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SOME physicists believe that the Universe may contain wormholes, ‘tunnels’
in the fabric of space-time which provide a shortcut between far-flung parts
(see ‘Wormholes, time travel and quantum gravity’, New Å®ÉúСÊÓƵ, 28 April).
But wormholes do not have to be large.

Matt Visser, of Washington University, St Louis, Missouri, has studied
tiny wormholes, which might be produced on a sub-atomic scale by quantum
fluctuations in the energy of the vacuum. According to Visser, these quantum
wormholes change our picture of the ‘origin’ of the Universe in the big
bang.

Wormholes have some bizarre properties. For example, ‘macroscopic’ tunnels
– that is, ones large enough to travel through – open up the possibility
of time travel. Quantum wormholes could also allow the creation of entire
‘baby universes’ that bud off from our own space-time, like little bubbles
pinched off from the surface of a balloon.

Time travel is an uncomfortable thing for physicists to live with because
of the paradoxes that rear their ugly heads in a universe where it is permitted.
Visser has set out to study quantum wormholes that do not permit time travel.

Visser finds that time travel is made impossible only if ‘transient’
wormholes are forbidden. Also, any baby universe that forms must retain
its connection with our space-time, through a tiny umbilical wormhole (Physical
Review D, vol 41, p 1116).

However, Visser finds that permanent wormholes on this submicroscopic
scale are allowed. They might be threaded by loops of magnetic flux (or
other fields), giving them the appearance of magnetic monopoles, or charged
particles. Physicists have been looking for magnetic monopoles for a long
time because they carry a single magnetic pole.

The wormhole picture changes our view of the ‘origin’ of the Universe
in a big bang, which is now seen simply as the event corresponding to our
Universe branching off from the greater ‘multiverse’, to which we must still
be connected by an umbilical wormhole. The multiverse can be visualised
as an infinite froth of interconnected bubbles. According to Visser, ‘the
big bang has nothing to do with questions of the ultimate origin of the
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