X-Message-Number: 29715
From: "Basie" <>
Subject: Time travel now possible 
Date: Thu, 9 Aug 2007 13:28:48 -0400

Time travel could be possible ... in the future
By Roger Highfield, Science Editor
Last Updated: 7:01pm BST 08/08/2007

It may take more than a nuclear-powered De Lorean or a spinning police box, 
but time travel could actually be a possibility for future generations, 
according to an eminent professor of physics.

How the machine works
When would the rich and famous travel to?
Your view: Where would you go if you had a functioning time machine?
Prof Amos Ori has set out a theoretical model of a time machine which would 
allow people to travel back in time to explore the past.

Prof Stephen Hawking refutes the possibility of time travel
The way the machine would work rests on Einstein's theory of general 
relativity, a theory of gravity that shows how time can be warped by the 
gravitational pull of objects.

Bend time enough and you can create a loop and the possibility of temporal 

Prof Ori's theory, set out in the prestigious science journal Physical 
Review, rests on a set of mathematical equations describing hypothetical 
conditions that, if established, could lead to the formation of a time 
machine, technically known as "closed time-like curves."

In the blends of space and time, or spacetime, in his equations, time would 
be able to curve back on itself, so that a person travelling around the loop 
might be able to go further back in time with each lap.

In the past, one of the major challenges has been the alleged need for an 
exotic material with strange properties - what physicists call negative 
density - to create these time loops.

"This is no longer an issue," he told The Daily Telegraph.

"You can construct a time machine without exotic matter," he said.

It is now possible to use any material, even dust, so long as there is 
enough of it to bend spacetime into a loop.

Even though Prof Ori, of the Technion-Israel Institute of Technology, 
believes his new work strengthens the possibility of a real Tardis, he would 
not speculate on when a time machine would be built, or even if it would 
ever be possible.

"There are still some open questions."

The main remaining issue is the stability of space time, the very fabric of 
the cosmos, in time travel scenarios.

But overcoming this obstacle may require the next generation of theory under 
development, called quantum gravity, which attempts to blend general 
relativity with the ideas of the quantum theory, the mathematical ideas that 
rule the atomic world.

Time travel has long been a fascination, HG Wells grappled with the 
scientific issues in his 1895 science fiction classic, The Time Machine, Dr 
Who is still fighting the time war and Hollywood insisted all that was 
needed for time travel was a De Lorean and a good flash of lightning.

But more serious work on general relativity first raised the astonishing 
possibility of time travel in the 1940s.

In the half century since, many eminent physicists have argued against time 
travel because it undermines ideas of cause and effect to create paradoxes 
so that a time traveller could go back to kill his grandfather so that she 
is never born in the first place.

In 1990, the world's best known scientist, Prof Stephen Hawking proposed a 
"chronology protection conjecture", which flatly says the laws of physics 
disallow time machines.

Three years later, Prof Ori concluded that the possibility of constructing a 
time machine from conventional materials could not be ruled out.

Prof Hawking then fought back with his Cambridge University colleague 
Michael Cassidy and they concluded that time loops are extremely unlikely.

Tongue in cheek, Prof Hawking added that there is experimental evidence that 
time travel doesn't exist: "We have no reliable evidence of visitors from 
the future. (I'm discounting the conspiracy theory that UFOs are from the 
future and that the government knows and is covering it up. Its record of 
cover-ups is not that good.)"

But now, in Physical Review, Prof Ori has provided some more advanced 
solutions to the problems of time travel outlined by the likes of Prof 
Hawking, helping to realise an idea that dates back millennia and appears in 
18th century literature, Harry Potter, Dickens, sci-fi movies and much more 

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