Taking a Fresh Look at the Physics of Radiometers.
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From: Tim BandTech.com on 11 Jun 2010 14:24 On Jun 11, 1:53 pm, NoEinstein <noeinst...(a)bellsouth.net> wrote: > On Jun 11, 7:38 am, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > Dear Tim: The 'spin' of a NATO (or other) bullet isn't some huge > additional momentum. If the KICK of the gun is 30 pounds, and the > inertia of the gun is 10 pounds (the static weight), then the total KE > is just 40 pounds, including the angular "KE" of the spinning bullet. > That spin is produced by sacrificing some of the forward momentum. > The effect is to rotate the gun in the direction opposite to the spin > of the bullet. It isn't the KE nor the momentum of the bullet causing > the penetration as much as the REDUCTION in the strengths of the > materials that are hitwhich don't "like" rapidly applied loads, nor > loads of more than one stress type at the same time. NoEinstein > > > > > On Jun 10, 10:31 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > > > > On Thu, 10 Jun 2010, Tim BandTech.com wrote: > > > > On Jun 10, 3:19 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > > > > > On Jun 10, 9:43 pm, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > > > > > On Jun 9, 3:40 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > > > > > > > On Jun 10, 4:10 am, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > > > > > > > > If we had, say, a large lead ball hanging on a > > > > > > > > string in stasis, and sent a tiny steel ball into the lead ball at > > > > > > > > high velocity then we would observe some heating, but too achieve the > > > > > > > > level of heating that light achieves will be quite some trick to mimic > > > > > > > > in the terms of massive collisions. > > > > > > > > Not at all. Wikipedia tells me that the energy of a typical 5..56mm > > > > > > > NATO bullet when fired is 1.7kJ. Shoot them into a massive target at a > > > > > > > little under 1 round per second, and you achieve approximately the > > > > > > > same heating. (Not the same force as with light! Just the same > > > > > > > heating.) > > > > > > > Here again I see your obfuscatory tactic. Firstly you falsify and in > > > > > > your conclusion you agree. > > > > > > You were quite specific: "level of heating that light achieves will be > > > > > quite some trick to mimic". This level of heating is easy to mimic. > > > > > > > The amount of heating that light is capable > > > > > > of when absorbed versus the work that can be done mechanically due to > > > > > > that absorption are remarkable in comparison to your NATO bullet. > > > > > > So, you want to change "level of heating" to "amount of heating versus > > > > > work"? If you meant this in the first place, you weren't clear enough. > > > > > To criticise my reply to your actual original words on the basis of > > > > > your _changed_ version lies somewhere on the scale from weaseling to > > > > > complete bullshit. > > > > > I'll have to own here that I should have used the word 'relative' > > > > within the context, but I see it is fairly easy to interperet since > > > > the context of the whole argument is still present. Hell, I can match > > > > the heat of sunlight rubbing some steel on a rock. The lead of the > > > > bullet will melt on impact. Your interpretation of my writing is > > > > clearly not coherent at many levels. > > > > Your original argument wasn't coherent, then. As far as I could tell, you > > > thought it improper that almost all of the energy should go into heating, > > > not work. > > > Jeeze. I pity any onlooker who attempts to decode your own position. > > Now, via double crossing, I must admit that I do agree with your > > statement above and that this is exactly what I've been discussing all > > along. > > > > We see the same thing in Newtonian mechanics for a light object in > > > inelastic collision with a heavy object. Qualitatively, the same type of > > > thing, most of the energy going into heating. > > > It is a peculiar thing to discuss an inelastic collision this way. > > There are more dynamics here and the options as to what happens with > > the energy are numerous. For instance, if we could design a spring > > with a ratchet to capture the projectile then we would only heat by > > the inefficiency of the spring device, rather than by the objects > > entire kinetic energy. Likewise as I stated before, this capture > > mechanism could as well generate electricity, and of course this is > > the quest of many right now; to capture electricity from the sun, and > > to do it at a better margin than 20%. We cannot grant the heat clause > > unconditionally, and instead want the mechanism of that heating. It is > > not so difficult to see electron disturbance; literally microcurrents > > flowing in short circuit fashion which provide the heating effect. > > That these charge concerns are so nearby to the Nichols device is a > > caveat on the operation of that device. That your light traps are so > > behaved is likewise a caveat. Some would like to free these electrons > > to take a larger path. Others would