Richard Feynman Commemorative Cancel

A special postal cancel was authorized by the United States Postal Service to honor the 80th birthday of Richard Feynman.  This cancel was used in Lake Worth, Florida, home of the Tannu Tuva Collectors Society.  For this special day, the post office was renamed "Feynman Station."

The Feynman Diagram used for the postal cancel on this envelope depicts what is known as a "bubble process."  It shows a high energy particle (a), for example, a cosmic ray from a distant supernova, which emits a high energy photon, for example, a gamma ray (b).  The photon, in turn, creates a particle (c) and an anti-particle (d) that exist for a brief moment and then recombine.  As Feynman liked to point out, an anti-particle is the same thing as a particle with negative energy traveling backward in time (which is why the arrow at d points backwards, i.e. to the left).  So you could say the photon created only one particle that, at first, traveled forward in time (the bottom semicircle) and then reversed and went back in time (the top semicircle) and annihilated itself!  By inventing diagrams like this, Richard Feynman made it much easier to understand what is going on in the interactions between sub-atomic particles without getting lost in tremendous amounts of tedious math.

View the front and the back of the limited edition cover.  The cover features the cancel illustrated above and Mayan heiroglyphics honoring Richard Feynman.