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#2855 08/29/05 07:55 PM
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Since photons move throug the 3 dimensions of space with the speed of light (or at least very close to it considering the none-vacuum enviroment) it should pretty much stand still in time right? But what does that mean with respect to the photons position? Should it be considered everywhere at once? (everywhere it could possibly be considering it's direction and what-not ofcourse)


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#2856 08/29/05 08:03 PM
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Photons, by definition, move at the speed of light: Always. That doesn't mean the speed is constant ... just that it IS the speed of light. And thus a photon, to the best of our knowledge, does not experience time.

Positionally it seems quite likely that is present at all possible positions where it is possible simultaneously: Whatever that means. A conclusion that seems as likely correct as it is confusing.


DA Morgan
#2857 08/29/05 08:25 PM
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I see, thanx.
The reason I asked was because something a professor said on the introductory lecture in a quantum physics course that started today. It was about wave-particle duallity. I thought that the reason photons often seem to decide where they are retroactivly is because they are everywhere at once, but as I'm writing this I realize that it don't make sense. Funny how a thougt often only reveals it's impotense after it has been verbalized.


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#2858 08/29/05 08:33 PM
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That it doesn't make sense doesn't make it any less adequate an explanation given our limited understanding of QM.

To quote Niels Bohr:
"No, no, you're not thinking; you're just being logical."

and one of the following three is hopefully accurate. No doubt the differences from translation.

"If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet."
or
"If anybody says he can think about quantum physics without getting giddy, that only shows he has not understood the first thing about them."
or
"If somebody says that he can think about quantum physics without becoming dizzy, that shows only that he has not understood anything whatever about it."

And his conclusion:
"Never express yourself more clearly than you are able to think."


DA Morgan
#2859 08/30/05 12:28 AM
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A photon's point of view is not an inertial frame of reference. That is one of the big concepts of Special Relativity. Refractive index is caused by absorption and re-emission of photons. Look at the relationship between refractive index and dielectric constant, then the (never observed) Scharnhorst effect,

http://arXiv.org/abs/gr-qc/0107091
http://arXiv.org/abs/quant-ph/0010055
Phys. Lett. B236 354 (1990)
Phys. Lett. B250 133 (1990)
J Phys A26 2037 (1993)

Light travels at lightspeed regardless of the medium. The frequency is not altered by refractive index, only the wavelength.

Quote:
I thought that the reason photons often seem to decide where they are retroactivly
Don't anthropomorphize. Look up quantum eraser and quantum double eraser experiments.

Google
"quantum eraser" double 593 hits

Remember what Feynman said about quantum mechanics, "shut up and calculate."


Uncle Al
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(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz3.pdf
#2860 08/30/05 03:26 AM
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Remember what Feynman said about quantum mechanics, "shut up and calculate."
REP: Thats amazingly true.
===============================
Since photons move throug the 3 dimensions of space with the speed of light (or at least very close to it considering the none-vacuum enviroment) it should pretty much stand still in time right?
REP: What moves through the space is determined by the choice of your experiment.Share the thought experiment and I will try to help you.
=================================
But what does that mean with respect to the photons position? Should it be considered everywhere at once? (everywhere it could possibly be considering it's direction and what-not ofcourse)
REP:Are you asking this question to photon? He doesnt ask it to himself.
==================================

#2861 10/18/05 12:46 PM
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I'm so sick of hearing about time as a physical thing with a direction and a form! Can someone please explain to me how it is at all possible for anything to 'stand still in time'? It seems to me that light-speed had deluded people into believing there are regions in space where ?time slows down?. Time is not slowing down, nor CAN it slow down. The only thing slowing down are electromagnetic waves, which, at the moment are the fastest things known that can carry information. The fact that these ?information carriers? can be slowed should never suggest that time is being slowed. It would be the equivalent to saying a parked car is ?standing still in time?.

#2862 10/18/05 05:02 PM
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Al you wrote:
"Light travels at lightspeed regardless of the medium. The frequency is not altered by refractive index, only the wavelength."

Would you care to revisit this statement? Is it what you intended? Can you separate frequency and wavelength?


DA Morgan

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