like to ignore them for their > > inconvenient truth. > > > > > The context of the discussion for me revolves around the photon energy > > > > and how we can come to attribute the photon momentum to the photon > > > > energy without concern for such things as angular momentum. > > > > We're not attributing the photon momentum to the photon energy. > > > > For a moving bullet, does the kinetic energy cause the momentum? Does the > > > momentum cause the kinetic energy? Do we attribute one to the other? > > > > For the photon, consider a spin +1 photon. How much of its energy is "in" > > > the angular momentum? > > > > Be specific: consider a 500nm photon, with hbar angular momentum. We can > > > write down 3 numbers: its energy, its momentum, and its angular momentum. > > > How are these 3 related to each other, showing appropriate concern for > > > angular momentum? > > > > How about for a 5Hz photon? Do the same. Does this mean that a 5Hz photon > > > shouldn't have any momentum? > > > > The ratios or values of energy, momentum, and angular momentum, as > > > commonly stated for photons, come straight out of classical > > > electromagnetic theory. Are these ratios or values wrong? Yes or no, no > > > handwaving, no waffle, just a straight answer. > > > From what I've read of the quantum stuff the angular momentum is not > > so easy to observe. They even go so far as to grant a photon an > > orbital angular momentum, though the orbital context is not present in > > freely propagating light. And yet the light as an oscillation is still > > a coherent concept, and so the rotation momentum that I am considering > > is more like your NATO bullet spinning. > > > As I recall the 5Hz photon will have the same quantum angular momentum > > than will the 500nm photon, but will have less total energy via e=hf. > > > As you seek a straight answer I must ask you how crooked is the path > > of modern theory? Yes, we'd all like a straight answer, yet we do not > > actually have one yet. This is not to say that we should give up. We > > seek a straight answer, but I must admit that I do not yet have one. > > Simply eating particle/wave duality will deny a straight answer, but > > beyond this it seems that in the accumulation the overlap of radiation > > pressure with photon momentum has gotten lost in the shuffle. This is > > a great topic, and so difficult to discuss that I believe you and I > > both deserve credit, even while this discussion erodes. > > > - Tim- Hide quoted text - > > > - Show quoted text -- Hide quoted text - > > > - Show quoted text - That seems alright to me. When we get into photons we're talking about frequencies of 6E14 Hertz for Timo's 500 nm light source. If this is a rotational figure then clearly we've got quite some difference to the NATO bullet. Now, I'll admit that this crux of claiming a rotational component inherent to the energy of the light is incomplete, but this is still a fairly coherent way of thinking. Thinking on these terms nobody ever seems to puzzle over the wavelength character of the photon too terribly much beyond the spectroscopic aspects. It is a shame that the light wavelength has not taken more of a literal interpretation than a sinewave. Still, this is how I come to express that frequency and it is pretty standard theory. I'm for breaking into this, but my position is incomplete. I'm just trying to crack the thing open enough to fit a wedge in. A shim is a wonderful thing, and the slight photon momentum must be something like a shim itself. At least noone will quibble over lights ability to shimmer. I don't reccommend shimmying up all the way to the top of modern theory, for if the thing fails it will be a long fall down. I'm sure you remember Humpty Dumpty, but that is another allusion altogether. - Tim
From: Timo Nieminen on 11 Jun 2010 16:17 On Jun 11, 9:38 pm, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > On Jun 10, 10:31 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > > On Thu, 10 Jun 2010, Tim BandTech.com wrote: > > > On Jun 10, 3:19 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > > > > On Jun 10, 9:43 pm, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > > > > On Jun 9, 3:40 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > > > > > > On Jun 10, 4:10 am, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > > > > > > > If we had, say, a large lead ball hanging on a > > > > > > > string in stasis, and sent a tiny steel ball into the lead ball at > > > > > > > high velocity then we would observe some heating, but too achieve the > > > > > > > level of heating that light achieves will be quite some trick to mimic > > > > > > > in the terms of massive collisions. > > > > > > > Not at all. Wikipedia tells me that the energy of a typical 5.56mm > > > > > > NATO bullet when fired is 1.7kJ. Shoot them into a massive target at a > > > > > > little under 1 round per second, and you achieve approximately the > > > > > > same heating. (Not the same force as with light! Just the same > > > > > > heating.) > > > > > > Here again I see your obfuscatory tactic. Firstly you falsify and in > > > > > your conclusion you