Classroom Notes Notes - Teaching Strategies - Research Guidance - Sample Classroom Activities The QuarkNet Detector Experiments Students Can Perform Calibrations and performance studies Flux experiments Muon lifetime experiments Shower studies Other studies devised by students Calibrations and Performance Studies Before students can "trust" the cosmic ray equipment, they should do some calibrations to study the response of the counters and the board. Calibration studies include plateauing the counters, threshold selection and barometer calibration. In addition, the QuarkNet online analysis tools include a "system performance" study for uploaded data. Flux Experiments Your students can do a variety of flux experiments investigating such things as cosmic ray flux as a function of time of day, solar activity, angle from vertical, barometric pressure, altitude. The list goes on. This can be an exciting set of experiments as students study the factors that they want to test. Muon Lifetime Experiment to Verify Time Dilation A classic modern physics experiment to verify time dilation is the measurement of the muon mean lifetime. Since nearly all of the cosmic ray muons are created in the upper part of the atmosphere (>>30 km above the earth's surface), the time of flight for these muons as they travel to earth should be at least 100 microseconds: This calculation assumes that muons are traveling at the speed of light - anything slower would require even more time. If a student can determine the muon lifetime and show that it is significantly less than this time, they are presented with the wonderful dilemma that the muon's time of flight is longer than its lifetime! This time dilation "proof" assumes that all muons are created in the upper atmosphere. Although this is actually a good approximation, your students cannot test it. However, by using the mean lifetime value and by measuring flux rates at two significantly different elevations, you can develop experimental proof for time dilation. This experiment requires you to have access to a mountain, an airplane, or collaboration with a team from another school that is at a significantly different altitude! Here is a wonderful opportunity for schools to work together proving time dilation. A very thorough explanation of this experiment is outlined in the 1962 classroom movie titled, "Time Dilation: An Experiment with Mu Mesons." (This 30 minute movie can be ordered on CD for $10 from www.physics2000.com/.) This movie helps you (and your students) understand how the muon lifetime measurement (along with flux measurements at two different altitudes) can be used to verify time dilation. Shower Studies With the GPS device connected to your DAQ board, the absolute time stamp allows a network of detectors (at the same site or at different schools) to study cosmic ray showers. Your students can look for small showers or collaborate with other schools in your area to look for larger showers. The QuarkNet online analysis tools allow students to not only look for showers but to calculate the direction from which the shower (and thus the primary cosmic ray) originated.