Wikipedia:Reference desk/Archives/Science/2010 August 18

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August 18

Blood arc?

Hi,

While shaving over a stopped porcelain sink, i accidentally nicked myself. A few drops fell into the water and I noticed that around the edge where the water met the porcelain, the blood appeared to arc (picture a solar-flare) up the wall on the sink then back down. Is this some form of diffusion? What is this phenomenon called? TIA PrinzPH (talk) 00:52, 18 August 2010 (UTC)

A guess: The drop of blood landed on the edge of the sink, and the edge of the drop left a half circle of blood. The rest of the droplet hit the water and caused the water to splash back up (have you ever seen that in slow motion?) and that water washed some of the blood, leaving the arc. Ariel. (talk) 02:22, 18 August 2010 (UTC)

I'm not a shill, but a modern razer (think of the brand name yourself) wouldn't cut you like that (unless you use the same one for six months or something). 92.230.233.158 (talk) 08:38, 18 August 2010 (UTC)

Oh yes it would. The new ones give you the worst cuts, too, if you're not careful. --Dr Dima (talk) 09:01, 18 August 2010 (UTC)

@Ariel - I distinctly recall the drop(s) landing in the water, in fact the only thing which got me interested about the occurrence was that I saw the 'blood' arc slowly. It took roughly 2 secs to complete a ~1.5 inch arc (from the waterline to the peak of the arc). And as I recall, it wasnt like the 'whole blood', just some particles (could it possible be just the red blood cells?). Maybe it has something to do with the water in the sink having soap while the walls of the sink not having as much? An no, I don't think I was hallucinating... I hope not :P PrinzPH (talk) 20:43, 19 August 2010 (UTC)

Here is a possibility. Take a washable marker and make a strong dot on a paper napkin, then release a drop of water in the middle of the dot. The colors of the ink will spread out and make circles of different colors (you can also try a regular pen and alcohol). Perhaps the blood did the same thing? Ariel. (talk) 01:34, 22 August 2010 (UTC)

Origin of "Global Health"

I'm looking for info on the origins of the term "global health". To my understanding, this is a relatively new term meaning public health on a global scale; i.e. accounting for the threat posed by pandemics, mass migration, climate change, etc. Any idea where the term was first used and what public health/philosophical agenda is behind it? --Whoosit (talk) 03:18, 18 August 2010 (UTC)

This article provides some context, including a statement in the second paragraph of the introduction regarding its origins in the 1970s, and then citing a relevant article on "Global Health" and the WHO (PMID 16322464). The latter, in full text here, provides data and speculation directly addressing your questions (it's a complex issue and the article is freely available, so I won't try to summarize here). -- Scray (talk) 12:15, 18 August 2010 (UTC)

Might this be related to the concept of Gaia's health? ~AH1^(TCU) 13:37, 18 August 2010 (UTC)

Thanks both. That article is a good start. Astro, I think global health is more of a gloabalist extension of public health, i.e. concern for welfare of human populations (which implies human populations are the source/origin of human diseases), where the Gaia health notion is one of ecology and systems biology, i.e. concern for the welfare of the biosphere as a whole and how this affects human populations (which implies an unhealthy environment is the source/origin of disease) --Whoosit (talk) 14:51, 18 August 2010 (UTC)

To give an example, the Global Health Council was named "National Council of International Health" until 1998.[1] Surprising that it took them so long to change a name like that. Wnt (talk) 16:41, 18 August 2010 (UTC)

How does an Epipen helping with an allergic reaction?

How does shooting epinephrine help someone who is allergic to bees and gets stung by one? Does the person still need to see an emergency room after using an Epipen? Thanks! —Preceding unsigned comment added by 76.169.33.234 (talk) 05:57, 18 August 2010 (UTC)

According to Anaphylaxis#Management, epinephrine (aka Adrenaline) is the standard treatment for anaphylactic shock for any allergic reaction, not just bee stings. Since the things about anaphylaxis that can kill you (mainly airway restriction and loss of blood pressure) are directly combated by epinephrine (mainly by opening airways and raising heart rate and blood pressure), its a logical and consistant treatment. To answer your second question, ABSOLUTELY, if anyone has a severe alergic reaction to anything, they should immediately be seen by a medical professional. Epipen is basically designed to combat the immediate, life-threatening aspects of anaphylaxis, but in no way does this mean that the danger has dissapeared or dissipated. --Jayron32 06:04, 18 August 2010 (UTC)

Also, people often carry more than one epipen because the first isn't always enough. If one doesn't always work, there is no reason to think that two will always work. You should always call an ambulance for anyone showing signs of anaphylactic shock. --Tango (talk) 07:09, 18 August 2010 (UTC)

Hell, even if it works the absolute best it can, you still need urgent medical attention. The epipen, like CPR, is just a way of (hopefully) surviving until medical help arrives. 86.164.66.83 (talk) 10:42, 18 August 2010 (UTC)

In many places the epinephrine pen injector requires a prescription; in that situation, the user should follow whatever instructions they were given by the prescribing provider and on the package (rather than ones provided anonymously here on Wikipedia, for example). -- Scray (talk) 12:08, 18 August 2010 (UTC)

