# Heat

The **heat** of an oscillator or spaceship is the average number of cells that change state in each generation. For example, the heat of a blinker is 4 because 2 cells are born and 2 die every generation – the four cells that change state each generation are highlighted in green to the right. Similarly, the heat of a lightweight spaceship is 11 because 9 cells change in its odd-numbered generations (3 cells die and 6 are born) and 13 cells change in its even-numbered generations (8 cells die and 5 are born), for an average of 11 cells changing per generation.

For a period n oscillator with an r-cell rotor, the heat is at least 2r/n and no more than r(1-(n mod 2)/n). For n=2 and n=3 these bounds are equal.

Temperature is a metric of heat in proportion to the total number of active cells.

## External links

- Heat at the Life Lexicon

- Nathaniel Johnston. Re: Golly scripts (discussion thread) at the ConwayLife.com forums (script to calculate heat of spaceships and oscillators)