Planetarium facts for kids
A planetarium is a special kind of theater where you can learn about space and the night sky. It's a fun and educational place to explore the universe.
Most planetariums have a huge, dome-shaped screen. This screen acts like a giant window to space! Projectors show realistic images of stars, planets, and other amazing things in the sky. These images can move, just like they do in real space. Planetariums use different kinds of projectors, like "star balls," video systems, or lasers. They can even show you what the sky looked like long ago, or what it will look like in the future. You can also see the sky as if you were standing anywhere on Earth.
Planetariums come in many sizes. Some are huge, like the one in St. Petersburg, Russia, which has a dome 37 meters (about 121 feet) wide! Others are small, portable domes that can be inflated, where you sit on the floor. The largest planetarium in the Western Hemisphere is in New Jersey, USA, with a dome 27 meters (about 88 feet) across. The Birla Planetarium in India can seat 630 people, making it the biggest by seating capacity.
Sometimes, the word "planetarium" can also mean other tools that show the Solar System, like computer programs or mechanical models called orreries. A "planetarian" is a person who works at a planetarium.
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How Planetariums Started
People have been trying to show how the sky works for a very long time!
Early Space Models
Long ago, in ancient Greece, a smart person named Archimedes might have made an early device to show the movements of the Sun, Moon, and planets. Later, a discovery called the Antikythera mechanism proved that such machines existed even in ancient times. These early devices were often called orreries. They were mechanical models that showed how planets moved around the Sun. Many modern planetariums still use projectors to show the Solar System moving on their domes.
In 1229, a ruler named Frederick II of Hohenstaufen had a special tent with holes that looked like stars. Inside, a spinning table made the tent rotate, showing the stars moving.
In the 1700s, some people tried to make bigger versions of these models for public shows. Adam Walker created a huge machine called the Eidouranion. It was 20 feet tall and 27 feet wide! The planets seemed to float in space and move on their own. These shows were more about amazing the crowd than being perfectly accurate.
The oldest planetarium that still works today is in a house in the Netherlands. It was built by Eise Eisinga in his living room. It took him seven years to finish it in 1781!
In the early 1900s, a German museum director named Oskar von Miller wanted to create a better way to show the sky. He worked with the Carl Zeiss company. They built a huge mechanical planetarium that showed planets moving on overhead rails. It was displayed in 1924.
While that was being built, they also worked on a new idea: a projector that could create all the star and planet movements from one central machine. In 1923, the very first Zeiss planetarium projector showed images of the night sky onto a 16-meter (about 52-foot) dome. The first public show was in Munich, Germany, on October 21, 1923.
After World War II
After World War II, the Zeiss company was split into two parts. Both continued to make planetariums. Other companies also started building their own unique projectors. For example, the Korkosz brothers built a large projector that was one of the first to show the planet Uranus.
The "Space Race" in the 1950s and 60s made planetariums very popular. Many high schools in the United States installed them to help students learn about space.
A man named Armand Spitz realized that smaller, cheaper planetariums were needed. His first model, the Spitz A, used a special shape to project stars. Later models, like the A3P, could project over a thousand stars and show the movements of the Sun, Moon, and planets. Hundreds of these were installed in schools and museums.
Japan also started making planetariums in the 1960s. The Japanese Ministry of Education even put small Goto models in every elementary school in Japan!
In the 1970s, the IMAX Dome movie system was created to work on planetarium screens. Today, some planetariums are called "dome theaters" and show all kinds of movies, laser shows, and full-dome videos.
In 1977, the first easy-to-carry portable planetarium was created by Learning Technologies Inc. This meant planetariums could visit schools and community centers.
Computerized Planetariums
In 1983, a company called Evans & Sutherland made the first digital planetarium projector. It used computers to create graphics. This new technology allowed planetariums to show the sky not just from Earth, but from anywhere in space and time! Newer digital projectors can show full-dome videos, meaning they can project any image onto the dome.
How Planetariums Work
The Dome Screen
- Examples of planetarium domes
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The dome of the Vilnius University Planetarium.
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The dome of the Athens Planetarium.
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The Hamburg Planetarium
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The Large Zeiss Planetarium in Berlin, 1987.
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Inside of the Planetarium located in the Science Factory (Vitenfabrikken) in Sandnes, Norway.
