An Intriguing Look at Chronobiology

The Solar Secrets and Lunar Legacies of Life on Earth: A Fleeting Look at Chronobiology by Noah CannonThe star which our planet orbits, the Sun, is a massive beacon of energy. Energy being information which is radiated upon our planet and has delicately intertwined itself into our biology, defining many aspects of the living world. The sun’s mythical counterpart is our one and only satellite, known to us as “the Moon,” Luna has snuck its way into our biology as well. Both of these bodies operate in predictable cycles. These cycles have been shown to have a tremendous effect on life on Earth. The study of these endogenous biological rhythms which are regulated by the energies put forth from the Sun and Moon, our most revered galactic bodies, is called chronobiology. This branch of science is really only forty years old, very exciting and Microsoft Word is trying to tell me “chronobiology” is not a word! Within this paper I would like to outline the effects each of these bodies has on our biology as well as the biology of life around us. The information will be presented in the following categories of biological rhythms: Circadian Rhythms (daily), Ultradian Rhythms (less than daily), Infradian (longer than a day), Tidal Rhythms (around 12 hours) and finally Gene Oscillations (rhythmic gene expression).

Circadian rhythms are the most commonly studied example of chronobiology and are concerned with a period around 24 hours, our rotational cycle or “day.” Although most people rarely discuss the cosmos nor biology, one can be assured discussions of chronobiology are even more scarce which, for me, is almost worrying as “All eukaryotes and some microbes (e.g., cyanobacteria) display changes in gene activity, biochemistry, physiology, and behavior that wax and wane through the cycle of days and nights” (Kimball). These Circadian rhythms are paramount to all animals. They influence sleeping and eating patterns, core body temperature, brain wave activity, hormone production, cell regeneration, blood pressure, production of hormones, digestive secretions and other biological activities (Quraishi). In addition, “photoperiodism, the physiological reaction of organisms to the length of day or night, is vital to both plants and animals, and the circadian system plays a role in the measurement and interpretation of day length” (Zivkovic).Thus, these rhythms seem to almost assess the season and inform the body so it can act accordingly. When animals, you included, are tired; it is a direct result of our circadian rhythms assessment of what time of day it is, as well as what season! 

       Circadian rhythms are controlled by a circadian pacemaker, or a biological clock. This “clock” is the section of the brain known as the suprachiasmatic nucleus (SCN). The SCN is a pair of structures that contain about 20, 000 neurons and is located in the hypothalamus above where the optic nerves cross. This proximity to the optic nerve explains its reaction to light. Signals from light are received by the SCN taken in by the retina. Circadian rhythms include three different parts, a central oscillator, afferent pathways that carry environmental information to the oscillator, and efferent pathways that communicate the rhythm of the oscillator to the physiology and behavior of the organism (Quraishi).

Measuring the amount of light, the brain provides instructions to our bodies. This is true with both solar and lunar light. The most blaring example is the melatonin released by the pineal gland, a light sensitive circadian controlled gland. This melatonin not only controls your wake-sleep cycle and regulation of melatonin production but because melatonin can be found in some foods it is not surprising that an animal’s Circadian biological “clock, set by light/dark cycles, is the master clock as long as food is available all the time” (Kimball). Hunger is also highly regulated by circadian rhythms and can even interrupt its regularity. For most of us in the United States food is available all the time and thus our biological clock is most distracted by artificial lighting or spending long periods without light. Come on, we all know that feeling when you come out of a movie theater and feel at a loss with your sense of time and don’t feel quite right until your body regulates. For those persons without eye sight, who are living in “total blindness experience life-long sleeping problems because their retinas are unable to detect light” (Arm Med Media) but of course not all of them – we are highly adaptable seemingly complex creatures who today thrive, for the most part, in baths upon baths of artificial light at odd times and in huge concentrations. It seems these daily rhythms provide us with a daily guide book it seems as handed down by the Sun and Moon and likely all other celestial bodies – but daily rhythms are just the beginning.

