sci.physics.electromag

On Thu, 20 Mar 2008, Szczepan Bialek wrote:

> "Timo A. Nieminen"
>>
>> That would tell us the (temporal) coherence of the source. Experiments
>> showing that atomic absorption and subsequent re-emission of photons, the
>> transition from one electronic energy state to another, occurs in a much
>> shorter time than the coherence time of the source were done more than
>> twenty years ago.
>
> Now we have the equations and we can calculate how big a photon is. The
> coherence time was probably estimated in time of Newton rings. Are now
> available measured coherence times for different sources?

Yes. For example, various laser sources can have coherence lengths (which
might also be worth googling; it is of course directly related to
coherence time by the speed of light) varying from mm or cm to 100s of m,
or even many km. I'd expect that even longer coherence lengths/times are
possible at RF.

> Is agreement between the photon theory and the packed theory (in textbooks
> in the chapter "Optics" no photons - there is coherence time).
> Maybe that photons are only math.

As mentioned before, time of emission/absorption is _not_ compatible with
the suggestion that "coherence length" = "length of photon". Note that
coherence time is important in classical optics, but photons aren't. More
evidence that they're not the same thing at all.

>> The goal was to try to measure how long the absorption or emission of
>> photons took. All they could say was that it took less time than they
>> could measure. At least some of the experiments looked at transitions with
>> narrow frequency spectra, implying wavefunctions _much_ longer than the
>> emission/absorption times.
>
> I have found that interference is seen if the distanne (thru air gap) is
> smaller than 100 wave lenght. It meens that the packet is very short.
> Between packets must be pauses. Pauses also should be measured. Are they?

Not generally. Coherence length is not the length of wavepackets, so
there's no need for pauses.

>> There were multiple experiments, from the early or mid 1980s or so. Most
>> of the papers I read were from Phys Rev [X]. "Quantum jump" might have
>> appeared in some titles if you want to search.
>
> I try to search more abour the coherence time but in Optics area.

--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html