Lee Smolin
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Lee Smolin at Harvard
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| Born | June 6, 1955 |
| Nationality | American |
| Alma mater | Hampshire College (B.A., 1975) Harvard University (A.M., 1978; Ph.D, 1979) |
| Awards | Majorana Prize (2007) Klopsteg Memorial Award (2009) Queen Elizabeth II Diamond Jubilee Medal (2013) |
| Scientific career | |
| Fields | Physics Cosmology |
| Institutions | Perimeter Institute, University of Waterloo |
| Doctoral advisor | Sidney Coleman Stanley Deser |
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's 2006 book The Trouble with Physics criticized string theory as a viable scientific theory. He has made 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 (1999-2001) before becoming one of the founding faculty members at the Perimeter Institute in 2001.
Theories and work
Loop quantum gravity
Smolin contributed to the theory of loop quantum gravity (LQG) 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. (See main
page loop quantum gravity.)
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 to provide a fundamental
formulation of string theory that does not depend on approximate
descriptions involving classical background spacetime 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 (with João Magueijo, independently of work by Giovanni Amelino-Camelia) and of relative locality (with Amelino-Camelia, Laurent Freidel and Jerzy Kowalski-Glikman).
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 interpretation 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.
Black holes have a role in natural selection. In fecund theory a collapsing black hole
causes the emergence of a new universe on the "other side", whose
fundamental constant parameters (masses of elementary particles, Planck constant, elementary charge,
and so forth) 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.
Alternatively, black holes play a role in cosmological natural
selection by reshuffling only some matter affecting the distribution of
elementary quark universes. 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.
Even Stephen Hawking, who was the largest proponent of the idea that
information is lost in a black hole, later reversed his position.
The implication is that 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 returned to
lower the mass threshold for production of a black hole. A
1.97-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 the 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 written 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" (p. 179). 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 was 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 (2002), 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 (the sentences in italics are quotations):
- 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 on similar grounds to his objections against the multiverse.
He does not definitively exclude or reject religion or mysticism but
rather believes that science should only deal with that of which is
observable. 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.
(2) 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." (Time Reborn p 265.)
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 (AAPT) 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. 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, Ontario. His brother is law professor David M. Smolin.
Publications
The following books are non-technical, and can be appreciated by those who are not physicists.
- 1997. 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
