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May 12

Guinea Pig head bump

I have two guinea pigs, and when i gently place my hand on either's noses, They quickly thrust their heads up. Why is this? Gbgg89 (talk) 04:29, 12 May 2008 (UTC)

Maybe it is a response to a nearby source of food, so perhaps to bite your finger? Astronaut (talk) 09:29, 12 May 2008 (UTC)

Guinea pigs are herbivores, so that's unlikely. Given that noses are very sensitive organs in most species, my money is on it being a protective reaction. Since guinea pigs are also social animals, a submissiveness reaction may also be possible. 71.236.23.111 (talk) 16:33, 14 May 2008 (UTC)

Maps and Time lines of plants, insects, sm. animals, and terrain.

I am looking to assemble a wide verity of information grouped together covering a certain area of land.

Along the border of China and Mongolia. 100 miles south of border to north 200 miles inside Mongolia From western border to eastern border

All from the time of 125 million to 300 million years ago.

Maps and graphs containing:

-Topographical : - Terrain

                - Water levels highs and lows
                - Some research sight (containing programs as to what the place looked like
                  back then

-Time lines of : - insects (paleontology)

                - sm. animals
                - fossils
                - charts graphs

WHY:

First Flower PBS Airdate: April 17, 2007 Professor Sun Ge, from China's Jilin University, is certain that early flowers evolved here, in northern China, and he is determined to find the world's first.

Not far from the border of Inner Mongolia, there is a remarkable fossil site that is revealing what the Earth looked like more than 100,000,000 years ago. —Preceding unsigned comment added by Coffee1030 (talk • contribs) 05:15, 12 May 2008 (UTC)

ARUN SINGH BAGH

WHAT IS THE NAME OF THE WOODEN BLOCK ON WHICH THE WINNERS IN OLYMPICS STAND WHEN THEY GET FIRST SECOND AND THIRD POSITION —Preceding unsigned comment added by 195.189.142.54 (talk) 06:03, 12 May 2008 (UTC)

It is called a medal podium. Rockpocket 06:12, 12 May 2008 (UTC)

telecommunication-microwave survey as used in network establishment

elecommunication-microwave survey as used in network establishment — Preceding unsigned comment added by 61.246.1.108 (talk) 07:30, 12 May 2008

Do you have a question? Astronaut (talk) 09:07, 12 May 2008 (UTC)

It could be a site survey. Graeme Bartlett (talk) 04:55, 13 May 2008 (UTC)

Insanity

I don't know a lot about psychology (I got as far as AP psych in high school, so I know the basics), but I've recently gotten curious about how people go crazy. Since I don't have much background in the area, I don't where to go to learn about it. Any ideas? Also, as a subquestion, does insanity universally degrade a person's ability to succeed, or are there cases of people who become smarter, more creative, what-have-you after losing it than they were before? Black Carrot (talk) 07:35, 12 May 2008 (UTC)

The answer will depend on which specific conditions you group under the umbrella term of insanity - note that "insanity" is no longer considered a medical diagnosis (although it is still a rather loosely defined legal term in the UK and the USA). A fairly generic answer to your various questions might be as follows:

1. Many psychiatric conditions may be diagnosed in childhood, in adolesence, or appear in later life, possibly due to an event that triggers or exacerbates a previously unnoticed condition.
2. There are several autobographical and semi-autobiographical accounts of the onset of a psychiatric condition - see Girl, Interrupted, I Never Promised You a Rose Garden, The Bell Jar.
3. Most psychiatric conditions, as long as they are properly diagnosed and managed, do not prevent a person living a "normal" and indeed successful life. There are several well-known examples of people with a psychiatric condition that appears to be intimately linked to their success in a particular field - see, for example, John Forbes Nash (schizophrenia); Vincent van Gogh (possibly schizophrenia or bipolar disorder); Stephen Fry (bipolar disorder); Richard Borcherds (Asperger syndrome) ... Gandalf61 (talk) 10:25, 12 May 2008 (UTC)

Try reading up on: biopsychiatry and causes of mental disorders. Re Gandalf61, see creativity and mental illness. --Mark PEA (talk) 20:00, 12 May 2008 (UTC)

Entropy and Creationism

A common argument for Creationism is that as entropy can only increase there must be a start where everything is in order, which is when God created the universe. What is a rebuttal for this argument? How come entropy was so low after the Big Bang? --antilived^{T | C | G} 07:38, 12 May 2008 (UTC)

See Objections_to_evolution#Evolution_violates_the_second_law_of_thermodynamics, Entropy and life and Five Major Misconceptions about Evolution at TalkOrigins. Guettarda (talk) 07:53, 12 May 2008 (UTC)

OK that makes sense but how come the universe didn't go into heat death as soon as it was created? What had caused the disequilibrium (if that's a word)? --antilived^{T | C | G} 08:10, 12 May 2008 (UTC)

"Why was the entropy of the early universe so low ?" is a good question, and one of the big puzzles of cosmology. Rogare Penrose addresses the question at some length in The Road to Reality. There are several candidate explanations:

1. The universe has a very, very long pre-Big Bang history, and what we think of and observe as the Big Bang was a random fluctuation in which all the matter of the universe happened to arrange itself into an especially low entropy state (remember that processes that reduce entropy are not absolutely impossible, they are just very unlikely, and anything that is not impossible can happen if you wait long enough). In this view, our current state of increasing entropy is a relativley short-lived phase in the mega-history of the universe.
2. A large number of universes are continually being created, possibly by some sort of quantum "budding" process. Those that start in high entropy states are spectactuarly dull places and do not give rise to life. Only a universe that starts in a low entropy state could eventually give rise to beings that ask the question "why was the entropy of the early universe so low ?". This is a version of the strong anthropic principle.
3. Some mechanism active only in the early universe, and possibly connected with cosmic inflation, drove the universe into a low entropy state. Such a mechanism would break the second law of thermodynamics, so it cannot be active in the universe as we observe it today.

So there are various possible explanations - we just don't yet know which one is correct. Gandalf61 (talk) 09:25, 12 May 2008 (UTC)

And note that even if you want to say that God had a hand in this, it still requires an understanding of what naturalistic process God would have used to do it. "God did it" doesn't relieve the need for a physical explanation—even if it was done by some sort of intelligent deity there still would be a corresponding physical expression of that action. --98.217.8.46 (talk) 15:02, 12 May 2008 (UTC)

The first two options don't work at all, and Penrose should realize this. They're the cosmological equivalent of the 747-from-a-junkyard argument against biological evolution. Darwinian evolution is not a 747-from-a-junkyard theory, and if it were then it would be as useless as the ID people think it is. It would be unfalsifiable and predict nothing. Option 3 isn't an option, it's practically a definition of what it means to explain something. Explaining something doesn't mean showing that the world can be that way, it means showing that it couldn't have been some other way. You have to produce a mechanism that makes the world we see more likely than it appears on the surface. You have to rule out something beyond what you ruled out a priori with your anthropic (or aeronautic) principle.

In principle the idea of anthropic reasoning makes sense. What scientists do is reason from the available evidence to a theoretical model that explains it. One piece of evidence available to us is the existence of homo sapiens. If you reason from that evidence to a theoretical conclusion, you've engaged in anthropic reasoning. But in practice no one ever succeeds in doing that; it's too hard. Progress in natural philosophy began when people started to gather evidence about much simpler things, like the motion of a wheel on an inclined plane. As far as I know there has never been a successful anthropic argument in the history of science. All of its claimed successes are co-opted. Fred Hoyle reasoned from the observed abundance of carbon in the universe to a prediction that carbon must have a particular energy level, which was later found. This was claimed as an anthropic prediction. Why? Because human beings contain lots of carbon. It could just as well have been lithium instead of carbon that went into his argument, and then no one would have called it anthropic. Even worse is the current claims of anthropic reasoning in string theory. They want to narrow down the possible flux compactifications in string theory by requiring that they produce a universe consistent with the one we see. This is known as "fitting the model to the data", and it's what scientists have always done. The data is this case is that which supports the Standard Model and the existence of a small positive cosmological constant. It seriously scares me that prominent string theorists think they're "reasoning anthropically" when they do this. That, more than anything else, makes me worry that they've completely lost sight of reality. -- BenRG (talk) 16:56, 12 May 2008 (UTC)

Not going to pretend that I understand what triggered that particular rant, but let's clarify something for the record. Penrose doesn't actually come down in favour of any of the above three explanations. In fact, he sets them up in order to knock them down in favour of his own explanation, which is connected with quantum gravity. Gandalf61 (talk) 21:55, 12 May 2008 (UTC)

The argument that "some supernatural entity must have started the universe in perfect order" is hardly an argument for big-"C" Creationism, since that entity could have been anything. --Sean 13:08, 15 May 2008 (UTC)

Oh - this is a classic numbskull creationist argument. You have to be careful with the OP's statement about entropy. It is NOT true to say that "entropy can only increase". You missed the first half of the second law of thermodynamics. The correct way to simply state this is: "Within a closed system entropy can only increase." (To quote entropy: Spontaneous changes, in isolated systems, occur with an increase in entropy.) So if we consider the Earth to be a closed system (which it's not - but we'll quietly pretend that it is) - then evolution can create localised pockets of decreasing entropy at the cost of increasing entropy much more steeply elsewhere on the planet. Thermodynamics allows this. For example, take 20 dice in a cup. You can go and painstakingly take each one from the cup, turn itto show a 6 and line them up into a nice neat row. The entropy of the dice decreased - they are now much less random. But it took energy to make that happen. In using your hands to straighten them up - you consumed a few more calories and you might maybe eat a little more as a result. Just toss 20 nicely ordered dice onto the table without going to a lot of effort - and guess what? Entropy kicks in and they're all disordered again. Entropy only decreased when you put energy into the system from outside. Taking nice well-ordered food energy and turning it into disorderly end products increased the entropy of our world by considerably more than straightening up the dice did. Humans are going around forcing local pockets of entropy to reduce all the time by activities such as collecting up scattered amounts of iron ore and making cars out of them...but in the process, we are consuming energy and creating lots of ugly chaos elsewhere in the process. So when animals evolved, their LOCAL entropy went down - but the entropy of the planet went up by more than enough to compensate for that. Entropy LOCALLY decreases in all sorts of natural situations - the growth of crystals in a liquid solution for example. It's only within a closed system that entropy increases. You can't use a misstatement of a law of physics to prove or disprove anything! 66.137.234.217 (talk) 15:12, 17 May 2008 (UTC)

Michelson Interferometer

If the mirror is moved away then the number of fringes appearing in the microscope would change or not? If so then it is because the length of path is changing and so fringes are closely spaced. —Preceding unsigned comment added by MAQMAQ (talk • contribs) 08:54, 12 May 2008 (UTC)

Please do your own homework.

Welcome to the Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. But here is a hint to help you: consider what the interferometer is doing, how the fringes are created and what happens if one of the mirrors is moved.

Please attempt to solve the problem yourself first. The Michelson interferometer article might help, or you can search Wikipedia or search the Web.

Astronaut (talk) 09:27, 12 May 2008 (UTC)

Aloe Vera

I have been told that Aloe Vera Gelly will kill ear mites in dogs. Can anyone confirm this? Mr Beans Backside (talk) 10:12, 12 May 2008 (UTC)

Please ask your veterinarian. -- Coneslayer (talk) 11:47, 12 May 2008 (UTC)

Petroleum jelly and mineral oil are sometimes used to kill parasites on animals - mainly through suffocation. However, proper application can be tricky, and severe infestations may require additional medical help. Phoning your veterinarian's office is highly recommended - depending on your particular situation, they may be able to help you over the phone, without necessitating an office visit. -- 128.104.112.147 (talk) 22:27, 13 May 2008 (UTC)

Plants

When do plants use the cyclic electron pathway instead of the noncyclic pathway? Mr Beans Backside (talk) 10:13, 12 May 2008 (UTC)

You mean, "why do plants use the non-cyclic pathway?" The cyclic pathway has as its sole useful product ATP, whereas the non-cyclic pathway also produces NADPH (in addition to oxygen), which is necessary for driving the calvin cycle. Indeed, the cyclic pathway is considered more primitive; any photosynthetic organism relying solely on that process would have a fine source of ATP only in the daylight, and would need yet another process for using that energy to obtain or build the various molecules it needs. An organism using the non-cyclic pathway can use the NADPH to drive the conversion of CO2 into sugars, which can be used as stable stores of energy, polymerized into structural molecules, or converted into virtually any other molecule the plant needs. Someguy1221 (talk) 15:24, 12 May 2008 (UTC)

Global warming

What are some simple steps or creative ideas that people can take at home and work to combat global warming? Mr Beans Backside (talk) 11:50, 12 May 2008 (UTC)

• Ditch your SUV for something that uses less than 6 litres of petrol per 100km
• Plant a tree
• Turn down the temperature on your geyser or get a blanket to insulate it (in SA we use electrically powered geysers and our electricity is generated from coal (mostly) so this may not apply to you) and don't waste energy
• Make sure your house is well insulated
• Vote for politicians who are committed to reducing CO2 levels
• Recycle

I see there are quite a few wiki articles but linking all of them will make you less inclined to read any of them so I'll wait for someone to link the best one.

Zain Ebrahim (talk) 12:49, 12 May 2008 (UTC)

For those not familiar with British idiom, a geyser in this context is a water heater, and not an erupting hot spring. TenOfAllTrades(talk) 13:52, 12 May 2008 (UTC)

Is it some dialect? I'm British (North-West) and did not recognise the term, though I did surmise the correct meaning. --Seans Potato Business 14:14, 12 May 2008 (UTC)

I'm British, South-East, and didn't recognise it either. Zain mentions SA (South Africa, presumably) - I guess it's a term local to there. --Tango (talk) 14:18, 12 May 2008 (UTC)

Oh Sorry! I've only ever referred to it as a geyser and assumed it was a universal term. It not only heats the water but it also stores the heated water. Does a water heater do that as well or do you guys store the water elsewhere? Zain Ebrahim (talk) 14:42, 12 May 2008 (UTC)

Modern systems heat the water as its needed. You switch on the tap and the heater (or "boiler") switches on and hot water comes from the tap. This system is more energy-efficient than trying to store a quantity of hot water. Such storage systems do exist in the UK but are comparatively rare in low-usage applications (average household). ----Seans Potato Business 15:16, 12 May 2008 (UTC)

Interesting. Thanks. Zain Ebrahim (talk) 16:10, 12 May 2008 (UTC)

In the United States, the systems that Seans Potato Business described are uncommon. The common heater is the kind with a storage tank, like you described. However, the term "geyser" was completely unfamiliar to me. We just call them "water heaters" (or, rather strangely, "hot water heaters"). -- Coneslayer (talk) 16:32, 12 May 2008 (UTC)

Interestingly enough, the disambiguation page for "geyser" says that is can be "A water heating system, in British English". Although I have lived in the USA all my life, as a self-described Anglophile I understood geyser as used by Zain, so I'm perplexed by our NW and SE British colleagues indicating non-awareness of the term. Perhaps you need to read more Agatha Christie ;-) The various types of heaters and some of the terminology are discussed in the article water heating. --LarryMac | Talk 17:14, 12 May 2008 (UTC)

Geyser is also the Dutch word for an old-fashioned water heater (nowadays 'everyone' uses boilers). I wonder if this has anything to do with Afrikaans stemming from Dutch. DirkvdM (talk) 08:34, 14 May 2008 (UTC)

What I know as geysers used to be fairly common in the UK in my younger days - at least up to the 1970s. They were gas-powered devices where the main gas burner would ignite from a pilot light, usually with a terrifying whoomph, when the water was turned on. There was great skill required in getting the rate of water-flow just right: too fast and it wouldn't get hot enough, too slow and the gas would go out. AndrewWTaylor (talk) 19:58, 12 May 2008 (UTC)

I know these things as "boilers". In my experience, the hot water is usually stored in the UK. You have a boiler and a hot water tank. Heating the water immeadiately before using it sounds hard, since you need to heat it really quickly (certainly more efficient, though). --Tango (talk) 10:58, 13 May 2008 (UTC)

That kind is called a demand or on-demand or tankless water heater. --Anon, 22:22 UTC, May 13, 2008.

Eat less meat or go vegetarian. 200.127.59.151 (talk) 15:54, 12 May 2008 (UTC)

He was talking about lowering global temperature, how does eating less meat contribute? Mac Davis (talk) 17:55, 12 May 2008 (UTC)

200 was probably referring to Attribution of recent climate change#Key attributions#Land use#Livestock and land use. Zain Ebrahim (talk) 18:14, 12 May 2008 (UTC)

(edit conflict) In theory, less people eating meat would mean less land used for grazing lands. Less rain forests clear-cut to create grazing lands leaves more trees. More trees consume more carbon dioxide. And so on. Of course there's all that methane not being produced by farting cattle as well. --LarryMac | Talk 18:18, 12 May 2008 (UTC)

It's not in the farts, the cows breathe out (most of) the methane. DirkvdM (talk) 08:34, 14 May 2008 (UTC)

Change your incandescent lightbulbs to compact fluorescent lamps.118.90.102.125 (talk) 12:38, 13 May 2008 (UTC)

As it is scientifically proven that humans emit carbon dioxide, the best way to reduce CO2 emissions is to engage in genocide of the human race.--WaltCip (talk) 12:59, 13 May 2008 (UTC)

Nope, Humans themselves are carbon neutral. All the CO2 you emit ultimately comes from plants who sucked it out of the atmosphere. Some serious suggestions are:

• Walk short distances and use a bicycle for medium ones. Also good for your health.
• Use less air conditioning (and lobby for reasonable settings in public buildings). If it's 35 degrees Celsius outside, its nonsense to cool a building to 20. People adequately dressed for outdoors will catch a cold...
• Preferably buy food that is in season, and from local suppliers if possible.
• Stop whining about high gas prices. Indeed, lobby for a tax system that taxes products roughly proportional to environmental impact. This motivates people to invest in energy-saving devices.
• Buy electricity from renewable sources, if available. In this case the market impact is probably more in the signal than in the direct effect (many electricity companies split their existing mix and sell the clean part at a higher price, and the remaining worse mix to people who don't care...), but it still is a signal.
• A solar warm water system is cost-effective in many regions. Consider this especially if you have a pool or other large consumer.
• Most important is probably to work towards a general recognition that this is a problem, but that many solutions have upsides that compensate for costs (better quality of live, cleaner environment, less dependency on foreign oil, more jobs in new industries). Existing large players stand to lose (e.g. the oil and coal industry), but the overall economic impact may well be positive. Germany, e.g., is creating a lot of high-tech jobs in the solar and wind energy industries. Pro-environment does not have to be anti-market! --Stephan Schulz (talk) 13:27, 13 May 2008 (UTC)

I know someone mentioned this above, but I'm not sure it was taken seriously - eating vegetarian is probably the most influential thing a person can do to personally reduce climate change - according to a recent UN report, http://www.un.org/apps/news/story.asp?NewsID=20772&Cr=global&Cr1=environment, "Cattle-rearing generates more global warming greenhouse gases, as measured in CO2 equivalent, than transportation". Pretty impressive. --Bmk (talk) 19:20, 13 May 2008 (UTC)

It is indeed astounding how little useful information can be found about this. Switching to fluorescent lamps is mentioned quite a lot, but lighting only represents a few percent of CO2-emissions. As I understand it, the really big energy guzzlers are transportation and heating/airco, which together cause almost half the CO2-emissions. Of course, with the temperature control it depends a lot on where you live (hot or cold climate). Wearing a sweater indoors in winter in a cold climate can help a lot. Concerning transportation, options range from keeping your car tires sufficiently inflated to living close to where you work (or vice versa). Most cars are waaaaay to powerful, so get the most energy-efficient one (can still be luxurious - why not?). And don't accelerate too fast. That really makes a big difference and it one of the easiest things to do. And of corse, in concurrence with Zain, the easiest thing you can do is vote for the party that is most focused on solving this problem (both the reduction of energy use and the development of alternative energy sources). I've been doint that for over ten years now. I've become a one-issue voter. DirkvdM (talk) 08:34, 14 May 2008 (UTC)

I think one of the reasons why fluorescents often come up is because even though the amount they contribute may be small, switching is easy to do, relatively painless for the vast majority of people and generally quite cost effective even in the relatively short term. Improving insulation, particularly in temperate countries, is another common suggestion but it can be expensive. Common methods to try and do this include better building standards, so all new homes at least have a resonable degree of insulation and some sort of tax relief for people carry out renovations to improve their insulation. Over powered cars is a factor, but it's something difficult for governments to deal with directly without too much controversy. But resonable petrol taxes for example, which encourage the efficient use of petrol (and therefore the use of energy efficient i.e. not overpowered cars) can help (they also have the added bonus of reducing the subsidy other people pay to road users and making it easier to subsidise things like public transport which have a far greater benefit then excessive road building). The recent high price of petrol has definitely helped, particularly in the US which has always had very low petrol taxes compared to much of the rest of the world although it hasn't always had the completely desired effect (for example, the growth in hybrid SUVs in the US which will good, it would have been far better if the people had chosen less overpowered vehicles). Stuff like going vegetarian, which while an excellent idea in practice, isn't something you can convince a lot of people to do Nil Einne (talk) 11:42, 19 May 2008 (UTC)

Protoplast fusion

while performing protoplast fusion we have to chop leaves into very fine peices before proceeding for actual fusion. so why don't the cells die out at that moment?--Kayatheangel (talk) 13:19, 12 May 2008 (UTC)

Presumably the cellular metabolism continues. Plant cells may not have to be so isolated from their neighbours by an intact cell wall to function in the short term. You would have to keep a large number of the organelles intact. Some of the membranes could reform spontaneously. The cells would die in the natural environment when chopped apart, because they would dry out and lose their root nutrient supply. Graeme Bartlett (talk) 21:46, 13 May 2008 (UTC)

Finding CpG islands with genomic databases

How do I determine which area of a gene can be designated 'CpG' island? Suppose that I'm interested in this gene; I vcan see that it has a lot of CpGs but can I get a program (preferably online) that defines the CpG island(s)? ----Seans Potato Business 13:34, 12 May 2008 (UTC)

• http://www.cpgislands.com/
• http://www.bioinformatics.org/sms2/cpg_islands.html
• Or, normally, you can go to the contig viewer in Ensembl [1], go to the "detailed view" section and in the menu bar, click on the "features" tab. The check the "CpG island" check box, close the tab, it you should see a track on the viewer showing islands in the context of your gene. Ensembl seems to be having technical issues at the moment, and it finds an error when I do it, but it should be working again soon. Rockpocket 19:47, 12 May 2008 (UTC)

Widely-distributed, semi-technical history of moon shot?

