[extropy-chat] Do the laws of nature last forever?
eugen at leitl.org
Thu Sep 28 15:53:57 UTC 2006
From: Jef Allbright <jef at jefallbright.net>
Date: Thu, 28 Sep 2006 08:25:40 -0700
To: Extropy-Chat List <extropy-chat-bounces at lists.extropy.org>
Subject: [Philosophy of Science] Do the laws of nature last forever?
An item by Lee Smolin in the September issue of New Scientist caught
my attention, both for the good points that it makes, and some bad
assumptions that it harbors. I apologize for the long inclusions,
necessary since this essay is not entirely available online.
Do the laws of nature last forever?
* 21 September 2006
* Lee Smolin
In science we aim for a picture of nature as it really is,
unencumbered by any philosophical or theological prejudice. Some
see the search for scientific truth as a search for an unchanging
reality behind the ever-changing spectacle we observe with our
senses. The ultimate prize in that search would be to grasp a law
of nature - a part of a transcendent reality that governs all
change, but itself never changes.
The idea of eternally true laws of nature is a beautiful vision,
but is it really an escape from philosophy and theology? For, as
philosophers have argued, we can test the predictions of a law of
nature and see if they are verified or contradicted, but we can
never prove a law must always be true. So if we believe a law of
nature is eternally true, we are believing in something that logic
and evidence cannot establish.
Of course, laws of nature are very useful, and we have in fact been
able to discover good candidates for them. But to believe a law is
useful and reliable is not the same thing as to believe it is
eternally true. We could just as easily believe there is nothing
but an infinite succession of approximate laws. Or that laws are
generalisations about nature that are not unchanging, but change so
slowly that until now we have imagined them as eternal.
These are disturbing thoughts for a theoretical physicist like
myself. I chose to go into science because the search for eternal,
transcendent laws of nature seemed a lofty goal. However, the
possibility that laws evolve in time is one that recent
developments in theoretical and experimental physics have forced
me, and others, to consider.
The biggest reason to consider that the laws of nature might evolve
is the discovery that the universe itself is evolving. When we
believed that the universe was eternal it made more sense to
believe that the laws that governed it were also eternal. But the
evidence we have now is that the universe - or at least the part of
it we observe - has been around for only a few billion years.
We know that the universe has been expanding for about 14 billion
years and that as we go back in time it gets hotter and denser. We
have good evidence that there was a moment when the cosmos was as
hot as the centre of a star. If we use the laws that we know apply
to space-time and matter today, we can deduce that a few minutes
earlier the universe must have been infinitely dense and hot. Many
cosmologists take this moment as the birth of the universe and
indeed as the birth of space and time. Before this big bang there
was nothing, not even time.
Why these laws?
So what could it mean to say that a universe only 14 billion years
old is governed by laws that are eternally true? What were the laws
doing before time and space? How did the universe know, at that
moment of beginning, what laws to follow?
Perhaps the solution to this is that the big bang was not the first
instant of time. However, this raises a new question, which has
been championed by the great theoretical physicist John Wheeler.
Even if we believe the universe evolved from something that existed
before the big bang, we have no reason to believe the laws of that
previous universe were the same as those we observe in our
universe. Might the laws have changed when our universe, or region
of the universe, was created?
This question came to the fore in 1973, when physicists first
developed a theory of elementary particle physics called the
standard model. This theory has successfully accounted for every
experiment in particle physics before and since that time, apart
from those that involve gravity. It only required a small
modification to incorporate the later discovery that neutrinos have
mass. As for gravity, all experiments support the general theory of
relativity, which Einstein published in 1915. There may be further
laws to discover, to do with the unification of gravity with
quantum theory and with the other forces of nature. But in a
certain sense, we have for the first time in history a set of laws
sufficient to explain the result of every experiment that has ever
As a result, in the past three decades the attention of physicists
has shifted from seeking to know the laws of nature to a new
question: why these laws? Why do these laws, and not others, hold
in our universe?
