Another Asimov Anthology, this one of pieces that appeared in The Magazine of Fantasy and Science Fiction. (Fact pieces are the cachet of some of the more distinguished sci fi mags.) Several essays, timed to the Bicentennial and featuring the author as historian, are interesting examples of Asimovian logic applied to urban problems (he is a true New-York lover), to the Civil War, to the general theme of history as reflecting changes in technology. All are reasonable, with occasional too-facile-by-half conjectures corrected by scholars whose minor criticisms are appended. Several of the scientific essays fall into groups: the opening ones dealing with speculations on the nature of trans-uranium elements and a second set treating, with spanking success, of ice ages. One by one, Asimov describes the perturbations in Earth movement that account for the seasons and the various disequilibriums which have led to ice ages past and hold the potential for future ones. The concluding sections take up themes pertaining to the solar system and the cosmos. Here we find the title essay, an account of the mapping of the heavens from naked-eye numberings of stars in the days of Hipparchus to the latest estimates of the luminosity of such ultra-distant phenomena as quasar 3C279. At its peak, the quasar's brilliance is estimated to be 100,000,000,000,000 times that of the sun. Leave it to Asimov to supply such figures, along with familiar comparisons and ingenious analogies, which together make the revelations of science wondrous and never tedious.