IF YOU COULD LIFT A CORNER of the veil that shrouds reality, what
would you see beneath? Nothing but randomness, say two Australian physicists.
According to Reginald Cahill and Christopher Klinger of Flinders University in
Adelaide, space and time and all the objects around us are no more than the
froth on a deep sea of randomness.
Perhaps we shouldn't be surprised that randomness is a part of the Universe.
After all, physicists tell us that empty space is a swirling chaos of virtual
particles. And randomness comes into play in quantum theorywhen a particle
such as an electron is observed, its properties are randomly selected from a
set of alternatives predicted by the equations.
But Cahill and Klinger believe that this hints at a much deeper randomness.
"Far from being merely associated with quantum measurements, this
randomness is at the very heart of reality," says Cahill. If they are
right, they have created the most fundamental of all physical theories, and its
implications are staggering. "Randomness generates everything," says
Cahill. "It even creates the sensation of the 'present', which is so
conspicuously absent from today's physics."
Their evidence comes from a surprising quarterpure mathematics. In 1930, the
Austrianborn logician Kurt Gödel stunned the mathematical world with the
publication of his incompleteness theorem. It applied to formal systemssets
of assumptions and the statements that can be deduced from those assumptions by
the rules of logic. For example, the Greeks developed their geometry using a
few axioms, such as the idea that there is only one straight line through any
pair of points. It seemed that a clever enough mathematician could prove any
theorem true or false by reasoning from axioms.
But Gödel proved that, for most sets of axioms, there are true theorems
that cannot be deduced. In other words, most mathematical truths can never be
proved.
This bombshell could easily have sent shock waves far beyond mathematics.
Physics, after all, is couched in the language of maths, so Gödel's
theorem might seem to imply that it is impossible to write down a complete
mathematical description of the Universe from which all physical truths can be
deduced. Physicists have largely ignored Gödel's result, however.
"The main reason was that the result was so abstract it did not appear to
connect directly with physics," says Cahill.
But then, in the 1980s, Gregory Chaitin of IBM's Thomas J. Watson Research
Center in Yorktown Heights, New York, extended Gödel's work, and made a
suggestive analogy. He called Gödel's unprovable truths random truths.
What does that mean? Mathematicians define a random number as one that is
incompressible. In other words, it cannot be generated by an algorithma set
of instructions or rules such as a computer programthat is shorter than the
number. Chaitin defined random truths as ones that cannot be derived from the
axioms of a given formal system. A random truth has no explanation, it just is.
Chaitin showed that a vast ocean of such truths surrounds the island of
provable theorems. Any one of them might be stumbled on by accidentan
equation might be accidentally discovered to have some property that cannot be
derived from the axiomsbut none of them can be proved. The chilling
conclusion, wrote Chaitin in New Scientist, is that randomness is at the
very heart of pure mathematics (24 March
1990, p 44).
To prove his theorem, Gödel had concocted a statement that asserted that
it was not itself provable. So Gödel's and Chaitin's results apply to any
formal system that is powerful enough to make statements about itself.
"This is where physics comes in," says Cahill. "The Universe is
rich enough to be selfreferencingfor instance, I'm aware of myself."
This suggests that most of the everyday truths of physical reality, like most
mathematical truths, have no explanation. According to Cahill and Klinger, that
must be because reality is based on randomness. They believe randomness is more
fundamental than physical objects.
At the core of conventional physics is the idea that there are
"objects"things that are real, even if they don't interact with
other things. Before writing down equations to describe how electrons, magnetic
fields, space and so on work, physicists start by assuming that such things
exist. It would be far more satisfying to do away with this layer of
assumption.
This was recognised in the 17th century by the German mathematician Gottfried
Leibniz. Leibniz believed that reality was built from things he called monads,
which owed their existence solely to their relations with each other. This
picture languished in the backwaters of science because it was hugely
difficult to turn into a recipe for calculating things, unlike Newton's
mechanics.
But Cahill and Klinger have found a way to do it. Like Leibniz's monads, their
"pseudoobjects" have no intrinsic existencethey are defined only
by how strongly they connect with each other, and ultimately they disappear
from the model. They are mere scaffolding.
