- Smolin, Lee.
Time Reborn.
New York: Houghton Mifflin, 2013.
ISBN 978-0-547-51172-6.
-
Early in his career, the author received some unorthodox career
advice from Richard Feynman. Feynman noted that in physics, as in
all sciences, there were a large number of things that most
professional scientists believed which nobody had been able to
prove or demonstrate experimentally. Feynman's insight was that,
when considering one of these problems as an area to investigate,
there were two ways to approach it. The first was to try to
do what everybody had failed previously to accomplish. This, he
said, was extremely difficult and unlikely to succeed, since it
assumes you're either smarter than everybody who has tried before
or have some unique insight which eluded them. The other path is
to assume that the failure of numerous brilliant people might
indicate that what they were trying to demonstrate was, in
fact, wrong, and that it might be wiser for the ambitious
scientist to search for evidence to the contrary.
Based upon the author's previous work and publications, I picked up
this book expecting a discussion of the
problem of time in quantum gravity.
What I found was something breathtakingly more ambitious. In essence,
the author argues that when it comes to cosmology: the physics of
the universe as a whole, physicists have been doing it wrong
for centuries, and that what he calls the “Newtonian
paradigm” must be replaced with one in which time
is fundamental in order to stop speaking nonsense.
The equations of
general relativity,
especially when formulated in attempts to create a quantum theory of
gravitation, seem to suggest that our perception of time is an
illusion: we live in a timeless
block universe,
in which our consciousness can be thought of as a cursor moving through
a fixed, deterministic spacetime. In general relativity, the rate of
perceived flow of time depends upon one's state of motion and the
amount of mass-energy in the vicinity of the observer, so it makes no
sense to talk about any kind of global time co-ordinate. Quantum
mechanics, on the other hand, assumes there is a global clock, external
to the system and unaffected by it, which governs the evolution of the
wave function. These views are completely incompatible—hence the
problem of time in quantum gravity.
But the author argues that “timelessness” has its roots much
deeper in the history and intellectual structure of physics. When one
uses Newtonian mechanics to write down a differential equation which
describes the path of a ball thrown upward, one is reducing a process
which would otherwise require enumerating a list of positions and times
to a timeless relationship which is valid over the entire trajectory.
Time appears in the equation simply as a label which causes it to
emit the position at that moment. The equation of motion, and, more
importantly, the laws of motion which allow us to write it down for
this particular case, are entirely timeless: they affect the object
but are not affected by it, and they appear to be specified outside the
system.
This, when you dare to step back and think about it, is distinctly
odd. Where did these laws come from? Well, in Newton's day
and in much of the history of science since, most scientists would say
they were prescribed by a benevolent Creator. (My own view that they
were put into the
simulation
by the 13 year old superkid who created it
in order to win the Science Fair with the most interesting result,
generating the maximum complexity, is isomorphic to this explanation.)
Now, when you're analysing a system “in a box”, it makes perfect
sense to assume the laws originate from outside and are fixed; after all, we can
compare experiments run in different boxes and convince ourselves that
the same laws obtain regardless of symmetries such as translation,
orientation, or boost. But note that once we try to generalise this
to the entire universe, as we must in cosmology, we run into a philosophical
speed bump of singularity scale. Now we cannot escape the question
of where the laws came from. If they're from inside the universe, then
there must have been some dynamical process which created them. If they're
outside the universe, they must have had to be imposed by some process
which is external to the universe, which makes no sense if you define
the universe as all there is.
Smolin suggests that laws exist within our universe, and that they
evolve in an absolute time, which is primordial. There
is no
unmoved mover:
the evolution of the universe (and the possibility that universes
give birth to other universes) drives the evolution of the laws of
physics. Perhaps the
probabilistic results we observe
in quantum mechanical processes are not built-in ahead of time
and prescribed by timeless laws outside the universe, but rather a
random choice from the results of previous similar measurements.
This “principle of precedence”, which is remarkably similar
to that of English
common law,
perfectly reproduces the results of
most tests of quantum mechanics, but may be testable by precision
experiments where circumstances never before created in the universe
are measured, for example in quantum computing. (I am certain Prof.
Smolin would advocate for my being beheaded were I to point out the
similarity of this hypothesis with
Rupert Sheldrake's
concept of
morphic
resonance; some years ago I suggested to Dr Sheldrake a protein
crystallisation experiment on the International Space Station
to test this theory; it is real science, but
to this date nobody has done it. Few wish to risk their careers testing
what “everybody knows”.)
This is one those books you'll need to think about after you've read it,
then after some time, re-read to get the most out of it. A collection
of
online appendices
expand upon topics discussed in the book.
An hour-long video
discussion of the ideas in the book by the author and the
intellectual path which led him to them is available.
June 2013 