Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

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.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

June 25

Help needed to identify tiger breed

Could someone please identify this tiger? Any information helps! Leave a talk back template on my talk page if you leave a message though as my watch list gets flooded often. Cheers, Riley Huntley _talk No talkback needed; I'll temporarily watch here. 00:04, 25 June 2012 (UTC)

He looks like Tony in 7B? Actually, the subspecies differ in size and striping patterns so even if a definite identification were possible it might take a full body foto to do it. Eye color might be a hint. See Tiger#Subspecies μηδείς (talk) 02:27, 25 June 2012 (UTC)

Looks like a 3/4 grown Siberian to me, but remember , with zoo animals, that there has been a lot of cross breeding between races. — Preceding unsigned comment added by 124.191.176.130 (talk) 06:29, 25 June 2012 (UTC)

Thanks for the help. I do remember the zoo guide saying it is pure breed. Cheers, Riley Huntley _talk No talkback needed; I'll temporarily watch here. 20:44, 27 June 2012 (UTC)

Big Bang (not TV show) kickoff

Saw Hawking's TV show on cable the other day, where he points out that, just as time stands still inside the event horizon of a black hole because of the enormous gravitional field, so time would be stationary at the enormous density of the universe at the time of the Big Bang, thus questions such as "what was there before the Big Bang?" are meaningless. New argument to me, and fair enough. But...... if time was stationary, then by definition, how could anything "happen" to either kick off the Big Bang, or for it to spontaneously occur; or to put it another way, given that something changed, then it would be absolutely incorrect to say that time was stationary. Given that the whole thrust of his argument was to point out that the supernatural actions of a Deity are not necessary to explain the creation of the universe, and that I'm sure as heck incompetent to pick holes in his theoretical physics, there must be some loophole here.... ? Gzuckier (talk) 03:29, 25 June 2012 (UTC)

Perhaps rather than saying that time didn't exist, it might be better to say it was undefined. In a world without matter (or with one singularity containing all matter), how could the passage of time be marked ?

Also note, that, since the cause of the Big Bang is unknown, the cause of time being unknown doesn't really make it any worse than it already is. StuRat (talk) 04:59, 25 June 2012 (UTC)

Thanks for the reply. But I do think that having the cause of the BB be unknown is one thing, but having it operate within an environment such that time is stationary is quite another... Although Hawking didn't seem to think it needed comment, so I figured there must be something obvious I'm missing. Gzuckier (talk) 06:08, 25 June 2012 (UTC)

Nothing can really be properly explained before the end of the inflationary epoch. We don't know why there was cosmic inflation or why it stopped and our best job of papering over that hole is to say "different laws of physics applied back then". Really smart people might even start talking about the vacuum undergoing a phase transition to cause those differences in the laws of physics, but that doesn't make it any easier to know what the hell they were.1.124.255.232 (talk) 06:35, 25 June 2012 (UTC)

These are just my own personal thoughts, but I like to think that time exists (past tense) before the Big Bang. I don't know if anything existed or happened a billion years before the Big Bang, but if nothing did, then I would assume that prior to the Big Bang there was nothingness. That's just an assumption though. InforManiac (talk) 06:54, 25 June 2012 (UTC)

Let me add a little bit more to the comment I just posted up above. From a multiverse point of view, it especially makes it easy to think that time existed before the Big Bang. Even if the Big Bang took place 13.75 billion years ago, going back 15 billion years on a timeline, there just might not be anything happening in this particular universe. InforManiac (talk) 07:11, 25 June 2012 (UTC)

When talking about such things one has to be very careful what one means by "time." In Einsteinian physics, time is not a transcendental property that exists separate from space (see spacetime). There is no "universal time" running in the background under this model, there is no "clock of the universe." This is but one of the reasons that talking about time prior to the existence of space (much less matter and energy) is often assumed to be somewhat meaningless — no space, no time. Regardless, time is a tricky concept — it seems much more obvious than it is. --Mr.98 (talk) 16:24, 25 June 2012 (UTC)

For a long time Hawking has been pushing a no-boundary model of the early universe, where instead of there being a beginning of time, the time dimension fades smoothly into a fourth spatial dimension, and the "beginning" is just a region of four-dimensional space that's like a portion of the surface of the earth. No particular point of it is "before" any other point, and it doesn't begin anywhere, just as the surface of the earth doesn't begin anywhere. If this show really was quoting Hawking, he was probably talking about that. But saying that this is like the event horizon of a black hole makes no sense to me, because it isn't like that at all.

It's worth mentioning that Hawking is more popular with the general public than with other physicists. Most of his ideas are pretty far from the mainstream. This no-boundary idea, in particular, has never been part of standard cosmology. -- BenRG (talk) 08:06, 26 June 2012 (UTC)

Absolutely. Time in black hole and time at big bang is just for analogy, not to be taken literally. High density alone does not cause time to slow down, it is Stress-Eenergy_tensor that causes time dilation. Time began at big bang, everything before is speculation. manya (talk) 08:21, 26 June 2012 (UTC)

Thank you all. This has been most stimulating, Wikipedia at its best. Gzuckier (talk) 13:35, 27 June 2012 (UTC)

Do choanoflagellates have distinct personalities?

Do choanoflagellates have distinct personalities? It is said that they are "considered to be the closest living relatives of the animals" and that a "number of species such as those in the genus Proterospongia form simple colonies," so do any have buddies or rivals? InforManiac (talk) 03:36, 25 June 2012 (UTC)

Yes. μηδείς (talk) 04:08, 25 June 2012 (UTC)

You're joking, right ? I can't imagine such a simple organism having a complex social structure. Perhaps a simple social structure, like bees, or ants, but I don't think of them having personalities, either. StuRat (talk) 04:52, 25 June 2012 (UTC)

What does personality have to do with social structure? 1.124.255.223 (talk) 04:56, 25 June 2012 (UTC)

Well, it's part of a complex social order, where different relationships are formed with each individual in the group, and personalities determine how each individual relates to the others (some are bullies, some are friendly, etc.). Absent any social interaction, a "personality" is harder to define, although I suppose you could say "this lizard prefers to bask on the rocks while that one likes to swim". StuRat (talk) 05:03, 25 June 2012 (UTC)

Of course I was referring to simple personalities. Subtle differences. InforManiac (talk) 05:09, 25 June 2012 (UTC)

Would it be fair to say that you wanted to know if they possess individuality?

No. I just wanted to know if they have any kind of varying simple personality traits. InforManiac (talk) 05:21, 25 June 2012 (UTC)

On second thought, I guess you could call it individuality. I'm just curious about whether any two from the same colony would have differing behavior patterns. Even the slightest of differences. InforManiac (talk) 05:29, 25 June 2012 (UTC)

Well if you're going to adopt behaviorism for this question, which is wise, then (my guess is) sure, they would definitely display consistent differences in behavior, due to both genetic and environmental reasons. The genetic part is kind of the basic assumption of evolution, after all. Gzuckier (talk) 06:14, 25 June 2012 (UTC)

Thank you. I've been wondering about this for quite some time. InforManiac (talk) 06:18, 25 June 2012 (UTC)

Resolved

Thank you for answering my question. InforManiac (talk) 04:18, 25 June 2012 (UTC)

Actually, if you are talking about members of the same colony, they will be clones. Individuals derived from different zygotes will potentially show genetic variation resulting in behavioral differences. μηδείς (talk) 17:22, 26 June 2012 (UTC)

While clones are more similar in behavior, they are not guaranteed to be identical. Identical human twins, despite the name, do not always exhibit identical behavior. This is presumably due to slight differences in environment. In the coral example, different temperature or salinity of the water, different amounts of sunlight, and different food and predators on each side of the coral could change their behavior patterns. StuRat (talk) 17:30, 26 June 2012 (UTC)

I never really thought of this aspect before. Are all choanoflagellates clones? Are all colonies consisting of clones descending from an original choanoflagellate, or was there sexual reproduction somewhere along the line to create zygotes? InforManiac (talk) 20:08, 26 June 2012 (UTC)

I am finding all of this to be very interesting and informative. Thank you, everybody, for all of your input. InforManiac (talk) 19:12, 26 June 2012 (UTC)

I'll keep checking back from time to time to see what else has been written here. This is all very good. InforManiac (talk) 19:20, 26 June 2012 (UTC)

Any updates on Lake Vostok search for life?

I'm sure scientists have had a chance to put some of the water samples from Lake Vostok under a microscope. Has there been any news about if they've found any life in those samples? I haven't been able to find any good updates about it. InforManiac (talk) 04:09, 25 June 2012 (UTC)

From the article you linked to in your question, "Samples of the freshly frozen water in the ice well are expected to be collected at the end of 2012 when the new Antarctic summer starts." 1.124.255.223 (talk) 04:43, 25 June 2012 (UTC)

Thank you for bringing that to my attention. For some reason, I must not have seen that sentence. I'm kind of surprised that they didn't get at least a little bit of fresh water when they first reached liquid water. I thought I read before that they did gather some, but I am probably mistaken. I will be waiting anxiously for 2012's end to find out. InforManiac (talk) 05:00, 25 June 2012 (UTC)

The water only remains liquid when it's under pressure. Removing the drill allows the pressure to drop and it freezes. By the time they could get something down there to get a sample it would be ice. They'll be back to collect that ice later this year. 1.124.255.232 (talk) 05:34, 25 June 2012 (UTC)

That makes sense. Thanks for the info. InforManiac (talk) 05:40, 25 June 2012 (UTC)

Have they figured out how to prevent contamination of the lake with outside organisms ? StuRat (talk) 04:49, 25 June 2012 (UTC)

"According to the head of Russian Antarctic Expeditions, Valery Lukin, new equipment was developed by researchers at the St. Petersburg Nuclear Physics Institute that would ensure the lake remains uncontaminated upon intrusion. Lukin has repeatedly reassured other signatory nations to the Antarctic Treaty System that the drilling will not affect the lake, arguing that on breakthrough, water will rush up the borehole, freeze, and seal..." 1.124.255.223 (talk) 04:51, 25 June 2012 (UTC)

"rush up the borehole, freeze, and seal".. Is that one of those "eats shoots and leaves" things? Gzuckier (talk) 06:17, 25 June 2012 (UTC)

They'll need to be very careful about what they find under the Ice. μηδείς (talk) 17:19, 26 June 2012 (UTC)

Plant identification requested

I would like some help in identifying two plants growing in my suburban garden in south London. Both of them (as far as I can remember) were planted last year on the basis of being annual bedding plants, but both seem to have survived the winter and are currently flourishing. See http://www.flickr.com/photos/19482747@N00/7439490128/ and http://www.flickr.com/photos/19482747@N00/7439489884. My records of what I planted last year don't seem to give much of a clue. One plant has pretty pink flowers about 1 cm across. The other doesn't have any flowers at present (I think there were some flowers at some time last year) but has green leaves edged with white about 1 to 2 cm across. It overgrew the other plants in its bed last year, seems to send out shoots that root, and is trailing along underneath a wall. Both photos were taken today. Any help welcome! --rossb (talk) 11:53, 25 June 2012 (UTC)

The first one looks to me like a Diascia cultivar. Compare the image here. Deor (talk) 12:17, 25 June 2012 (UTC)

I think the first one is a Mimulus and the second one is a Plectranthus. --TammyMoet (talk) 12:19, 25 June 2012 (UTC)

Agree first is Diascia possibly a cultivar called Sunshine. (or maybe not). Second is Plectranthus, possibly "amboinicus variegata", so-called varigated Cuban Oregano. Richard Avery (talk) 15:07, 25 June 2012 (UTC)

No, the first photo shows identical plants to the photo shown in the Mimulus article to which I linked. --TammyMoet (talk) 18:28, 25 June 2012 (UTC)

Sorry, but I disagree, Tammy. The OP's flowers don't look at all like Mimulus to me. I'm also dubious about the Plectranthus identification; that genus seems to have rhomboid-to-ovate leaves with pinnate venation, whereas the OP's plants clearly have palmate venation and are more cordate/reniform in shape. Deor (talk) 22:49, 25 June 2012 (UTC)

OK I'll give you the Diascia, but I still think the photo in the Mimulus article is remarkably similar. Plectranthus is quite diverse and as our article on it says, a reassignment of certain plants to and from that genus has taken place recently - certainly after I last bought a plant sold as Plectranthus, which I still have and looks just like the OP's picture! --TammyMoet (talk) 09:33, 26 June 2012 (UTC)

Is it theoretically possible to make an artificial sweetener that tastes exactly like sugar?