agree. > > > > > You were quite specific: "level of heating that light achieves will be > > > > quite some trick to mimic". This level of heating is easy to mimic. > > > > > > The amount of heating that light is capable > > > > > of when absorbed versus the work that can be done mechanically due to > > > > > that absorption are remarkable in comparison to your NATO bullet. > > > > > So, you want to change "level of heating" to "amount of heating versus > > > > work"? If you meant this in the first place, you weren't clear enough. > > > > To criticise my reply to your actual original words on the basis of > > > > your _changed_ version lies somewhere on the scale from weaseling to > > > > complete bullshit. > > > > I'll have to own here that I should have used the word 'relative' > > > within the context, but I see it is fairly easy to interperet since > > > the context of the whole argument is still present. Hell, I can match > > > the heat of sunlight rubbing some steel on a rock. The lead of the > > > bullet will melt on impact. Your interpretation of my writing is > > > clearly not coherent at many levels. > > > Your original argument wasn't coherent, then. As far as I could tell, you > > thought it improper that almost all of the energy should go into heating, > > not work. > > Jeeze. I pity any onlooker who attempts to decode your own position. > Now, via double crossing, I must admit that I do agree with your > statement above and that this is exactly what I've been discussing all > along. So, you agree that "improper that almost all of the energy should go into heating, not work" is a fair summary of your original argument? Then what complaint do you have against the bullet example? In the bullet example, almost all of the energy goes into heating. Surely this is just as "improper". If it's OK for most of the KE of a bullet to end up heating the target, rather than doing work, why is somehow wrong for a photon? Note well that in both the bullet and photon cases, you get a force if the bullet/photon is reflected with no loss of energy. It's simpler to consider the reflection case, since you avoid the complications you get into below. > > We see the same thing in Newtonian mechanics for a light object in > > inelastic collision with a heavy object. Qualitatively, the same type of > > thing, most of the energy going into heating. > > It is a peculiar thing to discuss an inelastic collision this way. > There are more dynamics here and the options as to what happens with > the energy are numerous. For instance, if we could design a spring > with a ratchet to capture the projectile then we would only heat by > the inefficiency of the spring device, rather than by the objects > entire kinetic energy. Likewise as I stated before, this capture > mechanism could as well generate electricity, and of course this is > the quest of many right now; to capture electricity from the sun, and > to do it at a better margin than 20%. We cannot grant the heat clause > unconditionally, and instead want the mechanism of that heating. It is > not so difficult to see electron disturbance; literally microcurrents > flowing in short circuit fashion which provide the heating effect. > That these charge concerns are so nearby to the Nichols device is a > caveat on the operation of that device. That your light traps are so > behaved is likewise a caveat. Some would like to free these electrons > to take a larger path. Others would like to ignore them for their > inconvenient truth. Yes, we can explain the heating when an EM wave is absorbed in terms of electrodynamics. Are you seeking to attribute the observed forces to electron ejection? The atom trapping experiments show it isn't so, very clearly. Given that the observed forces are predicted by conventional theory to within the experimental error (i.e., better than 10% in the less accurate experiments, 0.1% in good experiments), it doesn't appear to be significant in the macroscopic experiments either. Does the magnetic force on a current-carrying wire depend on electron ejection? If not, why should the forces due to an EM wave? > > > The context of the discussion for me revolves around the photon energy > > > and how we can come to attribute the photon momentum to the photon > > > energy without concern for such things as angular momentum. > > > We're not attributing the photon momentum to the photon energy. > > > For a moving bullet, does the kinetic energy cause the momentum? Does the > > momentum cause the kinetic energy? Do we attribute one to the other? > > > For the photon, consider a spin +1 photon. How much of its energy is "in" > > the angular momentum? > > > Be specific: consider a 500nm photon, with hbar angular momentum. We can > > write down 3 numbers: its energy, its momentum, and its angular momentum. > > How are these 3 related to each other, showing appropriate concern for > > angular momentum? > > > How about for a 5Hz photon? Do the same. Does this mean that a 5Hz photon > > shouldn't have any momentum? > > From what I've read of the quantum stuff the angular momentum is not > so easy to observe. They even go so far as to grant a