October 28, 2021

I, Science

The science magazine of Imperial College

Faiza Peeran finds that animals can use the colour of the sky to tell the time

1280px-Van_Gogh_-_Starry_Night_-_Google_Art_Project“It often seems to me that the night is even more richly coloured than the day, coloured with the most intense violets, blues and greens,” wrote Van Gogh, while painting The Starry Night. He wasn’t the first to be inspired by the colour of light in the sky, nor the last. But whilst the colours continue to enthral us, they may have an even greater impact on our lives – as they have shown to be a key factor influencing our body clock.

“It’s a fundamental part of all organisms on the planet,” explains Dr Tim Brown, from the University of Manchester, who has long been fascinated by the body clock. Our bodies are governed by regular rhythms controlled by our internal clock, with our sleep-wake cycle one of the most prominent. We’ve known for many years that light is one of the key signals synchronising it – i.e. by detecting the amount of light in the environment, the body clock can then infer the time of day. But Dr Brown and his team didn’t think that this was the whole story. They believed that the colour of the light might also have an impact.

Purple Haze
A view of Howe Sound from Whytecliff Park at twilight

Like brightness, colour changes throughout the day. For example, light becomes bluer at twilight, as it passes through more atmosphere to reach us. To investigate if colour did affect the body clock, the team created an artificial sky, which mimicked daily changes in brightness and colour. They found that when mice were placed under this sky, they became most active during the night, normal for nocturnal creatures. But when conditions were altered so that the colour did not change, the mice became active earlier, indicating their body clock was out of sync. “This shows that the ability to detect colour is really important for the body clock to correctly align itself to the environment,” says Dr Brown.

If this finding is reflected in humans, we could use colour to manipulate our own body clocks. Specialised lighting could be used to help those who suffer from sleep problems due to shift work and jet lag. The team is fairly confident that this could happen. “There are already some suggestions that the colour mechanisms might affect the body clock in humans,” Dr Brown explains. So whilst admiring the colour in Van Gogh’s works may satisfy our cultural needs, perhaps a colourful solution could also solve our biological ones.

Faiza Peeran is studying for an MSc in Science Communication

Images: Van Gogh, The Starry Night (Wikimedia Commons); Purple Haze by Bruce Irschick (Flickr; Creative Commons)

Citation: Walmsley, L. (2015) Colour As a Signal for Entraining the Mammalian Circadian Clock. PLoS Biology DOI: 10.1371/journal.pbio.1002127