This is a question about O'Neill cylinders and other spinning habitats.
We repeatedly hear that any space colony must be X big because spinning any faster than Y will give people motion sickness.
But motion sickness as I understand only happens when your vestibular system conflicts with what your eyes see.
My personal experience supports this. I once rode the Carowinds' Oaken Bucket ride, which was just a big vertical-axis cylinder room where we would lay back against its curved wall while it spun up. I kept my eyes closed, and the only sensation was that I felt like I had tilted backward, the wall became a floor under my back, and I felt enormously heavy under the higher G's. No motion sickness. My nose was the new up, and that was that.
The only study I ever saw on spinning people never specified whether the test subjects could see outside their frame of reference. Does anybody have any science, one way or the other, that smooth vibration-free spinning makes you sick even if you can't see outside your cylinder?