Throughout history, mariners have infrequently reported witnessing bizarre nightime displays where the surface of the sea produces an intense, uniform, and sustained glow that extends in all directions to the horizon. This phenomenon has also occassionally been reported in ship’s logs and there is even a fictional account in Jules Verne’s 20,000 Leagues Under The Sea. There has been speculation that these events are due to the accumulation of massive populations of natural and marine bioluminescent bacteria and one such “milky sea” was corroborated in 1995 when a satellite imaged a glowing portion of the Ocean, the size of Yorkshire, off the Somalian coast. The light then produced by these bacteria obviously can penetrate from the Earth’s atmosphere, and into space beyond, and so a very long time before we developed the ability to do this, bacteria were sending electromagnetic signals into space, and which could be conceivably be detected by extraterrestrials.
Based on the above findings, this is a largely symbolic, and also very simple, attempt to send a biological electromagnetic signal to other worlds.