Laplace's demon

Laplace's demon

Ask a question about 'Laplace's demon'
Start a new discussion about 'Laplace's demon'
Answer questions from other users
Full Discussion Forum
In the history of science
History of science
The history of science is the study of the historical development of human understandings of the natural world and the domains of the social sciences....

, Laplace's demon was the first published articulation of causal or scientific determinism by Pierre-Simon Laplace
Pierre-Simon Laplace
Pierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...

 in 1814. According to determinism, if someone knows the precise location and momentum of every atom in the universe, their past and future values for any given time are entailed; they can be calculated from the laws of classical mechanics
Classical mechanics
In physics, classical mechanics is one of the two major sub-fields of mechanics, which is concerned with the set of physical laws describing the motion of bodies under the action of a system of forces...


English translation

This intellect is often referred to as Laplace's demon (and sometimes Laplace's Superman, after Hans Reichenbach
Hans Reichenbach
Hans Reichenbach was a leading philosopher of science, educator and proponent of logical empiricism...

). Laplace, himself, did not use the word "demon", which was a later embellishment. As translated into English above, he simply referred to: "Une intelligence... Rien ne serait incertain pour elle, et l'avenir comme le passé, serait présent à ses yeux."

Arguments against Laplace's demon

Due to its assumption of determinism, Laplace's thought experiment is inherently incompatible with quantum mechanical
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...

 theories, where chance is an essential part of the world's unfolding. The Heisenberg Uncertainty Principle, for example, states that exact measurements of positions and momentum may not be defined (and observed) together with more than a given precision.

John Polkinghorne
John Polkinghorne
John 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...

 argues that nature is cloud-like rather than clock-like and points out that, apart from any other problems, uncertainty about the exact position of an electron on the other side of the universe would be sufficient to invalidate a calculation about the position of an O2 molecule in air after 50 collisions with its neighbours (i.e. in about 0.1 ns), even if they were solely influenced by Newton's laws.

According to chemical engineer Robert Ulanowicz
Robert Ulanowicz
Robert Edward Ulanowicz is an American theoretical ecologist and philosopher who is best known for his search for a unified theory of ecology. He was born September 17, 1943 in Baltimore, Maryland....

, in his 1986 book Growth and Development, Laplace's demon met its end with early 19th century developments of the concepts of irreversibility
In science, a process that is not reversible is called irreversible. This concept arises most frequently in thermodynamics, as applied to processes....

, entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...

, and the second law of thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...

. In other words, Laplace's demon was based on the premise of reversibility
Reversible process (thermodynamics)
In thermodynamics, a reversible process, or reversible cycle if the process is cyclic, is a process that can be "reversed" by means of infinitesimal changes in some property of the system without loss or dissipation of energy. Due to these infinitesimal changes, the system is in thermodynamic...

 and classical mechanics; however, under current theory, thermodynamics (i.e. real processes) are thought to be irreversible in practical terms (compared to the age of the universe, for instance).

In 2008, David Wolpert used Cantor diagonalization to disprove Laplace's demon. He did this by assuming that the demon is a computational device and showing that no two such devices can completely predict each other. If the demon were not contained within and computed by the universe, any accurate simulation of the universe would be indistinguishable from the universe to an internal observer, and the argument remains distinct from what is observable.

Recent views

There has recently been proposed a limit on the computational power of the universe, i.e. the ability of Laplace's Demon to process an infinite amount of information. The limit is based on the maximum entropy of the universe, the speed of light, and the minimum amount of time taken to move information across the Planck length, and the figure was shown to be about 10120 bits. Accordingly, anything that requires more than this amount of data cannot be computed in the amount of time that has elapsed so far in the universe.

