Science desk
< May 30	<< Apr \| May \| Jun >>	June 1 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

May 31

Ants, fruit, and sand

I am in possession of an ant farm. Inside the transparent plastic box is a brown plastic "ant hill" that the ants can crawl around on, and it has sand that is at the base of the brown plastic ant hill. The brown plastic ant hill is hollow and it's full to about the 90% level with sand. Yesterday, I dropped a little piece of banana onto the brown plastic ant hill, not close to any sand. An hour later, when I looked, the banana was covered with a single layer of sand grains. Today, I dropped a little piece of about 1/4th of a blueberry next to the banana, and in an hour, when I looked, the blueberry fragment was also covered with about a single layer of sand grains. (My unnecessarily long description of my ant farm was to try to avoid responses suggesting that the ants dragged the fruit across some sand — the fruit is where I left it, and it is not near any sand.)

Why are the ants bringing sand grains to the fruit? Are they doing this intentionally or accidentally? I am wondering whether my ants are imbeciles. Comet Tuttle (talk) 05:42, 31 May 2011 (UTC)[reply]

If you are saying that the ants partially buried the fruit, I think that is quite common behavior in a number of species. Try making the pieces smaller to see if they change from burying it to transporting it. Sean.hoyland - talk 05:49, 31 May 2011 (UTC)[reply]

Agreed. They likely have an instinct to bury food too big to move, to prevent anything else from taking it. They aren't bright enough to figure out that this instinct is silly in the ant farm, since there's nothing there to steal the fruit. StuRat (talk) 08:48, 31 May 2011 (UTC)[reply]

Interesting. This makes sense; thank you. To answer Sean.hoyland's question, it would be a stretch to say the fruit pieces are "partially buried"; it's more like the fruit pieces are sitting on a piece of plastic with sand grains all over them now. I'll try tinier pieces. Thanks! Comet Tuttle (talk) 16:54, 31 May 2011 (UTC)[reply]

Need Best online software training

I am prasanth B tech graduate, I want to start carrier in software field so please guide me for best institute… — Preceding unsigned comment added by Nvprasanthmax (talk • contribs) 06:37, 31 May 2011 (UTC)[reply]

Are you prepared to travel internationally and pay plenty of money. If so MIT is famous. Graeme Bartlett (talk) 09:05, 31 May 2011 (UTC)[reply]

They did say "online", so I'm guessing they aren't willing to travel any further than their computer room. StuRat (talk) 09:24, 31 May 2011 (UTC)[reply]

Starting a technical career is often better done by trying to start a career directly than any online courses, in the US, at least. Many managers will simply disregard potential employees whose only credentials were earned online. i kan reed (talk) 21:33, 31 May 2011 (UTC)[reply]

MIT does have free online courses such as http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/. MIT was one of the first places to have this sort of thing. Graeme Bartlett (talk) 22:03, 31 May 2011 (UTC)[reply]

For online software training there are several sites. one of them are good depending on the training requirement. I found one one online software training institute: http://www.svrtechnologies.com. many other similar sites i found but go with this for less training cost. — Preceding unsigned comment added by 125.99.194.118 (talk) 10:01, 1 June 2011 (UTC)[reply]

Isolating the "celibacy factor" in clergy child sex abuse

Have any attempts been made to scientifically measure the extent of the influence of the "celibacy requirement factor" on rates of child sex abuse by members of the clergy? For example, comparing abuse rates amongst those religious denominations which demand their clergy be celibate (mostly the catholic church, but there are no doubt others) and those denominations which allow married priests? I'd prefer to find studies which attempt to adjust for other factors and isolate the "celibacy factor". (Other factors can include the pre-screening of potential clergy, responses to allegations - hiding abusers versus rigorously investigating and removing / reporting them, level of unsupervised access to potential victims, etc). IMHO, it's not that celibacy makes people into molesters, it's that the celibacy requirement means the average, mentally healthy heterosexual individual is discouraged from joining. The result being, the ranks are disproportionatly filled with "others" (such as homosexuals and pedophiles) who don't care to marry anyways (and may in some cases even prefer not having to explain a lack of interest in marrying). Ending the requirement would not eliminate abuse (nothing can - child molestation can occur in any society) but would likely reduce it. But the issue here is not my opinions - I'm looking for studies. Eliyohub (talk) 07:17, 31 May 2011 (UTC)[reply]

