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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)

I suffer from an as yet undiagnosed ailment where I go blind for a few hours every few days, besides being incredibly painful, it is interesting to note that I do not see anything during these periods, not black, not white, not darkness, not light, not red like one sees when you close your eyes and look at a light. I see nothing. I just wish my doctor would get off her arse and cure me.

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.

--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 [1]
[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.[2] 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)

See Seneca Valley virus-001. -- 110.49.205.195 (talk) 00:27, 25 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)

Doan's pain pills (Magnesium salicylate) were at one time treated with an indigetible blue dye (methylene blue, IIRC) which would turn your urine distinctively blue. This was so you'd know when it was safe to take more pills. --Jayron32 04:52, 25 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)

Isn't it just a redox reaction involving the hydrogen and magnesium? The oxygen is along for the ride (H/Mg exchange on the O in a molecular sense). Lots of metals do this at various rates, sometimes requiring added heat, pH changes, or other initiators to get a noticeable reaction rate. More active metals (potassium) don't require being ignited to cause the reaction. DMacks (talk) 18:00, 24 July 2010 (UTC)

As pointed out - it does - but the cooling effect of the water tends to halt the reaction. On the other hand the reaction with steam works always (even with no air) - in fact even iron reacts with steam and glows like it is burning. Aluminium reacts even better. I think there are videos on youtube of both of these.83.100.252.126 (talk) 03:58, 25 July 2010 (UTC)

It should be pointed out that Magnesium does burn readily in both pure carbon dioxide and pure nitrogen (forming Magnesium Carbonate and Magnesium Nitride, respectively). It's one of the rare substances that does. You can look up YouTube videos or Magnesium burning in Dry Ice; its quite cool. I've seen it live in person, and its always interesting. If it were molten magnesium, it may react readily with water. Molten iron will react with water to form iron oxide/iron hydroxide, and liberate hydrogen gas. --Jayron32 04:40, 25 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)

This article - and the articles that it links to - may answer your question: Apparent temperature. Mitch Ames (talk) 09:10, 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)

The bell pepper is a member of the Solanaceae family, also known as the nightshades. Another member of that family is the tomato. If you imagine a tomato with all the parenchyma-y goop inside gone, you've got something not unlike a pepper. Check this picture for a visual comparison. And given the variety of tomatoes (beefsteak, cherry, plum etc) no doubt a lot of cultivation has gone on for peppers too, like Bugs has said. Brammers (talk/c) 07:59, 24 July 2010 (UTC)

This homework sheet provides a possible rationalisation of the large size of peppers, although it doesn't give any sources so handle with care. Brammers (talk/c) 08:02, 24 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 [3] [4] [5] 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 [6] 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)

I believe some broken bones in dinosaur tails are ascribed to the problems they had mating. They obviously went n for S&M :) Dmcq (talk) 14:14, 24 July 2010 (UTC)

Is it bad that the first thing I thought of was this? sonia^♫♪ 14:33, 24 July 2010 (UTC)

That would depend on the flavour of the jello. 87.81.230.195 (talk) 14:40, 24 July 2010 (UTC)

Mating under water would obviate the weight issue. Cuddlyable3 (talk) 15:59, 24 July 2010 (UTC)

Dinos did not live in water, so mating there would be odd. If you are thinking about Ichthyosaurs or Plesiosaurs, those are not dinosaurs; if you are thinking about Sauropoda, know that those are old ideas of them living in water. QFL 24-7 ^{bla bla bla ¤ cntrb ¤ kids ¤ pics} 21:39, 24 July 2010 (UTC)

Many of the larger sauropods are believed to have lived much of their lives in or near water, even though they didn't swim. Their enormous size is believed to have made living on dry land difficult. This is not settled theory; there are others that claim that their structure would have made breathing and maneuvering in the water difficult. But there are some credible theories that some of the largest dinosaurs did live a partially aquatic lifestyle. Also, be careful asking "how did dinosaurs mate". Its like asking "how do mammals mate". Dinosauria was a massive, diverse clade which existed for hundreds of millions of years (and still does, in the form of birds). There was likely a huge diversity in the manner in which dinosaurs mated, considering they ranged in size from the perhaps 60-meter long Amphicoelias to some that were only a meter or smaller. They were two-legged or four-legged, and came in two very different types of hip configurations (Ornithischia and Saurischia). Making definitive statements over how such a diverse group of animals may have behaved is practically impossible. --Jayron32 04:32, 25 July 2010 (UTC)

Check here and corresponding link... the "in or near water" is old ideas that have been refuted as much as the lumbering, small-brained, cold blooded side of Dino lure. QFL 24-7 ^{bla bla bla ¤ cntrb ¤ kids ¤ pics} 04:48, 25 July 2010 (UTC)

July 24

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) —Preceding unsigned comment added by Jon Ascton (talk • contribs) 24 July 2010 (UTC)

I would still guess a millipede. --The High Fin Sperm Whale 17:32, 24 July 2010 (UTC)

