January 17, 1994. The San Fernando Valley trembled under a large earthquake of magnitude 6.7 that shook the city of Los Angeles with terrible severity. As is normal after a disaster like thisthe emergency lines were soon filled with calls from terrified neighbors. There were many common warnings, but there was a much more curious call which was repeated ad nauseam. That of a lot of neighbors scared by the enormous silver strip that had opened in the sky. What they saw, far from being something dangerous, was a clear sign of the light pollution that already covered Los Angeles 30 years ago.
It was just the Milky Way. In reality, what these neighbors saw was neither more nor less than the Milky Way. Many of them were not used to traveling outside big cities, so they had not seen our galaxy crossing the sky in their entire lives. This is precisely why this true story is often used to raise awareness about the risks of light pollution.
Why is it not seen? Artificial light from streetlights, monuments or illuminated shop windows is reflected and dispersed in the atmosphere, so that it illuminates the background of the sky. Normally, we see stars because there is a great contrast between them and the dark sky. However, this scattered light almost completely destroys said contrast. From Earth, the Milky Way appears as a very faint band of light. Therefore, if there is not enough contrast it is practically impossible to see it. It’s still there, but it’s hidden from our eyes.
The more pollution, the worse. The suspension of particles in the air can cause artificial light to scatter even further. Therefore, the problem in large cities, like Los Angeles, is twofold. On the one hand there are many streetlights and other luminaires and on the other hand there is usually a lot of pollution. It is normal that so many people have never seen the Milky Way.
Getting worse. This event took place more than 30 years ago. Although today there is more awareness about the problem of light pollution and the City Councils of some cities design lighting projects advised by astronomers and other experts, the situation has not improved. In fact, currently is calculated that 80% of the world’s population lives under light-polluted skies.
Using the striking case of the Milky Way as a reference, a study published in 2024 point because 60% of Europeans and 80% of Americans have never seen the Milky Way. The case of people who believed that the sky had cracked is just an anecdote. However, the reality is that the heavens are no longer what they were. If the problem of light pollution is not solved, future generations will not be able to enjoy many of the spectacles that the sky has given us.
Image | Magnificent
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