Wikipedia:Reference desk/Archives/Science/2011 January 4

= January 4 =

Lines when you squint at a bright light
When I squint at a bright light, I see long lines the same colour as the light eminating in many directions from the light. Why is this?--92.251.255.15 (talk) 00:56, 4 January 2011 (UTC)
 * It's diffraction from your eyelashes. Ariel. (talk) 01:47, 4 January 2011 (UTC)
 * I do not believe that is correct.--Gr8xoz (talk) 10:42, 4 January 2011 (UTC)


 * Nevertheless, it is correct, or at least by far the most likely explanation, though I might add eyelids.--Shantavira|feed me 11:24, 4 January 2011 (UTC)

Relatively invariant.
I'm reading the appendix, entitles Physics and Perception, of David Bohm's "The Special Theory of Relativity". Bohm uses the term relatively invariant a lot, but I'm not sure what he means by it. I'll give you an excerpt of the opening paragraph: "Throughout this book we have seen that in Einstein's theory of relativity, the notions of space, time, mass, etc., are no longer regarded as representing absolutes, existing in themselves as permanent substances or entities. Rather, the whole of physics is conceived as dealing with the discovery of what is relatively invariant in the ever-changing movements that are to be observed in the world, as well as in the changes of points of view, frames of reference, perspectives, etc. that can be adopted in such observations. [...] [Einstein] was led to make the revolutionary step [...] of ceasing to regard the properties of space, time, mass, etc., as absolutes, instead treating these as invariant features of the relationships of observed sets of objects and events to frames of reference. In different frames of reference the space coordinates, time, mass, energy, etc. to be associated to specified objects and events will be different. Yet there are various sets of transformations (e.g., rotations, space displacements, Lorentz transformations) relating the many aspects of the world, as observed in any one frame to those as observed in another. And in these transformations, certain functions (such as the interval [does he mean space-time interval?] and the rest mass) represent invariant properties, the same for all frames of reference, within the set in question."

Can anyone shed some light as to what he means by relatively invariant? I can quote more of the book if needed. 65.92.7.244 (talk) 01:03, 4 January 2011 (UTC)


 * Invariant literally means not changing. Most measurements in relativity are relative i.e. they change depending on how you look at them, but the invariant ones don't change no matter how you look at them. Ariel. (talk) 01:46, 4 January 2011 (UTC)


 * What Bohm is talking about is the revolution in physics which changed what "invariant" properties were. There was a time when concepts like "distance" and "time" and "mass" were considered invariant, while concepts like "speed" and "density" were considered infinitely variable.  Einstein flips everything on its head, showing us that distance and time are relative; but even in Einstein's physics, there are certain things, like "rest mass" and "speed of light" are invariant.  Bohm's point is that there are still invariants in physics, its just that what we consider "invarieant" has changed as a result of special relativity and general relativity.  -- Jayron  32  03:47, 4 January 2011 (UTC)


 * He's talking about Lorentz covariance. In particular, scalars are Lorentz invariant, and Lorentz covariant equations are also sometimes called "invariant".  Red Act (talk) 04:18, 4 January 2011 (UTC)

How will Black & Decker get a Hydrator to work in just 4 years?
See http://backtothefuture.wikia.com/wiki/Hydrator

You see, on Back to the Future II, a 4-inch dehydrated pizza takes a few seconds to grow to 15 inches, ready to consume.

Allegedly, this Hydrator is supposed to be found in a typical kitchen in just 4 years.

What would it take to invent a real-working hydrator, and what are the prospects of making it happen by 2015? --65.64.191.135 (talk) 03:17, 4 January 2011 (UTC)


 * There's lots of food which is dehydrated and then able to rehydrated later. It normally doesn't take anything more than water to do so.  The idea that you could dehydrate and the rehydrate a food as complex as a pizza, and get the results obtained in the movie, is pretty much as realistic as the Replicator in Star Trek.  That is, it is complete bullshit invented for the movie.  Actual food dehydration and rehydration is covered in the overview article Drying (food) and links that follow from there.  -- Jayron  32  03:43, 4 January 2011 (UTC)


 * The reason is that there are one-way chemical processes which happen during dehydration, and they can't be reversed later on. A raisin soaked in water does not become a grape, for example.  Depending on the food, the rehydrated version may be recognizable, perhaps even edible, but rarely is it exactly the same as the original. StuRat (talk) 04:45, 4 January 2011 (UTC)


 * I wouldn't worry too much about Black & Decker getting it right in time. If they don't, you can always hop on your hoverboard and pick up a fresh pizza yourself. HiLo48 (talk) 07:42, 4 January 2011 (UTC)
 * Uncited nutritionists wearing white coats and horn rimmed spectacles have perfected a recipe for the super thin pizza of the future that can be delivered by Fax. Cuddlyable3 (talk) 21:31, 4 January 2011 (UTC)
 * I heard it is extremely high in fiber. Googlemeister (talk) 21:42, 4 January 2011 (UTC)

Phosphenes!!!
I have always enjoyed watching phosphenes. Except my eyes have never been able to focus on them properly. Why?

Also how can I induce them? One time I was lying down to enjoy some mondo-radical phosphene bodaciousness, dude and I was getting some pretty chill phosphenity going on and then SOMEONE decided to turn on the lights and then I turned them off and I couldn't see crap in the sea of eigengrau. What gives, bro?

ZigSaw 03:49, 4 January 2011 (UTC)
 * You can't focus on them because they aren't actually objects. They are basically stimulations of your retina due to pressure fluctuations in the Vitreous humour of the eye.  It happens behind the lens of your eye; the lens is the thing which does the focusing, so you're never going to be able to focus on it.  The article you link gives some causes of them.  -- Jayron  32  03:55, 4 January 2011 (UTC)


 * Well, Wilhelm Reich suggested an apparatus...... :) Wnt (talk) 06:43, 4 January 2011 (UTC)

Active Stealth
Other than plasma stealth are there any other technologies that can actively stealth an aircraft? ScienceApe (talk) 04:12, 4 January 2011 (UTC)


 * There is white wave technology, which is possibly used on the B-2. It sends out an exactly opposite wave to the radar hitting it, cancelling it out. I'm not sure if we have an article one it. --  T H F S W  (T · C · E) 05:47, 4 January 2011 (UTC)
 * See electronic countermeasures. Nimur (talk) 15:14, 4 January 2011 (UTC)

Number of cell in a human body -- a contradiction?
Human flora currently states: "Bacterial cells are much smaller than human cells, and there are at least ten times as many bacteria as human cells in the body (approximately 1014 versus 1013)" (the reference, Microbial Ecology of the Gastrointestinal Tract, gives those numbers), but Gut flora states: "The human body, consisting of about 100 trillion cells, carries about ten times as many microorganisms in the intestines" (references not publicly & freely viewable) , and Cell (biology) states: "Humans have about 100 trillion or 1014 cells" (unreferenced). Approximately how many eucaryotic animal cells comprise the average human body? -- 119.31.121.89 (talk) 05:41, 4 January 2011 (UTC)
 * Wolfram alpha gives 1e14, . It gives no references so I do not know how mush it should be trusted. Other sources gives figures between 1e13 and 1e14,, , non seem to be really reliable. --Gr8xoz (talk) 10:34, 4 January 2011 (UTC)


