Notes

This is astronaut Scott Kelly. He's 52 years old he's safely back to earth from the International Space Station after a year.
A year in space has had some serious effects on Scott's body. Those effects have been the focus of a NASA experiment. Scott has an identical twin who used to be an astronaut too. He's been going through tests here on earth while his brother's been up in space. By comparing the two, scientists can know how Scott's been affected by his time in zero gravity. Which could be realy important for longer missions to space. So what has changed is when Scott landed he was five centimetres taller than when he left. It's because there's no gravity pulling on the human body so his spine stretched out. You can test yourself. When you sleep your the normal size. But when you wake up, you're a little bit taller. But it's not permanent. As the day goes on you shrink back to your normal size. But NASA wants to know more about Scott than just how tall he got. how his immune system is doing, and if he lost much bone and muscle mass. That last one is a biggie. With no gravity, the body doesn't have to work as hard to move around. That means bones and muscles can seriously weaken, especially in the lower body. So astronauts have to spend around 2.5 hours a day doing exercises like running and weightlifting, to look after themselves.