Content deleted Content added

Inline

Revision as of 04:43, 29 September 2012

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

Shortcut

WP:RD/S

Want a faster answer?

Main page: Help searching Wikipedia

How can I get my question answered?

Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
Post your question to only one section, providing a short header that gives the topic of your question.
Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
Don't post personal contact information – it will be removed. Any answers will be provided here.
Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
Note:
- We don't answer (and may remove) questions that require medical diagnosis or legal advice.
- We don't answer requests for opinions, predictions or debate.
- We don't do your homework for you, though we'll help you past the stuck point.
- We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

September 24

Black rat taxonomy

Per Special:ArticleFeedbackv5/Black_rat/159109, why does the black rat have the same genus and species, i.e. Rattus rattus?Smallman12q (talk) 01:39, 24 September 2012 (UTC)[reply]

Because that's what Linneus named it. He, and others after him, did that for several type species: Bufo bufo and Gorilla gorilla are other examples. Dominus Vobisdu (talk) 01:47, 24 September 2012 (UTC)[reply]

Also Puffinus puffinus - which confusingly isn't a Puffin. AndyTheGrump (talk) 01:52, 24 September 2012 (UTC)[reply]

One of my favorite species is Gulo gulo. See also

Alces alces Anser anser Axis axis Bison bison Bubo bubo Bufo bufo Buteo buteo Capreolus capreolus Ciconia ciconia Cochlearius cochlearius Crocuta crocuta Dama dama Gallinago gallinago Gazella gazella Genetta genetta Gorilla gorilla Himantopus himantopus Huso huso Hyaena hyaena Iguana iguana Lutra lutra Martes martes Mercenaria mercenaria Meles meles Mephitis mephitis Nasua nasua Nycticorax nycticorax Oingo Boingo Oreotragus oreotragus Papio papio Porphyrio porphyrio Redunca redunca Salamandra salamandra Tadorna tadorna Tyrannus tyrannus Vicugna vicugna Vulpes vulpes

and our articles reduplication and binomial nomenclature--although it does not seem we have info on reduplicated binomials. μηδείς (talk) 03:22, 24 September 2012 (UTC)[reply]

Tyrannus tyrannus? Most disappointing. I was hoping for something much bigger, scalier, and more likely to tear large chunks out of passing herbivores... AndyTheGrump (talk) 03:59, 24 September 2012 (UTC)[reply]

The bird called Tyrannus tyrannus could well be descended from a dinosaur. Maybe it should be called Tyrannosaurus Ex. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:11, 24 September 2012 (UTC)[reply]

It is undoubtedly decended from a dinosaur, see Origin of birds. Also, as birds are therapods (at least by cladistics), they are likely close cousins of T-Rexes, though not likely direct decendents. --Jayron32 04:17, 24 September 2012 (UTC)[reply]

Danny Elfman would like to have a word with you... --Jayron32 03:31, 24 September 2012 (UTC)[reply]

Not interested. Tell him to send over Jenna and then we'll talk. μηδείς (talk) 03:39, 24 September 2012 (UTC)[reply]

There's also the Aha ha. μηδείς (talk) 03:51, 24 September 2012 (UTC)[reply]

And don't forget the Ladybug Ladybug. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:09, 24 September 2012 (UTC)[reply]

Among the cats are Uncia uncia, Caracal caracal, and Lynx lynx μηδείς (talk) 04:31, 24 September 2012 (UTC)[reply]

We've dealt with this on the ref desk before. Relevant WP pages are Tautonym and List of tautonyms. Deor (talk) 09:15, 24 September 2012 (UTC)[reply]

I was wondering why I couldn't find any reduplicated plant names. μηδείς (talk) 16:39, 24 September 2012 (UTC)[reply]

Does Rose is a rose is a rose is a rose count? -- ♬ Jack of Oz ♬ ^{[your turn]} 19:34, 24 September 2012 (UTC)[reply]

Regarding plants: Botanical nomenclature is handled differently, by a different organization, with different naming rules, than animal nomenclature is. See also Nomenclature codes. --Jayron32 19:46, 24 September 2012 (UTC)[reply]

ANTI MICROBIAL CLOTHING

I HAVE SEEN CLOTHES TREATED WITH A "ANTI MICROBIAL" FINISH. WHAT EXACTLY ARE THEY TREATED WITH? AND WHY DOSENT IT WASH OUT?--Wrk678 (talk) 02:31, 24 September 2012 (UTC)[reply]

We actually have it mentioned in our Textile finishes article, but it doesn't really answer your question. Try this link, I don't have time to read it but it looks like it has more information. Vespine (talk) 03:15, 24 September 2012 (UTC)[reply]

(ec) Is this (and this) the stuff you mean? (There are, in theory, an unlimited number of ways to make anti microbial clothing) The link concerns attachment of layers of quaternary polyethylenimine to fabric with ultraviolet light. Wnt (talk) 03:16, 24 September 2012 (UTC)[reply]

hurricane, cyclone & typhoon

In terms simple enough to be understood by a child, please explain the differences between a hurricane, a cyclone and a typhoon. Please limit, if possible, to one paragraph.

Thank you, TLM80209 — Preceding unsigned comment added by TLM80209 (talk • contribs) 03:41, 24 September 2012 (UTC)[reply]

According to Tropical cyclone, they are regional terms used for the same type of storm. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:50, 24 September 2012 (UTC)[reply]

The answer is: They are the exact same weather phenomenon, but we use different names depending on what part of the world it occurs in. If it occurs near the Americas, it's a Hurricane. If it occurs near East Asia, it's a Typhoon. If it occurs near Australia or India, it's a Cyclone. --Jayron32 04:13, 24 September 2012 (UTC)[reply]

However, note that "cyclone" is sometimes misused, in the US, to mean a tornado (see def 3). StuRat (talk) 04:30, 24 September 2012 (UTC)[reply]

Note that cyclone lists tornadoes as a variety; it is quite a general term and includes more than a "synoptic scale" (to quote the article without really understanding it) tropical cyclone. Even so, I don't feel like people in the U.S. have really called tornadoes "cyclones" since The Wizard of Oz (1939 film). Wnt (talk) 18:17, 24 September 2012 (UTC)[reply]

This article contains a reference to that term from a couple of weeks ago.[1] Less common, but still used. It was first coined in reference to a tropical cyclone that hit India in the mid-19th century, and was soon picked up in reference to tornadoes.[2] Both "tornado" (from Latin) and "cyclone" (from Greek) convey the idea of spinning rapidly. This USAToday article from 5 years ago[3] states that the term "cyclone" is still used by the public (sometimes) in reference to a tornado, and that technically a tornado is a type of "cyclone", i.e. rotating cloud. The term used to be much more common. The Hall of Fame pitcher Cy Young always claimed that the "Cy" stood for "Cyclone", not for implying he was a rube. (That was Waddell or Marquard). ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:03, 25 September 2012 (UTC)[reply]

Synoptic scale meteorology deals with large, continent-sized weather trends, contrast with mesoscale meteorology and microscale meteorology. The difference is akin to the distinction between (imperfect analogy): Macroeconomics and microeconomics. --Jayron32 19:42, 24 September 2012 (UTC)[reply]

And to add to the confusion, in the USA a Hurricane force wind warning is issued for strong winds explicitly NOT associated with a tropical cyclone or hurricane. And "hurricane force" is the formal name for the highest wind speeds on the Beaufort scale. HiLo48 (talk) 04:41, 24 September 2012 (UTC)[reply]

A cyclone is a large weather pattern of rotating winds spiraling inward towards an area of low pressure in the center. When the winds become very strong, it is called a tropical cyclone. Americans call them hurricanes, while in Japan they're called typhoons...? I think you might be better off with a website for kids. Ssscienccce (talk) 02:49, 25 September 2012 (UTC)[reply]

As your friendly meteorology student here I would like to clarify that basically while all hurricanes/typhoons are cyclones not all cyclones are hurricanes/typhoons. A cyclone is basically any weather system that is rotating in a cyclonic direction, that is counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere. Mesocyclones, tornadoes, hurricanes/typhoons/tropical cyclones, Extratropical cyclones, and polar lows are all cyclones. The terms hurricane and typhoon refer exclusively to tropical cyclones (which are in come parts of the world known simply as "cyclones". Ks0stm ^{(T•C•G•E)} 20:38, 25 September 2012 (UTC)[reply]

supernova

the article's intro says that most or all of the star's material is expelled, but in most examples nutron stars or black holes are left over after. what am i missing here?165.212.189.187 (talk) 16:14, 24 September 2012 (UTC)[reply]

Most is not a synonym for all. --Jayron32 16:24, 24 September 2012 (UTC)[reply]

That is one good (antonym of bad) observation, thank you. You forgot much is not a synonym for most, or is it?165.212.189.187 (talk) 16:37, 24 September 2012 (UTC)[reply]

Yes, but you never used the word much, so I had no reason to bring that up. --Jayron32 18:45, 24 September 2012 (UTC)[reply]

yes you did: the article says much whereas Op incorrectly replaced it with most, which means Op also missed that, or you both did.GeeBIGS (talk) 03:43, 25 September 2012 (UTC)[reply]

I looked at that source, and I didn't notice anything in it about supernovas that emit all their material. Can you really have a supernova and it doesn't leave anything behind, not even a Genesis planet? ~~I'm thinking, "bad edit".~~ Thanks for your response below! Wnt (talk) 16:46, 24 September 2012 (UTC)[reply]

Type Ia supernova are believed to emit all of their material. They generate more energy than the gravitational binding energy of the star and heat the entire interior, with the implication that the entire star becomes superheated and blows away. Compact objects are not expected to remain after Type Ia supernova. The more common core-collapse supernova (Types II and Ib / Ic) treat the core of the star and it's bulk differently, and generally are expected to leave compact core remnants, i.e. neutron stars / black holes, at the center of the explosion. Dragons flight (talk) 19:11, 24 September 2012 (UTC)[reply]

PS. The cited source does say that the white dwarf in a Type Ia supernova is "completely disrupted", which is essentially the same as noting that all of the material is emitted. Though I would say that the point could be made clearer. Dragons flight (talk) 19:23, 24 September 2012 (UTC)[reply]

"could be made clearer" is probably a completely true statement regarding 99.9999% of our articles on scientific or technical subjects. --Jayron32 19:39, 24 September 2012 (UTC)[reply]

Since we have 4 million articles, and perhaps even 1 million articles on science / technical topics (broadly construed), that leads me to wonder which 1 article do you think is completely clear? ;-) Dragons flight (talk) 21:41, 24 September 2012 (UTC)[reply]

The one on transparency. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:25, 25 September 2012 (UTC)[reply]

I would have thought that no matter how the star broke apart, that there'd always be some spot in the middle which didn't know "which way to go" and would collapse back in for the lack of a bearing. How does the star get around that? Does the stuff simply stay at such superheated temperatures for so long that its gravity can't hold it together? Wnt (talk) 20:08, 24 September 2012 (UTC)[reply]

The star is only held together by its gravity. When most of the mass is lost, there is nothing that keeps the superhot, superdense core together anymore, and it flies apart. --Stephan Schulz (talk) 20:15, 24 September 2012 (UTC)[reply]

Of course, but even a gas giant has enough mass to stay together. I suppose it's a matter of trying to understand how absurdly hot the gases of the exploding star become, and how long it takes them to cool off, and plugging it into some kind of scale height equation? Wnt (talk) 23:25, 24 September 2012 (UTC)[reply]

If the average speed of the gas molecules (which is what we mean by temperature) then enough molecules will have escape velocity that the remaining cloud of gas dissipates. You will get a kind of evaporative cooling, but as gas escapes the gravity reduces and the escape velocity comes down. I'm not sure which affect is faster, but you could certainly get down to a very small amount of gas remaining before it cooled enough to become gravitationally bound (and it wouldn't surprise me if you just end up with complete dissipation). --Tango (talk) 20:23, 25 September 2012 (UTC)[reply]

And add to that the possibility of Gamma-ray burst emission mechanisms#Reverse shocks and the optical flash (the reverse shock being the important part), and Supernova#Asymmetry, and there's a good chance that the minor "cooled" remnant stuck in the middle will be disrupted in the aftermath of the supernova{OR}. Exactly how the disruption works is probably unknown, but it will probably be a phase of decreasing degeneracy followed by a more or less classical expansion driven by the heat at the core. Asymmetry and reverse shock, given their magnitude and the diameter of a hot, non-degenerate target, should be more than enough to disrupt anything that survives both phases. - ¡Ouch! (^{hurt me} / _{more pain}) 08:38, 26 September 2012 (UTC)[reply]

