Lee Smolin is an American theoretical
physicist, a faculty member at the
Perimeter Institute for Theoretical
Physics, an adjunct professor of physics
at the University of Waterloo and a
member of the graduate faculty of the
philosophy department at the University
of Toronto.
Smolin is best known for his
contributions to quantum gravity theory,
in particular the approach known as loop
quantum gravity. He advocates that the
two primary approaches to quantum
gravity, loop quantum gravity and string
theory, can be reconciled as different
aspects of the same underlying theory.
His research interests also include
cosmology, elementary particle theory,
the foundations of quantum mechanics,
and theoretical biology.
Early life
Smolin was born in New York City. His
brother, David M. Smolin, became a
professor in the Cumberland School of
Law in Birmingham, Alabama.
Education and career
Smolin dropped out of Walnut Hills High
School in Cincinnati, Ohio, and was
educated at Hampshire College. He
received his Ph.D in theoretical physics
from Harvard University in 1979. He held
postdoctoral research positions at the
Institute for Advanced Study in
Princeton, New Jersey, the Kavli
Institute for Theoretical Physics in
Santa Barbara and the University of
Chicago, before becoming a faculty
member at Yale, Syracuse and
Pennsylvania State Universities. He was
a visiting scholar at the Institute for
Advanced Study in 1995 and a visiting
professor at Imperial College London
before becoming one of the founding
faculty members at the Perimeter
Institute in 2001.
Theories and work
= Loop quantum gravity=
Smolin contributed to the invention of
loop quantum gravity in collaborative
work with Ted Jacobson, Carlo Rovelli,
Louis Crane, Abhay Ashtekar and others.
LQG is an approach to the unification of
quantum mechanics with general
relativity which utilizes a
reformulation of general relativity in
the language of gauge field theories,
which allows the use of techniques from
particle physics, particularly the
expression of fields in terms of the
dynamics of loops. With Rovelli he
discovered the discreteness of areas and
volumes and found their natural
expression in terms of a discrete
description of quantum geometry in terms
of spin networks. In recent years he has
focused on connecting LQG to
phenomenology by developing implications
for experimental tests of spacetime
symmetries as well as investigating ways
elementary particles and their
interactions could emerge from spacetime
geometry.
= Background independent approaches to
string theory=
Between 1999 and 2002, Smolin made
several proposals for the still open
question of giving a fundamental
formulation of string theory that does
not depend on approximate descriptions
involving classical background
space-time models.
= Experimental tests of quantum gravity=
Smolin is among those theorists who have
proposed that the effects of quantum
gravity can be experimentally probed by
searching for modifications in special
relativity detected in observations of
high energy astrophysical phenomena.
These include very high energy cosmic
rays and photons and neutrinos from
gamma ray bursts. Among Smolin’s
contributions are the coinvention of
doubly special relativity and of
relative locality.
= Foundations of quantum mechanics=
Smolin has worked since the early 1980s
on a series of proposals for hidden
variables theories, which would be
non-local deterministic theories which
would give a precise description of
individual quantum phenomena. In recent
years, he has pioneered two new
approaches to the interpretation of
quantum mechanics suggested by his work
on the reality of time, called the real
ensemble formulation and the principle
of precedence.
= Cosmological natural selection =
Smolin's hypothesis of cosmological
natural selection, also called the
fecund universes theory, suggests that a
process analogous to biological natural
selection applies at the grandest of
scales. Smolin published the idea in
1992 and summarized it in a book aimed
at a lay audience called The Life of the
Cosmos.
The theory surmises that a collapsing
black hole causes the emergence of a new
universe on the "other side", whose
fundamental constant parameters may
differ slightly from those of the
universe where the black hole collapsed.
Each universe thus gives rise to as many
new universes as it has black holes. The
theory contains the evolutionary ideas
of "reproduction" and "mutation" of
universes, and so is formally analogous
to models of population biology.
The resulting population of universes
can be represented as a distribution of
a landscape of parameters where the
height of the landscape is proportional
to the numbers of black holes that a
universe with those parameters will
have. Applying reasoning borrowed from
the study of fitness landscapes in
population biology, one can conclude
that the population is dominated by
universes whose parameters drive the
production of black holes to a local
peak in the landscape. This was the
first use of the notion of a landscape
of parameters in physics.
Leonard Susskind, who later promoted a
similar string theory landscape, stated:
"I'm not sure why Smolin's idea didn't
attract much attention. I actually think
it deserved far more than it got."
However, Susskind also argued that,
since Smolin's theory relies on
information transfer from the parent
universe to the baby universe through a
black hole, it ultimately makes no sense
as a theory of cosmological natural
selection. According to Susskind and
many other physicists, the last decade
of black hole physics has shown us that
no information that goes into a black
hole can be lost. Indeed the debate over
this issue has been resolved with
Stephen Hawking, the largest proponent
of the idea that information is lost in
a black hole, reversing his position. In
this light, information transfer from
the parent universe into the baby
universe through a black hole is not
conceivable.
