The Many Worlds of Hugh Everett III: Multiple Universes, Mutual Assured Destruction, and the Meltdown of a Nuclear Family
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16 Bohr, N. and Rosenfeld, L. (1933). 479. In later chapters, we will further explain Bohr’s outlook.
17 Wheeler to NSF, 1/13/55.
1 DeWitt, B. and Graham, N. eds. (1973). 134.
2 Probability waves move through an infinite-dimensional “configuration” space and are picked out by our limited senses as particles taking definite positions in a three-dimensional space.
3 Feynman, R. (1965). 141.
4 Technically, it is the modulus of the probability amplitude, a complex number, which is squared. This ensures that the resultant probability will be positive, as complex numbers can be negative. Because these numbers can be negative, wave functions can cancel each other.
5 The mathematical “linearity” of the “unitary” Schrödinger equation conserves probability in the sense that after all of the elements in a superposition are measured, their probabilities total 1 (100 percent). This is a mysterious and deep property of quantum mechanics: chance is not lost, but neither is it chance until it is measured.
6 Born, M. (1926). 54.
7 Born, M. (1926B). 804.
8 Heisenberg, W. (1927B). 83.
9 Ibid. 73.
10 Spin is a purely quantum mechanical property having to do with angular momentum and magnetism. Spin “up” and “down” are convenient notations describing configurations of this property.
11 Jeffrey Barrett remarks, “On the standard theory, the measurement instantaneously affects the other particle, not by changing the determinate properties of the other particle, but by affecting the composite entangled state, and the two entangled particles only have a well-defined composite state (that is, they do not even have quantum mechanical states to call their own).” Barrett, private communication, July 2009.
12 Two decades later, John Stewart Bell proved mathematically that quantum mechanics is fundamentally non-local; experiments back him up. More on this later.
13 Schrödinger, E. (1935). 30.
14 Mott, N. (1929). 129–134.
15 Schrödinger, E. (1952A). 240–242.
16 Schrödinger, E. (1935A). 160.
17 Schrödinger, E. (1995).19–20; Sean Boocock observes that in modern quantum mechanics (due to decoherence), “the weird jellification that Schrödinger worries about does not come about on large scales simply because the probability of us ever being able to perceive it is too phenomenally low.” Private communication, 2009.
18 Schrödinger, E. (1935A). 154.
1 Frank, P. (1949). 234.
2 Zeh, private communication, 2008.
3 von Neumann, J. (1932). 619.
4 Ibid. 620–621.
5 Jammer, M. (1974). 475.
6 Ibid. 621–622.
7 Ibid. 623.
8 Beller, M. (1999). 159, 162.
9 See, for example, Jammer, M. (1974). 98–99, on Bohr’s de facto acceptance of wave function reduction when he privileges classicality. For a different reading of Bohr, see Howard, D. (2004).
10 Bohr, N. (1949). 17-18. Italics added.
11 Jammer, M. (1974). 474.
12 Bohr, N. to Hansen, H. P. E. 20 July 1935.
13 Bohr, N. (1956). 10. A mimeograph of this paper was in Everett’s papers.
14 Beller, M. (1999). 205.
15 Petersen, A. (1968). 142.
16 Petersen, A. (1968). 59–61. Italics added.
17 Bohr, N. (1956). 12.
18 Eddington, A.S. (1929).
19 Frank, P. (1954). 17; Philosophers were not united in this fear. Sean Boocock points out that the neo-Kantian philosopher of science, Ernest Cassirer, wrote in Determinism and Indeterminism in Physics (1936) that were quantum mechanics to be indeterminist, free will would be endangered. Ethics would be problematic in a world in which the course of one’s actions were subject to probability at all times. One philosopher’s free will is another philosopher’s ineluctable fate. Boocock, private communication, 2009.
20 Bohr, N. (1957).
21 Jammer, M. (1974). 330, quoting Belifante, F.J. (1970).
22 Google “Hugh Everett God exists” for treatises using Everett to support Deist theories.
1 Planck cited by Kuhn. T. S. (1962). 151.
2 Cartwright. N. (1987).
3 Since Jammer wrote his history, much research has been done on the subject of interpretation in quantum mechanics, but his book is a valuable resource for explicating the philosophy of quantum mechanics as it was understood in Everett’s day.
4 Jammer, M. (1974). 87.
5 Ibid. 250.
6 Margenau to Everett, 4/8/57. Enclosed in the letter was a copy of Margenau, H. (1956) from which the quotation is drawn.
7 Margenau, H. (1950). 422. Italics added.
8 Margenau, H. (1963).148; Margenau proposed a “latency” interpretation of quantum mechanics: see Jammer, M. (1974). 504–507.
