Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: PAOLO137 on 21/06/2013 13:55:14

Title: Richard Feynmann's QED
Post by: PAOLO137 on 21/06/2013 13:55:14
I am an aged and retired physicist. For this reason I enjoy reading all possible books concerning the subjects that have to do with the second half
of last century, trying to understand the maximum. This time I found myself in difficulty with that marvelous book by Richard Feynman.
He probably had the intention of being understood in the best way, but instead I found some very obscure concepts. I wonder if somebody can clarify those to me. He suggest the reader to imagine the travel of a photon through the space made up of a succession of "arrows" each one  attached to the previous one. (A common sum of vectors). Then he suggests to imagine , attached to each of these arrows, something like a
small clock, with a single hand rotating at very high speed. The combination of the point of the arrow and of the position (angle) of the little hand
of the clock, would give the information required to draw the following arrow. I must confess that I have not understood the meaning of this little watch. Is it intended to represent the phase of the wave who "forms" the travelling  photon? I think to understand that it was an idea to facilitate
the understanding of the people attending the lectures from which the book was transcribed, but he should have been more clear. Thank you for
any comments, Paolo .
Title: Re: Richard Feynmann's QED
Post by: imatfaal on 21/06/2013 15:55:48

If I remember correctly it is the vector - representing the state of whatever is being measured at the time - which can be visualized as taking on a direction dependent on time (ie rotating).  Ie the vector sums of various paths can be then added and the directions of the vectors can lead to an analogy of constructive, destructive interference

I have attached a link of the Feynman lectures at the University of Auckland - which I believe were a more popular version of his magnum opus on qm

Not sure if any of above helps - but I hope so
Title: Re: Richard Feynmann's QED
Post by: PAOLO137 on 27/08/2013 18:23:59
You  gave me a wonderful hint. Reading "QED" I knew that Feynman wished to try a reharsal of
his lectures in New Zealand, just to be confident people was ready to accept the unusual things
he was going to tell, in such a far away location. To have the chance to watch that story "live"
was a real emotional adventure for me. Thanks to you!! Paolo.