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It`s Okay To Be Smart, Why the Stars Are Disappearing

Why the Stars Are Disappearing

Hey smart people, Joe here. For pretty much all of human history, this

has meant the end of our day. Sure, we harnessed fire, and some artificial light, but we are

not natural creatures of the night. But now we're able to be part of the night like

never before in human history. All thanks to the invention of the light bulb. Try to

imagine modern life without artificial lighting. It just isn't possible.

But… all of that light comes with a dark side.

On January 17, 1994, a powerful earthquake struck the Los Angeles area and caused a massive

blackout. Nearby Griffith Observatory started receiving calls from residents asking about

the strange sky they were seeing. What those people saw was… the Milky Way. With no artificial

light, the sight of the night sky was so unfamiliar; they didn't know what they were looking

at.

Today, more than 80% of the world and more than 99% of the U.S. and Europe live under

light-polluted skies. A third of humans on Earth can never see the Milky Way. And places

like Singapore are so polluted by light that people's eyes never fully adjust to the

dark.

While researching light pollution the past couple months, I learned a new word: Scotopic.

It's the type of vision we use in very low light levels. Whereas our normal, bright-light

photopic vision is produced by three types of color-sensitive cone cells, dark scotopic

vision is produced by the eye's rod cells, which are great at sensing something's brightness,

but can't discriminate different colors.

Anyway, the reason I'd never heard of scotopic vision before is that most of us don't experience

it much. Night has been taken over by light.

It still gets dark at night. Unless you're near the north or south pole in summer, the

sun still goes down every day. But it's not real darkness.

So, then… what is real darkness? I've been struggling for a way to explain it, because

how do you describe the absence of something? Well, I figure you don't try describe what's

missing, you look at what was hiding there all along.

Now I'm not the world's best astro-photographer or anything, but I've been lucky enough

to take pictures in some of the darkest places left in North America: Big Bend National Park.

The Grand Canyon in Arizona. And here at McDonald Observatory in West Texas.

And while I was out there, I met someone who's trying to save darkness.

I'm Bill Wren, special assistant to the superintendent at the University of Texas

McDonald Observatory

And my job is to keep the skies dark for ongoing astronomical research here at the observatory

“The places where you can go to see a naturally starry sky are vanishing, they're shrinking,

they're becoming fewer and farther between. You have to travel great distances from cities

in order to see a naturally dark sky.”

An amateur astronomer named John Bortle came up with a scale to measure the night sky brightness

based on how many objects are visible

In perfectly dark skies, Bortle scale 1, there's between maybe four and five thousand stars

bright enough to be visible to the naked eye from any spot on Earth. I used some software

called Stellarium to give you an idea of what that looks like. It's actually hard to even

pick out constellations. But most Americans live at Bortle scale 5

or higher, which means they aren't seeing 98% of the stars in the sky.

We see people all the time at our public star parties who have never seen the Milky Way and they're just awe inspired

Now the beauty of the night sky is one thing, but there's a bunch of other reasons we

should protect dark skies. For astronomy I guess it's pretty straightforward.

We've gotta be able to see the stars in the sky to do astronomical research. And

there's other questions about exposure to too much artificial light at night not being

so good for your health. In fact, it affects the biorhythms of all living creatures on

the planet. There's a cost efficiency question, in terms

of how much light we're wasting into the night sky, by poorly designed and poorly installed

light fixtures. On the order of billions of dollars of electricity are wasted into

the night sky in the US alone. “This is about dark skies, not dark ground… no reason

to shine it wasted above the horizon and into the sky”

We've lit up streets, parking lots, buildings and every populated space we can mostly to

make the night more safe.

So when you hear people saying we should use less light at night, your first reaction might

be “That'll make us less safe!” right? But as hard as it is to believe, no study

has ever shown that more light leads to less crime. Most property crime occurs during the

day. Even the worst crimes, like sexual assaults, that we normally associate with bad guys in

dark alleys, are far more likely to occur indoors at the hands of someone the victim

knows. And bad lighting can actually make bad guys harder to see.

More light at night can actually make us less healthy too. For hundreds of thousands of

years, humans evolved with the rhythms of night and day. Like other creatures, we have

a natural biological clock, our circadian rhythm, that's controlled by the cycle of

light and dark.