 * This is obviously a pretty difficult question to answer, but considering that the 1013 claim is referenced to a review that is more than 30 years old, I'd be inclined to say that that article is wrong. The question has been asked here before e.g. here and here and the consensus both times was that it was somewhere between 1013 versus 1014 This press release by the Nobel Prize Committee (I hope they know what they're talking about) says that there are approximately 109 cells per gram of tissue, so for someone skinny like me, that would work out as ~7x1013 which is nicely in the range (fat cells are really large and you supposedly don't grow new ones as you get fatter, so this rule won't hold if you are overweight). This based on a project at MIT says there are ~6x1013 Looking at other less reliable websites from a google of "number of cells in a human body" it looks as if the general consensus is that 1013 is definitely too low, and the lower limit is 5x1013. SmartSE (talk) 10:20, 4 January 2011 (UTC)


 * Our article on red corpuscles says that the average adult human body contains 2–3 × 1013 of them, and these should be about the easiest cells to count, so it seems likely that 1013 is too low. (The article also says that red corpuscles make up about a quarter of the cells in the body.  All in all it seems likely that 1014 is in the right neighborhood. Looie496 (talk) 19:17, 5 January 2011 (UTC)

Hammer and feather
The article Newton's law of universal gravitation states:

''Every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is directly proportional to the product of the two masses and inversely proportional to the square of the distance between the point masses''.

So, why do we say that without an atmosphere, all objects would fall at exactly the same speed towards the Earth regardless of their weight? (i.e., why do we only take into account the "Earth mass" and not "the two masses"?). Newton's law seems to imply that a hammer, being more massive than a feather, will increase ever so slightly the "product of the two masses" and so fall a tiny bit faster.

Is my reasoning wrong? Leptictidium (mt) 07:17, 4 January 2011 (UTC)


 * The force of attraction on the hammer is proportional to the mass of the hammer, but the acceleration of the hammer when allowed to fall in a vacuum is inversely proportional to its mass (Newton's 2nd Law) so the mass of the hammer cancels and the result is that a hammer, and a feather, and anything else in a vacuum at the Earth's surface, will accelerate at the same rate, namely about 9.8 m.s-2. If the hammer is not falling in a vacuum there will be resistance caused by movement relative to the air and this resistance will slow the rate of acceleration.  However, the air resistance will be a much smaller proportion of the weight of the hammer than the air resistance on a feather so the hammer will accelerate in air more rapidly than the feather.  Dolphin  ( t ) 07:28, 4 January 2011 (UTC)


 * You are not wrong, basically while the earth moves the hammer toward it, the hammer causes the earth to move toward the hammer. But the difference is so small, i.e. the earth moves so little, it's unmeasurable, so it's ignored. Also if you do actually drop a feather and a hammer at the same time, they will both cause the earth to move, so they will both hit at the same time. What I mean is that the hammer does not fall faster because it's heavier, rather the hammer causes the earth to move, which makes the distance slightly shorter. Ariel. (talk) 07:29, 4 January 2011 (UTC)


 * You are wrong in using the phrase "ever so slightly". We do take into account the two masses.  The force of gravity on the hammer is thousands of times the force of gravity on the feather, but then, so is its mass (in the same proportion), so the acceleration is the same. (as explained by Dolphin.  I'm still thinking about Ariel's moving earth - what happens if the "earth" is just twice the mass of the "hammer"?    D b f i r s   08:28, 4 January 2011 (UTC)


 * Db, when you say that "ever so slightly" is wrong, you are missing Ariel's point.


 * Sorry, yes, I was replying to Leptictidium about the forces and the incorrect reasoning, and didn't have time to think through Ariel's reply. Perhaps Leptictidium was implicitly considering the movement of the earth in the question, but I didn't read it that way.    D b f i r s   21:55, 4 January 2011 (UTC)


 * Let's do this algebraically. Say the earth has mass M, the hammer mass H, and the feather mass F.  Then the hammer feels a force GMH/r², and by Newton's Second Law it accelerates at (GMH/r²)/H, which is GM/r².  Similarly the feather accelerates at (GMF/r²)/F, which is again GM/r².  They both accelerate at the same rate (if there is no air friction).
 * But the Earth also feels a force of GMH/r² for the hammer and GMF/r² for the feather. Therefore it will accelerate toward the hammer at (GMH/r²)/M, which is GH/r², and toward the feather at (GMF/r²)/M, which is GF/r².  Since M is hugely greater than H or F, these numbers are ever so tiny in comparison with the hammer or the feather's acceleration of GM/r².  But they are not quite zero.  As Ariel says, the hammer (dropped on its own) will hit the Earth ever so slightly sooner than the feather (dropped on its own), because the Earth will come up to meet it ever so slightly faster.  For all practical purposes this can be ignored, so we usually do ignore it.  By the way, r is also changing ever so slightly while the object is falling; this too can be ignored for practical purposes, and it doesn't affect the conclusion in any case.  --Anonymous, 11:12 UTC, January 4, 2010.
 * Oh, good. I was worried there for a moment that all objects everywhere might be attracted together at the rate of a falling hammer, which would have got uncomfortable quickly. 81.131.22.240 (talk) 11:20, 4 January 2011 (UTC)
 * So, even if there is a tiny, insignificant difference, there is some difference? Leptictidium (mt) 13:56, 4 January 2011 (UTC)
 * Yes, there is a tiny, almost insignificant difference. Not because the hammer accelerates faster (it doesn't), but because the Earth accelerates faster. &mdash; Sam 63.138.152.135 (talk) 14:34, 4 January 2011 (UTC)
 * The Earth falls as quickly toward a pound of hammer as a pound of feathers. And vice versa.  A pound of feathers is bigger, and could experience more tidal force in free fall, but overall a spherical object of any size, whether made up of hammer or feathers, acts like all its mass is concentrated in its center in a uniform gravitational field.  Now of course the Earth's gravitational field is not uniform, and I think this leads to a slight difference on this basis.  For example, a pound of feathers of the spotted astrasphinx consumes a volume a light year in diameter; when such a ball just grazes the Earth's upper atmosphere, a small region of it undergoes a noticeable gravitational attraction - I think this will contribute more force than is experienced by a pound of hammer half a light year from the Earth, though I'm not sure. Wnt (talk) 14:41, 4 January 2011 (UTC)
 * Fearsome though the astrasphinx is, the OP isn't asking about a pound of feathers, but about two objects of different mass ("a hammer, being more massive than a feather...") 213.122.31.229 (talk) 16:07, 4 January 2011 (UTC)
 * Aha! but if you used a pound of gold against a pound of hammers, the earth would accelerate more from the hammers then the gold. Googlemeister (talk) 17:02, 4 January 2011 (UTC)
 * The usual conditions for the thought experiment on this are to have the hammer and feather dropped simultaneously side by side in vacuum. Under those circumstances both hammer and feather will hit at the same time, even after taking account of the immeasurably small movement of the earth due to the combined mass of hammer and feather.  Sp in ni  ng  Spark  14:55, 4 January 2011 (UTC)
 * The thought experiment implicitly takes place in the reference frame that keeps Earth stationary. In any other non-privileged (equally valid) reference frame, Earth and the hammer accelerate towards each other at 9.8... m/s2.  But for the purposes of practicality, we consider that specially constructed reference frame that is centered at Earth.  In this frame, all objects accelerate toward Earth; and because dependence of the gravitational force on the other object's mass cancels out the "F = ma" in the object's acceleration, (in other words, the gravitational mass and the inertial mass of the test-particle (hammer or feather) are always exactly identical).  Acceleration is equal to F/m, which is proportional to mgravitational/minertial, which is exactly one; therefore gravitational acceleration is a constant for all test particles (hammers, feathers, the Sun, and so on), when viewed from the stationary, inertial reference frame of Earth. This exact equality between inertial mass and gravitational mass is one of the interesting observations that led to Einstein's understanding of gravitation in nonprivileged reference frames.  Nimur (talk) 15:08, 4 January 2011 (UTC)
 * Nimur, what you wrote isn't accurate (assuming you are still comparing a heavy hammer and light feathers). The earth and the objects do not accelerate toward each other at the same rate - the hammer accelerates faster, and it doesn't matter which reference frame you use. If you use one centered on the earth, then the motion of the earth toward the hammer is not felt by you, but it makes it appear that the hammer is accelerating faster toward you. If you use one external to both, then you see the earth accelerating toward the hammer, and it does that faster than toward light feathers. So the net acceleration between them is higher. Ariel. (talk) 21:11, 4 January 2011 (UTC)
 * I don't agree. The gravity constant g, as observed near Earth, is the same for all objects, irrespective of their mass.  This is a basic tenet of gravitation.  In other words, the hammer and the feather both accelerate toward Earth at the same rate.  The weight force depends on the mass of the test-particle; and the acceleration of the test-particle is inversely proportional to the same mass, so the acceleration is a constant for all objects.  Nimur (talk) 22:05, 4 January 2011 (UTC)
 * You are ignoring the fact that the earth is simultaneously accelerating and moving toward the hammer. So if you measure acceleration by simply checking the distance between the object the acceleration is higher for heavier objects. Ariel. (talk) 22:12, 4 January 2011 (UTC)
 * So the correct answer to the question is that the apparent acceleration of gravity, in the obvious reference frame of the ground under your feet, is not constant, but varies "ever so slightly" with mass, not because of the "product of masses", but because it depends on the sum of masses: g = G(M+m)/R2   D b f i r s   22:42, 4 January 2011 (UTC)

