Wikipedia:Reference desk/Archives/Science/2008 January 5

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January 5

Dawkins' Selfish Gene on sex

I am reading The Selfish Gene and I'm having some problems understanding a particular argument, on page 44 paragraph 2 Dawkins writes

A gene 'for' sexuality manipulates all the other genes for its own selfish ends. So does a gene for crossing-over. There are even genes--called mutators--that manipulate the rates of copying errors in other genes. By definition, a copying error is to the disadvantage of the gene which is miscopied. But if it is to the advantage of the selfish mutator gene that induces it, the mutator can spread through the gene pool. Similarly if crossing-over benefits a gene for crossing over, that is a sufficient explanation for the existence of crossing-over. And if sexual, as opposed to non-sexual, reproduction benefits a gene for sexual reproduction, that is sufficient explanation for the existence of sexual reproduction.

I don't undertand how crossing-over or inducing mutation can benefit any gene, much less the genes responsible for the those particular behaviors. What am I missing? -- Diletante (talk) 04:10, 5 January 2008 (UTC)

Crossing over means that there can be many different neighbors from the gene pool for any particular allele. This is good since it is more likely to survive selection if it has desirable neighbors and crossing over makes this more likely. David D. (Talk) 05:49, 5 January 2008 (UTC)

Would it be correct to say that crossing over can increase the fitness of the organism and therefore the fitness of the gene for crossing over? -- Diletante (talk) 18:02, 5 January 2008 (UTC)

As regards to the inducing mutation example, have a look at genetic hitchhiking, I believe it explains a mechanism by which a mutator gene could selfishly propagate itself. Hope that's what you're looking for. Azi Like a Fox (talk) 12:53, 5 January 2008 (UTC)

I am still a bit confused on the paragraph I quoted but I can understand the mutator gene example now after reading that article. I know I am going to have to re-read the chapter a few times. -- Diletante (talk) 18:02, 5 January 2008 (UTC)

Dawkins is pushing a very particular 'level' of selection; the gene level. As such, he is trying desperately to counter arguments that suggest that mutation and sex are selected for at the organism or population levels. His argument is obviously strongest in the case of transposons, but he needs to overcome the arguments about Muller's Ratchet, among others, to deride the implied benefit of sex to the organism (sometimes cast as dogmatically adaptationist). He also needs to demonstrate that the cost to the organism is overwhelmed by the benefit to the gene directly. I'd suggest reading carefully about all the literature about bacterial sex, viral sex, particularly the interesting work by Prof. Paul Turner and others. Dan Hartl may also have interesting things to say about the topic. Bckirkup (talk) 20:10, 10 January 2008 (UTC)

Jet injector

Are these painfree or at least noticeably less painful than needles? Google results seem to contradict . --Taraborn (talk) 08:50, 5 January 2008 (UTC)

A hygiene conundrum

I have an uncle (who's a little nutty, although fairly smart) who has this theory that he refuses to use the blow-dryers in public restrooms (you know those things on the walls that blow hot air air and sounds like a 747 taking off?) because he argues that they just recycle the dirty air in the washroom and puts all these nasty bugs on your hand. What he does is just leaves his hands wet and let them dry off by themselves. I contend that that is insane, because all air is filled with dangerous stuff that sticks to a wet hand, and it is in fact safer to not wash your hands at all than to leave them wet (a fact which I first found out about in a Slate Explainer). So he shouldn't wash his hands at all. Of course, this means that the blow-dryer also is a pretty bad way to dry your hands (since it uses air), but I argue that it least it is really hot and that the warmers inside kill a bunch of the bugs, unlike normal air.

And here we are at the standoff: assuming that regardless of safety, you really want to wash your hands after using the toilet (to get off the urine, and all), what is safer at a public restroom without paper towels: using the blowdryer, or letting your hand dry off by itself? 83.250.203.75 (talk) 09:16, 5 January 2008 (UTC)

Just wipe your hands on your pants. Nobody has time to wait for the blow dryer to do its work. SpinningSpark 11:11, 5 January 2008 (UTC)

Your uncle's reasoning is completely absurd. However, the only time I've used a blow dryer in a public restroom was once that I had my pants wet. --Taraborn (talk) 11:33, 5 January 2008 (UTC)

Using a hand dryer is almost definitely more hygenic then simply let your hands dry naturally (note it isn't just the air your pick up germs from, you're likely to be touching a number of surfaces with your wet hands potentially including the toilet door) and you may very well touch your wet, contaminated hands to your face greatly easing transfer of whatever you've picked up. There is some comparison of paper towels versus hand dryers on the wikilinked article (with paper towels usually coming across as more hygenic). (These have mostly be from studies relating to best practice in a hospital context where there is far greater concern.) On the whole, most comparisons have concentrated on the economical & environmental efficiency side of things (which hand dryers usually winning there, [1] and [2] seem to be the best for that area) although there's a lot of dubious research and claims from either side. BTW, just an educate guess but wiping your hands on your pants is probably more unhygenic then either suggestion but still probably better then leaving them wet in most cases. Of course, the biggest problem with hand dryers is that most of them take too long (there are apparently some new ones which are a lot faster but I've never seen them) and so a lot of people don't use them or at least don't use them for long enough. Of course most people don't really wash their hands properly either (if you take a look the recommended practice)... P.S. does your uncle hold his breath from the moment he enters the toilet? Nil Einne (talk) 14:00, 5 January 2008 (UTC)

Also worth noting is that the air from the drying is quite hot; most bugs don't like being heated up and dried out. While it's no substitute for an autoclave cycle, a hot air dryer will certainly take the wind out of most critters.