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Dome of the Planetarium Science Center of the Bibliotheca Alexandrina
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A small inflatable portable planetarium dome.
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GM-II starfield projector at Priyadarshini Planetarium, Trivandrum, India
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Priyadarshini Planetarium, Trivandrum, India
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Planetarium, Copenhagen, Denmark
Planetarium domes can be from 3 to 35 meters (about 10 to 115 feet) wide. They can hold from 1 to 500 people.
- Portable domes are inflatable and can be set up quickly. These are great for planetariums that travel to schools.
- Permanent domes are built from materials like fiberglass or aluminum. Modern domes are often made from thin aluminum with tiny holes. These holes help with sound, letting speakers project sound through the dome. They also help with air circulation for heating and cooling.
To make the images look real, the dome needs to have good contrast between dark and light. Sometimes, domes are painted a mid-grey color instead of white. This helps make the dark parts of the sky look truly black.
It's important that the seams where the dome pieces join are almost invisible. This makes the projected sky look smooth and continuous.
Most older planetarium domes were flat, matching the horizon. But today, many domes are tilted a bit (5 to 30 degrees). This makes it more comfortable for people to look up at the sky. Tilted domes often have stadium-style seating, like in a movie theater.
Some planetariums even have buttons or joysticks on the seats. This lets the audience interact with the show in real time!
Around the bottom edge of the dome, there are often:
- Models of local buildings or landscapes to make the horizon look real.
- Lights that can create the effect of twilight or city light pollution.
Modern planetariums use LED lights for these effects. LEDs save energy and last a long time.
The world's largest mechanical planetarium is the Kovac Planetarium in Wisconsin, USA. It's 22 feet wide and weighs two tons!
Some new planetariums even have a glass floor. This lets you stand in the middle of the dome and see images projected all around you, even below your feet. It feels like you're floating in outer space!
Traditional Projectors
Older planetariums used a "star ball" projector. This was a hollow ball with a light inside and tiny holes for each star. Brighter stars had small lenses to make them sharp. These star balls could rotate to show the Earth's daily spin and to change the view for different locations on Earth.
These projectors could show fixed stars, the Sun, Moon, and planets. Larger ones could also show comets and nebulae. Extra projectors added things like the Milky Way, coordinate lines, and constellations.
Each planet was projected by a special spotlight. These planet projectors had gears to move them and show the planets' paths.
One challenge with these older projectors was that light levels were low, so your eyes needed time to adjust to the dark. Also, they could only show the sky from Earth. And sometimes, a planet's image might show stars shining through it, which wasn't very realistic.
However, newer optical-mechanical projectors use fiber optics to create a very realistic view of the sky.
Digital Projectors
More and more planetariums now use digital technology. Instead of many separate projectors, a computer creates the entire image. This means less maintenance and more reliability. Some planetariums even use both traditional and digital projectors together!
In a fully digital planetarium, a computer generates the image. Then, projectors (like those using LCD, DLP, or laser technology) shine it onto the dome. Sometimes, one projector with a special fisheye lens covers the whole dome. Other times, several projectors around the dome's edge blend their images together.
Digital systems create images using tiny dots called pixels. The more pixels a system has, the clearer and more realistic the image will be. Modern high-end digital projectors can create images so clear that they look almost real to the human eye.
Laser projectors are becoming very popular because they create bright images with great contrast and a wide range of colors.
What You See at a Planetarium Show
Most planetariums offer shows for the public. These often include topics like "What's in the sky tonight?" or shows about special events like a Christmas star. Many places prefer live shows with a speaker who can answer questions.
Since the 1990s, digital planetariums have made shows even more amazing! They can simulate views from anywhere in space, not just Earth. This means you can "fly" through the universe! This helps people understand that space has depth. You can see that stars in a constellation like Orion are actually very far apart, even though they look close from Earth. This kind of experience can be very educational and exciting.
See also
In Spanish: Planetario para niños
- Antikythera mechanism
- Armillary sphere
- Astrarium
- Astrolabe
- Astronomical clock
- Fulldome video
- List of observatory software
- List of planetariums
- Observatory
- Orrery
- Planetarium projector
- Prague Orloj
- Torquetum
- Star atlas
- Space-themed music
