Reversing The Effect?

James Blish, Midsummer Century, 4.

Martels wants to get:

"...back to his home century; and only in human techniques were there any hints of possible help in this direction. That malfunctioning perisher of a radio telescope had sent him up here, and that had been a human artifact; surely by now, there must be some simpler way of reversing the effect." (p. 27)

Surely nothing of the sort! Martels lost consciousness in 1985 and regained consciousness in 25,000 A.D. That implies merely that he had been unconscious for about 23,105 years. That process is not reversible, i.e., when someone wakes in the morning, he cannot be reversed to a moment after he had gone to sleep the previous night.

Even if Martels' intuition that he had not existed in an unconscious state for 23,105 years but had jumped across the temporal gap is valid, he as a physicist should not assume that it is possible to jump back. He has to reckon with entropy, causality and the arrow of time. When the question of returning Martels to 1985 is addressed, the discussion is unsatisfactory. See here.