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April 29

Hardened Boron Alloy Vs. Hardened Steel

If I have a padlock with a hardened boron alloy shackle(boron being a 9.3 on Moh's scale) would hardened steel bolt cutters be able to cut it?(hardened steel being in between 7 and 8 on Moh's scale)? Thanks, this has been driving me crazy —The preceding unsigned comment was added by 69.150.14.3 (talk) 06:53, 29 April 2007 (UTC).

I'd say it depends, bolt cutters rely more on leverage then hardness to cut something. If the bold is within the tolerance of the cutters I'd say there is a good chance that the cutters will cut it. Just because you are trying to cut something harder with something softer doesn't mean it will automatically fail. You can imagine cutting titanium foil with a pair of ordinary scissors, that's because of the design of the scissors, it is also easy to imagine an ordinary pair of scissors being destroyed by attempting to cut a titanium bolt. I think it would be a similar case with the bolt cutters. If you are actually trying to do this then one thing to remember is that the inside of the cutters, the point furthest in towards the hinge is where the most force is generated so if you were trying to cut something very hard try to stick it as far into the jaws as you can, but cut slowly and WATCH carefully, if the edges of the jaws start deforming a lot more then the bolt then you'll probably destroy the cutters if you squeeze harder. Vespine 03:04, 30 April 2007 (UTC)

Are we talking about cutting a piece of pure boron, or an alloy (boron melted into other stuff)? Hardness of 9.3 is for the element, not an alloy, and an alloy can have drastically different properties than any of its components in their pure states. DMacks 00:08, 1 May 2007 (UTC)

I would be very careful about "WATCHing" carefully. Hard materials tend to be brittle, and I can image either the bolt or the cutter exploding into some very sharp shards. So I wouldn't keep my face anywhere near the action. Bunthorne 03:27, 1 May 2007 (UTC)

beetle

I found an infestation of small; slightly larger than a ladybird, beetles covering tubs of rosemary and lavender...the beetles are very pretty; metallic green and bronze striped, head to toe. I had noticed the plants suffering but only recently seen the adult beetles... have a feeling i saw one pictured in RHS garden magazine a while ago, but cannot trace it.

Any idea what this is, and how to treat it? —The preceding unsigned comment was added by 84.70.57.152 (talk) 10:43, 29 April 2007 (UTC).

Could it be Chrysolina americana aka the Rosemary Beetle? (Wikipedia has an article on its family the leaf beetles or Chrysomelidae.) Here's a google image search. Is this your bug? ---Sluzzelin talk 13:17, 29 April 2007 (UTC)

My first thought was Japanese beetles. whatsthatbug.com is a good place for this kind of query. --TotoBaggins 13:23, 29 April 2007 (UTC)

Cancer in Argentina

Unpleasant subject but I need to ask. The average (According to Wiki) consumption of meat in Argentina in 100kgs per annum per person down from a high of 180kg in 19th Century.

Is this reflected in cancer statistics ?

Its a sensible question as we are told meat kills you etc. But does it.

If it doesnt I then have to look at other lifestyle choices in Argentina.

I do not know how to say thankyou beacuse of the structure of Wikipedia. So thanks now.

Paul

81.86.166.234 12:24, 29 April 2007 (UTC)Paul.mckenna at mac.com

I don't have the answer, but let me point out a few things to consider on the comparison:

1) Many other changes have also occurred since that time, so it would be difficult to determine which differences in health are due to which changes in diet and environment. There no easy way to compensate for this.

2) In the 19th century many more people likely died before they had the chance to develop cancer. For example, many women died in childbirth which would survive today and later develop cancer. So, you may actually find there was a lower rate of cancer long ago, along with many other diseases which tend to affect older people disproportionally. To compensate for this, you would need to look at the cancer rates for people of the same age. StuRat 17:04, 29 April 2007 (UTC)

Sound of P38 lightning

Hello

The P38 lightning was equipped with a forced induction apparatus known as a "turbosupercharger" It is because of the turbos the lightning lacks the raspy raw sound of its non turbo peers, notably the mustang, spitfire, and others. It has come to my attention however, that the wastegate on the lightning is fully open during takeoff. All of the gases are escaping unimpeded. I greatly enjoy the drone of the p38 engines and I attributed it to the fact that it was turbocharged, another aspect I enjoy. My question therefore is "why does the lightning still sound like a turbocharged engine at takeoff and is my logic behind liking the sound ill founded? —The preceding unsigned comment was added by 69.42.233.219 (talk) 18:59, 29 April 2007 (UTC).

Ah, flying machines! Do you have an audio recording? —Bromskloss 19:37, 29 April 2007 (UTC)

It is perhaps worth noting that the Lightning has two engines while the Mustang and Spitfire (and most other fighters) have only one each. I'd think that fact, and all the various sound interference and such that goes with two similar-but-not-identical noise sources, is a significant component of why you find the P-38's sound distinctive. — Lomn 15:19, 30 April 2007 (UTC)

Electromagnetic radiation as particle and wave

I'd like to understand the connection between the particle description and the wave description of electromagnetic radiation. For instance, how to describe a radio wave in terms of photons and how to describe a single photon as a wave? Thanks for opening my eyes. —Bromskloss 19:08, 29 April 2007 (UTC)

See wave-particle duality, wave function, photon, electromagnetic field, and electromagnetic radiation. If you want to go much deeper, look in to QED. Sorry for providing a bunch of links, but yours is a very broad question to which there isn't a short answer (or at least, not one that I'm capable of concocting). -- mattb 19:19, 29 April 2007 (UTC)

As far as I can see, the articles don't have an awful lot to say on what I am looking for. As an effort not to be too broad, let me give a specific example of what I would like to know: When analysing the properties of an antenna, we may calculate the electric and magnetic field it generates as functions of space and time. Could these fields be interpreted as photons? Could a static (electric or magnetic) field be? —Bromskloss 19:33, 29 April 2007 (UTC)

As the opening paragraph of the wave-particle duality article explains, (the) duality addresses the inadequacy of conventional concepts like "particle" and "wave" to fully describe the behaviour of quantum objects that on the quantum scale. quantum particles sometimes exhibit the properties of waves, sometimes of particles, sometimes the property seems to change depending on HOW you attempt to measure it. Trying to describe some of the behaviour as either particle or wave is what caused the duality in the first place. Vespine 02:45, 30 April 2007 (UTC)

Since you're not having much luck here, you might try posting your question at physicsforums.com. This kind of query is their bread and butter. --TotoBaggins 01:58, 30 April 2007 (UTC)

To clarify that: You cannot describe any situation with particles and you cannot describe any situation with waves. It is always wrong in both models. Just sometimes more wrong in one than in the other. —The preceding unsigned comment was added by 84.187.41.149 (talk) 04:00, 30 April 2007 (UTC).

Ah, that's a good point you (and Vespine above) make. Still, given an (inadequate) wave description, what would the (also inadequate) particle description be? —Bromskloss 07:55, 30 April 2007 (UTC)

Well... The de Broglie hypothesis is one useful relationship... -- mattb 13:49, 30 April 2007 (UTC)

But it doesn't tell you everything – there could be many different waves with that specific wavelength. —Bromskloss 15:10, 30 April 2007 (UTC)

Thanks for the suggestion. —Bromskloss 07:55, 30 April 2007 (UTC)

You might also find these equations helpful - Jefimenko's equations, which are the classical treatment, and the Liénard-Wiechert Potentials. Both of these deal with the ways that single particles interact with electromagnetic fields. In the most complicated analysis, you can use quantum mechanical effects; but you can decide what level of detail is necessary for your particular application. Nimur 20:25, 30 April 2007 (UTC)

fabic

At what temperture does rayon melt , does it have a lower melting point than ployester?

I don't have an actual answer for you, but you might find some useful information on google or elsewhere if you fix some of your spelling thusly: fabric, rayon, polyester. Confusing Manifestation 23:08, 29 April 2007 (UTC)

according to [1], "Rayon does not melt but burns at high temperatures" - Nunh-huh 05:52, 30 April 2007 (UTC)

Yeah, that sounds right. Rayon is made from wood fibre, it isn't a synthetic. Or, more accurately, it's not a petrochemical synthetic. Anchoress 05:58, 30 April 2007 (UTC)

Eye Colour and Genealogy

I am a white Briton and have green eyes. Does this mean I can say that I am descended from Celtic or Slavic stock with any degree of certainty? FreeMorpheme 23:02, 29 April 2007 (UTC)

Why would you think you're Slavic ? StuRat 03:46, 30 April 2007 (UTC)

In short, no. While "Green eyes are most often found in people of Celtic, Germanic and Slavic descent" they are also found "to a lesser extent in southern Europe (Portugal, Greece, Italy, Spain)." [2] There are three known loci and multiple alleles that account for eye colour. Even if you knew your genotype at these loci, is is unlikely to be sufficient for any type of definitive genealogical analysis. Rockpocket 05:31, 30 April 2007 (UTC)

Cyclone Technology

I was looking at the Cyclonic_separation article but it does not tell me when the technology was invented and who invented it. 202.168.50.40 23:08, 29 April 2007 (UTC)

April 30

Random Numberon calculator

Any idea how does a calculator produce a Random Number?? —The preceding unsigned comment was added by 210.212.194.209 (talk) 08:12, 30 April 2007 (UTC).

