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June 9

Lightbulb question

Just now I heard a quiet, high pitched noise in my room. At first I wasn't sure where it was coming from, and my wife couldn't even hear it at all. This might sound funny, but it reminded me of the almost non-existent sound my Nintendo DS makes when the battery's charging. I discovered it was coming from my lamp and when I touched the bulb, it was extremely hot (more than usual) and when I twisted it, it died. Is that sound normal? What does it mean? I've never heard a noise coming from a dying light bulb before. Thanks! ?EVAUNIT^{神になった人間} 06:45, 9 June 2010 (UTC)[reply]

I've heard this before, and I've guessed that the interior is a partial vacuum and that corrosion has caused a tiny inward leak of outside air, including oxygen which causes the filament to burn out. Our article Incandescent light bulb says that the bulb contains a low-pressure inert gas. Dbfirs 06:55, 9 June 2010 (UTC)[reply]

What kind of lamp? Incandescent, or fluorescent? Ariel. (talk) 07:18, 9 June 2010 (UTC)[reply]

I've seen some bulbs where the part of metal filament was not well secured and could vibrate at twice the power frequency or a multiple of it. Some brands and styles are more prone to it than others. Visible vibration has long been noted in bulbs, and might be observable with a microscope as an apparent "broadening" of the filament when lit with alternating current. I have not noticed it being an indication the bulb was near its end of life, but I suppose local erosion of the filament might make it more flexible and prone to vibration. The cause of the vibration might be the slight expansion and contraction as it heats up and cools off slightly twice per cycle of the alternating current. If it were near a strong magnetic field, there could have been a 'motor effect" from the passage of current in the field causing motion, as in this 1896 "Nature" report. I think it may be more of a problem if the bulb is on a dimmer circuit which chops the current off at some spot in every half cycle. Oxygen in the bulb would cause a darkening of the glass and a swift burnout. How confident was the OP that the bulb was "hotter than usual" versus "hot to the touch?" An incandescent bulb normally gets way too hot for sustained contact with the finger. Edison (talk) 13:18, 9 June 2010 (UTC)[reply]

I think this is likely to be where the filament has got so thin it can no longer carry the current, and the electricity effectively arcs from one side of the filament to the other. The noise heard is the arcing. When the buld is shaken or turned off, the arc is broken and the filament falls away. --Phil Holmes (talk) 17:35, 9 June 2010 (UTC)[reply]

No, the noise I've heard (twice in the fifty years since electricity first came to this area) was a high-frequency "whistle" that I assumed was what the OP was describing. At well above above 10KHz, it is unlikely to be generated by mains frequencies in an incandescant light-bulb, though I accept that the other sounds described above are possible, and higher frequencies are generated in other light fitting types, but they are all "buzzes" not "whistles". Dbfirs 20:24, 9 June 2010 (UTC)[reply]

The whistle you describe could easily be the sound make by an arc. --Phil Holmes (talk) 20:51, 9 June 2010 (UTC)[reply]

I've heard lots of arcs and none of them sounded like the light bulb fault. Dbfirs 23:01, 9 June 2010 (UTC)[reply]

The light is incandescent, and I guess it may have been a normal temperature, as I'm used to changing bulbs when they have not been on for awhile, whereas this bulb was on for hours when I touched. Do you think there could be anything wrong with my lamp? ?EVAUNIT^{神になった人間} 09:50, 10 June 2010 (UTC)[reply]

Probably not (though you should check that the new bulb fits firmly). If it happens again, then look for arcing in the switch or elsewhere in the lamp, but the probability is perhaps 99% that the fault was in the bulb, whatever the cause of the sound. If you know a friendly electrician, then get the lamp checked just to be sure. Dbfirs 12:10, 10 June 2010 (UTC)[reply]

Nodules on high tension lines

What is the name/purpose/etc of the nodules I sometimes see on high tension lines? I've seen a few different styles (north-east US), but vast majority are the one one in red in the image to the right (click to see greater detail--thumb here for context/placement relative to tower). DMacks (talk) 07:00, 9 June 2010 (UTC)[reply]

This is just a guess, but for line maintenance, linemen will sometimes hang a harness on the line, and pull themself along while dangling from it. So my guess is that those things prevent the lineman from accidentally pulling himself too far. Ariel. (talk) 07:17, 9 June 2010 (UTC)[reply]

For video of such work, see this YouTube video. Dismas|^(talk) 07:37, 9 June 2010 (UTC)[reply]

That's the one! But watch this version. (That video has been re-uploaded so many times, it's nuts, some of the later ones are pretty blurry, this is the earliest one I could find.) Ariel. (talk) 08:37, 9 June 2010 (UTC)[reply]

Wow! incredible. Those scary sparks as he approaches the line and then if you look closely there are more sparks leaping across as the helicopter draws away from the line. whoa, some people live on the edge. 86.4.183.90 (talk) 15:32, 9 June 2010 (UTC)[reply]

But the most incredible thing about this is, most of their accidents come from helicopter crashes rather than electrocutions -- those folks are so well-equipped and highly trained that their chances of getting zapped while working on a live 100-kV power line are less than those of you or me getting zapped while fixing the fuse box in the home. 67.170.215.166 (talk) 03:02, 10 June 2010 (UTC)[reply]

Isn't it a Stockbridge_damper (a type of tuned mass damper), to dampen wind-induced vibrations in the lines? CS Miller (talk) —Preceding undated comment added 09:31, 9 June 2010 (UTC).[reply]

Just to second CS Miller, this is definitely a vibration damper. Take it from someone in the industry ;) More images at this Google search. Zunaid 11:32, 9 June 2010 (UTC)[reply]

Thanks! DMacks (talk) 19:21, 9 June 2010 (UTC)[reply]

Red liquid in sprinkler

I can find a bunch of sources on the net that explain that the red liquid will break the glass at 68 C but nothing that says what the liquid actually is. So, what is it? Some sort of alcohol? Dismas|^(talk) 07:49, 9 June 2010 (UTC)[reply]

I can't find an answer, but it seems that it's not any one standard thing - each manufacturer can choose any liquid he wants, as long as it meets the specs. One place mentioned they mix two liquids, which lets them pick any temperature between a range. Ariel. (talk) 08:56, 9 June 2010 (UTC)[reply]

I pulled up the (delightfully retro) datasheet for the "Type 817" bulb from Day-Impex, and as Ariel suggests, they just refer to a "special blend of thermally expansive liquids." But as to the red color, note that the color corresponds to the temperature at which the sprinkler activates. You can see the different colors and temperatures at the aforementioned site or our fire sprinkler article. -- Coneslayer (talk) 11:45, 9 June 2010 (UTC)[reply]

Many thermometers use red-coloured alcohol, which expands with rises in temperature. So its probably that. 92.24.182.110 (talk) 11:52, 9 June 2010 (UTC)[reply]

I've never seen any discussion of what the liquid is either, and I review sprinkler submittals routinely. "Special blend of thermally expansive liquids" is all I see too, but alcohol is a good bet - it would be immediately diluted by the water flow. The heads are usually color-coded according to the activation temperature, with higher-temperature heads used in places like boiler rooms, attics, or in high places near large banks of windows. Acroterion _(talk) 15:44, 9 June 2010 (UTC)[reply]

Titanium Cup

how come this same Titanium Cup has a rough edge is a single wall design but a smooth one in the Double-Wall design please compare and click on zoom

http://www.cabelas.com/cabelas/en/templates/links/link.jsp?id=0013258514880a&type=product&cmCat=froogle&cm_ven=data_feed&cm_cat=froogle&cm_pla=1510203&cm_ite=0013258514880a

http://www.rei.com/product/659999?preferredSku=6599990014&cm_mmc=cse_froogle-_-datafeed-_-product-_-6599990014&mr:trackingCode=EE734FFE-FB85-DE11-B7F3-0019B9C043EB&mr:referralID=NA —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 08:33, 9 June 2010 (UTC)[reply]

If you are talking about the "bumps" on the upper left corner, those are caused by whoever edited the photo. They were in a hurry and did a bad job of cutting the photo away from the background. Ariel. (talk) 08:45, 9 June 2010 (UTC)[reply]

Muntjacs

We are plagued by Muntjacs in our garden but they are mainly very shy of people and retiring. However they make a din with very loud barking noise; enough to bring everyone out of the house (most recently giving birth a week ago). So why so noisy? If they are so fearful the noise must attract more danger at a rather vulnerable point with a baby deer (which now beds down with mother everynight under a brushwood pile). Any idea what the advantage is to them in the load bark? --BozMo talk 11:06, 9 June 2010 (UTC)[reply]

According to our article on the Indian Muntjac, they bark when disturbed to tell the predator that they know it is around. Their main predators seem to be stalkers, so they predators, hearing they have been detected probably look for an easier animal to sneak up on. Googlemeister (talk) 19:25, 9 June 2010 (UTC)[reply]

Curved horizon?

It is asserted above that "the horizon is curved not straight". I do not think that is true. The horizon, if you were standing on a boat in the middle of an ocean on a calm day, would be a straight horizontal line which wraps around you 360 degrees (since the angles and distances involved are identical in all directions). Anyone who has been to the seaside can tell you that the sea horizon is a straight line. On the other hand, photographs from spacecraft show that if you get far enough away from earth, then the horizon is curved. So what determines when the horizon is curved or not? Since there is unlikely to be a sudden cut-off point, how much curvedness would you get for a observer with an eye-level five or six feet above sea level? Thanks. 92.24.182.110 (talk) 11:49, 9 June 2010 (UTC)[reply]

See the horizon article. 92.24.182.110 (talk) 12:08, 9 June 2010 (UTC)[reply]

Actually, if the horizon were a line then if you look in different directions the horizon would farther in some directions than others. The fact that it's the same distance in every direction shows that it's a circle. To answer the height question, it's probably the hight of the smallest cone that can fit over the earth without going through it. At that point you will be able to look "down" on the earth, and clearly see it silhouetted against space. Ariel. (talk) 12:19, 9 June 2010 (UTC)[reply]

The point is, from the point of view of an observer as described above it is a straight line that wraps around the observer 360 degrees. If you traced this line on the earth with a giant pen and then looked at it from above, then it would be a circle as you say. But this big circle is not the horizon, its a big circle. 92.24.182.110 (talk) 12:43, 9 June 2010 (UTC)[reply]

It's the same view from the boat and from space, just with a different perspective. Consider: the astronaut looks directly at the Earth (i.e. straight down) and observes that the horizon is a circle. The sailor looks directly at the Earth (again, straight down) and observes that the horizon is a circle. The only difference is the relative position and apparent size of that circle, and that's a function of altitude. Characterizing the horizon as a straight line is a function of (a) only observing a portion of the horizon and (b) using only an approximation of a line. There is no absolute "cut-off point", as the horizon is never a truly straight line*, and personal interpretations of when curvature is apparent will vary.

*With the possible trivial exception of the distance-zero horizon from a plane tangent to the surface. — Lomn 14:16, 9 June 2010 (UTC)[reply]

That is mostly repeating what was said in the question. 92.15.21.24 (talk) 20:06, 9 June 2010 (UTC)[reply]

Nope - you are 100% wrong. Imagine you are way out in space, looking back at the earth - the horizon is undoubtedly a circle. As you get closer, the circle gets bigger and bigger. When you are a mile up, it's still a circle around you. When you are 5 feet above the water in your boat, it's STILL a circle - although it's so edge-on, that it looks only very subtly curved. Only when your eye is actually precisely at the height of the water (at 'sea level') is the circle perfectly edge-on - and therefore could be considered to be 'straight'. However - in the perfectly idealised spherical world - with no waves disturbing that line, the distance from your eye to the horizon gets smaller, the lower you are. When your eye is perfectly on the surface of the sphere - the distance to the horizon is zero - so there is no horizon and you can't argue that it's straight. So no! Categorically, the horizon is NEVER a straight line - not even in a perfectly spherical world with idealized-everything. It's either curved or non-existent. In the 'real' world, things like waves make it not-straight, so you can't win that way either. SteveBaker (talk) 16:14, 9 June 2010 (UTC)[reply]

If the horizon you see standing in a boat is curved, then this would imply that when you turn 180 degrees, the horizon should be lower, due to the curve forcing it down. Part of the curve would have to be convex, and part concave, otherwise it would never join up. But it is not, it is just the same. And why would there be a difference between the upper and lower parts of the curve? The horizon is all the same - same distance, same angle of declination. 92.15.21.24 (talk) 20:06, 9 June 2010 (UTC)[reply]

The horizon is straight if your camera takes a picture that's a cylindrical projection of the environment (I don't know any physical cameras that do this, but my raytracer is happy to simulate them for me). In a cylindrical projection (which doesn't have to have a 360-degree field of view, but typically does), as you rotate the camera on a vertical pole, the position of objects doesn't change vertically. But with an ordinary perspective camera (or your eyes), as you rotate the camera, objects on the horizon will appear lower if they are further towards the edge. The next question to ask is "what about objects behind you -- what height are they?", but that's a trick question; an ordinary perspective projection makes no sense with a 180-degree field of view or higher (and as you get closer to that, the image will look increasingly weird).

For a similar phenomenon, see how spheres don't look like circles unless they're in the center of your view. Usually, our cameras (and, effectively, our eyes) have narrow enough fields of view that we don't notice this or the curvature of the horizon. Paul (Stansifer) 21:13, 9 June 2010 (UTC)[reply]

Photo stitchers like hugin can make cylindrical projections, and most of the stitched panoramas on Commons, for example, are cylindrical. The discussion at the Povray wiki that you linked is not very accurate. The issue is not which way you're looking, it's where you are. If the location of your eye relative to the on-screen image is the same (up to an overall scaling) as the location of Povray's virtual aperture relative to its virtual film, then all objects in the frame will appear undistorted. If your eye is elsewhere, there will be distortion. Right now, my eyes and the sides of my display screen form about a 30–75–75 triangle, so full-screen images with a horizontal FOV of 30° will be undistorted. The trouble shows up when people render with high FOVs like 60° or 90°. This distortion only exists when an image is recorded, projected, and then viewed from the wrong location. There is no such distortion if you view the original scene directly, because there is no viewing of a projected image (homunculus argument). -- BenRG (talk) 03:07, 10 June 2010 (UTC)[reply]

I think that you and the FAQ are saying the same thing, but I'm not sure. To go back the the OP's question: The special thing about about the way that cameras and raytracers usually work is that 2D image looks like the 3D scene when displayed on a flat surface (provided that you view it from the exact right point). If the camera was above the ground, the image of the horizon will be slightly curved. The horizon does appear straight in 2D in a cylindrical projection, but in order to make the image "look right", you need to display it on a curved surface. So there's no way to take an accurate (in some sense) picture of the horizon without it being curved (in some direction). Paul (Stansifer) 00:22, 11 June 2010 (UTC)[reply]

This whole business of picking a cylindrical projection is cheating - I can grind a lens or craft specialised ray-tracing software or build image distortion software that would turn a pretzel into a straight line! Does that make a pretzel "straight"? Only by some very curious use of the language! I can make literally anything look "straight" by these kinds of techniques - so are we going to say that absolutely everything in "nature" is straight - or that nothing is? You can't have it both ways! SteveBaker (talk) 01:29, 11 June 2010 (UTC)[reply]

You're arguing semantics. The horizon is curved in the sense that it does not trace a straight line in three dimensional space. It joins up with itself. If you're at a low enough altitude (ie: Standing on the ground) then the horizon appears to be a circle that completely encircles you.

If I had a glass cylinder and drew a line around its equator, no one would argue that the line was straight in 3d space. However, if I placed a camera in the center of the cylinder, exactly level with the line, it would be easy to get a 2d image of the line that was perfectly straight.

Of course, you're not exactly level with the horizon, you're slightly above it. So even a 2D photo would betray some slight curvature if it were possible to magnify it enough. (This isn't too hard to understand if you visualize it right, and it does not show the "never joining up" effect you describe. Imagine holding a hoola-hoop at waist level. It looks curved. Now turn around, it still looks curved, in the same direction.) APL (talk) 01:30, 10 June 2010 (UTC)[reply]

The horizon would only appear (very slightly) curved under normal conditions if you have a disability that prevents you ffom moving your eyes or your neck. If you do not have this disability, then you move your eyes along the horizon, and its straight. 92.15.4.200 (talk) 14:41, 11 June 2010 (UTC)[reply]

Vernier calipers

How is the least count of the vernier calipers calculated? —Preceding unsigned comment added by Camusrajmohan (talk • contribs) 12:19, 9 June 2010 (UTC)[reply]

Are you asking how to use and read a vernier caliper? -- 58.147.55.151 (talk) 12:58, 9 June 2010 (UTC)[reply]

Photons

If photons are their own antiparticle, why doesn't shining two lights toward each other make an explosion? --76.77.139.243 (talk) 12:45, 9 June 2010 (UTC)[reply]

Very low collision Cross section (physics) for foton-foton interations, and the energy that is released when it does happen is no larger than the photon energies were in the first place (i.e. not nearly large enough to create an explosion, photons have no rest mass thus no energy is released from mass-energy equivalence, unlike massive particle-antiparticle collisions). 157.193.175.207 (talk) 13:01, 9 June 2010 (UTC)[reply]

But shouldn't they still make everything dark when they annihilate, even if they don't release any energy? --76.77.139.243 (talk) 13:02, 9 June 2010 (UTC)[reply]

"Everything dark" is taking the concept too far, but yes, photons can destructively interfere. This phenomenon can be observed easily in many settings -- however, the destructive interference of two photons has no effect at all on the untold legions of other photons. — Lomn 14:08, 9 June 2010 (UTC)[reply]

Particle-antiparticle annihilation turns the particles into photons, so if two photons annihilate each other and turn into photons, you still have two photons left - there is no significant change. --Tango (talk) 16:24, 9 June 2010 (UTC)[reply]

The photons can't simply disapear into nothing (Keep in mind that energy conservation must be preserved). They can either do nothing at all (pass each other), produce more photons (scattering of light by light has a fairly low cross section), or follow an inverse anihilation reaction and produce (for instance) electrons and positrons. The last possibility requires the photons to have enough energy to begin with (at least about ten billion kelvins), so visible light cannot do it. Dauto (talk) 18:18, 9 June 2010 (UTC)[reply]

Another important point implicit in what I said above is that anihilation doesn't necessarily turn particles into photons. For instance, when a proton and an anti-proton anihilate they are far more likely to produce a meson shower. Dauto (talk) 00:53, 10 June 2010 (UTC)[reply]

Mushroom cloud

Would any large-enough explosion make a mushroom cloud, or only atomic explosions? --76.77.139.243 (talk) 12:47, 9 June 2010 (UTC)[reply]

See our article on mushroom cloud. In short, large explosions often produce mushroom clouds—they are caused primarily by a ball of heated gas rising and cooling. --Mr.98 (talk) 12:57, 9 June 2010 (UTC)[reply]

Any large enough explosion can do it. --Tango (talk) 16:59, 9 June 2010 (UTC)[reply]

Do deep underwater explosions create mushroom clouds? (underwater ones, not in the air above the water) Googlemeister (talk) 18:28, 9 June 2010 (UTC)[reply]

No, because there's no such thing as a cloud underwater. If you tracked the convective movement of the explosion-heated water, I'm sure it would form the shape of a mushroom due to entrainment, but there would be no way to visualize it.-RunningOnBrains^(talk) 19:08, 9 June 2010 (UTC)[reply]

The relevant article, I suppose, is underwater explosion. It sounds like in some circumstances it has a mushroom like appearance but it is not quite the same thing at all as the surface mushroom cloud. --Mr.98 (talk) 19:16, 9 June 2010 (UTC)[reply]

Check out the article about Operation Crossroads, it's got a pretty impressive picture of an underwater nuclear explosion. 67.170.215.166 (talk) 03:05, 10 June 2010 (UTC)[reply]

Though as the article I linked to pointed out, it was a very shallow one. The only images of a deep underwater explosion that I've found are in Operation Wigwam, but they are just the result of the bubble formed hitting the surface. I couldn't find any images of what such an explosion would look like from under water before it hit the surface. ---Mr.98 (talk) 12:26, 10 June 2010 (UTC)[reply]

The question is probably academic since anything close enough to view a deep underwater explosion form a mushroom cloud would be totally crushed by the shockwave. I mean usually good visibility underwater is measured in hundreds of feet, not miles. Googlemeister (talk) 13:30, 10 June 2010 (UTC)[reply]

I'm not sure it's entirely academic—knowing how the shockwave would form and what it would do to the water around it is surely something that the nuclear strategists have studied (indeed, it is probably why they detonated the Wigwam blast in the first place). I am sure that in one of the Wigwam reports they have diagrams of this. --Mr.98 (talk) 16:27, 11 June 2010 (UTC)[reply]

Endurance of an unused automobile

I know that if one is preserving a classic automobile, it's wise to drain it of all fluids so as to minimize corrosion. But perhaps because that's such reasonable advice, I can't find any hard numbers on how long an automobile will last if you don't drain it. What are the best-case and worst-case scenarios for how long I could leave an automobile (let's say, a brand new American-made sedan, if that matters) with gas, motor oil, etc., completely unattended and ignored in a garage? What are the odds that it would start up again with just the turn of a key, or just some minor tune-ups, after a month, a year, or a decade? Thanks for any help. --M @r ē ino 14:19, 9 June 2010 (UTC)[reply]

As you've noted, there's not going to be much in the way of hard numbers. However, I can say that the first wear item you'll have to deal with is the battery -- depending on the condition of the battery and the storage conditions, even a month could be enough time for the battery to be no longer capable of starting the car. After a year I'd guess that odds are better than not that the battery won't be able to start the car. On the other hand, replacing the battery probably lands under "minor tune-ups". — Lomn 14:26, 9 June 2010 (UTC)[reply]

Well assuming your vehicle is gasoline powered, after a couple of years, I would imagine that the gasoline would have gone bad (the best volatiles will have evaporated) and you would not get a start. It is pretty easy to take a battery out of the car, but as noted above, leaving the battery in will drain it over the course of months. Googlemeister (talk) 14:28, 9 June 2010 (UTC)[reply]

I've restored cars that have been left in a garage for 10 years. I'm not convinced that draining the fluids makes much difference either way. The worst problem I see is that the tyres go flat and the weight of the car on the deflated tyre bends the steel belting and produces a 'flat spot' - making the tyres useless. It's really frustrating to have to junk four nearly new tyres! So the most important thing (IMHO) is to put the car up on blocks so the wheels are off the ground. I agree that the issue with the volatile fractions of the gasoline evaporating is all too real - when you come to restart the car, you'll certainly want a couple of gallons of fresh gas in the tank - and since disposing of the old stuff is a pain, it's better to drain the gas tank and actually use the gas for something else before you abandon the car.

