Astronaut Scott Kelly returned to Earth today after nearly a year in space to find he has become younger than his identical twin brother – by a fraction of a second.
He landed near the town of Zhezkazgan, Kazakhstan, with veteran cosmonaut Mikhail Kornienko after both had spent 340 days aboard the International Space station. With them in their Soyuz TMA-18M capsule was Sergey Volkov who spent six months in space.
The three men left the orbiting outpost after saying an emotional goodbye to their crewmates, including Brit Tim Peake. Scott, 52, handed over command of the station to NASA colleague Tim Kopra.
As they left, Peake, 42, tweeted: “Farewell Expedition 46 – an honour and a privilege to serve with such great crewmates.”
Scott’s lengthy stay was planned to help prepare for future manned missions into deep space, including to Mars. Scientists wanted to see see how the human body can cope for long spells away from the Earth’s gravity.
Scott’s health and physical condition were continuously monitored, while similar tests were being carried out on his former astronaut twin Mark Kelly back on Earth. NASA wanted to identify any subtle changes caused by spaceflight.
But one effect that was predicted by brilliant boffin Albert Einstein’s General Theory of Relativity was that Scott’s 5,280 orbits at a speed of more than 17,000 mph caused him to age at a slower rate than his identical twin.
The twin paradox identified by Einstein in 1905 shows that Scott Kelly is now about 10 milliseconds younger than he was before.
Scott has now clocked up 520 days in space, over four spaceflights, a U.S. record. The record for a single stay is by Russian cosmonaut Valeri Polyakov who spent more than 14 months on one trip to the Mir space station in 1994-95.
NASA Administrator Charles Bolden said: “Scott has become the first American astronaut to spend a year in space, and in so doing, helped us take one giant leap toward putting boots on Mars.”
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