Many lives in many worlds


Author: Max Tegmark

Abstract: I argue that accepting quantum mechanics to be universally true means that you should also believe in parallel universes. I give my assessment of Everett's theory as it celebrates its 50th anniversary.

Reference info: 0707.2593 [quant-ph]. Nature, 448, 23-24 (July 2007)

Download: The Nature version with nice graphics is freely available here. You can download the quant-ph version (with inferior graphics) here.

Comments: This paper is extremely brief because of the Nature boundary conditions. You'll find more meat in the papers described further down on this page. Also, please take a look at the fascinating Everett biography that's available here.

Tegmark & Wheeler: 100 Years of the Quantum

The paper described below appeared in the February 2001 issue of Scientific American.

What goes at the top?

Please click here to download a PDF file with the paper.

100 Years of the Quantum

Authors:

Max Tegmark & John Archibald Wheeler

Abstract:

As quantum theory celebrates its 100th birthday, spectacular successes are mixed with outstanding puzzles and promises of new technologies. This article reviews both the successes of quantum theory and the ongoing debate about its consequences for issues ranging from quantum computation to consciousness, parallel universes and the nature of physical reality. We argue that modern experiments and the discovery of decoherence have have shifted prevailing quantum interpretations away from wave function collapse towards unitary physics, and discuss quantum processes in the framework of a tripartite subject-object-environment decomposition. We conclude with some speculations on the bigger picture and the search for a unified theory of quantum gravity.
 

Reference info:

quant-ph/0101077. Scientific American, Feb. 2001, p68-75

Comments:

The paper available above is the original (``director's cut'') version of the Scientific American article, with more text and inferior graphics. If you find this paper interesting, you might also want to look at two papers of mine going into greater depth on Everett's Many-Worlds Interpretation of quantum mechanics and on ``Theories of Everything''. You'll find a useful set of Many-World links in the Stanford Encyclopedia of Philosophy and below.
If you prefer non-technical articles, this paper of mine was covered by New Scientist and the the Guardian.

The Interpretation of Quantum Mechanics:

Many Worlds or Many Words?

Please click here to download the paper (PDF).

Author: Max Tegmark


Abstract:

As cutting-edge experiments display ever more extreme forms of non-classical behavior, the prevailing view on the interpretation of quantum mechanics appears to be gradually changing. A (highly unscientific) poll taken at the 1997 UMBC quantum mechanics workshop gave the once all-dominant Copenhagen interpretation less than half of the votes. The Many Worlds interpretation (MWI) scored second, comfortably ahead of the Consistent Histories and Bohm interpretations. It is argued that since all the above-mentioned approaches to nonrelativistic quantum mechanics give identical cookbook prescriptions for how to calculate things in practice, practical-minded experimentalists, who have traditionally adopted the ``shut-up-and-calculate interpretation'', typically show little interest in whether cozy classical concepts are in fact real in some untestable metaphysical sense or merely the way we subjectively perceive a mathematically simpler world where the Schrodinger equation describes everything - and that they are therefore becoming less bothered by a profusion of worlds than by a profusion of words.

Common objections to the MWI are discussed. It is argued that when environment-induced decoherence is taken into account, the experimental predictions of the MWI are identical to those of the Copenhagen interpretation except for an experiment involving a Byzantine form of ``quantum suicide''. This makes the choice between them purely a matter of taste, roughly equivalent to whether one believes mathematical language or human language to be more fundamental.

Publication info:

quant-ph/9709032, in proceedings of UMBC workshop ``Fundamental Problems in Quantum Theory'', eds. M. H. Rubin & Y. H. Shih (1997)

This cartoon illustrated the reader comments when my paper was featured in New Scientist (in the issue of January 24, 1998)
 
 



 
  My original paper, upon which this article was based, is at the top of this page (click here).

Quantum immortality

I've been getting lots of emails about whether the many-worlds interpretations implies subjective immortality more generally. Here's an email I wrote on the subject:

From max@sns.ias.edu Sat Nov 28 13:20 EST 1998
To: everything-list@eskimo.com, max@sns.ias.edu
Subject: Quantum immortality

Hi guys,

Here's a brief comment on the issue of whether the MWI implies subjective immortality. This has bothered me for a long time, and a number of people have emailed me about it after the Guardian and New Scientist articles came out. I agree that if the argument were flawless, I should expect to be the oldest guy on the planet, severely discrediting the Everett hypothesis. However, I think there's a flaw. After all, dying isn't a binary thing where you're either dead or alive - rather, there's a whole continuum of states of progressively decreasing self-awareness. What makes the quantum suicide work is that you force an abrupt transition. I suspect that when I get old, my brain cells will gradually give out (indeed, that's already started happening...) so that I keep feeling self-aware, but less and less so, the final "death" being quite anti-climactic, sort of like when an amoeba croaks. Do you buy this?

I think a successful quantum suicide experiment needs to satisfy three criteria:
  1. The random number generator must be quantum, not classical (deterministic), so that you really enter a superposition of dead and alive.
  2. It must kill you (at least make you unconscious) on a timescale shorter than that on which you can become aware of the outcome of the quantum coin-toss - otherwise you'll have a very unhappy version of yourself for a second or more who knows he's about to die for sure, and the whole effect gets spoiled.
  3. It must be virtually certain to really kill you, not just injure you.
Most accidents and common causes of death clearly don't satisfy all three.

Links

You'll find a useful set of Many-World links in the Stanford Encyclopedia of Philosophy. Related papers: This site also contains the latest versions of some closely related papers of mine: Return to my home page
This page was last modified July 18, 2007.
tegmark@mit.edu