Was there anything like the Smyth Report for the Apollo program, or for the Apollo 11 mission (moon landing) specifically? The Smyth Report was a government-produced history of the atomic bomb that came out contemporaneously with its use, to explain in more detail what people were seeing on the front pages of newspapers after the bombings of Hiroshima and Nagasaki. Anything like that for the space race? I don't mean official histories that came out years later, or unofficial histories/popularizations. --140.247.242.128 (talk) 17:16, 12 May 2008 (UTC)

While I can't directly answer the question, bear in mind that the Apollo program, and the related programs preceding it, were carried out in view of the public, in contrast with the secret Manhattan Project. There is not, as a result, the need for a parallel to the Smyth Report. — Lomn 19:45, 12 May 2008 (UTC)

Oceans, Lakes, and Seas

What is the differance between an ocean,lake,and a sea? —Preceding unsigned comment added by Unclejojo (talk • contribs) 17:43, 12 May 2008 (UTC)

(I made a new section, if no one minds) An ocean is a large salty body of water that is part of Earth's main body of water, a lake is a body of water surrounded by land, and a sea is a body of salt water surrounded by land and connected to the ocean (however, some salty lakes are called seas). 206.252.74.48 (talk) 18:46, 12 May 2008 (UTC)

A "sea" can also be a (pretty arbitrary) geographical region of an ocean, for example, the Sargasso Sea, the South China Sea.

Atlant (talk) 19:05, 12 May 2008 (UTC)

Well, you would know, Atlant! I'll also point out that in addition to the above usages, the Earth's main body of water can be called "the ocean" or "the sea". --Anonymous, 22:27 UTC, May 13, 2008.

:-). It's not a coincidence, by the way.

Atlant (talk) 17:14, 14 May 2008 (UTC)

So the Salton Sea and the Dead Sea are lakes. Edison (talk) 03:38, 14 May 2008 (UTC)

Earthquakes

I understand how earthquakes start - the release of pressure from two tectonic places which are pushing against each other or rubbing across each others boundary's - but how do earthquakes stop? What stops the plates from continuing to move? Mr Beans Backside (talk) 18:08, 12 May 2008 (UTC)

As I understand it, the plates are moving pretty much the whole time. An earthquake happens when the plates get stuck and pressure builds up until it is forcefully released and the plates continue moving again. --Tango (talk) 18:18, 12 May 2008 (UTC)

Or put another way, the plate portions right at the boundary get stuck again when enough strain energy has been released. Stress starts to build up again, since the plates as a whole are moving, but they are jammed against each other at the boundaries. Rub your fingers hard across a rough surface - you hand is moving continuously, but your skin is stopping and starting. Franamax (talk) 19:16, 12 May 2008 (UTC)

What you describe are interplate earthquakes. There is another kind Intraplate earthquakes. They are rarer, but generally more destructive. You might also want to have a look at Subduction. Lisa4edit (talk) 20:21, 12 May 2008 (UTC)

Paleontology

How do paleontologists determine the sex of a fossilized creature? Mr Beans Backside (talk) 18:09, 12 May 2008 (UTC)

I think it depends on the creature, but there are usually things that differ between the sexes. The total size, the size of certain body parts, the shape of certain body parts, etc. --Tango (talk) 18:16, 12 May 2008 (UTC)

But all you would have is bones? Does the bone structure differ between the sexes? Mr Beans Backside (talk) 18:24, 12 May 2008 (UTC)

Bone structures often (although not always) differ by sex. If the creature is extant (still alive somewhere), the skeletons of the male and female can be compared for differences. The specific differences between sexes vary by species. For instance, the presence of a baculum is an indicator of male (although females can have a baubellum) in most mammals; likewise antlers in deer, pelvic structure in humans, etc. might be used. For extinct species the work is mostly analogy to living relatives, although this can be difficult. The use of ancient DNA has also been able to shed light on some of the more recently extinct creatures. Some genetic work on moa (extinct, flightless birds of New Zealand), for instance, was able to show three "species" (classified by bones) were really one species of bird but of different sexes (two sexes, of course, the original classifier, Richard Owen working in the 19th century, had based the distinction largely on size). --TeaDrinker (talk) 18:31, 12 May 2008 (UTC)

Our Tyrannosaurus article has some interesting bits on this topic. Matt Deres (talk) 20:14, 14 May 2008 (UTC)

Male to female ratio

Human offspring are roughly balanced 50% male to 50% percent female. Does this balance exist throughout nature, or has evolution resulted in more useful proportions for some species? For example, more male dear because some might die fighting each other. If proportions are unbalanced in some species, how does this work? Mr Beans Backside (talk) 18:45, 12 May 2008 (UTC)

Have you read sex ratio? -- Coneslayer (talk) 18:49, 12 May 2008 (UTC)

I'm not sure but I think animals like aphids have females or males which can reproduce asexually during certain seasons. Surely this would create such an 'unbalance'. Regards, CycloneNimrod^Talk? 18:51, 12 May 2008 (UTC)

Actually the human sex ratio is not balanced at birth, since males tend to die faster. Evolution has resulted in this proportion, 50.5:49.5 as a response.

In some other species, the sex-ratio changes in response to food availability, more males in times of abundance, more females in times of scarcity. Franamax (talk) 19:21, 12 May 2008 (UTC)

More detailed answers: Wikipedia:Reference desk/Archives/Science/2007 October 26#gender ratios in a species. Rockpocket 22:01, 12 May 2008 (UTC)

Does the universe spin?

The planets, solar systems, star clusters, and galaxies all spin. Does the universe itself spin? Mr Beans Backside (talk) 19:58, 12 May 2008 (UTC)

We have no evidence that it does and no reason to expect that it would. The systems you mention, from planets to galaxies, are all examples of systems that have coallesced under the force of gravity. Gravitational contraction preserves any initial angular momentum a system may have had at random, and as a result amplifies a system's rate of rotation. However, by contrast, the universe as a whole is not a gravitationally collapsed system, and hence the same dynamics will not apply. Dragons flight (talk) 20:04, 12 May 2008 (UTC)

Apparently there are a lot of bored theorists, cause it isn't that hard to google papers on rotating universe versions of cosmology. This quotes a limit of 2×10⁻¹³ radians/year, or one revolution every 30 trillion years. Dragons flight (talk) 22:17, 12 May 2008 (UTC)

Hot, thankee. WilyD 13:10, 13 May 2008 (UTC)

This is making my head spin

Isn't "spinning" defined in relation to surrounding space? But what if there is no surrounding space? How could you tell the Universe is spinning if you have nothing outside the Universe to compare its changing position to? Just curious.  :)  The Transhumanist 21:28, 12 May 2008 (UTC)

Excellent question, and not an easy one to answer. I'm not sure if there even is a generally accepted answer. Consider this: You have two masses connected by a string, you set them spinning around their common centre of gravity and the string will go taut. What happens if you do it in an otherwise completely empty universe? They're not spinning with respect to anything else, since there isn't anything else, so does the string go taut? --Tango (talk) 21:39, 12 May 2008 (UTC)

Yes the string would go taut, the physics to calculate this does not involve any other entity. spin is not relative. It is a bit too abstract for me to talk about an entirely empty universe, instead consider a very empty space, very large space, you know the string would be taut in this case. If you want some more interesting physics, Black holes preserve angular momentum as one of the few properties that exists beyond the event horizon. GameKeeper (talk) 22:35, 12 May 2008 (UTC)

The short answer is "no" - you can tell if something's spinning due to the appearence of interial forces, namely the "centrifugal force". I don't believe this has ever been measured for the universe, which'd give some low upper limit, but I don't know what it is. WilyD 21:57, 12 May 2008 (UTC)

I'll back up this 'no'. Spin is not relative, it's not measured in relation to the surrounding space but can be absolutely determined due to the accelerations it involves. The maximum spin of one revolution every 30 trillion years (as mentioned above), would mean the universe would have to be 2000 time older than current best estimates before it did one rotation. Something rotating at a maximum of such a rate most definitely would not be described as spinning. GameKeeper (talk) 22:27, 12 May 2008 (UTC)

You can construct theoretical models of a rotating universe. There's no axis of rotation (much like there's no center to the expansion), but there is a direction (of the angular momentum vector), so these models violate the cosmological principle. This would be visible as an anisotropy in the cosmic microwave background. There was actually a claim a few years ago that such an anisotropy does exist (astro-ph/0502237). I don't know what the current status of this is, but the evidence for it is weak at best. -- BenRG (talk) 23:35, 12 May 2008 (UTC)

I'm surprised no one has mentioned Mach's principle. -- BenRG (talk) 23:35, 12 May 2008 (UTC)

Yes of course, that's why I left this thread alone. Basically (if I understand it right), the only way you know for sure you're spinning is because of the presence of distant "fixed" stars. It is the presence of those incredibly distant stars that establishes your own local inertial frame. Put another way, if the whole universe was spinning, how would you know? There would be nothing to measure it against, and you could equally say that the whole non-universe was spinning and the universe was standing still. It would make no difference. Franamax (talk) 03:12, 13 May 2008 (UTC)

Of course, there's no particular reason to believe Mach's principle is true... WilyD 04:42, 13 May 2008 (UTC)

One could easily apply Newton's Bucket argument instead - which seems just as reasonable, and experimentally indistinguishable. WilyD 04:44, 13 May 2008 (UTC)

Newton? That hack couldn't even dodge a falling apple! Reading through that article, beyond the fact that there is an external observer of the bucket, I see "true motion can be understood only in reference to absolute space" - but the notion of absolute space has been pretty throughly destroyed, along with absolute time. We're only left with relativity, and Mach used the relation to fixed/distant stars. The central axis of the bucket is pointing to one particular star, the rotating reference frame of the water is defined by the fact that other distant stars "revolve around the bucket". The point here though is that if there is nothing outside the bucket-universe, "spinning" loses all meaning, you can't define spinning if there's nothing outside to look at. That article could probably use an update to elaborate how the view of absolute measurement has since fallen apart. Franamax (talk) 07:25, 13 May 2008 (UTC)

Without doing the same experiment in an empty universe, you cannot establish Mach's Principle - there's no result anywhere, either theoretical or observational, to invalidate the bucket experiment - it does, in fact, demonstrate that linear motion is relative, but accelerations are absolute - this is the result of GR - all Mach's Principle suggested is that mass is normalised by the mass of the universe. I would argue GR is suggestive of Bucket, not Mach, but it's really neither here nor there until we get a second universe to test in. WilyD 13:09, 13 May 2008 (UTC)

It's a curious observation that many people seem naturally predisposed to think of motion as absolute and rotation as relative, when the laws of physics, as deduced over time from detailed observation of how things actually work, say it's exactly the other way around. I suspect it's because, in the everyday world we live in here on Earth, there exists an obvious absolute reference for motion (the Earth itself), but no such reference for heading, the Earth's surface being, to a first order approximation, anisotropic. We then, somehow, are prone to generalize this lack of an absolute reference from heading to rotation; even though centrifugal and Coriolis effects should be familiar to anyone who has ever ridden a carousel, somehow our conviction of the relativity of rotation is so strong that many, if they puzzle over the seeming contradiction at all, end up concluding that these effects must result from some unseen influence of the surrounding, "counterrotating" world.

Perhaps it's because humans tend to be visually oriented creatures, whereas the direct effects of absolute rotation upon our own bodies are only observable through the non-visual (kinesthetic and balance) senses. If you're sitting in a rotating chair in a windowless room, to your eyes it makes no difference if it's the chair or the room that rotates, even though, if the speed is more than a few rpm, the difference would be easy enough to feel. We don't trust our muscles and inner ear as much as we trust our eyes, and if we notice the discrepancy, it's easy enough to suspect that our non-visual senses are somehow detecting the orientation of the Earth through the walls; after all, we sense the Earth's gravity too, don't we? And the same argument can be used to explain away any other means of directly detecting the rotation of our hypothetical room, such as by holding a pendulum and seeing if it precesses or by watching the surface of water in a bucket: maybe the Earth "counterrotation" is also affecting the motion of the pendulum and the water, just as it, so the explanation goes, affects our inner ear.

Of course, counterexamples to these simple theories of "relative rotation" are easy to find, but the catch is that the theory can always be extended, for example by assuming that the rotation we feel isn't actually relative to the Earth, or to any other nearby mass, but to the entire mass of the Universe. And since we can't actually give the entire Universe a spin and see what happens, the theory then becomes unfalsifiable. Of course, at that point Occam's razor should suggest that there are easier explanations, but this does not make a particularly convincing argument if one's intuition says otherwise, particularly if one is not sufficiently familiar with physics to see that the theory without these "Machian" effects really is simpler. —Ilmari Karonen (talk) 18:53, 13 May 2008 (UTC)

Cloned fingerprints

Would a genetic clone have the same fingerprints as the original? Mr Beans Backside (talk) 20:05, 12 May 2008 (UTC)

I seem to remember hearing that identical twins have different fingerprints, so I would expect a clone to have different prints too. --Tango (talk) 20:08, 12 May 2008 (UTC)

Similar but not identical.[2] There are lots of sources on this. Gwen Gale (talk) 20:18, 12 May 2008 (UTC)

Are fingerprints also dependent on environmental factors? Would that cause a sufficient difference for them to be distinguishable? Mr Beans Backside (talk) 20:24, 12 May 2008 (UTC)

Yes. Gwen Gale (talk) 20:26, 12 May 2008 (UTC)

Hi. On the other hand, irises are even more unique than fingerprints. Even identical twins will have different iris patterns. Hope this helps. Thanks. ~AH1^(TCU) 23:10, 12 May 2008 (UTC)

I would expect clones would have an even greater difference then an identical twin since it would have a far greater environmental difference (in the womb) then a twin Nil Einne (talk) 16:34, 14 May 2008 (UTC)

shortwave radio

hi, I am interested in buying a shortwave radio (not to transmit just to receive) but am interested in hearing ham radio too.

I am confused as to if i need ssb (short sideband??) with also usb, lsb and cw.

can someone clarify? also can i spend $100/£50 rather than a lot , if so please post a link.

thx —Preceding unsigned comment added by 78.144.146.123 (talk) 21:25, 12 May 2008 (UTC)

According to our article on Single-sideband modulation, you will need it to hear ham radio. See also sideband for more info on bands. As with most things, you get what you pay for, the cheaper radios seem to only receive normal shortwave broadcasts. You might also need a big antenna to pick up ham transmissions. Try googling "buy shortwave radio", there are hits for information and purchasing. Franamax (talk) 22:06, 12 May 2008 (UTC)

Just to get the terminology straight, if a radio is capable of receiving "Single Sideband" (SSB), it can receive either the "Upper Sideband" (USB) or the "Lower Sideband" (LSB). It can also receive Morse code ("continuous wave"/CW) transmissions. And I think any radio that can receive SSB (as used by most amateur radio operators) can also receive ordinary amplitude modulation (as used by most commercial and state-run shortwave radio stations. But not all AM radios can receive SSB; that takes extra circuitry in the receiver.

Atlant (talk) 00:33, 13 May 2008 (UTC)

Trivia note: if you're driving in Canada and see a license plate starting with "VE", that's a ham radio operator, the license number is their call-sign, they get it for free. Ram their car, you can ask them all sorts of questions while you wait for the police ;) Franamax (talk) 03:05, 13 May 2008 (UTC)

For several decades, amateur radio "hams" have used ssb for their voice transmissions, because it transmits farther for a given power limit and per government regulatins. Without SSB your receiver would only make their transmissions sound like Donald Duck. Look for a receiver with SSB. A Beat frequency oscillator (BFO) is needed to pick up Morse code transmissions. A radio which picks up SSB should also pick up CW (Morse code). Without the BFO capability, a radio would only pick up shortwave transmissions like goverenment radio stations (news, propaganda, etc). I have used a radio frequency signal generator with a non-ssb receiver to pick up ssb and cw transmissions, but I do not recommend it. Edison (talk) 04:34, 13 May 2008 (UTC)

Ordinary cheap shortwave receivers will have a difficult time picking up amateur radio signals. The problem is that the normal broadcast stations have a much stronger signal which will cause the weak HAM radio signal to become swamped in intermodulation noise. You need a more expensive communications receivers to be able to enjoy listening to HAM radio. If you want a good deal, you should try to get hold of a second hand communications receiver. There are many exellent communications receivers that are no longer manufactured that would cost you $1000 or more if bought new. But the second hand price will be significantly lower. E.g. why not buy a second hand Kenwood R-5000? Count Iblis (talk) 13:42, 13 May 2008 (UTC)

I have picked up hams as well as international broadcasters on old and cheap sw receivers. The broadcasters tend to be in different bands from the hams. Also the ham might be in the next town and the internatinal broadcaster might be a continent away. But CW and SSB are tricky to receive without the aforementioned special circuitry. Radio Shack had a fairly cheap receiver a few years ago which included SSB and CW reception. Edison (talk) 03:36, 14 May 2008 (UTC)

Don't know if that would affect what you are looking to set up, but have a look at Scanner (radio)#Legal issues before you get yourself into trouble. Disclaimer: Not advice, just a friendly hint.Lisa4edit (talk) 05:33, 14 May 2008 (UTC)

Edison, I agree. However, the fact that the hams operate in different bands is not enough for the cheaper radios to prevent strong intermodulation effects. Even on my R-5000 I can notice very small intermodulation effects if I listen to air traffic communication on, say, 5658 KHz. This is because when you tune to that frequency the RF stage will let the frequencies in some block through that in case of the R-5000 includes the 49 meters band. And then it is inevitable to get third order intermodulation effects caused by powerful stations on 49 meters band. This problem is much more severe on my cheaper radio. What is especially annoying is that if you listen at night (on the cheaper radio) the intermodulation effects will drown out even strong signals on the 5600 khz band.

So, before you buy a radio, you should really think about what your primary focus will be. If it is listening to broadcast stations and to ham stations, the latter only occasianaly and it wouldn't be a big deal if you can't some stations, then you could go for a radio priced $100 or even cheaper. But if you would be dissapointed if you can't receive amateur stations very well you should consider spending just a few hundred dollars more to buy a good second hand communications receiver. Count Iblis (talk) 17:38, 14 May 2008 (UTC)

Sociocultural evolution

Sociocultural evolution, the progression:  Hunter-gatherer bands → Social rank → tribes → Social stratification → chiefdoms → Neolithic Revolution →→→ Civilization: Agrarian society (Pre-industrial society): Agrarian villages → Towns → Cities → City-states → Nation-states →→ Industrial Revolution → (Modern) Industrial society →→ (Postmodern) Post-industrial society → Informational Revolution → Information society → Digital Revolution →→ Globalization → World government?

Is that correct?

The Transhumanist 21:30, 12 May 2008 (UTC)

you missed off this one:

http://en.wikipedia.org/wiki/United_Federation_of_Planets —Preceding unsigned comment added by 78.144.146.123 (talk) 22:13, 12 May 2008 (UTC)

Is it correct? Only if you assume evolution of this sort is both linear (non-branching) and teleological (driven towards a specific end). Neither of which are reasonable assumptions (or supported by evidence) in either biological or sociocultural evolution. --98.217.8.46 (talk) 00:41, 13 May 2008 (UTC)

The thing which might make World government inevitable is the failure of so many to have achieved the first tier and fewer the next and so on. -- Taxa (talk) 01:41, 13 May 2008 (UTC)

You missed out religion, which has always played a major role in social development (kings often relied on a priest-class to confirm their divine origins). That influence has varied through time and directed sociocultural evolution into several divergent paths. (Note, you can always play Civ3 to check your theory out:) Franamax (talk) 03:01, 13 May 2008 (UTC)

That seems more or less a correct hierarchy of least to most complex societies. Keep in mind that societies, as 98.217.8.46 implied, may move "backwards" so to speak. The collapse of the Roman Empire was a step back from the nation-state to the city state for parts of Europe. They may also skip steps. The Native American tribes have pretty much been absorbed into the American nation-state.

Durant has a hierarchy of his own going:

• family
• clan: a group of related families occupying a common tract of land, having the same totem, and governed by the same customs or laws
• tribe: a group of clans united under the same chief
• state: based on geographical contiguity rather than kinship
• ...

I'm sure he goes on, though I haven't gotten very far in The Story of Civilization. — Ƶ§œš¹ _{[aɪm ˈfɻɛ̃ⁿdˡi]} 05:45, 13 May 2008 (UTC)

An excellent read along with The Story of Philosophy. 71.100.14.205 (talk) 11:02, 13 May 2008 (UTC)

Brown versus green (fuel/CO₂ versus O₂ production)

Suppose I have 50 acres covered with a 15 year old stand of pine trees (another 5 years of growth needed to become suitable for harvest as lumber) for which I'm offered a certain amount to harvest now. The amount of the offer sounds reasonable but a higher reward might be possible from firewood than lumber. Before I make a decision I need to know how much energy and carbon dioxide the stand can produce and how much oxygen will be lost in order to make the right green decision. Is there a template I can use to facilitate this analysis or is all this talk about green just meaningless theory? 71.100.14.205 (talk) 22:02, 12 May 2008 (UTC)

If you want to reduce CO₂, then lumber is the way to go. If you burn the wood, all the CO₂ gets released back into the atmosphere, if you keep it as wood, it's stored up. --Tango (talk) 10:47, 13 May 2008 (UTC)

Unfortunately economics have to be made part of the equation such as in maximizing the profit by using the energy availability as a positive and the co2 output as a negative. A template for determining the amount of timber per acre would probably help. 71.100.14.205 (talk) 11:27, 13 May 2008

(UTC)

The "economy" depends on you location. This link gives one example for US Mississippi [3]. This may not be representative or relevant to your location. Ecologically the more uses a product gets before it is decomposed the better. Your timber will eventually either rot or get burned, but can go through quite a few cycles of use in-between. 71.236.23.111 (talk) 20:04, 13 May 2008 (UTC)

If you want to reduce CO₂, then lumber is the way to go. If you burn the wood, all the CO₂ gets released back into the atmosphere, if you keep it as wood, it's stored up.

But if this used as a substitute for fossil fuel use then the answer is not clear cut. Would it save more than sequestration through lumber? -- Q Chris (talk) 07:12, 14 May 2008 (UTC)

In Australia at least, the pine would have a much greater dollar value as lumber (and pine bark potting mix) than firewood anyway.Polypipe Wrangler (talk) 20:31, 15 May 2008 (UTC)

Ergonomics of press-up exercise

Are press-ups an ergonomic exercise or do they cause undue strain on the wrists? ----Seans Potato Business 22:04, 12 May 2008 (UTC)

May 13

Can my macaw breed with his macaw?

Mine: Female hyacinth macaw

My friend's: Male red and green macaw

Supposing that the two birds get along and eventually pair up, will they be able to breed? --81.77.245.65 (talk) 00:21, 13 May 2008 (UTC)

I'm no expert, but it should work. Hyacinths are reported to be very difficult to breed, though. Considering that our page lists hyacinth macaws as endangered, wouldn't you rather want to see if a zoo or breeder in the area has a male hyacinth and breed yours with that one? Just a suggestion. -71.236.23.111 (talk) 01:44, 13 May 2008 (UTC)

I don't think so. They aren't even in the same genus. bibliomaniac15 04:22, 13 May 2008 (UTC)

Bird hybrid has a couple of examples. Somewhere it said that different genera don't breed in nature, but some mate successfully in captivity. It would just be a pity in this case because the species needs the contribution of every surviving member for genetic diversity. Hope you'll decide to get a suitable hyacinth gentleman for her. Lisa4edit (talk) 05:37, 13 May 2008 (UTC)

From what I've read on the internet, any large macaw can breed with any other large macaw and produce fertile hybrid offspring. As I understand it, it can be quite a common occurrence if you have an aviary containing several different species. The other day, I saw a picture of a third-generation 'mutt' hybrid which was (apparently) descended from four different species. I've seen a few photos of Hyacinth x Ara macaw hybrids too - they do look rather odd and (IMO) quite ugly. Imagine a Hyacinth Macaw-sized/shaped head and bill on a much smaller and thinner body, with random bald patches scattered around the face.

