The Gulf is Deep (Heinlein)

  The novella Gulf predates almost all of Heinlein’s novels. Online version. The book Friday (1982) is a loose sequel. Wikipedia: Gulf is a novella by Robert A. Heinlein, originally published as a serial in the November and December 1949 issues of Astounding Science Fiction and later collected in Assignment in Eternity. It concerns a secret society …

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Varieties of Time Travel

My kids have been reading lots of books over the break, including an adventure series that involves time travel. Knowing vaguely that dad is a theoretical physicist, they asked me how time travel works. 1. Can one change history by influencing past events? OR 2. Is there only one timeline that cannot be altered, even …

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