Sporting night vision goggles, a scientist probes the internal clocks that help parasites infect people

In the 1700s, French astronomer Jean-Jacques d’Ortous de Mairan noticed that the leaves of the mimosa plant opened towards the sun and closed at dusk. His discovery was in keeping with thousands of years of observations. But de Mairan also found that the plant followed the same rhythm even in the constant darkness of a cupboard, suggesting that some innate metronome kept the plant in sync with the rotation of the earth. Centuries later, scientists now know this to be a circadian rhythm, a 24-hour cycle that readjusts in response to environmental cues such as sunlight.

When Filipa Rijo-Ferreira, then a graduate student at the University of Porto in Portugal, first read about circadian rhythms, it seemed they set the clock for just about everything. Studies show that wounds heal faster during the day, and patients over 65 produce more antibodies if they get a flu shot in the morning. Disruption of circadian rhythms has been linked to sleep disorders, diabetes, Alzheimer’s, and cancer.

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