As others have alluded to, it's probably best to find another Hyacinth if you're planning on mating her. Intentionally breeding hybrids of endangered species is something that is somewhat frowned upon amongst macaw enthusiasts. --Kurt Shaped Box (talk) 14:27, 13 May 2008 (UTC)

Why are they considered separate species, then? Isn't being able to produce viable offspring together the definition of being the same species? There might be some blurred lines between species within a genus, but I would have thought species from different genera would be more distinct. --Tango (talk) 22:14, 13 May 2008 (UTC)

Not "viable", "fertile". But there are other factors. Tigers and lions breed in captivity. In nature they have different ranges, so they don't meet. Birds also seem to be a bit more flexible reproduction wise than taxonomists gave them credit for. Some of their hybrids are fertile and do reproduce. --Lisa4edit (talk) 05:20, 14 May 2008 (UTC)

What's the technical definition of "viable", then? --Tango (talk) 14:38, 14 May 2008 (UTC)

The dictionary says this [4] for fertile they use the "reproduce" meaning [[5]]. Have some mercy on the taxonomists. What are they going to do? They spent all this time sorting things into a system splitting the finest of hairs and then those animals just go ahead and mate in some cage and throw everything off kilter :-) 71.236.23.111 (talk) 17:05, 14 May 2008 (UTC)

Go easy on the hybrid macaws too. No-one ever told them that it was scientifically-impossible for them to reproduce. :) --Kurt Shaped Box (talk) 22:32, 14 May 2008 (UTC)

Thanks for all the answers. I wasn't definitely going to attempt to breed her with my friend's macaw. Just sounding out the possibilities. I feel sorry for her when she starts going broody at about this time every year and I see her go through all that nest making behaviour for nothing. I've considered obtaining a male Hyacinth for her but they seem to be very expensive these days. Since when did that happen? My bird was only slightly more expensive than a large 'Ara' macaw when I got her in the early 80s. --90.242.185.237 (talk) 21:51, 15 May 2008 (UTC)

If your hyacinth macaw gets suffientily lonely, she may even try to breed with a water hyacinth, but I would think the probabilty of this mating producing any offspring would be rather low. :-) StuRat (talk) 12:26, 16 May 2008 (UTC)

Don't know when they became rare. Depending on where you are there's likely to be a "parrot society" or some such in the area where you might find someone with a male. If you happen to be in the U.K. the London Zoo has a breeding program. Contacting any such sources is likely to come you a lot cheaper than buying another bird. Since you've found out what they cost, I guess you can do the math of what a successful mating might result in. Someone with a male might be very willing to split the spoils. Don't plan on celebrating yet. There are many reports that say they are hard to breed successfully. Lisa4edit (talk) 05:24, 18 May 2008 (UTC)

Animal stripes

<moved from misc desk>
Do baby tigers, leopards, and zebras get more stripes or spots as they grow older, or do the stripes and spots they are born with get bigger? Mr Beans Backside (talk) 19:07, 12 May 2008 (UTC)

Don't know about either leopards or tigers, but ozelots and domestic cats are born with a fuzzy version of their general fur pattern that gets more defined with age. Some changes happen, but mostly in the "belly" area (what you see when the cat lies on its back]. Lion cubs are born with spots that disappear as they mature. OR one of our domestic cats had white tufts behind her ears, that disappeared as she matured. Some cats that appear black (Melanism) at birth can later grow stripes or spots. Hope this helps. --71.236.23.111 (talk) 20:16, 13 May 2008 (UTC) For further reading Gene expression and Cat coat genetics could get you started.Lisa4edit (talk) 21:04, 13 May 2008 (UTC)

With dogs the spots definitely get bigger - not more numerous. We have photos of our dog (a Border Collie/something mix) when he was 1 month old and about 6" long. The spot pattern is IDENTICAL to photos we have of him at 10 years old and four feet long. It's true in humans too! My son was born with a dark birthmark and a patch of starkly white skin (both on his stomach) - both have grown bigger with him to age 17 (although they've both faded towards more normal skin color to the point where you can hardly notice them). 66.137.234.217 (talk) 14:24, 17 May 2008 (UTC)

Push/press ups with equipment

Following the ergonomic question above, I was wondering why people recommend using equipment for pushups, say holding small dumbells to the floor. Does this technique work different muscle sets or is it a ploy to sell more equipment? Julia Rossi (talk) 02:13, 13 May 2008 (UTC)

Personally, hands flat on the floor stresses the wrists more than using little things with handles which allow the hands to be more curved. Edison (talk) 04:27, 13 May 2008 (UTC)

Thanks Edison. Julia Rossi (talk) 09:58, 13 May 2008 (UTC)

Now things have changed since we thought that knuckle press-ups were "better" because they hurt more! -- Q Chris (talk) 07:09, 14 May 2008 (UTC)

Pushups using dumbells or similar are better because you can get a deeper pushup, resulting in more muscles working harder. Luxosus (talk) 14:05, 14 May 2008 (UTC)

help in cleaning up a dog's skull

Hi what steps should I take to clean up a skull that I found. here are the specifics:

1. Found half-buried in sand used for construction (the greyish one)
2. Most of the skull is dark brown in color. An unburied part is cracked and whitish.
3. The lower jaw is missing.
4. My female co-worker was disgusted when I picked it up and kept it.
5. It looks like a dog's skull, about 15-20 cm long.
6. It still has teeth.
7. It smells funky but I can't find any flesh clinging to it. No idea regarding the brain though

I want to make it sparkling white and tough to boot. I hope the ingridients that you would reccomend are easily found and cheap.--Lenticel ^(talk) 06:03, 13 May 2008 (UTC)

For a similar question in March 08[6] and preserving a rabbit's skeleton in Feb 08 here[7] with one of the answers as ants ants ants. On a documentary I saw a forensic scientist using detergent with its enzymes or whatever, breaking down pig's parts, but don't remember that it mentioned skeletons, only ways of getting rid of bodily crime evidence. Julia Rossi (talk) 06:16, 13 May 2008 (UTC)

You should win a prize for hitting on a topic for an article missing from wikipedia. Our articles mention "preparation" and "preparator", but there's no page. Taxidermy doesn't cover it. Pathologists' Assistant I thought was a very odd link from the German wikipedia, which does have and article. --Lisa4edit (talk) 06:24, 13 May 2008 (UTC)

Then there's google[8] cleaning your own animal bones by soaking in water with some detergent and more – like how to clean a skull (taking care not to overdo things) here[9]. This article has really clean white skulls. All common ingredients and cheap as so good luck, Julia Rossi (talk) 06:33, 13 May 2008 (UTC)

I like the last two sources. I'll have a sparkling skull in no time. Thanks!--Lenticel ^(talk) 07:05, 13 May 2008 (UTC)

hydrocarbons

what is the formula for finding how many isomers a hydrocarbon has? —Preceding unsigned comment added by 41.204.224.23 (talk) 10:20, 13 May 2008 (UTC)

Homework alert. Read the notice at the top of the page, we will not do your homework for you. Regards, CycloneNimrod^Talk? 12:09, 13 May 2008 (UTC)

On the contrary, I think it's unlikely to be a homework question (if so, it's a trick question, because there is no formula you can just write down). For questions like this the On-Line Encyclopedia of Integer Sequences is an invaluable resource. The sequences you're looking for are OEIS: A000602 and OEIS: A000628. —Keenan Pepper 19:33, 13 May 2008 (UTC)

Current in capacitor and nature of magnetic fields

I have a difficulty understanding how current passes between an insulator in capacitors. Also what exactly is the nature of magnetic fields? What passes in flux lines? Is it a particle, a massless thing with momentum? Or something else entirely? Bastard Soap (talk) 10:48, 13 May 2008 (UTC)

Current doesn't really pass across the insulator of a capacitor. What happens is that electrons accumulate on one plate of the capacitor and "holes" (the absence of electrons that would normally be there when the material is neutrally charged) accumulate on the other. The resulting electric field results in a voltage difference between the plates. (You could think of this as analogous to blowing up a balloon; the air you blow isn't really going anywhere, but is building up until the pressure exerted by the atmosphere and the strain of the rubber equals the pressure at the mouth of the balloon, or until the balloon pops of course.) The amount of charge it takes to produce a given voltage difference is defined as the capacitance of the device:

$C={\frac {q}{v}}$

If you connect a DC voltage source (e.g. a battery) directly to the terminals of a capacitor, current will flow and charge will build up until the voltage across the capacitor equals that of the voltage source, and then no current will flow. That is why capacitors are treated as an open during DC analysis of an electronic circuit. --Prestidigitator (talk) 16:44, 13 May 2008 (UTC)

But in practice it is not correct before the capacitor charges up right? Bastard Soap (talk) 16:58, 13 May 2008 (UTC)

If you mean the treatment of the capacitor as open, yes, it's not correct until then. I don't think the reason current "passes through" a capacitor is much different from the reason it passes through a conductor. The electromagnetic repulsion between the charge carriers can get through the insulator; it's only the charge carriers themselves that can't. If you force charges to accumulate on one side of a capacitor, they repel the charges on the other side, leading to a current there. The only difference is that, since the charges have nowhere to go, there's a limit to how far you can push them before you reach the voltage limit of your battery (or whatever) and no more current flows. In the case of AC there's no net motion of the charges and so no net buildup, and the capacitor is not much different from a segment of wire. As for the nature of magnetic fields, I'll leave that for someone else to answer. -- BenRG (talk) 18:01, 13 May 2008 (UTC)

I see capacitors as very different from mere wires for AC. The "non-wire" nature of capacitors in AC circuits is useful in oscillators, filters, motor-starting, power factor correction, and phase shifting circuits. Edison (talk) 03:32, 14 May 2008 (UTC)

So nobody knows what the damn flux is? It keeps it's cards close to it's chest Bastard Soap (talk) 16:38, 18 May 2008 (UTC)

Darwin

Was Charles Darwin a eugenicist or a social Darwinist? --Begantrue (talk) 22:01, 13 May 2008 (UTC)

Neither, as far as I know. They're not really opposites, either, so I'm not sure I understand your question... You would probably be better off on the humanities reference desk - this isn't really a science question. --Tango (talk) 22:11, 13 May 2008 (UTC)

Neither. He was a naturalist. Also, what's this troll smell? — Kieff | Talk 23:12, 13 May 2008 (UTC)

It's a legitimate question, one historians have been asking for some time now. It's a question about what beliefs he held and wrote about, not his occupation. He did write on both topics. --Captain Ref Desk (talk) 02:48, 14 May 2008 (UTC)

For a fairly complete approach, by a respected historian of heredity, you might look up this article: Diane B. Paul, "Darwin, social Darwinism and eugenics", in Jonathan Hodge and Gregory Radick, eds. the Cambridge Companion to Darwin (Cambridge University Press, 2003), 214–239.

In short: Darwin was on the fence in both cases. He valued his cousin Francis Galton's work primarily because Galton established, as far as Darwin was concerned, that intelligence was as inheritable as stature and skin color. He believed that it was possible, as Galton claimed, that society could be breeding itself into inferiority, but he was not at all sure that society could or should do anything about that. He considered Galton's view of a state that could help regulate breeding as "utopian". Neither he nor Galton believed at all in anything that looked or sounded like even the coercive form of eugenics practiced in the United States, much less under National Socialism.

Darwin's intellectual priority was convincing people that evolution was plausible. He did this by looking for things in animals that he saw in man, as a way of bridging the gap. He was not interested in how human societies should organize themselves, not like Galton and Spencer were.

That being said, he didn't totally disown these ideas either. But eugenics was brand new and not totally formulated; social Darwinism was not yet a coherent set of principles (and certainly not under that name). Did he believe evolution applied to society? Yes, but he and everyone else just called it Darwinism at that point.

But in all things, the most salient aspect of Darwin is his fence-sitting. Read the sections on society in Descent of Man—he goes back and forth, is eugenics sensible, is it moral, does it make sense, over and over again, back and forth. (Origin of Species is written in much the same fashion, he circles around and around.) In the conclusion of that book he gets as close as he ever did to saying that perhaps the state should be keeping track of whether people marry their own cousins (he tried to get his friend Lubbock to pass a law that would mandate an investigation of this—and he himself always felt that his own children's sickly demeanors came from the fact that he had married his own cousin) and that people should give more attention to the heredity of their spouses than they usually did. But it is not very forceful, it is not the cry of what we would today consider a real eugenicist or social Darwinist. He did not denounce the ideas very strongly, but he did not support them very strongly either. They were not major forces on his agenda. --Captain Ref Desk (talk) 02:48, 14 May 2008 (UTC)

kitty's diet

If I give Fluffie nothing but meat and water, is that a guarantee that she'll get enough taurine? Is there any bird or mammal meat that's low in taurine? —Tamfang (talk) 22:09, 13 May 2008 (UTC)

Unfortunately it isn't that simple. I'm no expert in this area but a google search turns up many exceptions to the general rule that meat=taurine. There are so many exceptions that I can only suggest that you speak with your vetinarian concerning your pet's diet. BTW, the general rule is that mammal meat and fish are good sources of taurine. Poultry is not included in that rule. In fact, This Yahoo answer states that poultry is low in taurine. This paper says ruminants are a poor source of taurine. This page supports the previous two, indicating that chicken and beef are low in taurine. (Subscription required) states that raw rabbit diets are low in taurine. The list of exceptions keeps getting longer the more links I check. The best bet is to ask your veterinarian. 152.16.59.190 (talk) 06:41, 14 May 2008 (UTC)

Apart from really asking your vet. You should at least put out a pot of grass for your cat. Although cats are carnivores, that doesn't mean they only eat meat in the sense of carcass that we consider such. A catch like a mouse or a bird contains plant matter and cats also eat insects if they get to go outside. That gives them a lot more variation in their diet than "meat only".Lisa4edit (talk) 07:29, 14 May 2008 (UTC)

Thanks all! —Tamfang (talk) 16:04, 14 May 2008 (UTC)

Thailand food production

What is one way that a country can increase the amount of food they can create without hurting the environment, while increasing their economy, making a valuable asset to their people, and making it a productive and sustainable part of their agriculture for future generations? Aka- Im doing a project on Thailand and I have to find An alternative or more efficient method of food production that would be benificial, economically sound, & environmentally sustainable for Thailand. —Preceding unsigned comment added by Sleppytime (talk • contribs) 23:57, 13 May 2008 (UTC)

Not hurting the environment is a difficult one, since pretty much everything carries a risk of some damage. Ignoring that requirement, there are all kinds of options: selectively bred varieties of crops, genetically modified crops, new pesticides, new fertilisers, new agricultural tools (better tractors, ploughs, harvesters, etc), introduction of new insects to fertilise crops, the list goes on. Of course, Thailand already has quite advanced agriculture, as far as I know. There's always room for improvement, but I doubt there are any obvious things that would have a major impact, since they would have done them already if there were. --Tango (talk) 21:05, 14 May 2008 (UTC)

There is no way to create more rice without changing the environment. Rice, like all plants, animals, fungi, bacteria, and otherwise, will naturally increase and decrease in population, and drastically is very common. Environmental change will naturally happen. Mac Davis (talk) 17:23, 15 May 2008 (UTC)

May 14

MnO₂

Hello. If manganese(IV) oxide is ionic (not covalent), then why is it commonly called manganese dioxide? Calling MnO manganese monoxide is a little bit ridiculous. Thanks in advance. --Mayfare (talk) 00:55, 14 May 2008 (UTC)

So you can forget the roman numerals and everyone still knows what you're talking about? The term predates IUPAC, anyway. Someguy1221 (talk) 01:17, 14 May 2008 (UTC)

Well, the term dihydrogen monoxide is widely known. :D --JDitto (talk) 03:33, 14 May 2008 (UTC)

Natural vibration of solids

So I was thinking, if a solid already vibrates naturally, what happens if it's made to stop vibrating? Does the material become more durable or more brittle? Thanks. --JDitto (talk) 03:07, 14 May 2008 (UTC)

Vibration could be due to heat, impinging sound, impacts by particles. Removing the vibrations will be the same as removing heat, or lowering the temperature. The solid will contract, it may recrystallize in another form, it may become more brittle. If you reduce the temperature close to absolute zero you will minimize the vibrations, but you will still get quantum fluctuations or zero point energy. Graeme Bartlett (talk) 03:59, 14 May 2008 (UTC)

Other interesting properties will result if you can get the temperature extremely low, where the material is in the lowest quantum state. Friction can vanish in a supersolid, and with tighter and tighter upper bounds on temperature, and therefore momentum and movent of the sonstituent particles, the location of the solid becomes vague and a Bose-Einstein condensation occurs. Graeme Bartlett (talk) 04:14, 14 May 2008 (UTC)

PHYSICS- "FORCE"

Which force is responsible for the noise made by the dry hinge of the door? —Preceding unsigned comment added by 117.96.7.67 (talk) 05:35, 14 May 2008 (UTC)

Electrostatic (repulsion between the surfaces in the hinge) and gravity (attracts the door to the Earth) --Shniken1 (talk) 05:51, 14 May 2008 (UTC)

It's sound created by friction. Wisdom89 _{(T / ^C)} 05:54, 14 May 2008 (UTC)

And as Shniken1 suggests, friction is one of the many manifestations of the electromagnetic force. Algebraist 08:48, 14 May 2008 (UTC)

More specifically, it's the stick-slip phenomenon that relates to the friction.

Atlant (talk) 13:00, 14 May 2008 (UTC)

technological pudding

What does it supposed to mean? --Omidinist (talk) 06:52, 14 May 2008 (UTC)

It would help if you could supply some context.--Shantavira|^{feed me} 07:14, 14 May 2008 (UTC)

"Modern science has succeeded in vastly increasing our knowledge of nature,
from the microworld of subatomic particles to the vastness of intergalactic space.
The proof is in the technological pudding"
(Clifford D. Conner, A People's History of Science, p. 497). --Omidinist (talk) 10:58, 14 May 2008 (UTC)

It is a rephraseing of "the proof of the pudding is in the eating". In this case, technology is the proof. 206.252.74.48 (talk) 12:26, 14 May 2008 (UTC)

Great. Thanks. --Omidinist (talk) 13:07, 14 May 2008 (UTC)

Auntie, what's the matter?

Is matter-antimatter annihilation the only way to obtain 100% conversion to energy? Clarityfiend (talk) 07:14, 14 May 2008 (UTC)

Even this is a problem as proton connecting with antiproton also produces electrons and positrons. Graeme Bartlett (talk) 11:27, 14 May 2008 (UTC)

It is far and away the closest approximation, however. — Lomn 13:11, 14 May 2008 (UTC)

Accretion onto a black hole is probably the runner up, with efficiencies in the double-digit percent range. -- Coneslayer (talk) 13:18, 14 May 2008 (UTC)

I think Hawking radiation has the same conversion rate as matter/antimatter. — DanielLC 20:35, 14 May 2008 (UTC)

CO2 + energy = fuel. But how?

Taking CO2 out of the atmosphere (or oceans) would get an extra impulse if we could do something useful with it. Such as make fuel. Since petrol is transformed into CO2, releasing energy, can't one do the reverse, take CO2 out of the atmoshere (or oceans), add energy and make a fuel, preferably one that cars can run on? In other words, I want to reverse the arrow in the exothermic reaction equation in the combustion article (eg with x=8 to make octane). But is this as simple as burning? And in what form would the energy then have to be added? Heat? Or can it also be electricity? Of course, plants do something like this with light through photosynthesis, but that has a maximum efficiency of 6%. Artificial photosynthesis is just in its early stages I understand and the first stage produces hydrogen, but it is going to take decades until the hydrogen economy has a complete infrastructure. And the second stage produces glucose, just like plant photosynthesis, something that existing cars can only use as an additive (as is done in Brazil). Is it difficult to produce the longer molecules in petrol that cars can use as-is? And which alkane would be the most logical choice? Octane seems like the most logical choice for the car, but how well can cars run on other hydrocarbons that might be more easily produced? Are longer chains more energetic?
Also, since chemical energy storage is all about the exchange of electrons (yes?), doesn't it make more sense to use those directly, in other words, use electricity for reduction to combine the short CO2 into long carbon chains?
In short, can windmills and solar cells produce petrol? And shouldn't we have a carbon energy article? After all, that is the driving force of life on earth.DirkvdM (talk) 07:48, 14 May 2008 (UTC)

Cars with proper engines run fine on alkohol or biodiesel, both of which are fairly easy to produce from e.g. plant matter. Current engines may have problems because the alternative fuels have different lubricating properties and may act as solvents for gaskets. But solutions for these problems exist - see e.g. Ethanol fuel in Brazil, a large country that is using bioalcohol as fuel for 30 years. Synthesizing e.g. octane from CO2 and, say, water, is certainly easily done in the lab, but I don't think that there is an efficient industrial process for doing this. --Stephan Schulz (talk) 08:50, 14 May 2008 (UTC)

Actually, I don't think turning CO2 into octane can be done easily/efficiently through chemical processes even at the laboratory scale. I'm sure it can be done, but there are quite a large number of steps along the way, plus wasted energy and lost material. Dragons flight (talk) 09:11, 14 May 2008 (UTC)

I did not say efficiently ;-). And I mean "easily" not as in "it takes a few minutes" but as in "a competent chemist with a laboratory and a library will figure out how to do it without new research". --Stephan Schulz (talk) 09:33, 14 May 2008 (UTC)

Bear in mind that even thoug biofuel or some alternative like hydrogen may be necessary for things like boats, planes and cars travelling long distances, a large proportion of human travel can probably occur with direct use of electricity. Intracity/commuter travel via trains and plug-in electric cars, long distance transport of good within a country or even between countries with trains. Shipping (with ships) is probably one of the most significant things going to require some form of fuel, but shipping is AFAIK already very efficient (see food miles) and may get even more so with a return to wind assisted shipping[10]. Whether this fuel will be in the form of synthetic petrol, biofuel, hydrogen or something else is anyones guess but at the moment petroleum is still cheap enough that it's unlikely to be a problem for the few things that actually need fuel. As others have stated, biofuel is actually fine as a fuel for cars, the bigger problem is the cost. Nil Einne (talk) 13:14, 14 May 2008 (UTC)

Shipping may be efficient but due to its fuel (bunker oil) is one of the most polluting.[11][12] Iceland is disscussing converting their fishing fleet to hydrogen power, however. Rmhermen (talk) 14:54, 14 May 2008 (UTC)

