It's not new in the sense that the so-called many worlds hypothesis
has been around for around fifty years. As far as I can tell as of
yet nothing has been out there that falsifies the many-worlds
hypothesis against the Copenhagen interpretation. Deutsch claims that
quantum computation could prove his point (something about conscious
reversible quantum computers that I cannot get my mind around). Asher
Peres, an outspoken critic of the MWI and expert on quantum
information theory, noted that the MWI is merely a formal
transformation and thus may not even qualify as a proper
interpretation of quantum mechanics. He also noted that an infinite
number of non-communicating Universes is highly suspect and violates
Occam's Razor by not minimizing the number of hypothesized entities.
Note the following in the Scientific American blog:
August 2, 2007
05:47:18 pm, Categories: Philosophy, Physics, 1275 words
Many worlds in Oxford
Last month marked the 50th anniversary of the launching of the "Many
Worlds" Interpretation of quantum mechanics, in which parallel
universes are constantly branching off from the one we experience,
with different events taking place in them. The Many Worlds
Interpretation competes with the Copenhagen Interpretation,
championed by Niels Bohr, in which the quantum state of a system
often abruptly changes when it is observed ("the collapse of the wave
function"). One outcome is seen to happen and according to the
Copenhagen Interpretation the parts of the quantum state predicting
other possibilities simply vanish. Many Worlds says those other parts
still exist, just not in our branch.
In a future issue we will have an article by journalist Peter Byrne
about the author of the original Many Worlds paper—Hugh Everett III—
including some little-known history of events around its publication
in 1957 and afterward. A couple of weeks ago Peter was at a
conference in Oxford on the Many Worlds theory and he sent me the
following report to post here. (I wish I had thought to invite him to
do this earlier. No, wait—I wish this were the branch of the universe
in which I did think to do so earlier!)
— Graham P. Collins
Many Worlds in Oxford
By Peter Byrne
Meeting for three days in the rain-swept United Kingdom in mid-July,
a roomful of philosophers and physicists heatedly discussed a theory
that multiple universes exist. The occasion for the debate was the
"Everett@Fifty" conference sponsored by the Foundational Questions
Institute and hosted by the Philosophy Faculty of the University of
Oxford in a building near Logic Lane in Oxford. Most of the
participants took it for granted that the Copenhagen Interpretation
of quantum mechanics, which dominated the philosophy of quantum
physics from the 1930s until quite recently, does not adequately
describe the continuous evolution of atomic reality because it
arbitrarily separates the quantum and "classical" realms from each
other.
Eager to improve upon the Copenhagen Interpretation, the thirty-odd
academics differed on the best ways to talk about a completely
quantum mechanical (non-Copenhagen) universe. Some think of it as
"Everettian," i.e. as a "multiverse" composed of a large but
indeterminate number of branching autonomous "worlds" in the sum of
which everything that is physically possible happens. Others,
including the "Bohmians," say there is only one universe and that the
very concept of probability only allows that some things, not all
things, happen. Be that as it may, fifty years ago, it would have
been difficult to imagine this debate taking place at all—except,
perhaps, inside the insane asylum of Bedlam.
In July 1957, Reviews of Modern Physics published an abridgement of
the doctoral dissertation of Hugh Everett III, a student at Princeton
University. Taking the mathematics of quantum mechanics at face
value, Everett claimed to have solved the "measurement problem," i.e.
the problem of accounting for how a definite classical reality
emerges from quantum uncertainty. But his solution to the problem was
challenging to say the least. The sticking point was not his logic or
his mathematics, but the implication that in some sense (hence the
name "Many Worlds" theory) it pointed to the actualization of all
possibilities. It posited that every individual is constantly
"splitting" into non-communicating copies of herself along with her
immediate environment. It has taken a half century for Everett's
peculiar theory to become a topic of serious scientific and
philosophical concern to mainstream academics.
[More:]
At the conference, the strongest "Everettian" was physicist David
Deutsch of the Center for Quantum Computation at University of
Oxford. Deutsch asserted that people have been wasting time for
decades debating whether or not the Copenhagen Interpretation is
meaningful because, "Only Everett's theory consists of taking quantum
mechanics seriously." Deutsch was joined in that analysis by
conference organizers Simon Saunders and David Wallace of Oxford;
both have written extensively on how to deal with uncertainty in an
Everettian multiverse wherein all outcomes are realized.