photon an > orbital angular momentum, though the orbital context is not present in > freely propagating light. And yet the light as an oscillation is still > a coherent concept, and so the rotation momentum that I am considering > is more like your NATO bullet spinning. > > As I recall the 5Hz photon will have the same quantum angular momentum > than will the 500nm photon, but will have less total energy via e=hf. Keep it simple,. don't worry about orbital angular momentum. If you can't answer the simple question, why make it more complicated. Don't get sidetracked into pretty pictures of photons, either, or long philosophical tracts. Answer the simple question first. If the momentum and/or angular momentum are attributed to the energy, how much of each, in each case, for the 500nm photon and the 5Hz photon? Angular momentum hbar, E=hf, p=h/lambda. Write down the numbers, and say how much of the energy is "in" the angular momentum (or whatever you mean, when you say that having angular momentum means that less energy must be "available" for the momentum). (There are 2 potential nuggets to be had here, if you bother to do it.) [moved] > > The ratios or values of energy, momentum, and angular momentum, as > > commonly stated for photons, come straight out of classical > > electromagnetic theory. Are these ratios or values wrong? Yes or no, no > > handwaving, no waffle, just a straight answer. > > As you seek a straight answer I must ask you how crooked is the path > of modern theory? Yes, we'd all like a straight answer, yet we do not > actually have one yet. This is not to say that we should give up. We > seek a straight answer, but I must admit that I do not yet have one. If you can't say straight-out that it's right or wrong, from what information are you arguing? It's simple in a way. We can, directly from Maxwell's equations, by finding the induced currents and dielectric polarisation, find the force acting on the current and polarisation, via the Lorentz force, and find the work done on the current by the field (which is the heating). > beyond this it seems that in the accumulation the overlap of radiation > pressure with photon momentum has gotten lost in the shuffle. No. Or if it did, stop shuffling it. It isn't an overlap, one is the rate of change of the other. For a beam of light, the radiation force is the change in the momentum flux when the beam is reflected, refracted, or absorbed. For a photon, the impulse imparted to a reflector, refractor, or absorber, is the change in the photon momentum when it is reflected, refracted, or absorbed. If light has momentum, there must be a force when this momentum changes. If light can exert a force, it must have momentum. The simple versions of the derivation of radiation pressure make use of this explictly, which isn't what I would call "getting lost". This is just Newton's laws of motion, just a statement of the conservation of momentum. (It isn't a full application of Newtonian mechanics, with Newton's momentum = density * volume * velocity, but Newton's laws of motion are fine.) Newton 2 works for radiation, for waves, for photons. Force is the rate of change of momentum, imoulse is the change in momentum. This isn't lost. If you prefer to think about photon momentum or wave momentum instead of force or radiation pressure, go ahead. But don't forget Newton 2!
From: Sue... on 11 Jun 2010 17:35 On Jun 11, 7:07 am, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > On Jun 9, 5:55 pm, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > > > > > On Jun 9, 2:20 pm, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > > > On Jun 7, 8:58 pm, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > > > > > On Jun 7, 6:42 pm, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > > > > > On Jun 7, 5:55 pm, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > > > > > > > On Jun 7, 7:41 am, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > > > > > > Beyond this thermodynamics remains open in my book. > > > > > > > This is a bit disturbing at this point in the thread. > > > > > > Reynolds explained Crooks radiometer with > > > > > > ~thermodynamics~ . > > > > > > > Your discussion with Timo seems to be about > > > > > > Nichols radiometer. The distinction was > > > > > > made earlier in the thread but you will be > > > > > > talking past one another if you are not > > > > > > about the same device and effect. > > > > > > Thanks for the attempt at resolution, but we are on to other aspects > > > > > now. > > > > > He seems to think that when you attribute all of a photons energy to > > > > > momentum that somehow the energy is independent of that momentum. I'm > > > > > not going to buy that, but if you can falsify either of us then I > > > > > think that input is very welcome. > > > > > I'll take your side because radiation~suction > > > > fits an induction gravity mechanism better. > > > > > (Timo can conscript a few students if he > > > > thinks we are ganging up on him.) > > > > > > We're really not beyond anything > > > > > more than > > > > > e = h f , e = m c c , > > > > > > and such simple product relationships. > > > > > I don't