Other noteworthy hard SF authors include Arthur C. Clarke , Hal Clement , Isaac Asimov , Greg Bear , Larry Niven , Robert J. Sawyer , Stephen Baxter , Alastair Reynolds , Charles Sheffield , and Greg Egan . Other noteworthy hard SF authors include Isaac Asimov , Arthur C. Clarke , Hal Clement , Greg Bear , Larry Niven , Robert J. Sawyer , Stephen Baxter , Alastair Reynolds , Charles Sheffield , Ben Bova , and Greg Egan .