If a tree falls

Errr, how does this go? Err, (*blink*)Since when is "yellow" defined like that? It does? And what would be the colour of a 10m wave?This message has been edited by cavediver, 12-30-2005 03:52 PM

Well, not in any of mine, nor those that I have helped edit, nor have I ever taught any of my students such absurdity. No it is not. It is a meaningless concept outside of the visible range. Colour is neither a synomym for frequency nor wavelength.As an astrophysicist I never used nor heard use of nor saw written in any journal the word colour being used to describe any part of the elctromagnetic spectrum outside of the visible range. To do so would be utterly confusing. As a mathematical physicist I never used nor heard use of nor saw written in any journal the word colour being used to describe an attribute of a photon. To do so would be utterly confusing.

Yes, of course it does...and no, it most definitely does not...What are we using to define sound?The cymbal obviosuly makes no vibrational air waves as there is no air. No sound. The cymbal itself will set up compression waves within its own structure by virtue of the collision with the floor. Sound.Forgive the use of Wikipedia but it serves a purpose here:

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Sound is vibration, as perceived by the sense of hearing.

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Wiki on sound

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In more technical language, sound "is an alternation in pressure, particle displacement, or particle velocity propagated in an elastic material" (Olson 1957)

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Wiki on sound

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series of mechanical compressions and rarefactions or longitudinal waves that successively propagate through media that are at least a little compressible (solid, liquid or gas but not vacuum).

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Wiki on sound

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A pressure wave with a frequency detectable by the human ear (approximately 20Hz to 22kHz.)

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A dictionary of science to hand

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sensation caused in the ear due to vibration of surrounding air or other medium

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Oxford English

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the sensation produced through the organs of hearing

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Other dictionarySo, Rrhain may have the final divine answer to "what is sound", but for the rest of us mortals, the word sound carries too many meanings to have any hard and fast definition.

Rrhain, I am long past the point of reading physics text books to improve my physics Other than in areas with which I have very little experience. Light, photons, QED, etc are not areas in which I have little experience.As for the rest of your post, was it meant to demonstrate my position over yours, or was there something missing?The following snippets from your quotes may help:

Did so. My original post remains Rrhain writes:

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Red is defined theoretically, not perceptually: It is the range of photons with wavelengths between 625 and 740 nm.

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Rrhain writes:

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"Color" is a reference to the frequency/wavelength of light. Since every photon has a frequency/wavelength, then every photon has a color. Don't confuse the fact that we have not named every single wavelength with a unique color term to mean that it doesn't have a color.

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Now tell me again how your references back up these gems?This message has been edited by cavediver, 01-02-2006 07:21 AM

:cough:

Good question. As you infer, the effective vacuum prevents the generation of external sound waves. The different vibrational modes will reflect off the object boundaries, and the waves will persist for much longer than if the cymbal was in air. However, as with all (non-quantum) energetic phenomena, the wave energy will gradually heat the cymbal, reducing the waves until they are effectively dampened. The excess heat will then slowly radiate away.

One of the main differences is that the stellar vibrations are forced, i.e. energy is being continually added via the convection cells, which in turn are driven (eventually) by the fusion in the core. So the vibrations are not dying out. But otherwise, similar enough Except that I would not normally consider quite so many modes in looking at the vibrations of a cymbal! 37 is quite extreme...Oh, and thanks for reminding me of this; it's great stuff. Their paper is a good read (which is why it's taken 10mins to get this post out!) I sometimes really regret leaving practical astrophysics for the theoretical stuff

I'm sure that's right, but as it's half past midnight I'll refrain from reading any more papers tonight The reason though will be the same as the stellar seismology... it's a wonderful probe of the interior densities of the object in question. Just imagine, we are analysing the INTERNAL structure of a star light years (well, 4) away!

I prefer my anonymity here. Not that I have any papers on QM per se... my work and papers are in relativity, quantum gravity and string theory. Still, I was considered to posses sufficient competence to tutor Advanced QM to graduates at Cambridge. Not that that course came remotely close to the levels of informal debate and investigation we would have on the subject in the Relativity Group. So I would describe my understanding of QM as reasonbably above half-assed.But if you want to think me a liar, that's fine by me

1.61803 is correct. A field is not a "force field". It is "force" that is "instantaneous" or "action at a distance" in the context of "force of gravity" or "electric force"/"magnetic force". The concept of field was introduceed with Maxwell (and Faraday) and although Maxwell was completely unaware of it, his e/m field had relativistic causality built in. Einstein realised that and it led him to Special Relativity. The next field theory was his General Relativity, where the causal metric (tensor) field replaced the instantaneous force of gravity.Now photons are the quantum particles of light, as suggested by the Einstein's Photoelectric Effect as you mentioned. The Maxwell's wave nature was augmented (but not wholly replaced) by this particle nature. However, the quantum mechanical version of the wave (the photon's wave function) did not sit happily with its classical origin. Furthermore, the quantum mechanics of photons was incapable of dealing appropriately with interactions: the photon "disappears" or is "absorbed" on interaction with an electron. This is impossible in the quantum mechanics of particles.Which brings us back to fields. Quantum Field Theory or 2nd Quantisation is the next development of quantum mechanics, taking everything back to the original classical field theory, quantising it directly, and doing away with the particle description. This enables the possibility of creation and annihilation of "particles", where these particles are merely local excitations of quantum modes of the field. Imagine a spring mattress. A particle is simply the propegation of a vibration through the mattress. This doesn't just apply to the photons but also the electrons. Electrons are merely excitations of the quantum electron field.The QFT of photons and electrons is known as Quantum ElectroDynamics (QED) and won Feynman his Nobel Prize. We also have Quantum ChromoDynamics (QCD) for the quarks and gluons, and finally ElectroWeak Theory which unifies QED with the Ws, Zs and the rest of the leptons (neutrinos, muons and tauons).This message has been edited by cavediver, 01-03-2006 04:23 AM