Wikipedia:Reference desk/Archives/Science/2011 January 7

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January 7

Yellow zinc passivated screws and chrome-6 carcinogen

I've bought some "yellow zinc passivated" woodwork screws, and after looking up on the internet what "passivated" means, I've found information like this page http://www.ewes.se/doc.asp?M=100000096&D=600000326&L=EN which says that some kinds of passivation use a "grade 1" carcinogen, described as chrome six, and are in the process of being banned by the EU.

The screws I've got look reddish with a little pale green rather that the "yellow" of the label. Have I bought the bad kind that are beginning to be banned? Thanks 92.24.188.63 (talk) 00:15, 7 January 2011 (UTC)

See zinc chromate. --98.221.179.18 (talk) 01:19, 7 January 2011 (UTC)

I understand that what is to be regulated are the exposure of industrial workers to the carcinogenous chemicals, and use of the plated surfaces in medical or food preparation applications. The woodwork screws may one day be marked Unsuitable for these but I doubt that sale of them will be banned.Cuddlyable3 (talk) 02:11, 7 January 2011 (UTC)

The answer appears to be "probably". Hexavalent chromium and passivation are relevant. 92.24.178.121 (talk) 11:11, 7 January 2011 (UTC)

I agree; avoid exposure to hexavalent chromium. If you're just using a handful of screws, wear gloves and/or wash your hands. If you're a carpenter, buy galvanized screws or screws passivated with a different oxide instead. 71.198.176.22 (talk) 14:00, 7 January 2011 (UTC)

It is better to get other types of screws like galvanized ones. --98.221.179.18 (talk) 21:48, 7 January 2011 (UTC)

The passivateisation (sp?) is applied on top of the zinc galvanisation, and is said to reduce the corrosion by several times beyond that of plain zinc galvanisation. There are various treatments that can be used to do the passivateisation, and I'm not clear which are believed to be harmless. Dipping the screws in paint might be an alternative to passivatisation, although I don't know by how much this would reduce corrosion. 92.15.24.121 (talk) 11:31, 8 January 2011 (UTC)

Of course it's a cost-benefit analysis with corroded screws on one hand and decreased lifespan and medical bills from cancer on the other. It just seems inconceivable to me that there isn't a nontoxic alternative of approximately equivalent cost and effectiveness in this case. 71.198.176.22 (talk) 16:39, 8 January 2011 (UTC)

New Jersey Department of Fish and Wildlife field guides

I would like to know if these are copyrighted. --98.221.179.18 (talk) 01:19, 7 January 2011 (UTC)

Probably. In the U.S., the only things which are safe to assume are in the public domain are those a) expressly released into the public domain by the rightful copyright holder b) published before 1923 or c) published before 1978 whose copyright was not registered or renewed properly before 1978. Anything created and published since 1978 is presumed to be under copyright to someone unless expressly released into the public domain. --Jayron32 02:45, 7 January 2011 (UTC)

Things created by an employ of the federal government, as part of their capacity as a federal government employee, are also considered non-copyrightable: Copyright status of work by the U.S. government. However, this does not apply to state governments or employs. The State of New Jersey specifically claims copyright to the NJDEP Division of Fish & Wildlife webpage (at the bottom), so I think it's likely that they'd claim copyright to the guides as well. I don't see a specific copyright claim on the guides, but as Jayron pointed out, there doesn't need to be a claim to copyright to be copyrighted. It also remains unclear whether the state of New Jersey holds the copyright to the work, or the authors ("Schwartz, V. & D. Golden", as attributed). I am not a lawyer, but in general, I believe it's only the owners of the copyrighted material that are allowed to sue (or issue Takedown notices)

Of course, depending on what you're using the material for, copyright may or may not matter. Something like Wikimedia Commons will only accept work that is truly under a free licence, but in many cases, if you're confident that the copyright holder won't sue, you can do whatever you like with the material, irrespective of the law. I'm not sure if the state of New Jersey (if they are indeed the copyright holders) is likely to sue anyone over some obscure field guide, even if they don't do find out. If you intend to use the material in any serious way, it would be a good idea to seek the advice of a lawyer. You could also send a polite e-mail to the New Jersey Department of Fish and Wildlife inquiring about the work. Even if they aren't willing to release the material under a free licence, they may be willing to grant you permission to use it in specific ways. Buddy431 (talk) 03:38, 7 January 2011 (UTC)

Edit: NJ Division of Fish and Wildlife Contact Info. Buddy431 (talk) 03:46, 7 January 2011 (UTC)

Edit: I did find one example of a New Jersey government agency suing Youtube for a copyright infringement, [1], so I guess they're willing to protect their copyright if they want to. I'll let you interpret the article as you will, but I think it's likely that the copyright concerns were not the NJTA's chief concern in trying to get the material removed from Youtube. Buddy431 (talk) 03:44, 7 January 2011 (UTC)

Speed of gravity

If nothing escapes from a black hole,how does gravity which also travels at the speed of light?02:09, 7 January 2011 (UTC)118.208.93.193 (talk)