Let me re-read reduced mass, mess with some equations on paper, and get back. You may be correct. In any case, we all agree that the practical difference in accelerations between hammer and feather is minuscule, if not identically zero. Nimur (talk) 22:57, 4 January 2011 (UTC)
 * Ok, my maths is pretty weak but I'll give it a crack. The force of gravity acting on a 1kg hammer is about 10 newtons, acting on a 1g feather is 0.01 newtons. The earth rounded up is 6 x 10^24 kg. Since F=MA ;the earth will accelerate A = 10/10^24 = 1x10^-23 meters per second towards the hammer and 1x10^-26 towards the feather.  Rounding to orders of magnitude, the diameter of an atom is in the order of 1x10^-10, an electron is about 1x10^-15, so it's much less then that, but a Planck length is 1x10^-35 so the earth would definitely move a non zero amount. I have possibly made a fundamental error in working this out.  Vespine (talk) 00:03, 5 January 2011 (UTC)

The most relevant response of the Earth is not via the center of mass motion of the whole Earth. The Earth, obviously, won't react as a rigid body when the masses are released. If you imagine standing on the Earth inside a vacuum chamber and holding a mass, then your feet are depressing the surface a bit. If the mass is released, there is a sudden rebound of the surface. This generates a shock wave that travels through the Earth. The moment the object hits the surface, another shockwave is generated. The surface waves of that first shockwave will cause the mass to hit the ground later or sooner than computed without taking the response of the Earth into account. This effect is many orders of magnitude larger than the center of mass motion of the Earth. Count Iblis (talk) 01:33, 5 January 2011 (UTC)
 * lol, of course, unless you've only done high school physics and everything is still perfectly smooth, rigid and frictionless. *facepalm.. ;) Vespine (talk) 05:38, 5 January 2011 (UTC)
 * Ok, hang on! I've just had another thought, perhaps to redeem myself: If that hammer originally came from the ground, and was lifted up to whatever height and then dropped, wouldn't the sum of all the vectors just cancel out to zero anyway? No net effect? Vespine (talk) 05:46, 5 January 2011 (UTC)


 * Look, you guys have completely obfuscated the real answer here for the OP. The reason that the hammer and the feather fall at the same rate (at least, within the range of human perception) is because the earth is SO FREAKING HUGE compared to the difference in mass between the hammer and the feather that we cannot detect the difference between the rate that they fall.  It's a problem of significant figures more than anything else; there is a real calculatable difference, it is just insignificant on any standard measuring device, so we ignore it.  If you take the other extreme, and look at two hammers in space and two feathers in space, and look at the acceleration at which the two hammers will be pulled together, it will be much greater than the two feathers.  But you only notice that difference because of the similarity in mass between the objects.  Once you start working on differences of 1024 in mass, it becomes silly.  Does anyone here have a stopwatch accurate to 24 digits?  I thought not... -- Jayron  32  05:49, 5 January 2011 (UTC)
 * Don't forget to account for the mass both objects lose in potential energy at E=mc2 on their way down! --Sean 16:15, 5 January 2011 (UTC)

Spring
can spring be considered as a link.what kind of link. rigid,etc? —Preceding unsigned comment added by 59.93.130.219 (talk) 07:32, 4 January 2011 (UTC)
 * A carabiner with a spring gate is sometimes called a spring link.  Sp in ni ng  Spark  12:15, 4 January 2011 (UTC)


 * The question isn't about chain-type links, it's about links in a linkage. So far as I know, springs are modeled as forces rather than links.  In any case, they wouldn't be a ridid link, as that's sort of the opposite of a spring. Andrew Jameson (talk) 16:57, 4 January 2011 (UTC)

there are three kinds of links ..rigid.fluid and flexible link(belt,rope).it seems springs can also transfer motion in one direction only.. can it be a flexible link —Preceding unsigned comment added by 59.93.130.68 (talk) 17:27, 4 January 2011 (UTC)


 * Not necessarily - a compression spring can transfer in all directions. An expansion spring is flexible in one direction, but rigid in the other. Ariel. (talk) 21:28, 4 January 2011 (UTC)