Of course, I like the paper towels because I can use them to open the washroom door after I'm done. About half of all people don't wash their hands regularly after using a public washroom, and the first thing they touch after doing their business is the door of the washroom. By the same token, if I'm using an older hot air dryer that doesn't come on automagically, I press the button with my elbow. TenOfAllTrades(talk) 15:20, 5 January 2008 (UTC)

Am I the only one who dries his hands by running them through his hair? Two birds with one stone is how I see it--dries my hands and keeps my hair neat. --Trovatore (talk) 21:55, 5 January 2008 (UTC)

Backcrossing

MyD88-/- mice were generated as described and backcrossed for 9 generations on an H-2d (BALB/c) background. - what's the backcrossing necessary for? --Seans Potato Business 20:15, 12 December 2007 (UTC)

When generating knockout mice, it's generally necessary to mix two different strains of mice. Backcrossing is used to reduce the genetic components of one of the founding strains. — [[Scientizzle 21:16, 12 December 2007 (UTC)

Here is an ugly graphical representation. After several generations of backcrossing, one can assume that the only non-BALB/c DNA in these mice is from the regions flanking the knocked-out gene — Scientizzle 21:21, 12 December 2007 (UTC)

That's great; thanks. So you only need to perform backcrossing when you have the knockout in a different genetic background than the one you want? Would it not be simpler to have performed the knockout in the genetic background in which you wanted it in the first place? Are some backgrounds in some way easier to use for producing knockouts? --Seans Potato Business 22:07, 13 December 2007 (UTC)

The formation of a genetic knockout mouse is moderately complex. A genetically modified embryonic stem cell of strain 1 is placed in the developing blastocyst of strain 2. In order to determine the efficacy of the implantation (and to plan subsequent breeding), it's useful to produce a chimera of strains with different coat colors. There's more information at Knockout mouse. — Scientizzle 22:22, 13 December 2007 (UTC)

But the diagram you link to uses three different strains. One cell type endures the knockout and is put into a blastocyst of another type. They then try to get the transgene in a C57BL/6 background by "backcrossing". If they (the scientists involved) had used C57BL/6 cells in the first place, they could put those cells in the same blastocyst as before, breed with a C57BL/6 mouse, and just like that, all the black offspring are heterozygous for the knockout and fully C57BL/6; no backcrossing necessary. --Seans Potato Business 13:30, 15 December 2007 (UTC)

As far as I can tell that is what this diagram shows. The founder is a chimera of C57BL/6 (abbreviated as B6) and 129/Sv cells and it is backcrossed to C57BL/6 mice. That is just two strains. However, you don't put B6 cells into a B6 blastocyst, because then its is much more difficult to identify which offspring are chimeric. Typically need your null allele to be incorporated into the DNA from a strain with a different coat colour, since this is the way you can identify your founders (129 mice are white, and B6 mice are black - chimeric mice will be a patchwork of white and black). So at N1, the first backcross, you will select mice that have one allele that is B6 and the other has to be the null allele, which is on a 129 background. Thus, at that point, you will have a 50/50 mixed genetic background. Rockpocket 19:35, 21 December 2007 (UTC)

Having a coat color chimera allows for a greater simplicity in creating a knockout strain--the chimeric progeny of a successful incorporation will be obvious, they're adorable little multicolored animals with the coat colors of both the recipient cell and the donor cell (the cell w/ the altered DNA). Those that have the color type of the donor in higher ratio, and especially if that coat color is found near the reproductive organs, are more likely to be heterozygous for the _target mutation in their germ cells, which is the key. The progeny of those animals become your F1 generation if germline transmission is received. Because raising animals is expensive, and genotyping a new mutation can be difficult/expensive/time consuming, these shortcuts make it simpler to produce a strain.

One note--the mice I've been involved with ususally only use two strains, 129/SvEv cells injected into C57BL/6J, then further backcrossed onto C57BL/6J, for example. Why one would use three strains, I don't know...but using only one strain would cause large difficulties...it would be effectively impossible to determine the efficacy of any blastocyst implantation; one would be left with attempting to test every possible F1 pup for the genotype of interest. — Scientizzle 20:35, 21 December 2007 (UTC)

But aren't you assuming that the coat colour is linked to the chromosome holding the knockout? In reality, they will probably separate, being on different chromosomes, leaving a mouse with grey colour but homozygous positive (no knockout), indistinguishable from a mouse that has the same colour and is heterozygous.

