Time-travel sex tourism is not quite as straightforward as you'd think

A friend of mine claims to have invented a rudimentary time machine that will allow him to travel back and forth over relatively short distances in time. He says that he is planning a little jaunt to the tail end of the 20th century (mainly for shopping purposes), but has been losing sleep over a rather tricky ethical question. He reckons that if he successfully engineers this trip back in time, he will be tempted to look up his missus as she was in the early days of their marriage and, as the saying goes, ‘get it on’ with her. His wife took up professional wrestling a few years ago, and has bulked up to an extent that he is not entirely comfortable with, but is afraid to comment on for fear of hurting her feelings, or indeed, suffering physical reprisals. That is at least part of the appeal in hooking up with her as she was in 1998.

He believes that he could probably talk his ‘1998’ missus into doing it because: a) she was always game for a laugh before she took up the wrestling, and
b) she would have been gullible enough to have bought the line that the ‘1998’ her having sex with the ‘2012’ him could not be construed as actual adultery as he is /was still the person that she is /was married to, albeit one with unusually variable temporal co-ordinates.

If this plan works, his dilemma can be summarised as follows: When his 1998 missus succumbs to the charms of the  2012 version of him, will she be being unfaithful and will he have grounds for divorce when he returns from his late-nineties sex /shopping trip? Could any act they commit in 1998 be legally and /or morally construed as adulterous behaviour? His view is that he won’t be betraying his 2012 wife by having sex with her in 1998, because she’ll have been aware of, and complicit in, that very act and will have remembered it as just another roll in the hay with her husband (again, notwithstanding those rather unusual circumstances). In addition, she couldn’t really have betrayed her 2012 self in 1998 by agreeing to become the mistress of her 2012 husband, because, in 1998, the 2012 ‘her’ didn’t yet exist.

The real difficulty, however, occurs when my friend considers the fact that this 1998 liaison will have been hidden from the ‘him’ of the last fourteen years. The time-travel sex in 1998 will be a new experience for the 2012 him but -when he returns to the present- it will have been an old experience for the 2012 version of his wife. After 1998, it will always have been an old experience for her, meaning that his 2012 missus has been hiding this (possibly) adulterous act from him all these years. Unless his wife is exceptionally dim, she must know that, at some point, he is going to find out what went on, because –once he returns from the time trip- he’ll have remembered making it happen and he’ll know that she allowed it to happen. And that, clearly, would make a cuckolded fool of the 1998 him (and all the other ‘hims’ from then, right up to the point at which he goes back in time).

Obviously, he has no recollection of this event because it hasn’t yet happened to him, but if he succeeds in making it happen, the ‘pre-time travel’ 2012 version of him will have been kept in the dark all of these years, which will make the ‘post-time travel’ version of him feel angry and a bit stupid for having suspected nothing all this time. Not only will his wife have been lying to him, but –technically speaking- he’ll have betrayed himself by persuading her to have committed adultery with an older man.

Of course, there is always the possibility that his time machine won’t actually work and he won’t be faced with this dilemma at all. If the grouting he did for me last year is anything to go by, I suspect the odds are probably against a successful expedition.