In darkness, our bodies produce a hormone called “melatonin” that helps us sleep,

boosts our immune system, and helps a bunch of organs function. Light at night, especially

blue light, can mess with that. And LED lighting, while it saves energy and money, often peaks

in the blue part of the spectrum, making this problem worse. Night work has even been classified

by some medical groups as a risk factor for many cancers.

So consider putting this away at night, and if you do have to look at a screen, use night

mode or an app to reduce the blue light given off by your screen.

The more that scientists study this, the more it looks like we've underestimated the negative

effects of light, that it is truly a “pollutant” in its effect on humans and on wildlife.

There are countless wild species being negatively affected by our light pollution, whether they

are nocturnal (active at night) or crepuscular (active during twilight). Everything from

fireflies that can't find mates to dung beetles who can no longer navigate by the

Milky Way and from baby sea turtles walking into roads instead of the sea to millions

of birds killed every year in collisions with buildings.

Every September 11th in lower Manhattan, 88 7,000 watt searchlights shine into the night

sky as a “Tribute in Light”

It's one of the brightest light installations ever constructed, and even though it's only

on for one night a year, over a million birds have been lured in by these lights, disrupting

their annual migrations, and many have died after colliding with buildings. That is, until

scientists started working with the people running the Tribute in Light to keep that

from happening. Now, if more than a thousand birds are counted in the lights, they're

turned off for twenty minutes. You can watch on this radar image as the lights alternate

between on and off, and huge clouds of disoriented birds go safely on their way.

I think this is an inspiring example of how humans and nature can co-exist in a world

of artificial light. Because stopping light pollution doesn't mean getting rid of all

artificial light. That's crazy. Light pollution is not “all light at night”.

It's “light out of place”. The reason satellite views of the dark side of our planet

look like this, is because we're wasting that light by shining it up into space, instead

of using it to light our way down here.

Light pollution is unique because it's the only kind of pollution we can clean up instantly.

Polluted water and air take decades to cleanse them of human impacts, but cleaning up the

night skies is easy. Just turn out the light.

“Definitely a sense of awe to stand and look up at the milky way and see the stars

splashed across the sky, and realize the 3-dimensional, the depth that you can see when you look into

the plane of the galaxy. Just the scale that surrounds us, the dimensions of the universe

on the grand scale is just awe-inspiring.” “I do believe that seeing a naturally dark

sky provides one with a sense of context, that sense of living in a very large space,

and being part of something on a very grand scale, and it does give one a sense, just

a thrill. Sometimes a chill up the spine. To realize that we came out of this universe

as opposed to being put into it… but we won't get too philosophical here.”

Well, Bill may not want to get philosophical, but I think that beautifully sums up why dark

is just as important to our lives as the light.

Now, many of the beautiful shots of the night sky you've seen in this video are time lapses,

made with long-exposure photos that show you a bit more than you can see with your own

eyes. But I wanted to give you some idea of what you really can see with the naked eye

under those dark skies so few of us get to experience.

and while it's not the crispiest shot in the world, I hope it captures a feeling

for you…

I've been trying to think of a way to describe what it is like to see this. And it is really

hard to come up with the words. It is something that you just have to see. And it's something

that I hope people still get the chance to see. It makes you feel small and big at the

same time. It makes you feel far away and connected at the same time. And all I know

for sure is… it's good for ya.

Stay curious.

Hey. You want more space? PBS is bringing you the universe with SUMMER OF SPACE, which

includes six incredible new science and history shows streaming on PBS.org and the PBS Video

app, along with lots of space-y episodes from PBS Digital Studios creators

Follow me over to AMERICA FROM SCRATCH to check out their Summer of Space episode on

WHETHER OR NOT WE SHOULD COLONIZE MARS.

Big thank you to McDonald Observatory for having me out to experience their dark skies.

McDonald Observatory and the International Dark Sky Association have some fantastic resources

on which types of lighting to minimize wasted light, and maximize useful light without unintended

effects on wildlife and plants. We'll put links to that and a lot more down in the description.

