This article is from the soc.history.what-if FAQ, by Anthony Mayer firstname.lastname@example.org with numerous contributions by others.
It's a reference to S.M. Stirling's ISLAND IN THE SEA OF TIME (book one of
the Nantucket Trilogy), which sends 1998 Nantucket back to 1250 B.C.
through some unexplained mechanism and follows its inhabitants' subsequent
The book's publication sparked a large set of threads asking about the
impact of sending various areas or groups back in time. It is now a
newsgroup practice to give any such time-travel question a subject heading
"[whatever] in the Sea of Time", or just "ISOT."