This is anecdotal evidence only, but a friend of mine who at the time was studying to become a catholic priest and lived in a seminary once told me about the huge poster of a naked man which one of the students in another (German) seminary had in his room. My friend was generally amused that so many want to become a priest because, according to them, being homosexual they have no problem with celibacy anyway. But even he seemed surprised that a student in that seminary was so open about it, with no apparent consequences. So I believe you are definitely up on to something. Unfortunately I am not aware of any such studies (and wouldn't expect to be). Hans Adler 08:24, 31 May 2011 (UTC)[reply]

Hans: for interest, the English idiom you were looking for is "on to something" meaning one is "on the right track", is "approaching the truth" etc. The expression "you are up to something" means "you are doing something - I'm not sure what - that is probably wrong or illegal." I'm sure you didn't mean to imply that Eliyohub is "up to no good." :-) {The poster formerly known as 87.81.230.195} 90.201.110.101 (talk) 17:56, 31 May 2011 (UTC)[reply]

Thanks, fixed. Hans Adler 21:17, 31 May 2011 (UTC)[reply]

The casual grouping together of homosexuals and pedophiles as "others" is provocative because the former are a minority that is sizeable, legal (in most countries), politically active, healthy (by our standards) and possibly inclined to marry, while pedophiles are none of those things. The OP is disingenuous about seeking confirmation of their stated hypothesis that ending the celibacy requirement "would likely reduce clergy child sex abuse". Cuddlyable3 (talk) 09:25, 31 May 2011 (UTC)[reply]

I did NOT mean to morally equate homosexuality and pedophilia - I should have made that more clear. Apologies for the misconception. However, my point was that they both aren't interested in "marriage" in the catholic sense, thus the celibacy requirement isn't necessarily a hurdle. If they wanted to be openly gay and / or marry another man, they likely wouldn't expect to remain catholic, would they? (Again, this is NOT saying the two are remotely comparable from a moral standpoint). As an brief (and probably irrelevant) aside, to answer your other points Pedophilia is not in itself illegal (you can't outlaw an inclination) it's acting on one's feelings that's usually a crime (and rightly so). Pedophiles can engage in political activism too, albeit unlikely to be very successful or popular. The only thing pedophiles and homosexuals have in common in my hypothesis is that both are less likely to be bothered by the celibacy requirement. A hypothesis is only a hypothesis - thats exactly why I'm seeking studies on the matter, to find out if it correct. (In case this needs saying: I am NOT a pedophile.) Eliyohub (talk) 11:05, 31 May 2011 (UTC)[reply]

I think pedophiles might be inclined to marry, if they could. Child brides (no article ?) are still legal in a few places, including, until recently, some US states (to which Jerry Lee Lewis can attest). StuRat (talk) 18:18, 31 May 2011 (UTC)[reply]

The article you're looking for is Child marriage (as opposed to Child Bride). Red Act (talk) 19:51, 31 May 2011 (UTC)[reply]

OK, I added a redirect (I wish Wikipedia would automatically look for a case-insensitive match if it doesn't find one with the same case). StuRat (talk) 23:37, 31 May 2011 (UTC)[reply]

It is worth noting that the distinction between homosexuality and pedophilia was, unfortunately, quite a recent development in the U.S., with the two being conflated as "pederasty" even in such liberal icons as Allen Ginsberg's poem Howl, not to mention I believe one of Eugene McCarthy's later pronouncements on the topic in the 1968 election (didn't find that one though and I might have it mixed with 1972). In Russia, which has lagged behind the U.S. in this regard, apparently the distinction is only now beginning to be drawn.^[1] This evidence would seem to indicate that it is law that determines culture, not the other way around. Wnt (talk) 19:11, 31 May 2011 (UTC)[reply]

Back to the original question? Any studies you can point me to which attempt to isolate the "celibacy factor" on rates of molestation by priests? Eliyohub (talk) 09:29, 1 June 2011 (UTC)[reply]