The recipe is simple: take some pseudoobjects, add a little randomness and let
the whole mix evolve inside a computer. With pseudoobjects numbered 1, 2, 3,
and so on, you can define some numbers to represent the strength of the
connection between each pair of pseudoobjects: B_{12} is the strength
of the connection between 1 and 2; B_{13} the connection between 1 and
3; and so on. They form a twodimensional grid of numbersa matrix.
The physicists start by filling their matrix with numbers that are very close
to zero. Then they run it repeatedly through a matrix equation which adds
random noise and a second, nonlinear term involving the inverse of the
original matrix. The randomness means that most truths or predictions of this
model have no causethe physical version of Chaitin's mathematical result.
This matrix equation is largely the child of educated guesswork, but there are
good precedents for that. In 1932, for example, Paul Dirac guessed at a matrix
equation for how electrons behave, and ended up predicting the existence of
antimatter.
When the matrix goes through the wringer again and again, most of the elements
remain close to zero, but some numbers suddenly become large. "Structures
start forming," says Cahill. This is no coincidence, as they chose the
second term in the equation because they knew it would lead to something like
this. After all, there is structure in the Universe that has to be explained.
The structures can be seen by marking dots on a piece of paper to represent the
pseudoobjects 1, 2, 3, and so on. It doesn't matter how they are arranged. If
B_{23} is large, draw a line between 2 and 3; if B_{19} is
large, draw one between 1 and 9. What results are "trees" of strong
connections, and a lot of much weaker links. And as you keep running the
equation, smaller trees start to connect to others. The network grows.
The trees branch randomly, but Cahill and Klinger have found that they have a
remarkable property. If you take one pseudoobject and count its nearest
neighbours in the tree, second nearest neighbours, and so on, the numbers go up
in proportion to the square of the number of steps away (click on
thumbnail graphic below). This is exactly what you would get for points
arranged uniformly throughout threedimensional space. So something like our
space assembles itself out of complete randomness. "It's downright
creepy," says Cahill. Cahill and Klinger call the trees
"gebits", because they act like bits of geometry.

Tree roots:
pseudoobjects link up into random trees, which link into ever larger
structures. The hierarchy of neighbours is just like that of points in 3D
space

They haven't proved that this tangle of connections is like 3D space in every
respect, but as they look closer at their model, other similarities with our
Universe appear. The connections between pseudoobjects decay, but they are
created faster than they decay. Eventually, the number of gebits increases
exponentially. So space, in Cahill and Klinger's model, expands and
acceleratesjust as it does in our Universe, according to observations of the
recession of distant supernovae. In other words, Cahill and Klinger think their
model might explain the mysterious cosmic repulsion that is speeding up the
Universe's expansion.
And this expanding space isn't empty. Topological defects turn up in the forest
of connectionspairs of gebits that are far apart by most routes, but have
other shorter links. They are like snags in the fabric of space. Cahill and
Klinger believe that these defects are the stuff we are made of, as described
by the wave functions of quantum theory, because they have a special property
shared by quantum entities: nonlocality. In quantum theory, the properties of
two particles can be correlated, or "entangled", even when they are
so far apart that no signal can pass between them. "This ghostly
longrange connectivity is apparently outside of space," says Cahill. But
in Cahill and Klinger's model of reality, there are some connections that act
like wormholes to connect farflung topological defects.
Even the mysterious phenomenon of quantum measurement can be seen in the model.
In observing a quantum system any detector ought to become entangled with the
system in a joint quantum state. We would see weird quantum superpositions like
Schrödinger's aliveanddead cat. But we don't.
How does the quantum state "collapse" to a simple classical one? In
Cahill and Klinger's model, the nonlocal entanglements disappear after many
iterations of the matrix equation. That is, ordinary 3D space reasserts itself
after some time, and the ghostly connection between measuring device and
system is severed.
This model could also explain our individual experience of a present moment.
