Why do candles flicker?
For grown-ups: the science
Candles flicker because moving air changes the shape and brightness of their flames.
A candle flame is affected by convection: heated gases rise, drawing in cooler surrounding air. Small drafts and changing airflow alter the flame’s shape, temperature, and oxygen supply, which changes its brightness.
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Transcript
A little candle flame wiggles and dances in the air. Why does it flicker?
The flame heats the air around it, and the warm air rises. New, cooler air rushes in to take its place.
Moving air can push the flame from side to side. Even a tiny breeze can make its bright shape wiggle.
The flame also uses oxygen from the air to keep burning. As fresh air moves in, the flame changes shape and brightness.
So candles flicker because hot air rises and fresh air moves around the flame.