Topic says it all. ScienceApe (talk) 16:02, 25 June 2012 (UTC)

I recall reading something in high school about measurement of sweetness. While I think that the same value of sweetness may be artificially obtained, making all the other parameters of taste equal to that of sugar might be difficult. Different reaction rates, different solubilities etc. might lead to a difference in overall taste. I'm just shooting in the air over here; might be worth to wait for a more qualified answer. Lynch7 16:16, 25 June 2012 (UTC)

Well, not all. Let's make this a slightly more scientifically refined question: Is it theoretically possible to develop a compound which the human tongue finds indistinguishable with sucrose yet the human body does not metabolize in a way that results in significant food energy OR is so potent that metabolically insignificant amounts are necessary to replicate the flavor of sucrose? (Most artificial sweeteners are far more sweet than sugar; the entire game is to make something that is highly sweet for the amount of calories it conveys, so you only need tiny, tiny amounts to get an equivalent sweetness to sugar.) I don't know nearly enough about how the tongue distinguishes between very similar molecules, though, to say for sure, assuming you are ignoring the difficulty of fabricating arbitrary molecules in useful quantities. --Mr.98 (talk) 16:18, 25 June 2012 (UTC)

I don't see why it wouldn't be theoretically possible. I doubt if we have perfect detection of sugar. Such a substance would have to exploit whatever imprecision exists for sugar detection. It would have to elicit the same response that sugar does. Bus stop (talk) 16:22, 25 June 2012 (UTC)

Left-handed sugar. --TammyMoet (talk) 18:26, 25 June 2012 (UTC)

Good point, Mr 98; aren't artificial sweeteners just other kinds of sugars that the body can't break down? Nyttend (talk) 18:26, 25 June 2012 (UTC)

Some of them seem to be, but others are just much sweeter than sugar and thus less of them are necessary. The articles we have on the specific ones are not always clear to me as to which they are (or whether it's a mixture of both). --Mr.98 (talk) 19:13, 25 June 2012 (UTC)

How about ambidexterous sugar, that way you avoid suffering from diarrhea when consuming large amounts of laeft handed sugar? Plasmic Physics (talk) 03:14, 29 June 2012 (UTC)

Note that even if you had such a perfect sugar substitute (tastes exactly like sugar, but has zero calories and side effects), this still might not help anyone on a diet. Current artificial sweeteners don't seem to help, because your body expects to be fed when you taste sugar, and if it isn't, it kicks your hunger into overdrive until it gets what it expected. This would still happen with even a perfect sugar substitute, unless it has an appetite suppressant built-in, too. StuRat (talk) 19:21, 25 June 2012 (UTC)

If I have this straight, the distinctive taste of cane sugar comes from the impurities that remain in it after refinement. It's basically the taste of molasses, but greatly attenuated. I suppose in principle you could duplicate that taste by removing the sucrose from molasses and adding a little bit of what remains to an artificial sweetener. Sucrose per se, as far as I know, does not have a distinctive taste. Looie496 (talk) 04:19, 26 June 2012 (UTC)

That doesn't sound right to me. I don't believe molasses remains in any detectable quantity in cane sugar. We can, of course, taste sucrose itself. With artificial sweeteners we also taste whatever else comes with them. (And they also make me feel lousy after.) StuRat (talk) 04:28, 26 June 2012 (UTC)

Yeah no, that's not right. Commercially available cane sugar is very very pure. I did an industrial visit as part of my undergrad degree at a sugar refinery's quality control lab in Bundaberg, and the sugar crystalls have basically no inclusions. 112.215.36.172 (talk) 00:23, 27 June 2012 (UTC)

Agreed. The white color indicates that no significant quantity of the black molasses remains. StuRat (talk) 00:28, 27 June 2012 (UTC)

@op...did you look at sugar substitute?Smallman12q (talk) 20:22, 28 June 2012 (UTC)

water cooled centrifugal chiller delta pressure across dooler/condenser

dear all, with reference to the above mentioned subject, i request you to clarify my question.

in the design data sheet of chiller, the pressure drop or pressure difference across cooler and condenser is provided by manufacturer, this press.drop is to be maintained for chiller accurate performance or this is the pressure drop to be considered for calculating pressure head for pumps across chiller (chilled water/condenser pumps).

for chiller performance is delta p important of flow to be maintained is important? please advise. regards, wikichilleraaminah — Preceding unsigned comment added by Wikichilleraaminah (talk • contribs) 19:56, 25 June 2012 (UTC)

To the last question, Yes delta p is important. See our artcle Chiller for many other things that are important. Without seeing your application and data sheet, asking the manufacturer is probably your best source of information. DriveByWire (talk) 21:51, 25 June 2012 (UTC)

HEMOLYSIS IN BLOOD SPECIMEN

I WORK IN A ER,IN A HOSPITAL.THE QUESTION I AM ASKING,CAN A COMPREHENSIVE PANEL BLOOD TEST HAVE HEMOLYSIS IN 3 OF 21 TEST ON A REGULAR BASIS — Preceding unsigned comment added by 206.205.82.3 (talk) 21:40, 25 June 2012 (UTC)

Go and ask your boss. We don't give medical advice. SmartSE (talk) 21:55, 25 June 2012 (UTC)

I work in an ER also, and there's no way easy answer here. I'm guessing you're not happy with your laboratory making you re-draw labs for being hemolysed. There's no way of knowing how frequent it will be, as there are too many variables. Likely A) whoever is drawing the blood did it incorrectly, B) the vials were compromised after draw, or C) there was a failure in the lab which ruined the specimen. This article from 2002 is the closest I could find to a proper study. — The Hand That Feeds You:^Bite 20:55, 26 June 2012 (UTC)

Telescopes one and two - new or used? what resolution?

The National Reconnaissance Office recently gave NASA two telescopes that it doesn't need that are apparently "better than Hubble". This NYT article makes it sound as if they were previously in space, rather than being kit that was never used. If that's the case, how could they have got them down? Secondly, they have 7.9 m mirrors - is it possible to guesstimate what kind of resolution would be achieved by having that point down at Earth? SmartSE (talk) 22:02, 25 June 2012 (UTC)

To me, the NYT article doesn't make it sound at all as though the telescopes were previously in space. It calls them "spare, unused 'hardware'" and "'bits and pieces' in various stages of assembly". Sounds to me like stuff that was intended to be sent into space but wasn't because of redundancy, because the spooks developed even better technology, or for some other reason. Deor (talk) 22:36, 25 June 2012 (UTC)

It says 7.9 FEET, not metres! 7.9 foot is 2.4 metres. Vespine (talk) 22:40, 25 June 2012 (UTC)

Which is the same as the Hubble. The Hubble Space telescope is supposed to be diffraction limited, which gives it a resolution of about 0.05 arcseconds for visible light (see the graph on the first linked article, which includes a line for the Hubble). Pointing at earth from an orbit of, say, 300 km, this limit corresponds to about 7 cm. The telescope also has to see through the Earth's atmosphere, so in practice, the true resolution is probably somewhat less than the diffraction-limited resolution (but probably on the same order of magnitude - good enough to see a person, but not to read the classified documents that he's carrying). Buddy431 (talk) 23:28, 25 June 2012 (UTC)

These "stubby hubbles" are either unused KH-11 Kennan or unused prototypes of its abortive replacement, Future Imagery Architecture. It's long been suspected that Hubble and KH-11 where very similar airframes - both were integrated by Lockheed Martin and shipped from their Sunnyvale, CA plant in very similar containers. These two ex-NRO birds are indeed physically broadly similar to Hubble, with the same primary mirror size. The KH-11 article does the same maths that Buddy431 did, and comes to much the same answer ("6 inches") neglecting the distortion from the atmosphere. If you're curious what this might tell you about capabilities of the current NRO, probably not too much. Very little is publicly known about Misty or Misty-2, and both appear to be shrouded (literally and figuratively) to conceal their position and characteristics. The Hubble's 2.4m mirror is a big piece of glass, but Delta IV can have a payload fairing of 5m, which would allow for a single-glass mirror of maybe 4.3m. Beyond that they'd have to do something like the James Webb Space Telescope and have a segmented mirror which they unfurl on orbit (which wouldn't be that surprising an achievement). -- Finlay McWalterჷTalk 00:12, 26 June 2012 (UTC)

If it's so stubby then maybe the field of view is wider and they gave it more megapixels to compensate, due to a lower focal ratio. Sagittarian Milky Way (talk) 19:09, 27 June 2012 (UTC)

As Deor notes, these devices weren't ever in orbit. Had they been, it is (at least in theory) possible for them to be retrieved from orbit by the STS (doing this to fix Hubble was one idea toyed with). Indeed, the technical synergies between Kennan and Hubble signpost the deeper influence the NROs spacecraft had on the shuttle design itself. The final shuttle design was larger and heavier than NASA needed, but they had to work with the USAF to afford the thing, and USAF had to launch NRO's systems. So the shuttle is big enough to launch a Kennan (but turned out to be too heavy to put one in a polar orbit, to the NRO's chagrin) and its predecessor, KH-9 Hexagon. I don't think it's publicly acknowledged who built the primary optics for KH-11, but for KH-9 it was PerkinElmer, who also built Hubble's big mirror. So Hubble was built by the same people who built spy satellites, and designed to launch (and maybe be fixed or retrieved by) an STS designed to do the same for spy satellites; so conversely it's not a big surprise that an unneeded spy satellite might make for the foundation of a decent Hubble. This article in The Space Review has some interesting stuff about the influence of NRO on the shuttle, and their fears and unhappiness regarding it. -- Finlay McWalterჷTalk 00:52, 26 June 2012 (UTC)

Would the Hubble mirror have been ground the same way as the other mirrors? Bubba73 ^{You talkin' to me?} 01:27, 26 June 2012 (UTC)

Very possibly by the same people on the same machine, but I don't think to the same curvature. Hubble's flaw (which they did detect, but discounted) was bad setup, bad QA, and bad procedure - they didn't just forget and put a spy satellite mirror in an astronomical instrument. -- Finlay McWalterჷTalk 01:39, 26 June 2012 (UTC)

That is exactly what I was wondering! At the time of the Hubble error, they said that the mirror was precisely made but to the wrong specifications. I knew that it must be very similar to those used in spy satellites, so I got to wondering if perhaps the spy satellite mirrors are ground one way to focus a few hundred miles away whereas the Hubble mirror was supposed to be ground to focus at infinity. Bubba73 ^{You talkin' to me?} 06:02, 26 June 2012 (UTC)

I'd just be speculating if I said anything about optical spy satellite optics beyond "big mirrors good". But note that the orbits of some of the KH-11s are (relatively) eccentric (e.g. perigee 408 km apogee 931 km), and at these relatively low altitudes their orbits will decay and have to be reboosted (like that of the ISS). And the Earth is very far from spherical; for something in a highly inclined orbit the oblateness of the Earth is the biggest factor that varies actual altitude). So they have to work with a range of altitudes between the instrument and its target, not a perfect fixed distance. -- Finlay McWalterჷTalk 10:49, 26 June 2012 (UTC)

