Quantum physics: Is time travel theoretically feasible?

No

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by John Traveler

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Of all the attributes which define the universe we find ourselves in, time presents us with the most perplexing of issues. Some will suggest that time does not exists while others propose that it is a medium that can be exploited for voyage into time already past and to the future as well. No one has yet proposed any theoretical notion of how time travel in any physical sense might be facilitated, and therefore it remains but a whimsical human fantasy. But such fantasies have often in the past become the substance upon which profound realities have been erected.

Until 1905, time was thought pretty much to be a constant, but a young graduate student in theoretical physics discovered through rational induction some awesomely new perceptions about time. His name of course was Albert Einstein and the notion that he would bring to us, was that time was not a constant but a variable. It was part of his theory of special relativity. Over the next forty years, as Einstein's notions became better understood, the idea of time dilation evolved in the minds of some humans into a conceptual status which supported the idea of time travel. You would not find any mention of the concept in respected journals of physics, but realized instead on the pages of comic books and dime store novels. Here in the repository of fictional possibilities, one could find realities of every conceivable notion. Super heroes, ray guns, spaceships and machines which could transport mortal humans between different dimensions of time.

Some early novels like Mark Twain's 1889 novel, "A Connecticut Yankee in King Arthur's Court" by Mark Twain" presuppose the essence of time travel, but offered no concept of its mechanism. In 1895, the British author, made most famous for his War of the Worlds, wrote a novel titled "The Time Machine," which introduced for the first time the idea of a vehicle which could transport its occupants back in time. The author envisions time as a fourth dimension, an astute observation for sure, but he provides little explanation of the principle upon which his machine facilitates temporal transport. Is it possible that some thoughts about time could have been fashioned in the mind of a young Albert Einstein, through reading books like Well's Time Machine? Perhaps. In 1960, H.G. Wells novel the Time Machine was adapted for the big screen, and if time travel was not already a subject of intrigue in the minds of many baby boomers, it soon would be. Indeed, in 1966, Irwin Allen, brought the concept of time travel to every TV screens across America with the show "The Time Tunnel." The show lasted only two seasons but in the minds of many of the baby boomers who absorbed it, the idea of time travel became common place.

So, by the mid 1960's the concept of time was well established as a fictional reality, but could it also be a true physical reality? Did Einstein's theories of special and general relativity open the door to a practical conceptualization of temporal transparency? Anyone with even an elementary understanding of special and general relativity might conclude that the curvature of space time would permit passage through a sort of temporal membrane from one instant to another, either forward or backward. But one proverbial fly in the ointment of this perception would come to light in 1943, and is referred to as the "grandfather paradox." We have novelist Ren Barjavel to thank for this bit of logical extrapolation in his book "The Imprudent Traveler." The paradox simply put states: if you were to go back in time and kill your own grandfather, then how could you ever have existed in the first place. If this paradox did not eliminate the possibility of mobilization into the past, it certainly complicated the issue.

But there may be some other physical ramifications which call into question altogether the feasibility of time travel. This quandary comes to us not from science fiction nor logical speculations, but through a perception of quantum mechanics called the uncertainty principle. In 1905, Einstein had obliterated Isaac Newton's notion that time was absolute, and in so doing redefined the fundamental precepts of physics. In 1927, Einstein's good friend and colleague, Werner Heisenberg, would do no less. Heisenberg's notion of quantum uncertainty represented that it would be impossible to know the precise position of a particle like a photon or electron, and its momentum (given that momentum is a factor of velocity times mass) at the same instant in time. This principle in a way of looking at it suggested a flaw in Einstein's handiwork with respect to relativity which from Einstein's perspective was not acceptable. Einstein believed that there were no random possibilities, as he put it "God does not play dice with the universe."

But suppose for a moment that Einstein was wrong, and in fact there was and is a component of randomness which governs order in the universe. Consider that at any instant of time each particle of matter occupies a precise location of space time, and that the totality of the universe represents only instances of random order - like frames of a moving picture- that can never be reduplicated at any future instant in time. In essence each instant of time dissolves and is replaced by a new one. From the overall perspective time seems just like a movie but in reality it is simply a presumably perpetual status of separate instances. Now, considering that the quantum uncertainty principle suggests that it is impossible to predict exactly what the position and velocity of any particle in the universe is, it would therefor seem equally unfeasible under any circumstance to exactly recreate any random instantaneous existence of the universe. And yet, this is exactly what a time machine would have to do. To move forward and backward in time you would have to be able to position every particle in the entire universe in the exact position it occupied at any previous or future point in time and then be able to predict how far and in which direction each particle would move in the next or previous instant of time. The problem is that Heisenberg's principle of quantum uncertainty, in any physical sense of time travel, precludes any realization of its' possibility.

Thinking of this in more human terms, the atoms which constitute any being are constantly on the move and being exchanged by the billions every day. At any former or future instances in time the exact atoms which define a being in that instant are likely to have being somewhere else. Therefore, the reconstruction of any configuration of atoms in a different instant in time would be impossible, because it would require the same atoms to occupy two or more different positions in the universe at the same instant in time. This notion, would presuppose the existence of multiple universal dimensions, and while some minds can conjure up such, no evidence exists in reality which would support any rational consideration of it.

The question in this debate is whether time travel is theoretically possible, and presumably anything is, but in this case the stipulation confines us to consideration only of theoretical validity within the confines of the principles of quantum mechanics. Given this stipulation, and the forgoing contentions, the answer to this question must be NO.

REFERENECES AND FURTHER READING:

Walter Isaacsin, "Einstein his life and Universe", Simon and Schuster, 2007

Wikepedia, "Grandfather Paradox," Online: http://en.wikipedia. org/wiki/Grandfather _paradox
(H.G. Wells), "The Time Machine," Online:http://en.wik ipedia.org/wiki/The_ Time_Machine

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