Drawing faster than your own shadow

Lucky Luke is famous for drawing faster than his own shadow. I've come to think, doesn't practically everyone draw faster than their own shadow? I mean, when you move your arm, light moving from the sun (or other similar light source) hasn't yet reached the place where your arm used to be, so the corresponding place in the shadow stays dark. On the other hand, light that previously reached the place where your arm is now is still moving towards the background, so the corresponding place in the shadow is lit. Of course, given that the speed of the light is so great, this happens so fast that the human eye cannot really distinguish between it and instantaneous movement of the shadow. The speed of your movement doesn't matter - for there to be noticeable difference, your shadow should be a great distance away. On the other hand, the event portrayed in the parody comic "Rocky Luke" - drawing slower than one's own shadow - is impossible. Have I got this right? JIP | Talk 18:12, 24 September 2012 (UTC)[reply]

Correct. I suppose a person might try to force some order onto the comedy, if desired, by saying that a slow motion view of the draw should see a noticeable difference in the rate of the draw, i.e., that the person should draw at something on the order of the speed of light (so that say a 1 foot motion to draw is only half completed by the shadow four feet away, making your speed 1/8 light speed). Wnt (talk) 18:21, 24 September 2012 (UTC)[reply]

And note that from the POV of the person drawing, their view of their distant shadow is delayed by the speed of light over twice the intervening distance, as first their shadow must travel that distance, and then the image of their shadow must make the return trip to their eyes. StuRat (talk) 18:45, 24 September 2012 (UTC)[reply]

So actually no one can even theoretically see his/herself as drawing faster than his/her own shadow, but an outside observer could see such a person drawing faster than his/her own shadow? JIP | Talk 18:48, 24 September 2012 (UTC)[reply]

No, that's exactly wrong. A person sees himself drawing slower than his or her shadow as light has to travel twice the distance between himself and his shadow. A person who was situated opposite a person and their shadow (i.e. going light-artist-shadow-observer) would see the shadow draw first, before seeing the person draw, while an observer situated between the two, but off to the side a bit, would see them draw simultaneously. An observer situated behind the artist would see the artist draw first, then the shadow. These three situations are a demonstration of relativity of simultaneity. --Jayron32 19:24, 24 September 2012 (UTC)[reply]

Wait a minute - see the shadow draw first? Simultaneously, I can picture, but how is the light going to the shadow going to outrace the light to the observer, even if you put some slow glass in there somewhere? Wnt (talk) 20:05, 24 September 2012 (UTC)[reply]

The artist-observer-shadow (assuming the shadow falls on a wall or other similar opaque object) is always going to make a triangle, and the relative lengths of the legs of the triangle determine how long the light takes to reach the observer. Insofar as one can construct a triangle where the distance from the shadow to the observer is the shortest of the three legs, there will be many situations where the observer can see the shadow draw first. There are also constructions where one could see them draw simultaneously, or where one could see the artist draw first. --Jayron32 20:19, 24 September 2012 (UTC)[reply]

Ummm, you do remember that the light has to go from the "artist" to the shadow before the shadow does anything at all? One of us is seriously confused at this point... Wnt (talk) 21:59, 24 September 2012 (UTC)[reply]

Indeed - see triangle inequality. The shortest distance between two points is a straight line, so the direct route from artist to observer has to be quicker than going via whatever the shadow is being cast on. --Tango (talk) 20:26, 25 September 2012 (UTC)[reply]

I think, somewhere along the line, someone misinterpreted which sense of the word draw is being used here. Luke is a quick-draw artist, but as far as I know not an "artist" in the sense of creating visual representations. --Trovatore (talk) 20:49, 24 September 2012 (UTC)[reply]

In any event, the above observations are failing to take into account the limitations of the observers; human photosensory capability and visual cognition processing, while seemingly instantaneous to our perception, are in fact many orders bellow the speed the light and as a result, at any distance where a human shadow would be seen by the person generating it, the movements occur simultaneously, to human perception. That is, no human being has the capability to detect the minute difference in time between the movement of the person generating the shadow and the movement of the shadow itself as a result of the upper threshold on the "refresh rate" of the human photosensory package (and if they could, they'd be perceiving light in a very different way from how we experience it). In fact, not only is the human nervous system not capable of parsing data into discreet enough chunks to make this detection, but so is all but our most advanced photonics technology. Of course, I assume when people use the term "observer" above that they are using it in the sense common to the physical sciences -- a theoretical thought experiment construct not constrained by our physical limitations -- but the distinction is still worth making when answer the OP's question. Snow (talk) 22:34, 24 September 2012 (UTC)[reply]

Luke draws his gun faster than his shadow can. If his shadow were to try to get the drop on Luke, Luke would shoot the shadow dead. --Trovatore (talk) 22:39, 24 September 2012 (UTC)[reply]

Maybe not! Since the amount of time between the start of the events is so small and the air between the two shooters is not perfectly uniform, there's every chance that the shadow's bullet will strike Luke first, simply if there was the smallest difference air density anywhere along the trajectory of the bullets (which, when we're looking at things on this scale, there would be). However, both are going to get "hit" if either of them is, since the reaction time between the two actors could not be significant enough to change this outcome, even if the shadow could operate independently. Lucky for Luke (pun totally intended) shadow guns have notoriously bad stopping power. Snow (talk) 22:56, 24 September 2012 (UTC)[reply]

I agree with Wnt that it's not possible to see the shadow first, as the only way for this to happen is if the hypotenuse is longer than the sums of the other two sides of the triangle, which isn't possible. - Akamad (talk) 22:18, 24 September 2012 (UTC)[reply]

The point in the whole faster-than-his-own-shadow thing is that he can shoot before his shadow draws. Here is a famous image: [4] (the bullett hitting before the shadow draws has issues but let's not go there). PrimeHunter (talk) 22:48, 24 September 2012 (UTC)[reply]

If you think that's fast... Cool Papa Bell could turn off the bedroom light and be in bed before the room got dark. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:02, 24 September 2012 (UTC)[reply]

Nay, that's just outrunning electrons. Depending on the inductance of the circuit it's possible any old lady could do it. (Not one that passes the building code though ;) ) Wnt (talk) 23:15, 24 September 2012 (UTC)[reply]

Good point. You can maybe outrun the house current, but you can't outrun the building inspectors. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:24, 25 September 2012 (UTC)[reply]

Doppler effect

Hi all. From wave physics we have that for a source of a frequency f_s moving at speed v_s towards a stationary observer, the observer perceives a frequency f_obs of $f_{obs}={\frac {v}{v-v_{s}}}f_{s}$ . For an observer moving at speed v_obs towards a stationary source of a frequency f_s the observer perceives a frequency f_obs of $f_{obs}={\frac {v+v_{obs}}{v}}f_{s}$ , where unsubscripted v is just the speed of sound. If one is moving away from the other, we can just set either v_obs or v_s negative, and we can combine these two formulas into the general $f_{obs}={\frac {v+v_{obs}}{v-v_{s}}}f_{s}$ . My question is, since motion is relative, why the distinction between a moving source and a moving observer? For example, if an ice cream truck was moving towards a stationary me at a speed of 5 m/s emitting a proper frequency f_s, wouldn't it be the same as me moving at 5 m/s towards a stationary ice cream truck emitting the same frequency? Thanks. 24.92.74.238 (talk) 20:07, 24 September 2012 (UTC)[reply]

Motion is not relative in that scenario. The sound propagates at a constant speed with respect to the atmosphere, which forms an absolute reference frame. Looie496 (talk) 20:17, 24 September 2012 (UTC)[reply]

Note that the "v-v_s" can go to 0, creating an "infinite frequency", i.e. a sonic boom or shock wave not covered by this mathematics when it exceeds the sound barrier. But for the hypothetical observer (who we imagine as having no physical effect on the system himself, like a ghost) the frequency merely doubles when he approaches at the speed of sound. (Question: is it possible to design an instrument boom at the front of a real supersonic aircraft so that it hits undisturbed air from in front of the shock wave and takes recording studio quality sound of the peace and quiet it is about to destroy, for miscellaneous espionage purposes?) Wnt (talk) 23:31, 24 September 2012 (UTC)[reply]

Motion is relative, but the effect depends on the relative speeds of the emitter, receiver and medium, not just the emitter and receiver. -- BenRG (talk) 03:27, 25 September 2012 (UTC)[reply]

September 25

Can DNA be used for data storage ?

More information about using DNA as an data storage for electronics such as PC. Purine and Pyrimidine are used as 0 and 1. — Preceding unsigned comment added by 24.63.135.59 (talk) 00:30, 25 September 2012 (UTC)[reply]

I added a title. StuRat (talk) 00:44, 25 September 2012 (UTC) [reply]

It doesn't seem like a very good choice to me, as writing to and reading from DNA chains isn't very fast. It does store a lot of data in a small space, but there may be a way to store data as individual atoms embedded on the surface of crystals, which would allow for even denser data storage. StuRat (talk) 00:47, 25 September 2012 (UTC)[reply]

How would you read the crystal without breaking it apart? Seems like a form of write-only memory to me... Whoop whoop pull up ^{Bitching Betty | Averted crashes} 00:53, 25 September 2012 (UTC)[reply]

You wouldn't need to break it apart, just bounce some photons off the crystal, and you can tell what atoms are there based on the spectrum reflected back. It would be ROM, which I think is what this Q is about. Using DNA for active memory seems like an even worse idea. StuRat (talk) 01:00, 25 September 2012 (UTC)[reply]

As of last month, thanks to scientists at Harvard Medical School in Boston, the answer is YES. I'm guessing you didn't see this story last month? Vespine (talk) 01:24, 25 September 2012 (UTC)[reply]

Interesting. That's sort of a hybrid of the two ideas, by embedding DNA fragments on small glass chips. Unfortunately, they didn't say how fast it is. StuRat (talk) 02:10, 25 September 2012 (UTC)[reply]

I heard about it on a podcast and they said it's no where near fast enough to use as computer memory at this stage, it would only be useful as archival storage that could be kept for years or decades at a time. Vespine (talk) 03:54, 25 September 2012 (UTC)[reply]

By an amazing coincidence, that's how we use it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:41, 26 September 2012 (UTC)[reply]

endermologie

Shouldn't there be an article about endermologie? Endermologie is very different than liposuction. There's no "digging" involved. I've seen endermologie videos on YouTube. One featured Denise Austin. Another featured Brian Joubert. I have no medical expertise, what-so-ever. But somebody should do an article on endermologie. Who agrees?142.255.103.121 (talk) 08:23, 25 September 2012 (UTC)[reply]

doi:10.1007/s002669900085 might help to answer this question.--Stone (talk) 08:55, 25 September 2012 (UTC)[reply]

Crystalline ceramic vs. salt

How do I distinguish? Which one is chromium hydride? Plasmic Physics (talk) 11:27, 25 September 2012 (UTC)[reply]

Hey for the solid the answer is neither. Chromium hydride is crystalline. It is a metallic hydride conducting electricity and looking somewhat like a metal. The H to Cr ratio is not very fixed showing that there is not a + and - charge that needs to be balanced, so you would not call it a salt. Also it is not a ceramic formed by heating and cooling, and in fact it is destroyed by heat due to loss of hydrogen. Graeme Bartlett (talk) 12:35, 25 September 2012 (UTC)[reply]

What is it then, an alloy? I'm looking for a material science term. Plasmic Physics (talk) 12:57, 25 September 2012 (UTC)[reply]

If there's enough hydrogen in it to affect the material properties, you could call it a hydrogen-embrittled metal. It's an example of a transition metal hydride, though it's not mentioned explicitly in that article.--Wikimedes (talk) 08:43, 26 September 2012 (UTC)[reply]

That sounds very much like an alloy. Plasmic Physics (talk) 09:52, 26 September 2012 (UTC)[reply]

If I compare it with carbon steel. Plasmic Physics (talk) 10:20, 26 September 2012 (UTC)[reply]

(Carbon-embrittled iron). Plasmic Physics (talk) 13:51, 26 September 2012 (UTC)[reply]

According to Inorganic Chemistry by Wiberg, Holleman, and Viberg, p.259, the Cr-H bonds are metallic, so that would make it an alloy. (LiH, on the other hand, is called a saline hydride (i.e. salt) by Cotton and Wilkinson in Advanced Inorganic Chemistry p.206.)--Wikimedes (talk) 07:31, 27 September 2012 (UTC)[reply]

