Have you heard about the gravity chairs you will train on if you want to become an astronaut? They spin you around and around, at increasing speed, until you experience up to 6 g, which is about 6 times more than you feel in a starting aeroplane. And which is close to the max a human body can cope with, at least for a short time. I was always intrigued by that experience, but as I get motion sick very easy, becoming an astronaut never was an option.     So…