Replacing the battery is also a good idea - lead-acid batteries are not designed to run completely dead flat - and that's going to happen after just a few months of not driving it. If you can't arrange to periodically recharge the battery - expect to have to replace it after a year or two. As for the other fluids, you could drain the radiator - but the biggest corrosion issue is inside the engine block and with most cars, there isn't a handy drain plug to get the water out of there. Having lots of antifreeze in the water is important because it contains corrosion inhibitors...and you don't want the water in the block to freeze and crack it! Brake & clutch fluids, transmission and engine oil can be left in place - they don't cause corrosion - if anything, they prevent it.

Don't park with the car in gear or in park or with the parking brake on. Leave it with the brakes off and the shifter in neutral - since it's going to be up on blocks anyway, that's unnecessary and brake pads/drums tend to seize up and lock on - and the parking brake cable will stretch because it's under tension. I'm not sure why leaving it in neutral is important - but many people whom I trust on car matters have assured me that it matters. With cars in long storage, rubber hoses and seals tend to 'dry out' and they often fail only after you have the car running again when the pressures go up and vibration sets in - there isn't much you can do to prevent that - but just be aware that just because the car starts, that doesn't mean that you can immediately head off on a 100 mile road-trip! If you can, you should lubricate everything before you try that though...the engine may run, but there are lots of other things that may have seized up.

Cars left in a garage can also attract rats and mice - so it's worth popping the hood and pulling out any obvious nests and doing a cursory check for chewed wiring and/or hoses before you attempt to run the car.

As for starting, I've found that cars that were running OK when they were put away can usually be started with not much more than a new battery and fresh gas...but all too often, people put their cars away when they WEREN'T running (for whatever reason) - so you first have to diagnose and fix the original problem BEFORE you can start work on improving it's condition. If you are putting a car up like this for decades - you might want to do yourself/your ancestor a favor and buy a set of the most obvious spare parts for the car...in 10 or 20 years time, they might be almost unobtainable...or at least horribly expensive! (Also buy an owner's manual while you still can!) SteveBaker (talk) 15:50, 9 June 2010 (UTC)[reply]

We bought our current car when it was 21 years old, with just 6000 miles on the clock. Now it hadn't just sat in the garage, but it had only been taken out a couple of times a year for many many years. You need to be careful with anything that's rubber – tubes, seals and, obviously, tyres – the rubber will harden with age whether the car is used or not, and if it's not used then there won't have been any incentive to change anything. We found a rubber seal on the steering column which was about to break, which could potentially have caused the steering to lock, and one of the tyres (we changed all four) that was about to blow through hardening-cracking. Otherwise, we've had the car for three years now, and it runs fine. Physchim62 (talk) 17:42, 9 June 2010 (UTC)[reply]

In addition to rubber cracking, you can also have the insulation on your electrical items dry out. This can cause electronics problems in the car and can be fairly difficult to repair. Whether it would interfere with the engine running, or just make your radio not work is going to depend on which wires wear out. Googlemeister (talk) 18:27, 9 June 2010 (UTC)[reply]

I think you would like this story of a brand new car that was buried in a time capsule for 50 years. Water got in the capsule and the car was pretty rusty when removed. Ariel. (talk) 19:27, 9 June 2010 (UTC)[reply]

Thanks, everyone -- this is a wealth of good information! --M @r ē ino 17:47, 10 June 2010 (UTC)[reply]

All the above is very true and one other thing to add is that environment plays a big role in how fast all that stuff wears out. Just as museums diligently maintain constant temperatures and humidities, so too do you need to keep these at stable levels or things will wear a LOT faster. From personal experience I can attest to this; gasoline in a garage without much fluctuation will likely be as good as new in two or three years' time (I have proven this on two occasions) but sitting outside left to the elements it will be "sour" in less than a year. --144.191.148.3 (talk) 20:22, 10 June 2010 (UTC)[reply]

I once owned an old Buick that vandals had slashed the tires of, and I could not at the time replace them. It was in a bitter cold northern US winter, but I went out every month, chipped away the ice from the driver's door and started it and ran it for a few minutes to keep the battery charged and the engine lubricated. It started fine with this once per month activation. In the Spring, after 5 months of this regimen, I replaced the tires, started it and put it in gear. The transmission made funny noises, but it went around the block ok and drove fine afterwards. If attempting that again, I would add Sta-Bil to the gas to prevent it gumming up. Edison (talk) 02:37, 11 June 2010 (UTC)[reply]

how to functionalise a carbohydrate with acetylene?

This is not for a problem set... it's for a real life problem. Many many things will turn out excellently if I can functionalise a carbohydrate with acetylene (most notably I can perform the click reaction)... conveniently. Preferably this involves reagents that aren't too terribly toxic. If I have a polymer of saccharides, perhaps I can use the straight-chain / cyclic equilibrium of one of the terminal ends and use sodium acetylide there to attack the aldehyde form? John Riemann Soong (talk) 15:20, 9 June 2010 (UTC)[reply]

^{Way over my}_head.--Chemicalinterest (talk) 17:44, 9 June 2010 (UTC)[reply]

There are some reactions of Lithium acetylyides here [1] they do react with ketones and aldehydes.

Sodium acetylide could work too eg [2]

For either reaction you'll need to protect any potentially acidic groups - if you are thinking of explotting this reaction - there's a OH produced in the ring opening reaction of sugars.

There are alternative ways to add an alkyne group - eg Propargyl chloride , propynoyl chloride (HCCCOCl) etc.87.102.13.111 (talk) —Preceding undated comment added 18:11, 9 June 2010 (UTC).[reply]

I think zinc acetylides are tolerant of hydroxyls (still nucleophilic towards aldehydes, but not nearly as basic as lithium/sodium ones). DMacks (talk) 19:18, 9 June 2010 (UTC)[reply]

Thanks guys. Do you know of an adaptable protocol I could use ... my supervisor sort of wants that (as opposed to me trying to design a completely new one). John Riemann Soong (talk) 19:34, 9 June 2010 (UTC)[reply]

I'm not sure but are Zinc acetylides safe? (copper acetylides aren't, and zinc alkyls aren't so...) - all I can find is that it's water sensitive though.83.100.132.26 (talk) 19:43, 9 June 2010 (UTC)[reply]

Propargyl chloride or bromide should functionalise your sugar (there are numerous ways)

One example here [3] see Scheme 1 , reaction e using: CH≡CCH2Br, NaH, THF / DMPU - note the sugars where already protected with OAc.83.100.132.26 (talk) 20:19, 9 June 2010 (UTC)[reply]

Reading a book similar to this https://doi.org/10.1007%2F3-540-06649-7_3 should give many possibilities.83.100.132.26 (talk) 20:23, 9 June 2010 (UTC)[reply]

Uh.... I don't like the use of acyl chlorides and the use of alkyl halides sounds potentially problematic. Could I use an acetylene-functionalised carboxylic acid and toss in some EDC and HOBT? (Does that work less well with alcohols?) John Riemann Soong (talk) 21:48, 10 June 2010 (UTC)[reply]

Carbodiimides can be used to make both esters and amides...87.102.13.41 (talk) 22:39, 10 June 2010 (UTC)[reply]

Blue and red cobalt(II) hydroxide

Why does the article say the red form is more stable when every time I form it, it is blue. Is it because I only use ammonium hydroxide to react with cobalt(II) chloride(forms blue-green precipitate)? Also, the cobalt carbonate article says that it is a red powder. When I react cobalt chloride with sodium carbonate, I obtain an indigo-colored compound. Why isn't it red? --Chemicalinterest (talk) 15:22, 9 June 2010 (UTC)[reply]

Cobalt hydroxide

With hydroxide and Co²⁺ the initial product is blue, this should change (on boiling) or after ~8hrs to the pink/red form - there are two forms with different structures. It's described here [4] - to save you the trouble of reading that the initial form is called the alpha form, or α-Cobalt (II) hydroxide, the more stable form that forms later is called the beta form or β-Cobalt hydroxide.

Suggest using NaOH (caustic soda) instead of ammonia , and waiting to see the other form - avoid mixing the hydroxide with air since this will oxidise it.87.102.13.111 (talk) 16:06, 9 June 2010 (UTC)[reply]

Cobalt carbonate

Cobalt carbonate is usually 'violet' (is that the same as your indigo?) (yes--Chemicalinterest (talk) 17:37, 9 June 2010 (UTC))[reply]

See these images http://www.google.co.uk/images?hl=en&q=cobalt+carbonate&um=1&ie=UTF-8&source=og&sa=N&tab=wi

If your produce is blue possibly you are forming the hydroxide due to the basicity of sodium carbonate .. as before allow time for the reaction or boil - this should give the carbonate eventually.87.102.13.111 (talk) 16:29, 9 June 2010 (UTC)[reply]

It should be pink usually though - eg images 87.102.13.111 (talk) 16:58, 9 June 2010 (UTC)[reply]

There's some instructions for making the basic carbonate here from Cobalt (II) chloride and sodium carbonate. [5] 87.102.13.111 (talk) 17:13, 9 June 2010 (UTC)[reply]

I dried the hydroxide in air and it turned dark green. --Chemicalinterest (talk) 17:39, 9 June 2010 (UTC)[reply]

Its blue probably because of the mixture of the red carbonate and the greenish-blue hydroxide. I boiled that mixture and it did not turn red. I think the carbonate resists conversion. --Chemicalinterest (talk) 17:43, 9 June 2010 (UTC)[reply]

Look on cobalt carbonate for the picture. --Chemicalinterest (talk) 18:33, 9 June 2010 (UTC)[reply]

Yes that's the right stuff (probably) - colour is also known as Mauve 87.102.13.111 (talk) 18:50, 9 June 2010 (UTC)[reply]

I boiled the blue hydroxide (still using ammonia) and it stayed blue. As I have no NaOH for the time being, I have to use my KOH/K₂CO₃ mixture. Hope it works. --Chemicalinterest (talk) 18:33, 9 June 2010 (UTC)[reply]

The ammonia will affect the reaction. You can get pure (99% or better) NaOH from hardware stores - usually in 'pearl' or 'flake' form for about the same price as bleach. eg google shops - similar price in rest of world Check the label though - some versions (intended for drain cleaning) contain aluminum - don't buy that stuff. (It's very caustic - and does hurt a lot if you get it on your hands - it also has a tendency to heat water to boiling if you add a lot of it to water - the dissolution reaction is very exothermic.)87.102.13.111 (talk) 18:50, 9 June 2010 (UTC)[reply]

When I precipitated the Co²⁺ with the KOH/K₂CO₃ mixture, there was some fizzling (probably acidity of Co²⁺ and HCl impurities in the test tube) and a red precipitate was formed. I am drying it now. It may be a mixture of beta-cobalt(II) hydroxide and cobalt carbonate.--Chemicalinterest (talk) 19:02, 9 June 2010 (UTC)[reply]

using a car 12 volt alternator as a generator when its removed from the car

what problems are likely if i periodically spin a small 12 volt car alternator, at approx. 1000 rpm, with a 12 volt motor (eg a battery screwdriver) which is itself connected to one of the 12 volt batteries that im charging with the alternator. i intend for the outfit to be mounted on a 36 volt power assisted pushbike correctly wired in parallel to charge the 3 times 12 volt batteries, as im riding. also can you point any pitfalls in the above idea generally as i would like to power small 240 volt appliances via invertors using the same type of outfit. thanks —Preceding unsigned comment added by 85.189.247.67 (talk) 16:03, 9 June 2010 (UTC)[reply]

It's not clear to me what is your source of energy. Dauto (talk) 16:42, 9 June 2010 (UTC)[reply]

An alternator generates electricity. Spinning it with a battery-operated screwdriver doesn't make any sense to me - you'll get more energy back just by taking the batteries out of the screwdriver and attempting to use them to power the appliances. That being said, I don't think that those batteries contain enough energy to make that practical, even with inverters, though since I'm not an electrician I could be wrong. Okay, nevermind... I see now that that's not what you are trying to do, but I'm extremely confused as to the nature of your setup now. Falconus^{p t c} 17:05, 9 June 2010 (UTC)[reply]

Your statement may not be what you intend to say... You state that you have a generator charging a battery. The battery is connected to an electric screwdriver. The electric screwdriver is spinning the generator... which is charging the battery. The effect is simple: You will reduce the charge in the battery because it is not a perfect system. There is loss. So, the amount of electricity used to turn the screwdriver and the generator is less than the amount of electricity being charged back into the battery. -- kainaw ™ 17:13, 9 June 2010 (UTC)[reply]

People have tried many times in the past to make these perpetual motion machines but they never work. Even the earth is slowly slowing down.--Chemicalinterest (talk) 17:36, 9 June 2010 (UTC)[reply]

If you are saying you've got 3 12V batteries in series, and you want to charge one of those batteries whilst still in the circuit - then yes you can do that.. though your charging device will also have to supply current to drive the main circuit if it's on, and will need to provide a sufficient overvoltage to charge.

It doesn't seem likely that a 12V screwdriver will have sufficient power to do that. But it might. The 12V screwdrivers I'm thinking of definately wouldn't be able to turn a car alternator at the required speed. Also you would need a rectifier to convert the AC output from the alternator to DC. 87.102.13.111 (talk) 18:26, 9 June 2010 (UTC)[reply]

(EC) It sounds to me like 85.189.247.67 is trying to power things with a bicycle (in which case their muscles or food or whatever are the source of energy). However I don't get why the set up is so complicated. I'm also not sure what the 'power assist' is for. Are they trying to make some sort of 'regenerative breaking'? Or to help them go up hills by doing more work (to charge the batteries) while on flat bits? P.S. Be aware that you shouldn't expect good returns from whatever you do do. It wouldn't surprise me if you get an efficiency of less then 10% Nil Einne (talk) 18:28, 9 June 2010 (UTC)[reply]

One problem you will have is that alternators need to be energized with current before they will do anything. (As opposed to generators that just need to be spun.) The strength of the current being fed into them determines the voltage. They do that to keep the voltage steady even when the alternator spins at varying RPMs. They need rather a lot of current. Ariel. (talk) 19:35, 9 June 2010 (UTC)[reply]

I didn;t realise that - you could try this [6] - also it seems that car alternators have a built in rectifier (so ignore my comment above, now crossed out)>83.100.132.26 (talk) 19:59, 9 June 2010 (UTC)[reply]

If your motor and alternator are 80% efficient, then about 36% =(1 -.8²) of the energy will be lost converting mechanical rotation of the motor to the generation of electricity, and the power originally stored in the battery will not be replenished by the alternator, so the system will fail in short order. In addition, the wires will dissipate energy as heat. This is a best case scenario. Edison (talk) 02:30, 11 June 2010 (UTC)[reply]

Question about birth change

Lets imagine someone is making sex and some months later a baby is born. Now lets imagine that is this example the couple started make sex just 3 seconds later. My question is, in the second example, a another baby could be born in the place of the baby that I said before or no baby be born at all?

Before you ask: Why you want to know this? I am just curious if a time traver woud be able to create a paradox so easily.

PS: Because of the extreme chains of changes that those new things on the second example will create this would easily create a paradox. 187.89.81.94 (talk) 16:19, 9 June 2010 (UTC)[reply]

(ec) You may find the article human fertilization useful to analyze the extremely complex and largely random set of events that lead to (usually) a single human sperm fertilizing the egg. Clearly, even a slight perturbation in any way could permit a different sperm to be the one that reaches the egg. Biologically, the result would be an individual that is genetically distinct from the (now hypothetical) individual who would have otherwise been born. Whether those biological distinctions result in a "different" human individual is a matter of philosophical debate; but undoubtedly, even a tiny perturbation in conditions would, with overwhelming certainty, result in a different sperm reaching the egg. Nimur (talk) 16:43, 9 June 2010 (UTC)[reply]

(ec) The key question here is whether the particular sperm that happens to fertilize the egg would make it back to that egg again. My understanding (based mostly on a "competitive sperm" graphic from my sex education days) is that if you varied the conditions slightly, that the odds that another sperm would "make it" is probably fairly high. I'm not sure if 3 seconds would make a large difference but some amount of time would. As for whether the other baby is "another baby", it depends on your interpretation of the philosophy behind this. In any case, it's worth remembering that the egg would be the same in either case.

That being said, I'm not sure how the time travel connection plays in. Would said time traveler show up, delay his parents having sex by five minutes, and thus a paradox is formed? It's kind of an awkward situation to imagine. (Especially since time travel and potential paradoxes created by it is not exactly a subject that current science can explain meaningfully.) --Mr.98 (talk) 16:46, 9 June 2010 (UTC)[reply]

I endorse Nimur's answer about the butterfly effect. Yes, the time traveler could destroy his own existence by delaying the sex act for a second. Since you're interested in speculative fiction involving this, I should point you to Watchmen, in which Dr. Manhattan has an insight related to this whilst on Mars. Comet Tuttle (talk) 16:56, 9 June 2010 (UTC)[reply]

It just strikes me that delaying sex for just a second would be quite difficult from a practical point of view. "Oh, hi there, didn't realize someone was in here! Please continue!" --Mr.98 (talk) 19:04, 9 June 2010 (UTC)[reply]

Not so difficult. When I said delaying a sex for just some seconds. Some very small changes like the time traveller killing a fly could trigger this. In the original timeline this fly was not killed, making the father arrive one second later in the house (the fly bothered the father for about 1 second while he was walking on the street and this makes he arrive one second later in sex).This second later would influence on the kid he would have.

Something about this kid: When I said a different kid, I was talking about a kid that is at least a little different (personality, body skills, or appearance) from the other kid, those littles difference would create chain reaction that would later create a father paradox, or sometimes other paradox.

A little different kid could lead to a different name, kids in school not creating a nickname based on something about him he would have on the other timeline[...], and this would lead to bigger changes that would lead to changes that would create the paradox.

If this father is the father of the time traveller, this is even more simple. This new kid, would not be him, and BANG!, father paradox.

I asked this question, because if this birth thing was true, this would make paradox almost impossible to avoid, because tiny changes would (in a direct way or because of buttlefly effect) make someone (that would later have a kid) make sex earlier or later, resulting a different kid, then the bigger changes woud start to happen or small changes that would led to big changes.187.89.177.139 (talk) 21:14, 9 June 2010 (UTC)[reply]

The thing about the infamous "butterfly effect" is that we do not have a scientific model of human behavior that is sufficiently accurate that we could make meaningful predictions. If you want to consider a human to be an enormously complex state machine, and then presume that we could conduct a controlled experiment where the two hypothetical stimuli are simulated (with and without a fly, for example), we would need some way to generate a reliable model of human behavior, compute a predicted outcome based on all the circumstantial and situational inputs, and then observe some set of responses. This level of accurate and rigorous modeling for human behavior does not exist. Similarly, we can't accurately model the rest of the universe to the level of accuracy that would be needed to precisely predict such complex states. As such, it is useless to analyze whether killing a fly (or similar "insignificant" changes of state due to hypothetical time-travel scenarios) would or would not change some perceivable/measurable outcome. For these reasons, "butterfly effect" speculations remain fairly philosophical and are rarely subject to any kind of actual physical or mathematical analysis. Nimur (talk) 22:14, 9 June 2010 (UTC)[reply]

Given enough time, I think the time traveller could drastically change his future time by doing nothing more than sending a single photon back in time. The consequence of change is usually more change - and chaotic systems are rather more common than self-correcting ones - so eventually, any change - no matter how small - will have 'macroscopic' consequences that would be noticable. SteveBaker (talk) 00:36, 11 June 2010 (UTC)[reply]

Sinkhole debris

I'm looking at pictures of this massive 300-foot-deep sinkhole from Guatemala. That is a lot of sediment - a lot of material. Hundreds of thousands of cubic meters of debris. Where does it go? Is there so much pore space between the overburden material that it can just compress at the bottom and form a denser sediment, or is there actually a large void, cavern, or geological water-pipe that the sediment all piles into at the bottom? I see a lot of discussion about "eroded" limestone, which makes me wonder if there were actually large cavernous hollow spaces that the sediment rested above. Nimur (talk) 18:30, 9 June 2010 (UTC)[reply]

Similar question not long ago Wikipedia:Reference_desk/Archives/Science/2010_June_1#Sinkhole

It's actually described at sinkhole I'm sure. The limestone underneath is dissolved over time by underground streams, a relatively thin lid is on top of the hole.

See http://www.change.freeuk.com/learning/geog/caves.html for info on the underground geology of limestone areas .. (87.102.13.111 (talk) 18:42, 9 June 2010 (UTC)[reply]

By the way the examples seen are extreeeeeme examples - in the UK in limestone areas sinkholes are common - but they are usually less than 1m accross, and usually don't result in a huge pipe, and may only go down a few metres.83.100.132.26 (talk) 19:03, 9 June 2010 (UTC)[reply]

You can read my old question on sinkholes here http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2009_February_5#Sinkholes_-_Geology

google maps Here's some more modest sinkholes - they're the line that looks like someone has pricked the ground with a pin.83.100.132.26 (talk) 19:16, 9 June 2010 (UTC)[reply]

Awesome. This topic has clearly been addressed thoroughly. It seems like the consensus then is that there are actual large limestone caverns underneath the surface. Sorry for my failure to check the archives - I've just reconnected to the Internet after a long absence and am slow to catch up on my Science Desk archives... Nimur (talk) 19:31, 9 June 2010 (UTC)[reply]

Actually, there is some suggestion that the Guatemala sinkhole was not caused by limestone dissolution but by the washing away of soft rock (loose pumice) according to this article. Mikenorton (talk) 22:25, 9 June 2010 (UTC)[reply]

See this article. Do we have an article on cenotes? DuncanHill (talk) 22:29, 9 June 2010 (UTC)[reply]

Cobalt compounds yet again!!!