Another theory suggests that if Laplace's demon were to occupy a parallel universe or alternate dimension from which it could determine the implied data and do the necessary calculations on an alternate and greater time line the aforementioned time limitation would not apply. This position is for instance explained in David Deutsch
David Deutsch
David Elieser Deutsch, FRS is an Israeli-British physicist at the University of Oxford. He is a non-stipendiary Visiting Professor in the Department of Atomic and Laser Physics at the Centre for Quantum Computation in the Clarendon Laboratory of the University of Oxford...

's The Fabric of Reality
The Fabric of Reality
The Fabric of Reality is a book by physicist David Deutsch written in 1997. It expands upon his views of quantum mechanics and its implications for understanding reality....

, who says that realizing a 300-qubit
In quantum computing, a qubit or quantum bit is a unit of quantum information—the quantum analogue of the classical bit—with additional dimensions associated to the quantum properties of a physical atom....

 quantum computer
Quantum computer
A quantum computer is a device for computation that makes direct use of quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from traditional computers based on transistors...

 would prove the existence of parallel universes carrying the computation.

In popular culture

  • In Rozen Maiden
    Rozen Maiden
    is a manga series created by Peach-Pit. The story centers on Jun Sakurada, a young hikikomori boy that forms a bond with Shinku, a living doll of the "Rozen Maiden" series, who was created by the mysterious dollmaker Rozen hundreds of years ago...

     by Peach-Pit
    is a female manga artist duo in Japan, made up of and . Their group name derives from the diner hangout Peach-Pit from the TV show Beverly Hills, 90210. Although both have similar styles, with some artwork it is possible to identify which artist drew it. Both are known for their bishōjo styled works...

    , Laplace No Ma (Laplace's demon) is a character that prompts the Rozen Maiden's mission with riddles, and appears only in the N-field. He looks like a white rabbit in a tuxedo but acts more like the Cheshire Cat
    Cheshire Cat
    The Cheshire Cat is a fictional cat popularised by Lewis Carroll's depiction of it in Alice's Adventures in Wonderland. Known for his distinctive mischievous grin, the Cheshire Cat has had a notable impact on popular culture.-Origins:...

    , an obvious play on both characters from "Alice's Adventures in Wonderland
    Alice's Adventures in Wonderland
    Alice's Adventures in Wonderland is an 1865 novel written by English author Charles Lutwidge Dodgson under the pseudonym Lewis Carroll. It tells of a girl named Alice who falls down a rabbit hole into a fantasy world populated by peculiar, anthropomorphic creatures...

  • In Adam Fawer
    Adam Fawer
    Adam Fawer is an American Novelist. Improbable, his first novel, has been translated into eighteen languages and won the 2006 International Thriller Writers Award for best first novel...

    's "Improbable
    Improbable is a 2005 science fiction thriller novel by Adam Fawer, about a gambler who gains the power to predict the future. It was awarded the 2006 International Thriller Writers Award for best first novel.-Plot summary:...

    : A Novel", the main character becomes a personification of Laplace's demon.
  • Laplace No Ma (Laplace's Demon) is a 1993 video game for the SNES
    Super Nintendo Entertainment System
    The Super Nintendo Entertainment System is a 16-bit video game console that was released by Nintendo in North America, Europe, Australasia , and South America between 1990 and 1993. In Japan and Southeast Asia, the system is called the , or SFC for short...

  • The Masoukishin Cybuster
    is a 26 episode anime that aired in Japan between May 3, 1999 and October 25, 1999.-Plot:The story is set in 2040 after a disaster happens in Tokyo in 2029. The main character Ken Ando joins up with a company designated to clean up Tokyo, called DC...

     from the Super Robot Wars
    Super Robot Wars
    is a series of tactical role-playing video games produced by Banpresto, which is now a Japanese division of Namco Bandai. The main feature of the franchise is having a story that crosses over several popular mecha anime, manga and video games, allowing characters and mecha from different titles to...

     metaseries possesses the 'Laplace's Demon Computer' which gives it the ability to predict the future as well as editing/altering events in the timeline itself. A similar (though less powerful) device is used by another giant robot, the Unicorn Gundam
    Mobile Suit Gundam Unicorn
    is a novel by popular Japanese author Harutoshi Fukui . The novel takes place in Gundam's Universal Century timeline. Character and mechanical designs are provided by Yoshikazu Yasuhiko and Hajime Katoki, respectively...

