Science in the Fourth of July Sky

About a thousand years ago a Chinese monk stuffed gunpowder into a piece of bamboo and tossed it into the fire. He wanted to make a noise loud enough to scare away ghosts.

If you head out to a fireworks display tonight, you'll get more than a big bang. The designs and colors we see in the sky are a result of chemistry. Inside the fireworks are pellets of the sparkly stuff that burns in the sky. The pattern you see in the sky results from how those pellets are placed inside the firework. They may explode outward in shapes that look like fronds of a palm tree or a brittle star. Or they might snake across the sky. You can read more about patterns here.

The colors come from burning different metal salts: barium chloride for green, lithium carbonate for red, copper compounds for blue, and sodium - like the salt you shake onto your potatoes - for yellow. Here's a handy color chart.

Have fun on the fourth, and remember: it may look like a fireworks show but it's Science in the Sky!

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