Some of the above is straying toward the sort of "medical advice" that Wikipedia editors aren't trusted to give and readers shouldn't count on; but to get back to the question, the reason is that adrenaline (= epinephrine) in the EpiPen is a simple catecholamine hormone that has evolved as part of the fight-or-flight response, which puts top emphasis on maximizing heart and lung function for crisis situations. It's one of the major products of the adrenal glands, two little "epipens" nearly everyone carries. (If you can pay attention when something scares you, I think you can actually feel the adrenals inject their product into your bloodstream, but I might be misattributing the sensation) I think that this means that anaphylactic shock is not one of those situations where the only thing to fear is fear itself, and the victim needs to be calmed with gentle words and reassured that help is coming - rather, the hormones that come with the fear should be a lifeline. But I didn't quickly find a good source for this; here's one perspective about the idea. [2] Wnt (talk) 14:51, 18 August 2010 (UTC)

Whoa whoa whoa! Beware of that article. Not only is it written with a few weird points of confusion, that suggest a layperson trying to summarise things they've read and didn't completely understand, but the bit at the end about fear isn't actually talking about what you were talking about. The end of the article is talking about conquering your fear that you will have a reaction and go into shock so that you can actually take action to avoid the allergen and prepare for if you have a reaction. It acknowledges that some level of fear is rational and necessary to motivate yourself to act appropriately. It is not about conquering or using fear once you have gone into shock. Frankly, if you're going into anaphylactic shock, you probably don't have time to decide what level of fear is appropriate or helpful.

If you have an epipen or similar, you can consult the pamphlet that came with it, your chemist (at least in the UK), and your doctor. There are also various organisations which try to provide accurate and up-to-date information based on medical concensus. An example in the UK would be the NHS or the Anaphylaxis Campaign. 86.164.66.83 (talk) 22:11, 18 August 2010 (UTC)

Voyager 2 propulsion

What kind of propulsion used by Voyager 2? And is it the same propulsion used by Voyager 1, Pioneer 10, and Pioneer 11? How they avoid space debris or asteroids in their way? Do they have wings to steer it? Is it controlled by man or done automatically? What frequency they used for communication? Thanks... roscoe_x (talk) 06:10, 18 August 2010 (UTC)

According to Voyager 2, it is identical to Voyager 1. According to Voyager 1, the probe uses Gravity assist as its main means of propulsion. Voyager Program#Power discusses other power systems on the craft. --Jayron32 06:19, 18 August 2010 (UTC)

As for debris and asteroids, I'm going to make an educated guess that they simply don't need to. Outside of low Earth orbit, the density of space debris is very very small. The dense asteroid fields imagined in Star Wars and countless other movies and video games don't exist. Someguy1221 (talk) 06:25, 18 August 2010 (UTC)

Yeah, there's almost nothing in space. I seem to recall that sometimes spacecraft going through the asteroid belt will have their courses adjusted in order to make them fly by an asteroid close enough to take a picture. Paul (Stansifer) 12:46, 18 August 2010 (UTC)

I think the original poster is imagining that these spacecraft are being continuously propelled, like some science-fiction ones. That is wrong. They were launched by rockets originally, and they carry small rockets that were used to refine their course to reach the relevant planets. But for the most part, and probably all the time since their last planetary encounters, they are just moving in free fall. --Anonymous, 23:41 UTC, August 18, 2010.

Also note that wings don't do anything in space. Wings need air to be functional. - Akamad (talk) 13:44, 18 August 2010 (UTC)

NASA Jet Propulsion Laboratory's official Voyager webpage has technical information. The high-gain antenna received S-band uplink and transmitted X-band downlink. The S-band also participated in the Radio Science Experiment, in which the communication-data radio-signal was analyzed. The RSS website explains the spacecraft radios pretty thoroughly: S-band receiver (2115 MHz nominal frequency) and transmitters at both S-band (2295 MHz nominal) and X-band (8415 MHz nominal). Exact frequency (as received at Earth) was measured to 1/1000th of a Hz and varied with spacecraft/earth relative velocity and plasma-properties in the interplanetary space. As you may recall (those of you who closely followed the Voyager mission sequence - I wasn't quite alive yet) - there was a malfunction in the transmitter on one of the spacecraft in the early 1980s, and it was only by carefully loading new software code into an image-processing computer that the redundant transponder was made to work (I have a whole book on this, I can post more when I get home). Nimur (talk) 18:10, 18 August 2010 (UTC)

I think that the reference to a transmitter failure here may possibly be an erroneous recollection of the Galileo spacecraft rather than one of the Pioneers or Voyagers. Galileo's main antenna, which was stored compactly inside the spacecraft during launch, failed to open properly and they had to use a secondary antenna with a much lower data rate, and I remember they did some special programming to partially overcome that limitation. --Anonymous, 21:15 UTC, August 18, 2010.

There was definitely a PLL failure on Voyager 2. Here's a JPL progress-report that discusses the failure, and workarounds to keep the RSS experiment alive. This transponder failure was also described in Flyby by Joel Davis. Nimur (talk) 00:01, 19 August 2010 (UTC)

Thanks for the correction. --Anon, 16:31 UTC, August 20, 2010.

