## Time Dilation

Verified Einstein’s Time Dilation with a field trip with several of our detectors to the top of the Sears Tower! A talk given at Argonne National Lab describes our trip and the results on time dilation.

Figure below shows the rate of cosmic rays on the roof of the Sears Tower (Yes, Sears not Willis!) as a funtion of Pb shielding. It is compared to the same measurement on the ground without shielding. The shielding compenstates for muon energy loss in the extra 300m of air that lies between the roof and ground locations. The result is that the rates agree to within 4%, whereas we expect 52% of the muons to decay before reaching the ground, if there is no effect of time dilation predicted by Einstein. Einstein wins this one!