What topic dominated science fiction during its early days? (use references) What topics do you think dominate it in the 21st Century? Why?

Early days is
an ambiguous term, as is Science . But let us say Jules Verne represents early days. The
Science fiction bonanza of the 1950s (Bradbury, A.E. Van Vogt,, etc.) features explorations into
human psychology and whether there was such a thing as human nature.   Would the future, with
its new...