  • The character Sion Eltnam Atlasia, from Type-Moon
    is a Japanese game company, best known for their visual novels, co-founded by author Kinoko Nasu and illustrator Takashi Takeuchi. It is also known under the name for its publishing and corporate operations...

    's PC game Melty Blood
    Melty Blood
    , is a visual novel and fighting game, co-developed by dōjin circles Type-Moon and French-Bread, originally released at Comiket on December 2002...

    and all practitioners of her branch of alchemy employ a method for predicting the future modeled after Laplace's demon.
  • Laplace's Demon appeared, alongside Maxwell's Demon
    Maxwell's demon
    In the philosophy of thermal and statistical physics, Maxwell's demon is a thought experiment created by the Scottish physicist James Clerk Maxwell to "show that the Second Law of Thermodynamics has only a statistical certainty." It demonstrates Maxwell's point by hypothetically describing how to...

    , in Animal Man
    Animal Man
    Animal Man is a fictional character, a superhero in the . As a result of being in proximity to an exploding extraterrestrial spaceship, Buddy Baker acquires the ability to temporarily “borrow” the abilities of animals...

    #86. The Demon does not move and does nothing, driven insane by its task.
  • In The Hitchhiker's Guide to the Galaxy
    The Hitchhiker's Guide to the Galaxy
    The Hitchhiker's Guide to the Galaxy is a science fiction comedy series created by Douglas Adams. Originally a radio comedy broadcast on BBC Radio 4 in 1978, it was later adapted to other formats, and over several years it gradually became an international multi-media phenomenon...

     series' fifth book (Mostly Harmless
    Mostly Harmless
    Mostly Harmless is a novel by Douglas Adams and the fifth book in the Hitchhiker's Guide to the Galaxy series. It is described on the cover of the first editions as "The fifth book in the increasingly inaccurately named Hitchhikers Trilogy"...

    ), the guide mark II is said to have "no filters" and has the ability to perceive all time, matter and tangent universes similar to Laplace's Demon.
  • In the video game Shin Megami Tensei: Devil Survivor
    Shin Megami Tensei: Devil Survivor
    Shin Megami Tensei: Devil Survivor, known in Japan as , is a role-playing game for the Nintendo DS. It was released in Japan on 15 January 2009 and was released in North America on June 23, 2009. Its character designs are handled by Suzuhito Yasuda...

    , the protagonists are sent daily "Laplace Mails", e-mails that predict various deaths and disasters that are certain to occur later that day unless the protagonists intervene.
  • Dresden Codak
    Dresden Codak
    Dresden Codak is a webcomic written and illustrated by Aaron Diaz. Described by Diaz as a "celebration of science, death and human folly", the comic presents stories that deal with elements of philosophy, science and technology, and/or psychology...

     features a comic titled "Exorcising Laplace's Demon".
  • Dr. Manhattan in Allan Moore's Watchmen resembles Laplace's Demon in that he can perceive the past, present, and future.
  • In the Phineas and Ferb
    Phineas and Ferb
    Phineas and Ferb is an American animated television comedy series. Originally broadcast as a preview on August 17, 2007, on Disney Channel, the series follows Phineas Flynn and his English stepbrother Ferb Fletcher on summer vacation. Every day the boys embark on some grand new project, which...

    episode "Ask a Foolish Question", Phineas and Ferb build a supercomputer that can "answer any question." Upon booting up, the computer scans the entire city, creating a starting data-set like that of Laplace's Demon. Given that the instructions in the computer's cryptic answers take advantage of wind-currents to achieve results, it is implied that this computer can predict the future, sharing the properties of the Demon, but possibly on a smaller scale.