The Importance of Science
What is the importance of science??--Marcella Shine Michael (talk) 13:10, 4 January 2011 (UTC)♥


 * I gave your question a heading (hope I did it right). 213.122.31.229 (talk) 14:29, 4 January 2011 (UTC)


 * (ec) Science is important because it provides us with a way of understanding how things work. Matt Deres (talk) 14:31, 4 January 2011 (UTC)


 * Science is the antithesis of ignorance. -- &oelig; &trade; 15:04, 4 January 2011 (UTC)


 * It's something to do with "the grain in the stone" and "the hidden structure", according to The Ascent of Man. 213.122.31.229 (talk) 15:29, 4 January 2011 (UTC)


 * If you lean toward Primitivism and yearn for the Golden Age, then science does not have much value. If you use a computer and think it valuable for finding answers to questions, thank science. SemanticMantis (talk) 15:38, 4 January 2011 (UTC)


 * Science provides us with continually improving explanations of how stuff works. It allows the human race to better adapt to its environment, which is one of humanity's strongest traits. HiLo48 (talk) 17:43, 4 January 2011 (UTC)


 * Agreed. It prevents us from moving backwards, into believing incorrect things, as happened when much of the science of the Greeks and Romans was lost in the Middle Ages, due to rise of organized religion and suppression of science. StuRat (talk) 18:20, 4 January 2011 (UTC)

Breathing underwater
Why can't our lungs extract oxygen from water like gills can? If the lungs were filled with water, naturally the body would die from lack of oxygen, but would they be able to extract any oxygen into the blood at all? How close are the structures to something that could function as gills -- given several million years in a water-filled Earth, could we evolve the ability to breathe underwater with just a few dozen mutations? &mdash; Sam 67.186.134.236 (talk) 13:13, 4 January 2011 (UTC)


 * I looked at Artificial_gills_(human), which links to this: Why don't people have gills?. The mutation to breathing water would require us to either develop very large gills, or else to need less oxygen somehow. This doesn't really answer the main thrust of your question, the matter of whether lungs would function as gills if we had the lower oxygen requirements of a fish. 213.122.31.229 (talk) 13:51, 4 January 2011 (UTC)


 * Lungs encounter some problems with trying to breathe liquids, even ones that are highly oxygenated. See liquid breathing.  Googlemeister (talk) 14:14, 4 January 2011 (UTC)


 * Bit more information at Drowning, where it says that fresh water in the lungs is absorbed into the blood by osmosis and leads to bursting of the red blood cells. So if we're going to become fish, looks like the best option is to be salt water fish. 213.122.31.229 (talk) 14:21, 4 January 2011 (UTC)


 * What about Amniotic fluid? I've always wondered how it is that a fully-formed fetus can 'breathe' liquid one minute, be born, then breathe air as an infant the very next minute. -- &oelig; &trade; 16:01, 4 January 2011 (UTC)


 * The fetus does not oxygenate blood via amniotic fluid. Oxygen is transferred from the mother's blood to the fetus via the placenta.  One thing that makes this possible is that fetal hemoglobin holds on to oxygen more strongly than adult hemoglobin and can therefore extract the oxygen that diffuses into the mother's bloodstream.  The rather instantaneous change from being dependent on the maternal circulation to requiring lungs for oxygenation is indeed spectacular, and it involves closure of the ductus arteriosus shortly after birth.  During fetal development, breathing of amniotic fluid plays an important role in lung maturation; see pulmonary hypoplasia for a discussion of how lack of amniotic fluid can cause problems during development. The infant rapidly inflates the lungs with the first breath, and the remaining amniotic fluid is either reabsorbed or coughed out.   --- Medical geneticist (talk) 17:16, 4 January 2011 (UTC)


 * Some concepts:


 * 1) There's more oxygen in air than in water. Thus, lungs can be less efficient than gills at extracting oxygen.


 * 2) One difference is that gills often have a continuous flow direction, while we reverse the flow direction of air as we breathe in and out. This leads to mixing of good air and bad, and thus reduces efficiency. StuRat (talk) 18:17, 4 January 2011 (UTC)


 * The fact that gills are a countercurrent exchange but our lungs are not is also relevant, as the diagram in that article shows, we can only ever absorb 50% of the available oxygen in the air, whereas fish can extract close to 100% of it. SmartSE (talk) 23:41, 4 January 2011 (UTC)


 * Well, even if we could extract the oxygen from the water, our lungs would still be crushed from the amount of water breathed in Crimsonraptor &#124; (Contact me) Dumpster dive if you must 20:58, 4 January 2011 (UTC)


 * And not only do we need to get O2 in, we need to get CO2 out. Googlemeister (talk) 17:26, 5 January 2011 (UTC)


 * Yes, but that's a lot easier, as nothing needs to be in the air or water for you to extract. StuRat (talk) 19:49, 5 January 2011 (UTC)


 * I tried to figure out what problems Googlemeister was alluding to with the link to Liquid breathing, and it seems the viscosity of PFC (and water, it is implied) makes it hard to dissolve CO2 into it (something about the pressure of CO2 in the blood being too low) meaning that you'd have to breath unfeasibly hard. I was going to mention this, but got confused by the image of the mouse breathing PFC while floating in it (a ubiquitous pop science image, as hard to escape as that picture of the frog levitating in a big magnet). If the mouse doesn't need mechanical assistance to get its CO2 out of its lungs, why would a human? Maybe the task scales badly. 81.131.14.88 (talk) 15:04, 6 January 2011 (UTC)


 * Humans may be able to breathe liquids (though not water). I read it in New Scientist awhile ago, (found online link here but you can't read most of it without a subscription) and apparently if the liquid has a large amount of oxygen in it (more than normal water) it is physically possible to breathe it. Application is available to divers (as per article!) as having liquid breathing means problems such as the bends can be avoided. Rumours are the US military has tried it, although they faced problems, due to the fact that humans really aren't used to breathing anything but air! Chipmunkdavis (talk) 05:42, 7 January 2011 (UTC)


 * I believe another possible application is for a patient with a collapsed lung. StuRat (talk) 05:52, 7 January 2011 (UTC)

mesons
How do mesons containing up anti-up or down anti-down quarks exist.i mean shouldn't they annihilate each other  — Preceding unsigned comment added by Raky rough (talk • contribs) 15:15, 4 January 2011 (UTC)


 * You are right. They do not exist for long! []Zzubnik (talk) 15:41, 4 January 2011 (UTC)


 * See meson. The longest lifespan of a meson is about 10-8 seconds.  Mesons themselves are basically gluon transporters; they basically are little taxicabs that carry gluons between different nucleons in the nucleus, providing the nuclear force.  Another way to think of mesons is as the particle form of the energy needed to shuttle gluons around the very short distances between nucleons.  Given their job, its not much of a surprise they exist for a very short time indeed.  -- Jayron  32  21:14, 4 January 2011 (UTC)