No real propulsion was on board. For corrections 90kg of hydrazine monopropelant was on board. 16 0.89 Newton and 4 22.2 Newton rocket motors are on board, which used nearly 60 kg of the fuel till 2000.--Stone (talk) 18:43, 18 August 2010 (UTC)

All four space crafts used a very similar propulsion system.--Stone (talk) 18:47, 18 August 2010 (UTC)

the role of condensed milk in the imbibement of coffee?

What is the role, chemically, olfactorily/gustatorily, of the supplementation of condensed milk in the imbibement of coffee process? —Preceding unsigned comment added by 92.230.233.158 (talk) 08:35, 18 August 2010 (UTC)

Adding condensed milk to coffee is said[3] to soften the taste. Wikipedia has articles about Condensed milk and Coffee. Condensed milk has advantages over ordinary milk of indefinite storage life, and less cooling effect on one's hot coffee than adding cold milk. Cuddlyable3 (talk) 10:02, 18 August 2010 (UTC)

I don't think it's a scientific matter, but condensed milk usually includes sugar, and logically it requires less dilution of the coffee (or more in the cup to start with) for the same amount of milk components added. Wnt (talk) 16:48, 18 August 2010 (UTC)

What is the primary purpose of the compression stage in a jet engine?

What is the primary purpose of the compression stage in a jet engine? I can understand the need for compression at high altitude, where the air is thin, but I suspect that it is not the primary reason for having a compression stage. Is there a reason why a jet engine won't work without compression even at low altitude? --173.49.11.120 (talk) 12:12, 18 August 2010 (UTC)

The Turbojet article is a great resource on this, and it has a section on the compressor. Simplistically, I think it's accurate to describe the jet engine as a continuous-flow combustion engine, such that there is no structural barrier to flow in either direction (fore or aft). As a result, the combustion chamber must be preceded by a high-pressure (compression) chamber to drive the combustion products rearward; otherwise, the jet wouldn't eject rearward and provide forward thrust. -- Scray (talk) 12:51, 18 August 2010 (UTC)

The compressoion stage pumps air into the engine to mix with fuel and burn, it also gives the air more energy by heating it up and putting it under greater preasure before being burnt with fuel. Without it the engine would not be able to funtcion at low speed, and would need help reaching a high enough speed so the high speed flow of air into the engine would compress the air itself. This is why ramjets and scramjets require another engine to bring them up to a supersonic speed before they can opperate. If you were to try to start a stationary ramjet or scramjet, you wouldn't get any thrust because they have no means of compressing the air, and the exaust gasses would simply exit out the front and the back of the engine providing no net thrust. In other words, the compressor pumps air into the engine that the engine needs to run and produce thrust out of the nozzle at the end of the engine, you can get rid of the compressor to make the engine simpler and opperate at higher temperatures, but then you need some other engine (conventional turbojet, turbofan, or rocket) to get that engine to the speed (several mach) that it needs for the air to compress itself with out the aid for a compressor.--74.67.89.61 (talk) 15:54, 18 August 2010 (UTC)

See Overall pressure ratio and Brayton cycle. The amount of thrust produced by a jet engine when compared with the rate of flow of fuel into the engine is the engine's thermal efficiency. A high thermal efficiency requires a high overall pressure ratio. If there was no compression of the air going into the combustion chambers the thermal efficiency would be so low the engine would produce little or no thrust, even though it was burning fuel. The same is true of the reciprocating engine in a conventional motor vehicle. Dolphin (t) 23:21, 18 August 2010 (UTC)

It's the same as the reason you'd put a turbocharger (or a supercharger) onto a car engine. The amount of fuel you can burn (and therefore the amount of energy you can extract) is limited by the amount of oxygen in the air. When the oxygen is all used up, combustion stops and no more fuel can be burned. The only way to get more air into the engine is to make the engine bigger or to compress the air to make it more dense. Since there is a limit to how big you can make a practical airplane engine, compressing the air is the only viable approach to getting more power. That's why you can get the same amount of peak horsepower from a 1.6 liter turbocharged car engine as from a 2 liter engine without a turbo. The air compression stage in a jet engine is powered by the outgoing exhaust gasses spinning fan blades at the back of the engine - which also parallels the way the turbocharger in a car is powered by diverting the exhaust gasses through a turbine. SteveBaker (talk) 02:43, 19 August 2010 (UTC)

Life extension versus curing diseases one by one

I have found out just recently, to my amazement, that old age is not a cause of death (in humans), even beyond the age of 100^[4]. At advanced ages it becomes very probable that in some important place the blood will either become solid when it should remain liquid (thromboembolism, infarction) or stay liquid when it should turn solid (ruptured aneurysm, haemorrhage, etc.) i.e. the leading cause of death at advanced ages is "failure of the blood to be in the correct phase of matter", rather than "old age", and if that doesn't finish you off, cancer or an infection likely will. So, purely hypothetically of course, if we cure the diseases of old age and create "smart blood", and subsequently live to 160, is that "life extension"? Why do so many people think "life extension" is unethical but yet trying to treat, prevent, and cure the common diseases of old age one by one is not? 129.2.46.178 (talk) 13:21, 18 August 2010 (UTC)Nightvid

