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International Dark Sky Week – April 21-27, 2025

International Dark Sky Week is marked every year during the week of the new moon in April and this year it will be observed from April 21 to 27. It is a week to switch off the lights in the evening and marvel at the infinite grandeur of the night sky. The universe is a visual extravaganza for the eyes, and we can observe its beauty during the night. However, due to light pollution, we are not able to observe more than some stars. In 2003, high school student Jennifer Barlow of Midlothian, Virginia, felt disturbed that she could not observe the beauty of the night sky and kick-started the week.

History of International Dark Sky Week

Have you ever gone outside on a dark night to watch the stars or moon? Have you ever attempted to make shapes from the alignment of stars? Then you will have noticed that we can only see so many stars in the night sky. But we all know there are trillions of stars out there. There are billions in our Milky Way alone. So why is it that we are only able to observe a few thousand of them during the night? Light pollution is the major culprit behind this.

A few decades ago, people were able to watch a hazy band of white light, some 30° wide, arching the night sky. It is the part of the Milky Way galaxy visible from the Earth in the night sky. There are billions of stars in our galaxy alone. But most of them are so far away that our eyes are not able to grasp them individually, and we see them as white haze arching the sky. The Milky Way is not visible to most of us. People living in a city can only see an orange sky at night. This is due to the light from all the human-made sources scattering through the air. The fog of thick air made from the smoke of vehicles and industries only makes it worse for stargazers. Even with all this pollution, the amazing view of the sky is still possible to be seen from remote corners of the earth, where light pollution is not that prominent.

Jennifer Barlow started the week in 2003 to make it possible for everyone to enjoy the beauty of the night sky. She realized that just by switching off our lights, we can decrease light pollution to get a much better view of the starlit sky. The International Dark-Sky Association, the American Astronomical Society, the Astronomical League, and Sky & Telescope, understood the importance of her action and went on to endorse the day. It grew in popularity, and now it is an international week celebrated on the darkest week of April during the week of the new moon.

International Dark Sky Week timeline

The Great September Comet

The Great September Comet, brighter than the moon, passes near the sun.

The Earth Hour

Organizers of International Dark Sky Week coincide the week with Earth Hour.

The International Year of Astronomy

The United States Dark Sky Week becomes the International Dark Sky Week

The International Dark Sky City

Flagstaff, Arizona in the U.S. emerges as the first international dark sky city.

International Dark Sky Week FAQs

Should you have outdoor lights?

Outdoor lights are good for security. But they also cause light pollution and affect the plant and animal life around them.

Is the Milky Way visible from Earth?

Yes, it is. We can see the Milky Way if there is no light pollution and there is a dark sky.

Why do we need to look at the stars?

Because it helps us to become well acquainted with what is out there besides life as we know it on earth.

How to Observe International Dark Sky Week

  1. Buy a telescope

    A telescope is an essential tool for everyone who loves to watch the night sky. Buy one and let your friends also enjoy the view.

  2. Switch off the lights

    Light pollution is a major headache for everyone trying to watch the beautiful sky. Switch off unwanted lights during the night and decrease the pollution as much as you can. Make sure no lights are on during International Dark Sky Week.

  3. Use lights that won't cause pollution

    Lights can not only harm the night sky view. There are migratory birds that depend on the position of stars to travel. Light pollution can disrupt their travel routes as well.

5 Intriguing Facts About Artificial Lights

  1. Artificial lights and plants

    Artificial light during the night can affect a plant’s response to the changing of seasons.

  2. Artificial lights and sea turtles

    Artificial light is affecting the nesting and breeding of female sea turtles that lay eggs on beaches.

  3. Artificial lights and birds

    Around 10,000 migratory birds collide with skyscrapers and high-rises each year due to high-intensity lights.

  4. Artificial lights and the Milky Way

    The Milky Way is now a rare sight for more than one-third of people on Earth because of light pollution.

  5. National wastage of energy

    According to the U.S. Department of Energy, 0.5 kilowatt-hours of energy per house, per night, is wasted by bad lighting.

Why International Dark Sky Week is Important

  1. We love sky watching

    We love watching the sky, the moon, and the stars. So naturally, we love a day dedicated to watching the night sky without pollution.

  2. It can improve so many lives

    Light pollution affects the quality of life of many living beings. We love it when we can shut down these lights and work toward a better future for other animals.

  3. It is good for the environment

    Light pollution can even affect plants’ health. By having a week to shut down the lights and by raising awareness, we are essentially helping nature heal a bit.

International Dark Sky Week dates

2022April 17Sunday
2023April 15Saturday
2024April 2Tuesday
2025April 21Monday
2026April 13Monday

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