This week I care for two interns (from a Cologne school, 15+16 years old) in our Lab!

Part of their job here is to measure the traces of the reactor accident in Tchernobyl in 1986, that can still be seen in the gamma-ray spectra of some earth-samples (especially one sees Cs-137, that has a half-live of 30 years). To measure the spectra they use a superconductor counter (Ge)...

As I described some effects that may happen in such a detector due to the radiation, I told them about Positrons, that are Anti-Electrons. I told them, that after a Positron is produced it annihilates with the next best Electron and we measure gamma-rays (with the popular energy of 511 keV).

They never heard, that Antimatter is doing this annihilation, (neither they don’t know Star Trek!)—so one of their questions was “Why do Positrons and Electrons annihilate anyway?”...

Puh, ... Pretty good question! I never really thought about it! For me it was clear (big problem for a scientist, isn’t it?)

Anyway—I found this and that it is more a philosophical question… Like almost everything, that seems to be clear for us?!

Cheers,
Thomas