The Problem with Time Travel

The Problem with Time Travel
Artists and scientists alike have contemplated time travel in one guise or another for centuries. Despite the many significant technological hurdles preventing time travel from becoming a reality, many theoretical physicist continue to speculate on how time travel may in fact be possible. It may just be a matter of time before human technologically stumbles upon the answer.

Perhaps some day the physics for transporting any type of matter through time may be possible, but in the mean time, I would like to perform a mental exercise about some of the related challenges of time travel, specifically the fundamental problems related to defining the destination parameters if time travel were possible.

For instance, suppose you were to develop a machine capable of transporting you through time based here on earth. All you hav to do is stand on a platform or inside the machine and it will wisk you off through time to whatever point you choose. You decide to set up your device and settle on transporting back in time six months from today's date. You set your device and transport yourself back in time exactly six months. What happens? Well, in the moments before your brain is sucked dry in the vacuum of space as you stare at a distant sun and even more distant planets with no sign of earth anywhere in sight, the last thought to cross you mind will probably be what went wrong? The answer of course is that nothing went wrong. You went back in time exactly six months to the date, which of course means the Earth is now exactly six months "away" from where you now occupy space in the universe. That is, the earth is now on the other side of the sun from your current physical location, the same locatoin in space from which you left. You moved through time, but you did not move through space.

Just because you are able to move through time itself does not mean that you are also moving through physical space. By going back six months, you appear in exactly the same location in the universe from which you left, and arrived at that location at a different time from when you left. If that period was six months, then the earth would be in its location around the sun six months prior to the date you left. Therefore your dead in this senerio.

How did this happen? The problem is never addressed in science fiction books or films, and seldom (to my surprise) by the theoretical science community. The assumption is that a person can move in both time and space, however, the sheer amount of energy it takes just to move great distances in three dimensions are already pretty incredible. How many more magnitudes of difficulty would it be to move in both time (which we can't do yet) and through space (planes, trains and automobiles) during the same event? Science Fiction always has the time travels appearing back in time, sometimes in completely different locations from where they left, without any difficulties related to the spacial location of the departing and arriving locations. In my opinion, the two are related. You may be able to depart in time, but not your location in the universe. You can leave your location in the universe, but only move linearly in time.

So if that's the case, the simple answer would seem to be only transporting in time in exact increments of 354.37 earth days at any given point. Aughh, but wait! There's more to the story. Our Sun is just one star among several hundred billion others that together make up the Milky Way Galaxy. Each star is itself moving. Any planet orbiting a star will share its motion through the Galaxy with it. In addition to the individual motions of the stars within it, the entire Galaxy is in spinning motion like an enormous pinwheel. Although the details of the Galaxy's spin are complicated (stars at different distances move at different speeds), we can focus on the speed of the Sun around the center of the Milky Way Galaxy. It takes our Sun approximately 225 million years to make the trip around our Galaxy. This is sometimes called our "galactic year". Since the Sun and the Earth first formed, about 20 galactic years have passed; we have been around the Galaxy 20 times. On the other hand, in all of recorded human history, we have barely moved in our long path around the Milky Way. Therefore, your physical location in the universe at your departing point in time will never be exactly the same physical location in the universe in the past or future. It may be possible to travel a few years, maybe even a hundred years, into the past or future because the movement of the earth in the space of the universe might be insignificant for that period. However, if you were standing on the flat surface of the earth and departed in time for exactly one year in the past from that days date, you may discover yourself either appearing inside or even above the earth by a few meters or more.

This does not necessarily mean time travel could not be accomplished from a vessel capable of travel in space. A space vessel with time travel capability could depart its location in time and arrive at nearly any point in the past with relatively little to be concerned about. Unless of course, it appeared when a meteor or asteroid was passing by that particular spatial location at that specific point in time. An extremely complex map of all known astronomical debris would be only the first necessary knowledge to safely travel back into time. I personally wouldn't want to be the first space vessel time travel crew traveling back in time to an unknown physical reality just to map the pasts debris.

But long before the complexity of a space based time travel vessel would be even thought of as being operational or even testable, some type of empirical data proving the validity of time travel would surely be required and in my opinion would most likely be earth based. As discussed, an individual may be able to travel a few years in time (in either direction), but much more than that, and the distances in the physical locations from the departure point and the arrival points in time are physically too far off to be done safely.

Some ideas that may be worth farther thought and mental exercise might include earth based time travel in the earths atmosphere, or in the earth's oceans. Most likely any atmosphere based time travel would require loud, obvious modern engines and travel much beyond when the devices were build would not be recommend if maintaining anonymity is high on your list.

Ocean based time travel may be a little more promising. In a submarine time travel vessel, there might be a little more forgiveness for the differences in spacial distances over time. A vessel departing at 100 meters depth in a deep, wide underwater trench measuring kilometers deep and wide could arrive in the past/future time with the offset in difference being absorbed by the massive ocean and a change of depth serving as a buffer zone. Several hundred meters in any direction of arrival would not be a problem. Of course underwater sea life could pose a difficulty, if say the submarine appeared inside a whale.

Bryan Beach
Baltimore, MD
Aug 26, 2008