And PerkinElmer's wasn't the only Hubble mirror made, just the only wrong one. NASA got Eastman Kodak (themselves no stranger to overhead reconnaissance optics) to build a spare. Of this backup the Allen Report (linked above) says "The backup OTA primary mirror was polished at Eastman Kodak Company using both a refractive and a reflective null corrector of a completely different design from the Perkin-Elmer version. This mirror matched the templates of the two null correctors to better than 0.014-wave rms wavefront error at 632.8 nm, and the Board has every reason to believe it is the correct hyperboloidal shape." p4-6 -- Finlay McWalterჷTalk 11:04, 26 June 2012 (UTC)

Hard contact lenses vs soft lenses

Hello signori i cognoscenti :) I have heard that hard contact lenses are generally recommended for higher presciptions and soft lenses are generally prescribed for lesser prescriptions, all other things equal. Now considering only minus prescriptions (i.e., to correct myopia), approximately what is the general lowest (or cutoff, or border, etc.) prescription for which hard lenses would be prescribed over soft (not taking into account other factors such as general eye health, age, sensitivity, etc. though an optometrist normally would)? Thank you. 152.97.171.80 (talk) 22:16, 25 June 2012 (UTC)

Here's an article on them, but there isn't a specific cut-off point: [1]. StuRat (talk) 22:23, 25 June 2012 (UTC)

Wikipedia has the article Contact lens. For individual attention which strangers on the Internet cannot give, ask a qualified optometrist. DriveByWire (talk) 22:28, 25 June 2012 (UTC)

If it helps, I've had soft contacts for a -6.2 prescription. I have no idea how much further past that they go. I think they're continually improving them. 209.131.76.183 (talk) 12:14, 26 June 2012 (UTC)

How to improve chandelier efficiency ?

I have a lighting fixture with 12 candelabra base incandescent "flame tip" clear 25 watt bulbs, at present. That's 300 watts total, at 110-120V. It's on a dimmer switch. It puts out a small quantity of rather yellow light and a great deal of heat with those 300 watts. I don't want to replace the entire fixture, and would like to be able to continue to use the dimmer. I was considering getting 12 candelabra base to medium base converters, and then putting in 40 watt equivalent CFL bulbs (which actually use around 9 watts each). However, most CFLs don't work well with dimmers. Those that are "dimmable" apparently only dim 10-25%. This site warns that you can't use regular CFLs and just always keep the dimmer on maximum: [2].

1) Why is that ?

2) How else can I improve efficiency ?

3) Is the situation any better with LEDs ? StuRat (talk) 22:51, 25 June 2012 (UTC)

Some LED lamps can be dimmed, and those that are will dim over the full range. But LEDs are still expensive, so 12 of the will cost quite a bit (my brief browsing of Amazon suggests $80 ish). -- Finlay McWalterჷTalk 01:12, 26 June 2012 (UTC)

Is that $80 for one (which is terrible) or $80 for 12 (which is great) ? StuRat (talk) 06:46, 26 June 2012 (UTC)

I found some for around $10 each, which are 40 watt equivalent and dimmable, and I could just do 6 instead of 12 (that would give me 240 watts equivalent instead of 300). However, these use a medium base, so I'd also need the converter from the candelabra base for each. Also, these bases are pointing upwards, and LEDs are like spotlights, so they would light up the ceiling, leaving the dining room table beneath it in shadows. So far, this seems to be the best option for saving electricity, though. StuRat (talk) 04:04, 26 June 2012 (UTC)

Good advice from Finlay, and you're right about dimming CFLs being dicey. As for "how else" I'll add that I rent a few of these fixtures, 4-8 bulbs x 25-40 watt (what a crappy design :-/). I have taken to only filling ~1/2 of the slots with incandescent bulbs, and that usually meets my lighting needs. It has low initial investment, and saves considerable power. Maybe worth investing in the LEDs if you're in it for a longer haul. SemanticMantis (talk) 02:06, 26 June 2012 (UTC)

That's exactly what I've done as an interim solution. However, 150 watts of dull yellow light and heat still isn't very acceptable. StuRat (talk) 04:07, 26 June 2012 (UTC)

Related question: do empty sockets use 0 watts? SemanticMantis (talk) 02:06, 26 June 2012 (UTC)

To a very good approximation, yes. I think if you are really particular, the socket is a very bad capacitor, so for AC, some very little current will go in- and out of it, which results in some loss to resistance. But this would not be measurable without very good instruments. --Stephan Schulz (talk) 10:35, 26 June 2012 (UTC)

You could also replace the incandescents with quartz halogen globes. At least in this country (Australia) they are available in a wide range of bases, wattages, and some different shapes. There are dimmable and give a good white light. Unfortunately they are only about 25% more efficient than standard incandescents, and cost is quite high. Ratbone58.170.176.182 (talk) 02:10, 26 June 2012 (UTC)

Halogen bulbs with increased efficiency over regular incandescents have started to become available in the U.S. as incandescents are being phased out. I'm not sure if they are available in a 40 W candelabra base bulb, though.--Srleffler (talk) 04:04, 28 June 2012 (UTC)

What if I do replace the chandelier ?

I'd still like to be able to get a variable amount of light out of it, but dimmer switches seem to require expensive LED lights. So, do they make chandeliers where you have switches that can turn each bulb on and off individually, and each has a medium base, so I can use cheap CFLs ? StuRat (talk) 18:56, 26 June 2012 (UTC)

well, without thinking it all the way through; home depot and (i assume) elsewhere have ceiling fan remote controls which are actually little wireless transmitter/receivers, where the receiver end mounts under the appliance baseplate and has a single AC circuit in, but two different AC circuits out (for fan and for light). the fan output has 3 remote selectable settings plus off, the light is continuously dimmable; my thinking is that the fan side could certainly be used for half your individual bulbs and the light side for the other half. they have different kinds of remotes; the slick one has a universal tv remote built in (but died within the year; apparently that's not unusual, and isn't in the store any more), the other kind is the same size/shape as a wall switch and is intended to replace it in the wall, but is acutally self contained and runs off a 9 volt battery so i just use it as a regular remote that i carry around and lose under the couch, etc.

but also; do they really make candelabra base to regular base adapters? i would think there might be a wattage overload safety issue?Gzuckier (talk) 20:27, 26 June 2012 (UTC)

Yes they do. Here's the cheapest one I found: [3] (better ones are made of ceramic). And yes, if you put a 100 watt incandescent in there, you might well have a problem. However, as I intend to use CFLs, and a 100 watt equivalent CFL is only 23 watts, that's under the 25 watts of the current incandescent bulbs, so should be fine, and give me way more light. (I'd probably only use 40 watt equivalent CFLs, which use 9 watts, so I can save energy and get more light/less heat).StuRat (talk) 20:34, 26 June 2012 (UTC)

ok, experimental data: happened to pass by the local job lot store which was selling "U Lighting America" brand (i.e. cheap brand i never heard of made in china 2 for $6) dimmable 23 watt mini cfls (not very mini, about regular bulb size, spiral cfls) so i got a pack and replaced one of the 40 watt incandescents in the ceiling fan attached to the aforementioned remote fan/light dimmer to see how much dimming can a dimmable fluorescent dim (if a dimmable flourescent can dimly flouroesce). Three observations; 1) at full blast the 23 watt cfl is a heck of a lot brighter than a 40 watt incandescent, as expected, 2) at lowest level the cfl is maybe slightly less bright than the 40 watt incandescents at full brightness, I'd say closer to 25% bright than 75% bright, and 3) what i didn't expect, at lowest level with the cfl in one of the 4 bulb sockets, the other 3 incandescents wouldn't go down all the way anymore, i.e. whatever impedance/reactance thing prevents the cfl from going all the way down to zero also works on incandescents in parallel. But my takehome is that maybe you should give a set of dimmable cfls a try. If you want really really bright light i imagine a dozen 23 watters oughta do it, if your concern is more just a reasonable amount of light and dimmable to a reasonably low level but not 0 then smaller cfls. Gzuckier (talk) 00:43, 27 June 2012 (UTC)

The safe limits of operation of a fixture do not depend just on the electrical power consumed. A fixture that is rated for a 40 W maximum incandescent may well fail if used with a 23 W CFL. The reason is that an incandescent bulb dissipates a lot of the energy it consumes as infrared radiation. A CFL or LED dissipates almost all of its waste energy by heat conduction through the base of the bulb and convection carrying heat away from the surface. The 23 W CFL may dump more heat into the fixture than the 40 W incandescent.--Srleffler (talk) 04:10, 28 June 2012 (UTC)

•  Comment: In a perfect world all of our lighting would be fibreoptic from one source. The streetlights outside your house would be cheapest. Someone should invent a chandelier that is 6-20 fibreoptic strands to each light point and run them all from one LED that is on a dimmer. I think the cheap dimmers now still don't increase efficiency. They just dissipate the unused power in heat. CFLs are still a problem with all the mercury, 1-5mg per lamp. Workers in China are getting poisoned in the lamp factories from it. You also may be able to replace the sockets themselves to the larger size and save the cost of adaptors.--Canoe1967 (talk) 22:57, 26 June 2012 (UTC)
  • the solid state dimmers are (i assume) still based on the triac tech that we used to homebrew such things with 50 years ago when they were cutting edge technology, and they actually do not dissipate the excess in heat; they are basically switches that are adjustable for what portion of the AC cycle they conduct. As with any kind of switching circuit, they are highly efficient because when they are on, the voltage across them is very low, and when they are off, the current through them is very low, so the total power, as I*E, across them is always very low except during the very short periods each cycle while they are in the actual process of turning on or off. Gzuckier (talk) 00:43, 27 June 2012 (UTC)

• OK, I was scared off of dimmable CFLs by that statement that they only dim 10-25%, but if you say you tested them and they are decent, I'll give them a try. StuRat (talk) 04:19, 27 June 2012 (UTC)

UPDATE: I found some dimmable, 25 watt equivalent (5 watt actual) CFLs that fit in a candelabra base, eliminating the need for an adapter to change it to a medium base. They dim about as Gzuckier described in his test, and have a "torpedo" shaped clear bulb around the spiral (you can still see inside). The light is whiter than the incandescent's yellow light, which is good. However, at $7 per bulb they are a bit pricey, so I've decided to only get 6 (if they were 100 watt equivalents, I probably could have gotten by with 2). I will use the 6 CFLs in summer, when the heat is a big negative, and switch back to incandescents in winter, when the heat is appreciated. StuRat (talk) 04:33, 30 June 2012 (UTC)

June 26

Sucking on a button to combat dehydration?