John Cowell

Although perturbations to the curvature of spacetime, i.e., gravitational waves, are thought to travel at the speed of light, the curvature of spacetime in the vicinity of a black hole is in a steady state. As physicists say, "black holes have no hair". There's no gravitational information to escape. Red Act (talk) 02:18, 7 January 2011 (UTC)

And the gravity field starts before the black hole is formed, and perhaps the black hold never forms in the reference frame of those outside it. Graeme Bartlett (talk) 07:58, 7 January 2011 (UTC)

Some things can escape a black hole: see Hawking radiation, which is an effect of quantum-theoretical behaviour. However physicists don't fully understand quantum gravity, so the precise nature of gravity isn't fully explained under existing theories. --Colapeninsula (talk) 13:58, 10 January 2011 (UTC)

Alan Guth's inflation period.

If matter,time and space were created in the big bang and Alan Guth claimed everthing accelerated beyond the speed of light then; What force accelerated it? What did it expand into? If it exceeded the speed of light then it would be travelling into a past that never existed, What FTL force decelerated it.

John Cowell118.208.93.193 (talk) 02:30, 7 January 2011 (UTC)

The expansion of the universe is not the result of a force moving matter around. It's not the objects themselves moving. It is the actual space itself being created. See Metric expansion of space. There's nothing pushing because matter itself isn't being moved. It's the space between the bits of matter that is getting bigger. And space, lacking a mass, requires no force to make it accelerate. --Jayron32 02:40, 7 January 2011 (UTC)

Nothing has really accelerated to a speed greater than the speed of light (c). The rate at which the distance between very distant objects increases can be a faster rate than c, but that's because the space itself is growing, not because any objects are moving faster than c within space. All objects are locally traveling at a speed less than c, as measured in any (local) inertial frame of reference. Red Act (talk) 04:04, 7 January 2011 (UTC)

The balloon example is often used to explain this (and to make physics students cringe at the absurd oversimplification of the example). Blow up a balloon. Place two dots on the outside of the balloon. Those are two points in space. By law, nothing can travel across the outside the balloon faster than a certain speed (c). All is well. Now, blow up the balloon some more. The dots move apart, from your perspective of looking at the whole balloon, but from the view of the points, they haven't moved at all. So, the speed limit wasn't affected by blowing up the balloon. Continuing, you can blow up the balloon faster than the speed limit, making the two points move away from each other faster than c. From your point of view of looking at the whole balloon, they are breaking the speed limit, but they aren't really. The speed limit states that nothing can travel across the surface of the balloon faster than c. The two points aren't moving at all from their perspective. All in all, it is has to do with what the speed is relative to - hence relativity. With that understanding, you can see how a person can say that the dots on the balloon are expanding faster than c, but they aren't actually moving at all. So, there is no concept of force involved. Therefore, asking what force moved them is missing the point of the expansion theory. -- kainaw™ 14:40, 7 January 2011 (UTC)

At what temperature does the volume of water decrease, regardless of whether your increase or decrease the temperature?

Assuming 1 atmosphere of pressure.--70.122.125.20 (talk) 03:23, 7 January 2011 (UTC)

See Properties_of_water#Density_of_water_and_ice. Its right in the first paragraph, and in the chart at the right. --Jayron32 03:40, 7 January 2011 (UTC)

You are really just asking the temperature at which water has the minimum density (at 1 atmosphere), right ? StuRat (talk) 04:00, 7 January 2011 (UTC)

Maybe I'm misreading - but there is no temperature where the volume decreases when the water is either warmed or cooled. At 4 celcius, the density will decrease in either direction on the temperature scale; volume will increase. Nimur (talk) 04:02, 7 January 2011 (UTC)

Ah. That is what he said. In that case liquid water has a minimum density at the boiling point. Gaseous water has no minimum density, due to the fundemental nature of gases. Solid water (ice) has numerous allotropic forms, each with their own behavior in regards to temperature, so its difficult to answer. --Jayron32 04:08, 7 January 2011 (UTC)

Liquid water at 100°C isn't a right answer, though, because if you increase the water's temperature a bit, it will turn to gas, and the water's volume will increase.

The question specifies a pressure of 1 ATM. If you freeze liquid water at 1 ATM, it will form ice I_h (normal ice). Normal ice at 0°C has a density that's at a local minimum (volume at a local maximum), because if you increase its temperature a little, it will turn into liquid water and shrink, but if you cool the ice, it will also shrink (see Ice#Characteristics). Red Act (talk) 05:02, 7 January 2011 (UTC)

ball bearing

what kind of link a ball bearing forms(a turning pair,a spherical pair etc..,what?). i know its higher pair. —Preceding unsigned comment added by 115.248.161.154 (talk) 04:27, 7 January 2011 (UTC)

It's called a rolling pair[2][3]. Red Act (talk) 06:36, 7 January 2011 (UTC)

gravitational acceleration

what is the relation between gravitational acceleration and gravitational constant? — Preceding unsigned comment added by Dev follower of maths (talk • contribs) 08:27, 7 January 2011 (UTC)

