Imagine our world as a giant clock that tells everything alive when to wake up, when to eat, and when to sleep. For billions of years, this clock has used the sun for day and darkness for night. But now, something new is messing with this clock: too much light at night!

The amount of light at night is growing really fast all over the world. From 2012 to 2016, the amount of outdoor light increased by about 2% each year. Over an even longer time, from 1992 to 2017, the amount of light pollution grew by almost 50%! That's much faster than how much the world's population grew.

Now, over 80 out of every 100 people in the world live under skies affected by skyglow. In places like the U.S. and Europe, almost everyone lives under skies where it's hard to see the stars because of all the extra light.

We're talking about Artificial Light at Night (ALAN). It's not just streetlights; it's all the bright lights from buildings, signs, security lamps, and even car headlights that stay on after the sun goes down. Think of it like a new kind of pollution, but instead of dirty air or water, it's too much light!

There are different ways this extra light shows up:

Skyglow: This is when the night sky over cities looks hazy and bright, so you can't see many stars. It's like a big glowing bubble.
Glare: This is when a light is so bright it hurts your eyes or makes it hard to see clearly.
Light Trespass: This happens when someone's outdoor light shines into your house, even when you don't want it to. It can make it hard to sleep.
Too Much Light: Sometimes, people use way more light than they need, like having super bright lights in a small space.
Light Clutter: Imagine a bunch of bright, flashing lights all close together on a road. It can be confusing and even dangerous for drivers.

All these lights are changing the natural night, and it's a big deal! It's like we're changing the planet's bedtime story, which animals and plants have known for a very, very long time.

Where does all this light come from? Mostly from our cities growing bigger and bigger. We use lots of lights on streets, in parking lots, for sports, in greenhouses, and around our homes. Sometimes, the lights aren't designed very well, like lights that shine up into the sky instead of just down where we need them.

We use a lot of energy to power all these lights, and sometimes that energy is wasted. New, super-efficient LED lights were supposed to help save energy. But guess what? Because they're cheaper to run, we've started using even more lights, and making them brighter! This is like buying a super-fast car that uses less gas, but then you drive it everywhere, all the time, so you end up using more gas than before.

As countries get richer, they tend to use more and more light. It's like people think that more light means more progress. And those new, energy-saving LED lights? While they're great for saving energy, many of them are very blue and bright, and this blue light actually makes skyglow worse, even if the total amount of light isn't much more.

Most of the new light is popping up in places like South America, Africa, and Asia. Some countries, like Italy and the U.S., have managed to keep their light levels steady or even reduce them a little. Also, if there are lots of clouds, they can make skyglow seem even brighter because the light bounces off them.

How Light Harms Animals

Imagine trying to go to sleep with a flashlight shining in your eyes all night, every night. That's kind of what it's like for animals when there's too much light at night!

Many animals need natural dark and light cycles for important things like finding a mate, hunting for food, sleeping, and even moving from one place to another. Too much light at night messes up these natural routines.

Just a little bit of extra light can make animals like fish stop making a special "sleep hormone" called melatonin. This messes up their normal daily rhythms, how they have babies, and how they behave. Some fish might not even have babies if there's too much light.

Plants also need dark! Too much light at night can make trees grow leaves too early in the spring and keep their leaves green too long in the fall, which isn't good for them.

Eating and Being Eaten

Light at night also changes how predators (animals that hunt) and prey (animals that are hunted) interact. Small prey animals, like little fish or bugs, become much easier for bigger animals to see when it's bright. It's like they have nowhere to hide. Some predators, like foxes, might even be drawn to lit areas because it's easier to find food there. This makes it unfair for the prey.

Breaking Up Homes

Imagine if a bright wall of light appeared in the middle of a forest, and began shining in your eyes. That's what too much light can do to animal homes. It breaks up their habitats and makes it hard for them to move around.

