The Bactra Review   Bloom
The idea that life-forms could (as the poet says) ``plunge from world to
world'' by means of radiation pressure seems to have begun with the Swedish
physical chemist Svante Arrhenius, as part of his theory of panspermia. If
the spores are small enough, light enough, do not mind extreme cold or
impact, and can be gotten up into space in the first place, it'll work.
(It's easy to calculate the maximum size of the spores, if you ignore the
effects of the solar wind and just rely on radiation pressure.) Olaf
Stapeldon used the idea in The Last and the First Men; probably
other science fiction writers have too.