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July 20

Unidentified Insect

Hi. I was hoping for some help from anybody with knowledge of British entomology.

Earlier today, I had an insect fly into my house in Devon that I don’t believe I’ve ever seen before. It appeared bigger than a common wasp but rather smaller than a hornet. It had a round but, perhaps, slightly flat yellow body with two extremely well defined stripes circling the abdomen (this was the most immediately striking thing about it – the stripes were not blotchy and poorly defined as on most bees and wasps but perfectly defined, like you’d expect to see on a T-shirt and there were definitely only two stripes) and very big, bulbous grey eyes just above and either side of a bright yellow wasp-like mouthpart. Its thorax looked to be a dark brown colour (perhaps with a hint of red) and its legs (which seemed very long for a wasp) were most definitely reddish. It was so wasp-like that I assume it’s a member of hymenoptera but, given my lack of insect knowledge, I suppose it could conceivably be something else indulging in a bit of mimicry, although I doubt it. Any ideas?

Thanks Pantscat (talk) 00:54, 20 July 2010 (UTC)

Can you get a photograph of it?

See anthing similar in http://commons.wikimedia.org/wiki/Category:Wasps

Some mimic images here http://www.pbase.com/tmurray74/wasp_mimics&page=all

Hoverflys might have the flat abdomen - the eyes are distinctively 'flyish' though eg http://www.google.co.uk/images?q=hoverfly&um=1&ie=UTF-8&source=og&sa=N&hl=en&tab=wi&biw=1280&bih=937 178.78.65.223 (talk) 01:30, 20 July 2010 (UTC)

(edit conflict) I think that most "like a wasp but not a wasp" sightings turn out to be hoverflies, but there are so many different species of the critters that identifying the one that visited your house may be difficult. Do any of the ones pictured here look at all like your visitor? Deor (talk) 01:35, 20 July 2010 (UTC)

There's a list of common uk hoverflies here http://www.microscopy-uk.org.uk/mag/artmay07/cd-hoverflies.html I can't see your two stripe one, but your description of "big bulbous eyes" suggests a fly and not a wasp - which have big eyes - but I wouldn't call them bulbous.178.78.65.223 (talk) 01:40, 20 July 2010 (UTC)

I did get a photo of it but I'm not sure how good it was and am not at all sure how I would get it onto here even if it was a good one. I haven't yet found out what it was but I'm now reasonably confident that you guys are right and that it was a hoverfly (although I didn't realise they could be that size) as it looked similar (although not identical) to Epistrophe grossulariae. http://bugs.decemberized.com/images/Epistrophe_grossulariae_female.jpg

Must be a fairly close relative I would have thought. Pantscat (talk) 02:19, 20 July 2010 (UTC)

If you need more you can upload the image using the a button on the left hand margin - select "upload file" which should take you here http://en.wikipedia.org/wiki/Wikipedia:Upload - you'd need to give it a license since everything uploaded has to be shared. Uploading to commons is recommended http://commons.wikimedia.org/wiki/Commons:Upload , then just paste the link here...87.102.13.208 (talk) 02:41, 20 July 2010 (UTC)

How about this one - found nearish your region and has two yellow bands http://www.cornwalls.co.uk/photos/img2270.htm 87.102.13.208 (talk) 02:53, 20 July 2010 (UTC)

Yep, that's the fella. Looked just like that one and sounds about the right size. So I now have a name - Volucella zonaria or the Hornet Mimic Hoverfly.

Thanks, guys Pantscat (talk) 12:32, 20 July 2010 (UTC)

And we do have an article, with some other images. Deor (talk) 17:59, 20 July 2010 (UTC)

Elements in the human body

How many elements are necessary for human survival? So far I have listed:

• Hydrogen
• Oxygen
• Carbon
• Nitrogen
• Phosphorus
• Iron
• Calcium
• Sodium
• Magnesium
• Sulphur
• Potassium
• Iodine

Please list any more that I haven't named, and tell me if any of theses are not needed for humans. Thanks, --The High Fin Sperm Whale 01:38, 20 July 2010 (UTC)

Technically you need http://www.soils.wisc.edu/~barak/soilscience326/listofel.htm essential plant elements unless you want to starve. or Plant nutrition

See also Dietary mineral which I hope is a complete list.01:44, 20 July 2010 (UTC) —Preceding unsigned comment added by 178.78.65.223 (talk)

We need salt, and that has Chlorine in it. Maybe. I'm not a scientist, though. 142.104.215.130 (talk) 01:45, 20 July 2010 (UTC)

Both sodium and chlorine are in the list in dietary mineral.178.78.65.223 (talk) 01:47, 20 July 2010 (UTC)

You check out Composition of the human body yet? APL (talk) 01:50, 20 July 2010 (UTC)

Or better yet, Dietary mineral, which lists (in a convenient periodic table graphic) all of the elements typically in a human body (in reasonable amounts), and also what the different elements do. Buddy431 (talk) 03:22, 20 July 2010 (UTC)

That actually lists the minerals that people need to eat, which is an important distinction. Ariel. (talk) 13:54, 20 July 2010 (UTC)

I would be surprised if there were any reasonably common elements that we don't need for something. Either as a part of our bodies - or as a part of our food sources or some other subtle thing. Possibly the nobel gasses (helium, neon, etc) aren't necessary - but I wouldn't even want to bet on that. SteveBaker (talk) 04:26, 20 July 2010 (UTC)

Acording to the linked article: "An exception is aluminium, which is the third most common element in the Earth's crust (after oxygen and silicon), but seems to serve no function in living cells. Rather, it is harmful in large amounts." Rmhermen (talk) 04:46, 20 July 2010 (UTC)

Despite being linked to 3 (now 4) times the article Dietary mineral seems strangely inaccessible to some - to simplify I've copied the relevant data below:77.86.76.212 (talk) 20:35, 20 July 2010 (UTC)

H																		He
Li	Be												B	C	N	O	F	Ne
Na	Mg												Al	Si	P	S	Cl	Ar
K	Ca	Sc		Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn	Ga	Ge	As	Se	Br	Kr
Rb	Sr	Y		Zr	Nb	Mo	Tc	Ru	Rh	Pd	Ag	Cd	In	Sn	Sb	Te	I	Xe
Cs	Ba	La	*	Hf	Ta	W	Re	Os	Ir	Pt	Au	Hg	Tl	Pb	Bi	Po	At	Rn
Fr	Ra	Ac	**	Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg
			*	Ce	Pr	Nd	Pm	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu
			**	Th	Pa	U	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No	Lr

The four organic basic elements

Quantity elements

Essential trace elements

Pervasive but no identified biological function in humans

Lemon Juice - alkaline or acidic?

I've heard that although lemon juice in its raw form (squeezed from the lemon) is acidic, once it enters your stomach it somehow becomes alkaline and has an alkaline affect on the pH of your stomach - is that true? And if so, by what process is the citric acid converted into an alkaline substance? —Preceding unsigned comment added by 118.139.32.234 (talk) 01:59, 20 July 2010 (UTC)

Once cells metabolise the citric acid to carbon dioxide and water, it will leave behind the alkaline components in the juice such as potassium ions. The carbon dioxide will equilibriate to bicarbonate ion in the body, which is mildly alkaline. The biochemistry that handles this is the citric acid cycle. Graeme Bartlett (talk) 02:40, 20 July 2010 (UTC)

... and, of course, even the most acidic lemon juice has a pH of about 2 which is similar to the average pH in the stomach. The pH of Gastric acid at the point of secretion can be as strong as 0.8. Dbfirs 08:23, 20 July 2010 (UTC)

Don't forget that the carbon dioxide equilibriates to bicarbonate and protons. --Chemicalinterest (talk) 10:49, 20 July 2010 (UTC)

I'm pretty sure that CO2 dissolved in blood is acidic. John Riemann Soong (talk) 18:57, 20 July 2010 (UTC)

It is. Protons are much more acidic than bicarbonate is basic. --Chemicalinterest (talk) 19:36, 20 July 2010 (UTC)

But that's only once the acid has diffused out of the stomach, so it won't have any effect on the pH of the stomach. Even before that lemon juice isnt really going to change to the pH of your stomach - pH is measured on a logarithmic scale - this means that to change the pH of the stomach from 1 > 2 would require diluting the acid with 10 times as much water. So no, lemon juice can't change the pH of your stomach. Smartse (talk) 00:08, 21 July 2010 (UTC)

But most of the CO2 is breathed out losing that acid producing carbonic acid and leaving behind the potassium bicarbonate. But this is not in the stomach, it is in the body cells. That CO2 goes on to acidify the oceans instead. Graeme Bartlett (talk) 06:11, 21 July 2010 (UTC)

Does not... The plants take it and produce O₂, completing the cycle. If the CO₂ is breathed out, then the bicarbonate and carbonic acid are released because the equilibrium shifted. Why it is alkaline is because the K⁺ ion is basic in comparison to gastric acid with its H⁺ ion. --Chemicalinterest (talk) 14:44, 21 July 2010 (UTC)

Under normal conditions, the K+ ion is neither basic or acidic. It is ever so weakly Lewis acidic, even more than Na+. If you take the potassium salt of fluoroantimonic acid suddenly the normally stabilised K+ ion will become a strong Lewis acid indeed.

Also, breathing CO2 out does not leave behind bicarbonate. CO2 is breathed out by protonating bicarbonate. Blood near the lungs is more acidic than blood in the systemic capillaries. This does two things: diioxygen's affinity for haemoglobin increases, while bicarbonate is protonated and released from transporter complexes. All that is left behind is the water that the CO2 reacted with in the first place, at the actual site of metabolism. Bear in mind, blood pH is buffered by bicarbonate. John Riemann Soong (talk) 15:49, 21 July 2010 (UTC)

age

Can there is a medicine aur ane thing bye which the growth of child increse?? example like in movies now days actors age of about 15-17 look much younger than mormal .. —Preceding unsigned comment added by 115.248.45.13 (talk) 06:08, 20 July 2010 (UTC)

Nothing that would be remotely legal to administer to a child to alter their appearance for acting purposes. Film directors cast actors who look the right age for the part, and some people look older and some younger than the average, so an actor who looks young will be preferred (as they will have more acting experience than someone really that young), and such actors will specialise in such roles. Make-up also contributes, of course.

There are treatments to help the growth of people whose growth is less than it should be because of some medical problems, of which there are several. See, for example, Growth hormone. 87.81.230.195 (talk) 07:10, 20 July 2010 (UTC)

I'm confused why you want medicine to increase the growth of a child. Do you think actors age 15-17 need to be given it to look older? As 87 has said, this seems strange, actors who look young are generally preferred so there's no reason why anyone, either the director/s or the actor/s are going to want to take it. If you think actors age 15-17 have been given medicine to make them look young then logically it's medicine which reduces the growth of a child not increases. Nil Einne (talk) 20:48, 20 July 2010 (UTC)

Acting a part is more than just "being" the part. Early silent movie actress Lillian Gish said that director D.W. Griffith told his young adult actresses to hop and skip and jump around to look more like children. Today they just look like the are hyperactive or ate too much speed or sugar. Actors or comics today still use certain mannerisms when playing younger characters. Edison (talk) 19:58, 21 July 2010 (UTC)

Strange worms - Could anyone tell me what these are?

I've seen quite a few of these worms in covered areas (mostly on stored plush fabrics, boxes, bags, etc.) and have always wondered what they are. I most often find dead ones, but I've also noted a few live ones in some old carpets.

Most of the worms I've come across are about .3-.5cm in length, but, in the most extreme cases, I've seen them go up to 1cm.

Here is a picture of the one that I normally see: http://eepromeagle.dyndns.org/unknownbug/IMGP4319.JPG And a larger one: http://eepromeagle.dyndns.org/unknownbug/IMGP4322.JPG

EEPROM Eagle (talk) 06:35, 20 July 2010 (UTC)

It might help someone to make an identification if you tell us approximately where in the World you are, since insect species are very numerous and different continents and climates have markedly different populations. These look as if they may be the caterpillars of some kind of moth (so not a "worm" except in a very non-scientific sense), but beyond that we need geographical clues to narrow down the possibilities. 87.81.230.195 (talk) 06:57, 20 July 2010 (UTC)

Beetle larvae (not worms) - possibly Dermestidae Shyamal (talk) 07:01, 20 July 2010 (UTC)

Yes, it looks like the cast off shell of the larvae of the larder beetle. I get them in my flat, I wish I didn't. 213.122.7.114 (talk) 09:29, 20 July 2010 (UTC)

Heh, yes. I said worm just to say to what they kind of looked like to me. I was pretty sure they were larvae. To answer the above question, I'm in Massachusetts. Thanks for the information! EEPROM Eagle (talk) 22:01, 20 July 2010 (UTC)

would it be possible to duplicate, mechanically, the action of a modern CPU (obviously at up to minutes per clock cycle).

A modern latest CPU like the Intel i7 can have 8 megabytes of cache, which is 67 million bits (or a square array of 8185 by 8185 bit-representing elements). Then it has 731M transistors. That's a square array of 27038 x 27038 elements. However, they are constrained to work on a very, very small scale, as they must operate at close to or somewhat over 3 GHz. Now, in 3 GHz, light only travels 10 centimeters, so obviously the overall size can't be huge.

Our mechanical design has no such constraints: it's fine to be many feet by many feet (by many feet, since you can use vertical space more easily when assembling wooden parts by hand).

If "speed is no object", and it is fine to take as long as you want to go through one clock cycle, is it feasible to duplicate the action of this CPU mechanically, such that if you mechanically set the input of the "wooden processor-equivalent" it will churn and eventually give the same output as the actual Core i7?

Secondly, if you imagine this mechanical processor, what do you think the fastest spinning gear is, and how fast does it have to spin to complete one "clock cycle" in wood in, say, 30 seconds? Then, if we take that RPM and do simple multiplication, what RPM is the Intel i7 at 3 GHz equivalent to in wood and metal rpms? Say, 18 trillion RPM? Thanks. 84.153.247.76 (talk) 11:00, 20 July 2010 (UTC)

Charles Babbage nearly did something similar with his Difference engine and Analytical engine in Victorian times. 92.15.7.17 (talk) 11:18, 20 July 2010 (UTC)

(Well, he did make working 'designs' - but none of his designs were actually completed until the British Science Museum recreated one of them a couple of years ago). SteveBaker (talk) 11:54, 20 July 2010 (UTC)

Please read the third word in the sentence above. Incomplete parts of the machines were made under his supervision. 92.15.7.17 (talk) 12:49, 20 July 2010 (UTC)

I did read what you wrote - but "nearly" is a pretty weak explanation and I think it needs amplification. What Babbage achieved is widely misunderstood. He produced a complete design for the difference engine (which is NOT a computer - but more like a fancy printing calculator) and he made many partial designs for the analytical engine (which would have been, recognizably a "computer" - but for narrow technical reasons is not properly "Turing complete"). During his lifetime, only about 10% of the difference engine design was ever actually constructed - but it was fully completed recently by the science museum in London - and with a simple correction to the original drawings (where the orientation of some part was reversed) it was made fully functional. But the design for the analytical engine - which would have been "the world's first computer" is not complete enough to be constructed. What I think is most impressive is that the first ever computer program was written for the analytical engine (although there is some controversy about whether Babbage or Ada Lovelace actually wrote it). SteveBaker (talk) 00:18, 21 July 2010 (UTC)

You certainly wouldn't "duplicate" the way a modern CPU actually works. But it's certainly possible to build mechanical computers - and many people have done that. (I actually own one - you can see a photo I took of it in our Digi-Comp_I article). There is a mathematical law called the Church-Turing thesis that says that any computer that passes a certain minimal level of capability (a "Turing-complete" computer) is - in principle - capable of the same things as any other Turing-complete computer...providing you have enough time and memory to complete the calculation. So we could build a relatively small, fairly simple computer (like this one - which is made from Lego) and it could simulate an Intel i7 - eventually - and given enough memory...which is just a matter of being patient enough, and owning enough Lego! SteveBaker (talk) 11:54, 20 July 2010 (UTC)

you say "you certainly wouldn't "duplicate" the way a modern CPU actually works" (my emphasis). Why not? You say that it's not possible if the input, off the bus, is fed via braille, to get the same output as the i7, having taken the same intermediae processing steps??? Well why not... aren't all the little transistors basically just doing boolean logic? THere's nothing "magic" or analogue about an i7 that you couldn't do with another, logically equivalent, design: after all, before they ever built one, Intel surely modeled the i7 in software... 84.153.247.76 (talk) 12:30, 20 July 2010 (UTC)

I Imagine Steve's point is that although you could (in theory) duplicate the 731 million transistors of the i7 in a mechanical computer, that wouldn't be a rational way to design a mechanical computer. With a mechanical computer, costs of fabricating and maintaining individual components become significant, and factors such as friction increase with the number of components, so it would be better to go for a design that minimised the number of components, even though it did less in parallel and took more clock cycles to process each instruction than a mechanical i7 clone would. Gandalf61 (talk) 13:08, 20 July 2010 (UTC)

Well, I don't know what you guys think I might want with a mechanical computer, but it's nothing at all. I have absolutely no need for a mechanical computer, I am only interested in the Intel i7, and the only reason for asking about a mechanical computer is whether one could, theoretically, at great cost and impracticality, be created that was logically equivalent to it. If so, how long could we estimate it would take to "render" (or "virtualize" or in some way be equivalent to) one clock cycle on the i7? Going from that, how many RPM would it go at to, say do an i7 clock cycle in 30 seconds? Thanks. 84.153.247.76 (talk) 13:39, 20 July 2010 (UTC)

A mechanism that was "logically equivalent" to the i7 (i.e. gives equivalent outputs when presented with equivalent inputs) would not need to replicate the i7's internal design. So - do you really mean "logically equivalent", or do you mean a mechanical copy of the i7, where you could identify each i7 transistor with a specific mechanical widget ? Gandalf61 (talk) 14:10, 20 July 2010 (UTC)

There's no easy way to know this without actually spending the rest of our lives designing the machine. The mechanisms of an electronic chip (Transistors, etc.) do not exactly translate into mechanical constructions. Babbage's proposed computers used gears, but he was designing a new system from the ground up, taking full advantage of the parts he had available. It's not at all clear to me that an exact duplicate of the i7 could be built that way. In fact, pneumatic systems would be a closer analog to electronic circuits than gears would.

This is an important point because how that mechanism is crafted will be a large portion of what determines the speed that your machine runs at.

