Wikipedia:Reference desk/Archives/Science/2008 June 3

= June 3 =

Better name for 'africanization'
Somehow the author chose not to say 'desertification' in this NYT article. Probably motivated by the fact not all African landscape is a desert. But what is the correct term for it? 217.168.1.158 (talk) 00:01, 3 June 2008 (UTC)


 * Simple: drought. The article is about a drought in Spain, but it is using the ongoing drought conditions in Africa as well as the centuries-old shift from lush greenery to deserts to give the drought a name. -- k a i n a w &trade; 01:55, 3 June 2008 (UTC)


 * I don't agree. A drought is usually a short-term event with few permanent implications, while desertification means a permanent shift in the climate of a region towards a dryer climate.  This tends to happen over centuries or millenia, although global warming may serve to help things along. StuRat (talk) 02:35, 3 June 2008 (UTC)


 * I used drought because I saw nothing in the article that justifies desertification. They are describing a drought and using "africanization" to make the reader think all of Spain will be a desert in a few days. -- k a i n a w &trade; 12:22, 3 June 2008 (UTC)


 * The author says "officials visibly stiffen when asked about the "Africanization" of Spain’s climate — a term now common among scientists", but I don't buy it. Doing a Google Scholar search for "Africanization climate -honeybee" shows nothing about weather in the first page.  "Africanization" usually refers to renaming places like Victoria Falls to Mosi-oa-Tunya.  Her assertion about the term is perhaps an example of the rhetorical technique known as "making stuff up".  --Sean 10:11, 3 June 2008 (UTC)
 * A bit more luck with ghits in Spanish Can't say how many of those are scientific, though. --76.111.32.200 (talk) 14:54, 3 June 2008 (UTC)

Inverted icicle mechanism
Usually when I make ice cubes, I fill the ice tray from the tap. A few months ago I decided to make ice cubes from some highly purified water (1 ppm total dissolved solids). To my surprise, two of the ice cubes exhibited inverted icicles; tendrils of ice that grew upward as the water froze. This was such a strange phenomenon that I decided to take the picture to the right. Click on it to see the full details.

Does anybody know what mechanism might have caused this?

My best guess is that the water must have froze around the edges first, leaving an opening in the top. As the water froze further, it expanded, pushing water out the hole, and the edge of the hole kept freezing to build the tendril higher.

I'm skeptical that this is what happened. If the water formed a frozen tube to grow in, it should have frozen shut well before the thin part of the tendril could grow so long.

Any ideas? =Axlq 00:10, 3 June 2008 (UTC)

Looks like an Ice spike-- Lenticel ( talk ) 00:15, 3 June 2008 (UTC)
 * Kudos to Lenticel for showing the amazing range of phenomena which have Wikipedia articles. Edison (talk) 00:21, 3 June 2008 (UTC)


 * Question: what is it about tap-water that prevents this? Zain Ebrahim (talk) 00:34, 3 June 2008 (UTC)
 * Impurities in the tap water acts as a Ice nucleus so the water freezes before an ice spike can form.-- Lenticel ( talk ) 02:00, 3 June 2008 (UTC)
 * I have seen a spike in an ice cube made with water that (depending on who filled the tray) was either straight from the tap or had gone through an ordinary household water filter. Not distilled or specially purified water. --Anonymous, 23:50 UTC, June 3, 2008.

Amazing. I second the kudos to Lenticel. My question has been answered. Wikipedia really does have an article on everything! I guess my hypothesis on how the formation came about was correct, too. Thanks. =Axlq 04:14, 3 June 2008 (UTC)

Serious question about masturbation
If you consider that a hand feels like different from a vagina, should we expect that people who maturbate too much have a problem with 'normal' sex? GoingOnTracks (talk) 00:28, 3 June 2008 (UTC)
 * Why should we? Boxers also feel different from a vagina, but not going commando doesn't seem to cause an issue for people. &mdash; Lomn 00:50, 3 June 2008 (UTC)
 * What do you mean have a problem with? Is it (A) you mean they do not enjoy it as much, have something against it, or (B) they're no good at it (there is a problem they have)?
 * If you mean A then it's entirely possible and very often the case that those who do it too often simply don't have access to intercourse. Of course that doesn't mean that one who has access to it will not do it on there own, but statistically men who have sex masturbate less often.
 * If you mean B then it could be there is some problem with them having it. Or again simply that they don't have access to it.  In all honesty though you'd probably be hard pressed to find a male who would prefer solo over the alternative if both were options. Chris M. (talk) 05:31, 3 June 2008 (UTC)


 * There may be the issue of what sex columnist Dan Savage calls the "death grip", in which the masturbator uses a great deal of force and friction when masturbating, and becomes so accustomed to it that no lesser stimulation will do. In these cases, no actual intercourse is going to be enough to get them to climax, which can obviously be problematic. But that's more a question of habit than anything else, though, and easily avoided. In itself, masturbation isn't going to affect anyone's sexual prowess, and in any case, it's very common for people in sexual relationships to masturbate anyway -- in some cases precisely because a hand feels different from intercourse, variety being the spice of life and all that. (The mistake lies in thinking that because something is different, one of them must be "better" on some absolute scale and therefore always preferable -- but in real life, people tend to prefer different things and sensations at different times.)


 * As for males who exclusively or almost exclusively prefer masturbation to intercourse, Chris -- as it happens, the latest Savage Love column features a letter from just such a man. Certainly an exceptional individual, I'm sure, but still. -- Captain Disdain (talk) 09:06, 3 June 2008 (UTC)

Platypus and falsifying the nested hierarchy
Assume we are trying to falsify the established phylogeny of common ancestry. The platypus can lay eggs, and also has venom. Both are not common in mammals. Why does this not violate the nested hierarchy? After all, if we were to find a human with a plant cell wall, it would falsify the phylogeny right? Why not the platypus? I think I know the answer already, but I want to hear more... ScienceApe (talk) 01:17, 3 June 2008 (UTC)
 * Platypus was a useful read and could help explain some things. Chris M. (talk) 05:34, 3 June 2008 (UTC)


 * Egg laying is an ancestral character that other mammals (except the echidna) have lost, but the platypus has retained. The poisonous spur is a derived character that is unique to the platypus (among extant species). Thus (put very simplistically) there is no "violation of the nested hierarchy". Now, if it were found that the platypus produced venom in exactly the same way (anatomically and chemically) as some distantly related placental mammal, that would create a problem; because that would imply that the venom-producing character was due to common ancestry, not convergent evolution. However, the few venomous mammals have poisonous bites, something that is quite different from the platypus leg spur.--Eriastrum (talk) 19:25, 3 June 2008 (UTC)

Is wikipedia a conscious entity?
Terrence Sejnowski considered a similar question about the entire Internet some time ago. Wikipedia is more organized than the entire Internet. Wiki links on a page on some topic try to define the subject in terms of more fundamental concepts. This is similar to when the brain perceives something. Then a pattern is recognized which consists of more basic patterns which in turn consist of even simpler patterns etc. etc.

