|The Science of Time Travel and its Humanistic Implications|
Why is the Notion of Time Travel Important?
In his book, A Brief History of Time, Stephen Hawking records the changes in our perception of the universe from a time when humans were trying to appease invisible gods who were said to populate relief forms, celestial bodies, and natural objects over Laplace's scientific determinism at the beginning of the 19th century to the uncertainty principle of quantum mechanics in our present time. As Hawking observes, the task of modern science has been redefined to discover "laws that will enable us to predict events up to the limits set by the uncertainty principle." If our future seems to be well taken care of, our past, that is, the initial configuration of the universe is still a riddle: "How or why" - asks Hawking in the same place - "were the laws and the initial state of the universe chosen?" While Laplace leaves these laws entirely to God, Einstein leaves his famous question: "How much choice did God have in constructing the universe?" for the next generations to answer. (Rather frustrated generations, too, if we take into consideration Kip Thorne's title Black Holes and Time Warps - Einstein's Outrageous Legacy). Nevertheless, it seems that, in a temporal sense, science is able to generate responses for our metaphysical quests.
If time travel were possible, it would provide us with the key to the secret door: the existence of God, the emergence of human civilization, and our purpose on earth would perhaps become clear. We could, as the poet William Blake said, "hold infinity in the palm of [our] hand/and eternity in an hour." Made possible, time travel would have an immense humanistic impact on all branches of science and humanities. Will we ever come into the possession of this key?
"If we were to place a living organism in a box, one could arrange that the organism, after an arbitrarily lengthy flight, could be returned to its original spot in a scarcely altered condition, while corresponding organisms, which had remained in their original positions, had long since given way to new generations. So far as the moving organism was concerned the lengthy time of the journey was a mere instant, provided the motion took place with almost the speed of light."
For the passengers of the space ship, time would have become frozen. This phenomenon is termed time dilation, and it has negated our conventional understanding of time as a leisurely-flowing stream. As Macvey points out, such "relativistic travel" can theoretically take place only into the future, and not into the past. As time is being stretched, space is being compressed.
To cause time to freeze, one would need an intense gravitational field, which can be found at the margins of what is popularly called a black hole. The main difficulty consists in finding such a hole - as far as scientists are presently aware, they lie at remote distances from our Solar System. Despite theoretical optimism, we seem caught here in a practical conundrum, since time, interstellar, or intergalactic travel through a black hole presupposes employing travel at relativistic velocities to a black hole in the first place. The following section optimistically ignores technical details and describes the possibility of traveling between two universes.
"When we are confronted by black holes, Einstein-Rosen bridges, and time dilation, we are being asked to deal with phenomena that are totally out of accord with the universe we understand -- or think we understand. We cannot visualize them - only accept them. Until someone improves upon or replaces Einstein's General theory of Relativity - and at present this seems highly improbable - there is no alternative. If rotating singularities exist, and there is increasing reason to accept that they do, then the possibility of time travel, including travel into the past, has to be accepted, however fantastic it may seem."
Except for technological restrictions, maybe the most serious impediment in the way of time travel resides in our incapacity to find solutions outside the realms of our limited universe. It seems that we are caught in a vicious circle - we cannot really know our universe until we are able to escape it, while, at the same time, we are cannot escape it until we know it sufficiently.
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