Well, dying from 'old age' is sort of an all-encompassing term, referring to a multitude of things in your body that can go wrong as a result of it. I think the answer of your question (a very good one, by the way) has to do with the way we perceive the concept of 'life extension'. If one does manufacture 'smart blood', that's going to cure a multitude of ailments. If one cures a single disease, many others will still die of other problems. However, if you cure a multitude, you start noticing the life expectancy go up. Life extension is more of a term used to describe extending one's life past the point of when one would have naturally died (for me it is). However, if you cure these diseases, you are extending the natural lifespan (without the support of other modern technologies). Tyrol5 [Talk] 13:48, 18 August 2010 (UTC)

There is a distinction between fighting senescence per se and fighting diseases; some of the more intriguing results in lifespan extension involve not just longer life and protection from disease, but also prolonged vigor.[5] Wnt (talk) 14:56, 18 August 2010 (UTC)

Asking why do so many people think life extension is unethical ... ... ? is not a question that can be answered by science. Firstly, science doesn't even have evidence that any, or many, people think it is unethical. Secondly, any response to this question is only a matter of opinion. It is stated above that this Reference Desk does not provide opinions. Dolphin (t) 23:30, 18 August 2010 (UTC)

This may be splitting hairs, but science could possibly answer why people think it is unethical (social and religious influences, fear of "playing god", etc), given the desire (and funding) to go out and do so. In fact, some poor sociology graduate student is probably doing exactly that right now. It cannot, however, answer whether life extension is or isn't unethical. – ClockworkSoul 00:26, 19 August 2010 (UTC)

While it is true that death by "old age" is always death by the failure of some important bodily subsystem (heart failure, liver failure, etc) - those failures are not happening by random chance - if they were then people would be as likely to die at 100 years as they are at 20 years. But when someone dies in a car accident, it going to be because one or more body-systems failed - yet we still say that the person died because of the car wreck. Hence it's not unreasonable to say that someone died of old age even when we know of some very specific, detailed reason.

At least some of the reason why that happens relates to things called telomeres. When a DNA strand replicates, the last sequence on the end of the strand doesn't get copied - this causes the DNA to gradually shorten as it gets copied over and over as you get older. The body places 'junk' DNA at the end of the strand that doesn't code for anything useful ("telomeres") - and each time a cell divides, you lose a telomere. When you get old enough - you run out of telomeres and on the next cell replication, you have some of the important DNA going missing. That might not kill you - but eventually (and inevitably), you'll lose something critical and perhaps be unable to produce any healthy new heart cells - and not long after, you're going to have heart problems, then death.

If you recall "Dolly" - she was a clone of a 6 year old sheep. Her cells were made from 6 year old cells that had already lost most of their telomeres. Not surprisingly then, despite the best possible medical care, she suffered a bunch of typical "old age" symptoms and died at just 6 years old - when sheep of her breed usually live to age 11 or 12. At age 6, her cells had suffered 12 years of telomere loss (6 years in her "mother" and 6 years in her own life) - and the consequences were entirely as expected.

There is a suggestion (which has been tried in some simple animals) of adding more of these telomeres to the end of DNA strands - and even of using a specific chemical to do that. However, there is a problem. When a cell goes crazy and starts replicating very rapidly (a "cancer" cell) - then the telomere mechanism provides a natural way to shut it down...the very fast replication causes the cancerous cells to lose telomeres more quickly - and eventually die off (that's if they don't kill you first). If we go in and "fix" the telomere problem in order to get longer life - we may cause ourselves to lose all of our natural ability to fight off cancer.

So having people live forever isn't just a matter of fixing individual problems like heart disease, liver failure, etc. When your body is incapable of making any new heart cells, nothing short of a transplant is going to fix that. When no more liver cells can form - you need another transplant. Gradually, more and more parts of your body will run out of telomeres - and soon you're going to need more and more transplants - ultimately, you have to replace every single part of your body...and that is a fundamental problem because at that point you aren't "you" anymore.

It's not impossible that we can fix all of these things - but what our OP suggests isn't enough. We have to figure out how to beat the telomere problem as well as fight off all of the more normal causes of death.

SteveBaker (talk) 02:33, 19 August 2010 (UTC)

Note that the "Dolly" story doesn't match what is said at that article. I think that in the vast majority of cell types, telomere length never becomes an issue - maybe not in any. Well, alright, lymphoid lineages in HIV patients...[6] While telomeres do shorten with aging, and as explained in that article, there is some C. elegans work suggesting that telomerase can oppose aging, we should be wary about jumping to a simple cause-and-effect conclusion. Wnt (talk) 05:38, 19 August 2010 (UTC)

Indeed, New Scientist of 7 August 2010 ran a 7-page feature on cloning by Ian Wilmut, which naturally makes extensive references to Dolly. In part this reads:

"Dolly developed breathing problems and a cough in February 2003 [aged 6½]. We suspected she was suffering from pulmonary adenomatosis, a disease that is not uncommon in adult sheep, which is caused by the jaagsiekte retrovirus . . . . Dolly was sent for a CT scan . . . [which] revealed the full extent of her lung tumors . . . [she] was never allowed to recover from the effects of the general anaesthetic she'd been given for the scan . . . . Although there has been much speculation about how the process of cloning had affected Dolly, the post-mortem revealed nothing particularly unusual for an animal of her age and weight."

