nothing quite like a delay in one's travel plans to cause rumination on time travel, eh?...and yes, i know i may be aping for the first bit, but just wait

however, i had an uneasy feeling as i read the above, and despite the credential differences involved (physicist vs. failed physics major) at least felt that describing the queasiness might lead to its abatement.

the author proposes four "fundamental ground rules" of time travel, which are the following:

1. Only one universe (no multi-verse)
2. No travel before your machine was built
3. Can't kill grandpa
4. You really don't have free will

after even a brief skim, it becomes obvious that rules 2-4 are simply ways to avoid the paradoxes inherent in positing rule 1 plus time travel. and while i'm sympathetic to number 4 (especially if combined with a corollary that nothing is fated either - all is ultimately random), such sympathy adds little to a series of rules which essentially rule out time travel itself. after all, if one's appearance (using t-travel) is unable to change any future event merely by presence alone, then one is existing in a world with rules that totally contradict relativistic and quantum mechanical physics as we know it.

the author's "dogmatic" insistence on rule 1 seems to be the primary villain, as he notes that no one has disproved the notion of multiple universes, and he then brandishes einstein to banish these universes. naturally there is no mention that einstein himself was completely unwilling to accept quantum mechanics, which is now fully accepted by the physics community, proving that even genuises can become hide-bound and conservative.

the solution is more simple than these rules - multiple universes, with every action shifting one onto ever differing planes. sure, you can kill your own grandfather, but the universe you will then inhabit will not include a second you later in time, should you decide to wait and see. this does produce one irritation, as anyone living with a time traveler would not ever see them again, as they would shift onto a different universe with their very first trip. while bad for movie-romances, perhaps it would at least achieve the benefit of being paradox-free...