Resolved

In the movie Cube (film), the characters are stranded without water. One of the character swallows a buttons and claims it "keeps the saliva flowing". Does this trick actually work? I have my doubts because a small pebble would work just as well as a button so if this technique really worked it would have been discovered millenniums ago and be much more well-known. Anonymous.translator (talk) 00:12, 26 June 2012 (UTC)

Army trainees on maneuvers in the desert around Fort Bliss, Texas, during WWII used to be told to suck on pebbles to allay their thirst; I used to know one such veteran who told me that. Never tried it to see how effective it is, myself. But yes, the technique is an old one, not unknown. Textorus (talk) 00:17, 26 June 2012 (UTC)

Like text says, if it allays anything, it might allay thirst. But that's not going to actually fight dehydration. It's not like your body can just make new water for the saliva. Someguy1221 (talk) 00:21, 26 June 2012 (UTC)

Wow, 5 minutes. Thanks for the quick answer, guys. Anonymous.translator (talk) 00:28, 26 June 2012 (UTC)

My old Scout Leader in the UK told us about sucking pebbles to prevent thirst on a hot day. We thought that it fell (like much of his advice) firmly into the bracket of old wives' tales. Alansplodge (talk) 00:45, 26 June 2012 (UTC)

Some more old wives here, here, here and here. Alansplodge (talk) 00:54, 26 June 2012 (UTC)

I remember reading about sucking on pebles in Baden-Powell's book Scouting For Boys when I joined the Scouts in the 1960's. This book had been published about 50 years before but was still the primary text for boy scouts (10 to 12 year olds) at that time. I think Scouting For Boys would be the original source for the pebbles advice. I don't have the book now, but I think the advice was aimed at distracting boys from wanting a drink too often while on treks (as the average boy would be accustomed to having a drink any time he liked at home), and not expected to counter genuine thirst, and certainly not dehydration. Other advice in the book was very good, as I recall (except the advice to help old ladies across streets - I tried that once and got told "piss off sonny"). Wickwack120.145.57.11 (talk) 04:10, 26 June 2012 (UTC)

Old boy, the book is scanned here and it still makes a jolly good read. It doesn't mention any "pebles" but says: "If you keep your mouth shut when walking or running, or keep a pebble in your mouth (which also makes you keep your mouth shut), you do not get thirsty as you do when you go along with your mouth open, sucking in the air and dry dust." pp. 160 Scouting for Boys. "When in the street, always be on the look-out to help women and children. A good opportunity is when they want to cross a street, or to find the way, or to call a cab or bus. If you see them, go and help them at once - and don't accept any reward." -- ibid. pp. 178 DriveByWire (talk) 17:51, 26 June 2012 (UTC)

OP, I'm interested in the verb "shallows" in your question. At first I assumed it was a typo for "swallows", but surely you weren't talking of swallowing buttons or pebbles, and the header is about sucking, not swallowing. I checked wikt: shallow but it has no meaning equivalent to "suck". Can you explain this word "shallow" to me, please? -- ♬ Jack of Oz ♬ ^{[your turn]} 19:03, 26 June 2012 (UTC)

Typo.Anonymous.translator (talk) 20:14, 26 June 2012 (UTC)

As a side note, this is how I [4] handle typos.Anonymous.translator (talk) 20:20, 26 June 2012 (UTC)

Thanks, but I still don't understand why you'd be advocating the actual swallowing - not just sucking - of small pebbles. Did you really mean physically ingesting of anything that's not food and not digestible and potentially harmful? -- ♬ Jack of Oz ♬ ^{[your turn]} 20:31, 26 June 2012 (UTC)

I tried the pebble trick as a Scout, and it did not seem to accomplish anything toward "reducing thirst." If 1,000,000 kids each picked up a pebble from the ground and walked around for a few hours with it in his mouth, how many would become ill from crud deposited on the pebble while it was on the ground, how many would accidentally get the pebble stuck in his windpipe, requiring a Heimlich maneuver or tracheotomy, like other boys who placed pebbles in the mouth to keep it moist?See also another case of a 7 year old who had a pebble held in the mouth slip into the trachea. Edison (talk) 13:25, 27 June 2012 (UTC)

Discovery of Uranium in Russia

I am withdrawing this question.

Medical treatments for "Exhaustion"

This is not a request for medical advice, but for referenced information about hospital treatments for this condition, not presently found in the relevant Wikipedia article. There are news stories from time to time about celebrities, musicians, actors, and politicians hospitalized for "exhaustion." Searching for this malady in Wikipedia, one finds a redirect to Fatigue (medical). Leaving out obvious and readily treated causes of various forms of the malady such as physical muscular fatigue (someone trying to swim 100 miles), or sleepiness after staying awake for 4 days, there remains a vague condition. I once read an article (citation not at hand) which said that ordinary people are never hospitalized for "exhaustion" as are celebrities, whose exhaustion may consist of substance abuse, eating disorders, dehydration, "burnout," stress or depression. The "exhaustion" description is sometimes said to be a public relations code word for mental health issues and substance abuse. The relevant Wikipedia article does not describe how exhaustion is treated in a hospital. Any reliably sourced info for current medical practice in treating "exhaustion" in those hospitalized for it? Edison (talk) 04:00, 26 June 2012 (UTC)

No useful answer can be given beyond "rest", as the treatment would vary enormously depending on cause and symptoms, which, as you note, vary enormously themselves. Dominus Vobisdu (talk) 04:12, 26 June 2012 (UTC)

Agreed. The only way that true exhaustion wouldn't be solved by rest is if they have a sleep disorder, and then the hospital/clinic would diagnose and treat that.

Also note that lack of sleep and substance abuse are often combined in celebrities, like Judy Garland, Marilyn Monroe, and, more recently, Micheal Jackson. They can take (or be forced to take) drugs to keep them going while filming, rehearsing a concert tour, etc. A nasty cycle can form where they take "pep pills", such as amphetamines, to stay awake, then take sleep meds to sleep, gradually upping the dose of each to counter the other. In such a case, the hospital/clinic would need to treat the drug addiction first. Then, after they recover, hopefully they can be less ambitious, and maybe do only half as many concerts or movies, or as many as they can handle in a healthy manner. StuRat (talk) 04:14, 26 June 2012 (UTC)

"Exhaustion" is a symptom, not a condition, and it would be possible to be hospitalised with that symptom while the physical cause of the exhausion is investigated. Conditions such as some endocrine disorders (hypothyroidism, myasthenia gravis) could be indicated. --TammyMoet (talk) 09:19, 26 June 2012 (UTC)

"Exhaustion" in these cases invariably means drug or alcohol abuse and its after-effects. μηδείς (talk) 17:13, 26 June 2012 (UTC)

• In the article I read years ago, a doctor or nurse asserted that a publicist may tell reporters that a celebrity was "hospitalized for exhaustion," but that within the hospital, that would not be the diagnosis, illness, or condition shown on the patient's chart, which might indocate detox from painkillers, alcohol etc, or treatment for depression. Yet our article lists diagnosis codes for "exhaustion" per se. So might a patient's chart actually indicate he is "exhausted" and so needs to be in a hospital bed for some days to become "unexhausted?" Edison (talk) 13:09, 27 June 2012 (UTC)

What are galaxies made of?

SN 1994D, a type Ia supernova in the NGC 4526 galaxy (bright spot on the lower left)

How do we know that galaxies are made of stars instead of gas? Have anyone taken a picture of a galaxy which one can see individual stars in it. The milky way does not count. If we cannot see individual stars in a picture of a galaxy what's to say that it is not made up of gas instead? Maybe it's all just gas swirling around a big black hole. 220.239.37.244 (talk) 12:42, 26 June 2012 (UTC)

Yes, we can easily resolve individual stars in many other galaxies. Up until the middle of the 1920s there was a debate, but then Edwin Hubble first identified individual stars in some near galaxies. See Great Debate (astronomy). --Stephan Schulz (talk) 13:00, 26 June 2012 (UTC)

And occasionally we see them blow up. Blakk and ekka 15:30, 26 June 2012 (UTC)

Galaxies glow; big clouds of gas do not. If galaxies did not contain lots of glowing stars, we could not see the galaxies. There are big clouds of gas and dust around which don't contain stars, and we can only detect them when the pass between us and glowing things, the light of which they obscure. -- Finlay McWalterჷTalk 13:08, 26 June 2012 (UTC)

Nebula don't glow? ScienceApe (talk) 15:16, 26 June 2012 (UTC)

Nebula only glow because there are stars in or behind them which are lighting them up. There's no know process where a large, diffuse (cold) cloud of gas by itself can sustain light output for a prolonged period of time. If galaxies outside the milky way were just gas, they wouldn't be visible, as they wouldn't be able to emit light themselves and there would be nothing behind them to illuminate them. (P.S. Galaxies are made up of both stars *and* gas.) -- 71.35.99.136 (talk) 15:36, 26 June 2012 (UTC)

Clusters of galaxies as well as large elliptical galaxies are embedded in hot tenuous gas that radiates in X-rays. This gas is hot because it's in a deep gravitational potential well (it attained its temperature through shock heating when falling into the cluster potential), not because it was heated by stars. In the early stages of galaxy formation, before stars were formed, you could imagine a potential well just being filled with (glowing) gas. The things closest to that scenario are probably Lyman-alpha blobs. --Wrongfilter (talk) 15:45, 26 June 2012 (UTC)

Well then doesn't it stand to reason that there might be a lot of gas in galaxies that we can not detect, and therefore the so called "missing mass" from galaxies does not exist, and that dark matter is probably just undetectable gas? ScienceApe (talk) 18:02, 26 June 2012 (UTC)

No, because we could detect them, due to their absorption spectrum effect on the light from the stars behind them. The missing mass must neither emit nor absorb light or other frequency on the EM spectrum. StuRat (talk) 18:07, 26 June 2012 (UTC)

It's actually not such an easy problem. The majority of astronomers don't think that gas could account for dark matter, but there is a minority who aren't sure, and the arguments are pretty difficult. Looie496 (talk) 18:18, 26 June 2012 (UTC)

The article on dark matter doesn't make any mention of gas as a possible explanation. The only alternative hypotheses it lists are to do with alternate theories of gravity. As I understand it models of galactic evolution put the bulk of dark matter in dense "halos" above the galactic plane, so if dense clouds of gas were present there, they would be easily detectable. 112.215.36.174 (talk) 10:33, 30 June 2012 (UTC)

You might want to read the articles on Uniformitarianism and Astronomical spectroscopy. We do not need to assume, but can directly observe that the laws of chemistry are the same everywhere. μηδείς (talk) 17:11, 26 June 2012 (UTC)

Why does new year start from Jan 1? Why not synchronize it to vernal equinox or winter solstice?

why is the gregorian calendar designed so that new year starts from where it starts now? wouldn't it be better if the new year started from a day more remarkable like one of the solstices or equinoxes? 117.216.157.33 (talk) 17:12, 26 June 2012 (UTC)

Well, the solstices and equinoxes aren't always on the same calendar day every year, so that would make it difficult to tell on any given year when the new year even starts. Mingmingla (talk) 17:56, 26 June 2012 (UTC)

You're saying in effect that it would not be the simplest thing in the world to convert between the Gregorian calendar and a solstice– or equinox-based calendar; but that's not a valid point against the latter. —Tamfang (talk) 20:42, 26 June 2012 (UTC)

We start the year on January because the Julian calendar, which 2,000 years ago was already the same as what we use now, except for one rule, started on January. If it were on the winter solstice, say, you couldn't say "December 2012" because then it'd be like which December 2012?, the one before the solstice or the one after? Now you could change the months to start on the equinox but why!? We've accumulated a large number of laws, records, birthdates, and holidays that would all have to be changed if we did that. You'd have to relearn everything. What day will be Christmas? NewJanuary 4th? Ultradecember 5? Halloween will be SuperOctober 10. Titanic sinks SubApril the 26th. And either the current August 21st would have to be fall or June 20th in spring, for the Northern Hemisphere, which doesn't seem right. Sagittarian Milky Way (talk) 18:04, 26 June 2012 (UTC)

Excepting all of mine, best help-desk post ever! μηδείς (talk) 03:16, 27 June 2012 (UTC)

hehe, yeah i agree on the uselessness of the excercise. but many other calendars roughly coincide with spring equinox as new year, so i thoght it might be probable that the new year was actually designed to start on winter solstice, but over time, has moved 10 days further due to various probable reasons (historical, astronomical, etc). just a thought. 117.216.157.33 (talk) 18:40, 26 June 2012 (UTC)

I don't think the new year was reckoned as starting on January 1 until the late 18th Century. It used to start on March 1. thx1138 (talk) 18:42, 26 June 2012 (UTC)

I was wrong, it's more complicated than that: Gregorian calendar#Beginning of the year. Anyway, the reason the Julian calendar originally used January 1 as the beginning of the year is because at that time, that's when Roman consuls started their terms of office. thx1138 (talk) 18:45, 26 June 2012 (UTC)

hmm, that's pretty arbitrary. too bad, I was hoping to find a more interesting answer :P

Could it be that January 1 was the winter solstice at one time in the distant past?165.212.189.187 (talk) 18:44, 26 June 2012 (UTC)

Jan 1 was once the solstice in the Julian calendar, but before there were Romans. That's only because of the Julian calendar's inability to track it well, not because it really moved that much. Sagittarian Milky Way (talk) 19:43, 26 June 2012 (UTC)

so it might not be all that arbitrary at all? 117.216.157.33 (talk) 19:59, 26 June 2012 (UTC)

my doubts are exactly the same. 117.216.157.33 (talk) 18:47, 26 June 2012 (UTC)

Just a guess, but Christmas day is on the 359th or 360th day of the year, so I'm thinking they wanted 360 "normal days", ending in Christmas, which makes for 12 months of exactly 30 days, followed by 5 extra days, at the end of the year. StuRat (talk) 18:51, 26 June 2012 (UTC)

But according to Gregorian_calendar#Beginning_of_the_year, Jan 1 was new year since 153 BC; before the tradition of christmas started. 117.216.157.33 (talk) 19:00, 26 June 2012 (UTC)

When was Saturnalia, the Roman pre-Christian festival? Maybe it had something to do with that.

