On Earth your inner ear works every second of your life so quietly you never feel it — but in orbit there is no gravity left for it to measure, so it simply falls silent and the brain rebuilds around

The vestibular system in each inner ear works a thousand times a second for a human lifetime without ever asking to be noticed. In orbit it goes silent, and the brain performs one of the fastest rewirings in adult neurology — a rewiring that reverses, painfully, the moment the capsule lands.