HD sunglasses and paint

I have now seen commercials for both paint and sunglasses claiming their products to somehow be related to high definition. It seems completely bogus to me (HD is about resolution on a monitor, not how bright colors are to the eye), but am I missing something?  ?EVAUNIT^{神になった人間} 06:49, 24 July 2010 (UTC)

Well for paint I would assume that the HD means "heavy duty" rather than High Definition. Sunglasses wise i think they're definitely using HD as 'short hand' for high quality because consumers associated HD as being high-quality so they want you to associate your sunglasses with that. Can't see there being a genuine application of HD in sun-glasses but you never know! (Oh and the paint company may be doing the same as the sunglasses one just instant assumption was 'heavy duty' when you say HD and paint). ny156uk (talk) 10:12, 24 July 2010 (UTC)

No, it's not "heavy duty". I've also seen paint marketed as "high definition", which in that case really just meant they were trying to sell bright, bold and "vibrant" colors. Obviously it has nothing to do with HD displays, and would seem they are just trying to ride the coattails of the larger awareness about HD. I don't know about the sunglasses, but I would suspect that is also a marketing ploy. Dragons flight (talk) 16:57, 24 July 2010 (UTC)

It's meaningless advertizing burble. I've seen mineral water be advertized a "fat-free" along similar lines! Physchim62 (talk) 19:26, 24 July 2010 (UTC)

Well, at least that statement is objectively true — there really isn't any fat in mineral water. I agree that it's meaningless in the sense that it fails to distinguish the product from any other brand of mineral water (or any water...), but I'd say it's a grade of meaningless one above the "high definition" paint. In a similar vein, I saw a box of microwave popcorn proudly announcing that it is "100% whole grain". Well, yes — it won't pop otherwise.... TenOfAllTrades(talk) 19:41, 24 July 2010 (UTC)

Fat free just makes people want to buy it. Just a gimmick. --Chemicalinterest (talk) 23:17, 24 July 2010 (UTC)

If you know English and only English...

...what are you missing in the field of science/technical developments? Is something out there of importance that is not being published in English?--Quest09 (talk) 13:29, 24 July 2010 (UTC)

Slovenian poetry criticism and so on... 84.153.194.192 (talk) 14:11, 24 July 2010 (UTC)

Did you mean science/technical Slovenian poetry? Cuddlyable3 (talk) 15:42, 24 July 2010 (UTC)

Well, it seems so that all scientific innovations are monopoly of English using world, but it is not so. For example Japanese are actually ahead in many a field. Likewise the Germans were far ahead of us durning WW2 etc.  Jon Ascton  (talk) 14:27, 24 July 2010 (UTC)

Yes the English speaking world (especially the US) is falling behind in most scientific achievements and manufacturing; just see where most things are made. The US is on a declining slide. --Chemicalinterest (talk) 14:54, 24 July 2010 (UTC)

Chemicalinterest, I'm sorry for failing to understand whether your above comment is a joke or not. --Theurgist (talk) 15:20, 24 July 2010 (UTC)

I am sure Chemicalinterest is not joking and that the proportion of new US patents granted to various countries is evidence for what he/she says. Cuddlyable3 (talk) 15:40, 24 July 2010 (UTC)

It is not a joke. I really mean that. Compare US vs. China 100 years ago to US vs. China today. --Chemicalinterest (talk) 15:46, 24 July 2010 (UTC)

That compares the two countries, but does it say anything for the information available in the language? Do the Chinese (for example) have a load of knowledge which has never been translated into English? Vimescarrot (talk) 16:29, 24 July 2010 (UTC)

And citation needed anyway. Chemicalinterest, you've managed to give a number of GIGANTIC generalizations lately on here — could you please either spend some time elaborating on your own sources for this information, or provide some? Because otherwise this whole thing degenerates into Yahoo! Answers very quickly, and it is not helpful. --Mr.98 (talk) 16:30, 24 July 2010 (UTC)

As Vimescarrot has hinted at, a large amount of scientific research is published in English, no matter the native language of the researchers. And colloboration largely happens in English. There are frequently postdoc programmes in countries like Japan which require no Japanese (although some basic level may be recommended/required so the people can live in Japan, e.g. [7]). This isn't to say there are no non English scientific journals, e.g. as discussed in Academic publishing in China there are. However many countries even those where English is not the native language may also have local English journals. And generally speaking if a researcher feels their research is particularly significant, they're going to try to publish it in a reputable international English journal as in the China case. In other words, while there is a fair amount of stuff out there that isn't in English, it won't generally be major breakthroughs that are missed.

