**Lee Smolin** is an American theoretical physicist, a researcher at the

Perimeter Institute for Theoretical PhysicsPerimeter Institute for Theoretical Physics is an independent, resident-based research institute devoted to foundational issues in theoretical physics located in Waterloo, Ontario, Canada. Perimeter Institute was founded in 1999 by Mike Lazaridis...

, and an adjunct professor of physics at the

University of WaterlooThe University of Waterloo is a comprehensive public university in the city of Waterloo, Ontario, Canada. The school was founded in 1957 by Drs. Gerry Hagey and Ira G. Needles, and has since grown to an institution of more than 30,000 students, faculty, and staff...

. He is married to Dina Graser, a communications lawyer in

TorontoToronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...

. His brother is

David M. SmolinDavid Mark Smolin is a professor of law at Cumberland School of Law in Birmingham, Alabama where he is the Harwell G...

.

Smolin is best known for devising several different approaches to

quantum gravityQuantum gravity is the field of theoretical physics which attempts to develop scientific models that unify quantum mechanics with general relativity...

, in particular

loop quantum gravityLoop quantum gravity , also known as loop gravity and quantum geometry, is a proposed quantum theory of spacetime which attempts to reconcile the theories of quantum mechanics and general relativity...

. He advocates that the two primary approaches to quantum gravity, loop quantum gravity and

string theoryString theory is an active research framework in particle physics that attempts to reconcile quantum mechanics and general relativity. It is a contender for a theory of everything , a manner of describing the known fundamental forces and matter in a mathematically complete system...

, can be reconciled as different aspects of the same underlying theory. His research interests also include

cosmologyCosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...

,

elementary particleIn particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which...

theory, the foundations of

quantum mechanicsQuantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

, and theoretical biology.

## Early life

Smolin was born in New York City to Michael Smolin, an engineer, and Pauline Smolin, a playwright. His brother,

David M. SmolinDavid Mark Smolin is a professor of law at Cumberland School of Law in Birmingham, Alabama where he is the Harwell G...

, became a professor in the

Cumberland School of LawCumberland School of Law is an ABA accredited law school at Samford University in Birmingham, Alabama. The 11th oldest law school in the United States, it is 160 years old and has more than 11,000 graduates. Its alumni include two United States Supreme Court Justices; Nobel Peace Prize recipient...

in Birmingham, Alabama. He was educated at

Hampshire CollegeHampshire College is a private liberal arts college in Amherst, Massachusetts. It was founded in 1965 as an experiment in alternative education, in association with four other colleges in the Pioneer Valley: Amherst College, Smith College, Mount Holyoke College, and the University of Massachusetts...

. He received his Ph.D in

theoretical physicsTheoretical physics is a branch of physics which employs mathematical models and abstractions of physics to rationalize, explain and predict natural phenomena...

from

Harvard UniversityHarvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

in 1979.

### Fecund universes

The

**fecund universes** theory of

cosmologyPhysical cosmology, as a branch of astronomy, is the study of the largest-scale structures and dynamics of the universe and is concerned with fundamental questions about its formation and evolution. For most of human history, it was a branch of metaphysics and religion...

advanced by Lee Smolin, also called

**cosmological natural selection** theory, suggests that a process analogous to biological

natural selectionNatural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

applies at the grandest scales. Smolin summarized the idea in a book aimed at a lay audience called

*The Life of the Cosmos*The Life of the Cosmos is a 1997 book by theoretical physicist Lee Smolin. In the book, Smolin details his fecund universes theory which applies the principle of natural selection to the birth of universes. Smolin posits that the collapse of black holes could lead to the creation of a new universe...

.

The theory surmises that a collapsing

black holeA black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...

causes the emergence of a new universe on the "other side", whose fundamental constant parameters (

speed of lightThe speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

,

Planck length and so forth) may differ slightly from those of the universe where the black hole collapsed. Each universe therefore gives rise to as many new universes as it has black holes. Thus the theory contains the evolutionary ideas of "reproduction" and "mutation" of universes, but has no

*direct* analogue of

natural selectionNatural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

. However, given any universe that can produce black holes that successfully spawn new universes, it is possible that some number of those universes will reach

heat deathThe heat death of the universe is a suggested ultimate fate of the universe, in which the universe has diminished to a state of no thermodynamic free energy and therefore can no longer sustain motion or life. Heat death does not imply any particular absolute temperature; it only requires that...

with unsuccessful parameters. So, in a sense, fecundity cosmological natural selection is one where universes could die off before successfully reproducing, just as any biological being can die without having offspring.

