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How do leaves make themselves?

How do leaves make themselves? -Francesco R.

Dear Francesco,

Last fall, my friend Lee Kalcsits and I went exploring in the apple orchards of Wenatchee. The apples were ripe and the leaves were changing from green to gold. We plucked a few leaves and took them back to his lab. » More …

How do chameleons change color?

Dear Dr. Universe, How does a chameleon change colors? -Jasmine B. 12, Nepean, Canada & Marie F., 11, Ghana

Dear Jasmine and Marie,

There’s something about a chameleon’s darting eyes, long tongue, curled tail, and ability to climb that makes it a fascinating animal to watch. Especially when it’s changing colors.

And the latest research on your question suggests that how a chameleon changes has more to do with light than scientists once thought. » More …

Can you hear in space?

Hi, Dr. Universe, Can you hear in space? -a curious reader

Dear curious reader,

Your question reminds me of an experiment: You put a ringing alarm clock in a jar and use a hose to slowly suck out all the air. As the air escapes, the ringing gets quieter until there’s no sound at all.

The inside of the jar becomes what scientists call a vacuum. It’s empty. Just like space. » More …

Why is liquid nitrogen so cold?

Why is liquid nitrogen so cold? -Aaron, 9, Seattle, WA 

Dear Aaron,

When I got your question, I headed straight for my friend Jake Leachman’s lab at Washington State University. He’s an engineer who knows a lot about what happens to things when they get super cold.

» More …

Why do trees have rings?

Why do trees have rings? -Cynthia, 8, Seattle, WA

Dear Cynthia,

While walking in the woods with my friend Gary Chastagner, we stumbled upon some old tree stumps. The stumps had so many rings we had to use our magnifying glasses to see them all. » More …