Also renewable power sources are not without issues, the biggest one being storage. Since most renewable sources are not reliable and depend on the conditions it's ideal if you can store the power for use when power output is low. Batteries are too low density for this sort of thing. Pumped hydro (which is inefficient and needs somewhere to store all the water) or using the energ to produce a fuel (hydrogen for example) is probably the best option we have nowadays. Nuclear power plants of course have a somewhat similar problem in that their output can only be regulated slowly unlike fuel power stations which can generally be shut down or start-ed up at will depending on need. Non-pumped hydro can of course be used as one source to release power at will although it may mean some 'waste' (when your power output from other sources is so high and your dam is full you just have to it go) and there is always the risk if you have exceptionally low rainfall you hydro backup will run out. You can of course at a pump to a hydro power plant in some instances. The other issue is of course availability. The desert is a very good place to make solar power plants but many are not surprisingly sparsely populated and deserts are quite far from a lot of Western Europe for example. So either you need very long power lines which of course means very high losses (unless you make a room temperature super conductor) or you need to convert the energy to some sort of fuel (hydrogen perhaps). You can of course build solar and other renewable power plants in Western Europe but for solar anyway deserts are probably close to being the best location. Nil Einne (talk) 15:59, 14 May 2008 (UTC)

Public transport and electric/hydrogen cars might be a nice ideal, but it will remain a reality for a long time that private cars running on petrol are the preferred mode of transport and we need something that works now. And what is un-pumped hydro and how do you let a car run on it? And transport of hydrogen and electricity is indeed more of a problem than a liquid (at room temperature) fuel. So that's why I want a liquid fuel. DirkvdM (talk) 10:46, 15 May 2008 (UTC)

"Unpumped Hydro" refers to normal water-power, using natural run-off (though usually dammed). "Pumped Hydro" is only a somewhat inefficient but cheap way to store surplus power for load equalizing. Essentially, when your grid is delivering more than you need (because of all the base load power stations running at the optimum level and low demand), you pump water from a lower reservoir back up the mountain. See Pumped-storage hydroelectricity. --Stephan Schulz (talk) 11:46, 15 May 2008 (UTC)

So back to my (now adapted) question. Is there a way to make a liquid fuel that existing cars can run on with CO2 and an electric charge? How can you make this form hydrocarbon chains? DirkvdM (talk) 10:46, 15 May 2008 (UTC)

If octane burns with oxygen to yield heat with products of combustion carbon dioxide and water, how much more energy would be required to reverse the process, ideally? What would be entailed in such a synthesis? Above it was said ""a competent chemist with a laboratory and a library will figure out how to do it without new research"." but what might go on in a future reaction vessel which had water, carbon dioxide and electricity as raw materials and octane as a product? Edison (talk) 19:13, 15 May 2008 (UTC)

In New Scientist magazine earlier this year there was an article using CO2 this way. It started with using a ceramic which was heated and cooled in a cycle to remove one oxygen to form CO gas. experimental stuff. Polypipe Wrangler (talk) 20:49, 15 May 2008 (UTC)

The chemists here have not shed much light on the mystery of how it could be done in the lab or scaled up to a synfuel factory. I found some discussion of the hydrogenation of carbon dioxide at [13]. I found a United States Patent 6987134 issued 17 Jan 2006 for a process [14]. Maybe Craig Venter can do it with Frankenscience: [15] , [16]. He says in 18 months he can have microorganisms pumping out octane from CO₂. Edison (talk) 22:29, 16 May 2008 (UTC)

Where to get the CO2 from

The above question led me to wonder where one could best get the CO2 from; So where are the CO2-concentrations highest? this source says the concentration in the oceans is 60 times higher than in the atmospere. I assume that is volume-based. But if that is averaged out for the atmosphere (to which height?) then that number doesn't help because I want to know how the concentrations compare at ground level (and surface level for the oceans, or is it more evenly distributed there?). Of course, there is also the question how easily the CO2 can be extracted from water or air, but that may be affected by the method by which it is transformed into fuel. DirkvdM (talk) 07:48, 14 May 2008 (UTC)

Well, currently the easiest way is to burn less fuel in the first place. The process of converting CO2 (probably plus water if you want petrol-like stuff) back into usable fuel is even in the theoretical best case less than 100% efficient - the second law of thermodynamics sees to that. In practice, the efficiency will be fairly abysmal, I suspect - heat engines are only at 40% or so with the currently feasible or even plausible future materials. So unless you have spare energy that is not from fossil fuels, its easier and more efficient to not produce CO2 in the first place. If you decide to extract CO2 anyways, because you have spare energy (Iceland comes to mind), there are two less hopeless ways of doing it. First, collect it where it is produced - at the tailpipe or the chimney. That way you have a decent concentration to start with. Secondly, the smart way it indeed to let plants do the collection and concentrate on the conversion of plant matter into fuel. Sure, photosynthesis may only be 6% efficient, but then the solar cells grow themselves for free. --Stephan Schulz (talk) 08:39, 14 May 2008 (UTC)

You really want CO2 in the sea. Assuming all factors are yielding positive for the local phytoplankton, including the ill-sought after iron, marine snow will be capable of bringing certain amounts down to several kilometers below sealevel, which in theory can help on the greenhouse effect. I digress on your topic, but thought this was a relevant and not uninteresting bit of information, as there's a certain level of "saturation" for CO2 in water, which phytoplankton has an impact on. 213.161.190.228 (talk) 11:16, 14 May 2008 (UTC)

If you want effortless biomass, so from a natural surrounding (forest or such), then efficiency is even less than 1%, I believe (that 6% is a theoretical maximum). And then you have to harvest that and convert it to a useable fuel, each with their own (in)efficiencies. In comparison, the efficiency of solar cells is over 10% (and rising).

Anyway, the question here is about the concentration in water or air. You've got a good point with the CO2 from tailpipe or chimney, but I'm thinking about a way to harvest wind energy at sea, so not near such CO2-sources. DirkvdM (talk) 11:27, 14 May 2008 (UTC)

You could put your turbine on the coast and then grow algae in a tank. As Stephan said your "production cost" would be minimal and you'd get at the CO2. If you use wastewater to feed the algae you might get a twofer. 71.236.23.111 (talk) 16:15, 14 May 2008 (UTC)

(EC) Don't forget you need a way to convery your electricity to some sort of fuel, so your 10% quickly goes out the window. If you're using CO2, it simply doesn't seem feasible to me since we not only have no way that I know of to convert it to a fuel in mass quantities that I'm aware of, you're also almost definitely going to have to concentrate it somehow which is not going to be cheap energy wise. Hydrogen might be a better bet but even it's still far from being practicable not to mention the infrastructure investments required. Bear in mind if you're using something like jatropha or palm oil you can use the oil as a fuel with minimal processing. Obviously the planting, growing and harvesting is not free but the biomass you have left behind is probably the biggest problem sicne you're losing a lot of what your producing which is why people are trying to find ways to convert it to something usable. Algae fuel is another alternative which removes the land issue and also should eb a lot easier to harvest etc, but we still don't have a good algae Nil Einne (talk) 16:20, 14 May 2008 (UTC)

You might be interested in this lecture. [17] Some of the base data is a bit out of date, but the general principles still apply for the most part. (I think you'll need one of the players to get the full lecture.) Lisa4edit (talk) 03:09, 15 May 2008 (UTC)

WMD

I recently read some facts on Weapon of mass destruction. I have some questions on WMD especailly about the destructive power.

1. How many nuclear warheads (each 15 KT) will be able to completely destroy a large city like the New York City?
2. Which is more dangerous - Biological weapons or nuclear weapons i.e. which have more destructive and killing efficiency?
3. What will be the effect on ecosystem of the planet as a whole if 1000 nuclear warheads (each 15 KT) are blasted above ground? Otolemur crassicaudatus (talk) 09:55, 14 May 2008 (UTC)

The first part is odd: 15kT is a tiny nuke, like the WW2 ones. Do you mean 15 MT TNT equivalence? What do you mean by completely destroy? Just killing all the people or completely incinerate the deepest cellar? The second part is a bit odd too: either could completely render humanity extinct. Presumably biological agents would always leave some non-human residue but so what. See Nuclear Winter for the third part. --BozMo talk 11:37, 14 May 2008 (UTC)T

He probably means something that terrorists could get ahold of. A terrorist isn't going to have a 15Mt weapon. They might be able to get a 15kt weapon, though—you could make something like that if you had the right materials and resources. No small, non-state entity is going to build a hydrogen bomb, though. --Captain Ref Desk (talk) 13:36, 14 May 2008 (UTC)

1. No idea.
2. Nukes are rare and expensive. It also needs technical knowledge to launch (you can't launch one on a slingshot) but is more devastating and efficient than bioweapons as it can affect larger areas. Bioweapons on the other hand is cheap, easily mass-produced and can be concocted in your parent's backyard. When released, it would only affect a small area and must be manually and stealthily released (you can't load a canister of virus/bacteria in a missile warhead, it will be incinerated) but the mass production part will compensate that disadvantage. Vaccines and drugs can also be used to diminish the weapon's effect so minus points on killing efficiency.
3. See Nuclear winter and the more poorly written Nuclear summer.--Lenticel ^(talk) 11:45, 14 May 2008 (UTC)

For the first question, I mean 15 KT TNT equivalence. I just want to know an estimation that approximately how much such nuclear overheads will be able to destroy cities like the New York City. Destruction means complete destruction of buildings, all major artificial structures including the entire city population. Otolemur crassicaudatus (talk) 11:50, 14 May 2008 (UTC)

Immediate total destruction will require an implausibly large number. Going for the last few survivors in deep cellars is extremely expensive. To destroy New York as a working community so that it will fall apart without massive outside help is only a few nukes, especially if this includes ground bursts with massive fallout. So what is your setting? A few terrorists exploding 4 bombs will do massive harm, but the city will be rebuilt. An all-out global nuclear war with a 4 bomb share for New York will probably finish the city, at least for generations, if not forever. Without the industrial base and organized society, rebuilding will not happen. --Stephan Schulz (talk) 12:07, 14 May 2008 (UTC)

I do understand the cities will be rebuilt. I have only confusion about how many weapons will be able to destroy a big city. Tokyo is the most populous city in the world with a population of 33,600,000. During the Atomic bombings of Hiroshima and Nagasaki, Hiroshima's population was 255,000 and 140,000 people died in Hiroshima within 1945. Hiroshima has an area of 905.01 km². Tokyo has an area of 2,187.08 km² i.e. approximately four times of Hiroshima. Little Boy dropped over Hiroshima had an yield equivalent to 13 kt TNT. So an estimation can be made from this that to completely destroy Tokyo, at least 4 Little-boy sized nuclear weapons will be needed. And to completely destroy the New York City also, at least 4 Little boy sized nuclear weapons (each having an yield equivalent to 13-15 kt TNT) will be needed. Is the calculation right? Otolemur crassicaudatus (talk) 12:41, 14 May 2008 (UTC)

• That's not correct per your criteria above. Hiroshima was far from "completely wiped out"; the Hiroshima Peace Memorial survived being only 150m from Little Boy's hypocenter; at least one person survived only 100m away. Even one nuke is enough to do massive harm; as Stephan Schulz said, complete destruction per your standards is utterly implausible. — Lomn 13:09, 14 May 2008 (UTC)

• (ec, and somewhat repetitive now): Again, this depends on your definition. Strongly-built structures in Hiroshima withstood the blast even near ground zero, and there were even survivors (someone in a bank vault, I think) close to ground zero. Also, much of Hiroshima was lightly-build. Modern skyscrapers probably can withstand the blast better. As a lower bound, and depending on the definition of "destruction", your estimate may be right. But a single 15MT explosion will have a much stronger effect on most targets... --Stephan Schulz (talk) 13:30, 14 May 2008 (UTC)

1. A 15kt nuclear weapon would have a radius of total destruction of about 1.81 km / 1.12 mi (high blast pressure + fireball + ionizing radiation), or around 10 km²/ 4 mi². Just eyeballing it, you'd need around 10-12 or so if you were totally ignoring the effects of fire (which is hard to predict, but caused most of the damage and death at Hiroshima and Nagasaki). Or, if you had just 1Mt warhead, that would do the trick in taking out all of Manhattan and most of the surrounding boroughs.

2. It depends who has them and who is going to use them and how many are going to be used and so forth. Personally I think nuclear arms are easier to control that biological arms, but a well-placed nuclear weapon can easily be more destructive than biological weapon.

3. Where, presumably, are 1000 15kt weapons to be found? Now you're into the realm of talking about the arsenals of states, which are not 15kt fission weapons, but in 100s of kts in fission-fusion weapons, which have a very different fallout profile. --Captain Ref Desk (talk) 13:36, 14 May 2008 (UTC)

Check out list of nuclear tests to see just how little 1000 * 15kt is compared to the atmospheric testing that actually was done. Just the Tsar Bomba alone is several times higher yield than those 1000 bombs put together, although yield is not the most important factor in determining environmental effects. --Sean 14:24, 14 May 2008 (UTC)

The fact is that we do not know what the effects of modern biological weapons would be because they were never used. Lenticel's comment above is incorrect in that highly effective agents cannot simply be prepared in your backyard and biological agents were certainly planned to be deployed by missiles - even as recently as in Iraq. While toxin-type biological weapons (which require contact with the deployed agent) would probably not approach the death tolls of a nuclear blast, infectious-type weapons (which only require contact with an infected victim) might be another matter. Let's hope we never find out. Rmhermen (talk) 14:40, 14 May 2008 (UTC)

It's exciting to be able to fill your brain with so much information, but then it begins to itch. You want to share this knowledge to an equal intellengent person who might understand. But, as I heard befor -you can get so busy thinking up answers the question you might have though: should you share. You guys are talking Monsters. Your wilding the answers around on an open page like a kid with toy gun to some you don't even know and in todays world Monsters aren't the same as 20-30 years ago and neither are people. I know you can hungerly serch for answers, but some answers will give you nightmares for the rest of your life. Sharing these answers stuck in your Pandor's Box while may seam relaxing but your the one that hurt your brain. You need to be responsible for your Monsters. Keeper of WMD. —Preceding unsigned comment added by 69.44.236.100 (talk) 15:12, 14 May 2008 (UTC)

... what? Nimur (talk) 16:24, 14 May 2008 (UTC)

Um... If some 'mad terrorist' who wants to destroy the world is relying on the reference desk to find out the potential destructive power of nuclear and biological weapons, I think we're safe especially since the biggest problem is not knowing how destructive they can be, but actually producing them Nil Einne (talk) 16:27, 14 May 2008 (UTC)

It may also be worth pointing out that security through obscurity is not highly regarded as a defense mechanism. Open access to information encourages effective defense systems. Nimur (talk) 16:35, 14 May 2008 (UTC)

In any case, none of these questions would be useful in destroying anything. They're just about effects, and are easy to look up. You want to stop nuclear terrorism? Encourage your governments to do more to help secure nuclear materials in unstable countries. Encourage them to move towards more open relations with countries that stand a high chance of proliferation—the biggest antidote for proliferation is increased openness and exchange, it makes it both harder to hide and reduces the motivation. People asking questions on the internet has nothing to do with proliferation or terrorism. Knowing how many nuclear weapons it takes to destroy New York isn't going to help anybody out at actually doing it. --98.217.8.46 (talk) 02:08, 15 May 2008 (UTC)

For question 2, I'd say bioweapons have the potential to be more dangerous than nukes. If a bioweapon could be developed that is highly infectious, say being both airborne and waterborne, 100% fatal, and has a long incubation period, say a year, it could wipe out almost all of humanity. The long incubation period would give infected people more time to spread the disease before they show symptoms and also would delay work on a cure and/or isolation measures until everyone was already infected. StuRat (talk) 12:14, 16 May 2008 (UTC)

A more effective way to cause massive damage is to alter the course of an asteroid to make it hit the desired target. This can also be used to our benfit. E.g. if we know that the Yellowstone supervolcano will erupt within, say, the next century, we could evacuate the entire US and then let a 1 km diameter asteroid slam into it to trigger the eruption. :) Count Iblis (talk) 18:46, 16 May 2008 (UTC)

Masturbation

Hi,

If a woman masturbates continously, is it will be a problem on her menstrual period and is it will effect her body?—Preceding unsigned comment added by 202.124.160.212 (talk) 12:19, 14 May 2008 (UTC)

Yes, the splashing will soil the bed sheets.

Atlant (talk) 12:55, 14 May 2008 (UTC)

Replacing reply OP removed - please don't do that! I'm afraid we cannot provide medical advice. If you are concerned, you should consult a doctor. --Tango (talk) 14:28, 14 May 2008 (UTC)

What do you mean by 'continuously?' If you mean, without stopping at all, for several days, then she will suffer the normal effects from not sleeping, eating, or drinking. -FisherQueen (talk · contribs) 15:13, 14 May 2008 (UTC)

As FQ said, it depends what you mean by 'continously'. Presuming you simply mean regularly, according to [18] and [19] masturbation can be helpful in alleviating menstrual cramps. According to [20] 'solo' masturbation is not sufficiently associated with to maintainece of a fertile pattern of menstrual cycles, you need at least one sexual partner (male or female) for that (although coital intercourse is not necessary). My guess even if it isn't sufficient, a 'young' woman who masturbates regularly will still on average have higher fertility and a more regular menstrual cycle then someone who does not. According to [21] masturbation may or may not increase in the later luteal phase and may affect testosterone levels. It also appears woman has a higher desire for sex and an increase in sexual feelings in the midfollicular phase suggesting that there will likewise be a stronger desire to masturbate in this phase. Nil Einne (talk) 20:00, 14 May 2008 (UTC)

STEAM

WHEN WATER BOILS THERE IS STEAM. BUT, WHEN, WHAT TEMPERATURE IS STEAM CONSIDERED STEAM. IS IT ANYTHING PAST 212 DEG. OR STEAM PER USE REQUIRED? THANKS, DARRELL CHAPMAN —Preceding unsigned comment added by 69.44.236.100 (talk) 14:04, 14 May 2008 (UTC)

Please don't write in all capital letters, it is considered rude (and hard to read). Anyway, you may be interested in our articles on steam and superheating. While I cannot definitively answer what defines "steam" (perhaps a dictionary would be useful as well), I can conclusively state that "H₂O beyond 100°C" is insufficient, even ignoring atmospheric pressure. — Lomn 14:14, 14 May 2008 (UTC)

Steam is tiny water droplets suspended in air, this is distinct from water vapour. --Tango (talk) 14:26, 14 May 2008 (UTC)

There are a lot of different uses of terminology by both laypersons and experts; I'd be cautious about drawing such a sharp distinction. In engineering, steam is the gas that you get from boiling water; it is – or ought to be – pure water, containing very little air. At 1 atmosphere of pressure, you can make it by heating liquid water past 100°C and waiting until it has all boiled into the gas phase.

Live steam is steam that's held at a temperature above 100°C. All of the water remains in the gas phase. If you pull heat out of steam – as by running it down a long, uninsulated conduit – then its temperature will remain at 100°C, but some of the gas will condense into droplets of liquid water. Engineers will often discuss steam quality, where poor-quality steam contains a lot of water droplets. Steam turbines (for example) hate poor quality steam, as the liquid water droplets are murder on rapidly moving turbine blades.

In lay usage, the term 'steam' is often used to describe the cloud that appears above the spout of a kettle. There, it's a mixture of proper steam, water droplets, and air. (If you look closely at the space right above the spout of a hard-boiling kettle, you can usually see a small region where the cloud hasn't yet formed; that ought to be essentially live steam containing no water droplets or air.) TenOfAllTrades(talk) 15:15, 14 May 2008 (UTC)

Interesting. That's a very different definition than the one I know. Is it unique to engineers? --Tango (talk) 15:55, 14 May 2008 (UTC)

It's just a semantic definition based on "purity" of the gaseous H20. Such a quantitative measure would be useful if you were doing something with the steam (as driving a turbine). Nimur (talk) 16:27, 14 May 2008 (UTC)

I believe the answer needed was 100 deg C and the area between the steam cloud and the end of the kettle. In plants where steam is generated if you walk through steam pipeways you have to carry a broom handle with you. You wave it in front of you as you walk through. if and when a flange gasket gets a pin hole (leak), a pincle thin shot of -invisible- steam will shoot out. If you pass that broom handle through that it WILL slice through that stick and or arm. Thanks. —Preceding unsigned comment added by 69.44.236.100 (talk) 18:32, 14 May 2008 (UTC)

Coiling a wire is easy. Just carefully wrap it around a circular object - a thread spool, a pencil... if you want to go all out, you can purchase ferrite cores for a few cents each, and wrap it with a high-gauge ("thin") wire. Neodymium magnets are easy enough to get and are about as strong as you'll find. Your construction quality will affect how well you produce electric power; you may also want to think about mounting lots of magnets around the wheel to get a continuous flux. Alternatively, you could have one magnet which sweeps past the inductor once per wheel-revolution. This will generate a brief pulse of (high?) power; you could build a circuit which tries to spread that power over the full cycle until the next time the magnet comes back around. I doubt this will work very easily, since I think you will not get a whole lot of electric generation even with a good magnet. Nimur (talk) 16:32, 14 May 2008 (UTC)

If the point is to make the LED flash briefly as it passes a magnet fixed to the frame (or vice-versa), this should be a pretty easy circuit to engineer and a casual attempt at winding your own inductor will probbaly work. You should use two LEDs in antiparallel or place an ordinary silicon diode in antiparallel with the LED, though. Put a hundred turns on a steel bolt serving as a core, arrange the magnet to sweep by in close proximity, and see what happens. Try several magnet/bolt orientations. If nothing happens, add more turns to the coil until you get flashes.

Atlant (talk) 17:05, 14 May 2008 (UTC)

Theoretically The flux through an element of area perpendicular to the direction of magnetic field is given by the product of the magnetic field and the area element. you should get the best effect if you strung your wire along the wire rim. Practically I'd go with Atlant's idea. 71.236.23.111 (talk) 17:18, 14 May 2008 (UTC)

I noticed something that said that the voltage(?) would increase if the size of the circle were larger, but is this the case even if the loop is huge compared to the magnet? Would a wire wrapped around the rim of my wheel (I think this is what you are saying) really generate a current when wizzing by my little magnet attached to the fork?

Also, what is the best configuration for a given length of wire? Huge circle with fewer loops (say, around my wheel) or smaller circle with more loops? — Sam 17:45, 14 May 2008 (UTC)

Possibly you have misunderstood .111's idea (or maybe I have). 111 is not suggesting winding along the rim, rather, 111 is suggesting winding toroidally around the rim. A wire laid along the rim will not succeed in cutting any lines of magnetic flux from a fixed magnet attached to the frame. I think 111 has suggested themself that this is not very practical, you would need to wind over the face of the tyre which would rapidly destroy the wire on most road surfaces. Either that or wind underneath the tyre, but this would probably still result in the wire not lasting very long and would do nothing for tyre fit either. SpinningSpark 22:04, 14 May 2008 (UTC)

It should work fine, but you will be a sitting duck with no light when you stop, which would be very unsafe. The commercial version offers a backup so the light keeps flashing when you are stationary. I wonder if a coil (complete with iron core) from a doorbell/door buzzer would work as the pickup coil, with neodymiuym magnets attached to the spokes? Depending on how much electrical energy is supplied when the magnet passes the coil, you might feel an annoying pulsation in the pedal effort, as if the brakes were applied slightly. Normal LED bike lights run for a considerable time on very small batteries, so the energy per flash might be too slight to notice. But you never get something for nothing when extracting electrical power from human powered movement. Edison (talk) 22:37, 14 May 2008 (UTC)

Diabetes and the treatment of warts

(This is not a solicitation for medical advice. I’m asking the question out of intellectual curiosity. I have access to professional medical care, but I won’t bother my doctor with questions about medical conditions that I neither have nor have a reason to worry about.)