Though the feature doesn't go into the telomere issue, this suggests that Dolly did not, at the age of 6, generally exhibit the age-related characteristics of a 12-y-o sheep. Although our own article says she also suffered from arthritis, this can also occur in younger people (and presumably sheep), and it also describes only as speculation by some the suggestion that her shortened telomeres contributed in any way to her death.87.81.230.195 (talk) 17:32, 19 August 2010 (UTC)

Weight of one phytoplankton cell

Yes, I know that this is impossible to determine because it's so small and there are about 5000 species, but I don't need a precise figure. Basically I've followed up my previous question with a bit more research, and I know the scale of plankton generation we were talking about is massively infeasible, but to prove it I need to know roughly how much the stuff weighs. Even if its only a really rough figure, or even just an order of magnitude, that would be enough for my purposes, because it's so infeasible to do this that even a massive exaggeration of their weight would still make it look impractical to generate that much plankton. Anyone know a figure that would help me?

Thanks! Dan Hartas (talk) 13:27, 18 August 2010 (UTC)

I would imagine that only one weighs far less than one microgram (e.g. really, really light). I'm afraid I can't give you a much more definite answer than that. Tyrol5 [Talk] 13:35, 18 August 2010 (UTC)

Heh yeah, "really, really light" is about all I know as well lol. Dan Hartas (talk) 13:52, 18 August 2010 (UTC)

Well, the problem you encounter as you reach these low figures is that the numbers keep getting smaller and smaller indefinitely (in essence, you never hit zero by counting back). Tyrol5 [Talk] 14:08, 18 August 2010 (UTC)

Obviously the answer is "0", just as the answer to the question "what is the thickness of a piece of paper?" is "0". A piece of paper is physically two-dimensional, it doesn't have thickness, and a phytoplankton cell is physically zero-dimensional, it doesn't have depth, breadth, height, or weight. (Unlike the other zero-dimensional object, the black hole, which obviously does have weight). Hope this helps. 92.230.233.158 (talk) 13:42, 18 August 2010 (UTC)

That's a ridiculous answer. A piece of paper is obviously a three dimensional object. Please don't answer questions you don't have the first clue about. Matt Deres (talk) 14:26, 18 August 2010 (UTC)

I'm glad you noticed. The obvious is not always true, however, and string physicists would say that the paper is much more likely to be 11-dimensional. If it is 11-dimensional, the sum of those two digits is 2 (as I said originally), but there is no obvious way to get from 11 to 3. So if either of us is in some sense right, it would be me. Cheers, 92.230.66.177 (talk) 18:53, 18 August 2010 (UTC)

Haha, oh wow. What is that, dialectic physics or something? (e • nn • en!) 04:05, 19 August 2010 (UTC)

To estimate the weight of a phytoplankton cell, have a look at our articles on the different species of phytoplankton. Many of these articles include approximate sizes of these organisms. Using the estimated sizes, calculate a rough volume (note that 1 cubic micrometer is equal to 1 femtoliter), and figure that the density of of these organisms is probably within shouting distance of the density of water (1-2 picograms per femtoliter). Since the size of phytoplankton varies across at least two or three orders of magnitude – depending on species – you're only going to get a very rough estimate anyway.

That being said, for your study, what you're probably more interested in is not the mass of an individual cell, but rather the mass density of phytoplankton which can be cultivated in a cubic meter of seawater. (More specifically, how much carbon is bound within the phytoplankton one can culture in a cubic meter of seawater.) The number of individual cells is virtually irrelevant to the sequestration; one cell gives rise to a billion billion daughter cells after just sixty doubling periods, so once the culture is up and running, maintaining the numbers shouldn't be an issue. TenOfAllTrades(talk) 14:37, 18 August 2010 (UTC)

Using TenOfAllTrades' method for Chlamydomonas reinhardtii gives you a wet weight of 1 nanogram, having a stab in the dark, I'd guess the dry weight would be around 1% of the wet weight - 0.01 nanograms. Smartse (talk) 16:12, 18 August 2010 (UTC)

Even in a good source [7] the wet:dry weight ratio seems remarkably uncertain (10% or 20% by assumption) but I don't know of any living thing that is 99% water. Also see "Net-plankton biomass in the Manazuru Harbor varied from 4.1 to 410 mg m–3 in dry weight; from 2.0 to 200 mg m–3 in ash-free dry weight; from 0.98 to 78 mg m–3 in organic carbon (Fig. 1)." [8] (These are just top two Google hits; serious research may find better data) Also note that one report claims we are making negative progress on your idea.[9] Wnt (talk) 16:24, 18 August 2010 (UTC)

Crowded cell environment anyone? I am pretty sure that water does not make up more than 90% of a cell by wt. It's probably even less. John Riemann Soong (talk) 21:22, 18 August 2010 (UTC)

Another issue: apparently picoplankton and nanoplankton pass right through plankton nets, and only microplankton are usually caught; but it is the former two that make up most of the biomass.[10] Depending on your situation you may care about the total or just the larger cells. Wnt (talk) 16:31, 18 August 2010 (UTC)

Well let's use more feasible units you could use under a microscope. The issue of a mass of a cell is important, when you're say trying to assay one cell culture and differentiate it from another. John Riemann Soong (talk) 19:23, 18 August 2010 (UTC)

Adult male cat being breastfed by another cat

The male is black-and-white. The female is blue. The image might not represent the actual breastfeeding.

