Types of Time Machines and Practical Time Travel

by Charles Tandy

ABSTRACT

Based on specified logical, ontological, and other relevant considerations, it is concluded that in the very-long-run: (1) forward-directed time travel capacity is highly likely; and, (2) past-directed time travel capacity is likely. Four logically possible forward-directed, and four logically possible past-directed, types of (hypothetical) time machines are identified. Two different approaches (the “practical”; the “bi-temporal”) are utilized in attempting to characterize the meaning of time travel. It apparently turns out that the concept of “embedded-subjective time” (i.e. the embedded-temporality of the human time-traveler, as distinguished from either merely-subjective time or literal-wristwatch time) is especially helpful in characterizing whether time travel did or did not occur in a particular circumstance.

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