I think a bit more and say he has a point. But with regard to the
above even after thinking about it a bit I am not so sure. wrote:
[snip]

i know this bull****, pointparticle, but taking into account
that 700nm wavelength will describe a photon as being so
big, the question was how small a radio photon could be

PD defined them as being photons, not me


Yes, but the name "photon" does not imply an object of definite size.
It means something that carries certain quantum numbers (like charge,
spin, etc.), and carries a specific amount of energy and momentum. Some
of these properties are connected to its wavelike properties, as well.

PD

N:dlzc D:aol T:com (dlzc) wrote:
Photons have been experimentally determined to be of zero size.
Certainly many orders of magnitude less than their "wavelength".

This is not true. Photons have no definite size, and their "size" cannot
be measured. About the closest one can come is to measure the coherence
length of a monochromatic source -- for lasers that can be a few cm
(ordinary He-Ne lasers) up to many meters (single-mode He-Ne lasers),
and for radio waves it can be many kilometers.

Transversely, you will naturally ascribe the "width" of a photon to be
the width of your detector. E.g. for a CCD camera that is on the order
of a few microns -- it is not a single-photon detector but each photon
interacts in a single pixel (or none).


Tom Roberts

thanks

Dear Tom Roberts:

"Tom Roberts" wrote in message
om...
N:dlzc D:aol T:com (dlzc) wrote:
Photons have been experimentally determined to be
of zero size. Certainly many orders of magnitude
less than their "wavelength".

This is not true. Photons have no definite size, and
their "size" cannot be measured.

OK, Tom, you've popped the blister. Franz Heymann pointed me to
two papers indicating that they show the photon is of "zero"
size. Now he may have done that knowing that it would "stun me
into silence" (which it did, as I was deep in my near-crank phase
at the time, as if I ever left), or he may have done that so that
it would spark some hunger in me to learn more (it did that too,
but I can't go back until my kids go first).

URL:http://xxx.lanl.gov/abs/hep-ex/9807017
"Photon Structure and gamma-gamma Physics"

URL:http://xxx.lanl.gov/abs/hep-ex/9708006
"Two Photon Physics at LEP2; including data Monte-Carlo
comparison"

Do you care to add anything?

About the closest one can come is to measure the
coherence length of a monochromatic source -- for
lasers that can be a few cm (ordinary He-Ne lasers)
up to many meters (single-mode He-Ne lasers), and for radio
waves it can be many kilometers.

Transversely, you will naturally ascribe the "width"
of a photon to be the width of your detector.

Don't use the word "you" here. I would ascribe something
entirely different to the width, and no need to get into my
(other) problems here. Rather say "one will naturally...".

E.g. for a CCD camera that is on the order of a few
microns -- it is not a single-photon detector but
each photon interacts in a single pixel (or none).

I would not use detector size to infer the size of the
"detected", no. If a detector is a nail, then it is no judge of
the size of the hammer. I would use something like the exclusion
principle, asking where did the photon *absolutely not* go in its
trip from emitter to detector. That I would use to judge its
"size". But I am also perfectly happy with it being a point
particle (which I understand is the inverse of the previous
sentence).

David A. Smith

is zero size a point?

if zero the it cant have r() coordinates

Dear destiny:

"destiny" wrote in message
oups.com...
is zero size a point?

if zero the it cant have r() coordinates

A single photon has neither position nor path. It departs and it
arrives, and its path is unknowable by mortal man. Much like
women. ;)

David A. Smith

A single photon has neither position nor path. It departs and it
arrives, and its path is unknowable by mortal man. Much like
women. ;)

David A. Smith

oh ya, i forgot, thanks remainding me


don let my name fool you, im not a women

maybe should change may name again

Dear destiny:

"destiny" wrote in message
oups.com...

A single photon has neither position nor path. It departs and
it
arrives, and its path is unknowable by mortal man. Much like
women. ;)

oh ya, i forgot, thanks remainding me


don let my name fool you, im not a women

Didn't intend to imply you were. "Mr. Destiny" is already a
movie...

maybe should change may name again

Whatever you think you need to do. I find it annoying, but that
is just me.

David A. Smith

chronos wrote:
can a single photon exists? how fast would it fly

Depends how quickly it wants to get down to the dating agency and find
a mate.

(1) can a single photon exists?
Quantum dot creates single photon source (June 2005) - News ...
Nanotechweb.org is a global nanotechnology portal including latest
research
articles, industry news, features, companies, events and links to other
online ...
- 17k - Jun 4, 2005
http://nanotechweb.org/articles/news/4/6/4/

http://ipeqwww.epfl.ch/qd/html/singleqddevices.htm
http://www.toshiba-europe.com/resear...uantumdot.html

(2) how fast would it fly

About 300 million meters per second.

Sue...