See Pseudorandom number generator. Simon A. 09:07, 30 April 2007 (UTC)

Some calculators use physical characteristics of their microprocessors to drive a hardware random number generator. Here is a hardware-level description of how random numbers can be generated using the clock systems in a family of Texas Instrument microprocessors. Gandalf61 09:26, 30 April 2007 (UTC)

So if you buy two brand new calculators and hit "Random number" will they both bring up the same number? Aaadddaaammm 09:29, 30 April 2007 (UTC)

Not if they use a hardware random number generator, or even a pseudo-random number generator (PRNG) seeded by some hardware characteristic that is difficult to replicate. A seed based on the number of microprocessor clock cycles since the calculator was switched on, for example, would be very difficult to replicate exactly on two different calculators - and the output of a good PRNG will be very sensitive to small differences in the seed. Gandalf61 10:47, 30 April 2007 (UTC)

Exactly, imagine the clock on the little microprocessor is ticking a few million times per second. If you counted the number of clock ticks and displayed (say) just the righthand three digits of the number when the user hit the RND button - then the result would depend on when you hit the button - and unless you could do that with a precision of maybe a thousandth of a second, the number you'd get back would look pretty random! If you then (in effect) scramble those numbers by pushing them into a PRNG and the result will be a very high quality random number. You can't use just the clock by itself if the calculator is programmable - because there would be a risk that the number of instructions between two consecutive calls to the random number generator would produce results that were very similar - but using the clock to seed a PRNG fixes that. SteveBaker 12:07, 30 April 2007 (UTC)

Weight Loss Overnight

I'm monitoring my weight for health reasons at the moment, and as I was curious I weighed myself before going to sleep for the night, and straight away when I woke up. Before sleep I was 15 stone 10 pounds, but 8 or 9 hours later after sleep my weight was 15 stone 6 pounds.

Does anyone know where that 4 pounds went to? Surely I didnt sweat it?

ta -stubblychin —The preceding unsigned comment was added by 213.212.70.122 (talk) 08:14, 30 April 2007 (UTC).

Well, you may have sweated (or exhaled) some moisture - and you shed some dead skin cells and you inhaled lightweight oxygen and breathed out heavy carbon dioxide in its place - but I agree that four pounds sounds way too much. My best guess is that your bathroom scales just aren't that accurate. All it would take would be a 2% error - and I bet you can make the reading change that much by shifting your weight from one foot to another or leaning forwards or backwards or perhaps by getting off and then back on again. SteveBaker 11:46, 30 April 2007 (UTC)

Do an experiment. Place something of constant mass on your scales. Do it at various times of the day. Record down all the values. It should show the same value everytime, if not then your scales are not accurate. 1.8 kg / 99.88kg = 0.0182 hmmnn.. Perhaps your scales are only accurate at 1.8% at around 90-100kg. Ohanian 12:26, 30 April 2007 (UTC)

Actually, I've done this a few times over the last couple of days, and they are a pair of (supposedly) accurate digital scales. I had lost 2 pounds this morning overnight and I checked it twice. My girlfriend had lost even more! I'll test the same weighted thing on it though. Maybe it is atmospheric. -stubblychin

If you took a dump consider that water weighs about a pound a pint and solid waste is also dense. Edison 14:21, 30 April 2007 (UTC)

Yea, you probably just urinated and forgot about it. StuRat 17:45, 30 April 2007 (UTC)

Yeah! a pint of water weighs a pound and a quarter (in UK) so if you exhale a couple of pints overnight (not unknown) you have 2.5 lbs! —The preceding unsigned comment was added by 88.109.137.137 (talk) 21:25, 30 April 2007 (UTC).

I'm still really sceptical that the scales are that accurate. Perhaps the things are temperature sensitive and maybe it's colder in your bathroom in the morning than the evening? Maybe the battery in the scales is going flat and giving a different reading each time. There are a bunch of reasons why the scales could have a 2% error (and now you are telling us that this time it's only 2lbs which is a 1% error) - all of those are more likely than that you lost 2lbs overnight just by sleeping! You say "supposedly accurate" - but how accurate do you expect them to be?! A 1% error for a consumer grade product like that is not at all unreasonable...particularly because they have to weigh you when you are standing a bit off to one side or wobbling a bit as it weighs you. The error bars are just too large with a machine like that to claim a scientific result. SteveBaker 02:37, 1 May 2007 (UTC)

For what it's worth, I have no problems thinking you could lose a few lbs overnight. According to my scale, it happens to me sometimes. My weight seems to fluctuate pretty regularly throughout the day. Maybe my scale is wonky, but I have no reason to particularly doubt it. Friday (talk) 02:44, 1 May 2007 (UTC)

Well, I guess we could figure this out. If you take an average of 18 breaths per minute with a tidal volume of 500ml per breath - then over (say) 8 hours of sleep - you'll have taken in 4320 liters (4.32 m³)of dry air and expelled it at somewhere near body temperature and at 100% humidity...then about 3% of that (by mass) is water vapour - 4.3 cubic meters of air at 1.2kg/m³ means that assuming the air you are breathing is utterly dry - and what you breath out is 100% humidity then at most - you breathed out 0.15kg of water....that's just about a third of a pound. In reality it'll be a lot less than that because you are unlikely to be breathing in utterly dry air - in part because a lot of the air in the room is what you just breathed out! Also the 18 full breaths per minute with 500ml tidal volume is for someone who is awake - you breath more slowly and less deeply when you are asleep. I'd bet that the total is more like 0.1 lbs due to breathing. Now - how about perspiration? Well, this article says that when you are doing a high activity cardiovascular workout, you can sweat 1.2lbs in an hour. If you are claiming to have sweated that amount over maybe 2 or 3 hours of sleep?! And in any case - just think how wet your bed would be if you tipped two to four pounds of water into it each night! No way! NO! Simply not possible. I would be very surprised if you were sweating at even a tenth of that rate. Your scales simply aren't accurate enough - period. SteveBaker 03:25, 1 May 2007 (UTC)

Could it be air pressure changes due to temperature? Or maybe you are wearing different clothes?

A change in air pressure wouldn't affect your true weight - so we'd be talking about how it might affect your scales. If it's an fancy digital gizmo then it's probably using the piezoelectric effect - it it's an old style mechanical one then it's using simple springs and stuff - neither of those mechanisms would be affected by air pressure changes. Temperature changes could make a significant enough difference though. If different clothes were being worn then 'Duh!' - but I presume our questioner has more intelligence than that! SteveBaker 21:57, 1 May 2007 (UTC)

Any reports of Abduction phenomenon in the neighborhood? Succubi? Vampires? Missing kidneys [3]? Edison 19:36, 1 May 2007 (UTC)

people lose weight all the time they aren't eating as their body uses its stores of energy (fat), basically to keep you alive all night :) Whilst sleep doesn't need much energy, if you spend enough time doing it, it can soon add up :) Try finding your BMR, then working out how much of the day you spend asleep and see how much enery that is :) I'm sure someone could tell you how much fat you would have to burn using that much energy :) HS7 16:11, 2 May 2007 (UTC)

But the energy doesn't weigh anything (well, e=mc² but c is huge - so m is quite utterly negligable). What has weight is the byproducts - which includes: Pee and pooh (ruled out because nobody visited the bathroom between weighings), water - exhaled and sweated, CO₂ breathed out. I did the math (see above) - all of those come to a fraction of a pound. Sorry - but your explanation simply doesn't fly. SteveBaker 00:02, 4 May 2007 (UTC)

Global Warming

It was suggested that if ocean going ships were to spread plankton (or some other organism) as they were passing then they would absorb excess CO2 and convert it to carbonates.Any idea why has that not been implemented? —The preceding unsigned comment was added by 210.212.194.209 (talk) 08:19, 30 April 2007 (UTC).

You first need to have the plankton. Therefore, the idea is not to spread plankton itself, but rather to fertilize the ocean with iron in order to stimulate the growth of algae and other plankton living an algae. This idea, including the problems, is discussed in the iron fertilization article. Simon A. 09:11, 30 April 2007 (UTC)

Agreed, as much plankton as can grow (under current conditions) is currently growing. Thus, to make more grow, we need to change the conditions. StuRat 17:41, 30 April 2007 (UTC)

There's also the general concern that the environment should not be tinkered with lightly. One would want to explore the possible side-effects from such a scheme very carefully — otherwise you could quite possibly end up with the very common situation in the history of purposeful environmental meddling where 1. you end up creating a new calamity where one didn't exist and 2. you don't even end up really accomplishing what you set out to accomplish. --24.147.86.187 01:46, 1 May 2007 (UTC)

Why is the F/A-18 Hornet so good?

Looking at the characteristics of the F-14 Tomcat with the F-18, the F-14 excels in nearly all areas, the most obvious being its speed (Mach 2.34 vs Mach 1.8). The Tomcat has a greater combat radius, and can carry nearly twice as much weight in equipment. So why were they all changed to F-18s in every squadron after 2006? They are so slow they could not catch even the oldest types of MiGs. This strange aircraft replacement can be observed in some post-Warsaw Pact European countries, where the good old MiG-21s are being replaced with the newer, more expensive, and less proficient Grippens. No conspiracy theories and nasty money things please. --V. Szabolcs 08:30, 30 April 2007 (UTC)

Costs and agility. - Dammit 09:59, 30 April 2007 (UTC)

Well, "nasty money things" is hard to avoid. The F-14 is quite the modern marvel of engineering and electronics, but the frames are becoming old, and it is quite a tormenting task to overhaul a F-14, whereas the F-18 may be considered better on these areas. Logistics is very important, extremely much so aboard aircraft carriers and such. Also when you say "good old MiG-21", it is true that these aircraft have a very good performance history, but the agility is nowhere near what the Swedish Grippen has to offer. Also consider the fact that as airframes age, you can only adjust them so much to carry new equipment (see F-16 Falcon) before in the long run, a new frame is preferable. If this does not answer your question well enough, do let us know. 81.93.102.185 10:59, 30 April 2007 (UTC)