Scheme:

Chimeric + White =

Grey hetero

Grey hetero + White =

Light grey hetero and light grey homo +ve

--Seans Potato Business 23:07, 21 December 2007 (UTC)

No.

1. DNA-altered ES cell from gray-coat-colored strain added to developing blastocyst of a black-coat-colored strain.
2. Resulting offspring are chimeric: stripes & patches of black and gray. The level of gray coloration is suggestive of the extent of the expansion of the altered cell into the various tissues, including the germ tissues.
3. Those mice are crossed with black mice. Those offspring will only be heterozygous for the mutation if their chimeric parent's germline cells were derived from the altered (gray) stem cell. Coat color may be, at this point, genetically independent of the mutation, as you suggested. (But! pups of variable color--half completely black and half of the litter completely gray--are suggestive of gray-type DNA in the germ cells, so that's usually a good sign.)
4. These putative F1 mice are then genotyped...and the rest is history.

The key to the whole process is that the genetically altered stem cell must end up as a progenitor to germline cells in order for the whole scheme to work. Mixing coat colors is a way to measure that efficacy. I'm not saying this is the best way to do it, but it is why it's done. If one only uses C57 cells in C57 embryos, one cannot easily know if any step (incorporation of ES cell, expansion of that cell into relevant tissue, inheritance of said cell's coat color phenotype) along the way, until genotyping the F1, has worked. — Scientizzle 23:59, 21 December 2007 (UTC)

Okay, I understand it. I'll try to make a nice SVG diagram for the article. Here's a method that I think would be better though; it requires approximately eight genotypings but no backcrossing. Is it flawed?

1. Transduce C57 cells and insert in 129 blastocyst
2. Cross chimera with C57 mice
3. Black offspring are heterozygous
4. Cross black offspring
5. Genotype approximately four males and four females to find one double negative of each type.
6. Breed as much as you like. They're all fully C57 background and so no backcrossing required. --Seans Potato Business 09:52, 22 December 2007 (UTC)

Sorry Sean, your scheme doesn't look too good. #3 is wrong because, unless the mutation of interest is on the same chromosome as the coat color gene(s), one cannot assume that the black offspring are the hets. In fact, if unlinked, black offspring have same odds of heterozygosity as non-black.

The backcrossing is necessary because any het F1s would, by definition, have ~50% 129 strain DNA. (The chimera parent has a mostly C57 body, but must have 129 sperm or eggs in order to contain the mutation.) Each F1 het would have a different profile of C57 and 129 DNA, too, so crossing them could make offspring that are between 0 and 100% genetically 129. Continued backcrossing against C57 +/+ animals reduces, each generation, the amount of (mutated-chromosome-unlinked) 129 DNA by 50%, until only the region of the altered chromosome is non-C57. This is important because different inbred mouse strains can have wide variability in many important features, including behavioral measures, drug metabolism, cancer development, etc. — Scientizzle 20:53, 22 December 2007 (UTC)

Okay, I messed up on the first scheme, but I'm not through yet!

=== Revolutionary Nobel-prize-winning method ===

1. Transduce C57 cells and insert in 129 blastocyst
2. Cross chimera with mouse of C57 background
3. 50% of black offspring are heterozygous - genotype approximately two males and two females to find one heterozygous of each gender
4. Cross heterozygous black offspring
5. 25% of offspring are homozygous negative - genotype approximately four males and four females to find one homozygous knockout of each gender
6. Breed as much as you like. They're all fully C57 background and so no backcrossing required

Stats to achieve two homo.neg. in required background: Total crossings = 2, total genotypings: 12

=== Standard Leading-brand method ===

1. Transduce 129 cells and insert in C57 blastocyst
2. Cross chimera with mouse of C57 background
3. 50% of not-black offspring are heterozygous - genotype approximately two mice to find a heterozygous negative mouse
4. Cross heterozygous negative with mouse of C57 background
5. Offspring are all about 75% C57 and 50% are heterozygous - genotype approximately two mice to find a heterozygous negative mouse
6. Repeat steps 4 and 5 10 more times to achieve mice with 99.98% C57 genome and genotype approximately two male and two female mice to find one heterozygous mouse of each gender
7. Cross these two mice to achieve 25% homozygous knockout mice with 99.99% C57 genome - genotype approximately four males and four females to find one homozygous knockout of each gender

Stats to achieve two homo.neg. in required background: Total crossings = 13, total genotypings: 32

Am I right in my understanding of the backcrossing procedure and/or my assertion that reversing the roles of the C57 and 129 mice is a sound suggestion? --Seans Potato Business 16:10, 25 December 2007 (UTC)

