Goodbye, dark sky. The stars are rapidly disappearing from our night sky

Most Canadians are about as likely to see the Milky Way as they are to see a beaver riding on the back of a moose.

That's because almost three-quarters of Canadians live in brightly lit cities, leaving just a smattering of stars visible to the unaided eye. 

Now, a new study has found that the night sky may actually be brightening faster than once thought, and that has consequences for humans, ecosystems and more.

In a paper published in Science on Thursday, the authors used data collected from citizen scientists who took part in the outreach program Globe at Night, in which participants look at particular constellations and record how many stars they can see.

What they found was that, over the past 12 years, stars are becoming increasingly difficult to see, possibly due to increasing light pollution. The change was a seven to 10 per cent annual increase in sky brightness, far more than what satellites have detected.

To put it in perspective, the authors noted that someone born in an area where 250 stars could be seen would see fewer than 100 in the same place 18 years later.

Satellite data previously put the growth in light emissions at 2.2 per cent per year from 2012-16 and 1.6 per cent during 1992-2017, which is in stark contrast to the new findings.

But there may be a reason for that.

Those satellites weren't purpose-built for the research, so they were limited in what they can see. As well, satellites could see light emitted straight up, but not from the sides.

There may be other explanations including in the increased use of LEDs, which are brighter and contain more blue light.

"Blue light scatters more in the atmosphere, so you get more light scattering back down to Earth," said the study's lead author Christopher Kyba, a light pollution physicist at the GFZ German Research Centre for Geosciences in Bochum, Germany.

"[And] when our eyes are dark adapted, they're more sensitive to blue light. So replacing that long-wavelength light by blue light makes things look brighter and makes it harder to see the stars."

Kyba also theorizes that a trend toward more decorative lighting — on the sides of buildings and in people's homes, for example — that shine in directions other than upward, could be a factor. 

The research "confirms something that many of us have suspected for a while, which is that the rate at which light pollution is growing throughout the world is much faster than we previously appreciated," said John Barentine, the executive officer and principal consultant at Dark Sky Consulting, LLC and former head of the International Dark Sky Association, who was not involved in the study.