see how e = hf applies where there > > > > may be no atomic absorption. > > > > > <<The requirements of energy and momentum > > > > conservation generally forbid the absorption > > > > of photons by free carriers, and the process can > > > > only take place by interband transitions or with > > > > the assistance of phonon absorption or emission. >> http://www.colin-baxter.com/academic/research/downloads/prl063802.pdf > > > > > http://en.wikipedia.org/wiki/Nichols_radiometer http://en.wikipedia.org/wiki/Boltzmann_constant > > > > > > > Apologies if I am covering old ground but > > > > > > it is a long thread and I got here late. > > > > > > Hey Sue, no problem. I guess one of the key points is that the > > > > > radiometer itself is not quite what most of the discussion is about. > > > > > Isolation of radiation pressure from the radiation is more like it. > > > > > What I now understand and had overlooked for much of the thread is > > > > > that the radiation pressure is merely the photon momentum, as is > > > > > overlooked at > > > > > http://en.wikipedia.org/wiki/Radiation_pressure > > > > > and likely elsewhere. Nichols work is here: > > > > > http://books.google.com/books?id=8n8OAAAAIAAJ&pg=RA5-PA329#v=onepage&... > > > > > <<Theory > > > > It may be shown by electromagnetic theory, by quantum > > > > theory, or by thermodynamics, making no assumptions as > > > > to the nature of the radiation, that the pressure against > > > > a surface exposed in a space traversed by radiation > > > > uniformly in all directions is equal to one third of the > > > > total radiant energy per unit volume within that space.>> > http://en.wikipedia.org/wiki/Radiation_pressure > > > > > Hmmm... 1/3 is a pretty nice number and the statement > > > > is very inverse square-ish. Is it too late to > > > > switch to Timo's team? I am a sore looser. > > > > > I see the traversed volume here: http://hyperphysics.phy-astr.gsu.edu/hbase/forces/isq.html > > > > But all of it, half of it or 1/3 of it is not > > > > doing anything for me unless we put some gas in > > > > it and give it a temperature. > > > > > Yeah... That's the steam. > > > > Eggs explode in my microwave oven because > > > > of radiation pressure. > > > > > > which is actually linked to in that wiki you just gave. > > > > > Some if his argumentation is quite poor imo. There is a 1933 paper by > > > > > a woman Bell that I do not have access to which claims to resolve the > > > > > study down to 10E-6 torr. I posted that link a few days ago here. > > > > > In fairness, I should read about Timo's light-bullets > > > > a bit closer before we declare victory. > > > > > Photons (Phonons?) can be a pretty good model translating > > > > angular momentum in a dielectric. I am becoming > > > > sceptical however because acoustic radiation pressure > > > > is lumped in, apparently as the same effect. > > > > > If it is just molecules in the traversed volume > > > > jiggling more, induction gravity should be unscathed > > > > and it really shouldn't matter how you describe the > > > > heating process. light bullets, flaming arrows, or > > > > Ella Fitzgerald on Memorex. > > > > Well, if the photon momentum is taken to be coming from the entire > > > photon energy, then there is no room for the rotational quality to > > > contain more energy. This is the logical trouble with the existing > > > theory. > > > The light is *all* angular momentum until charges in > > the gas convert it through interaction. Antenna are > > necessary for any directed energy. > > > (With a minor exception) <<for a highly relativistic > > charge the radiation is emitted in a narrow cone > > whose axis is aligned along the direction of motion.>> http://farside.ph.utexas.edu/teaching/jk1/lectures/node33.html > > > > As you say, we should take freedoms in describing these > > > things. Ella Fitzgerald may be going a bit far, > > > The wiki references indicate the principle is the same > > for sound so Ella is not "too far" but specifically > > included. Anything that heats the media is what > > I understand for the Nichols device. ============== > > Hmmm... I thought by going to 10E-6 torrs that the temperature effects > were being diminished. Likewise sound does not travel in a vacuum- > although this very word 'vacuum' is pretty dubious. As soon as you put > anything in a vacuum it cannot be a vacuum anymore. So as soon as we > plop down a Nichols device within the vacuum we ought perhaps to state > that the Nichols device has been isolated, rather than use the vacuum > terminology. Still, to what degree is the isolation perfect? Just tap > the lab table and you've got your sound transmission again. > Metallic vanes and glass surfaces can spoil a vacuum too. I don't know who went there and measured it but I have some information that if you want vacuum better than 1 atom per cc you have to visit another universe. But let's say for the sake of argument that you could sweep ALL the gas out of a Nichols device. The electrons in the vanes and the electons in the glass will still jiggle from illumination and a few will still try to fill the space with even greater repulsion from the