Re-reading Linenger's Off the Planet and encountered a question from long ago that I never had found an answer to.
During Mir's troubled old age, the attitude control computer would fail frequently. The station then immediately started rotating and the solar panels stopped tracking the sun. This resulted in a long, multi-orbit process of slowly recharging the batteries and essentially rebooting the station.
But...why did Mir start to rotate immediately when the computer failed? The lack of control in and of itself wouldn't cause the station to rotate. There must have been some external torque that the system was constantly compensating for, but what?