Light Pollution


new york light pollution.jpg

This photo was taken at night.

Seriously. At night.

But…it looks too bright for the night. I’ll bet I wouldn’t even have to shine a flashlight to see my way around here.

Need proof? Here’s New York City during the day.

new york daytime.jpg

The lighting comes from the sun. Not the billboards and flashing advertisements.

Who needs that many adverts in their life, anyway?

But I’m not interested in judging New York City…all I want is to make a protest against light pollution.

What is light pollution, anyway?

Light pollution is basically what we call it when artificial light scatters into the night. And New York City’s not the only culprit.

usa light pollution

See all those bright spots on the map? Those are lights as seen from above. This is a satellite image. That means it’s not computerized. All of this is real, not a model or a diagram. We literally have that much light getting lost to the sky.

Wait…what do I mean, lost? How do you lose light?

You lose light all the time.

Here’s why.

Unshielded-Light-Waste.jpg

Here’s an example of what we call unshielded light. There’s nothing to aim this light at the ground. In fact, there’s something to aim it up rather than down—it’s supported from below only. So none of the light is going to point directly down.

You really don’t need this much light. Light rays are scattering from these bulbs in all directions, and last I heard, you can’t fly that low above the ground. There’s no reason to shine light above the light source itself.

Also notice that only 40% of the light here is actually useful. Only 40% is hitting the ground.

Not convinced you should change your lighting? Let me show you something else.

glare3.jpg

In the first image, you see nothing but glare and darkness. But as soon as you block that light in the background, you see a person standing right next to the sidewalk.

Okay, so that person shouldn’t be wearing such dark clothes at night anyway. But the glaring light behind them doesn’t help. In fact, it’s dangerous. What if you were biking late at night and hit this person?

Or what if this happened in a parking lot, and you didn’t see a person standing in a parking spot before you chose to park there?

I know that’s an unpleasant thought. But it’s happened before. My dad has a picture taken in a parking lot of a man who’s completely obscured in the glare of a background light.

There is nothing good about light pollution—especially for astronomers.

Astronomers base their world around light. They depend upon telescopes, which are used to focus light. But they only want light from distant objects. And a lot of the time, the objects they want to see are so faint as to be nearly invisible.

It doesn’t help when light from light pollution is scattered throughout the sky, drowning out the stars…

lightPoll_12

This is why astronomers hate light pollution.

The movement against it is worldwide. Most of what I know about it, I learned from my dad, who’s been active in astronomy for as long as I can remember. And for as long as I can remember, he’s been a light pollution activist.

But that seems to imply there’s a way to stop it…

Indeed there is.

light pollution1.png

All you need to do is use shielded lighting.

What does that even mean?

lightPoll_22

A shielded light is just a light with some kind of hood over it. Any light rays that point upward into the sky just end up bouncing off the shield, and all light gets directed at the ground.

This eliminates glare. It uses all that wasted light for actually seeing what you want to see. And best of all—for astronomers, that is—it doesn’t compete with the night sky.

Here’s some examples of shielded lighting…

find-lighting.jpg

All of these lights keep light rays from shining up at the night sky and getting lost to the atmosphere. And astronomers would greatly appreciate it if you used these for your homes and businesses.

But you can take it one step further, and specifically use low-pressure sodium lights.

These are lights that only shine at a few wavelengths. They compete with the stars a little, but not much, as you can see below.

lightPoll_32

I like the analogy my dad used here—that white light is like a picket fence. White light is made up of every color of the rainbow. Imagine that every color is one picket. In order to see the stars, you need to look through the picket.

spaced-picket-fence-1024x574.jpg

Honestly, if the leaves here were stars, astronomers would have a hard time studying them. Imagine an ecologist trying to study those plants from through this picket fence. Not easy, is it?

But low-pressure sodium lights are like looking through just a few pickets. So you can see more stars.

broken-beach-fence-stock-image-936175.jpg

Think you can see through the hole in this picket fence pretty well?

Imagine trying to study stars beyond that hole. A low-pressure sodium light is like a picket fence like this that’s broken and open in a lot more places. Well, most places. That’s the whole point—you can see through it for the most part.

It’s not hard to change up your lighting and get shielded lights.

In fact, a lot of major businesses near my hometown have done that. You can even talk to your city council about controlling the city’s lighting—that’s what my dad did, and now we’ve got rules about how businesses can light up their properties.

Next up, we’ll take a dive into the modern telescopes of the era…

About Emma

I'm a college student, astronomer, writer, Democrat, global warming activist, hardcore trekkie, daring adventuress, and dreamer. I have four blogs to date. The primary one is Science at Your Doorstep, but I also post to The Sojourns of Star Trek, Common Sense Politics (US), and Toleventures. I guest post to A Momma's View. I write for different reasons. Sometimes because I want to share my process of discovery with others. Sometimes because I think a story is too incredible to keep it to myself. Sometimes just because I want to be heard. Regardless, I hope you enjoy it!
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