Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
Thirty years ago, astronomer Carl Sagan convinced NASA to turn a passing space probe’s instruments on Earth to look for life — with results that still reverberate today.
Computational rules might describe the evolution of the cosmos better than the dynamical equations of physics — but only if they are given a quantum twist.
Thomas Young’s double-slit experiment originally served to prove that light is a wave — but later quantum versions have made for a much fuzzier picture.