Most of our experience with the Search for Extraterrestrial Intelligence (SETI) has focused on capturing radio signals that alien species have sent out, whether intentionally or unintentionally. That creates a huge “synchronicity” problem—what if there aren’t any alien civilizations broadcasting radio signals now, but there were a billion years ago? The Milky Way is around 13 billion years old—hoping that we exist at the same time as an alien civilization that happens to be actively messaging is a huge leap of faith.