We have articles on Gravitational constant (denoted G) and Gravitational acceleration (usually denoted g), and the approximate relationship (ignoring rotational effects) is

g = GM/R² (where M is the mass of the earth, and R is its radius). The second article explains the subtleties. Dbfirs 09:54, 7 January 2011 (UTC)

electronics

describe of ac and dc? — Preceding unsigned comment added by Dev follower of maths (talk • contribs) 08:28, 7 January 2011 (UTC)

The articles on Alternating current and Direct current should answer your question (basically DC is electricity that flows one way, whereas AC changes direction), but please come back to ask again if you don't understand them. Dbfirs 09:59, 7 January 2011 (UTC)

Ceramic flat iron

Can someone explain to me how,infrared ceramic flat irons work? I bought one in Europe and it makes a humming noise but no detectable "heat" the brand is ASCET...the iron came with no instructions............. —Preceding unsigned comment added by 24.127.222.196 (talk) 10:15, 7 January 2011 (UTC)

Are you using it on the recommended supply voltage (i.e presumably the same as the country in which you bought it)? If not, it will never work.--Shantavira|^{feed me} 12:09, 7 January 2011 (UTC)

...or at least not work well. Europe has (nearly?) universal 230V/50Hz. The US has 120 V. As a consequence, unless there is a universal power supply, a simple heating element will dissipate about 1/4 of the expected power on a US mains outlet as opposed to a European one - it might become warm, but very probably not hot. And if it has more complex electronic components, it will probably not work at all. --Stephan Schulz (talk) 12:46, 7 January 2011 (UTC)

Removing a mole

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

Please speak to your family physician or another qualified medical professional if you have any questions about how to perform a medical procedure on yourself or others. TenOfAllTrades(talk) 15:03, 7 January 2011 (UTC)

To remove a mole, put a hose down it's hole and fill with water. :-) StuRat (talk) 19:10, 7 January 2011 (UTC)

Those who do not write well do not read well. Cuddlyable3 (talk) 01:42, 8 January 2011 (UTC)

Cuddlyable3 vs. It's; 2011 court case. --Chemicalinterest (talk) 14:10, 8 January 2011 (UTC)

Ha! I see you also followed the Internet Spelling Flame Rules, in that your comment itself contains a speling mistake:) Court cases are "X v. Y" not "vs.". DMacks (talk) 18:34, 8 January 2011 (UTC)

The loneliest thing in the universe

Hello,

Imagine a lone elementary particle which is so far away from everything else that it interacts with nothing and is beyond the reach of any force. What effects would this total release from outside influence have on properties such as charge, spin, etc.? To what extent does interaction with the elementary forces shape the properties of elementary particles?

I know we couldn't observe such a particle if it existed, I just want to know what the theory tells us. Thank you. Leptictidium (mt) 12:33, 7 January 2011 (UTC)

There are no particles within the observable universe which aren't effectively gravitationally and electromagnetically bound to other particles to some extent. The ratio of leptons such as photons to baryons is just too large for a person to meaningfully comprehend. Light from other galaxies is visible to the naked eye. 71.198.176.22 (talk) 13:51, 7 January 2011 (UTC)

This is a "What sound does a falling tree make when nobody is listening?" type of question, isn't it? Any physical measurement requires interaction. As soon as we try to measure the charge, spin, etc. we have to interact with the particle, and therefore we cannot answer your question by measurement. I don't think any theory would predict anything other than that the particle has the charge, spin, etc. appropriate for its type. Anyhow, whatever a theory says, it would be an untestable, therefore from a scientific viewpoint useless, statement. --Wrongfilter (talk) 14:02, 7 January 2011 (UTC)

If such things amuse you, you may look up Mach's take on the bucket argument. Beware, however, that Mach's position on this is nowadays considered to be wrong. Einstein, among others, tried hard to find a way in which it could be right, but with no success. –Henning Makholm (talk) 15:48, 7 January 2011 (UTC)

Holy shit! That bucket argument was what I tried to ask my physics teacher 10 years ago, and they stared at me blankly! Just so I'm clear, is Einstein's position that, if the bucket of water were the only thing in the universe, the water would still have a concave surface because it is rotating relative to the geodesic formed by the mass of the water and bucket? Or is his position that it couldn't be said to be spinning at all, and thus the water would be flat (although I suppose the water might be convex if the only gravity is the water and the bucket, but the question remains of whether it would experience centrifugal 'force')? Perhaps rephrased as 'if a gaseous planet were the only thing in the universe, can it be said to spin, and would it therefore bulge?' And is the situation of a real gas giant bulging said to be because it is spinning relative to the gravity fields of everything else in the observable Universe? Would it bulge less if the Universe were smaller in terms of mass? <sorry if this is threadjacking: I got overexcited. Should I start a subsection? 82.24.248.137 (talk) 22:56, 7 January 2011 (UTC)

Einstein and modern science in general (and the General Theory of Relativity in particular) say, unambiguously, that a rotating gas giant in an otherwise empty universe would bulge. Space itself knows what "non-rotating" means; it is an absolute -- in stark contrast to "non-moving", which has no inherent meaning except relative to a particular frame of reference.