9 Gell-Mann, M. (1994). 170; Baggot, private communication, 2009.
10 Bohm, D. (1952). 369.
11 Ibid. 392.
12 Jammer, M. (1974). 280.
13 DeWitt, B. and Graham, N. eds. (1973). 113.
14 Ibid. 112.
15 Ibid. 114–115.
16 Jammer, M. (1974). 440; Einstein, A. (1949). 671.
17 Quoted in Jammer, M. (1974). 440.
18 Einstein, A. (1949). 670.
19 Ibid. 671.
20 Ibid. 674.
21 DeWitt, B. and Graham, N. eds. (1973). 112.
22 Wigner, E. (1961). 169.
23 Ibid. 179.
24 Wigner, E. (1963). 338.
25 Jammer, M. (1974). 509, 517. Italics added.
26 DeWitt, B. and Graham, N. eds. (1973). 115.
1 Fromm, E. (1955). 170–171.
2 Wheeler, J. A. and Ford, K. (1998). 270.
3 The New York Times, 4/14/2008.
4 DeWitt-Morette interview, 2006.
5 Kenneth Ford interview of Wheeler on behalf of author.
6 Wheeler, J. A. and Ford, K. (1998). 109.
7 Ibid. 139.
8 Ibid. 124: “I am uneasy [because] I see no bedrock of logic on which quantum mechanics is founded. What is the underlying reason for quantum mechanics? I keep asking myself. It has to flow from something else, and that something else remains to be found.”
9 Wheeler, J. A. and Ford, K. (1998). 140.
10 Gleick, J. (1992). 93.
11 Wheeler, J. A. and Ford, K. (1998). 155.
12 Gleick, J. (1992). 107.
13 Gleick, J. (1991). 147.
14 Wheeler/Ford, transcript X, AIP.
15 Wheeler had many graduate students who made major contributions to physics. And Feynman’s work was of a very different nature than Everett’s—for one thing, it was experimentally verifiable.
16 Wheeler, J. A. and Ford, K. (1998). 42; Wheeler is not on record visiting the ruins of Dresden, Tokyo, Hiroshima, or Nagasaki to bear witness to American barbarism.
17 U.S. National Archives, Record Group 77, Records of the Chief of Engineers, Manhattan Engineer District, Harrison-Bundy File, folder #76.
18 Wheeler, J. A. and Ford, K. (1998). 226.
19 Wang, J. (1999). 7–9.
20 Due to his pacifism, physicist-biologist, Linus Pauling, was also forbidden to travel abroad without restrictions, until he won the Nobel Prize in Chemistry in 1954. Wang, J. (1999). 275.
21 Wheeler, J. A. and Ford, K. (1998). 216.
22 Wang, J. (1999). 272, 283.
23 Wang, J. (1999). 8, 290.
24 Wheeler, J. A. and Ford, K. (1998). 161.
25 Mills, C. W. (1956). 216–218.
26 Aaserud, F. (1995). 41.
27 Wheeler/Ford, transcript VIII, AIP.
28 Wheeler, J. A. and Ford, K. (1998). 193.
29 Rhodes, R. (1995). 527–528.
30 Wheeler, J. A. (1956). 43.
31 Wheeler, JAM. (1998). 225; Wheeler/Ford, transcript VIII, AIP.
32 Wheeler, J. A. and Ford, K. (1998). 227.
33 See Finkbeiner, A. (2006).
34 Aaserud, F. (1995).
219.
35 Wheeler/Ford, transcript IX, AIP.
36 Wheeler/Ford, transcript XI, AIP.
37 Wang, J. (1999). 289.
1 DeWitt, B. S. (1970).
2 Everett to Petersen, 5/31/57.
3 Zurek interview, 2006.
4 Wheeler, J. A. (1979). 183.
5 Tauber, G. E. (1979), 187.
6 Misner private communication, 4/25/08.
7 Everett to Jammer, 9/19/73.
8 Ibid.
9 Ibid.
10 Although, there could be “maverick” universes in which the laws of physics as we know them do not apply.
11 Bohm, D. (1951). 584.
12 Ibid. 583.
13 Ibid. 626.
14 Ibid. 627–628.
1 Quoted in Pais, A. (1991). 295.
2 Everett thesis abstract.
3 Wheeler to Dennison, 1/21/56.
4 Wheeler to Bohr, 4/24/56.
5 Everett to NSF, Fellowship Report for 1955–56, 6/24/57.
6 These changes could have been made before DeWitt offered to print the manuscript, but it is not likely that they were made before it was bound and sent to Bohr in 1956 as the notes are very messy and hard to follow, making that section of the manuscript difficult to read. So, although Everett did tell one correspondent in the late 1970s that he had done no more work on the theory after it was first published, it is likely that he was keen to fix what he saw as an inadequate presentation of his argument on the role of information theory in deriving probability from the quantum mechanical formalism, and that he did so before sending the manuscript to DeWitt and Graham for typesetting.
7 DeWitt, B. S. (2008A).
8 Although the non-communicating branches are causally separate (physically “orthogonal” in the parlance of physics), there is a sense in which as part of a reality described by a universal wave function they can have some influence on each other through interference effects. David Deutsch asserts that a quantum computer would straddle multiple worlds. Deutsch, D. (1997). 216.
9 Everett, H III. (1956A). 5.
10 Ibid. 4.
11 Ibid. 8.
12 See also: “In fact, … whenever any two systems interact some degree of correlation is always produced…. Consider a large number of interacting particles. If we suppose them to be initially independent, then throughout the course of time the position amplitude [i.e. wave function describing all possible positions] of any single particle spreads further and further, approaching uniformity over the whole universe, while at the same time, due to the interactions, strong correlations will be built up, so that we might say that the particles have coalesced to form a solid object.” Everett, H III. (1956A). 6.
