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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.

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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 …

Why is yawning contagious?

Why is yawning contagious? -Grant, 10, Pullman, WA

Dear Grant,

When I got your question, I met up with my friend Hans Van Dongen, a scientist at Washington State University in Spokane. He works in a research lab where they study sleep. As a cat who appreciates naps, it’s one of my favorite places to visit. » More …