protons in their host matter. Electron valves (vacuum tubes) don't malfunction if we take too much gas out. Eh? http://en.wikipedia.org/wiki/Thermionic_emission http://en.wikipedia.org/wiki/Paschen%27s_law > > > >but as you take > > > interest in gravitation there is room for a photon relationship with > > > gravitation to provide gravitational shadowing, which could then > > > provide the dark matter resolution. > > > The term shadowing has a negative connotation > > from some dubious shielding experiments but yes there > > is mechanism for enhancement or attenuation > > along a gravitational path so the "shadowing" > > label seems to stick. > > > It is not as bad as a big red "A" on your > > blouse and it might even be a source > > of pride when Mercury and Hulse-Taylor are > > considered. > > Well, I looked at some Hulse-Taylor links. I suppose if it is true > that gravitational shadowing is an effect then the planetary orbits > will take on more dynamics and might help explain all of the strange > angles of rotational axes, magnetic axes, maybe even how they can be > in such a clean plane. That would be quite some fine tuning and would > put the inner planets as the leaders. Anyway Sue it's nice to see you > consider this idea, though cryptically. I don't buy into the notions about quadrupole moments from a monopolar ~antenna~. So induced gravity explains Hulse-Taylor and a quite LIGO very nicely, (tho only qualitativly) :-( > > Here is a simple question for you: Is radiation pressure a unique > effect from photon momentum? Qualitatively no. Because photons are pseudoparticles. But they are powerful modeling tools. If the maths is rigourous and makes better predictions there is every reason to favour their use in explaining an phenomena. If atom "D" absorbs a unit of energy with some causal link to atom "S" loosing a unit of energy, call it a photon. But don't try to say too much about the path. That requires classical electromagnetism. > My answer is no, but I am still not > getting much clear feedback on this, and as I read there is little > direct connection made, though the math appears to work out directly. > This is based on a wiki link number of the sun's radiation pressure, > so I'm not feeling so solid. As I recall it is 4.6E-6 Pascals of solar > radiation pressure here on the earth's surface from 1375 watts of > solar radiation energy per square meter. It's rather alot of heat for > a little kick. I'm trying to give this theory a kick in the pants. > Speaking of panting, I'd better see what Timo has been up to on this > thread. Well... Timo threw a nearly atomic scale experiment at us with the tweezers, so we have to keep him honest and make sure it scales to Nichols radiometers and solar-sails. I don't see any thing about Boltzmann constant or traversed volume in his most recent post. I won't say his technique can't leapfrog all that, it may. But I am not seeing it yet. Sue... > > - Tim
From: spudnik on 11 Jun 2010 17:57 sounds interesting, but I doubt that you will get much of a reading, since M&M et sequentia did not -- but, it was *a* reading. now, you'd probably call that, entrained aether, but I really don't see any need for such in "electromagnetism with no Pascalian (perfect) vacuum" (and I recall reading, the air is half hydrogen, 500 miles out e.g.) > I can get Earths speed and direction without reference to any stars! thus&so: I read [*] the name of the unindicted co-conspirator of HDubya in Iran-contra, Oliver "Buck" Revell, who laid down the law at the NSF meeting, that "global" cooling would henceforth not be funded. see, I put that word in scare-quotes, becuase it was the self- same flat-map miscomprehension of insolation -- merely the differential from pole to equator -- that presupposes that glaciation requires a lesser temperature, or that deglaciation'd require a greater one. * http://tarpley.net/online-books/george-bush-the-unauthorized-biography/ --Stop BP's and Waxman's arbitrageur's delight, the cap&trade that the WSUrinal *calls*, Captain Tax (but, there seems to be no provision for goment revenues )-!... Fermat's Next Theorem: http://wlym.com
From: Sue... on 11 Jun 2010 21:24
On Jun 11, 4:17 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > On Jun 11, 9:38 pm, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > > > > On Jun 10, 10:31 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > > > On Thu, 10 Jun 2010, Tim BandTech.com wrote: > > > > On Jun 10, 3:19 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > > > > > On Jun 10, 9:43 pm, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > > > > > On Jun 9, 3:40 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > > > > > > > On Jun 10, 4:10 am, "Tim BandTech.com" <tttppp...