Preserving probability (in the form of the Born Rule) is critical for
the acceptance of the Everett method. The Born Rule defines how to
determine the probability that we will see various outcomes when we
observe a system that is in a particular quantum state. For example,
it may indicate we have a 99% chance of seeing an electron at
location A and only a 1% chance of seeing it at location B. But what
does it mean for location A to be 99 times more likely than location
B when each outcome has a branch of the universe in which it occurs?
Our hold on the mathematics of quantum mechanics depends upon being
able to assign probability measures to events occurring inside the
universe we experience, and as well as to events inside the universes
we do not see! (And exactly who "we" are in this scheme that contains
vast but indeterminate numbers of fractured selves is an ontological
question related to the probability problem.)
Wayne C. Myrvold of the University of Western Ontario and Hilary
Greaves of Rutgers University made a presentation backing up previous
work by Deutsch, Saunders, and Wallace delineating a "decision-
theoretic" statistical method that purports to preserve the Born
Rule, i.e. probability, throughout Everett's multiverse. David Z.
Albert of Columbia University objected to this argument: "Talk about
the probability of this or that future event would seem to make no
sense unless there is something about the future of which we are
uncertain, and there seems to be no room for any such uncertainty in
the context of anything along the lines of an Everettian picture."
Albert critiqued the Everettians for trying to prove that their
theory allows for the Born Rule to function by assuming the belief
that the Everett theory is true (they should rather show how a non-
believer could come to believe it to be true). Albert, who is
sympathetic to the "pilot wave" or "non-local hidden variables"
interpretations of quantum mechanics originally made by Louis de
Broglie and David Bohm, described the Everettian's explanation of
probability as at best explaining our betting behavior, which as an
explanation of physical evidence is "sheer madness."
Tim Maudlin of Rutgers University is also an admirer of the Bohmian
approach. He critiqued the Everettians for not being able to tie
their abstract theory to the world of experience and for failing to
provide evidence of probability. Jeffrey Bub of the University of
Maryland and Itamar Pitowsky of The Hebrew University of Jerusalem
attacked both the Everettians and the Bohmians as "dogmatic" for
assuming that there is a solution to the measurement problem. And
James Hartle of the University of California, Santa Barbara,
succeeded in carving out an ideological space somewhere between the
competing factions. He said that modern cosmologists owe a debt to
Everett for his insight that a closed universe can be described by a
single wave function.
In a very animated talk, metaphysician John Hawthorne of University
of Oxford strongly critiqued the Everett Interpretation as "vague"
and "not explanatory." In an emotional response, Michel Janssen of
the University of Minnesota, an Everett partisan, exclaimed, "Science
is not metaphysics!"
The debate, although fifty years in the making, is just starting to
get hot. It continues from September 21 to 24 at the Perimeter
Institute in Waterloo, Canada. Whereas at Oxford, the philosophers
outnumbered the physicists, that ratio will reverse at the Perimeter
meeting. Many sparks will fly.
URLS:
http://blog.sciam.com/index.php?
title=many_worlds_in_oxford&more=1&c=1&tb=1&pb=1&more=1#comments
http://www.perimeterinstitute.ca/manyworlds/
On Sep 30, 2007, at 4:45 AM, Iain Strachan wrote:
> This seems to have come up in the last week, originally reported, I
> believe in New Scientist.
>
> http://www.breitbart.com/article.php?
> id=paUniverse_sun14_parallel_universes&show_article=1&cat=0
>
> The punch-line is:
>
> The Oxford team, led by Dr David Deutsch, showed mathematically
> that the bush-like branching structure created by the universe
> splitting into parallel versions of itself can explain the
> probabilistic nature of quantum outcomes.
>
> Does anyone know anything about this? Is it really anything new
> (one expert commenting in New Scientist) says it will go down as
> one of the most important discoveries in the history of science. In
> the absence of details, it's hard to tell whether or not this is
> just journalist hype.
>
> It seems to me that showing mathematically that the branching
> structure of the universe can explain the probabilistic nature of
> quantum outcomes is NOT the same as proving that the parallel
> universes exist, and falls foul of the same fallacy as the Design
> argument - because we know that Designers can explain intricate
> mechanisms from watches is not the same thing as saying that the
> existence of apparent design implies the existence of the Designer.
>
> In order to show that the parallel universes really exist, one
> would have to find independent predictions from the theory, that
> differ from, say Copenhagen, which can be tested against.
>
> It is of great interest that a forthcoming Christians In Science
> meeting in Oxford on October 15th is on multiverses.
>
> Iain
>
> --
> -----------
> After the game, the King and the pawn go back in the same box.
>
> - Italian Proverb
> -----------
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Received on Sun Sep 30 09:25:07 2007
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