Wikipedia:Reference desk/Archives/Science/2007 April 5

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April 5

Lifespan of cats

this is my first reference desk question but what is the average lifespan of a cat? yuckfoo 03:01, 5 April 2007 (UTC)

I don't know precisely, but cats kept indoors as pets can live somewhere around 15 years, while outdoor pet cats and wild/feral cats don't live nearly as long. StuRat 03:15, 5 April 2007 (UTC)

The average lifespan of a cat is nine times the median age of cats when they die. 202.168.50.40 03:03, 5 April 2007 (UTC)

Maximum life span says the record is 34. Clarityfiend 03:21, 5 April 2007 (UTC)

can we add this to the cat article once we are sure about it yuckfoo 03:19, 5 April 2007 (UTC)

For domestic cats, estimates range from 10-18 years [1], 10-12 years [2] and 9-15 [3] though factors such as whether a cat is permitted to go outside will influence their average lifespan. [4] Rockpocket 06:52, 5 April 2007 (UTC)

The Impact of the Immune System on the Nervous System

Hey. I've been exploring a bunch of topics on the development of cephalization in humans, and I recently came across "neuroimmunology." I have seen a few studies on how the nervous system can impact the immune system but none for the reverse. I wouldn't readily assume that the immune system would have such an effect (unless it was detrimental as in autoimmune disease), but is there any literature on the subject? Thanks. Robinson0120 05:09, 5 April 2007 (UTC)

I'm not sure how you define "impact", but there is certainly evidence that key molecular players in the immune system can have a role in neuronal signaling. Major histocompatibility complex molecules have been implicated in synaptic development and plasticity. (PMID 16698261) In addition MHC-binding peptides have been shown to activate neurons of the vomeronasal organ and thus act as putative pheromones. (PMID 15528444) Rockpocket 06:42, 5 April 2007 (UTC)

Sorry, I was vague. I was looking more along the lines of behavioral modification, but pheromones and plasticity look like great starting points. Thanks for the input! Robinson0120 07:02, 5 April 2007 (UTC)

Instructables web site

I know that the Wikipedia is an encyclopedia and frowns on articles that include a "how to" section (except maybe a list of useful formulas, etc.) so I went looking for sites that could help me figure out stuff like how far apart I can spread the fork on a bike to fit a new axle and came across a site that is just what the Wikipedia is not and does not want to be. Its the Instructables web site. So my question is how come the Wikipedia does not have an article on this very extremely useful site? Nebraska bob 05:26, 5 April 2007 (UTC)

Because you haven't created one yet ? Seriously, go ahead and add it, it sounds like a good addition to Wikipedia. StuRat 05:47, 5 April 2007 (UTC)

Well, Stu this would be my first article and I want to start off doing it right. Even though this is a wiki there are some things you have to live with which the first editor does like the name of the article for instance. So what should I use for the title, "Instructables web site" or just "Instructables"? (Thanks for the vote of confidence, which I do not deserve BTW. I created the "Instructables web site" article page and put a REDIRECT tag on "Instructables" in preparation for development but a couple of BOTS immediately posted SPEEDY DELETION TAGS stating the subject is not "notable." . Nebraska bob 12:25, 5 April 2007 (UTC)

Excuse me, but I'm not a bot, and I'm pretty sure Longhair isn't either. You created an empty page that included an external link and a broken redirect. That is a textbook candidate for a speedy deletion tag. I've since commented on your talk page about what you might want to start with and even offered to search for sources myself. --Onorem 12:53, 5 April 2007 (UTC)

You are how the things under your control act. (Mighty jumpy if you ask me.) Nebraska bob 13:00, 5 April 2007 (UTC)

You really need to put together at least a couple of paragraphs and one solid reference (perhaps testing it out in the Wikipedia:Sandbox) before you paste that into the edit box to create the article - that way there is never a time when it looks like someone just stuck a random link onto a page for promotional reasons (which is probably why your first attempt was killed). However, there is a good chance that your article would get deleted anyway if the web site in question is deemed 'non-notable'. You should first check up on Wikipedia's standards for this in WP:NOTE...or more specifically: Wikipedia:Notability (web) - I strongly suspect that this site is not going to meet the guidelines...but I confess I'm not all that familiar with it. SteveBaker 14:49, 5 April 2007 (UTC)

Forgotten just how I came across this site... probably from a search for something... oh yes if a rear triangle could be spread 30mm... Anyway a few things caught my eye that I may have seen somewhere else and so I started browsing. You know sometimes policy in general is probably a good thing if you do not let it go to your head. After all it is possible to sacrifice usability for showmanship or so called professionalism. Anyway I found the site to be notable (unlike even some of the very good RC sites) simply because it is a wiki (or actually a user blog where other can comment on the stuff you have contributed but not flush it, for others but only for themselves, down the can.). That said it is notable to me and maybe to others but that will not change the fact that it is notable to me. If the Wikipedia wants to go "High Brow" hey that's fine with me. Just find it strange the first time I stick my toe in the water it gets bitten off by a couple of piranhas. Nebraska bob 15:07, 5 April 2007 (UTC)

You have to put this in context. The problem is that tens of thousands of web site owners have had the idea of creating a Wikipedia page that points to their web site (and says almost nothing else) - relying on Wikipedia's page rank score (which is astronomical) to boost their own ratings on Google, etc. In fact, this doesn't work (for technical reasons to do with how Wikipedia presents outside links) - but that doesn't stop people from trying. The result of this is that dozens and dozens of these things get created every hour of every day. There simply isn't time and/or effort to carefully examine each one to see if it's valid or not - so they tend to get speedily deleted without much care. Sadly, your article looked 100% identical to the other gazillion 'junk articles'...whether you planned to eventually expand it or not. That's why I suggested that you write a good chunk about the web site BEFORE you create the article - so it starts off as a substantial chunk of text. However, even if it were a substantial article, that's not enough to meet the 'notability' criteria...so it might be problematic even if you spent a lot of time on improving it. It's unfortunate that this has badly affected your first experience with Wikipedia - but I ask that you consider it from our point of view. We simply cannot allow the kinds of abuse that your initial effort looks so much like. If you had created an article about (say) a car or a bird or a Romanian emperor or...almost anything other than: (i) a web site, (ii) a living person or (iii) a band - it would not have been deleted. But those kinds of subject are subject to continual abuse 24/7 and the consequences for those with something serious to say are rather nasty. SteveBaker 16:16, 5 April 2007 (UTC)

You might try to create an article about HOW TO web sites in general in order to avoid the perception of bias. Of course you would include the instructables site and maybe add some others like wikihowCzmtzc 15:53, 5 April 2007 (UTC)

Okay, I'm working on composing an article off-line and will upload it as soon as Eric Wilhelm, (instructable's owner) can send a history file.

