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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 …

What happens under a volcano?

What happens under a volcano? -Graylon W., 6, Milton, Ontario

Dear Graylon,

Your question takes us on a journey deep into the Earth. Figuratively speaking, of course. It’s really hot under Earth’s surface. It’s so hot it can melt rock. This melted rock is known as magma. And anything that erupts magma is a volcano. » More …

How are magnets made?

Dr. Universe, How are magnets made-Andrea, 8, Berkeley, CA                                                                                     

Dear Andrea,

When I saw your question, I headed straight for the Magnetics Lab and met up with my friend John McCloy. I found out the word “magnet” comes from a Greek word for the region of modern-day Turkey we once called Magnesia. That’s where people found magnets in nature. » More …