I'm not suggesting that wikipedia "understands" the contents of its own pages. Instead, the entirety of all the wikipedia pages with their interdependence may give rise to conscious experiences. A wiki page will simply be a pattern that could be part of some larger pattern that perhaps gives rise to some subjective experience. Count Iblis (talk) 01:35, 3 June 2008 (UTC)


 * It depends on how you define consciousness, of course. John Searle would say definitely no, and I'm inclined to agree, in this case—where does the consciousness come into being, other than in the fact that it is a system used by conscious entities?
 * I think you could say that it is easy to abstract Wikipedia—via metonymy—as if it were a conscious entity, as if Wikipedia answered your questions, as if Wikipedia understood. But it doesn't—you're just ignoring the people who really do the work, abstracting them into the system in which they operate, taking part of the whole as the whole (taking the site to be the same thing as the many networks, social and technical, that makes the site work). Wikipedia, the site, knows no patterns. The human beings that use it, do.
 * Wikipedia isn't answering your question, I am. I am a human being. I am sitting in a green chair in a room with green walls with a green bed in a little suburb in the Massachusetts (you know, I never noticed how much green was in here, until now). Don't give Wikipedia credit for something I'm doing! ;-) --98.217.8.46 (talk) 02:20, 3 June 2008 (UTC)


 * Wikipedia gives credit to volunteers. Check About —Preceding unsigned comment added by Ranemanoj (talk • contribs) 04:01, 3 June 2008 (UTC)


 * Sometimes I joke with friends saying that eventually a bot will be created that will be able to fully understand context and will scan the entirety of Wikipedia and find the underlying pattern linking all of the articles, "truth" :). Then, the bot can simply create random articles until one matches it and we can solve all of the world unanswered questions. Chris M. (talk) 05:25, 3 June 2008 (UTC)
 * (In response to OP) You might like to have a look at "The Emperor's New Mind" by Roger Penrose in which he argues that there is something inherently non-algorithmic about minds and that complexity doesn't automatically lead to consciousness (if I got that right). It's a fairly dense book though. ReluctantPhilosopher (talk) 09:24, 3 June 2008 (UTC)


 * We have an article about his (and Stuart Hameroff's) hypothesis, too: Orch-OR. If they're right, then nothing like the internet or Wikipedia could be conscious.  --Allen (talk) 14:26, 3 June 2008 (UTC)


 * If wikipedia were a conscious entity, what is it conscious of? What stimulus does wikipedia respond to? I'm not familiar with Sejnowski's work, but I have encountered theories of consciousness ascribing personality traits, intentionality and propositional attitudes to large organized systems. A nice exemplar is a corporation. One reason this is a good example is because it exists in an environment (the market) in which it competes with other similar 'organisms' for resources. If we are to treat wikipedia like an organism, what is its environment? what stimulus does it respond to? If it's conscious, what is it conscious of? --Shaggorama (talk) 04:59, 4 June 2008 (UTC)


 * Different angle: An intelligence can emerge from dumb parts. Our cells are dumb, but together they form an intelligence (without knowing it!). So could all humans together form a single intelligence (without the indivuduals knowing it)? They would have to be able to communicate, just like brain cells passing on 'impulses' that cause a reaction, which causes impulses to other individuals, rippling through humanity. Speech already does that. Books (and other printed stuff such as newspapers) helped spread the ripples further. And eventually faster. Radio and tv added to that. And then came the Internet, greatly increasing the scope and speed. But is simple communication enough? What constitutes intelligence? At the very least, there should be a method that creates a single structure that develops a sense of 'I'. And Wikipedia does indeed do something like that. So can Wikipedia be conscious? Can a human brain be conscious without it's surroundings (including the body it occupies)? An intelligence isn't something isolated. So for Wikipedia or the Internet to be conscious it needs at least the humans who are an integral part of it (its 'sensors'?). Who in turn need their surroundings to survive. But where is the sense of 'I' located? If Wikipedia becomes conscious, what does it think it is? Who do we think we are? Our bodies? Our brains? Or is that because we are selfconscious? What does a dog think it is? Does it have a more holistic view of itself because it is not self-conscious? (Or is it really not?) And if we can't even fathom the consciousness of a dog, then what chances do we have with something so different from biological intelligence? Or does that actually make it easier? Can we look for signs of intelligence in the Internet superstructure, thus understand intelligence better, and as a result ourselves?
 * Sorry, more questions, but that's what you're likely to get when you ask a philosophical question. But it sounds rather gaia, doesn't it? :)
 * Oh, and will this thread spread through the Internet and cause it to become selfconscious? DirkvdM (talk) 08:03, 4 June 2008 (UTC)


 * I don't see how Wikipedia, in itself, could be considered conscious under any theory of conscious, or at least any more conscious than a rock. Unlike a human, or the Chinese Room, or a neuron, or even a thermostat, Wikipedia doesn't process any information.  It just sits there.  It contains information, but so does any book.  It inspires people to do a lot of information processing around it and change it accordingly, but I don't know any theory of consciousness where that would matter.  (MediaWiki processes information, of course, but it isn't Wikipedia itself.)  --Allen (talk) 15:41, 4 June 2008 (UTC)

birds and current
why do not birds feel current while sitting on high voltage wires? and wat if we some person made to hang on the same wires without having any contact with earth?Lovindhawan (talk) 08:21, 3 June 2008 (UTC)lovindhawan
 * That is because when birds site on a high voltage wire their entire body potential becomes equal to the wire's potential and there is no current flowing through their body since they are not in contact with anything else which could be at a different potential. If some person was made to hang on the same wires without having any contact with earth, they would similarly feel no electric shock. ReluctantPhilosopher (talk) 08:34, 3 June 2008 (UTC)


 * They probably do feel something, as would a person in the same position, if the voltage is high enough. A field is produced in the space around the wire 120 times a second, a strong field if it's transmission lines. This will move electrons in the body. The birds don't get fried by the electricity running in the wire because there is practically no potential difference between their two feet, the resistance of that extent of transmission line being essentially zero ohms. --Milkbreath (talk) 10:23, 3 June 2008 (UTC)
 * Which amounts to the same thing, namely that the only potential difference across the body of a bird sitting on a wire is across its two feet, which is not enough to cause a significant current flow given the bird's resistance; this changes if the bird's body is grounded somehow. ReluctantPhilosopher (talk) 11:20, 3 June 2008 (UTC)


 * At a high-enough voltage, corona effects start to be important, though. The bird sitting on the wire represents a sharp point which will readily create corona and this (or the related charging currents in and out of the bird) would be uncomfortable, injurious, or fatal to the bird. That's why you mostly see birds sitting on local distribution wires (up to, say 33KV) but essentially never on long-haul transmission lines (at 110KV and higher).
 * Atlant (talk) 11:50, 3 June 2008 (UTC)
 * Hmmm, that was insightful, thanks! ReluctantPhilosopher (talk) 13:18, 3 June 2008 (UTC)


 * As for a human doing the same thing, check out this amazing video: . --Sean 10:32, 3 June 2008 (UTC)


