Up, Up and Away

Author(s): Tim Brouk
Photographs by: Tim Brouk and David Sederberg


The view from the first balloon as Purdue Physics Outreach prepares to measure cosmic rays.

Physics outreach took to the skies over Indianapolis in March when a group of Purdue physics students and instructors teamed with a high school student and teacher for a hot air balloon trip to measure cosmic rays at 10,000 feet.

The dizzying heights were required to recreate an experiment by Nobel Prize-winning Austrian physicist Victor Hess, who discovered 101 years ago that cosmic rays came from outer space. The original thought was that radiation came from the Earth.

Sponsored by Physics Outreach, the experiment used cosmic ray detectors to collect data. The equipment is composed of scintillation plates and photo multiplier tubes that send readings to a computer. The device measures “counts,” which increase when levels of cosmic radiation are more intense. The cosmic ray detector can give real-time results and draw graphs as soon as the counts come in.

Three balloons, owned and operated by Midwest Balloon Rides, made the trip. One, ascending to 10,000 feet, carried McCutcheon High School senior Stephen Claypool and Purdue physics senior Chris Kraner. Claypool is one of the Tippecanoe County high school’s top science students and is adept at physics as well as technology. The second balloon held physics professor Matthew Jones and Winamac (IN) High School physics teacher Jeremy Wegner. Physics Outreach director David Sederberg rode in the third balloon to 10,000 feet. His balloon served as a guide for the larger balloons.

Wind and haze provided some challenge during the flights, which took to the sky a little after 7:30 a.m., but the scientists were pleased with the data they collected. Wegner, Claypool and Kraner recorded the altitude in logs for their respective balloons using Google’s cellphone app MyTracks.

“The data shows that the rate at which cosmic rays hit our detector almost doubles by the time we reach about 6,500 feet altitude,” Jones says of his March 30 findings.

Jones says he had to think quickly on his feet to get the equipment configured in the hot air balloon basket. The detector and laptop had been in airplanes and vehicles before but in the open air with two educators and a balloon pilot, it made for some tight quarters.

“In the end, we piled everything on the bottom of the balloon, put the laptop on a fuel tank, and started everything up,” Jones recalls. “It wasn’t pretty, but the initial data looked OK, so we just left everything the way it was. We had to keep moving the laptop to let the pilot check fuel levels, but in the end it wasn’t as bad as I had initially feared it would be.”

Jones says the high-altitude experiment reminded him of his particle physics work on the ground in world-famous labs like CERN and Fermilab.

“Sometimes we have a very short window of opportunity to go into an experimental area and fix something or record data, and you have to learn to keep cool, stay focused, think about what you’re doing, use whatever information you have to tell if things are working and try to anticipate anything that could go wrong,” Jones explains. “I expect that Victor Hess had to deal with the same issues: You plan everything carefully, but you always have to be ready to react to the unexpected. From our data, we can clearly see the trend that earned Victor Hess the Nobel Prize in 1936, but without any prior information I can imagine that he and others would have been anxious to repeat the flight because the increase in rate is so dramatic that it must be telling us something really significant. In fact, Victor Hess conducted balloon experiments from 1911 to 1913, so technically we didn’t miss the 100th anniversary of at least one of his balloon flights.”

The experience was not without a little drama. Sederberg’s balloon and Kraner and Claypool’s dirigible touched down on farmland a few miles from Greenfield, Indiana. Jones and Wegner’s balloon circled back to Indianapolis Metropolitan Airfield for its landing.

After two hours in the air, high school student Claypool was satisfied with his data as well as the opportunity to be a part of a unique physics experiment.

“Science is something that can be repeated with the same results,” Claypool says. “That’s what makes it science. You can keep testing it over and over with different hypotheses and figure out a result in the end. Then if you go back and try it again, you will most likely get the same result unless there is some discrepancy to begin with.”

That science holds true even a century later.

cosmic ray detector

Purdue Physics' Chris Kraner (center) and McCutcheaon senior Stephen Claypool (right) set up a cosmic ray detector.