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Is Time Travel Possible?

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  • iammrparanormal
    Playing fast and loose with time: a new study suggests that time travel is not quite impossible. by William F. Allman Time travel has popped from the annals of
    Message 1 of 1 , Jun 29, 2008
      Playing fast and loose with time: a new study suggests that time
      is not quite impossible.

      by William F. Allman

      Time travel has popped from the annals of science fiction into the
      realm of scientific respectability at least in theory, that is.

      By combining two well-established principles originally outlined by
      Albert Einstein nearly a century ago in his theories of relativity,
      three theoretical physicists have proposed a novel scheme that appears
      to permit a limited sort of time travel. The scientists' result is
      not antything close to a blueprint for building the sort of time
      machine that science-fiction heroes are forever leaping into to
      explore the lives of cave men or peek into the future. But it
      suggests that either Einstein's equations are wrong or that the
      universe is governed by some very different principles from what
      physicists have long assumed.

      The notion that the causes of an event taking place in the present
      could be eliminated by traveling into the past and changing history
      has always made physicists (not to mention stock speculators and
      newspaper publishers) squeamish about the idea of time travel;
      physicists have thus held that there must be laws that provide a kind
      of "cosmic censorship" that prevents moving through time, and thus any
      tampering with the sequence of events. Various theoreical scenarios
      for time travel have been cooked up in the past, but in each case
      physicists have found physical laws that blocked it.

      The new study, however, appears not to violate any known physical
      laws. "We're asking, if you take Einstein's equations far enough,
      will they get you in trouble?" says Michael S. Morris of the
      University of Wisconsin, one of the co-authors of the new study.
      "We're suggesting that maybe they will, because at some level we may
      have to abandon either Einstein or causality"-the' basic principle of
      physics that one event

      Time flies. The authors' hypothetical time "machine" starts with
      Einstein's famous, and apparently paradoxical, discovery that time is
      not constant throughout the universe, but rather varies depending on
      the velocity at which the timekeeper is traveling. While to an
      astronaut, a clock on board a speeding spaceship will appear to tick
      at a normal rate, to a stationary observer on Earth, the clock will
      appear to be marking time very slowly. This apparent slowing of time
      applies not only to clocks but to everything in the spaceship,
      including the astronauts, and has given rise to what is known as the
      "twin paradox": When the speeding astronaut returns to Earth, he will
      have aged less than a twin brother he left behind. This bizarre
      time-slowing effect has been demonstrated by researchers who
      synchronized two highly accurate atomic clocks and then flew one of
      the pair aboard a high-speed jet for hours. When the two clocks were
      reunited, the airborne clock had fallen slightly behind its stationary

      The second Einsteinian principle that goes into the time machine is
      the warping of space by gravity. This idea is often explained by
      analogy to a worm crawling over a sphere. To the worm, the world is
      flat. Crawling from one spot on the sphere to another in what seems
      to be a straight line, the worm doesn't realize that it is actually
      tracing out a path that curves in three-dimensional space to follow
      the sphere's contour. The worm also doesn't realize that it could
      take a shortcut by burrowing through the core of the sphere.
      Similarly, what appears to us as three-dimensional space is, according
      to Einstein's theory of relativity, bent in dimensions that we cannot
      easily imagine, and a "wormhole" could connect two seemingly distant
      points in space.

      To turn a wormhole into a time machine, say the physicists,
      technicians in some "arbitrarily advanced" civilization could harness
      the gravitational forces necessary to make one end of the hole move
      back and forth at extremely high speed while keeping the other end
      stationary. Like the astronaut in the twin paradox, this rapidly
      moving end of the its stationary counterpart. By entering the "older"
      end of the wormhole and coming out the "younger" end, a person could
      theoretically travel from the present to the past.

      Keeping the door open. While the physicists' calculations suggest
      there's nothing to prevent all this from happening, they admit that no
      one has actually ever seen a wormhole. Calculations by Morris and
      co-authors Kip Thorne and Ulvi Yurtsever of the California Institute
      of Technology imply that a wormhole can be kept open only under some
      strange and exotic physical conditions. Phenomena that under normal
      circumstances exist only in infinitesimally small particles for
      infinitesimally short periods of time would have to exist throughout
      the wormhole for as long as it remained open.

      Even if a wormhole time machine were possible, it wouldn't permit the
      kind of time travel fancied by H. G. Wells and others who have mused
      on the possibility of traveling far into the past or future. Even
      though members of an advanced civilization might be able to cause one
      end of a wormhole to age less slowly than the other, at best they
      would only be able to make time stand still at the instant the tunnel
      was created, not move it back any further into the past, and they
      couldn't move the other end ahead into the future.

      There's at least some circumstantial evidence that the more
      far-reaching kind of time machines envisioned by sciencefiction
      writers will never be created, even by the most technologically
      advanced civilization imaginable. If such a machine were ever to be
      built, a traveler from the future probably would already have shown up
      here by now.
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