 * That is such a cool video, thanks!--Shantavira|feed me 12:39, 4 June 2008 (UTC)

greenhouse effect
is sulphur dioxidea greenhouse gas? —Preceding unsigned comment added by 59.99.88.195 (talk) 09:03, 3 June 2008 (UTC)
 * Not according to the IPCC list of greenhouse gases but i'm sure it's not beneficial to have lots of it in the atmosphere. Regards, CycloneNimrod talk?  contribs? 10:58, 3 June 2008 (UTC)
 * I suspect that it is probably not listed because sulphur dioxide does not remain in the atmsophere for long before it is washed out as acid rain which is a much bigger problem for this chemical. Because it is heavier than air and reacts with water to form suphuric acid which then precipitates out, it does not get in to the upper atmsophere in large quantites.  Sp in ni  ng  Spark  11:22, 3 June 2008 (UTC)
 * If I recall from my environmental chemistry module, sulfur dioxide may actually have an inverse greenhouse effect because it induces cloud formation and hence increases the Earth's albedo and hence the amount of solar radiation reflected away. But I may be thinking of something else - and the other negative effects of sulfur dioxide (ie acid rain and asthma) make it an undesirable pollutant anyway. ~ mazca talk 13:09, 3 June 2008 (UTC)


 * Nobel chemistry prize winner and atmosphere expert Paul J. Crutzen has a fairly controversial idea of putting massive amounts of sulphur into the upper atmosphere to put a radical stop to climate change. Just very recently, Tim Flannery went and suggested a similar plan for the same reason. -- Captain Disdain (talk) 14:49, 3 June 2008 (UTC)


 * Hi. If I remember correctly, volcanoes can eject sulfur into the atmosphere, briefly cooling the atmosphere for as much as 1C. Mount Pinatubo is a recent example, while prehistoric eruptions such as Mount Toba made temperatures so low it wiped out more than 99.9% of all human civilization. Hope this helps. Thanks. ~ A H  1 (TCU) 22:42, 3 June 2008 (UTC)
 * I believe volcanoes do indeed release sulfur, but I thought it was the dust thrown up blocking the sun that causes the global cooling. It may be a combination, of course. --Tango (talk) 23:56, 3 June 2008 (UTC)


 * I believe the form of sulphur that causes cloud formation is dimethyl sulphide (I am British...) or DMS

How do Fleas find their hoasts?
How do adult Fleas find their hoasts? Do they use their sense of smell or some kind of thermography? I remmember that fleas used to be drawn to warm places when I had a small flea invasion in my home (gone in to days after applying a "spot-on" anti-flea substance to my dog). Mieciu K (talk) 10:26, 3 June 2008 (UTC)


 * Take a look at the flea article which has all the answers to this.  Sp in ni ng  Spark  11:26, 3 June 2008 (UTC)


 * Ok, thanks. Mieciu K (talk) 18:37, 3 June 2008 (UTC)

About career options
–NOW, AS I'M HEADING FOR CLASS 11TH, I WISH TO TAKE SCIENCE STREAM. PLEASE TELL ME ABOUT THE SUBJECTS THAT WILL BE BENEFICIAL, AS I AIM FOR ENGINEERING & THEN MBA. ALSO TELL ME ABOUT OTHER DEGREES AS MBA. DO GIVE ME INFORMATION ABOUT IIT-JEE, ENGINEERING, MBA & OTHER COURSES.TELL ME ABOUT THE PREPARATIONS. —Preceding unsigned comment added by 59.182.115.66 (talk) 10:42, 3 June 2008 (UTC)
 * You will be better advised to visit career counselling websites rather than ask at the Wikipedia reference desk. Since you seem to be from India, sites like Rediff might have useful information of a general nature, and educational sites based in India may have more specific information you are looking for. And don't write in capital letters, it amounts to shouting. ReluctantPhilosopher (talk) 10:48, 3 June 2008 (UTC)
 * In general the subjects of importance for engineering will be Mathematics, Physics, English Language, and Computer Programming.

Colleges near Mumbai
PLEASE GIVE ME THE LIST OF SCIENCE COLLEGES IN MUMBAI IN WESTERN -SUBURBS. —Preceding unsigned comment added by 59.182.115.66 (talk) 10:53, 3 June 2008 (UTC)


 * You can sort out from List of Mumbai Colleges.
 * And can you hit that CAPS LOCK button once? —Preceding unsigned comment added by 203.129.237.147 (talk) 11:39, 3 June 2008 (UTC)

how do u fit a knife in2 an electric sokket?
how? —Preceding unsigned comment added by 82.10.79.163 (talk) 12:11, 3 June 2008 (UTC)


 * simply use the knife for a self-lobotomy first and you cannot go wrong! —Preceding unsigned comment added by 78.144.96.61 (talk) 12:18, 3 June 2008 (UTC)


 * Pretty much the same way you stuff beans up your nose. -- Coneslayer (talk) 12:19, 3 June 2008 (UTC)
 * I can confirm first-hand that beans up the nose is a bad idea. 81.93.102.185 (talk) 12:28, 3 June 2008 (UTC)
 * Try phoning the local mental heath unit, I'm sure they have a lovely padded room you can practice in to your heart's content. --Tango (talk) 13:45, 3 June 2008 (UTC)


 * EZ U go 2 a Master Electrician, complete an apprenticeship and take classes where they'll tell you all about patch panels and breakers. Then you become a licensed electrician, go to your basement, find your patch panel, switch off that magic mains breaker, protect it against some wisea## switching it back on and can finally put anything you d## well please into your sockets.  It is highly recommended to remove any foreign object from outlets before switching the power back on.  If for no other reason than to prevent severe head injuries due to your spouse beating you about the head. --76.111.32.200 (talk) 22:01, 3 June 2008 (UTC)

this appears to be a silly comment on another comment from a question on this desk from a few days ago, about making a strobe light. Reference_desk/Science. Ilikefood (talk) 20:49, 6 June 2008 (UTC)

Order
If there's an order called Carnivora, why isn't there one called Herbivora? Interactive Fiction Expert/Talk to me 12:14, 3 June 2008 (UTC)


 * According to Carnivora, there is quite a big difference between being a member of that order and being a carnivore. While most members are carnivores, not all are, and plenty of carnivores aren't members (all the non-mammals, for a start). It's best not to read too much into the names of these things - there are probably historical reasons for the name that don't really apply to its current usage. --Tango (talk) 13:51, 3 June 2008 (UTC)


 * While Tango's reply is completely right, I think there's another assumption in the question which is worth examining. As humans we are very ready to divide things into two by some feature, and then at some level equate the two categories. Two particular examples which come to mind are vertebrate vs invertebrate and dicotyledon vs monocotyledon. While I don't think 'invertebrate' has been counted as a taxon for a long time (I've a feeling that Linnaeus had a 4-way classification of mammals, birds, reptiles and Ver (Lat. 'worm') meaning invertebrates), until recently dicots and monocots were simple the two divisions (or orders, in some classifications) of angiosperms, whereas now the monocots are regarded as a clade but the dicots are polyphyletic - i.e. a collection of different clades which do not belong together.


 * My point is that even if Carnivora really were distinguished by carnivorous habit, (which is conceivable, even though it happens not to be true), this would give no reason to suppose that non-carnivores formed a similarly related group; but our penchant for binary classification might still incline us to expect such a classification. --ColinFine (talk) 20:05, 7 June 2008 (UTC)

Oil crisis and food crisis, the next 50 years.
The oil will dwindle down in the next 50 years and become too expensive, to combat this I see a shift towards Bio-diesel. Now I read that the world is running out of food part of which I suspect is rising fuel costs.



So, in the next 50 years I see a dilemma , not enough land for food crops AND fuel crops and an ever increasing population.

Is there a sensible solution to this?

