Halpern ( Time Journeys ) tackles the No. 1 recreational problem of theoretical physics: actual applications of special relativity to create the possibility of spacetime travel. The "intersteller shortcuts" in the subtitle is an oxymoron in present technical terminology, so Halpern himself is free to travel freely between the ground of astrophysical theory and the speculative time-travel canon. Indeed, he borrows his illustrations from Asimov and Heinlein as often as from Thorne and Morris. The result is more a colorful survey-style lecture script than a coherent theory, sufficient to general readers and certainly inspiring to a science fiction following but without a firm sense of scale of the science involved (and none of the mechanics or mathematics). Halperns wormholes appear deus ex machina, nearly the last loop of this joyride through astrophysical theory, and somehow one cant help wanting to get back on line. Halpern teaches mathematics and physics at the Philadelphia College of Pharmacy and Science.