Not really. Your idea of reversing the roles of C27 and 129 is flawed because of the dominance relationship of alleles of the tyrosinase gene. The Tyr⁺ allele is dominant to the Tyr^- allele. 129 mice are Tyr^-/- which makes them albino. C57 mice are Tyr^+/+ which makes them melanic. At step 2, all the offspring from the cross will be melanic (either Tyr^+/+ or Tyr^+/-) Therefore there is no way of knowing, by looking at the offspring from step 2, whether the transgene went germline in the chimera. As Scientizzle notes above, the key to the whole process is that the genetically altered stem cell must end up as a progenitor to germline cells in order for the whole scheme to work, your suggestion does not help us determine whether that step has occurred. Rockpocket 05:34, 29 December 2007 (UTC)

Thinking about this further, I fear I have given you misleading information. While my points are correct in reference to the original 129/SvJ strain, it turns out that typical 129 available mice today are actually from a congenic substrain called 129/Sv-Sl/+,+^p,+^c. The coat colour in this mouse is from a mutation at the Steel locus, giving the mouse a "steely" white/grey colour. Importantly, this is dominant to the C57 Steel allele, so if one were to use this substrain then my criticism is no longer valid. However, there is another technical problem, and that is that pretty much all the embryonic stem cells lines widely available (in which you need to make your knock-in/out) are from the 129 strain. Again, there are a number of technical and historical reasons for this. If you could get adequate C57 ES lines, then I think your strategy would work. However, as with most revolutionary Nobel-prize-winning methods, you are not the first to think it up - the Gene _targeting Facility at the University of Virgina already offer this service using their own source of C57 derived ES cell lines. [3] Rockpocket 09:33, 29 December 2007 (UTC)

Okay, thanks for the insight. I've made a schematic for the backcrossing article. Comments? --Seans Potato Business 14:11, 1 January 2008 (UTC)

I don't see anything at that link, I'm afraid. Rockpocket 03:06, 2 January 2008 (UTC)

Apparently you need to click on another link to get to the actual file. It confused me for a while, too, since the page you get at first looks just like a typical parked domain.

Anyway, the picture seems basically correct (and rather funny, too) to my untrained eye. It's somewhat confusing though — I had to look at it several times to figure out which mouse was the offspring of which mating. Perhaps it would be better to use more whitespace, and to draw an explicit family tree with lines connecting each mated pair and pointing to each of their offspring. —Ilmari Karonen (talk) 17:24, 2 January 2008 (UTC)

Here is Mk II. Is it any better family-tree-wise? Do you still think it needs white space, and if so, between which elements exactly? Your input is valuable and appreciated. ----Seans Potato Business 00:38, 3 January 2008 (UTC)

Yes, that's definitely better. —Ilmari Karonen (talk) 23:40, 5 January 2008 (UTC)

That's weird...we answered this question on Dec 12th. What's it doing back here again? The OP's signature is even from Dec 12th. SteveBaker (talk) 21:04, 21 December 2007 (UTC)

Sean brought it back for round 2... — Scientizzle 21:09, 21 December 2007 (UTC)

RockPocket brought it back for Round 3 now? Are we attempting to make this the thread that never dies? Should we give it its own subpage? ;-) Nil Einne (talk) 08:53, 29 December 2007 (UTC)

Not me. This is Sean's baby. Rockpocket 08:57, 29 December 2007 (UTC)

Ooops sorry then, I thought it was you who brought it back with your response but I guess Sean brought it back because he'd received no response Nil Einne (talk) 09:08, 29 December 2007 (UTC)

Aha! I hadn't tracked it down, but this explains why the RD archiving script has been complaining on and off for the past month or so about an "orphaned" entry from December 12 that it declines to archive because it's out of sequence. (Lord knows what the poor script will do now that the beleaguered orphan has wandered into a completely different year...) —Steve Summit (talk) 14:08, 5 January 2008 (UTC)

• Final round! I just want feedback on whether my diagram is fit for use or needs tweaking. --Seans Potato Business 13:50, 5 January 2008 (UTC)

No I'll kill myself if this thread ends! (j/k) Nil Einne (talk) 14:01, 5 January 2008 (UTC)

Three minutes into the fourth round... K.O.! Any comments re: my diagram at backcrossing should be directed to my talkpage. Thanks for all the explanations, everyone! --Seans Potato Business 19:09, 6 January 2008 (UTC)

Is cannabis good for you?