78.144.96.61 (talk) 12:16, 3 June 2008 (UTC)andy


 * Yes, possibly. There are many reliable scientists who state that bio-fuels are not the way forward, for the reasons you have mentioned and the fact that it is not actually as evironmentally friendly as it is made out to be. So many are of the opinion that renewable sources of energy are the way out. Wind, Wave and Hydroelectric being the main ones. Nuclear power is also less damaging to the environment, but iranium will run out eventually (though not for a very long time) and the possibility of an accident resulting disaster must be taken into consideration. There is not really a solution to the population problem. We can kill billions of people but that would be illegal, inhumane and cruel. We could follow China's exemple and offer incentives to people to only have one child but that is also regarded as cruel and should not be allowed. So, we having thought that we had risen above nature find that we can only fall back. Other animal's population is regulated by the food supply, and this was something we historicall never worried about but now we are beggining to realise that our population will be, in the end regulated by our food supply. This will be called awful and terrible by people but the will realise that there is very little thay can do. The poorer countries will be affected first as they do not have the money to buy enough food for their populations, the richer countries will try to help but will find that if they do so then they will not have enough money to buy food for their people. To make matters worse the global communications we have set up make us think that any food trouble is far away and we have never had to say 'I will only have one child becausee I cannot feed two' it is a foriegn idea. So we will continue to expand and noone will be able to tell us not to as that would be cruel! So humanity is doomed! (by our intelligence) :) Or we could colonise another planet but with no air there is no food so earth would have to supply another planet too. (Unless we found one that could support life). <span style="font-family:Zapfino, sans-serif; color:DarkRed">Harland1 (t/c) 12:45, 3 June 2008 (UTC)


 * "Iranium" ? Is that what Iran is using for it's nuclear weapons program ? :-) StuRat (talk) 00:15, 4 June 2008 (UTC)


 * When considering overpopulation, it's important to remember that much of the developed world is actually at, or approaching, sub-replacement fertility rates. If it weren't for immigration, the populations would actually be reducing. If you want to reduce overpopulation, you have to do so in poorer countries, not rich ones. One way to do that may be to help them become developed, it seems the incentive to have large families reduces when you are reasonably wealthy (I'm sure plenty of studies have been done into this, but I haven't read them, so I'm not sure of the exact reasons). --Tango (talk) 13:36, 3 June 2008 (UTC)


 * That's less a scientific than a political and economical questions. I strongly believe that we have the science to smoothly move to a high-tech, mostly clean lifestyle based primarily on renewable energy - wind, sun, hydro, tidal, geothermic, biomass. The sooner we start, the easier the transition will be. Solar warm-water is cost-effective in most of the industrialized countries even now - in many the advantage is compelling. Go to Greece, and you will see a simple solar-thermic system on nearly every roof. Wind is a largely unused reserve - Denmark is producing 20% of its electricity with wind, and has yet to significantly tap offshore wind resources. However, as in all large economical shifts, the incumbents are expected to lose, which results in a certain inertia. In Germany, the influential car industry lobbies for stricter environmental laws concerning old cars (to entice people to buy new cars), but against strict absolute limits on emissions and mileage, as German cars are on the large and heavy side (for European cars). If I own a couple of oil fields, my economic interest wil likely by against competition from other energy sources. The US is spending about US$10 per citizen per week for the war in Iraq - imagine that amount of money going into support for a shift to renewable energies. --Stephan Schulz (talk) 13:23, 3 June 2008 (UTC)


 * Significant problems still exist with alternate sources, especially with respect to intermittancy and energy storage. The Denmark examples is a good illustration - even at "only" 20% wind-based the national grid is inherently unstable because the wind doesn't always blow. Denmark is forced to rely on balancing its grid with imports and exports to other nations with more traditional power sources. See Wind power. Rmhermen (talk) 16:33, 3 June 2008 (UTC)


 * Indeed. Denmark is a) small, so local fluctuations don't even out, and b) very flat, so pumped hydro is not an option. To solve this, they export energy to Norway, which has an enormous potential of hydro (both conventional and pumped) that can conveniently buffer irregular supplies. But these are not fundamental scientific questions, but part engineering and part economical. --Stephan Schulz (talk) 16:51, 3 June 2008 (UTC)


 * The problem is reasonably easy to overcome, there are lots of other sources of energy, at the moment they are simply more expensive, so no-one bothers much with them. Once the cost of fossil fuels gets high enough, it will make good business sense to shift to other sources, so people will do so. Common sense would suggest shifting *before* we run into trouble (which would be about now), but unfortunately business sense and common sense don't quite match up, so there will probably be a short period of difficulty before the switch is completed. --Tango (talk) 13:36, 3 June 2008 (UTC)


 * There is, in general, more than enough land for most purposes. Water for irrigation, people to tend the crops, money, and so on tends to be more of a problem.--Fangz (talk) 20:37, 3 June 2008 (UTC)


 * Your assessment that overpopulation is the source of the problems is spot on. Energy we can possibly get around, as almost unlimited nuclear energy could be made available if we wanted to build the plants (I suggest building them in stable underground sites in unpopulated areas to protect the population from any radioactivity).  This could provide electricity for electric cars, heating, air conditioning, etc.  Food is a more serious long-term issue, as food production is limited by the amount of farm land, which is finite (and which we would prefer doesn't expand to include all of the remaining rain forests).  (Hydroponic food is an exception to the land requirement, but is far too expensive to feed the starving people of the world.)  Poor nations, on the other hand, have the potential for their populations to increase infinitely, unless limited by starvation, war, and disease (which we would also like to avoid).  The question is, then, do we prefer to continue to limit population by starvation, war, and disease, or would we be willing to use coercive means to limit fertility ?  I'd suggest a simple method, if someone is starving, only give them food if they agree to be sterilized.  If they agree, they stop having children they can't feed.  If they refuse, they starve, and also stop having children they can't feed. StuRat (talk) 00:30, 4 June 2008 (UTC)
 * And when they don't have enough children to work their farmland, they also starve... In most parts of the poor world, the decision to have large families is motivated by the apparent usefulness of free familial labor.  No one wants to have children that they expect will starve to death.  Dragons flight (talk) 03:10, 4 June 2008 (UTC)
 * A problem here is medical care and slow human adaption. People had loads of children because lots of them did die. But where modern medicine has stopped or reduced this problem culture hasn't suddenly changed to have fewer children. Actually, human fertility is designed to have about a dozen children per female. With modern medicine we need unnatural means (condoms, abortion) to keep our fertility drive in check. DirkvdM (talk) 08:35, 4 June 2008 (UTC)

Solar power satellites, powering the production of hydrogen fuel from water. Use the land for food production, not fuel production. --arkuat (talk) 07:05, 4 June 2008 (UTC)


 * A problem with alternative energy sources that is often overlooked is that most of them (solar, wind, hydro, nuclear) are used with technologies that create electricity. But only 20% or less of our energy consumption is in the form of electricity. Another 20% is used by cars.
 * So what can we do?
 * switch to electric cars
 * use an intermediary, such as hydrogen
 * stop driving cars. Well, use them less. Or make them more fuel efficient (oddly, we're massively doing the opposite, driving ever heavier cars). Or drive them more fuel efficiently. Or reduce traffic jams. You get the point.
 * switch to biofuel
 * die
 * Or, of course, a combination of the above.
 * But a more specific answer to your question. Lately, I've read in several sources that there is plenty land, plus the technology, to grow both food and biofuel for everyone. But it's the same old story. The means to make this happen are present in rich countries, but since we don't own the poor countries, fuck 'm. Let them solve their own problems. Maybe decolonisation wasn't such a good idea after all? Note that that is a question, not a statement. DirkvdM (talk) 08:35, 4 June 2008 (UTC)

