How to Punk Your Steam Part 10.2: Make it Travel Through Time (Rewind)
Hindsight being 20/20 and all, I am sure there has been some time in your life when you wished your older and wiser self could travel back in time and warn your younger self to avoid a or just to give encouragement that things will eventually look up. As grown-ups, we know that the drama of high school quickly falls away after graduation, and that college life undergoes the same treatment within a few years of moving into the working world. But, in our limited conception of time we are always going to see what is in front of us as the sharpest, strongest, most important thing that is happening and will happen.
My personal time travel wish isn’t much. If I could, I would take a peek at my future just 6 months from now. By then, I will know where my husband accepts a job, where we will be moving off to next, if I was accepted to any MFA programs, and/or if we are really going to embark on this whole being a parent thing I keep hearing so much about. Of course, as we discussed last time, I will get there eventually no matter what I do, because we are always traveling into the future. The tricky part would be getting back to “now” after I took my peek.
Moving forward in time is supported by scientific experimentation and pretty straightforward math (by professional mathematician standards anyway), but going in reverse is a lot trickier. Once again, much of this article is adapted from an essay by Stan Love, who tells his readers that he learned most of what he knows about traveling backward in time from Kip Thorne, so if you want all the details, check out Thorne’s book, Black Holes and Time Warps: Einstein’s Outrageous Legacy.
There are actually several theoretical methods for creating a time machine, there just hasn’t been any way to test it. And there likely won’t be any way to test it for hundreds, if not thousands of years. But, waiting is no fun, and a good imagination is great replacement for hard facts, so let’s move on to the theories. Now, bear with me, I am not a physicist nor a mathematician, but this is all weird and wonderful food for thought.
One theory involves an infinitely long cylinder. We are not just talking about the width of the known universe here, this would be infinity. Apparently, physics allows that if this cylinder existed, and was turning at nearly the speed of light, then vehicles moving through it would be able to make specific flight paths to the location they left, but at an earlier time. The best part? We may not even have to build this infinite cylinder ourselves. There is room within our current understanding of physics for a naturally occurring structure with these properties to already exist. It is a “linear black hole”, also known as a cosmic string.
This is not to be confused with a wormhole, which would be a tunnel created by the connection of two black holes. In general, this theoretical mode of travel (also known as an Einstein-Rosen bridge) is most often associated with moving faster than light speed over great distances, it is also related to time travel. In General Relativity, Einstein shows that space and time are two aspects of the same thing. You cannot mess with one without influencing the other. So, an astronaut traveling through a wormhole that is essentially warping space, will also experience a shift in time as well. If one could manipulate the wormhole to pick you up and spit you out relatively close in space (think like a big C shape with the earth being embraced by the arms), then you return to Earth, you could theoretically travel back (or forward) in time. The catch? You can’t ever travel back farther in time that when the wormhole was established, because you need an end to come out of. But, people living far enough into the future could take a jaunt back to meet their great-great-greats.
Alright, so we have a couple theories that involve black holes, which do exist. But, there is that whole spagettifcation problem that came up last time. Black holes are made of incredibly destructive forces that pull things apart atom by atom, so even if a wormhole existed and we could make it point where we wanted, how would we survive the trip? Black holes are extremely unstable, and any tunnel created by joining two of them would be likely to collapse at any moment. We would need to use something that is emptier than a vacuum and lighter than nothing to counteract the effects of the gravity well. Sound impossible? Nope.
Through something called the Casimir effect, it is actually possible to create negative pressure. There is a long explanation that has to do with making photons do weird things between materials that are poor conductors, but just take my word for it. If one were to construct two spheres, one inside of the other, out of these poorly conducting materials, and trap photons between the two layers, the photons outside the spheres would cause this negative pressure to occur. Granted, it has only been measured in extremely tiny increments, BUT, it has been measured.
But, as I said, hard science can only take us so far. The implications and intellectual appeal of time travel has very little to do with physics in the end. So, for the final installment of this How to Punk Your Steam article, I will be looking at time travel paradoxes and how to resolve them.