Note that an even without a language barrier, the poor regard of some of the journals, lack of indexing, lack of interest etc means that a fair amount of stuff may not be considered or well known among researchers in other countries. An example, I was looking in to cloud seeding a while back when it came up in an RD discussion. This is something widely praticed in China and from my searches, I found there was a fair amount of published research in English and more in Chinese however the state of play in Chinese research wasn't generally reflected or well discussed in more Westernised things I read. Another example, in Malaysia where English is largely the scientific language, various issues means from my experience many academics have rather poor publishing records particularly when it comes to internationally recognised scientific journals. They do publish somewhat in local journals which are usually in English but (well this was ~2-5 years ago) they were barely known or unknown, often not indexed nor easily available (well I'm sure you could get them via interloan) and I do wonder about the quality of the peer review (some of them may not even have been peer reviewed). Of course a lot of this is fairly applied research, relating to tropical plants and the like which isn't generally of that much interest to people in temperate countries. (Bearing in mind I have somewhat of a biological background so my greatest experience is there.)

Nil Einne (talk) 18:02, 24 July 2010 (UTC)

In the 15th and 16th century did scholars who read Latin but not English, German or French miss out on all the scientific and mathematical development, since folks in Germany, France and Britain were making breakthroughs in math, chemistry and physics? Not all that much, because Latin was a common language of publication then, just as English is now. English might even be a common language of publication researchers in different regions of China might or different regions of India, whose local dialect is not that intelligible nationally. Edison (talk) 19:58, 24 July 2010 (UTC)

I know my answer above does not have anything to do with the question. The trend has been that way. China used to be a poverty-stricken, backward country... now it rivals the US. --Chemicalinterest (talk) 23:16, 24 July 2010 (UTC)

As a rule, if people make a discovery that they think the world should know about, they will make every effort to publish it in English. There is also significant science published in French, Russian, Japanese, and Chinese. Many of these journals, though, are abstracted in English or even fully translated. A person competent only in English will have no difficulty following developments in virtually any modern science. Looie496 (talk) 23:44, 24 July 2010 (UTC)

There was a time a few decades ago where, if you were a chemistry major in the U.S., you were usually required to learn German. That's because most of the major players in the chemisty industry that weren't in the U.S., like DuPont and Dow and Gen Chem, were in Germany, like BASF and Bayer and IG Farben and the like. That's because, in the early 1900's, Germany had a near monopoly on the coal-tar dye industry, and that was at the time a major source of research in pure chemistry. Over time, petrochemicals became more important, but historically the two most important languages for a chemist to know were English and German. Even in the mid 1990's, when I was in school, it was still highly recommended to learn German as your required second language. (I chose French as my langauge, as I already had 7 years of it under my belt at that point). The rationale was that, although most modern literature was availible in English, much of the historical literature was in German, and if you wanted to get to the original paper on something, you had to read it in the original German. Today, however, almost everything is in English. It has become the lingua franca of most scientific literature. Even foreign journals often (but not always) publish an English version, and lots of research from non-English speaking countries is published in major English-language journals. --Jayron32 04:15, 25 July 2010 (UTC)

Yes. As an undergraduate Science student in Australia 40 years ago, I was required to demonstrate my skills in a "Science Language". One had a choice of French, German or Russian. Given my current (lack of) ability in any of those languages, I am thrilled that almost everything is very quickly published in English these days. I've seen a couple of writers recently refer to Globish, reflecting the takeover of English in the science/tech world. HiLo48 (talk) 04:20, 25 July 2010 (UTC)

poison ivy

if somebody got poison ivy in their eyes, would they get blind?--Horseluv10 15:16, 24 July 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs)

My understanding is that corneal damage is possible and that a doctor should be consulted in that situation. Looie496 (talk) 23:46, 24 July 2010 (UTC)

We have several articles on the general topic of Toxicodendron species and their effects, the big three being poison ivy, poison oak (mainly Toxicodendron diversilobum), and the particularly brutal but luckily less common poison sumac. We also have a general article on urushiol-induced contact dermatitis, which is where the information on the medical effects should probably be centralized. Unfortunately it appears that the information on contact with the eye is somewhat limited; maybe that should be fixed. --Trovatore (talk) 00:00, 25 July 2010 (UTC)

If someone got poison ivy or any other toxin in their eyes, their best bet would be to get to an emergency room ASAP, rather than poking around on the internet. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:22, 25 July 2010 (UTC)

Multimeter

I have a multimeter as shown. Can I use it to measure AC mains ? In India it's about 220 v, I think. Is't safe ?  Jon Ascton  (talk) 15:52, 24 July 2010 (UTC)

This is the sort of thing if you have to ask then the answer is likely no. Working with mains voltage can be very dangerous and you should not try it unless you know what you're doing. If you really are determined, make sure you connect everything before you turn on the mains switch. Do not touch the meter or cords while the switch is on. If you are trying to measure because you think something is broken then again you probably shouldn't do it at all. Nil Einne (talk) 16:20, 24 July 2010 (UTC)

There will generally be a sticker somewhere on the meter (on that photo it's clearly visible around the sockets) that describes what safe range of voltages, currents etc you can work with. I would suspect 220v mains may be outside the recommended range of most normal multimeters. ~ mazca ^talk 16:48, 24 July 2010 (UTC)

Actually, even $20 multimeters are usually rated for voltages above 220 AC. I'm not sure I have ever seen a multimeter that could not measure wall voltages. That said, I agree with Nil. If you aren't sure what you are doing, then you probably shouldn't be doing it. Dragons flight (talk) 17:07, 24 July 2010 (UTC)