Not only that, mechanical linkages have problems that electronic ones don't. (Biggest issue : friction adding up over all those gears.) So something will have to change regardless for that to be fixed. APL (talk) 14:54, 20 July 2010 (UTC)

To be clear, there is no theoretical reason you couldn't build a mechanical copy of an i7. In practice, mechanical computers tend to work differently though because binary logic is not easily modeled with gears. (Think: What is the mechanical analog of a transistor, or an AND gate, etc.? Such things could be created, but the individual elements would tend to be more complex than is practical.) You'd also have to design so that the total friction in the system was manageable and the amount of force between individual gears was never so great that the gears would break. I would speculate that if you tried to follow i7 logic directly using wooden gears (as you suggest), then you'd probably fail both of these constraints. In practice, it would be much more reasonable to think about designing a system that takes i7 inputs and gives back i7 outputs, but was internally redesigned to operate mechanically. As Steve mentions, there are a wide variety of ways that could be accomplished. However, questions like "how fast is the fastest gear" and "what RPM" are largely pointless without considering a specific design and such values could be changed by orders of magnitude based on engineering choices that have no impact on overall performance. So I don't think there is any useful answer to those questions without considering a specific model. You could look at some of the historical mechanical calculators and try to figure out how much longer they take to operate than a modern CPU given the same operation, and that is perhaps the most useful comparison I could suggest. Dragons flight (talk) 13:48, 20 July 2010 (UTC)

It might be theoretically possible, but it would be an engineering wonder, and easily the most complicated machine ever constructed. Googlemeister (talk) 13:52, 20 July 2010 (UTC)

If the chip has 700 million transistors, and each one requires a few moving parts, you're talking billions of moving parts (compare to the Space Shuttle's 2-3 million mostly non-moving parts). I think it would be a statistical impossibility that they would all be functioning at the same time, even for a moment. --Sean 15:09, 20 July 2010 (UTC)

Let's think about this the way a computer-designer actually thinks about this. Every few years, a new VLSI process is introduced. Sometimes, they just make this year's process smaller; but sometimes they fundamentally change something - like the order that individual chemical layers get deposited. When those changes happen, the chip designers don't sit around thinking "darn, now we have to translate the i7 core, device by device, 731 million times." This is critical - a modern processor has 731 million pieces (or whatever) - so to build it, you must have another machine to macro-ize construction operations 731 million times. Instead, they just "recompile" their design for a new process, and then spend some effort "tuning" for performance. Here's how it works. First, you ask yourself how to build one transistor in the new process. And you come up with a transistor macro; and then you consider how you need to interconnect two transistors; and then after some time, you end up with a set of macros to represent a lookup table, a bit of a register, a multi-bit vector, and so on. Now, the i7 core is described somewhere deep in the vaults of Intel's research and development lab; and it is described in a language like verilog or VHDL (or more likely, some bizarre combination of both that gets woven together by incomprehensible perl scripts and passed down by an elite cabal of engineers and computer architects). Then it gets run through a different machine that maps each high-level interconnection description into a series of device-layer connections - called place and route or VLSI synthesis. So - let's get back to the horrifyingly huge wooden contraption. How do you build one transistor in mahogany and teak? Well, let's think about what a transistor actually is - and remember, we have the luxury that we really only care about digital logic, so we really just want a high-gain inverting transistor. This is a simple device that takes one input and produces an output at the opposite value of the input. So, let's think of your wooden device as some kind of lever or piston or something; it has to take a high- or low- input (maybe it gets poked by the position of another lever or piston, and then pokes the next lever with the opposite polarity). Of course friction has been brought up many times; transistors deal with this too, it is called the "static current draw" or the quiescent current. Even the best amplifiers waste some energy. If you look at a circuit schematic for a transistor, you will always see both a signal input and a power input. Thermodynamics requires that power be consumed. The difference is that one transistor is ridiculously close to the theoretically most-efficient system; whereas your wood/pneumatic piston is not. But oh well; nobody really worries about energy problems in modern computers anyway. Let's say you just attach an air-compressor to every piston, and power all the pneumatics using fossil fuels, (keeping the analogy to modern electronic computers). So we now have one wooden transistor, and we need to interconnect it to others to form basic building-block devices, like truth tables, clocks, registers, and arithmetic units. Then, we design the macros for each of these, and provide the list of available macros (and their description in terms of boolean logic) to the VHDL synthesizer software. That will crunch out our design for about 24 hours, and finally spit out a list of all 731 million wooden/pneumatic devices - including where to place them, and what to connect them. Now, you could require those placements to be exactly in the same location and connection pattern as an i7 core - but that would be stupidly inefficient. The i7 core has been optimized for the speed of propagation of 32-nm silicon CMOS. The number of cache-lines, and the number of bits per cache-line, for example, are directly determined based on real latency to main memory in the particular technology it was designed for. Much of the complexity comes about from these specialized hardware and process tuning. But, for the sake of exploration, let's say that your wooden memory timings are exactly scalable to those of a modern DRAM. Now you just need a way to fabricate 731 million pneumatic elements. In CMOS, this is easy - we call it photolithography - but you can probably find some way to easily obtain all the parts, lay them out, and operate on them in bulk. Don't forget to build redundancy into your design - because in 731 million wooden pistons, termites will bore out the innards in 1 in a million wooden pistons. So, at the wooden CPU factory, you need to be able to build everything - test everything - and then automatically reroute to a redundant piston any time a sub-unit doesn't work. Alternately, you can spend your whole life trying to de-termite your fabrication-process to obtain a 100% yield; but that is less efficient. So, in summary, yes it could be done. If the explanation above has served any purpose, it is to convince you why microfabrication and silicon are the only realistic ways to do processor design using reasonable quantities of time, resources, and engineering effort. VLSI is amazing stuff - it's got room for innovation - but it really is centuries ahead of any other mechanical manufacturing process. Nimur (talk) 16:02, 20 July 2010 (UTC)

Wait, I notice a couple of times the question-asker uses the phrase "logically equivilant". If all you want to do is mimick the inputs/outputs of the i7 then Steve's method above would work just fine. Any Turing compatible CPU can be made to mimic the inputs/outputs of any other Turing compatible CPU.

All you'd need is an additional mechanism to map certain parts of the mechanical Turing machine's 'memory' to the input/output pins, and run the 'memory' through that device at the end of every simulated cycle. APL (talk) 20:47, 20 July 2010 (UTC)

My first answer is still the right one. Let's refer to the actual wording of the question: "would it be possible to duplicate, mechanically, the action of a modern CPU". The "action" of a modern CPU can been seen at various levels. At the level of software - the Church Turing thesis says that, yes, any Turing machine could be programmed to accept a computer program for an Intel chip and produce the same numerical answers. At the level of voltages on pins of the ship, obviously a purely mechanical computer fails because it can't accept electrical signals without some kind of tiny low current/voltage motor.

The fuzzy answer of whether you could simulate an Intel chip by somehow simulating each of it's internal logic gates out of mechanical systems is tough...I don't think that's relevant to the original question though - you don't have to do a 1:1 simulation to fulfil the requirements to simulate that chip perfectly. For example - when the engineers at Intel are designing a new CPU, they don't draw out this vast circuit - then manufacture one - then see if it works. Turning a paper design into a chip costs millions of dollars - you don't do that until you have a known-working design. So they start out by simulating the new design - first at the level of registers and such - then at the level of gates, then at the level of transistors. Those simulations are 1:1 identical in function to that of the real chip - so that when they manufacture the chip, it should work the first time. Since that exact simulation of the chip is a computer program - the Church-Turing thesis says that we can precisely simulate the chip (right down to measuring the voltages at the inputs and outputs of transistors) on any sufficiently large Turing machine. We could even have our mechanical Turing machine have a mechanical display of some sort (imagine lots of multicolored cubes that rotate on rods to show different colored faces or something) - and display the interior logic of the Intel chip. So yeah - we can do a perfect simulation on any Turing machine.

Another branch of this discussion has been talking about the size and speed of a mechanical computer. But let's think out of the box here. A mechanical computer could be vastly faster than the fastest hardware we have today. Calculations on the possible speeds of a nanotechnological computer in which the mechanical parts were (let's say) 100 atom carbon chain push-rods, levers and cams suggest that it would be vastly faster than the fastest machine we could build out of electronics. The fastest transistors we have can switch at perhaps 100GHz - but moving 10 atoms a distance of just a few times the size of an atom can happen WAY faster than that. There is much debate about whether such machines are possible - but if they are, they will almost certainly be teeny-tiny mechanical turing machines.

SteveBaker (talk) 23:59, 20 July 2010 (UTC)

Did you mean to type "simulating each of ITS internal logic gates" ? Cuddlyable3 (talk) 15:44, 21 July 2010 (UTC)

It's an interesting idea and I certainly hope someone looks into it. But I'm not going to invest any money I can't afford to lose. Intuitively it seems to me the big problem is going to be reliability. How many of your enormous number of rods and cams and levers are going to get stretched, or squashed, or broken, in the course of a computation?

By the way I also think that's why your big version made out of wood probably won't work. Babbage never tried to represent a billion bits. At some point, changing one bit will require changing so many others, that the force you have to exert at the input level will simply break something along the way. But as I say, that's intuition; if you have a design that gets around the problem it would be interesting to see it. --Trovatore (talk) 00:32, 21 July 2010 (UTC)

That's why you need a wooden buffer amplifier - you must expend power in order to isolate each stage from the others. But this means that any individual wooden lever does not have to push a billion others - it just has to drive its own output. The friction of later stages is totally isolated. Each stage consumes power from an external power-supply, so that the signal input does not have to provide power input as well. Nimur (talk) 00:58, 21 July 2010 (UTC)

Hmm, might work. I'm still skeptical that it can be done reliably enough to simulate a modern computer. --Trovatore (talk) 01:15, 21 July 2010 (UTC)

Babbage had worked out some clever tricks to avoid the problem of changing one digit and thereby causing a whole bunch of gears to turn at once. The obvious worst case would be when if you added 0000000001 to 8999999999 - resulting in 9000000000 and the force of one tiny gear wheel changing would have to turn (in that case) 10 other wheels. Babbages difference engine used something like 30 decimal digits of precision (VASTLY more precise than a modern computer in full double-precision mode!) - so in his case, turning one wheel might cause 30 others to have to turn - which would have caused serious mechanical issues. Those kinds of problems had beset previous efforts at building mechanical calculators - resulting in them being restricted to low precision calculations and making them highly temperamental. He came up with a rather clever way to fix that problem so that the amount of force required to do a worst-case 'carry' was no different than for a simple non-carry addition. However, the way he did it in the Difference Engine was rather slow - basically, the turning of a result wheel from 9 to 0 tripped a little "carry" lever and didn't propagate the carry on to the next digit - then this little spiral gizmo went down the column of levers one at a time rotating the wheel by one unit whenever the previous wheel's carry lever was sticking out - resetting the carry lever and possibly tripping the next carry lever down the stack. If you watch the machine in the London Science Museum doing this while it's adding random numbers together, it's kinda hypnotic! The machine performs about one addition per second - so these things happen rather quickly! For his later "Analytical engine", he came up with an even more devious mechanism that avoided the mechanical force issues and didn't consume significant extra time by doing a kind of 'carry prediction' trick. The interesting thing about that was that it made the adding mechanism so freaking complicated that he gave up the idea of every stack of gears that represent a number having the "ADD" capability. Instead it would copy the numbers from a "memory register" into the "mill" where the addition would take place and the result copied back into the register. This is eerily similar to a modern CPU where numbers are stored in dumb memory and all of the math happens in one central unit rather than having full arithmetic capability at every single byte of RAM! SteveBaker (talk) 21:36, 21 July 2010 (UTC)

You could have small wooden balls to simulate electrons. It would then be the size of a skyscraper. 92.28.255.176 (talk) 08:59, 21 July 2010 (UTC)

For that you must have very small balls. Making DRAMs would be difficult. Cuddlyable3 (talk) 15:48, 21 July 2010 (UTC)

Skyscraper? No, it would be a few miles on a side at least. The i7 has a minimum feature size of 32nm. If you make the reasonable assumption that your wooden device will have a minimum feature size of half an inch, you wind up with a device roughly 400,000 times the original. APL (talk) 15:56, 21 July 2010 (UTC)

On early vacuum tube computers, the mean time between failure of the few thousand tubes (valves) was a practical limit on complexity (as was power consumption). What is the MTBF for a high speed wooden gear and pinion, or lever action? How many times can it repetitively click and clack at high speed before it wears or warps? There may be a practical limit on what fraction of a modern computer chip could be physically modelled in wood, and how many clock cycles it could complete before repairs/replacements/adjustments were necessary. As complicated wooden mechanism, various early automata, the Jacquard loom, the [Tracker action| tracker organ] and other musical instruments, and the wooden clock come to mind, so somewhat complex wooden gadgets can function thousands of times, or tens of thousands of times, with levers moving levers or gears turning pinions. A chip goes at many millions of operations per second and many seconds are required for some calculations or programs. It would be instructive to make a mechanical analog of an amplifier, an invertor, basic logic gates, or a flipflop. But I would not expect to see a wooden computer which would click and clack and invert a large matrix, say. Edison (talk) 19:40, 21 July 2010 (UTC)

A Pneumatic Transistor

Here's how to make a pneumatic (P) transistor (reverse the spring and gate for the N equivalent). You'll also need pneumatic "wires" (copper pipe will do the trick and give the whole thing an attractive old-world charm) and a few other simple device equivalents such as resistors (constricted pipes) etc. Once you've got the handful of fundamental devices, you can build and model a standard cell library, and enter it into your synthesis libraries. Run through the standard EDA flow as described above to get a fully mechanical pneumatic CPU.

The simulation part of the EDA flow will give you an estimate of the highest reliable clocking frequency as well as static and dynamic current (pressure) consumption. The MTBF of a pneumatic transistor is likely much lower than for a semiconductor one which will shorten your CPU's lifetime accordingly (perhaps to less than the time required for a single operation). David Carron (talk) 14:39, 22 July 2010 (UTC)

The first computers built by Konrad Zuse were mechanical. They were rather specialized as they worked in floating point but the design could be changed pretty easily to do what modern computers do except you'd need a lot more memory and they'd be very slow. The only electrical bits were the motor and tape reader. The mechanical memory was more compact than anything else for another twenty years. Dmcq (talk) 14:35, 24 July 2010 (UTC)

how did the Greeks discover the earth was round?

How did the Greeks discover the Earth was round? 84.153.247.76 (talk) 13:36, 20 July 2010 (UTC)

Well, the first guy who estimated the diameter was named Eratosthenes who did this around 250BC or so, but I think they knew it was round before that. Googlemeister (talk) 13:47, 20 July 2010 (UTC)

Because it looks round. My history of science tutor believes it was pretty obvious to any seafaring nation that the horizon was curved, and it was not a 'discovery' at all. The idea that it was flat wasn't one ever held by the Greeks, or by western civilisation at all, but found only in civilisations constrained to land (egypt, babylon, the western populace prior to civilization per se), where a smooth horizon is hard to come by, and so because the surface of a sphere locally approximates to euclidean, the ground appears flat. —Preceding unsigned comment added by 129.67.116.122 (talk) 13:58, 20 July 2010 (UTC)

I doubt the Greeks had Wikipedia back then, but we do now, and it has a page specifically about the issue: spherical earth. DMacks (talk) 14:15, 20 July 2010 (UTC)

Perhaps by considering the fact that the shadow at noon is not vertical in places to the north and south. But another explaination for that could be a flat earth and a nearby sun. 92.29.123.248 (talk) 13:00, 21 July 2010 (UTC)

Late response, but an early proof was the curved shadow on a lunar eclipse. Awickert (talk) 02:53, 24 July 2010 (UTC)

Website which shows raincloud movement for the next few hours (in UK)?

In the Netherlands, there is a well known website that lets you see where rainclouds will be moving over the next few hours. It's pretty accurate, 'cause it's only predicting the next few hours based on radar data of cloud movements. Do we have such a website for the UK? ----Seans Potato Business 13:40, 20 July 2010 (UTC)

Have you tried the Met Office web site ? This app shows cloud cover forecasts in map form, and this one shows rainfall forecasts. Both show snapshots every 3 hours for next 24 hours, then two snapshots per day for following 3 days. Gandalf61 (talk) 13:50, 20 July 2010 (UTC)

You might also try http://news.bbc.co.uk/weather/ - click on the more uk weather link to access various interactive time-lapse displays of recent actual and future forecast rain etc, though unfortunately the scope and options of these seem to have been restricted quite recently. 87.81.230.195 (talk) 18:24, 20 July 2010 (UTC)

induction

would it be possible to induce a polar or overall charge on an incoming bullet usign static electricity or someother means and then using a high power magnetic field to deflect it away?--91.103.185.230 (talk) 14:01, 20 July 2010 (UTC)

In theory, yes. In practice, no. — Lomn 15:07, 20 July 2010 (UTC)

I agree. To elaborate, start by reading muzzle energy. A modern rifle round carries thousands of joules of kinetic energy. To "stop" this bullet, you need to dissipate that energy; to deflect it, you need to impart enough momentum to meaningfully change its trajectory. If you consider the energy involved, we have no machinery that can practically or safely deliver that amount of energy in a focused way to induce current or magnetic force on a bullet. An easier way to deflect such a bullet would be to detonate a large explosive in its trajectory. Alternately, you can dissipate bullet energy effectively by hiding behind a sandbag barrier. Because the bullet impacts inelastically with sand, sandbags are a better defense against rifle and machine-gun rounds than steel-plate armor. When you consider alternatives, you have to keep thinking about how much energy you need to dissipate, and/or how much momentum you need to null out or deflect. Nimur (talk) 16:26, 20 July 2010 (UTC)

It depends on what is meant by 'deflect'. I can conceive of a laboratory-demo-type experiment in which a bullet is fired, is given a static electric charge, and then passes through an intense magnetic or electric field and suffers a small deflection. In that situation, a shot aimed at a relatively distant target might be deflected by a few inches — enough to miss the person at whom it was aimed. Mind you, I can't think of a practical use for this sort of scheme; a small-angle deflection is only useful if it can be applied far, far from the target. TenOfAllTrades(talk) 18:26, 20 July 2010 (UTC)

(ec) If the bullet is linear dielectric it would be attracted to a point charge with a force that scales r^-4. This would make it practically hard. —Preceding unsigned comment added by 92.8.29.89 (talk) 18:31, 20 July 2010 (UTC)

Suoermagnetman recommends using magnets to break the motion of metallic bullets (and so do I) ( http://www.youtube.com/watch?v=iABmUEH5s0k&NR=1&feature=fvwp )(see also Eddy current brake). The motion is close to critical damping, see Damping. 77.86.76.212 (talk) 19:33, 20 July 2010 (UTC)

You could do a calculation to determine how much momentum you need to impart to yield a 12-inch deflection on a round that is traveling at 900 m/s. If you begin applying an acceleration orthogonal to the round as it exist the muzzle, you have less than 1/3 of a second before it reaches its target (at maximum range). How much force is required to accelerate a 5 gram object so that it gets a 0.25 meter displacement in 0.3 seconds? This is elementary physics: I'm getting a force appoximately equal to 1 newton. Does anyone know a way to focus an electromagnetic or electrostatic field at a distance of 300 meters and impart a 1 newton force on a lead/copper bullet? As far as I know, there is no such technology capable of that. Take a look at our article on magnetic force. Electrostatic acceleration is just implausible; magnetic induction is equally unlikely (you must first produce eddy currents, and then subject the magnetized object to an additional external field to apply a force to it). The physics just is not on your side with this one. Even if you fired the round into a specially-constructed laboratory setup, some kind of tube or tunnel surrounded by magnetic coils... that's still a lot of force to produce strictly by induced magnetic interaction. The idea is fun to toy with in theory, but when you start looking quantitatively at feasibility, it is no surprise that today's best defense against bullets is still low-tech sandbags. The laws that govern energy and momentum are unchanged by our ability to harness electromagnetism. Nimur (talk) 20:13, 20 July 2010 (UTC)

