*Einstein's fibre optics (Image:
Gregor Schuster/Getty)*

Predicted by Einstein's general theory of relativity, wormholes are tunnels
connecting two points in space-time. If something could traverse one, it would
open up intriguing possibilities, such as time travel and instant
communications.

But
there's a problem: Einstein's wormholes are notoriously unstable, and they don't
stay open long enough for anything to get through. In 1988, Kip Thorne at the
California Institute of Technology and his colleagues speculated that wormholes
could be kept open using a form of negative energy called
Casimir energy.

Quantum mechanics tells us that the vacuum of space-time is teeming with random
quantum fluctuations, which create waves of energy. Now imagine two metal plates
sitting parallel in this vacuum. Some energy waves are too big to fit between
the plates, so the amount of energy between them is less than that surrounding
them. In other words, space-time between the plates has negative energy.

Slow
collapse

Theoretical attempts to use such plates to keep wormholes open have so far
proved untenable. Now Luke Butcher at
the University of Cambridge may have found a solution.

"What
if the wormhole itself could take the place of the plates?" he says. In other
words, under the right circumstances, could the tube-like shape of the wormhole
itself generate Casimir energy? His calculations show that if the wormhole's
throat is orders of magnitude longer then the width of its mouth, it does indeed
create Casimir energy at its centre.

"Unfortunately, this energy isn't enough to keep the wormhole stable. It will
collapse," says Butcher. "But the existence of negative energy does allow the
wormhole to collapse very slowly." Further rough calculations show that the
wormhole's centre might remain open long enough to allow a pulse of light to get
through.

A
wormhole is a shortcut
through space-time, so sending a light pulse through one could allow
faster-than-light communication. And as the two mouths of a wormhole can exist
at different points in time, in theory a message could be sent through time.

Butcher cautions that a lot more work is needed to confirm that other parts of
the wormhole besides the centre remain open long enough for light to make it all
the way through. He also needs to work out whether a pulse large enough to
transmit meaningful information could sneak through the slowly collapsing
throat. And, of course, we are a long way off translating the theoretical
equations into a physical object.

"Does
this mean we have the technology for building a wormhole?" asks Matt Visser at
the Victoria University of Wellington in New Zealand. "The answer is still no."
Still, he is intrigued by Butcher's work. "From a physics perspective, it may
revitalise interest in wormholes."

Reference: arxiv.org/abs/1405.1283v1

**
Source: New Scientist URL:
http://www.newscientist.com/article/dn25596-skinny-wormholes-could-send-messages-through-time.html#.U3wawdIW3mU
**