Here are some notability references:

• Time:

“step-by-step instructions for making things you never knew you wanted”

• The Village Voice

“you’ll find detailed, well-illustrated, friendly instructions for constructing your own at instructables.com”

• Lifehacker

“This is a great place to start if you’re looking to find a cool DIY project to try out”

In the meantime I suggesst everyone have a visit and explore... Lots of fun! Nebraska bob 16:34, 5 April 2007 (UTC)

You may not know this, but you can also create pages in your own user area, like say, User:Nebraska_bob/instructables, just by adding a slash and word after the web address at your own home page. Pages you create in your own user area generally go unmolested, (unless you invite people to molest them). This will allow you to test all the links and get the page up to a high quality standard to avoid the problem of it being immediately deleted when you first create it (because it's not yet perfect). StuRat 19:52, 5 April 2007 (UTC)

Alcohol's effect long-term effect on growth

Does ingesting ethanol during puberty really stunt one's growth (i.e. diminish one's final adult height)? Anti-drug websites claim so, but they'll claim anything they can get away with. Academic sources are preferred. Thanks, ^L_Wizard @ 07:26, 5 April 2007 (UTC)

I'm a teacher. Kids that I've known who came to school drunk were shorter than others. Coordination and motor control are damaged from alcohol use in young, whose brains have not fully developed before 23 years of age (female average) and 25 years of age (male average). Size tends to be related to diet from birth to age three. Genetics is also important. Poor diet in adolescence still affects height. I suspect the science would show Alcohol provides no benefit to children, and will harm health, but as to restricting size, I can omly go on observation. DDB 11:52, 5 April 2007 (UTC)

Alcohol affects smaller people more than larger people. It could be that they were all drunk, but only the smaller ones showed symptoms. Think outside the box 12:08, 5 April 2007 (UTC)

Also note that this refers to alcohol abuse ("getting drunk"). Small amounts of alcohol (such as naturally occurs in food) can be metabolized by the liver before any damage is done. StuRat 19:42, 5 April 2007 (UTC)

The need for a balance in relation to Energy articles

Hi, I notice that Nuclear power by country is a featured list, and that Nuclear power is included in the 2006 Wikipedia CD Selection, or is a candidate for inclusion in the next version. But what about the important and broad topic of Renewable energy?

Are there any comparable high-quality renewable energy articles? Or is it possible to get an indication of renewable energy articles which are potential candidates and just need some further work?

It seems very one-sided to be showcasing nuclear power and not renewable energy -- Johnfos 09:47, 5 April 2007 (UTC)

Renewable energy tends to fall into categories of Solar Energy, Wind Power, Water Power Generators or Geothermal Power. There are advantages and disadvantages of each.

Geothermal is not yet used anywhere in industrial size, although some baths are powered by it, and plans are being made. It requires a substantial water supply.

Solar power is not yet cost effective, and does not run for an entire day.

Wave Power generators have been blocked on ecological grounds. Water power through dams is less popular as fresh water increases in value.

Wind Power has been blocked on ecological grounds, and is unreliable.

One brilliant idea is a km high tower which uses convection currents through a green house to turn wind turbines. It has been promised at most state elections in Australia since '96 but to little effect. DDB 11:44, 5 April 2007 (UTC)

I think you are way out of date in your assessment of renewables. Please take a look at Renewable energy commercialization, Renewable energy commercialization in Australia, Wind power in Germany, Solar power plants in the Mojave Desert and Deployment of solar power to energy grids to see what has been happening recently.

But I'm not asking for a debate about renewables vs nuclear. I'm writing about WP articles in these areas, and asking if there are any renewables articles that are seen to be of high quality, in the same way that some nuclear articles have been identified as being of high quality. Or if there are any renewables articles that could be high quality articles if a bit more work was put in. -- Johnfos 12:14, 5 April 2007 (UTC)

It takes a lot of time and effort to get an article to featured status and only a very few editors can be bothered with the amount of hassle and red-tape involved. So the matter of which articles are pushed to featured status is not a decision made by Wikipedia as a whole - it's a matter of whether (typically) a single individual editor has enough passion for the subject, knowledge about it (and, rather crucially) books on the subject sitting on his/her bookshelf so that the article can be sufficiently well referenced. Hence the spread of articles deemed good enough for the CD selection is not so much determined by an attempt to get a balanced view of the universe of knowledge (although that is a consideration) as it is by the set of articles that particular editors had an interest in. Only a few hundred editors out of the millions who come here manage to get an article to featured status and less than a tenth of one percent of articles ever get to that level. Worse still, the quality bar for featured status is rising all the time - and many former featured articles have been downgraded in light of 'modern' standards. SteveBaker 14:38, 5 April 2007 (UTC)

Many renewable energy sources have their uses, although no single renewable source has the ability to replace all nonrenewable sources at this time. I believe only a few places have sufficient geothermal energy to power industry, such as Iceland and Yellowstone National Park in the US. Solar power can be quite useful for places which are "off the grid", especially in desert environments. Wind is similarly most useful only in a few places with consistently strong winds. Hydroelectric power (dams with turbines), however, has been used for many years to power cities around the world on an industrial scale. Other forms of renewable energy have their places, too, like wave and tidal power. Wood, ethanol, and other biofuels do tend to create greenhouse gasses, just like fossil fuels, but are good alternatives in other ways, like energy security. But, back to the original question, we would be very pleased if you would take on one or more of the renewable energy articles and improve it to featured article status. StuRat 19:38, 5 April 2007 (UTC)

Worldwide installed capacity and prediction 1997-2010, Source: WWEA

As with any energy source, renewables have their advantages and disadvantages, and we need to work with these. But I must say I'm surprised by some of the comments above in relation to wind power, such as this "Wind Power has been blocked on ecological grounds, and is unreliable" and this "Wind is similarly most useful only in a few places with consistently strong winds" How then do you explain the graph shown, or the installed capacity of 20,621MW in Germany in 2006, and the fact that Denmark gets 20% of its electricity from the wind? Thirteen countries around the world now have over 1000 MW of wind generating capacity and more wind farms are planned in most of these countries.

I'm not trying to be argumentative in saying this. I'm just trying to bring a few basic facts to the fore, which help to underscore the growing importance of renewables.

