siiky
2023/09/13
2023/09/13
2023/09/13
post,biology,science
In April of this year, Spanish athlete Beatriz Flamini emerged into the light after a 500-day stay in a cave. Her descent underground is probably the longest undertaken by a long stretch. Flamini says she lost all sense of time on the 65th day. But can she really be sure it was the 65th day? By way of comparison, in 1962 France’s Michel Siffre surfaced from the Scarasson chasm in Italy after spending what he thought was 33 days there. In fact, he spent 58 days underground.
And these rhythms have many repercussions, not least in terms of public health. Indeed, a number of diseases are episodic – for example, asthma is more severe at night, while cardiovascular accidents are more frequent in the morning. Another example is shift work, which disconnects people from their environment. It may be associated with an increased risk of cancers in workers, prompting the WHO to label it as a probable carcinogen.
The regular alternation of day and night has, for example, favoured the evolution of the circadian clock (circa, meaning “approximately”, and diem, “day”).
So that's where the word comes from!
Environmental signals in general, and light in particular, help to re-synchronise the individual: light perceived at the end of the night moves the clock forward, while light perceived at the beginning of the night delays it. Light perceived during the day has no effect.
With Homo sapiens‘ intrinsic circadian period spanning an average 24.2 hours, it is easier for us to travel west and lengthen our days than to travel east and shorten them. This is also why athletes and researchers who isolate themselves in the depths of the Earth end up being out of sync with time on the surface, and ultimately perceive fewer days than 24-hour solar days.