Health effects of Tobacco

In the forementioned article, explicitly defined were several chemical reactions producing compounds both carcino- and mutagenic in nature discovered by medical research. Some of those reactions appear to be considered inconsequential or deliberately omitted for the general purpose of the theme of the essay. This appears to be the gospel according to the temple of the A.M.A. Several tobacco companies (Boo, Hiss) have been raked over the coals for the modifications in the additive qualities of cigarettes and was deemed adulteration. What I do not see within the article is the effects upon the chemical reactions when an oxidizer is made to be introduced into the manufacture process (an Adulteration). In the state of Oklahoma, under state statute euphamistically defined as Fire Safety Code, Chapter 40, though I am unaware as to what extent such legislation has expanded throughout the Union at this time, every cigarette sold within this state is required to be so treated by law. Under Chapter 40, the Oklahoma Fire Marshal is required to receive and accept performance data as to cigarette combustion and certify said results prior to affording tax stamps. One such requirement, I am given to understand, is self snuffing or extinguishment obtained through an oxididzer to alter combustion characteristics. Specifically, an oxidizing compound, when ignited, produces a controlled thermal range so that the original composite compounds burn at differing rates designed to produce excess residual tars, in concentration. Thereby, having accumulated sufficient residue, produces extinguishment. In the text which I have examined, carefully withheld is what exactly is the oxidizing chemical or compound used in the adulteration? Does the administration of the chemical or compound alter the composition with the introduction of the energy source (combustion) to produce reactions which are not disclosed in the article? Can those reactions create a greater toxic effect than the orginal Tobacco or in greater concentration? In a nation known for having performed unconsented human experimentation, both federal and state entities have negated the individuals' right of consent. Having been made a scapegoat, who is next, besides the overweight? — Preceding unsigned comment added by 98.160.104.90 (talk) 17:06, 25 September 2012 (UTC)[reply]

Wouldn't adding an oxidizer just make the fire burn hotter and faster, the exact opposite of any proposed self-extinguishing capability? Rmhermen (talk) 17:13, 25 September 2012 (UTC)[reply]

You may be interested in our article Fire safe cigarette. I don't know if it fully addresses your question, but it does mention possible health impacts. It does not seem from a casual reading of the article that these cigarettes work the way you describe. I agree with Rmhermen that it is not likely that they make fire-safe cigarettes by adding an oxidizer. Rather, it looks like these cigarettes are designed to reduce oxygen availability to the burning material.--Srleffler (talk) 17:40, 25 September 2012 (UTC)[reply]

According to Phillip Morris, they don't use any materials in their fire-standards compliant cigarettes that were not used in the earlier non-compliant ones.[5]--Srleffler (talk) 17:45, 25 September 2012 (UTC)[reply]

Personally, I can't help but think that the tobacco companies, despite their many lethal sins, were treated wrongly in FDA v. Brown & Williamson Tobacco Corp. The idea of Y1 (tobacco) was to provide twice the nicotine in the same amount of tobacco with the same amount of tar. The FDA portrayed this as "manipulating tobacco to be more addictive". But I don't see why this can't equally well be seen as being 50% of the way toward switching the addicts over to an "electronic cigarette". It would seem like they could get the same fix with half the cancer risk (though nicotine still kills by heart disease). It is ironic that after so many decades of lying and misleading and killing people, when one tobacco company tries on a lark to do a good deed, that is what gets them all punished. Wnt (talk) 23:53, 25 September 2012 (UTC)[reply]
- If you want to reduce the cancer risk, it would be better to require the tobacco companies to reduce the level of nicotine in cigarettes, phasing it out over the course of a year or two from current levels to zero. Anyone who wants to continue smoking would be free to do so, but no one would be addicted.--Srleffler (talk) 16:44, 26 September 2012 (UTC)[reply]

Prohibition never works. Near beer never really caught on. If your scheme were implemented, people would hoard the powerful cigarettes, sell them at an increasing premium as the others became weaker, and eventually transition to a full black market as with other drugs. While cigarettes are obviously not a healthy solution, we have yet to experience the horrors of people warring over black market nicotine used by intravenous injection. Wnt (talk) 15:34, 27 September 2012 (UTC)[reply]

baking soda would have an extinguishing effect by producing CO₂ when heated. Sometimes used in home-made smoke bombs to slow combustion, or in slow fuses. But the problem is more the oxidizer added to the paper to keep it burning. Hand rolled cigarettes using thin untreated paper go out unless you take a puff once or twice a minute. Ssscienccce (talk) 08:18, 26 September 2012 (UTC)[reply]

Leaf growth and development

There's a tree outside my house in New Jersey and the leaves are lobed. But I noticed what appeared to be full grown leaves on the tree that are not lobed, suggesting that the leaves are not formed already lobed but rather become lobed after reaching a certain size. But then I noticed very small leaves that are already lobed -- they appear as miniature forms of the large lobed leaves. So do lobes form before, after, or both and it depends on which tree we're talking about? DRosenbach ^{(Talk | Contribs)} 17:30, 25 September 2012 (UTC)[reply]

What kind of tree is it? --Jayron32 17:44, 25 September 2012 (UTC)[reply]

I can't tell. DRosenbach ^{(Talk | Contribs)} 18:00, 25 September 2012 (UTC)[reply]

Could you take some pictures of the tree and of its leaves so maybe someone here could help? --Jayron32 18:15, 25 September 2012 (UTC)[reply]

There are many different types of variations in leaves over time and at different parts of a plant. Juvenile leaves are often different from mature leaves. In NJ, the young leaves of the Sassafras will have a single lobe, while leaves grown as the plant ages will look like mittens or have three or more lobes. The lowest leaves on holly trees have the most spines, while those at the top of a tree may even lack them. Cannabis leaves first develop with single leaflets, then leaves with three, five, seven, and more leaflets. We need to have a picture for a better explanation. μηδείς (talk) 19:14, 25 September 2012 (UTC)[reply]

To be fair, a cannabis "tree" would have likely caught the attention of someone of authority. --Jayron32 19:19, 25 September 2012 (UTC)[reply]

The green bark on young growth of a sassafras tree has a distinctive appearance and quite pleasant and allegedly carcinogenic flavor, so you should be able to tell us if that is the one you are interested in. Wnt (talk) 23:56, 25 September 2012 (UTC)[reply]

So, are we waiting for the OP to come back and say, yes, the bark tastes pleasantly carcinogenic? Hehehe. μηδείς (talk) 02:28, 26 September 2012 (UTC)[reply]

I'm not above nibbling on a bit of it myself in the woods - my feeling is that the allegation is probably overblown based on fear of what would happen if it were mass-produced as an artificial sweetener, or even due to its usefulness in producing MDMA. I see sassafras oil actually goes over this pretty well. Wnt (talk) 16:39, 26 September 2012 (UTC)[reply]

Another possibility is that you have two or more trees grown together, and you are looking at leaves from different species. StuRat (talk) 20:34, 25 September 2012 (UTC)[reply]

Besides the sassafras, another common tree (weed, really, in my part of the world) that has both lobed and unlobed leaves is the paper mulberry. I agree with Jayron and Medeis that we'd probably need to see a picture to identify your tree; but as far as I know, individual leaves don't "become" lobed—they're either lobed or unlobed from the beginning. Deor (talk) 00:32, 26 September 2012 (UTC)[reply]

Yes, we've got them all over and they leaves are a bit more varied in form than you can tell from the pictures in the article. μηδείς (talk) 02:30, 26 September 2012 (UTC)[reply]

I would hope it was clear I was giving examples of plants with different leaf growth forms, not suggesting those three were the OP's most likely candidates. I guess it wasn't. μηδείς (talk) 01:07, 26 September 2012 (UTC)[reply]

OP Here -- sorry about the delay but I didn't realize this would generate so much conjecture so soon and yesterday was YK and I couldn't get on. I've added a photo for identification and included my fingers in two shots to give you a sense of dimension. As you can see, there are small leaves with lobes and large ones without lobes, although most of the large ones are similar to the small one in that they have lobes. DRosenbach ^{(Talk | Contribs)} 14:52, 27 September 2012 (UTC)[reply]

Looking at your pics, I'm gonna venture it is a White Mulberry. I used the tree identification guide at arborday.org which is very useful for these purposes. See Morus alba for that specific species. --Jayron32 15:03, 27 September 2012 (UTC)[reply]

Interesting -- after reading the article, it seems that there's some variation in the leaves, and I now suppose that this variation occurs not only between trees but also among the leaves of a single tree. Thanx! DRosenbach ^{(Talk | Contribs)} 18:29, 27 September 2012 (UTC)[reply]

Unidentified spiders from Brazil

I am unsure concerning the identification of these two spiders from Mato Grosso, Brazil.
The left one might be Lasiodora klugi or another Lasiodora species.
The one on the right sitting on the wall was approx. 8 cm big. It belongs to the Sparassidae family. It might be Polybetes sp., but this is only a guess. --Leyo 21:22, 25 September 2012 (UTC)[reply]

By what factor can a nose get desensitied to a smell?

Even if it's something that's not a physical irritant such as chlorine shouldn't there be a limit to how much you can get used to it? Can you "get used to it" without conscious perception if it increases slowly enough? How long does it take to go back to the "maximum gain setting"? A genie once took a man into his lamp. He held his nose and said "How could you could live with this smell?" The genie said "Oh, you don't even notice it after a few hundred years." 96.246.70.87 (talk) 21:23, 25 September 2012 (UTC)[reply]

I once drove through Colorado, and reserved rooms ahead of time. I chose a hotel in Sterling, Colorado, because, for some reason, their rates were half all the other places. When I got there I discovered the reason, a huge cattle feed lot made the entire town smell like manure. I asked if it always smells like that, and they said "Smells like what ?". They weren't joking, apparently. StuRat (talk) 21:51, 25 September 2012 (UTC) [reply]

See sensory adaptation and olfactory fatigue. I can also tell you that having nasal polyps removed may result in a significant clinical loss of the sense of smell. μηδείς (talk) 22:32, 25 September 2012 (UTC)[reply]

It's an essential property of the olfactory system. If the olfactory system didn't adapt, you would never smell anything except the inside of your own nose. Looie496 (talk) 02:19, 26 September 2012 (UTC)[reply]

On occasion one does, with certain infections, smell one's throat or sinuses. μηδείς (talk) 02:25, 26 September 2012 (UTC)[reply]

...usually right before hacking up something green. StuRat (talk) 04:56, 26 September 2012 (UTC) [reply]

Charming. Don't you know it's rude to talk about that sorta stuff while people are eating their dinner? -- ♬ Jack of Oz ♬ ^{[your turn]} 07:48, 26 September 2012 (UTC) [reply]

Well thanks right back at you, now that I know I have to imagine you eating as you type your responses here. μηδείς (talk) 16:31, 26 September 2012 (UTC)[reply]

I drink lustily to your enjoyment of such imaginings. In fact, I think I'll have two extra turkeys in honour of this wonderful occasion. In some parts I'm known as La Plus Grande Bouffe, not without good reason. Nine years of Wikipedia and other sundry activities just have to be fitted in between gorgefuls as best I can. What a try-hard that Mr Creosote was. -- Jack of Oz (Talk) 09:48, 27 September 2012 (UTC) [reply]

Children and sugar

Most kids get all hyper after eating lots of sugar, while most adults do not. Why the difference ? StuRat (talk) 23:20, 25 September 2012 (UTC)[reply]

The idea that sucrose is a stimulant is a common myth, but it's still a myth. It provides food energy rather efficiently, but in and of itself does not cause hyperactivity or result in any other stimulant-like effects. See Sugar#Health effects. Evanh2008 ^{(talk|contribs)} 23:28, 25 September 2012 (UTC)[reply]

I think it is still unclear what the role of sugar is - see [6]. Oddly, the notion seems to be that sugar causes hyperactivity by causing hypoglycemia, leading to an adrenaline response when the food is too little to match the amount of insulin solicited by it. Now, two things I don't see mentioned there, which I'll just put out for discussion (not an answer): first, for diabetics, there is largely a lack of distinction between sugar and other carbohydrates, and so I have to wonder whether studies could show sugar to be "harmless" by comparison to other carbs. And second, given how many adults in modern times verge into prediabetes if not full blown type II diabetes - it seems possible that as the pancreas' response weakens, the adrenaline response no longer occurs, and so by that model the "hyper" reaction should end. Wnt (talk) 23:43, 25 September 2012 (UTC)[reply]

I only heard about it through American tv-series (Simpsons most likely). As far as I know, at least in Flanders (no pun intended) the concept was unknown. Ssscienccce (talk) 07:28, 26 September 2012 (UTC)[reply]

Have to agree with Ssscienccce that I don't think this is universal. While the idea apparently has some currency in NZ [7] [8], the more common claim (which may not be totally a myth) is that artificial colourings cause hyperactivity. As for sugar, as this says [9] the link is controversial at best, Hyperactivity notes the majority of studies show no linkage between sugar and hyperactivity. Nil Einne (talk) 08:01, 26 September 2012 (UTC)[reply]

By "hyper", I don't mean that it causes permanent hyperactivity, I just mean a temporary increase in activity level. StuRat (talk) 08:13, 26 September 2012 (UTC)[reply]

Maybe the excitement of getting candy or the transition from one activity to another may have an effect? Children could be more active the first few minutes of any activity. Comparing their behaviour when they've been playing (or sitting in class) for an hour with the behaviour when they go back to playing (or class) may show a difference that isn't caused by sugar alone. Ssscienccce (talk) 08:40, 26 September 2012 (UTC)[reply]

