Light is fundamental it interacts with life in profound ways. But light is changing, dramatically, with artificial light pollution, and we don't truly understand the consequences. Nature writer Anna Levin explores the impact on the planet and on human health.

Artificial light is voracious and spreading. Vanquishing precious darkness across the planet, when we are supposed to be using less energy. The quality of light has altered as well. Technology and legislation have crushed warm incandescent lighting in favour of harsher, often glaring alternatives. Light is fundamental - it really matters: it tells plants which way to grow, birds where to fly and coral when to spawn. It tells each and every one of us when to sleep, wake, eat.

We mess with the eternal rhythm of dawn-day-dusk-night at our peril. But mess with it we have, and we still don't truly understand the consequences. In IncandescentWe need to talk about light, urgently. And ask the critical question: just how bright is our future?