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