This principle, by definition, will come to apply to intra-galactic communication with virtual timeless consciousness. We are in the extreme early stages of communication within the Galaxy and have encountered barriers to the two-way principle in the minds of those who fear that by reaching outwards the world will in some way bring disaster upon itself.
Water is life's basic ingredient.
We assume naturally that life in the galaxy will involve water. The wavelengths for broadcasting in the Galaxy are virtually infinite. One expects that minds will have much in common, that highly evolved intelligence seeking to reach out will select first a band common to biological life. The broadcaster has evolved further than just the listener. We have seen the metamorphosis from analogue to digital while the Information Age continues an exponential development.