Yes, they may have positioned Christmas at that time of the year, since nobody really knows when Jesus was born. StuRat (talk) 19:54, 26 June 2012 (UTC)

All these dates come in a very small range (arnd 10 days within each other); so it might be possible that some shift might have taken place either due to faulty calculation of dates or (less likely) due to some astronomical phenomena (i dunno, slowing down of earth, or whatever)

uh....::::precession....!?68.83.98.40 (talk) 04:37, 27 June 2012 (UTC)

No precession. In 12,000 years the winter constellations will be best viewed in summer and have had to have been renamed twice. Same for the other seasons. And how wrong the Western sun signs are changes by 1 day every 70 years. (Because they refuse to just rename them 1, 2, 3 and 4 after they grow out of date) But but that's about it. If the solstice is changing by 10 days in 1,000 years then one day it will be snowing in June, and your calendar is not doing it's job, not that anything's moving. (Well, it's not possible to make a perfect season tracking calendar as the eccentricity of the Earth makes the solstices and equinoxes move around a bit, but the it shouldn't ever get further from it's average date by about 21/3 days (and even that takes longer than our months have existed), plus 1¼ day if you have to wait 400 years for the all the leap days to average out like this: .

Add 1 more day inaccuracy every 3,200 years away from now due to a need for longer term leap year rules, or maybe not, this is beyond our predictive abilities). I'm pretty sure no one had thought of January yet when the Julian solstice was on January 1. Season seems to indicate that they started their year at March because it was the start of spring (when it was warm enough to make wars again, typical Romans), so that might be why the months start when they do. Rome winters end earlier than most of the Western civilization that adopted it's calendar, due to it's mediterranean climate, so I assume that's why they didn't make their seasons a little later. Maybe it's not so bad. Though Mother Nature sometimes has the nerve to make it too cold to skinny dip and sleep outside naked well into June, and it's still warm in early Sept., it's not very bright then and the long days are a part of summer too, right? Sagittarian Milky Way (talk) 20:37, 27 June 2012 (UTC)

Until recently, Christmas wasn't a big deal, unlike Easter. —Tamfang (talk) 20:42, 26 June 2012 (UTC)

If I were Pope Gregory's advisor I'd say: each month shall have 30 days until some month ends or begins on a solstice or equinox, and thereafter the sequence shall be 30 31 30 31 30 31 30 31 30 31 30 30¼. —Tamfang (talk) 20:42, 26 June 2012 (UTC)

No, because the goal was to bring the day of the vernal equinox back to when it was at the First Council of Nicea (325AD). Unless skyviewcafe.com is sufficiently inaccurate, it seems they chose the correct number of days to drop (whether Rome, Jerusalem or Nicea local mean time doesn't make a difference). What's puzzling is why it's mentioned alot that they wanted March 21 when they knew the year to less than a minute of accuracy. March 20 is closer, both in 325 and in 1582. It seems like if anything they wanted March 20. It was March 21st around 200. Maybe the current Easter rules (equinox, full moon, sunday) were developed around then? Also, how would you make a month 30¼ days long? Have it end at 6am? Sagittarian Milky Way (talk) 21:38, 26 June 2012 (UTC)

Since no one already said this: The current calendar has a month of 28¼ days, in the sense intended. —Tamfang (talk) 06:23, 2 June 2018 (UTC)

Roman calendar gives more info about older calendars. In particular, Martius/March was once the first month, as is evidenced even now by the names of September through December. The OP would have been happier then: "Roman writers claimed that their calendar was invented by Romulus, the founder of Rome around 753 BC. His version contained ten months with the vernal equinox in the first month". The insertion of January & February is attributed to Numa Pompilius.John Z (talk) 03:43, 27 June 2012 (UTC)

Note to non-classicists: septem, octo, novem, decem = 7, 8, 9, 10. QED. Ghmyrtle (talk) 13:37, 27 June 2012 (UTC)

Is it possible to make a sneaker that makes you run faster?

Topic says it all. ScienceApe (talk) 18:00, 26 June 2012 (UTC)

With little rocket engines on the back, 0.01 millimeters thick, and made of carbon nanotubes? Sagittarian Milky Way (talk) 18:07, 26 June 2012 (UTC)

Acme Corporation should have those in stock. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:55, 27 June 2012 (UTC)

It's easy. You just put some big old springs on it. There are some disadvantages to that approach, though, including an increase in the likelihood of hurting yourself. Looie496 (talk) 18:14, 26 June 2012 (UTC)

Oscar Pistorius would say yes. But the fitting process is a big problem... SemanticMantis (talk) 18:15, 26 June 2012 (UTC)

In addition to adding springs to change the impact energy (normally turned into heat) into kinetic energy, sneakers can also help you run faster by protecting you from injury. Somebody less afraid of injury will run less timidly, and somebody uninjured will also run faster. Sneakers also can get better traction on slick surfaces.

On the other hand, sneakers can keep your feet warm and moist, which is an ideal breeding ground for various nasties, which can reduce your running speed. And then there's the extra weight carried around (and accelerated then decelerated with every step). So, well-designed running shoes, which fit properly, likely increase your running speed, while cheap sneakers may even make it worse. StuRat (talk) 18:22, 26 June 2012 (UTC)

As I sit here on hold for Blockbuster Video's through the mail service, let me speculate that a good pair of well fitting sneakers will allow you to run your best (if not faster) while bad shoes will slow you down compared to bare feet. μηδείς (talk) 00:38, 27 June 2012 (UTC)

I sure I wish I had thought to say that right before you did. :-) StuRat (talk) 02:03, 27 June 2012 (UTC)

So you are about to cancel your through-the-mail account with Blockbuster as well? I have never been so disappointed. After I waited a week for it the first time, then drove it to the store to hand it in with a complaint to the clerk, they sent me the same cracked DVD a second time in a row! μηδείς (talk) 03:11, 27 June 2012 (UTC)

I have Netflix, but dropped the DVD delivery when they upped the price, and now watch streaming only. StuRat (talk) 07:17, 29 June 2012 (UTC)

I'd consider that but my computer chair is way less comfy than my TV chair. —Tamfang (talk) 06:06, 1 July 2012 (UTC)

The OP must not have seen the ads for PF Flyers in the 1960s.  :-) Bubba73 ^{You talkin' to me?} 03:03, 27 June 2012 (UTC)

http://www.rockcreek.com/vibram/flow-mens/13215.rc Count Iblis (talk) 19:25, 27 June 2012 (UTC)

This would be a fine question for the computer who wore tennis shoes. Clarityfiend (talk) 22:01, 27 June 2012 (UTC)

Rectal Swab vs Stool Test

Hello. When might a doctor order a rectal swab over a stool test? The stool test, where the patient defecates into a bag, seems more comfortable than the rectal swab, where the patient picks his rectum with a stick. Thanks in advance. --Mayfare (talk) 18:18, 26 June 2012 (UTC)

The rectal swab would provide more of a local test, while the stool sample is more of a general test of the entire digestive system. So, the rectal swab might be useful if a rectal problem is suspected (like a tear in the lining which then became infected). StuRat (talk) 18:30, 26 June 2012 (UTC)

That's not correct. First of all, a swab is a lot easier to collect than a stool sample. It's fine for detecting bacterial infections like salmonella where only a tiny sample is needed. Stool samples are needed to detect parasites, though, and usually more than one sampling is needed because the concentration of parasites is often low and they are relatively difficult to detect. The third type of test would be the test for occult blood, which requires a sample about the size of a BB. It detects bleeding anywhere in the GI tract, either from cancer or from a bleeding ulcer. Dominus Vobisdu (talk) 18:53, 26 June 2012 (UTC)

Did you say anything that conflicts with what I said ? StuRat (talk) 19:56, 26 June 2012 (UTC)

Yes. The swab does not detect localized problems, but problems with the entire digestive tract, just like the stool sample does. The difference is the kind of pathogen being tested for, with swabs working well enough with bacteria, fungi and viruses, and (multiple) stool samples being necessary for parasites.

One exception is the "scotch tape prep" for pinworms. This involves folding a two inch length of scotch tape over on itself sticky side out, sticking one side to a tongue depressor (or spoon), then sneaking into the sleeping victims room with a flashlight at about 5 am, yanking the covers off, pulling their shorts down, and touching the sticky tape firmly to the skin around their their bunghole all with lightening speed. In the lab, the tape is examinined under the microscope for pinworm eggs. The worm crawls out the butt at night and lays them there in large numbers. Dominus Vobisdu (talk) 21:44, 26 June 2012 (UTC)

Certain medical tests are meant as discouragements to would-be patients, of course. μηδείς (talk) 03:55, 27 June 2012 (UTC)

...and even more of a discouragement to nurses and interns. StuRat (talk) 03:59, 27 June 2012 (UTC)

Sodium fuel

Since sodium, as with other alkali metals, are so reactive, even to water, can we use them like gasoline (in the same way gasoline combusts) as a fuel source for cars? 64.229.5.242 (talk) 20:31, 26 June 2012 (UTC)

There are probably ways that energy could be harnessed from pure sodium. But it is unlikely that there would be a safe and efficient system for doing so, and the production of pure sodium would require much more energy than you will get out of it (sodium metal does not exist in nature, so energy would be required to convert available sodium cations to sodium metal). — Preceding unsigned comment added by 148.177.1.210 (talk) 20:34, 26 June 2012 (UTC)

Agreed. Also, if you react it with water you get a salt, which is rather corrosive, and shouldn't be released into the environment in quantity or it will kill the plants by the roads and the fish in the rivers where it ends up. StuRat (talk) 20:51, 26 June 2012 (UTC)

It's a salt but not NaCl, there's no chlorine. Hot sodium hydroxide and hydrogen maybe? Ech, even worse effluent. You could melt human flesh with that. Sagittarian Milky Way (talk) 21:42, 26 June 2012 (UTC)

Or clean your car. :) Matt Deres (talk) 22:10, 26 June 2012 (UTC)

Well it would be far more efficient to using it in a sodium battery as efficiency may be over 50% rather than a chemical reaction making heat. The above water reaction would produce hydrogen, and probably in a more compact and efficient storage form than those liquid hydrogen fueled cars.