What Einstein felt, on philosophical grounds that he attributed to Mach, is that it ought not be so -- that the universe would be a beautifuller place if it were governed by a theory where "non-rotating" doesn't need to be a built-in primitive property of space. But he never succeeded in constructing such a theory, and neither has anyone else. –Henning Makholm (talk) 02:39, 8 January 2011 (UTC)

Thanks, this is very cool and exactly what I wish my teacher had said :) 86.163.214.50 (talk) 21:28, 11 January 2011 (UTC)

For an actual answer, we can look at the Schrodinger Equation. One of the first exercises in a quantum mechanics course is to take a lone particle in empty space, as you describe, and watch it evolve in time. Basically the particle, without anything to constrain it, expands out into the void. It becomes everywhere and nowhere until it has some constraint, something with which it can interact. If you know some mathematics, picture a Normal Distribution that just gets infinitely wider. The particle is there, but found anywhere with equal probability - it will "stick" to whatever it can find, but if alone it will be without definition forever.

When you expand the situation to include Quantum Field Theory, you get vacuum fluctuations which spontaneously appear and are able to localize the particle. To me, this is the most intuitive aspect from which to "trust" quantum mechanics: the void is equally nothing and anything, for if it were entirely nothing, then the universe is a contradiction. SamuelRiv (talk) 20:39, 7 January 2011 (UTC)

Primordial black hole evaporation as gamma ray bursts

The Primordial black hole article says, "The evaporation of primordial black holes has been suggested as one possible explanation for gamma ray bursts. This explanation is, however, considered unlikely.^{[by whom?]}"

That's what I want to know: By whom? And why is it considered unlikely? Gamma-ray burst#Progenitors cites Cline, D.B. (1996). "Primordial black-hole evaporation and the quark-gluon phase transition". Nuclear Physics A 610: 500.... as supporting the possibility, but doesn't say what the evidence against it might be. The "Related Articles" on that cite include [4], [5], [6], and [7], which don't seem to discount the possibility either. Why is it unlikely? 71.198.176.22 (talk) 13:42, 7 January 2011 (UTC)

A disappearing black hole should give a burst that rapidly rises in strenght and then suddenly stops, where as the burst actually appear to be steady. Also the optical counterparts look like supernovas, you would not expect to see much from a black hole evaporation from a long distance. And finally you have the energy levels involved, the black hole releases far less energy than a supernova and would not be observable half way across the universe. Graeme Bartlett (talk) 22:58, 7 January 2011 (UTC)

Relativity

If time is relative, and speed is relative, then what about size, shape, and distance? —Preceding unsigned comment added by 165.212.189.187 (talk) 14:37, 7 January 2011 (UTC)

In a nutshell: yes, because if time and speed are relative, it affects how you measure length in profound ways. See Length contraction for the full discussion. ("Shape" is only a "yes" if you mean the general dimensions of something, not "it's a square no wait it's a circle." Ditto "size.") So two observers traveling in different reference frames will disagree on the length of space and length of objects in rather striking ways. The Ladder paradox illustrates this rather vividly. --Mr.98 (talk) 14:58, 7 January 2011 (UTC)

Please explain what you typed in parentheses. shape is either yes or no. I mean square vs. circle, duh. —Preceding unsigned comment added by 165.212.189.187 (talk) 15:43, 7 January 2011 (UTC)

An intrinsically circular object will be seen measured as being elliptical in a coordinate system that moves with respect to it. Incidentally, the theory of relativity is more concerned with absolutes or invariants rather than relative (coordinate-dependent) things, and Einstein himself later regretted the name he had given to his theory (I don't have a quotation right now). I struck out "seen" because miraculously an individual observer always perceives a sphere as a sphere albeit rotated. --Wrongfilter (talk) 16:09, 7 January 2011 (UTC)

I've forgotten most of the relativity that I ever knew (and that wasn't much) but I thought that the relative view was effectively a rotation (as mentioned by Wrongfilter), so that a rod viewed from the side would appear shorter, but a sphere would maintain its "apparent shape" , and a cube would appear rotated with the trailing side being visible when it "shouldn't be". What would one "measure" to record an ellipse? Dbfirs 17:57, 7 January 2011 (UTC)

... (later) Oh, yes, I "see", one would measure the distance between two marks on the original sphere at opposite ends of the diameter along the direction of motion in its rest-frame. If the moving sphere had its "pole" pointing towards the observer, and had a circle painted round the equator, the observer would see this circle as an ellipse only if the sphere was transparent, otherwise part of it would be hidden. Is this correct? Dbfirs 17:59, 7 January 2011 (UTC)