NO MEDICAL ADVICE - EVEN IF YOU SAY IT'S NOT A SOLICITATION FOR MEDICAL ADVICE !!

[In response to edit by 66.137.234.217:] The question is related to medicine, but there is no solicitation for medical advice. It does not ask for diagnosis, or treatment advice/recommendations. If you assume good faith, the question is not about the condition(s) of any particular person, named or otherwise, and whatever answer offered is not going to be relied upon. In what sense is the question a solicitation for medical advice?!

It's unfortunate that the first answer offered here was phrased in such a way to make the contributor look like he/she might be offering advice, but the wording those contributions does not determine whether the question is for medical advice.

If you're a position of authority to ban any and all questions related to medicine here, please just make the policy say so. If it is not the intent of Wikipedia to ban all questions that have anything to do with medicine, whether or not medical advice is sought, please don't be overzealous in labeling reasonable factual/scientific questions as solicitations for medical advice. Your unjustified assumption of bad faith, as well as your imputation of intent contrary to the apparent stated intent for no good reason, is offensive.

I’ve seen warnings on some over-the-counter medications for treating warts that the medications/treatments are not for people with diabetes. What’s the connection between diabetes and wart treatments? I assume that a doctor would have more options in treating a patient who suffers from both diabetes and warts. How may a doctor treat a warts patient who’s also diabetic? —Preceding unsigned comment added by 72.78.102.153 (talk) 16:21, 14 May 2008 (UTC)

People with diabetes mellitus are more likely to develop plantar warts which are caused by the human papilloma virus and these take longer to heal. I'm not sure on the physiology of why you can't use the treatments, however. Regards, CycloneNimrod^Talk? 18:55, 14 May 2008 (UTC)

The warning is to avoid being accused of causing or aggravating a diabetic foot ulcer. The salicyclic acid in the wart preparations can damage normal skin and some people with diabetes have reduced sensation and impaired circulation and healing. If the warning is understood and the preparation is used with care, it is not otherwise risky to diabetic feet. —Preceding unsigned comment added by 159.14.240.230 (talk) 21:03, 14 May 2008 (UTC)

Salicylic acid (the common ingredient in wart cures) is chemically very similar to acetyl-salicylic acid which is just aspirin. According to our article Aspirin: Aspirin is known to displace a number of drugs from protein binding sites in the blood, including the anti-diabetic drugs tolbutamide and chlorpropamide....I think it's safe to assume that displacing anti-diabetic drugs would be "A Bad Thing" for a diabetic. So yeah - it's quite likely that wart cures will screw with your diabetic medication - which could easily kill you stone dead. Given that there is an explicit warning on the wart treatment, I think we should regard advice to ignore it as an incredibly stupid thing to post in answer to a question here. Please ignore preceeding advice and consult a doctor. That's why we aren't allowed to give medical advice here - we screw it up all too often and in potentially dangerous ways. 66.137.234.217 (talk) 14:47, 17 May 2008 (UTC)

And thanks for providing another example of "screwed up" medical advice. Topical salicylic acid does not get absorbed, does not enter the bloodstream, and does not "screw with your diabetic medication"-- it simply burns whatever cells and skin it is painted on, whether warts or normal skin. The warning is also found in hot tubs and gadgets designed to burn off warts--- people with diabetes need to be careful about things that might damage the skin of their feet if they have any reduction of sensation. 159.14.240.230 (talk) 15:48, 18 May 2008 (UTC)

healthcare Infomatics

What is the meaning when information articles are characterized as "white page or white page article" ?Rlhandy (talk) 18:17, 14 May 2008 (UTC)rlhandy

Maybe it's a white paper? DMacks (talk) 19:20, 14 May 2008 (UTC)

My understanding of "white page" is that nothing has yet been decided or written and the writer is therefore free to make a construction from scratch. If the OP would give a link to where this was seen it would help to decide if this is the meaning. SpinningSpark 21:51, 14 May 2008 (UTC)

Avoidance of other people embarrassing themselves

Social anxiety can include avoiding social interaction out of a fear to embarrass oneself. But is there a technical term for (pathological) avoidance of situations where other people could potentially embarrass themselves? I've looked around this site, but I can't seem to find it. Social anxiety by proxy maybe? 82.210.125.161 (talk) 18:57, 14 May 2008 (UTC)

Agoraphobia is the closest thing I can come up with off the top of my head. Wisdom89 _{(T / ^C)} 22:32, 14 May 2008 (UTC)

:-) Overanxious mother syndrome? I'd say you are on the right track with social anxiety. If avoidance is involved I'd go with "a type of social phobia". That's the closest I'd know, but I'm no expert. --71.236.23.111 (talk) 22:38, 14 May 2008 (UTC)

I would think that it would be related to a very high (overly high?) sense of empathy. Feeling anxious when other people are in terribly embarrassing situations (like many of us experience while watching embarrassing scenes in movies) is because of our ability to put ouselves into other people's shoes and feel like these things are happening to us, in the same way that watching someone in pain can be exceedingly painful. — Sam 13:19, 15 May 2008 (UTC) —Preceding unsigned comment added by 63.138.152.238 (talk)

Psychological projection might have something interesting. But still no definite term.Lisa4edit (talk) 13:58, 15 May 2008 (UTC)

Does stars have that divine light , the reason for creation? Which guides humanity and other creatures? if so, where are they channelized?

I was reading a book, which says if we can attain oneness, we can attune with the nature around.. as well as with the oness of other creatures.is this oness..or the divine light..or the golden light..suppossed to come from one channel ( we call Heaven)-& perceived by only those , of the likes - Jesus, Hindu Gods - Shiva, Durga, Allah?--who have same commn star..to guide & protect them? also does this energy frm the light of stars affect ur lives, which can inturn mark the change in century? Trekkersdelight (talk) 21:26, 14 May 2008 (UTC)

Doesn't really seem to be a science question. Try the Humanities Desk. SpinningSpark 21:46, 14 May 2008 (UTC)

The common star for all these is the sun, and this surely does affect our lives. But the basis of this book does not sound like science, so this is probably not the desk to ask this question or make your statement. Stars do not mark centuries, these are a human creation as part of the calendar. Graeme Bartlett (talk) 21:47, 14 May 2008 (UTC)

Stars are often "channeled" or "channelized" here --Bmk (talk) 01:48, 15 May 2008 (UTC)

If oneness is attained how could there be stars, light, channels, perception, protection, guidance, lives, centuries, etc? If these differences remain, it's not oneness. Pfly (talk) 06:35, 15 May 2008 (UTC)

Tapeworms as a weight-loss aid?

Does WP have an article on this, as a matter on interest? Occasionally, I have read about people intentionally cultivating their own internal parasite(s), the thinking being that healthy, well-fed worm = slimmer human. Don't know if it actually works or not (I suspect that the effect is minimal) but I would like to read more about it. --Kurt Shaped Box (talk) 22:27, 14 May 2008 (UTC)

The pathology section of the Tapeworm does mention weight-loss as a possible symptom, but there's not much information. I think if you read the other symptoms you'll agree that self-infecting with Tapeworms is a terrible, terrible idea. And I might mention that I think vitamin deficiency is more likely than weight-loss. Ugh. --Bmk (talk) 00:16, 15 May 2008 (UTC)

On the other hand, is keeping a pet tapeworm in your innards particularly more extreme/nasty in terms of unwanted effects than some of the other methods that people try in an attempt to control their weight - Olestra, amphetamines, Liposuction, Stomach stapling, various diet pills etc.? --Kurt Shaped Box (talk) 00:29, 15 May 2008 (UTC)

I would definitely prefer getting Liposuction over self-infecting myself with a tapeworm *spine shivers* 76.196.10.3 (talk) 01:22, 15 May 2008 (UTC)

That's a fair point KSB, but I still would rather have surgery or some other treatment than tapeworms, even if they worked well - they give me the creeps. --Bmk (talk) 01:45, 15 May 2008 (UTC)

Agreed. Plus you may end up actually gaining weight, because your body will try to compensate for the lack in nutrients by making you eat more. --71.236.23.111 (talk) 02:04, 15 May 2008 (UTC)

worms can also help against asthma :) Count Iblis (talk) 02:29, 15 May 2008 (UTC)

Just a rumour? Maria Callas' radical weight loss raised speculations, among them, tape worm.  ; ) Julia Rossi (talk) 11:03, 15 May 2008 (UTC)

That's a great article idea, we should have at least a well-done section about it. Mac Davis (talk) 17:17, 15 May 2008 (UTC)

I'm having a deja vu moment here, didn't I just ask a question about this recently ? I believe I mentioned that other seemingly disgusting creepy crawlies are sometimes used medically, like maggots to eat away gangrene and leeches to restore blood flow after finger reattachment surgery. Our tapeworm article says that, while many nasty effects can happen from tapeworms, they rarely do: "According to Intestinal Cestodes, authors Craig, and Ito 2007 suggest that the effects of this gut dwelling Cestodes are usually very minimal". This compares with the very common and disgusting side effects, such as anal leakage, associated with commercial weight loss formulae like Alli. StuRat (talk) 11:45, 16 May 2008 (UTC)

One thing I could imagine regularly occurring amongst tapeworm aficionados, which might lessen the effectiveness of the method is the "I've got a worm inside me, so I can get away with eating more now!" effect. --Kurt Shaped Box (talk) 12:18, 16 May 2008 (UTC)

Yes, but people who are candidates for bariatric surgery have no self-control to begin with, that's why they are morbidly obese. StuRat (talk) 23:53, 16 May 2008 (UTC)

I actually saw a jar of tapeworms in a museum of pharmacy products from the early 1900s. There's a picture of an advert here. They were sold as a weight-loss aid. ~Amatulić (talk) 21:03, 19 May 2008 (UTC)

Trees in paper

If you have 100 cubic feet of wood with whatever density most trees have, how many 8.5" x 11" pieces of paper can you get. Inversely, how much wood goes into making 100 sheets of paper? Not homework, by the way. Thanks, schyler (talk) 23:16, 14 May 2008 (UTC)

The first problem is determining how much of the tree's lignum can be converted to cellulose. Figures differ depending on the method applied and who states the figures for what purpose.

Figures on cellulose content I've found range from 30% [22] to 50-55 % of a tree’s volume [23]. Wood pulp describes various methods for turning wood into pulp from which cellulose can be produced. Each method offers a distinct rate of efficiency with trade offs in quality, energy use and water pollution. So there is no direct answer. Maybe someone else can narrow it down some. --71.236.23.111 (talk) 02:00, 15 May 2008 (UTC)

The number of sheets of paper you can make will depend highly on the thickness of the paper. The amount of wood needed for a 100 sheets of tissue-thin paper (say for a bible) will be different than that for 100 sheets of thick letterhead. - You may want to look at the Papermaking article. -- 128.104.112.147 (talk) 23:06, 15 May 2008 (UTC)

subquestion: how much wood would a woodchuck chuck if a wood chuck could chuck wood? --Shaggorama (talk) 07:30, 19 May 2008 (UTC)

May 15

Identify the spider

Who am I?

I'm sure it's a pretty common species, and we probably already have zillions of photos of it on Commons... but still... what kind of spider is it?

Photo was taken in Indianapolis, Indiana in July of last year. ~ ONUnicorn^{(Talk|Contribs)}problem solving 02:29, 15 May 2008 (UTC)

That appears to be a grass spider, genus Agelenopsis (all I did was look up "common spiders" and found it pretty quickly...) --DrVornado (talk) 02:34, 15 May 2008 (UTC)

Thanks. It does look like the spiders on that page... though the web it was on sure seemed sticky (see all the stuff stuck to it in the picture?) :) ~ ONUnicorn^{(Talk|Contribs)}problem solving 12:37, 15 May 2008 (UTC)

Inventions & Inventors

1. Like to know the names of atleast 5 inventors who died testing their invention 2.Kindly provide a brief detail about the invention and how the person died

Thanks 118.92.106.168 (talk) 06:17, 15 May 2008 (UTC)

• William Bullock died after getting caught in his rotary printing press.
• Otto Lilienthal died from injuries after a gliding accident
• Franz Reichelt died testing his parachute-coat.
• Thomas Midgley, Jr. invented a system of strings and pulleys to lift him from bed after he contracted polio. He got entangled in the ropes of this device and died of strangulation.
• Alexander Bogdanov experimented with the concept of blood transfusion. He died after blood of a student suffering from malaria and tuberculosis was given to him in a transfusion.
• Marie Curie developed the radium isolation process. She later died from aplastic anemia, likely due to exposure to radiation. As our article says, "much of her work had been carried out in a shed with no safety measures. She had carried test tubes containing radioactive isotopes in her pocket and stored them in her desk drawer, remarking on the pretty blue-green light the substances gave off in the dark."

Rockpocket 06:45, 15 May 2008 (UTC)

Believe it or not we actually have an article on the subject: See List of inventors killed by their own inventions. --Cameron (t|p|c) 08:55, 15 May 2008 (UTC)

Wikipedia, you never cease to amaze me! DMacks (talk) 16:38, 15 May 2008 (UTC)

Sinking of London

London is sinking by 1-2 mm per year due to sea-level rise. If London is sinking by 1-2 mm per year, then a calculation can be made that by 2100, London will sink 100 mm and by 2200, it will sink upto 200 mm. My question is that if a city like London sinks 200 mm, then what will the effect? Will it become inhabitable? Otolemur crassicaudatus (talk) 09:02, 15 May 2008 (UTC)

The last major flood in central London was the 1928 Thames flood. Today central London has excellent flood defences - see Thames barrier. Other parts of England are not so fortunate - see 2007 United Kingdom floods. Gandalf61 (talk) 11:01, 15 May 2008 (UTC)

This may be completely irrelevant but there was recently a film on TV about the flooding of London. It was cleverly named 'Flood', this is the link if you're interested: Flood (film). --Cameron (t|p|c) 11:03, 15 May 2008 (UTC)

I am not talking about flood, I am talking about permanent sea level rise due to global warming. What will be the effect if London permanently sinks by 200mm? Otolemur crassicaudatus (talk) 11:30, 15 May 2008 (UTC)

The only logical assumption I could make is that the water level of the Thames and other rivers will also rise by 200mm? It's clearly not a huge issue for London anyway. The Thames Barrier has more than enough leeway for 2cm of water rise. Either of two things would be needed for a devastating effect: a) a significant flood which the barrier can't handle or b) global warming to continue rising the sea level until the level of the Thames is too high. Regards, CycloneNimrod^Talk? 12:03, 15 May 2008 (UTC)

The Thames Barrier only protects against floods when it's closed. If sea levels rose, it would have to be closed more often, which could hurt the city's economy a bit, I expect. If they rose enough that the barrier had to be permanently closed, a new solution would have to be found. --Tango (talk) 12:59, 15 May 2008 (UTC)

I guess not a lot, except they may have to raise flood defences by a similar amount. 20cm isnt that much anyway. -- Q Chris (talk) 12:05, 15 May 2008 (UTC)

You can't make this calculation without some theoretical model of the future behavior of the London-Thames system. It's looks like you're linearly extrapolating the data without any theoretical motivation, which would make this similar to the prediction that the entire world's population will consist of Elvis impersonators by 2015. -- BenRG (talk) 13:11, 15 May 2008 (UTC)

BenRG is right about it not being linear. Firstly there are two processes combining: relative to a fixed point (eg. the centre of the Earth), there is an isostatic subsidence of the land due to the effects of ice during the last ice age, and the global rise in eustatic sea level due to the various effects of global warming. The subsidence may be approximately linear, although it's probably slowing down slightly. The rate of global sea level rise is controversial, but likely to be increasing. There's a more detailed explanation of the figures here, and some interesting stuff on the Thames barrier here. Eve Hall (talk) 17:56, 15 May 2008 (UTC)

As an aside, London is currently inhabitiable. That is to say, it is able to be inhabited. The question is whether or not London would be made uninhabitable due to its sinking. Ahh, English! — gogobera (talk) 17:21, 15 May 2008 (UTC)

Hi. Well, the 10 cm of sinking in 100 years might not be a problem, but sea level rise in 100 years might be, as it could be anywhere between 200 - 2000 mm. If it's closer to the latter, then more than likely the Thames Barrier would have to be permanently closed, or else 3 million Londoners would need to find new homes. Also, the sea level rise might speed up the sinking, by compressing the soil and eroding it. Venice is also sinking, and sea level rise would make it worse, but make coastal city-dwellers could learn from the Venicians and survive by paddling through the streets. Thanks. ~AH1^(TCU) 17:42, 15 May 2008 (UTC)

Permanently closing the barrier isn't an option - where would all the rainwater from upriver go? If sea levels rise such that the barrier can't at least be opened at every low tide, some other solution would have to be found. What is the typical tidal variation at the barrier, anyone know? --Tango (talk) 13:33, 16 May 2008 (UTC)

Just to clarify, but if I'm reading the introduction to the article correctly, the "sinking" is not due to sea level rise, but combining with it to produce a "double whammy". That is, any sea level rise is a separate issue from the landmass sinking. I didn't have time to read the article, but shouldn't the islands still be rising from post-glacial rebound? Matt Deres (talk) 18:31, 15 May 2008 (UTC)

London isn't too bad off compared to other parts of the North Sea. Dragons flight (talk) 18:56, 15 May 2008 (UTC)

Cold Cathode Fluorescent Lamps used as Backlights in LCD computer monitors and televisions

With reference to the Wikipedia article on Cold Cathode:

http://en.wikipedia.org/wiki/Cold_cathode

I should be very grateful if either a contributer to the article or a user knowledgeable about the construction and technology of CCFLs used as LCD backlights in televisions and computer monitors could clarify whether these CCFLs actually do contain a radioactive material that emits beta particles to start the ionization of the gas. If this is the case, then would it be correct to assume that facing the back of the computer monitor where the backlight can be seen shining through the grill that one is being exposed to ionizing radiation - since the fast moving beta particles would penetrate the thin glass of the backlight? 78.147.162.37 (talk) 12:13, 15 May 2008 (UTC)

Julia Howard —Preceding unsigned comment added by 78.147.162.37 (talk) 12:01, 15 May 2008 (UTC)

I'm no expert, but I should think any possible risk is very, very low here. Please consider self-powered lighting. There, a much more powerful source of beta radiation (that is, a source of high-energy electrons) is used to directly cause the phosphor coating of the tube to glow. Yet the enclosing tube is still glass (albeit, possibly leaded glass) and there seem to be few worries about radiation exposure unless the glass tube is ruptured. In a CCFL, any possible radiation source is there just to facilitate initial ionization, much like in many neon lamps (where ionization sources are definitely used). The magnitude of the radiation from this source must be many orders of magnitude lower than with the self-powered-lighting.

Atlant (talk) 12:47, 15 May 2008 (UTC)

Heel on wooden floor

When we move on a wooden floor with heel shoe why marks or scratches are left on the floor? —Preceding unsigned comment added by MAQMAQ (talk • contribs) 12:08, 15 May 2008 (UTC)

I'm not sure I understand the question so let me ask a clarifying question: Are we talking about shoe heels in general or a stiletto heel? In the first case, marks can be left because the rubber material of the heel can rub-off and transfer to the floor. Alternatively, small abrasive particles such as sand that become embedded in the heel can abrade the floor. In the second case, the concentration of weight on the very small area of the stiletto heel can exceed the strength of the floor, causing crushing of the material of the floor.

Atlant (talk) 12:57, 15 May 2008 (UTC)

Discharging a capacitor on a metal sheet

Hi all,

Let's say I charge a capacitor. The capacitor now has one plate with more negative charges than positive, and one plate with more positive charges than negative. If I then touch one of the plates to a hunk of metal, will I discharge half the capacitor? I'm guessing yes, because the charges between the plate and the metal will balance out, and since the tiny capacitor won't make much of an effect on the hunk of metal, both the plate and the metal will end up with (almost) no net charge. Is that right?

Second question: What will happen if I touch the negative side of a battery to a hunk of metal? Anything at all? Thanks!

You still have a capacitor, but now it's formed between the one original plate of the capacitor and the other plate acting in combination with the hunk of metal. The charge that was on the plate of the capacitor that is now in contact with the hunk of metal sheet will re-distribute itself among the new, expanded plate so as to minimize the stored potential energy. If you then separate the capacitor plate from the added hunk of metal some of the charge will be left behind on the hunk of metal and the original capacitor will end up holding less differential charge than when you started.

Atlant (talk) 15:59, 15 May 2008 (UTC)

However, it seems like the electrostatic field between the positive and negative plates of the capacitor would tend to keep the charges on the plates rather than letting them disperse much onto the metal sheet. Attraction between those positive and negative charges and all that. --Prestidigitator (talk) 16:06, 15 May 2008 (UTC)

Something similar will happen with the battery: a bit of charge will leak off the battery to the hunk of metal and remain there when you remove the battery, but not much. In the case of the capacitor the charge on each side of the dielectric is fixed but the voltage will change slightly when you add the hunk of metal; in the case of the battery the voltage across the terminals is fixed but the net charge on each side will change slightly. -- BenRG (talk) 19:09, 15 May 2008 (UTC)

Mice and candle wax

Do mice eat candle wax because it is good for them or because there is nothing else and they are hungry? Because my bro said the mice in his house were eating the candle wax from his candles. What nutritional benefit would a mouse get from eating the candle wax from a candle? Terror toad (talk) 13:13, 15 May 2008 (UTC)

Depending on what the candles are made of, they can certainly be nutritious. I did a bit of survival training as a Scout and one of the things we were told was good to have with you is an old fashioned tallow candle. It can provide light, help light a fire and if you get desperate, you can eat it - it's just animal fat. Beeswax is also edible. I'm not sure paraffin wax would be too nice to eat, though, and that's the most common wax in modern candles according to candle. --Tango (talk) 14:10, 15 May 2008 (UTC)

I've wondered the same about soap, which mice will regularly consume from my parents' summer cottage. Can they really digest the saponified fatty acids? —Ilmari Karonen (talk) 15:54, 15 May 2008 (UTC)

spectral lines of helium

What is the formula for the spectral lines of helium? Em3ryguy (talk) 14:16, 15 May 2008 (UTC)

I don't think "formula" is quite the right term, as there's no f(x)=y sort of thing, but here's helium's spectrum. — Lomn 14:47, 15 May 2008 (UTC)

If you're talking about singly-ionized helium, you can use a version of the Rydberg formula. -- Coneslayer (talk) 15:36, 15 May 2008 (UTC)

No. The full spectrum. Em3ryguy (talk) 15:54, 15 May 2008 (UTC)

Well, you can look up all the spectral lines of hydrogen in the CRC handbook here (warning - large PDF file). Does that help? --Bmk (talk) 17:06, 15 May 2008 (UTC)

You may also find this page helpful. -- Coneslayer (talk) 16:01, 15 May 2008 (UTC)

Joules, Newton Meters, and Foot Pounds

I know in metric/SI units that Joules referes to mechanical work and newton meters refers to torque, even though they're bot N x m. But foot pounds are a little more ambigious. Is it acceptable to use foot pounds interchagably between mechanical work and torque? Thanks Deltacom1515 (talk) 16:14, 15 May 2008 (UTC)

No idea why that's not formatted correctly. Deltacom1515 (talk) 16:14, 15 May 2008 (UTC)

According to our article on torque and our article on foot-pound, the foot-pound is a standard unit for both torque and work (in the US customary units system). And btw, if you have a space at the beginning of a paragraph, wikipedia puts the whole paragraph in a weird boxy thing (I fixed it for you). --Bmk (talk) 16:19, 15 May 2008 (UTC)

And as foot-pound notes, some people use "pound-foot" as the unit of torque, reserving "foot-pound" for work. -- Coneslayer (talk) 16:21, 15 May 2008 (UTC)

Yes. Further, that's what I was taught forty years ago, so it's not exactly a new convention :-)

-- Danh, 70.59.79.51 (talk) 21:09, 15 May 2008 (UTC)

Wow, way to read. I completly missed that. Guess that answered my question. Deltacom1515 (talk) 16:33, 15 May 2008 (UTC)

Area of cathode in an MFC

It is said that the area of the cathode in an MFC helps improve the efficiency of the MFC. Is this true? Why is it so? —Preceding unsigned comment added by 59.92.47.158 (talk) 16:39, 15 May 2008 (UTC)

Particle deceleration

note: question moved from Wikipedia talk:WikiProject Physics

I was wondering, since it's possible to accelerate particles to near the speed of light, is it possible to decelerate particles, and if so, how? (nb. I failed physics, so I wouldn't know myself)Avnas Ishtaroth (talk) 12:49, 15 May 2008 (UTC)

Yes. The easy way is to put a nice thick lead wall in front of your particle beam, then stand well away from the Bremsstrahlung radiation. You can also (in a hand-wavy sort of sense) reverse your particle accelerator to extract work - the physical processes involved work both ways. See laser cooling and Bose-Einstein condensate for some how and why getting a group of particles moving really slowly in some particular reference frame. - Eldereft ~(s)talk~ 16:46, 15 May 2008 (UTC)

What particles? Kamiokande uses water. In this case you get Cherenkov radiation. --Lisa4edit (talk) 17:04, 15 May 2008 (UTC)

The question of "decelerating" a particle is really a question of giving your particle a negative acceleration. That is to say, it's velocity should decrease with time. Of course, the smallest velocity a particle can have is zero. But the question remains, zero velocity with respect to whom. For instance, say you have some charged particles traveling and accelerating to the right due to an electric field pointing to the right. If you turned off the field, the particles would simply travel to the right at some constant speed. (They're in a vacuum so there is no friction.) If you turn on an electric field in the opposite direction, they would "decelerate" until they stopped and then begin accelerating to the left.

