The Possibility of Time Travel

by Sam Wass(Class of '06)

Time travel is the main theme in works of literature, H.G Wells The Time Machine and works of film, such as the “Back to the Future” series. But is time travel, the concept of physically moving backwards and forwards through time, actually possible? Some prevailing theories used to describe how the universe works, most notably Einstein’s special theory of relativity, do not forbid time travel. Einstein’s theory declares that relative to a stationary observer, time seems to pass more slowly for a faster moving body. For example, if a person were to observe a clock moving close to the speed of light, the movement of the hands on the clock would be so slow the observer would think that the clock was not working at all. Thus time is a totally relative concept, there is no possibility of their being a clock at the center of the universe by which everyone could set their watches. For an alien traveling at the speed of life, our lives on earth could be blink of an eye. Einstein’s theory could allow time travel because unlike Newton’s mechanics which treat gravity as a force, the general theory of relativity defines gravity as the movement of matter along the shortest space in a curved spacetime. Spacetime as a four dimensional model which combines three dimensional space with one dimensional time, a concept first designed by Hermann Minkowski.

Others believe that time travel could possible through manipulating worm holes, hypothetical topological features in spacetime which are possible through solutions in general relativity equations that are solved with substances of negative energy. A worm hole serves as a link between two distant points in spacetime. Hypothetically, with some exotic future technology one end of the worm hole would be accelerated to the speed of light and then brought back to its original location. Due to time dilation, the phenomenon where the observed time rate is different for two unique reference frames, the accelerated end would have experienced less time relative to the stationary end. This would mean that an object that enters the stationary end would come out in the past relative to the time it entered. A significant limitation to this concept is that one can only travel as far back in time as the initial creation for the technology and thus the technology itself cannot move backwards through time.

Many people believe that direct travel into the past is impossible because of the paradoxes that arise. For example imagine if a person were to travel back in time and kill his grandfather. This would mean that he would have never been conceived and thus would not have been able to travel back in time in the first place. Or consider a person who travels back in time a kills Adolf Hitler, thus preventing World War Two from occurring. This person would have gone back in time with the intent of killing Hitler, but if he were to kill Hitler then he would not be able to have the intention of killing Hitler in the first place.

It is very fascinating to ponder what humans will learn on the nature of time travel in the next century to come. In 1895 Lord Kelvin state, “heavier than air flying machines are impossible”, but we now have technology to travel out of the earth’s atmosphere. Hopefully one day all of our questions about the way the world works will be answered.

References:
http://www.pbs.org/wgbh/nova/time/through.html
http://en.wikipedia.org/wiki/Time_travel#The_possibility_of_paradoxes
http://en.wikipedia.org/wiki/Time_travel
http://science.howstuffworks.com/time-travel.htm