As for a possible feature article on renewables, I appreciate the comments made. I'd be prepared to put significant effort into Renewable energy, but would need more guidance as to specific areas that need to be improved. Would anyone be willing to provide some comments in relation to that article please? -- Johnfos 01:29, 6 April 2007 (UTC)

Wikipedia:Featured article criteria lists some suggestions. After that you would probably get more help from Wikipedia:Peer review. Shinhan 19:13, 6 April 2007 (UTC)

Hepatitis B vaccine

Are all three of the doses of the Hepatitis B vaccine (given over the course of 6 months) identical? —LestatdeLioncourt 12:16, 5 April 2007 (UTC)

Some googling (look for keywords like hepatitis b vaccine schedule) suggests that the schedule for Hep B vaccination can be rather flexible, and in some places Hep B vaccines are combined with vaccines for other maladies.

For the three-jab Hep B-only vaccination, the three inoculations are identical in composition and dosage. TenOfAllTrades(talk) 15:24, 5 April 2007 (UTC)

Cardiac Cycle

Many books/online sources etc refer tot he cardiac cycle in 2 phases: systole and diastole (ventricular), with diastole encapsulating atrial systole (PQ interval). Some sources say that it begins at SL valve closure (others say after ventricular pressure reaches maximal) and ends with AV valve closure (ventricular systole initiated). Could someone clear up exactly where and when each phase begins/ends (have read wiki!).

And on a related note, could someone please explain to me exactly when day begins, as opposed to night? Some sources say that it begins when there is light enough for someone with normal vision to read unaided, and ends when light is insufficient for reading, Others relate it to the position of the sun with respect to the horizon. Could someone clear up exactly where and when each phase begins/ends (have read wiki!). --62.16.173.45 20:05, 5 April 2007 (UTC)

Is that hard to distinguish in Norway?

Hearing tests

what is the advantage of the absolute bone conduction test in comparison with other tuning fork tests, i.e. rinne's test and weber's test?

Weber test, Rinne test, absolute bone conduction (bottom of page 4) --JWSchmidt 21:51, 5 April 2007 (UTC)

It's not exactly an advantage - it's a different test. Listening to a tuning fork requires that eardrums are working and nicely flexible. Very, very overly-simplistic: The bone conduction test tests the inner parts of the ear only. So if you can't hear the tuning fork - but you can hear the bone conduction test - then your outer ear is faulty - if you can't hear either of them then your inner ear is the problem. SteveBaker 04:24, 6 April 2007 (UTC)

Why does hot water clean better than cold?

I was curious why hot water (with detergent) cleans better than detergent in cold water. Not necessarily laundry, but also housecleaning and sidewalk cleaning. --24.249.108.133 16:56, 5 April 2007 (UTC)

I would guess because it has more energy in it, the water molecules have a higher KE, which is what temperature is—more bumping and rubbing around? [Mαc Δαvιs] (How's my driving?) ❖ 17:37, 5 April 2007 (UTC)

When dealing with fats, they gradually become more liquid and less solid as they are heated up. The more liquid they are, the easier it is for them to be washed away by water. StuRat 19:24, 5 April 2007 (UTC)

Also, when the detergents are supposed to do a chemical reaction (e.g. a redox reaction in case of acidic or basic detergents), the Arrhenius equation tells us that mnost chemical reactions happen faster at higher temperature. User:sanders_muc 85.127.180.138 20:06, 5 April 2007 (UTC)

Solubility of most substances increases with temperature. If you make a substance more soluble, it will be easier for it to dissolve in water and be carried away. Johntex\^talk 20:38, 5 April 2007 (UTC)

(edit conflict) As well, the goal is often to dissolve the dirt, not just physically move it away, and solubility often increases with temperature (see how much and how fast you can dissolve sugar in hot tea vs iced tea). DMacks 20:39, 5 April 2007 (UTC)

Also, hot water has less surface tension allowing it to penetrate fibres better. —The preceding unsigned comment was added by 209.53.180.29 (talk) 23:02, 5 April 2007 (UTC).

What if... Earth was frictionless?

Here's one of those silly Wiki hypotheticals. What would a frictionless or very low friction planet be like? (like all surfaces were super smooth and slick) --24.249.108.133 17:03, 5 April 2007 (UTC)

it would be like asteroids (game). Seriously. -- Diletante 17:07, 5 April 2007 (UTC)

I love that game! and lets just say there would be no need for car breaks as they wont work XD Maverick423 17:29, 5 April 2007 (UTC)

Just as a note, cars would break fine. It's the braking that would be an issue.

To the original question, though, consider an ice rink, and then expand it globally. That's what a low-friction planet would be like. — Lomn 18:38, 5 April 2007 (UTC)

Continuing that direction (sorry:) hockey goals don't slide around because they are anchored below the surface. Even if there weren't a non-frictionless sublayer, one could use an expanding bolt to fix things in place. That would allow one to move around in a controlled manner by gliding from fixed object to fixed object, similar to how a mountain climber moves from hand-hold to hand-hold. DMacks 18:44, 5 April 2007 (UTC)

Actually car brakes would work perfectly fine. The car would never move anywhere, though, no matter how fast the wheel spun, because the planet surface would have no static friction. If you study the wheel movements, you'll notice that the wheel needs high friction at the contact point with the ground, and low friction at the contact point with the axle. Nimur 21:03, 5 April 2007 (UTC)

You could never drill or set the expanding bolt. But there would still be wind, and we would blow all over the place. :) —The preceding unsigned comment was added by Zeizmic (talk • contribs) 22:15, 5 April 2007 (UTC).

The exhaust/intake would provide a small force to move the car. Planes would fly perfectly fine, would "frictionless Earth" have drag? What other effects would that cause? -- atropos235 ✄ (blah blah, my past) 00:24, 6 April 2007 (UTC)

Who said anything about drilling? One gun, two bullets: get two holes in the ground. Two sticks, now you've got two things to hold, and you can move around in any direction from them...even just one would be enough if the pole didn't rotate freely in its hole. If you've got strong enough arms, you can keep your legs motionless and still cross-country ski. You could even drill if you had a counter-rotating mass to keep you stationary (or an air jet or somesuch)...consider the tail rotor on a helicopter. DMacks 02:16, 6 April 2007 (UTC)

Sorry - won't work. You make a hole in the ground - but the total lack of friction between particles of dirt and rocks would cause the hole to fill back in almost as soon as you made it. In fact, dirt and sand would be like a liquid - we'd sink in up to about our chests in the dirt - think 'quicksand'. Buildings and roads and anything that's heavier than the soil beneath would sink without trace. This is a pretty silly question. SteveBaker 04:21, 6 April 2007 (UTC)

IT sounded like we were talking about the surface being frictionless "like an ice rink", not "the whole material of the earth is frictionless including lack of cohesion". DMacks 04:25, 6 April 2007 (UTC)

Really interesting insights! My original concept imagined all surfaces coated with frictionless nano particles. --24.249.108.133 17:22, 9 April 2007 (UTC)

How do satellites orbiting the earth avoid colliding with each other?