Leonard SusskindLeonard Susskind is the Felix Bloch Professor of Theoretical Physics at Stanford University. His research interests include string theory, quantum field theory, quantum statistical mechanics and quantum cosmology...

, who promotes a similar

string theory landscapeThe string theory landscape or anthropic landscape refers to the large number of possible false vacua in string theory. The "landscape" includes so many possible configurations that some physicists think that the known laws of physics, the standard model and general relativity with a positive...

, stated:

"I'm not sure why Smolin's idea didn't attract much attention. I actually think it deserved far more than it got"

Smolin has noted that the string theory landscape is not

Popper falsifiableSir Karl Raimund Popper, CH FRS FBA was an Austro-British philosopher and a professor at the London School of Economics...

if other universes are not observable. This is the subject of the Smolin-Susskind debate. There are then only two ways out: traversable

wormholeIn physics, a wormhole is a hypothetical topological feature of spacetime that would be, fundamentally, a "shortcut" through spacetime. For a simple visual explanation of a wormhole, consider spacetime visualized as a two-dimensional surface. If this surface is folded along a third dimension, it...

s connecting the different parallel universes and "signal nonlocality", as described by

Antony ValentiniAntony Valentini is a theoretical physicist and a professor at Clemson University. He is known for his work on the foundations of quantum physics.- Education and career :...

, a scientist at the Perimeter Institute.

In a critical review of

*The Life of the Cosmos*The Life of the Cosmos is a 1997 book by theoretical physicist Lee Smolin. In the book, Smolin details his fecund universes theory which applies the principle of natural selection to the birth of universes. Smolin posits that the collapse of black holes could lead to the creation of a new universe...

, the astrophysicist

Joe SilkJoseph Ivor Silk is the Savilian Chair of Astronomy at the University of Oxford. He came back to the UK in 1999 to take up the position, following a nearly 30-year career at the University of California, Berkeley. He was educated at Tottenham County School and Cambridge University . He held...

suggested that our universe falls short by about four orders of magnitude of being maximal for the production of black holes. In his book

*Questions of Truth*Questions of Truth is a book by John Polkinghorne and Nicholas Beale which offers their responses to 51 questions about science and religion...

, the particle physicist

John PolkinghorneJohn Charlton Polkinghorne KBE FRS is an English theoretical physicist, theologian, writer, and Anglican priest. He was professor of Mathematical physics at the University of Cambridge from 1968 to 1979, when he resigned his chair to study for the priesthood, becoming an ordained Anglican priest...

has another difficulty with Smolin's thesis, in that one cannot impose the consistent multiversal time which would be required to make the evolutionary dynamics work, since otherwise short-lived universes with few descendants would dominate long-lived universes with many.

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. If a more massive neutron star was ever observed, it would show that our universe's natural laws were not tuned for maximum 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, so that cosmological natural selection has been falsified according to Smolin's own criteria.

## Controversy

The 2006 publication of

*The Trouble with Physics* generated debate about the merits of string theory. The book was criticized by physicists

Joseph PolchinskiJoseph Polchinski is a physicist working on string theory. He graduated from Canyon del Oro High School in Tucson, Arizona in 1971, obtained his B.S. degree from Caltech in 1975, and his Ph.D. from the University of California, Berkeley in 1980 under the supervision of Stanley Mandelstam...

and

Luboš MotlLuboš Motl is a Czech theoretical physicist who keeps a blog commenting on physics, global warming and politics. His scientific research concentrated on string theory, of which he has been a passionate defender. He proposed Matrix string theory in 1997.Motl was born in Plzeň, Czech Republic...

.

In his earlier book

*Three Roads to Quantum Gravity*Three Roads to Quantum Gravity is a 2001 book by theoretical physicist Lee Smolin. He discusses three potential approaches by which a unified theory of quantum gravity, arguably the foremost issue in theoretical physics, may be realized. Approaches discussed include string theory, M-theory, and...

(2002), Smolin stated that

loop quantum gravityLoop quantum gravity , also known as loop gravity and quantum geometry, is a proposed quantum theory of spacetime which attempts to reconcile the theories of quantum mechanics and general relativity...

and string theory were essentially the same concept seen from different perspectives. In that book, he also favored the

holographic principleThe holographic principle is a property of quantum gravity and string theories which states that the description of a volume of space can be thought of as encoded on a boundary to the region—preferably a light-like boundary like a gravitational horizon...

.

*The Trouble with Physics*, on the other hand, was strongly critical of the prominence of

string theoryString theory is an active research framework in particle physics that attempts to reconcile quantum mechanics and general relativity. It is a contender for a theory of everything , a manner of describing the known fundamental forces and matter in a mathematically complete system...

