Online English Listening Practice
Audio file: 2:02 min
Story length: 274 words
Here is the listening file for this lesson.
Why is the sky blue?
Why is the sky blue? That question can be answered with some basic science that helps us understand air and light.
If you look up into the air on a clear day, you might think there’s nothing up there. But that would be wrong. Air contains a great number of things. It’s mostly gas, but there are other things like small pieces of dirt, water drops, and ice. All of these things together are called the atmosphere.
When light comes to earth from the sun, it moves through the atmosphere. When this light hits atmospheric gas, something special occurs. The blue light in the sun’s white light is separated from the other six colors.
Remember, white light contains seven colors which the human eye can see: red, orange, yellow, green, blue, indigo, and violet.
The size of blue light is really small compared to the other colors. Because of its tiny size, it can go inside a piece of gas. For a short moment, that piece of blue light hits the inside part of the gas and then exits. But now it’s moving in a different direction.
Now think about all the gas in the atmosphere. It’s changing the direction of a lot of blue light which is moving left, right and all around.
Eventually, it reaches earth. That’s the blue we observe when we look at the sky.
So, why is the sky blue? Actually, it’s not blue at all.
When we see blue, we’re not looking at the sky. Instead, we are looking at blue light which has collided with billions of bits of gas and traveled down to the earth’s surface.
Here’s a gap fill exercise. Download the sky blue printable worksheet (pdf file). Listen to the story and fill in the blanks.
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