Ultradian rhythms are those rhythms which occur more often than Circadian rhythms often multiple times per day. It is often used to describe the 90 minute period of rapid eye movement during dreaming and “other ultradian cycl[es] of the body [include] hormonal release, heart rate, thermoregulation, urination, bowel activity, nostril dilation and appetite” (Kramlinger). These rhythyms are those which affect our mood at any given time throughout the day. Hormonal release from the onset of season and the light changes involved affects an organism’s daily decision making. Different times of day are broken down by nature as the most beneficial and energetically economic to perform certain tasks of survival. On the most basic level a worm’s scheduled daily multiple defecations is a beautiful example of ultradian rhythm – just like our own ultradian defecation system but a bit shorter in length. Often operating within other Circadian rhythms; these functions of an organism are so interesting in their widespread presence throughout the body and bodies of the animal world. Understanding these rhythms could play a huge role in therapy and scheduling a good day for one self.  Also, the mystery of sleep and dreaming has yet to be solved – the realization that this may have something to do with your connection to the effects of the energy broadcast by the Sun and Moon is a real and scientific one which necessitates further exploration.

 Our own exploration continues to those rhythms which operate outside the Circadian 24(ish) hour cycle and on to those known as infraradian cycles; those cycles longer than a day. These cycles can be monthly to annually. The most recognizable annual cycles are migration amongst many types of animal species. In humans, the menstrual cycle is infraradian in cahoots with the lunar cycle (29.53059 days) which affects much more then you could imagine!  “The lunar cycle has an impact on human reproduction, in particular fertility, menstruation and birth rate. Other events associated with human behavior, such as traffic accidents, crimes, and suicides, appeared to be influenced by the lunar cycle,” said Dr Michael Zimecki of the Polish Academy of Sciences. He commented further 

It is suggested that melatonin and endogenous steroids [which are naturally occurring in humans] may mediate the described cyclic alterations of physiological processes. Electromagnetic radiation and/or the gravitational pull of the Moon may trigger the release of hormones (How the Moon rules your life). 

This apparently omnipresent lunar power doesn’t stop there. The moon’s gravitational pull we of course know creates the tides!

The tides are the formative energies of the ocean the yin and yang, ebb and flow, pull and push of nearly three quarters of the earth. Tides create the waves that punish our coastlines without relent at any given time somewhere on earth. These coastlines though are teeming with life which takes solar and lunar cues; these intertidal organisms which then tend to operate their many biological cycles right alongside the lunar cycle. Could mathematical similarities in cycles link evolutionary cousins?

The final and most bizarre chronobiological perk is that of gene oscillation. The simplest way I can describe this is turning on and off expression of certain genes at certain times in your life, during the day, or just for lunch. It’s not fully understood but some research is being done into its effect on Alzheimers where a gene just turns off and doesn’t turn back on creating a hereditary disease(Ying-Hui Wu*). This happens on many levels and thus may play a function in the passing on of traits. Imagine if this was something which came under our control?

The constant barrage of cosmic energy received from the Sun and Moon and their cyclical nature have taken a major part in life’s evolution on Earth. These energies continue to hugely impact our seconds, minutes, hours, days, months, years and lives – all these cycles, in their entirety. I have included a highly informative diagram which displays human chronobiology, almost eerily for someone unfamiliar, and makes me ponder of the possibilities offered to those who incorporate this knowledge into their daily lives. There are many aspects of chronobiology which need to be explored, fields to which it can be applied and secrets to be uncovered, let’s just hope we have the time. 

Works Cited

ArmMed Media.  Circadian rhythms: Physiological Basis of Sleep and Wakefulness. Aug 22, 2007.


Independent. How the Moon rules your life. Sunday, 21 January 2007.


Kimball, W. John. Online Biology Textbook []

Kramlinger KG, Post RM. Br J Psychiatry. Ultra-rapid and ultradian cycling in bipolar affective illness. 1996 Mar;168(3):314-23. Associated Articles and Links [ ubmed&list_uids=8833685&dopt=Books]

Quraishi , Sabah. Circadian Rhythms and Sleep


Ying-Hui Wu. Pineal clock gene oscillation is disturbed in Alzheimer’s disease, due to functional disconnection from the “master clock.”  The FASEB Journal. 2006;20:1874-1876.


Zivkovic, Bora. Clock Tutorial #16: Photoperiodism – Models and Experimental Approaches.

July 25, 2007. []

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