Your life does get easier if you assume a muzzle velocity of 300 m/s (typical of a handgun) rather than 900 m/s (a supersonic rifle round). If we assume a 300-meter range, then the constant force over that distance to achieve a 0.25 meter deflection of a 5-gram object is just 0.0025 newton. If we apply a constant one newton force, then we only need to apply it over the first 0.5 meters (roughly) to generate a 0.25-meter displacement 300 meters downrange. TenOfAllTrades(talk) 21:00, 20 July 2010 (UTC)

TOAT, handguns at 300 yards? You must have watched different Westerns than I did! Physchim62 (talk) 23:03, 20 July 2010 (UTC)

I didn't say it was a good idea, just that a 'best-case' scenario for some sort of deflection device. I'll admit that expecting a handgun to be accurage within a foot at that distance is pretty unlikely. TenOfAllTrades(talk) 01:47, 21 July 2010 (UTC)

Unlikely? Try miraculous. Googlemeister (talk) 14:17, 21 July 2010 (UTC)

Some electromagnetic and electrostatic effects on projectiles could in principle make the difference between hitting or missing a target, but might require expensive equipment. A deflection applied near the muzzle, or over a large portion of the path, will have a larger deflection than one applied only near the target. How hard does the wind push on a bullet? Marksmen spend enough time adjusting for windage, which would otherwise deflect the bullet at distances rifles commonly shoot. A rubber comb, with a small static charge can deflect a falling stream of uncharged water dramatically. Static electricity should be able to deflect a bullet some if the bullet were charged. Electric guns firing ferrous projectiles illustrate how powerfully induction can accelerate a projectile longitudinally. A copper disc dropped between the poles of a strong magnet seems to stop in its descent before descending slowly due to induced currents. A charged round projectile like a BB would retain charge better than a bullet shaped one, and would follow a curving trajectory when it passed through a strong transverse magnetic field. As a thought experiment, if a BB gun were charged from a Van de Graaf to 100kv, then fired at a target, the aim could be made such that the drop due to gravity placed it in the bulls eye at some distance, like 10 meters. Now consider if the first meter it travels between vertical plates either side of the path, charged to plus and minus varying voltages, spaced just far enough apart they did not arc. How many cm of deflection could be achieved? It is like a mechanical analog of an oscilloscope. An uncharged steel bb could be similarly deflected by passing through a magnetic field. Edison (talk) 19:24, 21 July 2010 (UTC)

how do you tell if a plant cell has apoptosed?

I can see stuff through the cell wall (DIC microscopy) and it looks like a mess. However, it's not quite like the arrangement when animal cells die (they give off apoptosis "bubbles"), so I'm not sure. They are also onion cells, so I'm not sure if those are simply lots of storage vesicles clumped together. John Riemann Soong (talk) 16:31, 20 July 2010 (UTC)

Ok I used a 700 nm filter (for gold nanoparticles lol) and I can see distinct intact nuclei...wow I didn't think that reducing the light levels by 20 times would help me see inside the cell. Because I don't fully understand DIC -- I want to ask, is it because cellulose doesn't diffract 700 nm light very well? (I get lost when it comes to diffraction and polarisation and not simply absorption/emission). John Riemann Soong (talk) 16:45, 20 July 2010 (UTC)

odorless mineral spirits

How strong (harsh, corrosive) is odorless mineral spirits compared with 70% rubbing alcohol? I would like to use the spirits to clean off kitchen countertops, and formica kitchen table. —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 17:41, 20 July 2010 (UTC)

The article White spirit has some information about toxicity. It's not a good idea to wipe down counter-tops with white-spirits unless you are going to thoroughly wash them again straight afterwards (presumably you're asking because Formica doesn't work well with household Bleach]?). ny156uk (talk) 18:15, 20 July 2010 (UTC)

Is there something particularly horrible you're trying to clean off? White vinegar does a decent job of disinfecting surfaces and is obviously okay for food handling areas. I'd be leery of using anything as toxic as paint thinner on something I was going to leave food on. Matt Deres (talk) 18:53, 20 July 2010 (UTC)

Do any of these solvents contain OH groups? John Riemann Soong (talk) 18:54, 20 July 2010 (UTC)

will odorless mineral spirits damage the surfaces how strong is it —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 19:52, 20 July 2010 (UTC)

The strength of household white vinegar will vary from brand to brand, but you're typically going to find stuff that is around 5% to 8% acetic acid. As with any other acid, I would hesitate to use it on marble (which is essentially calcium carbonate), as it would eventually etch the surface. I use vinegar as my standard cleanser on glass, porcelain, chrome fixtures, and my countertops. I also use it to disinfect my plastic and wooden cutting boards (see here). I know a lot of people prefer diluted bleach for disinfecting surfaces, but I prefer the smell of vinegar and I like the convenience of not having to worry about getting the dilution correct - you just use it straight up. After applying vinegar, you need to wipe it off afterwards as it can leave a residue if you let it puddle. Matt Deres (talk) 23:46, 20 July 2010 (UTC)

Note: This follow-up question read "will it damage ..:" when Matt Deres responded. It was later changed to "will odorless mineral spirits damage ..."

Few countertops (worksurfaces in the UK) are made of marble in the strict sense, because it's not good to have a polished surface that you can easily etch with spilt lemon juice, vinegar etc. Most of them are some form of igneous rock (although very little of what's sold as granite is genuinely granite), which will probably survive most of the chemicals mentioned. Mikenorton (talk) 12:21, 21 July 2010 (UTC)

note the OP asked about a 'formica' worksurface. . OP - This link http://www.naturalhandyman.com/iip/infcountertop/infcleaningformica.html may be of use. ny156uk (talk) 17:41, 21 July 2010 (UTC)

Anything science still can't do?

Is there anything, after all these years, that science still can't do?

Any number of things; check out science fiction. — Lomn 21:02, 20 July 2010 (UTC)

It apparently can't make everyone know that there is no "end of science". See our Science article. Comet Tuttle (talk) 21:03, 20 July 2010 (UTC)

Well it depends what you mean 'science still can't do' since since isn't something that does stuff. But anyway at a guess at what you mean the answer is a arguably an unlimited number of things. We still haven't mastered nuclear fusion for electricity generation, we still haven't made spaceships capable of 0.1C... You could include things believed impossible like faster then light travel. Nil Einne (talk) 21:05, 20 July 2010 (UTC)

There are certainly things scientists can't do. APL (talk) 21:08, 20 July 2010 (UTC)

Science seems to find it difficult to explain why so many supposedly well educated people, totally willing to use the fruits of its discoveries, reject it publicly in favour of mystical explanations for many perfectly natural phenomena. HiLo48 (talk) 21:12, 20 July 2010 (UTC)

Science find it difficult to explain why so many supposedly well educated people, totally willing to use the fruits of its discoveries, reject it publicly in favor of unscientific random changes for many perfectly natural phenomena. --Chemicalinterest (talk) 21:48, 20 July 2010 (UTC)

Actually, human susceptibility to superstition seems to be reasonably well understood. APL (talk) 22:29, 20 July 2010 (UTC)

Try List of unsolved problems for starters.

Ben (talk) 21:15, 20 July 2010 (UTC)

BTW, thank you for that article / category; it is great. Comet Tuttle (talk) 23:48, 20 July 2010 (UTC)

I was expecting the link to economics' unsolved problems to just be a redirect to economics. :) Matt Deres (talk) 00:00, 21 July 2010 (UTC)

Go back in time. Otherwise, science could do whatever science CAN do at any time. Googlemeister (talk) 19:53, 21 July 2010 (UTC)

It's common to confuse science and technology. Although they're usually pretty closely linked, they're not the same thing. Dear OP, if you were you asking whether there's anything that science still doesn't understand, the answer is yes, and I sincerely hope that it always will be. Science doesn't ever end because most — if not all — any scientific advances let us ask more questions that we wouldn't have known to ask previously. For example, we couldn't begin to address the cure for cancer without first developing cell theory. – ClockworkSoul 22:00, 20 July 2010 (UTC)

Well, if you want a specific example, science can not explain why animals sleep. There is discussion on memory and stuff, but even flies sleep. Ariel. (talk) 22:36, 20 July 2010 (UTC)

Science will never explain why I love my partner, and I prefer it that way ;) everything thing in its right place! Physchim62 (talk) 22:59, 20 July 2010 (UTC)

It actually can probably give a variety of good accounts for that. --Mr.98 (talk) 23:54, 20 July 2010 (UTC)

I think that science actually can explain why animals sleep. To my mind the "synaptic homeostasis" theory of Giulio Tononi is very strong, and I have the impression that it's gradually gaining favor in the community. The basic idea behind the theory is that learning and memory produces increases in neural connection strength that destabilize brains, and it's necessary to have an off-line period in which memory is switched off so that the problem can be fixed. Flies need to sleep because flies have memory -- using mechanisms surprisingly similar to the ones in humans. Looie496 (talk) 04:13, 21 July 2010 (UTC)

The consequence of not sleeping, Fatal familial insomnia, can at least allow science to infer some things, e.g. that the brain has a critical need to rest periodically (as does the heart). ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:29, 21 July 2010 (UTC)

"synaptic homeostasis" doesn't really answer the question though. You also need to explain why it's not possible to build a brain without this need. In an animal that must not sleep (dolphin), instead of changing the brain (as you might expect), the brain sleeps one half at a time. Ariel. (talk) 12:14, 21 July 2010 (UTC)

There are plenty of problems that are considered outside the purview of scientific practice. Of course, it has been a long struggle over the centuries as various problems considered "outside" of science have found their way into it. --Mr.98 (talk) 23:54, 20 July 2010 (UTC)

Ah, but were they considered outside science by scientists or by other people that wanted to keep control over them? --Tango (talk) 23:58, 20 July 2010 (UTC)

Both. But of course the lines are blurry a lot of the time. Nobody wants to control like the status quo. --Mr.98 (talk) 13:14, 21 July 2010 (UTC)

Mankind can put a man on the moon but forget about plugging a hole in the ground. Also explain the interactions of certain subatomic particles. Also brains in general... ZigSaw 13:11, 21 July 2010 (UTC)

For the record Ziggy, plugging an oil well a mile underwater is much more an engineering problem then a science problem (and last I heard it WAS plugged). Googlemeister (talk) 14:15, 21 July 2010 (UTC)

See Opinion: The Limitations of Science - TIME (Friday, May. 07, 1965).—Wavelength (talk) 01:44, 22 July 2010 (UTC)

Measuring temperatures in Ireland in the late 17th century

When I was a boy, I spent a summer in Northern Ireland; that year, 1995, had what we heard was an all-time high temperature for Belfast, at 86ºF. From what we were told, they'd kept records since the Glorious Revolution. Since the Fahrenheit scale was only proposed in 1724, how was temperature measured in Ireland before that time? Nyttend (talk) 21:58, 20 July 2010 (UTC)

Thermometer#Early_history "However, each inventor and each thermometer was unique—there was no standard scale. In 1665 Christiaan Huygens suggested using the melting and boiling points of water as standards, and in 1694 Carlo Renaldini proposed using them as fixed points on a universal scale. In 1701 Isaac Newton proposed a scale of 12 degrees between the melting point of ice and body temperature" and Category:Units of temperature (earliest about 1701)

I would guess that they had records of comparative but non-standardised temperatures. Galileo is reported to have had a type of thermometere [1] (not to be confused with the Galileo thermometer) and predates the glorious revolution - so maybe they used something like that.77.86.76.212 (talk) 22:54, 20 July 2010 (UTC)

This site is quite interesting http://www.mastco.net/home16.html in that it mentions alcohol in glass thermometers as early as 1641, and refers to one used by Robert Hooke in 1644. It's decribed in his micrographia [2] or [3] or [4] (different editions) It seems likely that they may have used Hooke's scale if they were associated in some way with the Royal Society .77.86.76.212 (talk) 23:09, 20 July 2010 (UTC)

By the way do you have any clues as to who had the records - eg Queen's University Belfast opened 1845, but Ireland was then politically one so maybe Trinity College, Dublin which dates back to 1592. Or perhaps it was some seafaring organisation or similar in Ireland that kept the records? or an amateur clergyman or gentry?? any clues? That might help find the answer. 77.86.76.212 (talk) 23:19, 20 July 2010 (UTC)

Sorry, no clue. As I said, I was just a boy; my parents told me that the all-time-record thing was from the Telegraph. Nyttend (talk) 17:00, 21 July 2010 (UTC)

July 21

A Shocking Experience ?

Can a car battery (12 volt) kill a person ?  Jon Ascton  (talk) 06:41, 21 July 2010 (UTC)

Absolutely, yes it can. The odds of a fatal event will vary greatly depending on the nature of the exposure, the current path through the body, and the availability of life saving efforts. Dragons flight (talk) 06:56, 21 July 2010 (UTC)

You mean, inspite of the fact that it's only 12 volts...

I agree with Dragons flight on the possibility, though you would need to go to very great lengths to kill someone using the car battery alone (except as a blunt object, or by extracting the acid!) . Under normal conditions, the resistance of human skin is sufficient to prevent any harm when handling 12 volts. Dbfirs 07:06, 21 July 2010 (UTC)

Yeah, that's the answer - theoretically it can. But practically there will be problems, like the skin's thickness etc.

A Darwin Award has been made in respect of a death by 9 volt battery. --Tagishsimon (talk) 10:23, 21 July 2010 (UTC)

This is at least the third time we have heard of the Snopes article and the claimed electrocution by ohmmeter. I doubt that it happened. But it is a fair cautionary note, since someone, somewhere might manage to pass enough current from a 9 volt battery through their bodies to stop the heart. If passing current from the 9 volt battery in my ohmmeter stopped my heart, I would be shocked, so to speak. Edison (talk) 19:01, 21 July 2010 (UTC)

If you just shock a vital area of your body, you will be dead; even if the voltage is so low. --Chemicalinterest (talk) 10:57, 21 July 2010 (UTC)

Uh, maybe because voltage has nothing to do with lethality? It's the amperage that kills you. A 12-volt battery can start a V8, a 20,000-volt taser can't. The former has amps, the latter doesn't. Vaguely related: don't put your finger on a spark plug and turn the ignition. It will hurt like hell. No amps, so not lethal, but Christ that stings ZigSaw 13:06, 21 July 2010 (UTC)

This is a silly, oft-repeated oversimplification. Amperage is a good way to measure lethality, but voltage has *everything* to do with how much amperage will be present given a circuit's resistance (even when a human body is that circuit). Given the same resistance (say, a human body) low voltage will *always* result in low amperage, where high voltage will result in high amperage. --144.191.148.3 (talk) 15:15, 21 July 2010 (UTC)

Yes, under normal circumstances, voltage determines whether a source is dangerous, but I have (in my younger and more foolish days) succeeded in giving myself quite a hefty shock (tens of milliamps) from a 12v battery. I won't tell you the method here in case anyone with a weak heart tries it and kills themselves. The probability of death is extremely low, but I cannot afford the law suit. Dbfirs 17:13, 21 July 2010 (UTC)

Actually, stopping the heart with a DC shock won't kill you: it will immediately start up again. AC is much more dangerous because the oscillations can set up a disrupted heart rhythm, leading to fibrillation. The only way a DC shock can produce death is if it has a timing and amplitude precisely balanced to disrupt the heart without fully resetting it. There was a man named George Ralph Mines who did pioneering work on heart rhythms, and apparently died that way as a result of experimenting on himslef, but it isn't clear what voltage levels he used. (See this paper for the story.) Looie496 (talk) 23:08, 21 July 2010 (UTC)

Yes, the body is sensitive to rate of change of current, so one would have to repeatedly connect and disconnect the DC voltage to produce a dangerous effect. Personally, I think the death by ohmmeter article is an urban myth but I presume that George Ralph Mines applied voltages direct to his heart muscle. Dbfirs 06:41, 22 July 2010 (UTC)

Why do we need oxygen?

After reading Alternative_biochemistry, i got wondering, could life exist in other types of atmosphere? The article mentions chlorine but doesn't really elaborate on why. So the question is what is so special about oxygen that we need it and theoretically could this be done by other gases? --90.210.25.177 (talk) 10:59, 21 July 2010 (UTC)

Both oxygen and chlorine are Oxidizers. See Redox for some of the details on what this is. There are lots of other things that can act as oxidizers but oxygen itself works very well, and has a few benefits: it's a very common element (astronomically speaking). When reacted with an even more common element (hydrogen) it produces the universal solvent called water. Chlorine would work as an oxidizer does doesn't do so well with hydrogen. (Hydrogen chloride). The group carbon-oxygen-hydrogen is really quite special in how versatile it is, and simultaneously how common those elements are. Ariel. (talk) 12:26, 21 July 2010 (UTC)

I was checking various hydrogen-oxidizer molecules, and oxygen is really quite the outlier amongst them. Also, in a world with a hydrogen chloride atmosphere or surface, water would be a very powerful corrosive. Ariel. (talk) 12:35, 21 July 2010 (UTC)

Does that mean that independently evolved space-aliens are likely to be oxygen breathers too? 92.29.123.248 (talk) 13:06, 21 July 2010 (UTC)

We don't use oxygen because it produces water. We use oxygen because it can be derived from water. Before the first cyanobacteria started splitting water, life used redox reactions like organosulfur chemistry, oxidiser like nitrates and Fe(III) and so forth. John Riemann Soong (talk) 15:18, 21 July 2010 (UTC)

Hmm, not quite. We use oxygen because you can get a hell of a lot of energy out of oxidizing carbohydrates to CO₂ and water; also because it's there! There's some plausible speculation that water-splitting photosynthesis actually evolved from H₂S-splitting photosynthesis. Physchim62 (talk) 15:50, 21 July 2010 (UTC)

I really don't think that's why we use oxygen. I mean, if life really wanted to make energy-dense compounds, they'd make alkyne motifs all over the place. Much of the water on this planet was carried here by asteroids, probably because most of it boiled off in the initial formation of the Earth. Take the amount of energy not captured by cytochrome complexes in the electron transport chain -- that last jump from complex IV (cytochrome c oxidase) to oxygen is so energetic, the proton gradient it contributes to hardly compensates; most of it is wasted as heat. John Riemann Soong (talk) 16:05, 21 July 2010 (UTC)

Btw, all of this is lifetalk centric to bioorganic chemistry, which if you realise, is really unique to Earth's 1 atm and 1g. A hydrogen sulfide world based on row 3 elements or a mercury world could possibly evolve. Hell, why not a world strongly dependent on a eutectic-based mixture of liquid Fe and specific crystal structures of iron that can only exist at a narrow range of atmospheric pressures and temperatures? The crystal structure is just right to allow for the diffusion of many dislocations and other bulk defects, and atoms travelling in the "solution" can diffuse. Rather than forming cells or membranes, life and "genetic replication" is strongly dependent on crystal growth and chemical networking. The equivalent of cell division would proceed by crystal cleavage, and these microstructures are stabilised by protective network formations and other sophisticated structures based on host-guest chemistry.

