 (UTC)

We have a list of potential viral bioweapons. These are all mosquito-borne illnesses with the exception of smallpox, which is not the most contagious virus if you are able to avoid all contact with infected persons. Someguy1221 (talk) 03:25, 10 December 2016 (UTC)

galaxies
how many galaxies are cataloged by astronomy?--2001:B07:6463:31EE:E14B:27D7:9305:98C2 (talk) 11:41, 10 December 2016 (UTC)


 * Galaxy says "tens of thousands". List of galaxies says that the Morphological Catalogue of Galaxies, which lists 30,642, is putatively complete to a photographic magnitude of 15.  Rojomoke (talk) 13:03, 10 December 2016 (UTC)


 * The Sloan Digital Sky Survey has found nearly 50,000,000 galaxies. Only 999,950,000,000 to 1,999,950,000,000 more to go. Sagittarian Milky Way (talk) 15:02, 10 December 2016 (UTC)


 * Isn't it handy how the total number of galaxies, 2000000000000, turned out to be such a nice round number ? :-) StuRat (talk) 17:06, 11 December 2016 (UTC)

Is there any medical value when a care provider talk to his trauma patient?
It's well known that in cases of trauma (in physical medicine) always the care provider (paramedic / physician) would try to talk to their patient in order to keep him/her in conscious. It's known also from movies as the sentence "Stay with me, man!" etc.

My question if there is / are any medical value to do that while it doesn't seem to be matter to talk someone that lost a lot of blood, if he will he loose his conscious he will loose it with or without conversation. Then I would say that the only medical value that I can think about, is just to observe and monitor the patient but not as a tool to keep him in conscious. Is that right? 93.126.88.30 (talk) 13:40, 10 December 2016 (UTC)
 * Yes, absolutely there is value in keeping the patient conscious. The reasons are not entirely clear, but probably a major one is that the body's ability to deal with a challenge is much better when the sympathetic nervous system is strongly activated, and the sympathetic nervous system is usually much more active in a person who is awake than in a person who is unconscious.  An EMT can compensate by giving drugs, but in the first response before drugs can take effect consciousness is definitely an asset. Looie496 (talk) 13:53, 10 December 2016 (UTC)
 * Determining the neurological status of the patient is easier when the patient is conscious and responsive. Talking to the patient also helps reduce stress and anxiety. Roger (Dodger67) (talk) 13:59, 10 December 2016 (UTC)
 * Yes, sure, but the more crucial point is that keeping the patient awake helps keep the patient alive. Also stress and anxiety may actually be helpful in a person who has lost a lot of blood. Looie496 (talk) 14:11, 10 December 2016 (UTC)
 * I would like to see any scientific reference that supports the claim that it helps actively to keep the patient in conscious. 93.126.88.30 (talk) 15:37, 10 December 2016 (UTC)
 * This source claims it's a myth, but their own source is now a deadlink unfortunately. Someguy1221 (talk) 19:41, 10 December 2016 (UTC)

Birds seen at SeaWorld San Diego
Yesterday I went to SeaWorld San Diego, and they have a bunch of birds in aviaries with no explanatory signage that I could find. I also saw some waterfowl which might or might not have been captive, and which I don't know what they were. Can anyone identify the birds in these photos? 2602:306:321B:5970:DC8B:6096:3C9F:E457 (talk) 16:12, 10 December 2016 (UTC)
 * It's a goose of some sort. My guess is a snow goose.  -- Jayron 32 19:32, 10 December 2016 (UTC)


 * The fourth picture down looks to me like a female common merganser, and the bottom image is definitely of red-breasted geese. Deor (talk) 22:28, 10 December 2016 (UTC)
 * I did some browsing and I think that one looks more like a Hooded Merganser. Thanks for the goose ID! 2602:306:321B:5970:7820:D5BB:F3E0:F8BC (talk) 00:30, 11 December 2016 (UTC)
 * Thanks for your thanks. The third picture is of a (male) rosy-billed pochard. Deor (talk) 05:46, 11 December 2016 (UTC)
 * #6 is almost definitely a yellow warbler. #8 is a finch of some sort I think, likely a goldfinch or a greenfinch or a canary of some sort.  There's like 100 different yellowish finches that all look similar.  -- Jayron 32 01:59, 12 December 2016 (UTC)
 * (OP here) I don't think that's a yellow warbler; it's too big, doesn't have orange chest stripes, and the beak is the wrong shape. I think it might be another type of canary? And I've identified bird #7 as a turaco and #2 as a white-rumped shama.The remaining birds, all odd-looking waterfowl, I still have no idea about. 2602:306:321B:5970:BDDF:9E21:94D1:2258 (talk) 03:59, 12 December 2016 (UTC)
 * Does This help any? -- Jayron 32 09:49, 12 December 2016 (UTC)


 * I agree that the narrow-beaked duck is a hooded merganser, female, or perhaps juvenile. The duck right after her is a wigeon. The small goose at the end is an easy ID as red-breasted goose, one of the smallest geese, I think. The duck right before them is a moulting or perhaps hybridized ruddy duck, note the distinctive tail. The mostly black duck with red bill is definitely a rosy-billed pochard. I'm pretty familiar with common waterfowl, and together with the snow goose (which seems a bit small...) I think you have all the pictured waterfowl identified now. SemanticMantis (talk) 20:02, 12 December 2016 (UTC)


 * The seventh one (the large blue fellow) may be a curassow; not sure of the species. I think I see the characteristic crest. Matt Deres (talk) 17:39, 13 December 2016 (UTC)

plane of simultaneity link
- there is a link to this phrase in the Rietdijk-Putnam page yet it takes one to the Relativity of Simultaneity page, where its only occurrence is in the text of diagram 2. I can find no explanation of exactly what is meant by this phrase.