New Guinea forest wallaby
Is there an article on the New Guinea forest wallaby under a different name? There is the Black Dorcopsis which inhabits New Guinea but nowhere can I find the New Guinea forest wallaby (Dorcopsis veterum). It does exist. <span style="font-family:Zapfino, sans-serif; color:DarkRed">Harland1 (t/c) 12:59, 3 June 2008 (UTC)
 * This page says that Dorcopsis veterum is a synonym of Dorcopsis muelleri. We have an article on D. muelleri (not much of one, admittedly) at Brown Dorcopsis. If you can add any information to the article, I'm sure it would be appreciated. Deor (talk) 16:41, 3 June 2008 (UTC)
 * Thanks very much! <span style="font-family:Zapfino, sans-serif; color:DarkRed">Harland1 (t/c) 12:51, 4 June 2008 (UTC)

Food/drink to help your memory
Have just read that smoking dope can reduce your memory capacity by up to 15%. Can this be compensated by regularly eating any food that stimulates your brain/memory area? Thanks for info. --AlexSuricata (talk) 13:09, 3 June 2008 (UTC)
 * Cannabis reduces your short-term memory capacity, i'm not convinced it's as bad as 15% but it certainly does. I'm also unsure of long-term memory loss. There are many artificial ways of improving cognitive abilities including caffeine and other CNS stimulants but again, I don't know in terms of a percentage how this would work out. Regards, <font face="Tahoma" size="2px">CycloneNimrod talk?  contribs? 13:42, 3 June 2008 (UTC)


 * You can't just add performance increase and performance decrease percentages and pretend that there are no interaction effects! This is a complex system; these "performance variations" are averages over large sample sizes, and don't even begin to encapsulate the complexity of drug interactions with physical or mental abilities.  Nimur (talk) 15:53, 5 June 2008 (UTC)

Do Marsupial mammals have placentas?
I've read Marsupials and placenta, these articles said that marsupials do not have placentas. But do these animals have any primitive organ that structurally or functionally like a "primitive placenta"? Luuva (talk) 13:40, 3 June 2008 (UTC)


 * Dont know about marsupials but look at these:http://io.uwinnipeg.ca/~simmons/16cm05/1116/34-19-AmnioticEgg-L.gif http://en.wikipedia.org/wiki/Allantois Em3ryguy (talk) 15:01, 3 June 2008 (UTC)
 * According to marsupial: "The pregnant female develops a kind of yolk sac in her womb which delivers nutrients to the embryo." That would be the functional equivalent, in that in provides nutrients to the embryo, but it seems it works in a very different way. It sounds like store of nutrients that is created before or soon after conception, rather than being a link between the mother and embryo. --Tango (talk) 15:48, 3 June 2008 (UTC)
 * The placenta also provides oxygen and eliminates waste. Also, placental embryos possess both a placenta and a yolk sac. Em3ryguy (talk) 18:16, 3 June 2008 (UTC)

??Lightning
Today it started raining in Mumbai. Before the rains there was lightning. During that time i witnessed a huge white coloured ball moving quickly in the clouds. It was flashing. When it appeared there was thunder. Can this be a lightning?? —Preceding unsigned comment added by 120.138.111.13 (talk) 15:58, 3 June 2008 (UTC)


 * Perhaps it was ball lightning? --98.217.8.46 (talk) 16:03, 3 June 2008 (UTC)
 * It could have been clouds illuminated by a series of lightning strikes. I think that ball lightning is smaller than this sounds. Graeme Bartlett (talk) 22:20, 3 June 2008 (UTC)

Glyceryl Trinitrate and Phlebotomy
I have been working as a phlebotomist for a year alongside university to help pay my nights out. Today on my way to a ward another phlebotomist was tellin gme that one day she was having problems finding a vein on a larger gentleman and that a young doctor gave her a spray bottle of Glyceryl Trinitrate/Nitroglycerine and sprayed it on the venipuncture site and Ta-da, the veins popped up. Is this true, is this safe etc? 92.0.228.141 (talk) 16:23, 3 June 2008 (UTC)


 * If the person doing it was a qualified doctor, they probably know better than the people here (unless there happens to be a doctor here, of course, which is entirely possible). I seem to remember hearing that one of the reasons for rubbing alcohol on the area first (in addition to sterilising it), is because it makes the veins easier to find. This is probably a similar idea. --Tango (talk) 16:37, 3 June 2008 (UTC)
 * (After ec)True, most definately. This is a "trick" of sorts usually employed when all else fails. Safe? Probably. Vasodilating nitrates are available without prescription in many places, and one single, topical application is trivial. BUT I couldn't find a study to categorically show safety, so ask the nearest Doctor before performing this trick. Fribbler (talk) 16:38, 3 June 2008 (UTC)
 * Would it hurt more than performing the procedure without it? 92.0.228.141 (talk) 16:42, 3 June 2008 (UTC)
 * There is no reason why it would be more painful using nitrates. GTN merely dilates blood vessels. In fact the opposite may be the case, as there is less "poking-about" involved. Fribbler (talk) 16:46, 3 June 2008 (UTC)

Are they available over the counter in pharmacies in the UK? Also, what would be the smallest needle which could be used (gauge wise) to allow safe collection of blood without rupturing blood vessels? The smallest we use is 23g —Preceding unsigned comment added by 92.0.228.141 (talk) 16:55, 3 June 2008 (UTC)
 * GTN is an over-the-counter medication in the uk . As for needle-bore calibre...I haven't a clue. Not my forte, I'm afraid. Thats a question for a senior phlebotomist or a doctor who takes bloods regularly.
 * Regarding needle calibre, it depends on technique, medical condition of the patient, and the intended use of the blood (and I assume the original poster intended to say, "...without rupturing blood CELLS", rather than "vessels"). Smaller-bore needles will increase risk of cell lysis, but this can be reduced by avoiding extreme suction.  Might be a bigger issue in people with fragile red or white cells (e.g. leukemia).  Also a bigger issue if trying to measure something like potassium that is particularly affected by hemolysis.  Blood coagulation parameters seem pretty unaffected by small-bore needles based on this study.
 * 18 or 20 gauge is ideal for blood collection. A larger bore (gauge less than 18) makes damage to the blood vessel more likely, a smaller bore (gauge more than 20) makes hemolysis more likely. 23 gauge really is as small a bore as you'd want to use to collect blood, though you can use smaller bores for IV infusions. GIven that 18 gauge is more painful than 20, I think most phlebotomists would use 20 gauge as a default and mentally go up or down from there based on other intangibles. - Nunh-huh 05:13, 4 June 2008 (UTC)

Zits
As I looked in the mirror this morning, a couple questions popped into my mind.