The mission of these aircraft has also changed quite a bit. US aircraft are not likely to be dogfighting with other modern planes at close quarters (especially the US Navy/Marines aircraft - dogfighting is for F16's). For most missions these guys will be undertaking, it's down to stealth, long range targetting, fancy sensors to be able to find the enemy while they are still 60 miles away, stability as a camera platform and fuel capacity. Lifetime operating costs and mission flexibility are more important than capital costs and ability to excel in one particular area. Top speed is largely irrelevent. If the enemy have fighter aircraft at all, they will mostly be taken out by trashing their airfields from high altitude, radar-invisible bombers or cruise missiles - and if any do make it into combat, long range air-to-air missiles are what wins the battle - not flying really fast in tight circles blazing away with machine guns like in the movies. Remember the first Gulf war? Saddam flew what was left of his airforce to Iran to avoid them getting splatted. Since then, I doubt that the US Airforce/Navy/Marines has faced a single enemy plane! SteveBaker 11:59, 30 April 2007 (UTC)

Agreed. The major current threats to fixed-wing aircraft are surface-to-air missiles, small arms fire at take-off and landing (for land-based planes), and mechanical failure (with sand as a contributing factor). StuRat 17:36, 30 April 2007 (UTC)

I believe the F-14 is considered a much better combat fighter and has all the things you mentioned including a much better radar. The F/A-18 is single man crewed and has much better ground attack capabilities. Every air wing on a carrier can now carry out ground attack missions which makes them significantly more effective in operations such as Iraq and Afghanistan. The Super Hornet closes the gap in interceptor capability. Essentially variants on the F/A-18 are used for every role and this helps reduce cost, improve aircraft availability (all spares are the same and allow cannabilism in a pinch), reduce crew training (both support and flight), standardized ordninance, improved overall program cost and the reliability of more modern airframes (the F/A-18 is still 20 years old, super hornet is newer). The current mission of the U.S. Navy is threat projection. this is somewhat different from the cold war role of Nuclear Strike Force. --Tbeatty 07:03, 1 May 2007 (UTC)

what is science?

—The preceding unsigned comment was added by 80.87.65.22 (talk) 11:29, 30 April 2007 (UTC).

By the way, you can use the Wikipedia:Sandbox or any of your own pages to do "experiments." The preview button is also probably better than either of those. [Mαc Δαvιs] ❖ 13:36, 30 April 2007 (UTC)

They probably pressed the Example Image button by accident, I've removed it from their post--VectorPotential^Talk 13:39, 30 April 2007 (UTC)

Science has a pretty decent overview... -- mattb 13:45, 30 April 2007 (UTC)

Science is the systematic rational investigations of natural phenomenon. The question you should be asking is "what are rational methods?" and "what are natural phenomenons?". 202.168.50.40 22:09, 30 April 2007 (UTC)

It's not phenomenons, it's phenomena (do do doo doo doo, phenomena) 137.138.46.155 06:59, 1 May 2007 (UTC)

I liked that movie, Phenomenon [Mαc Δαvιs] ❖ 13:11, 1 May 2007 (UTC)

growth plates

how do you know when growth plates are closed or still open without an x-ray or do you need one show it and am i still growing? im turning 16 this year and im currently 5"8 / 5"8.5 (im not sure which one :D ) —The preceding unsigned comment was added by 80.42.1.152 (talk) 13:25, 30 April 2007 (UTC).

well as far as the growing thing yes you are. i belive it was at the age of 20-21 that a person stops growing. thats why they dont recomment Lasic operations on your eyes till then. although i dont think this is relevent to what your asking; it shows how long our bodys keep changing though. Now growth plates ill leave that to someone else User:Maverick423 If It Looks Good Nuke It 13:48, 30 April 2007 (UTC)

What does LASIK have to do with growth plates? Splintercellguy 15:03, 30 April 2007 (UTC)

LASIK is not recommended for people that are still growing. This medical recommendation is an indirect report of when growth stops. Czmtzc 15:23, 30 April 2007 (UTC)

i have good eyesight so i dont really need laser eye surgery :D

Yep it was just to be used as a comparison of when growth stops. =) User:Maverick423 If It Looks Good Nuke It 17:02, 30 April 2007 (UTC)

When you stop growing will probably depend largely on your genetics. Although many do continue growing into their early twenties, some do not. It does depend on the person - and is probably to do with genetics and probably also things like diet etc. It'll generally depend on when you reached puberty. Earlier puberty = stopping growing sooner, generally speaking - although it's probably not quite that simple. I stopped growing when I was 15 at 6'0". One or two in my year at school stopped earlier. Many of my friends were still growing near 18. It all depends - and the only sure way of checking would probably be a bone age test. 83.67.65.69 17:37, 30 April 2007 (UTC)

Picture identification

I saw this strange plant and photographed it. Does anyone know what it is? J Are you green? 22:20, 30 April 2007 (UTC)

Is it right side up, or did you photograph it sideways? Some kind of pollen?--VectorPotential^Talk 23:29, 30 April 2007 (UTC)

Plant location, image with leaves would be helpful bmk

It is right side up; it was growing out of a possibly dead, leafless bush-like plant in an abandoned field. The ball itself was about 2 or 3 cm in diameter if I remember correctly. J Are you green? 01:31, 1 May 2007 (UTC)

By "location", I'm guessing bmk meant something both more and less specific than "an abandoned field", namely: what part of the world? Country/province/state/city? —Steve Summit (talk) 02:19, 2 May 2007 (UTC)

I can't tell for certain if it's from the plant, but there appears to be a strand of silk which might indicate an insect or other animal life which contributes (partially or wholly) to the fuzzy appearance. 128.12.131.62 01:35, 1 May 2007 (UTC)

The underlying brown stalky bits look very much like the old remains of an umbel, the seed bearing part of an Apiaceae plant (such as carrot, fennel, celery etc). But the stalks to the seeds have been broken off. The white fur may be a fungus such as mould. GB 01:24, 2 May 2007 (UTC)

May 1

Top Ten parasites

Ive looked every were and havent found any thing im trying to find. I some way to identafy the top ten worst parasites. Every were i go nothing tells me anything ive tried Google ask jeeves but nothing so i hope u can help me.

70.133.64.95 00:52, 1 May 2007 (UTC)Tony

How do you define "worst"? -- mattb 00:54, 1 May 2007 (UTC)

Make your choice from Category:Parasites. However, if you wish to know which parasites have the greatest impact on human mortality and morbidity, this page might help. Rockpocket 01:09, 1 May 2007 (UTC)

For simply bizarre and horrific parasites, see this page. --Joelmills 01:17, 1 May 2007 (UTC)

I've always been partial to dracunculiasis and the dread loa loa worm, but on television recently it seems the more popular alternative is the penis worm. - Nunh-huh 01:57, 1 May 2007 (UTC)

The family of parasites that cause African sleeping sickness and chagas are pretty nasty when you consider that they cross the blood-brain barrier. - AMP'd 01:56, 1 May 2007 (UTC)

Candirú should have an honored position on such a list. --TotoBaggins 02:02, 1 May 2007 (UTC)

If your intrested in animals like this you should check out animal planet or National geographic chanel they have little specials on animals like this =) you might get lucky and catch one sooner or later. User:Maverick423 If It Looks Good Nuke It 15:13, 1 May 2007 (UTC)

E. Coli

Escherichia coli does not seem to mention how the bacteria get in to a human. Billions or trillions of E. coli cells live in an average human. I imagine that a newborn baby does not have such bacteria inside; by what age is it fair to say "most" humans have a healthy population of E. Coli? If it is pres<link rel="stylesheet" type="text/css" href="http://en.wikipedia.org/w/index.php?title=User:MarkS/XEB/live.css&action=raw&ctype=text/css&dontcountme=s">ent since birth, is it really fair to call the E. Coli a separate organism from the human host? Nimur 01:46, 1 May 2007 (UTC)

In fact, E. Coli make up only about 1% of the intestinal flora of adult humans, but is one of the predominant members of the flora of the intestines of infants (along with lactobacilli and enterococci). The E. Coli, like all other commensal flora of the gut, enters the gut when it is ingested. And, yes, of course E. Coli and humans are separate organisms. - Nunh-huh 01:54, 1 May 2007 (UTC)

To elaborate a bit on Nunh-huh's last comment. E.coli is a seperate organism because it is happy to live by itself outside the human body. It is not dependent on us for its replication, it has its own DNA and will happily grow any place where the conditions meet it's standards (which aren't very high btw). E.coli just finds our colon a very nice place to hang out. We give it nutrients, warmth and moisture and in exchange E.coli gives us vitamin K. PvT 13:40, 1 May 2007 (UTC)

E. coli will get into the human via the mouth. Because there are so many of these bacteria around, every time we eat we will be consuming some E. coli along with the food. It is hard to keep a baby completely sterile. At some point the cells evade digestion in the stomach and make it to the intestine where they grow. GB 00:44, 2 May 2007 (UTC)

Edde triggered logic

Any idea how can edge triggered logic be implemented behaviorally??59.92.241.28

Not sure what you're after, but have you read flip-flop? -- mattb 12:58, 1 May 2007 (UTC)

I don't think there actually exists such a device as an "edge-triggered latch"; we just use that term as a sort of short-hand because it's an approximately-correct description of the observed external behaviour. Internally, I think all edge-triggered devices are really more like "transparent latches" that are "opened" by a pulse derived from the clock passing through a delay stage. That is, the delay stage sets the amount of time that the transparent latch is open, and for most purposes, it's an infinitesimal period of time that roughly corresponds to just the edge of the clock pulse.

If you look in the old TI 54/74 series TTL handbook, you'll find detailed diagrams for most of the common flip-flop families.