Or US$3 ones [8]. Okay that's actually measuring 110V but it looks like this [9] which is $9.99 not $5 but does have a 750V setting. I actually don't think I've seen one that doesn't have a similar setting although I've only seen a few (largely cheap) ones Nil Einne (talk) 18:05, 24 July 2010 (UTC)

Clockwise of the off position on the dial is the setting for 750V ac - this is the one you would use - if you knew what you were doing.. As you have to ask about this I'd suggest getting some more experience on using multimeters (is there someone you can ask who can show you?) before plugging yourself into the mains. 83.100.252.126 (talk) 17:22, 24 July 2010 (UTC)

I would never connect a cheap meter to a mains circuit at voltages of 480 volts or higher, unless the probes had fuses capable of interrupting a fault at the voltage level in question and at the maximum available fault current. The clearances and insulation levels are likely to be inadequate. Even so, the operator might need protective high voltage gloves, eye protection, and perhaps special protective garments. High voltages can sustain an arc which can incinerate everything for several feet around. A cheap meter could have leads which short, or could have an internal short. I am personally not as scared of 220, but I would treat it with respect. The suggestions of connecting the meter with the circuit dead are good if you are not experienced. Just because a voltage rating is on a meter does not automatically make it a safe operation to test at that voltage. Edison (talk) 19:48, 24 July 2010 (UTC)

Yes. Set the switch to just right of the OFF position to the setting for 750 VAC. Do not use any other setting and take good care not to come in contact yourself with the mains that you are probing. The warnings above are well intentioned but overblown. The probes, cables and meter are adequately insulated for 220V measurements and the notion of having fuses in the probes and special garments for a domestic mains voltage measurement is frankly ridiculous. Cuddlyable3 (talk) 23:09, 24 July 2010 (UTC)

Cuddlyable3: With your condescending "frankly ridiculous" attack: Have you had any formal training in electrical safety for testing in high voltage/high fault current situations? Have you personally ever been in an electrical vault when the 480 volt leads from a large power transformer were inadvertently shorted, and seen the severe burn injuries which can result? Note that I wrote about 480 volts and higher (the cheap meter illustrated has a 750 volt range), which can sustain an arc capable of incinerating the switchgear and everything in the vault. Yeah, a cheap meter never had an internal short, a test lead never had frayed insulation, and a plug never popped out of a meter and shorted to ground. A cheap meter is not necessarily safe to use at the highest voltage level selectable. I personally would not hesitate to test domestic 220 or 240 volt outlets with the meter shown. A careless or inexperienced person could get into serious trouble touching test leads to such a meter to a high fault current source at the highest voltage level shown on the dial. One problem area is that if a meter shows no voltage the circuit is not necessarily dead, since a test lead may have developed an open circuit or the meter might have a blown fuse or other problem. Edison (talk) 04:27, 25 July 2010 (UTC)

My multimeter works fine measuring 120V power in the US. --Chemicalinterest (talk) 23:14, 24 July 2010 (UTC)

I think Edison is right here. The probes should have fuses capable of interrupting the maximum available fault current at the voltage level in question. —Preceding unsigned comment added by 88.104.95.35 (talk) 23:23, 24 July 2010 (UTC)

All the words of caution given here are most appropriate. My first Multimeter was an analogue machine - moving coil galvanometer etc. I was excitedly measuring everything I could find, including the resistances of all my electrical appliances and the mains output (240 V). After measuring a resistance I moved on to check the output from one general purpose outlet but I forgot to reset the Multimeter from "Resistance" to "AC voltage". Instantly one of the resistors in the Multimeter fused! I think it is still an open circuit to this day, so that is one "Resistance" setting that doesn't function. Don't bother measuring mains output until you have gained a lot of experience with your Multimeter and you are supremely confident you are following all the precautions you have been given here. Dolphin (t) 00:51, 25 July 2010 (UTC)

Check whether the meter is certified as IEC 61010 CAT-III 600V (yes, six hundred) or better. Don't use it on mains equipment unless it is. (Merely been rated at 220V or 600V, or even higher is not sufficient. It must be CAT-III.) Even if the meter is correctly rated, electricity can kill. If you had to ask the question at all you should call a licenced electriction. Mitch Ames (talk) 04:21, 25 July 2010 (UTC)

Playing Pokemon today and I wondered...