Bugs: Flying insects are often attracted to lights. They fly around them until they get tired or even get burned. This means fewer bugs are out doing their natural jobs, like helping plants grow, and they become easy snacks for predators gathered around the lights.

Bats: Bats hate light! They fly away from it. So, if there are lots of lights, bats can't get to their hunting grounds or places to rest. It's like a bright fence they can't cross.

Deer and Snakes: Deer often avoid crossing roads that are lit up, which limits where they can go. Young snakes also run away from light to hide from animals that want to eat them.

Birds: Get confused, crash into things, get lost during migration, have trouble finding mates and laying eggs

Ocean Animals: Sea turtles can't find nesting spots, baby turtles get lost, fish can't lay eggs, food chains get messed up.

When one animal is affected, it can cause problems for many other animals. For example, if little ocean creatures called zooplankton are confused by light and stay deep in the water, the fish that eat them won't have enough food. And then the tiny plants that zooplankton usually eat will grow too much.

Even more surprisingly, new studies show that the problems caused by light pollution can even be passed down from parents to their babies! This means that the harm from too much light can last for a very long time.

Saving the Dark: Dark Sky Places!

To fight against light pollution, there are groups like the International Dark-Sky Association (IDA). They started in 1988, and their main goal is to bring back natural darkness and protect animals and people from too much light.

The IDA does this in a few ways:

They teach people about light pollution.
They help places get special "dark sky" certifications.
They suggest good lighting products that don't cause a lot of pollution.

One of their coolest programs is the International Dark Sky Places (IDSP) program. This program gives special awards to communities, parks, and other areas around the world that promise to keep their skies dark by using smart lighting and teaching people about it. Since 2001, over 200 places in 22 countries have become Dark Sky Places!

International Dark Sky Park: A park (public or private) with amazing starry nights, where they teach people about the dark sky.

International Dark Sky Sanctuary: The most faraway and darkest places in the world, often very special and needing protection.

International Dark Sky Reserve: A dark "middle" area surrounded by a town or city that has rules to keep the middle part dark.

Urban Night Sky Place: A place in a city that still tries to give people a good view of the night sky, even with city lights around.

International Dark Sky Community: A town or city that has good rules for outdoor lights and teaches its residents about dark skies.

DarkSky Approved Lodging: Hotels or places to stay overnight that have great starry nights and use dark-sky friendly lighting.

To become a Dark Sky Place, they have to use good outdoor lighting, have rules to cut down on light pollution, and keep working to protect the dark. They also have to let people visit at night to enjoy the stars.

We can all help reduce light pollution! It's like turning down the volume when the music is too loud.

Smart Lighting Rules

The best way to light up our world at night is to follow these five rules:

Useful: Only use light when you really need it.Turn off lights that aren't needed.

Targeted: Point the light exactly where you want it, not up into the sky.Use lights that have a "shield" so the light only shines down.

Low Levels: Don't use lights that are brighter than you need.Use light bulbs with lower power, and remember that bright surfaces can reflect light.

Controlled: Only use light when and for as long as you need it.Use timers, motion sensors, or dimmers so lights aren't on all night.

Warmer Color: Use lights that have a warm, yellowy glow, not bright blue-white light.Choose LED lights that say "3000K" or less.

It's not just about how bright a light is, but also its color. Those bright, blue-white LED lights can actually make skyglow worse. So, choosing warmer-colored lights is very important!

Using smart lights with motion sensors and timers is a great idea. This means lights only turn on when someone is there, and they turn off when no one is around.

What You Can Do

Even small actions add up!

Turn off lights you don't need.
Use shielded lights outside your home.
Choose lower power light bulbs.
Install timers and motion sensors for your outdoor lights.
Pick warm-colored LED lights for your house.
Try to keep light from inside your home from spilling outside.
Talk to your family and friends about light pollution.
Support groups like the IDA that are working to save the dark.

How You Can Protect Wildlife From Artificial Light at Night