The male is black-and-white. The female is blue. The image might not represent the actual breastfeeding.

I've seen an adult male cat being breastfed by a cat whose kittens had just stopped suckling. The two did not know each prior to the breastfeeding and that did not occur only once. The tomcat was certainly adult; he was larger than the female who was breastfeeding him. This lasted for several days, until the tomcat disappeared. I'd like to know:

1. What made the cat breastfeed another adult cat?
2. What made an adult cat suckle another cat?
3. How (un)common is this behaviour? The Spy Who Came in from the Cold (talk) 17:25, 18 August 2010 (UTC)

Maybe they had sex just after that. I have seen this behavior in horses. Sometimes just before the male starts fucking he causally licks the tits of the mare (though there is no milk there). And of course we (human) do it too.  Jon Ascton  (talk) 20:23, 18 August 2010 (UTC)

They did not mate. But thanks for not helping. The Spy Who Came in from the Cold (talk) 22:32, 18 August 2010 (UTC)

This is both a little surprising and a little unsurprising. If the momma cat's kittens weaned a little ahead of schedule, she may have become engorged with milk - which can be quite uncomfortable. The male cat may have been doing her a favor in that case. However, in most mammals (but not most humans) adult animals are naturally lactose intolerant and their digestive systems cannot handle milk. Of course everyone knows that cats like milk...right? Well, maybe - but it's not that good for them. SteveBaker (talk) 01:58, 19 August 2010 (UTC)

My experience of cats (and I'm not a fan), is that it's not unusual for adult cats to attempt to breastfeed and they aren't fussy about the target species either e.g. it could be a large primate watching TV for example. I should add that I also think it can be triggered by visual cues i.e. seeing and recognising a nipple. Perhaps you could ask Anne Corwin, who carries out marvelous experiments on her cats, to investigate it. Sean.hoyland - talk 03:50, 19 August 2010 (UTC)

Car mirror -- "closer than they appear"

Why would the passenger side mirror show objects farther than they actually are -- isn't it just a regular mirror? DRosenbach ^{(Talk | Contribs)} 19:45, 18 August 2010 (UTC)

As curved mirror#Uses notes "The passenger-side mirror on a car is typically a convex mirror. In some countries, these are labeled with the safety warning "Objects in mirror are closer than they appear", to warn the driver of the convex mirror's distorting effects on distance perception." This paper is very relevant. -- Finlay McWalter ☻ Talk 19:51, 18 August 2010 (UTC)

but aren't all objects closer, since the ray from the object describes two sides of a triangle (object to mirror, mirror to your eye) where the direct view from your eye would be the third side of the same triangle? As long as the lengths of two sides of a triangle have to add up to more than the length of the third side, objects in mirror will be closer than they appear. 92.230.66.177 (talk) 20:05, 18 August 2010 (UTC)

The label is imperfect. It should be interpreted, "Objects are closer than they would appear if viewed through a flat mirror." The purpose is simply to remind drivers that the curved mirror has affected depth-perception differently than a flat mirror would. Nimur (talk) 20:10, 18 August 2010 (UTC)

• I think you mean, "Objects are closer than they would be if they were seen in a flat mirror and appeared the same size." Which I think we can agree is not a very practical wording. --Anonymous, 21:18 UTC, August 18, 2010.

In other words, the driver, when he sees through back-mirror is under illusion that vehicle behind is quite far away, but really it is not as far away as it seems  Jon Ascton  (talk) 20:18, 18 August 2010 (UTC)

The reason why objects are made to look further away is so that you can see more of them within the narrow field of view provided by the mirror. It's just like a microscope, which lets you see an object very close, but only a tiny portion of it - just in reverse. Wnt (talk) 20:27, 18 August 2010 (UTC)

How a 3-year-old might participate in sharing his "knowledge" on Wikipedia: Deep Sea Tube Worms

I'm writing on behalf of my 3-year-old son. Somehow I got him all excited about the fact that wikipedia is an encyclopedia to which everyone on the planet can contribute. He kinda got the wrong idea. So, he loves to review the article on Giant Tube Worms (http://en.wikipedia.org/wiki/Giant_tube_worms ) and wants to contribute this bit of fiction. Obviously, there's not really a place for that, so I guess our question is: are there any discussion pages on Wikipedia where people can have casual discussion on a topic? (we already think the answer is "no" after listening to "what Wikipedia is not," but I don't want to totally discourage him from participating in the future in a genuine way, so I'm wondering if there might be a way to validate his interest in participating, not just reading, but also to not just create junk. Maybe there's a kids' website along these lines that somebody knows about and can direct us to?!) Anyway, here's his bit of story: 'After deep sea tube worms disappear, the other animals come back and don't see the deep sea tube worms and think, "Huh, the deep sea tube worms aren't here." They aren't there!' --24.22.93.88 (talk) 23:10, 18 August 2010 (UTC)