There are thousands of satellites in near-space orbit. How do they not hit each other? Is there a navigational database to track them? Can satellites change their orbit in order to prevent foreseen collision with other satellites or space debris?141.213.90.148 17:10, 5 April 2007 (UTC)

Suppose that there are 10⁵ satellites in orbit (unlikely), and that each of them is a square sail 10 meters on a side (100 m² in area: very large) presenting itself perpendicular to its motion (for best collision chances), and that they all orbit in circular orbits between 200 and 250 km in altitude (many are much higher) at a speed of 8 km/s with an inclination of no more than plus or minus 15° (many are polar). Then the volume of space they peruse is that bounded by the (two-cut) spherical caps between the minimum and maximum latitudes at the minimum and maximum altitudes. The mean radius of the earth is about 6370 km, so the area of our orbital region is a bit more than the average of $2\pi (r+h_{1})(2(r+h_{1})\sin 15^{\circ })=1.40\times 10^{8}{\mbox{ km}}^{2}$ and $2\pi (r+h_{2})(2(r+h_{2})\sin 15^{\circ })=1.43\times 10^{8}{\mbox{ km}}^{2}$, so call its volume $7.1\times 10^{9}{\mbox{ km}}^{3}=7.1\times 10^{18}{\mbox{ m}}^{3}$. Our ridiculous fleet of oversized satellites traces out a total of $8\times 10^{10}{\mbox{ m}}^{3}/{\mbox{s}}$, so even if they were not almost all travelling in the same direction we should expect collisions to occur on about the same order of time as it would take them to sweep out the entire volume: 88.8 million seconds, or about 2.8 years. (Recall that we made the probability much higher by restricting the orbits and using a rather large number of giant satellites.) In other words, they manage to not hit each other because they would have to try very hard to hit each other. It won't happen by chance. --Tardis 17:50, 5 April 2007 (UTC)

While the probabilities of collision are very low, satellite orbits are very carefully catalogued. The UN, among other organizations, maintains a thorough listing that is publicly searchable. See International Designator, and note the external links at the end. Note also that military satellites are generally not in public databases. — Lomn 18:46, 5 April 2007 (UTC)

It's also worth noting that while Tardis references the big sky theory, it's primary caveat (namely, that it's far less effective if conditions are restricted) applies in full force. There are comparatively few classes of orbit suitable for most satellites, and geostationary orbits in particular are subject to relatively high volumes of satellites. — Lomn 18:50, 5 April 2007 (UTC)

But, of course, objects in geosynchronous orbits aren't moving at all (relative to the Earth's surface) or are moving at the same speed and direction (relative to the Sun), so they can't hit each other. A bigger concern than satellites hitting each other is all the space junk out there in essentially random orbits. This includes nuts and bolts, tools, spaceship components, etc., that were intentionally discarded or accidentally lost. There are databases of such objects, but many are also unlisted. StuRat 19:20, 5 April 2007 (UTC)

Lots of stuff is carefully tracked and catalogued by the government, military, and commercial contractors. Take a look at this cartoon animation by Analytical Graphics, which demonstrates the ability to monitor not just satellites, but debris and dust, via radar. Nimur 21:37, 5 April 2007 (UTC)

“ China has acknowledged that it tested an antisatellite missile on January 11 when it targeted and destroyed an aging Chinese weather satellite. Along with fueling debate on global space control, the incident has raised concerns that the debris could jeopardize satellites in low-Earth orbit (LEO), including the International Space Station (ISS). ”

More details from the AGI website... Nimur 21:36, 5 April 2007 (UTC)

I put the animation on YouTube in case anyone wants to see it without a 50 MB download. Nimur 23:35, 5 April 2007 (UTC)

Nuclear Shelter

hey guys well i was checking out some stuff about nuclear shelters however i want to know what kind of walls will make it 100% radiation proof? besides that, is it logical to have a window in one? wont radiation go in through a window? and if not then how will a person inside it be able to renew the air already inside so as to not sufficate? Maverick423 17:26, 5 April 2007 (UTC)

100% stoppage is virtually impossible. That said, have you checked fallout shelter? Gamma rays are the deepest penetrator (that is, anything stopping them will stop alpha and beta particles as well. — Lomn 18:23, 5 April 2007 (UTC)

Not virtually impossible, theoretically impossible on many orders assuming you want a physical wall. Even, all baryonic matter is radioactive. Keep in mind there are several different types of radiation, and nuclear radiation. Try reading the articles! You should get enough out of them to know. [Mαc Δαvιs] (How's my driving?) ❖ 21:44, 5 April 2007 (UTC)

A window is definitely out. Some type of well filtered air intake could work, however, as most of the radioactivity is in particles floating in the air, not in the air itself. If you can remove those particles, you can get breathable air. Another approach would be to have a supply of compressed air and/or reuse the air with equipment to remove the CO² from the air and split it into carbon and oxygen, the latter of which is then returned to the air. Some combo might be best, such as using stored air during the first few days or weeks, when fallout would be heaviest, then going with filtered outside air after that. StuRat 19:10, 5 April 2007 (UTC)

While it is impossible to build a wall that is guaranteed to stop absolutely 100% of incident radiation, it's relatively straightforward to construct a wall which will block a large enough fraction of radiation to preserve and protect the soft and squishy living matter inside. A meter of concrete or soil will probably protect you adequately from radiation at any distance from a nuclear blast that doesn't physically destroy your shelter. The half value layer for lead and 1 MeV gamma rays [5] is 9 millimeters; ten centimeters will attenuate incident gamma rays to 1/2000 of their original intensity.

Windows are possible, but costly and a weak point; you'll want to look into a thick layer of lead glass. It's used regularly in the radiology and nuclear industry. Most fallout radioactivity comes from radioactive solid material affixed to dust particles; you'll want to have a HEPA-filtered air system to remove the bulk of these particles. As others have noted, our article on fallout shelter should give you a good summary of the important construction considerations. TenOfAllTrades(talk) 14:55, 6 April 2007 (UTC)

field lines

respected sir/madam,

i have a wireless router(wr) connected to the modem.i wanted to ask you what was the pattern of field lines created by wr & acc. to it what could be the best position for convenience122.162.99.104 17:31, 5 April 2007 (UTC)

Perhaps radiation pattern can help you? -- mattb @ 2007-04-05T19:03Z

The best position for your conveniece could be iether the bolw or the cistern, but not both! —The preceding unsigned comment was added by 88.109.246.75 (talk) 01:24, 6 April 2007 (UTC).