Sodium metal, while very malleable, isn't a liquid. It would therefore be difficult to meter precisely. There are also logistical problems of refueling without causing an explosion; providing a transport mechanism from your fuel reserve to the engine; and transporting large quantities of sodium to fuel stations around the country/world . Also because it is so reactive, if any water got into your tank, boom. A little water in your gas tank is not really a problem. Gasoline is a much more stable fuel. Mythbusters tried a similar experiment with gun powder, they were unable to get it to work. Bcr666 (talk) 16:08, 1 June 2018 (UTC)

June 27

Why do dolphins kill sharks?

Why do dolphins kill sharks? — Preceding unsigned comment added by 68.83.98.40 (talk) 04:32, 27 June 2012 (UTC)

Because sharks kill dolphins. Looie496 (talk) 05:40, 27 June 2012 (UTC)

Not being a marine biologist, I'd say Looie's answer is pretty spot-on. My guess is that sharks and dolphins also compete for certain sources of food, but I may be wrong about that. Evanh2008 ^{(talk|contribs)} 05:55, 27 June 2012 (UTC)

OK, can someone point me to something saying that dolphins actually do kill sharks? Between a single dolphin and a single shark, I'd bet on the shark, though I could believe that dolphins might be able to use their intelligence to kill a shark with teamwork. --Trovatore (talk) 07:03, 27 June 2012 (UTC)

Here's something on the behaviour of bottlenose dolphins [5](bottom of page). Mikenorton (talk) 07:15, 27 June 2012 (UTC)

(e/c) I cannot speak as to reliability but per here: "The idea that dolphins will seek out sharks for undersea battle is largely incorrect. It is the unfortunate perception stemming from the 60's "Flipper" generation..." and continues from there.--Fuhghettaboutit (talk) 07:17, 27 June 2012 (UTC)

These sources [6] [7] seem to agree that dolphins rarely attack sharks. Nil Einne (talk) 07:19, 27 June 2012 (UTC) Edit: Also [8]

What kills more dolphins: sharks or humans?165.212.189.187 (talk) 13:17, 27 June 2012 (UTC)

(Based on a more careful check of the mortality rate of dolphins from humans, I've reconsidered the answer hence the strike-out.) Considering the above sources suggest sharks don't really compete with dolphins that much, the likely answer is humans. This non-RS [9] makes the claim (edit: that humans kill more dolphins then sharks) but I don't vouch for it as it provides nothing to back up the claim, however it does mention tiger sharks, great white sharks and bull sharks as the likely shark predators of dolphins (one of the other sources mentioned tiger sharks as well). [10] claims that despite a frequent attacks by tiger sharks, the number of dolphins killed is small. (I don't know if the other source really contradicts this as it just said the person had found many dolphins in tiger sharks, the percentage may still be low.) Edit: In any case, it appears to me the mortality rate of dolphins from sharks is not that high although I don't have any specific numbers.

This will also depend on how you define 'kill'. I presume your excluding very indirect methods like overfishing. Are you including slightly less indirect methods like PCB contamination and other forms of pollution or habitat destruction? (I don't know if these are significant enough to be considered.) I presume you're including direct but inadvertent methods like deaths due to bycatch. On that point, I can't find any good non activist recent sources on overall mortality rates how what I've found suggests it's generally low. For example [11] suggests a rate of less then 5000 for those caught for the US market and [12] suggests a rate of 2600 in the eastern Pacific in 1996. You can add to that a few thousand killed by hunting, see e.g. Dolphin drive hunting. Based on this, the answer may very well be sharks in some cases although I have no idea of the mortality rate from sharks. (Definitely based on earlier rates of 100k+ humans seem hard to beat, see also [13].) Of course this does depend on the precise species of dolphin and where they live. I strongly suspect even ignoring habitat loss and degradation, many more Orcaella brevirostris are killed by humans then sharks. Nil Einne (talk) 18:48, 27 June 2012 (UTC) Edit2: Noticed we also have a Cetacean bycatch which seems to support the idea overall the numbers are low now although there may still be some at risk. Dolphin#Human threats also mentions the other threats.

While I wouldn't expect dolphins to kill large adult sharks, juvenile sharks (or adults of small species of sharks) would just be another fish they would eat. I believe the size threshold would be what the dolphins could swallow whole. StuRat (talk) 18:17, 27 June 2012 (UTC)

If humans kill more dolphins than sharks do, both directly and indirectly, then why don't dolphins kill us?165.212.189.187 (talk) 19:51, 27 June 2012 (UTC)

Because sharks have been killing dolphins for millions of years, which is enough time for dolphins to evolve an anti-shark bias, while humans have only been killing dolphins for a few thousand years. Also, if they did kill humans, it would be counter-productive, we'd just wipe them out. However, when dolphins are captured (with their families killed), held captive and forced to do tricks, like at Sea World, they do occasionally get even by killing people (although it's hard to tell if those deaths are on porpoise). Then there's the Simpson's episode where the dolphins take over the land and force all humans into the ocean. :-) StuRat (talk) 21:14, 27 June 2012 (UTC)

You do realize that didn't really happen, since it was a Halloween special? μηδείς (talk) 01:34, 28 June 2012 (UTC)

And the rest of the Simpson's, of course, is a factual documentary of their real lives. StuRat (talk) 01:46, 28 June 2012 (UTC)

Did you guys miss all the stuff up above, demonstrating that dolphins do not in fact kill sharks, at least in numbers large enough to be noticed? --Trovatore (talk) 21:21, 27 June 2012 (UTC)

And did you see Nil's 3rd link, which confirms, as I suggested, that dolphins will attack small sharks, which they don't see as dangerous ? StuRat (talk) 21:39, 27 June 2012 (UTC)

Are you referring to the link which shows that dolphins will attack certain sharks if trained by the US navy, but not large ones? If so I'm not sure that is particularly relevent. Unless I missed it, none of the links indicated there's any real evidence of dolpins regularly attacking sharks big or small. (It does demonstrate that dolphins have evolved an anti certain dangerous animals bias, but I'm not sure if Trovatore was disputing that. The bias appears to be in the form of avoiding dangerous animals rather then trying to kill them as is hardly surprising.) Nil Einne (talk) 19:34, 28 June 2012 (UTC)

Dolphins do kill humans [14] :-P (I primary mention this because a common question and one which confuses results when trying to find out dolphin mortality from humans vs sharks appears to be whether dolphins or sharks kill more humans. The answer appears to be sharks, since I only found one human death attributed to a dolphin in the wild. There are some near misses like a woman who got dragged down 100 feet and also some other results which confuse matters like people who died swimming with dolphins but where the death appears to have been natural causes. Not that sharks actually kill many people any way. BTW the other result which confuses search attempts on the dolphin mortality issues is of course dolphins occasionally saving humans.) More seriously beyond what has been said above, while dolphins are intelligent, as I mentioned above many of the mass killings in particular were from by catches so the connection to humans is rather indirect. Even if there was time to evolve, this would be to avoid nets or boats or otherwise escape from them rather then to kill humans. Note that while evolution may sometimes provide the tools to kill potential predators or other hazards, usually it also evolves towards using them sparringly. It doesn't tend to act towards killing these predators or hazards on sight, that's rarely a productive strategy. As StuRat has hinted at, it's particularly true with humans. While I'm not saying we would wipe them out, I think it's clear the idea of dolphins as cute, intelligent docile creatures you can swim with is one of the reasons people are so much more concerned with killing them then of the many, many 'killer'/'dangerous' sharks killed by humans each year. (Even if these concepts are not particularly accurate.) Nil Einne (talk) 19:55, 28 June 2012 (UTC)

Dolphins do mob sharks: Bottlenose_dolphin#Predators. μηδείς (talk) 01:33, 29 June 2012 (UTC)

Resolved

Which model of Citroën DS?

Citroën DS 21?

I saw and photographed this car in Paris earlier this month. It looks kind of neat IMO. But exactly what type of car is it? I suppose it is a Citroën DS, but this model has been manufactured in many variants. Being a car ignorant myself, could someone help me getting closer to which exact variant it is? --Slaunger (talk) 14:41, 27 June 2012 (UTC)

Looks like Citroen DS cabrio, as pictured at Citroën DS and [15]. Bazza (talk) 18:21, 27 June 2012 (UTC)

File:1974 Citroen DS23 Pallas.jpg Looks very similar to this one.--Canoe1967 (talk) 18:28, 27 June 2012 (UTC)

Thanks for the hints! I think it is some variant of the Citroen DS Cabrio. It looks very much like this DS Cabrio. But the Cabrio appears to be made with different front light systems, like this DS Cabrio. The Pallas referred to by Canoe has many similarities, but the elevated rear light system found in my photo is not on the Pallas, but seems to be on all the Cabrios found in the link provided by Bazza 7. --Slaunger (talk) 18:39, 27 June 2012 (UTC)

With help from elsewhere it has been confirmed that it is a Citroën DS 21 Cabriolet. --Slaunger (talk) 15:06, 28 June 2012 (UTC)

Resolved

BSP WASHER SIZES

IS THERE A STANDARD FOR BRITISH STANDARD PIPE THREAD WASHERS AND A TABLE OF SIZES ? — Preceding unsigned comment added by 195.74.125.225 (talk) 15:23, 27 June 2012 (UTC)

YOU MEAN THIS? OR MAYBE THIS? ←BASEBALL BUGS ^{WHAT'S UP, DOC?} CARROTS→ 19:47, 27 June 2012 (UTC)

Friction

Can anyone direct me to research regarding the ratio of static friction and kinetic friction, i.e. I am interested in $\mu _{s}:\mu _{k}$. — Fly by Night (talk) 20:04, 27 June 2012 (UTC)

I'd think the highest difference would be in a case where the surfaces actually break. For example, two sheets of sandpaper might have the sand grains ripped off when the object starts to move, greatly reducing the friction. StuRat (talk) 22:06, 27 June 2012 (UTC)

Fiddlesticks. DriveByWire (talk) 00:34, 28 June 2012 (UTC)

How about a flour avalanche in a slowly turning drum? Plasmic Physics (talk) 04:05, 28 June 2012 (UTC)

June 28

skin flora

is mainting your skin flora helpful in preventing skin infections like mainting your vaginal flora is good?--Wrk678 (talk) 02:19, 28 June 2012 (UTC)

Yes. Specifically, killing off the skin bacteria can allow fungi to grow there. StuRat (talk) 02:26, 28 June 2012 (UTC)

The desk appreciates contributions from owners of good vaginal flora. DriveByWire (talk) 13:05, 28 June 2012 (UTC)

Wife, responding to husband who brought her flowers for no reason: "So now I suppose you expect me to spread my legs ?"