Confronting this question while working on string theory in the
1980s, a few of us began to wonder whether the laws might have
changed at the big bang, just as Wheeler had suggested. It was
obvious that we could make a connection to biology. I wondered
whether there might be an evolutionary mechanism that would allow
us to answer the question of "why these laws?" in the same way that
biology answers questions like "why these species?". Perhaps the
mechanism that makes laws evolve also picks out certain laws and
makes them more probable than others. I found such a mechanism,
modelled on natural selection, which I called cosmological natural
This is possible because string theory is actually a collection of
theories: it has a vast number of distinct versions, each of which
gives rise to different collections of elementary particles and
forces. We can think of the different versions of string theory as
analogous to the different phases of water - ice, liquid and steam.
When the universe is squeezed down to such tremendous densities and
temperatures that the quantum properties of space-time become
important, a phase transition can take place - like water turning
to steam - leading from one version of the theory to another.
The many different phases of string theory can also be seen as
analogous to a variety of species governed by different DNA
sequences. They can be imagined as making up a vast space, which I
called the "landscape", to bring out the analogy to a "fitness
landscape" in biology that represents all possible ways genes can
Cosmological natural selection makes a few predictions that could
easily be falsified, and while it is too soon to claim strong
evidence for it, those predictions have held up (New Scientist, 24
May 1997, p 38). At the very least, it opened my eyes to the
possibility that a theory in which the laws changed in time could
still make testable predictions.
It turns out that I had been beaten to the punch: some philosophers
had confronted these issues over a century ago. In 1891 the
philosopher Charles Pierce wrote that it was hardly justifiable to
suppose that universal laws of nature have no reason for their
special form. "The only possible way of accounting for the laws of
nature, and for uniformity in general, is to suppose them results
of evolution," he added.
Pierce went much further than I have done, asserting that the
question "Why these laws?" has to be answered by a cosmological
scenario analogous to evolution. But was he right?
Let us start with an obvious objection: if laws evolve, what
governs how they evolve? Does there not have to be some deeper law
that guides the evolution of the laws? For example, when water
turns into ice, more general laws continue to hold and govern how
this phase transition happens - the laws of atomic physics. So
perhaps, even if a law turns out to evolve in time, there is always
a deeper, unchanging law behind that evolution.
As Smolin says, "perhaps", but why must there be "deeper, unchanging
law"? Granted, we are left with the mystery of the ultimate substrate
of the universe, but isn't it simpler and reasonable to think in terms
of an open-ended algorithmic process from which emerges increasing
complexity that "works" within the preceding context but not within
any absolute context? We tend to imagine processes playing out within
a stable computational substrate, like a simulation within one of our
computers, but this is an unnecessary assumption -- our impression of
stability instead due to our being the result of a long chain of
evolutionary processes that "worked" given their preceding context.
Shapes of things to come
Another example concerns the geometry of space. We used to think
that space always followed the perfectly flat Euclidean geometry
that we all learn in high school. This was considered one of the
laws of nature, but Einstein's general theory of relativity asserts
that this is wrong. The geometry of space can be anything it wants
to be: any of an infinite number of curved geometries is possible.
So what picks out the geometry we see?
General relativity asserts that the geometry of space evolves in
the course of time according to some deeper law. Today's geometry
is what it is because it evolved from a different geometry in the
past, following that definite law.
However, there is a big problem with this kind of explanation,
which has to do with the fact that the laws that govern the
evolution of geometry are deterministic. They share this feature
with most laws studied in physics, including Newton's laws and
quantum mechanics. Consider Newton's law of motion for an object.
If we know where the object is now and how it is moving, and we
know the laws that govern the forces it encounters, we can predict
where it will be and has been for all time, past as well as future.
General relativity is the same. If we know the geometry of space at
a particular time, and how it is changing, we can predict the whole
history of space-time. To apply these deterministic laws, however,
we have to give a description of the system at one point in time.
This is called the initial condition. If we do not specify an
initial condition, the laws cannot describe anything.
This is why Einstein's equations do not fully explain why the
geometry of space is what it is. They require an initial condition
-the geometry at an earlier time. This brings us back to the
dilemma about the big bang. Either the universe had no beginning,
in which case the chain of causes goes further into the past,
before the big bang; or the big bang was the beginning, and we
require some explanation as to why it started and with what
So we have arrived at a conundrum. It appears that if laws evolve,
other laws are required to guide their evolution. But then, the
evolution of a law is just like the evolution of any other system
under a deterministic law. We cannot explain why something is true
in the present without knowing its initial state. Applied to laws,
this means we cannot explain what the laws are now if we do not
specify what the laws were in the past. So the idea of laws
evolving by following a deeper rule does not seem to lead to an
explanation of "why these laws?".