This link mentions that in 1990, 58% of clergy abuse reports were from Protestant ministers, most of whom I would assume are not celibate. 75.155.136.49 (talk) 20:40, 1 June 2011 (UTC)[reply]

The United States is about 25% Catholic. 66.108.223.179 (talk) 12:54, 2 June 2011 (UTC)[reply]

Pedophilia

How should one say "baby-philia", i mean; Pedo-philia is for children let's say by the age of 3-10 and Hebe-philia is to early adults in the age of 10-14. but how should one say Baby-philia? (0-3), and, did the Psychiatric literature ever documented such behavior ? - By the way, will we call the Normal "philia" ?, the one for (generally) from age 14? thanks. 79.183.27.165 (talk) 08:27, 31 May 2011 (UTC)[reply]

A pediatrician is a physician for children and babies[2] [3] which suggests that there need be no lower age limit for the object of Pedophilia. Alternatively Infantophilia and nepiophilia have been used to refer to a sexual preference for infants and toddlers. I altered the section title for ease of reference. Cuddlyable3 (talk) 09:02, 31 May 2011 (UTC)[reply]

The suffix -philia is rooted in the Greek philos loving or dear. It can occur in harmless examples of enthusiasm such as audiophilia. Cuddlyable3 (talk) 10:42, 31 May 2011 (UTC)[reply]

I have to say, I'm surprised that there isn't some Latin-based language where people say that the local priest is a pedophile because he loves children ... in an innocent sense ... with inane consequences. But in reality there's the incident mentioned by Richard Dawkins^[4] where, it is said, vigilantes in Wales trashed a pediatrician's house...^[5] (perhaps they should have pursued separatism instead?) Wnt (talk) 18:17, 31 May 2011 (UTC) [reply]

Should mothers trust someone who says "Let the little children come to me..." ? Cuddlyable3 (talk) 19:40, 31 May 2011 (UTC)[reply]

By the way, by the age of 14 you're probably into the territory of ephebophillia, since most people are through the first stages of puberty by that point. 98.209.39.71 (talk) 20:46, 31 May 2011 (UTC)[reply]

Herpes zoster

Can one suffer from shingles (Herpes zoster) multiple times, or is it one of the once-you-have-it-you-can't-get-it-again illnesses? I've read the article, but if it says anything to answer my question, I missed it. Nyttend (talk) 12:39, 31 May 2011 (UTC)[reply]

This following is pure OR. You get shingles after having chicken pox. The virus becomes dormant in the nerves, and is awakened at some future point by a trigger. The answer to your question is, you can only get chicken pox once but once you have had it, you can get shingles many times. --TammyMoet (talk) 13:29, 31 May 2011 (UTC)[reply]

I expected there would be something in the article (which is fairly detailed) and after some searching (first tried 'multiple', then 'more t') found:

Repeated attacks of herpes zoster are rare,[10] and it is extremely rare for patients to suffer more than three recurrences.[14]

In retrospect repeated or recurrence should have been the first and second things I tried.

Nil Einne (talk) 14:32, 31 May 2011 (UTC)[reply]

Some (older) GP's think Zoster is getting more common. In times past, people that got chicken-pox developed full immunity which was repeatedly reinforced by contact with teenagers suffering the diseases. However, immunologist are now thinking that inoculation against this virus means that the immune response only produces a sort term antibody response which wears off with time. This results in an attack of very painful shingles because their other immune responses have not been primed. Of course, if everybody in the world could be given chicken-pox inoculations, then maybe it could be eradicated -but the Gates foundation is concentrating on other viruses. So to answer the OP. Yes, if an individual's congenital natural immunity does not protect it from an acute chicken-pox infection and if the same individual is denied the the primary response being reinforced by contact with other infected individuals, then there exists ample opportunity for further shingles attacks. But don't worry, this is mainly a problem for those that live in the US where chicken-pox inoculations are common. Of course, for those who's primary immunity saves them from contracting chicken -pox in the first place, then they don't have to worry about get shingles later.--Aspro (talk) 22:13, 31 May 2011 (UTC)[reply]

