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Getting ready for the Next Generation Science Standards? This e-Lab meets ALL NGSS science and engineering practices. See Standards link in the menu for listing.
Working in a research group, students experience the environment of scientific collaborations in this series of investigations into high-energy cosmic rays. From start to finish this is a student-led, teacher-guided project. Schools with cosmic ray detectors can upload data to the web. A virtual data portal enables students to share these data and associated analysis code with students at other schools whether or not those schools have their own cosmic ray detectors.
Students begin their research by watching a Cool Science video to understand the context of they project. They check the performance of the detectors they have chosen for their study. Then they can perform one of three investigations: muon lifetime, muon flux or extended air showers. Students can use the project milestones to conduct their research and can record their work and reflect on their progress in their e-Logbook. Students post the results of their studies as online posters. The real scientific collaboration follows. Students can review the results of other studies online comparing data and analyses. Using online tools, they can correspond with other research groups, post comments and questions, prepare summary reports and, in general, participate in the part of scientific research that is often left out of classroom experiments.
Two sample posters are available:
Introduction to Cosmic Ray Research
Cosmic rays are typically protons, neutrons, gamma rays or other particles that originate in any number of astronomical objects. When these "primary" cosmic rays encounter earth's atmosphere, they can interact with nuclei of atoms and produce new, often unstable particles (e.g., pions and kaons). In turn, these secondary cosmic rays further decay and create muons, electrons, photons and neutrinos. If these cosmic rays are sufficiently energetic, they can reach the earth's surface and be detected. (Neutrinos are capable of passing through the earth and are generally undetected.)
Occasionally the primary cosmic ray possesses tremendous energy, creating many decay products. An array of detectors on the earth's surface can indirectly measure the energy of the primary by counting the number of particles in the detector array simultaneously. These observations can lead to a calculation of the part of the sky that the primary came from. Many experiments have measured cosmic array showers, including:
Good Research Questions
How much area can a cosmic ray shower cover? Where do cosmic rays come from? Students can pose a number of questions and then analyze the data for answers. Some answers are new to students but well answered by physicists. These include the muon lifetime, rate of cosmic ray arrival as well as the source of low-energy air showers. However, the origin of the highest-energy cosmic rays is an open question—scientists are trying to answer this question now. Students may be able to contribute data to these efforts. Students will be able to look into the size of cosmic ray showers by comparing their cosmic ray detector data with that from others across a wide area to see where particles struck earth's surface in closely correlated time windows. (Data contain time and geographic location information.) Students will be a part of this ongoing research by providing data to a collaboration of their peers.
Student Prior Knowledge and Skills
Before doing this project, students should know how to:
We provide refresher references for students who need to brush up on these skills. Students access these from "The Basics" section of the Project Map.
Learner Outcomes and Assessment
Students will know and be able to:
Assessment is aligned to learner outcomes. While many teachers will want to design their own assessments, we provide some options.
Suggestions for Getting Started
A good way to begin cosmic ray studies is to invite the class to watch Cool Science together. Play the Standalone Movie and enlarge the window.
Detectors Students Use
The data for this e-Lab comes from detectors operated by high school students around the world. If you have a detector, you should become familiar with how to set it up and take data.
To obtain a detector, pending funding, contact:
Fermilab gathers the requests, place orders for the parts in early spring and fills the orders throughout the summer.
Experiments Students Can Perform
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 - 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 Experiments - 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, students cannot test it. However, by using the mean lifetime value and by measuring flux rates at two significantly different elevations, one can develop experimental proof for time dilation. This experiment requires 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 Physics2000.) This movie helps students understand how to verify time dilation using the muon lifetime measurement (along with flux measurements at two different altitudes).
Shower Studies - With the GPS device connected to the DAQ board, the absolute time stamp allows a network of detectors (at the same site or at different schools) to study cosmic ray showers. Students can look for small showers or collaborate with nearby schools 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.
Other Studies Devised by Students
Help Desk & Sharing Ideas
e-Lab Technology Requirements
Ask your tech support person if you need help with browser settings. The Resources in the Library and the background material may include YouTube videos and java applets, but these are not critical for using the e-Lab.