Ever been on a plane? On a boat? Ever notice that a plane would go up and down on the way to its destination? Ever notice that a boat would also go up and down as it rode the waves from Point A to Point B? Ever notice that, even after leaving the boat/plane, you can still feel that rocking sensation?
Maybe there’s a scientific explanation, I don’t know. What I do know is that the sensation is the same. As a kid, it was a funny sensation. As an adult, however, I start to critically think about it, asking why it is so.
Even days after the trip, if you sit still, you can still feel it. Maybe it has something to do with the ears, since they allow for the brain to process changes in position. Or maybe it’s just psychological for those who are not so keen on those modes of transport, I’m not sure.
Chances are that, after a trip in a plane with lots of turbulence, walking on a straight line would be rather difficult.