Physicists generally talk about acceleration in different directions (to the left and right, etc), rather than "deceleration". Heh, even the deceleration article simply redirects to acceleration! — gogobera (talk) 17:40, 15 May 2008 (UTC)

I don't believe it's possible to decelerate all particles, however. Photons can't go slower than the speed of light and the theoretical tachyon always travels faster than the speed of light. StuRat (talk) 11:21, 16 May 2008 (UTC)

Well, photons travel at the speed of light in the medium in which they are travelling (see refractive index). For anything other than a vacuum, that is a speed less than what is colloquially called "the speed of light" (c). Again, follow Lisa4edit's advice to see Cherenkov radiation (I'll add it as a see-also to refractive index). DMacks (talk) 14:45, 16 May 2008 (UTC)

And in that sense light can actually be decelerated a lot! --169.230.94.28 (talk) 02:41, 17 May 2008 (UTC)

Dandelion invasion

Hi. Today when I hid the sun behind an object that just obscures the sun's disk, I saw what looked like a heavy snowstorm, only it was May, and the sky was a clear blue with only a few fractus clouds in the distance. Anyway, and this is not homework, I speculated that they were dandelion seeds, which was confirmed when I saw them close up. However, around the sun, several hundred seed packets could be seen, ranging from probably 1 - 50 metres above ground. The wind was strong and from the north, I live in southern Ontario. Anyway, there must have been one per every cubic metre or two, as the highest ones near the sun were maybe as small as 10 arcmins apart from each other. Where did they all come from? To my north there are about 20 hectares of land capable of producing seeding dandelions. This means there must have been over a million individual seeding dandelions producing seed packets! In early to late June, there may be as many as 500 dandelions per square metre in some places, I estimate, if they haven't been mowed yet. Are they an invasive species in North America? If the climate warms a few degrees, warm conditions become longer throught the year, and rainfall becomes sporadic but interspresed with heavy and brief downpours, will there be more invasive dandelions? If so, what will happen to the local ecosystems? Also, do flowering dandelions close and reopen to become seeding ones, and how long does this take? A look at any random part of the sky or landscape for a few seconds will reveal at least a few of these seed packets, and sometimes several dozen! Do people consider them weeds because they're an invasive species or because they choke other vegetation? Thanks. ~AH1^(TCU) 17:34, 15 May 2008 (UTC)

Have a look at the dandelion article to answer some of your questions. A weed is not the same as an invasive species which in turn is not the same as an introduced species. If you get dandelions in your lawn you'll consider them a weed, even if they are useful to local wildlife and co-exist with indigenous species. An introduced species can adapt and become part of the local ecosystem, it may cause some temporary imbalances, or displace a local species, though. If it doesn't multiply in excess and is not harmful to local wildlife, ideally finding some animal that finds it palatable, an introduced species is no better or worse than an indigenous species. (Debatable if it replaces one that then becomes extinct.) An invasive species disrupts the local balance and multiplies in excess. (Common definition). Not all invasives are non-native, but it is easier for an introduced species to become one, because it may lack natural enemies. Temporary proliferation of a certain plant doesn't mean it is invasive. It may serve as a much needed food-source for animals. Dandelions are rather undemanding when it comes to growing conditions, so they can grow in a wide range of habitats. They are rather tasty though (even to humans - try them in a salad), so any mass of them will soon find something to nibble off the leaves. Hope this helps. --Lisa4edit (talk) 18:04, 15 May 2008 (UTC)

Does light attract itself gravitationally?

The other day I saw an interesting episode of The Universe which discussed the end of the universe through heat death, with the final dark age of the cosmos being one in which all black holes have finally evaporated and all that is left are stray random photons.

This got me wondering, though. Since light is a form of energy, and general relativity says that energy as well as matter bends space/time, does it follow that light can attract itself through gravitational force? After all, if a photon of light contains energy than it should, I think, very slightly bend space/time and thus attract energy and matter. Would it follow that two beams of light fired initially in parallel would slightly bend toward each other even in the absence of other energy or matter? And if so, would it be possible that in the universe's final dark age that stray photons could very, very slowly bend towards each other into wide orbits, producing large galactic size pockets of slightly higher than normal electromagnetic energy or heat? Dugwiki (talk) 17:41, 15 May 2008 (UTC)

• does it follow that light can attract itself through gravitational force?

  Yes, light has a gravitational effect that can attract other light. Dragons flight (talk) 18:16, 15 May 2008 (UTC)

• Would it follow that two beams of light fired initially in parallel would slightly bend toward each other even in the absence of other energy or matter?

  Not exactly. Gravitational fields propogate at the speed of light as well. Parallel photons would not interact because the gravitational field from one photon could never catch up to the other one. However, if you imagine these as beams of light with many photons, then yes they would interact. The gravitational field from early photons in one beam would effect later photons in the other. This effect would be ridiculously small. Dragons flight (talk) 18:16, 15 May 2008 (UTC)

Gravitational fields propogate at the speed of light as an older physicist this was not established in my day but was expected to be true, if this has changed can you link me the experimental evidence! (very interesting question, this bit in particular, by the way). Two photons bending towards one another is excactly the sort of evidence that was/is required. GameKeeper (talk) 22:23, 16 May 2008 (UTC)

See Speed of gravity#Experimental measurement?. The evidence seems to support the theory, but apparently not everyone is convinced. --Tango (talk) 22:27, 16 May 2008 (UTC)

• would it be possible that in the universe's final dark age that stray photons could very, very slowly bend towards each other into wide orbits, producing large galactic size pockets of slightly higher than normal electromagnetic energy or heat?

  I think the answer is no, but I'm not entirely sure. No matter how large you imagine the universe to grow, I don't think you could every get a large enough density of photons (given initial conditions such as exist today) to create bound orbits for other photons. I think the energy density of light is too low and the velocity too high to ever allow for gravitationally bound conglomerations of photons in the future universe. Dragons flight (talk) 18:16, 15 May 2008 (UTC)

  That sounds right. For photons to orbit, you need something close to a black hole (I think something 8/27 times the density of a black hole would work - a very large neutron star, maybe). Radiation density on the scale of neutron stars seems highly improbably, if even possible. --Tango (talk) 18:43, 15 May 2008 (UTC)

  Remember that black holes don't have a single density (even an average one): the Schwarzschild radius scales with the mass, which in turn scales with the radius cubed at constant (average) density. So any substance whatsoever can form a black hole if it fills a large enough spherical region. The cosmic background, say, with a density of 4.64×10⁻³⁴ g/(cm³), would form a black hole as a ball with a radius of two trillion light years. (It might be closer to 1.4 trillion; I'm not sure that I shouldn't give it a gravitational density of ${\frac {2u}{c^{2}}}$; see my oft-repeated link on the subject.) Using instead the critical density of 9.2×10⁻³⁰ g/(cm³) the radius is 14 billion light years; that this is approximately the age of the universe times the speed of light is not a coincidence. --Tardis (talk) 17:57, 16 May 2008 (UTC)

  Excellent point, however even with such a large universe the CMB wouldn't allow for photon orbits - they are usually calculated for a black hole in otherwise empty space, if the universe has roughly uniform density, all the gravitational forces roughly cancel out and you won't get orbits. It's not the density that needs to be on those scales but rather the variation of density (or some function of it, I don't have an envelope to hand). --Tango (talk) 18:18, 16 May 2008 (UTC)

  Not true, Tango. The presence or absence of a spherically symmetric mass distribution outside of a given spherical surface has no effect on the gravitational field inside that spherical surface. This is the Shell theorem, which follows from Gauss's law for gravity. (This is why classical models of a static universe are gravitationally unstable.) Tardis's argument is valid. --169.230.94.28 (talk) 02:36, 17 May 2008 (UTC)

  I can't see how that can work when you're talking about the universe as a whole. By symmetry, it has to cancel out, otherwise the net pull would be in a certain direction, destroying isotropy. --Tango (talk) 12:05, 17 May 2008 (UTC)

(Edit conflict) While photons don't have rest mass, they do have relativistic mass. However, it certainly isn't much mass (for example, I believe a 400 nm photon should have a mass of about 6×10⁻³⁶ kg). The wave nature of photons causes beam divergence (see diffraction), and as far as I know any gravitational curving of the path due to other photons is negligible compared to that. --Prestidigitator (talk) 18:25, 15 May 2008 (UTC)

Suspensions

I am looking for examples of situations where there is a need to keep solid particles suspended in water. One example I know of is oil drilling - as the drill progresses the little bits of broken rock need to be carried away in a stream of water - certain additives are added to the water to help keep the rock bits in suspension. Can you think of any other situations? I am more interested in industrial or agricultural applications, less in medical or food applications. Thanks! ike9898 (talk) 17:42, 15 May 2008 (UTC)

Magnetorheological fluids, though I think those generally use oil, presumably for its higher density and viscosity. One of the ways of making artificial diamonds uses a slurry of diamond grit slowly deposited by a controlled temperature differential. Generally, a gritty liquid like you describe is called a slurry. - Eldereft ~(s)talk~ 20:55, 15 May 2008 (UTC)

Detergents have non-surfacant ingredient. This keeps the dirt from settling back on the clothes or other surfaces, so it can be flushed through the drain. --Lisa4edit (talk) 06:44, 16 May 2008 (UTC)

greenhouse gases

how much methane and CO2 do 6 billion people breate out or fart out each day? Paul kahlich (talk) 17:49, 15 May 2008 (UTC)

We emit 1.5-3.5 kg of CO2 per person per day (1-2 lbs of carbon per day per person). But that doesn't matter because all the carbon we emit comes, directly or indirectly, from plants which gathered their carbon out of the atmosphere in the first place. Hence respiration has no impact on the global carbon balance. Dragons flight (talk) 18:01, 15 May 2008 (UTC)

If that were true - why would we be concerned with emissions from cows? The problem is that while you're correct in saying that the CO₂ production is balanced by the carbon we consume in eating plants - the methane we produce is not. Methane is a much worse greenhouse gas than CO₂ (75 times worse!) and it's not reabsorbed by the next generation of plants that we grow to replace the ones we ate. Eventually, methane does decompose into CO₂ - but it has a half-life of something like 100 years and since human populations are growing, we're inherently increasing the greenhouse problem. However - as bad as this is, it's nothing like as bad as with animals like cows who ruminate on their food - producing vastly more methane pound-for-pound than humans. 70.116.10.189 (talk) 04:29, 16 May 2008 (UTC)

Correction. See the methane article, second paragraph. The half life in the atmospere is 7 years, not 100. And because of the decay, the effect gets ever smaller, so one can never state the global warming potential (the effect compared to CO2) without specifying over which period. Most quoted is a number of 23 (stronger than CO2), which apparently is for a period of just over 100 years. Note that 105 years is 15 half-life periods (15 x 7), so by then the amount of methane is reduced to 1/(2^15) = 0,00003 times the original quantity. In other words, it's almost all gone and any global warming effect will be by the resultant CO2. Amrad (talk) 10:41, 16 May 2008 (UTC)

But temperatures have gone down in spite of rising CO2 levels... isn't global warming attributed to water vapor or sunspots?--WaltCip (talk) 12:16, 16 May 2008 (UTC)

Temperatures have gone down? Are you joking or do you read taboids of the worst kind? Maybe you read that at some localities temperatures have dropped, but globally, the rise in temperature is so immense that even after a few decades it's a certainty even for the scientific community (as opposed to individual scientists), which is usually extremely careful with its claims. And concerning the solar activity, yes, that plays a role, but it's negligible compared to the effects of the rise in CO2 levels. Btw, sun spots are just another effect of increased solar activity, certainly not a cause for warming. Amrad (talk) 13:46, 16 May 2008 (UTC)

density of paraffin wax

I'm looking for the density of paraffin wax in liquid phase. The wax we're using melts at 85°C (used in a car thermostat just in case you're wondering) but I'm not familiar with any good sites or databanks? Thanks in advance —Preceding unsigned comment added by 193.190.253.149 (talk) 18:58, 15 May 2008 (UTC)

Well, a database referenced in our paraffin article, found here, lists "paraffin oil" as 0.8 g/cm^3. Nevermind - turns out paraffin oil is another word for kerosene (as I found out in our paraffin oil. --Bmk (talk) 20:28, 15 May 2008 (UTC)

It seems that mineral oil is at least close to being liquid paraffin (the alkane lengths seem somewhat smaller than in paraffin wax, but that probably doesn't matter too much). (Its density is actually given only in the latter article and not its own; should fix that.) --Tardis (talk) 16:15, 16 May 2008 (UTC)

Trees vs Lamp posts

What are the relative strengths of lamp posts and trees (say, of equal width?) when struck, such as by a speeding car? Has there been experiments done on this?--Fangz (talk) 19:30, 15 May 2008 (UTC)

Well, many lamp posts and street signs are designed to collapse when hit by a vehicle (rather than kill the occupant), so that would definitely need to be taken into account. I saw a bus hit one once and it just toppled over without any resistance whatsoever. --98.217.8.46 (talk) 19:39, 15 May 2008 (UTC)

A lamp post that's solidly planted in the ground will be much stronger than an equivalently-sized tree. However, every lamp post I've seen has had a breakaway joint at the bottom that shears off easily when struck by a vehicle, but I've never seen a tree with a breakaway joint. --Carnildo (talk) 22:16, 15 May 2008 (UTC)

Apropos safety, shouldn't those falling lamp posts have a speaker that goes "timbeeeeeer", to warn pedestrians? Amrad (talk) 10:28, 16 May 2008 (UTC)

A few questions about neurotransmitters

1. Is it possible for the brain/nervous system to run out of transmitter chemicals? 2. If so, how and from what is the supply replenished? 3. If neurotransmitters are re-used, where are they stored when not in use? —Preceding unsigned comment added by 69.224.182.55 (talk) 20:37, 15 May 2008 (UTC)

Is the infomation in neurotransmitter not suffient for your needs? DMacks (talk) 20:57, 15 May 2008 (UTC)

[EC] Certainly not under normal circumstances - neutotransmitters are manufactured within neurons. I would recommend reading our article on the chemical synapse - I think it will clear things up. According to that article, most neurotransmitters are taken into either the presynaptic or postsynaptic cell for some degree of decomposition, and then either recycled or disposed of. --Bmk (talk) 20:59, 15 May 2008 (UTC)

Squirrel feces

Why don't you ever see Squirrel feces on the ground? You see Bird / duck feces, but never other large animals like raccoons. LLOTAAMI (talk) 20:56, 15 May 2008 (UTC)

I see squirrel feces all too often. Just put a bunch of birdseed on the ground, and wait. -- JSBillings 22:40, 15 May 2008 (UTC)

That works for raccoon doo-doos too. They really liked corn on the cob we had dangled from the gutter! (Don't try this if you have a cat! The raccoon may get hungry after it's done with the bird seed.)--70.91.165.182 (talk) 00:49, 16 May 2008 (UTC)

I have a science project that I am allowed to get help for some information

Hi, my name is Lindsay, a fifth grade student. I need help with this topic: LIST WATER'S FREEZING POINT AND MELTING POINT IN BOTH DEGREES, CELSIUS AND FAHRENHEIT.I really need help on it and I couldn't find any imformation on it. I'm still doing my rough draft that is due May 20,2008.PLEASE HELP ME!!!! —Preceding unsigned comment added by 71.243.52.218 (talk) 21:56, 15 May 2008 (UTC)

The Reference Desk has a firm policy that we will not do your homework for you. However, since this is a project about water, I suggest you start at our water article. The top of that article notes that for chemical and physical properties (such as freezing point), you'll want to refine that to water (molecule) (I'm listing both to illustrate the research process). If necessary, Google can be used to do the Celsius/Fahrenheit conversion: search "98.6 fahrenheit in celsius", for example, and Google will return 37 degrees celsius, which is the average human body temperature. The relevant formulae can be found at both Celsius and Fahrenheit, incidentally. — Lomn 22:02, 15 May 2008 (UTC)

If you don't already know it, the freezing and melting point of a substance are both approximately the same temperature. Also note that "the freezing/melting point of water" can mean different things. 100% pure water has one freezing/melting point, while the salt-water found in the oceans has a different one. If the teacher didn't specify, they probably mean 100% pure water. The pressure also affects the freezing/melting point, but I'd assume they mean normal air pressure at sea level, called "one atmosphere", unless otherwise specified. You should say all this in your results, though: "The freezing/melting point of 100% pure water at one atmosphere pressure is ...". There are two other temperature scales, named the Rankine scale and Kelvin scale, so including the freezing/melting point of water on those scales might impress the teacher. You might also want to include the freezing/melting point of ocean water on all 4 temperature scales. That should be enough to get an A, I would think. StuRat (talk) 11:04, 16 May 2008 (UTC)

Benzene resonance

Are benzene and other aromatic compounds are often represented as a resonance of 2 structures with double bonds. Is benzene really a superposition of 2 cyclohexatrienes, i. e. if you somehow detect an electron between carbon 1 and carbon 2 and then do a measurement (very quickly after the first measurement) is there a higher chance of finding an electron between carbon 3 and carbon 4 or carbon 5 and carbon 6 than in the other gaps between the carbon atoms? Thanks. 201.66.22.129 (talk) 22:31, 15 May 2008 (UTC)

Resonance is a single hybrid structure that is an average of the individual resonance structures, not a set of discrete structures that rapidly change one to another. If you could freeze the pi electrons in-place and observe where these electron particles are at a certain time there may be more between some carbons than others, but a series of such measurements would not have them jumping one position to the next around the ring at alternate times, and that's a poor description of how electrons actually are anyway. So the "real" picture is that there is some pi bond at all positions at all times, but not equivalent to a normal "double bond" at any position ever. DMacks (talk) 22:45, 15 May 2008 (UTC)

Thanks, I didn't say "very quickly" because I thought of alternating states but because I thought the measurement could disturb the molecule. I am more interested in knowing if the electrons are really entangled in such a way that a measurement would cause them to fall into one or the other configuration for a short time. 201.66.22.129 (talk) 23:32, 15 May 2008 (UTC)

No. The actual molecular orbital diagram for a conjugated system is completely non-classical: looks very little like "double bonds in various places" at all. If one tried to figure out where each pair was (either by freezing in place, or by somehow observing them), one wouldn't see any pair that was anything like an alkene. Actually, the electron pairs aren't even all equivalent to each other, so the whole concept of three alkene-like pairs chasing each other around (or merging into a single cloud) is pretty wrong. But rather than the electrons themselves being entangled or the "cause" of this mess, it's more that all the p orbitals are entangled (LCAO is a reasonable approximation) and then pi electron pairs simply (fill the lowest molecular orbitals). Each molecular orbital looks almost nothing like an alkene. WP really needs a MO diagram for an aromatic system but doesn't seem to have one. Here is what I mean: notice the shapes of the colored regions for each pair. DMacks (talk) 01:39, 16 May 2008 (UTC)

I'm surprised that $\pi _{2}$ through $\pi _{4}$ aren't degenerate sums of three MOs, that might be split by an impressed magnetic field. (I.e., shouldn't the geometric symmetry in the molecule under rotation by 60 degrees in the plane result in additional orbitals at these energy levels?) -- Fuzzyeric (talk) 00:41, 18 May 2008 (UTC)

May 16

Transformer configurations.

I work for an electric company. I quote distribution transformers on different configurations but since I am not an engineer there are some things I dont fully understand. I do understand the basics of transformers and electricity but I cant seem to understand the difference between a Y and a GY. I mean I do recognize the physical differences but I dont really understand why you would ground the neutral or why WHY! you would put both neutrals together in a Y-Y transformer. How come that doesnt create a short circuit or something like that?. I also dont understand why Deltas are ungrounded, is it not necessary? When and why is it necessary? Thanks a lot in advance, guys. —Preceding unsigned comment added by 200.56.210.20 (talk) 01:12, 17 May 2008 (UTC)

All electricity supply systems need to be grounded for safety. It is also the law that they must be grounded. :[24]. Continuity of the neutral conductor is :mandatory in law.

A Y (or star) connected transformer sometimes needs the star point connected to earth. This I imagine :would be achieved using the GY type (ie the star point is brought out for connection to earth). The normal Y :transformer may not have the star point connection brought out. If you connect one Y transformer to another :Y transformer via some overhead lines, it is my understanding that the star point of one of the transformers :should be earthed (you dont need to connect the other one to earth to achieve adequate system grounding).

Delta transformers may be connected to Y transformers via lines and therefore dont need grounding because the Y :transformer is grounded at its star point. In the case of delta to delta connection, since there is no neutral :connection available, I believe earthing transformers are used between each line and earth to ground the system. —Preceding unsigned comment added by 79.76.158.222 (talk) 06:45, 17 May 2008 (UTC)

I was reading FANCD2 article.