Blackbirds falling from the sky
There have been reports of thousands of birds falling dead from the sky simultaneous with thousands of fish dying in Arkansas. The state wildlife commission has given glib and unconvincing explanations such as "some disease killed the fish" and "the birds were scared to death by fireworks" while some necropsies find "massive physical trauma" in the birds. When people have attempted to kill or drive away nuisance collections of birds by shotgun blasts or noise from loudspeakers, the birds just shrug it off. Other explanations are the thousands of birds "were killed by hailstones" (which somehow did not pile up on the ground as did the dead birds) or "they were struck by lightning" (which somehow simultaneously covered a 1 mile diameter). Mightn't it justify its own article, beside the brief mention in the article for the Red-winged Blackbird and for Beebe, Arkansas, since other species also died, and a similar dieoff occurred shortly afterward 300 miles away in Louisiana? From 1968 to 1975 the Smithsonian hosted the Center for Short-Lived Phenomena. Did their records include similar mass trauma killing of thousands of birds over a 1 mile area? Is there a listing of historic mass bird dieoffs? I expect domestic turkeys to run around in a panic and die when there is a disturbance, since they are not bred to have any common sense, but wild birds generally have not seemed so prone to fly around in a panic and die when there is noise, by crashing into each other, trees, houses, or the ground as some have suggested.. They have had millions of years of natural selection operating in a world where there is lightning. Edison (talk) 17:30, 4 January 2011 (UTC)


 * You seem to have citations from a couple of independent sources. A new article would seem valid, but do steer away from conspiracy theories. New Year celebrations and holidays can delay good responses from authorities. Just present what those media reports have told us actually happened. And be prepared to update it as further news comes to hand. HiLo48 (talk) 17:41, 4 January 2011 (UTC)


 * I could not gain any insights from that website, but if there were an official coverup claiming updrafts or hail, perhaps someone would be savvy enough to make sense of the data there. The rising barometer would be generally disproof of extreme weather events in the place at the time of the thousands of bird deaths. Edison (talk) 01:29, 5 January 2011 (UTC)
 * The mass dieoff in Arkansas may have motivated the media to publicize a later smaller dieoff in Louisiana. The species included other than redwing blackbirds, although they seem to be most numerous in the two cases this month. An article collecting unrelated dieoffs might be WP:SYNTHESIS or WP:ORIGINALRESEARCH, but not if CNN and other news media link the incidents in one article. Conspiracy theories? Christian Science Monitor specifically discussed these dieoffs in relation to such theories on January 3. Edison (talk) 18:01, 4 January 2011 (UTC)


 * The hailstone theory sounds reasonable, and the stones would then melt in short order, if temperatures were high enough. If this was in an isolated area, then people would likely discover the birds only after the stones were gone, especially if it happened when everyone was asleep.  Volcanic gases could also kill off a flock of birds, but this would be obvious.  As for fish, in addition to disease, there can be water quality problems, such as incorrect pH or a lack of oxygen, which can cause massive fish kills. StuRat (talk) 18:07, 4 January 2011 (UTC)


 * FWIW, there was a news report on this on the UK's BBC Radio 4 within the last 90 minutes - I think on the 17:30-18:00 PM programme - in which the senior veterinary official for Arkansas (can't remember his exact title) was interviewed. His general thesis was that fireworks had startled the roosting redwing blackbirds, which being unable to see at night then blundered into buildings and structures, injuring themselves. Other witnesses reported hearing loud bangs "like cannon fire" after dark and then seeing the birds flying into obstructions. 87.81.230.195 (talk) 18:59, 4 January 2011 (UTC)


 * There is a BBC report here. Ghmyrtle (talk) 19:09, 4 January 2011 (UTC)
 * Fireworks is rather unconvincing since the tens of thousands of other fireworks that are shot off each January 1 and July 4 don't kill thousands of birds. Googlemeister (talk) 19:34, 4 January 2011 (UTC)
 * Check out raining animals; this week's birds and fish might merit a mention there (but a special article sounds like a good idea to me). Robinh (talk) 19:50, 4 January 2011 (UTC)
 * Wouldn't WP:NOTNEWS apply? Googlemeister (talk) 20:16, 4 January 2011 (UTC)


 * OR, but it's worth noting that at this season of the year, red-winged blackbirds tend to flock in huge numbers. My guess is that a flock of them got caught in a strong updraft inside a thunderstorm, which could easily have carried them to an altitude of 20,000 feet or higher, where they would have died of suffocation and cold, and the bodies would have been scattered over a pretty broad area.  If this is what happened, then I think there should be signs of it that are visible at autopsy. Looie496 (talk) 20:31, 4 January 2011 (UTC)


 * This isn't the first news item I've seen about a flock of birds falling down dead - here's one about 76 dead starlings in Somerset: . Here's one about several hundred mysteriously inebriated parrots: . It's all very Fortean. This one  is about 200 dead seagulls in Perth, and mentions a previous incident of 5000 dead birds which was established to be lead poisoning. This story in Pravda  from four years ago says that "Doctor Scientist Oleg Kiselyov" (presumably not this Oleg Kiselyov) estimates 2 million birds fall dead from the sky every month, and for some reason he blames them all on bird flu. 213.122.29.106 (talk) 20:38, 4 January 2011 (UTC)
 * The problem is, multiple bird species were affected. There's the red-winged blackbirds, but also starlings and grackles. I agree with the IP above me that this seems very Fortean indeed, but I would see what the autopsies say to get a clue on what on earth happened. Crimsonraptor &#124; (Contact me) Dumpster dive if you must 20:53, 4 January 2011 (UTC)


 * Sounds like a job for Centre for Fortean Zoology if the Arkansas wildlife officials are not forthcoming. A weather updraft which carried thousands of birds to 20,000 feet, or which dropped so much hail that it killed the birds (but did not strike cars and things on the ground) should have left weather radar evidence. I am reading that a) the birds flew into trees and houses and died, and b) they were taken up in a windcurrent to 20,000 feet. It seems unlikely that both happened. Also they fell in a 1 mile square area or larger, rather a large distribution for the inhabitants of one or a few trees startled by a nearby noise. How many skyrockets and explosives would a town of 4,930 fire off on New Year's Eve, especially if there was some massive lightning storm and hailstorm? I didn't hear but a few firecrackers in my own larger city. It is easy to find present weather radar for any locality, such as Beebe, Arkansas, but I cannot find a way to scroll back and see the weather radar for that location on December 31. Anyone know how to access such historical information? One site shows nothing unusual there (in nearby Searcy, 16 miles away) on New Year's Eve, just scattered clouds, 52 degrees Fahrenheit. Precipitation for the day was 0.01 inches, none after 9 AM. Notably, the barometric pressure was rising all afternoon and evening, atypical for turbulent weather moving through. Edison (talk) 21:23, 4 January 2011 (UTC)
 * Edison, you might start looking at NOAA's NEXRAD RADAR Mosaic archive. It's sort of "low resolution" for your needs, and I seem to recall much higher-resolution NEXRAD data archive somewhere on the NOAA website; (maybe the RADAR Resources / Free Data Products page); so try clicking around on that page and/or web-searching the NOAA site.  (I'll take a look later as well).  Worst-case, you can email a NOAA scientist at the National Climatic Data Center contacts page... Nimur (talk) 00:28, 5 January 2011 (UTC)
 * Aha, here. NEXRAD Data Inventory.  Though, you may need to be a bit of a WSR-88 enthusiast to interpret this stuff, (even the "Level III data products" are still very technical compared to ordinary weather maps you see on TV). But NOAA does make a lot of very useful software and source-code available, here's their data access tools page.  You're pretty tech-savvy, but lemme know if you need assistance.  Nimur (talk) 00:35, 5 January 2011 (UTC)
 * I could not gain any insights from that website, but if the "official explanation" is "Amazing Upcurrents" or "Rain of Hail" or "Lightning Blasts," perhaps that data can disprove it (unless it gets "tweaked") . Edison (talk) 02:02, 5 January 2011 (UTC)