Atlant 13:13, 1 May 2007 (UTC)

CRT Tube

Any idea what picture characteristics should degrade and in what amount in a CRT tube??Well my comp monitor is about 5years old with about 4000hrs usage, and the sides seem a slight blur(out of focus).Is this normal or can it be corrected?59.92.241.28

You can usually cure that blurring by degaussing the CRT. the internal degaussers (if any) may be insufficient to completely degauss the CRT. The main age item for a color CRT is the phoshpors. The colors tend to go off.This is noticable when you have CRTs of various ages in the same location. Of course, you can "burn" an image into a location on the screen if that image remains fairly constant for weeks at a time.The originaljustification for "screensavers" was to avoid this effect.I do not know if modern CRTs still suffer from this. -Arch dude 02:22, 1 May 2007 (UTC)

That sounds like it could use some degaussing - but modern monitors do that automatically every time you turn them on. Perhaps if your has a 'Menu' or 'Settings' button on the front, you could try looking through the menu system to see if there is a 'Degauss' option. If you find it, the monitor should emit a loud click - then the screen will shimmer a bit - and maybe - if you have lead a blame-free and moral existance - the monitor will sharpen up a bit. Sometimes you have to do it several times. But that might not be it. If the 'blur' is actually colour alignment (if you put a white dot in that blurry area of the screen, do you see three overlapping red/green/blue dots?) then it's possible that you can realign the thing - again using the front panel controls if it has them. It's hard to describe what to do without seeing the screen and knowing what (if any) menu items are available from the monitors front panel controls...but look for controls that talk about colour alignment or something similar. If the worst comes to the worst and you can't fix it either of those ways - you could reduce the size of the image on the screen (again - assuming you have a monitor menu) so that there isn't any image in the blurry areas. SteveBaker 02:23, 1 May 2007 (UTC)

(Edit conflict) CRT stands for cathode ray tube, so CRT tube is like saying cathode ray tube tube. - AMP'd 02:24, 1 May 2007 (UTC)

Sounds like someone is suffering RAS Syndrome. Vespine 03:33, 1 May 2007 (UTC)

The focus of the CRT is set by (manually) adjusting a fairly high voltage, and it's pretty common for older monitors to drift out of proper adjustment. A qualified person may be able to re-adjust your focus, but please note that it is a high voltage (thousands of volts) so caution is needed!

Also, as SteveBaker said, color CRTs also depend on having three electron beams converge at the same point on the screen; this convergence can drift over the years leading to the red image shifting slightly from the green image which is shifted slightly from the blue image; a casual look might perceive this as an "out of focus" condition as well. Convergence can usually be adjusted (at least a bit) from the monitor's on-screen setup displays.

Atlant 13:18, 1 May 2007 (UTC)

Non-exploding Sun

When I was at school in the UK we went on a trip to a planetarium. I asked the guy the following question which he was unable to answer, can anyone help?

If the sun is one massive burning ball of gas, why doesn't it explode all in one go rather than burning for millions of years? Thanks, Kirk. —The preceding unsigned comment was added by 91.84.75.27 (talk) 06:31, 1 May 2007 (UTC).

Is the Sun one massive burning ball of gas? A.Z. 06:43, 1 May 2007 (UTC)

No the sun isn't burning in the conventional sense, it is powered by nuclear fusion reactions, which happen in the core where the pressure is high enough. The reason it isn't just blown apart is the massive force of gravity acting on such a big object. Also when it's described as a ball of gas, it means gas in the sense of a state of matter (i.e. not solid or liquid) rather than natural gas or something explosive like that. Stars mainly contain helium (which doesn't burn) and hydrogen, which would burn on earth but requires oxygen, which is not available in space. No doubt better details are in the articles on sun and star.137.138.46.155 07:05, 1 May 2007 (UTC)

(via edit conflict) The tricky word there is "burning" ("gas" isn't entirely correct either, but I'll let it stand for now). Burning implies combustion, which is what happens when you combine (for example) hydrogen gas, oxygen gas, and a little spark to ignite it. What happens on the Sun, on the other hand, is a nuclear fusion reaction where individual protons (aka hydrogen nuclei) combine to form (with a few other processes and particles involved) alpha particles (aka helium nuclei). Now, the reason the sun doesn't explode all in one go is still a rather interesting one, and there are a couple of factors involved: first, nuclear reactions are somewhat haphazard, and require conditions to be "just right" before they'll take place. Thankfully, in the Sun there is so much scope for conditions to be "just right" that it takes place fairly often.

Secondly, the Sun has a lot of fuel, so it has the ability to "burn" for a long time.

Third, the main reason the energy from the nuclear reactions doesn't just cause the whole Sun to explode (aka expand highly rapidly in all directions, ejecting matter and energy at massive rates) is gravity. In a main sequence star like the Sun, the fusion reactions taking place do cause huge outward pressures, that unchecked would cause an explosion (like a supernova), but the force of gravity pulling all the parts of the star in towards its centre counteract those pressures, and things hang in a rather precarious equilibrium. When that equilibrium is disturbed (by a whole lot of factors including the exhaustion/"burning up" of all the hydrogen fuel, several quantum mechanical effects involving neutrinos, and the Pauli exclusion principle, to name a few), the star does "explode", or at least its outermost layers do, in a supernova, which leaves behind a tiny remnant that may be a white dwarf, neutron star, or even a black hole.

(Incidentally, the matter in the Sun isn't really in a gaseous state so much as it is a plasma.)Confusing Manifestation 07:11, 1 May 2007 (UTC)

See Stellar evolution. The sun fuses hydrogen into helium and the rate is determined by the mass of the sun. --Tbeatty 07:12, 1 May 2007 (UTC)

Well, Kirk, I hope you got a gold star for asking a really excellent and insightful question. To complete the picture, the plasma that makes up the Sun behaves like an electrically conducting fluid, so it is affected not just by gravity and pressure, but by a complex interplay of magnetohydrodynamic forces as well. No wonder the planetarium guy couldn't answer your question ! Gandalf61 11:07, 1 May 2007 (UTC)

WOW! I would never have thought that such a seemingly simple question had so much heavy science behind its answer. Now at 34 (a few years after primary school), I finally have an answer. Well done Wikipedia! Thanks everyone and regards from the UK. Kirk

Formaldehyde

I was reading the article and i found this "Formaldehyde is converted to formic acid in the body, leading to a rise in blood acidity (acidosis), rapid, shallow breathing, blurred vision or complete blindness, hypothermia, and, in the most severe cases, coma or death." I think I understand how everything arises except the hypothermia thing. Can anyone explain how it kicks in place?Bastard Soap 10:52, 1 May 2007 (UTC)

(Off topic story.) Once in chemistry class, we were presented to formaldehyde and our teacher told us "go on, take a breath, it will kill some bacteria for you". Of course, I had to try, so I stuck my nose right to the bottle and inhaled. GAAAAH, how it felt like burning in my throat. Fun thing to do anyway. :-) —Bromskloss 12:52, 1 May 2007 (UTC)

PMID 6955953 looks like a good place to start. I don't have access to the article, was just something I found by keyword search. DMacks 13:19, 1 May 2007 (UTC)

When did plant roots first evolve?

I tried looking at our article on Root but it doesn't say anything about when and why plant roots first evolved. I would be grateful for any information. Capitalistroadster 11:08, 1 May 2007 (UTC)

in Silurian. You are welcome. Dr_Dima.

Wikipedia is severely lacking in Plant evolution. This major topic should have its own article. Nimur 20:45, 1 May 2007 (UTC)

Hurricane

What would happen if you exploded a bomb in the eye of the hurricane, or outside it? Would it be possible to stop it with such a device?Bastard Soap 11:13, 1 May 2007 (UTC)

No. Look at Hurricane. The total energy and feeder zone are so huge that it could not be disrupted. As well, our scientific knowledge is not sufficient, we would just as likely do something to strengthen it. --Zeizmic 12:32, 1 May 2007 (UTC)

forgive me for sorta hijacking this question but i think it should also be asked (im courious to know). what about liquid nitrogen?. we know hurrcains are powered by the warmth of the ocean, wouldnt lets say 50 tons of it or more (of course leaving out that cost factor) dropped in the eye walls and eye itself, at least weaken if not disrupt the hurricane? it should cool it down a bit no? User:Maverick423 If It Looks Good Nuke It 15:25, 1 May 2007 (UTC)

Once again the truly incomprehensible scale differences between the lab and the world come into play. A square plate of water one centimeter deep and 67 meters on a side weighs 50 tons. So, even supposing that LN₂ can "dehurricanize" water — that is, cool it enough to make it useless for the hurricane overhead — at a mass ratio of 3000:1 (ridiculous), it takes less than a square 4km on a side to have the top centimeter of water be all that is affected by your cold bomb. A hurricane covers a much bigger square, and the ocean is much deeper. It would cost less to fly the entire population of the affected area somewhere else, with all their personal belongings on additional cargo planes, than to "dilute" a hurricane with such a tactic. --Tardis 15:48, 1 May 2007 (UTC)

wow i dont know why i thought it would work. well lets say it was possable to disrupt a hurricane, what kind of thing would do it? and what kind of energy would be involed in doing this? we said nukes arnt enough (and obvious other reasons too), but what would stop one? only another force of nature? User:Maverick423 If It Looks Good Nuke It 17:02, 1 May 2007 (UTC)

You might be able to shade the hurricane out of existence, say by dusting the air above it to absorb or reflect sunlight. Hurricanes typically lose strength at night, so if you could make a "night" long enough (without at the same time greatly enhancing the local greenhouse effect) you could perhaps starve it over a few days. But the extra heat introduced in the upper atmosphere (or the overall lowered temperature if you reflected the sunlight back into space) might very well cause worse weather somewhere else. The problem is that you're basically fighting energy conservation here: unlike, say, a human, a hurricane doesn't continue to exist because it somehow defends itself from damage or disruption, but rather because it is the natural result of the energies and materials that are present. One might as well attempt to deal with a mudslide by somehow convincing the mud not to go downhill once it is loose and flowing (rather than, say, adding walls, terraces, or vegetation that give it the strength to stay put). --Tardis 17:30, 1 May 2007 (UTC)

Ok, so a hurricane is too huge, but immagine a huge bomb or a small tornado, the answer would still be "highly improbable but we don't know enough to exclude it"?