Well, measuring means taking the coordinates of various points simultaneously (in your rest frame). Imagine placing two rulers in the path of the moving sphere, one aligned with its direction of motion, the other perpendicular. Then mark simultaneously (in your restframe) the points where opposite sides of the sphere are on those rulers. The marked length in the direction of motion will be shorter than that perpendicular to it. If you trace out a cross-section of the sphere, it will be an ellipse. "Seeing" means perception by an individual observer. Consider two photons that hit your retina at the same time, one from the near side, one from the far side of the sphere. The latter photon will have travelled a longer distance, hence it was emitted earlier than the former one. In fact, it will have been emitted when the sphere was actually farther away. Taking the light travel time into account returns the ellpsoid to a sphere. --Wrongfilter (talk) 18:29, 7 January 2011 (UTC)

What I'm worried about is what you mean by "opposite sides of the sphere". Is that "opposite ends of a diameter in its own rest-frame", or opposite ends as the observer "sees" it. I think these would be different. Dbfirs 08:18, 8 January 2011 (UTC)

Sorry, forget the worry, these are the same if the the observer is at the centre of the sphere but not moving with it. Dbfirs 22:36, 9 January 2011 (UTC)

What about SIZE??? —Preceding unsigned comment added by 165.212.189.187 (talk) 21:21, 7 January 2011 (UTC)

Since no-one else has replied, I'll venture an inexpert opinion that it depends on what you mean by "size". In its own rest-frame, an object's dimensions do not change with speed, so size is unchanged. In an inertial frame that is moving at speed with respect to the object, the dimension along the direction of the speed appears is measured as contracted, but islooks as if it is "actually just rotated". If the observer measures just that dimension then it seems to be reduced in "size", but if the observer "looks" and interprets what he "sees", then the moving object will just appear the be the same "size" of object, but rotated. One interpretation of this might be that "size" and "shape" have not changed, but that "orientation" has changed. Distance perpendicular to the direction of motion is unchanged in any interpretation. As pointed out by Wrongfilter above, there is a difference between "seeing" and measuring just one dimension. Perhaps an expert can comment on my "actually just rotated" interpretation. Dbfirs 10:14, 9 January 2011 (UTC)

Um, no, that is backwards. In the non-comoving frame, the object is actually contracted, but may look "just rotated" to an observer that is not too close to it. The rotation is a purely optical effect; length contraction is real. –Henning Makholm (talk) 17:08, 9 January 2011 (UTC)

Yes, perhaps you are correct, though it all hinges on simultaneity. I object to the phrase "is actually contracted", but I'll re-read Ladder_paradox#Bar_and_ring_paradox. If size really changes, then a sphere would fit through an oval ring at speed. Dbfirs 17:30, 9 January 2011 (UTC)

As measured in an inertial frame of reference, an object is measured to be shorter along the object's direction of travel, and unchanged in size in the other two spatial dimensions. E.g., an object that's measured to be a sphere in its own rest frame will when moving be measured to be an ellipsoid. Objects are not measured to have been rotated at all (unless you count a Lorentz boost as a kind of 4-dimensional rotation); they are purely measured as being compressed along the direction of travel.

As seen by a hypothetical insanely high-speed camera, this same compression along the direction of travel is also seen, but there in addition appears to be a kind of distortion, which is different from a rotation. For example, a sphere directly in front of the camera but moving perpendicular to the camera's axis will appear to have been compressed in the direction of travel, i.e., the object's image will have an outline that's an ellipse rather than a circle, and the sphere will also appear to be distorted such that a dot on the part of the sphere closest to the camera will appear to be further in the direction of travel than where the center of the elliptical outline is. But the image will appear somewhat different from the image of a sphere that's been rotated and then compressed. Parts of the object around the object's outline will show less apparent rotation before compression than will that dot that's closest to the camera.

As another example, a sphere directly in front of the camera that's moving directly toward the camera will be seen as having a circular outline, but any picture on the sphere will be distorted such that the picture is stretched out from the center toward the outline. But the part of the sphere that's closest to the camera will appear in the center of the image, so the distortion again is different from a rotation. Red Act (talk) 18:24, 9 January 2011 (UTC)

Thanks for the expert view. I think I was confusing measuring with seeing, and I realised soon after I suggested it that the rod through a ring explanation doesn't extend to 3-D. I've modified my answer above in view of Red Act's and Henning Makholm's expertise, so that it doesn't mislead the OP. I still think that a sphere will still "look" spherical, and this seems to be confirmed by Terrell rotation, but I agree that "seeing from a distance" is not "observing". Experiments on high-speed particles seem to confirm that the reduction in size (and consequent increase in density and charge concentration) are "real" in a fundamental way for measurements taken by the observer in a different inertial frame. Dbfirs 21:21, 9 January 2011 (UTC)

I need to look into Terrell rotation more, which I probably won't have time to do today, but at first glance it looks like I was wrong about a photo of a moving sphere having an elliptical outline. However, from the last paragraph before the References section of this paper, it looks like I was right about the distortion involved not really being equivalent to the sphere having been rotated. I have put strike-throughs in my post above, to eliminate the part about the sphere appearing compressed in a photo. Red Act (talk) 23:55, 9 January 2011 (UTC)

The effect is that of an exact rotation in the limit where the object you look at spans only a small angle of your vision, so what we see becomes an orthographic projection. If you can see the object with the unaided eye, expect some additional distortion, but if you need to use a telescope, it will look very nearly like a rotation -- at least geometrically (color and illumination are of course subject to Doppler effect that Terrell/Penrose say nothing about).