In order to settle a dispute I have with User:Pundit over Cannabis Culture magazine as a source for the article on Chocolate Thai, I request that anyone address the question: Is cannabis good for you? It's important because the claim was made by one of the editors of Cannabis Culture magazine in this forum thread, suggesting they're not a reliable source on anything, including cannabis. Zenwhat (talk) 16:35, 5 January 2008 (UTC)

Isn't this pretty much impossible to answer? Is morphine good for you? Yes, if you're in a lot of pain it can surely help, but... Well, you get the point. What exactly are you asking about, the health benefits of smoking pot? ;) Aeluwas (talk) 16:45, 5 January 2008 (UTC)

Let me add that I don't think this question is in any way relevant to our dispute. I myself do not smoke marijuana and I believe the health risks (especially in case of asthmatics) are bigger than the benefits. But I think that this kind of a question is only for each of ourselves to ask and no poll can help. Pundit|utter 16:47, 5 January 2008 (UTC)

I'm asking: Is there any reliable evidence to suggest marijuana may have negative health effects? The editor of Cannabis Culture magazine strongly said no. They literally said, "Cannabis is good for you," as if it were a vitamin or essential nutrient. They appear to push fringe theories about Cannabis and I'd like to confirm this.Zenwhat (talk) 17:01, 5 January 2008 (UTC)

I am pretty sure you can find both information on general negative effects (AFAIK possible increase of allergies) as well as long-term influence on psyche (I recall an article I read in New Scientists or something like that). But in the question as you ask it I would assume the thesis is not that there are no negative effects, but rather that the positives are bigger. In any case, the question is so subjective that we all can answer it to ourselves, as Aeluwas pointed out (health is not the universal value to many people and some prefer e.g. pleasure - it is difficult to define "good" in this respect). Pundit|utter 17:10, 5 January 2008 (UTC)

Jogging is good for you, unless you slip on ice. Democracy is good for you, unless you elect a moron. Medicine is good for you, unless something goes wrong. Water is good for you, unless you are drowning. "X is good for you" is not a rigorous statement by itself, it can't be easily evaluated and can't be the sole basis as to whether a source is good or bad. --24.147.86.187 (talk) 17:28, 5 January 2008 (UTC)

Pundit: That's my point. There is conflicting research. The idea that inhaling tar -- even if it's cannabis tar -- is "good for you" is absurd. Specifically, THC may have some medicinal and therapeutic effects if used in a certain way, as prescribed by a doctor, but it is not a vitamin and excessive recreational use of cannabis is likely unhealthy. As I said in that thread, even if THC is an anti-depressant, the recreational use of anti-depressants is widely acknowledged by Psychologists to be mentally unhealthy. They dispute that claim and endorse recreational use of cannabis as being beneficial to health, which seems to violate WP:FRINGE. According to them, everybody should smoke weed because "Cannabis is good for you." Zenwhat (talk) 17:34, 5 January 2008 (UTC)

Sure, you're right. It is just, as I wrote to you before, that in NRA publications you will also see a glorification of possessing guns, although independent research may show that having a gun increases the statistical likelihood of being shot. Also, I think what they're doing is reporting ONLY good sides of cannabis - just like Men's Health recent article on why is drinking beer good for health (and their objective was not to go into negatives). Nevertheless, just "being good for someone" is a vague category and not possible to evaluate scientifically for or against. Pundit|utter 17:38, 5 January 2008 (UTC)

Zenwhat, using a single line of such an ambiguous and unrigorous nature as a way of trying to discredit an entire publication as a reliable source is absurd. The line doesn't imply that the editors are unaware of potential health detriments nor does it imply that they think it is a vitamin or that "everybody should smoke weed". You're being a little silly here in your zeal to discredit a source, especially since you are not taking your claims from the source itself but a forum post made by one of the individual editors. (I honestly don't know if they are a good source or not, but this is not the way to determine it.) --24.147.86.187 (talk) 19:27, 5 January 2008 (UTC)

Dear anonymous editor, don't call your opponents silly. It is a personal attack and in some cases qualifies for blocking. Also, consider registering an account - it is much easier to talk with somebody known at least from their nickname and edits history. Pundit|utter 22:30, 5 January 2008 (UTC)

Opponents? We're all here to build the wiki, not to slug things out. This isn't a forum. 24 merely pointed out that you seem to have got a bit carried away in your zeal to discredit a source, and have strayed into saying some rather silly things. That is not in any way a personal attack. (Oh, and many of us around here know 24 from their IP and edit history, but I would personally find your comments unpleasant even if I were not familiar with the person they were aimed at) Skittle (talk) 23:17, 5 January 2008 (UTC)

If you read the discussion above, which I'm assuming you didn't, you'd see that it would be quite hard for me to be zealous in discrediting a source, as I was the main opponent of Zenwhat. "Opponent" is a typical term used in academic discourse for a person taking a different (opposing) stance (read the definition). Saying that somebody is a little silly is a personal attack and is a personal remark, rather than a remark about a statement. I disapprove of such behavior. In the same time I humbly accept your judgment of my comment as being silly, but I don't think such a judgment as yours is particularly constructive either. Of course, any user has a right to remain anonymous. I don't think it simultaneously means that registered editors should be disallowed to encourage IP users to register. You may want to read why is it a good idea to log in. Pundit|utter 14:27, 6 January 2008 (UTC)

