Wikipedia:Reference desk/Archives/Science/2015 January 10

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January 10

Butterfly Flight

How does a butterfly flap its wings and change direction while in flight?--75.171.82.75 (talk) 01:11, 10 January 2015 (UTC)

They use muscles on their abdomen to flap the wings, and changing direction, I suppose, involves flapping one side harder than the other. Another possibility is wing warping. StuRat (talk) 01:21, 10 January 2015 (UTC)

The aerodynamics of butterfly flight has been the subject of multiple scientific studies - it is more complex than it might at first seem, and may involve different mechanisms for different phases of flight. This [1] Nature paper is unfortunately behind a paywall, but is well worth looking at if you can access it. AndyTheGrump (talk) 01:40, 10 January 2015 (UTC)

Here is a full text version of the paper. Mikenorton (talk) 10:37, 10 January 2015 (UTC)

Thanks to all for your time and effort to provide an answer to my question. I just read the Nature article referenced by AndyTheGrump, through the link provided by Mikenorton. Andy, your comment "is more complex than it might at first seem" is a major understatement. I am left thoroughly amazed at the potential complexity of the techniques these small creatures can utilize while in flight - and all by virtue of instinct. I highly recommend using this link to all who have an interest in the mechanics of insect flight. Thanks again guys for this incredible eye-opener!75.171.82.75 (talk) 18:40, 10 January 2015 (UTC)

Welch's

The method of pasteurizing grape juice to halt the fermentation has been attributed to a British physician and dentist, Thomas Bramwell Welch (1825–1903) in 1869. I am not happy with the wording and lack of a source. Wasn't pasteurization known before? Are there any specifics to that method? Isn't "has been attributed to" classic weasel wording that should be avoided? --92.202.13.41 (talk) 03:16, 10 January 2015 (UTC)

That doesn't indicate that he invented it, only that he used it. According to Louisization Pasteurization, the process was invented in 1864 , initially for milk of course. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:58, 10 January 2015 (UTC)

Reading the article you just linked to shows that "initially for milk of course" is quite incorrect; the process was for wine and beer -- "it would be many years before milk was pasteurized". --jpgordon^{::==( o )} 16:32, 10 January 2015 (UTC)

D'oh! You're right. I was more concerned with the date, which was five years before Welch applied the process. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:41, 10 January 2015 (UTC)

Welch's history page shows in the 1869 entry Bramwell and a couple of labels for his "unfermented wine". It looks legit. --Mark viking (talk) 04:56, 10 January 2015 (UTC)

PG-1302-possibly a pair of black holes close to colliding

The news article I just read said these 2 black holes will probably collide in a million years. It also said the energy released at that time could be as much as 100 million supernovae, with spacetime warping effects. My questions are 1) Even allowing for the very great distance, billions of lightyears, could that released energy, a million years from now, still damage the life on Earth, assuming life on Earth then is similar to life on earth now? 2) Could the spacetime warping be large enough, even with the very great distance, so that in ordinary life,(not just when using sensitive scientific instruments) a human's senses could notice definite effects on spacetime, assuming humans exist then? thanks.2601:7:6580:5E3:9138:4390:6740:EBCC (talk) 03:41, 10 January 2015 (UTC)

There are masses of binary star systems in every galaxy and most even seem stable. Given the fact that "black holes" are very small stellar objects it seems near impossible that two such black holes will ever come into contact. They will always miss eachother and that way develope into one (exeptional) binary system. --Kharon (talk) 04:27, 10 January 2015 (UTC)

These are very massive black holes, perhaps millions or much more of solar masses. Read the recent Michael Franco at CNET or Dennis Overbye at New York Times.2601:7:6580:5E3:9138:4390:6740:EBCC (talk) 05:16, 10 January 2015 (UTC)

It's always an interesting calculation to identify the event horizon or Schwarzchild radius for objects with the mass of the sun or earth. "Small" isn't quite the right word when it physically warps space into itself. A black hole with the mass of the sun wouldn't be "smaller" but the rulers would be longer. --DHeyward (talk) 07:11, 10 January 2015 (UTC)

Ok, but these aren't small in any case. theyre not stellar black holes, they seem to be supermassive black holes, two galaxies may be colliding.2601:7:6580:5E3:4D7:335A:100B:7C6B (talk) 09:23, 10 January 2015 (UTC)

Coorbiting black holes are predicted by Einstein to lose energy via gravitational radiation. This causes their orbit to decay and makes a collision inevitable for compact binary systems. Dragons flight (talk) 20:11, 10 January 2015 (UTC)

Back of an envelope calculation - 100 million supernovae at a distance of 3.5 billion light years is equivalent to one supernova at a distance of 350 thousand light years (inverse square law). That is about 3 times the diameter of our own galaxy. So it doesn't sound like we need to be worried about this. Gandalf61 (talk) 13:30, 10 January 2015 (UTC)

Chemicals used to enhance flavor in food?