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Why the Stars Are Disappearing Warum die Sterne verschwinden Pourquoi les étoiles disparaissent-elles ? Perché le stelle stanno scomparendo 별이 사라지는 이유 Waarom de sterren verdwijnen Porque é que as estrelas estão a desaparecer Почему исчезают звезды Чому зникають зірки 為什麼星星會消失

Hey smart people, Joe here. For pretty much all of human history, this Гей, розумники, це Джо. Протягом майже всієї історії людства, це

has meant the end of our day. Sure, we harnessed fire, and some artificial light, but we are |||||||||ovládli jsme|||||||| |||||||||gezähmt|||||||| |||||||||controlled and used|||||||| betekende het einde van onze dag. Natuurlijk hebben we vuur gebruikt en wat kunstlicht, maar dat zijn we wel

not natural creatures of the night. But now we're able to be part of the night like

never before in human history. All thanks to the invention of the light bulb. Try to |||||||||||||light source||

imagine modern life without artificial lighting. It just isn't possible.

But… all of that light comes with a dark side.

On January 17, 1994, a powerful earthquake struck the Los Angeles area and caused a massive ||||seismic event|||||||||

blackout. Nearby Griffith Observatory started receiving calls from residents asking about ||Griffith Park Observatory|astronomical observation center|||||||

the strange sky they were seeing. What those people saw was… the Milky Way. With no artificial ||||||||||||Milky Way||||

light, the sight of the night sky was so unfamiliar; they didn't know what they were looking

at.

Today, more than 80% of the world and more than 99% of the U.S. and Europe live under

light-polluted skies. A third of humans on Earth can never see the Milky Way. And places |contaminated by light|nighttime skies||||||||||||||

like Singapore are so polluted by light that people's eyes never fully adjust to the ||||||||||||anpassen|| |the city|||||||||||||

dark.

While researching light pollution the past couple months, I learned a new word: Scotopic. ||||||||||||scotopisch|scotopisch |||light contamination||||||||||Low-light vision

It's the type of vision we use in very low light levels. Whereas our normal, bright-light ||||||||||||zatímco||||

photopic vision is produced by three types of color-sensitive cone cells, dark scotopic fotopická||||||||||||| photopisches|||||||||||||dämmerungssehen daylight-adapted||||||||||color-sensitive cells||| fotopisch zicht wordt geproduceerd door drie soorten kleurgevoelige kegelcellen, donkere scotopische

vision is produced by the eye's rod cells, which are great at sensing something's brightness, |||||eye's rod cells|photoreceptor cells||||||||light intensity zicht wordt geproduceerd door de staafcellen van het oog, die goed zijn in het waarnemen van de helderheid van iets, зір виробляється паличковими клітинами ока, які чудово відчувають яскравість предметів,

but can't discriminate different colors. ||rozlišovat|| ||distinguish between||

Anyway, the reason I'd never heard of scotopic vision before is that most of us don't experience |||||||skotopické vidění|||||||||

it much. Night has been taken over by light.

It still gets dark at night. Unless you're near the north or south pole in summer, the

sun still goes down every day. But it's not real darkness.

So, then… what is real darkness? I've been struggling for a way to explain it, because

how do you describe the absence of something? Well, I figure you don't try describe what's

missing, you look at what was hiding there all along. зникнення, ти дивишся на те, що ховалося там увесь цей час.

Now I'm not the world's best astro-photographer or anything, but I've been lucky enough ||||||astronomy photography||||||||

to take pictures in some of the darkest places left in North America: Big Bend National Park. |||||||least lighted|||||||||

The Grand Canyon in Arizona.  And here at McDonald Observatory in West Texas. ||Deep, narrow valley||||||Observatory in Texas||||

And while I was out there, I met someone who's trying to save darkness. І поки я був там, я зустрів того, хто намагається врятувати темряву.

I'm Bill Wren, special assistant to the superintendent at the University of Texas |||||||Schulleiter||||| ||Bill Wren||aide|||chief administrator|||||

McDonald Observatory

And my job is to keep the skies dark for ongoing astronomical research here at the observatory ||||||||||probíhající|||||| ||||||||||||||||Observatorium

“The places where you can go to see a naturally starry sky are vanishing, they're shrinking, ||||||||||hvězdnatá|||||zmenšují se ||||||||||sternenklar|||||schrumpfen ||||||||||filled with stars||||| "Місця, куди можна піти, щоб побачити природне зоряне небо, зникають, вони скорочуються,

they're becoming fewer and farther between. You have to travel great distances from cities їх стає все менше і менше. Доводиться долати великі відстані від міст

in order to see a naturally dark sky.”

