RCUSpace Library · Ages 8–12
What is the universe?
A journey to discover the enormous home of stars, planets, and galaxies.
Let's begin
Have you ever looked up at the sky and wondered, “Where does all this end?”
That is a giant question. Above us is a great adventure: the universe. It is everything that exists: space, time, matter, and energy. Yes, that includes stars, planets, clouds of gas, Earth, and you.
An amazingly big home
Imagine your bedroom is planet Earth. Your house would be the solar system: the neighborhood where the Sun and the planets that travel around it live. Then, your city would be a galaxy. A galaxy is a huge family of stars, planets, gas, and dust held together by gravity. Gravity is the force that pulls objects toward one another.
Our galaxy is called the Milky Way. The Sun, our star, lives in it. The Sun looks big because we are close to it. The stars we see at night are suns too, but they are so far away that they look like tiny bright dots.
And the Milky Way is not alone. There are many other galaxies. Some look like spirals, like a whirlpool; others look like a soft ball or a patch of light. The distances between galaxies are so enormous that a spacecraft would need much longer than a human lifetime to cross them.
Essential ideas
Pieces of the cosmic puzzle
Stars
They are huge, hot balls of gas that make light. The Sun is our star.
Planets
They do not make their own light. They travel around a star, like Earth around the Sun.
Galaxies
They are giant groups of stars and other materials found in space.
Examples you can picture
Think of a beach. Each grain of sand could be a star. Now imagine not one beach, but many whole beaches: that is how plentiful the stars in a galaxy can be. But remember, the universe is not a packed box. Most of it is empty space.
You can also think of light as a speedy messenger. Light from the Sun takes about eight minutes to reach us. When you look at a faraway star, you see its light after a long journey. Looking at the sky is like looking at messages sent from the past.
Did you know?
Four little surprises from space
Sunlight takes about 8 minutes to reach Earth.
A teaspoon of material from a neutron star would weigh an incredible amount, but these strange objects are very far away.
The Milky Way, our galaxy, has hundreds of billions of stars.
The stars you see at night can be so far away that their light travelled for years before reaching your eyes.
Glossary
Words for your space backpack
- Universe
- Everything that exists: space, time, matter, and energy.
- Galaxy
- A huge group of stars, gas, and dust held together by gravity.
- Gravity
- The force that attracts objects toward one another.
- Orbit
- The path an object follows as it travels around another object.
- Light
- Energy that travels and lets us see.
What we learned
The universe is our great home
- It includes everything that exists, from a speck of dust to a galaxy.
- Earth lives in the solar system, inside the Milky Way.
- Stars, planets, and galaxies are separated by huge distances.
- Curiosity helps us keep discovering this amazing place.
Actividad · Easy
Challenge: universe explorers
Choose one answer for each question. You will get a clue right away, and finish in under five minutes.
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