ASK JiMMY ThE BUG

Hi Bug! Leo A. from Pennsylvania asks: Why are gases invisible?

Vision expert Dr. Larry Thibos explains that most things are opaque-light doesn't pass through them. They are visible because they soak up or bounce back some or all of the light that falls on them. You see objects like the moon, a mountain, or a mouse because they reflect light back to your eyes.

Gases are transparent. Like glass, you see through them. They are invisible because they don't reflect light back to your eyes. Instead, light passes through them.

But when charged with an electric current, gases can emit light. That's how a neon sign works. When electricity flows through the pure neon gas inside, it glows red. The red light passes through the clear glass tube, zips through the air-a mixture of invisible gases-and enters your eyes. Your brain decodes: "Eat at Joe's." You go inside for a bean burrito, glad that gas is invisible.

Hey kids!

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Send them to ASK, 70 E. Lake Street, Suite 300, Chicago, IL 60601, or send them by email to ask@caruspub.com.

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