Girls in grades 5 through 8 flock to the hands-on science exhibits at the Sally Ride Science Festival.

Some of the girls who took part in the Sally Ride Science Festival on March 19 learned that “sour power” concerns more than the tartness factor of candy.

By attaching wires to a piece of copper and a simple household nail implanted in each of a half dozen lemons, Sour Power! workshop participants learned how the citrus fruit can be used to power an LED lightbulb.

Katya Zinn-Bjorkman, 10, and Natalie Harmon, 9, discovered that their tiny blue light illuminated when they pushed their lemons apart, rather than leaving them bunched together on a paper plate. “We spread them out and the light went on, and when they touched each other the light went out,” said Zinn-Bjorkman.

The workshop was one of 23 offered to the more than 1,000 girls in grades 5 through 8 attending the festival, held annually at Caltech since 2002. Each participant took part in two workshops, which covered a gamut of topics such as chemistry, biology, medicine, aerospace, and geophysics. Many of the discovery workshops offered hands-on activities designed to spark a sense of discovery and possibility; others featured female scientists discussing their work.

Workshop presenter Meghan Adams, a Caltech graduate student studying developmental biology, told the girls how humans develop from a single cell. She also answered the eternal question: which came first, the chicken or the egg? Her answer: the egg.

A participant in the Sour Power! discovery workshop turns lemons into a power source for an LED light bulb.

The festival is the brainchild of Ride, the nation’s first female astronaut. Her mission nowadays is to improve the percentage of women in science. According to the latest statistics, eight of the 10 fastest-growing occupations are science or technology related. Yet women make up only 25 percent of the technical workforce. Beginning in about sixth grade many girls begin to turn away from these subjects, despite possessing the interest and aptitude to pursue them, Ride says.

Ride presented a keynote address and question and answer period, in which she encouraged the girls to pursue math and science and get prepared academically for all of the possibilities the future may offer them. In her case, pursuing advanced physics at Stanford University led to her joining NASA’s astronaut training program and participating in two space shuttle Challenger missions, in 1983 and 1984. She is now a professor of physics at UC San Diego, as well as a member of the Caltech Board of Trustees.

She fielded questions including “How do you shower in space?”, “Do you float while you are asleep during a space mission?”, and “How long do you train for each mission?” Then came the question Ride said she usually gets first: “How do you go to the bathroom in space?”

The day’s intermittently rainy weather didn’t seem to detract from attendance: hundreds of girls registered at the event, joining about 800 who had preregistered. The festival also offered workshops for parents and educators, as well as a street fair.
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