I just watched Looper the movie. It is such a good movie and a great story. But then I’m biased. Anything with Bruce Willis is a great movie. Bruce Willis is getting older, which reminds me so am I!

For those who have not watched Looper I won’t give the story away … Looper is a must watch for science fiction fans. And there were other great movies and episodes about time travel. The three Back to the Future, and the Star Trek episodes, for starters.

That was the good news, and now for the bad news. Time travel is impossible. The mathematics behind time travel is excellent, but the physics is not. In contemporary physics, the mechanism of time travel requires wormholes. You get into a wormhole on one side and you pop out the other side either in the future or in the past, depending on what the wormhole was designed to do.

I did some digging, and found the Polchinski’s billiard ball paradox which is a version of the matricide paradox (travelling back through time before one’s birthday and killing one’s mother, hey what about father?) without the free will component. “A billiard ball sent through a wormhole which sends it back in time. In this scenario, the ball is fired into a wormhole at an angle such that, if it continues along that path, it will exit the wormhole in the past at just the right angle to collide with its earlier self, thereby knocking it off course and preventing it from entering the wormhole in the first place.”

Then Kip Thorne’s students came up another solution “to avoid any inconsistencies, by having the ball emerge from the future at a different angle than the one used to generate the paradox, and deliver its younger self a glancing blow instead of knocking it completely away from the wormhole, a blow which changes its trajectory in just the right way so that it will travel back in time with the angle required to deliver its younger self this glancing blow.”

Add to this second scenario that one collects the older billiard ball in a basket. Of course there are some boundaries driven by conservation of mass and when the wormhole was created, that constraint what is observed. But this then raises some questions. How many balls are there in the basket at the start? How many billiard balls does one observe in the middle of this experiment? Think parallel processing not sequential logic.

And, what can I do?” That is, since cause and effect no longer have a consistent relationship, if the basket fills up with billiard balls before I set off the experiment, can I choose not to set off the experiment?

It is sufficient to stop here to make the case that time travel is not possible.

I’m sure Kip Thorne, his students and many, many others are doing good work to develop theoretical models. I hope these older theoretical wormhole models would evolve to new ‘tunneling’ models that do not allow for inconsistent relationships between cause and effect. And these new ‘tunneling’ models will one day allow us to do interstellar travel using some kind of tunneling technology.

Right now time travel is just too easy to debunk. We are not there, yet.

The next in the Debunking Series.

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Benjamin T Solomon is the author & principal investigator of the 12-year study into the theoretical & technological feasibility of gravitation modification, titled An Introduction to Gravity Modification, to achieve interstellar travel in our lifetimes. For more information visit iSETI LLC, Interstellar Space Exploration Technology Initiative.

Solomon is inviting all serious participants to his LinkedIn Group Interstellar Travel & Gravity Modification.