To avoid this we need an evolutionary mechanism that will allow us
to deduce features of the present without having to know the past
in detail. This is where Pierce's statement, which appears to
invoke biological evolution, comes into its own.
In biology, many features of living organisms can be explained by
natural selection, even if one doesn't know details about the past.
As the process is partly random, we cannot predict exactly what mix
of species will evolve in a given ecosystem, but we can predict
that the species that survive will be fitter than those that don't.
This is, I believe, why Pierce insisted that any explanation of
"why these laws?" involves evolution. And using this kind of logic,
cosmological natural selection makes some predictions without
detailed information about previous stages of the universe.
But even this is unsatisfactory: it doesn't address the question of
how a law that guides the evolution of matter in time could also
change in time. For that, we have to examine the way we think about
There are big problems with time, even before we start thinking
about the evolution of laws of nature. Nowhere is this more
apparent than in the field of quantum gravity, which attempts to
pull quantum theory and general relativity together into one
consistent framework. This is because the two theories each use a
different notion of time. In quantum theory, time is defined by a
clock sitting outside the system being modelled. In general
relativity, time is measured by a clock that is part of the
universe that the theory describes. Many of the successes and
failures of different approaches to quantum gravity rest on how
they reconcile this conflict between time as an external parameter
versus time as a physical property of the universe.
However these questions are eventually resolved, there are still
deeper issues with time. These arise in any theory in which the
laws are taken as being eternal. To illustrate this, we can take a
simple example, such as Newton's description of a system of
particles. To formulate the theory we invent a mathematical space,
consisting of all the positions that all the particles might have.
Each point in the space is a possible configuration of the system
of particles, so the whole space is called the configuration space.
As the system evolves over time, it traces out a curve in
configuration space called a history. The laws of physics then pick
out which histories are possible and which are not.
The problem with this description is that time has disappeared. The
system is represented not by its state at a moment of time but by a
history taking it through all time. This description of reality
seems timeless. What has disappeared from it is any sense of the
present moment, which divides our experience of the flow of time
into past, present and future. This problem became particularly
acute when it emerged in Einstein's theory of general relativity.
Solving the theory gives a four-dimensional space-time history and
no indication of "now".
Why centralize the notion of a subjective sense of "now" when
describing processes within a much larger -- indeed, cosmological --
context? I understand that importance of the role of the observer in
any description, but it perpetuates paradoxical thinking to misplace
the subjective point of view. The sense of "now" is a result -- an
output -- of systems operating with the larger context; not something
intrinsic to reality. Otherwise, one is forced to impute
consciousness existing since the big bang and long before any
self-aware biology, a notion with some appealing romantic
connotations, but requiring expensive scaffolding for its support.
Some, looking at this picture, have been tempted to say that
reality is the whole timeless history and that any sense we have of
a present moment is some kind of illusion.
Shades of David Chalmers! We seem to have here a presumption of
humans as privileged observers of the universe. Not that that isn't
strongly reinforced by individual perception and cultural
reinforcement, but again, such conceptual scaffolding is expensive in
the longer term.
Even if we don't believe this, the fact that one could believe it
means that there is nothing in this description of nature that
corresponds to our common-sense experience of past, present and
future. This is called the problem of transience.
Ah, I suppose my Buddhist training is helpful to appreciate such
The sense of the universe unfolding or becoming in time, of "now",
has no representation in general relativity. But in truth the
problem was always there in Newton's physics and it is there in any
theory in which some part of nature is described by a state that
evolves deterministically in time, governed by a law that dictates
change, but never changes.
The illusion of now
The philosopher Roberto Unger of Harvard University calls this the
"poisoned gift of mathematics to physics". Many believe that
mathematics represents truth in terms of timeless relationships,
based on logic. It allows us to formulate physical laws precisely:
this is the gift. By doing so, however, mathematics represents
paths in configuration space unfolding in time by logic, and this
logic exists outside of time. The poison in the gift is the
disappearance of any notion of the present or of becoming.
