Structure and Optics of the Atmosphere

Abstract

Among the latest achievements of science has been an increased understanding of the earth’s atmosphere — its structure and the processes operating within it. Still far from complete, these concepts have been worked out just in the past quarter century (see, for example, [175]). Scientists of the elder generation well recall the time when the atmosphere above 10-12 km was considered a dreary wasteland where there was nothing but crystal clear air at a temperature falling off smoothly with height, and a good many observations that did not harmonize with this scheme were thought to be erroneous. But modern research, at first performed indirectly through observation from the ground, and subsequently by direct study from aircraft, stratospheric balloons, rockets, and most recently from artificial earth satellites, has completely overturned the early ideas. Today the pace with which data are accumulating on the physical conditions prevailing at various heights is rapid without precedent, and this applies not only to numerical findings but to many hypotheses of. a qualitative character which only recently seemed questionable. Nevertheless, we already have a fairly confident understanding of the atmosphere in basic outline. We must pause to review this topic here, for otherwise no analysis of the twilight phenomenon would be meaningful.