Huh?Edison 04:38, 6 April 2007 (UTC)

Ha. Fvasconcellos 22:47, 6 April 2007 (UTC)

Driver programs for wireless lan cards can usually display the strength of the received signal (this is similar to the signal strength display on most mobile phones). You can use that to experiment with different placements. Note also many buildings have iron in the beams which is an obstacle for reception. – b_jonas 10:52, 9 April 2007 (UTC)

Burying carbon dioxide

There are plan for some coal-based power plants to catch the carbon dioxide resulting from burning the coal and stash it away somewhere where the sun doesn't shine so that it cannot contribute to global warming. Am I missing some facts or is this raw political nonsense? Wouldn't it be far safer (outgasing), cheaper (no or nearly no preprocessing) and easier (no gas involved) to bury some sewer sledge with the same carbon content instead? 84.160.247.123 18:32, 5 April 2007 (UTC)

The key is carbon versus carbon dioxide. While sewer sludge may well be rich in carbon, that carbon isn't CO₂ and so isn't capable of contributing to a greenhouse effect. As for how CO₂ would be captured and buried... beats me. I have no idea if that's raw political nonsense or not. — Lomn 18:56, 5 April 2007 (UTC)

See also Carbon capture and storage and Carbon dioxide sink. DMacks 18:59, 5 April 2007 (UTC)

(After edit conflict) Right, carbon is not carbon dioxide, but the idea is to take away carbon that takes part in the carbon/carbon dioxide cycle to compensate for the coal that wasn't part of it previous to burning. The carbon of the sewer sledge will become carbon dioxide via bacterial decomposition soon enough. (And I didn't really expect an answer on the 'political nonsense' part here, not in the science section anyway.) 84.160.247.123 19:07, 5 April 2007 (UTC)

I would expect that, proportionally, comparatively little sludge is converted to CO₂. — Lomn 21:33, 5 April 2007 (UTC)

Oxydizing sewage is the main thing a sewer plant does, aside from concentrating and dehydrating the sledge. If it is not done by the plant it's done by the unlucky river or lake downstream. Of course, main portions are minerals and water but, what is easier and cheaper to bring deep down and keep it there: 1kg of artificially compressed and cooled gas or, say, 50kg of sledge? 84.160.225.164 22:47, 5 April 2007 (UTC)

Sledge is solid/liquid and will have minimal impact on the atmosphere compared to CO2, which is immediately released. Carbon sequestration can turn the evil coal-burning powerplant into something that emits virtually nothing, but is still cheap and safe. I'm not sure what oxydizing sewage means, but it doesn't mean that all the carbon in it is converted to CO2. Sewage is typically aerated near the end of the journey so it's not totally devoid of oxygen so it doesn't suffocate fish, to destroy some of the nasty anaerobic microorganisms present, and to allow other microorganisms to further process the sewage. -- atropos235 ✄ (blah blah, my past) 01:11, 6 April 2007 (UTC)

Oxidizing sewage is turning it into carbon dioxide http://en.wikipedia.org/wiki/Sewage_treatment#Aerobic_digestion. As it takes a while to build a power plant, deep down depositing of sewer sledge (= carbon containing material whose carbon would otherwise be converted into carbon dioxide within a short time) could start well 3 years ahead, so the net balance of carbon dioxide in the atmosphere would be the same. But I see the point: the evil coal burning plant would still be an evil coal burning plant, it's not so much about reducing the net release of carbon dioxide to the atmosphere but to make the guilty power plant look better. 84.160.225.164 10:33, 6 April 2007 (UTC)

shape of ionic compounds

I was tutoring chemistry, and drew a simple picture of NaCl, where the Na ions and Cl ions formed a lattice with the atoms alternating Na - Cl - Na - Cl etc., chessboard fashion (so no Na was orthogonally adjacent to another Na). Then a problem occurred to me: I had absolutely no idea what the shape of, eg. Magnesium Chloride was. There are two Cl ions for each Mg ion. How do they arrange themselves into a lattice? The Mad Echidna 19:14, 5 April 2007 (UTC)

I was part-way through writing the answer, when I happened to look at the page for your specific case, magnesium chloride and saw that there was a whole section of "Structure" information in the infobox in the upper-right portion of that page...see especially the Crystal Structure information and links. DMacks 19:18, 5 April 2007 (UTC)

Cubic crystal system may help also, it's a common way to categorize a lot (all?) ionic compound crystal structures. Nimur 21:07, 5 April 2007 (UTC)

For this particular case, the link Cadmium_chloride#Crystal_structure seems most useful (found following DMacks's idea), although it takes a while to 'see' where everything is. Skittle 22:33, 5 April 2007 (UTC)

Thanks folks for these answers, and sorry for not checking myself. It didn't quite dawn on me that the structure might be given for individual compounds, so I had only searched for the general term "ionic lattice". Even so, if I had searched for Magnesium Chloride, I would probably have missed the structure section in the infobox anyway. So I'm glad I asked. Fascinating how the lattice "knows" to just knock out a neat layer and leave everything else intact. The Mad Echidna 16:51, 7 April 2007 (UTC)

Lambertian verus Batwing radiation

Where can I find a comparative description for Lambertian versus Batwing radiation patterns. Nebraska bob 20:38, 5 April 2007 (UTC)

Lambertian reflectance is probably the same as radiation: it is isotropic, meaning the emitted light is the same at all angles. This might be described as a diffuse light source, as opposed to a spot-light or specular lighting. Batwing seems to be more of a "marketing" term, presumably for lighting and LEDs, as well as some antennas. This LED[6] seems to generate this batwing pattern. Nimur 21:18, 5 April 2007 (UTC)

Also, schematic of a batwing beam pattern and a technical article and a datasheet with graphs. Nimur 21:23, 5 April 2007 (UTC)

Open to Suggestions

Hypothetically, lets suppose that I live with a family member who for practical purposes displays obvious signs of unhappiness with his job and his life. Lets further suppose that he runs his own business, but it is in finiacial trouble because the mans unhappiness with his job has resulted in serious slide in business. Those around this person believe that he probably suffers from clinical depresseion, but the man in question refuses to believe it and, having a background in medicine, would likely know how to spot and stop any attempt made to treat such a condition. Furthermore, lets suppose that his co-workers, friends, and family are trying to help him, but are not sure what should be done to get the man back to his former self. Would anyone have any suggestions about what should be done? I'm desperate here, so I'll take any advise I can get. 70.254.22.164 22:32, 5 April 2007 (UTC)

May I ask why you are desperate for this hypothetical situation? − Twas Now ( talk • contribs • e-mail ) 01:34, 6 April 2007 (UTC)

I've lost friends to military moves. I would rather not lose my house and my parents to a divorce. Thats why I ask. I relaise that Wikipedia doesn't offer medical or legal advice, I just want some brainstorming help so I can try and save what little I have left. 70.254.22.164 03:05, 6 April 2007 (UTC)

Since this calls for speculation, I've answered here: [7]. StuRat 02:03, 6 April 2007 (UTC)

I would suggest that you talk with a psychologist, psychiatrist, therapist, or social worker. Be prepared to spend a bit of money; it's worth it. Obviously, the person who really needs help is this "hypothetical family member", but equally obviously, having that person talk to the psychologist etc. is not an immediate possibility. But (a) a professional might be able to help you figure out how to get this person the help they need, and (b) let's face it, you do need help, too -- otherwise you wouldn't be asking the question!

