I was just reading about astronaut Scott Kelly who spent about a year in space. Before he travelled to space, he was exactly the same height with his twin brother. Now he is 2 inches taller than his twin, and he isn’t 17-years-old or even 21.
You ask how? Well, it turns out that the absence of gravity causes the spine to elongate out there, but when they come back to earth, the spine quickly contracts. So, expect him to measure exactly the same height as his twin soon.
But the lesson to be learnt is to always stand upright, as that naturally makes your spine straighter.
Read more about Scott Kelly’s increased height: Astronaut Scott Kelly taller after space stint – CNN.com