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Why some flames are blue and others are red?

0:28EnglishBy minutephysicsTranscribed Jul 17, 2026
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Chemistry may tell us the recipe for

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combustion, but the light show is all

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physics. When a flame burns cleanly,

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like a gas flame, blowtorch, or the base

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of a candle, the heat excites the

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molecules to release light, usually pale

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blue, from atomic transitions. That's

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quantum mechanics.

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>> [music]

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>> Now, when the fuel isn't as pure and

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doesn't entirely burn, like wood fire,

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coal fire, or the top of a candle flame,

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there's still some blue light, but you

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don't see it because it's overpowered by

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light from all the particles of soot and

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smoke. They're glowing red hot.

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