First of all, why do humans (or at least me) feel the need to pop/remove/otherwise destroy a zit, blemish, blister, scab or other such abnormality on the skin? My hypothesis would be that removing foreign objects on the skin (leeches, parasites etc.) may have been a mechanism in ancient times for mitigating the damage done by said parasite, but I'm curious as to why we don't recognize scabs/blisters/etc as parts of our bodies and lose the urge to pick at them.

Secondly, is there any real health detriment caused by zits? I know they look like hell, but does a seething white pustule really do any damage per se? The same goes for a generally bad complexion (oily skin, not-washing-your-face-osis etc). Is there some other health detriment besides looking bad? A zit seems like a neutrally-inclined mass of dead bacteria and leukocytes and pus. Of course a lump of dead bacteria on your face sounds gross but why are people so obsessed with good complexion? Is this solely vanity, or is there actual medical wrongness with poor facial hygiene?

<font color="#339900">Ziggy <font color="#999999">Saw <font color="#CCCC66">dust  16:31, 3 June 2008 (UTC)


 * In answer to your first part, I think we do it to relieve discomfort (either pain, or itchiness). I think itching does have to do with removing parasites - itch will probably tell you more. Pain is generally to stop you doing something harmful - I don't expect zits hurt for any specific reason, they just happen to stimulate the nerve endings in the same way other harmful things do. As for your second part, I think that probably counts as medical advice, so all I can say is: Contact a doctor. --Tango (talk) 16:41, 3 June 2008 (UTC)


 * First question I think can be answered better by a psychological standpoint. You see a zit and you worry about what other people think about you, so you feel the need to pop it. I don't think it's any 'built in mechanism' really. Second question — not really, but it does often cause scarring of the skin, especially if you pop the zit and it bleeds. Regards, <font face="Tahoma" size="2px">CycloneNimrod talk?  contribs? 17:44, 3 June 2008 (UTC)


 * Thoughts on a built-in mechanism: if you put a chimpanzee in front of a mirror with a dot of red paint on its forehead, it will scratch around and remove it. Researchers have used this experiment to determine that chimps can tell that a mirror is a reflection of them (dogs and cats just ignore the reflection in the mirror, at best, or think it is another animal, at worst), and thus have some sort of abstract concept of selfhood. So maybe there is something to that urge to remove the blemish, to restore the self, whatever, that goes beyond simple rationality—if a chimp cares about having a little mark on its face, maybe it's no surprise that we do too. Just a speculation. --140.247.11.15 (talk) 18:44, 3 June 2008 (UTC)
 * That test is just meant to show they have an understanding of self, rather than any desire to restore the self. Removing a dot of paint and removing a zit are different matters - cleanliness is common to a lot of animals (for a variety of reasons, I expect), so removing a foreign substance from your face is quite normal. A zit isn't foreign, though, it's part of you. --Tango (talk) 20:09, 3 June 2008 (UTC)
 * It's part of you, but not part of your preferred image so becomes a focus of annoyance even if releasing the infection is a valid response to pressure in the skin. Julia Rossi (talk) 02:15, 4 June 2008 (UTC)


 * Popping a zit is fun! &mdash;Tamfang (talk) 21:08, 4 June 2008 (UTC)

Drixoral
Fribbler (talk) 19:10, 3 June 2008 (UTC)

US upcoming analog to digital TV change over
I've read and understood what I could find on the upcoming changeover from analog to digital formats for TV in the US. I'd like to know if the major cable companies will still be offering analog cable after the changeover date. ike9898 (talk) 19:57, 3 June 2008 (UTC)
 * As the commercials have (much to the annoyance of many) said, if you have cable you are unaffected by the change over. Analog cable with still be offered. See the US government's website on the matter for more information. To be perfectly explicit ONLY if you get TV over an antenna do you need to anticipate any changes, and even then only if your TV was purchased before March 1, 2007. See their FAQ for more information. EagleFalconn (talk) 20:12, 3 June 2008 (UTC)
 * Yes, they see it as a sales advantage. If they are selling you analog conversion, you will stick with them rather than buy a new set.  --BenBurch (talk) 20:16, 3 June 2008 (UTC)


 * That said, I fully expect to see the cable companies start moving to digital-only within a couple years of the broadcast change. Digital (standard-def) channels require less bandwidth than their analog counterparts and confer greater content control to the cable provider, both incentives for cable to switch. &mdash; Lomn 21:26, 3 June 2008 (UTC)
 * My digital cable box here feeds my analog TV just fine. That is ALSO a conversion service even though it happens in the set top box.  --BenBurch (talk) 21:32, 3 June 2008 (UTC)
 * Yes, but that's not the point. The digital box in and of itself solves neither of the problems with analog cable mentioned above.  Cable has a strong incentive to drop analog altogether, and it's only a matter of time. &mdash; Lomn 22:11, 3 June 2008 (UTC)


 * well, that brings up the question: comcast (for instance) currently still offers an "analog package" as well as digital packages; to the end user, this makes no difference, they're just different packages you pay different amounts for and still hook up to your analog TV. Different converter boxes, I guess. in fact, the bottom digital package offers more than the analog package, for cheaper; so I assume they're only still offering the analog package because they've got enough analog converter boxes around to make it worthwhile, and they're not starved enough for bandwidth. oh i just realized; lots of people have the cable just feeding a "cable ready" analog tv with no cable box, so they need the analog cable. i betcha that's going to go away, and you will need the converter, no direct feeding. Gzuckier (talk) 15:39, 5 June 2008 (UTC)


 * Some of this is covered in this section of the DTV FAQ. Note particularly "the FCC requires cable companies to continue to provide local stations in analog as long as they provide any analog service, even after February 17, 2009" and "Your cable company may decide to move certain cable channels off of its analog service tier and onto a digital service tier, or it may decide to switch to all-digital service at once, so that there is no analog service tier for any subscribers."  In that latter case, this would force a customer to rent a set top box from the cable company.  I know that Verizon's FIOS service in many (all?) areas has eliminated all analog service, and Comcast has been moving more and more stations to their digital tier. --<font color="#3EA99F">LarryMac <font color="#3EA99F"> | Talk  13:38, 4 June 2008 (UTC)


 * Where I live, Comcast offers analog standard cable and digital standard cable with exactly the same channels (minus some music only stations and a very limited on-demand service for digital standard). However the analog standard is still cheaper so there is no real incentive to switch.  I wouldn't mind switching if there was an advantage to doing so, but so far that has yet to materialize (in my market).  Dragons flight (talk) 15:52, 5 June 2008 (UTC)


 * Note that (as far as I understand it) the digital/analog thing only really applies to the RF connectors (coaxial cable). If you have a cable converter box and the connection between the cable box and the TV is something other than coax (composite video, component video, DVI, HDMI, etc.) than the digital/analog issue is already determined by the connection type, and any relevant conversions are handled by the cable box. The only reason you would have to worry about NTSC vs. ATSC is if you don't have a cable box, and plug directly into the coax coming out of the wall. If that is true, when the cable company decides to switch their signals, they'll probably be able to provide you with a set-top box box at that time. -- 128.104.112.147 (talk) 17:15, 5 June 2008 (UTC)

Color variation in the mallard duck
I've seen some male mallard ducks whose heads were a purple-indigo color instead of the usual dark green. This is apparently not unheard of, as Google turns up some photos of similar ducks. And I don't think it was a trick of the light, since the heads of the ducks I saw looked purple from all angles. Are these a recognized sub-species or mutation of mallards, or a different species? 69.111.189.55 (talk) 21:10, 3 June 2008 (UTC)


