British astronaut Major Tim Peake has said he could come back from his landmark space mission younger than when he left.
The first Briton to be selected by the European Space Agency (ESA), Maj Peake has been training for the six-month Expedition 46 to the International Space Station (ISS) in December this year.
Speaking to BBC Radio 5 Live, the 42 year old from Chichester, West Sussex, revealed how his preparations for the scientific mission had been going, including living underwater for 12 days.
He spent time in the world's only undersea research station Aquarius with Nasa's NEEMO programme, but said he did not get claustrophobic.
And when asked about the ageing process in space, he said: "Well if you're going into the theoretical physics of how fast we are travelling, we go at about 17 and a half thousand miles an hour so yes, you will come back a little bit younger because of course, the faster you travel, the slower time goes - but really, you're talking fractions of a second.
"But in terms of ageing as far as the effect of living in space I guess, yes the body will take a bit of a punishment, it will get a large dose of radiation. The bone density will reduce no matter how much we work out and also lose some muscle mass.
"Now, most of these effects you fully recover after about two years, but obviously the radiation dose which you just accumulate throughout your life (is) equivalent of probably someone working in the radiation industry for their entire life. It's probably equivalent of a six-month stay on board the International Space Station but it's certainly well within the safety limits so you do have to be aware of the risks involved."
The former Army Air Corps helicopter pilot, who previously admitted the hardest part of training was learning Russian, also said he had signed up to 30 different physiological experiments, measuring factors such as how the body reacts to zero-gravity and impacts on the immune system.
He also revealed he had chosen to have a menu of curries, beef stews and granola breakfasts while on the ISS, as well as food cooked by celebrity chef Heston Blumenthal - part of a schools competition run by the ESA.