What Is Light?

Did you know the sun gives Earth more light than anything else? But what is light? Why does it matter so much?

The sun is very hot. It makes gases that give off light and heat. This is called energy. Light carries energy. Long light waves carry less energy. Short light waves carry more energy.

What do you think of when you hear the word "energy"? Maybe you think of a fast race car. Maybe you think of a strong wind that can knock down a tree.

Guess what? Light can have even more energy than a car or the wind!

Light moves very, very fast. It travels 186,000 miles every second! (A vacuum is empty space with nothing in it — that's how fast light moves there.) Light is so fast, it could zoom around the whole Earth more than seven times in just one second! Nothing people have made can go that fast. Not a jet. Not even a rocket!

Light travels in waves, like the sun's light does. Scientists can measure these waves. Some waves are long. Some are short. Some light waves we can see. Some we cannot see. Whether we can see a light wave depends on how long the wave is.

We see the longest light wave as the color red. We see the shortest light wave as the color violet (a purple color). Short waves carry the most energy.

The sun makes what people call "white light." You might think sunlight has no color. Or maybe you think it looks yellow. But here's a surprise: sunlight is actually made of all the colors of the rainbow mixed together! White light has many different waves inside it — and those waves make up all the colors we can see.

The sun's light has just a little bit more yellow than the other colors. That's why the sun looks yellow in the blue sky. But really, sunlight has every color hiding inside it.

You will learn more about white light and colors later in this book.