In case anyone has any concerns about notability, this news has now reached The Age in Melbourne, Australia, which, as was said far too many time when Oprah was here last month, is a very long way away. HiLo48 (talk) 06:55, 5 January 2011 (UTC)


 * Interestingly, a very similar event has also happened recently in Sweden - here. Ghmyrtle (talk) 10:45, 6 January 2011 (UTC)


 * Interesting because the question is: is this actually a thing, or just an artifact of media interest in stories about dying birds? 213.122.26.117 (talk) 14:08, 6 January 2011 (UTC)


 * I've seen stories like this before, and the answer is usually (if not always) Starlicide. Wnt (talk) 17:09, 8 January 2011 (UTC)

LHC
why is it required that collisions in LHC take place at 99.999% speed of light Raky rough (talk) 18:47, 4 January 2011 (UTC)


 * Because it takes a lot of energy to accelerate the incoming particles to that speed. When they collide, all of that energy is released and becomes various other stuff, and the scientific point of the LHC is to study what the "various other stuff" is. Somewhat simplified, the point is not just to "smash things together", but to concentrate a lot of energy in a small space and see what it does. That's where speed / kinetic energy comes in -- small particles at high speed is the only practical way to deliver a lot of energy to a sufficiently small volume in a somewhat controlled way. –Henning Makholm (talk) 19:30, 4 January 2011 (UTC)


 * It certainly is all a matter of energy. If the OP is wondering about the apparent diminishing returns, then consider that a particle traveling at .99999 m/s has only 0.018% more kinetic energy than when traveling .9999 m/s, but, due to special relativity, a particle traveling at .99999 c (99.999% the speed of light) has more than 3.19 times the kinetic energy (219% more KE) than when traveling .9999 c.  That close to the speed of light, the kinetic energy of a particle will increase by just over a factor of √10 ≃ 3.16 each time you add another "9" to the string of 99.999999...%. -- 119.31.121.88 (talk) 01:06, 5 January 2011 (UTC)

Actually, it's 99.999999% c; the energy is 7 GeV and the relativistic formula for the velocity is $$\frac{v}{c} = \sqrt{1 - \frac{1}{(\frac{energy}{m c^2} + 1)^2}}$$, and you can look up c and the proton mass. 99.999% c has been achieved a long time ago. Icek (talk) 01:28, 5 January 2011 (UTC)
 * I think you mean 7 TeV... Nimur (talk) 01:43, 5 January 2011 (UTC)
 * So one second to the accelerated particle would seem like 7071 seconds to the operator of the LHC? See . Edison (talk) 02:00, 5 January 2011 (UTC)
 * Sounds about right, since the proton (rest) mass is slightly less than 1 GeV/c² and the accelerator pumps each proton up to about 7,000 GeV. –Henning Makholm (talk) 03:29, 5 January 2011 (UTC)

benzene
why does benzene cause cancer but xylene dosent after all it dimethylbenzene  — Preceding unsigned comment added by Tommy35750 (talk • contribs) 20:55, 4 January 2011 (UTC)
 * All aromatic compounds are somewhat carcinogenic, even xylenes. See This paper from 1988 which indicates that Toluene (monomethylated benzene) and xylenes (dimethylated benzenes) are carcinogenic in animal studies, though only at a higher concentration than benzene.  It should be noted that methyl groups are not inert, they have a weak electron donating effect and are mildly activating on the aromatic system; I have no idea how this may work mechanisticly in causing cancer, but apparently it decreases (but does not eliminate) carcinogenic effects; perhaps (a bit of a WAG) by making the aromatic ring more susceptible to attack by substances which may eliminate it from the body before it can do harm; benzene, being more inert than the others, may stick around so much longer in the body.  -- Jayron  32  21:02, 4 January 2011 (UTC)


 * The claim that "all aromatic compounds are somewhat carcinogenic" seems to refer either to a very broad sense of "carcinogenic" or to a rather narrow range of "aromatic compounds". Can, for example, niacin or phenylalanine usefully be said to be carcinogenic? –Henning Makholm (talk) 21:55, 4 January 2011 (UTC)


 * Fair enough. I should have said that benzene and its simple derivatives are all likely to be somewhat carcinogenic.  You got me.  -- Jayron  32  03:08, 5 January 2011 (UTC)

i remember reading that benzene caused red blood cell problems, but xylene and Toluene dont. whats the explanation for this? — Preceding unsigned comment added by Tommy35750 (talk • contribs) 21:14, 4 January 2011 (UTC)


 * Substituted aromatic compounds get oxidized at the side chain in the body. Thsi oxidation is necessary to get ride of the compounds because only water soluable compounds can leave the body in the urine. The oxidation of benzpyrene or benzene is done on the ringsystem and than you form a three membered ring with one oxygen at the armoatic ring. This epoxide is highly reactive and has the tendency to move to the nucleus. There the ring opens and reacts with the DNA. The toluene is transformed into benzoic acid and with the addition of one aminoacid you get hipuric acid which leaves the body without problem. --Stone (talk) 15:41, 5 January 2011 (UTC)
 * This is only based on logic rather than sources I'm afraid, but red blood cells themselves are unlikely to be damaged by benzene directly because they contain no DNA, and damaged DNA is what leads to cancer. They are formed in bone marrow however by rapidly dividing cells, which may be more susceptible to DNA damage, resulting in damaged RBCs. I assume you've read the about the health effects of benzene, which says it can cause acute myeloid leukemia which is also related to problems in the bone marrow. Regarding the differences between benzene and xylene, it's worth remembering that small changes in molecules can have big effects - for example sickle cell disease is caused by a single mutation in haemoglobin, a tiny difference. On a more similar note to benzene and xylene, THC and CBD, two compounds found in cannabis are tautomers, but with very different effects on the brain. SmartSE (talk) 12:13, 6 January 2011 (UTC)