No, I am not talking about complex chemicals called "spices". I am talking about monosodium glutamate and other flavor enhancers. I watched a documentary, and one part said that there are actually various flavor enhancers in food (i.e. citrate?). I do not remember the specifics, so can anyone list all the flavor enhancers that have been used in modern times to enhance the flavor of processed foods? 71.79.234.132 (talk) 05:20, 10 January 2015 (UTC)

Plain old sodium chloride (table salt) is the most common one. StuRat (talk) 05:23, 10 January 2015 (UTC)

Capsaicin is what makes peppers hot, and that's added to many foods as a flavor enhancer, although too much overpowers every other flavor. StuRat (talk) 05:25, 10 January 2015 (UTC)

No, it was not capsaicin or table salt. It was a chemical with a very scientific name and no common name. Capsaicin and table salt are not part of the list. 71.79.234.132 (talk) 05:34, 10 January 2015 (UTC)

Monosodium glutamate?129.178.88.82 (talk) 09:40, 12 January 2015 (UTC)

List of food additives, Category:Flavour enhancers. Mr.Z-man 05:58, 10 January 2015 (UTC)

Why does new york city have a continental climate?

If new york city is right beside the ocean, why does it have a continental climate? — Preceding unsigned comment added by 199.119.235.169 (talk) 06:38, 10 January 2015 (UTC)

The prevailing wind direction is critical here. If the wind blows off the continent, then you get a continental climate. StuRat (talk) 06:52, 10 January 2015 (UTC)

It's a little more complicated than that, but you're right that prevailing wind direction is crucial. Let me add a pointer to our continental climate article. Looie496 (talk) 16:58, 10 January 2015 (UTC)

I think the oceans are naturally warmer for New York than other countries at the same latitude. Compare swimming season for New York vs. Northern California, Europe, Japan at the same latitude. Pure anecdotal evidence so could be wrong. --DHeyward (talk) 08:41, 10 January 2015 (UTC)

The large-scale oceanic gyres are clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere, because of the differing sign of the Coriolis parameter. This means ocean currents in both hemispheres tend to be relatively warm off the east coasts of continents (e.g., New York) and relatively cold off the west coasts. Short Brigade Harvester Boris (talk) 18:56, 10 January 2015 (UTC)

• Who says it does have a continental climate? The NYC article certainly doesn't. μηδείς (talk) 20:55, 10 January 2015 (UTC)

• • Try Climate of New York. Very first sentence. Short Brigade Harvester Boris (talk) 23:29, 10 January 2015 (UTC)

You've confused two very different things, User:Short Brigade Harvester Boris. Look at the first sentence of this thread. μηδείς (talk) 00:18, 11 January 2015 (UTC)

Ah. Right. The NYC metropolitan area has an average January temperature right around 0 C. This puts it into the C Koeppen primary classification rather than the D classification that applies to most of the state, knocking it out of the Df "humid continental" range.

More complete response to OP: Keep in mind that the names for the Koeppen classifications are somewhat arbitrary and there's no agreed upon quantitative definition of "continental." Over the years there have been various indices proposed for continentality. A fairly well known one is the Conrad index. Using the Conrad index NYC (Central Park) has a continentality of 39. This compares to a value of 13 for London and (perhaps surprisingly) is not much below the value of 42 for Moscow. Short Brigade Harvester Boris (talk) 01:26, 11 January 2015 (UTC)

Yes, having lived in Philly, Atlantic City, New Brunswick, NJ, NYC, Ithaca, NY, as well as briefly in places like Hempstead, NY, Cape Cod, Binghamton, NY, Melrose, MA, Long Beach, NY, I can assure you NYC is humid subtropical, and much milder than inland continental climates. Indeed, I don't believe I have ever worn a jacket in NYC before Thanksgiving, while interior NJ can be inbearable both in summers and winters. μηδείς (talk) 01:48, 11 January 2015 (UTC)

does re-enamel toothpaste work?