Is there any real animal that has an actual metal shell or exoskeleton? Or something close to that? I know that shells contain calcium but I was thinking more of something that eats minerals and then secretes pure metal on the outside. --95.148.106.219 (talk) 16:29, 24 July 2010 (UTC)

Humans do excrete globs of liquid mercury if they get an overdose, but there is no animal I have ever heard of with a metal shell. --The High Fin Sperm Whale 17:30, 24 July 2010 (UTC)

Many arthropods (and some worms, maybe Nereis - not sure) have increased metal (Mn, Zn, Fe) concentration in the parts of their exoskeleton that must be most wear-resistant. For insects that would be primarily the mandibles. Concentration of metals can reach over 10% by mass (!) according to the literature. What is not known, though, is whether those metals are incorporated in the chitin & protein matrix as nanoparticles, as mineral inclusions, or as ions. It is only pure, elemental metal (particles or nanoparticles) that you are asking about, AFAIU. --Dr Dima (talk) 18:21, 24 July 2010 (UTC)

yes Nereis has zinc , some have metal-protein bonds, other have mineralised inorganic deposits (same ref) , this is mineralisation, not unlike teeth or odontodes, not pure metal.83.100.252.126 (talk) 19:50, 24 July 2010 (UTC)

Is it that difficult to detect? Just put the insect part under a high-res DIC microscope and use an appropriate wavelength corresponding to the plasmon resonance of the metal. As long as the particles are not much smaller than 50 nm in diameter, they should be easy to detect. John Riemann Soong (talk) 18:48, 24 July 2010 (UTC)

Beats me, too. If you can do it conclusively and in reasonable time, it could be a good paper. Just make sure you (a) ask your boss first if he or she doesn't mind you spending time on this, and (b) search the literature thoroughly to see if no-one has tried this before. I am a neuroscientist, so my knowledge is not exactly on the cutting edge of the insect mandible research, no pun intended. --Dr Dima (talk) 19:03, 24 July 2010 (UTC)

Am I the only person here thinking about mantises (manti?) with hardened bio-metallic blades now? That would be an extremely fearsome mini-beast. --Kurt Shaped Box (talk) 22:52, 24 July 2010 (UTC)

They're not animals (rather, they're algae) but diatoms have a silica cell wall, which is quite unusual. Brammers (talk/c) 18:24, 24 July 2010 (UTC)

Grasses (Poaceae) also have silica crystals incorporated in their leaf-blade structure. It is thought to offer some protection against grazing. Silica is silicon dioxide, not a metal, though. --Dr Dima (talk) 18:34, 24 July 2010 (UTC)

And silicon itself looks sort of metallic, but is not a metal — unless you're an astronomer. --Trovatore (talk) 22:57, 24 July 2010 (UTC)

can silver nitrate eat cloth?

Last year after a particularly long organic chemistry lab I spilled a test tube and wiped it up with a towel. 2 weeks later at checkout, the towel had gone black, brown and blue and crumbled to dust when you touched it. 1 day later after touching the towel, I suddenly noticed my fingernails and parts of my hand had been stained black.

Now in that lab I had worked with sulfuric acid and silver nitrate. Silver nitrate seems likely for staining my hands (the skin recovered within a week...the fingernails took several months to grow out) ... but would it eat cloth? It seems unlikely I would have worked with both in the same test tube (doesn't the combination make an especially strong oxidiser? how strong of a Lewis acid is Ag+ anyway)? John Riemann Soong (talk) 18:43, 24 July 2010 (UTC)

Silver nitrate is both oxidising and corrosive [10], similarly mineral acids will destroy cellulose over time too.83.100.252.126 (talk) 20:07, 24 July 2010 (UTC)

white horse wind wave.

Description of a "white Horse" wind wave. The Wikipedia listings of the Beaufort wind scale use the term "white horse" to describe a white cap at low wind velocity. There is no clear definition or illustration. What exactly is a "white Horse" in this context? Science Searches lead nowhere or to the color of horses. —Preceding unsigned comment added by RManns (talk • contribs) 21:03, 24 July 2010 (UTC)

A white horse is just the breaking cap of a wave. Once the wind reaches about 7 knots (Force 3), a few white horses become visible, by the time the wind speed has reached about 22 knots (Force 6), white horses are everywhere. The photos of sea states from the NOAA here are not great but they may help. Mikenorton (talk) 23:19, 24 July 2010 (UTC)

Doesn't seem to be a scientific term, but Google Web and Google Books searches find usages. The term was defined as long ago as the Encyclopedia Americana of 1829. Looie496 (talk) 23:25, 24 July 2010 (UTC)

Pocket Monsters Special Yellow (final battle): Lava surfing?

Is it possible to surf on lava, or is it to viscous? --138.110.206.99 (talk) 21:52, 24 July 2010 (UTC)

Melt your surfboard. --Chemicalinterest (talk) 23:09, 24 July 2010 (UTC)

More like incinerate. Pāhoehoe lava might be liquid enough to surf on, but a bit on the warmish side. Looie496 (talk) 00:31, 25 July 2010 (UTC)

Assuming you could make a surfboard that could withstand the heat, and you could withstand the heat, then yes, you could. Because even the lowest-viscosity lava (flood basalt) is more viscus than water, than it might be easier to surf on it. Now, some lava is too viscous, like rhyolite lava (about consistency of toothpaste), so surfing may not work on that. On the plus side, it's cooler in temperature... QFL 24-7 ^{bla bla bla ¤ cntrb ¤ kids ¤ pics} 04:31, 25 July 2010 (UTC)

Budgerigars and reflection recognition

Anyone that's ever owned a budgie will probably have seen this - they seem to have an ability to recognise even the smallest and most fractured reflection of itself as another bird with which to interact. For example, a budgie can see another budgie and recognize it as another budgie (speaking from personal experience) in items such as a tarnished, scratched-up Zippo lighter, the wooden top of a speaker cabinet, a metal clip used to hold cuttlefish bone (reflective bit can be no more than 2mm square), fingernails, the scratched-up screen of a mobile phone, a bit of clear plastic shrink wrap from a CD...