I think he might be more welcome over at the Simple Wikipedia. He can contribute here but the populace over there tends to be much younger. It's good to know we have toddlers interested in the site but one concern of mine is that his age will be known if he just pops up and people connect the dots. I'm off to something right now but if you have any concerns, please feel free to pop by my talk page. Kevin Rutherford (talk) 23:21, 18 August 2010 (UTC)

You are welcome to go to the Wikipedia Sandbox and select Edit. If there is already some text there, just delete it. You can write it up in as much detail as you like and hit the Show preview button. You will then see your work previewed on the screen. Alternatively, you can hit the Save page button and see it in a slightly different format. Either way, it can stay on your screen for as long as you like, so long as you don't select a new page. (Within minutes the sandbox will be refreshed by someone else's experimenting.) If this will satisfy your son it is a quick and simple way of beginning to interact with Wikipedia. Best wishes! Dolphin (t) 23:42, 18 August 2010 (UTC)

Well, young contributors are welcome to Wikipedia! But we do not make special exceptions to our rules about encyclopedic content & style or verifiability. I hope the young contributor will understand - this is not meant to discourage imagination and enthusiasm for interesting things, but to modulate those ideas by reality and verifiability. Other internet sites, (ones that are not encyclopedias), will be a better place to submit pure works of imaginative fiction. Obviously, a 3-year-old's "knowledge" about deep-sea tube-worms is severely limited by a lack of experience - so it's probably best to have him or her learn about tube-worms before contributing to our encyclopedia article. You can make this a very educational project: consider going to the library or researching in other reliable sources - and then process through the information you learn together, and finally contribute (factually correct, verifiable content) to the articles. Nimur (talk) 00:07, 19 August 2010 (UTC)

I think the answer may be this:

• First, create an account for yourself and/or your son on the system. When you do that, you get a web page called "User:yourname" where you can put stuff about yourself. It is acceptable to create a "sub-page" from there, for the purpose of doing test editing. So you could create: User:yourname/Tube_Worms - and copy into that page as much or as little of the tube worm article as you'd like. Then you and your son have your own private copy of the article that you both can edit it to your heart's content - add stories, go nuts. In the unlikely case where someone complains that you have no right to do that, point them to Wikipedia:USERPAGES#Common_uses_of_userspace which explains that you can have 'working drafts' of articles there - and use them for editing practice.

Sadly, this doesn't give you a place to discuss tubeworms with other Wikipedians. The way we're set up here doesn't really provide anyplace like that.

• Sometimes you will find this kind of discussion on the 'discussion' tab of the article itself - but that's not strictly what that is for. That space is for discussion of the article itself (how it could be improved, what is wrong with it, etc) - and not for discussion about the subject of the article. However, that rule is very often breached and people are generally fairly relaxed about it...although that might change if you let a 3yr old loose with the keyboard in there!
• This reference desk is a fine place to ask questions. We don't encourage random discussions here - but if you should find that your son has a question about tube worms (or anything else for that matter) then you both can ask it here and we'll do our best to answer it. If you wish us to use simpler language to describe the answer, then you should probably mention that in the question.
• If your son gets very deeply into Wiki's in general, you can get yourself a web site someplace (I use 'DreamHosts.com') for between $5 and $10 per month and create your very own Wiki! I've done that (http://www.sjbaker.org/wiki) and my son (who is now 19 years old) and I make stuff there free of all of the Wikipedia rules and regulations - and what goes in there is entirely at my own whim! (Check out http://www.sjbaker.org/wiki/index.php?title=Measuring_hard_things_with_easy_experiments for stuff your kid will one day have fun with and one day http://www.sjbaker.org/wiki/index.php?title=A_Year_of_Learning_Fractions_in_Ten_Simple_Rules which will one day save him no end of grief in math class).

Good luck! The world needs more parents who can get their kids interested in tube-worms...or whatever!

SteveBaker (talk) 01:33, 19 August 2010 (UTC)

Wow -- thanks so much to all of you who offered these very helpful suggestions! I think he would, in fact, love to start his own experimental wiki, as Steve suggested, and now we know how! I wanted to walk that fine line between encouraging him and respecting everyone else's expectations not to have inappropriate material/discussion posted on the site, and all of these help give me a great framework within which to do that. This whole business today of him wanting to contribute to the tube worms page has helped initiate a great family conversation about "fact" versus "fiction," the roles and importance of each, and how they intersect (he wanted to cite some material he learned about tubeworms from a Magic Schoolbus kids' book, and we're still scratching our heads about appropriate citation sources, but we're figuring it out!). Thanks again! --24.22.93.88 (talk) 01:50, 19 August 2010 (UTC)

If your son is still looking for a place to host/expand on his Giant Tube Worm story, you can explore the various collaborative fiction sites with him. For example:

• Protagonize
• My Baby Monsters (this is geared towards kids)