Husband: "Why, don't we have a vase ?" StuRat (talk) 07:14, 29 June 2012 (UTC)

trees of interest

Berberis gagnepainii thorns

is there a tree or a bush that has about 2 inch thorns on it where every leaf is. — Preceding unsigned comment added by 2602:306:CCF5:E7F0:FDBA:5660:E85A:B5BF (talk) 03:19, 28 June 2012 (UTC)

According to this site, the red hawthorn has 2-4 inch long thorns: [16], although I'm not sure how they are spaced relative to the leaves. StuRat (talk) 03:36, 28 June 2012 (UTC) I've taken the liberty of correcting the 'hawthorn' spelling to link it. Richard Avery (talk) 07:42, 28 June 2012 (UTC)

Thanks, but unfortunately that doesn't appear to be the same species. Crataegus columbiana, Crataegus chrysocarpa, and Crataegus rotundifolia were the three species listed at my link as "red hawthorn". StuRat (talk) 07:06, 29 June 2012 (UTC)

Acacia tortilis the Umbrella Thorn http://www.google.com/search?q=acacia+tortilis&num=100&hl=en&newwindow=1&safe=off&client=safari&rls=en&prmd=imvns&source=lnms&tbm=isch&sa=X&ei=b-PrT5-lFoyA6QH_k6niBQ&ved=0CPgDEPwFKAE&biw=1027&bih=739 μηδείς (talk) 04:56, 28 June 2012 (UTC)

A couple of Berberis species have decent thorns, Berberis julianae and Berberis gagnepainii, the thorns of which are pictured. Richard Avery (talk) 07:39, 28 June 2012 (UTC)

In northern Europe, the Blackthorn has the most evil thorns in town, beating the Hawthorn hands down. A friend had one punch through the sole of his work boot and I've heard of people losing eyes to them. If one gets lodged under your skin, it festers horribly. It is considered unlucky to bring blackthorn into the house the UK, apparently because it was believed to have been used for the Crown of Thorns.[17] Alansplodge (talk) 18:52, 29 June 2012 (UTC)

Sorbothane

Can anybody familiar with this material take a look at this question on the Language reference desk? Bus stop (talk) 03:22, 28 June 2012 (UTC)

Effect of over speed test on large steam turbine (>600mw) last stage lp blades->900 mm length

As per iso standards over speed test on large(>600mw)turbine lp rotors is carried out to ensure the intigrity of rotor blade assembly and "permanent set" if any.Generally the over speed holding period is between 2 to 10 minutes as per the design requirement.Over speed run normally is carried out at 120% of the rated speed.Such over speed tests are carried out once in the life time of any rotor and not repeated. 1-It has been observed that certain manufacturers of large steam turbines do not carry out the over speed test on l P rotor (with last stage blade height >930 mm) at 120% but do it at 115% holding for two minutes. 2-In other case the above lp rotor is over speeded at 120% momentarily and the speed is brought down. the bladed lp rotor weight is about >90 mt. my questions are a-Is it detrimental to carry out over speed test-run at 120%? b-Can such over speed run for two minutes impair the blade/rotor material strength/properties? c-Such constraint in conducting over speed test and holding for two minutes--can be attributed to dynamic balancing/ over speed set up or design inadequacy? — Preceding unsigned comment added by Rwgkw81 (talk • contribs) 05:01, 28 June 2012 (UTC)

Refactored to eliminate shouting. Evanh2008 ^{(talk|contribs)} 05:08, 28 June 2012 (UTC)

Wikipedia has an article about Nondestructive testing which is the main intention here, combined with a bedding in process. The given period at given overspeed is chosen by the manufacturer to fulfil the latter process. I expect the turbine is fit to continue indefinitely at the given overspeed, but the manufacturer may be able to give a lifetime estimate based on experience. DriveByWire (talk) 12:55, 28 June 2012 (UTC)

Climate change evolution

I was talking to my grade 9 science (major in biology) teacher about a month ago, and asked if it was possible for humans, as with most other life forms, to naturally evolve to survive in the changing climate (i.e., temperatures). She said that there's not enough time for us to do so, that it would take thousands or millions of years, and the change is happening at a fast rate. However, I was watching a few Richard Dawkins videos about evolution, natural selection, etc. and he mentions that scientists had brought a species of lizards into a new island, and within decades, not millions of years, the species had changed their facial features, as well as their stomach, to adapt to the new environment and foods. So, is my teacher wrong? Could humans, along with other species, evolve in order to cope with the climate change? Thanks, 64.229.5.242 (talk) 07:13, 28 June 2012 (UTC)

Even in the most extreme models of climate change, the actual changes taking place are rather benign as far as the integrity of life is concerned. A lot of people might drown due to increased flooding, and others may starve due to crop failures, but we're not talking fireballs coming down from the sky or anything like that. What specific changes did your science teacher think you were talking about? Someguy1221 (talk) 07:26, 28 June 2012 (UTC)

[18] If humans do nothing about climate change half the currently inhabited earth could become literally too hot for humans to live in. That's still something I'd want to avoid at nearly all costs. Sagittarian Milky Way (talk) 17:54, 28 June 2012 (UTC)

If you think about it, the time between generations in organisms such as lizards is much, much shorter than in humans. Humans have to wait about 20 years to sexually mature and produce offspring, and then that offspring has to wait about 20 years to mature, whereas a lizard may have offspring after 9 months - 1 year, and that offspring can reproduce after 1 year. So 20 generations in a lizard takes 20 years, whereas in a human 20 generations takes 20 times 20 = 400 years. (I'm talking round figures here.) So humans could evolve to take account of climate change, but because their reproduction rate is so much slower than other species, it would take much longer, in which time the changes could wipe the species out. The faster reproducing species are at a greater advantage as far as evolution is concerned when it comes to adapting to rapid changes to the environment. --TammyMoet (talk) 08:38, 28 June 2012 (UTC)

It may just be that humans are already naturally evolved to adapt to climate change. Humans have evolved preconditions to produce and modify technology which can act much quicker to address stressful environmental conditions than genetic adaptation can. All that is needed is the proper resource allocation to solve the problems faced with better technologies or societal organisation. Think about it for a minute, a human without technology would die if left exposed to an English winter or the Saharan desert. It will be the other animals without technology that are to be doomed by extreme or rapid climate change. SkyMachine ⁽⁺⁺⁾ 09:04, 28 June 2012 (UTC)

Wikipedia has a featured article about Evolution. Evolution works by the selective survival of progeny that adapt best to a changed condition. Human evolution today is driven less by natural selection than by social pressures and economics. A sudden climate change that leads to widespread fatalities might be expected to favour certain inheritable human characteristics that already exist in the population but it is difficult to speculate which ones. Perhaps slim people would survive better than obese people in a sudden global warming. DriveByWire (talk) 12:42, 28 June 2012 (UTC)

People are now living quite happily in climates that are much hotter than Europe, say, will ever be even under the most pessimistic scenarios for climate change. It is the rapid change that is dangerous, and that is dangerous for the survival of societies rather than for the survival of the individual. Consequently, climate change does not actually present environmental pressure for humans to evolve biologically. This is in contrast to the lizards which had to adapt to a new environment with different food sources than what they were used to and adapted to before. That's very strong evolutionary pressure, which leads to very rapid evolution - if you can't deal with the new food, you're out. --Wrongfilter (talk) 17:03, 28 June 2012 (UTC)

Agreed, to quickly evolve a species must suffer massive fatalities (or infertility) from the condition to which they must adapt to survive. StuRat (talk) 20:01, 28 June 2012 (UTC)

The question you have to ask is, how would climate change prevent people from reaching adulthood and/or having children? Lamarckian evolution, where individuals pass on hereditary characteristics acquired during life is a fallacy - evolution is essentially driven by premature death. My guess as to the biggest climate change driven force would be the increased prevalence of tropical diseases such as malaria, with them extending into areas and populations previously unaffected. As said above, humans reproduce (and therefore the species evolves) very slowly however. LukeSurl ^{t c} 00:54, 29 June 2012 (UTC)

Actually, there seems to be some support for a very minor effect similar to what Lamark proposed. There was a study showing that the descendents of people who had suffered malnutrition (in Norway ?) had altered DNA. It seems that periods of starvation cause one's descendents to put on more weight, when the opportunity arises.

As for malaria, yes, that is a major killer, and humans have evolved a response, in the sickle cell gene, which might become more prevalent as malaria spreads. StuRat (talk) 06:59, 29 June 2012 (UTC)

RESISTIVITY OF PLASTIC COVER TO HEAT IN PRESENCE OF WATER

WHEN A PLASTIC COVER FILLED WITH WATER, HELD TIGHTLY AT THE OPENING OF THE COVER[AT THE TOP] AND IF THAT COVER IS EXPOSED TO HEAT WHETHER THE HEAT SOURCE MAY BE ANYTHING THE PLASTIC COVER MAY NOT DAMAGE NOTHING HAPPENS TO THE COVER..........,,,WHY ? WHY ? WHY ???????? — Preceding unsigned comment added by Madhu Sagar (talk • contribs) 10:48, 28 June 2012 (UTC)

Please note that typing all in capitals is like shouting - it is bad manners. In any case, what you have written is poor english and I cannot work out what it is you are asking. You may like to clarify. Wickwack120.145.74.189 (talk) 11:35, 28 June 2012 (UTC)

The water is absorbing the heat and pulling it away from the container fast enough that it can't get hot enough to burn. A common example is using a candle to boil water in a paper cup. 209.131.76.183 (talk) 11:58, 28 June 2012 (UTC)

It's the same with paper. Just Google "paper kettle instructions", or see here for a paper frying pan.--Shantavira|^{feed me} 11:19, 29 June 2012 (UTC)

Where was the first ever plastic bag ban implemented?

After asking all these questions about plastic bags bans, I was wondering, once and for all, where was the first plastic bag ban in the world implemented? I know that San Francisco was the first American city to ban such bags, and Bangladesh was the first country to do so, but where was the first ever such ban implemented? Was it Bangladesh, a small village in Australia, or somewhere else? Narutolovehinata5 ^tccsdnew 11:24, 28 June 2012 (UTC)

"Ireland began charging 19 cents for each single-use plastic bag taken at the checkout in 2002, reducing consumption by 95% and raising millions of dollars for environmental programs. In 2001, Taiwan instituted a 3-cent fee and reduced single-use bag consumption by 69%. In 2002, floods caused by plastic bags choking drainage systems led Bangladesh to ban plastic bags entirely." from http://plasticbaglaws.org/wordpress/wp-content/uploads/2010/02/The-Evolution-of-SFs-Plastic-Bag-Ban.pdf --Canoe1967 (talk) 19:17, 28 June 2012 (UTC)

12th Century people in 21st Century times

I remember watching a scene in the film Just Visiting where the two 12th century characters were vomiting in a car, saying that it was going too fast. I was just wondering if the 12th century people were time traveled to today, what shocks to the system whould they experience medically, psychologically, etc.? Reticuli88 (talk) 18:33, 28 June 2012 (UTC)

They would have no immunity to many current diseases and would likely be carrying a few, as well as lice and worms, themselves. μηδείς (talk) 19:51, 28 June 2012 (UTC)

what kind of worms? Reticuli88 (talk) 19:57, 28 June 2012 (UTC)

Cestoda - tape worms. --Tagishsimon (talk) 19:59, 28 June 2012 (UTC)

Psychologically, culture shock is the relevant concept. 12th century to 21st century will be far more extreme than our article suggests, quite possibly to the point of being functionally debilitating. — Lomn 20:12, 28 June 2012 (UTC)

They would be psychologically disturbed by the fact that everyone else would say they smelt bad. HiLo48 (talk) 20:22, 28 June 2012 (UTC)

It's highly unlikely they would understand what people are telling them. Is there any current language that is mutually intelligible with it's 12th century "ancestor"? Roger (talk) 20:39, 28 June 2012 (UTC)

Church Latin is a good bet. --Carnildo (talk) 01:00, 29 June 2012 (UTC)

How about danish? Plasmic Physics (talk) 03:34, 29 June 2012 (UTC)

Icelandic, maybe. -- ♬ Jack of Oz ♬ ^{[your turn]} 04:50, 29 June 2012 (UTC)

Well, in the movie, a car moving at 20 miles/hr was too much for them and kept telling the driver "too fast" while barfing, providing comedy relief for the movie. I wondered would that happen to someone in reality if they were never in a car before? Also, the culture shock thing was referenced in the movie, when the two characters stepped out into a busy city street. They were overcome with the noise and the movements because they could not comprehend what was happening and ran to the nearest shelter to hide. Another scene was when they approached a modern toilet. One of the characters thought of it as a wash bowl and promplty washed his face with toilet water.

