At 4.02am on 2 November 1892 near Thirsk railway station in Yorkshire, an express train crashed into a goods train. Ten people were killed and 39 injured. Nearly 100 years later, at 1:23am on 28 April 1986, the No 4 reactor at the Chernobyl Nuclear Power Plant exploded, killing two people instantly followed by multiple deaths from radiation. Highly radioactive fallout was sent into the atmosphere and the long-term cancers are still being assessed. Understanding how these seemingly unrelated tragedies are connected requires an understanding of biological time.
Our lives are ruled by time. But the alarms that drive us out of bed in the morning or tell us that we are late for a meeting are recently-arrived chronometers. Life answers to more ancient beat that probably started to tick early in evolution. Embedded within our genes are the instructions for a biological or “circadian clock” that regulates our sleep patterns, alertness, mood, physical strength, blood pressure and much more. Normally we experience a 24 hour pattern of light and dark, and this signal is used to align our day to the Earth’s rotation. The clock is then used to anticipate this rotation and fine tune physiology and behaviour in advance of the changing conditions. Temperature, blood pressure, cognitive performance all decline in anticipation of sleep. Before dawn, these processes are slowly reversed in anticipation of the new day.
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