Other anatomical changes associated with long-duration space flight are definitely negative: the immune system weakens, the heart shrinks because it doesn't have to strain against gravity, eyesight tends to degrade, sometimes markedly (no one's exactly sure why yet). The spine lengthens as the little sacs of fluid between the vertebrae expand, and bone mass decreases as the body sheds calcium. Without gravity, we don't need muscle and bone mass to support our own weight, which is what makes life in space so much fun but also so inherently bad for the human body, long-term.
Chris HadfieldWhen I stand on the edge of a cliff or right at the edge of a building or something, it's one of the few things that gives me kind of a deep, overwhelming, irrational fear where it affects my physiology.
Chris HadfieldSo without that Canadian invention we were grounded. And so that was a really important and key part of the mission and Canadians should take real pride in it.
Chris HadfieldIf you haven't learned to ride a bike by the time your peer group has, then suddenly it's an embarrassment and you'll avoid opportunities where you're expected to ride a bike. And then it starts shaping your behaviour. Reading is much subtler, but much more destructive if you have not - for whatever reason - learned to read by the time you should.
Chris Hadfield"What's the next thing that's going to kill me?" is a mantra for pilots and astronauts.
Chris Hadfield