Smolin has noted that the string theory
landscape is not Popper-falsifiable if
other universes are not observable. This
is the subject of the Smolin–Susskind
debate concerning Smolin’s argument:
"[The] Anthropic Principle cannot yield
any falsifiable predictions, and
therefore cannot be a part of science."
There are then only two ways out:
traversable wormholes connecting the
different parallel universes, and
"signal nonlocality", as described by
Antony Valentini, a scientist at the
Perimeter Institute.
In a critical review of The Life of the
Cosmos, astrophysicist Joe Silk
suggested that our universe falls short
by about four orders of magnitude from
being maximal for the production of
black holes. In his book Questions of
Truth, particle physicist John
Polkinghorne puts forward another
difficulty with Smolin's thesis: one
cannot impose the consistent multiversal
time required to make the evolutionary
dynamics work, since short-lived
universes with few descendants would
then dominate long-lived universes with
many descendants. Smolin responded to
these criticisms in Life of the Cosmos,
and later scientific papers.
When Smolin published the theory in
1992, he proposed as a prediction of his
theory that no neutron star should exist
with a mass of more than 1.6 times the
mass of the sun. Later this figure was
raised to two solar masses following
more precise modeling of neutron star
interiors by nuclear astrophysicists. If
a more massive neutron star was ever
observed, it would show that our
universe's natural laws were not tuned
for maximal black hole production,
because the mass of the strange quark
could be retuned to lower the mass
threshold for production of a black
hole. A 2-solar-mass pulsar was
discovered in 2010.
In 1992 Smolin also predicted that
inflation, if true, must only be in its
simplest form, governed by a single
field and parameter. Both predictions
have held up, and they demonstrate
Smolin’s main thesis: that the theory of
cosmological natural selection is Popper
falsifiable.
= Contributions to philosophy of
physics=
Smolin has contributed to the philosophy
of physics through a series of papers
and books that advocate the relational,
or Leibnizian, view of space and time.
Since 2006, he has collaborated with the
Brazilian philosopher and Harvard Law
School professor Roberto Mangabeira
Unger on the issues of the reality of
time and the evolution of laws; in 2014
they published a book, its two parts
being authored separately.
A book length exposition of Smolin's
philosophical views appeared in April
2013. Time Reborn argues that physical
science has made time unreal while, as
Smolin insists, it is the most
fundamental feature of reality: "Space
may be an illusion, but time must be
real". An adequate description according
to him would give a Leibnizian universe:
indiscernibles would not be admitted and
every difference should correspond to
some other difference, as the principle
of sufficient reason would have it. A
few months later a more concise text has
been made available in a paper with the
title Temporal Naturalism.
The Trouble with Physics
Smolin's 2006 book The Trouble with
Physics explored the role of controversy
and disagreement in the progress of
science. It argued that science
progresses fastest if the scientific
community encourages the widest possible
disagreement among trained and
accredited professionals prior to the
formation of consensus brought about by
experimental confirmation of predictions
of falsifiable theories. He proposed
that this meant the fostering of diverse
competing research programs, and that
premature formation of paradigms not
forced by experimental facts can slow
the progress of science.
As a case study, The Trouble with
Physics focused on the issue of the
falsifiability of string theory due to
the proposals that the anthropic
principle be used to explain the
properties of our universe in the
context of the string landscape. The
book was criticized by the physicists
Joseph Polchinski and other string
theorists.
In his earlier book Three Roads to
Quantum Gravity, Smolin stated that loop
quantum gravity and string theory were
essentially the same concept seen from
different perspectives. In that book, he
also favored the holographic principle.
The Trouble with Physics, on the other
hand, was strongly critical of the
prominence of string theory in
contemporary theoretical physics, which
he believes has suppressed research in
other promising approaches. Smolin
suggests that string theory suffers from
serious deficiencies and has an
unhealthy near-monopoly in the particle
theory community. He called for a
diversity of approaches to quantum
gravity, and argued that more attention
should be paid to loop quantum gravity,
an approach Smolin has devised. Finally,
The Trouble with Physics is also broadly
concerned with the role of controversy
and the value of diverse approaches in
the ethics and process of science.
In the same year that The Trouble with
Physics was published, Peter Woit
published a book for nonspecialists
whose conclusion was similar to
Smolin's, namely that string theory was
a fundamentally flawed research program.
Views
Smolin's view on the nature of time:
"More and more, I have the feeling that
quantum theory and general relativity
are both deeply wrong about the nature
of time. It is not enough to combine
them. There is a deeper problem, perhaps
going back to the beginning of physics."