I wonder what would happen if someone transplanted us to 700 years from now and how we would be 'shocked' or what behaviors or mannerism would be considered backward or old fashioned, etc. Reticuli88 (talk) 21:23, 28 June 2012 (UTC)

A horse at full gallop can run well over 20 mph, and they had horses then, right? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:47, 29 June 2012 (UTC)

There would be some rough real-world parallels - Uncontacted peoples are generally expected to be living a stone age-like existence. There will be records of what happens when first contact with between the outside world and these isolated tribes occurs. That said, such peoples don't get transported to "very modern" urban environments such as Chicago. LukeSurl ^{t c} 00:41, 29 June 2012 (UTC)

A hint of what it might be like is sometimes made public when someone awakens from a coma after several years. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:47, 29 June 2012 (UTC)

The behaviour of the visitor from the past would resemble that of this rat but with (hopefully) some ability to empathise and adjust. DriveByWire (talk) 15:23, 29 June 2012 (UTC)

May I recommend the French film Les Visiteurs which has exactly this scenario. Tres drole. Alansplodge (talk) 18:26, 29 June 2012 (UTC)

D'oh! I've just seen that the film you linked is a Hollywood remake of the French original. I still recommend it though - US remakes of French films are always a bit poor in comparison. Alansplodge (talk) 18:40, 29 June 2012 (UTC)

recent xkcd cartoon. SCNR Уга-уга12 (talk) 19:34, 29 June 2012 (UTC)

Evolution

Non-question removed. Please don't use the reference desk as a forum to post links for the purpose of general discussion.112.215.36.172 (talk) 04:48, 29 June 2012 (UTC)

Cost of interstellar colonization

I'm trying to understand the construction cost assumptions in Ceyssens et al (2011) relative to the much more rigorous Moir and Barr (2005) which doesn't discuss construction costs, only acceleration costs. Assuming a sleeper ship is more economical than a generation world ship in this case, are Ceyssens' estimates unreasonably high? 75.166.192.187 (talk) 22:22, 28 June 2012 (UTC)

I'm not familiar with the papers you cited (I will look into them), but isn't estimating the cost of a sleeper ship kind of difficult given that they don't actually exist? A generation world ship is, roughly speaking, plausible with our current level of technology. Sleeper ships are a whole nother deal, and to my knowledge actually getting one up and running would be contingent on some unforeseeable advancement in cryonics, the cost of which is surely incalculable (in the true sense of that word, not the "really, really big" sense). Evanh2008 ^{(talk|contribs)} 03:24, 29 June 2012 (UTC)

I don't think so. The capacity of vitrification freezers increases at a fairly constant rate. We can make assumptions such as that suspending and reviving someone would generally require an anesthesiologist and a couple clinicians on hand, except for the first people revived, which would have to be done by robot. I think the biggest expense is for the landing craft. 75.166.192.187 (talk) 04:55, 29 June 2012 (UTC)

And another option is the have the vast majority of the crew in stasis, while a small crew, perhaps multi-generational, maintains the ship. Or, instead of one group of people kept awake permanently, you could wake each person in stasis, for maybe a 1 year maintenance shift, then put them back under. StuRat (talk) 06:28, 29 June 2012 (UTC)

For voyages on the order of 50,000 years, I think everyone is going to want to sleep through them in stasis. 75.166.192.187 (talk) 06:39, 29 June 2012 (UTC)

Another reason to wake occasionally is that the stasis won't be quite perfect, and waking them would allow their body to repair accumulated damage from gamma rays, etc. StuRat (talk) 06:48, 29 June 2012 (UTC)

Also, having the entire crew in stasis, perhaps even frozen in liquid helium where the human body becomes far more hardy, you could accelerate the ship at rates that would kill an unfrozen human. As for coming out of stasis to repair damage, even with future technology the act of freezing/unfreezing may still cause far more damage than the inbetween. Someguy1221 (talk) 06:51, 29 June 2012 (UTC)

I agree with waking occasionally, on systems alarm or timer if all clear, to measure health and radiation exposure (which you would want to minimize with asteroid rubble shielding) because nobody will have ever been in stasis for that long. Primary power would probably be aneutronic fusion but a sleeper ship could probably work on hydrocarbon fuels. The difference would be how fast it could accelerate. However, I'm not sure how much of a difference that would actually be, because propellant is limited in both cases. I am not sure about the radiation/acceleration trade-off. Slow acceleration over lengthy periods of time can indeed achieve impressive speeds, but you need almost the same amount of propellant to slow down at the other endpoint. The optimization problem is probably about the same with and without the relativistic component. 75.166.192.187 (talk) 18:05, 29 June 2012 (UTC)

June 29

Rat poison

I have a pretty severe rat infestation in my house. The rats seem to mostly live in my roof and just come down to eat food. I've tried using warfarin based poisons to kill them. I placed them inside the roof through the manhole. The baits get eaten completely, but the rats don't die. The amount of poison I have placed up there has been up to 1kg of 0.105% warfarin. Essentially all of it was gone within a week but the rats were not. It's possible that the rats are warfarin resistant, but there's no other options at the local shops here. I'm thinking of taking a cereal and potassium cyanide and mixing together with honey to bind it and placing that in the roof. I don't have any pets or children. Would this be an effective mixture for erradicating my rats? 112.215.36.172 (talk) 04:42, 29 June 2012 (UTC)

Try calcium phosphide, it isn't so much a poison really, but it works, unless the calcium phosphide is past it's best before date. On contact with acid, like stomach acid, it produces diphosphane, which is spontaneously combustable. Essentially, it turns a rat crispy on the inside. Plasmic Physics (talk) 05:27, 29 June 2012 (UTC)

Can I mix that with cereal and honey as I was going to do with the cyanide? 112.215.36.177 (talk) 06:11, 29 June 2012 (UTC)

Dealing with mice, I've found glue traps to be effective, although not at all humane (they rip their faces off trying to escape). If they make rat-sized glue boards, I'd try those. StuRat (talk) 05:32, 29 June 2012 (UTC)

Rat glue is available here, but I don't really know how to dispose of a live rat glued to a plate. I checked the instructions and their silence on the matter is telling. 112.215.36.177 (talk) 06:11, 29 June 2012 (UTC)

I'm guessing a high-tech euthanasia device is the preferred solution to that (*ahem*) sticky situation. Evanh2008 ^{(talk|contribs)} 06:16, 29 June 2012 (UTC)

For mice, I used one of those grabber thingies to get hold of the edge of the glue board, then put it in the sink and drowned it (had to hold it under with the grabby thing). If the rat is too big for that, drag it into a trash bag, take it outside, and crush it with a cinder block. Then toss it in the trash, or bury it if dead animals aren't allowed in the trash. Or, you could just let it die and rot in the attic, the smell will likely mostly go up and out. StuRat (talk) 06:22, 29 June 2012 (UTC)

What if the bait in the rat glue is also poison? Then it will die and I can just throw it away. Would that work? I'm also having trouble imagining how I would get a plate with a rat down from in the roof. I don't have an attic, just a crawl space so no lighting and very little room to move. The man hole is only about 1.5sqr feet, no fixed stairs or ladder and the drop is about 3m to the floor.112.215.36.177 (talk)

You could also shoot it on the glue board, perhaps a BB gun would work. Once you have it in the garbage bag (you might want to double bag it), just tie it shut and drop it down. Note that with poison they often die in really bad places, like in the walls, where they smell up the entire house. Or, worse yet, they can stagger into your living area, bleeding profusely. StuRat (talk) 06:41, 29 June 2012 (UTC)

This word count on the posts so far shows infestation by rodents:

• rat : 16
• man: 3

DriveByWire (talk) 15:03, 29 June 2012 (UTC)

Do you have any access to sodium azide-based pesticides? In sufficient quantity, the water-dissolved form should kill essentially anything. But given that, there may be restrictions on its use in your area, due to the potential for environmental contamination. If you are legally permitted to use it, simply spraying it on the glued rat should kill it, of course being very careful not to get it on yourself. Someguy1221 (talk) 06:29, 29 June 2012 (UTC)

I don't know of any sodium azide containing products that I have at my disposal. There's litterally piles of cyandide at the gold mine where I work, so I thought that would be the obvious choice. I also don't know where I would get the calcium phosphide mentioned above, but it sounds like it would allow me to not bother getting the corpses out of the roof, which is an advantage. I suppose the most important question is whether mixing any of these things with honey is going to liberate a toxic gas and kill me, or will it remain solid until the rat digests it. 112.215.36.177 (talk) 06:47, 29 June 2012 (UTC)

This is why we have professionals.--Shantavira|^{feed me} 11:47, 29 June 2012 (UTC)

The dangers of amateur poison warfarin' make one sigh an' hide. DriveByWire (talk) 15:15, 29 June 2012 (UTC)

Let me point out that the OP geolocates to Jakarta, Indonesia. I doubt that many people here are qualified to give advice on getting rid of rats in a place like that, especially not knowing the setting of the house in question. And in any case I certainly wouldn't give advice to anybody who starts talking about using cyanide. Looie496 (talk) 15:54, 29 June 2012 (UTC)

I would be interested to know which mining company would allow people to walk off site with cyanide in what looks like South Sulawesi. We live in a rat-rich tropical environment and our house sometimes has guests in the roof spaces. We don't do anything to control them other than figure out how they get up there and cut any tree branches etc they use, allow cats into the house and allow any rat snakes we see to stick around. It's pretty effective. Sean.hoyland - talk 17:15, 29 June 2012 (UTC)

Cheese with Polonium 210 Count Iblis (talk) 18:15, 29 June 2012 (UTC)

iodine reacting with titanium

A few months back I posted this

"I have a titanium mug/cup. After drinking some milk I forgot to rinse it out and it sat and became gross. I decided to add some tincture of iodine along with some water to help sanitize the cup. After adding this in letting it sit for about a minute it changed color and started a foul smell that made my nose sting. Is it possible it reacted with titanium to release some sort of harmful gas or substance? — Preceding unsigned comment added by 64.38.198.61 (talk) 00:08, 4 March 2012 (UTC)

The elemental iodine (I2) is probably reacting with the titanium in the same way it reacts with aluminium. The product of that reaction would be titanium iodide, which is a very soluble salt, but it would also generate heat which volatilises some of the remaining elemental iodine. That stuff's not very nice to breath in. 203.27.72.5 (talk) 00:55, 4 March 2012 (UTC)

According to the titanium alloy article, titanium is usually alloyed with aluminium anyway. The reaction between iodine and aluminium is very spontaneous and can result in iodine vapor. 203.27.72.5 (talk) 04:28, 4 March 2012 (UTC)

The thing is I didn't see any actual cloud of vapor rise from the cup I just smelled it is that normal for this type of reaction? — Preceding unsigned comment added by 64.38.197.212 (talk) 12:04, 4 March 2012 (UTC)

If there had been enough vapor for you to see it in the air it would have been at a lethal concentration. Tincture of iodine only contains a few percent of iodine and not all of it is elemental either. I can imagine it would have been enough to smell but not enough to see by several orders of magnitude. 203.27.72.5 (talk) 20:14, 4 March 2012 (UTC)"

I haven't used this cup since then but I liked it a lot and it was expensive so im wondering is it safe to drink out of it?--64.38.226.89 (talk) 05:04, 29 June 2012 (UTC)

Without giving medical advice, I can point out that the product of the reaction, titanium tetraiodide would be in low concentrations and is highly reactive with water, so a few good rinses should remove it all. Titanium metal in and of itself is nontoxic. Handschuh-^{talk to me} 09:37, 29 June 2012 (UTC)