Dr. Fred Ask Dr. Fred


by Dr. Fred Bortz

Safesurf Rated All Ages

For more than twenty years, Dr. Fred Bortz worked as a scientist, researcher, and teacher. Now he spends most of his time writing books and articles for young readers like you.

He enjoys both science and writing for the same reason: HE LOVES QUESTIONS. He writes for people your age because he knows you love questions, too.

To find hot-links to other "Ask Dr. Fred" questions and learn how to send Dr. Fred your favorite question, go to the main "Ask Dr. Fred" page.

This column is copyrighted material. If you plan to use it in the classroom or for other educational or commercial purpose, please click here.

This "Ask Dr. Fred" question comes from a girl named Stefanie, who was then a five-year-old student in Junior Kindergarten at the Embassy School in Faifax, Virginia. Her teacher was Ms. Shannon Cornell.

Stefanie wrote:
I wonder why the sky is blue?
I wonder why flowers have lots of colors?

Dear Stefanie,

The sky is blue because we have air. Without air, sunlight could only reach our eyes in a straight line. The sun would be very bright, but the rest of sky would be completely dark in every other direction. It would be so dark that we could see the moon and stars, even in the daytime.

Because we have air, sunlight can bounce off the gases that make up air. It also bounces from tiny bits of dust floating in the air. When we look at the sky in a direction away from the sun, we see light that has bounced or "scattered." That explains why the sky is bright, but it does not explain its blue color.

To explain the blue color, we have to start with the "spectrum" or the colors that make up sunlight. Sunlight contains all the colors from red to violet (red, orange, yellow, green, blue, violet and all colors in between). Light from the blue and violet end of the spectrum scatters more than light from the red and orange end, so more blue scattered light reaches our eyes than scattered light of other colors.

Scattering also explains why the sun looks red at sunrise and sunset. At those times, the sunlight travels through much more air to reach our eyes. More blue light is scattered away, so the sunlight that reaches us directly has more light from the red end of spectrum than from the blue end.

Nature gives flowers bright colors and interesting patterns to attract birds and insects. The flowers provide sweet nectar for those creatures to eat. While they enjoy the nectar, a substance called pollen sticks on their bodies. As they fly from flower to flower, they deposit pollen from one flower into another one. When that happens, the flowers start to produce seeds.

So the colors of flowers are important to keep nature in balance. The flowers provide food for insects and birds, and the insects and birds help flowers produce seeds. That's a story as beautiful as the flowers themselves.

I wish and all my readers blue skies and beautiful flowers.

Scientifically yours,
Dr. Fred

Find Out More

Click here to find a simple hands-on experiment that you can do (ask an adult for permission first). It comes from The Exploratorium, a wonderful science museum in San Francisco, and shows why the sky is blue and sunsets are red.

Click here for more "Ask Dr. Fred" questions.

Text copyright 2000-3 by Alfred B. Bortz, all rights reserved

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