Smolin does not believe that quantum
mechanics is a "final theory":
"I am convinced that quantum mechanics
is not a final theory. I believe this
because I have never encountered an
interpretation of the present
formulation of quantum mechanics that
makes sense to me. I have studied most
of them in depth and thought hard about
them, and in the end I still can't make
real sense of quantum theory as it
stands."
In a 2009 article, Smolin has
articulated the following philosophical
views:
There is only one universe. There are no
others, nor is there anything isomorphic
to it. Smolin denies the existence of a
"timeless" multiverse. Neither other
universes nor copies of our universe —
within or outside — exist. No copies can
exist within the universe, because no
subsystem can model precisely the larger
system it is a part of. No copies can
exist outside the universe, because the
universe is by definition all there is.
This principle also rules out the notion
of a mathematical object isomorphic in
every respect to the history of the
entire universe, a notion more
metaphysical than scientific.
All that is real is real in a moment,
which is a succession of moments.
Anything that is true is true of the
present moment. Not only is time real,
but everything that is real is situated
in time. Nothing exists timelessly.
Everything that is real in a moment is a
process of change leading to the next or
future moments. Anything that is true is
then a feature of a process in this
process causing or implying future
moments. This principle incorporates the
notion that time is an aspect of causal
relations. A reason for asserting it is
that anything that existed for just one
moment, without causing or implying some
aspect of the world at a future moment,
would be gone in the next moment. Things
that persist must be thought of as
processes leading to newly changed
processes. An atom at one moment is a
process leading to a different or a
changed atom at the next moment.
Mathematics is derived from experience
as a generalization of observed
regularities, when time and
particularity are removed. Under this
heading, Smolin distances himself from
mathematical platonism, and gives his
reaction to Eugene Wigner's "The
Unreasonable Effectiveness of
Mathematics in the Natural Sciences".
Smolin views rejecting the idea of a
creator as essential to cosmology. He
also opposes the anthropic principle,
which he claims "cannot help us to do
science." He also advocates “principles
for an open future” which he claims
underlie the work of both healthy
scientific communities and democratic
societies: “(1) When rational argument
from public evidence suffices to decide
a question, it must be considered to be
so decided. When rational argument from
public evidence does not suffice to
decide a question, the community must
encourage a diverse range of viewpoints
and hypotheses consistent with a
good-faith attempt to develop convincing
public evidence.”
Publications
The following books are non-technical,
and can be appreciated by those who are
not physicists.
1999. The Life of the Cosmos ISBN
0195126645
2001. Three Roads to Quantum Gravity
ISBN 0-465-07835-4
2006. The Trouble With Physics: The Rise
of String Theory, the Fall of a Science,
and What Comes Next. Houghton Mifflin.
ISBN 978-0-618-55105-7
2013. Time Reborn: From the Crisis in
Physics to the Future of the Universe.
ISBN 978-0547511726
2014 The Singular Universe and the
Reality of Time: A Proposal in Natural
Philosophy by Lee Smolin and Roberto
Mangabeira Unger, Cambridge University
Press, ISBN 978-1107074064
Awards and honors
Smolin was named as #21 on Foreign
Policy Magazine's list of Top 100 Public
Intellectuals. He is also one of many
physicists dubbed the "New Einstein" by
the media. The Trouble with Physics was
named by Newsweek magazine as number 17
on a list of 50 “Books for our Time”,
June 27, 2009. In 2007 he was awarded
the Majorana Prize from the Electronic
Journal of Theoretical Physics, and in
2009 the Klopsteg Memorial Award from
the American Association of Physics
Teachers for “extraordinary
accomplishments in communicating the
excitement of physics to the general
public,” He is a fellow of the Royal
Society of Canada and the American
Physical Society. In 2014 he was awarded
the Buchalter Cosmology Prize for a work
published in collaboration with Marina
Cortês.
Personal life
Smolin was born in New York City, USA.
His father is Michael Smolin, an
environmental and process engineer and
his mother is the playwright Pauline
Smolin. Lee Smolin has stayed involved
with theatre becoming a scientific
consultant for such plays as A Walk in
the Woods by Lee Blessing, Background
Interference by Drucilla Cornell and
Infinity by Hannah Moscovitch. He is
married to Dina Graser, a lawyer and
public servant in Toronto. His brother
is law professor David M. Smolin.
References
External links
A partial list of Smolin's published
work
A debate of the merits of string theory
between Smolin and Brian Greene, from
National Public Radio
"The Unique Universe": Smolin explains
his skepticism re the multiverse
Closer to the Truth: Series of
interviews by Smolin on fundamental
issues in physics
"Time Reborn: a new theory of time - a
new view of the world" on YouTube:
Smolin's presentation at the Royal
Society of Arts
Lee Smolin at the Mathematics Genealogy
Project
