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Why is air invisible? © Getty Images

Why is air invisible?

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Like the hair on your uncle’s head, gas molecules in the air are spread so thinly it's hard to tell they're there at all.

Asked by: Brittney W’s Grade 2 Class, via Twitter

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Air is made up mostly of nitrogen and oxygen molecules that are spread too thinly to affect light noticeably by, say, altering its colour or intensity. Even so, air’s presence is revealed in hot weather through the shimmering effect called ‘heat haze’. This is the result of the heat causing fluctuations in the density of the air, which in turn affects its optical properties.


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Authors

Robert is a science writer and visiting professor of science at Aston University.

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