Almost all the lights in Leiden went out for an hour and a half to look at the stars in the pitch dark

Leiden, Sunday evening. Queuing for the telescope during Seeing Stars, a project by artist Daan Roosegaarde.Image Raymond Rutting / de Volkskrant

First the street lighting, then most of the living rooms and after a few minutes the spotlights on the clock tower of the Pieterskerk: at the stroke of 10 p.m., lights went out everywhere in the center of Leiden on Sunday evening. Hundreds of people, shoulder to shoulder between the battlements of Leiden Castle, let out a collective cry of surprise as the lights went out. “I’ve never seen anything like it,” a bystander told his neighbor a few minutes later.

All this in the context of ‘Seeing Stars Leiden’, an initiative of artist Daan Roosegaarde in collaboration with Leiden, this year’s European City of Science. The idea: the less light, the more stars emerge, which otherwise remain hidden behind the glow of urban light. The hour and a half of darkness required months of preparation, ranging from informing and activating residents to experimenting with putting out blocks of street lighting.


The value of this venture is, to a large extent, philosophical: ‘By showing people the stars, we want to reconnect them with each other and with the cosmos,’ says Roosegaarde. ‘People have been inspired by the starry sky for millennia, but light pollution is slowly disappearing that connection.’

The relationship between humans and the starry sky is not the only thing that deteriorates due to light pollution. Another victim is our biorhythm. Light, natural sunlight, signals the brain to inhibit the production of the ‘sleep hormone’ melatonin. As soon as the daylight disappears, this plug is removed and melatonin is produced, resulting in drowsiness.

As far as the regulation of melatonin is concerned, it does not distinguish between sunlight and artificial light. This emerged from a playful study by the American sleep physiologist Ken Wright, who sent test subjects on a week-long camping trip with a strict ban on turning on artificial light in the evening. The result: they got tired on average two hours earlier.


Animals are also confused by artificial light: robins can be found singing under a street lamp at night, migratory birds continue to circle en masse around oil platforms without reaching their destination and sea turtles lose their way to the beach, where they lay their eggs. Even the increasing mortality of insects has been linked to artificial light: in the darkness, moths gather under artificial light, where they easily become prey to predators.

Moreover: artificial light is expensive, and also burns in places where it is of no use to anyone. Roosegaarde calls it ‘bullshit light’: light from empty office buildings or billboards, for example. To save money, the LED lamp is on the rise, but as a result the night is becoming increasingly blue, which many animals are extra sensitive to.

More and more people and organizations see the return of darkness as a way out of this cat-and-mouse game. For example, since 2006 provincial environmental federations have been organizing ‘The Night of the Night’ when winter time begins. Also this year, on October 29, lights will go out everywhere in the Netherlands, from restaurants, offices and highways to Ikea stores.

‘Dark Reserves’

In addition, the Netherlands has two ‘dark reserves’ with a strict policy against artificial light: Lauwersmeer National Park, on the border of Groningen and Friesland, and the Boschplaat on Terschelling. In these reserves you can even see the Northern Lights on a good day. These ‘Dark Sky Parks’ are nationally recognized and designated by the International Dark-Sky Association, which is committed to preserving darkness worldwide.

Crowds and togetherness during Seeing Stars in Leiden.  Image Raymond Rutting / de Volkskrant

Crowds and togetherness during Seeing Stars in Leiden.Image Raymond Rutting / de Volkskrant

There was no such absolute darkness in Leiden on Sunday. Many living rooms, shop windows and billboards remained brightly lit, and student associations such as Minerva also failed to do so. Moreover, the evening was cloudy: only half an hour pieces of the starry sky were clearly visible. Despite these setbacks, the evening’s goal had been achieved: “I now see about as many stars in the middle of the city as I would on any other day in the middle of the Polder,” said Tünde, an astronomy student who observed the stars in a park. showed with his telescope.

Volunteers were lined up in this manner all over town, and long lines of people were waiting at each telescope to take a look as well. ‘In terms of stargazing, it may not have been the best evening’, said Frans Snik, an astronomer at Leiden University and involved in organizing the event. ‘But it was a great social experiment. The crowds, conviviality and togetherness were the success. Everyone in Leiden looked up for a moment.’

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