 * There is no "recognized sub-species" of mallard with a purple head (as far as I know), and I can't say that I've seen one myself (I've been a birder for many years). And it is certainly true that the "green" of the male mallard head can look black or purple in certain light or at certain angles. However, if you are sure that the head was purple from all angles, it is possible that it was genetic due to hybridizing. Mallards are notorious for hybridizing with related species of ducks and with various types of domestic ducks. Many of the "mallards" that you see are not actually "wild" at all, but mixtures of feral hybrids. So that is a possibility.--Eriastrum (talk) 23:06, 3 June 2008 (UTC)


 * lots of these in my local pond (north east England) they have purple heads no green in sight. I don't know if they are mallards but they seem to resemble a mallard duck but with a purple head rather than a green one. —Preceding unsigned comment added by 89.240.140.140 (talk) 23:29, 3 June 2008 (UTC)

Red-winged blackbirds are seen quite frequently on mile marker posts, and along rural highways...why?
I read the segment in wikipedia about these birds but it didn't really explain this phenomenon. If you are driving through the country in the midwest US for example, you will see these birds along the road, sometimes on the ground, often on mile markers or guardrails, much more frequently than any other bird. I'm wondering it there is something about the roads that attracts them (besides spilled grain or corn). --Dbacksfanbrian (talk) 21:22, 3 June 2008 (UTC)


 * They're perching birds. You find them on mile markers for the same reason you find them on cattails: it's a vertical object they can perch on. --Carnildo (talk) 22:13, 3 June 2008 (UTC)


 * Where I live on the central coast of California I have a daily commute of 80 miles in a largely rural area. Red-wing Blackbirds are seen along most stretches of the highway (a poky, two-lane affair), because they are nesting in the tall weeds and cattails that are found along the edge of the road. There is no grazing directly along the road and the runoff from the road makes for fairly dense weed growth. In addition, there is often a ditch or minor streambed along the road that increases the amount of tall, reedy vegetation that the blackbirds find appropriate for breeding. This may be the same situation that you have observed in the midwest.--Eriastrum (talk) 22:57, 3 June 2008 (UTC)


 * Are the markers and rails taller than the surrounding vegetation? Perching birds generally like to find a good vantage point, which often equates to the highest available perch. --Kurt Shaped Box (talk) 23:03, 3 June 2008 (UTC)


 * (edit conflict) Here's some totally anecdotal stuff. I've been watching those birds my whole life, and that's just what they do in the springtime. They display. The males stake out a little territory in the reeds and perch high up on a reed and call to claim it. The ones who can't get the good spots in the swamp end up doing their thing where they can. Their whole purpose is to be seen and heard around this time of year, and that's why we see them perching all over the place and why our heads ring with konk-la-reeee. (I was listening to a mockingbird the other day, and he did a redwing, but he did a faraway one. He made it sound like it would have if it had been one a few hundred yards away where they hang out around here. It's hard not to attribute such virtuosity to something like intelligence, isn't it?) --Milkbreath (talk) 23:11, 3 June 2008 (UTC)


 * (In answer to Kurt's question) Yes, these are areas of rangeland where a fence parallels the road and behind it the land is densely grazed and of no interest to the blackbirds at all. Also note, these birds are breeding there, not just perching there. Early in the year the males show up and stake out their territories as soon as possible to get the upper hand (wing?). They all clear out by early to mid summer after breeding.--Eriastrum (talk) 23:13, 3 June 2008 (UTC)


 * Yes, it would certainly make sense that the males wish to make themselves as conspicuous as possible to the females at that time of the year. Higher up = better all-round view of their displays to hens looking for a mate in the surrounding area. --Kurt Shaped Box (talk) 23:35, 3 June 2008 (UTC)

I have no idea how to indent anymore, so feel free to correct my indentation. Rural highways are often edged by ditches which collect water. They are also edged by mile-marker posts. Redwinged blackbirds like to nest by water, in which cattails grow, for instance. (And cattails often do grow in the ditches along rural highways.) So there's a coincidence in space between mile-markers and redwinged blackbirds. --arkuat (talk) 06:56, 4 June 2008 (UTC)

Find out who cited an article?
How can I find out which scientific journal articles have cited another article (e.g. A genome-wide analysis of CpG dinucleotides in the human genome distinguishes two distinct classes of promoters) in which I'm interested? Seans Potato Business 21:48, 3 June 2008 (UTC)


 * With Google Scholar, of course. Search for the title of the paper, and then click the "cited by" link underneath the article. See here. Someguy1221 (talk) 22:02, 3 June 2008 (UTC)


 * ISI Web of Knowledge has a pretty rigorous citation indexing system (the Science Citation Index). I wouldn't rely on Google Scholar; it's still pretty patchy in its coverage. --98.217.8.46 (talk) 01:42, 4 June 2008 (UTC)

Biomes by latitude
If a planet's axial inclination is 19.37&deg;, as Billy Meier claims Erra's is, then what biomes would you expect to find at:

90&deg; north

80&deg;

70&deg;

60&deg;

50&deg;

40&deg;

30&deg;

20&deg;

10&deg;

The equator? Subliminable (talk) 22:37, 3 June 2008 (UTC)

Depends. How fast does the planet turn? How hot and far away is the sun? How much water is available? What's the spread of native life? What's the atmosphere? Etc, etc. Biomes are determined by much more than lattitude.--Fangz (talk) 22:50, 3 June 2008 (UTC)


 * That's very similar to Earth's, so all else being equal, you would expect pretty similar biomes to Earth. Of course, all else may not be equal, I have no idea what else has been claimed about this planet. --Tango (talk) 23:43, 3 June 2008 (UTC)


 * Latitude is just one of a number of factors that play into where a given biome occurs. The relationship of continents to oceans and the pattern of prevailing winds plays a major role. Also important is the location of mountains ranges. This is why, for example, the Pacific Northwest has a mild, temperate, maritime climate with cold rainforests along the coast (between the mountains the ocean) and an arid semi-desert climate east of the mountains. At the same latitude, approximately 50 degrees north, you can find a wide range of biomes, from tiaga to deciduous forest to desert to rainforest. In short, you need more than latitude to determine biomes. Pfly (talk) 03:20, 4 June 2008 (UTC)


 * 19 degrees inclination is less inclined than Earth, so the climate would vary less than Earth's does as you move from the equator. Day and night lengths would not vary as much as they do on Earth at 45 degrees latitude, for instance. The difference between winter and summer temperatures would be slightly less.


 * Uranus has no biomes as far as we know, but it's an excellent example of an unusually high inclination of equator to ecliptic. (See Uranus.) Such planets with extreme inclinations, if they have atmospheres, have some pretty dramatic storms and wind movements.
 * --arkuat (talk) 06:50, 4 June 2008 (UTC)
 * Reduced inclination will reduce seasonal effects, rather than latitude effects, surely? At a fixed point during the year, it shouldn't make any difference how the planet is tilted. --Tango (talk) 12:16, 4 June 2008 (UTC)

Photodissociation
In Photosystem II (during the light reaction of photosynthesis), sunlight is absorbed and used to charge up a single electron in the middle of the photosystem. This electron is taken to an electron transport chain, where it uses its energy to make ATP. To replace this electron, a water molecule is split into oxygen gas and protons (H+ ions) and electrons. The oxygen gas made here is the waste product of photosynthesis.

