For so many, the starry night is gone

Originally published 7 September 1987

Labor Day — tra­di­tion­al­ly the end of sum­mer vaca­tion. We are back from the moun­tains, the seashore, or sail­ing boats at sea, places where the sky is still inky dark and free of urban haze. Places where we had a chance to see the night sky as our grand­par­ents saw it, in the days before elec­tric lights and indus­tri­al pol­lu­tion oblit­er­at­ed the stars.

For those of us who live with­in 25 miles of a city, sum­mer vaca­tion may be our only chance to redis­cov­er the star­ry night. No mat­ter how many times it has hap­pened before, there is still a shock of sur­prise on that first clear night in Maine, or Nan­tuck­et, or some dark val­ley of the Berk­shires, when we lean back our head and exclaim with the poet Ger­ard Man­ley Hop­kins:

"Look at the stars! look, look up at the skies!
   O look at all the fire-folk sitting in the air!
   The bright boroughs, the circle-citadels there!
 Down in dim woods the diamond delves! the elves'-eyes!"

It is a pleas­ant coin­ci­dence that sum­mer vaca­tion coin­cides with the most rich­ly star-drenched skies of the year. In the evening hours of August and ear­ly Sep­tem­ber we look out from Earth toward the glit­ter­ing cen­ter of our galaxy, which we see as an espe­cial­ly dense con­cen­tra­tion of bright stars and a gashed drap­ery of milky light hung across the sky. I am think­ing of an evening a few weeks ago when I was far from city lights under a sky of crys­talline clarity.

The Earth was tent­ed with stars, stars so numer­ous they appeared as a con­tin­u­ous fab­ric of light. The Milky Way flowed like a lumi­nous riv­er from north to south, banked with dark shoals and eddied with glit­ter­ing pools. Our sis­ter galaxy in the con­stel­la­tion Androm­e­da was also vis­i­ble to the naked eye, a blur of light con­sist­ing of the glow of a tril­lion far­away stars. Mete­ors flashed like fireflies.

It was out of the expe­ri­ence of skies such as this that much of human cul­ture sprang. Cer­tain of the con­stel­la­tions are per­haps the old­est sur­viv­ing inven­tions of the human mind. The depth and gen­eros­i­ty of the night sky helped inspire reli­gious and philo­soph­i­cal spec­u­la­tion. Sci­ence and math­e­mat­ics had their ori­gin in ques­tions posed by the night, in the lop­sided cir­clings of sun, moon and stars and the move­ments of the plan­ets on their shut­tle­cock courses.

For a great por­tion of humankind the star­ry night is gone. It is a mea­sure of the degree to which we have pol­lut­ed our skies that while almost every­one has heard of the Milky Way, sur­pris­ing­ly few peo­ple have seen it. Ours is the first cul­ture any­where on Earth at any time in his­to­ry for whom the Milky Way is not a promi­nent and inspir­ing part of the nat­ur­al envi­ron­ment. Oth­er, more sub­tle lights in the night sky — the Great Galaxy in Androm­e­da, the dou­ble clus­ter of stars in Perseus, the Bee­hive star clus­ter in Can­cer — were once easy naked-eye objects; they are now avail­able only to those who have access to the dark­est, clear­est skies.

Magnitudes of brightness

Our present sys­tem for defin­ing the bright­ness of stars goes back to the astronomer Hip­parchus, who lived in the city of Alexan­dria at the mouth of the Nile Riv­er in the 2nd cen­tu­ry BC. The dozen or so bright­est stars in the sky Hip­parchus called stars of the first mag­ni­tude. The faintest stars that Hip­parchus could see (in those days before tele­scopes or any kind of opti­cal aid) he called stars of the sixth mag­ni­tude, a cat­e­go­ry that includ­ed thou­sands of tiny pin­points of light at the lim­it of vision. The oth­er stars he dis­trib­uted along the appro­pri­ate steps in between.

No sixth mag­ni­tude stars are vis­i­ble from the city of Alexan­dria today, nor from any city. On a clear night in Boston, a stargaz­er might see stars of the sec­ond or third mag­ni­tude only — a few hun­dred dots of light sprin­kled incon­spic­u­ous­ly across the sky. A more typ­i­cal evening might hide all stars but those of the first mag­ni­tude. Year by year, more and more of the star­ry night is dis­solved in the glow of street­lights and obscured by atmos­pher­ic pollution.

But get far away from city lights and it is stilquil pos­si­ble to recov­er the sky as Hip­parchus or Hop­kins saw it, awash with stars of the sixth mag­ni­tude, “dia­mond delves” from hori­zon to hori­zon. The sight of such a night can take one’s breath away.

What can be done to stop the ero­sion of the night? Prob­a­bly not much. Increas­ing­ly, civ­i­liza­tion pro­ceeds around the clock, and night­time activ­i­ty requires arti­fi­cial light. The need for secu­ri­ty in a dan­ger­ous and uncer­tain world brings arti­fi­cial light­ing even to the sub­urbs and the countryside.

Ama­teur and pro­fes­sion­al astronomers have mount­ed sev­er­al efforts to make gov­ern­ments and pri­vate cit­i­zens more aware of the impor­tance of dark skies — aes­thet­i­cal­ly, spir­i­tu­al­ly, and sci­en­tif­i­cal­ly. Sev­er­al mod­est vic­to­ries have been won on behalf of dark­ness. But it is not easy to be opti­mistic about the long-term prospects. The day is not far off when the stars will be some­thing city-dwellers read about in a book, as already the Milky Way has become some­thing heard of but not seen.

As the “bright bor­oughs” of Hop­kins’ poem become increas­ing­ly remote, not even a sum­mer on the shore of Nan­tuck­et or in the moun­tains of Maine will offer a chance to expe­ri­ence the undimmed star­ry night.

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If you would like to learn more about pro­tect­ing the night sky for future gen­er­a­tions, the Inter­na­tion­al Dark Sky Asso­ci­a­tion can help. ‑Ed.