Hi,

I was wondering if we had an article on re-enamel toothpaste, and also whether in general the consensus is that it works? I was surprised there's no Colgate Total + re-enamel for example? Despite the Triclosan controversy, the Triclosan ingredient is the reason I use colgate total products only (and I know about the cancer risk or whatever, and just take it as a given.) But I wonder why it is not combined in a re-enamel version? Do these things not work? Colgate does have re-enamel but not under its Total brand - despite the Total brand including lots of other sub-things, like a version for fresh breath, a version with whitening, and. All of these are popular: http://www.colgatetotal.com/toothpaste

but no re-enamel version. why not? Does that stuff not actually work / rebuild mineral into your teeth?

Thanks for any information.

212.96.61.236 (talk) 08:57, 10 January 2015 (UTC)

The active ingredient in such toothpastes is Amorphous calcium phosphate. Our article contains several references which indicate it does have some beneficial effect, although probably not as dramatic as the advertisments suggest. The first part of the question can only be answered by Colgate-Palmolive's marketing department, and I'm sure they keep their decision-making process highly confidential. See Brand management for our general article on the subject. Tevildo (talk) 09:43, 10 January 2015 (UTC)

But note that calcium and phosphate are already abundant in saliva and if you want more calcium phosphate, a good glass of milk will do the trick for non-vegans (it wasn't just old school dairy propaganda, milk really is pretty good for teeth, especially during development). Our (frankly kinda promotional-reading) amorphous calcium phosphate article seems to suggest it is the most ideal form of calcium phosphate and though I did not look into the ncbi articles it references in detail, I'm willing to buy that it might have some marginal advantages. But I will say that generally speaking the advantages of toothpaste are more in prevention than in repair. Tooth enamel will repair itself to an extent in healthy contexts, and fluoride is the real hero of toothpaste in this regard, so in this sense most all modern toothpastes are "re-enamel" toothpastes. I tend to be skeptical of any benefits from "amorphous" calcium phosphate being beyond (or even comparable to) to fluoride's. There's actually a journal specifically devoted to topics in this area, Cares Research and its website hosts abstracts for every article, and I couldn't find a single mention of calcium phosphate within it, though research found therein and elsewhere has deconstructed the efficacy of toothpaste from nearly every possible angle. Still, with enough persistence, one could probably find some relevant research therein. Snow talk 11:53, 10 January 2015 (UTC)

Guys, thank you. I found this incredibly helpful. As a non-expert, my impression had been that alternative toothpastes (Enamelon) figured out a way to remineralize teeth. It seemed to me that following this, it was incorporated into other products (this is Colgate's explicit offering, outside it's total brand: http://www.colgateprofessional.com/products/colgate-enamel-health/overview .) But what I didn't get is why it wouldn't ALSO include all the normal total stuff? Is it because they interfere with the remineralization process? Then why not brush with total first, for all its benefits, then rinse and use an enamelon-type product?

Now that I've seen your references though, my impression is different. My impression is that Enamelon or other enamel-building categories didn't discover anything new. It's not a truly new category. It isn't something Colgate actually adopts or can use. Because it doesn't really work, it's just an invented fad. So, with this conclusion it makes perfect sense for Colgate to just add "enamel" to its list of benefits on normal Total products, without explicitly making an enamel-building version. (Which doesn't work or exist measurably better than its normal total properties.) At least, this is my impression today. Here is a cateogry of all toothpastes that are branded into this new fad: https://www.google.hu/search?q=enamel+building+toothpaste&tbm=isch in 2010 the wsj seemed skeptical: http://www.wsj.com/articles/SB10001424052748704141104575588374178767514 and they basically repeated what you've said above. In essence then, I think I fell for the idea that the popping up of that whole category (which is an area of the toothpastes section in every drug store) actually reflects something. It simply doesn't (in my current impression). Like if there were Night Time skin creams section with SPF 20+ factors. Sure.  :)

Thanks for all of your work and references, Tevildo and Snow Rise. It was greatly appreciated. 212.96.61.236 (talk) 15:42, 10 January 2015 (UTC)

Not at all, it's what we're here for. Toothpaste advertising is not a good example of objective scientific research - I saw a poster a few weeks ago that promised "Up to 100% less plaque!", which I think counts as "not even trying". Tevildo (talk) 17:03, 10 January 2015 (UTC)