I reacted red cobalt(II) chloride with hydrochloric acid to get the blue-purple tetrachlorocobalt(II) complex. I reacted a tiny amount of the blue-purple tetrachlorocobalt(II) complex with 10 times its amount of hydrochloric acid to get a blue-green solution. It looks like a clear version of alpha-cobalt(II) hydroxide. Is it a hexachlorocobalt(II) complex? --Chemicalinterest (talk) 19:11, 9 June 2010 (UTC)[reply]

I'm not sure (it doesn't seem that likely) - what happens if you take a similar tiny amount of CoCl₄^2- and just dilute it. or use NaCl solution instead of HCl.83.100.132.26 (talk) 19:24, 9 June 2010 (UTC)[reply]

If you dilute a tiny amount of the CoCl₄² in water, you will get an extremely faint pink color of the Co²⁺ hydrate ion. The color is very vibrant; a microscopic amount of cobalt compound, such as cobalt(II) hydroxide, will react with concentrated HCl to form that color. --Chemicalinterest (talk) 19:28, 9 June 2010 (UTC)[reply]

Mmmh - but isn't that what you've just done in "test tube 3" and got green.. I'd try two things:

Do it again to double check (making sure the test tube is super clean)
Try with a NaCl solution of the same molar concentration as the HCl you used, eg this reaction is valid too:

CoCl₂ + 2NaCl >> CoCl₄^2- + 2Na⁺

If the product/colour from the above reaction is different on diluting the above reaction compared to the reaction of CoCl₂ with HCl_(aq) then it must be due to the acidity.83.100.132.26 (talk) 19:49, 9 June 2010 (UTC)[reply]

It forms when any cobalt compound, CoCO₃, Co(OH)₂, CoCl₂ is added in small quantities to concentrated HCl. It also forms when blue CoCl₄^2- is reacted with HCl. Here is the pattern: red + HCl → purple + HCl → blue + HCl → blue-green. I will try NaCl now, but NaCl is not as soluble and so will not be concentrated (12 molar) like HCl; probably won't get green coloration. --Chemicalinterest (talk) 20:17, 9 June 2010 (UTC)[reply]

It was a little greener when heated because the equilibrium toward blue is driven by heat and away from blue is driven by cold. It isn't as green as the HCl reaction though, but it is a brighter blue than the "normal" CoCl₄^2-. --Chemicalinterest (talk) 20:27, 9 June 2010 (UTC)[reply]

If you use dilute sodium chloride (e.g. in a test for chloride ions) it forms a blue-purple solution. --Chemicalinterest (talk) 20:29, 9 June 2010 (UTC)[reply]

It follows the same pattern as the spectrum on a "Create Custom Colors" section on a computer graphics program. --Chemicalinterest (talk) 20:31, 9 June 2010 (UTC)[reply]

The CoCl₂ + 2NaCl went green when hot? but not as much as the HCl CoCl₂ reaction?83.100.132.26 (talk) 20:34, 9 June 2010 (UTC)[reply]

See pics on right. --Chemicalinterest (talk) 20:43, 9 June 2010 (UTC)[reply]

This [7] and others agree that increasing Cl^- concentration as well as increasing temperature favour tetrahedral (blue) complexes. So that matches what you found.

I still can't find anything about the green colour though.83.100.132.26 (talk) 21:29, 9 June 2010 (UTC)[reply]

So the question is:What is the green color formed when small amounts of cobalt(II) salts are added to large amounts of concentrated hydrochloric acid? --Chemicalinterest (talk) 21:31, 9 June 2010 (UTC)[reply]

My guess would be [CoCl₅]³⁻, or possibly [HCoCl₅]²⁻. It won't be the hexachloro complex if it has a bright colour. Physchim62 (talk) 21:51, 9 June 2010 (UTC)[reply]

Phenol

If it's only mildly acidic, why is it so corrosive if you touch it by mistake? --75.25.103.109 (talk) 22:52, 9 June 2010 (UTC)[reply]

For the record, it's a popular misconception that all corrosives are acids. See Corrosive#Common types of corrosive substances. Regards, --—Cyclonenim | Chat 22:57, 9 June 2010 (UTC)[reply]

I know that bases are also corrosive, but I don't think that a single chemical can simultaneously be both an acid and a base. --75.25.103.109 (talk) 23:00, 9 June 2010 (UTC)[reply]

A corrosive is only a substance that hastens or causes the destructive decomposition of a material. --Chemicalinterest (talk) 23:56, 9 June 2010 (UTC)[reply]

Exactly, some oxidative molecules are corrosive, as are electrophilic salts. It doesn't have to be an acid or a base, but it often is. I'm afraid I can't answer the question directly regarding it's mechanism.

Ironically, one reason why phenol is so corrosive is precisely because it is a weak acid. A strong acid such as hydrochloric acid is completely dissociated in solution: that is, a solution of hydrochloric acid contains H⁺ and Cl⁻ ions. These ions cannot cross the epidermis, the top layer of dead skin cells: they have to burn their way through the epidermis before the acid can do any serious harm to living tissue. So, if you spill hydrochloric acid on yourself, you have a couple of seconds or so to wash it off before it starts doing real damage. Phenol, on the other hand, is most C₆H₅OH molecules in solution; that is, there is very little dissociation into ions. The neutral molecules can diffuse across the epidermis so, even if you wash the spill off, some phenol will already have reached the living tissue below and can continue doing damage. There are many other compounds which show a similar risk of corrosion through skin absorption, such as hydrofluoric acid, bromine and mustard gas. Note as well that phenol is quite toxic by skin absorption, and several deaths have been reported [8].

I couldn't find a good discussion about the mechanism of tissue damage (ie, corrosion) – most reference source just state that it is corrosive as well as toxic – but looking at some of the biochemical studies that have been carried out, I would guess that it acts by reacting with the proteins which hold cells together to form skin tissue, and so weakens the cohesion of the skin in that way. This is similar to the mode of corrosion with mustard gas, although obviously phenol is less corrosive than mustard gas. Physchim62 (talk) 00:51, 10 June 2010 (UTC)[reply]

Actually, that's almost the exact opposite of irony, but being the Science desk I'll let it slide :P

Being the non-chemist that I am, I'm a bit confused by this discussion. Everyone (including the article) seems to agree that the chemical is highly corrosive and damaging to biological tissue, yet there is a section which talks about its use in preserving tissue. Now that is irony (okay not exactly, I just wanted to link to that video):-D -RunningOnBrains^(talk) 14:41, 10 June 2010 (UTC)[reply]

June 10

Crystal Glass

What is crystal glass and its special properties? —Preceding unsigned comment added by Sksinghaijbp (talk • contribs) 00:09, 10 June 2010 (UTC)[reply]

Crystal glass is a common name for lead glass. It is glass with substantial proportion of lead oxide in the mix, typically around 30% by weight. The lead content increases the refractive index of the glass, which means it sparkles more (because of total internal reflection); it also means that crystal glass is notably denser than normal glass. Physchim62 (talk) 00:27, 10 June 2010 (UTC)[reply]

And also has a lower softening point, which allows it to be shaped more easily. 67.170.215.166 (talk) 06:29, 10 June 2010 (UTC)[reply]

Growing fruits & vegetables indoors...

Possibly an extremely stupid question... if one was to grow beans, or tomatoes, or what have you indoors - wherein there would be no natural pollinators (insects, wind, etc.) would the plants still produce vegetables/fruit? should the owner attempt manual fertilization by swabbing pollen around with ... swabs or something? 218.25.32.210 (talk) 00:53, 10 June 2010 (UTC)[reply]

AFAIK beans (Phaseolus) self-pollinate. However, tomatoes do not, see Buzz pollination. --Dr Dima (talk) 01:24, 10 June 2010 (UTC)[reply]

And BTW this is not a stupid question at all; it is a very good one. Regarding the cotton swabs -- they work for some plant species but not for others. --Dr Dima (talk) 01:28, 10 June 2010 (UTC)[reply]

You can grow most food plants without polination or seeds even, see Grafting, and especially Tomato grafting which details how the method is used for indoor growing of tomatoes in light of the exact problems the OP notes. --Jayron32 01:46, 10 June 2010 (UTC)[reply]

Pikachurin 3D structure

Where can I find an image of the 3D structure of pikachurin? --75.25.103.109 (talk) 00:58, 10 June 2010 (UTC)[reply]

I don't think it is known. Working out the 3D structure of proteins is extremely difficult at best, and this protein was only characterized last year. See protein folding for more information about why the problem is difficult. Looie496 (talk) 01:18, 10 June 2010 (UTC)[reply]

But they know its sequence (otherwise they couldn't engineer pikachurin-null mice for their experiments), so can't they determine how it will fold based on the order of amino acids? --75.25.103.109 (talk) 01:24, 10 June 2010 (UTC)[reply]

Nope. The cellular machinery that synthesizes proteins is excellent at getting them to fold into their native conformation (and other chain-chain interactions). We're very far from being able to predict that result from an arbitrary sequence. In some cases we can recognize certain sequences as being helix domains or other local shapes based on homology modeling from other known protein structures. As Looie496 said, "See protein folding for more information about why the problem is difficult." It's even worse than you think, I think, because you only need a few genetic markers in order to to gene knockout. For example, it might be sufficient to inhibit a promoter or other "start" sequence, or just delete a huge chunk of genome--I can't access the Nature article to see exactly what they did. But not all of the gene base-sequence might be used anyway (see intron), so "the order of amino acids" might not be known. And there might be other post-translational modifications that are critical for certain structural features but are definitely not knowable from just the amino-acid sequence. DMacks (talk) 02:14, 10 June 2010 (UTC)[reply]

Not to contradict any of that, but perhaps to clarify a bit, working out the sequence of amino acids is cheap and easy nowadays. Working out the 3D structure is orders of magnitude harder. In fact it is only feasible in special cases, such as proteins that can be crystallized. Finding a general method for predicting the 3D structure of a protein on the basis of its amino acid sequence is currently by far the most important unsolved problem in molecular biology. Looie496 (talk) 03:49, 10 June 2010 (UTC)[reply]

What if... we're the only intelligent life

There's ongoing research as to life on other planets. What if we discover that we're the only intelligent life that we can ever travel to? Would we continue to fund extra-terrestrial expedition? If we are never going to get to where other life exists and (presuming) they would never be able to get to us (of an intellectual nature) then what would be the point in spending exorbitant amounts of money, given that we are in a global recession? Is there any research into finding ETs that might have landed on Earth that might be too small for us to detect - tiny tiny aliens landing on Earth daily who might not even realise that people are people and have developed civilisation similar to their own. Sorry to ask so many questions all in one go, but they are inter-related. --russ (talk) 01:11, 10 June 2010 (UTC)[reply]

The initial question is moot, as you can't prove a negative. As for the rest -- no referenceable answers are possible. — Lomn 01:31, 10 June 2010 (UTC)[reply]

"Exorbitant amounts of money" should be put in perspective. The world spends many, many times more money on national defense every year than on space-related sciences. And another general point - we needn't go to another lifeform's location to communicate with it. Radio-based communication is already doable, provided we know someone else is listening. 218.25.32.210 (talk) 01:33, 10 June 2010 (UTC)[reply]

Given our understanding of the laws of physics, the first question's answer is undoubtedly "We are the only intelligent life we can ever travel to." Period. The nearest stars to ours would require many centuries earth time to reach, such that any report of such missions reaching distant worlds would be received by an Earth which may have forgotten the details of the mission thus sent. The topic has been explored in song by the band Queen, the song '39, which explores the problem of time dilation in space exploration. And before we poo-poo the idea of a pop-song about a scientific topic, remember that Brian May, the writer of said song, has a PhD in astrophysics, which means he probably has a deeper understanding of the topic of the OP's question than almost any one here... --Jayron32 01:43, 10 June 2010 (UTC)[reply]

NASA Budget has some annoying numbers, but the TOTAL expenditure on NASA in 2007 dollars has been either $416 billion or $807 billion, averaging $8 or $16 billion a year, respectively. From that same article, the aerospace industry (of which NASA is the largest, not sole, member of) "contributed more than $95 billion to U.S. economic activity." As a means of comparison, according to Military budget of the United States, the military expenditure for 2010 is/will be somewhere between $880 and $1000 billion. That may be a tad disingenuous since the military is the largest portion of the budget, but Medicare/aid and Social Security aren't far behind; the point stands, though - aerospace is not a huge source of spending, and almost certainly gives back more than it takes. (I'm using NASA since it's a. the largest of it's kind, b. our articles on the US are better/easier to find info on, and c. other agencies/countries aren't looking nearly as closely as the USA is.) ~ Amory (u • t • c) 14:07, 10 June 2010 (UTC)[reply]

Indeed, the dropping of the Orion spacecraft could easily be avoided if we went without an extra stealth bomber. Not that I disagree with the project's cancellation, mind you.-RunningOnBrains^(talk) 14:49, 10 June 2010 (UTC)[reply]

Before saying that the answer is undoubtedly that we are the only intelligent life we can ever travel to, take into consideration that it was once deemed impossible for man to sustain powered flight, and that I am told many felt the same way about breaking the sound barrier. Certainly within our understanding of physics we can't travel to other planetary systems, but that's assuming that we understand everything that we can about physics. I guarantee that in two-hundred years, some of our theories will be laughed at by our descendants (assuming, of course, that we don't destroy civilization before then). Falconus^{p t c} 04:02, 10 June 2010 (UTC)[reply]

Well, of course. If the world doesn't work how we think it works, then all bets are off. Magic fairies may someday take us to fantastical lands where we never grow up, but given that we don't have any evidence of such fairies existing, we must operate as if they do not. Likewise, until the real problems of the speed-of-light limit are shown to be false, we shouldn't operate as though it is really possible. If we ignore the laws of physics as we understand them to behave, then there's no need to confine ourselves to any reasonable answer within those laws. We could just travel to far away planets by flying carpet for all that matters... --Jayron32 04:48, 10 June 2010 (UTC)[reply]

See Fermi paradox. We might start to terraform other planets in the absence of life. ~A H 1^(TCU) 01:59, 10 June 2010 (UTC)[reply]

It's of note that the prospect of hanging out with intelligent life was never the official justification for space research and exploration. There are lots of other reasons to think that exploring space is a worthwhile endeavor (to at least certain costs). --Mr.98 (talk) 02:18, 10 June 2010 (UTC)[reply]

What if is not a very good title for a qustion. Dauto (talk) 02:22, 10 June 2010 (UTC)[reply]

I changed it. Ariel. (talk) 04:02, 10 June 2010 (UTC)[reply]

What does a global recession now have to do with spending money on space faring pursuits over a time span of hundreds or thousands of years? Dismas|^(talk) 02:52, 10 June 2010 (UTC)[reply]

I'm not sure who you're asking, but there's a real chance that we may have a limited window to take certain first steps. Energy and raw material shortages could make such big science projects more and more political unfeasible. The irony would be that a more advanced space program would help solve these issues, but if the underlying technologies haven't already been explored there's a chicken-egg problem. APL (talk) 05:18, 10 June 2010 (UTC)[reply]

to reiterate what Falconus said, the nature of science is such that every scientific claim implicitly ends with the phrase "...given our current state of understanding." The scientists 50 or 100 years from now will be just as astounded by our ignorance as we are astounded by the ignorance of people who believed in alchemy and divination. I mean really: Benjamin Franklin was a very bright guy by any standards, but he would have laughed at the idea that people could get from the Americas to Europe in a matter of hours by flying through the sky in a big metal tube, higher than any bird. --Ludwigs2 07:32, 10 June 2010 (UTC)[reply]

Nitpicking, but your scales are off. 50 years ago was the start of the space age, and 100 was a few years past the airplane. If you want to compare to Ben, you gotta look to 2250. ~ Amory (u • t • c) 13:43, 10 June 2010 (UTC)[reply]

nitpciking your nitpick, but you seem to think that technology is linear, where technology seems to be a more exponential model. Googlemeister (talk) 14:36, 10 June 2010 (UTC) [reply]

Uhm I'm in a position to give an authoritative answer. Intelligent life does exist outside this solar system and there is travel between different civilizations, even over distances of millions of light years. The human civilization on Earth, however, is not regarded to be a real intelligent civilization by most of these civilizations, though. To qualify, a civilization must have developed the technology to expand itself at an exponential rate. Human civilization has yet come up with any production process that is capable of exponential growth. E.g. think of nano-tech factories that can copy themselves.

Obviously, all the civilizations that meet the criterium for being an intelligent civilization, are machine civilizations. In some of these machine civilizations, the ancesteral biological beings are kept in Zoos or Wild parks. Population control usually proceed along these lines.

Despite the inferior nature of human civilization, I find the lack of imagination in this thread about space travel strange. I mean, isn't it obvious that space travel between civilizations happens using data transfer via wideband communication channels? If you want to transfer a file to someone living far away, you don't put your computer in your backpack and travel all the way to the destination, either! Count Iblis (talk) 14:50, 10 June 2010 (UTC)[reply]

^{[citation needed]}... Nimur (talk) 15:30, 10 June 2010 (UTC) [reply]

No...but if you want to travel to Prague you don't send someone in Prague an email. ~ Amory (u • t • c) 16:01, 10 June 2010 (UTC)[reply]

When you travel to Prague what you are doing is carry your brain to Prague. If your civilization were more advanced, your brain would run on some machine and you could upload it to a compatible machine in Prague. Count Iblis (talk) 16:24, 10 June 2010 (UTC)[reply]

So then would the consequences of a blue screen of death be literal death? Googlemeister (talk) 19:06, 10 June 2010 (UTC)[reply]

It must be pointed out that when a country spends a lot of money to create and launch a space probe, the country does not just gather a big pile of taxpayer cash and launch the money at Neptune, never to be seen again. Most of the money is paid over the years to the scientists, engineers, technicians, administrators, and other staff who work on the project, whether they're government employees or private vendors. All these people then use the money to pay rent, buy food, and go to the movies. Keynesian economics claims, among other things, that government spending like this increases demand and consumption, thus boosting and not degrading the economy. Also see the Government spending article. Comet Tuttle (talk) 19:33, 10 June 2010 (UTC)[reply]

What if we discover that we're the only intelligent life that we can ever travel to? -- I think we have already more or less realized that this is true. There does not appear to be any intelligent life other than us within our solar system - and getting to even the nearest other star is close to impossible. If we don't find intelligent life within (let's say) 50 light years (and we've certainly studied those few stars pretty carefully) - there is essentially zero chance that humans will ever go there in person. We just don't live long enough and the speed of light is a harsh mistress!
Would we continue to fund extra-terrestrial expedition? -- Evidently we do! Yes!
If we are never going to get to where other life exists and (presuming) they would never be able to get to us (of an intellectual nature) then what would be the point in spending exorbitant amounts of money, given that we are in a global recession? -- You have subtly switched from asking about intelligent life - to life in general. We are spending modest amounts of money looking for non-intelligent life in our solar system - but there are good chances that that could be successful. Outside of the solar system, really, the SETI program is the only substantial effort to look for intelligent life - and that organization is run on a shoe-string. But there would be immense value to humanity just to know that we are alone - or not alone...either way would probably have a fairly profound effect on us. Even finding unintelligent life with the solar system would tell us a lot about evolution and where we come from. If we found intelligent life within a reasonable number of light years, we could communicate with them by radio or perhaps laser and exchange knowledge. That would certainly be an exciting and valuable prospect.
Is there any research into finding ETs that might have landed on Earth that might be too small for us to detect - tiny tiny aliens landing on Earth daily who might not even realise that people are people and have developed civilisation similar to their own. -- Not really. There are quite serious limits to how small something can be and still have enough brain power to be called "intelligent". Notice that our computers are coming close to the limits of "Moores' Law" and they are nothing like powerful enough to be intelligent. The volume of the human brain is likely to be close to the smallest it can be for our level of intelligence...I would be very surprised if a life-form smaller than a mouse could possibly have enough computing capacity to be intelligent. So there is really no point in looking for microscopic-but-intelligent life. However, unintelligent "aliens" could easily be here in the form of bacteria and viruses that travelled here by comet or meteor from other planets or even further afield. The "panspermia hypothesis" suggests that it's possible that all life on earth originated elsewhere in the universe - and that we're all (in a sense) "alien".

