Rob Seaman said: >> As I've said before, eventually the notion that the solar day contains >> 24h of 60m of 60s will have to be abandoned. It'll be awfully hard >> to maintain when an "hour" involves two human sleep-wake cycles, >> out in the limit when the Moon is fully tidally locked and 1 lunar >> month = 1 solar day = 47 current solar days, more or less.
> Just returned from a conference three hours to the east. The > existence of > jet lag suggests significant evolutionary pressure locking human sleep > cycles to the length of the day. Actually, the evidence from experiments is that the "natural" sleep-wake cycle is about 27 hours long, but force-locked to the day-night cycle (it's easier to synchronise a longer free-running timer to a shorter external signal than vice-versa). So humans will cope until the solar day is about 27 (present) hours long, after which we'll probably start to move to a system of two sleep-wake cycles per day. -- Clive D.W. Feather | Work: <[EMAIL PROTECTED]> | Tel: +44 20 8495 6138 Internet Expert | Home: <[EMAIL PROTECTED]> | Fax: +44 870 051 9937 Demon Internet | WWW: http://www.davros.org | Mobile: +44 7973 377646 THUS plc | |