If you create a personal wiki, or post your son's fiction online, do drop us a link (on the Reference Desk talkpage in case this thread has already been archived). Cheers. Abecedare (talk) 03:40, 19 August 2010 (UTC)

As Abecedare suggests, Wikipedia isn't the only collaborative site on the Web. There are also Wikis on videogames and popular tween TV shows. Your 3-year-old probably isn't interested in either of these categories (and if he's smart enough to grasp the concept of reliable sources, then these places might not be the best, since they hardly get that concept themselves), but the Web is full of Wikis on a variety of topics, and they can be a great way for kids to improve their writing and reference skills while focusing on what they're passionate about in a collaborative environment. I imagine our future Wikipedians are on these sites right now!--el Aprel (^facta-_facienda) 03:58, 19 August 2010 (UTC)

I think that young children have a special talent for remembering facts precisely - for example, retelling a story just as they've heard it like a bard, or drawing a scene just as they've seen it like an artist. I do not know how this will play out in the modern age of Internet and Wikipedia; nonetheless, it seems possible that very young children who have recently been exposed to detailed facts from other sources may well be able to come forward and point out things that are missing in our articles, or provide acceptable original artwork. I think that the history of the past fifty years speaks to a remarkable improvement in the maturity of children - so much so that one wonders whether the college students of the 1950s would have the maturity expected of 7th-graders today. We should consider seriously that in time even three to five year old children may come to be valued contributors, no matter how impossible it might seem to us. Wnt (talk) 05:14, 19 August 2010 (UTC)

In all seriousness Wnt, have you had much interaction with children since you ceased being one yourself? I don't think they've changed much at all in the last few decades, and past writing on children still seems to fit. The areas of their expertise have changed, but their basic development hasn't. And have you looked at typical child art? Children tend to go through set phases in drawing, and I don't think you could call any of the young child phases 'drawing a scene just like they've seen it', assuming you meant something photorealistic here. The youngest make scribbles, round and round, which are then said to be things. Older toddlers - preschool drawers tend to draw symbolically and in a predictable manner: they will draw a person as a face, when slightly older they will add arms and legs directly to the face. By the time they're about 8, if asked to draw a still-life exactly as they see it the average child will produce something vaguely cubist: they will include information from different angles in a single drawing. Children only really tend to start drawing realistically what they actually see when they're about 10, and even then most children need some sort of training or explanation to do this. Left entirely to their own devices, most continue to draw more iconically. 86.164.66.83 (talk) 09:50, 19 August 2010 (UTC)

Ah, while not terribly well referenced, we do have an article Child art, complete with pictures. 86.164.66.83 (talk) 10:34, 19 August 2010 (UTC)

I suppose I should have stuck to science here... Children aren't really my calling, but I'm amazed at the level of restraint required today of young teens, under penalty of law, by contrast to the drunken brawling wild oats-sowing antics of young adults of previous eras. Not all child art is suitable for Wikipedia, yet in the examples from the article and elsewhere it is apparent that some can be. (Speaking of cubism... [11]) And children certainly are capable of taking up facts from a museum, book, or other source and telling them to whoever wants to listen (or not). I don't mean to suggest that you should loose young kids on Wikipedia unsupervised (whether you're concerned for our benefit or theirs), but I think they have capabilities yet to be known. Wnt (talk) 11:53, 19 August 2010 (UTC)

Where you live young adults aren't getting drunk, getting into fights and having sex? Nil Einne (talk) 15:01, 19 August 2010 (UTC)

There have always been gifted and precocious children, and of course what an individual can contribute or enjoy will vary based on the individual. That isn't because anything has changed, and it isn't because children as a group are ready to contribute earlier, it is simply a result of human variation. Which is a good thing. And of course if an individual child produces a useful image, and licences it properly, we'll be delighted to use it. But most children, particularly young children, won't produce something suitable to illustrate anything except as an example of what children draw: when they are older, and have developed their talent, they may well do. And we won't use an image that is good for the age of the person who made it, but not better than the other images available. In any case, the drawing discussed in that link is an entirely private, storytelling thing, not concerned with creating a useful graphic. Of course many children are capable of more than they are given to do, but that should not be confused with them having mystical abilities or astounding self-control. Having a bit of slack where they don't have to be achieving anything 'worthwhile' is an important part of childhood, and I would be worried more than impressed by a child who showed too much maturity in some ways. 86.161.255.213 (talk) 20:33, 19 August 2010 (UTC)

Wikiversity might be another option. They do have a Marine Biology Lesson Plan but it appears to be designed for 11th grade students. Nevertheless, you might ask around at their Help desk since their goals include being devoted to learning projects, unlike Wikpedia whose main goal remains writing an encyclopedia (reference desks notwithstanding). ---Sluzzelin talk 15:19, 19 August 2010 (UTC)

If you actually do decide to start your own Wiki - I'd be happy to help you set it up. It's not difficult - but you will want to take care over the security aspects of the thing...an unguarded Wiki rapidly gets spammed into oblivion - mostly with things you wouldn't want your son to be concerned about for at least another decade! If you go to my user page (User:SteveBaker), you'll see a link to my email and we could discuss it offline. SteveBaker (talk) 00:02, 20 August 2010 (UTC)