Welcome back to a Brief-ish History of SETI! In our previous installments, we examined the earliest attempts to find extraterrestrial intelligence (ETI) beyond Earth, as well as one of the most important philosophical underpinnings ( Fermi's Paradox ). We also looked at the first true example of the Search for Extraterrestrial Intelligence (SETI) experiment ( Project Ozma ) and the Drake Equation , followed by the first proposed searches for megastructures ( Dyson Spheres ) and classification schemes for ETIs (the Kardashev Scale ). Today, we'll examine the first attempt at "active SETI," aka. Messaging Extraterrestrial Intelligence (METI), and what remains the best candidate for a possible message of extraterrestrial origin. These are none other than the Arecibo Message , and the WOW! Signal , two pivotal moments in the history of SETI that remain unrivaled to this day. Buckle up, because some big concepts and big names (one of whom was the focus of Part II) are about to be dropped!…