On Wed, 07 Jul 2010 02:26:56 -0400, John Doe wrote:

On planet earth, the day is roughly 24 hours long.

On the ISS, a day is about 90 minutes long, but they fake 24 hour in
terms of sleep/awake cycles.

Have they (or do they plan) on experimenting with whether the human body
could adapt to a different length of a day ? (for instance, a 20 hour
day, or 30 hour day etc etc).

No, but in a sense the ground teams for Spirit and Opportunity on Mars
have already adapted to 24.5 hour days.

Brian