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 HadfieldThe emotional build-up and anticipation if you travel at Christmas can make it harder to enjoy a trip. I think sometimes it is better to travel outside of conventional holiday times for that reason.
Chris HadfieldScientific literacy is one of the underpinnings of everything I do. It's why I work with schools. It's why I teach at university. I do a lot of outreach to try and improve general scientific literacy, but the core of all scientific literacy is just literacy.
Chris Hadfield