They used word monoubiquinated. What dose it mean? "This protein is monoubiquinated" That is apparently taken from NCBI web site. I could have requested it in Wiktionary, but afraid it could take years before someone will create article there. Vitall (talk) 01:40, 16 May 2008 (UTC)

The protein had one ubiquinone unit attached to it. DMacks (talk) 01:52, 16 May 2008 (UTC)

Thank you! That's perfectly answered my question! Vitall (talk) 02:15, 16 May 2008 (UTC)

Be careful when reading, as proteins can also be ubiquitinated, which is something altogether different. -- 128.104.112.147 (talk) 15:57, 16 May 2008 (UTC)

Actually, I'm pretty sure that "ubiquinated" is simply an alternative spelling of "ubiquitinated". I don't think ubiquinone ever gets attached to proteins, but ubiquitin does that for a living. --169.230.94.28 (talk) 02:18, 17 May 2008 (UTC)

Higher frequency mean more bandwidth

Shorter wavelength mean more bandwidth. Like data could be transfered at higher speed, more bits per second. There should be a law/axiom or something clearly stating this. And I do remember I read about that here, in Wikipedia. Could someone point me to an article, preferably here, but anywhere in the internet would also be good enough. I did tried to Google for like 20 min but fail:( Vitall (talk) 01:49, 16 May 2008 (UTC)

Something like frequency modulation might have the info you want.--Fangz (talk) 03:18, 16 May 2008 (UTC)

I think you're looking for the Shannon–Hartley theorem. — Lomn 04:02, 16 May 2008 (UTC)

Shannon–Hartley theorem state, that the more bandwidth we got, more data(actual bits and bytes) we can transfer in a given time. That is excellent point, but it don't reflect wavelength bandwidth relation. Or am I missing something? Is it actually safe to say, that if we use ten times shorter wavelength we can reliably transfer 10 times more data using same amount of power in a given time(same signal to noise ratio)? Sorry if I making question even more complicated, but this whole thing is confusing. Vitall (talk) 05:09, 16 May 2008 (UTC)

Um as far as I'm aware there is no direct dependency between wavelength and bandwidth, however the shorter the wavelength, the higher the frequency and at a higher frequency you can have more bandwidth. For example, if your device works between 100-200mhz you only have 100 mhz of bandwidth. If your device works between 11-12ghz, you have 1ghz of bandwidth a 10 fold difference Nil Einne (talk) 06:37, 16 May 2008 (UTC)

From the article-Surprisingly, bandwidth limitations alone do not impose a cap on maximum information rate. This is because it is still possible for the signal to take on an indefinitely large number of different voltage levels on each symbol pulse, with each slightly different level being assigned a different meaning or bit sequence. If we combine both noise and bandwidth limitations, however, we do find there is a limit to the amount of information that can be transferred by a signal of a bounded power, even when clever multi-level encoding techniques are used. Em3ryguy (talk) 14:25, 16 May 2008 (UTC)

Endangered Species- Polar Bear

How can we save the polar bears from becoming endangered? —Preceding unsigned comment added by 75.108.103.100 (talk) 02:00, 16 May 2008 (UTC)

Reverse the effects of global warming (which unfortunately deflects a nearly impossible question with another nearly impossible question). The main threat to the polar bear is loss of habitat due to melting of sea ice. --Bmk (talk) 02:17, 16 May 2008 (UTC)

If we pray hard enough the Divine Intervention might save them. Vitall (talk) 02:36, 16 May 2008 (UTC)

I can't think of any course of action less likely to work. That kind of "wish things turn out" attitude is precisely the problem. Matt Deres (talk) 02:48, 16 May 2008 (UTC)

Well... Making sure all of the sea ice melts as quickly as possible might be even less likely to work than prayer, but apart from that... -- Captain Disdain (talk) 08:52, 16 May 2008 (UTC)

One radical solution might be to introduce polar bears to Antarctica, which will likely contain ice and snow long after it has all melted at the North Pole. This is because there is so much more ice in Antarctica to start with. Of course, this may have disastrous implications for other species in Antarctica now, such as penguins. StuRat (talk) 10:38, 16 May 2008 (UTC)

PAUA OPALS

WHAT ARE PAUA OPALS? —Preceding unsigned comment added by 66.191.157.101 (talk) 04:14, 16 May 2008 (UTC)

It's probably cut pieces of Paua or abalone shell. Graeme Bartlett (talk) 05:14, 16 May 2008 (UTC)

Cut and polished to resemble the iridescent disk of an opal though hardly like it, the name is linked with a desirable and more notable material to expand the market for what is as GB says, NZ abalone shell jewellery. In the business world the practice is called "tailgating" – a tactic to gain an advantage from something already established in a market – linking it in your mind, but not in reality. Julia Rossi (talk) 08:55, 17 May 2008 (UTC)

flame test

colour of tap water in a flame test

Did you read flame test? It will be coloured by the dominating metal, most likely sodium as it gives a much stronger emission than calcium or potassium. Graeme Bartlett (talk) 07:02, 16 May 2008 (UTC)

Airport X-rays

Do I need to protect electronics (computer, camera, …) from being irradiated by X-rays at the baggage inspection at an airport? Mabye it's necessary to differentiate between two cases: hand luggage and checked-in luggage. —130.237.2.72 (talk) 09:55, 16 May 2008 (UTC)

Consumer electronics are almost invariably not bothered by airport X-rays (I say almost because I'm sure as soon as I throw in an absolute, someone posts the counterexample). If some affected device exists, it will certainly be well-noted in the instructions. As previous similar topics have noted, the equipment used for carry-ons is less powerful than that used on checked luggage, so when in doubt, carry. Note also that the security of carry-on luggage is superior, and that some items (lithium ion batteries, for one) may be prohibited from checked luggage anyway. If something is really delicate, it's probably worth checking with your local post office to see if they x-ray shipments -- surely some non-x-ray transportation arrangement exists, though you're not going to find it at the airport. — Lomn 13:03, 16 May 2008 (UTC)

The airport's website will probably have a list of items that you shouldn't put in your baggage - I would expect that to include things that will be damaged in addition to the obvious security rules. --Tango (talk) 13:39, 16 May 2008 (UTC)

The electronocs of your camera will not be affected. If you are using film, however, you could be a little more cautious. Generally, x-rays are safe for film speeds up to 800 asa. For 800 and above they generally allow you to request screening by hand (though, in my experience, they do not always honor such requests). Even for film below 800 asa, however, you should try an avoid having un-processed film go through the machines several times. — Sam 14:16, 16 May 2008 (UTC) —Preceding unsigned comment added by 63.138.152.238 (talk)

Bush Stone Curlew

Hi What colour do the eyes of a bush stone curlew turn when it dies? —Preceding unsigned comment added by 121.217.227.24 (talk) 10:27, 16 May 2008 (UTC)

Exercise pill

After exercising, muscles which were flexed repeatedly, grow, of course. I believe this happens because the muscle cells reproduce. I would think this would require some chemical messengers, whether RNA, hormones, or other catalysts or proteins, to tell the muscle cells in the area to reproduce. Do we know what these chemical messengers are ? It doesn't seem to be testosterone or steroids, since increasing those levels alone doesn't cause muscles to grow, the exercise is still needed. I also suspect that the chemical messengers in question don't travel via the circulatory system, since exercising the right arm has no effect on the muscles of the left arm. Are they completely contained within the muscle cells, or do these chemicals diffuse through the cell walls to adjacent cells ? In any case, it would seem to be theoretically possible to provide those chemical messengers to the muscle cells, possibly using a modified virus to deliver them, in order ot get muscle growth without exercise. This would have several benefits:

1) Patients who are unable to exercise, due to a coma, spinal injury, etc., could maintain their muscles until healed.

2) Astronauts could maintain their muscles, which otherwise would atrophy due to weightlessness.

3) People with degenerative muscular diseases, like muscular dystrophy, could possibly be helped.

4) People too lazy to exercise could take a pill to get muscles.

So, does this sound theoretically possible ? StuRat (talk) 10:31, 16 May 2008 (UTC)

I *think* (or at least someone at the gym told me) that muscle growth occurs as a result of mechanical tearing to the muscle tissue (and the healing thereof) following exercise. I'm not sure as to how much influence chemicals have on the process, beyond those secreted as part of the body's natural healing response. Artificially stimulating cell growth sounds like a 'very bad idea' to me, considering that the heart is also a muscle (one which doesn't need, or like to be messed with) and that not all cell growth is strictly desirable. --Kurt Shaped Box (talk) 12:44, 16 May 2008 (UTC)

Agreed. Reading around in the following Skeletal muscle Sarcomere Myofibril Satellite cells Muscle contraction Muscle hypertrophy Muscle atrophy will help clarify what we know of the picture to date. Muscular dystrophy is distinct from atrophy because it affects the Sarcolemma. Muscle growth is guided by neuronal signals. They are location inherent. With a pill or virus you'd have no way of guiding the desired effect. Lisa4edit (talk) 19:14, 16 May 2008 (UTC)

And what causes the "neuronal signals" ? StuRat (talk) 23:11, 16 May 2008 (UTC)

Sorry a bit out of time right now Action potential has some info. The thing is that unless you know what causes the atrophy, just adding one of the factors that make muscles grow in a healthy system may/does not work. You can use electro-stimulation or hormones or exercise to grow muscles. (And those methods are used in your examples 1 and 2 to some degree.) But if there's some underlying disease/cause that interferes with the process you may be pouring water into a leaking bucket. 71.236.23.111 (talk) 00:37, 17 May 2008 (UTC)

Rolling

I asked this question a little while back, and when I did I suspected that the answer would be no, and that seemed to be the consensus amongst those answering. The question was whether a ball placed on a frictionless inclined plane would roll. I though that it wouldn't roll because it is the force of friction causing the torque, and so without friction there cannot be torque. However, I came across another method of dealing with the problem which has instilled some doubts. In this case, we will treat the axis of rotation not as the center of the object but as the point of contact between the inclined plane and the ball. The idea is that the ball will try to rotate about this axis, but would be unable to because of the normal force, which would redirect it to roll down the inclined plane. In this scenario, the friction force will not add torque because it is applying a force on the axis of rotation, so radius is zero. In fact, it would be gravity which causes the torque. Both methods predict the same acceleration of the ball. So, can a ball rotate on a frictionless inclined plane? —Preceding unsigned comment added by 74.15.138.130 (talk) 12:38, 16 May 2008 (UTC)

I think the answer we came up with before is correct. When you think of the ball as rotating about the point of contact that's because that point is stationary. There is no reason for it to be stationary if there is no friction to make it so. The ball can rotate if you start it rotating before you let go, but it won't actually roll (since the ball is accelerating down the slope it would need to rotate ever faster to roll, so you can't even start it rotating just the right amount for it to "roll" by coincidence - although you could if you gave it a push on a level plane). --Tango (talk) 13:45, 16 May 2008 (UTC)

If you move the origin of the coordinates to anywhere except the center of mass of the ball, you lose the nice symmetry and you should deal very carefully to make sure you have calculated all torques. The answer should be the same regardless of where you place the origin, but the natural (simplest equations) are obtained with the standard origin at the center. Nimur (talk) 15:00, 16 May 2008 (UTC)

Raise your ramp until it is vertical. The normal force is now zero since it is perpendicular to the direction of weight, and friction is zero whether the ramp is "frictionless" or not. In fact, this situation is equivalent to there being no ramp at all. But what happened to your sum of torques around the point of contact? Your logic would have the ball rotating about any point we choose on the ball (except for any point along the line between the top and bottom points). Obviously that cannot be. So what's the problem? ;-) --Prestidigitator (talk) 16:18, 16 May 2008 (UTC)

Where you set your pivot point is arbitrary. The ball does "rotate" with respect to the new pivot, but that rotation is actually a linear motion with respect to the center. Summing torques only tells you about rotation, or non-radial motion, with respect to the pivot that you select. If you want to know if the ball "rolls", you must take the pivot at the center of the ball, because that is what defines "rolling". SamuelRiv (talk) 16:51, 16 May 2008 (UTC)

Right. I may have worded my hint a little poorly, but that's the idea. Also many problems dealing with ramps and balls/cylinders assume the point of contact will remain stationary because of friction, which gives you a little more of a basis for dealing with "rolling", but only as long as the assumption holds. Of course, it is often a pretty safe assumption until the word "frictionless" is thrown in. --Prestidigitator (talk) 17:41, 16 May 2008 (UTC)

You can better imagine this with a slightly soft object like maybe a beanbag (I'm thinking of a roughly spherical cloth bag, stuffed with beans or sand or something so it's slightly 'squishy'). Place it on a ramp and if the friction is high enough, it'll roll like a ball - if the friction is not so high, it'll slide without rolling. If you have trouble imagining this, try imagining an even softer beanbag. Now, in the case of a rigid object, the rotational inertia of the object causes it to resist rolling - so if there is no frictional force to overcome that inertia - it'll just slide. In the case of the beanbag, some of the frictional force is consumed in moving the beans around to deform the bag enough to allow it to roll. Also it's not a perfect sphere, so in order to roll, the center of gravity may have to move upwards a little bit - and that takes energy too. So imagine a steel cube - it would "definitely" slide down your smooth ramp without rolling. Now imagine a dodecahedron - 12 pentagonal faces...well, it MIGHT roll - but it's not hard to imagine that it would just sit on one face and slide down a really gentle, smooth slope. Now think about an icosahedron, that's much more like a ball. But still - it has little flat, triangular faces and we could probably get it to slide down a sheet of wet ice or teflon or something. As you add more facets and make the object more and more ball-like, it seems more and more likely that it would roll instead of sliding. So if you have no problem imagining how and why my beanbag ball slides instead of rolling, or that a dodecahedron would either slide or roll depending on the amount of friction...then consider that in the real world - at the microscopic level - all balls are SLIGHTLY squishy and SLIGHTLY lumpy. In the real world, there is no such thing as a perfectly stiff, perfectly spherical ball so it's probably possible to get any ball to slide instead of rolling if you had a sufficiently low friction surface. In the case of a zero friction surface (such a thing is impossible of course) then even a perfectly stiff, perfectly spherical ball would fail to roll. In the real world, it's a contest between the friction between ball and ramp and the degree of imperfection of the ball. 66.137.234.217 (talk) 13:41, 17 May 2008 (UTC)

Eating freshly harvested grains

Generally we boil dried rice and cook food made from dried wheat flour. Are there any people who eat freshly harvested rice, wheat or rye? How do the "wet" rice and wheat taste?

I wonder if I can put fresh raw fish on freshly harvested raw rice. I may start a revolution in Japanese cuisine! -- Toytoy (talk) 12:39, 16 May 2008 (UTC)

From rice: 'Raw wild or brown rice may also be consumed by raw foodist or fruitarians if soaked and sprouted (usually 1 week to 30 days).' Algebraist 12:41, 16 May 2008 (UTC)

"Freshly harvested" would not be good for you. Grains should at least be either soaked or sprouted. Original Muesli recipes called for the grain (oat) to be soaked overnight. Grains contain many substances that make food preparation a good idea. Just a few I've come across : phytic acid Enzymes Glycosides. Prepared grain is "predigested" so the body can use the starch and nutrients inside. Also see Ruminant. --Lisa4edit (talk) 22:40, 16 May 2008 (UTC)

I dispute this logic. I don't think phytic acid or glycosides are destroyed by cooking. Enzymes would be denatured, but so what? Which enzyme would you be concerned about ingesting? What does ruminant have to do with this question? I think this is an interesting question that deserves a more complete answer. ike9898 (talk) 12:17, 17 May 2008 (UTC)

I presume she's referring to the fact that ruminants are capable of fairly fully digesting complex carbohydrates such as those found in uncooked rice and other grains (as well as cellulose of course which even cooking won't help you use much). Humans, not so much... You could try eating your shit (Cecotrope) like some rodents do, but this probably still won't work very well, plus being fairly unappealing to most people... Nil Einne (talk) 20:13, 17 May 2008 (UTC)

I somewhat doubt you'd start a revolution in Japanese cuisine. While the Japanese do some crazy stuff, most of the stuff they do eat at least tastes somewhat okay or has sometimes special about it. There is nothing special about uncooked rice. It's just hard, without much taste. You can't make sushi, or anything of that sort from it since it won't stick to itself. Raw foodists and stuff aside, there is a reason why we cook a lot of our food, and it isn't just to aide digestion or to kill harmful pathogens or to remove harmful compounds like cyanogens (ala tapioca, cashew nuts etc). It's because it often tastes better too. If you don't believe me, try actually eating some raw rice (or other grains) or raw potatoes or raw whatever you think is going to taste good Nil Einne (talk) 20:43, 17 May 2008 (UTC)

What if the Ice Age never happened?

What would the earth be like? Most importantly, how would human beings be like? --Vincebosma (talk) 13:43, 16 May 2008 (UTC)

There have been many ice ages in Earth's history. Do you want to cancel all of them, or just the most recent? Algebraist 13:48, 16 May 2008 (UTC)

cancel all of them --Vincebosma (talk) 13:48, 16 May 2008 (UTC)

(edit conflict) It's worth pointing out that there is no "the ice age", there have, in fact, been several (see ice age#Major ice ages). The first difference to spring to mind would be the lack of any U-shaped valleys. I'm not sure what differences it would have on life, but there would certainly be some - various species have been forced to migrate or evolve (or both) in order to survive an ice age, or have simply died out. --Tango (talk) 13:52, 16 May 2008 (UTC)

If you cancel all ice ages, then the history of life on earth would be radically different for at least the last few hundreds of millions of years. I doubt anything sensible can be said about what humans would be like in such a circumstance; it's not clear that there would be anything even vaguely humanlike around at all. Algebraist 14:10, 16 May 2008 (UTC)

OK, how about just cancelling the most recent one? --Vincebosma (talk) 14:24, 16 May 2008 (UTC)

Well here's one observation: Native Americans came to North American via the Bering Land Bridge created by low sea levels during the last glaciation. Remove that and North American history certainly changes. In addition, if the overkill hypothesis for the Pleistocene extinction of North American animals is correct, you'd also substantially change the distribution of animals in North America. Dragons flight (talk) 14:33, 16 May 2008 (UTC)

You'd also destroy environments created by glacial activity. For example, the entire environment of the Ozarks region of Missouri exists as the result of glacial activity. Without glaciers, the mineral deposits that were pushed southward wouldn't be on the north side of the ozarks, most of the lakes wouldn't be there, and the mountains would be more mountainy and less hilly. That would affect the wildlife that lives there. Do that on a global scale and you affect all wildlife pretty much everywhere. -- kainaw™ 15:41, 16 May 2008 (UTC)

There is steadily mounting evidence that the Bering Land Bridge migration had a much smaller influence in populating the Americas than previously believed. One of the most recent [[25]]. But since the age of sites still falls within the last glacial, the ice sheet might have helped quite a bit. Comparing [[26]] and [[27]] may be useful in seeing how the mineral deposits Kainaw mentioned help agriculture. Lisa4edit (talk) 16:48, 16 May 2008 (UTC)

Indefinite Viral Carriers

I have been reading about common contagious viruses in humans. Some are commonly transmitted through fecal contact (ie: Coxsackie A virus). Is there a classification of viruses that are indefinitely reproduced in the intestines of humans? I'm looking into reading about treatments to try and eradicate indefinite viral infections in the intestines. If the virus dies out on its own, there obviously won't be a treatment. That is why I'm interested in finding the classes of viruses that don't die out. -- kainaw™ 15:37, 16 May 2008 (UTC)

Don't all viruses replicate indefinately? Otherwise they would die out? Fribbler (talk) 16:32, 16 May 2008 (UTC)

Yes. They replicate indefinitely, but the body fights off the virus and eventually wins out, eradicating it from the body. Some viruses are not beaten - just beaten into submission. I'm interested in viruses located in the human intestines that remain there throughout life but cause contagious diseases. Specifically, I am looking for classification names to help me in searching medical publications. -- kainaw™ 17:29, 16 May 2008 (UTC)

You could search for "virus carrier" and "carrier state virus" or ("name of virus" + "chronic carrier state") - though I don't know that you'll find much involving intestinal viruses, which tend to be evanescent. Viruses that persist in the body, and so induce a carrier status, tend to infect cells elsewhere - HIV, hepatitis B & C, herpesviruses, etc. (HIV -> lymphocytes; hepatitis -> liver; HVZ -> ganglia; mumps -> conjunctiva, etc.) Unfortunately you'll get a lot of "noise" when searching, because cell cultures are also called "carriers", and you're not interested in them. - Nunh-huh 20:22, 16 May 2008 (UTC)

I know about the noise. That is why I was hoping there was some weird Latin term for "chronic carrier of an intestinal virus" that I could use to narrow down the noise. Thanks though. It is nice to know that my difficulty in finding research on this isn't "just me." -- kainaw™ 20:31, 16 May 2008 (UTC)

CO2

What is the weight ratio of CO2 released to fuel burned? LLOTAAMI (talk) 16:11, 16 May 2008 (UTC)

Depends on the fuel. DMacks (talk) 16:19, 16 May 2008 (UTC)

You get 3.7 kg of CO2 per kg of C in the fuel. A fuel like gasoline is about 85% C by mass. Dragons flight (talk) 16:22, 16 May 2008 (UTC)

(Edit conflict) I believe the best-case scenario would be complete combustion of pure hydrocarbons, which would produce a number of CO₂ molecules equal to the number of carbons in the fuel combusted. So you might want to start by trying to find out the typical composition (and probably density since we usually measure fuel in terms of volume not mass) of the fuel you are interested in. If combustion is not complete (which you can bet on) you'll get less CO₂ but lots of stuff that is worse. So in any case you should be able to come up with a decent upper-bound, best case figure. --Prestidigitator (talk) 16:40, 16 May 2008 (UTC)

Dragons flight is completely correct - and here is why: Weight of one mole of Carbon is 12 grams - weight of one mole of Oxygen is 16 grams. If combustion is complete then for every atom of carbon you started with, you end up with one atom of carbon and two atoms of oxygen. So for every mole of carbon, you added two moles of oxygen. So if you completely burn 12 grams of carbon to form CO₂ then you have 12+16+16=44 grams of CO₂ at the end. For every kilogram of carbon you burn, you end up with 44/12 = 3.7 kilograms of CO₂. In reality, complete combustion is rare - you'll always end up with some carbon monoxide and various other byproducts that depends on the nature of the fuel you started with. Since carbon monoxide is lighter than carbon dioxide, you get less weight of CO - but because it reacts to form Methane - it's a much nastier greenhouse gas. 66.137.234.217 (talk) 12:50, 17 May 2008 (UTC)

Well, Dragons flight would be correct in a perfect world. Carburetors were not perfectly stoichiometric in their burning of fuel. (Reference: Fuel injector#Supersession of carburetors) However, stoichiometric burning is not always feasible or desirable. (References: Fuel injector#Functional description, Air-fuel ratio#Synopsis) Gasoline:air ratios may range from 1:10 to 1:18. Many real fuels have additives that change the stoichiometric air-fuel ratio by as much as a few percent. (Reference: Air-fuel ratio) —Preceding unsigned comment added by Fuzzyeric (talk • contribs) 00:27, 18 May 2008 (UTC)