An amateur astronomer named John Bortle came up with a scale to measure the night sky brightness ||||||||||||||||jasnosti |non-professional||||Astronomer Bortle||||||||||| Астроном-любитель на ім'я Джон Бортл придумав шкалу для вимірювання яскравості нічного неба

based on how many objects are visible

In perfectly dark skies, Bortle scale 1, there's between maybe four and five thousand stars

bright enough to be visible to the naked eye from any spot on Earth. I used some software

called Stellarium to give you an idea of what that looks like. It's actually hard to even |Astronomy software||||||||||||||| genaamd Stellarium om je een idee te geven van hoe dat eruit ziet. Het is eigenlijk moeilijk om zelfs

pick out constellations.  But most Americans live at Bortle scale 5 ||star patterns|||||||

or higher, which means they aren't seeing 98% of the stars in the sky.

We see people all the time at our public star parties who have never seen the Milky Way and they're just awe inspired |||||||||||||||||||||úžasní|ohromeně |||||||||||||||||||||Ehrfurcht|

Now the beauty of the night sky is one thing, but there's a bunch of other reasons we

should protect dark skies. For astronomy I guess it's pretty straightforward. ||||||||||jednoduché ||||||||||einfach |||||stargazing|||||

We've gotta be able to see the stars in the sky to do astronomical research. And |||||||||||||astronomický výzkum||

there's other questions about exposure to too much artificial light at night not being ||||expozice|||||||||

so good for your health. In fact, it affects the biorhythms of all living creatures on ||||||||||biorhythmus||||| ||||||||||biological cycles|||||

the planet. There's a cost efficiency question, in terms

of how much light we're wasting into the night sky, by poorly designed and poorly installed

light fixtures. On the order of billions of dollars of electricity are wasted into |svítidla|||||||||||| |Leuchten|||||||||||| |lighting equipment|||||massive amounts||||energy consumption||| verlichtingsarmaturen. In de orde van grootte van miljarden dollars aan elektriciteit wordt verspild aan

the night sky in the US alone. “This is about dark skies, not dark ground… no reason

to shine it wasted above the horizon and into the sky”

We've lit up streets, parking lots, buildings and every populated space we can mostly to

make the night more safe.

So when you hear people saying we should use less light at night, your first reaction might

be “That'll make us less safe!” right? But as hard as it is to believe, no study

has ever shown that more light leads to less crime. Most property crime occurs during the |||||||||||majetková||||

day. Even the worst crimes, like sexual assaults, that we normally associate with bad guys in |||||||napadení|||||||| |||||||Übergriffe||||||||

dark alleys, are far more likely to occur indoors at the hands of someone the victim |temné uličky|||||||||||||| |narrow passageways|||||||inside buildings|||||||

knows. And bad lighting can actually make bad guys harder to see.

More light at night can actually make us less healthy too. For hundreds of thousands of

years, humans evolved with the rhythms of night and day. Like other creatures, we have ||evolutioniert||||||||||||

a natural biological clock, our circadian rhythm, that's controlled by the cycle of |||||cirkadiánní|||||||

light and dark.

In darkness, our bodies produce a hormone called “melatonin” that helps us sleep, ||||||hormon||melatonin|||| ||||||chemical messenger||sleep-regulating hormone||||

boosts our immune system, and helps a bunch of organs function. Light at night, especially posiluje|||||||||||||| |||||||||body parts|||||

blue light, can mess with that. And LED lighting, while it saves energy and money, often peaks ||||||||||||||||dosahuje vrcholu

in the blue part of the spectrum, making this problem worse. Night work has even been classified

by some medical groups as a risk factor for many cancers. ||||||||||rakoviny ||||||||||types of cancer

So consider putting this away at night, and if you do have to look at a screen, use night

mode or an app to reduce the blue light given off by your screen.

The more that scientists study this, the more it looks like we've underestimated the negative ||||||||||||podcenili|| ||||||||||||undervalued||

effects of light, that it is truly a “pollutant” in its effect on humans and on wildlife. ||||||||znečišťující látka||||||||životní prostředí ||||||||harmful substance||||||||animals and plants

There are countless wild species being negatively affected by our light pollution, whether they

are nocturnal (active at night) or crepuscular (active during twilight). Everything from |noční|||||šera||||| ||||||dämmerungsaktiv||||| ||||||active during twilight|||||

fireflies that can't find mates to dung beetles who can no longer navigate by the svítilny||||partnery||hnojiště|hnědé brouky||||||| fireflies struggling to||||partners for reproduction||animal droppings|insects|||||||