This is important as, by inference and reading between the lines it seems as if it only arises from a lack of understanding of Relativity.

(Let me say that I am writing this here as I don't yet understand the correct place to write it - some help on this, please?)

It seems to me that the very idea of planes of simultaneity arises from inferring how 'now' looks from a moving observer. But this is never the case! The 'now' of any inertial frame of reference will lie a parallel to the x axis; as from any inertial frame of reference the observer is at rest! They can only be moving observed by an observer moving relative to them.

Let me put that another way: take the two pedestrians in the Andromeda paradox;  they are each at rest in their own reference frame and moving in that of the other. So each will have the identical view of Andromeda - while insisting the other will see different timings. It is all RELATIVE!

Exactly what Einstein wrote in

Viz.: ″ Events which are simultaneous with reference to the embankment are not simultaneous with respect to the train, and vice versa (relativity of simultaneity). ″

To restate this once more (for clarity and to emphasise what may at first site seem a rather obscure point); a plane of simultaneity can only be seen second hand: that is to say that pedestrian A will say that B (who is moving relative to A) will see it while B will say it is only A (who is moving relative to B) that will see it; while neither will actually observe it for it cannot really exist because the plane of simultaneity only exists for a moving observer and no inertial observer is ever moving in their own reference frame. For how can an observer who is permanently at the origin of a frame of reference be moving relative to that frame of reference?

I apologise for restating this so many times but due to my lack of correct scientific terminology I am trying to ensure that my true meaning is understood and not changed by anyone trying to reset into the correct terminology and thereby losing my meaning... D1d4 (talk) 16:45, 10 December 2016 (UTC)


 * If I understand you correctly, then you would by analogy deny that you had a sagital plane; only people who are facing in a different direction from you have such planes? (Link Rietdijk–Putnam argument here for convenience of other readers).


 * In any case, whether an event in the Andromeda Galaxy is to one side or the other side of your plane of simultaneity (assuming it is outside of your light cone), has no more significance than whether that galaxy is to your left or to your right (which side of your sagital plane it is) - it just depends on which way you are facing. (Apologies if I have not properly understood the question). --catslash (talk) 16:50, 11 December 2016 (UTC)

Pleven
In our article Pleven it is said: Pleven is located 170 kilometres (106 miles) away from the capital city of Sofia, 320 km (199 miles) west of the Bulgarian Black Sea Coast and 50 km (31 miles) south of the Danube. Using Google maps it seems to me that the smallest distance between Pleven and the Danube is approximately 31 km (not miles). How are these two measurements compatible with one another? --151.41.129.212 (talk) 17:16, 10 December 2016 (UTC)
 * If there is something wrong, you're allowed to fix it. Just find a reliable source, and cite it.  You don't need anyone's permission.  -- Jayron 32 19:26, 10 December 2016 (UTC)
 * Also, this has about 49 km. -- Jayron <b style="color:#090">32</b> 19:26, 10 December 2016 (UTC)
 * But that's a distance by road. The sentence in the article doesn't say it's by road.  The distance from Sofia also appears to be by road, and the distance from the Black Sea coast is either by road or it's based on a direct east-west line instead of choosing the nearest point on the coast.  In short, this needs redoing. --76.71.5.45 (talk) 23:35, 10 December 2016 (UTC)
 * No one has yet tried to stop you from doing so. -- Jayron <b style="color:#090">32</b> 01:53, 12 December 2016 (UTC)
 * However, road distance might be a more useful measure, unless you happen to be a crow. Alansplodge (talk) 15:36, 13 December 2016 (UTC)
 * My math says Pleven is the sum of Zeven and Jour. :) Wnt (talk) 16:49, 13 December 2016 (UTC)

Is it possible to project the human voice faster than the speed of sound?
Either naturally by yelling, or by artificial means? I know it's a silly question, but I'd like to hear a serious answer to this, and if there's any relevant Wikipedia articles I could be pointed to. Thanks. -- &oelig; &trade; 22:50, 10 December 2016 (UTC)


 * How can sound move faster than the speed of sound? ←Baseball Bugs What's up, Doc? carrots→ 23:09, 10 December 2016 (UTC)


 * Try shouting into a diamond! Our article speed of sound states sound travels at 343.2 m/s in air,  1,484 m/s in water, 5,120 m/s in iron and 12,000 m/s in diamond which is around the maximum speed that sound will travel under normal conditions. DrChrissy (talk) 23:18, 10 December 2016 (UTC)