13 Everett, H III. (1956A). 6. Italics added.
14 For Everett, macroscopic objects are quantum mechanical systems. But Everett’s use of “environment” is not necessarily the same as how environment is utilized by decoherence theorists. The role of the environment in interpretations of decoherence will be described in detail in a subsequent chapter as it greatly impacts modern interpretations of Everett’s work, and vice versa (i.e., the many worlds theory impacted the development of decoherence theories).
15 Everett, H III. (1956A). 9.
16 Wheeler also wrote in a note to Everett about the mini-paper: “Can one generalize your definition of correlation, which is inv’t [invariant] so to speak in the scheme of spec[ial] rel[ativity] (against linear transf) [transformation]) so it will be inv’t in the sense of general relativity? Probably not except in a very artificial way—but what does this circumstance tell about the meaning of correlation?” Wheeler to Everett, 9/21/55.
17 Wheeler to Everett, 9/21/55.
18 “It is meaningless to ask the absolute state of a subsystem - one can only ask the state relative to a given state of the remainder of the system.” DeWitt, B. and Graham, N. eds. (1973). 49.
19 Probability measurements via the Born rule are physically correct “relative to their information,” he wrote, but subjective because “they depend upon the information of the observer.” In other words, “The paradox is resolved easily since the outside wave function [the universal wave equation that includes the observer’s branch] possesses more information, i.e. phase factors, etc. for the interaction, so that it leads to a causal description.” Quotations from typed and handwritten (basement) versions of “Objective vs Subjective Probability.”
20 DeWitt, B. and Graham, N. eds. (1973). 111.
21 Everett to DeWitt, 5/31/57.
22 DeWitt, B. and Graham, N. eds. (1973). 111. To deal with quantum uncertainty, Everett suggested treating microscopic systems at a “coarse” level of observation, where approximations override the problem that the position and momentum of a particle cannot be simultaneously and precisely measured.
23 Ibid. 134.
24 DeWitt, B. S. (2008A). 4.
1 Feynman, R. (1965). 123.
2 Everett repeatedly wrote that the branches are “equally ‘real.’” On the reasonable premise that he considered at least one branch to be “real,” then, for him, all are “real.”
3 “Multiverse” has several meanings in modern physics (see Epilogue), but we use it here as denoting the quantum mechanical superposition of all physically possible events as describable by a universal wave function. Energy is conserved in this model of branching universes.
4 Also in his notes, he wrote: “Information: definition – plausibility hypothetical games – entropy = -I.” He was clearly thinking about defining probability as purely subjective in terms of “utility,” which accords with his game theory background.
5 “Emphasize basic, inescapable fact that state functions for macroscopic objects do not generally describe single, definite configuration, but only superposition of such configurations.” Handwritten notation, “Random Notes on QM thesis.”
6 Wigner, E. (1961). In a footnote to the section of this paper on the measurement problem that leads directly to the “Wigner’s friend” argument, Wigner commented, “The contents of this section should be part of the standard material in courses on quantum mechanics. They are given here because it may be helpful to recall them [and] because the writer is well aware of the fact that most courses in quantum mechanics do not take up the subject here discussed.” It is not a stretch of the imagination, therefore, to suppose that Wigner did talk about the measurement problem and some version of his “friend” argument in the course that he taught to Everett at Princeton.
7 Wigner, E. (1961). 168; Wigner, E. (1963). 338.
8 Jammer, M. (1974). 480–482.
9 DeWitt, B. and Graham, N. eds. (1973). 6.
10 In his handwritten notes: “Bring out the view that it is not proper to consider apparatus as converting pure state into mixture (one or the other of which is regarded as ‘really existing’), since [there is] always the possibility of developing interference properties between the elements of the superposition, all of which must therefore be considered equally valid, or ‘real.’ … All elements of resulting superpositions must, to avoid error, be considered equally valid, or ‘real’, since the view that ‘really’ one or the other of them has somehow been realized, to the exclusion of the remainder, can lead to contradictions…. In terms of the theory, all branches are regarded as equally ‘real’ since the fundamental entity is Ψ itself. In interpreting the theory one should not think of one outcome being selected out of the many possibilities, but of all outcomes existing simultaneously, each with a corresponding observer who perceives that outcome.” Source: “Random notes on QM thesis.” A “pure” state can be a superposition; a “mixture” is a collection of non-superposed states.
11 Schrödinger, E. (1952).
12 DeWitt, B. and Graham, N. eds. (1973). 9.
13 “Speech to Academy 1946,” quoted in Conway, F. and Siegelman, J. (2005). 164.
14 von Neumann, J. (1951). Everett also studied the classic paper, “Can a Mechanical Chess Player Outplay its Designer?” Ashby, W. R. (1952). Ashby�
�s paper, he noted, was a “good article on production of machines capable of surpassing designer—info theory—natural selection—non-deterministic machines, etc.”