Chelsea has a thing for teeth--old teeth. Very old teeth. It started when she was a sophomore. She teamed up Sisi Liang, then a senior, for a summer project to date the age of fossilized deer teeth excavated from a cave in Russia. The teeth proved to be 420,000 years old, making the cave the oldest archeological dig in Eastern Europe.

lei project
Chelsea Lei studying fossil teeth in the lab and a closeup of one of the teeth.
To determine such ancient dates, Chelsea and Sisi had to use pretty fancy equipment, called electron spin resonance. ESR measures the electrons in hydroxyapatite, a mineral in teeth enamel, and is accurate for dates up to a million years old. The more familiar carbon-dating technique couldn't be used because it relies on a radioactive carbon isotope that decays into ordinary carbon within 50,000 years.

For her latest project, Chelsea switched to neutron activation analysis (NAA) for 1,560 fossil teeth and soil samples from 57 archeological sites around the world. With NAA, samples get zapped with neutron radiation, and a special detector watches for gammay-ray emissions and measures their energy. Each energy level signals the presence of a specific chemical element. Chelsea tested for 14 elements in the teeth and soil samples, selected in part to provide glimpses of Earth's ancient environment.

She has assembled the results into a database covering 48 variables--chemical properties and other characteristics--at the 57 sites. Chelsea hopes it will prove useful for archaeological and paleontological research.

On another front, she expects the modern Eightfold Maze she designed before leaving China in 2001 will soon be open to people in Kunming. It should be a real challenge. Its concentric walls will have openings that open and close at random. Hopefully everyone will find their way out before they become fossils.

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Yingqiuqi "Chelsea" Lei

Robert F. Kennedy High School
Flushing, N.Y.

Hobbies: Piano, tennis, archeology, correspondent for China's Youth Daily, movie musicals (learned English from watching movies)

Ambition: International law