SteveBaker (talk) 00:24, 11 June 2010 (UTC)[reply]

I would point out, with regard to your point 1, that we might someday live longer. --Trovatore (talk) 00:27, 11 June 2010 (UTC)[reply]

We might - (although you'd need to be able to live for a few thousand years, cooped up in a tiny spacecraft, living on the same recycled food/water/air...that's one hell of a stretch!) but it would be wrong to conclude that SETI carry on their search in the hope that human lifespans will someday be long enough that we can travel the 100 light years it might take to get to the nearest intelligent aliens. They are doing it purely for the answer to the simple yes/no question "Is there anyone out there?" - even if they found an alien civilization via a radio message, it's very unlikely that anyone alive today would live long enough to talk to them! This is simple human curiosity - it has nothing to do with whether we might travel to meet aliens. SteveBaker (talk) 00:45, 11 June 2010 (UTC)[reply]

If we compare human colonization of other planets to human history then we are early humans stuck in a small range in africa. Eventually I think we will spread throughout the galaxy through colonization, although in small leaps of a few lightyears over a very long time, none of the colonies knowing of many others or being able ot contact many others. If a faster method of travel is ever discovered, then that will be like the beginings of current civilisation and as it is refined, exponential growth until the colonial age and now.--178.167.179.162 (talk) 22:59, 11 June 2010 (UTC)[reply]

Interesting properties of acetic acid

Hi. The chemical structure of acetic acid (CH₃COOH) appears to have the same number of each atom as the combination of methane (CH₄) and carbon dioxide (CO₂). Could lightning, for example, split the molecules should it strike vinegar and convert it into these two greenhouse gases? Could it similarly form acetic acid from the gases? Also, assuming that the acid is an aqueous solution, removing the water molecule produces C₂H₂O. Again separating H₂O would produce water and C₂, or diatomic carbon. Could a reaction between carbon and water from lightning, or even in carbonic acid, produce acetic acid (and oxygen, in the case of carbonic acid)? Could this be a useful way of obtaining vinegar by manufacturing it, or even producing hydrogen electricity by obtaining the hydrogen from the acid, or would that apply to all acids as well as water? As an aside, when metals react with strong bases such as sodium hydroxide and a thin layer of bubbles coats the metal, do the bubbles contain both hydrogen and oxygen gas? Thanks. ~A H 1^(TCU) 02:28, 10 June 2010 (UTC)[reply]

See the articles Carboxylation and Decarboxylation. The addition of carbon dioxide to methane to form acetic acid is an unsurprising reaction, as is the reverse, and these are routinely discussed in introductory organic chemistry classes and textbooks. A very similar reaction to what you describe, using electricity, is noted at Kolbe electrolysis. --Jayron32 02:50, 10 June 2010 (UTC)[reply]

Metals - just hydrogen gas in the bubbles.83.100.132.26 (talk) 15:12, 10 June 2010 (UTC)[reply]

Tiger question (not about the big striped cat)

Suppose an Allied commando team steals a Tiger tank from the Nazis and, while driving it toward the Allied lines, encounters another Tiger. Would the two Tigers be able to destroy each other, or would they end up shooting at each other without effect like the Monitor and the Merrimack? Or does it depend on their position relative to each other? (Assume that they both have identical 88mm guns and standard armor.) Thanks in advance! 67.170.215.166 (talk) 03:15, 10 June 2010 (UTC)[reply]

In Kelly's Heroes, a highly underrated movie, the point is made that the Tiger was quite weakly armored in the rear. So even if they could stand each other off face to face (which I'm not sure about), you would get an interesting situation once one passed the other. Looie496 (talk) 03:38, 10 June 2010 (UTC)[reply]

According to http://www.worldwar2aces.com/tiger-tank/ "Depending on the type of ammunition used, the Tiger's 88mm has a muzzle velocity of 930m per second and could penetrate up to 110mm of armor at a distance of 2000 meters"

According to http://www.fprado.com/armorsite/tiger1.htm the armour was 80mm at the rear, 100mm at the front at mostly nearly verticle angles, and 120mm around the gun mantle.83.100.132.26 (talk) 13:54, 10 June 2010 (UTC)[reply]

Clearly rear and side shots would work, frontal shots - don't know.. It's worth reading the whole article - thickness is one factor, quality is another - the tiger steel was rolled nickel alloy plate . it's not clear to what type of armour the penetration figures refer.83.100.132.26 (talk) 13:57, 10 June 2010 (UTC)[reply]

Even if you can not penetrate the armor in one hit, you could still cause damage. Spalling, hits to unarmored areas like tank tracks, multiple hits to one area of armor can all take a toll. Also, the above chart is done at a range of 2000 meters. If you are only 200 meters, your shot should have at least some additional power, perhaps enough to penetrate the armor anywhere on the tank. In the battle between bullet and armor, bullet almost always has the upper hand. Googlemeister (talk) 14:51, 10 June 2010 (UTC)[reply]

baking soda

why cant u eat baking soda unless its dissolved in water first. it says not to on the box, that it will cause some kind of severe stomach problem like bleeding ulcers or something. what will happen? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 03:47, 10 June 2010 (UTC)[reply]

Its probably a liability issue. Eating straight baking soda could cause problems because of the rapid release of carbon dioxide gas in your stomach, and the company needs to cover its ass by saying not to do it, so that you can't sue them if something goes awry. Baking soda certainly has medicinal uses, see Sodium_bicarbonate#Medical_uses, but the people who make boxes of baking soda are probably understandibly going to discourage you from using their product, unregulated, as a medication. --Jayron32 03:58, 10 June 2010 (UTC)[reply]

it says it fine eat use as long as u dissolve it in water first and drink it. why cant u eat it as a dry powder though? what kind of stomach problems can it cause? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 04:12, 10 June 2010 (UTC)[reply]

As a dry powder, it rapidly produces carbon dioxide gas when it comes into contact with any acid, such as the hydrochloric acid in your stomach. Even a few grams of sodium bicarbonate could produce several liters of carbon dioxide gas; this could be either uncomfortable or dangerous depending on how fast you could expel the gas relative to how fast it is produced. Basically, if you can't burp faster than the gas is produced you could do actual damage to your stomach. When dissolved in water, you are diluting the sodium bicarbonate to the point where it will produce carbon dioxide much slower, and thus is unlikely to cause a problem. --Jayron32 04:18, 10 June 2010 (UTC)[reply]

can it cause bleeding ulcers ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 04:23, 10 June 2010 (UTC)[reply]

Peptic ulcers are primarily caused by the Helicobacter pylori bacteria, so it is unlikely to cause "bleeding ulcers" under the conventional, medical definition of the term. However, if the gas pressure inside of your stomach due to the release of carbon dioxide is great enough, it could in theory cause the stomach to partially rupture, which can lead to bleeding of the stomach. So, yes, it can be accutely dangerous to consume spoonfulls of undiluted sodium bicarbonate. No, it cannot cause stomach ulcers, which are a chronic medical condition unrelated to what you eat. --Jayron32 04:30, 10 June 2010 (UTC)[reply]

I was under the impression that while most gastric ulcers contained H.p. bacteria, that it was not clear if the bacteria themselves caused the ulcer or if they just colonized it after it formed. I don't know if it has been definitively determined what precisely causes ulcers. Googlemeister (talk) 14:34, 10 June 2010 (UTC)[reply]

As mentioned in the Helicobacter pylori article (though somewhat buried) researcher Barry Marshall demonstrated that H. pylori can be the causative agent of ulcers by drinking a culture of them. Numerous subsequent studies have demonstrated that ulcers can be alleviated by treatment with antibiotics (also indicating a bacterial origin). Of course, that only shows that some ulcers are caused by H. pylori, not that all of them are. -- 174.24.195.56 (talk) 15:02, 10 June 2010 (UTC)[reply]

Most toy rockets use baking soda and vinager as a fuel to give you an idea of how dangerous consumming a spoonful of soda might be, especially on a full stomach with absolutley not room for any gas. 71.100.0.241 (talk) 12:51, 10 June 2010 (UTC)[reply]

question on cars and automated transmission...

Im a Medical Doctor so my knowledge on cars and engineering mechanics is limited so pardon me if the question is pretty infantile. however i would appreciate answers which are explanatory. question is : if we take two identical cars - say two toyota landcruisers, 6 cylinder 4 wheel drive top end model, one is manual transmission ( meaning manual gear system) and the other is automated transmission ( automatic gear change) which one would be more fuel consuming - or to put it the other way which model will consume less fuel?

most people say the automated transmission is a FUEL GUZZLER and would waste a lot of fuel but I feel in an anutomated transmission car, chances of the driver using the clutch and brakes are lesser and as a result it would actually save fuel... explain pls... —Preceding unsigned comment added by Fragrantforever (talk • contribs) 04:31, 10 June 2010 (UTC)[reply]

For the same model of car, the difference between a stickshift and an automatic transmission is small, but measurable. That is, a stickshift Hummer is unlikely to get better fuel mileage than a automatic transmission Honda Civic, but when choosing between to versions of the same model of car, the stickshift invariably gets a few better miles per gallon. See this article by Consumer Reports, which found that stickshifts got about a 2-3 mpg improvement over their automatic counterparts, and also performed better in terms of acceleration. I'll leave it to the engineers to explain why this is so, but it is undoubtedly a real effect. --Jayron32 04:41, 10 June 2010 (UTC)[reply]

Automatics are not the gas-guzzlers they once were, and the fuel efficiency of the manual depends on the driver's skill at manipulating the transmission, but in general they(automatics) are still less efficient.

It's important to note that an automatic transmission works differently than a manual one. It's not like you've got a manual transmission with a robot shifting for you, It's a different type of mechanism. So most of them do actually have less efficiency than a standard car of the same model, assuming the standard driver has a reasonable level of skill.

Nowadays, there seem to be exceptions to that once hard and fast rule, though. Check out these numbers for the 2000 RAV4 : [9][10]. If these numbers are right, then the auto is slightly more fuel efficient, especialy on the freeway. I'm not sure what causes that. APL (talk) 05:05, 10 June 2010 (UTC)[reply]

Autos always were less efficient since most of them use a torque converter instead of a clutch. This works rather like slipping the clutch all the time, and since it slips, it wastes power and therefore fuel. More modern autos can lock up the torque converter - normally in top gear - and this makes them more fuel efficient and approach the efficiency of manual transmission. My guess is that where the auto is more efficient than the manual (e.g. the RAV4 above), then this is down to the different gear ratios used - probably the auto has a higher ration "overdrive" top gear. --Phil Holmes (talk) 07:45, 10 June 2010 (UTC)[reply]

It should go without saying, but how the manual transmission vehicle is driven will also affect mileage. Consider the case of a driver travelling at constant speed. The automatic transmission will generally try to keep the vehicle in the highest reasonable gear in order to maintain the lowest engine speed and minimize fuel usage (I'm simplifying somewhat). In practice, this may mean shifting up into top (overdrive) gear even at quite moderate speeds, as long as the vehicle is not accelerating. The driver with a manual gearbox may not be quite so aggressive about upshifting (for convenience, out of absentmindedness, for fear of stalling, because they like to weave in and out of traffic and need the torque, or because they just never learned to do so). In this situation, the mileage of the automatic may well exceed that of the manual, where the manual is not being driven optimally for fuel economy. TenOfAllTrades(talk) 13:03, 10 June 2010 (UTC)[reply]

One additional factor is that a manual often (but not always) has more gears than an automatic of similar vintage. This can make it slightly more efficient also. There are even a few "automatic" transmissions these days that use the architecture of a manual, but with solenoids doing the clutching and shifting for you. These should be more efficient than a conventional automatic, but I believe right now they're found only on a few very high-end cars. Friday (talk) 14:57, 10 June 2010 (UTC)[reply]

Not anymore. The DSG is at least 6, more commonly 7 gears which is an overkill for a reasonable car with manual. As soon as the Japanese catch up ... East of Borschov (talk) 15:53, 10 June 2010 (UTC)[reply]

I'm not an engineer, but having about 20 years of observational experience I will say (for 90% of it) the difference is the number of gears. Automatics of yore had 3 (gasp!) or 4 gears, maybe one overdrive (basically a taller top gear) so when accelerating you spent a lot of time at a sub-optimal RPM. Manuals are typically always 5 well spaced gears, some 6. However; modern cars (mostly japanese and european) are making 5 or 6 speed automatic transmissions standard and on these models you are seeing the difference between the MPG rating of the manual and automatic versions almost disappear. Ultimately if you drive a modern car and if you are really soft-footed you can get a great MPG out of either kind of car. It all comes down to how much time the motor has to spend at an awkward (usually high) RPM. --144.191.148.3 (talk) 13:35, 11 June 2010 (UTC)[reply]

If you are a good driver, and you know how to shift such as to be fuel efficient you can save about 5% by driving stick - mainly because of losses through the complicated automatic transmission mechanism. If you are a terrible driver or if you simply enjoy revving the heck out of your car - then the automatic will be able to moderate that and you'll get better mileage with the automatic gearbox. However, you would be surprised at how hard it is to drive a manual gearbox in a really fuel-efficient manner...you need to keep the RPM strictly within the 1500 to 2500 range (or perhaps 2000 to 3000, depending on the type of car). I can practically guarantee, you'll notice you're going over that when accelerating in-town. To keep within that range, you'll be doing a LOT of shifting! SteveBaker (talk) 23:53, 10 June 2010 (UTC)[reply]

Thanks for all the answers...appreciated... Fragrantforever 05:10, 11 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

Sapphire Question

I had asked a question relating to Blue Sapphires earlier but this is different. To cut a long story short I finally found the Blue Sapphire I was looking for and a jeweller sold me a very expensive 5 carat sapphire set in a gold ring. Is it possible I could through some experiemnts/ tests confirm it is indeed a blue Sapphire and not any other imitation blue stone? Is it possible to check if the colour is indeed naturally deep blue or wheteher it was heat treated to take this brilliant deep blue hue colour? I have read unscruplous jewellers heat the Sapphire to increase the colour from a pale blue to a brilliant deep blue. Is it possible to check if the stone was heated to improve its colour? Though these questions might sound trivial, let me tell you I have very personal and sentimental reasons for asking - to ensure it is indeed a blue Sapphire and not any other imitation blue stone and that it is not heat treated Fragrantforever 07:22, 10 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

From what I could see on the article, it's pretty hard to tell (there is some mention of loss of "silk", making the stone more transparent). You more or less have to trust the certificate they gave you. You can try looking at it through a magnifying glass, but you would need to know what to look for. Did they give you a certificate? What does it say? Who's it from? Ariel. (talk) 08:47, 10 June 2010 (UTC)[reply]

What you do is to agree to buy the sapphire on condition that you may return it within (let's say) three days and get all of your money back. Then you go to a rival jeweller and state that you wish to sell this valuable Blue Sapphire. They will check it meticulously and tell you if it's a fake. If it is, you take it back, if it is not then you politely decline whatever money they offer you (unless it's way more than you paid for it!). SteveBaker (talk) 23:26, 10 June 2010 (UTC)[reply]

Not sure I agree with the entire thing here. If the second dealer you take it too is not 100% above board (and a significant % might not be), then he/she might try to take advantage of you by telling you that it is fake, or of low quality and will offer only a low amount, even if the sapphire is indeed high quality. Googlemeister (talk) 13:21, 11 June 2010 (UTC)[reply]

Thanks to Ariel and Steve for your replies, Steve your answer in particular is brilliant and yet a very easy solution to the vexing problem i face... yes I remember the jeweler telling us he would take the Sapphire back if I felt it wasnt lucky for me... so far its been lucky for us I guess... But I will follow your advice and take it to another jeweler telling them I wanna sell it... sounds like a brilliant suggestion... thanks for the answer. Fragrantforever 05:17, 11 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

indoor door frames

are indoor door frames made out of solid real wood or plywood. and is it a treated wood? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 10:33, 10 June 2010 (UTC)[reply]

If they are light, most likely they are just a plywood or particleboard box (hollow inside). --Chemicalinterest (talk) 11:18, 10 June 2010 (UTC)[reply]

Depends when the house was built. I've renovated a couple of Victorian houses in the UK, and the door and window frames were either pine or deal. Newer houses in the UK probably use pine. Can't say whether they're treated or not - what would they be treated with, and for what purpose? --TammyMoet (talk) 12:37, 10 June 2010 (UTC)[reply]

On that last point, I assume the reference is to pressure-treated wood or some other form of wood preservation. As far as I know this sort of thing is only done for wood to be used outdoors unpainted, where it will be exposed to weather. --Anonymous, 18:09 UTC, June 10, 2010.

The question is about frames. These need to be solid timber for strength, and the thickness will depend on the weight of the door(s). They would not normally be treated, except by being seasoned, and painted.--Shantavira|^{feed me} 12:36, 10 June 2010 (UTC)[reply]

The frame would indeed be "real" wood, though there may be multiple pieces of 2x4 or whatever to get the desired thickness. I don't think they're typically painted, though, as they're (usually?) internal - they provide the structural support and not much else). The opening of the door is also surrounded ("framed" in the everyday sense, though not the carpentry sense) by decorative material that often is painted and may be made of either natural wood or any one of the several kinds of composite wood-based products on the market. This decorative material is usually made to match either the footboards/toeboards or the door itself if it's been decorated. Standard pressure-treated lumber is not suitable for interior use because of the toxins it exudes (or at least used to; I'm not up on the latest developments). Matt Deres (talk) 18:58, 10 June 2010 (UTC)[reply]

You can see new door frames on sale in the UK at Wickes and B&Q, presumably in other countries you can see them in the equivalent DIY stores and ask what they are made of. In the UK they would be solid pine (could be FSC-certified) or MDF. In France the door frame and door are sold together (a "door set") and solid pine is common there too. Itsmejudith (talk) 22:47, 10 June 2010 (UTC)[reply]

glycemic load determination

Many people complain that while glycemic load determination methods try to address factors like particle size there are a variety of methods being used and only a relatively few foods are listed for each method. Wouldn't it be better to measure glycemic load by simply showing the rate at which a particular food is oxidized, i.e., converted to water and carbon dioxide similar to the way in which the speed of the wave front is used to determine the power of an explosive? 71.100.0.241 (talk) 12:19, 10 June 2010 (UTC)[reply]

Because particle size is related to the rate of reaction. To use your explosive analogy, one pound of gunpouder contains a fixed amount of energy. If I spread it in a thin layer in a pan, it will release the same amount of energy as when I pack it closely in a pipe. But, the rates of reaction, and the velocity of the shock wave (I doubt the pan will have a shock wave) will be different. —Preceding unsigned comment added by Hacky (talk • contribs) 17:49, 10 June 2010 (UTC)[reply]

So by the same token glycemic load is not accurate unless you state whether the ingredients were blended and liquefied or eaten whole so the method preparation has to be analyzed and stated. 71.100.13.202 (talk) 20:57, 10 June 2010 (UTC)[reply]

the best it could be?

Resolved

what about the argument that a huge company like Philip Morris has no interest in having their customers die off (perhaps accounted for as "attrition" in their sales forecasts), so insofar as they have any control over the formulation, yes, their R&D would make it as addictive as legally possible (or the most they can get away with in PR terms) but also the least lethal they can -- I mean doesn't that stand to reason? Philip Morris is a Fortune 100 company, I am sure their research department doesn't just get their additives from a tire melting plant on the theory that it is cheapest, indeed the tire melting operation could even be paying them to take the waste off their hands?

Note: I started smoking because of your health effects of smoking article, so if you want to attack me, why not go straight to that source and remove the spin, if you can - and if you can't, my theory is that it isn't spin. 92.229.12.67 (talk) 13:50, 10 June 2010 (UTC)[reply]

I'm not sure what the heck you're talking about. The article clearly states that smoking is a dangerous activity, that is likely to have many different, mostly negative, impacts on your health (Including a terrifying 1-in-5 chance of lung cancer!), and will significantly reduce your estimated life expectancy.

As for your theory, it's good as far as it goes, but there are two major strikes against it. First, unfortunately the basic operation is fundamentally dangerous. You're burning plant material, and sucking the resulting smoke into your lungs. They don't have to do anything special to cigarettes to make them dangerous, it's just that smoke itself is fundamentally bad for you. Second, most efforts to remove the dangerous components from smoke (better filters, etc) also remove the most flavorful components. In fact in some cases they might be the same components. The primary main concern of the cigarette manufacturers is to make sure that existing smokers choose their brand instead of competing brands. This makes sense. If Marlboro suddenly changed their cigarettes so that they were much safer, but had a boring taste, smokers would just smoke some other brand. Then Marlboro would go out of business, and the smokers would still destroy their lungs. APL (talk) 14:29, 10 June 2010 (UTC)[reply]

Someone who started smoking because they read an article saying it ruins your health, makes you impotent, and then it kills you. Should it have mentioned it give you bad breath and makes your toes fall off or would that have encouraged you? I think that merits the slow lingering Darwin Award. Dmcq (talk) 15:17, 10 June 2010 (UTC)[reply]

I can give you a line by line analysis of what parts, probably added by someone on Tobacco's payroll, convinced me. For starters, the article is called health effects: in English the grammatical meaning of that phrase is arrived at through association with other noun + noun phrases. What is a school bag? So, anyone who is worth six figures due to their education knows that "health effects" has a positive meaning, since health is a positive word. I can give you further analysis line-by-line, but the upshot is that the article convinced me to smoke, and is still convincing to this effect. 92.229.12.67 (talk) 15:24, 10 June 2010 (UTC)[reply]

(e/c) I think what the IP is trying to say (in a somewhat awkward manner) is that a company like Phillip Morris (or for that matter like Toyota, or BP, or Dow Chemicals) sees the deaths of clients or passers-by as a financial risk to be insured against rather than a moral dilemma. The tobacco industry is far more concerned about being asked to pay for lung cancer treatment than it is about being the cause of lung cancer, and it will continue to produce cigarettes so long as it can shift the financial burden of lawsuits and medical care (and etc) off onto the customer. which it does very effectively - why do you think the US government taxes the sale of cigarettes to apply to medical funds - which comes straight out of the consumers' pockets without affecting the corporations' bottom lines - rather than forcing the corporations to set up a medical trust - which would come out of corporate profits, and might affect shareholder interest.

According to classical macroeconomics, whether the tax is on the consumer's side or the supplier's side doesn't affect who is impacted the most -- only the elasticity of supply/demand. Unfortunately, the elasticity situation does minimal overall effect on the supplier at the expense of the consumer. (See tax incidence) John Riemann Soong (talk) 15:55, 10 June 2010 (UTC)[reply]

as to why the IP thought that our article was a good reason to start smoking... agree with the Darwin Awards suggestion, except that slow death by tobacco will allow him to live well past breeding age, and so his choice may not benefit the human genome. C'est la vie. --Ludwigs2 15:37, 10 June 2010 (UTC)[reply]

The ghoul in me says the original argument is flawed in that it supposes the current levels are substantially above what's necessary and sufficient to be likely addictive--that there really is a "therapeutic" window being exceeded. Even more ghoulish, they really do need to keep these levels as low as possible because "too much" toxin leads to too rapid a death...not living for many years of habitual smoking makes the product less profitable. DMacks (talk) 15:47, 10 June 2010 (UTC)[reply]

If you have specific concerns about an article, please discuss them on that article's talk page; the Wikipedia Reference Desk isn't really the appropriate place. Moreover, nowhere on Wikipedia is an appropriate place for soapboxing and general commentary; you can use your Facebook page or Twitter account for that. TenOfAllTrades(talk) 15:46, 10 June 2010 (UTC)[reply]

I particularly like 92.229's ham-fisted attempt at guilting us into doing ... something. Oh yes. "Because I detected some errors in your Wikipedia article, (Probably added by someone trying to introduce misinformation.) I have decided on a course of action that has very high likelihood of killing me." Very convincing narrative right there. It reminds me of the time I drove 185mph in a 35 zone because someone had used spray paint to graffiti the speed limit sign.

I'd better go turn the article into a ridiculous, cartoonish, hack-job so that someone like 92.229 doesn't start smoking because we didn't exaggerate its deadly effects enough!!!