I doubt it would solve anything. The goal is, as I understand it, to disrupt the spinning so the hurricane stops? It seems more likely that, if you had any effect at all, the thing would just soak up the forces and break up into several subsystems. Imagine two tectonic plates being pushed together, griding along their line of contact. Now imagine imbedding a bomb in the crevice, and blowing it up. The best effect you could have (ignoring the local devestation and the further effects propagated by the system itself; in the case of a storm, fallout from the bomb being carried for miles), would be to crack one of the plates into two smaller plates. It's unlikely, but maybe you'd get lucky. The forces that put the plates there in the first place, and that are pushing them together so hard, are still there and are still going to grind the plates against each other. The result, inevitably, will be earthquakes, but now along multiple fault lines. That's what they mean by it being the result of pre-existing forces. There is a lot of air, and it's the wrong temperature, and it has to go somewhere. It turns out spinning is the best way for it to get where it's going. Therefore it spins, and at best can be made to detour somewhat. Black Carrot 21:16, 1 May 2007 (UTC)

An idea I had for preventing hurricanes is to populate the tropics with floating solar cell rafts, which would collect electricity to sell and thus pay for themselves, and also reflect the light not turned into electricity. If you could have enough of these, they would prevent the water from overheating, which is what causes hurricanes. StuRat 05:03, 2 May 2007 (UTC)

Building inverters

hi i need ur help in getting results for building my own inverters. its really frustrating going through t6he rigours of finding results for the topic i have just mentioned kindly help me. thanks.

Power inverters (DC to AC)? Logic inverters? Optical inverters?

Atlant 13:22, 1 May 2007 (UTC)

what is the relationship between hardness and tensile strength of cast iron

Dear sir please give the answer of my question given below:

what is the relationship between hardness and tensile strength of cast iron? —The preceding unsigned comment was added by Pankaj raja (talk • contribs) 12:44, 1 May 2007 (UTC).

We don't do homework, but you might want to study our article on cast iron, paying particular care to the role of carbon and carbides.

Atlant 13:24, 1 May 2007 (UTC)

Death by Battery

Why do a few people each year die by licking a 9v battery? Is it something in their genes which makes them susceptible to it, or is it just pure chance? If so what is the probability? —The preceding unsigned comment was added by Nebuchandezzar (talk • contribs) 13:41, 1 May 2007 (UTC).

Have you seen a case of this ever happening? Provide a link and someone can then respond better to your question. Seems unlikely. Edison 13:50, 1 May 2007 (UTC)

That sounds like a myth to me. I don't think it's possible to die of 9 V unless you apply it directly to your heart or something. —Bromskloss 14:56, 1 May 2007 (UTC)

Agree, I doubt a DC 9 volt battery could electrocute someone. Maybe the battery casing was broken and chemical poisoning occurred? Nimur 16:18, 1 May 2007 (UTC)

if i recall my electrical trades class correctly, 1.5 volts is enough to stop your heart only if it was directly in contact with it. now i remember making a easy device with my friends that shocked us with 9 volts of electricity when the thing was turned on. it was pretty powerful for 9 volts, however one of my friends took a 120volt shock from a project once and she only made a squeak from it. she started sweating but thats pretty much it. and for me i got shocked with 300 + volts from a experiment with a super weak version of a jacobs ladder. and look at me im still here =)... i think what kills people from voltage was the AMPS if im correct. One Amp can kill a person. im not sure 100% how that amps thing works(didnt pay attention) so someone should be able to clarify it.User:Maverick423 If It Looks Good Nuke It 15:32, 1 May 2007 (UTC)

"Volts gives jolts but current can kill." Okay, the final alliteration is a bit off, but that's how I learned to remember what was what. "A lot of electrical flow" (high current) is what leads to the danger, not "a teeny amount of electricity flowing with great force" (high voltage low current). If I remember correctly, for externally-applied shocks under ideal conditions (minimal skin resistance, etc), lethality can be as low as 30V or so. DMacks 15:39, 1 May 2007 (UTC)

See alsoWilliam Kemmler for an account of the first use of electricity for capital punishment, and [[4]]. Hundreds of electrocutions were carried out smoothly after that one, in which the electrodes may have been incorrectly applied. High voltage AC (over 1000 volts) and several amps were used. Far less current and voltage can be lethal when you are NOT trying to kill someone, but merely come in contact with a frayed electric cord while standing barefoot on a concrete floor. Edison 15:57, 1 May 2007 (UTC)

The amount of current (not voltage) required to stop the human heart is usually cited in the range of a few milliamperes. The amount of potential required to cause that current to flow across the heart varies wildly depending on the circumstances. You can be electrocuted by thousands of volts and be lucky (if you can call it that) enough to have the current find a path that doesn't include your heart. People have survived lightning strikes, which are caused by hundreds of kilovolts of potential, and if you've ever felt a static discharge after shuffling around on the carpet on a dry day, you know what ten to twenty thousand volts can feel like. Alternatively, you could be killed by 120 VAC mains in the right conditions (like standing in the bathtub). Again, it's very dependent on the circumstances. However, 9 V does seem like a stretch. That's a pretty low potential, and even applied directly across the chest I doubt it would cause current flow greater than a few microamperes.

It should be noted, however, that sufficiently high potential can cause large currents, impact ionization, dielectric breakdown and a host of other conditions that may cause severe burns even if you aren't killed. Moral of the story: be careful around high voltages (over a few tens of volts). -- mattb 16:29, 1 May 2007 (UTC)

Jeez why didnt people tell me stuff like this when i was younger? like with the microwave that almost burnt down my home? or before my index finger print was permanitly burnt off from electricity =( well either way hopefully after this we wont hear news of people getting electricuted =) you got to admit though mattb electricity is really really fun to play with (caused some cool explosions and stuff) but defenitly if you take proper safty. Kids dont mess with Electricity! no matter how fun it is....User:Maverick423 If It Looks Good Nuke It 16:43, 1 May 2007 (UTC)

Sure, fun... I remember messing with 1500 F capacitors (not a typo) from a disassembled System/34 when I was a child. In retrospect I'm pretty sure the old man was trying to off me. Well I had better stop this nostalgia moment before it gets on a roll, this is off topic. -- mattb 21:51, 1 May 2007 (UTC)

Whoa! How is it possible to achieve such high capacitances? Are you sure they were that high? Do you have a reference? —Bromskloss 09:55, 2 May 2007 (UTC)

With so many lives at stake, you gotta do some reearch ;-) . If people were dying of 9 volt shocks, there should have been case reports published. Well, I searched PubMed and I've found nothing on fatal 9 volt shock. The lowest voltage for fatal electrocution I found in literature is 46 volts (in Patel & Lo, Stroke (1993), vol. 24 pp. 903-905), five times higher than the voltage in question. So, as Edison and other people have said here already, it seems highly unlikely that electrocution from a 9 volt battery results in several fatalities a year. BTW, look at electric shock article, it gives a pretty good intro to the subject. Cheers, Dr_Dima.

Sticking a battery on your tongue, as a kid at my school once found out, is like to give you an unpleasant shock, a swollen tongue, and the inability to speak properly for a few hours. And a very sheepish expression. Spiral Wave 17:10, 1 May 2007 (UTC)

I've put a 9-volt battery against my tongue many times and never had any sort of aftereffects. As to lethal shocks, I've read (but I can't cite the source, because I don't remember it) that the phase of the heartbeat is an issue. In other words, it's possible that a shock to the heart may be lethal when the same size of shock delivered 1/10 of a second later would be harmless. --Anonymous, May 1, 2007, 22:00 (UTC).

• snickers* all the good old days when people would fall for anything. anyways assuming you can trick someone into doing this, when they do keep a eye on their tongue, it wiggles and jerks around the whole time the battery is in contact. Wait what am i saying no dont do it to ppl try it on yourself and look in the mirror! shame on you! User:Maverick423 If It Looks Good Nuke It 17:17, 1 May 2007 (UTC)

In reply to the person with the rhyme: Its the volts that jolts, and its the mil(liampere)s that kills. Currents as low as 100mA (maybe even lower) can cause ventricular fibrillation —The preceding unsigned comment was added by 88.111.123.188 (talk) 22:44, 1 May 2007 (UTC).

color force behavious

I am interested to knoe if the color force exhibits bahavior proportional to 1/r8 (!1 divided by r to the 8 power) and if it does in what range.217.132.19.108 13:45, 1 May 2007 (UTC)

You might read strong interaction, but if I recall, the strengths of the nuclear forces do not have a well-established, well-agreed-upon direct radial dependence. I believe there are many other factors at play in the situation. Nimur 16:20, 1 May 2007 (UTC)

In fact the colour force gets stronger with distance, which is why you never get isolated colour charges.137.138.46.155 11:39, 2 May 2007 (UTC)

Curvature of the neck (cervical spine)

Somehow I ended up going to a chiropractor for an assessment and he took a bunch of xrays. (don't ask) ^{or do if you like}
He came back and showed me the xrays and on my neck he showed how I had no curviture in my neck at all! And I could see it on the xrays myself! He said my neck had 0° curviture and that a normal neck (showing me another xray) had about 18° curviture. He's warned me of some negative effects of this and says he can treat me and give my neck some curviture in about 3-6 months, and I don't know if I can trust him (he is a chiropractor after all, and not a "Conventional" doctor).

Seen as you can't give medical advice my questions are...

1. What is considered a "normal" curviture in the spine, particularly the neck (cervical spine)? and/or
2. Specifically what kind of doctor would be good to evaluate this?

Thanks so much for any help! —The preceding unsigned comment was added by 138.130.23.133 (talk) 15:01, 1 May 2007 (UTC).

