The Time Travel Fallacy, part 3

This is the third article in a mini-series on time travel. To read the first two articles click here and here.


Issue 3: What happens to a person who time travels?

There are two main questions I want to look at with regard to a time traveler's person. First, how does one's body time travel? This is much like the question of how one can teleport, as bodies are broken up into pieces of matter or energy and reassembled upon arrival--is the person who arrives the same as the one who embarked? And second, assuming the person remains the same after travel, what does the differing passage of time do to the traveler? Not only does time pass more slowly the faster one is traveling, but the process of time travel would mean that one who spends significant time in the past would return to the present measurably older than he left.

Now this is starting to get ridiculous...

Starting with bodily effects of time travel, the result would depend on what manner of travel is used. There are two main methods I can think of: travel by vehicle that moves beyond the speed of light and travel by "teleporting through time" in a stationary (or sometimes rotating) machine. While I can feasibly see the vehicle method resulting no physical changes in the traveler, I am more skeptical about the results of travel by teleportation.

As I understand it, such time travel involves the traveler being teleported from a particular place and time to another. I'm not sure how such a machine would accomplish the "time" portion of the teleportation, because it seems most theories of time travel require massive physical velocities to accomplish the slowing and reversal of time. Nevertheless, let's assume it's possible to be instantaneously zapped from one time to another. Even so, how does that work? Because such teleportation requires the disassembling and reassembling of matter at the molecular level, it would seem reasonable that--even if the same human form emerges on the other side, it would not be the same body of consciousness. In other words, outside observers would see the same person (and for all intents and purposes it would be the same person), but the consciousness and awareness that exists in that body would be different.

To break it down further, think of a person as an "original." When the atoms that make up that original are teleported, they must, theoretically, be broken down into energy (or at least to the smallest atomic structures possible). The thinking is that you can't pass a 160 lb. person through time and space in its entirety. Then, the body is reassembled on the other side (this would be the work of a retrieval machine that has scanned and stored the structural data of the traveler, e.g. the Transporter in Star Trek). In essence, the time traveler is scanned in the copy machine at the take-off point and printed out at the destination in another time and place.

Here we come across the troubling question: who is this "printed" person? I have to believe that consciousness can't travel across time in the form of atoms or energy in the way that a body can. If this is true, the person arriving would have the mental knowledge, wherewithal, and capabilities of the original, but it would not be the original in the true sense. This is of little consequence to the outside world, because your friend Dave would still be Dave--he remembers your trip to Vancouver, can still recite the Shakespeare he learned in college, and has the same character and personality traits as Dave has always had. But the original  "consciousness of Dave" is now gone. This may not matter to the larger world, but to the original Dave it's a pretty big deal!

Putting aside this concern, let's look briefly at the effect of the passage of time on the time traveler. We already know that time passes more slowly the faster something is traveling--at least, relative to its slower-moving counterparts. This has been observed in astronauts who spend large amounts of time aboard the International Space Station, who are a few seconds younger than they would have been on Earth during that span. Consequently, it seems reasonable to believe that a time traveler would age significantly slower during his travel, relative to time's passage on Earth. Because time travel theoretically requires movement beyond the speed of light, it would exhibit the ISS effect to the extreme.

However, what about one who spends time in another era? Presumably they would age at the normal rate of a being at rest in that time (that is, they would age at a 1:1 ratio with what is standard on Earth, if that's where they are). However, their age upon return depends entirely on (1) how long they were in that other era, and (2) what time they choose to return to, relative to their departure time. This second point means that  a person who spends a few years in another time and then returns to his contemporary time at even the exact moment he left will suddenly appear much older. Taken to the extreme, someone who chooses to return sometime before he left will compound the effect and age before he left.

As far as I can imagine, this aging phenomenon will only go one direction--forward. So time travel for long periods of time would become an "at your own risk" scenario, where one would essentially choose to live his live at normal speed and time in his contemporary age, or spend time traveling throughout the years. The more time travel a person undergoes, the less time he will have to spend in his contemporary time due to the ongoing aging. This doesn't account for the time slowing effects of extremely fast travel in a time machine that actually moves. However, even in such a case, the person will age once he reaches his time destination. That aging can't be undone, no matter when he chooses to return to the present.

In sum, it seems that time travel is a risky proposition for the one doing the traveling, even if all of the possible kinks are worked out. I'm not sure that I would volunteer for such a trip.