There magnetic interactions are just as important as polar bonding, and a "detergent" particle would have both diamagnetic and paramagnetic ends. Rich chemistry can be derived from a mix of Cr(III), Cr(VI), Cu(I),Cu(II), F- and other fun ions. The primary energy source is the planet's ever-churning and changing magnetic field. John Riemann Soong (talk) 15:33, 21 July 2010 (UTC)

The Earth's oxygen was actually created by life, so it couldn't possibly be required for life to exist. (Well, CO2 is required; it isn't clear whether the question means to include this.) Looie496 (talk) 22:57, 21 July 2010 (UTC)

It's true that life started without oxygen, but life as we know it today has probably adapted to living off of oxygen. Therefore, if oxygen were taken away, every animal on Earth right now, with the exception of the most primitive life forms, would probably die. Primitive life forms wouldn't have, but we're not primitive life forms, are we? The Raptor ^{Let's talk}/_{My mistakes; I mean, er, contributions} 23:02, 21 July 2010 (UTC)

Chemistry

Can i please get clear examples of sublimation and its opposite deposition? Is hail an example? why and/or why not? —Preceding unsigned comment added by 74.198.43.60 (talk) 14:56, 21 July 2010 (UTC)

There are a few good examples in Sublimation (phase transition), which you should definitely read if you haven't already. Hail can and does sublimate under the right conditions - ice held at temperatures significantly below its melting point does gradually sublimate to water vapour without melting - but dry ice is probably the easiest and most obvious example to use if you need one. ~ mazca ^talk 15:10, 21 July 2010 (UTC)

(edit conflict) Dry ice , Iodine and ammonium chloride are common examples of things that sublime - see Sublimation (phase transition)

According to Hail " hail forms in cumulonimbus clouds when supercooled water droplets freeze on contact with condensation nuclei" if that's true it's not sublimation since the water is in the form of droplets - which means it is liquid.77.86.76.212 (talk) 15:12, 21 July 2010 (UTC)

Indeed - the formation of hail (and indeed snow) definitely doesn't seem to be desublimation, rather a very fast freezing of liquid water. The appearance of frost on a very cold but non-foggy day is probably the best example of natural desublimation of water that I can think of. The other chemicals mentioned by 77 above are certainly easier examples to use for most things. ~ mazca ^talk 15:19, 21 July 2010 (UTC)

A possible household use is Dye-sublimation printer. Also the ice that forms in a freezer may be from sublimed ice in warmer parts of the freezer. 77.86.76.212 (talk) 15:35, 21 July 2010 (UTC)

You can get desublimation of CO₂ if you use a carbon dioxide fire extinguisher: as the pressurized gas comes out of the nozzle, it rapidly cools (this is the Joule–Thomson effect) and some of it solidifies as a fine white snow (it rapidly resublimes, but the effect is quite impressive). Physchim62 (talk) 15:27, 21 July 2010 (UTC)

Dry ice is the classic, but failing that, frost works too. If you look carefully, You'll notice that frost forms directly on surfaces without a liquid forming first (that's why it's lacy as opposed to being a solid film of ice) - that's deposition: a solid forming directly from a gas (water vapor). The opposite occurs with frost and snow too. In winter you may notice frost disappearing during the day or snowbanks shrinking, even though the temperature stays below freezing. This is because the frost and snow sublime (go directly to water vapor) in the dry air, without melting first. - 174.24.196.51 (talk) 16:46, 21 July 2010 (UTC)

Refrigerant leak?

The inside of both compartments of my refrigerator/freezer smells strongly of some organic solvent. It reminds me of 'model glue'. Does the refrigerant in a modern US refrigerator smell like that? If it is a refrigerant leak, is this generally a repairable problem or it on of those things where repair isn't practical? ike9898 (talk) 15:45, 21 July 2010 (UTC)

Assuming the fridge isn't brand new (in which case it could be the smell of glue used in the construction of it) - it may well be pentane which is a common refidgerant nowadays - in which case your fridge is leaking. It's possible that it could be fixed - but the important thing here would be not to use any naked flames, open all the windows, don't switch on any electrical items then call a fridge engineer from somewhere else and get them to come round - if your fridge is leaking pentane you have a very real explosion hazard.77.86.76.47 (talk) 15:53, 21 July 2010 (UTC)

On the other hand it may be an ozone-friendly fluorocarbon refrigerant with less flammability - it usually says on the fridge instructions or on the back of the fridge what type is used. Fixing a leak involves draining, finding the 'puncture', which may be brazed shut, and then refilling - however the fridge may not have been designed to be taken apart and put back together again (ie glue not screws) - making the repair problematic.77.86.76.47 (talk) 15:57, 21 July 2010 (UTC)

Also if it is leaking the gas may knock you out in sufficient concentrations - most refrigerants are heavier than air - which means they will settle lower down - important if the fridge is not on the ground floor or you have a basement where it can collect - in the worse case a fridge that is leaking is lethal. I would recommend getting it looked at.77.86.76.47 (talk) 16:01, 21 July 2010 (UTC)

Fluorocarbon refrigerants are usually fairly odorless, so yes, this sounds worryingly like a pentane leak. In theory, such a leak can be fixed but, for a domestic refridgerator, replacement may well be a cheaper option. You do need to get it looked at, though, because there is an explosion hazard from the light switch which operates when you open the fridge door... Physchim62 (talk) 16:06, 21 July 2010 (UTC)

Resolved

 – See this section for resolution.

Antibiotics

What kind of effect does a typical seven day course of antibiotics have on organisms that live in the human gut? —Preceding unsigned comment added by 129.67.119.150 (talk) 15:46, 21 July 2010 (UTC)

There are many hundreds of kinds of antibiotic preparations, so your question is too vague to give a definite answer. But "some antibiotics kill bacteria in the gut". You can read our Antibiotic article--I bet there is at least one section relevant to side-effects or somesuch. DMacks (talk) 16:22, 21 July 2010 (UTC)

See also gut flora#Effects of antibiotic use, as well as the individual on specific antibiotics (e.g. amoxicillin or ciprofloxacin). TenOfAllTrades(talk) 19:19, 21 July 2010 (UTC)

What do you call this sort of cytoplasmic channel?

Please help! Thanks, so I can search for it in the literature. I was observing a bunch of lung cancer cells (epithelial) under DIC microscopy. These cells had an initial connection of two tiny strands (nanotubules?) that later grew into an entire cytoplasmic channel. I saw a gold nanorod (25x73 nm) being transported across one of the stands as well as other vesicles crowding into the newly-formed channel. At the same time, I saw another cytoplasmic channel between the same cells being disassembled back into tububles; in time the tubules were even broken. The channel that formed remained strong though. What do you call these channels and tubules?

The particle being transported across the strand appeared not to be by free diffusion, but by actual binding (it stopped its flashy rotation behaviour while on the strand). I'm not sure if this is an actual microtubule or a complex of other types of polymers. Help! John Riemann Soong (talk) 16:38, 21 July 2010 (UTC)

Microtubules are part of the cytoskeleton and not actual "tubes" through which things are transported. Think of them as cables that motor proteins use to transport things around inside of a cell. There is no cellular component called a "nanotubule". You might be seeing a connection between two cellular protrusions, like filopodia, or the remnants of the cell membrane that sometimes happen after a cell divides but the daughter cells remain connected by retraction fibers (redlink? hmmm... might have to fix that). How close together were the two cells? Are your nanorods intracellular or extracellular? Can you post a photo? --- Medical geneticist (talk) 17:00, 21 July 2010 (UTC)

The cells (from memory) were separated by a distance about 2-5 micrometres apart. The nanorods were endocytosed and definitely intracellular. I was trying to witness an exocytosis event but the rods travelled across these strands instead. I don't know if the strands I saw were cables by which motor proteins were attached to, or actual very narrow channels. In time, membrane surrounded these strands and expanded to something like 10-20 times the strands' width (the strands were still the same width though). I took videos and photos which I may post soon, when I retrieve it from the lab hard disk. John Riemann Soong (talk) 17:18, 21 July 2010 (UTC)

How about membrane nanotubes? Maybe take a look at some figures in the references given in the article and see if they are similar. Smartse (talk) 20:18, 21 July 2010 (UTC)

I stand corrected! I would have used the term cytoneme but if people are calling those things "membrane nanotubes" these days it shows how long it's been since I learned cell biology! Back to the question... you probably are seeing some type of membranous tether between the cells. These things are sometimes hollow but often contain some type of structured cytoskeleton, usually actin and sometimes including microtubules, to allow for transport. When you see them expanding, I'd guess that's because they are filling up with cytoplasm. For what reason, I can't say. Still, sounds very interesting. --- Medical geneticist (talk) 21:56, 21 July 2010 (UTC)

Survival benefits of scratching

Deleted See July 19 for the same topic

Sheep breeding season

When exactly do sheep on farms (in temperate climates) tend to give birth? The domestic sheep article just says "in the autumn", which is not very specific. 86.143.231.207 (talk) 17:24, 21 July 2010 (UTC)

No, conception (tupping) is in the autumn. Lambs are born in spring. Dbfirs 18:07, 21 July 2010 (UTC)

Early spring, or technically late winter if memory serves. I think March is the most common month, but it might depend on where you are. Temperate climate is pretty broad. Googlemeister (talk) 19:48, 21 July 2010 (UTC)

Yes, where I live in the Pennines, sheep naturally lamb in April, but, for commercial reasons, many farmers (especially in milder climates) bring tupping forward to late summer and have lambs born indoors in January. Dbfirs 21:01, 21 July 2010 (UTC)

Note, however, that this technique is not known to have been practiced in 1st-century Judea :-). 87.81.230.195 (talk) 22:32, 21 July 2010 (UTC)

It is indeed thought that the true birthday of Jesus, assuming the biblical accounts about the shepherds are accurate, might well have been in the spring. The Romans choose the winter solstice as the time to celebrate Jesus' birth, as they already had spring covered by Easter. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:04, 22 July 2010 (UTC)

Wind Turbines on Cars

I was in the car with a couple of friends at the weekend, and one of them suggested putting a wind turbine on the roof in order to generate energy to subsidise the energy use of the car. I said that the turbine would create drag and would slow the car down, and so more fuel would need to be used to drive the same distance; meaning that net energy use would go up, and not down as desired. Even if the turbine converted energy perfectly, and without waste, the best that could be hoped for would be a constant net energy use.

One of my friends then suggested a turbine might be put behind the radiator grill of the car. Without the turbine, the air entering the radiator grill would be pushing against the car and impeding the car's progress. Putting a turbine behind the radiator grill would turn some of the stopping force of the wind into energy that could be used to propel the car.

Would the wind turbine still create drag, even though it was hidden away behind the radiator grill? The wind entering the radiator grill would otherwise just push against the car and slow the car. Would the turbine absorb some of this stopping energy, making the car slow less quickly, whilst at the same time generate energy to be used by the car? Are there any more comments and observations that you would like to make? I would really appreciate some input on this. •• Fly by Night (talk) 18:09, 21 July 2010 (UTC)

If I am not mistaken, the turbine would really not turn much, as the wind would pass through the turbine and stop on whatever is behind it, building up pressure, and trying to force itself back out. I could be wrong about how the turbine would behave, as I have never tried such an experiment, but laws of physics will tell you that you are not going to gain any energy by doing that. There are some things you can do to lose less energy, such as in a hybrid car (storing the stopping energy), but I don't think a wind turbine would help do anything on the car, except make it less efficient and heavier. Falconus^{p t c} 18:17, 21 July 2010 (UTC)

The air would flow past the turbine and into the radiator proper; where it would be used to cool the engine. In fact, some cars even have a fan on the other side of the radiator, powered by the fan belt, which pulls the air through the radiator. So I don't think there would be any build-up of pressure. Having said that, if there is a constant stream of air passing through the grill and then the radiator, assisted by the a fan then there's steady stream of air. That wouldn't stop the car as I thought. And putting a turbine in that air would again cause drag and hence slow the car... Does that sound right? •• Fly by Night (talk) 18:53, 21 July 2010 (UTC)

The Mitsubishi i-MiEV Sport concept car had wind turbines behind the grille. I don't know whether the production i-MiEV does or not. Adding wind turbines can increase overall efficiency; this doesn't violate any conservation laws. There was a ref desk thread on this subject recently: 2010 June 11#Windmill on a car ?. -- BenRG (talk) 19:01, 21 July 2010 (UTC)

(after edit conflict) ::Yes, I agree with Falconus that this is not a practical option. When turbines were last discussed here (thanks for the link, Ben), it was suggested that, in theory, a wind turbine mounted on a car could generate electricity from the wind without (in theory) needing to draw energy from the engine of the car. The problem seems to be, as you correctly stated, that drag on the structure would drain a greater amount of energy than would be gained. Your suggestion might work with some clever aerodynamic design to prevent back-pressure, but then the energy to drive the turbine could come only from a true headwind (or from the car engine). It's a clever idea, but the amount of energy to be gained is probably not worth the effort. Car aerodynamics are fairly complex, and I'm not sure how the change in airflow would affect drag. If the air has to flow through for cooling anyway, and energy can be harvested as it passes, then this is gain even if the energy does come from the engine in the first place. Dbfirs 19:18, 21 July 2010 (UTC)

This is not the same thing at all, but still a remarkable piece of engineering. It is a wind-powered car that can travel downwind faster than the wind is blowing. Enjoy! TenOfAllTrades(talk) 19:25, 21 July 2010 (UTC)

(ec, five times!) BenRG, this is not correct. It does cost energy. The turbine acts as resistance to the air. Instead of just passing through, the air is blocked. This resistance costs energy. However, if your design of the car is such that you have friction resistance anyway, and switch it to turbine resistance then that is a benefit - but in that case you would be better off just removing the friction resistance and leaving out the turbine. Ariel. (talk) 19:26, 21 July 2010 (UTC)

Perhaps a small turbine strategically placed over the radiator, facing down and properly shielded from the wind caused by the car's motion would be able to provide benefit from the heat rising off of the radiator. Googlemeister (talk) 19:47, 21 July 2010 (UTC)

The car is in motion, so the air would not rise. It would be swept backwards into the engine. •• Fly by Night (talk) 19:51, 21 July 2010 (UTC)

Ariel, nothing that you said contradicts anything that I said. -- BenRG (talk) 23:57, 21 July 2010 (UTC)

You said "Adding wind turbines can increase overall efficiency; this doesn't violate any conservation laws." But that's not correct, adding a turbine will add friction. Unless you mean to harvest energy from external wind, but if so it wasn't obvious to me that that is what you meant. Ariel. (talk) 02:38, 22 July 2010 (UTC)

If the turbine is directly in the flow of air then it will create drag. It will push back on the air that pushes it. Also, if the airflow is used to cool the radiator (and in turn the engine) then surely by putting a turbine in the airflow you will decrease the wind speed and so decrease the cooling ability of the air. That means that the engine would run at higher temperatures. •• Fly by Night (talk) 19:51, 21 July 2010 (UTC)

Land yachts (and especially ice yachts) can got several times the wind speed, by sailing at about 45degrees into to apparent wind . 62.56.49.134 (talk) 20:21, 21 July 2010 (UTC)

Yes, this, and TenOfAllTrades' link, prove that energy can be harvested from the wind whilst travelling, but there are problems implementing this effectively in a motor vehicle. Efforts at present go into reducing drag and improving the efficiency of engines, where there are much larger gains to be made. Dbfirs 20:47, 21 July 2010 (UTC)

Follow up refrigerant leak question

I seem to have a refrigerant leak in refrigerator/freezer. Both compartments have a strong solvent smell. I have a service tech coming in the morning.

So now for the question... In the meantime, is the food stored in this refrigerator safe to eat? There is no liquid residue anywhere in either compartment. I'm just concerned about whether the food or beverages would have absorbed the vapor in concentrations great enough to matter. Would absorption be greater for fatty foods? ike9898 (talk) 19:59, 21 July 2010 (UTC)

Update: I spoke with the manufacturer's tech support. They said the refrigerant in my model is freon, and that freon doesn't smell like that. They didn't think anything in the refrigerator should cause that smell. ike9898 (talk) 20:28, 21 July 2010 (UTC)

Perhaps it's rotten meat? Or spoiled milk? Is there anything like that in the refrigerator? The Raptor ^{Let's talk}/_{My mistakes; I mean, er, contributions} 20:44, 21 July 2010 (UTC)

Mmmmh. Could it be ripe fruit and veg - the cold temperatures mean than only the "high notes" of smells are volatile - these compounds are typically solvent like in smell and form eg small amounts of butane, butanal, acetaldehyde, ethylacetate.

Fridges do smell for this reason, even when cheese is removed - but I wouldn't say it is a strong smell.

Q. Is the smell 'alarming' - I'm not aware of this - but it seems likely/sensible for manufacturers to put a smelly compound in the freon in case of a leak.. 77.86.76.47 (talk) 20:48, 21 July 2010 (UTC)

When some plastics overheat, they can give off strange odours. Is anything getting hot? Dbfirs 20:49, 21 July 2010 (UTC)

A speculative suggestion, but partially consumed fruit juices (which on opening can be inoculated by wild yeast from the air much as in Lambic beer brewing) can if left long enough ferment and develop a noticeable alcoholic smell - it's happened in my own fridge! Could this be the source? 87.81.230.195 (talk) 22:28, 21 July 2010 (UTC)

To answer the original question, I don't think there would be any undue risk from eating the food in the fridge unless the food itself was smelly. If it a Freon leak, then Freon is notoriously non-toxic to mammals (except when it gets to the ozone layer, but that is not most people's definition of toxicity). In the case here, I would simply use my general judgement as to what to eat out of my fridge – if it looks or smells bad, don't eat it; if it looks and smells OK, eat it! Physchim62 (talk) 00:39, 22 July 2010 (UTC)

"Strong solvent smell" - could be ripe bananas. Have you tried removing everything from the fridge, cleaning it, and seeing if it still smells? 92.28.250.141 (talk) 10:00, 22 July 2010 (UTC)

Doesn't storing bananas in the fridge ruin them? Googlemeister (talk) 14:06, 22 July 2010 (UTC)

It makes the skin turn black and may negatively affect the texture but they definitely last longer (i.e. are edible/usable for longer) so it depends on what you mean by 'ruins' Nil Einne (talk) 15:16, 22 July 2010 (UTC)

Resolved

 – Original poster, ike9898 (talk)

I find this hard to believe, because it really, really didn't smell like rotten food, but it was. Some produce in the crisper drawer. The smell was actually strongest in the freezer; I suspect the freezer was acting as a condenser, and accumulating the volatiles. Thanks for all your help. ike9898 (talk) 14:28, 22 July 2010 (UTC)

For our own future reference (and current curiosity), are you able and willing to specify what the 'produce' was? 87.81.230.195 (talk) 17:04, 22 July 2010 (UTC)

I think it was carrots and celery (don't know if one or both were bad, we threw it all out). They were bad to the point that nasty liquid had drained off them and collected in the drawer. The funniest thing is that just smelling the drawer, the smell wasn't that bad. I hypothesize that the volatiles were getting concentrated in the freezer. ike9898 (talk) 17:43, 22 July 2010 (UTC)

Whole onions can smell like that when they start going soft. 92.29.117.211 (talk) 20:28, 22 July 2010 (UTC)

Avro Vulcan

What is the carbon footprint of the Avro Vulcan?

