Scott Kelly's ageing 'slowed down in space'
Nasa astronaut Scott Kelly is younger than he would have been had he stayed on Earth.
He is officially 1/100 seconds younger than he would have been had he stayed at home, according to Neil deGrasse Tyson, the American astrophysicist.
He told the Huffington Post: "Relativity tells us that when we (in this case meaning all of us on Earth) observe someone/something else that is moving relative to us (in this case the International Space Station ), we will see time running slower for the moving people/things.
"It's called time 'dilation' because you can think of the moving person's time as having 'expanded' (dilated) since less time passes for them than for us."