We are afraid of the dark. We should be. There are a lot of scary things out there. Not that long ago we had to learn to use the moonlight to extend the day. We navigated by the bright stars you could see at twilight before any of the others appeared, the same ones that could still shine through a mist or haze. At some point we lit the world with fire, but it was a pitiful effort against the immensity of the night. Then we figured out artificial lighting.

We got a lot out of it. Safer streets, for one. Encouraging commerce and such. Allowing for travel. Spreading the wealth. All the benefits of progress. Artificial lighting might just be the very thing we need to define progress. How lit up is YOUR country? Ours is WAY lit up! We’ve all seen the satellite photos of our country over the decades and we’ve seen the spread of lighting. Even the vast rural West is lit. Not all of it, of course, there are plenty of places that are still dark. But the tentacles of urbanization and the flagella of interstate highways continue their inexorable march.

Millions of us no longer have darkness. We have to travel to see it. The darkness used to be everywhere. Even in cities lit by fire the darkness was nearby—too close for comfort, in fact. But we no longer think about it. At least most of us. A vanishingly small segment of our population lives in proximity to the darkness if not in the midst of it. When we find ourselves in a place where the sky is far from the sources of artificial light we are amazed. We forget how spectacular the night sky is when you can see the Milky Way in all its glory. There are so many stars that you get lost. Familiar constellations are hard to find. The stars have color and depth that you don’t get in light-affected areas. There is a faint starlight that allows you to see even without a moon. It’s a special and memorable experience.

Much of the spread of lighting is due to advancements in technology that have lowered the cost and increased the efficiency. The consequence of conservation is over-use. That is, we need so much less money and energy to light things up so we light more things up. A few smart folks have calculated that artificial lighting is growing about 2% per year.

That doesn’t seem like much. Two percent. If you had a mortgage at 2% you’d be happy. An investment, though, would be under-performing at a mere two percent. But 2% is not trivial. If you think in terms of doubling time, it seems rather ominous. Now a banker would tell you to use the Rule of 72 and divide 72 by two and get 36. That’s thirty-six years. Two percent growth means whatever you have will double in 36 years. Your algebra teacher would probably insist on using the natural logarithm of two, and dividing by 2% (0.02) which would give you 34.7 years give or take. Close enough.

So if the world is this lit up NOW, thirty-five years from now (when I’m 93) the world will be TWICE as lit up! That’s a lot less darkness. Seems like you have to have darkness. Lots of creatures need the darkness. And by creatures I mean everything from bats to bacteria. Maybe we need darkness, too, even if we are scared of it. I don’t know. It seems like this is one of those fixable things. We were really smart and we invented cool things that use less energy and were less polluting. But we didn’t gain anything because we just wanted more of the same thing. We can’t be THAT scared of the dark, can we?

Standing under the stars is one of those things that makes you humble. And you have to have humility, because without it there is no empathy. And without fellow-feeling towards our brethren there’s not much point in social intercourse. You don’t have to love your human neighbors but you depend on them nonetheless, just as the single ant depends on the colony. I know we aren’t ants, but we are certainly social. We all live in this tenuous web we call civilization, and we are all kept afloat by the ties that bind us together.

The encroachment of artificial lighting into areas with dark skies is called light pollution. Over-lit areas, like big cities, are light-polluted. We need light, but we don’t need pollution. One of the groups most bothered by light pollution is astronomers. Observatories have to be on remote mountaintops, or in earth orbit, to escape the effects. They are a small bunch, overall, but they are like canaries in the mine. Darkness doesn’t seem like one of those natural resources you ought to conserve, but I think we ought to. Some things that are big and scary need to stay big and scary. Like the universe. And who says we can’t light up when we are scared? We just don’t have to be lit up ALL the time. We have to keep some darkness around for our own good.