Apart from the technical answer, can you please translate that into what that equates to compared to say, the Ford Fiesta, a London bus, Intercity 125, x flights to New York on a 747 or something we can more easily visualise!

Thanks. —Preceding unsigned comment added by EnglishNomad (talk • contribs) 20:47, 21 July 2010 (UTC)

It's not possible to answer your question as written. Are you asking about the fuel efficiency of this vs other vehicles? They hold different numbers of people, so do you want to take that into account? Why would you specify "to New York" - what different does the destination make? And you don't give the departure location (not that it matters if you just want fuel per mile - or do you?) All liquid hydrocarbon fuels generate more or less the same carbon dioxide, so just check the total fuel divided by maximum range for each of those. But it depends on the speed, basically this question is impossible to answer. Try: Fuel efficiency in transportation - it might have the answer to your question. Ariel. (talk) 20:56, 21 July 2010 (UTC)

An exact figure is truly impossible to estimate because we can't know how much went into manufacturing, servicing, etc. But simple fuel loads are easy - the thing carries 40,000 liters of fuel and it has a range of about 4,000km - so 0.1km/liter. A MkV Diesel Ford Fiesta does 30km/liter - so on a very rough estimate - the Vulcan is 300 times worse. SteveBaker (talk) 21:09, 21 July 2010 (UTC)

Keep in mind that unlike a car, an aircraft's fuel consumption rate can vary by orders of magnitude during a single flight. This is because of huge variation in the level of throttling, the immense change in mass as fuel is consumed (or combat payloads are deployed), climbing vs. cruising, and so on. Our article on jet aircraft range has some equations to calculate fuel consumption for an aircraft. Automobiles also have a "time-variation" in fuel consumption / mileage-per-gallon; but it usually doesn't vary by a factor of 100x over the course of a single drive outing, even accounting for things like acceleration and hills. Nimur (talk) 22:10, 21 July 2010 (UTC)

True, but a car's fuel consumption does vary by a factor of at least ten. (original research on local hills) Dbfirs 06:29, 22 July 2010 (UTC)

It has 4 rolls royce olympus engines - which have a fuel consumption to thrust ratio (see Thrust specific fuel consumption) of ~1.3 (imperial) - thrust is ~10,000ftlb each making the fuel consumption 40,000x1.3 = 52,000 lb/hr - in metric that's ~6.6kg/s of fuel in flight (2.2 pounds per kg, 3600 seconds per hour). Jet fuel has a calorific value of ~47MJ/kg (see Fuel_efficiency#Energy_content_of_fuel). So the machine is using 47x6.6 = 310MJ/s or 310MW (somebody should check these figures for mistakes)

That's approximately 100 Intercity 125's or 26 Eurostars , or 100,000 kettles. 77.86.76.47 (talk) 21:18, 21 July 2010 (UTC)

Assuming the thing does about 900km/hr at the above thrust (which is 0.25km/s) it does 0.25/310 = 0.0008km/MJ (or 1240MJ/km), but the crew is 5 so the figure for Megajoules per passenger kilometer is 1240/5 = 249 (which is about 100 times worse than using a bus) 77.86.76.47 (talk) 21:38, 21 July 2010 (UTC)

The Vulcan was not originally designed to be a passenger vehicle: if the question relates to the model of aircraft in general, one might wish to factor in the relative payloads of the vehicles being compared - a freight aircraft would arguably the 'fairest' comparison. On the other hand, the individual remaining airworthy Vulcan is used only for display and not to carry payloads (certainly not the specific ones it was designed for!) so perhaps comparison to passenger vehicles is more valid. Admittedly EnglishNomad did not actually ask for these nuances of interpretation. 87.81.230.195 (talk) 22:22, 21 July 2010 (UTC)

I multiplied force x velocity to determine power. The engines deliver around 13,000 lbf at around 925 km/hr, so 4 * 76 kN * 925 km/hr is around 100 megawatts of kinetic power. Assuming a ballpark thermodynamic efficiency of ~ 30%, 77.86's numbers seem to check out. Another way to look at it, 300 megawatts is about the instantaneous electricity consumption of a mid-sized city; so flying one combat bombing-run sortie of an Avro Vulcan to wipe one city off the map is tantamount to adding another city to the energy-economy, based on the aircraft's fuel-consumption alone. I suppose these things even out? Actually, on further reading, the Vulcan could carry two air-launched cruise-missiles, one under each wing pylon; so as usual, nuclear warfare does actually yield a net loss. Nimur (talk) 22:14, 21 July 2010 (UTC)

Colour-in 3D chick embryogenesis models/pictures?

I'm trying to study (as in reading, rather than experimenting) expression of a gene during in chick embryogenesis but it's difficult to keep a mental hold on the movements of the expression patterns. What would really aid me would be some 3D computer models of chick embryogenesis (HH stages in particular) to which I could colour in the locations of gene expression. 2D would be better than nothing, but would require two pictures to represent 3D patterns. Such blank pictures probably don't exist on the web for free, but I figured it's worth a shot. ----Seans Potato Business 21:01, 21 July 2010 (UTC)

Birds

is peanut butter bad for birds to eat? some books say it kills them and others say its a good treat for them.--Horseluv10 21:22, 21 July 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs)

I would expect it depends on which birds you give it to. Different birds have different diets. --Tango (talk) 21:44, 21 July 2010 (UTC)

see http://birding.about.com/od/birdfeeders/tp/birdfeedingmyths.htm --Digrpat (talk) 21:48, 21 July 2010 (UTC)

Considering how much many birds love peanuts, I have a hard time believing they'd die from peanut butter without a really good reference. Matt Deres (talk) 21:58, 21 July 2010 (UTC)

My understanding with peanut butter is that it's lacking in some amino acids, so if an animal feeds on it exclusively they will suffer from a form of Kwashiorkor. Ariel. (talk) 22:36, 21 July 2010 (UTC)

Do you have any reason to suspect that would affect birds, though? - not all animals need to intake the same amino acids (see essential amino acid); organisms may synthesize different amino acids internally. Many birds also seem to get by on a whole variety of seemingly narrow diets (pine cone seeds, sunflower seeds, etc.). I'm not saying you're wrong, I'm just saying that my understanding of bird diet would make me suspicious of the various claims in this thread (peanut butter is bad, an exclusive diet of peanuts/peanut butter would fail to provide all a bird's required amino acids) without a really good reference. If a crossbill can be so intimately tied to a particular species of pine seed that it suffers when it has to switch to a different species in times of hardship, that makes me think that birds don't generally need the same kind of variety of diet that people do. Matt Deres (talk) 01:01, 22 July 2010 (UTC)

Your average crow, for example, eats rotting carcasses on the road, so I doubt peanut butter would bother it much, except it might be kinda gooey. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:00, 22 July 2010 (UTC)

people say that it can clog their digestive system and kill them, that's why i was asking--Horseluv10 20:04, 22 July 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs)

Peanut butter is only a danger to birds because it's so sticky - it creates a choking hazard if you just dump a big glob of it out for the birds. If you cut it with with something to make it a little more liquid or offer it (in cold weather) is small bits it shouldn't be a problem. probably best to mix it with other materials - like seeds - as well, just for nutritional balance. --Ludwigs2 03:01, 23 July 2010 (UTC)

I heard that chocolate is toxic to birds. If you put some out, will they eat it? —Preceding unsigned comment added by FoulEmission (talk • contribs) 02:31, 23 July 2010 (UTC)

Our article on theobromine poisoning says that parrots are very susceptible to chocolate poisoning. Because they're often kept indoors as pets, they're probably more likely to come in contact with it... I would not leave chocolate out for birds to eat; it's likely just as toxic to finches and sparrows. In my house, chocolate doesn't get left lying around for long in any case... Matt Deres (talk) 13:19, 23 July 2010 (UTC)

Yosemite

hey all I am going to yosimite tomorrow and I want to know what the chance of me meeting/being attacked by a wild animal like a cougar or bear is and if there is anything I might do that would increase and anything that might decrease my chance of the same. Thnx. 76.199.166.85 (talk) 23:30, 21 July 2010 (UTC)

If you smear yourself with peanut butter and barbecue sauce and go walking naked through the woods at night, you'll increase your chances of being attacked by a bear. Basically the rule is, don't wave food in front of bears and you'll be okay. There are no other animals worth thinking about there. Looie496 (talk) 23:35, 21 July 2010 (UTC)

Here are Safety Tips, particularly as they pertain to bears and food storage. In truth, you have a greater chance of harm by falling off one of the waterfalls than by animal-attack. But, if you don't take proper precautions, especially if you are out of the valley, bears can be a real threat. Nimur (talk) 00:33, 22 July 2010 (UTC)

They are a threat to your food. Yosemite bears don't attack people unless the people try to take food away from them. Looie496 (talk) 00:52, 22 July 2010 (UTC)

(But they might tear your car door off). Nimur (talk) 20:03, 22 July 2010 (UTC)

Nimur, thanks for the image; I've uploaded it as File:Bear damage to car door.jpg and added it to Bear attacks. Nyttend (talk) 00:32, 25 July 2010 (UTC)

Excellent addition. You mis-labeled it as a Brown Bear attack, but it was a Black Bear attack in Yosemite. I corrected it on the image page and the article. For more information on brown vs. black bears in Yosemite: Bears in Yosemite. Nimur (talk) 23:47, 25 July 2010 (UTC)

Don't mess with any bear cubs (I mean don't get anywhere near them), or try to get a photo of you hugging the bear along with the above mentioned food advice and you should be ok. Googlemeister (talk) 13:22, 22 July 2010 (UTC)

The time-honored theory would be to bring along a friend that you're confident cannot run as fast as you can. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:58, 22 July 2010 (UTC)

July 22

Lily Flower Identification

I was wondering if anybody could help me identify this lily flower. It has six petals that are pink with purple spots towards the center of the flower. The stamens are full of brownish-yellow pollen and there is a large, yellow, three-lobed projection in the very middle. Here is a link to a photograph I took of this lily: Lily Flower. I took this photo on a property in Northern Wisconsin and I am assuming that this lily is not native to the area. I have looked online and in a flower identification book, but have had no luck. If anyone could help identify it, that would be great! Thanks! Stripey the crab (talk) 01:54, 22 July 2010 (UTC)

Telling the difference between free fall and micro-gravity

I am locked in a room with no windows in a future space ship. I am experiencing complete weightlessness. Is there a way for me to find out if I'm orbiting a planet in free-fall or if I'm actually between galaxies in micro-gravity? Looking for multiple methods if they exist.--mboverload@ 03:05, 22 July 2010 (UTC)

Einstein says no: Equivalence principle#The Einstein equivalence principle. TenOfAllTrades(talk) 03:10, 22 July 2010 (UTC)

If you were in orbit there would be tidal forces between two masses that are different distances from the center of the planet. These forces would be small but probably measurable. anonymous6494 03:16, 22 July 2010 (UTC)

I agree with TenOfAllTrades. As a side issue, in between galaxies you are in an environment of genuine weightlessness - weight is mass times local acceleration due to gravity, and local acceleration is close to zero. An astronaut orbiting the Earth, or a swimmer diving off a tower, or a trainee astronaut in a reduced gravity aircraft all claim to be weightless but of course they are not weightless because local gravity is significantly greater than zero. The reason they believe they are weightless is because the ground reaction force acting between them and their surroundings is zero.

So the original question could be re-worded to ask whether it is possible to distinguish between situations where the local acceleration due to gravity is close to zero, and where the ground reaction force is zero. Without being able to make a long-term observation of motion relative to the stars I don't believe it is possible to distinguish between these two situations. Dolphin (t) 05:32, 22 July 2010 (UTC)

While ToaT and Dolphin51 are I believe correct, note that the Principle of equivalence assumes that measurements are only made at one point (which is what "local" implies). If measurements are made at two points, even if (say) only a foot apart, there are sometimes ways of distinguishing between gravitational and accelerational effects. 87.81.230.195 (talk) 07:28, 22 July 2010 (UTC)

Tidal Forces

Take a look at the diagram showing two objects (your hands should do the trick) orbitting a big big blue planet (acceleration acting on the planet is not shown). The black arrows show acceleration due to gravity, The red arrows show the components of the acceleration toward the planet acting between the two objects (which a little bit of geometry shows is inversely proportional to the distance to the planet). If you feel more force pulling your hands together than you'd expect due to their usual mutual gravitational attraction, you're in orbit. David Carron (talk) 11:47, 22 July 2010 (UTC)

(Assuming I can remember my physics correctly...) A gyroscope will keep pointing in the same direction, relative to the rest of the universe. This can be used to tell if your spaceship is rotating. Accelerometers placed on the inside and outside edge of this rotation will indicate if the the ship is rotating around a point inside the ship, or an external point. In free movement, the centre-of-rotation will be the centre-of-mass. If you know where the centre-of-mass is you can tell if you are in orbit. If not, then a ship in orbit will tend to become tidally locked. During this process the ship's centre-of-rotation will move from outside the ship to the centre of the planet. Once the centre-of-rotation moves outside the ship, you can deduce that you are in orbit. A gradual movement of the centre-of-rotation is due to either tidal-locking or conservation of angular momentum due to objects inside the ship moving to, or away from, the centre-of-rotation, which will move the centre-of-rotation. CS Miller (talk) 11:39, 22 July 2010 (UTC)

Thinking about it more, until the ship is tidally locked, the reported acceleration will always have a component towards the centre of the planet, and thus will change over the course of each orbit (thanks David Carron, but the accelerometers are top and bottom, not front and back as in his diagram). So this can be used to deduce that you are in an orbit, without waiting for tidal locking to start. CS Miller (talk) 12:08, 22 July 2010 (UTC)

To expand slightly on my point, Einstein's statement of the equivalence principle (as described in the link I provided) does acknowledge that it only applies 'locally', and that the experiment needs to be 'small' with respect to variations in the ambient gravity field. That is, it doesn't work if your apparatus is sufficiently large and sufficiently sensitive to detect tidal effects across the length of your laboratory. Within the framework of the equivalence principle, I would argue that the rotation of the laboratory and the (eventual) establishment of a tidal lock constitutes such a 'non-local' experiment for our purposes. TenOfAllTrades(talk) 13:02, 22 July 2010 (UTC)

A gyroscope doesn't help at all, any more than noticing the local gravity inside a spinning spaceship would help. The circular motion of an orbit can be combined with any desired degree of rotation. --Tardis (talk) 14:53, 22 July 2010 (UTC)

Inertial navigation using gyroscopes is used for Apollo and the space shuttle. Gyroscopes are also used in the orbiting Hubble Space Telescope and its Rate Gyro Assembly can be seen here.Cuddlyable3 (talk) 15:18, 22 July 2010 (UTC)

What do blind people see?

I closed my eyes the other day and paid close attention to the little colors and whatnot and it got me thinking: if I had no eyes, what would I see? Does someone without eyes see black like when I close my eyes? Or do they not "see" anything, as in their minds just don't have a visual perception? I know it's hard to explain to someone who can see, but what is it like? 69.207.132.170 (talk) 05:57, 22 July 2010 (UTC)

I believe it varies from one person to another. Of course if you had no eyes, you would not see anything, by definition. However, you might be interested to read up on closed-eye hallucination.--Shantavira|^{feed me} 07:27, 22 July 2010 (UTC)

I get around 100000 Google hits on "What do blind people see?" A popular question! You may also be interested in Blind spot (vision). I once thought about using it to make an April Fool's joke claiming lots of people around the world were going blind for unknown reasons or a crazy reason like death rays from SN 1987A. The idea was to make a demonstration of the blind spot and claim it was just the start of gradually losing the whole field of view. However, I decided it was too cruel. PrimeHunter (talk) 14:29, 22 July 2010 (UTC)

Nothing. "Color" and "black" have no meaning to a person who is blind from birth. Cuddlyable3 (talk) 15:02, 22 July 2010 (UTC)

There has been a lot of research on this. My recollection from cog sci classes ages ago is that people born without sight generally don't have much of a concept of seeing at all and don't generally have a fully-developed visual cortex. People who become blind later in life—even after infancy—generally have a fully-developed visual cortex and describe their sight as black or white or gray or things of that nature. But this is a sketchy memory. "What made them blind" is important here, as well—people who are blind for defects in the eye probably have a different sense of it than those who are blind from defects in the brain. --Mr.98 (talk) 15:46, 22 July 2010 (UTC)

Ray Charles, who went blind when very young, said that he would dream about his mother's face. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:55, 22 July 2010 (UTC)

The colors and whatnot that you see when you close your eyes are discussed in our Phosphene article, and its "Electrical stimulation" section discusses electrically induced phosphenes in blind people. They weren't blind since birth. Seems like an easy question would be whether blind people see ordinary "pressure phosphenes" but I don't know. Comet Tuttle (talk) 16:31, 22 July 2010 (UTC)

I think it's also important to define what kind of blindness it is. I think if you are blind due the failure for reception of the visual signal (eye damage, optic nerve damage), it's going to be very different if there is damage in a perception portion of the brain (visual cortices). For the former I think it might be "black" with phosphenes, but for the latter I'll bet the person does not even realize that they are "missing" something. -- Sjschen (talk) 17:55, 22 July 2010 (UTC)

Soul

If my consciousness is not the product of my immortal soul, but only an illusion created by the electric impulses in my neurons, could other electric impulses - for example, in a computer network - also create the illusion of consciousness?--Quest09 (talk) 10:09, 22 July 2010 (UTC)

Have a look at Artificial consciousness. It might not have to be be an illusion. Zain Ebrahim (talk) 11:10, 22 July 2010 (UTC)

Yes - but it might take a very large and complex device to actually exhibit it. The human brain has 10¹¹ neurons and 10¹⁵ connections between them. A typical PC has only 10⁶ or 10⁷ transistors in the CPU - and the number of interconnections isn't much more than that. Worse still, a neuron is a more powerful computing element than a transistor - which almost certainly packs in another order of magnitude or so. So there are many more orders of magnitude of growth needed before we're really close to having a powerful enough computer to start considering whether it might be possible to endow it with a consciousness. Even if we succeeded in building a computer that said "I think, therefore I am" spontaneously and without us explicitly programming it to do that, people would likely refuse to believe it. Certainly computers can create the illusion of consciousness...and many researchers believe that our "consciousness" is also just an illusion. I have no way to convince myself that you are conscious and not just simulating that state. We certainly don't have a test for consciousness - nor even a particularly good definition of the word - and there is wide disagreement about whether (for example) a dog or a chimpanzee could be considered "conscious". I think most people would say that a bacterium isn't conscious - some would certainly argue that a housefly isn't conscious...but where exactly on the scale does this turn on? SteveBaker (talk) 22:00, 22 July 2010 (UTC)

"Illusion" is not a very good word to use here, and it doesn't add anything to the question. You could just as well have asked, "If my consciousness is not the product of my immortal soul, but only created by the electric impulses in my neurons, could other electric impulses - for example, in a computer network - also create consciousness?" Using the word illusion implies that there is something that the electrical impulses are an illusion of. Looie496 (talk) 23:10, 22 July 2010 (UTC)

Spider Identification Please

I live near Vancouver, British Columbia.