Now you're being silly. If saying someone is acting silly is a personal attack, then we're not going to get very far. The thrust of my argument had nothing to do with whether someone was being silly or not, incidentally. And I've edited on here for a lot longer than you have (almost four years, if you can believe it!); I log in when I need to. I should probably get a bumper sticker that says "My Other Account is an Admin" but that'd be a bit silly, no? ;-) If you're around here long enough you'll probably get to the point where you want to log out too. :-) --24.147.86.187 (talk) 21:27, 6 January 2008 (UTC)

Perhaps you have trouble recalling what you wrote. You were not describing an action, but a person, and you should know there is a difference. Calling an argument silly is just a bad rhetoric practice. Saying that a person is being silly is close to an insult, and definitely does not enrich the argument in any way, while may be unpleasant for the other party. Although I agree with the argument you made, I still disapprove with your way of addressing Zenwhat. I realize that being civil is sometimes difficult and, as an administrator on another project with some experience I honestly admit that it is occasionally hard for me as well. But recalling your big experience to justify the manner of speech in which you're calling your fellow editors silly (Merriam-Webster: weak in intellect : foolish b: exhibiting or indicative of a lack of common sense or sound judgment) is working against you - I would expect more civility from an experienced editor than from a newbie. And if you really are an administrator in the project, as you suggest (and which I doubt a little, for I can't see any reason why would an admin be ashamed to reveal his/her identity) then you should serve as an example to other editors. The fact that you have edited Wikipedia longer than me is something I very much respect and have in high regard. But respect is also something that bases more on behavior, than just on time. Pundit|utter 23:34, 6 January 2008 (UTC)

Can you see how silly you're being? You just spent 250 words trying to discuss my usage of the word "silly". You've devoted over 450 words to this particular topic so far. That's silly. Lighten up! :-) Collaborative projects go down the tubes when people spend more time talking about how to have a discussion rather that just having the discussion itself. --24.147.86.187 (talk) 01:56, 8 January 2008 (UTC)

I devoted all these words not to discuss your usage of words, but perhaps to encourage you to civilize yourself, you know, just a little :) But you certainly are right that there are better things to do. Your usage of smileys was enough to lighten me up, so have a good night and see you around ! Pundit|utter 05:20, 8 January 2008 (UTC)

The reference desk is not a soapbox. This question is not rigorous and depends entirely on the individual interpretation of "good." Nimur (talk) 01:19, 6 January 2008 (UTC)

I disagree, the question of whether it can provide medical benefits is a valid one. There may be few unbiased studies we can point to to answer the question accurately, but that isn't an issue with the question, but rather our ability to answer it properly. StuRat (talk) 17:05, 9 January 2008 (UTC)

No, it is definately not good for you. As well as causing psychosis, it is more carcinogenic than tobacco. See this page and the links to the right: http://news.bbc.co.uk/1/hi/england/cambridgeshire/7153698.stm (Its not illegal just because governments or the police are simply mean, is it?) 80.0.105.180 (talk) 19:56, 7 January 2008 (UTC)

I'd say smoking just about anything is unhealthy, as that's likely to cause lung cancer. However, cannabis can be consumed in other ways, as can the active ingredient, THC. That should eliminate the risk of lung cancer and possibly provide medical benefits. StuRat (talk) 17:09, 9 January 2008 (UTC)

Extend my antenna

My radio doesn't pick up a signal very well. Can I just attach a long wire to the radio's extendable antenna and drop it out my window? or attach it to my window screen? In general, will connecting more metal to my antenna improve matters?

Thanks! --Mike 17:32, 5 January 2008 (UTC)

Theory says "no", but I wish I had a nickel for every time reality made a monkey of theory (often there are too many variables). Try it. There is no way it can harm your radio. If the signal gets stronger, then great. By the way, inside or outside will make little difference, usually. --Milkbreath (talk) 18:33, 5 January 2008 (UTC)

The extendable antenna on most radios is for FM, and extending it to a great length will probably not increase the clarity of reception. A shortwave band receiver or AM receiver might benefit from a longer antenna if you have a way to attach it to the appropriate antenna terminal. Edison (talk) 20:22, 5 January 2008 (UTC)

An antenna increases the gain for a particular (range of) frequencies in a particular direction.

If you contect the wrong antenna, you will degrade the signal. If you connect the right antenna you will enhance the signal. If you are working at random, you wiil almost ceartainly degrade the signal instead of enhanceing it. To answer yojr question, we need the following information:

• transmissiion band
• polarization
• your location
• &location of the transmitter.