There is also a vaccine against shingles, though. It's one of the supermarket-type, so you don't even have to bother your physician (in the US). Like all medications, it will have risks as well as benefits, and I'm not qualified to comment on the balance between them. But I suppose I will probably get it when I get to that age, assuming no serious problems have shown up in the mean time. --Trovatore (talk) 22:30, 31 May 2011 (UTC)[reply]

Both of these are discussed in the article (from a community health POV):

Quoted from article Nil Einne (talk) 05:52, 1 June 2011 (UTC)[reply]

Multiple studies and surveillance data, at least when viewed superficially, demonstrate no consistent trends in incidence in the U.S. since the chickenpox vaccination program began in 1995.[53] However, upon closer inspection, the two studies that showed no increase in shingles incidence were conducted among populations where varicella vaccination was not as yet widespread in the community.[54][55] A recent study by Patel et al. concluded that since the introduction of the chickenpox vaccine, hospitalization costs for complications of shingles have increased by more than $700 million annually for those over 60 years.[56] Another study by Yih et al. reported that as varicella vaccine coverage in children increased, the incidence of varicella decreased and the occurrence of shinges among adults increased 90%.[57] The results of a further study by Yawn et al. showed a 28% increase in shingles incidence from 1996 to 2001.[58] It is likely that incidence rate will change in the future, due to the aging of the population, changes in therapy for malignant and autoimmune diseases, and changes in chickenpox vaccination rates; a wide adoption of zoster vaccination could dramatically reduce the incidence rate.[5]

and

A live vaccine for VZV exists, marketed as Zostavax.[25] In a 2005 study of 38,000 older adults it prevented half the cases of herpes zoster and reduced the number of cases of postherpetic neuralgia by two-thirds.[26] A 2007 study found that the zoster vaccine is likely to be cost-effective in the U.S., projecting an annual savings of $82 to $103 million in healthcare costs with cost-effectiveness ratios ranging from $16,229 to $27,609 per quality-adjusted life year gained.[27] In October 2007 the vaccine was officially recommended in the U.S. for healthy adults aged 60 and over.[25][28] Adults also receive an immune boost from contact with children infected with varicella (chicken pox), a boosting method that prevents about a quarter of herpes zoster cases among unvaccinated adults, but which is becoming less common in the U.S. now that children are routinely vaccinated against varicella.[8][29] The shingles vaccination can cut the risk of the severe disease by 55 percent.[30] The Centers for Disease Control and Prevention recommends shingle vaccine for use in people 60 years old and older to prevent shingles, but it is not recommended to treat active shingles or post-herpetic neuralgia (pain after the rash is gone) once it develops.[31]

In the United Kingdom and other parts of Europe, population-based varicella immunization is not practised. The rationale is that until the entire population could be immunized, adults who have previously contracted VZV would instead derive benefit from occasional exposure to VZV (from children), which serves as a booster to their immunity to the virus, and may reduce the risk of shingles later on in life.[32] The UK Health Protection Agency states that, while the vaccine is licensed in the UK, there are no plans to introduce it into the routine childhood immunization scheme, although it may be offered to healthcare workers who have no immunity to VZV.[33]

Nil Einne (talk) 05:42, 1 June 2011 (UTC)[reply]

Diastereomerism

I was unfamiliar with this myself. The papers I have been doing does not explain the nomenclature of diastereomers, except for cis and trans isomers. What about all these strange ones I find on the internet: allo-, myo-, scyllo-, chiro-, etc. What do they mean, what are their requisites? I tried googling for a definition, I tried my textbooks, no answer therein. Plasmic Physics (talk) 13:48, 31 May 2011 (UTC)[reply]

have you tried [6] or [7]? --Stone (talk) 18:33, 31 May 2011 (UTC)[reply]

A quick search for "scyllo-" led me to [8] - apparently, this is a system for cyclic diastereoisomers by H.G. Fletcher, L. Anderson, and Henry A. Lardy, J Org Chem 16, 1238 (1951). There are eight prefixes allo, cis, DL, epi, muco, myo, neo, and scyllo for the inositol configurations and ten prefixes allo, cis, epi, gala, muco, neo, proto, scyllo, talo, and vibo for the quercitol configurations. There's a table in the Google Books link explaining them as follows: (warning: typos possible)