I have taken many pictures of this spider I captured.

Can you identify which spider this is?

I found (and killed - was too scared to attempt capture) bigger spiders than this, so I am wondering if this spider can grow bigger?

I have taken a very high resolution of the picture. It is 3.6 MB. So you can download and zoom in.

I have more pictures if required for different angles.

File:Better Picture Spider.JPG

--33rogers (talk) 10:26, 22 July 2010 (UTC)

Those pics are too blurry to see much of anything. You might post some better ones or perhaps look through here to see if you see your bug. --Sean 15:28, 22 July 2010 (UTC)

Still, I'd geuss either the Wolf spider (Lycosidae) or the Giant house spider (Tegenaria duellica). --The High Fin Sperm Whale 20:04, 22 July 2010 (UTC)

Qualia

Why do qualia exist? --138.110.206.102 (talk) 12:42, 22 July 2010 (UTC)

Not a very well-formed question. Do you mean, why do they exist rather than not exist? Or do you mean, why have we (and probably other creatures) evolved sense systems that operate the way they do? Depending how you define qualia, you'd get different answers for the latter (in some definitions it seems rather peculiarly human, in some it is just a term that applies to anything that 'experiences', probably even machines). For the former, there are no good answers, because it is not a particularly good question. --Mr.98 (talk) 13:12, 22 July 2010 (UTC)

Actually it is an excellent question to which Wikipedia cannot offer a better answer than the article on Qualia. Cuddlyable3 (talk) 14:57, 22 July 2010 (UTC)

No, it's bad question because it is exceptionally vague about what it is asking. It would need to be clarified for us to even presume to point him in the right direction. Asking why things exist when they don't have to exist is not a good question either, in my opinion—it presumes a lot of unstated things, wrapped in a wooly tissue of metaphysics. --Mr.98 (talk) 15:51, 22 July 2010 (UTC)

Our Hard problem of consciousness article specifies those exact four words as one of the formulations of the hard problem of consciousness. As the article states, the problem is unsolved. Comet Tuttle (talk) 18:30, 22 July 2010 (UTC)

Without qualia (I prefer just to call them "qualities" though) it would be hard to tell a ripe tomato from an unripe tomato. You couldn't even tell after you bit into one, because texture and flavor are qualities just as color is. You also would have a hard time detecting injury, since pain is a quality. Examples can be multiplied indefinitely. Looie496 (talk) 22:56, 22 July 2010 (UTC)

That's completely missing the point. Qualia are the subjective experience of these things. The question above can be rephrased, "why is there subjective experience?".

It's not really answerable on a scientific level, because science is about what you can prove publicly, and as Steve notes abovesomewhere, you can't prove to the public that you even do have subjective experience.

Nevertheless I think it's a genuine question, because you (or, at least, I) do have subjective experience, even without being able to prove it intersubjectively. It's just nonsense to talk about it being an "illusion", as illusions themselves are subjective experiences. --Trovatore (talk) 01:39, 23 July 2010 (UTC)

What is the difference between the subjective experience of a quality, and a quality simpliciter? Can there be such a thing as a quality that is not subjectively experienced? Looie496 (talk) 04:14, 23 July 2010 (UTC)

Sorry, I'm really not following. My point is that, a machine, for example, can tell a ripe tomato from an unripe one, without having any subjective experience of ripeness, or indeed of anything at all. --Trovatore (talk) 06:37, 23 July 2010 (UTC)

That's not a valid argument. It's as if I said that the value of hemoglobin is to carry oxygen in the blood, and you said I was wrong because it is possible to design a machine that transports oxygen in the blood without using hemoglobin. Qualities have value for recognizing things -- the fact that machines might recognize things without using qualities is beside the point. Looie496 (talk) 17:38, 23 July 2010 (UTC)

Well, you can put it that way, I guess. But I still think that no answer from usefulness is ever going to answer why the qualia are experienced subjectively. I'm taking it, possibly incorrectly, that you're arguing evolutionary adaptation or something. But what's not clear is why such adaptive mechanisms wouldn't just have resulted in p-zombies, with all the neurological correlates of qualia but no actual qualia themselves. --Trovatore (talk) 18:49, 23 July 2010 (UTC)

Well, we don't know what the neural correlates of qualities are (many people think we do, but they're wrong), and we don't know what the neural correlates of subjective experience are, so it's very difficult to say what would happen if you had one without the other, or if that is even possible. I agree with you that it's not clear why such mechanisms wouldn't have resulted in p-zombies, but given our level of ignorance of how the mechanisms work, I don't think it is reasonable to demand clarity at this point. Looie496 (talk) 20:44, 23 July 2010 (UTC)

An engineer's answer to Looie496's question might be: Sure; we talk about how red something is; but we don't talk about how middle ultraviolet something is, because we don't have visual receptors that happen to be able to sense that light frequency, and our UV sensing machines simply translate the middle-ultraviolet light into frequencies that we can see. But that's one quale (ugh, this word is awkward) which must exist, but which is not being subjectively experienced by any currently living creature. (If someone now cites a creature that can directly visually sense middle-ultraviolet light, then, first, you're a smartass, and second, pretend I said "extreme ultraviolet" or whatever is just out of range of all current life forms.) Comet Tuttle (talk) 17:11, 23 July 2010 (UTC)

Qualities don't correspond to sensory receptors. We don't, for example, have a class of sensory receptors for the color yellow. Even the qualities red, blue, and green don't actually match up with the so-called red, blue, and green receptors. We don't actually have a good understanding of how qualities are implemented by the brain, even at a practical level. Looie496 (talk) 17:38, 23 July 2010 (UTC)

Mouse

I had a mouse that used to eat fingernails. When I held her in my hand she would immediately go to the end of my finger and start nibbling the nails, and if I cut a bit off and gave it to her she would gleefully take it and eat it. Why? What is in my fingernails she would like? —Preceding unsigned comment added by Can u read my poker face (talk • contribs) 13:19, 22 July 2010 (UTC)

Fingernails are made of Keratin. Mice and all rodents also like to gnaw - since their teeth constantly grow and need to be worn down.77.86.76.47 (talk) 14:53, 22 July 2010 (UTC)

Is protein deficiency likely? 67.243.7.245 (talk) 03:21, 23 July 2010 (UTC)

Negative energy?

Our article Dirac sea says this:

$E={\pm }mc^{2}.$

Here the negative solution is antimatter, discovered by Carl Anderson as the positron.

Whereas I was under the impression that the positron had a positive mass, and a positive energy (as positron would appear to confirm). Then, is the formula is identical for the positron not the same as it is for the electron? If we took E=-mc², would we not arrive at a negative energy? Thanks, Grandiose (me, talk, contribs) 13:27, 22 July 2010 (UTC)

The positron has negative mass and there is mutual annihilation when it meets an electron. Cuddlyable3 (talk) 14:53, 22 July 2010 (UTC)

I don't believe that's correct. As noted at our exotic matter article, virtually every modern physicist suspects that antimatter has positive mass and should be affected by gravity just like normal matter and bubble chamber experiments are often cited as evidence that antiparticles have the same inertial mass as their normal counterparts. — Lomn 14:57, 22 July 2010 (UTC)

(edit conflict) That may not be right - the antiproton has the same magnitude of mass as the electron, and opposite charge. They do indeed annilate one another: this can be interpreted 2 ways:

The mass is negative - simplifying mass balance equations eg Electron–positron annihilation the 'reactants' have net mass 0

The mass is positive - but the object is labelled an 'antiparticle'

There's a reason for this - if the mass were negative an positron would be repelled by normal gravity assuming Newton's law of universal gravitation and similar are functions of 'vector mass' and not of 'absolute mass' ie |M| - see Gravitational interaction of antimatter - there may be an ongoing debate.77.86.76.47 (talk) 15:03, 22 July 2010 (UTC)

All standard model particles have zero or positive mass. Some of them have "anti" in their names, but that doesn't mean much; "antiness" is not a property of particles. The gravitational behavior of many particles hasn't been experimentally tested, that's true. But the photon is its own antiparticle, as are the gluons that account for most of the mass of the proton and neutron. If antiparticles fell up then these particles would have to fall both up and down. Those experiments have been done, and they all fall down.

There is no such thing as "antimatter", exactly. There is a symmetry of nature that requires that fields/particles come in matched pairs with the same mass and spin and opposite values of all of their internal charges. There's a convention (inconsistently applied) of naming these particles "X" and "anti-X" for some X, but it doesn't matter which one gets the anti prefix. There's also no rule that these field pairs "annihilate" with each other. Because they have opposite charges, interactions of the form X + anti-X → Y + anti-Y are always possible as long as Y's mass is less than X's, because the charges on both sides add to zero. In particular, X + anti-X → 2γ is always legal (where γ is the photon). But this is just a special case of the general rules for interactions in quantum field theory. There's no point in speculating about why annihilation happens. It happens for the same reason everything else happens, whatever that is. -- BenRG (talk) 20:07, 22 July 2010 (UTC)

The argument given in Gravitational_interaction_of_antimatter#The_E.3Dmc.C2.B2_argument (for not using antimatter mass as negative) seems quite convincing to me.. (though perhaps it is less convincing if one is using E²=m²c⁴..etc. 77.86.76.47 (talk) 23:12, 22 July 2010 (UTC)

That article is a disaster. Please ignore it entirely. This Usenet Physics FAQ entry is far superior. Somebody should rewrite the Wikipedia article from scratch based on the FAQ entry and other accurate sources. I hope it won't have to be me. -- BenRG (talk) 04:30, 23 July 2010 (UTC)

That's actually not true. Acceleration due to gravity does not depend on the mass of the object under consideration (as demonstrated by Galileo) and that is true regardless of the sign of that mass. The m in F=ma cancels with the m in F=GMm/r², so the sign doesn't matter. An apple with a mass of -100g would still fall from the tree and hit Newton on the head. On the other hand, if the Earth had negative mass then it would repel everything (either of negative or positive mass). --Tango (talk) 22:41, 22 July 2010 (UTC)

Thanks for mentioning the sign cancelling when calculating acceleration - however if antimatter was negative mass an matter/antimatter gravitational interaction would result in the antimatter being attracted, but the normal matter repulsed - at least on simple analysis - I imagine this is one of the reasons why the Gravitational_interaction_of_antimatter#The_antimatter_gravity_debate has been well covered by various scientists and thinkers.77.86.76.47 (talk) 23:12, 22 July 2010 (UTC)

To answer the question - I recommend you read the linked essay from the article Dirac sea - it may actually help explain (or at least give context to) all this 'sweeping under the carpet' to do with negative mass and gravity and signs (hopefully).77.86.76.47 (talk) 15:19, 22 July 2010 (UTC)

Electrons that we observe have positive mass and negative charge. Positrons that we observe have positive mass and positive charge. The Dirac Sea is a way of interpreting the universe such that the natural (but unobservable) state of electrons is to have negative mass and positrons are an illusion created by the absence of electrons. The Dirac Sea conceives of the universe as being filled with an infinite number of negative mass energy "electrons". Sometimes, something comes along to kick one of these electrons out of the sea, across the mass gap, and into a state of positive energy. This positive mass electron then behaves as the electrons we know in ordinary life. In being excited, it leaves behind a hole in the sea. According to the Dirac Sea interpretation, a hole in the sea acts as though it has positive mass and the opposite charge as the electron that was excited. In other words, the hole acts as though it is positron, even though in the Dirac Sea model there are no such real particles as positrons. This interpretation of reality is rather counter-intuitive. It has some appeal because it resolves certain problems in understanding relativistic quantum mechanics. However, I would emphasize that the observable manifestations of the Dirac Sea are essentially identical to the traditional understanding of physics. In other words, it is mostly a way of interpreting reality (and giving different labels to the same phenomena), but it doesn't change the basic observations. Dragons flight (talk) 15:49, 22 July 2010 (UTC)

The problem with the infamous "E = m c²" equation is that "E" is vague. In fact, this subtle but essential clarification is the most important part of that equation. Invariant mass or rest energy is important to understand. So whether you need to add or subtract the quantity "m c²" depends on what you are actually doing. In the article linked, the explanation is a bit hazy, but I don't think it's suitable to assume that the negative sign on the square-root of the full equation is sufficient theoretical justification for the existence of negative mass. That's just a spurious root - it's tantamount to solving a quadratic-equation and obtaining both a valid and an invalid solution. Spurious roots can also used (invalidly) to prove that 1 = 0. They more often represent an incorrect assumption or a misuse of basic algebra, rather than any fundamental physical effect. Here's an article, Spurious Roots in the Algebraic Dirac Equation, that explores physical consequences of actual spurious roots of the Hamiltonian. Nimur (talk) 20:00, 22 July 2010 (UTC)

speeding up the cell cycle

I would like my human lung cancer cells to be encouraged to do mitosis while on my slide. What are some common techniques I can use? If it makes the cell skip some cell cycle checks it's OK -- as long as it doesn't cause any major nondisjunction events or make the cells kill themselves afterwards. Is mitosis inhibited at room temperature? John Riemann Soong (talk) 16:03, 22 July 2010 (UTC)

Just a quick point: if they're human lung cancer cells, haven't they already missed out some cell cycle checks? Regards, --—Cyclonenim | Chat  16:12, 22 July 2010 (UTC)

Or they could have some oncogenes, or suppressed p53. I don't really know -- I am just given them to work with. I think I catch a lot of cells with no (or a non-obvious) nucleus -- I thought they were apoptotic at first, but apparently a lot of them are just in prophase. But prophase takes waaaayyyy too long. (My time frame for observation is 3-6 hours.)

I suppose I could have them express fluorescent proteins (connected to cell cycle events) so I know which cells to look for or observe, but it might be a few months before I can do that. John Riemann Soong (talk) 16:18, 22 July 2010 (UTC)

Btw, when I incubate these cells at 37C in the presence of nanorods, I often see a few of them inside the nucleus (confirmed by focal plane checks). The only way this could have happened I see, is that the nucleus was dissolved during the incubation process and then reformed around some of the gold particles. Incubation takes 2.5 to 4 hours (usually ~3). Is it the temperature? John Riemann Soong (talk) 16:21, 22 July 2010 (UTC)

Why would the cells' nuclei dissolve during incubation at 37C? As I'm sure you're aware, that's body temperature and you don't catch nuclei dissolving in our bodies during cell division. I don't know why the gold particles are getting inside the nucleus, but I doubt it's because of the temperature. I can't really visualise how nuclei form during cell division very clearly. Do they form similar to the cells themselves and form from the division itself, or do the cells divide and then form new nuclei once separated? Either way, can't see why temperature would make gold nanorods appear in the nuclei.

On a less spectulative note, can't you just use a sort of rotation system with the cells you need to use? You mentioned that a lot of them were in prophase, but presumably not all of them. Can you just select the cells that are already undergoing mitosis/about to undergo mitosis and use those? Then, when you need more, go back and select the ones that have recently matured enough to undergo mitosis? Regards, --—Cyclonenim | Chat  17:20, 22 July 2010 (UTC)

The nucleus dissolves during prophase, doesn't it? Also, mu group is more chemical and microengineering than biological, so keeping track of lung cancer cell cycles would be rather new to them. But, it may be something I might do once I get back to my home institution. I meant to ask whether room temperature inhibits the onset or completion of prophase. John Riemann Soong (talk) 17:28, 22 July 2010 (UTC)

Speeding up the cell cycle is probably not what you want. You might be interested in cell synchronization. The easiest method would be to remove the serum (which contains all those tasty growth factors that cancer cells really love) by growing the cells in serum-free media for about 24 hours, which should arrest many/most of them in G1, then adding back serum-containing media to kick them back into growth phase. You might not necessarily have them exactly timed, but you'd probably be able to bias the population so that many of them would divide during the hours that you're observing them. --- Medical geneticist (talk) 19:03, 22 July 2010 (UTC)

Wow, thanks. And it can be pulled off within 1-2 days. (Important since my current research stint ends in 2 weeks.) Hmmm. Now to figure out how long the S and G2 phases of my particular strain of lung cancer cells are.. John Riemann Soong (talk) 23:36, 22 July 2010 (UTC)

Conservation laws and FTU

I have read that there were thought experiments with the constants to refute the concept of the fine-tuned universe, but what about the conservation laws? From what I know, if, say, the conservation of baryon number is violated, then the matter would become unstable and decays. Or if the conservation of linear momentum is violated, then, as the article suggests, the center of mass of any system of objects will always continue with the different velocity (which would yield quite harmful effects as I think). Looks quite strange for the randomly formed universe. Twilightchill t 18:43, 22 July 2010 (UTC)

Is there a question? My understanding is that this only applies to constants that seem totally arbitrary. i.e. those that either don't (seem to) have a reason for them, or a way to calculate them from other things. Ariel. (talk) 03:05, 23 July 2010 (UTC)

That is can conservation laws serve as an evidence of fine-tuned universe? Twilightchill t 03:51, 23 July 2010 (UTC)

Not necessarily. If all of the universe originated in a singularity which contained all of the mass/energy of the entire universe (the Big Bang), then the conservation laws are simply a consequence of the unequal spreading out of matter and energy following the Big Bang. The fine-tuned universe is simple a specific interpretation of the Anthropic principle. The fine-tuned universe theory is simply the Strong Antropic Principle taken to its strongest end. Its merely a tautology which states that the Universe is being observed by life, so the Universe must have properties which allow life to exist, else it would not be observed. In other words, since we exist, the properties of the Universe must allow us to exist; and a Universe with different properties would not allow us to exist. The idea that the Universe must be "fine tuned" for life isn't really required. The universe could have had any set of properties, many Universes could have existed which did not produce life. That is ultimately irrelevent, as there are perfectly valid and workable hypothesis which allow for infinite time. Given infinite time, all possible universes can come into existance, even those that have life. No need for fine tuning. Multiple universes can exist sequentially, or even simultaneously. For the extreme view on this, see Many-worlds interpretation, which holds that there are an infinite number of universes existing simultaneously. We live in those which allow life. Please note, however, that none of this actually precludes the existance (or non-existance) of God. Its perfectly safe to believe in God and also to study and understand His Creation... Just learn to accept Creation as it exists, not as you wish it to exist. --Jayron32 04:08, 23 July 2010 (UTC)