Seriously, how old are you? Ten? APL (talk) 16:08, 10 June 2010 (UTC)[reply]

Trolls are ageless. Comet Tuttle (talk) 20:46, 10 June 2010 (UTC)[reply]

Sorry, you people are misunderstanding why I say Philip Morris research would try to reduce the impact of death as far as they can: it is because the estates of deceased don't continue to buy cigarettes on behalf of the dearly departed. I thought it would be obvious. If I have dues-paying members of my cult, and my cult is a fortune 100 company, then why would I want any of them to die? Obviously I don't. 92.229.12.67 (talk) 16:04, 10 June 2010 (UTC)[reply]

We're not stupid. We understand your point. Now understand our point : You Are Wrong. There is no way to make cigs safer while keeping them desirable. It is the smoke itself which is dangerous. They could construct a cig so that less smoke goes into your lungs, but who the heck would buy that?

It'd be like McDonalds replacing all their unhealthy food with green salad. Sure their customers would live longer, but they wouldn't have any customers! Everyone would just go to Burger King. APL (talk) 16:08, 10 June 2010 (UTC)[reply]

However, you may be interested in Cigarette filter, and Light cigarettes which are efforts to make cigarettes safer, just like you say. Filtered cigarettes seem to have caught on, but most people say that lights just don't have the flavor they're looking for.

I'm not a smoker so I couldn't say for sure.

Doesn't matter though, research has shown that the health benefits of switching to "Lights" was almost worthless. In the US they're not even allowed to describe them that way anymore. APL (talk) 16:17, 10 June 2010 (UTC)[reply]

In the US much attention was made of the government decision to allow the FDA to regulate tobacco and health claims made [11]. This [12] (subscription required) for example explains some of the problems developing 'healthier' cigarettes, for example the problem with smoking machines. Nil Einne (talk) 17:46, 10 June 2010 (UTC)[reply]

As regards APL's claim that "there is no way to make cigs safer while keeping them desirable" — that is not clear to me at all. Actually I think it may well already have been done, with e-cigarettes, which give you the nicotine without the "tar".

The current hullaballoo about them seems to be related to avoiding creating the perception that e-cigs are safe. I'm sure they're not safe. But they may very well be safer. LET ME SAY VERY CLEARLY that I am not saying they are safer — it's out of my area of expertise. But to my naive eye it appears very plausible that they might be. And if so, I think it could be a terrible mistake to try to ban them, or otherwise discourage them from the market. --Trovatore (talk) 00:35, 11 June 2010 (UTC)[reply]

Most large corporations care nothing for public health, especially not MacDonald's. ExxonMobil is another example as it promotes climate change denial. ~A H 1^(TCU) 02:54, 11 June 2010 (UTC)[reply]

By indentation, that looks like a response to me, but it doesn't appear to be responsive to anything I said. --Trovatore (talk) 02:55, 11 June 2010 (UTC)[reply]

E-cigs may or may not be safer, but they're not cigarettes. Burning some tobacco and then inhaling the smoke is pretty much the quintessential cigarette experience. What you've got here is a nicotine delivery mechanism, like a patch or a chewing gum. It's the difference between a cup of coffee and a caffeine pill!APL (talk) 03:04, 11 June 2010 (UTC)[reply]

Hmm, no, it's the difference between a cup of coffee and a hot caffeinated beverage. The e-cig still delivers something recognizably smoke-like. Or at least so I'm led to understand (I don't smoke). --Trovatore (talk) 03:10, 11 June 2010 (UTC)[reply]

I think it's more like the difference between a cup of coffee and a caffeine pill dissolved in hot water. My chain-smoking friend tried to switch to an e-cig, and said it didn't taste like a cigarette. He also had difficulty controlling the dose, and kept either not getting enough (which didn't satisfy) or getting too much at once (which left him light-headed). He switched back to cigs after a couple of weeks. 86.164.69.239 (talk) 11:36, 11 June 2010 (UTC)[reply]

Anyway, the spirit of the question was that the cigs currently on the shelf must be safe because tobacco companies don't want to kill off their customers. This is false. The tobacco companies are far more concerned about losing customers to competing brands than to the Grim Reaper. APL (talk) 14:15, 11 June 2010 (UTC)[reply]

OP here. Thank you for the clear answer, I've put a resolved tag on. For reference, the exact fallacy in my thinking had been addressed with the line "There is no way to make cigs safer while keeping them desirable. It is the smoke itself which is dangerous." So, my logic IS right, but has no applicability: yes, cigarette companies have an incentive to add a magic additive that has no affect on taste but reduces mortality. However, there doesn't (in your estimation) exist any such magic additive. I am going to reduce my smoking to 1/18th of a normal smoking level, to get to the same risk I would have if I regularly drove: I don't drive at all. 92.224.205.209 (talk) 14:22, 11 June 2010 (UTC)[reply]

nothingness

Is there a theory that states why it is impossible for nothing to exist, ether mater or energy or space? 71.100.0.241 (talk) 16:22, 10 June 2010 (UTC)[reply]

Cogito ergo sum Staecker (talk) 16:43, 10 June 2010 (UTC)[reply]

Unfortunately, that theory includes the dimension of time, which would require the thinker to live forever to be valid. 71.100.0.241 (talk) 17:10, 10 June 2010 (UTC)[reply]

I don't see any mention of time. Does existing in only a limited region of spacetime not count as existing? --Tango (talk) 17:12, 10 June 2010 (UTC)[reply]

I did not include reference to time in the question so for clarity I will include it here. 71.100.0.241 (talk) 17:21, 10 June 2010 (UTC)[reply]

There couldn't be any such theory, because any theory must start with axioms. An axiom would only be useful here if it was more basic than the fact that something exists, and what could be more basic than that? However, you might be interested in reading about the anthropic principle in relation to this. Looie496 (talk) 17:06, 10 June 2010 (UTC)[reply]

Do you mean nothing at all anywhere? ie. there being no universe? There are plenty of theories about why the universe exists, but none are really anything more than guesses. --Tango (talk) 17:12, 10 June 2010 (UTC)[reply]

Yes. 71.100.0.241 (talk) 17:17, 10 June 2010 (UTC)[reply]

If matter, energy and space did not exist, who or what could have asked the question? 87.81.230.195 (talk) 17:23, 10 June 2010 (UTC)[reply]

it never fails that when a question is asked on the Wikipedia that at least one person will respond who has not read or understood it. 71.100.0.241 (talk) 17:29, 10 June 2010 (UTC)[reply]

Perhaps, then, you could kindly elucidate ". . . ether mater . . ." for us :-). 87.81.230.195 (talk) 00:13, 11 June 2010 (UTC)[reply]

This is a philosophical question about metaphysical nihilism, not a scientific question. Scientific experiments are conducted under the assumption that observation is somehow meaningful, and it's hard to imagine observation being meaningful without at least subject to observe and an object to be observed. Paul (Stansifer) 17:47, 10 June 2010 (UTC)[reply]

You are thinking, as everyone else that because the universe exists the impossibility of nothingness can naturally be assumed. 71.100.0.241 (talk) 19:12, 10 June 2010 (UTC)[reply]

It's not an assumption, it's a fact. The universe exists, therefore the probability of the universe existing is 100%. Probability is always conditional on the information we have. Once you have definite information about something, its probability becomes 100%. --Tango (talk) 21:12, 10 June 2010 (UTC)[reply]

The fact that things exist is a very flimsy theory of the impossibility of nothingness. People remember walking in and out of the World Trade Center and some considered doing so not just theory but proof of the impossibility of nothingness in regard to the existence of the Would Trade Center. For some it continues to exist in pictures and memory but their theory of the impossibility of nothingness in regard to the Twin Towers no longer exists, especially since they were not rebuilt and most likely will not be rebuilt. 71.100.13.202 (talk) 16:46, 11 June 2010 (UTC)[reply]

Observations of the World Trade Center are proof that the WTC definitely existed at the time it was observed. Observations of the universe now are proof that the universe definitely exists now. The universe existing now and nothing existing now are mutually exclusive options, so it is also proof that there is no nothingness now. --Tango (talk) 19:15, 11 June 2010 (UTC)[reply]

It's certainly a fact that something exists. The question is, is it a necessary truth, or a contingent one? Your response doesn't address that point at all.

It's true that this is not a scientific question in a narrow sense of the word. But there isn't any philosophy refdesk, and it's closer to science than anything else. Cosmologists do worry about things not that much more concrete than this. --Trovatore (talk) 21:45, 10 June 2010 (UTC)[reply]

I wasn't making an argument for the existence of anything (though I believe things do exist -- I've seen some of them!); I was just saying that science isn't meaningful unless stuff exists. Therefore, whether anything exists is not a question science has anything to say about. Paul (Stansifer) 21:28, 10 June 2010 (UTC)[reply]

Here's how I like to think about it - take a universe where nothing exists. Now since nothing exists everywhere, the universe is completely symmetric as a sphere, thus it has a shape and consequent physical laws governing it (this is a big important consequence of Noether's Theorem). Our current scientific theory of an empty universe is instead bound by quantum mechanics. A QM universe has a dynamic equilibrium - being static and void is "more something" than being in constant turmoil as nature tries to keep any harmony from existing, this being understood a little in the Heisenberg Uncertainty Principle, where being static does not exist (you are always blurry).

So a universe in its most simple form is in utter turmoil, a churning soup of micro-energy (and in some theories, micro-wormholes). The Inflation (cosmology) scenario is that from this quantum-mechanical turmoil, there is a probability that a "metastable" state called a false vacuum appears spontaneously, with some sort of random set of physical dimensions and constants, and expands rapidly. This is the Big Bang, the beginning of our universe. SamuelRiv (talk) 17:47, 10 June 2010 (UTC)[reply]

In order for "nothing" to exist, you must have some "something" to compare it to. For example, dark is the absence of light. So "dark" is a "nothing". But suppose I claim that right now it is "foo", because of the absence of "bar". So my "foo" is a "nothing" - but actually it's not. Since "bar" does not exist, there is no absence of it called "foo". In the same way the absence of a "something" (called "nothing") can not exist without the "something". As a side note, in Jewish philosophy the very first thing God created was nothing. i.e. the concept of nothing, also called a void. Ariel. (talk) 21:09, 10 June 2010 (UTC)[reply]

This question is addressed quite well in a book called God: The Failed Hypothesis. Stenger scientifically addresses not only why there is something instead of nothing, but also the appearance of order from chaos in the universe and the issues that raises regarding apparent decrease in entropy. Vespine (talk) 23:12, 10 June 2010 (UTC)[reply]

All classical physics theory takes as axiomatic that no matter, energy or space is empty of its laws. For example, Newton's law of universal gravitation denies that even the remotest space is void of gravitational influence. Religious belief systems that predicate an omnipotent Creator must conclude that His influence pervades all that can ever be (because He wills it so). However relativistic physics provides a conception of a nothingness being that which is beyond an Event horizon. Cuddlyable3 (talk) 23:36, 10 June 2010 (UTC)[reply]

I'm not sure that is correct. For example the constancy of the speed of light still exists, even beyond the event horizon. All the various laws still exist there, there is just no information/matter there. But the "basic framework" is everywhere. Just because I am not aware of something (or even if I can not) - doesn't meant it doesn't exist. Ariel. (talk) 23:49, 10 June 2010 (UTC)[reply]

Now you're going from physics to ontology. I would disagree, for example, is the speed of light in a Gravitational singularity still equal to c? I could be mistaken but I thought that time and space formed at the big bang, so even though it might be impossible to know what was before the big bang, one theory is that there was nothing. Vespine (talk) 00:15, 11 June 2010 (UTC)[reply]

To someone falling into a singularity everything looks normal, so yes, c is the same. And anyway, changing c changes the energy content of matter (e=mc2), so you most definitely can not change c. Ariel. (talk) 00:27, 11 June 2010 (UTC)[reply]

It doesn't make sense (within our science) to talk about conditions "in" a singularity. A singularity is a point where everything breaks down - mathematically we essentially treat the point as if it doesn't exist. --Tango (talk) 00:51, 11 June 2010 (UTC)[reply]

See reality, nothing, and variable speed of light. ~A H 1^(TCU) 02:50, 11 June 2010 (UTC)[reply]

you might also check out nondualism. --Ludwigs2 04:10, 11 June 2010 (UTC)[reply]

Returning to the original question - "Can nothing exist ?" - in physics the answer is "no", because of zero-point energy; in mathematics the answer is "yes", the empty set; in philosophy the answer depends on what you mean by "nothing" and "exist" - take n philosophers and you will get n+1 answers. Gandalf61 (talk) 09:32, 11 June 2010 (UTC)[reply]

The original question is not "...can nothing exist...?" The original question is whether of not there is a theory as to the impossibility of nothingness. Quite distinct and separate questions. 71.100.13.202 (talk) 17:00, 11 June 2010 (UTC)[reply]

This is an entirely reasonable question. Until recently, there was nothing but speculation about the fate of this universe; now, its likeliest fate is that it will continue to "exist" forever, eventually reaching a state of overwhelming emptiness (lack of density), but the possibility of it one day ceasing to "exist" was still an arguable position only a few decades ago. Meanwhile, as far as we know, NOTHING EXISTED fourteen bllion years ago (though one interpretation of space-time is that it is nonsensical to refer to "time" before the big bang). The question is highly relevant in terms of (at least) cosmology (whether "nothing" is a possible state is a crucial question in regard to the pre-big-bang multiverse ... IF THERE IS ONE!). 63.17.62.133 (talk) 10:18, 11 June 2010 (UTC)[reply]

Can we have more Lay explanations for phenomena under the physics heading?

I am a poorly educated person of middling intelligence, with an interest in physics of all sort, but no head for calculus or advanced mathematics.

I would like to understand more about particle physics, but many of the explanations on Wikipedia are too complex.

I suppose what I'm asking is can we have more articles where things are explained as if to a four year old?

When I leanred about the strong, weak and electromagnetic forces, I had them explained to me using the analogy of the four forces that act on an airplane: lift, drag, thrust and weight; and this explanation, while not technically accurate, at least gave me a sense of how the forces interacted.

When I wanted to learn about magnetism, I was directed to ferrous metals, which went on and on about fermions and atomic spin and did little to explain to me what makes a metal magnetic in a practical way an unintelligent person can understand.

Thank you all for your time and I apologise if my question was inane or misplaced. AWanderingFlame (talk) 17:09, 10 June 2010 (UTC)[reply]

I don't see how that analogy to an aeroplane is at all useful. There are no connections between the two. It would be great if we could explain all these subjects to everyone, but some things are just too technical to be understood without at least some of the background knowledge. You can come up with poor analogies that trick people into thinking they understand it, but I don't really see the point of that. --Tango (talk) 17:16, 10 June 2010 (UTC)[reply]

You have a valid point, but the fact is that Wikipedia articles are written by whoever wants to write them, and explaining technical concepts in nontechnical language is the most difficult type of science writing. Whether people who can do it choose to devote their time to Wikipedia is a matter of luck. Looie496 (talk) 17:23, 10 June 2010 (UTC)[reply]

I recommend the website www.howstuffworks.com. Their mission is to provide simple but accurate explanations for all sorts of science and technology questions. (It's basically a web version of the Discovery Channel, which makes sense since they're both owned by the same media company.) --M @r ē ino 18:05, 10 June 2010 (UTC)[reply]

The question is not at all inane or misplaced; we have many, many articles that were written with a disregard for the layman. As Tango writes, it's sometimes impossible to explain sufficiently advanced topics to the layman; but I think more often it's a lack of interest on the part of the editors who are inclined to work on these articles. (It's sometimes a hard task, surely.) One suggestion I've seen on the Reference Desk here in the past is that you check the Simple English Wikipedia; here is their article on particle physics; but the objective of "Simple" is to be the encyclopedia for those with limited English-language ability, not to be the encyclopedia with simplified explanations of everything. Comet Tuttle (talk) 19:05, 10 June 2010 (UTC)[reply]

The airplane analogy is not "technically inaccurate" - it is totally and entirely wrong. It is unfortunate that somebody would use the analogy of lift and drag to describe the fundamental forces - they have only served to confuse you and provide you with incorrect information. The four fundamental forces are fundamentally different types of interactions, hence their name. See fundamental interaction. Yes, it is complicated - these things are not very intuitive. If you're looking for a qualitative introduction to the Standard Model, maybe read the overview section at Standard Model - this is much more useful than trying to understand particle physics in terms of invalid comparisons to every-day scenarios. Nimur (talk) 19:45, 10 June 2010 (UTC)[reply]

The worst are articles that are just a wall of math without a single one of the variables being defined! If you already know the material, you know what those variables are. But if you know the material you don't need the article. If you need the article you can't understand it. The articles on gauge theory were ones I noticed recently. Ariel. (talk) 21:13, 10 June 2010 (UTC)[reply]

Wikipedia has a number of introductory articles, dedicated to providing a gentle introduction to complex subjects. See WP:List of Introductory Articles. Dolphin (t) 22:55, 10 June 2010 (UTC)[reply]

It is certainly true that many of our articles on science and math subjects are written at an unnecessarily high level. I think many editors are aware of this problem and there are people actively working to improve this situation. However, some subjects (and "How do magnets work?" is certainly one of them) are simply not explicable other than by reverting to complicated explanations and math. If everything in the universe could be understood easily by the layman - then we wouldn't need physicists...and if everyone could mend broken pipes - then we wouldn't need plumbers...since pretty much everyone can write, we don't need scribes. It's just a matter of degree. SteveBaker (talk) 23:13, 10 June 2010 (UTC)[reply]

Not entirely true, maybe people who can fix pipes just don't want to be bothered with it. Just about everyone could mow their lawn, but there are still plenty of yardwork businesses. That is called the service economy. Now we just need to find someone who wants to fill the service demand for interpreting the dense science, math and engineering articles we have that are mostly equations. Googlemeister (talk) 13:14, 11 June 2010 (UTC)[reply]

I don't believe Wikipedia has any article that explains as if to a four year old, though some of the pictures might capture a child's attention. WP:NOTCENSORED implies that Wikipedia is not an encyclopedia for children. Cuddlyable3 (talk) 23:46, 10 June 2010 (UTC)[reply]

I fail to see how WP:NOTCENSORED implies that Wikipedia is not for children. It probably implies that it is not for certain kinds of Americans.

I do think that the OP has a good point though. And I think the problem is routed deeper. I believe, I could give a pretty good explanation of how magnetism works that is essentially correct as a first approximation and understandable to the OP, but I would never get it in a Wikipedia article. The problem is that my explanation is utterly unverifiable, since by necessity it would be 'wrong' in all the details. Pretty much any explanation that hinges on an analogy (like the aeroplane forces or that pretty picture of electrons orbiting an atomic nucleus) are going to be fundamentally wrong by modern understanding of physics. Is an encyclopedia simply the wrong medium for generally understandable (i.e. simplified) explanations? How do printed encyclopedias solve the problem? BTW, a good attempt at explaining science at a general audience is Bill Brysons "A short history of nearly everything". Hundreds of errors in the details, but still correct in essence and an enjoyable read.213.160.108.26 (talk) 23:42, 11 June 2010 (UTC)[reply]

Do fish get mardy?

if you poke them or something? —Preceding unsigned comment added by 86.128.193.83 (talk) 18:13, 10 June 2010 (UTC)[reply]

Assuming this is not a joke at the expense of Mr. Mardy Fish, we have a couple of articles that are sort of related. Pain in fish discusses whether fish do feel pain; one scientist is quoted as doubting that fish really feel pain in the way we do, as fish lack a neocortex. This would seem to reduce the likelihood that fish get irritable or miserable. Related is Emotion in animals, which does have a "Fish" section, though its only claims are about different fish of the same species exhibiting different "personalities" — actually, different amounts of risk taking, being "sociable", and having different eating preferences. It'll always be hard to evaluate whether animals get "mardy" because of course they can't tell us. Comet Tuttle (talk) 18:59, 10 June 2010 (UTC)[reply]

They might if you try to trawl them. Richard Avery (talk) 16:08, 11 June 2010 (UTC)[reply]

Chloroform

http://www.mangafox.com/manga/pok_mon_adventures/v32/c358/5.html

Does chloroform really work that fast? (At least, I assume that that's chloroform in the rag/handkerchief.) --75.25.103.109 (talk) 22:20, 10 June 2010 (UTC)[reply]

No it doesn't (though our chloroform article doesn't discuss the question). According to Stratmann, Linda (2003). Chloroform: The Quest for Oblivion. Sutton. ISBN 0 7509 3099 3., p.120: "The dramatic evidence of a victim was often preferred to the sober oxpertise of a medical man, who knew that up to five minutes were required to anaesthetise even a willing subject." --ColinFine (talk) 22:49, 13 June 2010 (UTC)[reply]

June 11

hollow core door

is the vanear of a hollow core door made from solid real wood or plywood or MDF ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 02:36, 11 June 2010 (UTC)[reply]

It could be real wood or it could be some sort of plastic material. There's lots of different types of construction. By definition, a veneer is usually a singly ply, so something like MDF (basically high quality particle board) wouldn't hold up, and ply wood is basically multiple veneers pasted together. But there are real wood veneers, and there are plastic veneers made to look like wood to various degrees. --Jayron32 03:06, 11 June 2010 (UTC)[reply]

its not plastic its some kind of wood. how do i tell if its MDF or plywood or solid real wood —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 03:19, 11 June 2010 (UTC)[reply]

If it's a hollow core door, it will not be "real" wood in the sense that it's a series of sliced pieces of wood in a single layer. Rather, it can be plywood, MDF or hardboard. Most flush hollow-core doors are faced with plywood with Philippine mahogany, or "lauan" as the face sheet. It will show a slight texture and grain . MDF or hardboard will be smooth and grainless, with hardboard being, well, harder and slicker. The interior of the door usually contains a cardboard homeycomb spacer. Acroterion _(talk) 03:28, 11 June 2010 (UTC)[reply]

so if it is a single ply plywood does it have formaldehyde resin on it ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 04:02, 11 June 2010 (UTC)[reply]

There are no single-ply plywoods - plywood has at least three plies. That said, it might have formaldehyde resin in it,depending on when and where it was made. Recent plywoods in North America usually don't use formaldehyde resins for interior applications. Acroterion _(talk) 13:51, 11 June 2010 (UTC)[reply]

Katla eruption VEI

Hi. If Katla were to erupt in the near future, what scale would it fit on the Volcanic Explosivity Index? Would the effect of a subglacial eruption increase its explosivity? Also, would it release more ash than Eyjafjallajokull did? Thanks. ~A H 1^(TCU) 02:43, 11 June 2010 (UTC)[reply]

It is literally 100% completely impossible to predict. Scientists have been able, for 25 years or so, to roughly predict when some volcanoes will erupt to within a few weeks, once they start showing signs of activity. However, there is no reliable way to predict the size of an eruption before it happens, especially for volcanoes which are not currently active.. We can look at the relative sizes of past eruptions, but for a completely inactive volcano, it is someone less accurate to predict than throwing darts at a board blindfolded. Indeed, recent eruptions of Katla have been so small as to be barely detectable, according to the article and its sources. --Jayron32 03:02, 11 June 2010 (UTC)[reply]

Sure they are impossible to predict with any certainty, but I think that they are 100% impossible to predict is a little strong of an argument. I'm sure a thorough geologic and seismographical study of the area could at least make some conclusions about how it would erupt (VEI potential, mode of eruption, etc.); someone correct me if I'm wrong though. -RunningOnBrains^(talk) 04:40, 11 June 2010 (UTC)[reply]

I see your motivation, as listed in the article, being that Katla is extremely active and Icelandic authorities are already preparing for a sister eruption. In that case, I'd suggest that they're preparing for something similar to, say, the 1918 eruption and other historical eruptions, which are detailed in one of the citations for the main article. See the left-hand menu for a list of further information on historical Katla eruptions. SamuelRiv (talk) 05:21, 11 June 2010 (UTC)[reply]

Energy numbers to open a black hole

I'm not a physicist by any means, so I might be completely wrong here, but I know if enough energy was collected, a black hole could be created (a lot of time travel stuff I've heard talks about this). I recall a friend of mine once said that they would at least need the energy inside the sun to achieve this sort of thing. But how much energy would you need to actually accomplish this? If I had a giant battery the size of a planet, how many watts or horse power or some other measurement would I need to fill it to do this? ?EVAUNIT^{神になった人間} 05:16, 11 June 2010 (UTC)[reply]

Hi there, this is a terrific exercise for a student. You may have heard of escape velocity, which the moon rockets had to exceed to break free of Earth's pull. There is something called the Chandrasekhar limit which determines the mass and radius of a black hole after its formation. That is, when a star explodes, if it's remaining core is way too heavy (about 3 times the mass of the sun), then it collapses into a black hole. A black hole is so dense that light cannot escape.