Who's talking about permanent hyperactivity? Nil Einne (talk) 10:24, 26 September 2012 (UTC)[reply]

When you used the term "hyperactivity", that has that connotation, to me, of someone who is often hyper. The shortened form, "hyper", to me, means just one instance. StuRat (talk) 21:05, 26 September 2012 (UTC)[reply]

There is a reason I provided links.... Nil Einne (talk) 08:22, 27 September 2012 (UTC)[reply]

The studies I've heard about (I don't know what they are, so I couldn't provide sources) claim that children behaved differently because the responsible adults subconsciously treated them differently after they ate sugary foods (because of their belief that the sugar caused hyperactivity). The reason this doesn't happen to adults is because they aren't being given sugar by an authority figure. 146.87.16.182 (talk) 09:03, 26 September 2012 (UTC)[reply]

By googling "sugar rush" I found this site, which contains an experiment aimed at demonstrating a sugar rush. Make of it what you will. --TammyMoet (talk) 09:21, 26 September 2012 (UTC)[reply]

Eiyeiyei, that page is an example of how not to think about biology. Red food coloring is not blood, food is not digested in the blood, so... the rate at which food dissolves in water, without digestive enzymes present, has very little to do with the rate that nutrients eventually enter the bloodstream. And so in practice the difference between sugar and carbohydrate on blood glucose levels is not very much. Wnt (talk) 14:08, 26 September 2012 (UTC)[reply]

This page says; " In 1995 the Journal of the American Medical Association published a review of 23 comparatively rigorous studies conducted between 1982 and 1994... The results? No discernible relationship between sugar ingested and how the kids acted. It didn't matter how old they were, how much sugar they got, what their diets were like otherwise — nothing." Perhaps someone could find the original article - must dash now! Alansplodge (talk) 09:58, 26 September 2012 (UTC)[reply]

Here's the study: [10]. This is certainly persuasive, yet apparently it was not enough to close the issue. I should note that I am impressed that the control for all studies chosen was an artificial sweetener, not merely another food source. I haven't read the full study, but I should just mention that meta-analysis tends to be viewed with some skepticism, as it is not typically done unless there are some studies already published which have drawn the opposite conclusion. Nonetheless, their conclusions make sense - first, that the effects of sugar could be due more often to the expectation of parents, whose ways of controlling the kids are apparently not perfect. And second, their caveat that there could be a fraction of children who do become hyperactive in response to sugar, just not the majority. We know that the metabolic response to sugar is not perfectly regulated - some people become hypoglycemic, some become hyperglycemic, for example. It's not just that biology is imperfect - there's no perfect answer in the first place. Under varying circumstances over the course of evolution it may make sense to be sedate or hyperactive after eating, and I think the species will be equipped with a range of genetic responses. Wnt (talk) 14:21, 26 September 2012 (UTC)[reply]

I know that diabetics are advised, along with taking insulin, to exercise to burn off high blood sugar. So, yes, if children's systems aren't able to bring the BS level under control internally, then exercising to burn it off would be one way to prevent organ damage. So, that trait might very well have evolved, although I don't see why it would be limited to children. StuRat (talk) 21:11, 26 September 2012 (UTC)[reply]

Strangely, in my 1960s childhood, nobody ever suggested that eating lots of sugar made you behave badly, even though sugar was widely available. Alansplodge (talk) 00:21, 27 September 2012 (UTC)[reply]

I can think of at least 3 reasons

Children are smaller than adults, so one can of a sugary drink will affect them more.
Most sugary drinks are also caffinated, and its the caffeine that is causing the effect. Children tend to have a lower tolerance to caffeine that adults, through less habituation.
Adults have better self-control than children, so even if they are feeling equally hyper, adults will show it less.

Of course, these are sweeping generalisations, and could be wrong; I'm just putting them up for discussion. CS Miller (talk) 21:42, 27 September 2012 (UTC)[reply]

Nil Einne and Alansplodge have provided well-sourced answers. Speculating based on loose associations does not add to reliable sources cited by them. -- Scray (talk) 16:11, 29 September 2012 (UTC)[reply]

September 26

Space and radiative cooling

Assuming a distance of 1 AU, how fast (in terms of Kelvin per second) would a human cool when they are exposed to the vacuum of space, both in sunlight, and in shadow? This is not a homework question, just curiosity. Plasmic Physics (talk) 02:47, 26 September 2012 (UTC)[reply]

I assume you mean 1 AU from the Sun. The sunlight case is complicated. If they aren't rotating relative to the Sun, the side facing the Sun may actually get hotter, while the side away from the Sun freezes. Human bodies are fairly good insulators, especially after they die and their circulatory system stops. StuRat (talk) 02:57, 26 September 2012 (UTC)[reply]

I should then specify that heating/cooling takes place in an unpolarised fashion, and that the person remains alive. Plasmic Physics (talk) 03:06, 26 September 2012 (UTC)[reply]

Any object subject to purely radiative cooling can be approximated as a "black body", and thus obeys the various laws regarding black body radiation. I think you can derive cooling rates from the Stefan–Boltzmann law, which relates the "emissive power" (power is rate of work, so should be related to how quickly energy is emitted) of a black body to the fourth power of its absolute temperature. This may not be the exact right law, but one of those, or a related one, should have the right answer. That should cover the "cooling in shadow" event. As with every physics article at Wikipedia, there's very little here in terms of making it accessable to the non-expert. --Jayron32 03:12, 26 September 2012 (UTC)[reply]

See also Black-body_radiation#Temperature_relation_between_a_planet_and_its_star, since a human floating in space around the sun is just a really small planet, that should give good info. So, betweem the Stefan-Boltzmann law and the information on the planet-sun temperature relationship, one should be able to derive both scenarios (shadow and in sunlight) --Jayron32 03:16, 26 September 2012 (UTC)[reply]

Using the approximation Jayron suggested, calculating the radiative power of a human body for a given skin temperature is relatively easy, but it would be harder to calculate the time-evolution of energy loss from the body as a whole, because of the insulating effects Stu mentions. That is, the skin might get cool very quickly, greatly slowing radiative heat transfer, while leaving the inside of the body quite warm. There is substantial research in the forensic sciences on how the core body temperature evolves after death (useful in estimating how long a person has been dead), but I don't how easy it would be to apply that knowledge to this situation (perhaps there will be substantial research on it in the future, when dumping bodies into space becomes a common way to dispose of, or create, murder victims). Someguy1221 (talk) 03:28, 26 September 2012 (UTC)[reply]

Couldn't internal heat-transfer relationships within the body be approximated via Newton's law of cooling? --Jayron32 03:56, 26 September 2012 (UTC)[reply]

Live humans are quite good at internally conducting heat, due to blood circulation. If Stu or anyone else doubts this, try the following: Go into a reasonably large cold room, say about 12 to 16 C, without any clothes on. Place a 1200W electric bar heater about 500 mm from your feet, while you sit on something, so that almost all the radiated heat that falls on you falls on your legs. If you are like me, the skin on you legs will get quite noticebly hot, but not such that your skin will be harmed or even uncomfortable. What is important, is after 15 to 20 minutes or so, you'll be hot and sweaty all over, even though most of your skin is exposed to 12 to 16 C, normally low enough to produce shivering. (I'm accustomed to a mediteranian climate).

But what complicates the calculation the OP wants is that the body has the ability to reduce blood flow to the skin to very high and very low levels as required for core temperature regulation, and sweating will be turned on if core temperature cannot be controlled by only adjusting blood flow - same with shivering if you are too cold. It does appear that the body does not have the ability to adjust blood flow and sweating to selective areas if part of you is exposed to cold and part of you to hot. However, if skin does get very hot, an inflamation reaction will result, increasing blood flow locally.

Ratbone58.169.235.242 (talk) 04:53, 26 September 2012 (UTC)[reply]

Assuming black-body radiation, no sunlight, surface area of 1.9 m² for a man, dQ/dt=1.9*5.67 10^-8* T⁴ (ignoring background radiation; starting off at 37°C, heat loss would be at 995 Watt. But actual skin temperature and such would give different results. At 0°C skin temperature, loss would be 600W. For a 70kg body, equivalent heat capacity of 70% water, that would take 340 seconds to drop the mean body temp with 1°, assuming he's dead. More accurate calculations that include metabolism, insulation .. would be much work (would still be not very realistic anyway, without oxygen supply, embolism due to air bubbles killing him...) Ssscienccce (talk) 07:15, 26 September 2012 (UTC)[reply]

In sunlight, it would depend on the total surface area as seen from the sun (the area of the shadow he would cast if there was a plane perpendicular to the rays right behind him), logically that must be less than half of the total surface area (and I just realize that in the calculation above, 1.9 surface area would imply arms, legs, fingers, toes and even but cheeks outstretched, wide apart so they don't block/reabsorb the heat... so these numbers should be lowered a bit. Anyway, the solar constant is about 1.360 kW/m², so multiply with the surface area perpendicular to the rays and subtract from the heat loss to get net loss. Cooling would stop once equilibrium was reached. the figures of -18.8° to 1.3°C depending on albedo from the section Jayron32 linked to would be reasonable for our man in space i guess. Ssscienccce (talk) 18:52, 27 September 2012 (UTC)[reply]

Tuition returns on net present value of tax revenue

On the two graphs in Figure 2 on page 43 of this report we see the relative lifetime earnings of women and men who have attained five different categories representing various levels of education. I would like to use this data, along with college tuition costs, attrition rates and the like, to derive the net present value of government tuition subsidies on changes in future taxpayer revenue. I.e., I would like to know, for every $1 spent subsidizing college tuition, how many dollars in present value terms a government can expect to collect in additional tax revenue over the life of the taxpayer on whom the tuition subsidy is spent. What other information would I need to calculate this? What formulas do I need to use as a function of the variables involved? I haven't really ever done something this ambitious in math before, but I'm determined to stick with it until I get a valid answer. —Cupco 13:39, 26 September 2012 (UTC)[reply]

Calculating NPV can be as simple or as complex as you like and depending on circumstances. But as the graph plots earnings as a ratio to "ecomomy wide average", a lot of the work is already done for you. You can get a meaningfull NPV figure in your case by just suming the earnings ratios for each year. The basic priciple of NPV is that a dollar in the hand now is worth more than a dollar in the hand later, if the earning capacity of money exceeds the inflation rate. Normally, in calculating NPV, you scale the cash flow in each year upward for each year you need to come back to the present year. For example, if inflation is 3% per year, a dollar one year from now is the same as $0.97 now; a dollar 10 years from now is the same as 0.97^(10-1) = $0.76 now. Inflation is automatically accounted for in your case as it is built into the "ecomony wide average". In business, you would factor in a "cost of money" - this can be a borrowing/lending interest rate (as if you have a dollar now, you could lend it out and get interest, hopefully above inflation), or an opportunity cost - if you spend a dollar on x, then you can't spend it on y, z, etc, each of which will have some rate of return. Eg if we assume interest rate is 3%, a dollar 10 years from now is equivalent to 1.03^(10-1) = $1.31 now. Inflation brings NPV down, interest rates and opportunity cost increase it.

To sum up, to calculate NPV, you need to assume a value (different for each year if deemed appropriate) of inflation, and a value for the "cost of money" (interest or opportunity), again different for each year. You should see from this that in the conext of your specific question, there may be no one right answer, so just go with the simple solution above.

I usually, rather than use smart looking math formulae, just set up a simple spreadsheet with one column for each year for cash flow, and another set of colums ofr the NPV of each year. In most business planning, you don't know exact future inflation rates and costs of money, likewise you can only estimate cash flows as between a low and high value, with a typical or design centre value, and they all vary form year to year. So what you do is set up Lo, Med, and Hi cash flow columns. This is a very powerfull technique that can do what "smart" formulae cannot do.

