Why Ads?

The Big Bang

Prepare to expand your mind. Or to have the entire universe expanded. We are going to learn about the Big Bang theory. The Big Bang theory attempts to answer: How did the universe begin?

An image of how the big bang might have looked.

The Big Bang Imagined

Where did you, the earth, the stars in the sky, and the entire universe come from? Before the Big Bang theory, many people thought that the universe had never changed. They thought it always had its billions of stars and galaxies. Now, many scientists believe that it all started with the Big Bang.  

What is the Big Bang?

The Big Bang theory says the universe has a birthday. 13.8 billion (13,800,000,000) years ago was the beginning of time and the appearance of space.
The universe began as a very heavy, small, and hot ball of matter. It was a point no bigger than the head of a pin with everything squished together. It was very dense. Imagine 1 teaspoonful of space that contains 100 million trillion trillion trillion pounds. It was very hot. Think 10 billion degrees Fahrenheit.

Then, with a huge explosion of energy, the universe expanded! You can think of the universe like a balloon getting blown up bigger and bigger.

An image of a man blowing up a balloon.

The universe is like an expanding balloon.

It expanded close to the size the universe is now. As it expanded, it cooled, and the stars and galaxies formed. Eventually, the earth and all living things (including you) were born. The universe is still expanding now, all from its birthday, 13.8 billion years ago.

An image showing the timeline of the universe's expansion.

Timeline of Universe’s Expansion

In the first second…

The universe expanded super fast, faster than the speed of light. At this point, the universe was a hot soup of particles. These particles were something called matter and antimatter. Then these particles became protons, electrons, and neutrons. In fact, all of the current particles in the entire universe showed up during the Big Bang.

3 minutes later…


Atoms formed out of the protons, electrons, and neutrons. Then, helium and hydrogen showed up. Helium is the gas found in balloons, that makes your voice high.

An image of a galaxy.

A Galaxy

300,000 to 150 million years later…


The helium and hydrogen came together to create stars. Then, the stars came together to create galaxies. 

An image of the earth in space.

Earth viewed from space.

13.8 billion years later…

This is the time we are in now. The universe came to be what it is today. It has billions of stars and galaxies. And on a small, rocky planet amid the gigantic universe, here you are, reading the words on this page.
Remarkably, life is quite a new thing in the history of our universe! Cells developed in the last 4 billion years, and most animals evolved in the last 600 million.

Why do we think this?

It seems impossible; how could we know about the beginning of the universe and events that came before us? Yet, we have found clues.
For example, scientists discovered that stars and galaxies are moving away from us. This hints that the universe is still expanding today. From this, they believe that the universe began as only a single point a long, long time ago.

Other Great Resources

“What is the Big Bang:”

(Video) ‘The Beginning of Everything – The Big Bang:’

(Video) ‘Stephen Hawking – The Big Bang:’

Written by: Laura Fraher