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Feb
11

Classical Time Travel Isn’t Practical

Practical Time Travel for Beginners, Part 1

To begin with — for the sake of clarity — I want to distinguish my subject from a related topic with which it might easily be confused. So let me be clear from the start that I’m going to be writing about practical time travel, not standard or what I like to call classical time travel.

Now, you may not have realized that there are different varieties of time travel. But trust me — there are different kinds of time travel. At least two.  And probably many more than that.

Practical time travel, which is the kind we’ll be exploring in this series of articles, is a methodology for moving through time using resources and abilities that you already possess, or that you can acquire without too much difficulty. It requires first changing your thinking about time and your relationship with it and then quite literally altering how you move through time. It enables you to redefine your past and to choose virtually any destination you can imagine for your future.

It’s time travel, but without the magic or the time machines.

Classical time travel, on the other hand, is what people are generally talking about when they use the term “time travel.” It is above all a compelling idea that makes for wonderful stories and philosophical contemplation.

Classical time travel is what they do in all the time travel books, movies, TV shows, comics, and games. It means moving through time either 1) backward or 2) forward, but much more rapidly than normal. Put more simply, it means traveling into the past or into the future.

Where did such a notion ever come from? You might think that classical time travel is a fairly new idea, that it emerged  in the middle of the last century along with crazy ideas like space travel and personal computers. But that’s not the case. H. G. Wells published a short story entitled “The Chronic Argonauts” in 1888. A futurist inspired by emerging technologies such as telecommunication, automobiles, radio, aviation, and mass production, Wells framed time travel as a coming technological development. He wrote his book years before the first heavier-than-air flight or radio broadcast, but he would have been familiar with those concepts and would have thought their realization inevitable. With such wonders on the horizon, why not a machine that could propel a passenger through time the way the way a locomotive moves a train on a track?

In any case, while Wells may have been the first to frame time travel in strictly scientific and technological terms, the idea is not original with him. Not by a long shot.

Perhaps the earliest mention of time travel comes from Hindu mythology. There we read the  tale of king Kakudmi, a worried father whose daughter is being pursued by numerous suitors.  And I mean numerous. It seems that this young lady is not just an unparalleled hottie, she’s got that special ancient-world je ne sais quoi — that whole Helen of Troy thing. Kakudmi takes the responsibility of rearing such an exceptional offspring seriously, and he wants to be sure that he marries his daughter off to the right dude. Seeking advice in the matter, he takes the extraordinary step of securing a face-to-face with the god Brahma. And this is where it gets weird.  Kakudmi discovers  that while spending what seemed just a few moments in the god’s company, ages and ages have passed on earth. He travels so far into the future that the landscape has changed and people are noticeably different — they have gotten shorter, and are not as refined and genteel as they once were.

Being accidentally propelled into the future is a trope that has been repeated throughout literary history. An interesting example is Washington Irving’s tale of Rip Van Winkle — a fellow who falls asleep one fine afternoon in the Catskill mountains, after meeting up with some dwarfs who while away their days chugging beer and bowling.  Van Winkle dozes off after having perhaps just a bit too much fun and awakens to find that 20 years have passed. Whether one jumps ahead an entire Age of Man (as Kakudmi did) or a couple of decades (as Van Winkle did), what’s always interesting about the future is how much things have changed. Van Winkle falls asleep under the reign of King George and wakes up during the presidential administration of George Washington.  His wife is gone; his children are grown. It’s a pretty significant change for a relatively short jump. These two stories and their two very different leaps through time capture what is most interesting about going into the future. Either we want to know how much and in what way the world has changed, or we want to see how much our own world has changed.

Stories about moving backward in time work the same way, with time-travelers visiting (and usually making changes to) a previous historical era or an earlier phase in their own lives.  In Ray Bradbury’s short story “A Sound of Thunder,” big-game hunters travel millions of years into the past in order to track and kill dinosaurs. The present is secure from any changes the hunters make as long as they kill only the specific animal they have been told to go after, and as long as everyone stays on a pre-defined path. (Of course, someone steps off the path.) In the movie Back to the Future, Marty McFly travels 30 years into the past and accidentally prevents his parents from meeting — bringing his own existence into jeopardy.

This raises an important point, one that we will return to in some detail later. Most time-travel stories about visiting the past involve making changes to the past, but those changes themselves are not the point. The point of the story is generally how much the present has changed because of whatever was changed in the past. The big pay-offs at the end of both “A Sound of Thunder” and Back to the Future involve time travelers returning to their own eras only to find them fundamentally transformed.

The past is fascinating and a worthy travel destination in its own right, but in these stories the trip to the past serves primarily as a set-up for a trip to the future. (That is, the journey back from the past.) The big-game hunters in “A Sound of Thunder” return to the day they left only to find their world changed in a shocking (and devastating) way. It’s not as dramatic a set of changes as those that Kakudmi observes in his trip to the distant future, but very sweeping nonetheless. Marty McFly returns to the year 1985 to find a world that has been set right, and that is in many ways as different from his original present as Rip Van Winkle’s post-nap world is from his pre-nap world. It’s very telling that the story is entitled “back to the future.” The trip that ultimately matters the most is the one that goes forward in time.