Meso diastereomers
quercitol	fractional notation	inositol
cis	12345	1-deoxy-cis
muco	1245/3	3-deoxy-muco
neo	15/234	2-deoxy-neo
scyllo	135/24	1-deoxy-scyllo
Active or Racemic diastereomers
allo	1234/5	5-deoxy-allo
epi	1235/4	2-deoxy-epi
gala	125/34	2-deoxy-allo
proto	134/25	2-deoxy-dextro
vibo	124/35	1-deoxy-myo
talo	123/45	1-deoxy-neo

The second column numbers indicate OH up/OH down. If the lowest numbered group (usually 1) is up, it is L-enantiomer; down is D-enantiomer. The source gives some optical rotation data for the active forms (zero for the others and DL mixtures, by experiment). Note that position 6 in quercitol has no -OH (the only difference from inositol), which establishes the plane of symmetry: when 3, 24, or 234 are the odd groups out, the result is a mirror plane and hence no optical activity. By contrast inositol so happens to have only one form capable of chiral D and L forms (as shown in the first link in Stone's entry), which is the chiro- form.

Among these famous compounds are myo-inositol, the usual biological form, and scyllo-inositol, currently under investigation for Alzheimer disease. Wnt (talk) 18:46, 31 May 2011 (UTC)[reply]

OK, that be useful, but what about a more general description? I've seen some of those term used on other cyclic compounds, like 2-(aminomethyl)cyclopropane-1-carboxylic acid. Plasmic Physics (talk) 23:15, 31 May 2011 (UTC)[reply]

I think your table is back to front, deoxy means without hydroxy. Quercitol is without a hydroxy group, so what'sgoing on there? Plasmic Physics (talk) 08:45, 1 June 2011 (UTC)[reply]

cis-quercitol = 1-deoxy-cis-inositol, etc. The same compound is described by both names, but deoxy-inositol = quercitol. Wnt (talk) 17:28, 1 June 2011 (UTC)[reply]

OK, so what about the previous question? Plasmic Physics (talk) 01:10, 2 June 2011 (UTC)[reply]

From a quick look it seems like it is the "Elliott nomenclature" for cyclopropane: M. Elliott, A. W. Farnham, N. F. Janes, P. H. Needham and D. A. Pulman, Nature (1974) 248:710. Wnt (talk) 20:41, 2 June 2011 (UTC)[reply]

Unknown ladybug/ladybird

I have a question on the exact name of a unknown ladybug/ladybird, I made images from the larva, the pupal and the fresh bug. The images were taken in Göttingen in the centre of Germany beneath a tilia tree were thousands of those little larva fed on the aphids. Funny to watch that the pupal lift their back from the tree and after a vibration they go back flat on the tree.--Stone (talk) 13:46, 31 May 2011 (UTC)[reply]

If they are present in very high densities, Asian_lady_beetle is a good bet. Note that high-confidence species-level ID of insects is quite hard; you can't be certain unless you take a specimen to an entomologist, or work through a good taxonomic key yourself. (Learning how to use an insect ID key is itself no minor task.) SemanticMantis (talk) 14:17, 31 May 2011 (UTC)[reply]

I would agree that the lower photographs definitely show the larva and pupa of Harmonia axyridis, here in the UK most commonly called the Harlequin ladybird. The upper picture of a black ladydird with red spots could be a Pine Ladybird (Exochomus quadripustulatus). Richard Avery (talk) 19:03, 31 May 2011 (UTC)[reply]

Thanks! The black bug is also from the same larva and pupa, they were looking all the same and looking for several days I saw only one gray larva not looking like the thousand others. So it is a black form of the Harmonia axyridis, how boring! I will try to get another! --Stone (talk) 20:27, 31 May 2011 (UTC)[reply]

Centipedes in our house

File:Centipede floor.JPG

Centipede?

We are getting a couple of these a day in our house. They are some sort of centipede or millipede (they look like Narceus americanus). They are large - 9 to 10 cm long. When we find them they are usually leaving the area of two of the doors opening to the outside, making me think that they are getting in through the doors.

