Time Travel

In 1895, H. G. Wells classic story The Time Machine was first published in book form. Wells wrote, in The Time Machine, that "there is no difference between Time and any of the three dimensions of Space, except that our consciousness moves along it". From that point on man wondered about the possibility of time travel. So is time travel possible? If so, how? If we could do it, would we or should we? What problems might arise? First off, the answer to the first question is simple. Yes time travel is possible. We do it every day. Our best understanding of time comes from Einstein's theories of relativity. Prior to these theories, time was widely regarded as absolute and universal, the same for everyone no matter what their physical circumstances were. In his special theory of relativity, Einstein proposed that the measured interval between two events depends on how the observer is moving. For example suppose that Sally and Sam are twins. Sally boards a rocket ship and travels at high speed to a nearby star, turns around and flies back to Earth, while Sam stays at home. For Sally the duration of the journey might be, say, one year, but when she returns and steps out of the spaceship, she finds that 10 years have elapsed on Earth. Her brother is now nine years older than she is. Sally and Sam are no longer the same age, despite the fact that they were born on the same day. This example illustrates a limited type of time travel. In effect, Sally has leaped nine years into Earth's future. The effect known as time dilation, occurs whenever two observers move relative to each other. In daily life we don't notice these time warps, because the effects are only noticable when the motion occurs at close to the speed of light. Even at aircraft speeds, the time dilation in a typical journey is just a few nanoseconds. However, atomic clocks are accurate enough to record the shift and confirm that time really is stretched by motion. So travel into the future is a proved fact, even if it has so far been in small, unexciting amounts.
So time travel into the future is easy. But the main question we are concerned about is the past. As far as Einsteins theory of relativity tells us, there is no law that would prevent us from traveling into the past. The first problem is building a machine. In Scientific American Special Edition, Paul Davies tells us of one possible “machine” to the past. In 1974 Frank J. Tipler of Tulane University calculated that a massive, infinitely long cylinder spinning on its axis at near the speed of light could let astronauts visit their own past, again by dragging light around the cylinder into a loop. In 1991 J. Richard Gott of Princeton University predicted that cosmic strings--structures that cosmologists think were created in the early stages of the big bang--could produce similar results. With only these two proposals one may begin to think that time travel to the past is impossible. For example, how can you build an infinitely long cylinder? But in the mid-1980s the most realistic scenario for a time machine was proposed, based on the concept of a wormhole.
In science fiction, wormholes are sometimes called stargates; they are a shortcut between two widely separated points in space. Jump through a wormhole, and you might come out moments later on the other side of the galaxy. Wormholes are part of the general theory of relativity, because gravity warps not only time but also space.
With this theory, time travel to the past could be possible if a stable wormhole could be created and towed to desired spot.
But this does not answer the question whether or not time travel should be done. For example lets say that somehow one of the previously mentioned devises could be built, this causes some major paradoxes. For example what if a man where to travel back in time and meet his grandfather and kill him. That means that the man never would have been born to begin with so how would he have gone back in time to kill his grandfather if he where never born? Or lets say a man travels to the future and learns a new mathematical theorem, he then travels back in time and teaches it to a student who at a future date publishes that theorem, which is the same one that the man read in that future date. So where did the information come from?
Situations like this have led many scientists to believe that there is some undiscovered law that would forbid time travel to the past.
Thus far we have discussed physical time travel, But as mentioned earlier. Wells wrote, in The Time Machine, that "there is no difference between Time and any of the three dimensions of Space, except that our consciousness moves along it". There is a movie called somewhere in time. In this movie the main actor goes back in time buy making himself believe that he is. At first thought this seems very absured. But so did Wells book in 1895. What if time is not at all how we think of it? What if all of our minds are somehow connected to time and space? If time and the measuring of it is connected to our thoughts. We know so little about the human brain. Perhaps the key to time travel lies in concoring the human brain.
That recollection of a specific moment, called episodic memory separates people from animals--at least according to some scientists. Thomas Suddendorf of the University of Queensland in Brisbane, Australia, for example, has argued that evidence so far only shows that people can whoosh back to an instant in their memories or ahead to an imagined Sure in a process sometimes called mental time travel. ABSTRACT. This article contains the argument that the human ability to travel mentally in time constitutes a discontinuity between ourselves and other animals. Mental time travel comprises the mental reconstruction of personal events from the past (episodic memory) and the mental construction of possible events in the future. It is not an isolated module, but depends on the sophistication of other cognitive capacities, including self-awareness, meta-representation, mental attribution, understanding the perception-knowledge relationship, and the ability to dissociate imagined mental states from one's present mental state. These capacities are also important aspects of so-called theory of mind, and they appear to mature in children at around age 4. Furthermore, mental time travel is generative, involving the combination and recombination of familiar elements, and in this respect may have been a precursor to language. Current evidence, although indirect or based on anecdote rather than on systematic study, suggests that nonhuman animals, including the great apes, are confined to a "present" that is limited by their current drive states. In contrast, mental time travel by humans is relatively unconstrained and allows a more rapid and flexible adaptation to complex, changing environments than is afforded by instincts or conventional learning. Past and future events loom large in much of human thinking, giving rise to cultural, religious, and scientific concepts about origins, destiny, and time itself.



Davies, Paul1
Source:
Scientific American Special Edition; Feb2006 Special Edition, Vol. 16 Issue 1, p14-19, 6p, 1 chart, 1c
Document Type:
Article
WHERE'D I PUT THAT? (cover story) By: Milius, Susan. Science News, 2/14/2004, Vol. 165 Issue 7, p103-105, 3p, 3c; (AN 12261055)Notes: Print Journal Held Locally, Call Number Q1.S76, 1978 to present
Genetic, Social & General Psychology Monographs; May97, Vol. 123 Issue 2, p133, 35p