Don't know, but the quackwatch has a good dedication to being anti-chiropractor. Why don't you see a general practitioner about it? Couldn't he or she do it, or, if not, refer you to somebody afterwards. [Mac Δαvιs] ❖ 16:41, 1 May 2007 (UTC)

Maybe this is an obvious question, but doesn't the curvature of the cervical spine vary depending on how you bend your neck ? That is, couldn't the chiropractor have intentionally put you in a straight position for the X-ray and then concocted this BS story to drain your bank account ? Also, X-rays carry some (fairly low) risk of causing cancer, so I would only get them from a real doctor when medically necessary. StuRat 04:55, 2 May 2007 (UTC)

Determining the critical angle of the substance glycerol/glycerine (I think it's the same thing)

We did an experiment in class to find out what the critical angle of glycerol is. Some of my mates say it's 42,57°, but I figured it to be 132,57°. The two numbers differ by 90°, so I dunno if I just made a common error when I took the info.

Anyways, glycerol (glycerine) has a refractive index of 1,4729.

We had a beam of light reflect at 90° from a border between air and glycerol.

Can anyone please help me with this experiment? I really need to know this answer.

I tried using snell's law, n1sinθ1 = n2sinθ2, but when I substitute the information into the formula, 1sin42,57° = (1,4729)sin90°, it just doesn't make any sense. Maybe I did something wrong? Please please take some time to help me with this. Maybe you have an example in your physics text book, or you did this experiment yourself before? Any information will help.

Thanks in advance :D

► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 16:36, 1 May 2007 (UTC)

I'm afraid you've got it wrong. Look carefully at the drawing in Snell's law, and you will easily spot your mistake. Good luck, Dr_Dima.

So, basically, there's not much to it? ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 17:49, 1 May 2007 (UTC)

What do you mean by "not much to it"? You've got a problem to solve. Here on Wiki we do not solve homework problems, we help you to solve them yourself; that is how you learn. I'll give you a hint, though. What are subscripts "1" and "2" there for in the Snell's law? They denote, respectively, the first medium and the second medium through which the light goes. Which is the first one and which is the second one in your case? What is the refractive index of the first one and of the second one? At what angle to the normal the light is going in the first one and in the second one? Be careful writing these things down, and you'll spot the mistake you made when using Snell's law. Oh, and after you find the mistake, you may also take another look at the drawing and think why the angle cannot be anything like 132°. Good luck. Dr_Dima

Ok... sorry and thanks, lol. I've spotted my problem. I substituted the values of the different refractive indices as well as the different angles into the wrong parts of the equation, because I assumed the light beam was traveling from air to a surface with glycerol, which is false. The beam is traveling from glycerol to a surface with air, which makes n₁ = 1,4729 and Θ₁ would be the critical angle (42,57°). n₂ = 1 (because it's the refractive index of air at normal temperature etc., rounded) and Θ₂ obviously is 90°, because we are using the critical angle, thing, so we don't even need to measure it. Lol. Anyways, so it happens that (1,4729)sin42,57° = sin90°, which is 1 = 1, and there we know that all the information are correct. Thanks for all your help ; ) ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 21:46, 1 May 2007 (UTC)

You are welcome. Best regards, Dr_Dima.

Calcium in a bone

How muh Calcium is there in an average 1cm^2 section of bone? Yes, I know it varies between differnt bones and different parts of bone. It probably varies between people too. I just want a rough idea, but not too inaccurate. So..? —The preceding unsigned comment was added by 172.203.7.239 (talk) 19:42, 1 May 2007 (UTC).

Hi, in the future, could you please label your titles more concise, "science" doesn't explain anything at all about your question and pretty much makes it so anyone only using the watch list ignores you. Thanks! --KittenMya 20:04, 1 May 2007 (UTC)

I didn't see the answers in our bone density or osteoporosis articles, so will take a wild guess, instead. Since bones are hollow, containing marrow and such, I would guess they are maybe 10% calcium. So, then you would have 0.1 cm² calcium per cm² of bone. Bird bones, though, are considerably less dense (to keep the weight down), so would likely have less calcium. Perhaps elephant bones would need more calcium to support their weight. StuRat 04:49, 2 May 2007 (UTC)

Good grief. I thought this was the science reference desk, not the wild guess reference desk.

Gray's Anatomy, 1958 edition, says that "the bone 'salts' constitute the mineral constituents and confer on the bone its hardness and density. The most important constituents of bone 'salts' are calcium, magnesium, phosphate, carbonate, chloride, fluoride and citrate. The mineral substances of bone may be obtained by calcination, which destroys the organic matter. The bone retains its original form but is white and brittle, has lost about 1/3 of its original weight and crumbles under the slightest force." So in other words, in the solid matter of a bone, about 2/3 is mineral components and calcium is listed first among these. This would make sense if the calcium is something like 1/8 to 1/3 of the total bone mass, say.

I also note that Encarta's online article "Bone (anatomy)" says that the bones make up 14% of the weight of the human body, and Wikipedia's article Abundance of the chemical elements says that 1.5% of the human body is calcium. It would therefore seem that bones are about 1.5%/14% = 11% calcium. However, I'm dubious about these numbers. First, I found the same table of elemental abundance on another web page but identified as referring to the composition of the human body without the water, which obviously makes a big difference. Second, they could be defining "bone" differently, e.g. one counting only the hard stuff (as Gray's Anatomy evidently was) and the other including the marrow. And finally, none of these sources gave a range of values, but obviously people will vary.

Both of these calculations only with towards a value for the fraction of bone that is calcium, not the quantity of calcium per unit volume of bone as asked for (well, actually the original poster quoted an area unit, but I assume volume was intended). Unfortunately I did not find anything that stated the density of bone. In any case StuRat's point about hollow spaces in bones is relevant here: it's going to make a big difference whether you're talking about bone (the hard substance) or bones (including everything) or specific bones or what.

--Anon, May 2, 2007, 07:08 (UTC).

What Is the Greenish Layer of Some Hard Boiled Eggs

With hard boiled eggs, the yolk has a thin greenish layer where it is in contact with the white, while the inside of the yolk is yellowish as expected. The eggs are fresh. The cooking time is about 15 minutes. What is it that gives this green-like color?--JLdesAlpins 20:27, 1 May 2007 (UTC)

Iron and sulfur. --LarryMac 20:31, 1 May 2007 (UTC)

Thanks LarryMac. I will suggest that the section "Problems when cooking eggs" be moved in Hard_boiled_egg.--JLdesAlpins 20:36, 1 May 2007 (UTC)

15 minutes for boiled eggs? Wow, you are overcooking them to death! --24.249.108.133 04:18, 2 May 2007 (UTC)

Using magnetism to recover coins and jewelry

I have been using a heavy lift magnet in a local lake and in a canal to recover fishing rigs and various metal things like bikes from the waters. I realize magnets only work on ferrous metals but wonder if there is a way to induce some magnetism into more valuable objects like coins or jewelry. Is there an electrical magnet or device that generates enough of a magnetic field that it would attract nickel, gold etc. Thanks —The preceding unsigned comment was added by 137.246.193.233 (talk) 20:40, 1 May 2007 (UTC).

Nickel should not be a problem because it is ferromagnetic. You might want to see that article, which has a list of ferromagnetic materials. Nimur 20:58, 1 May 2007 (UTC)

• Hence the obvious solution, move the lake to Canada, where almost all coins are either nickel or steel! --Anonymous and very silly, May 1, 2007, 22:07 (UTC).

Yes of course! You can use lc ac (alternating current) to induce currents in the non ferromagnetic object and attract agitate it.

Sorry, eddy currents repel rather than arract non-ferromagetic conductors, see Magnetic levitation#High-frequency oscillating electromagnetic fields. --mglg_(talk) 23:31, 1 May 2007 (UTC)

the repelling force might be enough to stir the mud around the object, and so make its location noticeable.Polypipe Wrangler 23:35, 1 May 2007 (UTC)

A metal detector uses alterneting currents to detect non ferrous metals. You could use one in a lake to find your coins, although you would have to use another means to separate them from the mud.GB 00:30, 2 May 2007 (UTC)

Whilst lakes and canals attract bikes, shopping carts, bedsteads and bodies, I doubt they will ever be fruitful in terms of jewelry and coins. You'd be far better off employing a metal detector in parks and on beaches.--Shantavira 06:52, 2 May 2007 (UTC)

molarity question. help!

i have a 250 mL beaker, but I do not know how many mols of 4.00 M solution I should use to make a .500 M solution. Any suggestions? Thanks! —The preceding unsigned comment was added by 76.188.176.32 (talk) 20:47, 1 May 2007 (UTC).

What is the molecule/compound you're trying to solutinate? --KittenMya 20:56, 1 May 2007 (UTC)

NaOH Does this help??

Hi, I believe the formula for this is grams of NaOH = (solution required, ie .500) * (molecule weight, ie 40) * (amount to produce, ie 250ml) / 1000, though aplogies if I misread your question, I'm tired. --KittenMya 21:19, 1 May 2007 (UTC)

I don't understand how that all cancels out, and from where did the 1000 come?

The identity of the solute is irrelevant here. Do you really want to know "mols" of the 4.00 M solution, or maybe a volume (for example "mL") instead? Think about what molarity means, and what units are represented by "M". DMacks 21:26, 1 May 2007 (UTC)

Yes! I want to know the mL.

I have thought that perhaps I can find the mols of .50M solution by taking .50=mols/.250L which gives me mols=.125 mols NaOH But, I don't know where to go from there, and I don't even know if that is right.

Maybe I should use that mol number to do 4.00 M=.125mols/unknown L.... to find the mL? Any comments help.

Good! You found you need 0.125 mol to disolve in the 250 mL; that's equivalent to (the same ratio as) 0.5 mol dissolved in 1000 mL (= 1 L), and "mol per L" is the definition of the "M" unit of molarity. So now you're on the right track again: you need to figure out how much volume contains that 0.125 mol if it is a 4 M solution.