A small correction: what you wrote does not apply to the many-worlds interpretation, but rather to the Multiverse idea. Ariel. (talk) 06:33, 23 July 2010 (UTC)

redout

I looked at our article, but it was a bit short, so my question is, at what point would a person experience redout? Is it something that is rapid, or sustained? Would a -3g maneuver cause redout if it only lasted 15 seconds? Googlemeister (talk) 18:45, 22 July 2010 (UTC)

Here's a fun demo some web-searching turned up: Classroom demonstrations in aerospace physiology (1963). Build your own red-out simulator! I'm having a hard time finding exact numbers, but the higher the G-force, the shorter the exposure-time needed to cause redout or blackout. Nimur (talk) 19:09, 22 July 2010 (UTC)

That's a redoubtable simulator. Cuddlyable3 (talk) 21:35, 22 July 2010 (UTC)

Well, I had thought a merry go round could be used as a redout simulator by securing a person with their head at the outside edge and their feet closer to the center, but according to my calculations, -3g could only be achieved by having a 5m radius merry go round spinning at 23 rpm, which is probably not too realistic. Also, an interesting byproduct would be that while my head is at -3g, my feet would be at -1g. Googlemeister (talk) 13:48, 23 July 2010 (UTC)

Fall of the ant

Why does a small creature like ant does not die by falling ? Is it simply because of air-resistance ?  Jon Ascton  (talk) 18:50, 22 July 2010 (UTC)

I suspect gravity plays a part; ie small insects weight a lot less so don't hit the ground as hard when they fall. 82.43.90.93 (talk) 19:19, 22 July 2010 (UTC)

It's a consequence of the square-cube law. The amount of mass that is supported by (aerodynamic drag on) each unit of surface area of the falling ant is quite small, resulting in a very low terminal velocity. As well, the overall mass that must be decelerated on impact is quite tiny, even in proportion to the size of the creature's legs. TenOfAllTrades(talk) 19:33, 22 July 2010 (UTC)

(ec) :Yes, air resistance. In the simplest possible approximation, the air resistance (drag) force is proportional to the body surface area, that is, to linear size squared; whereas the gravity force is proportional to the body mass, that is, to the body linear size to the third power. The larger is the animal, the higher velocity it takes for the drag to balance the gravity pull. As a result, terminal velocity is roughly proportional to square root of the linear size. --Dr Dima (talk) 19:36, 22 July 2010 (UTC)

It's also a strength effect: if you approximate the ant as a cylinder (of fixed aspect ratio) hitting the ground end-on, then the kinetic energy to dissipate is proportional to the mass of the cylinder, but the compressive strength of the cylinder is proportional to its cross-sectional area. So even at the same speed (same KE/mass) a smaller cylinder will fare better. Consider that a cinder block may obviously be broken by being dropped from even a moderate height, but that it would be much harder to break the pieces again in the same fashion. --Tardis (talk) 19:55, 22 July 2010 (UTC)

Consider a spherical cow... Googlemeister (talk) 20:16, 22 July 2010 (UTC)

Does having an exoskeleton have anything to do with as well ?77.86.76.47 (talk) 23:39, 22 July 2010 (UTC)

Doesn't help the tortoise, does it? Or actually it may. When an eagle drops a tortoise on the rocks, the tortoise may survive the initial impact; but an animal of similar size but lacking a shell probably wouldn't. This is hearsay though; I never saw this actually happen. --Dr Dima (talk) 00:28, 23 July 2010 (UTC)

Seen it done with seagulls and clams on wet sand. Dropped from about 40-50 feet up, the clams shell cracks enough for the gull to get into it. --Jayron32 01:47, 23 July 2010 (UTC)

See the second paragraph of Bearded Vulture, Dima. Those with bald domes may want to avoid walking around hatless, courting the fate of Aeschylus (although it has apparently been decided to excise all mention of that legend from our article on the guy). Deor (talk) 11:28, 23 July 2010 (UTC)

That is false, a smal structure can take more force compared to its wight but this is compensated by shorter deacceleration distance.

The energy that can be absorbed by a spring is proportional to its mass. I think it is the air resistance that is the differnce.Gr8xoz (talk) 13:07, 23 July 2010 (UTC)

Meat

Why can't humans consume raw meat without getting sick while most other carnivorous (or in our case omnivorous) animals can eat it without getting sick? The Raptor ^{Let's talk}/_{My mistakes; I mean, er, contributions} 23:46, 22 July 2010 (UTC)

Humans can consume raw meat – think of sushi or steak tartare. Physchim62 (talk) 00:30, 23 July 2010 (UTC)

We only get sick if we keep the meat around long enough to rot. Other meat-eating animals either eat meat while it is fresh or else have digestive systems that are capable of handling the bacteria and toxins in partially rotted meat. Looie496 (talk) 00:33, 23 July 2010 (UTC)

There is a surprisingly wide range of digestive capabilities - even across mammals. There are a whole range of things (like partially rotted raw meat) that true carnivores can eat - and things like grapes and chocolate that humans can eat that are fairly poisonous to many carnivores. SteveBaker (talk) 01:22, 23 July 2010 (UTC)

And then there is the issue of parasites, even when the meat is fresh. Trichinella species, for example, can infect both humans and carnivores, but only humans seem to care :) --Dr Dima (talk) 01:25, 23 July 2010 (UTC)

One of the theories I've heard is that the human appendix is the leftovers from a time when people did consume all their meat raw. When we started cooking meat, which presumably had a lot of advantages over leaving it raw, and stopped eating raw meat, the theory is that the appendix no longer was necessary and now plays a very minor role in the human digestive system. Note that some cultures still eat meat raw (not saying exclusively) - I believe that some Inuits eat raw seal. Falconus^{p t c}

An additional note: You might get sick from eating raw meat because you're not used to it (or more specifically, your gut bacteria aren't used to it). In much the same way strict vegans often get sick if they go back to eating meat (at least the first few times), humans used to cooked meat may get sick if they eat raw meat. It's not an indication that they are incapable of processing it though, your gut flora just need time to adapt. —ShadowRanger ^(talk|stalk) 04:03, 23 July 2010 (UTC)

I'm surprised that nobody mentioned Salmonella, which can infect raw meat but can also appear in cooked meat. ~AH1^(TCU) 23:23, 23 July 2010 (UTC)

See-through ?

All of us have heard about a pair of spectacles that can supposedly enable one to see people naked even when they are not naked i.e. see-through their cloths. Do such things exist for real ? Jon Ascton  (talk) 01:24, 23 July 2010 (UTC)

Backscatter X-ray body scanners at airports. J-u-s-t a bit bulkier than spectacles though. Clarityfiend (talk) 01:31, 23 July 2010 (UTC)

And the other kind, millimeter wave scanner. 213.122.51.122 (talk) 01:38, 23 July 2010 (UTC)

That's a fairly common joke in the United States. They are not real - and I question how you could think they could be real. About a year ago there was a big thing about modifying digital cameras to allow you to barely see through certain fabrics. I don't know if it was actually real, though. --mboverload@ 01:32, 23 July 2010 (UTC)

Yeah, mboverload, that rings a bell! Is it right that certain kind of digital cameras can be modified to become "x-ray" ?

I have read about applications for mobile devices that make it possible to see thru the clothes. Even saw a demonstration video of such application. Twilightchill t 03:56, 23 July 2010 (UTC)

The modification that you asked about involves removing the infrared (IR) filter in a camera. It doesn't really give you X-ray vision, but some fabric that's opaque to visible light is not so opaque to infrared, and a digital camera with the IR filter removed may see through it. I've seen a pretty dramatic demonstration in which a modified camcorder saw through two layers of dark-colored trash bags, as if they were transparent. --98.114.146.237 (talk) 04:36, 23 July 2010 (UTC)

Oops, my mistake. The dramatic demo I was referring to was actually done using some kind of thermal imager, not a simply modified camcorder. --98.114.146.237 (talk) 04:54, 23 July 2010 (UTC)

Under the right lighting conditions - and with the IR filter removed from a digital camera (removed...not added!), it is possible to see IR light that is passing through some kinds of thin fabric. It's exceedingly tricky though - and it wouldn't (yet) fit into a pair of spectacles. However, there are many YouTube videos that claim to demonstrate this effect. A camera that's designed to be sensitive to just the right IR frequencies can see "heat" (well, technically, the IR radiation that comes from hot objects) coming from the body through even moderately thick clothing - but because warm air is trapped between clothing and body - you don't see a clear outline of the skin because the difference in temperature between different parts of the body is much greater than the difference between skin and trapped warm air - so you see something through the clothing - but it's not remotely like watching someone who is naked! SteveBaker (talk) 13:14, 23 July 2010 (UTC)

The night-vision/x-ray trick often requires adding a IR-pass filter, (ie: A filter that looks opaque-black to the naked eye, but is crystal clear to IR) and running the camera in "night vision" mode in bright sunlight.

Some cloth is remarkably transparent to this kind of photography, almost like saran wrap. But that's rare. Most cloth looks about like you would expect.

(The best cloth I've seen to demonstrate this effect is the black cloth covers used in front of certain large (older?) speakers. It's amazing. Looking through the camera you'd swear someone took cloth off your speaker.) APL (talk) 15:25, 23 July 2010 (UTC)

Wikipedia has an article on everything. Acroterion _(talk) 04:00, 23 July 2010 (UTC)

Amazing! The same man invented both X-Ray Specs and Sea-Monkeys. Where oh where is his Nobel Prize? Clarityfiend (talk) 18:22, 23 July 2010 (UTC)

July 23

How does the cut-off frequency in the photoelectric effect support the photon theory of light?

It doesn't really explain in the article photoelectric effect.--115.178.29.142 (talk) 02:55, 23 July 2010 (UTC)

If light only had wave-like properties, one would expect a gradual drop-off in the effect. The sudden stopping of the effect under a certain frequency indicates that light energy is quantized, rather than continuous, with regards to frequency. If light were just a continuous wave, then as electrons accumlated energy, they would eventually accumulate enough to be knocked free of their orbitals. Higher energy light would remove electrons faster, and lower energy light would remove them slower, but light of any energy should work, since a continuous energy model would imply that the light is able to accumulate on the electrons until they are knocked free. The sudden cut-off below the threshold frequency indicates that it isn't a continuous wave of light which is "energizing" the electrons, rather it is a single particle of light which is energizing a single electron; below the threshold frequency, no single photon has enough energy to excite the electron to leave its orbit. Since this is a particle-like behavior, it confirms the particle nature of light. --Jayron32 03:02, 23 July 2010 (UTC)

ammonia and baking soda

can u mix ammonia and baking soda ? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 03:32, 23 July 2010 (UTC)

yes.77.86.76.47 (talk) 03:54, 23 July 2010 (UTC)

Sure. You can mix anything. Just place them together. I suspect nothing much exciting will happen, as ammonium bicarbonate is just as soluble as sodium bicarbonate, so you'll just get a basic solution with sodium, hydroxide, bicarbonate, and ammonium ions floating around. --Jayron32 03:57, 23 July 2010 (UTC)

It won't react dangerously; actually the baking soda will neutralize the ammonia to form ammonium carbonate (provided the ammonia is in solution form.) --Chemicalinterest (talk) 11:25, 23 July 2010 (UTC)

will it form ammonium carbonate as a gas or a solid? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 17:36, 23 July 2010 (UTC)

Liquid household ammonia (smelly) will react with sodium bicarbonate to form a mostly odorless ammonium carbonate. It is probably dissolved in the liquid. BTW, sodium carbonate is produced too. See ammonium carbonate for more details. --Chemicalinterest (talk) 17:54, 23 July 2010 (UTC)

isint ammonium carbonate used as smelling salts? how will it be odorless? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 20:58, 23 July 2010 (UTC)

Hang on , carbonate is much more basic than ammonia, so the reaction above and below doesn't happen:

NH3 + HCO3- >> NH4+ + CO32-
Explanation:
[HCO3-] <> [H+] + [CO3--]   K = 4.8x10-11 [5]
[NH4+] <> [H+] + [NH3]  K= 5.7x10-10
So the equiilibrium constant for the reaction:
[HCO3-] + [NH3] <> [NH4+] + [CO3--] is 3.8x10-11 / 5.7x10-10 = 0.07

Ammonia solution and sodium hydrogen carbonate combined stays mostly completely as ammonia, sodium ions, and bicarbonate ions. Ammonium carbonate is not produced.

Smelling salts is Ammonium chloride Oops, smelling salts are ammonium carbonate, and do smell, but they're not produced by mixing ammonia and bicarbonate of soda . 77.86.82.77 (talk) 21:21, 23 July 2010 (UTC)

I was just going to correct you. So you are saying that the equilibrium tends to lean toward the bicarbonate and the ammonia rather than the ammonium and the carbonate? --Chemicalinterest (talk) 21:28, 23 July 2010 (UTC)

Yes.77.86.82.77 (talk) 21:42, 23 July 2010 (UTC)

0.07 ... that's a pretty significant equilibrium constant actually. And if he uses diethylamine or something ...ooh. John Riemann Soong (talk) 05:52, 24 July 2010 (UTC)

18 and acne normal?

Is it? --190.178.174.60 (talk) 05:03, 23 July 2010 (UTC)

We cannot give medical advice. If you have concerns about your acne, you should see a qualified physician, likely a dermatologist. Wikipedia has articles on Adolescence and Acne vulgaris. However, any specific problems you may be having should be discussed with the proper doctor. --Jayron32 05:06, 23 July 2010 (UTC)

Tut, Jayron32. You know this isn't a request for medical advice; it's a request for medical information. 190 is not asking for advice or anything involving a diagnosis. As our Acne vulgaris article states, the condition often lasts into adulthood, often disappearing after the early twenties but sometimes remaining into the thirties or beyond. There are some very effective treatments for it — for which, of course, you need a doctor's advice. Comet Tuttle (talk) 07:01, 23 July 2010 (UTC)

Of course this is a request for medical advice. Do you really think the OP is asking out of idle curiosity? The OP wants us to diagnose whether they have an underlying condition or if this is just regular teenage acne, which we certainly cannot do. The information you and Jayron have provided should be useful, but if the OP wants anything more specific to their case they need to see a doctor. --Tango (talk) 09:15, 23 July 2010 (UTC)

The above conversation makes me laugh. To answer the question, it's not abnormal, but still undesired. See a doctor and you can discuss options to clear it up. Regards, --—Cyclonenim | Chat  09:53, 23 July 2010 (UTC)

You can't know if it is normal or not because you haven't seen it. That is one of the reasons why we don't give medical advice. You don't have anywhere near enough information. --Tango (talk) 11:04, 23 July 2010 (UTC)

Hm, I see your point. You're probably right; I've stricken my tutting above. Sorry. Comet Tuttle (talk) 17:04, 23 July 2010 (UTC)

Doh.. Acne vulgaris aka 'teenage acne' is a common disease in teenagers. There are other forms of acne some more servere, others about the same - if you have acne it's a medical condition which a doctor (or possibly pharmacist) can help with.

As the article acne vulgaris says

Acne occurs most commonly during adolescence, affecting more than 96% of teenagers, and often continues into adulthood.

77.86.82.77 (talk) 21:34, 23 July 2010 (UTC)

smoking and the liver

what is the effect of smoking on the liver? 84.153.200.39 (talk) 09:54, 23 July 2010 (UTC)

According to Health effects of tobacco#cancer it causes liver cancer. --Chemicalinterest (talk) 11:29, 23 July 2010 (UTC)

Actually the article just says (uncited) there is "some evidence" that it contributes to "increased risk" of liver cancer. That's a considerably more precise and less straightforward statement than saying it "causes" it. The liver cancer article doesn't mention anything about smoking or tobacco — the primary causes of liver cancer are elsewhere. --Mr.98 (talk) 12:57, 23 July 2010 (UTC)

As a pure layman here, I'd note that small cell lung carcinoma, which is caused by smoking, is pretty likely to metastasize, and if it does so into the bloodstream then the cancerous cells may end up in the liver, as the liver performs its blood-filtering function, and the smoker ends up with metastasized lung cancer growing in his liver. He's in pretty bad trouble by then anyway. Comet Tuttle (talk) 17:02, 23 July 2010 (UTC)

but does the liver process nicotine from the blood (and additives) as it does alcohol? Or do other organs (kidneys etc) do that? 85.181.51.2 (talk) 19:22, 23 July 2010 (UTC)

This site claims that 80% of nicotine is broken down to cotinine by the liver. Comet Tuttle (talk) 04:37, 24 July 2010 (UTC)

immune system

would the body function better without an immune system, assuming viruses and bacteria etc didn't exist —Preceding unsigned comment added by Catapiie99999 (talk • contribs) 10:18, 23 July 2010 (UTC)

I think I see where you're going with this, and I guess the answer would be 'yes'. There's a cost involved in having an immune system. Were such a system unnecessary, then organisms could be relieved of its cost. Whether or not that amounts to "better" is a value judgement. --Tagishsimon (talk) 10:22, 23 July 2010 (UTC)

Except that the immune system doesn't just respond to microbial invasion - it also kills cancerous cells. See cancer immunology. Equisetum (talk | email | contributions) 10:59, 23 July 2010 (UTC)

...and without bacteria, we'd have no gut flora and be in deep trouble for that reason. When you have to take a large dose of antibiotic, this can kill off a lot of gut flora - causing diarrhoea and all sorts of other unpleasant digestive problems. (Trivia: There are 10 times as many bacteria in your gut than there are human cells in your entire body - and 60% of your poop is dead gut bacteria!) Also, consider that the "Seneca Valley Virus" has been found to kill some kinds of cancer cells vastly more effectively than chemotherapy - and without the associated toxicity.[6] Since we don't yet fully understand the role of viruses - this kind of result suggests the possibility that we'd be unable to survive without them. Over the very long term, periodic additions of viral DNA into our DNA drives evolution - so eliminating them could also cause problems over very long timescales. SteveBaker (talk) 12:55, 23 July 2010 (UTC)

Bacteria and viruses are not the only things that our immune system protects us from either. There are also fungi and molds that can be harmful to people. Also, without bacteria, the world would be very different because things would not really decay in the manner they do today, so there would probably be dead plants and animals everywhere. Googlemeister (talk) 13:29, 23 July 2010 (UTC)

Not to mention the fact that without microbes ruminant digestive systems wouldn't function, the nitrogen cycle would be seriously out of whack, and leguminous plants, temperate trees and many corals would have serious problems due to the lack of their respective microbial symbionts (Rhizobium, mycorrhizae and Symbiodinium respectively); but I digress. Equisetum (talk | email | contributions) 13:53, 23 July 2010 (UTC)

I'm not sure if this is the immune system per se, but if you get a splinter or something your body will often kick it out. I don't know if that's caused by associated infection, though. --Sean 15:52, 23 July 2010 (UTC)

The real cost of an immune system isn't the energy expenditure or whatever -- that's quite minimal. The adaptive immune system is supported by a ridiculously small number of memory cells. The real cost is autoimmune disease. In fact, I wonder what white blood cells evolved from -- I somehow get the idea that they evolved from a rather maverick predecessor, what with slipping between interstitial spaces and ambushing bacteria hiding in deep tissue. Like a spy movie almost. John Riemann Soong (talk) 16:15, 23 July 2010 (UTC)

evolution of the mammalian red blood cell

Are there any nonmammalian ancestors whose RBCs lacked nuclei? What was the main advantage of the loss of nuclei -- deformability, speed, or being unable to be infected by viruses? John Riemann Soong (talk) 16:06, 23 July 2010 (UTC)

Also the amount of oxygen 30 trillion RBCs can carry astounds me. When we run and become out of breath, but not so much that we start running anaerobically, I suspect the limiting factor is not actually oxygen transport, but decreased blood pH and rising CO2 levels. Also what is it that makes your chest feel painful? We don't feel light-headed or dizzy, so we must not use that much oxygen when running, right? John Riemann Soong (talk) 16:11, 23 July 2010 (UTC)

Paternosters

Are there any paternosters with fewer than six cabins? --84.61.131.18 (talk) 16:38, 23 July 2010 (UTC)

No idea, but thank you for the question -- I had no idea such a thing as a paternoster ever existed. Looie496 (talk) 17:49, 23 July 2010 (UTC)

No idea either, but since the number of cabs seems to be equal to, or greater than, two times the number of floors served, you'd be talking about one for only two floors. One wonders what the point would be. Deor (talk) 20:37, 23 July 2010 (UTC)

entry of gold nanoparticles into the cell nucleus

My boss tells me that when gold particles are tagged with DNA and incubated with cancer cells, over 50% of them can be seen inside the nucleus (versus the 2-10% I've been seeing when they are coated with just carboxylate groups).

