People cross at a pedestrian crossing in Tokyo, going about their daily routine like clockwork
Circadian Cities
We live in an urban millennium. Japan has two cities that top the world’s ten most populated - Tokyo and Osaka - with a staggering 37.4 million and 19.2 million respectively, according to data from the United Nations. To keep pace with the progressing urbanisation of megalopolises like these, humans have had to adapt to boundless changes in their habitats.

The human impact on oneself is unrivalled - anthropogenic light and noise have modified the natural order of day and night, interfering with our circadian rhythms. The ebb and flow of urbanised life - a dance between organic and man-made - a force to be reckoned with - and one that alters the temporal activity, patterns, and physiology in myriad creatures across the planet. In very few places is this more apparent than the urban sprawl of Tokyo and Osaka - truly 24 hour cities, whose inhabitants have created their own biological, technological, and environmental rhythms from which to live their lives.

Circadian cycles of bodily function and behaviour are inescapable physical marvels, a result of evolution to our natural world and our planetary journey on our own axis and around the sun. Wake. Eat. Sleep. Repeat... all responses to cyclic environmental signals. Yet what happens when we change these signals? The shift to a 24 hour society in Tokyo and Osaka has had astonishing reverberations where, despite their size, these vast municipalities are clean and ever-efficient, comfortable, and proffer a symbiosis between life in the dark and that in the light.

Here, photographer Dan Gillett, captures the metropolitan flow of life in these circadian cities.

Rachel E T Davies
Dan Gillett