(a)yahoo.com> wrote: > > > > > > > > > If we had, say, a large lead ball hanging on a > > > > > > > > string in stasis, and sent a tiny steel ball into the lead ball at > > > > > > > > high velocity then we would observe some heating, but too achieve the > > > > > > > > level of heating that light achieves will be quite some trick to mimic > > > > > > > > in the terms of massive collisions. > > > > > > > > Not at all. Wikipedia tells me that the energy of a typical 5..56mm > > > > > > > NATO bullet when fired is 1.7kJ. Shoot them into a massive target at a > > > > > > > little under 1 round per second, and you achieve approximately the > > > > > > > same heating. (Not the same force as with light! Just the same > > > > > > > heating.) > > > > > > > Here again I see your obfuscatory tactic. Firstly you falsify and in > > > > > > your conclusion you agree. > > > > > > You were quite specific: "level of heating that light achieves will be > > > > > quite some trick to mimic". This level of heating is easy to mimic. > > > > > > > The amount of heating that light is capable > > > > > > of when absorbed versus the work that can be done mechanically due to > > > > > > that absorption are remarkable in comparison to your NATO bullet. > > > > > > So, you want to change "level of heating" to "amount of heating versus > > > > > work"? If you meant this in the first place, you weren't clear enough. > > > > > To criticise my reply to your actual original words on the basis of > > > > > your _changed_ version lies somewhere on the scale from weaseling to > > > > > complete bullshit. > > > > > I'll have to own here that I should have used the word 'relative' > > > > within the context, but I see it is fairly easy to interperet since > > > > the context of the whole argument is still present. Hell, I can match > > > > the heat of sunlight rubbing some steel on a rock. The lead of the > > > > bullet will melt on impact. Your interpretation of my writing is > > > > clearly not coherent at many levels. > > > > Your original argument wasn't coherent, then. As far as I could tell, you > > > thought it improper that almost all of the energy should go into heating, > > > not work. > > > Jeeze. I pity any onlooker who attempts to decode your own position. > > Now, via double crossing, I must admit that I do agree with your > > statement above and that this is exactly what I've been discussing all > > along. > > So, you agree that "improper that almost all of the energy should go > into heating, > not work" is a fair summary of your original argument? > > Then what complaint do you have against the bullet example? In the > bullet example, almost all of the energy goes into heating. Surely > this is just as "improper". If it's OK for most of the KE of a bullet > to end up heating the target, rather than doing work, why is somehow > wrong for a photon? > > Note well that in both the bullet and photon cases, you get a force if > the bullet/photon is reflected with no loss of energy. It's simpler to > consider the reflection case, since you avoid the complications you > get into below. > > > > > > We see the same thing in Newtonian mechanics for a light object in > > > inelastic collision with a heavy object. Qualitatively, the same type of > > > thing, most of the energy going into heating. > > > It is a peculiar thing to discuss an inelastic collision this way. > > There are more dynamics here and the options as to what happens with > > the energy are numerous. For instance, if we could design a spring > > with a ratchet to capture the projectile then we would only heat by > > the inefficiency of the spring device, rather than by the objects > > entire kinetic energy. Likewise as I stated before, this capture > > mechanism could as well generate electricity, and of course this is > > the quest of many right now; to capture electricity from the sun, and > > to do it at a better margin than 20%. We cannot grant the heat clause > > unconditionally, and instead want the mechanism of that heating. It is > > not so difficult to see electron disturbance; literally microcurrents > > flowing in short circuit fashion which provide the heating effect. > > That these charge concerns are so nearby to the Nichols device is a > > caveat on the operation of that device. That your light traps are so > > behaved is likewise a caveat. Some would like to free these electrons > > to take a larger path. Others would like to ignore them for their > > inconvenient truth. > > Yes, we can explain the heating when an EM wave is absorbed in terms > of electrodynamics. Are you seeking to attribute the observed forces > to electron ejection? The atom trapping experiments show it isn't so, > very clearly. Given that the observed forces are predicted by > conventional theory to within the experimental error (i.e., better > than 10% in the less accurate experiments, 0.1% in good experiments), > it doesn't appear to be significant in the macroscopic experiments > either. Does the magnetic force on a current-carrying wire depend on > electron ejection? If not, why should the forces due to an EM wave? > > > > > > > The context of the discussion for me revolves around the photon energy > > > > and how we can come to attribute the photon momentum to the photon > > > > energy without concern for such things as angular momentum. > > > > We're not attributing the photon momentum to the photon energy. > > > > For a moving bullet, does the kinetic energy cause the momentum? Does the > > > momentum cause the kinetic energy? Do we attribute one to the