Following is the full transcript of former park ranger Diane Knutson’s TEDx Talk titled “Why We Need Darkness to Survive” at TEDxRapidCity conference. In this talk, Diane shares why light pollution needs to be reduced and some surprisingly simply ways we can all take action.
This meadowlark perches on a prairie flower singing its mating song. It’s customary for meadowlarks to sing toward the rising sun.
This one, however, was mistaken by the lights of Rapid City at 2 AM. Despite being 60 miles south of the Rapid City border and well within the boundaries of Wind Cave National Park, this songbird was singing out much too late to attract a mate.
Have you ever tried attracting a mate by calling them at 2 AM? My mother told me nothing good happens after midnight.
So why was this songbird so confused, mistaking the bright lights of Rapid City for the rising sun at 2 AM?
Improper lighting and the over-illumination of residential neighborhoods, business signage, and street lights brighten our night sky, creating an orange hue above the city for miles outside its border.
Over 100 years ago, all creatures could look up and see a spectacular starry night sky. But now, eight out of ten children will never see the Milky Way from where they live.
Light pollution doesn’t only impact our view of the universe, it also impacts our environment, our individual health, and energy consumption.
The three main components of light pollution include sky glow as well as glare and light trespass, which I will also explain.
Glare is the excessive brightness that causes us visual discomfort. We often illuminate areas in attempt to increase safety. As children, we’re afraid of the dark, so we flip on a night switch because “the night is dark and full of terrors.” And as adults, we do that now on a much grander scale.
A 2015 study published in the Journal of Epidemiology and Community Health looked at statistics where researchers studied lights that were turned on at certain hours, dimmed, or turned off completely, and found that it had no impact on traffic collisions or crime.
I want you to take a very close look at this picture. Mentally note what you see. With properly shielded lights, we can actually see what was there the entire time. Brighter does not mean safer.
The third component of light pollution is light trespass. To understand this, I want you to envision your bedroom. Could you sleep at night with no curtains? Or do you need those blackout shades tucked into every single crevice of that window pane, just in order to get a good night’s sleep?
If so, that is because of light trespass, the shining of light where it’s unneeded, and unintended, and unwanted, from another source originating somewhere other than your own.
Now that we’ve looked at what causes light pollution, let’s take a look at where light pollution is.
Here is a global map with light pollution depicted by various colors. Let’s zoom in to our local area of impact. This is Rapid City. We are on the front lines of a battle of lights versus dark.
Zooming in closer to South Dakota, I want you to envision that you’re downtown at Main Street Square, you’ve got your blanket, your chair, you’re ready to stargaze.
And then you look up, and you realize you can see relatively very few stars. You cannot even see the Big Dipper. So you pack up all your belongings, you get in the car, you drive to the city limits, where now you’re in the orange zone, where eight out of ten Americans live, and we have a local observatory.
You look up, you still cannot see the Milky Way. You keep on driving, you go deep into the Black Hills National Forest, and then you see it, the sky glow the meadowlark was singing toward. To get to a naturally dark sky, you would have to drive two hours north, to the corner of northwest South Dakota, an area called Slim Buttes, which has a Class 1 dark sky, a naturally lit sky, where the stars from the Milky Way shine so bright it will cast a shadow of you on the ground.
Rapid City is a Class 9 sky, the brightest depicted on the map, where light pollution is 100 up to 200 times brighter than our natural darkness. You cannot make out the North Star.
But the thing is Rapid City is not alone. Light pollution plagues every modern city and town. The good news, however, is that light pollution could possibly be the simplest problem to solve and could literally be done overnight, simply with the flip of a switch.
So if at any point in this presentation you decide that it’s important to protect our dark skies, I ask you to turn off your light in front of you, simply by twisting it off.
Now just like in real life, here’s a hint: You can ask your neighbor to shut off their light as well if their light is trespassing into your area and inhibiting your view of a TEDx presentation.
Even if we all turn out our lights, more is needed to be done. One hundred years ago, this is the view from Skyline Drive you would have seen. Today, this is a picture taken this year during the Rapid City Dark Earth Hour. Which one do you prefer?
So what are we going to do if we all turn out our lights and it’s still bright? We need to protect nocturnal habitats, stargazing opportunities, and our nocturnal plants and animals.
Now, bats. There’s an idea. I know what we can do. Let’s call Batman! He’ll know what to do! Send the bat signal! Right? Oh, wait, maybe he didn’t get the memo either. So let’s shift our focus to nocturnal plants.
In the Black Hills, there’s a moonflower that blooms only in dark nights.
Earth evolved with bright days and dark nights.
Another example of nocturnal life that needs darkness is the owl. Owls see five times brighter than we do as humans because in their eyes they have light detecting rods that are numbered at one million rods per square millimeter. Just because we can see with lights at night doesn’t mean other creatures can.
But even though we can see with artificial light at night, doesn’t mean that it’s healthy for us. The American Medical Association states “all creatures need darkness to survive.”
As light travels through our eye, it goes to a tract of a nucleus cluster of thousands of cells that send messages to our glands. Those glands secrete a naturally occurring hormone called melatonin.
The great thing about melatonin is it has great antioxidant qualities that rid our brain and body of free radicals that cause damage to our brain and body.
The Journal of Epidemiology Research shows that exposure to artificial light at night has been linked to an increase in Alzheimer’s, breast cancer, obesity, and depression.
Let’s take a look now at what our future holds. The map I showed you of South Dakota is a one from 1997, when in all reality, tonight’s dark skies is much more closely, really, like the map of 2025. In only eight years, it’s estimated that just eight dark sky places will remain in the United States.
So if we can’t call Batman, what are we supposed to do? OK, I have another idea, hold on with me, this is a little bit better. Let’s join the Dark Side. Maybe Kylo Ren and Darth Vader had it right all along. But all joking aside, there really is something about the color spectrum. This is a color Kelvin chart, rating color by its temperature.
The International Dark Sky Association rates colors below 3,000 Kelvins as dark sky friendly because it doesn’t impair night vision.
What else can we do? Address our fixtures, because dark skies doesn’t have to mean dark ground. We can point lights down, where the light is intended. The International Dark Sky Association estimates that all of the outdoor lighting wastes 30% of light that goes outward and upward where it is not needed or intended, wasting money and creating more carbon emissions.
In addition, this is a sample of a front porch light that could be converted into a full cutoff fixture, reducing glare, sky glow, and light trespass. Streetlights that point light outward and upward could be retrofitted to point the light downward. Paris, the City of Light, took solving light pollution to a whole new level. They enacted a lights-out curfew of 1 AM or one hour past the last employee’s departure time.
I challenge you to find your reason for #LightsOut. I wish you all a very dark night.
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