Cosmic rays in a thermos flask 1.European Physics Education Conference Bad Honnef Thomas Trefzger Universität Mainz

Motivation  Mystic experiments in school  Introduction to special relativity  Introduction to (astro-)particle physics  Minor complexity

Cosmic radiation  Interaction of high energetic primary particles (85% protons, 14% alpha particles) with nuclei of the atmosphere  Surface of the earth: a few hundred charged particles per qm per second  Mostly muons

The muon  Group of leptons  mass (muon) ~200 x mass of the electron  Mean lifetime 2.2 microseconds  Decay of the muon:

Decay of the muon Radioactive decay law Muons should not reach the surface of the earth 1 muon per second

Special Relativity  time dilation (observer at earth) v=0.9999c: muon lives longer:  Length contraction, 20km (observer moves along with the muon)

Experiment set-up Praxis der Naturwissen- schaften 4/51

Cherenkov radiation

First Experiment Measurement without water -> no signal Measurement with water -> signals Existence of something which gives a reaction in the thermos flask

Applied Statistics  Rate of muons (15 min), 10 second intervals Events/10 s

Applied Statistics  Rate of muons (40 hours), 10 second intervals Events/10s

Second experiment  Koincidence with two thermos flasks

Third experiment  Measurement at different places

Life after death  Fourth experiment: Lifetime

Lifetime– it is relative ! Number of events vs. microseconds 0 5 Microseconds linear logarithmic

What can we learn ?  Cosmic radiation is omnipresent and can be detected  Frequency of occurence, penetration rate, angular rate dependence  Statistical aspects, randomness of events

Didactic Potential  Exotic particles in school  Statistical aspects  Aspects of special relativity  Ongoing research  Elementary particles as part of our world  Computer in measurement control and analysis

Jugend forscht 2004 – state winner