Entry updated 2 March 2016. Tagged: Theme.
This scientific term has found much favour in sf Terminology. The stars constantly emit highly energetic particles as well as, of course, light, which is itself composed of tiny particles, photons (although here the word "particle" has a slightly different meaning). These particles exert a gentle outward pressure (which is why the tail of a Comet always points away from the Sun). A low-mass Spaceship with a huge, incredibly thin sail, perhaps made of aluminium or aluminized plastic film, could take advantage of this pressure just as a yacht uses wind – hence the 1960s proliferation of rather charming space-sailing stories, including "The Lady who Sailed the Soul" (April 1960 Galaxy) and "Think Blue, Count Two" (February 1963 Galaxy) by Cordwainer Smith, "Gateway to Strangeness" (August 1962 Amazing; vt "Sail 25" in Future Tense, coll 1964; vt "Dust of Far Suns" in Dust of Far Suns, vt of same coll 1981) by Jack Vance and "Sunjammer" (March 1964 Boys' Life; vt "The Wind from the Sun" in The Wind from the Sun, coll 1972) by Arthur C Clarke. The concept even features in a Mandrake the Magician cartoon strip from 26 April 1970.
A somewhat different light-pressure drive, using magic Technology to render the spacecraft briefly inertialess so that it instantly acquires (almost) the speed of light, appears in Robert A Heinlein's "Misfit" (November 1939 Astounding). Artificially boosting the solar wind with a massive planet-based laser installation to allow interstellar sail-flight is proposed in various later sf stories, such as Larry Niven's "The Fourth Profession" (in QUARK/4, anth 1971, ed Samuel R Delany and Marilyn Hacker) and Niven's and Jerry Pournelle's The Mote in God's Eye (1974).
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