Now here's where we get to do real physics. In the escape velocity article, we see that the velocity is

{\sqrt {2GM/r}}

, where G is the gravitational constant (the strength of gravity in human units), and M and r are the mass and radius of the object we're escaping from.

What you want is the energy density needed to make a black hole. Density is just mass over volume, energy density is energy over volume, and in the world of outer space, we can always say E=mc^2 to tie them together. For a black hole, the "blackness" starts where light can't escape - that is, where the escape velocity = c, the speed of light, so let's rearrange the escape velocity equation to solve in terms of energy (mass*c^2):

E=rc^{4}/2G

and

e_{density}=3c^{4}/(8\pi Gr^{2})

. The energy density is just energy divided by the volume of a sphere, 4/3 pi r^3.

Almost done now. We want to create an extremely small black hole with a usable amount of energy. Note that we'd need a lot less energy density to make a big black hole, but a lot more energy itself to make it big. We want to find a nice stable point in there, and unfortunately not a whole lot of Earthly machinery can reach that point. We can create a lot of energy but it needs too much time - we can't cram it all in there. Big colliders like the LHC are able to pack energy into extremely small spaces by colliding beams of particles at each other. The energy level in the impressive-sounding TERA-electron-volt collider is actually comparable to that of a bug accidentally flying into a window, and so plugging that into the equation for energy, we see the size (radius) of the black holes they'd like to obtain: r = 10^-39 meters. So that's a wee bit impossible (see Planck length), but the nice thing about quantum mechanics is that on those scales, impossible things always have a chance of happening. Anyway, you now have the numbers to plug in to see how much energy you need and how much you need in one place at one time (density) to have a similar possibility of creating a black hole as the pride of physics, the LHC. Does it help? Probably not. Is it neato? You betcha! SamuelRiv (talk) 06:03, 11 June 2010 (UTC)[reply]

Oh, actually, I can answer your original question without going through the last steps above. Take that first equation for energy. Power is energy per time (like watts are joules-per-second), and on these scales we can make a neat little guesstimate that the speed needed to make the hole is the speed of light (makes sense), so time = radius divided by c. Therefore, we take energy over radius*c, and get

P=c^{5}/2G

, which is a constant so P = 2.5 * 10^18 W. That's 2.5 billion billion watts, or 3.3 million billion horsepower. That's a lot of horses! SamuelRiv (talk) 06:18, 11 June 2010 (UTC)[reply]

SamuelRiv, what you wrote makes little sense to me. It's well known that you get the Schwarzschild radius if you set the Newtonian escape velocity equal to c, but it makes no sense theoretically to do that, so it doesn't seem like a very good exercise. You can combine c and G to get a quantity with units of power, but the relationship to making black holes is unclear to me. (Incidentally, c⁵/2G = 1.8×10⁵² W.) The people who talked about making black holes at the LHC were assuming large extra dimensions, which would make calculations involving G meaningless in that context (and the whole thing is wildly implausible anyway).

To the original poster: I think you're confusing science fiction with reality. Realistically, we can't make black holes. Unrealistically, I suppose the energy required would be the energy of the black hole, and black holes can have any energy... -- BenRG (talk) 21:01, 11 June 2010 (UTC)[reply]

Oh come onnnn Ben, using escape velocity is a common exercise for this kind of thing and gives a back-of-the-envelope guesstimate (a word that I used right in the beginning). And... black holes can't have any energy? I mean, my GR isn't great, but there is an equivalence to how mass and energy change the metric. SamuelRiv (talk) 07:50, 12 June 2010 (UTC)[reply]

BenRG's point is that yes, there is a relationship between mass and energy, and since there is no minimum mass necessary to form a black hole than there is also no minimum requirement of energy to form a black hole.

I also second his point that your answers weren't very helpfull.

174.58.105.234 (talk) 21:47, 12 June 2010 (UTC)[reply]

The problem here is not the energy but rather how to compress matter or concentrate energy to within its Schwarzschild radius. So, if you have a 10 km diameter asteroid, then how are you going to compress it to its Schwarzschild radius of about 10^(-12) meters. The energy contained in the asteroid comes free of charge, just pick one up. Count Iblis (talk) 01:01, 13 June 2010 (UTC)[reply]

if someone is scared into not riding in automobiles OR scared into not smoking, which would improve their mortality more?

So here is a scenario where someone is both a light smoker and an regular car driver/passenger: if they could be scared, by looking at car accident OR tobacco-related illness statistics, into either TOTALLY refusing to step into a car anymore (instead living locally, riding the metro, trains, etc) OR totally quitting the light smoking, respectively, then which one would improve their mortality rate more? We are talking about the average everyman, and I don't have an answer or am not pushing an agenda: I would just like to know how the two mortality rates compare. Thank you. 92.224.207.140 (talk) 09:00, 11 June 2010 (UTC)[reply]

I did a bit of fishing around for statistics. Obviously it depends where you live, but in the USA, for instance, it seems that in 2003-2004 the death rate in car accidents was about 14.75 per 100,000 head of population [13] whereas death from smoking-related illness ran at 263 per 100,000 [14]. This is a very crude comparison and doesn't take into account, for example, deaths among passive smokers or pedestrians hit by cars, which are still a risk for those who have themselves given up car travel or smoking. However, it would appear that stopping smoking is a more dramatic risk-reduction strategy, on paper anyway. Ka renjc 11:27, 11 June 2010 (UTC)[reply]

If you stop driving in cars, you'll probably still have to get yourself to and from places. So you'll switch to riding the bus, the subway, a bike, walking, etc. All of these carry different degrees of risk. (I imagine that in an american city riding the subway is basically 100% safe, while biking can be quite dangerous, but biking is a lot safer in most European cities.) These risks would be very hard to estimate and would vary dramatically based on the specific setting. Quitting smoking doesn't involve "switching" to other risky behavior (unless you start overeating or drinking or etc). So this'll make it even more beneficial to stop smoking. Staecker (talk) 11:57, 11 June 2010 (UTC)[reply]

Your personal driving risk will also depend on the number of miles you drive, and where you are driving. Someone who drives 4 miles, once a week is going to be in a lot fewer accidents then your sterotypical rural salesman who might drive 500+ miles a week. The same thing can be said with smoking. Someone who smokes 4 packs a day is going to have a higher risk level then someone who smokes 1 cigar every night. Googlemeister (talk) 13:07, 11 June 2010 (UTC)[reply]

Infra-terrestrial species

Lets first start with what I mean by 'infra-terrestrial'

An 'infra-terrestrial' species, is :

An inteligent non human-species (although the inteligence need not be comparable) that has developed complex social patterns (such as worker specialisation. ) within it's own species and it interaction with the wider ecosystem.

Which species on earth could qualify for 'infra-terrestrial' status, or do I need to provide a better definition?

Sfan00 IMG (talk) 09:05, 11 June 2010 (UTC)[reply]

Eusociality mentions ants, bees, wasps, termites naked mole rats and Damaraland mole rats. Staecker (talk) 12:01, 11 June 2010 (UTC)[reply]

It all depends on definitions. You could include, for example, lions. They are pretty smart, they live in complex social groups (prides) and have a division of labor when it comes to hunting - which is an interaction with their wider ecosystem. Rockpocket 13:14, 11 June 2010 (UTC)[reply]

Well, it's going to depend on what you mean by "intelligent". Dolphins are probably your best bet - they are generally considered to be one of (if not the) most intelligent non-human species and they live in very complex social groups each with their own language and culture. --Tango (talk) 19:34, 11 June 2010 (UTC)[reply]

Meerkats have pretty clear specialization of roles in their 'mobs' - sentries, child-care workers, tutors, foragers, etc. SteveBaker (talk) 15:56, 12 June 2010 (UTC)[reply]

Euscociality, Thanks , I knew there must be a term for it... The question was prompted by someone asking about SETI a couple of days ago. I wondered what the 'Aliens' already on earth might be :) Sfan00 IMG (talk) 20:46, 11 June 2010 (UTC)[reply]

Gyromagnetic ratio of mesons

Hello all. Would anybody know where I can find data on gyromagnetic ratios/magnetic moments/g-factors of mesons? I find everything about nucleons, electrons and muons, but that's about where it stops. Even the Particle Data Groups is silent about it. Or is there any reason why it is not possible to measure/define this? MuDavid (talk) 09:12, 11 June 2010 (UTC)[reply]

Sentience/consciousness

Besides humans, which animals are sentient/conscious? --76.77.139.243 (talk) 12:59, 11 June 2010 (UTC)[reply]

I think this question pivots on how consciousness is defined. Bus stop (talk) 13:04, 11 June 2010 (UTC)[reply]

How do you know that humans are sentient/conscious? You know that you are, but I don't know that you are (cogito ergo sum). Would a sentient race massacre their own kind for no reason other than they are different, or pump poison into the planet that supprots them, or build weapons that could kill billions of ppl? 76.230.7.123 (talk) 13:06, 11 June 2010 (UTC)[reply]

Sentience#Animal rights and sentience and the links therein may give you some idea on the different opinions out there. Rockpocket 13:09, 11 June 2010 (UTC)[reply]

We don't have a good scientific test for Sentience. However, "Self Awareness" is usually thought to be a requirement of sentience. So you might want to check out Mirror Test, which is the best test for Self Awareness we've got. (However it is far from perfect.)

Humans, Elephants, Bottlenose dolphins, Great Apes, and possibly magpies and Orcas all pass the Mirror Test APL (talk) 14:31, 11 June 2010 (UTC)[reply]

That's mirror test. Interesting/thought-provoking aspects of this test are that human babies under about 18 months of age fail it, whereas pigeons can be trained to pass it. Gandalf61 (talk) 14:45, 11 June 2010 (UTC)[reply]

Yes that is interesting, Pigeons seem to be good at those sorts of visual processing games. I've heard of experiments where they're used to visually inspect manufactured items for quality control purposes. And they can be trained to pilot missiles at enemy ships!

I wonder if all birds can do that sort of thing, or whether it has to do with pigeons' extraordinary homing ability. APL (talk) 15:14, 11 June 2010 (UTC)[reply]

Pigeons have to be trained to pass it. The test of sentience is whether an animal can pass the mirror test without training. --76.77.139.243 (talk) 15:57, 11 June 2010 (UTC)[reply]

Of course. To prove 'self awareness' it has to be intuitive. But it's still interesting that pidgeons can be trained to pass. APL (talk) 16:00, 11 June 2010 (UTC)[reply]

Indeed. If pigeons can be trained to pass the mirror test, whereas sentience is usually assumed to be innate, then it calls into question whether the mirror test is actually testing sentience. It's like the question of whether IQ tests actually test intelligence or simply test aptitude at passing IQ tests. Gandalf61 (talk) 16:04, 11 June 2010 (UTC)[reply]

You can train most animals to do just about anything in their physical capacity, similarly to Chinese room. The test of sentience would be whether you can do the task successfully without preparation of any kind; the same is true of IQ tests and intelligence. --76.77.139.243 (talk) 16:14, 11 June 2010 (UTC)[reply]

But, in that case, are toddlers self-aware? They've spent 18 months being casually trained ("Who's that in the mirror? Can you see Daddy? And Mummy? And Billy?") until the point they start responding as we expect. Is that really intuitive? 86.164.69.239 (talk) 22:06, 11 June 2010 (UTC)[reply]

Toddlers are probably not self-aware. They fail other cognitive tests, so why not tests for self-awareness? But you seem to be asking if they grow up to be self aware. Yes, because not all human being grow up around mirrors, but adults can figure out how they work without too much trouble. Because humans have an understanding that we ourselves are a human being living in the world, just like everyone else. As opposed to, say, a dog, which might have an understanding what a dog is, but doesn't comprehend the idea of a self, so it doesn't even understand the possibility that he himself might also be a dog.

Training something to specifically pass the test is much easier. The pigeon doesn't have to understand that it is a pigeon, or that it is seeing its own reflection. You just have to teach it that if the bird in the mirror has a spot on its beak, you perform some pre-defined action. You could probably train it just as well with pre-recorded videos of a baboon. Teaching a pigeon to pass the mirror test is like teaching someone the answers to an IQ test. You haven't made them smarter, you've just increased their score on the test. APL (talk) 22:21, 11 June 2010 (UTC)[reply]

Actually... In my anthropology class, we learned that there was evidence that a dog could be aware of the fact that not only is it thinking, but the dogs/people around him are too. I don't know how to explain that concept better, but that awareness of self and others is a theory as to why humans are compelled to communicate thoughts whereas chimpanzees are not. Interestingly, wolves are not believed to be aware in the same way that a dog is. I am thinking this is relevant to the discussion, because to identify sentience of oneself would (I would think) have to be a prerequisite for identifying the sentience of others. 65.87.167.166 (talk) 00:19, 12 June 2010 (UTC)[reply]

^{[citation needed]}, What evidence? I'd be interested in knowing, I thought that the mirror test was the only widely accepted test for this sort of thing, even with its flaws. The Wikipedia article supports that view, but perhaps it's missing whatever research you're talking about? APL (talk) 04:26, 12 June 2010 (UTC)[reply]

To be clear, the Mirror test does not test sentience. It tests "Self awareness" which is a component of sentience. APL (talk) 18:29, 11 June 2010 (UTC)[reply]

It's a pretty terrible test - if it works and the animal passes the test - then it shows...something. But if an animal "fails" the test, it could just be that the animal doesn't care - or that the animal has other senses that are not fooled by the mirror. Think of this from the point of view of (say) a dog: The blurry monochrome image doesn't smell like a dog...the end. From the point of view of a shark: The blurry image doesn't emit electrical pulses from muscular activity that can be picked up from your lateral line...so it's not relevent. Those animals could easily be self-aware, but simply not care about your wildly unrealistic tests. On the other hand, I could easily write a computer program for a robot that could detect it's own reflection - measure changes between images taken on consecutive visits past the mirror and react to differences accordingly. The robot would clearly not be "self-aware" in any interesting fashion...so even a positive reaction to a test doesn't actually 'prove' anything. Since neither a positive nor a negative result actually proves anything much - the test should be treated with appropriate amounts of skepticism. SteveBaker (talk) 15:38, 12 June 2010 (UTC)[reply]

Assuming the validity of the strong AI assumption, the answer is in principle contained in the algorithm that describes the animal. Count Iblis (talk) 16:12, 12 June 2010 (UTC)[reply]

Spoof SETI

How hard would it be to spoof SETI? I mean something like putting a satellite in geostationary orbit (or approximately anyways since the SETI equipment is not at the equator) and sending extremely low power transmissions back to them? Googlemeister (talk) 13:25, 11 June 2010 (UTC)[reply]

It would be trivial to determine the origin of any transmission from an object orbiting Earth. It would be only slightly less trivial to determine the origin of any signal from within tens of light years. So no, nobody is going to spoof SETI. — Lomn 13:30, 11 June 2010 (UTC)[reply]

I should explain a little bit. Any local signals can have their origin determined by parallax. In the case of Earth-orbit signals (and probably for anything within the main solar system), two receivers on opposite sides of the Earth create sufficient parallax to determine where a signal comes from. That would take a matter of hours, at most, to determine. For large distances (up to 1500 light years, give or take) you need up to six months, allowing the diameter of Earth's orbit to serve as the baseline. The only way you could "spoof" SETI would be to recreate the Wow! signal, which didn't last long enough to allow for more than one observation -- but since there wasn't more than one observation, SETI doesn't treat that as anything approaching a positive hit. So no spoof. — Lomn 14:08, 11 June 2010 (UTC)[reply]

Also, to be clear, large radio telescopes and arrays of telescopes have a small beam—they only "see" a small part of the sky at once, just like a large optical telescope only sees a small part of the sky at once. They're not going to detect any random signal sent to them, like a transistor radio would. They have to be pointed at the transmitter. -- Coneslayer (talk) 14:21, 11 June 2010 (UTC)[reply]

As an aside, anyone who has the enormous money and means to try place a satellite and attempt to fool SETI has a whole lot of more interesting things to do with their time and treasure. Richard Avery (talk) 16:05, 11 June 2010 (UTC)[reply]

That's not as true as it once was. Some tiny satellites are theoretically within the range of a middle-class individual. They wouldn't go into geostationary orbit, though, they'd be in much less desirable low-orbit locations. (You couldn't really run a con with a geostationary satellite anyway. They're too high-profile.)

If you can fit your SETI hoax into a satellite the size of a coke can, here's a launch option that might even fit on your credit card : [15] APL (talk) 22:34, 11 June 2010 (UTC)[reply]

Yes - but let's be really clear: SETI have comprehensive procedures that allow them to easily eliminate signals coming from airplanes and spacecraft within roughly the orbital distance of the moon. Beyond that - if a believable signal came from further away, they'd need to observe it for a while to be utterly sure that it was not something within the solar system, etc. Their processes are really meticulous - you couldn't 'spoof' them - it's just not remotely reasonable. (On the other hand, those coke-can sized satellite thingies are awfully interesting.) SteveBaker (talk) 15:24, 12 June 2010 (UTC)[reply]

You could fool them for a while if you know those comprehensive procedures well enough, though. Pick a SETI listening station and find out what station they use to corroborate signals and check the parallax. Then you use two unidirectional transmitters sending the same signal, with the appropriate phase difference, from two different blimps (or similar). The difference in the locations of the blimps would (if you calculated it right) look like the parallax from a signal several light years away. It wouldn't fool them for long (they would just need to check with a third listening station, which they would do very quickly), but you would cause a bit of excitement for a few minutes. --Tango (talk) 02:25, 13 June 2010 (UTC)[reply]

For the sake of answering this question, let's lump all of SETI into one category: "radio signal analysis." (Needless to say, there are other branches of SETI, but this is the most relevant to the question). Now, as you probably know, one of the most fundamental, oldest, and simplest techniques for analyzing radio signals is to detect the range and location of the source. Give the SETI guys some credit - if they detect a signal, don't you think they will attempt to determine where it came from? There are a lot of spoofs you could play - you could, for example, throw some electronic countermeasures technology on your satellite, (like a stealth aircraft), and try to fake your position - but it's much harder than you might think. Once the signal is analyzed from two or more stations, it will become obvious that your spoof signal is being injected from here on Earth. Nimur (talk) 01:37, 12 June 2010 (UTC)[reply]

Etching on the cheap

I'm an artist and I want to experiment with etching, so today I've been rounding up some equipment. I bought some ferric chloride from an electronics shop (they use it for etching circuit boards). Finding a cheap source of suitably-sized pieces of sheet metal was difficult: my current best option is some baking trays. These are "traditional tin plate", so I presume they're the same as tin cans, i.e. made using a tinning process. My plan is to paint the tray with "ground", engrave the image, pour in the ferric chloride, and when it is beautifully etched, print off a few copies by means of ink and paper and rubbing with the back of a spoon. What I want to know is:

Am I making a stupid chemical mistake which will create a cloud of poison gas?
What's a cheap supermarket-bought substance that might work as a "liquid hard ground"?

213.122.46.177 (talk) 15:53, 11 June 2010 (UTC)[reply]

1. No poison gas - (I'm not sure if ferric chloride will etch tin - but probably will). I'm nearly 100% certain than baking trays are not tin plated though.. You can get brass or copper sheet online (prices seem to be ~5£ (8$) for a small sheet). There's probably a cheaper way of getting etchable metal sheets - maybe "copper clad board" for pcb making would be suitable - they're cheap.

2. As a guess - nail varnish , don't forget the nail varnish remover - again online you can buy the remover very cheap as acetone. Possibly other forms of varnish ( eg wood varnish/lacquer) may be suitable.87.102.13.41 (talk) 17:21, 11 June 2010 (UTC)[reply]

You'll probably like this http://www.ganoksin.com/ftp/edinburg-etch.pdf not only does it describe ferric chloride etching - but has instructions on making grounds too. Acrylic paint might also be good - you can dissolve this using methanol, or acetone, or MEK amongst other methods.87.102.13.41 (talk) 18:01, 11 June 2010 (UTC)[reply]

Windmill on a car ?