Good luck. (And thanks for caring.) —Steve Summit (talk) 03:15, 6 April 2007 (UTC)

We cannot give medical advice or psychological counseling. That said, a person the depressed person trusts who is not a direct family member can sometimes be helpful in getting them to a psychiatrist or psychologist. Their trusted medical doctor is an extremely good choice to push them to get the help they need. A priest or minister or rabbi might also be useful. Depression can result from a bad situation which counseling can help or can reflect chemical imbalances correctable with medication. Edison 04:37, 6 April 2007 (UTC)

I didn't think about having a clergyman take the matter up with my "hypothetical family member", although that does sound like a good idea. On this issue of medicine: we tried that once, but our family members' medical background came to his defense; when he relized that we were trying to get him to take an anti-depressent medication he got very angry with us and accused us of trying to interfere in his life. If there was a way to get him to take the medacine without relising what it was we likely would have figured out how by now :/ 70.254.22.164 06:50, 6 April 2007 (UTC)

My psychiatrist takes referrals directly from religious leaders, as well as family doctors. For hereditary depression which comes out in the forties, a few pills are a life saver! Problem is that many self-medicate with drugs or alcohol, and deny they are depressed. This tends to lead to violence and suicide. I know many, many men who should take the pills... --Zeizmic 15:02, 6 April 2007 (UTC)

My advice will be rough but honest. There are two issues here. People you love and care about have issues in their lives. That's one. You might suffer in consequence, in yours. That's the other. The more others are not calm and thoughtful and running on copmmonsense, the more you yourself have to be - two dramatics tend to make a situation worse not better, and misery loves to influence others to support them (see Karpman drama triangle and Transactional Analysis).

A good solution here is for you to grow to the point that you can see things here from a more heightened perspective. (See transpersonal psychology for example.) Here are some truths that apply:

1. Each person has their own path. You can hope for the best, and work for the best, but you are not living their life, nor their yours. You cannot say for certain whether something that looks like a disaster really is or not. You don't know what lessons they will draw nor how it'll pan out, and you can't predict what's for the best or whether allowing or avoiding suffering is best.
2. Your best role is to be a reminder to them that whatever else, the core emotional needs are safe. They are loved, they are cared for, they will be supported no matter what, they have not failed so badly that it means they are worthless, rather they have tried stuff and learned. They can focus on what they want stepo by step, in the same way as a cardianc or stroke victim relearns stuff.
3. if there is genuine psychological issues, then support may be useful. Traditionally US doctors are very heavy handed on medications compared to European. Consider whether this is life stuff they are learning, or brain chemistry. Often depression is simply the recognition that ones historic mental agenda is doomed or dead ends... and its solution is to accept it as a good thing to know, and the body suggesting taking time to look within at it.
4. Don't buy in that mood means everything. It may not.
5. Not every relationship lasts forever. Loss may be one of your tasks to handle, and if separation is best for them, then your role may be to love them even so, and understand the sadness and necessity.

Some ideas. I hope you find a path through it. Remember, all the above apply to you. Split of no, you are human, and valued. You know this, inside. FT2 ^{(Talk | email)} 01:54, 11 April 2007 (UTC)

date format history

While exploring a Salado Indian ruin(about 600 years old)in central Arizona recently I came across graffiti with a date formatted as: 6/18/19. I am wondering if that date format was in use at the time indicated or is this a later, bogus entry. Thank you. macinyartMacinyart 23:08, 5 April 2007 (UTC)

I'm pretty sure that would have been added later, probably June 18th, 1919, but possibly June 18th, 1819. StuRat 01:35, 6 April 2007 (UTC)

What did the graffiti look like? Spray paint? Stone carving? − Twas Now ( talk • contribs • e-mail ) 01:59, 6 April 2007 (UTC)

If you are just asking if they used that sort of date notation then, the answer is probably yes. My guess is that it became common to use abbreviated dates like that sometime in the 19th century, with the rise of the bureaucratic state and the need to constantly fill out forms. But that's just a wild guess. --24.147.86.187 02:45, 6 April 2007 (UTC)

Candles were sometimes used by hikers to leave dates and initianls on rock walls in caves. I saw some that were 90 years old when a Scout many years ago. Edison 04:32, 6 April 2007 (UTC)

Thank you for your responses, in fact I am interested in whether the graffiti dated in 1919 was placed there at that time (using that date format) or whether it was written much later by a more modern prankster. It appeared to be in pencil, but I did not touch it, since that is sort of the rule when looking at antiquities. I know that simply finding out that the date format in question was used in 1919 proves nothing, but it makes its presence have a bit more credibility. I plan to put images taken that day on my website soon and wanted as much credibility as I could get. There were other examples of modern graffiti (as compared with those images done by the Salado) but this one was the best. Some of the art like works done by the Indians are remarkable and charming. These are heiroglyphs rather than petroglyphs and the artist utilized pigment rather than "pecking" the design in the rock. Great stuff. Thanks again for the responses. macinyartMacinyart 17:16, 6 April 2007 (UTC)

On a vaguely relevant point, I have at hand a British book "Railway Tickets, Timetables and Handbills" by Maurice I. Bray. It shows a number of late-19th-century tickets date-stamped with forms like "22 JA 96" and "17 SEP 90" and "NO 26 86". None of them use all-numeric dates, but they all use 2-digit years. So we can say at least that that convention was established in at least one country before 1900. --Anonymous, April 7, 2007, 10:11 (UTC).

Indeed, I have British postage stamps from the Victorian period which have cancels dated e.g. 15 JA 70. -- Arwel (talk) 23:12, 9 April 2007 (UTC)

Mushrooms

I always knew they were some kind of fungus but I recently discovered that fungi have a seperate kingdom than plants. So basically that means that fungi, including mushrooms are not plants!? so what do their cells look like, do they have the things that plant cells have and animal cells lack? do they have cell walls? photosynthesis capabilities?
So basically, we eat three things: animals, plants, and fungi?

