Spending time in space and having an unrivalled view of planet Earth is an experience many of us dream of.

However, the human body evolved to function in the gravity of Earth. So time in the weightlessness of space can take years from which to fully recover.

Astronauts Suni Williams and Butch Wilmore are back on Earth after their eight-day mission aboard the International Space Station (ISS) unexpectedly became a nine-month enforced stay. Now, their recovery begins.

"Space is by far the most extreme environment that humans have ever encountered and we've just not evolved to handle the extreme conditions," Prof Damian Bailey, who studies human physiology, at the University of South Wales, says.

Entering space changes the human body – and initially that feels awesome.

"It feels like a holiday," astronaut Tim Peake, who went to the ISS in 2015, says.

"Your heart is having an easy time.

"Your muscles and bones are having an easy time.

"You're floating around the space station in this wonderful zero-gravity........

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