A properly-designed antenna system can add more than 40dB to your link budget. -Arch dude (talk) 01:23, 6 January 2008 (UTC)

There are such things as random wire antennas. Anyway, whatever theory says, I have had good experiences with improving marginal FM reception with the simple addition of a very long wire to the antenna. Then again, I've also had surprisingly good results from the addition of a coat hanger and assorted kitchen utensils, tweaked and repositioned until reception was adequate. It was an ugly kluge indeed, but it did make the difference between static and music at the time. —Ilmari Karonen (talk) 00:44, 7 January 2008 (UTC)

If you want to improve the reception of a specific frequency, you can size the antenna according to the equation & diagram at Dipole antenna to optimize for just that frequency, without significantly worsening other frequencies. jeffjon (talk) 13:35, 7 January 2008 (UTC)

Orbital planes

Our solar system has a bunch of things going round the sun, all on the same (ish) 2D plane. Is is possible, and theoretically viable for life given right conditions, for a system's planets to not be all in a 2D plane but all over the place at all kinds of degrees up/down, a bit like the basic atom icon? Lady BlahDeBlah (talk) 18:08, 5 January 2008 (UTC)

Well, who knows what may be possible, as we only have one example, we can't draw any firm conclusions. However, the view is that such a system would be too unstable for life to be likely. Planets interacting with each other would cause huge changes in their orbits and consequently huge changes to their environmental conditions. It is even possible that a planet could be thrown out of the system altogether. I have seen this question discussed in New Scientist and elsewhere but I could not immediately find an article that directly addresses it. However, you will see from the Planetary habitability article that life needs a reasonably stable planet (or so it is thought). You might want to look at the Extraterrestrial life article also.

SpinningSpark 18:39, 5 January 2008 (UTC)

We don't only have one example; we have eight planets all aligned to each other. They're even rotating the same direction around the sun. This would be extremely unlikely if there wasn't a reason for it. Of course, it's probably possible that something like another star passing nearby could throw all the planets out of whack, and I suppose you could get a whole lot of dwarf planets the same way we got Pluto.

We do only have one example of abiogenesis, and thus don't really know what it takes for life to begin. Any unlikely things about earth could just be because it's required for intelligent life. We do know that life can evolve to survive most anything you can throw at them, so the planets would definitely be viable for life, but there's no guarantee they can start it on their own. — Daniel 18:55, 5 January 2008 (UTC)

What is that reason? Why couldn't Mars be above us, Venus far below and to the right and Jupiter perpendicular? Makes kid of an artistic 3D sense in my head, but I have a habit of fudging the laws of everything mentally before I hit the proverbial roadblock. I tried to find it and it's a bit...baffling. Lady BlahDeBlah (talk) 19:03, 5 January 2008 (UTC)

Any rotating gas cloud that undergoes gravitational collapse will tend to flatten into a disk. This is a consequence of the conservation of angular momentum coupled with internal friction. The planets (and most everything else) formed out of such a disk so they can be expected to all lie in roughly the same plane and be travelling in the same orientation. Dragons flight (talk) 19:17, 5 January 2008 (UTC)

(edit conflict answering Daniel) I meant one example of life, not one example of planet. I know the system described is highly unlikely for astrophysical reasons but I was trying to answer the question as put. I think my point was there is no long term viability, so as you say, life is unlikey to evolve there. But if something was to visit, sure it might be ok there for a while at least. SpinningSpark 19:07, 5 January 2008 (UTC)

By long term viability, do you mean life that gets there would die out? As I said before, life can survive a lot. — Daniel 20:48, 6 January 2008 (UTC)

It seems to me that harmful interactions between planets are less likely if orbital inclinations vary widely! — Even if there's no primordial disc, I imagine the system would tend to converge to a plane through exchanges of angular momentum; though that raises a question: why do globular clusters (which contain the oldest stars) exist? —Tamfang (talk) 07:43, 7 January 2008 (UTC)

Gravity and planetary bodies

Are there any instances, and is it theoretically possible, for two roughly equally sized planetary bodies to orbit around each other? Say, two planets as they orbit their star or two satellites as they orbit their planet/moon? As well, if it is possible, what gravitational implications would occur to the planetary bodies and any satellites orbiting them? -67.34.186.30 (talk) 19:01, 5 January 2008 (UTC)

Certainly; this is the case with Pluto the dwarf planet. It's called a Binary system. Daniel (‽) 19:15, 5 January 2008 (UTC)

(edit conflict) Yes, in fact the Earth and Moon are near enough to each other in size to be considered a double planet by some rather than a planet and moon. The gravitational effect would be what the moon does to us - tides. Saturns moon Janus has another interesting variation (possibly what you meant). It shares an orbit with the moon Epimetheus. One slowly catches up with the other over time. This does not result in a collision as you might expect. What happens is they orbit each other for a brief while until they have exchanged orbital positions. This results in what was the faster one now becoming the slower one. What was the slower one now chases the other around the entire orbit until it catches up and the whoe thing starts over again. SpinningSpark 19:22, 5 January 2008 (UTC)

Thank you very much. -67.34.186.30 (talk) 19:53, 5 January 2008 (UTC)

Asteroid 90 Antiope is remarkable in that its two members are nearly equal in size (and rather big). —Tamfang (talk) 07:55, 7 January 2008 (UTC)

