PARALLEL UNIVERSES PROOF BOOSTS TIME TRAVEL HOPES:
“Science
fiction looks closer to becoming science fact, reports Roger Highfield:
Parallel Universes really do exist, according to a mathematical
discovery by ‘Oxford Scientists’ that sweeps away one of the key objections to the mind boggling and controversial idea.
The
work has wider implications since the idea of Parallel Universes
sidesteps one of the key problems with Time Travel. Ever since it was
given serious lab cred in 1949 by the great logician Kurt Godel, many
eminent physicists have argued against Time Travel because it
undermines ideas of cause and effect to create paradoxes: a Time
Traveller could go back to kill his grandfather so that he is never
born in the first place.
But the existence of Parallel Worlds offers a way around these troublesome paradoxes, according to ‘David Deutsch of Oxford University’,
a highly respected proponent of quantum theory, the deeply
mathematical, successful and baffling theory of the atomic world. He
argues that Time-Travel shifts between different branches of reality,
basing his claim on Parallel Universes, the so-called “Many-Worlds”
formulation of Quantum theory.
The new work bolsters
his claim that quantum theory does not forbid Time Travel. “It does
sidestep it. You go into another universe,” he said yesterday, though
he admits that there is still a way to go to find schemes to manipulate
space and time in a way that makes time hops possible. ”Many Sci-fi
authors suggested Time Travel paradoxes would be solved by Parallel
Universes but in my work, that conclusion is deduced from quantum
theory itself”, Dr Deutsch said, referring to his work on Many Worlds.
The
mathematical idea of Parallel Worlds was first glimpsed by the great
Quantum pioneer, Erwin Schrodinger, but actually published in 1957 by
Hugh Everett III, when wrestling with the problem of what actually
happens when an observation is made of something of interest - such as
an electron or an atom - with the intention of measuring its position
or its speed. In the traditional brand of quantum mechanics, a
mathematical object called a wave function, which contains all possible
outcomes of a measurement experiment, “collapses” to give a single real
outcome.
Everett came up with a more audacious
interpretation: the universe is constantly and infinitely splitting, so
that no collapse takes place. Every possible outcome of an experimental
measurement occurs, each one in a Parallel Universe.
If one accepts Everett’s interpretation, our universe is embedded in an infinitely larger and more complex structure called the (M-Theory)
‘Multiverse’, which as a good approximation can be regarded as an
ever-multiplying mass of Parallel Universes. Every time there is an
event at the quantum level - a radioactive atom decaying, for example,
or a particle of light impinging on your retina - the universe is
supposed to “Split” into different universes. A motorist who has a near
miss, for instance, might feel relieved at his lucky escape.
But
in a Parallel Universe, another version of the same driver will have
been killed. Yet another universe will see the motorist recover after
treatment in hospital. The number of alternative scenarios is endless.
In this way, the “Many Worlds” interpretation of quantum mechanics
allows a time traveller to alter the past without producing problems
such as the notorious grandfather paradox. But the “Many Worlds” idea
has been attacked, with one theoretician joking that it is “cheap on
assumptions but expensive on universes” and others that it is
“repugnant to common sense.”
Now new research
confirms Prof Deutsch’s ideas and suggests that Dr Everett, who was a
Phd student at Princeton University when he came up with the theory,
was on the right track. Commenting in New Scientist magazine, Prof Andy
Albrecht, a physicist at the University of California, Davis, said of
the link between probability and Many Worlds: “This work will go down
as one of the most important developments in the history of science.”
Quantum
mechanics describes the strange things that happen in the subatomic
world - such as the way photons and electrons behave both as particles
and waves. By one interpretation, nothing at the subatomic scale can
really be said to exist until it is observed. Until then, particles
occupy nebulous “superposition” states, in which they can have
simultaneous “up” and “down” spins, or appear to be in different places
at the same time. According to quantum mechanics, unobserved particles
are described by “wave functions” representing a set of multiple
“probable” states. When an observer makes a measurement, the particle
then settles down into one of these multiple options.
But
the Many Worlds idea offers an alternative view. Dr Deutsch showed
mathematically that the bush-like branching structure created by the
universe splitting into parallel versions of itself can explain the
probabilistic nature of quantum outcomes. This work was attacked but it
has now had rigorous confirmation by David Wallace and Simon Saunders,
also at Oxford. Dr Saunders, who presented the work with Wallace at the
Many Worlds at 50 conference at the Perimeter Institute for Theoretical
Physics in Waterloo, Canada, told New Scientist: “We’ve cleared up the
obscurities and come up with a pretty clear verdict that Everett works.
It’s a dramatic turnaround and it means that people now have to discuss
Everett seriously.”
Dr Deutsch added that the work
addresses a three-century-old problem with the idea of probability
itself, described by one philosopher, Prof David Papineau, as a
scandal. “We didn’t really know what probability means,” said Dr
Deutsch. There’s a convention that it’s rational to treat it for most
purposes as if we knew it was going to happen even though we actually
know it need not. But this does not capture the reality, not least the
0.1 per cent chance something will not happen. “So,” said Dr Deutsch,
“the problems of probability, which were until recently considered the
principal objection to the otherwise extremely elegant theory of
Everett (which removes every element of mysticism and double-talk that
have crept into quantum theory over the decades) have now turned into
its principal selling point.”