other? > > > > For the photon, consider a spin +1 photon. How much of its energy is "in" > > > the angular momentum? > > > > Be specific: consider a 500nm photon, with hbar angular momentum. We can > > > write down 3 numbers: its energy, its momentum, and its angular momentum. > > > How are these 3 related to each other, showing appropriate concern for > > > angular momentum? > > > > How about for a 5Hz photon? Do the same. Does this mean that a 5Hz photon > > > shouldn't have any momentum? > > > From what I've read of the quantum stuff the angular momentum is not > > so easy to observe. They even go so far as to grant a photon an > > orbital angular momentum, though the orbital context is not present in > > freely propagating light. And yet the light as an oscillation is still > > a coherent concept, and so the rotation momentum that I am considering > > is more like your NATO bullet spinning. > > > As I recall the 5Hz photon will have the same quantum angular momentum > > than will the 500nm photon, but will have less total energy via e=hf. > > Keep it simple,. don't worry about orbital angular momentum. If you > can't answer the simple question, why make it more complicated. > > Don't get sidetracked into pretty pictures of photons, either, or long > philosophical tracts. Answer the simple question first. > > If the momentum and/or angular momentum are attributed to the energy, > how much of each, in each case, for the 500nm photon and the 5Hz > photon? Angular momentum hbar, E=hf, p=h/lambda. Write down the > numbers, and say how much of the energy is "in" the angular momentum > (or whatever you mean, when you say that having angular momentum means > that less energy must be "available" for the momentum). > > (There are 2 potential nuggets to be had here, if you bother to do > it.) > > [moved] > > > > The ratios or values of energy, momentum, and angular momentum, as > > > commonly stated for photons, come straight out of classical > > > electromagnetic theory. Are these ratios or values wrong? Yes or no, no > > > handwaving, no waffle, just a straight answer. > > > As you seek a straight answer I must ask you how crooked is the path > > of modern theory? Yes, we'd all like a straight answer, yet we do not > > actually have one yet. This is not to say that we should give up. We > > seek a straight answer, but I must admit that I do not yet have one. > > If you can't say straight-out that it's right or wrong, from what > information are you arguing? > > It's simple in a way. We can, directly from Maxwell's equations, by > finding the induced currents and dielectric polarisation, find the > force acting on the current and polarisation, via the Lorentz force, > and find the work done on the current by the field (which is the > heating). > > > beyond this it seems that in the accumulation the overlap of radiation > > pressure with photon momentum has gotten lost in the shuffle. > > No. Or if it did, stop shuffling it. It isn't an overlap, one is the > rate of change of the other. ============= > > For a beam of light, the radiation force is the change in the momentum > flux when the beam is reflected, refracted, or absorbed. For a photon, > the impulse imparted to a reflector, refractor, or absorber, is the > change in the photon momentum when it is reflected, refracted, or > absorbed. The notion certainly didn't come from the sci-fi shelves. It may be instructive to examine the differences in two concise statements. <<Since the force on a dielectric object is given by the change in momentum of light induced due to refraction of the light by the object, the total force on the object is the difference between the momentum flux entering the object and that leaving the object. The total force on an object due to refraction of light is therefore >> eq3,p2 "Optical Tweezers: Measuring Piconewton Forces" http://www.biophysics.org/Portals/1/PDFs/Education/williams.pdf > > If light has momentum, there must be a force when this momentum > changes. If light can exert a force, it must have momentum. The simple > versions of the derivation of radiation pressure make use of this > explictly, which isn't what I would call "getting lost". > > This is just Newton's laws of motion, just a statement of the > conservation of momentum. (It isn't a full application of Newtonian > mechanics, with Newton's momentum = density * volume * velocity, but > Newton's laws of motion are fine.) > > Newton 2 works for radiation, for waves, for photons. Force is the > rate of change of momentum, impulse is the change in momentum. This > isn't lost. If you prefer to think about photon momentum or wave > momentum instead of force or radiation pressure, go ahead. But don't > forget Newton 2! I get the impression the method is an approximation using kinetic theory to speed up calculations where molecular dynamics (many bodies) is more accurate, but too intense computationally for a laboratory tool. Just one more reason I hesitate to scale it up to larger objects. Can one learn about the Rayleigh regime and the Mie regime anywhere near books about the Mao regime? (Spudnik wanted me to ask because he is too shy) Sue... |