Spaceflight may look like fun on film. But, in reality, exploring the final frontier takes a serious toll on the human body.

Researchers have found that orbiting the planet in zero gravity for extended periods of time can trigger a series of effects similar to aging. Cardiovascular changes such as thickening of the carotid artery, muscle atrophy, loss of bone density, and even cognitive impairment, are just some of the shifts that afflict space travelers.

A contributing factor is the “phenomenon of fluid shifts,” said Brinda Rana, an associate professor at the University of California, San Diego, School of Medicine and a member of one of 10 NASA-sponsored research teams involved in a five-year project to examine what happens to astronauts during prolonged space flights.

On Earth, Rana explained, gravity pulls blood toward the feet while the pulmonary system effectively pumps it toward the head, maintaining an important balance. But in the absence of gravity, blood and other fluids freely shift upward. “Remember when you were a kid and you hung upside down on monkey bars, and that feeling of pressure in your head?” Rana asked the audience gathered Monday in Knafel Center for a talk that was part of the Radcliffe Institute for Advanced Study’s Undiscovered Science lecture series. “Imagine that for a whole year.”