In order to leave a trace, it is necessary for something to become arrested, to stop moving, and this can happen only in an irreversible process – that is to say, by degrading energy into heat. In this way, computers heat up, the brain heats up, the meteors that fall into the moon heat it; even the goose quill of a medieval scribe in a Benedictine abbey heats a little the page on which he writes. In a world without heat, everything would rebound elastically, leaving no trace.
Traces and heat