How does this work, exactly? As a human, I can *barely* make out a reflection of *something* in these things - yet the budgie will sing his little heart out and do his little display dances as though it's a brand new friend. --Kurt Shaped Box (talk) 23:01, 24 July 2010 (UTC)

Are you sure they think it's another budgie? Maybe they just like shiny things. But birds have much better (day) vision than humans. Ariel. (talk) 03:19, 25 July 2010 (UTC)

July 25

Ultra violet rays

Do ultra violet rays penitrate water? Any differnce between fresh water and salt water? Can a person get sunburned while swimming under water? —Preceding unsigned comment added by Wsccj8 (talk • contribs) 00:00, 25 July 2010 (UTC)

Yes. In fact many water purification systems depend on UV light. I don't think there is a difference between fresh and salt water, but murkiness makes a difference. You probably wouldn't get sunburned if you were more than a few feet down, but I get the worst sunburn of my life while snorkeling in the Caymans -- you don't have to spend much time at all near the surface for it to get you. Looie496 (talk) 00:37, 25 July 2010 (UTC)

Ultraviolet radiation can be sub-divided in several ways. One way is to sub-divide the ultraviolet family of radiation into ultraviolet A (UVA), ultraviolet B (UVB) and ultraviolet C (UVC). See Ultraviolet#Subtypes. UVA and UVB are the ones we are most familiar with, and they do not penetrate water for any significant distance. So sunburn is not a risk while underwater, but we mammals can't stay underwater continuously, and when we come up for air then we are vulnerable. UVC penetrates water and has application in disinfecting water because it is lethal to any living organism. See Ultraviolet germicidal irradiation. Fortunately UVC is not present in our environment because solar UVC is eliminated by the Earth's atmosphere! Dolphin (t) 01:06, 25 July 2010 (UTC)

Odd chemical reaction?

While on the road this afternoon, I ate a can of pineapple chunks packed in pineapple juice. Finding the fruit rather warm (it had been sitting in the car, unopened, for quite a while), I bought a bottle of Pepsi. After drinking most of the bottle, I returned to the pineapple; for the rest of the afternoon, I'd take a little of one, wait several minutes, take a little of the other, wait several minutes, take a little of the first, etc., until both pineapple and Pepsi were gone. Since that time, I've had an odd taste in my mouth; could a mix of the two substances produce an odd chemical reaction that would be responsible for this unique and long-lasting taste? Whatever it is, I know it's not harmful, so I'm not asking for medical advice. Nyttend (talk) 00:08, 25 July 2010 (UTC)

The taste is metal. You are not supposed to leave the pineapple in the metal can once it's opened. Pineapple juice is acidic enough to eat some of the metal in the can, and you can taste that. It'll be either zinc or steel (usually zinc). It's not toxic in low amounts, but don't do it often. I bet if you looked, you would see something like "After opening, store unused pineapple in a glass or plastic container in the refrigerator."[11] printed on the can. Ariel. (talk) 02:32, 25 July 2010 (UTC)

You probably mean tin not zinc - hence Tin can.83.100.252.126 (talk) 02:37, 25 July 2010 (UTC)

No I don't. Cans are not made of tin anymore, they are made of steel, and (when necessary) zinc coated. Ariel. (talk) 03:03, 25 July 2010 (UTC)

After doing some research, now I'm not sure about the zinc. I'm still pretty sure tin isn't used much in cans anymore. They seem to be steel coated either with plastic, or enamel. But no tin or zinc. Ariel. (talk) 03:16, 25 July 2010 (UTC)

There really isn't such a thing as a zinc coated food can. Zinc is too reactive. 'Lacquers' of various types are also used. A tin can is tin coated steel, aluminium, or coated steel. Just read Tin can. Tin is still used extensively.83.100.252.126 (talk) 03:18, 25 July 2010 (UTC)

Here's a proper reference (from 2005) [12] "Steel cans, often called "tin" cans because of their micro-thin tin coating, comprise more than 90 percent of the food can market" —Preceding unsigned comment added by 83.100.252.126 (talk) 03:23, 25 July 2010 (UTC)

Ariel, do you have a reference for that? I understand that many foods should be refrigerated once opened to prevent spoilage, but your reply suggests that the acid in the pineapple doesn't begin to leach metal from its container until opened. Is this because that reaction requires oxygen? Please explain. -- Scray (talk) 03:10, 25 July 2010 (UTC)

