Hi, John.
Your mention of the circadian rhythm reminds me of the first BIG use of
microcomputers, back in the late 1970's: Biorhythms!
Remember those? There were supposedly 3 life cycles for each of us that ran
from the day we were born. I don't recall what they were, maybe our
Physical cycle, Emotional cycle, Economic cycle - or something like that.
The cycles were about a month each and ran for similar but not identical
numbers of days - 23, 25 and 27 days, maybe. On our TRS-80s, Apples, IMSAIs
and other early computers, we would print out plots of the 3 cycles for the
current month on a page. When the 3 curves peaked, we could expect
wonderful things to happen to us. ;<) Kind of like astrology.
Ah, yes, Wikipedia has it:
http://en.wikipedia.org/wiki/Biorhythm
RC