Humans have been able to see the Milky Way galaxy for over 100,000 years, but now nearly 3 billion people are unable to see it due to light pollution. This issue has arisen in recent times, as a century ago even the largest cities still had dark enough skies to see the Milky Way. Light pollution occurs when lights are directed upward into the sky, and it comes from various sources such as streetlights, floodlights, billboards, and excessive indoor and outdoor lighting. This loss of visibility of the Milky Way has severed our connection to the cosmos and the sense of deep time it represents.
In the past, cultures around the world, such as the Aboriginal and Torres Strait Islander people in Australia, had detailed records and observations of the Milky Way, including dark patches caused by dust blocking starlight. However, light pollution began to be a problem in modern cities around a century ago. For example, the Melbourne Observatory had to stop astronomy observations in the early 1900s due to light pollution hindering their ability to study the night sky accurately. Mount Stromlo Observatory took over observing the Milky Way but had to find a new dark site, Siding Spring Observatory, due to the gradual loss of visibility caused by light pollution. Even Siding Spring Observatory now experiences the glow of light pollution from Sydney, located 450 kilometers away.
To address this issue, it is important to shield lights to prevent upward spill and direct light towards the ground. Canberra, for instance, has been changing streetlights to shielded lights that reduce light pollution. Turning off or dimming unnecessary lights is also crucial. Canberra has been dimming streetlights to 50% brightness during the night, saving energy and reducing light pollution. Additionally, using warm-colored lights instead of bright white LEDs and cold-colored lights can help reduce light pollution and benefit our eyes, sleep cycles, and native animals. By implementing these measures, we can restore the visibility of the Milky Way and regain our connection to the night sky.