You can often check to make sure your math is at least "reasonable" if you look at the units you are using. Math with unit symbols is the same as numerical math: in your first thought, you divided a number of mol by a number of L, which gives an answer that has units of "mol divided by L", which is the fraction "mol/L". DMacks 21:44, 1 May 2007 (UTC)

Well, I understand what you're saying. But, if .5mol/1L= .5M .... then is the problem set up as .125mol/X=4.00M? The answer just doesnt seem to make sense.

Its such a small answer in liters, that the number seems completely wrong when put into decimals, doesnt it?

• rolls eyes* OK, guys. Forget about moles. A concentration of 4 needs to be diluted to a concentration of 0.5. 4/0.5=8 therefore, you need to dilute your 4M stuff 8-fold. For example, take 10ml of your 4M solution and add 70mL of water. Et voila, 0.5M solution. If you need 250mL, divide 250mL by 8 = 31.25mL. So add 31.25mL of your 4M solution to 31.25x7=218.75mL of water. In summary, 31.25mL 4M solution + 218.75mL water = 250mL 0.5M solution. Aaadddaaammm 00:38, 2 May 2007 (UTC)

Eyebrow

What are the muscles that raise the eyebrow? My anatomy textbook doesn't really cover it. As far as I can tell, the muscle resposible for raising both eyebrows at once all along the forehead is the frontal belly of the occipitofrontalis. I can't seem to find the one that raises just one eyebrow way off to the side, though. Any suggestions? Black Carrot 21:23, 1 May 2007 (UTC)

I think the answer may be Occipitofrontalis muscle like you think. Look at facial muscles for the choice of muslces on the face, but there are no others in the area. In order to move just part of the eyebrow, only part of the muscle contracts. Different nerve fibres go to different parts of the muscle giving a finer control. GB 01:39, 2 May 2007 (UTC)

Dropstones and metals. Or just rubbish.

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

Above is a piece about dropstones which are interesting anomalies.

But what will happen millenia hence with the metals (ships and such) we have dropped on the ocean floor. Or metallic rubbish like stainless steel injection needles in our land fills.

Will they be absorbed and become little gaps in the rock or be preserved in the sedimenta.

Does steel under pressure degrade rust or defom ?

Sensible question. What will happen to our non organic rubbish millennia hence.

Thanks

Paul

81.86.166.234Paul.Mckenna at mac .com81.86.166.234 21:59, 1 May 2007 (UTC)

I presume a mechanism akin to fossilisation. As these metals corrode (and presumably the corrosion products get washed away) there is a race between that effect and the effects of sedimentation covering them up and shutting out the water and oxygen to preserve them. Where rates of sedimentation are high, and if the resulting rock is relatively impervious to water - then you'd end up with a kind of fossil of the metal chunk - if not then nothing. It's hard to say - but it almost certainly depends a lot on the rate of corrosion versus the rate of rock formation above them. SteveBaker 22:35, 1 May 2007 (UTC)

If the metal is buried where there is no oxygen, say along with much organic matter, it may stay unmodified for millions of years, but more normally the metal will react with oxygen, carbon dioxide, silica, or suphur and form more natural minerals that the artificial metal. You can expect metals such as gold or platinum to be dug up and recylcled! Land fills are likely to erode away in the distant future and so the metal content will be spread in to sediments elsewhere, but on the ocean floor may stay where they fall. GB 01:33, 2 May 2007 (UTC)

Nuclear hurricane

a question above about hurricanes got me thinking... what if a couple of nukes were dropped or detonated on a hurricane. the awnsers above stated that the hurricane wouldnt be dissapate, so there for would that mean that instead of having just a regular old hurricane comming our way, it would be a hurricane with nuclear fallout bearing down on us? and if thats the case wouldnt this be used as another weapon of mass destruction? and *of course jokeing* would the rain glow as it falls to the ground? User:Maverick423 If It Looks Good Nuke It 22:27, 1 May 2007 (UTC)

Yes, it would spread radiation all over the place, and probably into the jet stream. Titoxd^{(?!? - cool stuff)} 22:29, 1 May 2007 (UTC)

The rain wouldn't glow. It would probably be black, like the rain over Hiroshima was. As a WMD it would be less effective and less controllable than just dropping the bomb on the designated target. --24.147.86.187 23:05, 1 May 2007 (UTC)

Temperature of the sun

Does the sun get hotter year after year like other stars? If so, what is the effect on earth? —The preceding unsigned comment was added by 74.244.99.200 (talk) 22:52, 1 May 2007 (UTC).

Overall, in a multimillion year time span, the sun will be getting cooler. See red giant and white dwarf. However, in a reasonable time span of thousands or hundreds of years, it is variable and I am not sure a trend is known. If the trend is known to follow solar insolation (which is only found due to correlations with sunspots and the earth's orbit. Here's a graph of the theoretical solar insolation, on the top line in the graph[5]. [Mac Δαvιs] ❖ 02:09, 2 May 2007 (UTC)

If you mean "like other stars" as a main sequence-type change (see the Hertzsprung-Russell diagram), then yes, the Sun does get hotter. It's not really a year on year type of change though; it's measured over thousands and millions of years. Stellar evolution is the article you want. It will continue to steadily get hotter until it becomes a red giant.

As for its effects, it means the habitable zone around the Sun moves outwards. This is an imaginary ring around a star where a planet would be at the right temperature for liquid water. The Earth is 'lucky' in that we're always in the Sun's habitable zone - when the Sun formed we started just beyond the middle of it, and by the end of the Sun's lifetime we'll be just near the inner edge, because the ring gradually moves outwards as a star heats up; but we'll never lie outside it (at least before it all turns a bit nasty and red giant-ish). So in the far future the Earth will get considerably warmer, though not uninhabitable. It's not an effect you'll notice over a century or two though (though there may be other types of cycle that affect things on those scales - you should probably check Solar variation if that's the type of change that interests you. Global warming arguments and so on, in there). Spiral Wave 02:05, 2 May 2007 (UTC)

I stated that the sun would gradually cool and enlarge into a red giant, while you said it would heat. I thought that the star would expand enough that the increase in heat is overplayed, and overall the temperature would grow lower, while the amount of heat would grow higher. [Mac Δαvιs] ❖ 02:15, 2 May 2007 (UTC)

Well, perhaps once it starts getting closer to being a red giant, in a couple of billion years time. But in the current epoch I would have assumed the increase in temperature outweighed the difference - I thought it was still in the heating phase David Ruben pointed out below (albeit not as fast now). I'm quite prepared to be wrong though, and I take your point that eventually, as it grows the effective temperature will drop, well before it becomes a red giant. Nonetheless, I'm quite certain that the habitable zone moves outwards for the bulk of its lifespan (a process that isn't finished yet) and that would imply that the temperature at any given distance is increasing, which is still relevant to the second part of the question. So as David said below, it gets cooler, but we get hotter. Spiral Wave 03:10, 2 May 2007 (UTC)

It's misleading to say that a star cools when it becomes a red giant, as I understand it. The surface cools, but that's only because it's moved out so far. Inside the star is hotter than before, which is why it's giving off more heat than before. --Anon, May 2, 2007, 07:18 (UTC).

That's why I said the effective temperature. Thank you for making it clear though, I'm really not doing a very good job of this. Spiral Wave 09:18, 2 May 2007 (UTC)

The sun goes through various Solar variation cycles (e.g. solar cycle of sunspots). Over the longer term it is thought to have heated up by 40% since it reached the main sequence 4.6 billion years ago (see Star#Main sequence). Finally it will cool as it approaches the end and enlarges to form a Red giant. Whilst its surface temperature will then be lower, here on earth its reducing proximity will cause the earth to evaporate off before it is engulfed. David Ruben ^Talk 02:20, 2 May 2007 (UTC)

The sun has many cycles. I believe there is a cycle that correlates well to earths ice ages and the sun is currently warming. There are shorter and longer cycles in addition to the main sequence cycle. --Tbeatty 06:07, 2 May 2007 (UTC)

Lightbulbs

Why are lightbulbs measured in watts and not ohms? If I change the number of volts, does the number of watts not change for a lightbulb regardless of its designated number of watts? J Are you green? 23:18, 1 May 2007 (UTC)

Well, they are specified both in wattage and voltage - so you can figure out the resistance - but remember this is an AC powered device - and it's resistance varies with temperature - it's not as simple as you think! Since (as you say) you can calculate any one of watts/ohms/volts if you know the other two, they could have specified any two of those numbers. My guess as to why they did it is because people care about how much current they are consuming - not about some more abstract thing like resistance. The other problem (I suppose) would be that if you rated bulbs in ohms, lower numbers would be for brighter bulbs - which might be confusing. The whole rating system is a mess anyway - we don't really care what wattage or resistance the bulb imposes - what we mostly care about is how much light it produces. In that regard, a 40 Watt incandescent bulb produces much less light than a compact florescent lamp that consumed 40 Watts. SteveBaker 23:27, 1 May 2007 (UTC)

Yes, it would make a whole lot more sense to measure light, but for watts/ohms/volts, the lightbulb itself is the source of resistance. That is, if I take a 40 W bulb and turn it on with a 1 V power source, then increase the power to 2 V, won't the bulb become an 80 W bulb since the bulb's resistance is constant. If I understand this correctly, the number of watts has nothing to do with the bulb - only the resistance. As for your other point about lower numbers and brighter bulbs, why not measure in Ω^-1? I suppose none of this has a real application, but I am just curious to know. J Are you green? 23:38, 1 May 2007 (UTC)

