Poetry of Physics and the Physics of Poetry

Quantum Electrodynamics 223

The real photon turns into an electron positron pair. The electron then
exchanges a virtual photon with the nucleus.
Pair annihilation occurs in the following diagram, Fig. 22.5 through
the spontaneous emission of a photon by the electron followed by the
annihilation of the electron and positron into the second photon:

214 The Poetry of Physics and The Physics of Poetry

Pair annihilation occurs in the following diagram, Fig. 22.5 through

the spontaneous emission of a photon by the electron followed by the

One can look on this diagram as the e- exchanging a virtual e- and

turning into a photon. The positron then absorbs the virtual e- and also

turns into a photon. The last diagram has an interesting interpretation if

one assumes that a positron is an electron moving backwards in time.

Then the pair annihilation has the form where it would appear the

electron enters the diagram, Fig. 22.6, at the top and changes its direction

in time and exits the diagram at the bottom.

Fig. 22.6 Electron-positron pair annihilation in which the positron is

represented as an electron moving backwards in time

Fig. 22.5 Electron-positron pair annihilation.

One can look on this diagram as the e– exchanging a virtual e– and
turning into a photon. The positron then absorbs the virtual e– and also
turns into a photon. The last diagram has an interesting interpretation if
one assumes that a positron is an electron moving backwards in time.
Then the pair annihilation has the form where it would appear the
electron enters the diagram, Fig. 22.6, at the top and changes its direction
in time and exits the diagram at the bottom.

214 The Poetry of Physics and The Physics of Poetry

Pair annihilation occurs in the following diagram, Fig. 22.5 through

the spontaneous emission of a photon by the electron followed by the

annihilation of the electron and positron into the second photon:

Fig. 22.5 Electron-positron pair annihilation

One can look on this diagram as the e- exchanging a virtual e- and

turning into a photon. The positron then absorbs the virtual e- and also

turns into a photon. The last diagram has an interesting interpretation if

one assumes that a positron is an electron moving backwards in time.

Then the pair annihilation has the form where it would appear the

electron enters the diagram, Fig. 22.6, at the top and changes its direction

represented as an electron moving backwards in time

Fig. 22.6 Electron-positron pair annihilation in which the positron is represented
as an electron moving backwards in time.