Wickwack58.169.235.242 (talk) 15:02, 26 September 2012 (UTC)[reply]

There are many (im?)ponderables here. What will the country's emigration rate be? Will you train all these people and then they just leave when they're hired up for huge sums by the Eurekavilles that spring up after the Syrian Renaissance? But the first problem is that you're starting with a personal statistic and trying to get a national statistic. When that college graduate gets the good job and makes $1 million more, is there some lesser college graduate or dropout who is losing it and losing the equivalent amount? Wnt (talk) 15:36, 26 September 2012 (UTC)[reply]

Good points. I've got to assume no emigration which may or may not be unrealistic. The extent to which people taking advantage of subsidized education stay where they went to college seems to change over time, but it's not too unreasonable to assume that it will even out in the long run. I'm not trying to get any national statistics, just the change in taxable earnings for each individual. I need to think more about the displacement issue you raise; there is evidence that economic achievement isn't zero sum, but I'm not sure how convincing those arguments are. —Cupco 15:42, 27 September 2012 (UTC)[reply]

I also think that this is one of many topics where data aggregation obscures what is happening, rather than providing noise suppression via statistical averaging. Consider my territory - Western Australia: Due to having an ecomomy largely based on mining, coupled with a stupid government policy (govt since voted out) of encouraging university courses that have high female enrolment and discouraging courses with high male enrolment, graduating in engineering leads to high salaries thru supply and demand. However, sofware engineers don't do so well. Graduating as a nurse or schoolteacher affords you a low salary, lower than many tradesmen. However, in England, which historically has had an industrial focus and good universities, but now has little mining or industry, engineers don't get paid much at all. Also, consider medicine: The personal income of doctors is good but not that good (they have large overheads for receptionistes, nurses, offices, and equipment), but (in my country anyway) they spend up to 13 years at Uni and the courses are expensive to run. So the return on investment on a personal basis may be quite low. I've never met a specialist/consultant that didn't enjoy what they do though. I have a cousin who has a Masters level qualification in music and she's very talented. Her CD's have sold well, and she gets played on radio stations. But, she'd probably be just as well off without any qualifications at all. Talent is talent. On an NPV basis, her Uni course is probably very negative. Now, how much is job satisfaction worth? Wickwack121.221.26.222 (talk) 23:44, 27 September 2012 (UTC)[reply]

It's true that there is a large variation among professions, but I also want to assume that those average out to the population means over the long run. In the 1980s there was a huge glut of M.D.s in the U.S., but now there's a terrible shortage. At least it is equalizing general practitioner salaries with those of specialists, somewhat. But the data in the report linked above doesn't even consider the postgraduate professions. There's a 40% salary premium from high school dropout to college grad, and that has to mean a lot in present value for taxpayers to subsidize it. I took your advice about doing a spreadsheet, by the way. An analytic solution isn't possible because the curves are arbitrary. —Cupco 01:54, 28 September 2012 (UTC)[reply]

delayed capsaicinoid pungency

Some chilli peppers produce an immediate burning sensation when eaten, others produce a delayed and slowly increasing burn which continues to increase after consumption stops. Has any work been done to link the type of pungency with specific capsaicinoids? — Preceding unsigned comment added by 86.178.131.43 (talk) 14:39, 26 September 2012 (UTC)[reply]

That's going to be determined by three factors: (a) the concentration of the chemical; (b) the binding affinity of the chemical to capsaicin receptors; (c) the rate of clearance of the chemical from the area. If you have a high concentration, low binding affinity, and high rate of clearance, you get an effect that hits fast and doesn't last long. If you have a low concentration, high binding affinity, and low rate of clearance, you get an effect that builds gradually and lasts a long time. Our receptor (biochemistry) article contains additional information. Looie496 (talk) 15:51, 26 September 2012 (UTC)[reply]

Thank you, that clarifies the mechanism. But I believe that some capsaicinoids with a low degree of pungency are hydrolysed by the enzymes in saliva into a more active form, thus giving a delayed effect. I can, however, find no verification for this hypothesis.86.178.131.43 (talk) 21:09, 26 September 2012 (UTC)[reply]

You might also look into how the chilies are dried/cooked/prepared, as th eir preparation in oil or water and so forth will affect how they are presented to the taste buds. μηδείς (talk) 20:30, 26 September 2012 (UTC)[reply]

True, but some chillies seem to exhibit a delayed pungency regardless. 86.178.131.43 (talk) 21:14, 26 September 2012 (UTC)[reply]

Let me acknowledge that as you quite rightly point out, my answer only gave a set of basic factors that apply in all situations -- there are other factors such as chemical transformations, buffering, penetration through barriers, etc., that can affect the timing in particular situations. Looie496 (talk) 23:12, 26 September 2012 (UTC)[reply]

Thank you, your answers have been very helpful. I now have a much clearer understanding of the factors involved.86.178.131.43 (talk) 17:47, 27 September 2012 (UTC)[reply]

I don't feel like we gave a decent answer here, but it's a hard one to research. It would be easier if you could name one or more specific varieties of chili peppers that have this effect; then you or I could go to www.ncbi.nlm.nih.gov and see what we could come up with about their chemical constituents, then see what is known about the metabolism and receptor activity of each of those constituents. Wnt (talk) 21:46, 28 September 2012 (UTC)[reply]

Male pattern baldness

Hello. What type of doctor would be the best specialist to see concerning male pattern baldness? In other words, what type of doctor specializes in that field? Thanks! 64.252.1.35 (talk) 16:03, 26 September 2012 (UTC)[reply]

The branch of medicine that deals with the scientific study of the health of hair and scalp is called trichology. Gandalf61 (talk) 16:06, 26 September 2012 (UTC)[reply]

Thanks. I will read that page more thoroughly, as I only scanned it quickly just now. But, I am asking what specialization of medical doctors would one visit for this matter? A dermatologist? A urologist? Something else? I never heard of a doctor that goes by the title of "trichologist". Or are there such, out there? Thanks! 64.252.1.35 (talk) 16:15, 26 September 2012 (UTC)[reply]

Here is one such in the UK. You certainly wouldn't visit a urologist for male pattern baldness! --TammyMoet (talk) 16:32, 26 September 2012 (UTC)[reply]

Thanks. But Kingsley is not a medical doctor (from my reading of his website biography). A urologist specializes in the male reproductive system (e.g., hormones, testosterone levels, etc.) ... it's not such a stretch that he would/could deal with related hormonal issues (baldness, etc.). Thanks. 64.252.1.35 (talk) 16:50, 26 September 2012 (UTC)[reply]

Just a correction - a urologist specializes only in the urinary system (of males and females), so is concerned with the testes only to the extent that they are a peripheral part of the urinary system. One who deals with hormone levels (including the reproductive system, again of both males and females) is an endocrinologist. 24.92.74.238 (talk) 00:27, 27 September 2012 (UTC)[reply]

Yet when a man is forced through micturitic urgency to take a leak down an alley or beside a parked car, thinking and hoping nobody will see him, but he gets sprung by a passing police officer, he'll be accused of exposing not his urinary machinery but his sexual organs, when sex was absolutely thelast thing on his mind at that moment and all he cared about was relieving his bursting bladder. -- Jack of Oz (Talk) 09:26, 27 September 2012 (UTC)[reply]

Actually, shouldn't you just see your primary care physician for that? If you need a specialist, I would try a dermatologist. Their specialty does include care of the scalp and hair growth.--Srleffler (talk) 16:55, 26 September 2012 (UTC)[reply]

Since baldness is not a life-threatening condition, many nations allow non-doctors to treat it. The non-doctors would typically be cheaper, and insurance may not cover hair replacement, making a doctor too expensive for most people. Therefore, you may find very few actual doctors practicing in that field. StuRat (talk) 20:59, 26 September 2012 (UTC)[reply]

I don't believe there is an effective non-medical treatment for male pattern baldness. Going the route primary care physician > dermatologist OR plastic surgeon (for hair transplant) is probably the standard procedure. OsmanRF34 (talk) 15:00, 27 September 2012 (UTC)[reply]

I wouldn't call them "non-medical", but non-surgical options like finasteride and minoxidil are effective for some. StuRat (talk) 02:46, 28 September 2012 (UTC)[reply]

What causes these lines on paper birch leaves?

See:

Is this a worm? A larva? Something else?

What causes these lines on the paper birch leaves? These were in the South Chilcotin Mountains Park, in British Columbia, Canada.

Edit: This was probably trembling aspen, not paper birch.

66.183.102.159 (talk) 18:55, 26 September 2012 (UTC)[reply]

It's a larva, of the Birch Leafminer. See this pic: [[11]]. Dominus Vobisdu (talk) 19:10, 26 September 2012 (UTC)[reply]

I thought this, too, but why do all the leaves seem to only have a single trail? From Birch leafminer: "A single leaf can contain as many as 40 larvae whose mines may merge to destroy the total photosynthetic area of the leaf." Also, images from Google image search for birch leafminer damage look different. The second picture on the page you link to matches what I saw, though. 66.183.102.159 (talk) 19:12, 26 September 2012 (UTC)[reply]

And I'm seeing talk of kidney-shaped mine damage from leafminers & am as confused. --Tagishsimon (talk) 19:16, 26 September 2012 (UTC)[reply]

After a bit more searching, it looks more like the common aspen leaf miner. Perhaps I had the tree species wrong. 66.183.102.159 (talk) 19:18, 26 September 2012 (UTC)[reply]

Leafminers are not a single taxonomic group. That name refers to any insect whose larvae, well, mine leaves. They could be flies, beetles, butterfilies or wasps.

Common names don't really have any scienctific significance, and there are probably several different unrelated insect species that go under the name "Birch Leafminer". Each species has its own characteristic burrowing pattern, some, such as the one in question here, has what is called a "serpentine" pattern. Others have spindle-shaped or kidney-shaped patterns, etc.

My guess is that the culprit in question here is a species of Liriomyza. Your guess about Phyllocnistis is another possibility, and ther are undoubtedly other possibilities as well. Without examining the insect in question, though, it's impossible to tell. Dominus Vobisdu (talk) 19:41, 26 September 2012 (UTC)[reply]

Also, some leafmining insects are fastidious, meaning that they strongly prefer only one species or taxon of plant as their host. Others are more catholic in their choice of host. Dominus Vobisdu (talk) 20:31, 26 September 2012 (UTC)[reply]

At a molecular level

I've been informed in an advert that Esso fuel works at a molecular level. Wouldn't that be true of all fuels? Do they think the public are really stupid? Or am I stupid and missing something obvious? Itsmejudith (talk) 19:49, 26 September 2012 (UTC)[reply]

HAHAHAHAHAHAHaHaHaHaHaHahahahaha! Yes. See combustion and combustion engine. μηδείς (talk) 20:26, 26 September 2012 (UTC)[reply]

Slight correction - they know the public are really stupid. Adverts like that really depress me because marketing people for big firms like Esso tend to be very good at their jobs, so they wouldn't create adverts like that if they didn't work. --Tango (talk) 21:17, 26 September 2012 (UTC)[reply]

Public ignorance is one of the major pillars on which advertising is based. For me the best (or worst) example of using public ignorance is anti-ageing and anti-wrinkle creams, pure bull**it - the information, not the cream! Richard Avery (talk) 21:48, 26 September 2012 (UTC)[reply]

On the bright side, let's remember that only the stupidest part of the public seems likely to be affected by this kind of advertising in the first place, so I'd expect them to be pitched to an audience of well below average intelligence and/or educational level. Wnt (talk) 12:38, 27 September 2012 (UTC)[reply]

Another factor is that those who work at advertising agencies may not have any background in science, so they really don't know when they are spouting pure BS. A similar problem exists in the courts. StuRat (talk) 21:52, 26 September 2012 (UTC)[reply]

Well, that isn't exactly what they say, in the ads that show up when you Google. They say they have developed a fuel "that works at the molecular level to help remove engine deposits", or minor variations of that phrasing. That isn't really how I would say something, but it isn't quite as inane as the question suggests. (And it isn't true of all fuels, either.) Looie496 (talk) 23:05, 26 September 2012 (UTC)[reply]

What's the alternative to working at the molecular level ? Tossing sand into the engine to grind down the deposits ? I can't see any down-side there... :-) StuRat (talk) 23:10, 26 September 2012 (UTC) [reply]

"working at molecular level" is just an adman's perky way of saying "the chemistry of the additives does this...". Refineries have been adding deposit eliminating and removing substances to fuels for decades. If you include reducing/eliminating lead & lead oxide deposits, they've all been adding stuff to get rid of that almost since adding lead to increase the octane rating, and that began in the 1920's. Adding substances to reduce gums from rings etc has been routine for at least 30 years. See Internal Combustion Engines, 2d Ed, Richard Stone 1992, pub:SAE.

