After spending nearly a year aboard the International Space Station (ISS), astronaut Scott Kelly returned to Earth in March 2016. But his mission was far from over, as his job as a guinea pig for studying the physical effects of long-duration spaceflight was just entering a new phase.
His experiences aboard the ISS were documented for the Time and PBS special A Year in Space, the first part of which premiered in spring 2016. Part 2 of the documentary, Beyond a Year in Space, debuts on PBS Nov. 15 at 9pm ET (check local listings) and follows Scott as he readjusts to Earth’s gravity and scientists compare his physiology to that of his earthbound identical twin brother, Mark.
“Gravity definitely gives you a beatdown when you get back,” Scott says, having experienced aching muscles and joints, flu-like symptoms and severe skin sensitivity for weeks after his return to Earth. Extended space travel can cause musculoskeletal atrophy, and a weightless environment causes fluids to shift in the body. There is also the potential for damage to sections of DNA from exposure to cosmic radiation. “There’s a certain amount of radiation I got, and hopefully I’ll never know what the negative effect of that is,” Scott says. “But from a purely subjective look at my health, I feel back to normal.”
There’s also the “time dilation” effect explained by Einstein’s theory of special relativity, which states that time moves more slowly for objects in motion compared to a stationary observer. With Scott traveling at 17,500 mph, he aged slower than his brother on Earth. “I used to be just 6 minutes older [than Scott],” Mark says. “Now I am 6 minutes and 5 milliseconds older.”
— PBS (@PBS) November 13, 2017