This suggests an answer to a question raised by a colleague: is the purpose of a bed to approximate, as well as possible on the earth’s surface, the experience of sleeping in zero gravity? Unless I’m mistaken, the answer is no. Sleeping in space would be like sleeping on a bed that was too soft, with the same potential for back problems and so forth.
Let me be very clear, zero-gravity is no panacea. In space, people tend to get sick for other reasons than sea sickness (astronauts do barf in zero-gravity aircrafts where sea sickness is an issue). Some people suggest that space sickness which generally takes a day or two to get accustomed to, is related to the extension of the spine. However, having experienced zero-g with closed eyes, I can attest that it puts the experience right into one of those never ending fall scenario that makes up many nightmares. The astronauts I talked to told me that they never took long periods of sleep. In order to do so, they also have to be strapped into place so they have to feel something while sleeping (touching something seems important). One wonders if the short sleeping periods in space is the result of the excitement of being on a space mission or some more physiologically based mechanism at play. Recall that most people lose a large percentage of their bone mass in orbit and that there is a similar bone loss issue with people lying horizontally. Elderly folks for whom sleep is also an issue also have a bone depletion issue as well. In summary I would not be surprised if the amount and strength of the contact experienced by the body (that covers the issue of hard and soft beds) is directly related to something more physiological. We already know that some cells respond to gravity.
On a different note, when we flew a star tracker on Columbia, I got to be speak with the PI of an experiment on bone loss in space who was on our flight. He had tried for many years to get many different parties involved in that lengthy process of designing a conclusive space experiment focused on understanding the problem of bone loss in space. The loss of the Orbiter was sad on so many different levels.