Although astrobiological or SETI detections are possible, actual invasions of sentient extra-terrestrials or plagues of escaped alien microbes are unlikely. Therefore, an anthropological perspective on the question suggests that in the event of a detection, the vast majority of humanity will be dealing not with extra-terrestrial life itself (whether intelligent or not, local or distant), but wi...

James R. Karr, University of Washington Humans measure things to understand the past, to document the present, and sometimes to predict the future. But humans neither measure everything nor measure things at random. Industrialized humans measure some things because they give pleasure—batting averages of favorite baseball players, for instance—and they measure other things because they are assum...