How feasible is the idea of fixing a windmill like arrangement on a car, to generate some electricity, so as to say charge up the battery a little or power up the AC ? Is the idea worth giving an experimental trial ? Rkr1991 ^{(Wanna chat?)} 16:32, 11 June 2010 (UTC)[reply]

The laws of thermodynamics say it's not practical, assuming you mean you want to use the "wind" of the air staying in place as the car moves forward to spin the windmill. The extra energy needed to overcome the drag produced by the windmill and move the extra weight would be greater than the power produce because of inefficiencies. If you mean parking your car in a windy area and doing something for a while, then coming back and folding your windmill into your trunk or something before you leave, that's a different story. 76.229.205.199 (talk) 16:37, 11 June 2010 (UTC)[reply]

(ec)It depends. Putting a small windmill up there to take advantage of the wind when the car is not moving might be useful, to keep a battery topped up or even that car cold or warm without burning fuel. But if you want to utilize the air flow generated by the cars own movement, then no, its a waste of energy. Its less efficient than directly using the car's alternator. --Stephan Schulz (talk) 16:39, 11 June 2010 (UTC)[reply]

Your windmill idea is used already by airplanes, though — see Ram air turbine — but this is to generate power if all the engines fail, not to try and boost efficiency. Comet Tuttle (talk) 16:42, 11 June 2010 (UTC)[reply]

A turbocharger essentially uses the "wind" generated by expelled exhaust gases to improve the efficiency of the car engine by generating additional compression. The turbine in a turbocharger is not functionally different than a windmill. It just sits in the exhaust path inside the car rather than in the air outside of the car. --Jayron32 19:29, 11 June 2010 (UTC)[reply]

These are often used on yachts. It may harvest energy from the wind, as I expect cars spend most of 24 hours stationary, even though it would increase the drag of the car and hence increase the amount of fuel used. 92.15.25.9 (talk) 21:18, 11 June 2010 (UTC)[reply]

I actually saw on the freeway south of San Francisco a car with what seemed to be a wind turbine attached to the roof. Later I saw several of them in a parking lot at Google's Mountain View campus. I didn't investigate further, but now I wish I had because my web searches aren't turning anything up. My immediate reaction when I saw it was "that's ridiculous", but after thinking about it some more I'm not so sure. A turbine can obviously give you a net gain when the car is parked and there's a breeze, and it's not clear to me why that would cease being true if the car was moving. The air-ground speed differential exists independently of the car's motion. -- BenRG (talk) 22:40, 11 June 2010 (UTC)[reply]

Here's a proof of concept: a purely wind-powered vehicle that can travel downwind faster than the wind. -- BenRG (talk) 23:17, 11 June 2010 (UTC)[reply]

Going faster than the wind is used on sailboats, by the way, basically by keeping constant wind at an angle to the direction of motion so that some wind is always hitting your sail on the side. SamuelRiv (talk) 07:58, 12 June 2010 (UTC)[reply]

Thanks for a fascinating link. It proves that energy can still be obtained from the wind when moving downwind faster than the windspeed, but I would question whether the small amount of energy that can be obtained in this way will significantly affect fuel consumption. I would guess that most of the extra energy would be lost in an inefficient transmission and in extra drag from the supporting structure. Has anyone done any trials? Dbfirs 08:29, 12 June 2010 (UTC)[reply]

There actually is at least one example of a vehicular power system that used the energy of the vehicle's motion to produce electricity (for lighting etc.) as a normal mode of operation. The generator was driven by the wheels, not a windmill. I'm talking about passenger train cars. Today the electricity they need is generated on the locomotive ("head end power") and a set of wires runs through the train. But the steam locomotives that trains used to use didn't have generators on them, so the cars were provided with the wheel-powered generators instead. (There were batteries that provided power when the train was stopped and recharged from the generator when it was moving again). Similarly, train heating was provided by steam from the locomotive -- if these cars were used with a diesel locomotive, the train had to carry a boiler to generate steam for heating. --Anonymous, 10:40 UTC, June 12, 2010.

Correct me if I'm wrong, but I think some of the above answers seem to be a little confused..... There is most certainly going to be a drag as the car moves forward, and with respect to the car, a breeze flowing in the opposite direction. My idea is just to use that breeze to power a battery, energy which would have been wasted otherwise. I don't see why any laws of Thermodynamics would prevent me from getting useful energy out of this, despite the inefficiencies, and I also don;t see how the situation changes when the car is still or in motion..... With respect to the car, it's just the same, right ? As an extrapolation, how would the idea work, if applied to say trains, with rows of windmills on behind another on top of the train, all generating a little electricity ? Rkr1991 ^{(Wanna chat?)} 12:06, 12 June 2010 (UTC)[reply]

The breeze you feel when you move through still air, and the force that breeze might exert on a windmill, are examples of drag. It's just another way that your car would be less aerodynamically shaped. The more sources of drag there are, the harder the engine has to work or the slower the car would move than it would otherwise...i.e., your car becomes less energy-efficient at driving. So you use more fuel to drive the same speed--there's your added energy cost. The gain is that you can get some energy out of the windmill. But you will get less energy from the windmill than you put in as extra fuel (the engine->rolling-friction->air-turbulence->windmill->generator-friction all involve losses of efficiency). DMacks (talk) 14:53, 12 June 2010 (UTC)[reply]

Rkr1991, haphazardly adding windmills to a moving vehicle is unlikely to help matters, because it will add a lot of drag. But DMacks, I don't think there's a straightforward thermodynamic argument that windmills must be a net loss, and I don't even think it's true. For one thing, if the air is moving relative to the ground then energy can be extracted from that differential by a vehicle moving at any speed in principle. And even if the air is stationary relative to the ground, I see no reason why adding windmills coupled to the drive train in some way couldn't reduce your net loss to friction. Drag doesn't add linearly. I can't even see how to prove that adding a windmill in a carefully chosen location couldn't reduce the overall drag, even if you don't recover any power from the windmill—it seems very unlikely, but not obviously impossible. In fact, wouldn't a proof along those lines be worth a million dollars? -- BenRG (talk) 21:30, 12 June 2010 (UTC)[reply]

Per "with respect to the car, a breeze flowing in the opposite direction", I assumed the air current we're talking about--the air motion that would drive the windmill on the car, relative to its frame of reference--was due to that car motion. If there's additional air motion (actual weather/wind) relative to the ground, then you could recover that just as for a stationary windmill mounted on the side of the road. DMacks (talk) 22:11, 12 June 2010 (UTC)[reply]

Protein breakdown for energy... trigger?

What's the trigger for your body starting to break down protein for energy? I know this happens with long-distance runners who have no other alternative energy source. I'm looking for an exact mechanism; I assume it's triggered by a lack of glucose being detected, but what happens on the molecular level for this process to begin? Regards, --—Cyclonenim | Chat 17:07, 11 June 2010 (UTC)[reply]

This is not an area of expertise for me, but the "Regulation" section of the gluconeogenesis article gives some information. It says that the main activators are acetyl CoA, which is produced by metabolism of fatty acids, and citrate, which is produced in the basic Krebs cycle. Of course the availability of the substrate (unused amino acids) is also important. In fact any protein you eat that your body can't use will be converted to energy, because there is no other way for the body to get rid of it that isn't harmful. Looie496 (talk) 18:33, 11 June 2010 (UTC)[reply]

Looking at this again, I realize that I didn't actually address the question -- but the answer seems to be that the causes of protein catabolism aren't all that clearly understood. The breakdown of protein in lean muscle cells apparently results mainly from the ubiquitin pathway, but that's an extremely complex process that is affected by many factors. It seems, though, that low levels of insulin in the bloodstream are one factor that upregulates it. Looie496 (talk) 21:20, 11 June 2010 (UTC)[reply]

Right Handed Dominance

So, why is it that a majority of the population is right-handed? Why are there such things as right and left hand dominance and what purpose does this serve? Is this an evolutionary trait or what? Thanks! Stripey the crab (talk) 18:57, 11 June 2010 (UTC)[reply]

There is no proof that we know the answer, but the general story is probably that there are certain brain functions (most notably language) that don't work well when both sides of the brain participate in them, probably because of the time delays involved in sending signals from one hemisphere to the other. Thus, a number of functions get segregated mainly to just one hemisphere, some to the right, others to the left. This segregation would have to be controlled by genes, and it would be hard to design a genetic scheme that would, for example, place the language system on one side but be neutral about which side it is. It happens that fine motor control of the hand is segregated to the left hemisphere in most people (which controls the right hand). I realize that this explanation is a bit hand-wavy, but I don't think it is possible to be more specific based on what we currently know. Looie496 (talk) 19:23, 11 June 2010 (UTC)[reply]

(edit conflict) There is some discussion of the issue in the article Handedness, but the actual reasons why right handedness dominates are likely arbitrary. There's probably a good reason why one hand dominates, and it arbitrarily became the right hand. It likely could have easily been the left hand (cats, IIRC, are left-paw dominant usually), but it ended up being the right. There are some sketchy connections to "divisions of labor" in the brain (i.e. the "right handed people are analytical, left handed people are artsy), but these sorts of connections are VERY tenuous and have little scientific support behind them, they are mostly bullshit. The real reason is likely just random chance chose the right to be the dominant one in most humans, and it stuck. --Jayron32 19:24, 11 June 2010 (UTC)[reply]

it is because the physical environment is predictable and not at all postmodern, artistic, and emotional. if people were raised in a pure emotional environment in which repeating the same action did not result in the same effect from the physical environment, but rather depended on its "mood", you would find children would end up left-handed. This is my original research, so as with my other reply, if the nobel committee needs to contact me you will have to reply here as I am not allowed to include my email address. 85.181.50.245 (talk) 20:32, 11 June 2010 (UTC)[reply]

A related question involves amino acids. Philosophy of chemistry#Foundations of chemistry (permanent link here) says "Left-handed amino acids and right-handed sugars are the basis of the chemistry of life." -- Wavelength (talk) 21:47, 11 June 2010 (UTC)[reply]

Note for the gullible: 85's answer above is purest bullshit and should not be treated as even vaguely science. 86.164.69.239 (talk) 22:01, 11 June 2010 (UTC)[reply]

energy harvesting is so stupid

OR without a question, with a solicitation to the Noble/Nobel Prize Committee.

The following discussion has been closed. Please do not modify it.

i think the current ways of harvesting energy are really stupid, they should just build a couple of wormholes, one to the surface of the sun, and one to someplace cold, and use the heat differential to get energy. the wormholes don't have to be very big since you are not really transferring much through it. the text above told me not to include my email address so please reply here if you need to contact me. (nobel committee). 85.181.50.245 (talk) 20:26, 11 June 2010 (UTC)[reply]

Reply to what? ---Sluzzelin talk 20:32, 11 June 2010 (UTC)[reply]

to what I've written here. They might need it more fleshed-out before they go handing out the prize, which of course I understand. 85.181.50.245 (talk) 20:33, 11 June 2010 (UTC)[reply]

Yeah, but were not secretarys for the noble prize comittee - you need this webpage http://nobelprize.org/ I know geniuses have difficulty dealing with everyday things but this is ridiculous.77.86.125.56 (talk) 20:44, 11 June 2010 (UTC)[reply]

Were not secretaries for the noble prize committee what? What were they? 92.15.25.9 (talk) 21:23, 11 June 2010 (UTC)[reply]

There's a missing apostrophe - it should read "we're not" - most people would have been able to work that out.. you're obviously not of the same mental calibre as the original poster.77.86.125.56 (talk) 21:31, 11 June 2010 (UTC)[reply]

No one knows how to build a wormhole, and there are good reasons to think that wormholes may not actually exist. If you can demonstrate a way to create wormholes, you might well get a Nobel prize, but speculating about how hypothetical wormholes might be used isn't going to get you anything. Dragons flight (talk) 20:43, 11 June 2010 (UTC)[reply]

I recommend building a working prototype, and selling the electricity back to the power company. Your profits could easily exceed the Nobel prize money, and any additional surplus could be used to buy one of those nifty Nobel medallions used. APL (talk) 22:40, 11 June 2010 (UTC)[reply]

Ant stamina

I've had the opportunity over the last few days to watch ants crawling over my kitchen counter. I notice they don't stop to rest for any reason. In fact, they never stop moving. Do they get tired the way we mammals do? Or, do they go back to the nest to sleep? Hemoroid Agastordoff (talk) 21:10, 11 June 2010 (UTC)[reply]

There seems to be very little science relating to ant sleep, but this paper (published last year) reports that fire ants do sleep, but only inside their nests, and only in short bouts. Looie496 (talk) 21:27, 11 June 2010 (UTC)[reply]

June 12

Atomic mass unit

Why are the values for 1 amu different if you use 1/12 the mass of a carbon-12 atom instead of 1/16 the mass of an oxygen-16 atom? The former has 12 nuclear particles of equal mass, and the latter has 16 nuclear particles of equal mass to each other and to the particles in a carbon-12 atom. --75.25.103.109 (talk) 00:41, 12 June 2010 (UTC)[reply]

See Binding energy#Mass deficit. The different nuclei have different binding energies, so different mass deficits. It's also worth nothing that protons and neutrons don't actually have the same mass (although it is very close). That doesn't affect your example, since they each have half protons and half neutrons, so the average mass is the same, but if you are talking about heavier nuclei (which need disproportionately more neutrons to be stable) it becomes an important factor. --Tango (talk) 00:48, 12 June 2010 (UTC)[reply]

Tornado recurrence rate

I remember reading this in a book at some point, but I have never been able to find it since. What is the recurrence rate of a tornado striking any given point in the tornado-active areas of the United States Great Plains, say in Kansas or Oklahoma? The statistic I remember reading was something on the order of once every *insert number above 500 here* years, but I have never been able to find the statistic again. The context I remember it being used in was to explain how very rare and against all odds such events as Codell, Kansas's (struck by tornadoes on May 20th of three consecutive years) or Mulhall, Oklahoma's (struck by two violent tornadoes within a 2 hour time frame) tornado events are. Ks0stm ^(T•C•G) 02:47, 12 June 2010 (UTC)[reply]

This site says "Even in tornado alley, a twister hits a given square mile only once every 700 years" but it's not well referenced. Regards, --—Cyclonenim | Chat 11:19, 12 June 2010 (UTC)[reply]

Female Survival

Ok, I know this will sound incredibly stupid, but I'm going to ask it anyway. If a woman was stranded somewhere without food or water, could she drink milk from her own breasts to survive? Or would the lack of nutrients cause the milk to lack any nutritional benefits? Could the energy and nutrients be recycled through the body< of would it be lost? If so, how quickly? Again, I know this sounds incredibly stupid, but I realize that I have been wondering about this for quite a while now. Thanks for the help, and please don't think I'm some kind of weirdo for asking this! Stripey the crab (talk) 03:10, 12 June 2010 (UTC)[reply]

Of course not! It takes energy to produce milk - and by the basic laws of thermodynamics, it must cost more energy to make than can possibly be gained by consuming it! SteveBaker (talk) 03:40, 12 June 2010 (UTC)[reply]

However, she might be advised to read up on urophagia before getting stranded.--Shantavira|^{feed me} 06:23, 12 June 2010 (UTC)[reply]

Conservation of energy 82.43.89.11 (talk) 11:24, 12 June 2010 (UTC)[reply]

Yes, she could, but the longer she lived on the less nutrional it would be until she died of starvation. You could survive a while on your own scabs, excrement, urine etc. Only a bit longer than going without food but it would prolong life nonetheless.--178.167.206.65 (talk) 13:41, 12 June 2010 (UTC)[reply]

But would there be any advantage to drinking your own milk? If you stop breast feeding, you'll soon stop lactating and I would imagine any milk left would be reabsorbed. --Tango (talk) 17:06, 12 June 2010 (UTC)[reply]

A transverse wave

Visit [16] and go to question 12. These are my answers for part a:
Frequency: 10 Hz, 10 Hz
Amplitude: 0.2m, 0.15m (or perhaps 0.14m)
Wavelength: 2m, 1m
Speed of wave: 20m/s, 10m/s

But now I'm stuck on question b. How do you do it?--220.253.96.217 (talk) 04:10, 12 June 2010 (UTC)[reply]

From your answers to part (a), you can determine that the transmitted pulse (travelling to the right on the heavy string) will have a smaller amplitude than the original pulse. I would think that the reflected pulse (travelling to the left on the light string) would have an even smaller amplitude (most of the energy will go into the transmitted pulse) but it will be travelling twice as fast as the transmitted pulse. If you take a snapshot at, say, 0.1 s after the original pulse arrives at the junction, then the transmitted pulse will have travelled 1m to the right, and the reflected pulse will have travelled 2m to the left. You are only expected to sketch the appearance of the two pulses, and part (b) is only worth 3 marks as opposed to 6 marks for the quantative answers in part (a), so you don't need to very precise. Gandalf61 (talk) 09:35, 12 June 2010 (UTC)[reply]

The answer can be found here [17] by the way, but what I want is not the answer itself, but how you work the answer out.--220.253.96.217 (talk) 11:12, 12 June 2010 (UTC)[reply]

Computer components from petrochemicals

Which computer components (if any) are made from which materials derived from petroleum? -- Wavelength (talk) 07:17, 12 June 2010 (UTC)[reply]

The Integrated circuit encapsulation, any Insulator (electrical), epoxy in the Printed circuit board, engineering plastics in the DVD drive, external parts eg keyboard keys.77.86.125.56 (talk) 08:10, 12 June 2010 (UTC)[reply]

And lest we forget all the electricity needed to build the components, and where that comes from. Regards, --—Cyclonenim | Chat 11:17, 12 June 2010 (UTC)[reply]

It is unlikely that the electricity to manufacture electronic components comes from petroleum (or even natural gas). See the charts in electricity generation. For the United States, half the energy for electricity comes from coal, natural gas is nearly a quarter, almost all of what is left is nuclear; and the remainder is a tiny sliver of renewables, bio-fuels, hydro-energy, and geothermal. A tiny (minuscule) fraction of electricity comes from petroleum. An even smaller fraction comes from solar production. Furthermore, most electronics components are manufactured overseas (specifically, China, where coal is overwhelmingly the largest source of the energy for electricity). Very little petroleum is used to provide energy during the manufacture of those electronic components. Nonetheless, petroleum is used in massive scales to transport the materials - and transportation is the single largest energy-consuming sector (if you can call it a single sector). Nimur (talk) 16:35, 12 June 2010 (UTC)[reply]

heat

my power went out today when it came back on my gas central heat only pumps out cold air not hot air. i dont have any AC. how do i fix this ? its like my thermostat isint communicating with my heater properly. —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 08:12, 12 June 2010 (UTC)[reply]

It could be several problems. It could be a defective safety on your furnace to prevent keeping the flame on when no blower is on. It could be your thermostat, but that is more unlikely with battery powered thermostats. --Chemicalinterest (talk) 10:59, 12 June 2010 (UTC)[reply]

could the power going out ruined or damaged the thermostat? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 11:34, 12 June 2010 (UTC)[reply]

and whats weird it has a space for a battery but i havent used one in years. when the power came back on the thermostat wouldent even turn on and i had to put in batteries to even make the display show up. why is that? it ran for years fine on house power. in the past when the power went out it came back on no problem. —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 11:42, 12 June 2010 (UTC)[reply]

If your system is anything like my gas-fired hot water central heating system, Alexsmith44,then if your heater is not heating the air the burners may not be lighting, which suggests that the pilot light that ignites them may be out; this pilot light usually maintains a high temperature in a thermocouple which, if not hot, prevents gas from flowing to the pilot light and the main burners in order to prevent a large escape of gas blowing up your house. (Lighting the pilot usually requires you to manually over-ride the pilot light cutoff until the thermocouple is up to temperature.) Lighting the pilot usually requires either piezolectric spark ignition (usually achieved mechanically by pushing a button) or a spark derived from a battery or the mains electrical supply.

Is your pilot light lit? If not, the power cut may have caused it to go off for safety reasons, and you need to relight it, which will require the relevant components to be in good shape and the exact procedure in your appliance manual to be followed. If you are in any doubt about any of this (for example, if you don't have the manual) then call a qualified gas appliance engineer - gas appliances are too dangerous to be tinkered with by someone who doesn't know what they're doing.

If none of this is relevant, and/or you do know what you're doing (though if so why are you asking here?) then you have my apologies, but please don't risk blowing up yourself and your building! 87.81.230.195 (talk) 18:09, 12 June 2010 (UTC)[reply]

can anyone explain why when the power came back on the thermostat wouldent even turn on and i had to put in batteries to even make the display show up.

