1) Researchers at the Israel Institute of Technology have published a paper outlining a theoretical model for a time machine that overcomes some of the theoretical obstacles. 2) The model proposed by Professor Amos Ori involves a region of standard positive density material within a vacuum space, avoiding the need for hypothetical negative density material. 3) While the model solves some problems, Professor Ori acknowledges that significant challenges remain and the technology to control gravity at this level may never exist.

1. Time machine Theory: a sTep forward in
Travelling backwards?
From H.G Wells' classic novel to Bill and Ted’s Excellent
Adventure, the popular imagination has long been
enthralled by the prospect of time travel. Now
researchers at the Israel Institute of Technology,
Techion, have released a paper outlining theoretical
advances that could one day assist in liberating the
notion of a time-machine from the realms of pure science
fiction. The research by Prof. Amos Ori of the Technion’s
Faculty of Physics centers around a new model of space-
time that overcomes some (but not all) of the theoretical
stumbling blocks that would prevent the required
curvature of space-time needed to facilitate time travel.
The paper entitled “A Class of Time-Machine Solutions
with a Compact Vacuum Core” was published recently in
the scientific journal Physical Review and in it Prof. Ori
posits theoretical model for space-time that could
develop into a time machine.
“In order to travel back in time, the spacetime structure
must be engineered appropriately,” explains Prof. Ori.
“This is what Einstein’s theory of general relativity deals
with. It says that spacetime can be flat. That is – it has a
trivial, simple structure. But it can also be curved with
various configurations. According to the theory of

2. relativity, the essence of gravitational fields is in the
curving of spacetime. The theory of relativity also
defines how space is curved and how this curvature
develops over time.”
Einstein was a genius for good reason, and consequently
the idea of space-time is a very difficult concept to get
your head around. One analogy that’s often used is to
imagine a bowling ball resting on a large trampoline – if
the bowling ball is the sun, the sagging trampoline is akin
to space-time and a smaller ball will roll around it the way
the earth does. Thus gravity is really just a result of the
warping of the fabric space-time. This doesn’t really
explain how time gets involved in the equation, but
suffice to say that the idea of time travel involves
bending this fabric back on itself and somehow
connecting two different points to make travel between
present and past possible. Wormholes are seen as one
potential way to achieve this.
Prof. Ori’s model solves some of the problems associated
with theoretically achieving this bending of space-time.
One such problem is the belief that material with
“negative density” (it isn’t even clear whether this
actually exists in the quantities required) would be
necessary for the creation of a time-machine. Prof. Ori’s
theoretical model proposes a vacuum space that contains
a region field with standard positive density material and
therefore by-passes this problem.

3. “The machine is spacetime itself,” he explains. “Today, if
we were to create a time machine – an area with a warp
like this in space that would enable time lines to close on
themselves – it might enable future generations to return
to visit our time. We, apparently, cannot return to
previous ages because our predecessors did not create
this infrastructure for us.”
This final point means that – unless some ancient
civilization built a time machine or such a phenomena
somehow exists in nature – there is no way to go back in
time beyond the point at which the time machine was
constructed, even in theory.
Prof. Ori does not pretend that we yet have the
technology to control gravitational fields at will and
admits that a number of “non-trivial open questions”
remain unanswered… and indeed might remain that way
for ever.