Learn how to do cosmic rays studies in your classroom.
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.
