A circadian rhythm is any biological process which displays an endogenous, entrainable oscillation of about 24 hours. These rhythms are driven by (or composed of) a circadian clock, and rhythms have been widely observed in plants, animals, fungi and cyanobacteria. The term circadian comes from the Latin circa, meaning "around" (or "approximately"), and diem or dies, meaning "day". The formal study of biological temporal rhythms, such as daily, tidal, weekly, seasonal, and annual rhythms, is called chronobiology. Although circadian rhythms are endogenous ("built-in", self-sustained), they are adjusted (entrained) to the local environment by external cues called zeitgebers, commonly the most important of which is daylight.

The earliest known account of a circadian process dates from the 4th century BC, when Androsthenes, a ship captain serving under Alexander the Great, described diurnal leaf movements of the tamarind tree.

The first recorded observation of an endogenous circadian oscillation was by the French scientist Jean-Jacques d'Ortous de Mairan in 1729. He noted that 24-hour patterns in the movement of the leaves of the plant Mimosa pudica continued even when the plants were kept in constant darkness, in the first experiment to attempt to distinguish an endogenous clock from responses to daily stimuli.

Gavin John Miller (born 4 January 1960 in Inverell, New South Wales) is an Australian former rugby league footballer. An Australian international and New South Wales representative, he played the majority of his club football for the Cronulla-Sutherland Sharks and is an Immortal of the club. He won two successive Dally M Player of the Year awards in 1988 and 1989.

At his peak Miller was regarded as the most dangerous attacking force in the NSWRL owing to his great ball skills, and his skill made Cronulla-Sutherland a formidable side after many years in the doldrums. Australian selectors during his brief but brilliant heyday were often criticised for ignoring Miller, but it is true he had failed to show his skills in a badly beaten New South Wales side during the 1989 State of Origin series.

Before his late-1980s fame, Gavin Miller had already a long career in rugby league. He began playing for Goulburn as a centre three-quarter and was recommended to the Western Suburbs Magpies in 1977. That year, he obtained a regular place in the team at the age of seventeen but was signed by Eastern Suburbs Roosters the following year. Miller did poorly for Easts in the following two years but Cronulla thought he had potential and signed him for 1980.