Try reading up on fungi. Perhaps the main thing which distinguishes them from plants is that they don't do photosynthesis to get energy from the Sun. Instead, they mostly get their energy from decaying matter (although there are parasitic/carnivorous fungi). BTW, we also eat things that aren't plants, animals, or fungi, such as the bacteria used to make cheese, yogurt, etc. StuRat 01:26, 6 April 2007 (UTC)

Fungi are actually more closely related to animals than they are to plants! Check out Eukaryote#Differences between eukaryotic cells for some more info. − Twas Now ( talk • contribs • e-mail ) 01:31, 6 April 2007 (UTC)

Also, mushrooms are only the "fruit" of the fungus organism, the main part of which is underground and called mycelium. Pfly 03:28, 6 April 2007 (UTC)

It is odd that fungi are not considered to be plants - but when you consider things like yeast - which behaves much more like an animal than a plant, it's perhaps not so odd. But like with so many questions we get here, we shouldn't be surprised at the oddness of the choice of name...it's just a name. The fact that scientists decided to exclude them from the name plant is about as arbitary as the decision to exclude Pluto from the list of planets or the Chimpanzee from the genus Homo. It's just a name. SteveBaker 04:00, 6 April 2007 (UTC)

I don't agree that it's "just a name", since you seem to be saying it's an essentially arbitrary decision, like whether Pluto was classified as a planet. There are good reasons for most of the scientific classifications, such as similarity in form, genetics, and ancestry. There are a few cases where species may have been misclassified, but the classification of the majority of species are not in question. StuRat 04:07, 6 April 2007 (UTC)

I agree. Not being able to produce its own carbon through photosynthesis is a huge difference. In general, reproducing with spores is different too. Some things are arbitrary, but this is like classifying the stars from planets. There are clear distinctions. --Wirbelwindヴィルヴェルヴィント (talk) 05:35, 6 April 2007 (UTC)

It is just a name. What we recognize as "fungi" are polyphyletic. Fungus is a way of life, not a taxon. − Twas Now ( talk • contribs • e-mail ) 05:41, 6 April 2007 (UTC)

You misunderstand what I'm saying. I'm not saying that fungi should be classified in the same branch of the classification hierarchy as grass, trees, daisies, etc - I'm sure the present classification is 100% reasonable. I'm saying that our questioner finding it strange that 'Mushrooms Are Not Plants' is an arbitary fact of how the word "Plant" has been defined. If scientists had chosen some new term ("photoplant" say) to denote the organisms that photosynthesise and that are therefore not animals or fungi - and chosen to use the word "plant" to informally encompass both fungi and 'photoplants' (as most non-scientists would certainly do) then this question would never have arisen. The question is not about the nature of biological classification - no layman would be too surprised to find that fungi have their own branch in the classification system - the question is why such "obviously" plantlike things (to a layperson) are not called "plants" by scientists. That is a question about why scientists chose to use some particular word for some particular branch of the classification scheme (which is entirely a matter of history and linguistics) - it's not in any way a question about the biology of fungi. In that sense, it's no different from the "problem" of whether Pluto is a planet. The discussions about Pluto were not questions about it's mass, size, orbital characteristics...it was a discussion about what the historical/linguistic implications of the term 'planet' is. How many textbooks would have to be rewritten - how many signs in museum display cabinets would have to be corrected. No new science was involved. Choosing to exclude Pluto from the arbitary term "planet" was every bit as arbitary as using the common word "plant" to describe only photosynthetic organisms rather than using it's more common meaning which includes fungi. It's just a word. SteveBaker 15:54, 6 April 2007 (UTC)

I believe there was some new science that went into the Pluto decision, such as discovering that several Kuiper belt objects are similar in size to Pluto. This, combined with Pluto's peculiar highly elliptical orbit at a high inclination (out of the plane in which most planets orbit) caused speculation that Pluto was actually an Kuiper belt object captured by the gravity of Neptune. Thus, it's classification as a planet was called into question. StuRat 01:30, 7 April 2007 (UTC)

For what it is worth, the OED agrees with you. After defining "plant" as 1. an organism of kingdom Plantae, and then 2. "green plants", multicellular and photosynthesizing, there is a note about how bacteria used to be classes in kingdom Plantae but are not now, and that ..in the broadest (non-technical) sense, the term still may include fungi (and lichens), which are now classified in a separate kingdom, but were formerly regarded as lower (non-vascular) plants, together with algae and bryophytes.

Also, the requirement of photosynthesis for plants fails in some cases, such as Monotropa uniflora, which while clearly a kind of flowering plant, do not photosynthesize and behavior more like fungi -- in fact tricking other plants into thinking it is a friendly fungus, and receiving food from them. Pfly 19:55, 6 April 2007 (UTC)

Cravings

Why do women in labor have unreasonable cravings for inedible things (e.g. paint)? —The preceding unsigned comment was added by 209.53.180.29 (talk) 23:32, 5 April 2007 (UTC).

I don't know about inedible things, but their cravings for unusual foods are likely to provide vitamins and minerals needed for the baby (and later, for lactation). StuRat 01:23, 6 April 2007 (UTC)

Do you have any evidence for that rather startling statement Stu? —The preceding unsigned comment was added by 88.109.246.75 (talk) 02:06, 6 April 2007 (UTC).

I assume you're being facetious. :-) StuRat 03:41, 6 April 2007 (UTC)

Well, he didn't ask you for personal evidence, if that's what you mean! —Steve Summit (talk) 03:47, 6 April 2007 (UTC)

It's not in 'labor' - it's pretty much throughout pregnancy. It's an unconscious effort to get sufficient intake of odd-ball vitamins and minerals and such. With my wife it was Toblerone bars wrapped in crusty French bread...at 3am...on a Sunday...when the nearest store that was likely to be open and have anything approximating the required ingredients was 40 miles away. Yep - it's definitely not an urban legend. What's utterly miraculous is that the ladies seem to be able to somehow know precisely that certain foods contain whatever dietary thing is missing. They aren't reading the ingredient list...it's gotta be some amazing unconscious memory for the vitamin and mineral content of all of these obscure foods...very, very strange. SteveBaker 03:56, 6 April 2007 (UTC)

Gonna have to put a big tag on the claim that the pregnant woman has some near miraculous instinct telling her that if she doesn't get dill pickles and ice cream RIGHT NOW the baby will be missing earlobes or have a pointy head. Is there any scientific data to back up the claim, interesting as it is? In some cultures pregnant women eat clay. Correcting a dirt deficiency? Edison 04:30, 6 April 2007 (UTC)

It's not that pregnant women gain some instinct; we all have such an instinct. It just becomes more urgent, and the things needed change from those usually needed. Isn't it generally accepted that people tend to feel a need for things they need? Like thirst when thirsty, hunger when hungry, a craving for bananas (if you have previously eaten bananas) when low in potassium, etc? Skittle 17:58, 6 April 2007 (UTC)