The most hilarious fuel marketing campaigns occured in Western Australia in the 1960's and 70's. The prominent fuel companies, as measured by the number of branded service stations, back then were BP, Caltex, Shell, Esso, and Ampol. They all had marketing that claimed/suggested that each had their own special additives in the fuel. In fact, there was only one refinery and distribution system (owned by BP) - all service stations, regardles of branding, sold gasoline made by BP. Ratbone120.145.8.132 (talk) 00:19, 27 September 2012 (UTC)[reply]

That of itself does not invalidate the vendors claims. It is possible for a single manufacturer to blend petrol to different recipies for each customer. --Tagishsimon (talk) 12:59, 27 September 2012 (UTC)[reply]

Ain't they effective at removing oil deposits rather than engine deposits? ;) — Preceding unsigned comment added by One.Ouch.Zero (talk • contribs) 07:04, 27 September 2012 (UTC)[reply]

Was that deposits of oil, or something deposited by the oil? Actually, engine deposits come from all these sources: deterioration of oil, substances in the fuel, chemical reactions between fuel and oil and engine metal parts, and dust and other substances in the air (the air filter does not filter out everything). Ratbone58.164.231.128 (talk) 12:16, 27 September 2012 (UTC).[reply]

Deposits of oil. Many have been exhausted since the development of additives. So many that it cannot be coincedential. ;) - ¡Ouch! (^{hurt me} / _{more pain}) 15:17, 27 September 2012 (UTC)[reply]

Chimpanzee-Human percentage of relatedness

Old estimates were around 99%, but a paper in 2007 supposedly lowered it to 94%. Yet, the recently published data on the Bonobo genome says that they share 98.7% (again around 99%) with humans and 99.6% with chimps. Bonobos split from chimps, so there is no way they are closer to humans than chimps are to us. What is the most up-to-date analysis of chimpanzee-human relatedness? --Ghostexorcist (talk) 21:39, 26 September 2012 (UTC)[reply]

You get different answers depending on how you measure it. See the discussion near the bottom of this Q: Wikipedia:Reference_desk/Archives/Science/2009_November_5#Drosophila_melanogaster_and_human_genome_homology. StuRat (talk) 21:46, 26 September 2012 (UTC)[reply]

Is it so that DNA similarity is necessarily equivalent to relatedness? Perhaps in the technical use of the term, it might even be the definition of relatedness, but DNA is a very funny thing, and speaking of relatedness tends to take a journey into colloquial terms. I mean, turkeys have 80 chromosomes, while tigers have 38 and earthrworms have 36. I know it's not even remotely analogous to the point your making, but we don't take this to mean that earthworms are more closely related to tigers than either tigers and earthworms are to turkeys? I don't know...something just irks me about strictly defining relatedness by DNA. DRosenbach ^{(Talk | Contribs)} 15:04, 27 September 2012 (UTC)[reply]

But we know the reason why we have 46 chromosomes and chimps have 48 is because our chromosome #2 is simply a fused version of the corresponding primate chromosome. I've never heard anyone claim that animals with similar chromosome numbers were related. Tigers and worms are obviously not related because they are not even close to being apart of the same family. Animals can have different chromosome numbers and still be closely related. For instance, a horse has 64 chromosomes, while a donkey has 62. Relatedness is based on the similarity between DNA sequences, as well as other factors like anatomy. Horses and donkeys are obviously extremely similar in body form. The same goes for humans and primates. Creatures separated by large amounts of DNA differences tend not to be physically similar. For example, a cat is similar to humans because its a mammal, but a sea sponge isn't. --Ghostexorcist (talk) 16:43, 27 September 2012 (UTC)[reply]

A lot of DNA is junk, so it would be theoretically possible for two very closely related species to have all the important DNA in common and all the junk DNA be different, so that, by just comparing the amount of DNA in common, they would appear to be very distantly related. However, evolution just won't lead to such a result. So, measuring the amount of DNA in common is a rough way to measure how related two species (or individuals within a species) are. StuRat (talk) 02:40, 28 September 2012 (UTC)[reply]

The notion of "junk DNA" is on the decline, perhaps. -- Scray (talk) 04:31, 29 September 2012 (UTC)[reply]

September 27

magnetic sensor

does anyone know the basic design of a magnetic sensor? (accurate, fast, sensitive, and Price) also, i would like to know if, where, and for what price, i can get such a sensor. thanks, 70.114.254.43 (talk) 01:02, 27 September 2012 (UTC)[reply]

Have you read Magnetometer? Plasmic Physics (talk) 01:05, 27 September 2012 (UTC)[reply]

If you have some understanding of electronics, I recommend going to a good library (eg local university library) and searching thru the magazine Wireless World. An excellent article on the operation and home construction of a very good fluxgate magnetometer was published in this magazine in the 1980's. Many electronics hobbyist stores and electronics part suppliers (Eg RS Components) carry Hall Effect sensors, but these are rather insensitive. Keit124.178.132.245 (talk) 01:42, 27 September 2012 (UTC)[reply]

It all depends on what you need it for. Do you want to count rotations of a wheel that has a magnet on it, or do you want to detect iron objects 10 meter deep in the ground? You've got a Hall effect sensor for a dollar, a portable cesium vapor magnetometer will cost you twenty thousand. Ssscienccce (talk) 20:57, 27 September 2012 (UTC)[reply]

Ganglion cyst

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

--Jayron32 02:01, 27 September 2012 (UTC)[reply]

See discussion here: Wikipedia_talk:Reference_desk#Medical_advice_question_removed. StuRat (talk) 02:10, 27 September 2012 (UTC)[reply]

Could someone fix the Ununtrium articles, I don't trust my science skills

WikiProject Reference Desk Article Collaboration

This question inspired an article to be created or enhanced:

Ununtrium

Please consider contributing

Hello, It appears the following articles require being updated in light of the recent synthesis of ununtrium.

Ordinarily I would make the edits myself but am not a scientist and I do not trust myself to do so. In particular, there are some claims to earlier synthesis and I don't know how to determine which claims should be given priority in our articles.

Thanks. user:Agradman, logged out and editing as 99.100.214.111 (talk) 05:16, 27 September 2012 (UTC)[reply]

That's super cool! But this isn't really the place to make such requests. I think the talk pages of those articles are probably more suitable. Though no doubt you will reach a broader "sciency" audience of wiki editors here then just on those talk pages.. Also, keep in mind, an article in a newspaper isn't really a great source for "bleeding edge science" (not that I'm saying these claims aren't true), but usually it takes a little bit of consensus building before the very latest science makes it into a encyclopedic article. The finding hasn't even yet been confirmed. Vespine (talk) 05:30, 27 September 2012 (UTC)[reply]

Actually, this is really the place to make such a request. The Wikipedia:WikiProject Reference Desk Article Collaboration was created to facilitate the improving of articles by collaboration at the ref desks. I'm heading off to sleep myself soon, but there are many people here who would likely help with the request. Give it some time for people to come by and check it out, and I'm sure someone (if not me by tomorrow) will look this over and see if there isn't some way we can pitch in and help. --Jayron32 05:51, 27 September 2012 (UTC)[reply]

If anyone needs me, I'll just be over there eating my words... ;) Vespine (talk) 06:51, 27 September 2012 (UTC)[reply]

I have a recipe for a lovely salad that would complement that dish beautifully. -- Jack of Oz (Talk) 09:51, 27 September 2012 (UTC) [reply]

I've gone ahead and added a short sentence to the article Ununtrium, as the anouncement itself is probably as significant as anything else in the article, which discusses prior abortive attempts towards synthesis. I think we should probably wait to adding it to the other two articles noted until this is published in a peer-reviewed journal, which the L.A. Times notes has not been done yet. When it does appear in such a journal, we can expand more and put it in the other lists as "official". --Jayron32 13:46, 27 September 2012 (UTC)[reply]

Technically this isn't a new synthesis, but rather a confirmation of the old one from 2004. RIKEN did in fact synthesize IUPAC's discovery criteria when IUPAC reviewed the claims for the element with Z ≥ 113 last year. But now RIKEN synthesized it again, the new decay chain does have anchors to known isotopes, thus confirming the isotope ²⁷⁸113 beyond reasonable doubt. It's not an official discovery yet – IUPAC hasn't mentioned anything yet AFAIK – but we can probably expect them to say something about this within the next few years. (Note, however, that the JINR has also claimed that they synthesised element 113 just six months before RIKEN did.) Double sharp (talk) 14:59, 27 September 2012 (UTC)[reply]

Benefits/effects of fasting

I stumbled across this video and wondered whether the various claims it makes for the medical benefits of fasting stack up scientifically. Do they? --Dweller (talk) 13:32, 27 September 2012 (UTC)[reply]

Every person and every manner of fasting will be different, and so one should be wary of generalities. The Ramadan fast described in the video is of course different from the garden-variety hunger strike. Also note that Ramadan does not fall on a fixed schedule, nor is it observed in a fixed location, so the schedule of fasting for those practicing it will vary. As a rule, of course, humans are designed to be able to survive periods without food and drink as a matter of necessity; on the other hand, the urges people feel are usually (but not always) a guide to what is physically healthy.

To give a taste of the complexity of one specific instance, consider the guidelines used for diabetes: [12]. Various levels of risk exist depending on many medical parameters and the current mode of treatment. They can participate in the fast, but only with careful preparation. Obviously the nighttime period when food is eaten, and how insulin and blood sugar is managed then, and how much is eaten, is of key importance. On the other hand, a very low calorie diet, verging on a true fast, can be an excellent intervention for type 2 diabetics. So the net benefit/risk depends on many factors that go beyond the fast itself. Wnt (talk) 16:16, 27 September 2012 (UTC)[reply]

Another thing which I'll only ask - I haven't thought how to do a search for it! - is whether survival without water is something that can be "learned" or adapted to. After all, Islam has been prevalent in desert regions. If people don't drink anything for 12 hours for 30 days, does this make them more able to survive if they, say, get lost in a desert or have to make a sudden retreat over a vast expanse of arid landscape at some other time of the year? Wnt (talk) 16:22, 27 September 2012 (UTC)[reply]

Intermittent fasting and fasting has info. The health effects section in the fasting article seem to focus more on caloric restriction, not necessarily part of fasting or involving fasting. Speculation about the slowing of the aging process, and the potential to increase maximum life span in that regard is based on experiments with mice, and recent results of a long term study involving rhesus monkeys show no effect. The article on intermittent fasting mentions that eating a single meal per day worsens some cardiovascular disease risk factors. The claims in the video about removal of toxins, I'm not sure if these have any medical basis, doesn't look like it according to the detoxification (alternative medicine) article. If fasting offers health benefits, it would likely have to be done on a regular basis I suspect. Take physical exercise, doctors wouldn't advice you to do that one month each year. Ssscienccce (talk) 17:26, 27 September 2012 (UTC)[reply]

Every seventh ocean wave larger?

Is it true that every seventh ocean wave is larger? My casual observations seem to indicate that it is true, and I can see how that can happen by waves of two different frequencies combining. Bubba73 ^{You talkin' to me?} 13:45, 27 September 2012 (UTC)[reply]

Sneaker wave describes the "seventh wave" belief as folklore, but also says it has "some scientific basis, due to the occurrence of wave groups at sea". Gandalf61 (talk) 15:20, 27 September 2012 (UTC)[reply]

After spending many years studying wave mechanics (and watching the ocean - there's no substitute for empirical observations to enhance one's knowledge of physics!), I'm actually very confused by this belief, which cannot possibly be true. The swells of the ocean consist of a continuously varying motion of water, in which energy can propagate as a wave. Each crest or trough does not constitute a distinct wave. In fact, it is non-trivial to "count" the number of wave crests that have passed, unless you are very careful to define what constitutes a "crest" (presumably, by band limiting your observations). So, it's not clear how you would count "every seventh wave." See also: Crest (physics). Nimur (talk) 17:30, 27 September 2012 (UTC)[reply]

I'm thinking about ones that come up on shore. Bubba73 ^{You talkin' to me?} 19:28, 27 September 2012 (UTC)[reply]

I suspect the difficulty of definition is what makes the idea "true" - if you get your choice of three different "waves" for your measurement, on average the one you pick will be larger. Wnt (talk) 20:01, 27 September 2012 (UTC)[reply]

In other words, observer bias causes the result to seem true, because the observer may selectively define when a "wave" arrives, allowing them to fit the expected result. Nimur (talk) 22:16, 27 September 2012 (UTC)[reply]

For what it is worth, there is this. I know it is just a blog and carries very little weight. Bubba73 ^{You talkin' to me?} 01:51, 28 September 2012 (UTC)[reply]

And this oceanography textbook says that there is no fixed ratio of when larger waves occur. Bubba73 ^{You talkin' to me?} 02:01, 28 September 2012 (UTC)[reply]

I suppose you van get swells from different sources with different wavelength making a regular pattern of bigger and smaller waves. I have spent plenty of time as school looking out the window looking at waves. Sometimes it seems to be true and other times not. Graeme Bartlett (talk) 11:14, 28 September 2012 (UTC)[reply]

Color of the ocean

What determines whether the ocean appears blue-green, blue, or violet? From the shore it seems to me that there are distinct zones with pretty sharp dividing lines -- blue-green near shore, then vivid blue, then violet farther out. A reference in Ocean#Physical Properties mentions Colored Dissolved Organic Matter, but that's all I can find. I get the impression that depth of water near the shore matters, with very shallow water being more blue-green (perhaps because of the color properties of the sand underneath?). Also does the angle of the sun matter? What else? Duoduoduo (talk) 16:38, 27 September 2012 (UTC)[reply]

See Color of water. --Jayron32 17:12, 27 September 2012 (UTC)[reply]

Thanks, very helpful. But I still wonder why there appear to be very sharp dividing lines between different color regions of the sea as visible from the shore. Know anything about that? Duoduoduo (talk) 18:31, 27 September 2012 (UTC)[reply]

