"researchers have found that in darkness most people eventually adjust to a 48-hour cycle: 36 hours of activity followed by 12 hours of sleep". Wondering if thi

"researchers have found that in darkness most people eventually adjust to a 48-hour cycle: 36 hours of activity followed by 12 hours of sleep". Wondering if this would be possible under normal circumstances (without the isolation, in daylight, with no psychological side effects).