(gentle piano music) - When we talk about the night sky, it's not just the moon, and the planets, and the bright stars, but if the sky is really dark, you would see thousands of stars and you would see a rich Milky Way.

In some areas in the world where it's still not lost, the Milky Way is so dense and so bright you can see your own shadow cast on the ground just from the center of the Milky Way.

You appreciate you live in a galaxy.

You see the shape of it.

You see the dark lanes in it.

You see the spiral arms projected in front of each other.

It gives you like a perception of where you are in the cosmos.

You see what people in ancient Greece saw, you see what people in the Roman Empire saw, and you see actually what Vincent Van Gogh saw.

(dramatic piano music) If you look up at the night sky from New Jersey, all that is lost.

If the simple thing of just aiming the lights down would achieved, the night sky would come back.

(uplifting piano music) So back in the old days, I would say to maybe the mid 20th century, the astronomers actually worked from where they lived.

There was active observing going on from Harvard College Observatory from Cambridge, Massachusetts.

The telescopes were in operation till 1970.

Princeton University had a dome that was running till perhaps early 2000.

That's all gone.

You can't really do any serious work fro.. (bright upbeat music) This here is a, it's a long way, right?

You fly here from New York, and then take another flight, and then you drive two and a half hours, and then you're 100 kilometers from La Serena.

It's a big glow in the sky, and Santiago I see from here on photographs, which is very far.

You see light pollution basically everywhere.

It's impossible to escape.

And I mean if it was some necessary thing for our survival, right, that would be fine, I guess, but it's just a complete stupid waste of energy, resources, and destroying our nature.

I think it has to be recognized that the sky is part of our nature, and in fact, we're very lucky with this planet.

There's so many planets where there's a thick atmosphere and you don't see anything.

(rocks tapping) That's a good one.

(rocks tapping) Yeah, light pollution has been now measured from numerous satellites orbiting the Earth over the past decade.

It's getting rapidly much worse.

About 80% of the US has now lost the vision of the Milky way.

Light pollution has increased at least 50% in the past 25 years, but up to 400% in many places.

One reason is actually conversion to LEDs.

LEDs are inexpensive now.

They save energy.

They're extremely bright.

Now, instead of cutting back on the energy use, what was kept constant is the amount of money we pay for the energy or the amount of energy we waste and lights were made 10 times brighter.

I mean, we are in dusk.

The sun is just setting, and this is causing a gl..

If you're driving out from this direction, there's this bright light shining in your eyes.

It's not actually helping anyone.

First, we need to define what light pollution is.

It's the inappropriate or excessive amount of outdoor lighting.

So light actually goes in every direction.

At least half of this light, then, is totally wasted.

It goes out into the clouds.

But some of it actually is causing glare because it hits this house here with a window, someone trying to sleep.

Here in Princeton, the sun just set, and this is the parking lot of the YMCA.

You see these very bright white LEDs that are not good lights because they're too bright and they're not shielded.

They're aimed sideways and much of the light is escaping up in the air.

There are a couple of important aspects of light pollution.

I would probably start with health.

There is now ample scientific research in medicine showing that light pollution has strong adverse health effects.

It has been clearly linked to an increased rate of breast cancer by elevating the risk of breast cancer something like 20% or more for women who live or sleep at conditions with strong ambient light.

It has been linked clearly now to depression and diabetes.

This is fairly new research.

It's the result of the past maybe 20 years, partly because light pollution has been growing by hundreds of percent, and partly because there's more awareness now, but unfortunately, the practices that actually decreasing light pollution is lagging behind.

It's not happening.

(gentle music) The critters even in this tiny patch of wood would appreciate just the natural light and nothing else.

So light pollution has an enormous impact on the ecosystem on Earth.

It's not appreciated, but there are many creatures here that live under dark conditions and used to living under dark conditions.

For example, migrating birds navigate using the stars.

Other example is hatching turtles.

The little turtles hatch from the egg, and they look around, and they go towards the brightest lights, which unfortunately are not towards the ocean and not the stars, but they start going up to the highway.

Other example is insects.

There are studies showing that in England, at areas that are overly lit and light polluted, the amount of moths compared to previous years decreased by more than 50%.

And there are other crazy statistics showing of how many insects are just dying or not present anymore in the food chain.

So what we see here is like a jam of dead flies, and moths, and mosquitoes in the base of this lamp.

