A Smoky Candle (Science Advent 4)

(Every day until Christmas, I’ll be posting a science-related image.)

Day 4

Smoke from a recently extinguished candle demonstrates some beautiful physics. Near the wick, the smoke rises in an orderly way, exhibiting laminar flow. Higher up, interaction with air molecules (which move randomly) breaks the flow into delicate turbulence. [Credit: Jan Gottweiß]

Smoke from a recently extinguished candle demonstrates some beautiful physics. Near the wick, the smoke rises in an orderly way, exhibiting laminar flow. Higher up, interaction with air molecules (which move randomly) breaks the flow into delicate turbulence. [Credit: Jan Gottweiß]

Candles have a long association with the Christmas season, so it seemed fitting to talk about the smoke from a candle for today’s Science Advent installment. In this beautiful image, an ordinary candle was lit, then extinguished. The smoke nearest the slightly glowing wick rises in a a coherent pattern: you could trace the path of a smoke particle along a line. This is known as laminar flow, since the layers of smoke don’t mix together. (“Laminar” literally means “flat”, but in everyday usage, we usually mean layered instead, as in laminated paper or wood laminate.) However, air molecules move randomly, so as the smoke rises, it is increasingly buffeted by these other particles. The result is turbulence, where the layers of smoke mix together and billow. Turbulence is fractal in structure: if you could look closely at the smoke, you’d see that turbulence persists on the microscopic level, equally beautiful and equally complex as at the macroscopic level.

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3 Responses to “A Smoky Candle (Science Advent 4)”


  1. 1 prhscience December 5, 2012 at 13:54

    Did you know: you can relight the candle by lighting the smoke stream. It’s very cool.


  1. 1 A Phenomenal Galaxy (Science Advent 8) « Galileo's Pendulum Trackback on December 9, 2012 at 10:16
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