According to Einstein's theory of relativity, all of spacetime is laid out
like a fourdimensional map, with no special "present" picked out for
us to feel. "Einstein thought an explanation of the present was beyond
theoretical physics," says Cahill. But in the gebit picture, the future is
not predetermined. You never know what it will bring, because it is dependent
on randomness. "The present is therefore real and distinct from an
imagined future and a recorded past," says Cahill.
Sand castles
But why can't we detect this random dance of the pseudoobjects? "Somehow,
in the process of generating reality, the pseudoobjects must become hidden
from view," says Cahill. To simulate this, the two physicists exploited a
phenomenon called selforganised criticality.
Selforganised criticality occurs in a wide range of systems such as growing
sand piles. Quite spontaneously, these systems reach a critical state. If you
drop sand grains one by one onto a sand pile, for instance, they build up and
up into a cone until avalanches start to happen. The slope of the side of the
cone settles down to a critical value, at which it undergoes small avalanches
and big avalanches and all avalanches at all scales in between. This behaviour
is independent of the size and shape of the sand grains, and in general it is
impossible to deduce anything about the building blocks of a selforganised
critical system from its behaviour. In other words, the scale and timing of
avalanches doesn't depend on the size or shape of the sand grains.
"This is exactly what we need," says Cahill. "If our system
selforganises to a state of criticality, we can construct reality from
pseudoobjects and simultaneously hide them from view." The dimensionality
of space doesn't depend on the properties of the pseudoobjects and their
connections. All we can measure is what emerges, and even though gebits are
continually being created and destroyed, what emerges is smooth 3D space.
Creating reality in this way is like pulling yourself up by your bootstraps,
throwing away the bootstraps and still managing to stay suspended in midair.
This overcomes a problem with the conventional picture of reality. Even if we
discover the laws of physics, we are still left with the question: where do
they come from? And where do the laws that explain where they come from come
from? Unless there is a level of laws that explain themselves, or turn out to
be the only mathematically consistent setas Steven Weinberg of the University
of Texas at Austin believeswe are left with an infinite regression. "But
it ceases to be a problem if selforganised criticality hides the lowest layer
of reality," says Cahill. "The startup pseudoobjects can be viewed
as nothing more than a bundle of weakly linked pseudoobjects, and so on ad
infinitum. But no experiment will be able to probe this structure, so we have
covered our tracks completely."
Other physicists are impressed by Cahill and Klinger's claims. "I have
never heard of anyone working on such a fundamental level as this," says
Roy Frieden of the University of Arizona in Tucson. "I agree with the
basic premise that 'everything' is ultimately random, but am still sceptical of
the details." He would like to see more emerge from the model before
committing himself. "It would be much more convincing if Cahill and
Klinger could show something physicalthat is, some physical lawemerging
from this," says Frieden. "For example, if this is to be a model of
space, I would expect something like Einstein's field equation for local space
curvatures emerging. Now that would be something."
"It sounds rather farout," says John Baez of the University of
California at Riverside. "I would be amazedthough pleasedif they could
actually do what you say they claim to."
"I've seen several physics papers like this that try to get spacetime or
even the laws of physics to emerge from random structures at a lower
level," says Chaitin. "They're interesting efforts, and show how
deeply ingrained the statistical point of view is in physics, but they are
difficult, pathbreaking and highly tentative efforts far removed from the
mainstream of contemporary physics."
What next? Cahill and Klinger hope to find that everythingmatter and the laws
of physicsemerges spontaneously from the interlinking of gebits. Then we
would know for sure that reality is based on randomness. It's a remarkable
ambition, but they have already come a long way. They have created a picture of
reality without objects and shown that it can emerge solely out of the
connections of pseudoobjects. They have shown that space can arise out of
randomness. And, what's more, a kind of space that allows both ordinary
geometry and the nonlocality of quantum phenomenatwo aspects of reality
which, until now, have appeared incompatible.
Perhaps what is most impressive, though, is that Cahill and Klinger are the
first to create a picture of reality that takes into account the fundamental
limitations of logic discovered by Gödel and Chaitin. In the words of
Cahill: "It is the logic of the limitations of logic that is ultimately
responsible for generating this new physics, which appears to be predicting
something very much like our reality."