I do [13] yes - opened cans make it worse.83.100.252.126 (talk) 03:45, 25 July 2010 (UTC)

Maybe tin in the pineapple and phosphate in the coke reacted to make insoluble tin phosphate which has stuck to your tongue? What is the taste like anyway? fizzy, metallic, fruity ??? 83.100.252.126 (talk) 03:52, 25 July 2010 (UTC)

Sorry, I can't really say: I've never tasted anything like it before, and I didn't really experience it when my mouth was empty. I should clarify — (1) I was done with the pineapple perhaps 30 minutes after I opened it; and (2) I didn't notice the taste with either Pepsi or pineapple in my mouth; it was only 1½ hours later, once I reached home and drank milk from my normal cup, that I noticed anything. Nyttend (talk) 04:23, 25 July 2010 (UTC)

Absolute certainty

Is absolute certainty possible in science? For example, one of the fundamental axioms of relativity is that the speed of light is the same for all observers, but do we actually know this to be true beyond any doubt, or do we simply assume it to be true because we have never found a counterexample? Also, is absolute certainty possible in mathematics? For example do we know that $\ln(ab)=\ln(a)+\ln(b)$ is true for all a and b, or do we assume it to be true because we have never found a counterexample?--220.253.172.214 (talk) 03:14, 25 July 2010 (UTC)

Science is empirical. We gain evidence through observation, and extrapolate laws from the patterns we see in the evidence using inductive reasoning. This strategy can't tell things with absolute certainty, but for a lot of scientific claims we can be confident enough that for all practical purposes we can be certain. On the other hand it's been argued that induction has inherent flaws as a foundation for predicting how things will behave in the future (see Problem of induction). The math question is a bit trickier and I don't feel qualified to give a thorough answer so I will leave that to someone else. Rckrone (talk) 03:36, 25 July 2010 (UTC)

Absolute certainty is impossible. Are you absolutely sure you exist? Are you absolutely sure that what you are experiencing now is real and not a dream or a hallucination? Why are you so sure? How can you be so sure. At some level you must trust your own perception as reliable. Insofar as science is little more than the collective perceptions of humanity, organized into a certain system, we trust it. Science is as absolutely certain as it can be, given the limits of what certainty can be. It is also a flexible certainty, science at once expects its results to be reliable, and is also able to overturn past conclusions in the face of new, contrary evidence. --Jayron32 04:04, 25 July 2010 (UTC)

I contend that the empirical nature of science means that absolute certainty within science is impossible. However, I also contend that absolute certainty within mathematics is possible, because mathematical laws are derived from axioms which are defined such that they are true. For example, the equality operator "=" is defined such that $x=x$ is true for all x, and otherwise false. We can therefore be certain that $x=x$ for all x. This then becomes one of a set of axioms from which all other mathematical laws are derived, including for instance $\ln(ab)=\ln(a)+\ln(b)$. This means that we can be certain that $\ln(ab)=\ln(a)+\ln(b)$. Does anyone object to this or have anything more to add?--220.253.172.214 (talk) 04:17, 25 July 2010 (UTC)

No, you're talking about semiotics and not mathematics. You're defining the meaning of symbols, and declaring their absolute certainty. The definition of the equals sign is a linguistic issue, not a mathematical one. Again, your certainty with mathematics is still subordinate to your certainty of your own ability to trust your thoughts and perceptions, as well as the ability for the symbol to define the concept. You can trust mathematics to work only insofar as you can trust your perception of its own working. You still cannot escape your own mind, and so you must have faith that what you are experiencing in mathematical proof is really what exists. Furthermore, mathematics is not absolutely certain. All mathematical systems must be incomplete, and thus cannot be said to be completely certain. See Gödel's incompleteness theorems for more on these inherant incertainties in mathematics. --Jayron32 04:46, 25 July 2010 (UTC)

All right, absolute certainty is impossible, even in mathematics. However, some hypotheses must be more likely than others, otherwise science is pointless. Is there a way to quantify the probability that a particular hypothesis is true?--220.253.172.214 (talk) 05:09, 25 July 2010 (UTC)

"Absolute certainty" only exists within religions. The fact that their "certainties" vary from religion to religion is ironic, to say the least. The way to "quantify" a hypothesis is to perform experiments to see whether the hypothesis holds true. Science is a lot like math in that it relies on the concept of "if A is true then B follows". Consider geometry. The concepts of Euclidean geometry are absolutely true within that geometry. But you can create other geometries which have different truths. The likelihood of a given hypothesis being "true" would depend on the quality of the observations that support the hypothesis. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:20, 25 July 2010 (UTC)

By the way, I am familiar with bayes theorem which states that $P(H|E)={\frac {P(E|H)\,P(H)}{P(E)}}$, where H is a particular hypothesis and E is some new found evidence. This is generally the method used to quantify the probability that a hypothesis is true. However, how do we know that bayes theorem is correct if we don't have absolute certainty in mathematics? It would be ludicrous to use bayes theorem to quantify the probability that bayes theorem is correct.--220.253.172.214 (talk) 05:31, 25 July 2010 (UTC)

