Time-Travel Paradoxes

          Time-Travel Paradoxes

  

Lately time-travel seems to be a real possibility in physics, in nonlocal entanglement for quantum mechanics, and in closed timelike loops for general relativity. Time travel is notoriously paradoxical; it implies time paradoxes and time loops.

          Take for instance the Grandfather Paradox. What if a time-traveler kills his own grandfather; does he exist or not? If yes, then no; if no then yes.

          I dislike this formulation of the paradox, partly for its sensationalism. Brutality in tale-telling is counter-educational; it provokes anxiety not thought. Also missed in this gratuitously-violent story is the logical exit; the killer grandchild killed the wrong man. A more rigorous version of the tale would be a Time Suicide, who kills himself in the past; does he exist or not? The Time Suicide Paradox, though insane, is closer to pure paradox than the flawed Grandfather.

          The Time-Suicide Paradox can be written this way:

          Time-suicide lives      =        NOT(time-suicide lives) OR gun jams OR other mishap.

          So Murphy-esque glitches force the suicide’s failure. His attempts at retroactive self-destruction are physically impossible! The alternative is parallel worlds; in one the younger self dies, in the other one not; and the later travelers swap worlds in transit. That protects consistency; but it means that they rode alternate-world machines, not true time machines. The rider of a true time machine must respect temporal noninterference.

 

          Time-loops are self-consistent cycles of causation; they are allowed in general relativity, and hinted at by nonlocal entanglement. There are many examples in science fiction of time loops; for instance, “By His Bootstraps,” by Robert Heinlein. The paradox of time-loops is; where did the time-looping data come from?

          Consider “Time-Loop Biogenesis”.  Classic panspermia posits that bacteria inside rocks can survive being blasted into space by asteroid impacts; that they can hibernate for millions of years; and that they can thus travel from planet to planet or even star to star; and that life on our own planet arose from such colonization. Well, we do know that bacteria can indeed be revived after geological ages of dormancy; but that just puts the origin-of-life problem back to another planet; how did life arise there?

I speculate that due to general relativity, the giant spinning black hole at the center of the galaxy can act as a time machine; that there were potentially life-bearing planets near that black hole, early in galactic history; that the black hole can hurl bacteria-bearing rocks millions of years into the past; that some bacteria made that journey, landed on lifeless planets and colonized them; that those planets were then hit by asteroids, which sent bacteria-bearing rocks out into space, some of which encountered the same black hole, which hurled them into the past!

Thus life arose from a time-loop. It caused itself, via recursive circular causation along closed timelike paths. It’s a form of tunneling. Before the time loops were worlds on the brink of life; afterwards, worlds full of life.

This theory, if true, implies that life across this galaxy has the same biochemistry, including chirality and genetic code; that life in other galaxies may have different chemistries and codes; that the galactic core has (or had) lots of bacterial worlds.