A 1 V light globe is quite unusual - particularly one that consumes 40W. However if you increased the voltage to 2V and the resistance remained the same, the current would double, and the power consumed would quadriple, so it would burn 160W. Don't expect any light globe would work at double its rated voltage however. The filament would overheat and melt. GB 00:35, 2 May 2007 (UTC)

Oops. I meant in in theory, not as a real example, though. J Are you green? 00:43, 2 May 2007 (UTC)

Nobody seems to have mentioned the fact that the bulbs you put into your light fixture are expected to be operated at a fairly constant mains voltage, so the wattage rating does make a little sense. -- mattb 00:42, 2 May 2007 (UTC)

I realise that, but the wattage is independent of the lightbulb, isn't it? So why measure the bulb in something that it itself does not control? J Are you green? 00:45, 2 May 2007 (UTC)

What's the difference? People don't have a better idea of what a lumen is as opposed to 40 W. -- mattb 00:48, 2 May 2007 (UTC)

Well, say I take a bulb of 1 W at 1 V. If I then reduce the voltage to, say, .5 V, then the power likewise decreases. The watts never had anything to do with the actual lightbulb, only the bulb's resistance. Also, I really don't see how lumens tie in to this. J Are you green? 00:59, 2 May 2007 (UTC)

Well, the filament's resistance is a result of physical parameters like material composition, dimensions, temperature, and some quantum effects... It has plenty to do with the bulb itself. I'm not sure what your question is at this point. -- mattb 01:22, 2 May 2007 (UTC)

Yes, but it has equally plenty to do with the power source. J Are you green? 01:39, 2 May 2007 (UTC)

Getting back to the original question, changing the voltage will change the watts consumed for a globe, however the rated power in watts should apply if the rated voltage is used. GB 01:28, 2 May 2007 (UTC)

I cannot see why a manufacturer would stamp "80 W" on a bulb if its watts depends on the power source. That is the original question. J Are you green? 01:39, 2 May 2007 (UTC)

Yes, the bulb has a fixed resistance (more or less), but the resistance is not the only important attribute of the bulb. The bulb is designed to operate at a particular power. a one-ohm bulb designes to operate a 3V ( a flashlight bulb) is very different from a one-ohm bulb designed to operate at 120V. (desk lamp bulb). put 3V across the big buld, get no light. put 120V across the flashlight bulb, get lots of light -- for about one millisecond. The Wattage is a measure of the designed power output the bulb can sustain. -70.177.166.200 02:12, 2 May 2007 (UTC)

So, you are basically saying that the number of watts on a bulb is not an actual attribute of the bulb, but rather the power at which the bulb was designed to operate. So, the number of watts is not a necessarily constant but rather a recommendation given the bulb's resistance and its intended voltage. I see... J Are you green? 03:28, 2 May 2007 (UTC)

Correct. If you operate the bulb at a lower wattage, the filament temperature will be too low to emit white light. The light will be redish and you get less lumens per watt. If you operate the bulb at a higher wattage, the filament will be hotter, the ligh will be bluer, and the filament will burn out faster.-Arch dude 05:49, 2 May 2007 (UTC)

In any case the resistance of a light bulb is not constant either -- not even close. Someone mentioned above that resistance depends on temperature. Let me go into that some more. I just took a couple of light bulbs rated for 120 V. One is a 150 W bulb so you would expect its resistance to be 120×120/150 = 96 ohms; the other is a 60 W build so you would expect 240 ohms. I put a multimeter to them at room temperature and they were 6.3 and 18.5 ohms respectively. (And I checked the multimeter against some known resistances too; it was right.) Which means the 150 W bulb when first switched on draws more current, all by itself, than a 15 A circuit will take. But in a small fraction of a second, before the breaker can trip, its resistance rises to 96 ohms. If you operated it 9/10 of the voltage, 108 V instead of 120 V, then you might expect it to pass 9/10 as much current and so consume 150×9/10×9/10 = 121.5 W; but actually the resistance would be less than 96 ohms and it might consume say 130 W or 140 W. (But as noted above, it would burn cooler and thus less efficiently.)

In short, quoting the resistance would really be no more practical than quoting the wattage is.

--Anonymous, May 2, 2007, 07:55 (UTC).

May 2

Reaching the speed of light

In space since there is no drag, could not one moderatly accelerate to speed of light? —The preceding unsigned comment was added by 75.162.132.156 (talk) 01:05, 2 May 2007 (UTC).

Afraid not! Not through any means we're aware of, at least. By Newtonian mechanics it certainly seems possible, but our understanding of relativity lets us know that it would require infinite energy to accelerate any object with mass to the speed of light, and unfortunately there is only finite energy in the universe. The photon travels at exactly the speed of light, but it has no mass. -- mattb 01:19, 2 May 2007 (UTC)

No. First of all, you can't get to the speed of light if you have any mass. The only thing that can go the speed of light is light itself, and even that has all sorts of philosophical problems (i.e. photons don't experience time, for example). If you want the details you'll have to look over special relativity a bit and perhaps the Lorentz factor (look at what happens when you make v = c). And in any case as you accelerate towards v = c your mass will begin to increase towards infinity, and so will the energy required to accelerate to those speeds — see Mass in special relativity. So it's a losing game: the faster you get, the more energy you will need to go any faster, and at some point it just won't work out from either a practical or theoretical standpoint. At least, that's my understanding of it. Drag doesn't come into it at all in this case. --24.147.86.187 01:25, 2 May 2007 (UTC)

Breast enlargement (herbal supplements)

d they work? ...are they dangerous? what is the scientific status of this stuff? what is the medical status? —The preceding unsigned comment was added by 75.69.194.105 (talk) 01:10, 2 May 2007 (UTC).

I'm speculating here, but (a) no, (b) no, (c) pseudo, and (d) not efficacious. —Steve Summit (talk) 02:11, 2 May 2007 (UTC)

Although there is probably no way we can verify every herbal supplement, herbs and spices should generally be used for cooking, and are unhelpful to a "natural" breast or penis enlargement. I do not believe there is any scientific status. [Mac Δαvιs] ❖ 02:11, 2 May 2007 (UTC)

I think that I will say that (b) possibly. Some herbs can cause damage.--Kirby♥time 02:44, 2 May 2007 (UTC)

Phytosterols do not work for male bodybuilders who wish to grow muscle. So by analogy I do not suppose herbal supplements that encourage female hormones will work. To expand your knowledge I would suggest looking at female hormones and causes of feamle cancers and then decide where you want to go. Paul

Rock identification

Unknown rock found in England.

I need help identifying this rock. It was found (by my mother) a long time ago in England, and has spent many years in faithful service to me as a doorstop. It's fairly heavy/dense, and I was told by someone it could be a meteorite, although I don't know if I believe him. I've looked at many sites for identifying a meteorite, but am still not convinced either way. I know that identification through just an image is still shaky, and should probably still get some more info (density and compositional data (XRF) data in particular). I'm also curious as to what it looks inside, although I don't want to break it open. More pictures, as well as much larger pictures, can be found at my personal website. Thanks --Bennybp 03:23, 2 May 2007 (UTC)

It's brown. See Brown rock.  :) --Tbeatty 06:11, 2 May 2007 (UTC)

Some (not all) meteorites are made largely of iron. Is the rock attracted toa magnet? --Anon, May 2, 2007, 07:57 (UTC).

I know my rocks, and that doesn't look like much, just a typical glacial cobble, probably composed of some sort of granite or gneiss, with some inclusions. --Zeizmic 11:38, 2 May 2007 (UTC)

Beating Light?

I was wondering if light could beat in the same way sound waves do. If one had two slightly different colours shining at the same time, would they dim and brighten? Thanks in advance, Storeye 07:15, 2 May 2007 (UTC)

Yes. And [6] [7], etc. Light has wave properties, there's no reason it shouldn't behave similarly. -- Consumed Crustacean (talk) 07:17, 2 May 2007 (UTC)

Thankyou!!!Storeye 07:20, 2 May 2007 (UTC)

Also see interference.--Shantavira 07:40, 2 May 2007 (UTC)

Fuse

We know that a fuse wire melts due to overheating.But the practical resistance of a fuse is low. So how does that become equivalent to heat in melting the fuse, because P=i^2r? Also would it not cause a voltage drop??210.212.194.209

as you said, the fuse resistance is low, normally much lower than the resistance of the device which it protects (and with which it is connected serially). Thus, as long as fuse hasn't melted, the voltage drop on the fuse is rather small (but still nonzero, of course). When the fuse melts, the resistance of the fuse increases by several orders of magnitude, and now most of the voltage falls on it. That is how the standard fuse works. Now, your other question was about how the fuse melts. The answer is, the thinner the wire is the less energy (or power) you need to melt it. Thinner wire also means, for same length and material, a higher resistance. Since the current i is determined mostly by the resistance R of the device and not by the resistance r of the fuse (since R >> r), higher resistance r of the fuse means higher power P = i²r of Joule heating of the fuse wire. Thus, the thinner the wire is the lower the max current for the fuse is. BTW, in case of a slowly rising current it is indeed the power of Joule heating that governs the wire temperature (and hence the max current). In an opposite case of a "sudden" current surge it is energy rather than power that is important, hence different melting times for different fuses. (As you know, energy is power multiplied by time interval). Hope this helps. Bear in mind that I am a physicist, not an engineer ;) . Cheers, Dr_Dima.

Hypersonic

Any idea how hypersonic waves travel in straight lines??Also is it possible for the same phenomena to exist with electro-magnetic waves??210.212.194.209

Prevalence of Freezing Temperatures on Earth

Hi, everyone.

I've asked this question before, so I'm sorry for asking it again. If you've already read it, please don't be angry. I just really want a good answer. So, the question: What proportion of land/earth's surface/plants/organisms have to survive temperatures below freezing (0 C)? If you know of any peripheral statistics around this question, they would be great too. Thanks very much for your help. Aaadddaaammm 08:30, 2 May 2007 (UTC)