The explanation I find most intuitive takes off from the two snapshots Baez describes. They are taken at the same time and place; one of them by us and another by a hypothetical observer who has the same velocity as the object we're photographing. The mathematics of the pixel mapping (which Baez glosses over) works out to this fact: any sufficiently small area of one of the spherical snapshot is geometrically similar to the corresponding area on the other, but may be smaller or larger. This means that the image of the moving object we see will have exactly the same shape as the one the comoving photographer could take. This immediately implies that we cannot see any contraction (because surely the comoving photographer will not see one), but we may see the moving object as it looks from a somewhat different direction that we would expect -- because that is the direction in which the comoving photographer sees it.

For a simple example, suppose a fast spaceship is moving north and we photograph it exactly at the moment where we see it being due east of us. Our photograph will look exactly like the comoving photographer's image, but how is that? At the time we take the picture, the spaceship will already have moved quite a bit north of our latitude, and since the comoving photographer is here now, it means that he is really south of the spaceship. In our reference frame he trails it by up to the perpendicular distance between us and the spaceship's path, but in the photographer's own frame he can be arbitrarily far behind the spaceship, because the distance we measure is Lorentz contracted. So what his photograph (and ours!) will show is the spaceship seen obliquely from behind. The amount of apparent rotation approaches 90° when the spaceship approaches the speed of light, and will be smaller when we're observing it in directions that are not perpendicular to its velocity.

The point of the last paragraph of Baez's description seems to be about how the interaction between objects that move at different velocities (say, railway car and the track) look, and how we can deduce that something is awry by looking at how the image we see evolves in time. That is true as far as it goes, but does not contradict the illusion of rotation in instantaneous snapshots. (And as long as we observe only a single object and it is far enough away to appear like an orthogonal projection, radial movement would be invisible to us anyway, so it will be visually consistent to assume it is moving (very quickly!) in the direction its apparent rotation indicates). –Henning Makholm (talk) 01:04, 10 January 2011 (UTC)

Microwave oven flavor transfer

If someone heats up a spicy dish of food in a Microwave oven, and seconds after it is removed a cup of water is placed inside, (let's assume for the purposes of making tea or other hot beverage), could the water in the cup possibly obtain any of the characteristics of the flavors of the food previously heated? Could the water take on the smell or taste of the food? 10draftsdeep (talk) 16:42, 7 January 2011 (UTC)

Absolutely. Heating increases the rate of evaporation of any substance; so the microwave, after heating food, will likely have a non-trivial amount of smellable and/or tastable compounds in the air. The water that follows your burrito into the microwave can certainly collect some of these compounds. --Jayron32 16:50, 7 January 2011 (UTC)

(Edit Conflict) This seems to me, as a frequent microwave user, entirely possible and indeed likely, though not due to any mysterious properties of microwave ovens as such.

When one heats food in a microwave oven it becomes filled with water vapour laden with the odours of the food, some of which (depending on the efficiency of its ventilation system) both remains in the oven's air and is deposited as condensation on its inside walls. If one immediately afterwards places and heats a cup of water in that oven, it is quite likely that enough of that 'flavoured' vapour, both from the air and revaporised from the walls, will mix into the water so as to leave a detectable taint. I must confess I haven't experienced this, but only because I usually boil a kettle for my (often concurrent) tea or coffee (though I sometimes reheat an undrunk, cold cup in the microwave). On the rare occasions when I heat a meal's second course (a steamed pudding, say) in the same microwave, I usually try first to disperse/remove (by mopping condensation) as much as possible of the previous course's 'residue' precisely so as to prevent such taste taints. 87.81.230.195 (talk) 17:07, 7 January 2011 (UTC)

It's critical to dispel the myth that evaporation produces 100.0% pure steam. Even in professional grade distillation apparatuses, the evaporation process can create a vapor that may contain evaporated residues, or even solid particulate matter, from any compound that was dissolved in the water. I'm surprised we don't have a vapor transport article; it's a redirect to a related article. Nimur (talk) 19:57, 7 January 2011 (UTC)

It also bears reminding people that if you can smell it, it is in the air. If it is in the air, it can come back out again. --Jayron32 20:25, 7 January 2011 (UTC)

Definition of life

I was reading the "life" page on wikipedia. and the first definition of life seemed a little confusing:"systems that tend to respond to changes in their environment, and inside themselves, in such a way as to promote their own continuation." because every closed system containing chemical substances that are in a chemical equilibrium respond to the changes the same way (acording to Le chatelier principle) I know that life is not a closed system. but is this definition correct? can we say that such behaviors in living organisms is because of the chemical equilibriums in them? — Preceding unsigned comment added by Sina-chemo (talk • contribs) 20:06, 7 January 2011 (UTC)

