- Unger, Roberto Mangabeira and Lee Smolin.
The Singular Universe and the Reality of Time.
Cambridge: Cambridge University Press, 2015.
ISBN 978-1-107-07406-4.
-
In his 2013 book Time Reborn
(June 2013), Lee Smolin argued that, despite its extraordinary
effectiveness in understanding the behaviour of isolated systems, what
he calls the “Newtonian paradigm” is inadequate to
discuss cosmology: the history and evolution of the universe as a
whole. In this book, Smolin and philosopher Roberto Mangabeira Unger
expand upon that observation and present the case that the current
crisis in cosmology, with its appeal to multiple universes and
mathematical structures which are unobservable, even in principle, is
a consequence of the philosophical, scientific, and mathematical tools
we've been employing since the dawn of science attempting to be used
outside their domain of applicability, and that we must think
differently when speaking of the universe as a whole, which contains
all of its own causes and obeys no laws outside itself. The authors
do not present their own theories to replace those of present-day
cosmology (although they discuss the merits of several proposals), but
rather describe their work as a “proposal in natural
philosophy” which might guide investigators searching for those
new theories.
In brief, the Newtonian paradigm is that the evolution of physical
systems is described by differential equations which, given a set of
initial conditions, permit calculating the evolution of a system
in the future. Since the laws of physics at the microscopic
level are reversible, given complete knowledge of the state of a system
at a given time, its past can equally be determined. Quantum
mechanics modifies this only in that rather than calculating the
position and momentum of particles (or other observables), we
calculate the deterministic evolution of the wave function which
gives the probability of observing them in specific states in the future.
This paradigm divides physics into two components: laws (differential
equations) and initial conditions (specification of the initial state
of the system being observed). The laws themselves, although they
allow calculating the evolution of the system in time, are themselves
timeless: they do not change and are unaffected by the interaction of
objects. But if the laws are timeless and not subject to back-reaction
by the objects whose interaction they govern, where did they come
from and where do they exist? While conceding that
these aren't matters which working scientists spend much time
thinking about, in the context of cosmology they post serious
philosophical problems. If the universe all that is and contains
all of its own causes, there is no place for laws which are outside
the universe, cannot be acted upon by objects within it, and have
no apparent cause.
Further, because mathematics has been so effective in expressing the
laws of physics we've deduced from experiments and observations,
many scientists have come to believe that mathematics can be a
guide to exploring physics and cosmology: that some mathematical
objects we have explored are, in a sense, homologous to the universe,
and that learning more about the mathematics can be a guide to
discoveries about reality.
One of the most fundamental discoveries in cosmology, which has
happened within the lifetimes of many readers of this book,
including me, is that the universe has a history. When
I was a child, some scientists (a majority, as I recall) believed
the universe was infinite and eternal, and that observers at any
time in the past or future would observe, at the largest scales,
pretty much the same thing. Others argued for an origin at a finite
time in the past, with the early universe having a temperature
and density much greater than at present—this theory was
mocked as the “big bang”. Discovery of the cosmic
background radiation and objects in the distant universe which
did not at all resemble those we see nearby decisively decided
this dispute in favour of the big bang, and recent precision
measurements have allowed determination of when it happened and
how the universe evolved subsequently.
If the universe has a finite age, this makes the idea of
timeless laws even more difficult to accept. If the universe is
eternal, one can accept that the laws we observe have always been
that way and always will be. But if the universe had an origin we
can observe, how did the laws get baked into the universe? What
happened before the origin we observe? If every event has a cause,
what was the cause of the big bang?
The authors argue that in cosmology—a theory encompassing
the entire universe—a global privileged time must govern
all events. Time flows not from some absolute clock as envisioned
by Newtonian physics or the elastic time of special and general
relativity, but from causality: every event has one or more causes,
and these causes are unique. Depending upon their position and state
of motion, observers will disagree about the durations measured
by their own clocks, and on the order in which things
at different positions in space occurred (the relativity of
simultaneity), but they will always observe a given event to have the
same cause(s), which precede it. This relational notion of time,
they argue, is primordial, and space may be emergent from it.
Given this absolute and privileged notion of time (which many
physicists would dispute, although the authors argue does not
conflict with relativity), that time is defined by the
causality of events which cause change in the universe, and that
there is a single universe with nothing outside it and which contains all
of its own causes, then is it not plausible to conclude that the
“laws” of physics which we observe are not timeless
laws somehow outside the universe or grounded in a Platonic mathematics
beyond the universe, but rather have their own causes, within the
universe, and are subject to change: just as there is no “unmoved
mover”, there is no timeless law? The authors, particularly
Smolin, suggest that just as we infer laws from observing
regularities in the behaviour of systems within the universe
when performing experiments in various circumstances, these laws
emerge as the universe develops “habits” as interactions
happen over and over. In the present cooled-down state of the
universe, it's very much set in its ways, and since everything has
happened innumerable times we observe the laws to be unchanging. But
closer to the big bang or at extreme events in the subsequent universe,
those habits haven't been established and true novelty can occur.
(Indeed, simply by synthesising a protein with a hundred amino acids
at random, you're almost certain to have created a molecule which has
never existed before in the observable universe, and it may be harder
to crystallise the first time than subsequently. This appears to
be the case. This is my observation, not the authors'.)
Further, not only may the laws change, but entirely new kinds of
change may occur: change itself can change. For example, on
Earth, change was initially governed entirely by the laws
of physics and chemistry (with chemistry ultimately based upon
physics). But with the emergence of life, change began to be
driven by evolution which, while at the molecular level was
ultimately based upon chemistry, created structures which
equilibrium chemistry never could, and dramatically changed the
physical environment of the planet. This was not just change, but
a novel kind of change. If it happened here, in our own recent
(in cosmological time) history, why should we assume other novel
kinds of change did not emerge in the early universe, or will not
continue to manifest themselves in the future?
This is a very difficult and somewhat odd book. It is written in two
parts, each by one of the co-authors, largely independent of one another.
There is a twenty page appendix in which the authors discuss their
disagreements with one another, some of which are fundamental.
I found Unger's part tedious, repetitive, and embodying all of things
I dislike about academic philosophers. He has some important things
to say, but I found that slogging through almost 350 pages of it was
like watching somebody beat a moose to death with an aluminium
baseball bat: I believe a good editor, or even a mediocre one, could
have cut this to 50 pages without losing anything and making the
argument more clearly than trying to dig it out of this blizzard
of words. Lee Smolin is one of the most lucid communicators among
present-day research scientists, and his part is clear, well-argued,
and a delight to read; it's just that you have to slog through the
swamp to get there.
While suggesting we may have been thinking about cosmology all wrong,
this is not a book which suggests either an immediate theoretical or
experimental programme to explore these new ideas. Instead, it
intends to plant the seed that, apart from time and causality,
everything may be emergent, and that when we think about
the early universe we cannot rely upon the fixed framework of our
cooled-down universe with its regularities. Some of this is obvious
and non-controversial: before there were atoms, there was no periodic
table of the elements. But was there a time before there was
conservation of energy, or before locality?
September 2015 