Scenes of this set of stamps are taken from 1930s' visions of space travel. Such visions are able to bridge the gap between science fiction and futurology, the study of long-term trends in society in order to develop and promote alternative ways of dealing with future events or conditions. Futurists recognize the unavoidable uncertainty inherent in forecasting, so much of their work focuses on "what-if" examinations of alternatives rather than precise prediction.