Water which is of different salinity, or which contains differing concentrations of dissolved solids, doesn't readily mix as one would think. That is, different regions of water with different "stuff" in it will tend to remain seperate for a long time, sometimes indefinitely, which is why you can find differences in coloration and sharp dividing lines as you note. See this video which uses different colored sugar water of differing concentrations to demonstrate the effect. --Jayron32 19:39, 27 September 2012 (UTC)[reply]

What lies underneath the water also matters, if the water is shallow enough for light to reflect off the bottom. So, water above white sand will look much lighter blue or green than water above dark green seaweed or above a trench too deep for light to reflect off the bottom. This effect is stronger if looking at the water from above. Therefore, since the nature of the bottom of the sea can change rapidly, so can the apparent color of the water above it: [13]. StuRat (talk) 02:27, 28 September 2012 (UTC)[reply]

Slowing 'death by burning'

In the legend of the Ten Martyrs, it is said that damp wool was placed on the chest of Haninah ben Teradion in order to prolong his suffering. My question relates to the fact that it shouldn't matter how long one's heart is prevented from succumbing to burning if one's head is not similarly wrapped or placed in damp wool. Perhaps this portion is fabricated too, along with the joining of all ten rabbis together into one story when their deaths really occurred years apart. DRosenbach ^{(Talk | Contribs)} 18:53, 27 September 2012 (UTC)[reply]

Hm. You may be interested in Auto-da-fé, Death by burning, Tunica molesta (though that is a stub) and Sanbenito for what sounds like similar garments, though of the opposite effect. Maybe something was confused in the translation? --Jayron32 19:36, 27 September 2012 (UTC)[reply]

Is it possible that by "chest" they mean the entire trunk of the body, so as to ensure that the extremities and genitals would be worst affected? (Assuming the head remained somewhere out of the fire and visible so that they could get their special pleasure out of watching him scream) Wnt (talk) 19:59, 27 September 2012 (UTC)[reply]

Oh, what a dreadful thing to ask about. However, as you have asked. This is my take (without any citations to back it up). The executioners had probably watched many immolations and worked out how to prolong consciousness in the victim -by trial and error. The evaperative cooling effect and insulating properties of damp wool strategically placed may have keep the victim conscious for longer. The inhalation of fire kills in about twenty to thirty seconds but some placement of wet material may provide temporary relief. The brain -within the bony cranial cavity- is very well supplied with blood. With the flames liking up towards the nether regions the hart is probably pumping quite well – therefore, external heat to the skull is unlikely to induce acute heat-stroke if another parts of the body is sufficiently cool. Also, the historical accounts maybe over simplified as to the exact placement of the wool -so I don't think you will be able to get a definitive answer. Why do you ask? Has your local political representative done anything that you think deserves a slow roasting upon a spit?--Aspro (talk) 20:13, 27 September 2012 (UTC)[reply]

Post Script: The executioners time and expertise may have been wasted though. Whilst talking to people undergoing skin-grafts due to burns, they said that (and I paraphrase here) “what with the adrenalin flowing an' all, I did not realize that the heat was burning me” In other words: some tried to fight the fire when they really should have got out fast. So the martyrs may have quickly become anesthetized to the effects of the flames. In some situations (as had been also described by solder wounded in battle), the human body can sometimes block out pain that would normally immobilize the average John Doe in the street.--Aspro (talk) 20:33, 27 September 2012 (UTC)[reply]

That may be the case for people actively engaged in something important enough to ignore the flames; from personal experience I can say that suffering third degree burns and being unable to escape the flames is bloody painful all the way. Ssscienccce (talk) 08:35, 28 September 2012 (UTC)[reply]

Magnetic potential from current densitty

The current density on a disc of radius R is $K(r)=r^{3}(-\sin \phi {\hat {x}}+\cos \phi {\hat {y}})$ . Calculate the magnetic vector potential. From ${\frac {\mu _{0}}{4\pi }}\int \int _{A}{\frac {K(r)}{|x{\hat {x}}+y{\hat {y}}+z{\hat {z}}-r(\sin \phi {\hat {x}}+\cos \phi {\hat {y}})|}}dA$ I get ${\frac {\mu _{0}}{4\pi }}\int _{0}^{2\pi }\int _{0}^{R}{\frac {r^{4}(-\sin \phi {\hat {x}}+\cos \phi {\hat {y}})}{(x^{2}-2xr\cos \phi +y^{2}-2yr\sin \phi +r^{2}+z^{2})^{\frac {1}{2}}}}drd\phi$ . Can I evaluate the intigral, or is there an other way to get the magnetic potential?--150.203.114.14 (talk) 20:49, 27 September 2012 (UTC)[reply]

Is this homework? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 20:57, 27 September 2012 (UTC)[reply]

Probably, but this looks like a nice bit of transpositions to keep our brain cells from ceasing up. Just like my cat, I like to isolate the μ's...--Aspro (talk) 21:11, 27 September 2012 (UTC)[reply]

Yes, it is but I have shown my current working.--150.203.114.14 (talk) 21:01, 27 September 2012 (UTC)[reply]

Are you sure you stated the problem completely? Often problems like this only want the vector potential over a restricted region. For example, if you only wanted the potential along the z-axis, then the integral is solvable. I'm not sure if the general case can be integrated. Dragons flight (talk) 21:12, 28 September 2012 (UTC)[reply]

Hm, maybe; the next part of the question is to find the magnetic field at points on the z-axis by taking the curl, but to take the curl you still need to know the vector potential in all space (or at least some neighbourhood around the z-axis) don't you? 150.203.114.14 (talk) 00:45, 29 September 2012 (UTC)[reply]

White spirit/Mineral turpentine

Is there a difference between white spirit and mineral turpentine? —Ruud 23:08, 27 September 2012 (UTC)[reply]

According to the articles, yes. WS has a mixture of aliphatic and alicyclic C7 to C12 hydrocarbons. MT is a hydrotreated light distillate of petroleum, and consists of a complex mixture of highly refined hydrocarbon distillates mainly in the C9-C16 range. So close relations, but perhaps not on merging terms? --Tagishsimon (talk) 23:19, 27 September 2012 (UTC)[reply]

I don't quite trust what the articles say, however, and several pages on the Internet just point back to Wikipedia... (Surprisingly, the articles turn out to be created by the same person [14] [15].) I'm getting the impression they describe the same class of substances, which can have a range of chemical compositions (the lengths of the hydrocarbons) But I'm neither a professional chemist, nor a painter... —Ruud 23:31, 27 September 2012 (UTC)[reply]

Hmm. You may be right; or it may be a point of view. Inchem gives Mineral turpentine as a common synonym of white spirit, but uses the C7 to C12 definition, which on the face of it excludes the C9-C16. But C9-C16 is not referenced so... --Tagishsimon (talk) 23:39, 27 September 2012 (UTC)[reply]

That reference looks useful and would support them being the same substances. Also, Google tells me C9-C16 would be kerosene. —Ruud 00:12, 28 September 2012 (UTC)[reply]

Our WS article comments "it is merely a light grade of kerosene". Some more digging. Looking only at British Standards, there are a couple for Kerosene - BS2869:2010 and ASTM D3699 - 08, and a separate BS for Mineral Solvents - BS245:1976. There's no stand-alone BS for White Spirit or for Mineral Turpentine ... the first appears as a descriptor of BS254, the second does not. None of this is anywhere near conclusive, however. I've yet to find a standard for MT; I see hints thereof, but looking at something like this explanation of two classes of MT oil, characterised by different boiling ranges, it may just be different nomenclature in different markets. --Tagishsimon (talk) 00:57, 28 September 2012 (UTC)[reply]

I've seen the two products on sale side-by-side at different prices, and the ones I've bought seem to have marginally different odours, but I don't know whether there is an essential difference that is consistent between manufacturers. The two products are very different from kerosene (paraffin in the UK) and from other fuel oils. Dbfirs 07:56, 28 September 2012 (UTC)[reply]

coronene (chemical).

The article for "Coronene" lacks all the synonyms for the mineral form of same, and the article and its talk page are enough "locked up" that I can't conveniently pass along the information there. "Dana's New Minerology" 8th edn 1997 has the mineral form under the names Karpatite, Pendletonite and Coronene only. The monograph in the Merck Index 14th edn 2006 for Coronene has the mineral form listed only as Pendletonite. Would you please see to passing this along? TnxC.s.auaeginal (talk)c.s.auaeginal, 27 Sept 2012 Th. —Preceding undated comment added 23:25, 27 September 2012 (UTC)[reply]

Actually the article is unprotected and you should be able to change it by clicking on edit links. I have added a sentence to the article. Graeme Bartlett (talk) 11:01, 28 September 2012 (UTC)[reply]

September 28

Doldrums fact or fiction

When the winds are gone the sea actually has no swells, on a clear day the color of the sky is reflected in the water. At night the same effect, with no clouds or moon, gives one the effect of floating in space.

Is this statement from Doldrums actually true? Somehow this seems dubious to me...I've been under the impression that swells travel long distances across the ocean, thus why swell/waves from a hurricane between Puerto Rico and Bermuda can be a threat in the eastern United States. Ks0stm ^{(T•C•G•E)} 00:00, 28 September 2012 (UTC)[reply]

As originally posted,[16] it's quite obviously someone's personal opinion. I say zap it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:57, 28 September 2012 (UTC)[reply]

I agree. It's also unencyclopedic and poor English ("winds are gone", "actually" and "gives one the effect").--Shantavira|^{feed me} 10:48, 28 September 2012 (UTC)[reply]

The actual original statement was, "When the winds are gone the sea actually has no swells, on a clear day the color of the sky is reflected in the water. At night the same effect, with no clouds or moon, gives you the effect of floating in space. It's quite amazing to experience." Someone afterward tried to make it sound a tad more formal, but it's still just someone reminiscing about it, so I sent it to Davy Jones. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:58, 28 September 2012 (UTC)[reply]

Ketamine in the UK

Why is Ketamine not licensed for prescription in the UK? --TammyMoet (talk) 09:16, 28 September 2012 (UTC)[reply]

Are you sure about that? This suggests it is, or at least was in Scotland in 2009. Here is further evidence. It seems, though, that Ketamine is usually (only?) prescribed by hospital specialists and not local GPs - they want to keep you under observation whilst taking it, at least initially. - Cucumber Mike (talk) 10:43, 28 September 2012 (UTC)[reply]

That explains that then. Thanks. --TammyMoet (talk) 12:16, 28 September 2012 (UTC)[reply]

Van der Waals fugacity as a function of pressure, volume, and a and b. How do I eliminate molar volume?

The only equation for fugacity I can find for VDW requires calculation of the compressibility factor. However, the compressibility factor is often calculated from the molar volume. I am trying to plot fugacity against T and P of a Van der Waals gas, where constants a and b are known. How I do I convert the compressibility factor equation into a function of T,P, a and b? 128.143.175.21 (talk) 11:38, 28 September 2012 (UTC)[reply]

WHY DO PEOPLE ONLY GIVE COMPRESSIBILITY FACTOR AS A FUNCTION OF MOLAR VOLUME AND TEMPERATURE? HOW CAN I FIND IT AS A FUNCTION OF PRESSURE AND TEMPERATURE, IF MOLAR VOLUME IS UNKNOWN? 128.143.175.21 (talk) 11:44, 28 September 2012 (UTC)[reply]

Because of the Kronig-Classius equation - for any ideal gas, the molar volume is equal to:-

Vm = Ro T / P

where Vm is molar volume (m³); Ro is the universal gas constant (Avogradro Number x Bolzman constant) = 8.314 kJ/kmol.K, T is aboslute temperature (K); and P is pressue (Pa). Avogrado's number is the number of molecules in one mole of gas. Boltzman's constant relates kinetic energy to temperature for any gas molecule. Keit60.230.238.139 (talk) 15:53, 28 September 2012 (UTC)[reply]

If your gas is helium, a is nearly zero and it becomes easy to solve for molar volume. If not, the van der Waals gas equation can be arranged into a cubic equation in Vm. Cubic_equation#General_formula_of_roots gives the roots (1 real, 2 complex), but they're pretty messy. (Vm = Ro T / P is for an ideal gas, which this is not. Or equivalently it assumes the compressibility equals 1.)--Wikimedes (talk) 19:05, 28 September 2012 (UTC)[reply]

Banking your own blood for emergencies

On season 4 episode 11 of Breaking Bad, it's revealed that some of the characters had their own blood drawn, processed, and stored for emergencies. Is this ever done in real life? I can see the advantages of this approach over regular blood bags (no compatibility testing, retaining white blood cells, etc), but do these advantages actually outweigh the hassle? Apparently POTUS doesn't even get this kind of treatment.

