Paradox lost
Marcus Chown
QUANTUM THEORY may be losing its mystery. A physicist has shown how the bizarre
behaviour of the quantum world could arise from time warps that are created as
particles interact.
Myriad strange things happen in the quantum world. For instance, the properties
of a subatomic particle, such as its position and momentum, hover in fuzzy
superpositions of various states until the moment they are measured, at which
point they become certain.
But why does a measurement have this effect? Physicists have come up with many
speculative ideas, for instance, that the transition from uncertainty to
certainty somehow arises out of the interaction of the particle with a measuring
instrument, or even with human consciousness itself.
Mark Hadley, a physicist at the University of Warwick, claims he has cracked the
puzzle by drawing on Einstein's suggestion that particles might be tiny warps in
space. Hadley has developed this idea, treating particles as warps or kinks in
space-time called "geons".
Inside a geon, time could loop back on itself, allowing a particle to be
influenced by events in its future as well as its past. In earlier work, Hadley
has shown how this could lead directly to all quantum weirdness--from the
strange indeterminacy of properties like a particle's position and momentum to
the ghostly link between particles that are separated by large distances ("All
the world's a time machine", New Scientist, 7 March 1998, p 38).
Now Hadley says he has shown that the interaction of one geon with another can
constitute a quantum measurement. In a forthcoming issue of the International
Journal of Theoretical Physics, he points out that such an interaction must
involve a change in the shape, or topology, of space-time. For instance, when a
particle and its antimatter counterpart come together and annihilate to leave no
particles, space-time containing two knots transforms into space-time that is
flat.
Such changes would create the time loops needed to generate strange quantum
effects. Imagine a circle of space-time distorting to become two circles. When
this occurs, a timeline inevitably loops back on itself (see Diagram).
"Measurement is simply an abrupt change in the topology of space-time," Hadley
concludes. "The peculiar thing that happens to time when particles interact is
exactly what is needed to create all quantum weirdness."
"Hadley's work is quite a nifty way to show how weird and wacky things in
quantum measurement theory can be explained in a classical context," comments
Jonas Mureika, a physicist at the University of Toronto. But he urges caution
when playing games with time. "My question is: where does one draw the line? If
the direction of time can change on a quantum scale, why can't it change in the
large-scale Universe?"