Poison to cherished concepts that don't stand well without
Physicists and their predecessors have been eliminating time like
this since the days of Descartes and Galileo at least. But is it
the wrong thing to do? Is there a way to represent change through
time in a way that represents our sense of becoming, or of time
I don't know the answer, but I suspect this question is connected
to that of whether laws can evolve in time. One can only draw the
curve representing a history in time by assuming that the laws
which govern how the history evolves never change. Without a fixed,
unchanging law, one could not draw the curve.
Here is the question that keeps me awake these days: is there a way
to represent the laws of physics mathematically that retains the
notions of the present moment and the continual unfolding of time?
And would this allow us - or even require us - to formulate laws
that also evolve in time?
Again, I don't know the answer, but I know of a few hints. One
comes from theoretical biology. The configuration space for an
evolutionary theorist is vast, consisting of all the possible
sequences of DNA. At present, there is a particular collection
representing all the species that exist. Evolution will produce new
ones, while others will disappear. The interesting thing is that
natural selection operates in such a way that biologists have
little use for the entire configuration space. Instead, they need
study only a much smaller space, which is those collections of
genes that could be reached from the present one by a few
evolutionary steps. The theoretical biologist Stuart Kauffman of
the University of Calgary in Alberta, Canada, calls this the
This scheme allows laws to change. Consider the laws that govern
sexual selection. They do not make sense for any old biosphere, as
they only come into play when there are creatures with two sexes.
So in evolutionary theory there is no need for eternal laws, and it
makes sense to speak of a law coming into existence at some time to
govern possibilities that did not exist before. Furthermore, there
is such a vast array of possible mechanisms of natural selection
that it would not make any sense to list them all and treat them as
timeless. Better to think of laws coming into existence as the new
creatures that evolve in each step require.
Of course, one might reply that natural selection itself never
changes. But natural selection is a fact of logic, not a contingent
law of nature. Every real law in biology depends on some aspect of
the creatures that exist at a given time, which means the laws are
It is not impossible to achieve time-bound laws in physics. There
are logicians who have proposed alternative systems of logic that
incorporate a notion of time unfolding. In these logics, what is
true and false is assigned for a particular moment, not for all
time. For a given moment some propositions are true, others false,
but there remains an infinite list of propositions that are yet to
become either true or false. Once a proposition is true or false,
it remains so, but at each moment new propositions become decided.
These are called intuitionalist logics and they underlie a branch
of mathematics called topos theory.
Some of my colleagues have studied these logics as a model for
physics. Fotini Markopoulou of the Perimeter Institute for
Theoretical Physics in Waterloo, Ontario, Canada, has shown that
aspects of space-time geometry can be described in terms of these
logics. Chris Isham of Imperial College London and others propose
to reformulate physics completely in terms of them.
It is interesting that some physicists now propose that the
universe is some kind of computer, because similar questions are
being asked in computer science. In the standard architecture all
computers now use, invented by the mathematician John von Neumann,
the operating system never changes. It governs the flow of
information through a computer just as an eternal law of nature is
thought to guide physics. But some visionary computer scientists
such as Jaron Lanier wonder whether there could be other kinds of
architectures and operating systems that themselves evolve in time.
Biologically inspired computational architectures certainly have
promise, but one shouldn't imply that Jaron Lanier has been central to
Looking at biology, it seems there are advantages to what are,
essentially, time-bound laws. Evolving laws might make computer
systems similarly robust and less likely to do what the laws of
natural selection, it seems, never do: crash. The universe, too,
seems to function rather well, operating without glitches and fatal
Again confusing the varying levels of context. Of course, from the
ultimate objective point of view the universe never crashes -- it just
is -- but there can be no observer at that context. Within any actual
observer context, there will be unpredictable events -- crashes --
despite everything working quite deterministically.
Perhaps that's because natural selection is hard at work in the
laws of nature.
Yes, thanks for this and a few other valuable insights, glimpsed
through the scaffolding.
From issue 2570 of New Scientist magazine, 21 September 2006, page
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