I wouldn't be asking if this is any other TV show, but Breaking Bad had extremely accurate portrayal of science throughout so I'm giving the writers the benefit of doubt for now. A8875 (talk) 12:15, 28 September 2012 (UTC)[reply]

See our article on autotransfusion. Gandalf61 (talk) 12:42, 28 September 2012 (UTC)[reply]

Thanks, but I already read that article before asking the question and it doesn't say anything about preoperative autotransfusion. The entire article (except the first sentence) is about intraoperative autotransfusion, which has nothing to do with my question. A8875 (talk) 12:46, 28 September 2012 (UTC)[reply]

Then a quick Google search throws up this page (among many others) which says "Before surgery: You may schedule appointments and donate your own blood. This is known as autologous blood. It will be stored and reinfused as needed during or after your surgery". So, yes, it is done in real life. Gandalf61 (talk) 12:54, 28 September 2012 (UTC)[reply]

That's for planned surgeries. I'm asking about emergency surgeries. Suppose a VIP's life is in possible danger, does it make sense to draw blood from them on a weekly basis indefinitely? I'm sorry if I didn't phrase my question clearly, but I specifically mentioned "for emergencies" in my OP. A8875 (talk) 13:01, 28 September 2012 (UTC)[reply]

I found some use of the term "autologous self stored blood", e.g. here they say it may be useful for people with rare blood types. The blood keeps frozen for a couple of decades - and they'll want money for doing it for you. 88.112.47.131 (talk) 13:51, 28 September 2012 (UTC)[reply]

Thank you very much for the valuable data point. Frozen blood is completely unsuitable for emergencies according to that site: "Because of time required to thaw frozen Blood and deliver it to a where you are, frozen autologous Blood is not practical for emergency use. Thawing takes 60 to 90 minutes. Once your Blood has been thawed, it must be used within 24 hours."[17] So the verdict is still out for non-frozen autologous blood banking. A8875 (talk) 13:58, 28 September 2012 (UTC)[reply]

It makes no sense to me. By definition, in an emergency you need blood that can be got to you in the shortest possible time. As long as it's compatible it doesn't matter who it came from. Finding and then transporting your own blood from wherever it happens to be is bound to take far longer.--Shantavira|^{feed me} 14:07, 28 September 2012 (UTC)[reply]

Which is precisely why I asked the question. Whatever little benefits autologous blood transfusion has is completely overshadowed by the immediate availability of fresh blood from the blood bank. A8875 (talk) 14:24, 28 September 2012 (UTC)[reply]

I agree that the timing might be a problem, but don't agree with "As long as it's compatible it doesn't matter who it came from". People have gotten AIDS and hepatitis via blood transfusions from others, before blood banks were able to test for those conditions in donors. There might very well be other diseases which are currently not screened out of the nation's blood supply. So, if possible, using your own blood would be preferable. StuRat (talk) 02:35, 29 September 2012 (UTC)[reply]

How much biomass is in Canada?

I am looking for the total amount of biomass in Canada in forestry and agriculture.

This is what I have so far:

Forest Biomass: Standing Biomass / Bio-energy stock: The 245 M ha of Timber Productive Forest in

Canada has a biomass carbon stock of about 15,835 Mt C. This resource has an energy

content (566 EJ) that is equal to 69 years of Canada’s current energy demand that is met by

fossil fuels (8.24 EJ/yr).

Agricultural biomass: Energy EJ/Year: 1.96

Here is a link to the paper:http://www.biocap.ca/images/pdfs/BIOCAP_Biomass_Inventory.pdf. It was a report prepared for Industry Canada in 2003, so I don't know how much the numbers have changed since then.

Does anyone have any more up to date sources? Thanks. Eiad77 (talk) 19:46, 28 September 2012 (UTC)[reply]

I have no idea for sources whatsoever. But you might look for a workaround, such as an estimate that forests account for XX percentage of the biomass of Canada, and then work backwords from the total. It won't be hugely accurate, but it will be within an order of magnitude. It's the method we used in an undergrad class of mine to estimate the world's available fresh water supply from the volume of Lake Baikal. μηδείς (talk) 20:41, 28 September 2012 (UTC)[reply]

Chemistry and Molecular Mass

I am having trouble with the following question

The percentage C by mass in the above unidentified substance is 92.3%. It may also contain H and/or O, but no other element. What is the molecular formula of the substance?

My answer was CH24 but it is not right. Any help on how to solve this question would be appreciated. Thank you — Preceding unsigned comment added by 142.58.63.10 (talk) 20:28, 28 September 2012 (UTC)[reply]

Clearly the non-C portion is 7.7% = 1/12.987, which is close to 1/13. Carbon has average mass 12, which means that for every 1 carbon, there's 1 mass unit of something else. So, obviously... this is a diamond doped with about one oxygen for every 16 carbon atoms. Or maybe an -OH side chain for every 17. Or ... well, there are a lot of possibilities; maybe the first part of the question clears it up. 24 hydrogens for every carbon, though, is not among them. But just to be really uncreative - if we had one carbon and one hydrogen you'd have about 7.7% not-carbon. Or two carbons and two hydrogens, or three carbons and three hydrogens ... can you think of a compound (or derivatives thereof) that might have that ratio? (But there are lots of possibilities) Wnt (talk) 21:13, 28 September 2012 (UTC)[reply]

CH24is obviously wrong since carbon has a valence of +/-4, not 24. So there has to be at least one oxygen molecule. You can work out the possibilities. CH3OH is one; CH2(OH)2 or CH3OOH is the next, and so on. I am not going to do the math for you, but that is the way to proceed. μηδείς (talk) 22:33, 28 September 2012 (UTC)[reply]

Unless I seriously slipped up here, I don't see a way for one carbon and 24 hydrogens to have anything but about 33% carbon, not 92.3%. Wnt (talk) 03:09, 29 September 2012 (UTC)[reply]

GLP-1 agonists and exercise

Are there any sources which comment on the use of GLP-1 agonists like Victoza or Byetta and their use before or after, as opposed to just with exercise? μηδείς (talk) 20:38, 28 September 2012 (UTC)[reply]

Glancing over the articles, it looks like both these agents are injected once or twice a day, and so should be present at pretty high levels throughout all periods of activity and inactivity. Can you give further information about where you saw mention of the specific timing of exercise to begin with? (obviously exercise is good for diabetics and indeed non-diabetics) Wnt (talk) 21:26, 28 September 2012 (UTC)[reply]

There's no source I can refer to, or I'd look for it. (The question actually arose out of my interest in plant hormones, and having recently read about Gila Monster venom.) I suppose it's a question like the eat before or after you work out? dilemma. If someone works out once a day and takes a GLP-1 agonist once a day, it seems logical to wonder if the highest level of the day or the lowest level of the day affects the quality/benefit of the exercise or if pre- or post-injection exercise affects the efficiency of the hormone or not. Unfortunately, I have not been able to think of good search terms or find any resources that say anything other than people should, of course, exercise. μηδείς (talk) 22:26, 28 September 2012 (UTC)[reply]

Well, this being biology, we really don't know unless the experiment is done, and I'd bet money it hasn't been (I ought to look it up on PubMed, but it doesn't sound likely). A priori you could argue it a few different ways; my guess would be it's more effective to exercise when blood glucose is highest, because it's an available resource and because exercise causes muscles to absorb glucose more or less independently of insulin.[18] I should emphasize that this is purely a guess, and biology has an absolute right to give you an unexpected answer. Wnt (talk) 03:14, 29 September 2012 (UTC) (I eventually did look around in PubMed a bit - the most relevant paper I came up with was [19], but I still can't make up my mind what if anything this implies in regard to your question; only that natural GLP-1 itself has some effect on hepatic glucose production for exercise. Wnt (talk) 03:30, 29 September 2012 (UTC)[reply]

September 29

One's Sexuality

If one is sexually attracted to regular women and to women with dicks (or men with breasts, long hair, and a feminine face, arms, stomach, and legs), then what would be the scientific classification for one's sexuality? I am not asking you to make a diagnosis, only asking if scientists have commented on the sexuality of people who are attracted to women and women with dicks. Futurist110 (talk) 01:58, 29 September 2012 (UTC)[reply]

That would at least partly depend on whether one was male or female. HiLo48 (talk) 02:15, 29 September 2012 (UTC)[reply]

Let's go with one being male in this scenario. Futurist110 (talk) 02:18, 29 September 2012 (UTC)[reply]

Please refer to Gynandromorphophilia. Sucks how Wikipedia:WHAAOE works for everyone else except for me; whenever I urgently need an answer the relevant article just vanishes. A8875 (talk) 02:39, 29 September 2012 (UTC)[reply]

Wavelength

Let say I was given a picture of an object in space, cold be a star or anything that emit light or reflected light. And the question is what light wavelength is it in? The possbile answers are: "X-ray, UV, Optical, radio, IR". So how do I know which one is which? I meant like what are the features of each of the wavelength makes it stand out to the rest? How can I distinguish if it's either X-ray or UV or Optical or radio or IR light wavelength? Thanks!65.128.190.136 (talk) 03:22, 29 September 2012 (UTC)[reply]

The wavelength of light is its color. Those are analogous terms, though we usually preserve the word "color" to refer to wavelengths that human eyes can receive and interpret. If you are seeing the star with your eyes, unaided or with a simple optical telescope, the light's wavelengths you see are all in the visible range, by definition. There are also astronomical facilities like radio telescopes that receive light at non-visible wavelengths. Using some clever graphical processing, they frequently convert this data into a False color image so you can "see" what the radio telescope "sees", but your eyes and brain are not equipped to "see" light at those wavelengths. Does that help answer your question? --Jayron32 03:37, 29 September 2012 (UTC)[reply]

I'm not looking at anything with a naked eye. Ok let put it this way, someone takes a color picture of an object somewhere in the universe and that person can use any equipments to do it. After that give me the picture and asked: Which light wavelength is it in? I was given these choices:"X-ray, UV, Optical, radio, IR". So how do I know which one is which? What color would the object be if it is in X-ray? If it is in UV? If it is in Optical and so on... So I want to know how to distinguish X-ray light wavelength, UV light wavelength, Optical light wavelength, radio light wavelength, IR light wavelength. Hope I made my question clear this time.65.128.190.136 (talk) 04:43, 29 September 2012 (UTC)[reply]

@@ Line 368: / Line 368: @@
 == Wavelength ==
-Let say I was given a picture of an object in space, cold be a star or anything that emit light or reflected light. And the question is what light wavelength is it in? The possbile answers are: "X-ray, UV, Optical, radio, IR". So how do I know which one is which? I meant like what are the features of each of the wavelength makes it stand out to the rest? How can I distinguish if it's either X-ray or UV or Optical or radio or IR or light wavelength? Thanks![[Special:Contributions/65.128.190.136|65.128.190.136]] ([[User talk:65.128.190.136|talk]]) 03:22, 29 September 2012 (UTC)
+Let say I was given a picture of an object in space, cold be a star or anything that emit light or reflected light. And the question is what light wavelength is it in? The possbile answers are: "X-ray, UV, Optical, radio, IR". So how do I know which one is which? I meant like what are the features of each of the wavelength makes it stand out to the rest? How can I distinguish if it's either X-ray or UV or Optical or radio or IR light wavelength? Thanks![[Special:Contributions/65.128.190.136|65.128.190.136]] ([[User talk:65.128.190.136|talk]]) 03:22, 29 September 2012 (UTC)
 :The wavelength of light is its color.  Those are analogous terms, though we usually preserve the word "color" to refer to wavelengths that human eyes can receive and interpret.  If you are seeing the star with your eyes, unaided or with a simple optical telescope, the light's wavelengths you see are all in the [[visible light|visible range]], by definition.  There are also astronomical facilities like [[radio telescopes]] that receive light at non-visible wavelengths.  Using some clever graphical processing, they frequently convert this data into a [[False color]] image so you can "see" what the radio telescope "sees", but your eyes and brain are not equipped to "see" light at those wavelengths.  Does that help answer your question?  --[[User:Jayron32|<font style="color:#000099">Jayron</font>]]'''''[[User talk:Jayron32|<font style="color:#009900">32</font>]]''''' 03:37, 29 September 2012 (UTC)
+::I'm not looking at anything with a naked eye. Ok let put it this way, someone takes a color picture of an object somewhere in the universe and that person can use any equipments to do it. After that give me the picture and asked: '''Which light wavelength is it in?''' I was given these choices:"X-ray, UV, Optical, radio, IR". So how do I know which one is which? What color would the object be if it is in X-ray? If it is in UV? If it is in Optical and so on... So I want to know how to distinguish X-ray light wavelength, UV light wavelength, Optical light wavelength, radio light wavelength, IR light wavelength. Hope I made my question clear this time.[[Special:Contributions/65.128.190.136|65.128.190.136]] ([[User talk:65.128.190.136|talk]]) 04:43, 29 September 2012 (UTC)