Effect of salt on blood ADH concentration

Why would an injection of salt solution into a vein or eating large amounts of salt result in the production of Anti diuretic hormone by the pituitary gland? I've often heard it said that salt dehydrates the body. Any help would be great. —Preceding unsigned comment added by 92.21.248.149 (talk) 16:20, 16 May 2008 (UTC)

To retain water thus attempting to maintain an osmotic balance. Less urine is produced but it is more concentrated, eliminating salt. see Vasopressin. Fribbler (talk) 16:26, 16 May 2008 (UTC)

ADH secretion is stimulated by osmoreceptors in the hypothalamus, which respond, as the name suggests, to changes in plasma osmolarity which would change if blood volume decreased/increased or sodium chloride concentration were elevated or depleted. (well the ions). Wisdom89 _{(T / ^C)} 18:15, 16 May 2008 (UTC)

Speed of Thought

I was thinking (pardon the pun) the other day, and I wondered, what is the speed of thought? How long does it take, once you have enough information, to make a decision? Are all areas of the brain involved or is there a sort of "thinking center" where this takes place? Thank you. Jen17op (talk) 16:24, 16 May 2008 (UTC)

There are whole branches of science devoted to studying such things. Have you tried starting at the thought article? I'm sure there are lots of artificial intelligence related articles that will provide useful information as well. --Prestidigitator (talk) 16:47, 16 May 2008 (UTC)

I haven't read it (yet), but I would expect that Malcolm Gladwell's recent book Blink would be relevant to your question. -- Coneslayer (talk) 16:51, 16 May 2008 (UTC)

Another way to go is start at Brain and have a look at Electroencephalography Functional magnetic resonance imaging Neuron. Don't have the time now to dig up pages, but there have been quite a number of studies correlating increased brain activity in certain areas to corresponding induced thoughts. Having a scout around in the science magazine archives should get you some more information. Lisa4edit (talk) 17:17, 16 May 2008 (UTC)

It can take days or even years to make a decision even after the brain is in posession of all the information needed. Or it can take as little as 300 milliseconds if a simple decision must be made and a response given, including time for the stimulus to go from the ear or eye to the brain and the response to cause a physical movement, as when you must press one of two buttons depending on which of two tones you hear. A simple reaction time can be much shorter, if no decision is required (as when you know to press a button when a buzzer sounds). Edison (talk) 22:19, 16 May 2008 (UTC)

Surely it would be the same as the speed of electricity, although it would be slower when going accross synapses? --h2g2bob (talk) 22:53, 16 May 2008 (UTC)

200ft/second Ziggy Sawdust 23:21, 16 May 2008 (UTC)

It is way slower than the speed of electricity, which is like the speed of light. Nerve impulses travel by a chemical process along nerve fibers and across synapses. The decision part is what can be time consuming. Edison (talk) 03:38, 17 May 2008 (UTC)

The problem is that the speed of transmission from one neuron to another is not a measure of the time it takes to form a thought. The brain is a massively parallel computing machine and many parts are working on the problem at the same time. Most disturbing to me is that there have been some fairly robust studies showing that our conscious mind isn't really what's doing the work. Thoughts and even decision making happens at an entirely subconscious level and all that our conscious mind does is to retroactively justify those results. But certainly the speed of nerve impulses is positively sluggish compared to the speed of light and the speed of electricity. Studies that measure 'reaction time' are not really measuring the time it takes to make a decision because you've already decided that when the buzzer sounds or the light flashes, you're going to press the button. What those experiments measure is the time to ACT on a decision you've already made. Even something like the time it takes for you to stand on the brakes of your car if a kid runs out in front of you is only the time to act on something you already decided on. The fastest reactions of all (eg pulling your hand away when you touch something hot) don't even go as far as the brain. There is enough processing power in the spinal cord to deal with those kinds of low level emergency. The message that you touched something hot and moved your hand away does eventually reach the brain - and your conscious mind then carefully 'edits' your train of thought to make you THINK that you made the decision at a conscious level. 66.137.234.217 (talk) 13:19, 17 May 2008 (UTC)

I distinguished between simple reaction time, such as you describe, where the decision of what action to take is already made, and choice reaction time, where a decision has to be made before the response is initiated. The decision could be red versus green versus yellow light, word versus nonword, animal versus non-animal picture, match versus nonmatch of multiple stimuli, target list versus nontarget item, etc. Physiologist F.C. Donders in the 1860's introduced the method of subtracting simple reaction time from choice reaction time to determine the time required for the decision to be made. Much research was done in the 1960's and since along these lines, although a simple subtractive method has largely been discredited. As for there being physiological processes operating below and in advance of your mental life, I tend to agree. It is common to start, then realize it is because someone in a crowd spoke your name. Edison (talk) 19:44, 17 May 2008 (UTC)

I don't tend to have that problem (but I don't have people calling me in crowds much) but I do have the problem when I asked 'what?' or something of that sort then a few seconds later realise I actually understand what that person said... Nil Einne (talk) 20:03, 17 May 2008 (UTC)

Would the conscious mind perform said edit if one is fully aware of the process you describe? Zain Ebrahim (talk) 15:38, 17 May 2008 (UTC)

biology

what are prions??? what are the possible mechanisms through which they cause diseases??and what are the current techniques being employed to understand them and cure them??? —Preceding unsigned comment added by 220.226.30.96 (talk) 18:18, 16 May 2008 (UTC)

Have you read prion? --Tango (talk) 18:21, 16 May 2008 (UTC)

Prions are malformed/misfolded proteins (that you can ingest say from meat) that have the capability of inducing the misfolding of other crucial native proteins important in the brain. This leads to aggregation of the proteins and eventually plaques. Extremely long incubation time. That's it in a nutshell. Wisdom89 _{(T / ^C)} 18:32, 16 May 2008 (UTC)

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt to solve the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Thank you. -mattbuck (Talk) 19:09, 16 May 2008 (UTC)

Prions are similar to viruses. Prions are rampant proteins that make other proteins rampant. Mac Davis (talk) 22:09, 17 May 2008 (UTC)

They're like zombie proteins! --Bmk (talk) 02:48, 18 May 2008 (UTC)

Twaron subject to UV degradation?

I was reading the Kevlar article, and link hopped to the Twaron article, and I was wondering if Twaron shares Kevlar's vulnerability to UV radiation. Aradraugfea (talk) 22:44, 16 May 2008 (UTC)

Sailcloth#Twaron should answer your question pretty well :) Regards, CycloneNimrod^Talk? 22:54, 16 May 2008 (UTC)

That it did. Thank you very much. Aradraugfea (talk) 23:09, 16 May 2008 (UTC)

May 17

fossil fuel

How is coal and oil formed and what is the difference —Preceding unsigned comment added by 203.102.161.75 (talk) 00:45, 17 May 2008 (UTC)

I suggest you look at the articles on fossil fuel, oil and coal. -mattbuck (Talk) 01:02, 17 May 2008 (UTC)

When researching oil as a fossil fuel, our article on petroleum may be more useful in this context. 128.12.130.41 Nimur (talk) 23:57, 17 May 2008 (UTC)

DNA in multiregional model of human origins

As a layman, I don't understand how any species can emerge in more than one place or zone of places. My question is: under the multiregional model, how did genetic mutations become dominant traits in many different places, leading to speciation at different times and places? Are they suggesting that proto-members of the antecedent species had dormant DNA mutations, which in many different places and times became more successful because of similar environmental pressures? And that after the dormant DNA carried by the antecedent species spread out, it eventually flowered in different places in the same way? While still enabling successful breeding between members of the different groups constituting the new species, when eventually the geographically diverse people crossed paths again?

I guess the broader question is simply: Can any species emerge at different times and in widely-spaced locations? —Preceding unsigned comment added by 4.182.36.205 (talk) 04:59, 17 May 2008 (UTC)

Have you read Multiregional origin of modern humans? That details some of the different proposed mechanisms behind the multi-region hypotheses. Note that DNA isn't "dormant" per se, but genetic differences may not provide selective advantages until they "come into contact" the the right environment. If two geographically separated populations have the same source mutations and are exposed to a similar environment, they may Convergently evolve certain characteristics, but not all (since genetic mutation is an essentially random even). Its proposed that this happened to hominid species, who eventually met again to create the hybrid-origin of modern humans. Rockpocket 07:32, 17 May 2008 (UTC)

TY for this.

yes, I've read the source you refer to. Multiregional origin of modern humans

you wrote: "DNA isn't "dormant" per se, but genetic differences may not provide selective advantages until they "come into contact" the the right environment."

I meant to imply that point, in my badly written question. (i.e., I understand that.)

I'll read "convergent evolution."

It still seems like special pleading to me. —Preceding unsigned comment added by 4.182.36.205 (talk) 07:52, 17 May 2008 (UTC)

Convergent evolution, as I read it, refers to traits, not species -- of course, highly similar traits may evolve in widely divergent places and times ... but different species? I don't see how it makes sense. —Preceding unsigned comment added by 4.182.36.205 (talk) 07:56, 17 May 2008 (UTC)

and, WADR (with all due respect!), the article titled "hybrid-origin" is ridiculous and based on the fanciful notions of one S. Gooch, supported by no evidence ... —Preceding unsigned comment added by 4.182.36.205 (talk) 08:57, 17 May 2008 (UTC)

How Geology & Materail Science are related?

Other than Crystallography, How Geology pictures in in Material science?59.95.69.97 (talk) 09:35, 17 May 2008 (UTC)

Also bulk properties of rocks or the crust can be addressed with material science concepts. On the applications side, many materials are derived from geological sources, such as quarrying, or mining followed by refining or smelting. Primary metallurgy studies this. Graeme Bartlett (talk) 12:09, 17 May 2008 (UTC)

Television screens

Is there some medical disadvantage in watching an old tv (with cathode ray tube) as compared with a new flat screen tv? MilkFloat 09:48, 17 May 2008 (UTC)

Our article lists a few (fairly minor) health concerns related to CRT displays. LCD doesn't cover health, unfortunately, and I can't speak for that. Algebraist 12:50, 17 May 2008 (UTC)

The short answer is "No". There are no significant electromagnetic emissions from LCD flat panels (apart from the heat and light they emit of course!) - but I'm not so sure about plasma displays. Certainly any effects are going to be exceedingly minor. There are measurable radiation outputs from CRT's - but if there were measurable health risks from CRT's, we'd know about it. Studies of people who use CRT's a lot in their jobs have shown health problems - but they mostly relate to posture and keyboard use - not from the displays themselves. Perhaps the most concern would be related to eyesight and eye-strain and that would depend on the relative sharpness and contrast ratio of the displays - on which grounds a good CRT might actually be better than a flatpanel display - but even that is pretty negligable. 66.137.234.217 (talk) 13:07, 17 May 2008 (UTC)

Furthermore, the OP is asking about TVs and not computer monitors. At normal TV viewing distances, the already minor hazards of CRTs become negligible. --Heron (talk) 13:23, 17 May 2008 (UTC)

Indeed - when you double the distance from something that's emitting any kind of radiation - you reduce the amount that reaches you by a factor of four - so if there is no problem with CRT's when you are sitting with your head a foot away from the screen then at ten feet, there is a hundred times less risk - so as negligable as the risk of sitting in front of a computer screen for 8 to 10 hours a day is, the risk for watching TV for less time at longer distances is VASTLY less. 66.137.234.217 (talk) 13:47, 17 May 2008 (UTC)

Photosensitive epilepsy would be less likely with an LCD display. But it is rather rare to begin with. Lisa4edit (talk) 05:37, 18 May 2008 (UTC)

Forest

How is forest a habitat?117.99.32.175 (talk) 10:29, 17 May 2008 (UTC)

I find it good to first make sure I understand the words being used. Our article, you guessed it, "Habitat" calls it "an ecological or environmental area that is inhabited by a particular species. It is the natural environment in which an organism lives, or the physical environment that surrounds (influences and is utilized by) a species population." What a bunch of crap. How are we supposed to understand all that jargon? What, pray, is a "species population"? In what universe does "surround" mean "influence and be utilized by"? Is "ecological area" a sensible juxtaposition of words at all? It gets worse, too, as the article continues, but I'll spare us that.

I suppose we'll have to resort to the ordinary meanings of the words involved and hope for the best. Forest can be a habitat for arboreal animals, who are specially adapted for life in the trees and can't get their food or evade their predators or nest away from them. Many epiphytic plants need trees to cling to. The trees themselves live in a forest habitat, I suppose. --Milkbreath (talk) 12:07, 17 May 2008 (UTC)

If the Habitat article is too complicated by jargon, consider reading Habitat Article at the Simple English Wikipedia. Nimur (talk) 23:59, 17 May 2008 (UTC)

Distribution restriction

In the first reference sited by the article on spinosad there is the following statement "DO NOT DISTRIBUTE THIS TECHNICAL BULLETIN IN THE STATE OF NEW YORK." What is the reason behind this statement? 71.100.14.205 (talk) 14:58, 17 May 2008 (UTC)

That is really odd! I'd say it's a matter of law in New York State. Perhaps the legal eagles at the humanities desk could help? I for one would really like to know. Fribbler (talk) 20:26, 17 May 2008 (UTC)

That is a bit strange - I checked, and spinosad is listed as a permitted pesticide by the NYS Dept of Environmental Conservation (here's the document (warning - large PDF). -Bmk (talk) 00:22, 18 May 2008 (UTC)

how to determine the rate of reaction of haloalkanes?

how to find the rate of substitution of different haloalkanes?? —Preceding unsigned comment added by Danielezzat9654437047 (talk • contribs) 18:02, 17 May 2008 (UTC)

Please read the notice at the top, we will not do your homework for you. Regards, CycloneNimrod^Talk? 19:18, 17 May 2008 (UTC)

The article on haloalkane has some information. If you don't have a text of some kind to look in, try google or Wikibooks. --Bmk (talk) 19:41, 17 May 2008 (UTC)

it's not my homework!!!! i have three samples and all i know about them is that they are haloalkenes!!!! how can i differentiate between them???? I've thought of adding sodium hydroxide but the problem is they all turn to alcohols i need a way to differentiate between them!!! —Preceding unsigned comment added by Danielezzat9654437047 (talk • contribs) 20:45, 17 May 2008 (UTC)

I assume you've read and understood the information at haloalkanes. So, ... What measurement equipment is available to you? Can you measure any of: density, heat capacity, molecular weight, boiling point, hygroscopicity, index of refraction, dissolution limits of other halo-compounds, melting point? Can you identify any gas that may be evolved or any solid that may be precipitated during your NaOH experiment (which may suggest which halide has been substituted)? Can you measure diffusion (or effusion) rates of the gases? Can you perform a chromatography differentiation between your samples? Can you run your samples through a mass spec to limit the range of potential candidates? Are your samples flammable (suggests incomplete halide substitution)? How much oxygen is consumed/mass lost during burning (suggests unsubstituted fraction)? What gases are evolved during burning (may indicate which halide(s) is/are substituted)? What gases are evolved under oxygen-poor conditions and aggressive heating (may suggest unsubstituted fragments in the original molecules)? Have you attempted a fractionation (to determine whether your samples are single components or mixtures? Et c. ... -- Fuzzyeric (talk) 00:09, 18 May 2008 (UTC)

I need an experiment based on the isomeric halogenoalkanes with the formula C4H9BR reacting with water!!!! Plus i don't have any of this stuff, i can't perform a chromatography and i don't have any of the measurement equipment you just mentioned.When haloalkanes react with NaOH they release halides which are easy to identify if passed through silver nitrate. But i need to identify whether the haloalkane is primary, secondary or tertiary. And i think the only way to do so is by measuring the rate of the substitution of the halide. (There is no need to attempt a fractionation my samples are single components).Danielezzat9654437047 (talk) 03:29, 18 May 2008 (UTC)

Hydration in chemistry

What's it called when a bunch of water molecules gather round an entity as in MgCl₂*6H₂. We did something about it in A level chemistry but I guess those brain-cells haven't seen lot of use since. ----Seans Potato Business 18:56, 17 May 2008 (UTC)

Water of hydration? --Bowlhover (talk) 19:16, 17 May 2008 (UTC)

When it's a salt like that, it's referred to as a Hydrate. Wisdom89 _{(T / ^C)} 00:29, 18 May 2008 (UTC)

A well defined demographic barycenter

Hello,

sorry if this belongs in Humanities or Mathematics. One sometimes reads about "the demographic barycenter". It is used to denote where most people live in a certain region or state. But is this well defined? Has someone ever tried it?

My definition would be : make a vector (from the center of the earth ) pointing at an individual, add them all up and divide by the number of people in the region you want to consider.(note that we would be also taking into account some differences in height). Or would this not be suitable?

Has someone ever used a definition like this? Are there articles/websites/books actually providings maps to illustrate where the "demographic barycenter" is?

Many thanks,

Evilbu (talk) 19:13, 17 May 2008 (UTC)

Well, it's hard to say if it is a useful measure unless you know what you want to use it for. The definition you describe will indeed give you the demographic barycenter (or population barycenter, as I think it's more often called). Note that for regions that are large enough to have dimensions comparable to the earth's radius, that definition of barycenter will usually land you far underground; for instance if you do it for the entire planet, you will get a location deep inside the earth - that doesn't seem particularly informative to me. Of course, you can sidestep that issue by projecting the barycenter point radially onto the surface. --Bmk (talk) 19:23, 17 May 2008 (UTC)

May 18

Toyota Truck Ad off Cliff

In the Toyota Advertisement (http://youtube.com/watch?v=6HzegzpTSDI&feature=related ) where the Toyota truck pulls a cargo container up the side of a quarry, would it be possible, if the quarry was deep enough, and you were wearing a parachute, and the window was open, to, if the truck was pulled over the edge by the container: As the truck is falling, would I be able to escape through the window, push off the truck far enough to open the chute, and then survive? —Preceding unsigned comment added by 140.180.14.157 (talk) 00:30, 18 May 2008 (UTC)

If the quarry was deep enough, sure, why not. I'm not quite sure what "deep enough" would mean in this instance. I don't even know how low you could be and still make a parachute jump that would leave you alive and mostly unbroken, but at least one source indicates that the lowest parachute jump in history would be 29 meters. That's not a whole lot; it's the kind of a drop you might actually find in a quarry without looking too hard. But, of course, you would need the time to open the window (or wriggle your way through it -- or just open the door, which might be easier and faster), get in position to firmly push off and then yank that rip cord to open your parachute.

So. If we assume that you're absolutely ready to dive out, are already wearing the parachute and don't need to bother with taking off your seatbelt or anything of the sort, I would assume that it would take at least five seconds for you to get free of the truck, even if you had trained at that maneuver and got lucky with it or posses some kind of Jackie Chan-like qualities that enable you to do exit falling cars through side windows like it ain't no thang. For the sake of argument, let's say that you have and you do, and that you can pull that off even while you're in free fall.

Knowing, as we do, that ignoring air resistance, the speed of an object falling freely near the Earth's surface increases by about 9.8 meters per second every second. Because I'm lazy and absolutely can't be bothered to do the math, I do what all of us lazy bastards do and use the internet: apparently, in order to get about 5 seconds of free fall (which the ABSOLUTELY TRUE FACTS at my disposal have revealed to be the time you would need to kick free of the truck), you need to fall for about 125 meters. That in itself wouldn't be enough, though, because you would still need those 29 meters for the parachuting part. So... yes, provided that the quarry was 149 meters deep, you didn't waste any time getting out of the truck and popping the parachute, and didn't somehow screw it up, you could do it. Come to think of it, you would probably even have a little bit of extra time there, actually, since we're just ignoring air resistance here. It's not much, but hey, at this point, you'll want all the help you can get. You think you might need an extra second to get out of the truck? That'd be another 55 meters of free fall you need, then; that acceleration really is a bitch.

Personally, though, if I was in that position, I'd prefer to give myself a little more margin for error. Like, you know, a couple of kilometers. -- Captain Disdain (talk) 01:37, 18 May 2008 (UTC)

...also, I'm a little stupid, because I now notice that the 29 meter record is actually a BASE jump. That means that there's not a lot of acceleration before the jumper pops his chute. In this scenario, though, you would already have been falling for at least five seconds, which means the parachute would need more than the 29 meters to slow you down to keep you from breaking your legs or getting killed. Still, y'know, if the quarry was deep enough, sure, you could do it. -- Captain Disdain (talk) 01:41, 18 May 2008 (UTC)

Don't mean to be cynical here, but you could just turn the camera to vertical and walk away, Julia Rossi (talk) 10:15, 18 May 2008 (UTC)

Do I just suck?

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

We can't really offer you advice about your symptoms, including offering a possible diagnosis or prognosis for your condition. If you are concerned about your health, you should speak to an appropriate professional. TenOfAllTrades(talk) 01:01, 18 May 2008 (UTC)

Possible Fuel Alternatives

http://www.runyourcarwithwater.com

DISCUSS. Namely, discuss whether or not this is possible, or if it's nothing more than a scam.

216.178.50.4 (talk) 01:33, 18 May 2008 (UTC)

No, it's crap. The hint is the mention of 'HHO gas'—some nonsense espoused by noted crank Ruggero Santilli. Note that it also fails the 'too good to be true' test. TenOfAllTrades(talk) 01:43, 18 May 2008 (UTC)

Took me 3 seconds to call the scam. Apart from everything else wrong with it, the question is if its that easy, why isn't everyone doing it? It would solve the worlds energy problems. Luxosus (talk) 01:51, 18 May 2008 (UTC)

It's possible, but it's still a scam. You require more electricity to split water into oxygen and hydrogen that you'd get more power out of the battery converted to motion if you used the battery to run the car directly. --Wirbelwindヴィルヴェルヴィント (talk) 02:03, 18 May 2008 (UTC)

Basically, a solely water-fueled car would be possible in a frictionless, lossless universe - but that's just silly. If the fuel starts out as water and ends up as water, no energy has been extracted, so you can't give the car any energy to accelerate or counteract drag. This sounds like a repeat of Stanley Meyer's water fuel cell. In fact, how are these guys even aloud to do this, in lieu of the precedent set by the court case against Stanley Meyer? --Bmk (talk) 02:48, 18 May 2008 (UTC)

Actually, I didn't really look at it carefully - I guess this is different - they're claiming to have a gas-water "hybrid" engine. They don't say how it might work, so I guess it's hard to comment about its validity. --Bmk (talk) 03:04, 18 May 2008 (UTC)

See also: Water-fuelled car. --Heron (talk) 09:59, 18 May 2008 (UTC)

Just thought, this would be the same (actually theoretically worse) than running a electric car directly from the battery used in a normal car wouldn't it? Luxosus (talk) 12:55, 18 May 2008 (UTC)

Weight of the Universe

• 1) Was is the estimated weight of all the known and unknown universe, including all real and virtual matter and energy ?

• 2) What would the universe weigh if it was filled with milk or tomato soup ?

69.157.239.231 (talk) 13:01, 18 May 2008 (UTC)

Magnetism

How does a magnetic field exert a force? My thinking is it must be from an exchange of particles, similar to gravity and gravitons, however I've never heard of such a particle/theory. Luxosus (talk) 13:02, 18 May 2008 (UTC)

Photons transmit the electromagnetic force.--Shniken1 (talk) 13:14, 18 May 2008 (UTC)