The "absolute certainty" you're seeking in math is based on "axioms" or "laws" which define the specific mathematics. IF those laws are considered to be true, THEN the mathematical theoreoms follow. If you want a "universal" absolute, science and math are not the places to go. The theories are subject to change based on new observations. As would be the above equation, I expect. If you want "absolutes", you need to find a religion that works for you. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:39, 25 July 2010 (UTC)

The truth of a mathematical statement is completely determined by the meanings of the symbols in it; it has no factual content and cannot be falsified by empirical observations. If a mathematical statement has a well-defined truth value, its truth value is independent of any minds perceiving it. I think Jayron's answer is confusing two questions of "certainty", namely (1) whether a subjective feeling of being convinced of the truth of a mathematical statement necessarily means that the statement is true, and (2) whether a mathematical statement involving an infinite number of cases is only true to the extent that no counterexamples have been discovered. I think the OP's question is about the latter, and the fact is, some mathematical statements can be demonstrated to be true under the intended interpretations using sound inference rules. Strictly speaking, Gödel's incompleteness theorems do not say that all axiomatic systems are incomplete—only those whose language is sufficiently expressive, but that's a technical detail that's not very important to the discussion here. It is important to understand the implications of Gödel's theorems correctly. Incompleteness only means that some statements are true yet not provable with a given (decidable) set of axioms; it doesn't mean that no true statements can be demonstrated to be so by means of a formal proof. --96.227.54.59 (talk) 06:54, 25 July 2010 (UTC)

Actually, you kind of answer your own question by saying "we simply assume it to be true because we have never found a counterexample." Science does not concern itself so much with what's "true" but with what works. There was a question here recently about the relative motions of celestial objects. It's possible to construct a geocentric model of the universe, and it worked for hundreds and hundreds of years. And in practical, everyday life, it still pretty much works. The current model of the solar system, the galaxy and the universe in general are based on what we know so far. Unless we become God, we can't ever say that a theory is "absolutely right". But we can say that it "works" - the model constructed from that scientific theory provides consistent results. Hence, it's "good enough" for now. If we find inconsistencies, we make more observations and more hypotheses. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:47, 25 July 2010 (UTC)

In Kantian terminology, the mathematical fact is an analytic a priori, whereas the physical law is a synthetic a posteriori. Nothing is ever completely certain, but the only doubt about the mathematical fact comes from doubt about the ability of thousands or millions of humans to judge the validity of a mathematical proof. Looie496 (talk) 05:58, 25 July 2010 (UTC)

Is there anything at all that can be known absolutely certainly?--220.253.172.214 (talk) 06:53, 25 July 2010 (UTC)

Type of Current in Landline

What type of current is there in telephone line. I tried to measure, I think it's something near 48 volts DC. Our article POTS, I think, says that too. I can light up a LED with it. But why can't I run a DC motor with it ?  Jon Ascton  (talk) 04:44, 25 July 2010 (UTC)

Graph with an unexpected spike in it?

Many years ago, in what was probably the summer I took a year of chemistry I retained very little of, I remember being shown a graph of a smooth descending(?) curve that had an unexpected spike in it. It looked something like the graph here but I think(?) it dropped to zero at the origin. The quantity being measured was something absolute and objective, like specific heat versus the elements or something (forgive me if that is gibberish). The story was that for years people would do these experiments/measurements and due to the smoothness of the graph everywhere else they would disregard the spike that appeared at one data point, assuming it was an error. Then someone thought about what it meant if it wasn't an error, and discovered some new property. My prof was trying to make a point about the right way to do bias-free experiments, as well as possibly teach us something important, but apparently that last bit didn't work in my case.

I realize this is close to nothing to go on, but it might be one of those things that is blindingly obvious to someone in the right field and it's been itching my brain for years.76.105.238.158 (talk) 05:51, 25 July 2010 (UTC)

Not related, but a very famously wrong graph was the Ultraviolet catastrophe, a name given to the expected results when you calculate the wavelength of light emited by a blackbody radiation source compared to the intensity of the light. Classical physics predicts that blackbodies would emit light of infinite power in the ultraviolet range (hense "catastrophe", since infinite power is meaningless). It's one of the cornerstones in the development of quantum mechanics, which is a theory that much closely matches actual results in this realm. Another sort of "unexpected" result from graphs is the so-called Island of stability, which predicts that certain superheavy elements (not yet synthesized) would actually be more stable than lighter counterparts. The general trend is that heavier elements are progressively less stable than lighter ones. The island of stability is someone counterintuitive based on the trends of most of the transuranium elements. Again, not the answers you were looking for, but some examples of how unexpected results from graphs can be used to push forward scientific thinking. --Jayron32 06:25, 25 July 2010 (UTC)

Thanks Jayron... not what I was looking for, but definitely awesome. That island of stability weirds me out a little bit... isn't that sort of Ice_9-ish? 76.105.238.158 (talk) 06:59, 25 July 2010 (UTC)