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 gravityQuantum gravity is the field of theoretical physics which attempts to develop scientific models that unify quantum mechanics with general relativity...

, and argued that more attention should be paid to

loop quantum gravityLoop quantum gravity , also known as loop gravity and quantum geometry, is a proposed quantum theory of spacetime which attempts to reconcile the theories of quantum mechanics and general relativity...

, 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.

Smolin's thesis found support in one corner. In the same year as that in which

*The Trouble with Physics* was published,

Peter WoitPeter Woit is a Departmental Computer Administrator and Senior Lecturer in Discipline at Columbia University, known for his criticisms of string theory in his book Not Even Wrong, and his blog of the same name.-Career:...

also published a book for nonspecialists, whose conclusion was similar to Smolin's, namely that string theory was a fundamentally flawed research program.

Smolin was recently named as #21 on Foreign Policy Magazine's list of Top 100 Public Intellectuals.

Smolin is also one of many physicists dubbed the "New Einstein" by the media.

## Smolin-Susskind Debate

The Smolin-Susskind debate refers to the series of intense postings in 2004 by Lee Smolin and

Leonard SusskindLeonard Susskind is the Felix Bloch Professor of Theoretical Physics at Stanford University. His research interests include string theory, quantum field theory, quantum statistical mechanics and quantum cosmology...

, concerning Smolin’s argument: "[The]

Anthropic PrincipleIn astrophysics and cosmology, the anthropic principle is the philosophical argument that observations of the physical Universe must be compatible with the conscious life that observes it. Some proponents of the argument reason that it explains why the Universe has the age and the fundamental...

cannot yield any falsifiable predictions, and therefore cannot be a part of science".

## Views

Smolin does not believe that

quantum mechanicsQuantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

is a "final theory":

"I am convinced that quantum mechanicsQuantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

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

philosophicalPhilosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

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" multiverseThe multiverse is the hypothetical set of multiple possible universes that together comprise all of reality.Multiverse may also refer to:-In fiction:* Multiverse , the fictional multiverse used by DC Comics...

. 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 metaphysicalMetaphysics is a branch of philosophy concerned with explaining the fundamental nature of being and the world, although the term is not easily defined. Traditionally, metaphysics attempts to answer two basic questions in the broadest possible terms:...

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 SciencesThe Unreasonable Effectiveness of Mathematics in the Natural Sciences is the title of an article published in 1960 by the physicist Eugene Wigner...

".

Smolin is non-religious, believing that "there never was a God, no pilot who made the world by imposing order on chaos and who remains outside, watching and proscribing." He also opposes the

anthropic principleIn astrophysics and cosmology, the anthropic principle is the philosophical argument that observations of the physical Universe must be compatible with the conscious life that observes it. Some proponents of the argument reason that it explains why the Universe has the age and the fundamental...

, which he claims "cannot help us to do science."

## Publications

The following books are relatively non-technical, and can be appreciated by those who are not physicists.

- 1999.
*The Life of the Cosmos*The Life of the Cosmos is a 1997 book by theoretical physicist Lee Smolin. In the book, Smolin details his fecund universes theory which applies the principle of natural selection to the birth of universes. Smolin posits that the collapse of black holes could lead to the creation of a new universe...

- 2001.
*Three Roads to Quantum Gravity*Three Roads to Quantum Gravity is a 2001 book by theoretical physicist Lee Smolin. He discusses three potential approaches by which a unified theory of quantum gravity, arguably the foremost issue in theoretical physics, may be realized. Approaches discussed include string theory, M-theory, and...

- 2006.
*The Trouble With Physics*The Trouble With Physics is a 2006 book by the theoretical physicist Lee Smolin about the problems with string theory. Subtitled The Rise of String Theory, the Fall of a Science, and What Comes Next, the book strongly criticizes string theory and its prominence in contemporary theoretical physics,...

: The Rise of String Theory, the Fall of a Science, and What Comes Next. Houghton Mifflin. ISBN 978-0-618-55105-7.

## External links

- A partial list of Smolin's published work.
- A debate of the merits of string theory between Smolin and Brian Greene
Brian Greene is an American theoretical physicist and string theorist. He has been a professor at Columbia University since 1996. Greene has worked on mirror symmetry, relating two different Calabi-Yau manifolds...

, from National Public Radio
- "The Unique Universe." Smolin explains his skepticism re the multiverse
The multiverse is the hypothetical set of multiple possible universes that together comprise all of reality.Multiverse may also refer to:-In fiction:* Multiverse , the fictional multiverse used by DC Comics...

.
- Closer to the Truth Series of interviews by Smolin on fundamental issues in physics.