Any thoughts on how we can get rid of them or keep them out of the house? Bubba73 ^{You talkin' to me?} 19:55, 31 May 2011 (UTC)[reply]

By the way, its a millipede. --Chemicalinterest (talk) 20:37, 31 May 2011 (UTC)[reply]

Try Borax first. Google around for suggestions. In these days of insecticides, borax is often over-looked. PS. Why don't you like god's little creatures? They recycle organic matter.--Aspro (talk) 21:23, 31 May 2011 (UTC)[reply]

Well they probably won't get much organic matter in our house. If they would stay out, I'd leave them alone. Bubba73 ^{You talkin' to me?} 22:32, 31 May 2011 (UTC)[reply]

Sounds like you haven't got them properly toilet trained.--Aspro (talk) 22:38, 31 May 2011 (UTC)[reply]

I've had that happen once at my parent's house. It's a temporary population explosion, it only took until the begining of fall that they died back off. They don't really spread disease or anything, so if you're willing to wait, I'd go with that. Borax, as reccomended above, is a moderate risk to children and pets, so keep that in mind if you use it. i kan reed (talk) 21:31, 31 May 2011 (UTC)[reply]

(ec)Do cats not eat those things? Just thinking of my mother's cat - he always stalks bugs and creepy-crawlies around the house (only time he ever shows anything approaching courage). --Kurt Shaped Box (talk) 22:36, 31 May 2011 (UTC)[reply]

They are somewhat toxic — see millipede#Defense mechanisms. From the description there it doesn't sound like it would actually kill the cat (though who knows) but he might well learn to leave them alone. --Trovatore (talk) 23:32, 31 May 2011 (UTC)[reply]

Wikimedia Commons is short of images of these critters. Can someone help Bubba with uploading images and selecting the right licence. Oh. Don't it look cute? --Aspro (talk) 22:35, 31 May 2011 (UTC)[reply]

I just did the license thing. I just took a quick shot to identify it. If you want a better one, I can probably get a better one. Bubba73 ^{You talkin' to me?} 22:48, 31 May 2011 (UTC)[reply]

I need to change the description of you want to keep the photo. It looks like a Narceus americanus and fits the description, but I can't be sure. Bubba73 ^{You talkin' to me?} 22:54, 31 May 2011 (UTC)[reply]

If you want to keep it, I need to rename it too. Notice how it shows that their legs move in waves. Bubba73 ^{You talkin' to me?} 23:07, 31 May 2011 (UTC)[reply]

Try to recreate Arthropleura by selectively breeding them in a high oxygen environment. Count Iblis (talk) 23:19, 31 May 2011 (UTC)[reply]

Fractals in Radio Antenna and other comunitaction devices.

Why is it that a radio antenna that is bent into a fractal shape receives more bands than one that is not? --71.204.251.178 (talk) 23:38, 31 May 2011 (UTC)[reply]

Fractal antenna#Fractal antennas, frequency invariance, and Maxwell's equations explains it a little bit. That section also points to this paper, which probably answers your question fairly thoroughly, but unfortunately isn't free to read. Red Act (talk) 23:56, 31 May 2011 (UTC)[reply]

The explanation I heard is that a single fractal antenna can handle all frequencies needed, so can be bigger (and thus better) than the several smaller antennae needed to do this with non-fractal shapes, and yet still fit in the same space. StuRat (talk) 00:36, 1 June 2011 (UTC)[reply]

On the contrary, I thought a smaller fractal aerial would pick up much more signal than a conventional aerial of similar size. That is why mobile/cell phones now have tiny fractal aerials hidden inside them rather than a telescopic external one. I wish it were possible to buy a fractal aerial cheaply as I'd like to plug them in to my radios, but I expect they are covered by patents. 2.97.220.135 (talk) 15:18, 2 June 2011 (UTC)[reply]

One confusing factor is that more cell towers were installed at the same time as the switch to fractal shaped antennae, so the reduction in the size of the antenna may also be due to decreased range requirements to reach the nearest tower. StuRat (talk) 20:53, 2 June 2011 (UTC)[reply]

