I find it nearly impossible to keep a 24 hour day cycle and the developed world have been structured into the 8 hour work day where you have:

Eight hours labour, Eight hours recreation, Eight hours rest.

Are there strong physical and psychological reasons for keeping a 24-hour cycle beyond the benefit of being on the same time as everyone else? Are there cycles of sleep that we know to be bad, and which are shown to be beneficial?

Related to: Does polyphasic sleep work? Does it have long-term or short-term side effects?

  • 1
    Its important to realize that "the benefit of being on the same time" is not the only major external factor - daylight is a very strong factor on our bodies. A shifting daylight schedule every "cycle" could cause strong friction on your body's tendency to try to maintain a certain cycle. Therefore it's possible that you'd have more luck with a non-24 hour cycle in the absence of daylight, such as at the pole during winter or underground.
    – Nicole
    Mar 25, 2011 at 16:57
  • Daylight as a factor is weaker in some people. I can relate to the OP... See Circadian rhythm sleep disorders
    – Amadan
    Mar 28, 2011 at 2:46
  • 8 hours recreation? I'd bet not even with Google's 20% self time can you find 8 hours to play around in a work day!
    – cregox
    May 8, 2011 at 6:14

1 Answer 1


The Wikipedia page for Circadian Rythm gives you a quick overview about this subject, with lots of links for further reading.

A circadian rhythm is an endogenously driven roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed, in plants, animals, fungi and cyanobacteria.


A great deal of research on biological clocks was done in the latter half of the 20th century. It is now known that the molecular circadian clock can function within a single cell; i.e., it is cell-autonomous. At the same time, different cells may communicate with each other resulting in a synchronised output of electrical signaling.


Circadian rhythmicity is present in the sleeping and feeding patterns of animals, including human beings. There are also clear patterns of core body temperature, brain wave activity, hormone production, cell regeneration and other biological activities. enter image description here


The primary circadian "clock" in mammals is located in the suprachiasmatic nucleus (or nuclei) (SCN), a pair of distinct groups of cells located in the hypothalamus. Destruction of the SCN results in the complete absence of a regular sleep–wake rhythm.


Timing of medical treatment in coordination with the body clock may significantly increase efficacy and reduce drug toxicity or adverse reactions [...] There are many health problems associated with disturbances of the human circadian rhythm.


Although circadian rhythms are endogenous ("built-in", self-sustained), they are adjusted (entrained) to the environment by external cues called zeitgebers, the primary one of which is daylight.

  • 4
    Nice answer, but I'd like to see you go a bit deeper than just citing the wikipedia article.
    – anthony137
    Mar 25, 2011 at 15:05
  • 1
    So that's why I usually have to go #2 shortly after getting to work... Mar 26, 2011 at 3:19
  • added more links
    – Oliver_C
    Apr 17, 2011 at 11:25
  • i'd say while great, this is probably outdated and way too focused on circadian rhythms... this cycle is marked by sleeping and its regulation relies much more heavily on brain conditioning than molecules. lots of room for improvements! :D
    – cregox
    Jul 26, 2018 at 17:59

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