But water is a much more stable molecule than oxygen gas, so it takes a lot of energy to split it. In the photodissociation article it says that an empty photosystem is the strongest known biological oxidizing agent, so it has the power to split that water... but if it is such a strong oxidizing agent, then it should require a lot of energy to pull the electron off of it in the first place. It seems to me that two things happen in Photosystem II that require energy: ATP is made (on the electron transport chain) and water is split (in the oxygen evolving complex. I assume that both are powered by sunlight energy, but I'm not sure how it all works. Where does the energy to pull the electron off the photosystem come from? Does sunlight power the photosystem and the oxygen evolving complex separately, or does it power the photosystem first and the photosystem powers the oxygen complex? Thanks for the help :)

Jonathan talk 23:01, 3 June 2008 (UTC)


 * This is a great question that I don't how to answer. The first thing I'd look at is photon counts.  Each of these events is powered by a molecule that has been charged up (just like a battery) by absorbing a photon.  I'd parse your last question this way: do the photosystem and the oxygen evolving complex absorb charging-up photons independently of one another, or does a single photon absorption event power both the photosystem and the oxygen complex?  It may be (I don't know) that the splitting of water uses up some but not all of the ATP that is produced by the electron transport chain.  HTH. --arkuat (talk) 06:36, 4 June 2008 (UTC)


 * See oxygen evolution (very close to an article you already linked); it seems that Photosystem II prepares the OEC with some captured photons, while using other captured photons to drive the electron transport chain. --Tardis (talk) 13:27, 4 June 2008 (UTC)

Conversely, in cellular respiration, you use a high-energy electron from glucose to make ATP, but you also change oxygen gas back into water, which should produce a lot of energy... so it looks like you're getting energy from two different places there. Jonathan talk 13:54, 4 June 2008 (UTC)
 * In chemistry, it's almost always an energy difference that matters: glucose electrons have high energy relative to what? To the oxygen, of course, and adding the electrons and some handy protons to it, $$\text{O}^{2-}+2\text{H}^+$$, gives you the water.  In other words, it's only one process to say "use high-energy electron and change oxygen gas into water".  Better to say "benefit from letting oxygen gas take an electron from you and become water".  --Tardis (talk) 14:32, 4 June 2008 (UTC)

Alien life and falsifying our current theories of evolution
Lets say we find life on another planet. And this alien has a backbone, eyes, blood, and a genome that is very similar to life on our planet. Would this falsify our current theories of evolution since it would be impossible for this alien to have common ancestors with any life on our planet? ScienceApe (talk) 23:04, 3 June 2008 (UTC)


 * No, because some traits can develope similarly in different environments. Besides that having a similar genome doesn't mean anything. Some scientist believe that our genome is from outer space. GoingOnTracks (talk) 23:15, 3 June 2008 (UTC)
 * Parallel evolution --76.111.32.200 (talk) 23:24, 3 June 2008 (UTC)
 * Convergent evolution is when two dissimilar organisms develop the same trait. Parallel evolution is when two similar organisms develop the same trait. (Parallel evolution). Ζρς ι'β' ¡hábleme! 23:30, 3 June 2008 (UTC)
 * See Panspermia for more information about the possibility that life originated in outer space. --Tango (talk) 23:51, 3 June 2008 (UTC)
 * That would be kind of like convergent evolution (when two different species develop the same characteristic independently).--Ζρς ι'β' ¡hábleme! 23:26, 3 June 2008 (UTC)

But even with parallel and convergent evolution.... Wouldn't it be far fetched? ScienceApe (talk) 01:59, 4 June 2008 (UTC)


 * Would it? We don't really know the full steps of evolution as they occured. In the chemical sense, it may well be that life built on amino acids, fatty acids, and sugars with nucleic acid as a hereditary material is simply the chemically easiest way to go about things. So certainly, finding a cell bound by twin-tailed amphipathic lipids (like our phospholipids), using DNA or RNA as a hereditary material and using proteins for structure and metabolic function may actually be expected. And as far as killing evolution goes, looking at physical traits wouldn't even be that interesting; our traits evolved as the most viable random responses to the state of our world, and maybe the same conditions exist elsewhere. If we found life from another planet that use the exact same 20 amino acids for building proteins, have nearly identical ribosomes, or some other extreme and specific biochemical similarity...that might shake science. Someguy1221 (talk) 02:19, 4 June 2008 (UTC)


 * It would seem odd in itself for it to live in conditions where it could be the same, IMHO. Remember that key features of the Earth (especially the oxygen atmosphere) arose essentially out of chance. Also, whilst some convergence might be expected, in some issues, it's a bit implausible to argue that. For example, mammalian dominance arose very much due to a string of fortuitous extinctions. It would indicate at least that something interesting is going on. So in the end, it's a matter of how similar similar is, and whether justifications can be found for those similarities.--Fangz (talk) 05:37, 4 June 2008 (UTC)
 * I thought the oxygen atmosphere arose because of life, so life evolving elsewhere could make it quite likely that it would end up being in an oxygen atmosphere. --Tango (talk) 12:13, 4 June 2008 (UTC)


 * It really depends on the conditions of the alien planet in question. If it is similar to Earth, then it can well be argued that just as useful parts like the eye has evolved numerous times independently, hereditary structures such as DNA and RNA are the best in duplicating genes and thus should evolve in other similar planets as well. As someone has pointed out in another internet forum, life on Earth does not imply the existence of God. Life on an inhospitable planet might be. Imagine Reason (talk) 14:55, 4 June 2008 (UTC)


 * If these similarities between the alien and terrestrial species were coded in the same way (same DNA code, same genes, etc.), then they could not have evolved separately--they would have to have had a common ancestor. However, this would not falsify the theory of biological evolution by natural selection; it would simply provide very strong evidence for the theory of panspermia--the dissemination of life throughout the galaxy.--Eriastrum (talk) 16:59, 4 June 2008 (UTC)


 * "then they could not have evolved separately" -- The words "could not" are a bit too absolute IMO. "Then it would be extremely improbable for them to have evolved separately" might be better, but that is still, of course, making some assumptions about how environmental forces affect things. WDavis1911 (talk) 02:36, 5 June 2008 (UTC)


 * Of course, there's a distinction between "falsifying the theory of evolution" (ie: Proving that evolution can not ever happen.) and "falsifying the theory of evolution as an theory of human origins." (ie: Proving that evolution is not how we specifically came about.) The first one would be pretty hard to prove without millions of years of laboratory time.  But I would think that the second one would be thrown into some doubt if we suddenly discovered humans living on faraway planets with different conditions. APL (talk) 13:36, 5 June 2008 (UTC)


 * Jack Cohen has talked for many years about 'parochials' vs 'universals' (See for example Evolving the Alien). Universals are phenomena that have evolved more than once independently, such as eyes, wings, and intelligence. Parochials are structures or behaviours which as far as we know have only ever evolved once, such as haemoglobin, backbones and knees - and DNA. He argues that if we encountered alien life, we should expect to encounter universals, but be very surprised if we encounter parochials. --ColinFine (talk) 20:26, 7 June 2008 (UTC)