Baking soda as deodorizer
Baking soda is commonly claimed to have deodorizing properties, but our article baking soda only mentions briefly (without citation) that it can be used as an ingredient in home-made personal deodorant. Recently, a Ph.D. chemist told me that this claim is misleading. He said that if you put a carton of Arm & hammer in your fridge, the cardboard absorbs as much or more odor than the baking soda, i.e. bicarbonate is NOT an especially effective deodorizer. Can anyone help clarify if bicarbonate is a better absorber of odors than cardboard? SemanticMantis (talk) 21:43, 4 January 2011 (UTC)
 * The Arm and Hammer company has long advertised since the 1960's that baking soda [removes odors,, but they are hardly an independent and reliable source for a claim that probably results in more sales of their product than for cooking uses. Some books which say that baking soda is an effective deodorizer: , .  Google Book Search shows few claims that baking soda was a good deodorizer before 1900,(see  for one from 1898, but that said to boil baking soda in a cooking vessel to remove an odor from the pot. This use of it in solution was commonly recommended long before Arm and Hammer came up with the recommendation to leave a box of it in the refrigerator, which became "common knowledge" after their late 1960's advertising campaign. Other substances like wood ashes were recommended as a deodorizer, as were vinegar, sandalwood, or charcoal. Baking soda was only discussed as a food ingredient or to counteract acid. In the first half of the 20th century, Consumer Reports 1943 advised using baking soda as a personal deodorant: "CU recommends as "Best Buys" among deodorants either powdered boric acid or a solution of baking soda." (1943) "Farm Journal," 1949 said "To clean and deodorize freezers and refrigerators— sprinkle Baking Soda on a damp cloth and wipe inside surfaces. Wipe again with hot water and dry." in what might have been an ad. The ads from 1967 on such as  preceded the huge number of household tips books advocating a box of baking soda in the refrigerator. The Arm and Hammer company launched the "box of baking soda in the refrigerator" campaign in 1972 and sales rose 72% in 3 years, per . The claim just seems to have some face validity, and was "common knowledge" by the late 1970's.  I did not find a controlled experiment (even an anecdotal test like Mythbusters). Edison (talk) 21:58, 4 January 2011 (UTC)


 * Note that personal deodorants do not work by absorbing smell from the air; instead they suppress bacterial skin fauna that would turn (ordinarialy odorless) sweat into smelly compounds. Our sodium bicarbonate article does mention (with source) that it has some disinfectant and antiseptic properties. –Henning Makholm (talk) 22:17, 4 January 2011 (UTC)


