Where are the nights of yesteryear?

What does light pollution take away from us? For millions of years, human beings have been able to contemplate a clear night sky and see things which inspired religious, scientific, poetic ideas... We have not only lost many of the three thousand stars normally visible to the unaided eye. We are also losing:

The Milky Way, our 150-billion star home galaxy, a ghostly pale bridge across the sky: whether they believed it was the path of lost souls, mud churned up by a passing heavenly shark, or the seam which joined the two halves of the sky together, ancient peoples marvelled at this river of light. Now, most people in the developed world cannot see it. Most children have grown up unaware of their own galaxy. Thinking that the Earth is the only thing that exists is an ultimate and dangerous vanity.

Credit: The Milky Way by Paul Whitmarsh

These dancing lights (aurora), caused by solar outbursts, are not as rare as most people think. Even in areas well away from the poles, they were a common sight in the nineteenth century, but now glimmer unnoticed behind the sheen of wasted artificial light.

Credit: The aurora (the Northern lights) by David Briggs

Credit: Zodiacal light from the Isaac Newton Telescope, La Palma, by D.Baskill

The glow of zodiacal Light - sunlight reflected from billions of dust particles, left behind by passing comets, strewn across the plane of the Earth's orbit causes this faint glow at dawn and dusk. Our solar-system is essentially flat, and so forms a line of arc across the sky called the ecliptic; notice how the zodiacal light follows the line of the ecliptic. Alas, zodiacal light is hidden from view due to light pollution.

Credit: Comet Ikeya-Zhang, by C. Baddiley

Comets can be visibly the most impressive objects in the solar system, especially to the unaided eye, and so catch the publics imagination. We have been treated in the past decade to three fantastically bright comets; Hyukatake, Hale-Bopp and Ikeya-Zhang. However, light pollution has degraded the appearance of these treats of the night sky, as seen in the photo above.

At certain times of the year, the Earth in its orbit around the Sun ploughs through cometary dust. Like driving a car through snow, we see this dust burn up in the atmosphere as shooting stars, or meteors. We might see many shooting stars every night with darker skies, but nowadays only the brightest meteors are visible in light-polluted areas.

Credit: Wally Pacholka (Astropics) & Tony Hallas (Astrophoto) .

These sights have been, since about 1950, gradually taken away from us by the baleful glow of wasted light, escaping from poorly aimed and often over-bright artificial lamps, to be scattered by airborne particles and aerosols. Over great cities, towns and even small villages, light pollution robs us, in the last millisecond of its journey, of light which may have travelled for hundreds, thousands or even millions of years to reach our planet.

There is a trend nowadays for road lighting to be better directed, not least because of the efforts of concerned bodies of astronomers such as the International Dark-Sky Association and the British Astronomical Association's Campaign for Dark Skies . But most private lighting is not designed to restrict emissions to the premises to be lit, causing light trespass and nuisance to many non-astronomers, too. The fact that light is not legally considered a pollutant like noise and smoke means that victims of light pollution have little redress, and the stars have no protection in law. Here is a modern irony: spacecraft and telescope technology can deliver breathtaking views of the near and far universe, while the technology which lights our nights simultaneously draws a veil across the night sky. Are we cutting ourselves off from the direct experience of the rest of the universe?

Bob Mizon