Later On

A blog written for those whose interests more or less match mine.

Fear of the light: why we need darkness

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Amanda Petrusich reports in the Guardian:

Every civilisation we know of has devised a system – scientific, religious, what have you – to make sense of the night sky. The mystery of what’s up there, where it came from, and what it means has been inherited and puzzled over for generations. Those questions may be the most human ones we have.

Due to pervasive light pollution – glare from excessive, misaimed and unshielded night lighting – 80% of Europe and North America no longer experiences real darkness. For anyone living near a major metropolis, a satellite image of the Milky Way seems abstract: we understand it to be a document of something true, but our understanding is purely theoretical. In 1994, after a predawn earthquake cut power to most of Los Angeles, the Griffith Observatory received phone calls from spooked residents asking about “the strange sky”. What those callers were seeing were stars.

I grew up in a small town in the Hudson River valley, about an hour north of New York City. Like most children, I regarded the night sky (or what I could see of it) with wonder. I understood that nobody could say for sure what was out there. Little kids are often frustrated by the smallness of their lives – as a child, you can conjure complex worlds, but in your own life, you are largely powerless to make moves. Looking up, the tininess I felt was confirmed, but it no longer felt like a liability. If the night sky offers us one thing, it is a liberating sense of ourselves in perspective, and of the many things we can neither comprehend nor control.

“I wish to know an entire heaven and an entire earth,” Henry David Thoreau wrote in 1856. He understood those worlds as separate, but in some essential conversation with each other – to receive one without the other was to misunderstand both. But what happens when mankind divorces itself from a true experience of the cosmos, separating from the vastness above, taming it by erasing it? How can we ever come to know a heaven we can barely see?


Darkness is a complicated thing to quantify, defined, as it is, by deficiency. In 2001, the amateur astronomer John Bortle devised a scale to help. His classifications range from “inner-city sky” (class 9), in which the only “pleasing telescopic views are the moon, the planets, and a few of the brightest star clusters”, to a sky so dark “the Milky Way casts obvious diffuse shadows on the ground” (class 1). Most North Americans and Europeans live under class 6 or 7 skies, in which the Milky Way is undetectable and the sky has been smudged by “a vague, greyish-white hue”. In that kind of night, a person can wander outside, unfold a garden chair, open a newspaper, and read the headlines, if not the stories.

In addition to the Bortle scale, scientists often use photodiode light sensors to measure and compare base levels of darkness by calculating the illuminance of the night sky as perceived by the human eye. Unihedron’s Sky Quality Meter is the most popular instrument for this kind of work, in part because it is small enough to fit into your pocket and also because it connects to an online global database of user-submitted data. According to that database, Cherry Springs State Park – an 82-acre park in a remote swath of rural Pennsylvania – presently has the second darkest score listed. On the Bortle scale, Cherry Springs usually registers between 1 and 2. In 2008, the International Dark-Sky Association (IDA), a nonprofit organisation that establishes and supports dark-sky preserves around the world, designated it a gold-tier international dark sky park.

Earlier this year, I drove the six hours to Cherry Springs from New York to meet Chip Harrison, the park’s manager, his wife, Maxine, and a park volunteer named Pam for a 4.30pm dinner of baked fish. Afterwards, Chip had promised, we’d go and see stars.

“Most children, right now, growing up in the US, will never see the Milky Way,” Chip said while we waited for our main courses.

“Their parents never saw it either,” Maxine added.

“You come to a place like Cherry Springs, you’re gonna see four or five thousand stars, maybe more,” he continued. “I’ve seen people who are fairly serious amateur astronomers, and they can’t find their way around this night sky – there are too many stars.”

After supper, we drove to the park, arriving around sunset and unloading several bags of equipment from the trunk before setting out, together, into the blackness. White light isn’t permitted on the astronomy grounds, but red-filtered light, which won’t cause the rods of the eye to become overexposed and less efficient, is allowed, if not quite encouraged. . .

Continue reading. There’s a lot more and some good photos.

Written by LeisureGuy

27 August 2016 at 3:52 pm

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