You aren't alone in being confused. Defining life is a very fuzzy thing. It actually isn't that easy to do. For every actual written definition of life I have ever seen, there exists some obviously non-living thing which can be shown to meet it. It becomes especially tricky to define life when it comes to looking at the border cases, such as viruses and prions. --Jayron32 20:23, 7 January 2011 (UTC)

Keep in mind that in the Life article, it says: "Since there is no unequivocal definition of life, the current understanding is descriptive, where life is a characteristic of organisms that exhibit all or most of the following phenomena:..." Each of the phenomena can describe something non-living, it's the collection of phenomena that is used to define life. -- JSBillings 20:42, 7 January 2011 (UTC)

Also, the spectrum of definition ranges from mainstream biology, where the definition is a lot easier ("koala = alive, rock = not alive"); to extremophile biology (where the definition is much more complicated and requires detailed analysis of biochemistry); to the borderlines of current scientific knowledge (SETI and artificial intelligence both make efforts to scientifically define "life", sometimes coming up with something that could include astrophysical phenomena, sophisticated machinery, computer software, and so on); and at some point, we go off the deep end into fringe science and eventually "religion." (If they exist, is a "God" alive? And ghosts? Pseudoscientists actually suffer seriously from a lack of definition - which lends to the enormous gaping holes in their thought-process). Within any particular realm, the community will develop an operational definition. Most mainstream biologists use a few chemical indicators and particularly rely on the concept of tropic response, which can be more concretely defined (see the list at the bottom of our article). Nimur (talk) 21:17, 7 January 2011 (UTC)

Stuart Kauffman has written about abiogenesis via auto catalytic sets of chemical species. In short, properties similar to homeostasis can be exhibited by non-living things, and he argues that non-life can transition to life in this manner (See his book "At home in the universe" for an accessible pop-sci account). However, contrary to your example, chemical systems that look similar to life are generally not equilibrium systems, but far from equilibrium Dissipative systems. Essentially, pumping energy into the system allows the formation of stable, persistent structure. In this light, my personal favorite edge case for life is the Great Red Spot. Lastly, "obviously living" organisms, such as amoebae, lizards or humans, considered chemically/thermodynamically are far-from-equilibrium, not close to equilibrium as you suggest. SemanticMantis (talk) 21:26, 7 January 2011 (UTC)

More directly to your question, Le_Chatelier_principle explains that a new equilibrium can be reached after conditions are altered. But there is a change from the old equilibrium to the new one. The only thing that persists is the notion of equilibrium, and notions can't be alive (when ideas some similar properties in common with life , we call them memes). Because the original equilibrium A disappears and a new one B is formed with different properties, no state or aspect of the system has responded to the changed conditions in a manner that preserves itself. Whatever the (modern) definition of you choose, including the one quoted in our article on life, a closed system at equilibrium will not satisfy it. SemanticMantis (talk) 23:01, 7 January 2011 (UTC)

Gould on transitional fossils

Hi guys. I have a question about evolution. Creationists seem to think that, due to political pressure, in the early 80s the late Stephen Jay Gould reversed himself on whether good examples of transitional fossils exist. Examples:

http://creation.com/punctuated-equilibrium-come-of-age

http://www.discovery.org/a/7271

I should be candid: I suspect that they have a point. I cannot see how Gould’s earlier statements to the effect that “transitions between major groups are characteristically abrupt” [8] can be reconciled with later claims that “transitional forms are generally lacking at the species level, but they are abundant between larger groups.”[9] If Gould reversed himself on the status of transitional forms, the perennial charge that creationists “quote mined” his views seems a little silly.

What I’m asking is if anyone knows some scientific context that I’m missing here. Does “major groups” mean the same thing in both quotes? Before c~1980, did Gould ever clearly say that transitional forms or fossils exist, or cite some specific examples? I glanced through Gould’s papers from 1972 and 1977 but I’m afraid that they’re a bit too far over my head for me to be certain of their meaning.

I’m not a creationist and I’m not asking anyone to “argue me out” of creationism.

However, for my education, I would appreciate if anyone can point out something that I’ve missed.173.13.48.54 (talk) 20:07, 7 January 2011 (UTC)

I think that the above statements are, like most arguements out of the creationist camps, based on overanalyzing a tiny amount of data while ignoring the abundance of the rest of the data. I don't see the statements as contradictory at all. He says "transitions are abrupt" in the first one, but "transitional forms" in the second one, without defining how long is "abrupt". Transitions can be abrupt, but not so abrupt as to leave zero evidence. Also, science and scientists DO change their opinions about things over time. This is how science works. Perhaps Gould's earlier theories on punctuated equilibrium became more refined over time as new evidence became availible. That isn't a contradiction; its a refinement of the existing theory. I'm not sure which interpretation of Gould's statements is correct, but there are two alternate interpretations to the creationist one. Furthermore, you could just say "Come on, its two sentances made from a man who published enough works to fill a small library. Taking two statements, out of context, and attempting to "prove" that Gould somehow based his scientific pronouncements on "political pressure" rather than sound science is complete and utter bullshit. --Jayron32 20:16, 7 January 2011 (UTC)