The fractal antenna will pick up a similar amount of signal, but it will be better matched to the receiver and transmitter resulting in better efficiency. You can make an antenna by cutting out aluminium foil, or thin sheet metal, but for a radio, it will have to be pretty big and unwieldy. Graeme Bartlett (talk) 12:37, 3 June 2011 (UTC)[reply]

Do you mean that the signal strength is higher for mobile/cell phones than radios? I'm not sure if that is true as radios have large powerul transmitter aerials, but the mobile phone transmitter aerials are small. 2.97.223.90 (talk) 21:04, 3 June 2011 (UTC)[reply]

No I mean that the wavelength is longer, for FM radio it is around 3 meters, and AM radio around 300 meters, and this give a clue to the optimal size of antenna. I have better write that article on Chu limit that talks about small antennas! I have seen a nice spiral shaped antenna that operates close to the Chu limit, but another problem is the bandwidth. A fractal antenna will give great bandwidth but it has to be big. An FM band bandwidth will be around 20% of frequency and an AM radio bandwidth will be 100% of the frequency. Since the radio tunes to one channel at a time the bandwidth to frequency is actually much smaller , perhaps 0.1%. This means that the antenna can be tuned for efficiency and fractal nature is not required. But in practice the signal strength is high, the antenna is not tuned, and actually extraneous noise is the limit rather than the available level of incoming signal. Graeme Bartlett (talk) 06:36, 4 June 2011 (UTC)[reply]

Microwaves

Thus is in regards to the recent suggestions that cellphones may cause cancer. How can microwaves, which carry less energy than visible light, nonetheless cause more damage to human tissue? — Preceding unsigned comment added by 65.92.5.252 (talk) 23:45, 31 May 2011 (UTC)[reply]

Probably because they penetrate further. Light and UV do damage the skin, but mostly on the surface, which is soon shed, thus limiting the accumulation of damage. StuRat (talk) 00:33, 1 June 2011 (UTC)[reply]

Melanoma begs to differ. Microwaves do damage in different ways than visible, or especially UV light. In any case, as the article Mobile phone radiation and health points out, mobile phone radiation is classified as a Group 2B carcinogen ("possibly carcinogenic to humans"), while ultraviolet radiation is in Group 2A ("probably carcinogenic to humans"). Even if microwave radiation has a carcinogenic effect in humans, it's obviously quite small, wheras ultraviolet radiation has been strongly linked to skin cancer for decades. Buddy431 (talk) 01:22, 1 June 2011 (UTC)[reply]

The fact that most of it is prevented doesn't mean it never occurs. If skin was never shed, the problem would be far worse. StuRat (talk) 03:51, 1 June 2011 (UTC)[reply]

Anyone who is familiar with absorption spectroscopy would know that a large range of chemical moeties tend absorb in the infrared range, in particular the hydrogen-oxygen group as is present in water. Absorption of EMR by molecules is analogueous to spray painting over a stencil. It doesn't matter how much pressure you use, the paint will still only go where the stencil allows it to go. It doesn't matter how energetic the EMR is, the molecule will only absorb at a specific signiture of energies. That's why a microwave oven is so good at what it does. Plasmic Physics (talk) 02:53, 1 June 2011 (UTC)[reply]

Of course, when they absorb in the IR region, the molecules vibrate faster, heating up (like a microwave oven). They don't, however, have any electronic transitions. UV radiation, on the other hand, will cause electronic changes: it is ionizing radiation, and will create Free Radicals, which can be very bad from the cancer-causing standpoint. The mechanism by which cell-phone microwaves cause cancer (if they do at all - despite the WHO reclassification, the current evidence shows that the correlation between cell phone usage and Glioma, even if genuine, is small) is less well understood. Buddy431 (talk) 03:53, 1 June 2011 (UTC)[reply]

You're asking for a plausible theoretical mechanism by which cell phone radiation could cause cancer. The answer is that there is no plausible theoretical mechanism. And the experimental support is underwhelming at this point. This places cell-phone-induced cancer in the same category as power-line-induced cancer, psi powers, etc. -- BenRG (talk) 06:16, 1 June 2011 (UTC)[reply]