I agree that this seems unlikely - but the existance of cravings during pregnancy is exceedingly well documented...and it's evidently an evolved behavior because other mammals and birds exhibit it. The only explanation that has been put forth is a subconscious need to get some trace substance that is needed for fetal development. What is very stange is the extreme specificity of the craving. In my wife's case, no other chocolate than Toblerone would remotely satisfy her "need". But I certainly agree that it is dubious to claim that their brains have somehow memorised the exact content of a bazillion different foods and are homing in on the one thing that best matches this need...however, I don't know of any other explanation. But if we do buy into this explanation, it's not a "dirt deficiency" that's causing women to eat dirt - it's some obscure mineral - or trace element - or salt - that's likely to be present in dirt. It's weird - but it's hard to deny when you see it happening right in front of your eyes...and in that LONG 3am emergency drive to the Toblerone and French Bread store, you have plenty of time to reflect on the oddities of human biology and evolution! SteveBaker 15:34, 6 April 2007 (UTC)

Yes, that's actually an important nutrient for fetal development. "Then the LORD God formed man of dust from the ground" (Genesis 2:7). See also pica. DMacks 04:35, 6 April 2007 (UTC)

There are also some parrots that eat clay, apparently needing whichever mineral the clay has. StuRat 13:16, 6 April 2007 (UTC)

There are no scientific studies that have demonstrated the exact reason behind pregnancy cravings, but experts tend to suggest that it is associated with one or more of the following:

• A manifestation of a biochemical signal that the mother is lacking specific nutrients (the nature of the specific food craved appears to be culturally influenced).
• A result of altered hormone levels in pregnancy inducing olfactory and/or gustatory cravings.
• In the case of pica, the result of an iron or zinc deficiency.

The body of literature on the subject can be accessed here [8] Rockpocket 05:56, 6 April 2007 (UTC)

It is known that psychological cravings have nothing to do with "what the body needs," and we are very interested in finding out what is the cause of cravings. It isn't the same as being thirsty or hungry. [Mαc Δαvιs] (How's my driving?) ❖ 23:18, 6 April 2007 (UTC)

Really, do you have a source for that? My reading of the literature suggests the mechanisms driving craving are not known, so I would be interested to read about the experiment that demonstrates it has "nothing to do with" what the body needs. Rockpocket 00:10, 7 April 2007 (UTC)

I believe food cravings are due to a number of factors:

1) As stated previously, people tend to crave foods which contain nutrients their bodies need. This ability, providing a huge evolutionary advantage to those who possessed it, would have be strongly selected for. In pregnant or lactating women, many nutrients are removed from the body of the mother, causing her to crave foods which will replace those nutrients.

2) During most of human evolution, certain nutrients, such as salt, sugar, and fat, were in such short supply that we developed an almost insatiable desire for foods containing these things. Since few people encountered foods rich enough in those items to suffer from the problems caused by an oversupply, and many suffered from nutritional problems as a result of not having enough, our evolution guided us towards excessive consumption of these items in modern times.

3) Psychological factors can also play a part. For example, "comfort foods", which we associate with a pleasurable experience in the past, can cause the memory or feeling from that experience to return when we again consume those foods.

StuRat 01:12, 7 April 2007 (UTC)

There aren't many neurones which grow during life (it used to be thought none did). The sinuses contain some of them. In his book "Why zebras dont get ulcers" Robert Sapolsky hypothesises this is about parent bonding, and that the emergence of new tastes is due to new sensory neurone growth in the nose area. I might have that slightly wrong, but the general idea's about right. FT2 ^{(Talk | email)} 02:05, 11 April 2007 (UTC)

Olfactory sensory neuron regeneration (every 40 days or so in humans) is an interesting subject. The data in mouse seems to suggest that new neurons project to the same glomeruli in the olfactory bulb as the ones they replace, suggesting the retain a similar odor activation profile. However, this paper [9] suggests that regenerating neurons in the subventricular zone do populate the olfactory bulb in a manner influenced by odor environment. These become granule cells and result in a improved olfactory memory. This would suggest that the olfactory system is plastic enough to "adapt" to odorspace, but perhaps not at the level of the sensory neuron. Rockpocket 06:45, 11 April 2007 (UTC)

Population growth

If a city's population increases from 1,000,000 to 1,100,000 in 5 years, how do I calculate annual growth rate? im asuming 2% (one fifth of 10% in 5 years) close but not exactly the right answer, it should be a little less right?

Right. It would be calculated as follows:

{(1,100,000/1,000,000)^(1/5) - 1} x 100 = 1.924...%
See Compound annual growth rate for more info. adam the atomTEC 23:47, 5 April 2007 (UTC)

Yes, and the reason is that population growth is generally considered to be proportional to the current population, all other factors being constant. For example, a city with twice the population likely has twice as many babies born each year, and also twice the immigration, as there are twice as many jobs to be had and twice as many people to invite their relatives to live with them. StuRat 01:21, 6 April 2007 (UTC)

It is an example of exponential growth, which in early stages closely approximates linear growth, but which may vastly exceed linear growth in middle stages. DDB 08:50, 6 April 2007 (UTC)

Starlings - how do they know where the worms are?

As I was stood waiting for my bus today, I watched a couple of European Starlings pecking around on a nearby patch of grass. At first, it looked to me as though they were just wandering around and probing the ground randomly with their beaks - but they would frequently (maybe once in every four pecks) pull an earthworm from the ground. This suggests to me that the starlings were *not* just sticking their beaks into the soil at random and somehow knew the position of the worms beneath the soil (take a small pocket knife and stab it into the ground a few times - what are the odds of hitting a worm by chance?). How were they doing this? Any ideas? --Kurt Shaped Box 23:58, 5 April 2007 (UTC)

Worms leave little tunnels behind, which likely collapse noticeably when a bird pecks at the ground above them. The birds could then follow the tunnel to the worm with continued pecks. StuRat 01:18, 6 April 2007 (UTC)

I think I've heard that they can hear the worms burrowing through the soil, if they're close enough to the surface. —Steve Summit (talk) 03:05, 6 April 2007 (UTC)

Yes, they can hear the worms burrowing. Most birds eating worms use their ears to locate the prey. —The preceding unsigned comment was added by 195.236.222.1 (talk) 12:18, 6 April 2007 (UTC).

I don't know about starlings, but I have found a few references to a study by ornithologist Frank Heppner regarding how robins find worms, and the conclusion he came to is that they do it by sight. A brief item relating to the study can be found here (in the section titled The Eyes Have It. --LarryMac 20:10, 6 April 2007 (UTC)