As Telvido says, not a problem. I wouldn't go as far as to say that there haven't been developments in efficacy for toothpaste in recent times, by the way, but I think your skepticism about the branding is well-advised; for many consumer products relating to the body, diversification in the product field is as much or more the result of increased marketing efforts as genuine innovations in the products themselves -- a fact of which you are clearly aware. There's even a marketing term for the process by which competitors (or even a single company which own multiple brands) tend towards greater and greater differentiation in their branding and product claims, even if the product itself is identical, though I forget the term just now. I'm not willing to speculate that this is definitely the case with your re-enameling tooothpaste, but let's just say I'm not going to discourage you from the the belief either. Certainly the product line offerings raise the question that you point out: why not make a composite containing all of the elements that confer health benefits and other valuable properties (whitening and so forth); that's often the inconsistency a lot of companies have to just have to hope they won't be called on with regard to their massively diversified branding -- luckily the consumer is usually willing to meet them more than half way in suspending disbelief with regard to the "unique" properties of a particular variant of a product. Snow talk 20:49, 10 January 2015 (UTC)

See also Recaldent. Johnuniq (talk) 09:03, 12 January 2015 (UTC)

Structural system

http://www.retrotogo.com/2010/12/for-sale-grade-ii-listed-1950s-modernist-apartment-in-langham-house-close-ham-surrey.html What is the structural system of these types of flats often seen around the suburbs of major cities in the UK. I've seen much larger versions of these with multiple floors, up to 5 or 6. 90.194.54.111 (talk) 17:17, 10 January 2015 (UTC)

Hard to tell for sure, but it looks to be steel reinforced concrete with decorating/insulating bricks (a concrete exterior doesn't look very "homey" or keep you very comfortable inside). StuRat (talk) 18:12, 10 January 2015 (UTC)

Normal steel reinforcement or prestressed? 90.194.54.111 (talk) 18:25, 10 January 2015 (UTC)

Can't tell that from the pics. StuRat (talk) 21:37, 10 January 2015 (UTC)

What distribution are the most common?

Somehow this distribution is pretty common in nature and society, and I suppose it's the most common (correct me if I am wrong). Besides this, what are some distributions that arise everywhere and why? (I suppose the normal dist. is the result of several binary options.) --Noopolo (talk) 20:49, 10 January 2015 (UTC)

The Gaussian distribution, aka "normal distribution", is the most common. That's a consequence of the central limit theorem, which says that if you start with essentially any probability distribution with finite variance, and take the average of N independent samples, the larger N gets, the closer the probability distribution of the sample average to a Gaussian distribution. Probably the next most commonly encountered distributions are the Poisson distribution,the binary distribution, and the continuous uniform distribution. Looie496 (talk) 21:03, 10 January 2015 (UTC)

I see multimodal distributions frequently in my day job. Often, these are simple linear superpositions of n gaussian distributions with different parameters. Sometimes they are more pathological. Nimur (talk) 21:27, 10 January 2015 (UTC)

I think the most common continuous distribution is indeed the Normal distribution, also known as the Gaussian distribution. However, the most common distribution encountered by most people in their daily lives is probably the Bernoulli distribution, because so many things either happen or don't with some probability. This is so common that most people don't even notice it, but every time they say something like "the car might crash" or "this cake might be delicious" or "the bus will probably be here in a moment" there's a Bernoulli distribution involved. Other discrete distributions evolve naturally out of the Bernoulli distribution, and these in turn lead naturally to consideration of their continuous equivalents. RomanSpa (talk) 21:59, 10 January 2015 (UTC)

You may also wish to look at our list of common probability distributions, which can be found here. RomanSpa (talk) 03:52, 14 January 2015 (UTC)

Edibility/healthfulness of shellfish parts

What exactly are these shellfish parts? Are they safe/healthful to eat?

• The soft, pasty part at the back of a cooked shrimp's head
• The dark-colored, non-muscular part of a cooked mussel
• The blister-like part of a limpet above its "foot"

--96.227.60.16 (talk) 22:42, 10 January 2015 (UTC)

In the case of shrimp, that's their hepatopancreas. Quite edible; perhaps an acquired taste in some cultures, but I think it's yummy. --jpgordon^{::==( o )} 23:00, 10 January 2015 (UTC)

In shellfish, the stuff is called tomalley when eaten as a food stuff. The tomalley of lobster is a common enough delicacy. Shrimp have a lot less of it, but it is of course just as edible. I'm not sure which part of the mussel you're asking after; perhaps the Byssus, also called the "beard", which is not edible. Not sure on the limpet. Never eaten those. --Jayron32 01:56, 11 January 2015 (UTC)

I've not eaten limpets either. I've seen 2 YouTube videos in which limpets were collected, cooked, and eaten. In both cases, the presenters cut of the top part of the limpet bodies, consuming only the disc-like "feet". --96.227.60.16 (talk) 03:49, 11 January 2015 (UTC)