Paperback edition, 1993.
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One of my favorite movies as a child was The Time Machine which was based on a book by H. G. Wells.
It featured the very green, meat-eating Morlocks who lived underground and ruined the apparent paradise that the time traveler found in Earth's distant future.
Of course, Hollywood's version of time travel is nothing like what scientists think could really happen, even in an acclaimed movie series like Back to the Future.
Some people claim to have traveled through time--without a machine. I researched this possibility in my book How to Travel Through Time.
The book tells about real people who claim to have experienced time travel--and gives some ideas on how someone might make such a journey.
Whether you believe this may be possible (and Einstein did!), the book makes for interesting reading.