https://mysteriousuniverse.org/2019/09/mathematicians-solve-douglas-adams-meaning-of-life-42/#:~:text=People%20who%20have%20never%20heard%20of%20Douglas%20Adams,assumed%20mythical%20and%20mystical%20connotations%20amongst%20sci-fi%20fans.
From: The Hitchhiker's Guide to the Galaxy
Or - The angle at which light reflects off of water to create a rainbow is 42 degrees.