Obviously, classical time travel can provide for an endless supply of fun and thought-provoking stories, but could it ever happen? Is there any way to accomplish classical time travel in real life?

The short answer is…maybe. Some portions of classical time travel seem quite doable; others are a little more iffy. But even if classical time travel is possible, it is far from practical (thus the need for a practical alternative.)

Let’s explore the matter in a little more detail, beginning with the basics. Say you want to travel into the future. Congratulations — you’re doing it! One minute from now you will have moved exactly one minute into the future. But what good is that? It can hardly be called “time travel” (at least in the classical sense) if you don’t get to the future before everybody else. So the question is, is there any way to take a shortcut to the future?

Well, yes. As a matter of fact, there is.

Our universe will permit accelerated movement into the future. This is not just a hypothesis; it has been established through scientific observation. The theory of relativity allows for a phenomenon called time dilation, whereby increases in either gravity or velocity can cause time to “slow down” from the perspective of an observer exposed to the increase. Simply put, if you travel fast enough through space (or are exposed to a sufficiently strong gravitational field), you will move into the future more rapidly than individuals who have not attained the same speed or experienced the same level of gravity.

An astronaut  on the International Space Station is traveling at a high velocity, roughly 17,000 miles per hour. However, even a very long exposure to such velocity in space provides only a subtle, measurable-but-not-noticeable, boost in speed through time. An astronaut who spends several months on the ISS will travel a small fraction of a second into the future relative to those of us here on Earth.

What good is a trip a fraction of second into the future? Of course, that’s for the individual time traveler to decide. If you were that astronaut, you would experience arriving at the same moment that everybody else is experiencing back on earth, only having taken a tiny bit less time to get there than everyone else did. There would be no perceptible difference — you would have traveled into the future without experiencing anything out of the ordinary.

If it were me, I would feel cheated. I’m just saying.

So while there are without a doubt many good reasons to spend some time on the ISS if you’re so inclined and if the opportunity presents itself, I personally would not go just for the time travel. Your mileage may vary. Unfortunately, your experience of time dilation won’t vary from what’s predicted by the theory of relativity. That’s the problem.

To be sure, faster and more powerful spacecraft will one day achieve much greater speeds than anything available today. Eventually there will be spaceships that fly so fast they will effectively be timeships, propelling their passengers vast distances through space and at least some moderate distance through time.

Imagine a spacecraft that can travel at 99% of the speed of light, or roughly 40,000 times faster than the ISS. Suppose you took a 10-year trip on such craft. When you returned from the trip, you would be 10 years older. From your point of view, 10 years have passed. But from the point of view of everyone you left behind, 70 years have passed.

Now we’re getting somewhere. The craft you flew in is not only a spaceship, it’s a time machine — one that has propelled you 60 years into the future.

That’s not bad, but it will most likely be decades or longer before we see such craft. And unless things are very different in the future,we will have about as much chance of taking a long trip on one of these vessels as we currently do spending six months on the ISS.

That is to say, not much.

The gravity option is worse. Yes, exposure to a strong gravity field can push you forward in time, but there are a couple of problems:

1. A gravity field strong enough to provide a noticeable time-travel effect is also strong enough to crush you many times over — which takes some of the fun out of the whole experience.

2. In order to get to a body that can provide that kind of gravitational field, you’re going to have to take a long voyage through space, meaning once again that you’re going to need one of those yet-to-be-invented high-powered spacecraft that we were just saying you’ll most likely never get to use.

As it stands today, moving rapidly through space is the most practical and relatively “near-term” method for achieving classical time travel. And, as we have observed, it is neither particularly practical or near-term. Moreover, so far we’re talking about travel into the future in isolation. In most of the really fun time travel stories, movement through time is bi-directional. You travel forward into the future and then take a trip back in to the past to arrive at the original “present” you started from. Or as I mentioned earlier, you travel back in time and then later move ahead into the future, once again to get back to the present. But time dilation only works in one direction. Once you get to the future, you’re there — unless you decide to fire up your rocket and travel even further into the future. But there is no getting back to the present — which wouldn’t be the “present” any more anyway; the present would come along with you on the trip. Your old “present” would now be the past. (Obviously. That’s what always happens to your old present, when you think about it.)

The are other possible ways of traveling through time, methods that may work one day, and that may even provide bi-directional movement through time, but these will require extremely advanced  technology to achieve.

Most such models — which unlike time dilation are all theoretical, hypothetical, or otherwise unsubstantiated by any real-world testing or demonstration — rely on the creation of one or more wormholes in space.

Wormholes are theoretical structures that enable instantaneous travel through both space and time. There are no proven ways to create a wormhole, and even their hypothetical construction involves the implementation of technologies so advanced and exotic that they challenge the imagination. I’m confident that such technologies will one day exist, and that eventually we will have true “time machines” in the classical sense of the term. But the challenges that need to be overcome to get us there are many. And big.

Huge, in fact.

And the wait will likely be very long indeed.

On the other hand, the major challenges to Practical Time Travel are conceptual. We need to change our thinking about time. We need to come to a fuller understanding of what time is and what we truly experience when we move through it. That’s where we will pick it up next time.

(Image via Wikimedia Commons.)

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