Å®ÉúСÊÓƵ

Information and the Internal Structure of the Universe by Tom Stonier,
Springer-Verlag, pp 155, 13.50 Pounds hbk.

Complexity, Entropy and the Physics of Information edited by Wojciech
H Zurek, Addison-Wesley, pp 530, 24.25 Pounds pbk

All books contain a vast amount of order. Symbols are arranged on the
paper in a manner unlikely to have arisen by chance: ask the monkey with
the typewriter. But if we pick up a book in a language entirely unknown
to us, how can we tell what information it holds? It could be a truthful
autobiography or a translation of William Burroughs’s randomly composed
cut-up novels. Endless harmless fun can be had with such questions, especially
in the small hours of students’ nights.

And it is here that Tom Stonier begins his book with the proposal that
there is a serious need for a ‘general theory of information’. He will find
agreement from people working in fields as disparate as the quantum theory
of measurement and cognitive psychology. What of practical communications
engineers, who routinely work with the theory of information in messages
developed by Claude Shannon (the grandparent of communications theory),
and leave the tricky questions of information and meaning for their phone
companies’ customers to ponder?

Stonier also proposes ‘ .. that ‘information’ is as much a part of the
physical universe as matter and energy ..’; it ‘has an independent reality’.
As he first introduces this topic, his answers appear designed to deal with
Bishop Berkeley’s question: if a tree falls in the forest and no one hears
it, does it make a sound? Please answer yes, nor or don’t know.

So does information exist without someone to receive or interpret it?
Stonier answers ‘Yes’ emphatically. Our mystery book does contain information,
independent of any meaning that might be found in it by a reader. It is
disappointing that he does not explore further the philosophical questions
(‘reality?’, ‘independent?’, ‘has?’). Instead, we go on an excursion through
the relationship between the entropy of a message as defined by Shannon
and the entropy of a system defined on thermodynamics.

Stonier defines potential energy, as associated with a glass about to
fall off a table, as a quantity of information. He then goes on to explore
the implications of a universe composed of a trinity of matter, energy and
information (rather than merely matter and energy). He describes ‘infons’
(in an appendix) as massless particles such that ‘A photon is an infon travelling
at the speed of light.’

Here we come to a second attempt to deal with an intuitively troubling
question: that of the invariance of the speed of light in vacuum. Stonier
proposes that the only massless particles we can detect are those travelling
at the speed of light (photons): this entails rewriting the mathematics
of relativity. It also leads to the prediction that a telescope deep underground
might detect photons from previously unobserved stars moving towards the
Earth. Arriving at the Earth’s surface at the speed of light plus the closing
velocity of the star, some of these faster-than-light photons (or tachyons)
would slow down (as light is slowed in glass) to detectability at the speed
of light.

Such speculation is entertaining. It may have value in shaking up ideas
to let new ones emerge for rigorous testing. But it is marred by absurdities,
especially as Stonier tries repeatedly to illustrate what is apparently
an intuitive conviction about the ‘independent reality’ of information.
For example, thermodynamically reversible computation is possible, at least
in the relevant realm of the thought experiment. Patterns in cellular automata
(such as are manifest in the popular Game of Life computer programmes) surely
do not ‘require a continuous input of energy’; it is merely the representation
of these mathematical entities in a computer or a brain that consumes energy.
Information and the Internal Structure of the Universe contains less information
than its author hoped.

It’s a mind-bending relief to turn from this to the hard stuff – in
all senses of the phrase. Complexity, Entropy and the Physics of Information
contains 32 papers from a summer workshop in 1989 at the private Sante Fe
Institute. These range over computer science, experimental mathematics,
evolution, thermodynamics and quantum theory. Only a reader conversant with
the notations of all these disciplines will be able to extract the most
from every paper.

Several contributors discuss rigorously the relationship between Shannon’s
information entropy and thermodynamics. John Archibald Wheeler of Princeton
University, gives an engaging personal overview of the physics of information.
Murray Gell-Mann of the California Institute of Technology and James Hartle
of the University of California open modestly: ‘We sketch a quantum-mechanical
framework for the Universe as a whole.’ They make a brave start. Their ‘many
histories’ (as opposed to ‘many worlds’) approach takes an interesting sideswipe
at the anthropic principle (why does the Universe appear to be organised
exactly so that human observers are possible?). Stuart Kauffman of the University
of Pennsylvania addresses the question of why evolution is possible, emerging
with a quite unexpected connection with the mathematical behaviour of the
‘space’ of possible programmes.

This must have been a most remarkable symposium for those who attended;
although the participant who answered ‘don’t ask me, I’m a biologist’ to
my question about a physicist’s paper was certainly not alone in his puzzlement.
(What information is conveyed by the fact that all the recognisable names
are male?) This is hard stuff but it shows the way to solid new understandings
of information and the Universe.

Mike Holderness is a science journalist.