“We Went to NASA to Float on the World’s Flattest Floor: In a Warehouse in Alabama Is What May Be the Flattest Floor in the World—One That Can, in a Sense, Simulate Space. BBC Future—And Some Cats—Give It a Test Drive”, 2016-04-07 (; backlinks; similar):
I am sitting on a sofa, floating through the void. Above me, a massive silver sheet billows in a gentle breeze. The chair drifts on through the blackness, with nothing to stop it carrying on forever. The peculiar sensation of flying through space on a cushioned bench is extremely relaxing—disorientating but not dizzying. The smoothness of travel means that my companion on the sofa—a NASA spacecraft engineer—is sitting with her legs crossed and eyes shut in an apparent zen-like trance as we spin gently through the dark.
…Although the experience of the ride felt as if we were flying through space, NASA’s space sofa was actually floating only a fraction of a millimetre above a black polished, perfectly flat, floor on tiny columns of compressed air. Imagine a giant air hockey table but with the puck, rather than the floor, producing the jet of air. The Flat Floor is said to be the flattest floor in the world. Made of black epoxy resin, it covers the base of a 26-metre-long warehouse. Objects can be moved across it on a frictionless cushion of air. This means that once something starts moving, it stays moving (until you hit something)—just as it would in space.
…“The biggest problem we’ve ever had here was caused by cats”, admits Bryan, pointing out lines of blotchy spots crossing part of the floor. “These are cat prints—they used to live down in the tunnels of the building and use this as a playroom at night.” “Their little paw prints caused the epoxy to expand”, he explains. “We’ve put up walls to stop them coming in but we still have a permanent memory of their little paw prints.”