This article might be relevant as to the difference. The UN's dealing with this one. Grandiose (me, talk, contribs) 13:01, 1 June 2011 (UTC)[reply]

Here's the actual press release from the WHO that provoked the current round of news stories. The press release says that "A concise report summarizing the main conclusions of the IARC Working Group [...] will be published in The Lancet Oncology". This is not a new study; it is a new discussion of old data, data which is described in the press release as "limited" and "inadequate". Their decision to change the classification to 2B means that they think that further study is justified. Anything beyond that that you may have read was an invention of clueless reporters.

I agree with P.Z. Myers's reaction to this. (edit: Also, Orac's reaction is worth reading in its entirety.)

One of the reasons I mentioned psi powers is that parapsychological research was conducted at (and funded by) a number of prestigious universities including Stanford, Duke and Princeton, over a period of decades. Some studies found large deviations from randomness. Those studies turned out to be methodologically flawed or downright fraudulent. The AAAS still recognizes parapsychology as a science after all these years. Completely nonexistent phenomena can get a lot of legitimacy, for a while. -- BenRG (talk) 20:21, 1 June 2011 (UTC)[reply]

Who says microwaves carry less energy than visible light? Cuddlyable3 (talk) 12:51, 1 June 2011 (UTC)[reply]

You may have heard of a famous fellow called Max Planck, he says so. Plasmic Physics (talk) 13:09, 1 June 2011 (UTC)[reply]

Strictly speaking, this should be qualified - microwaves carry less energy per photon than visible light. As has been pointed out, that is not the only factor that needs to be taken into account here. You can't cook a microwave dinner by leaving it outside on a sunny day (unless you have one of these). Gandalf61 (talk) 14:49, 1 June 2011 (UTC)[reply]

I think the evidence for a link is extremely weak. One also has to take into account here that medical science is not a hard science. quite definite statements will sometimes be made, even if by the standards of the hard sciences, there isn't the evidence to support that. Take e.g. the much easier to investigate case of the relation between exposure to radioactivity and cancer. Even in that case, medical science has completely failed as pointed out here. Count Iblis (talk) 15:20, 1 June 2011 (UTC)[reply]

In the context of terahertz, I have read claims that twisting and stretching motions in the DNA could absorb in these frequencies. I remember seeing an article about an Army-funded study in which people were looking for specific absorptions from anthrax spores in the air to identify the species; they published 1/40 of the spectrum they intended to survey, citing a negative result. The military/terrorist importance of such research - for example, to identify the DNA of one person in a city from the air and to cause him (only) to develop a specific form leukemia - cannot be overemphasized. This is what makes nuclear weapons obsolete. Wnt (talk) 21:05, 1 June 2011 (UTC)[reply]

Huh? How would being able to target individual people for cancer make nuclear weapons obsolete? --Mr.98 (talk) 00:47, 2 June 2011 (UTC)[reply]

Which is the better bomb: the one that can blow up Moscow but leave Stalin and the military command structure alive to shoot back, or the one which can silently and anonymously delete every single member of the Communist Party? Wnt (talk) 19:48, 2 June 2011 (UTC)[reply]

It's not an either/or choice, since the nukes exist either way. There are plenty of ways to ensure second strike even after a "decapitation". (Whether it is anonymous hardly matters — target widely enough and only someone who was interested in nuclear winter would dare.) --Mr.98 (talk) 01:03, 4 June 2011 (UTC)[reply]

Op here: did the WHO try to rule out other possible explanations for a correlation between cell phone use and cancer (e.g. consumer habits)? 65.92.5.252 (talk) 03:40, 2 June 2011 (UTC)[reply]

It's not clear what they did because their report hasn't been published yet. All of the news stories are based on a short press release, which I linked above. The press release quotes the chairman of the IARC working group as saying "there could be some risk, and therefore we need to keep a close watch for a link". I take this to mean that he thinks the current evidence is insufficient to conclude there's a link, but sufficient to justify funding additional studies. -- BenRG (talk) 23:26, 2 June 2011 (UTC)[reply]