So, I jumped to that link for Antiope and learned all about this small binary. However, some of the numbers don't add up, the way I learned math. "Each component is about 86±1 km across, with their centers separated by only about 170 kilometers. This means that the gap separating the two halves is a mere 60 km, or so." Okay, assuming that they are roughly round, if they are ~86km across, they have a radius of ~43km. If the distance between centers is ~170km, then I get 170-43-43 = 84km of space separating the two halves. What am I missing? -SandyJax (talk) 18:52, 9 January 2008 (UTC)

Perhaps the orbit is highly elliptical, the objects aren't particularly spherical, and/or there is a lot of error in some of figures. 60 km may be the minimum and 84 km the average distance. StuRat (talk) 18:53, 10 January 2008 (UTC)

Sex

Which sex positions are most and least likely to result in pregnancy, assuming there is a difference? --67.185.172.158 (talk) 21:13, 5 January 2008 (UTC)

Well oral and anal sex tend to be ineffective at creating babies. Dragons flight (talk) 21:26, 5 January 2008 (UTC)

1 where the semen doesn't enter the cervix. Neal (talk) 21:51, 5 January 2008 (UTC).

A Google search turned up this site recommending the missionary position for maximum chance of pregnancy: [4]. I can't vouch for the website, but their logic seems sound. --Allen (talk) 22:42, 5 January 2008 (UTC)

My searches also suggest the missionary position or entry from behind (i.e. doggy position, n.b. in case it isn't obvious this means vaginal entry) are rcommended[5] [6] [7]. However an important point as mention in some of the sources is whether it has any real relevance. Sure it may increase chances of conception but by how much? 2%? In reality it's probably better to concentrate on being comfortable, enjoying the sex and mutual pleasure since this may very well in itself increase the chance of conception (improved arousal and many other factors combined) and it may also increase the frequency the partners have sex (which of course increases the chance of conception too) and will probably end up having a far greater percentage change in the likelihood of conception. If a couple is really having problems conceiving, they probably should see a specialist who will be able to discuss ways to increase fertility and I strongly suspect the position won't be a big consideration Nil Einne (talk) 08:44, 6 January 2008 (UTC)

One thing that's important to keep in mind here is that, while strictly speaking the answer doesn't change depending on its purpose, the way to think about the answer does change. If you're trying for a baby then every percentage point of improvement is all to the good; if a pregnancy would be a disaster then relying on a small difference in probability is a terrible plan. That's probably the reason that organizations trying to keep the public informed on such matters shy away from this topic -- they don't want to promote the idea that woman-on-top counts as a birth control method. --Trovatore (talk) 23:48, 5 January 2008 (UTC)

One that starts with you and/or your sleeping partner in the chemist buying some good-quality condoms is a effective position for not getting pregnant. Use a condom in the right way and the chance of pregnancy is very low. May I recommend the birth control pill too (although that won't protect against STIs)? -- _{Escape Artist Swyer} ^{Talk to me} _{Articles touched by my noodly appendage} 00:45, 6 January 2008 (UTC)

Solo masturbation is the most effective sex position for avoiding pregnancy Nil Einne (talk) 08:31, 6 January 2008 (UTC)

There is a mention of this question in the Sex Positions article although not terribly informative, it does debunk some myths. SpinningSpark 12:13, 6 January 2008 (UTC)

The varied colouration of Feral Pigeons...

I was just been reading this article, which was recently added to our Feral Pigeon article as a reference when the thought stuck me - could another reason that Feral Pigeons have never reverted to their ancestral 'classic' Rock Pigeon colouration be that the various shades of browns, greys and whites and differing plumage patterns that we see on our street pigeons (which the article supposes would single out the birds to predators, as compared to the original colouration) are not particularly any more or less noticeable from the air against the varied backdrop of the city vs. the original colouration? After all, the plumage patterns and colours evolved in the 'classic' species in order to camouflage it in a very specific *and* very different environment. Any thoughts? --Kurt Shaped Box (talk) 22:59, 5 January 2008 (UTC)

This would presume that there are enough predators of pigeons in cities for there to be a selective pressure in colouration. I'm not aware of there being any significant predators of urban pigeons (which is why there are so many of the little bastards). My professional opinion would be that it is a result of a combination of selectively bred birds polluting the natural colour morph, combined with genetic drift of pigment genes, because there are few natural predators that would select against them. Rockpocket 09:07, 6 January 2008 (UTC)

I know that various hawks prey on feral pigeons - to what extent, I'm not entirely sure (any idea how common urban hawks are, in general?). Interestingly (to me), whilst the feral pigeons still retain a fear of urban birds of prey (and scatter as soon as they notice one in the sky), they never seem to see it coming when an urban gull decides that it would like some fresh meat. It's not a widespread thing (it may only be the odd individual gull that bothers to hunt when discarded human food is so readily available) but the pigeon will happily continue sauntering around and pecking at the ground - until the gull is literally stood behind/next to it and ready to seize it by the throat and shake it to death. --Kurt Shaped Box (talk) 17:39, 6 January 2008 (UTC)