 * Looking at the book search results by the various historical periods, baking soda was recommended on a damp sponge or cloth, or in a liquid solution to be wiped over the surface such as a refrigerator interior, and as an alkaline perhaps it could discourage bacterial growth. Only in the 1960's-1970's did the manufacturer promote putting a fresh box in every 3 months for its supposed "odor absorbing" properties. (Admittedly, I always keep an open box in the refrigerator for that purpose).  This vastly more product than the average household would use for baking. Edison (talk) 22:32, 4 January 2011 (UTC)
 * Thanks for the great research. At the moment it seems that, while bicarbonate will absorb odor, it is not particularly more effective than cardboard or ash. SemanticMantis (talk) 23:04, 4 January 2011 (UTC)
 * Only in the 70s? Don't they currently sell it in special boxes with cloth-covered vents you can open on the side of the box specifically for this purpose? APL (talk) 23:18, 4 January 2011 (UTC)
 * "Since" 1972, not "in" 1972. If you can get consumers to buy and throw away a container of your product every three months, you are in "manufacturer paradise." Edison (talk) 01:13, 5 January 2011 (UTC)
 * Ah! I misinterpreted your line "Only in the 1960's-1970's" to mean that it occurred "only" during those years, when I see now that you meant that they "only" came up with this marketing angle sometime during that range, instead of earlier as someone might suppose. APL (talk) 05:33, 5 January 2011 (UTC)
 * This book says that because it can act as a weak acid and a weak base it can neutralise basic and acidic food odors, turning them into odor free salts. This (from 1992) says that it is just starting to be used in the cosmetic industry as an ingredient in deodorants because it neutralises short chain fatty acids which are malodorus. I don't think it absorbs odors more so than cardboard, but it can neutralise them, which I'm fairly sure that cardboard can't. SmartSE (talk) 00:00, 5 January 2011 (UTC)
 * I love chemistry, but do not claim to be a skilled chemist. Could those with more chemistry education comment on the unlikelihood of bicarbonate of soda being both a base and an acid? My 1945 29th Edition CRC Handbook of Chemistry and Physics, page 1374, says that a 0.1 N solution of sodium bicarbonate has a pH of 8.8, which would seem to rule out it being an acid. Edison (talk) 01:19, 5 January 2011 (UTC)
 * Sodium bicarbonate is NaHCO3. The H can be removed by reaction with a strong base, leaving sodium carbonate behind. See Chemistry section in sodium bicarbonate. --Chemicalinterest (talk) 01:26, 5 January 2011 (UTC)
 * You did not say if sodium carbonate is an acid or a base. It seems to be a base, so no support is provided for sodium bicarbonate being both an acid and a base as Smartse implied. (That would be a stretch even for GoatSe). Would putting a box of sodium bicarbonate in the refrigerator somehow cause a strong base to react with it, leaving the sodium carbonate? Seems rather unlikely. Edison (talk) 01:37, 5 January 2011 (UTC)
 * Sorry for not being more specific, if you check the first reference I gave, it says the HCO3- ion is what can act as both an acid and a base. I'm not a chemist, but you're right in that a solution of it is slightly basic and according to the same reference, this is what makes it better at neutralising acid odours compared to basic ones. As has been touched on below, this property is important in biology, in maintaining the acid-base homeostasis in our bodies. SmartSE (talk) 10:33, 5 January 2011 (UTC)
 * (ec) The bicarbonate (hydrogen carbonate, HCO3-) ion is definitely capable of being both an acid and a base, depending on your definitions; you'll find a good quick introduction in Acid–base reaction. In aqueous solution, it will exist in equilibrium with a protonated form (carbonic acid: H2CO3) and a fully deprotonated form (carbonate ion: CO32-.  Using the Brønsted–Lowry definitions, When it reacts with something less acidic (more basic) that itself (like ammonia, to form ammonium ion) and loses a proton then it's acting as an acid.  When it reacts with something more acidic (like acetic acid, forming acetate ion) and accepts a proton, then it is acting as a base.  It's not an either-or situation; bicarbonate ion is both a weak acid and a weak base. TenOfAllTrades(talk) 01:45, 5 January 2011 (UTC)
 * See also amphoteric, linked from the sodium bicarbonate article. –Henning Makholm (talk) 01:48, 5 January 2011 (UTC)
 * How likely are these reactions if the sodium bicarbonate is a dry power in a box in a refrigerator, as opposed to being in a reactant vessel in solution with powerful chemicals in a chemical plant or a test tube in a lab? Be real. Edison (talk) 01:50, 5 January 2011 (UTC)
 * I'm going to go with 'pretty', or even 'very'. A fine powder gives lots of surface area for reaction, and every time you open the refrigerator door you let in several cubic feet of air that's oversaturated with humidity &mdash; some of which will condense on those little sodium bicarbonate particles and make their protons and hydroxide available for chemistry, and the limited amount of solvent means everything has a very high effective local concentration.  Carbonate-bicarbonate-carbonic acid equilibria aren't particularly unusual or harsh chemistry; bicarb is the major buffer that maintains your blood's pH.
 * On the question of the box in the fridge, I might speculate that the volatile compounds responsible for fridge odor are going to be primarily uncharged molecules; charged ions have a low vapor pressure and don't fly well. When those compounds are exposed to bicarbonate, any parts of the molecule that are capable of either picking up or losing a proton have an opportunity to do so.  If any reaction occurs then our once-volatile compound takes on a net charge and its vapor pressure is likely to go waaaay down.  While the acid-base reaction is likely to be reversible to some degree, the compound is now spending some fraction of its time (possibly quite a very large fraction of that time) in a charged state crashed out in the box of baking soda.
 * Incidentally, Edison, what's happened? First a spurious goatse reference as an off-color gag, and now a 'be real'?  Your answers were really thoroughly researched at the beginning of the thread, and now you're snapping at people who are trying to respond helpfully to your concerns.  Is everything okay? TenOfAllTrades(talk) 02:21, 5 January 2011 (UTC)
 * I do not consider a "reality check" to be "snapping" at other posters. A relatively dry atmosphere at low temperature is not equivalent to a test tube filled with chemical solutions. I checked the box of sodium bicarbonate which has been in the fridge for many months and it looks, feels and tastes exactly the same. No indication that it has been chemically modified. I have trouble accepting that powerful chemical influences are somehow wafting around in the fridge as a couple of posts have implied, changing a base somehow to an acid. If a box of dry white powder modifies the odors in a fridge, might not it be by adsorption of the free floating molecules on the large surface area of the granules, rather than the baking powder turning from a base somehow to an acid? Do I have to get out the Litmus paper to confirm it is still a base? One works all day on improving Wikipedia, then someone is dismayed when one questions whether likely bs might in fact be real bs. Edison (talk) 03:52, 5 January 2011 (UTC)
 * You assume that "acid" and "base" are mutually exclusive categories. They are not. A molecule (such as bicarbonate) can be both at the same time. It does not need to be "somehow changed" from one into another. How it reacts just depends on which reactants presents to it for reacting.
 * A pH above 7 simply means that the solution (on short timescales) is less acidic (and more alkaline) than pure water; it doesn't mean that there is no capacity to react like an acid left. Water itself is perfectly willing to act either like a base or like an acid. The difference between water and bicarbonate solution shows up at slightly longer timescales: the bicarbonate that reacts will be replenished by protolysis by some of the carbolic acid in the solution. Therefore it can react with more base than pure water can before its pH rises much (and eventually dissuades new added base molecules from reacting).
 * Yes, of course, there are chemical influences wafting around in the fridge -- at least if there's something that smells in there. That's what a smell means: molecules that waft around in the air and can dissolve in liquids they happen to meet. If they meet the mucous membrane in your nose, they may dissolve and react with sensory cells there. If they didn't, they wouldn't be smelly in the first place. –Henning Makholm (talk) 04:29, 5 January 2011 (UTC)
 * Did you know that sodium hydroxide is the conjugate acid of sodium oxide? --Chemicalinterest (talk) 18:17, 5 January 2011 (UTC)
 * Two thoughts come to mind. First, sodium bicarbonate is described as hygroscopic - by sucking up water from the air, it might make stray bits of rotten food drier and presumably less ... juicy.  Apparently it's not truly deliquescent, however, and I don't really know how much water is actually absorbed by a package after it's already reached the retailer.  Actually, I don't even know the measurement units for a hygroscopic chemical!  Second, as a pH buffer, it might tend to absorb stray, strongly scented amines floating around in the air, which upon contact could take up an H+ from the HCO2- ions... but short of strong bases like ammonia itself this doesn't sound like an important reaction. Wnt (talk) 05:32, 5 January 2011 (UTC)
 * The answers from those skilled in chemistry were quite helpful. Plausible mechanisms were provided whereby the chemical might lessen the odor in a refrigerator. The odd thing is that, post 1972, dozens of "household hint" and "green living " books state as a fact that the "box of baking soda in the fridge, replace every 3 months" works, but nowhere did I see experimental verification. Refrigerators with some stinky contents (various odorants could be used: garlic, fish, rotten produce, sour milk) with no baking soda or with a box of baking soda, closed up for some standard period or varying periods, with blind testing by someone who rates the odor. Right up Mythbusters alley, or someone's science fair project. The experiment sounds too simple for publication in a scientific journal or for a masters thesis, but I suppose it would be mainstream Food science. Google scholar shows several publications related to "baking soda" "refrigerator:", most behind the usual paywall. Besides a bunch of patents, which prove nothing, there appear to be some relevant articles. Does anyone have library access to them, to shed light on effectiveness and method of effect from reliable sources? Edison (talk) 20:01, 5 January 2011 (UTC)
 * There are peer-reviewed journals devoted to Food Science; I'm not sure what the implication is in the juxtaposition of "food science" is against "publication in a scientific journal" seems to imply that there aren't serious, respected journals devoted to the subject. There are.  After a 30 second search, I found this one which looks like a good, generalist overview sort of journal.  -- Jayron  32  20:22, 5 January 2011 (UTC)
 * I was thinking of "chemistry" as more of a hard science, and could not see someone getting his masters thesis or doctoral thesis approved or publishing in a refereed chemistry journal the fridge and baking soda experiment outlined. On further study there are not many relevant studies seen at Google Scholar. One unpublished paper, from 2008 found that wrapping food waste in newspaper was far more effective than baking soda sprinkled on it or placed in a container in dry form, when it was left at 20 C for 14 days in a sealed container. The study was small (2 observers) with one of them knowing the experimental treatments of the containers, and the odors resulted from room temperature decomposition of moist food waste, where the drying effect of the newspaper may have been important. Perhaps someone with good library access could look at , an ACS publication which apparently says, per the snippet "..Hammer baking soda that we trustingly put in our freezers to absorb odors—they don't work.." Edison (talk) 20:44, 5 January 2011 (UTC)


 * Wow, lots of good points made here. As a parting argument from authority, this blurb from Argonne Nat'l Lab has been reposted all over the place: . It seems that, although bicarb has some chemical neutralizing properties that activated charcoal does not, the latter will likely provide better deodorizing per unit volume. Still, it does seem like cheap fodder for Mythbusters, maybe someone should drop them a note. SemanticMantis (talk) 21:14, 5 January 2011 (UTC)
 * I'm afraid something that turns on the presence or absence of smell wouldn't make for compelling TV... –Henning Makholm (talk) 23:04, 5 January 2011 (UTC)
 * In 2003 Mythbusters once put a dead pig in a car and sealed it up for 2 months, to find out if it was possible to get rid of the smell. It wasn't. I don't recall that they tried baking soda. Edison (talk) 23:36, 5 January 2011 (UTC)