the idea of trying to send messages to extraterrestrials has existed since at least the early 1800s ... starting in the 1820s various scientists (notably c.f.gauss) suggested signalling the moon by using such schemes as cutting clearings in a forest to illustrate the pythagorean theorem or reflecting sunlight from mirrors in different countries placed so as to mimic an observed constellation of stars ... in the 1890s radio signals were considered, and were tried by nikola tesla ... (stephen wolfram)

what i haven't known was that hans freudenthal created lincos 1960

specifically for extraterrestrial communication (sw)