Milky Way and from baby sea turtles walking into roads instead of the sea to millions ||||||želvy|||||||||

of birds killed every year in collisions with buildings. ||||||crashes into structures||

Every September 11th in lower Manhattan, 88 7,000 watt searchlights shine into the night |||||Manhattan||reflektory|||| |||||||Suchscheinwerfer|||| |||||New York City||powerful light beams||||

sky as a “Tribute in Light”

It's one of the brightest light installations ever constructed, and even though it's only ||||most luminous||artistic displays|||||||

on for one night a year, over a million birds have been lured in by these lights, disrupting ||||||||||||sváděny|||||rušící ||||||||||||attracted|||||causing disturbance to

their annual migrations, and many have died after colliding with buildings. That is, until ||seasonal movements|||||following|crashing into|||||

scientists started working with the people running the Tribute in Light to keep that

from happening. Now, if more than a thousand birds are counted in the lights, they're

turned off for twenty minutes. You can watch on this radar image as the lights alternate

between on and off, and huge clouds of disoriented birds go safely on their way. ||||||||confused and lost||||||

I think this is an inspiring example of how humans and nature can co-exist in a world

of artificial light. Because stopping light pollution doesn't mean getting rid of all

artificial light. That's crazy. Light pollution is not “all light at night”.

It's “light out of place”. The reason satellite views of the dark side of our planet

look like this, is because we're wasting that light by shining it up into space, instead

of using it to light our way down here.

Light pollution is unique because it's the only kind of pollution we can clean up instantly. |||||||||||||||okamžitě

Polluted water and air take decades to cleanse them of human impacts, but cleaning up the |||||desetiletí||očistit|||||||| |||||||purify or restore||||||||

night skies is easy. Just turn out the light.

“Definitely a sense of awe to stand and look up at the milky way and see the stars “Absoluut een gevoel van ontzag om te staan en naar de melkweg te kijken en de sterren te zien

splashed across the sky, and realize the 3-dimensional, the depth that you can see when you look into spread across sky|||||||three-dimensional||||||||||

the plane of the galaxy. Just the scale that surrounds us, the dimensions of the universe ||||Milky Way|||||encompasses||||||

on the grand scale is just awe-inspiring.” “I do believe that seeing a naturally dark ||||||úžasné|||||||||

sky provides one with a sense of context, that sense of living in a very large space,

and being part of something on a very grand scale, and it does give one a sense, just ||||||||velkolepém|velkém měřítku||||||||

a thrill. Sometimes a chill up the spine. To realize that we came out of this universe ||||Exciting shiver|||||||||||| een sensatie. Soms een koude rilling over de rug. Om te beseffen dat we uit dit universum zijn gekomen

as opposed to being put into it… but we won't get too philosophical here.”

Well, Bill may not want to get philosophical, but I think that beautifully sums up why dark

is just as important to our lives as the light.

Now, many of the beautiful shots of the night sky you've seen in this video are time lapses, |||||||||||||||||časosběrné snímky |||||||||||||||||time intervals captured

made with long-exposure photos that show you a bit more than you can see with your own

eyes. But I wanted to give you some idea of what you really can see with the naked eye

under those dark skies so few of us get to experience.

and while it's not the crispiest shot in the world, I hope it captures a feeling |||||nejkřupavější||||||||přenáší|| |||||most detailed||||||||||

for you…

I've been trying to think of a way to describe what it is like to see this. And it is really

hard to come up with the words. It is something that you just have to see. And it's something

that I hope people still get the chance to see. It makes you feel small and big at the

same time. It makes you feel far away and connected at the same time. And all I know

for sure is… it's good for ya.

Stay curious.

Hey. You want more space? PBS is bringing you the universe with SUMMER OF SPACE, which

includes six incredible new science and history shows streaming on PBS.org and the PBS Video

app, along with lots of space-y episodes from PBS Digital Studios creators ||||||||||||content producers

Follow me over to AMERICA FROM SCRATCH to check out their Summer of Space episode on

WHETHER OR NOT WE SHOULD COLONIZE MARS. |||||settle on|

Big thank you to McDonald Observatory for having me out to experience their dark skies.

McDonald Observatory and the International Dark Sky Association have some fantastic resources

on which types of lighting to minimize wasted light, and maximize useful light without unintended

effects on wildlife and plants. We'll put links to that and a lot more down in the description.