BP gulf oil issue: Geology question

Forgive my ignorance on the matter, but I was just curious about something: the world is focusing on the oceans and shores and flora/fauna, etc etc (and rightly so). But emptying at an estimated rate of 40,000 gallons a day, what's happening to the pocket where the oil is originally coming from? At what point would the pressure/weight of the ocean collapse the oil pocket? What would be the extent of the damage this incurred, or would the "earth" not even notice (like earthquake or tsunami, etc)? – Kerαunoςcopia^◁_galaxies 10:08, 12 June 2010 (UTC)[reply]

In most cases extracting oil or gas from a reservoir has relatively minor effects, as the hydrocarbon in the rock pores is replaced by water. The thing to remember is that we're not talking about a hole in the ground filled with oil, but a rock with maybe 20% porosity. Mikenorton (talk) 10:22, 12 June 2010 (UTC)[reply]

Just to expand a little on my response above, as the oil comes out, the pressure in the reservoir will reduce, something known as depletion, and this will lead to some compaction of the reservoir unit from the pressure of the overlying rock. In some cases this has led to induced seismicity on a small-scale [18] and minor seafloor subsidence [19]. Mikenorton (talk) 13:30, 12 June 2010 (UTC)[reply]

Cats and mirrors

A follow-up to the discussion above at Wikipedia:Reference_desk/Science#Sentience.2Fconsciousness, my cat will watch me reflected in dark glass (doors, windows, all at night, reflecting the lighted interior well), and if I walk up to him quietly and kneel down, he'll watch me, then turn around and come to me. He's also waited at the door to be let out, but instead of meowing at me me, he'll watch me in the reflection, and when I arrive, look up at me again. He's obviously aware that he's the "little guy" in the reflection and I'm the taller one lol. Um, I guess my silly question would be, what does this prove? – Kerαunoςcopia^◁_galaxies 10:15, 12 June 2010 (UTC)[reply]

it proves you have an enviable amount of free time! 92.230.234.180 (talk) 10:37, 12 June 2010 (UTC)[reply]

It means animals can understand mirrors. --Chemicalinterest (talk) 10:57, 12 June 2010 (UTC)[reply]

No, it means cats (not all animals) are aware of their own reflection and potentially other things in the reflection. Cats are creatures of habit, if they see a reflection every time before the door opens, they'll associate that reflection with an opening door. They're also acutely aware of their surroundings, just because he/she looks up at you as you arrive doesn't mean they necessarily saw you in the mirror. Regards, --—Cyclonenim | Chat 11:14, 12 June 2010 (UTC)[reply]

I don't see why any part of the OP's story means that cats are aware of their own reflection. The story was entirely about identifying a reflected human shape as a human (and the assumption about awareness of "the little guy" came out of the blue). The cat doesn't react to its own reflection as it might do to a real cat on the other side of the glass, but that doesn't indicate awareness, only some basic filtering out from the cat's attention of objects that move in sync with the cat's muscle movements. (There might be a name for this, I forget - proprioception?) 213.122.19.215 (talk) 11:26, 12 June 2010 (UTC)[reply]

How does anyone know that cats are not aware of their own reflection?--178.167.206.65 (talk) 13:44, 12 June 2010 (UTC)[reply]

See Mirror test. Deor (talk) 13:51, 12 June 2010 (UTC)[reply]

The problem with the mirror test is that it is incapable of distinguishing between self-awareness (in this sense, the ability to recognize that the object in the mirror is a reflection of the self) and self-consciousness (an ability to compare the reflection against an internal self-representation to note differences). Animals who fail the mirror test (such as cats and dogs) may in fact be aware that the mirror is reflecting them, but may not recognize that the test dye that the researcher placed on them is something unusual or abnormal. clearly some animals do fail the test completely (e.g. budgerigars and beta fish, who respond to reflections with affection/aggression, the way they would when confronted with a separate creature), and clearly some few non-human animals which are capable of self-consciousness, but there's a decent-sized grey area in between. --Ludwigs2 14:29, 12 June 2010 (UTC)[reply]

Wouldn't that be easy to check by first placing the paint somewhere that the cat doesn't need a mirror to inspect? I have a difficult time imagining a cat, looking down at its own paw and not being irritated by something that a researcher did to its fur. APL (talk) 15:28, 12 June 2010 (UTC)[reply]

you'd have to be careful not to be confused by cats' normal irritation at being messed with. for instance, if you were to put a cat under anesthesia first (so it wasn't aware of the process) and dye its paw blue, I am not at all sure how much the cat would be disturbed by its newly blue paw, assuming the dye was tasteless, odorless, not irritating, etc... Clearly primates would be disturbed by such things (as demonstrated by numerous pranks played on drunk dorm-mates), but cats and dogs? remember, cats and dogs are often taken if for grooming, which can involve extensive changes in bodily appearance as fur is shaved away, but they are not generally perturbed by it. --Ludwigs2 16:35, 12 June 2010 (UTC)[reply]

Clearly it implies that the cat does not fully understand mirrors, if it's treating the reflection and the person as separate entities. But I'm not sure that it even implies that very strongly. Even if it does understand mirrors it might be treating it as a separate entity for amusement. Cat's like toys. So I'm not sure that it proves or even strongly implies anything.

Anyway, The point of the mirror test is not to check if the animal understands mirrors in general, but to check if they can recognize their own image. APL (talk) 15:28, 12 June 2010 (UTC)[reply]

It surprises me how much importance people place on mirror recognition. For a cat to recognize its reflection in a mirror is not in principle different from recognizing its own paw when it looks at it -- the fact that the light bounces off a reflective surface before reaching the eye has no philosophical significance. All animals that are capable of damaging their own bodies need robust self-recognition mechanisms to prevent that from happening, and mirror recognition is just that same process in action, as far as I can see. It raises a number of interesting practical issues, certainly, but I don't understand why it would raise philosophical issues. Looie496 (talk) 17:21, 12 June 2010 (UTC)[reply]

This brings to mind the all the times I've seen cats fail to recognize their own paws, and accidentally start washing the furniture. 213.122.16.179 (talk) 19:23, 12 June 2010 (UTC)[reply]

Breathable boots

I was watching How It Works earlier and it showed a factory making breathable, waterproof boots using Gore-Tex. The commentator said that it keeps water out whilst allowing steam/sweat to leave because these molecules "are 20 times smaller than water molecules". I call bullshit on that, water molecules and steam molecules are going to be the same size because steam IS water, with more kinetic energy and less dense. This also raises the question of why steam would need to escape. As far as I'm aware, human feet don't get hot enough to generate steam! So how does this system really work? Regards, --—Cyclonenim | Chat 11:12, 12 June 2010 (UTC)[reply]

(commentator's explanation was wrong)

Goretex (which see) allows water vapour out via the tiny holes, but doesn't allow water droplets in. As you know water droplets tend to stick together, and thus do not tend to break up - so they don't/can't break into tiny water droplets to go through the tiny holes.77.86.125.56 (talk) 11:18, 12 June 2010 (UTC)[reply]

Also, water vapour forms below 100C - eg evaporation - when you sweat the water evaporates, but your skin is not at boiling point, the difference is that air below 100C can only have a certain smaller amount of water vapour in it.77.86.125.56 (talk) 11:21, 12 June 2010 (UTC)[reply]

Boiling point is the point where the pressure of the water vapour (see vapour pressure) is the same as the ambient pressure, which allows bubbles to form and rise to the surface, allowing very rapid evaporation. The amount of water vapour that can remain in the air is related (that amount is the vapour pressure), but it isn't the key difference, since it is a gradual change. --Tango (talk) 02:15, 13 June 2010 (UTC)[reply]

I would expect that condensation on the cool inner surface of the boots from the warm vapour from your warm body is going to ruin the breathability anyway. 92.15.30.42 (talk) 11:52, 12 June 2010 (UTC)[reply]

Grass in flower beds

I've always had a problem with lots of grass growing in my flower beds. I have two situations: a) ground dug up in the early spring, annual flower seeds sown. b) perennial or biannual plants sown last year, so the ground could not be dug over - the bed looks like uncut grass with leaves in it. Is there any solution to getting rid of the grass except pulling out every grass blade one by one, a Herculean task? Thanks 92.15.30.42 (talk) 11:44, 12 June 2010 (UTC)[reply]

Not really enough detail on what the plants are to answer this, and you might be better off in some of the excellent gardening forums around on the web. Depending on the perennial plants but in general grass is not very good at pushing through wood shreddings compared to many (but not all) perennials. Strimming down the grass as much as possible and then spreading a 2in layer of bark or wood chip over everything might work. --BozMo talk 12:46, 12 June 2010 (UTC)[reply]

That would probably kill all the plants as well though. 92.15.0.254 (talk) 18:08, 12 June 2010 (UTC)[reply]

This depends on whether the grass is perennial creeping or whether it is annually seeded. If it is annually seeded then you need to get on the job at regular intervals in the spring and summer and pull it out before it seeds. If the grass is a creeping perennial type then you have a much harder problem to solve. No amount of pulling out will kill the grass in the long term because you will almost certainly leave bits of root behind which will regrow, and they will come through wood chips without a problem! For perennial grass you will either have to dig up the whole plot at some point that will not disrupt the flower display or by very carefully using a small brush to apply herbicide to the grass - of course I understand this might be totally impractical. First determine by the careful removal of a dozen or so sample grass plants if they are annual (self-contained clumps with fine roots) or perennial (attached to underground spreading roots). It may be a mixture of both types. I hope for your sake it is the former. You are not alone [20] Caesar's Daddy (talk) 14:57, 12 June 2010 (UTC)[reply]

For particularly tough grass such as (couch grass), I find that the best solution is glyphosate weedkiller applied with a paint brush so as to avoid affecting the nearby plants. This requires lots of patience, but it is very effective. Dbfirs 15:47, 12 June 2010 (UTC)[reply]

Do you think it would work if I applied the weedkiller during the winter? Thanks 92.15.0.254 (talk) 18:12, 12 June 2010 (UTC)[reply]

The plant has to actually be growing, and not dormant to be killed in this way with glyphosate, but if your winter is warm enough for continual growth it should still kill it. Graeme Bartlett (talk) 21:56, 12 June 2010 (UTC)[reply]

gear box vs belt pulley

For an 18 KW motor (~25hp), I use a 'v' belt (c type) to convert the speed from 900 to 450 rpm. An alternative is to replace this with a gear box. I believe the advantage of the gear is higher efficiency although with maintenance issues. Now without having actual data about the difference in efficiencies of the 2 and the annual/monthly maintenance cost involved with the gear box, is there any reason to prefer one over the other? The load connected to the motor is prone to slight vibrations every now and then. Thanks —Preceding unsigned comment added by 122.169.217.4 (talk) 13:06, 12 June 2010 (UTC)[reply]

Wear on the belt system is primarily on the belt - maintenence is replace the belt, compare this with maintenence on the gears (which may not even be possible - ~~once the teeth are worn that's often it.~~) - the device will be out of action for much longer.

87.102.84.163 (talk) 15:13, 12 June 2010 (UTC)[reply]

What about a chain drive?87.102.84.163 (talk) 15:19, 12 June 2010 (UTC)[reply]

Actually summarised here [21] one big factor is if slip is acceptable, and the size of those torque variations.87.102.84.163 (talk) 15:22, 12 June 2010 (UTC)[reply]

Vellus hair

In Vellus hair it is said that exceptions (for vellus hair) include the lips, the backs of the ears, etc. The back of the ears usually has a very soft down generally and a few thick strands of hair occasionally. Isn't this an error then/?--117.204.94.179 (talk) 13:28, 12 June 2010 (UTC)[reply]

Pure OR of course, but the backs of my ears lack any hair apart from a few thick strands on the edge of the helix. Mikenorton (talk) 14:54, 12 June 2010 (UTC)[reply]

The backs of my ears are hairless but those of my cat are furry. I changed the title for easier reference. Cuddlyable3 (talk) 16:45, 12 June 2010 (UTC)[reply]

Are you sure? Those hairs are usually not dark and very short and almost invisible. You can try to pick them closely between two fingertips. Maybe, they are visible when you stand against bright sunlight as coming through the door way of a bright morning.--117.204.82.21 (talk) 01:41, 13 June 2010 (UTC)[reply]

You could have some moles on the backs of the ears that produce dark hair, I suppose. --Tango (talk) 02:10, 13 June 2010 (UTC)[reply]

How to get a sponsorship

Hello,

My research paper has got selected in an international conference by IEEE http://www.icmee.org/ . I was a student of my college a month ago when i submitted that paper.Currently i have passed out.So,i could not find that how could i arrange the huge sponsorship amount.scientists at that end,Kindly help.I have just graduated in b.tech mechanical Engineering. Pardon me for asking an off topic question. Sameerdubey.sbp (talk) —Preceding undated comment added 15:23, 12 June 2010 (UTC).[reply]

Welcome to the harsh world of science. You have to find funds to do research, it seems to me the most appropriate way in your case would be to apply for a Ph.D research position... 15:51, 12 June 2010 (UTC)

You could do well to write to people who work in your field of interest. Let them know that you know about their work (from publications?) and tell of your own. Suggest that you would like to meet at the conference. Listen to and value their advice. Cuddlyable3 (talk) 16:29, 12 June 2010 (UTC)[reply]

Your question is not entirely clear. Are you asking how you might obtain funding to cover the costs of attending the conference, or funding to cover the costs of continuing your research? If you need funds to attend the conference, I would be surprised if the college you were a member of cannot give you either a small grant for this purpose, or at least advice on where to apply elsewhere for one, since your achievement must reflect well on them. If you need funds to continue your career, again your former college ought to be able to give you advice, but attending the conference, talking to more senior scientists there about your paper, and asking them for advice or directly for employment would be one strategy. 87.81.230.195 (talk) 17:45, 12 June 2010 (UTC)[reply]

The OP is probably in India, where money does not grow on trees, and the conference is in Japan, which is expensive to visit. But the reality is that if the supervisor of the project can't fund the travel, it is unlikely that anybody else will. Some academic conferences pay for travel for a certain number of students, but IEEE is more business-oriented and probably doesn't. I should also point out that IEEE conferences generally accept everything that is submitted to them, so having a submission accepted isn't a mark of prestige. Looie496 (talk) 17:53, 12 June 2010 (UTC)[reply]

Sameer, I notice that quite a number of people on the Program Committee are from India. If one of them happens to be from your own college, or from nearby, you could contact him to ask for suggestions. Looie496 (talk) 18:06, 12 June 2010 (UTC)[reply]

One thing to bear in mind is the OP didn't actually say where their university/college was located. The OP is probably from India, but whether their university/college is there wasn't stated. I initially thought the OP has been studying at the US because they said 'college' but on second thought if they were doing a B.tech in ME they may have done it at something called a college in India. Nil Einne (talk) 22:40, 12 June 2010 (UTC)[reply]

Using sea water in toilets

What are the difficulties in using sea water (directly, without desalination etc) in Flush toilets ? Barring the additional cost of plumbing and also the problem of corrosion of the taps etc (which I suppose can be solved by using plastic or other corrosion resistant materials), what prevents us from implementing this ? It would save a lot of water (approx 20 liters per flush) - WikiCheng | Talk 17:01, 12 June 2010 (UTC)[reply]

A third problem is that waste water is treated with bacteria before the water is drained to seas/rivers/whatever, and currently known efficient bacteria won't live in salty water. If you manage to bioengineer salt resistant bacteria (if you are into biotech, there's a nice project for you, go for it!), I guess you are pretty much left with the financial equation: desalinate vs. invest in duplicate pipe systems. Or triplicate: where I live we have two drain systems, one for rainwater and one for sewage; salt water sewage might require a third one, unless you want to mix your kitchen sink sweet water sewage with the salty toilet sewage. 88.112.56.9 (talk) 17:20, 12 June 2010 (UTC)[reply]

The article Head (watercraft) notes the use of sea water to flush toilets on boats. In submarines the high external water pressure makes this difficult. Cuddlyable3 (talk) 17:49, 12 June 2010 (UTC)[reply]

One could also ask why we don't use grey water in toilets. I can't say for certain, but I imagine that it's primarily the difficulty of running/maintaining the extra set of piping and storage, rather than any properties of the water itself. Fresh water is still cheap enough in most places (especially with low flow toilets) not to be worth the hassle. Also, getting the sea water to Nebraska (or even 100 km inland) would be a hassle. -- 174.24.195.56 (talk) 18:02, 12 June 2010 (UTC)[reply]

Using industrial quality water is toilets is pretty common wherever it's cheap enough to have two sets of pipes (or simply not to pipe drinking water). Physchim62 (talk) 20:21, 12 June 2010 (UTC)[reply]

They have been doing exactly that in Hong Kong for quite a while now (see Water supply in Hong Kong). But unless it's a densely populated coastal city the cost of laying and maintaining 2 sets of pipes might more than offset the cost and fresh water savings. --antilived^{T | C | G} 01:39, 13 June 2010 (UTC)[reply]

Watering plants

Is it beneficial to urinate over garden plants? Or would the salt in the urine be harmful to them? A Wikipedia article says that drinking urine in survival conditions should never be done due to its salt content, so would urine be harmful to plants too? 92.15.0.254 (talk) 18:20, 12 June 2010 (UTC)[reply]

They'd get burnt from the acid too. YOu should see what female dog urine does to lawns! --TammyMoet (talk) 19:38, 12 June 2010 (UTC)[reply]

Yes, mostly the acid. Try urinating over a test plant, if you wish. You will quite quickly (one or two weeks of regular urinating, I'd say) that the plant turns brown and dry, just as if it were dead from lack of water. However, I know from observation of urinated-over lawns that some plants, especially some species of moss, survive the urine and thrive, whereas grass is burned. Of course the moss then makes it harder for the grass to grow back. In short, unless you want a moss garden, don't. --Alþykkr (talk) 22:33, 12 June 2010 (UTC)[reply]

I would guess that the moss is still being harmed by the urine, just not as much as the grass, so benefits from the lack of grass. The benefit from there being less grass around could very easily be greater than the harm from the urine. --Tango (talk) 02:09, 13 June 2010 (UTC)[reply]

(Edit Conflict) Actually wetting plants with urine would, as already stated, probably 'burn' them, but (human) urine is a useful source of nitrogenous fertilizer for the soil; discussions of this I have heard/read in the past usually recommend storing it for a time in a (sealed) container rather than adding it 'fresh' (just keep a plastic screw-top bottle next to the toilet, and add to it as and when). Googling on "Urine gardening" returns many hits discussing the topic in detail. 87.81.230.195 (talk) 22:37, 12 June 2010 (UTC)[reply]

brushed nickel

what is brushed nickel ? and can it cause dermatitis —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 20:05, 12 June 2010 (UTC)[reply]

See Nickel#Toxicity. hydnjo (talk) 20:25, 12 June 2010 (UTC)[reply]

yes but is brushed nickel the same as reg. nickel does it have a coating —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 20:29, 12 June 2010 (UTC)[reply]

According to the WP article "Brushed metal" it is perhaps hot rolled, annealed, pickled and passivated. Of course it can be coated (as anything else) but I don't think that's what you were asking. hydnjo (talk) 20:57, 12 June 2010 (UTC)[reply]

Rechargeable Battery: voltage rebound

When a device powered by rechargeable batteries depletes the battery, it stops working because the voltage is not high enough to power it. But I've noticed that if you leave the power off for a while, the voltage of the battery rises without charging. And if you wait long enough (10 min - 1 h) and then turn the device on, the it will work again, although probably with a low battery warning. I have seen this happen in cell phones, cameras, gameboys, and any device using rechargeable AA/AAA batteries.

What causes this voltage rebound? I'm taking about the NiMH and Li ion types mainly. --Yanwen (talk) 21:29, 12 June 2010 (UTC)[reply]

This is common across all cell types and is caused by Polarisation: "An effect produced upon the plates of a voltaic battery, or the electrodes in an electrolytic cell, by the deposition upon them of the gases liberated by the action of the current. It is chiefly due to the hydrogen, and results in an increase of the resistance, and the setting up of an opposing electro-motive force, both of which tend materially to weaken the current of the battery, or that passing through the cell." The effect vanishes when the battery is allowed to rest with no current. I'm looking for a Wikipedia article on this. Do we have one? Dbfirs 21:38, 12 June 2010 (UTC)[reply]

Depolarizer ? Battery chemistry is quite a big topic - I'm suprised there isn't more here.

... also from the history of cells at "Battery and Energy Technologies" [22] "Volta's simple voltaic cell cannot operate very long because bubbles of hydrogen gas collect at the copper electrode acting as an insulator, reducing or stopping further electron flow. This blockage is called polarisation. Daniell's cell overcomes this problem by using electrolytes which are compatible with the electrodes. Thus the zinc electrode is suspended in an electrolytic solution of zinc sulphate which is contained in the porous pot (Initial designs used sulphuric acid rather than zinc sulphate). The porous pot is in turn immersed in the copper sulphate solution which is contained in a glass jar into which the copper electrode is also suspended. The Daniell cell does not produce gaseous products as a result of galvanic action and copper rather than hydrogen is deposited on the cathode. Daniell's non-polarising battery was thus able to deliver sustained, constant currents, a major improvement on the Voltaic pile." The chemistry will be different in NiMH and Li ion types, but the principle is the same. The effect becomes more noticeable as the battery becomes weaker. Wikipedia does have a short paragraph at Primary_cell#Polarization. You might also be interested in this patent application. Dbfirs 21:52, 12 June 2010 (UTC)[reply]

The situation in Lithium batteries is different due to lack of production of Hydrogen - a similar effect may be produced in Li cells by locally (near the electrode) increased concentrations of Li+ ions reducing the cell EMF - these will take time to diffuse away. Note:this is one possibility - I haven't got a full analysis of the processes in Li cells.

I think this accumulation of reacted lithium is still a form of (ie is called) polarisation. 87.102.84.163 (talk) 01:03, 13 June 2010 (UTC)[reply]

Cauterization as an emergency measure

Why is it that cauterization is never mentioned as a possible (although obviously... not optimal) way to stop heavy bleeding in an emergency ? Is it only because of practical purposes (the emergency rescuer is unlikely to have a source of heat with him or near him), or because of inefficiency/dangers ? I know cauterization is extremely painful and causes tissue damage, but in the event bleeding can't be stopped even with a tourniquet (or if the tourniquet can no longer be maintained because of risk of limb loss), would cauterization be an interesting last-resort solution ? Thanks in advance, --Alþykkr (talk) 22:28, 12 June 2010 (UTC)[reply]

Probably because it is very rarely useful. Even tourniquets often aren't taught on first aid courses these days. Direct pressure, elevation and pressure points can do the job in pretty much all circumstances where tourniquets or cauterization would help. If cauterizing wounds was useful, it wouldn't be hard to include a suitable tool (either gas powered or electric) in the bags paramedics carry, or even in first aid kits. --Tango (talk) 22:58, 12 June 2010 (UTC)[reply]

According to the 'SAS survival manual' (probably not really - but that's what it was called, though I believe it was written by an ex-SAS guy) I had as a teen, cauterization is only to be used as a last resort in a situation where no rescue is imminent, say if your plane just crashed in the Andes (or something) and someone's legs are hanging off. There was a caveat that cauterization will actually cause some people to drop dead from shock. --Kurt Shaped Box (talk) 23:07, 12 June 2010 (UTC)[reply]

An observation by a nonmedical person: Cauterizing , say an artery after some traumatic amputation smacks of 18th century naval battles. But electrocautery does seem to be used today to stop small bleeders in operations. Edison (talk) 01:31, 13 June 2010 (UTC)[reply]

Indeed, it is used for small blood vessels that you can get to precisely. They only touch the cauterizing thing to the blood vessel itself. It is very different to cauterizing a wound from the outside with a big red-hot poker. That means there is no real tissue damage, other than to the blood vessel that has been damaged by severing it anyway. --Tango (talk) 02:06, 13 June 2010 (UTC)[reply]

June 13

Flaming blood

First, is there any way that a substance could be produced which would cause a person’s blood to burst into flames? Second, if such a substance could exist, could it be contained in a pill form?--99.251.239.89 (talk) 02:52, 13 June 2010 (UTC)[reply]