What if E.T. is out there but can't understand our messages?

“Many people would choose to construct a message containing sights and sounds of the human experience but overly anthropocentric signals that implicitly rely upon certain facets of human culture may go unnoticed by extraterrestrial listeners,” writes Atri, of the University of Kansas.

“Messages that rely on the specifics of human biology or culture will be less likely to effectively communicate to an unfamiliar extraterrestrial listener. This may require that the message attempts to represent Earth as a whole instead of focusing exclusively on humanity.”