Originally I thought the only way for these things to get inside the nucleus was during mitosis when the nuclear membrane dissolved and reformed around some of the particles.

However, my boss says that active transport of gold particles into the nucleus is possible. But it surprises me that it can be done so easily (and statistically favourably) -- since wouldn't cells want to curb the introduction of foreign DNA as a safeguard against viruses? Or is this some mechanism left over from our bacterial days? Previously I thought maybe when the nuclear membrane, DNA-carrying gold simply got "tugged" by the forming nucleus inside the membrane, thinking the DNA was one of its own. John Riemann Soong (talk) 17:27, 23 July 2010 (UTC)

Custom color urine

What is the mechanism as to how asparagus can your urine green, and beets can turn it red? How can we make artificial compounds such that, when consumed, will produce any color of urine we desire?--70.122.112.145 (talk) 17:33, 23 July 2010 (UTC)

Several tablespoons of concentrated food coloring? --Chemicalinterest (talk) 18:02, 23 July 2010 (UTC)

Colored urine means that there is some compound that is not metabolized by the body, but is excreted via the kidneys. Most compounds are metabolized into base elements, but some are not and are excreted unchanged (or are partially metabolized, and the metabolite is excreted). The compound doesn't necessarily have to be colored, but can react with something in the urine to make it colored. What specifically is in beets and asparagus I don't know. Eating too many carrots can cause carotenemia which makes a person orange (the skin). And silver can cause Argyria, which turns skin grey, there is also Chrysiasis from gold the turns skin blue or gray, and lycopenodermia from tomatoes which is deep orange. Presumably there are others, but I don't know them offhand. Ariel. (talk) 20:54, 23 July 2010 (UTC)

Mg + H2O

Can magnesium burn under water? --Chemicalinterest (talk) 18:02, 23 July 2010 (UTC)

Yes, it can. However, it is not easy to do. If you burn magnesium and dunk it in water, the water will cool the magnesium and make it stop burning. However, if you put an effort into limiting the cooling effect of the water, you will see that the magnesium will continue to burn. -- kainaw™ 18:45, 23 July 2010 (UTC)

Discounting the cooling effect of water, what is the oxidizer under water that is strong enough to burn Mg metal? --Chemicalinterest (talk) 19:08, 23 July 2010 (UTC)

Could it be the oxygen from the water?? Edison (talk) 20:07, 23 July 2010 (UTC)

Just the water itself. Even cold magnesium is oxidizing enough to reduce water to hydrogen (and magnesium oxide). The reaction is slow at normal temperatures, but would certainly work if there were already a heat source to get it going. Physchim62 (talk) 20:11, 23 July 2010 (UTC)

How can an oxidizing agent reduce?. I was wondering about the tightly bound H⁺ ions in water, whether they were the oxidizing agent, but even more reactive metals do not actually burn under water, the H₂ burns above water. --Chemicalinterest (talk) 20:39, 23 July 2010 (UTC)

As I understand the alkali reduction reaction, the magnesium (or other alkali metal) drags oxygen out of the water to form magnesium oxide, and/or magnesium hydroxide, releasing energy and hydrogen. Hydrogen, plus heat, then undergoes a second ("unrelated") reaction with the free oxygen (O2) in the air, yielding flame (and resulting in water vapor). If this reaction is correct, the flame can't exist underwater - all that will happen is formation of warm water and hydrogen bubbles. I recall performing an experiment in a chemistry lab some years ago (WP:OR) where we used this process to isolate pure H2 (trapping gas under water). Can somebody find a source that says otherwise? The MG + H2O reaction will yield MgO (or Mg(OH)2) + H2 + heat, but no flame; and the H2 will bubble up to the surface (by which time it is probably too cold to ignite). Nimur (talk) 20:47, 23 July 2010 (UTC)

heat and rain

What is the highest recorded temperature on earth while it is raining? Googlemeister (talk) 19:29, 23 July 2010 (UTC)

My guess would be 100F. --Chemicalinterest (talk) 19:34, 23 July 2010 (UTC)

Why? Vimescarrot (talk) 19:46, 23 July 2010 (UTC)

I suspect the highest temperature would be even higher than 100 degrees; if a storm is triggered by a cold front displacing a warm front with thermal inversion in the fronts, then the temperature at ground level as the rain began would be just as hot as it was before the rain arrived. I guarantee you that even somewhere with relatively pedestrian weather like New York City will have had the occasional 100+ degree day that suddenly turned into a thunderstorm, and during the early part of the storm, it would measure above 100 degrees. —ShadowRanger ^(talk|stalk) 20:29, 23 July 2010 (UTC)

It can easily be way above 100 when the rain starts, but it won't stay that way for long. Note that if the rain water itself was above 100, you could easily get heatstroke from being out in it, because your body would have no effective way to cool itself. Rain water in fact never gets anywhere close to that hot. Looie496 (talk) 20:53, 23 July 2010 (UTC)

You would only have heatstroke if you were out in it for a significant amount of time. Your average hottub water can easily be 105F, and you people are often in that water up to their neck. Googlemeister (talk) 21:01, 23 July 2010 (UTC)

The temperature can be hotter than 100F during thunderstorms around the start of the monsoon season in the Indian subcontinent, the Sahel and parts of the Middle East and even in Southern China. ~AH1^(TCU) 22:57, 23 July 2010 (UTC)

What do you retain from textbooks read years ago?

I've read a lot of textbooks in my time, I still do. If you do not recall the contents word for word, then what is the form of the knowledge that gets imprinted in your memory? How do words on the page get transformed into knowledge (which you may not even remember from which textbook or lecture it comes from) which you may make use of many years later? Do even books read ten years ago leave a trace on the brain? 92.15.3.219 (talk) 19:32, 23 July 2010 (UTC)

You probably still know your basic math and English skills. --Chemicalinterest (talk) 19:36, 23 July 2010 (UTC)

Psychologists have distinguished between "Semantic memory," which is things you maintain as part of your general knowledge, without linking it to a particular book, lecture, TV documentary, or life experience, versus "Episodic memory," which is in fact linked to such a specific source. Certainly we may remember in some cases a particular textbook, lesson, encyclopedia article, TV documentary or personal explanation whereby we learned a particular nugget of knowledge. Edison (talk) 20:06, 23 July 2010 (UTC)

This is merely an anecdote, but I was recently asked a question about a particular part of history. I could recall the exact layout of the page it was on in my high school textbook, but could not for my life remember what the sentences actually said. ?EVAUNIT^{神になった人間} 06:44, 24 July 2010 (UTC)

Katana

Would it be feasible to block bullets with a katana, or even slice them in half? (With enough training, of course.) --138.110.206.99 (talk) 19:46, 23 July 2010 (UTC)

I suppose it might be theoretically possible, if the bullet was extremely soft lead, and you basically fired the bullet at the edge of the katana. But no, no matter how much training you have, you can't move a sword fast enough or precisely enough to get it in the way of a bullet moving at several times the speed of sound. You might be able to move the sword into the path of the gun while someone was aiming (extremely difficult, but possible), but if they adjust the angle of the shot by fractions of a degree, your sword will be out of place, and human reaction times aren't fast enough to correct. And of course, even if they don't change their aim intentionally, the slight changes in angle triggered by the force they exert pulling the trigger, the recoil, etc., all combine to make it effectively impossible. —ShadowRanger ^(talk|stalk) 20:09, 23 July 2010 (UTC)

I should point out that this would depend greatly on the structural integrity of the katana, and even a good katana would probably be irreparably damaged. A lot of things marketed as katanas are just plain stainless steel; hard, but brittle, and would likely shatter if hit by a bullet. Traditional katanas have more flexibility, but the edge is still hardened steel and would suffer badly. —ShadowRanger ^(talk|stalk) 20:15, 23 July 2010 (UTC)

Here is some video of shooting a sword edge-on in laboratory conditions, and here is a guy who tried it in the real world. An important thing to consider is that you can't see bullets. For fun, take the fastest a human can move a limb (the fastest baseball pitch is probably close), the speed of a .22 bullet, and the width of your body you want to protect and see how far away you'd have to see the bullet to get your hand to the right place in time. --Sean 20:19, 23 July 2010 (UTC)

All I have to say is: Awesome links. —ShadowRanger ^(talk|stalk) 20:25, 23 July 2010 (UTC)

I don't understand japanese - was that a copper, lead, plastic or tungsten bullet? They're all different aren't they? 77.86.82.77 (talk) 20:55, 23 July 2010 (UTC)

Its just a name; see katana for details. The OP was probably asking about a normal bullet. --Chemicalinterest (talk) 20:58, 23 July 2010 (UTC)

I meant in the video linked above - what was the bullet made of?77.86.82.77 (talk) 21:43, 23 July 2010 (UTC)

So if the Japanese guy had Superman quality reflexes and held the sword in front of him just so, it would have split the bullet into two pieces which would each have hit him. Two small wounds instead of one big one, and less kinetic energy due to what was absorbed by the sword. A possible improvement. Holding an iron skillet, an anvil a sadiron or a manhole cover between oneself and the shooter might be preferable. Edison (talk) 01:35, 24 July 2010 (UTC)

In the video, it was indicated the bullet was made of lead. --Kusunose 04:42, 24 July 2010 (UTC)

How hot is it really?

The meteorologists are telling us it will be 96 degrees F (36 C) with heat indexes over 100 F (38 C) today in North Carolina. What they almost never tell us is that this is totally unrelated to being out in the sun. How much hotter would it be out in the sun, and would the heat indexes also have an effect on that?Vchimpanzee · talk · contributions · 19:53, 23 July 2010 (UTC)

Where do you live? I have very similar temperatures here in New Jersey. --Chemicalinterest (talk) 20:41, 23 July 2010 (UTC)

I updated my original question.Vchimpanzee · talk · contributions · 20:50, 23 July 2010 (UTC)

I think the heat index is just taking into account the humidity; the sun would be determined by several more factors, such as the color of your clothes, how much you sweat, how much wind there is, how much shade you are in, how much exertion you do, how you are positioned in relation to the sun, etc. --Chemicalinterest (talk) 20:56, 23 July 2010 (UTC)

I knew that, but in general, if someone is out in the sun, does anyone know how much hotter that makes it?Vchimpanzee · talk · contributions · 20:59, 23 July 2010 (UTC)

It's so variable that there's no point in trying to say anything. Did you ever see one of those pictures of somebody frying an egg on a hot sunny sidewalk? Looie496 (talk) 21:02, 23 July 2010 (UTC)

Surface temperatures are measured in the shade because the thermometers would give inaccurate readings in the sunlight. For example, the air temperature (often measured in Stevenson screens, which can still have an error of a few degrees) could be 35°C but the thermometer under intense sunlight could read 45°C or even 50°C. ~AH1^(TCU) 22:28, 23 July 2010 (UTC)

It's impossible to say anything about the temperature "in the sun" in general. The difference in air temperature between sun and shade is negligible, since convective and turbulent movements of the air will quickly equalize any temperature gradient. However, when you place a thermometer in the sun, it invariably spikes by several, if not dozens of degrees. Why is this?

It's because an opaque object such as a thermometer or your skin will absorb certain wavelengths of light from the sun; this will heat the surface of a thermometer or your skin by some significant amount. Because this varies strongly among different objects made of different materials and of different colors, it's impossible to make a general statement about how hot it is "in the sun". I suspect the color of your skin greatly affects how hot your skin actually gets. Would certainly make for a good science project! (with the proper sunscreen, of course :D) -RunningOnBrains^(talk) 05:17, 24 July 2010 (UTC)

add that the body is a self-regulating temperature system, so the effects of direct sunlight on the body change the perception of temperature without actually changing the surface temperature of your body significantly. It's much like watching ice melt: ice melts faster when the temperature is hotter, but the surface temperature of the ice (by definition) never strays far from 32° Fahrenheit during the entire melting process. --Ludwigs2 06:10, 24 July 2010 (UTC)

peppers

what is inside of a pepper, a gas or air? and how does it get in their?--Horseluv10 20:40, 23 July 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs)

Pepper skins are not airtight. The gas inside wouldn't be 100% ordinary atmosphere, but it would be pretty close. (Small differences in CO2 concentration, presence of a bit of ethylene, higher concentration of water vapor, etc.) Looie496 (talk) 20:48, 23 July 2010 (UTC)

that's a really smart question. 92.230.65.204 (talk) 20:55, 23 July 2010 (UTC)

What's smart? That air is a gas already? :o --Chemicalinterest (talk) 20:59, 23 July 2010 (UTC)

I think it is a pretty good question. What's surprising to me is that the inside is neither solid nor liquid. Why did the pepper even bother to grow larger than necessary to actually deploy its seeds? Does the air-space somehow improve the seeds' chance of growing, does it serve some other evolutionary purpose, or is it just a vestigial artifact of the way that pepper biology forms its plant-tissue structure? Nimur (talk) 21:45, 23 July 2010 (UTC)

It is hard to explain something like that by random change... Oh no... Not another fight --Chemicalinterest (talk) 21:59, 23 July 2010 (UTC)

The point being, it's probably cultivated that way. Artificial selection, as opposed to natural selection. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:00, 23 July 2010 (UTC)

(EC) It seems most likely to me the size & shape of the fruiting body relates to it's purpose, to attract birds. (The same is believed for the colour after all, as it is for most brightly colour fruits.) To put it a different way, to claim that it's larger then necessary to actually deploy its seeds is most likely wrong, it isn't anymore then a watermelon is. The fact that there's no liquid or solid inside likely arises somewhat from the evolutionary history and also the fact it isn't needed as the external skin already provides enough for the birds that eat it. After EC: Of course as BB has mentioned we also need to distinguish from completely naturally occuring chillis and those that have been cultivated at some stage in their hisotry, which can be rather difficult for something which has been cultivated as long as chillis have... Nil Einne (talk) 22:02, 23 July 2010 (UTC)

? Do wild, non-cultivated peppers have the air gap ? 77.86.82.77 (talk) 22:15, 23 July 2010 (UTC)

I would expect some although I have my doubts we'd see the very large sort of things like some modern capsicum for example. These [7] [8] [9] have some discussion of wild capsicum including some pictures. Bear in mind as I mentioned above determing if something has been influenced by cultivated varieties is usually rather difficult even with genetic analysis. In this case the refs all suggest the history has not even been well studied anyway. Nil Einne (talk) 22:33, 23 July 2010 (UTC)

"Locular gas composition pepper" seems a reasonable search and produces this [10] which might have the answer, but I can't read it..83.100.252.126 (talk) 22:45, 23 July 2010 (UTC)

How did dinosaurs mate?

Those big tails would have been hard for the females to curl out of the way, and their multi-ton weights would have made problems for the male mounting (especially in cases like the brontosaurus and brachiosaurus). The little forearms of the tyrannosaurus would have made it hard for the females to get down on her "elbows" and for the males to "hold on". And in the case of the stegosaurus, well, between the weight, the spines, and the big tails, they pretty much hit the anti-mating trifecta. 71.161.45.103 (talk) 22:49, 23 July 2010 (UTC)

Short answer: although we can draw inferences from the strategies of various modern reptiles and from birds (which technically are dinosaurs), we don't really know; for example, soft tissues like penises are almost never preserved by fossilisation, and although it's commonly assumed that (male) dinosaurs didn't have them, some of them may have (just as some modern birds do and some don't).

The question is addressed in more detail by some professional biologists and palaeontologists here, on the 'Ask a Biologist' website. 87.81.230.195 (talk) 23:20, 23 July 2010 (UTC)

Interesting article here : The Straight Dope : How did Dinosaurs Have Sex? APL (talk) 06:19, 24 July 2010 (UTC)

July 24

Photocell experiment

I need to perform an experiment confirming the inverse square relationship between the intensity of a light as perceived by an observer and the distance between the light source and the observer. To do this, I will shine a point light source upon a photocell, and record the current in that photocell and the distance between the photocell and the light source. I will then vary the distance between the light source and the photocell and repeat.
My first question is this: $Intensity\propto {\frac {1}{Distance^{2}}}$ or $Distance\propto {\frac {1}{Intensity^{2}}}$? (I'm pretty sure it's the former). Also, because the photocell and the light source are both protected by a glass casing, refraction occurs meaning that the apparent distance between the light source and the photocell is not exactly the same as the actual distance. How can I compensate for this effect?
Thanks––Wikinv (talk) 03:02, 24 July 2010 (UTC)

The device used is a phototube––Wikinv (talk) 03:06, 24 July 2010 (UTC)

What creature is this?

I found this this morning. What it exactly is ? Is it poisonous ?  Jon Ascton  (talk) 03:12, 24 July 2010 (UTC)

I would assume a millipede, but it's hard to tell what species it is, as it's so blurry. However, it is not poisonous unless you eat it (even then it may not be). Where do you live? Perhaps that would help identify it. --The High Fin Sperm Whale 03:41, 24 July 2010 (UTC)

I am in Punjab (North-Western India)