"Exhalation" is a science fiction short story by American writer Ted Chiang about the second law of thermodynamics.

It was first published in 2008 in the anthology Eclipse 2: New Science Fiction and Fantasy, edited by Jonathan Strahan.

The scientist dissects his own brain and discovers that it operates based on the movement of air through tubes with small flaps of gold leaf acting as switches.

The scientist hypothesizes that others' brains are computing more slowly because rising atmospheric pressure causes air to move the gold leaf at a slower rate, and that the subterranean supply of argon will eventually be depleted, equalizing the pressure between the two atmospheres.

[3] The Astronomical Society of the Pacific called it a "wonderful parable",[4] while The Encyclopedia of Science Fiction described it as "limpid"[5] and an "elegant thought experiment".