 * It wouldn't be any faster in a diamond than the speed of sound in a diamond. ←Baseball Bugs What's up, Doc? carrots→ 00:10, 11 December 2016 (UTC)


 * It does in the case of loud explosions. But you could argue (successfully) that it is still no faster than the local speed of sound. Or you could heat the air in the transmission path and then the speed of sound in the transmission path would increase. Or you could place an iron bar in the transmission path. But really you are just playing with words. A slightly related topic is active noise cancellation, particularly of random type noises. One method used is to place an accelerometer on the suspension and measure the vibration when you hit an impact. This signal is used to drive speakers in the car to suppress the noise. It only works because electronics are faster than the airborne/structureborne transmission path. Greglocock (talk) 23:21, 10 December 2016 (UTC)
 * The detonation velocities of high-order explosions are significantly faster than the speed of sound. --Modocc (talk) 07:40, 12 December 2016 (UTC)

Of course you can project your voice artificially faster than the speed of sound. See telephone. --76.71.5.45 (talk) 23:36, 10 December 2016 (UTC)


 * Or any form of radio, which would be near light speed. ←Baseball Bugs What's up, Doc? carrots→ 00:10, 11 December 2016 (UTC)


 * Eat it. Yes shock waves can travel faster than the speed of ssound in the medium.86.187.171.62 (talk) 01:32, 11 December 2016 (UTC)


 * I'm not so sure about that. And what has this Weird Al Yankovic song got to do with the subject? ←Baseball Bugs What's up, Doc? carrots→ 03:38, 11 December 2016 (UTC)


 * From the article: "Shock waves form when the speed of a fluid changes by more than the speed of sound." and this statement is supported with an inline citation. --Modocc (talk) 07:17, 12 December 2016 (UTC)


 * The speed of sound would be additive to the speed of the medium through with it travels, I believe. So, for example, in a wind tunnel, hurricane, or tornado, with air moving at 100 MPH, the sound would move measurably faster in the direction the wind is moving (as measured by a stationary observer) than in the opposite direction.  On a planet like Jupiter, with some serious winds, the effect would be even greater. StuRat (talk) 17:14, 11 December 2016 (UTC)


 * I'm not at all certain that's true. Can you find a link somewhere, in support of that? ←Baseball Bugs What's up, Doc? carrots→ 23:40, 11 December 2016 (UTC)


 * It is not true. Otherwise the speed of sound in your car when you drive at high speeds would change. In which case musical instruments like re corders or organs would go out of tune .Greglocock (talk) 01:21, 12 December 2016 (UTC)


 * It does change, to observers outside the car. See Doppler effect.  It doesn't change for the occupants, as they are all moving with the medium (the air in the car), so there is no motion of the medium relative to them or the sound source (the radio). StuRat (talk) 01:31, 12 December 2016 (UTC)
 * As far as I know, the Doppler effect has to do with the frequency, not the speed. ←Baseball Bugs What's up, Doc? carrots→ 01:39, 12 December 2016 (UTC)
 * Correct. Greglocock (talk) 04:46, 12 December 2016 (UTC)
 * There is no justification for leveling personal attacks, as you did in your edit summary. ←Baseball Bugs What's up, Doc? carrots→ 04:52, 12 December 2016 (UTC)
 * Stu is correct that currents affect the speed of sound for these change the timing that sound pulses arrive at their destination, but not their pitch or Doppler shift which is simply due to relative motion between source and observer (if we ignore quantities of the second order from the Doppler effect due to their motions relative to the medium). From this source on the speed of sound in water . "Reciprocal Transmission Just as a boat going downstream with the current in a river travels faster than a boat going upstream against the current, a sound pulse moving in the same direction as a current travels faster than one moving against the current. Sound pulses transmitted in opposite directions at the same time (called "reciprocal transmissions") will therefore have different travel times. The pulse traveling with the current will have a shorter travel time than the pulse traveling against the current. The difference between the two travel times can be used to compute the current." With a car, the interior air has been imparted momentum, so the speed of sound relative to the ground is additive, as Stu said, but that has no effect on its speed in the non-moving air further from the vehicle. Obviously, the sound of someone talking inside a supersonic jet is moving faster across the landscape in the direction of the jet than sound in the same direction in the open air near the ground.  --Modocc (talk) 05:21, 12 December 2016 (UTC)


 * Record it (onto a wax cylinder if you don't want to 'cheat' by using digital technology or radio waves) then carry it across the ocean in a supersonic aircraft. Smurrayinchester 09:24, 12 December 2016 (UTC)
 * On a more serious point, this comes down to the difference between group velocity/signal velocity and phase velocity. There are ways to create waves that move faster than the speed of sound, but these waves cannot carry information - or if they do, the actual information travels slower than the speed of sound. A shockwave might travel "faster than sound" from a certain perspective, but you can't convey speech that way. Smurrayinchester 09:42, 12 December 2016 (UTC)
 * The Q related to the human voice, not intelligible speech. The human voice can be represented as velocity or pressure waves in the medium.86.187.169.62 (talk) 19:27, 12 December 2016 (UTC)