In fact, I've seen some lamps where the entire bottom half was filled with bugs, so all the light was just going up in the sky.

There was a natural shade by poor dead bugs underneath the bulb.

What's fascinating about these lights is that even spiders figured out that there's light pollution and they cast all their webs right on the lights there because they somehow figured out that lights attract so many bugs that they can harvest those bugs by tactically placing their webs around them.

(dramatic piano music) In terms of the environmental impact of light pollution, let's also discuss the amount of energy we waste.

The current estimate is that about 40% of outdoor lighting in the US is wasted.

It just goes up in the sky.

So that corresponds to about $3 billion per year essentially lighting up the universe by converting carbon into photons.

That's equivalent to about 21 million tons of carbon dioxide emitted every year.

The problem is when you look at a street lamp, you don't actually see the smoke coming out.

They all look just fine because the energy that's being generated is far away, but one has to actually think about it, this enormous waste.

(gentle somber music) I don't want to force the beauty of astronomy in the night sky on really anyone.

I think it's beautiful, but I understand that people are less interested .. but I think everyone is interested about their health and everyone should be interested about the environmental impact of this and the waste of energy.

(gentle brooding music) Actually, what's really annoying about light pollution is that the solution is very easy, and yet we're not doing it.

And you see other areas like that with humanity.

The keywords are you need dim lights, you need well-shielded lights, and prefer warm red colors.

The lighting in this little alley is essentially perfect.

The light fixtures are perfectly well shielded.

The color is dim orange.

It's not overlit, and they're well spaced.

I actually don't understand why this is such a rare sighting, but unfortunately it's very rare to spot something like well designed and modest.

This is Princeton's First Aid Rescue Squad.

It's a relatively new building, and it has essentially perfect lights in front of it.

They're well shielded and they lead to a uniform illumination of this entrance where emergency vehicles would enter or exit the building.

This is a relatively dark field, but I don't think it's very dark.

There are still some lights around.

The reason we came here is an idea to establish something like a dark sky sanctuary within Princeton.

If you think about it, we don't just fill every available space with bui.. We need areas where we have a field, we have grass, we have a meadow, and we all feel the need for these areas.

Similarly, I think we could have an area which is dedicated to actually seeing the night sky, where we would guarantee that there are no bright lights around, no stray lights blinding us where we can come and see the stars or any kind of night sky phenomena.

If a bright comet appears in the sky close to the horizon, we would come out here and we would observe it.

Avoid excessive lights.

Again, that's the dim.

Shielded means it's not inappropriate.

It doesn't go to other houses, or to the woods, or to space.

And the red, the warm colors, are important because they are less of a disruption for our circadian rhythm and also they scatter less in the atmosphere.

They cause less of an air glow or like a night glow from light pollution.

So basically this fixture here, which I was showing, all you need to do is have a shield on top and make sure that no photon escapes above the horizon.

In fact, the shield should be such that all light falls to where it's intended to fall.

Use LEDs.

LEDs consume less energy, but don't overlight.

LEDs can be dimmed.

You can dim them from 10% to 90%, anywhere in the range.

So dim them.

Use smart technology.

There are many places on Earth where lights are dimmed at midnight.

If you go around in Princeton, you would see a parking lot flood lit at 4:00 AM in the morning on a winter night the same way as it is at 7:00 PM.

(melancholy piano music) There is a lack of education.

People, without any bad intentions, clearly they're just buying the cheap, super bright white LEDs.

They put it in the parking lot sideways and everything is flood lit.

They're unaware of all these effects, so it's just getting worse.

There's no central regulation of any sort about these practices.

So I think the predictions are unfortunately very bad, but to be a bit more optimistic, I think if anywhere, in Princeton, we could change that and could set a very good example that may be followed by other either campuses or little townships.

It can lead to potentially big change.

There were ways to reverse many other things in the history of environmental damage.

A century ago, it was perfectly fine to just burn any trash you had anywhere.

It was fine to operate factories in the middle of a city burning coal.

London was covered in black soot for a century and now it's not.

It was, again, as I mentioned, it was fine just to let your used motor oil down the drain and you can't do it anymore.

Factories could dump all their waste into riverways and right now you can't do it anymore.

So there were things that, at some point, probably seemed irreversible and terrible and yet they changed in a positive way.

I hope that light pollution, given the solution is so simple, can be reversed.

Again, we need to shield the lights, dim the lights, and use warm colors, and it will be better for everyone.

(uplifting music)