The Road to Reality: A Complete Guide to the Laws of the Universe
Encyclopedia
The Road to Reality: A Complete Guide to the Laws of the Universe is a book on modern physics
by the British mathematical physicist Roger Penrose
, published in 2004. It covers the basics of the Standard Model
of particle physics, discussing general relativity
and quantum mechanics
, and discusses the possible unification of these two theories.
The book is just over 1100 pages, of which the first 383 are dedicated to mathematics—Penrose's goal was to acquaint inquisitive readers with the mathematical tools needed to understand the remainder of the book in depth. Physics enters the discussion on page 383 with the topic of spacetime
. From there it moves on to fields
in spacetime, deriving the classical electrical and magnetic forces
from first principles
; that is, if one lives in spacetime of a particular sort, these fields develop naturally as a consequence. Energy
and conservation law
s appear in the discussion of Lagrangian
s and Hamiltonian
s, before moving on to a full discussion of quantum physics, particle theory
and quantum field theory
. A discussion of the measurement problem
in quantum mechanics is given a full chapter; superstrings are given a chapter near the end of the book, as are loop gravity and twistor theory
. The book ends with an exploration of other theories and possible ways forward.
The book discusses the physical world. Many fields that 19th century scientists believed were separate, such as electricity and magnetism, are aspects of more fundamental properties. Some texts, both popular and university level, introduce these topics as separate concepts, and then reveal their combination much later. The Road to Reality reverses this process, first expounding the underlying mathematics of spacetime
, then showing how electromagnetism and other phenomena fall out fully formed.
The final chapters reflect Penrose's personal perspective, which differs in some respects from what he regards as the current fashion among theoretical physicists. He is skeptical about string theory
, to which he prefers loop quantum gravity
. He is optimistic about his own approach, twistor theory
. He also holds some controversial views about the role of consciousness in physics, as laid out in his earlier books (see Shadows of the Mind
).
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
by the British mathematical physicist Roger Penrose
Roger Penrose
Sir Roger Penrose OM FRS is an English mathematical physicist and Emeritus Rouse Ball Professor of Mathematics at the Mathematical Institute, University of Oxford and Emeritus Fellow of Wadham College...
, published in 2004. It covers the basics of the Standard Model
Standard Model
The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Developed throughout the mid to late 20th century, the current formulation was finalized in the mid 1970s upon...
of particle physics, discussing general relativity
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...
and quantum mechanics
Quantum mechanics
Quantum 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 discusses the possible unification of these two theories.
The book is just over 1100 pages, of which the first 383 are dedicated to mathematics—Penrose's goal was to acquaint inquisitive readers with the mathematical tools needed to understand the remainder of the book in depth. Physics enters the discussion on page 383 with the topic of spacetime
Spacetime
In physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions...
. From there it moves on to fields
Field (physics)
In physics, a field is a physical quantity associated with each point of spacetime. A field can be classified as a scalar field, a vector field, a spinor field, or a tensor field according to whether the value of the field at each point is a scalar, a vector, a spinor or, more generally, a tensor,...
in spacetime, deriving the classical electrical and magnetic forces
Electromagnetism
Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
from first principles
First principles
In philosophy, a first principle is a basic, foundational proposition or assumption that cannot be deduced from any other proposition or assumption. In mathematics, first principles are referred to as axioms or postulates...
; that is, if one lives in spacetime of a particular sort, these fields develop naturally as a consequence. Energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
and conservation law
Conservation law
In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves....
s appear in the discussion of Lagrangian
Lagrangian
The Lagrangian, L, of a dynamical system is a function that summarizes the dynamics of the system. It is named after Joseph Louis Lagrange. The concept of a Lagrangian was originally introduced in a reformulation of classical mechanics by Irish mathematician William Rowan Hamilton known as...
s and Hamiltonian
Hamiltonian mechanics
Hamiltonian mechanics is a reformulation of classical mechanics that was introduced in 1833 by Irish mathematician William Rowan Hamilton.It arose from Lagrangian mechanics, a previous reformulation of classical mechanics introduced by Joseph Louis Lagrange in 1788, but can be formulated without...
s, before moving on to a full discussion of quantum physics, particle theory
Particle physics
Particle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...
and quantum field theory
Quantum field theory
Quantum field theory provides a theoretical framework for constructing quantum mechanical models of systems classically parametrized by an infinite number of dynamical degrees of freedom, that is, fields and many-body systems. It is the natural and quantitative language of particle physics and...
. A discussion of the measurement problem
Measurement problem
The measurement problem in quantum mechanics is the unresolved problem of how wavefunction collapse occurs. The inability to observe this process directly has given rise to different interpretations of quantum mechanics, and poses a key set of questions that each interpretation must answer...
in quantum mechanics is given a full chapter; superstrings are given a chapter near the end of the book, as are loop gravity and twistor theory
Twistor theory
In theoretical and mathematical physics, twistor theory maps the geometric objects of conventional 3+1 space-time into geometric objects in a 4 dimensional space with metric signature...
. The book ends with an exploration of other theories and possible ways forward.
The book discusses the physical world. Many fields that 19th century scientists believed were separate, such as electricity and magnetism, are aspects of more fundamental properties. Some texts, both popular and university level, introduce these topics as separate concepts, and then reveal their combination much later. The Road to Reality reverses this process, first expounding the underlying mathematics of spacetime
Spacetime
In physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions...
, then showing how electromagnetism and other phenomena fall out fully formed.
The final chapters reflect Penrose's personal perspective, which differs in some respects from what he regards as the current fashion among theoretical physicists. He is skeptical about string theory
String theory
String 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...
, to which he prefers loop quantum gravity
Loop quantum gravity
Loop 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 is optimistic about his own approach, twistor theory
Twistor theory
In theoretical and mathematical physics, twistor theory maps the geometric objects of conventional 3+1 space-time into geometric objects in a 4 dimensional space with metric signature...
. He also holds some controversial views about the role of consciousness in physics, as laid out in his earlier books (see Shadows of the Mind
Shadows of the Mind
Shadows of the Mind: A Search for the Missing Science of Consciousness is a 1994 book by mathematical physicist Roger Penrose, and serves as a followup to his 1989 book The Emperor's New Mind: Concerning Computers, Minds and The Laws of Physics....
).
Editions
- Alfred A. Knopf (publisher), February 2005, hardcover, ISBN 0-679-45443-8
- Vintage Books, 2005, softcover, ISBN 0-09-944068-7
- Vintage Books, 2006, softcover, ISBN 0-099-44068-7
- Vintage Books, 2007, softcover, ISBN 0-679-77631-1
External links
- Site with errata and solutions to some exercises from the first few chapters. Not sponsored by Penrose.
- Internet forum.