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Does this make your head explode? :-)

I have not gone through the paper on the link, but my first reaction was that it would be easy to calculate the length of a photon. We can claculate the energy of a photon of known wavelength, but to calculate the length of the photon, you'd need to know its amplitude.

At that stage I stopped thinking and assumed that this sort of thing is another example of where combining photon and wave theory fails miserably.
 
I think that there is a big hole in our knowledge at the quantum-level. I don't believe that anyone understands quantum theory. Use it and apply it yes but actually understand no. We still have this particle-wave duality to deal with and when you come to measurements you have the uncertainty from Heisenberg.

If I remember correctly Feynman obtained the speed of light as an average from his sum-over-histories and that means that over infinitesimally small distances photons may go faster and slower. From the photons POV it travels everywhere instantly or so our theory tells us. Unless I've missed it somewhere we still don't know the exact charge of the electron. Last I heard was that experiment and qed agreed very closely to umpteen decimal places but...... You might think so what we have soooo many decimal places but if the charge of the electron was just slightly different to what it is our Universe wouldn't exist.

I think this subject needs bright but young brains. Mines too old now.

Cheers,

DV
 
About 10 years ago we had a Leica salesman tell our Head of Dept that their new confocal microscope system could focus down to two photos. After ordering and installing two systems we found that neither the software or the hardware were capable of doing so.
I'm not sure that Photons are all that long but they are quite wide :)
 
I don't know about the width of a photon or its length, but its mass is really, really tiny — in fact, it's so tiny you could say a photon is travelling light.

Sorry, that was terrible.

Joe
 
Darth Vader said:
If I remember correctly Feynman obtained the speed of light as an average from his sum-over-histories and that means that over infinitesimally small distances photons may go faster and slower. From the photons POV it travels everywhere instantly or so our theory tells us.

DV
Click to expand...

Yes. In a way the argument of 'sum over all paths' is a parallel with the Abbe sine requirements. However the end curio for me is that accepting that the photon isn't experiencing any 'travel' at all doesn't tell us when *in our terms* it reaches anywhere. Almost as it it drops out of our universe, has a quick look at a map, and then drops back in again. Hence my curiousity about the time taken as seen by us. So far as I know, no-one has ever measured this using a single photon. They just use beams that contain a mass of them arranged in a neatly ordered pattern and get a 'statistical' result.

I neatly avoided the puzzle of using polarisers, though. 8-]
 
Jim Audiomisc said:
..So far as I know, no-one has ever measured this using a single photon...
Click to expand...
PET scanners work by timing pairs of gamma photons. Each positron-elecron annihilation creates a pair of gamma photons that go in exactly opposite directions and hit the detectors. The two detectors give a line and the time delays give a clue as to where on the line. Strictly particle stuff.
 
In principle, gamma spectrum photons would be Ok in space. The problem would be defining the mirror surfaces, making 100% reflectors, and getting them spaced to within a fraction of a wavelength over the long distances! 8-]

I don't know the frequency/energy the Bell tests have used. But I suspect it will be in the visible or near-visible region.
 
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