Furthermore, it also represents a fundemental flaw in the creationist strategy. Rather than reading Gould with an open mind, and lacking any preconceived notions, and then try to work out what he means and if it makes sense, the "contradiction" claim starts from the premise that Gould MUST be wrong, and if we dig hard enough we can find evidence to support that. And THIS evidence was the best they could come up with to verify their preconceived conclusions. That should tell you something. That doesn't mean that everything Gould ever published or ever had to say about evolution should turn out to be 100% correct. That isn't how science works either. Gould may have been wrong on some of his stuff. That doesn't mean that everything about evolution is just "made up" or "completely wrong". --Jayron32 20:20, 7 January 2011 (UTC)

I think Jayron's point about punctuated equilibrium is probably the germane one. Gould was the primary promoter of PE as an explanation for the gaps within the fossil record; my understanding of the situation is that most other evolutionary theorists didn't so much disagree with it as think he and Eldredge were putting more emphasis on it than they should (and, of course, many people simply thought it was a rewording of various other hypotheses - as our article goes into in some detail). As he became more and more the public figure in the case against creationism, I imagine Gould found himself in an uncomfortable position: any weakening of his support for PE would be used as fodder by the creationists to say that he was admitting that his understanding of evolution was wrong. It's tough enough to admit that you've mis-stated something or changed your opinion on something you used to promote, but it becomes extremely sticky when you know beforehand that your relatively minor change in evaluation will get turned into something completely other by professional liars. I've read a good bit of Gould's stuff (though it's been a while) and it's my impression (WP:OR alert) that, as evidence and support began to shift away from PE into a more gradualist view, Gould's popular writing at least began focusing on slightly different topics (the relationship of science to religion, his Full House book, etc.), perhaps as a way of avoiding (or at least downplaying) the issue. Matt Deres (talk) 20:35, 7 January 2011 (UTC)

I will note that the first quote doesn't include anything like its full context; even ignoring the rest of the document, it is illuminating to read the entire sentence from which the fragment was extracted. "All paleontologists know that the fossil record contains precious little in the way of intermediate forms; transitions between major groups are characteristically abrupt."

Note that he does not state that transitional forms are unheard of or nonexistent in the fossil record, only that they are rare. This would be exactly what is predicted under punctuated equilibrium. Pulling some plausible-sounding numbers out of thin air, let's suppose that 0.1% of fossils are the remains of transitional forms; that's just one out of every thousand fossils, certainly qualifying as "precious little". On the other hand, if paleontologists have collected and fully characterized a million different sets of fossilized remains, you'd still expect to find a full thousand transitional forms in the collection: "abundant" in terms of absolute number.

One could make a similar set of statements about diamonds. They're certainly quite rare; odds are that if you pick up a random rock, it won't turn out to be a diamond. Nevertheless, they're abundant — thousands are traded every day in New York and Amsterdam, and you can see dozens of examples in most jewellery stores. TenOfAllTrades(talk) 21:21, 7 January 2011 (UTC)

Yeah, but diamonds exist because God put them there. Checkmate, atheists!. TomorrowTime (talk) 23:35, 7 January 2011 (UTC)

It would be an interesting undergraduate research paper to try and ferret out the change in Gould's thinking. I think calling it "reversing" and impugning it as somehow meaning he is unreliable is clearly wrong. We stress different aspects of our arguments to different audiences, because we assume different things about what they know and how they will interpret our work. To other specialists, we emphasize the novelty of our own small tweaks (e.g. Gould arguing for PE as a preferred model over gradualism, all within the framework of Darwinian evolution); to a broader public, we try to make sure that our in-discipline arguments don't detract from larger understandings (e.g. Gould emphasizing that PE does not mean that there aren't transitional forms, or that Darwinism is wrong). These two statements of Gould's are not incompatible if you take the purpose of their broader context into account, but I think it's clear that in the later articles, Gould is really trying to debunk any notion that PE opposes Darwinism. I wouldn't call that a reversal, so much as, er, an evolution in his expression. I doubt his underlying opinions changed too much. But it would be interesting to actually track this down historically. --Mr.98 (talk) 01:10, 8 January 2011 (UTC)

One thing to bear in mind is that the form of a species may not be free to vary as much as the underlying genetics - two recognizable forms may exist that are functional, but the intermediates between them fail badly. This is best seen in a spatial distribution - hybrid zones - you can have a butterfly which mimics one group of species, or another very different group of species, but those intermediates get eaten, so they take up only a rather small band of territory - and outside the bands, the two forms don't get more and more extreme as you move away. This is maintained actively by selection, and presumably also by genetic mechanisms that tend to stabilize certain phenotypes (heat shock proteins are known for that). The same could happen over the course of time, with selection forcing a species first to resemble one standard appearance and then a different one. Wnt (talk) 06:46, 8 January 2011 (UTC)

The practice employed by the creationist websites is called quote mining, fyi. That article even has a section on Gould. --superioridad ^(discusión) 21:14, 9 January 2011 (UTC)