What Is the Universe Made Of?

Ages 3-5 Simple Explanation

You know how you can build all sorts of things with blocks, like towers, houses, and bridges? The whole universe is kind of built from really, really tiny blocks called atoms. Atoms are so small you cannot see them, but they make up everything, including you, your toys, the air, and even the stars!

Everything you can touch is made of atoms. Your hands, your food, water, rocks, trees, and even your pet are all made of these tiny pieces. Atoms stick together in different ways to make different things. It is like using the same blocks to build a million different creations!

The stars in the sky are made of atoms too, mostly a kind called hydrogen. Stars are like giant balls of fire that burn really bright. Our sun is a star, and it gives us light and warmth so that plants can grow and we can play outside.

Scientists are still learning about the universe because there is so much we do not know yet. There are things out there in space that we cannot even see! It is like a giant mystery that scientists are trying to solve, and every day they learn something new.

Ages 6-8 More Detail

Everything you can see, touch, and feel is made of incredibly tiny pieces called atoms. Atoms are so small that millions of them could fit on the tip of a pencil. These tiny building blocks combine in different ways to make everything in the universe: stars, planets, oceans, mountains, animals, and people.

There are about 118 different types of atoms, called elements. You might have heard of some of them, like oxygen (the gas we breathe), hydrogen (the most common element in the universe), gold, iron, and carbon. Different combinations of these elements make different things. Water is made of hydrogen and oxygen. Your body has lots of carbon, oxygen, and hydrogen in it.

Here is something amazing: the atoms inside your body were made inside stars billions of years ago. When old stars exploded, they scattered their atoms across space. Those atoms eventually came together to form our solar system, our planet, and everything on it, including you. You are literally made of star stuff!

But here is the really wild part: all the atoms and everything we can see make up only about 5 percent of the universe. The rest is made of two mysterious things called dark matter and dark energy. Scientists know they exist because of how they affect things we can see, but nobody has figured out exactly what they are yet.

Scientists use giant telescopes, particle smashers, and space probes to learn more about what the universe is made of. Every year, they discover something new. The universe is like the biggest puzzle ever, and scientists have been putting the pieces together for hundreds of years and still have a long way to go.

Ages 9-12 Full Explanation

The universe is made of everything that exists: all matter, energy, space, and time. But when scientists talk about what the universe is actually "made of," the answer is both amazing and mysterious. The stuff we can see and interact with, the stars, planets, people, and everything else, makes up only about 5 percent of the total universe. The other 95 percent is invisible and largely unexplained.

The visible part of the universe is built from atoms. Atoms are the basic building blocks of matter, and there are about 118 known types, called elements. Hydrogen is the simplest and most common element in the universe. Stars, including our sun, are mostly hydrogen and helium. Heavier elements like carbon, oxygen, iron, and gold were forged inside stars and scattered across space when those stars exploded in events called supernovae.

One of the most mind-blowing facts in science is that the atoms in your body were literally made inside ancient stars. The calcium in your bones, the iron in your blood, and the oxygen you breathe all originated in stellar explosions billions of years ago. As the famous astronomer Carl Sagan put it, we are made of "star stuff."

The mysterious 95 percent of the universe is divided into two categories. Dark matter makes up about 27 percent. Scientists cannot see it or detect it directly, but they know it exists because its gravity affects how galaxies move and hold together. Without dark matter, galaxies would fly apart. The remaining 68 percent is dark energy, an even more mysterious force that seems to be causing the universe to expand faster and faster over time.

At the very smallest scale, atoms themselves are made of even tinier particles. Each atom has a nucleus made of protons and neutrons, with electrons orbiting around it. Protons and neutrons are made of even smaller particles called quarks. Scientists use enormous machines called particle accelerators to smash particles together and study what comes out, trying to understand the deepest building blocks of reality.

The study of what the universe is made of is one of the most active areas of science today. New telescopes, space missions, and experiments are constantly pushing the boundaries of what we know. The fact that we understand so much and yet so much remains a mystery is what makes science so exciting. Every generation of scientists uncovers new pieces of the puzzle.