Re: [asa] Many Worlds - Quantum Mechanics

The many worlds of interpretation (MWI) of quantum mechanics, introduced by John Wheeler's student Hugh Everett in the mid 50s, is _one_ possible interpretation of quantum theory. In particular, it is one way of understanding what happens when a measurement is made on a system. Instead of the state of the system (i.e., its wave function) collapsing to one in which the measured quantity has a definite value (as in the Copenhagen interpretation), there in in MWI a split in different worlds, in each of which the system has one of its possible values. (& in each world there is the observer observing that value.)

As I said, this is one possible interpretation. It is of particular interest if one wants to apply quantum theory to the entire universe, for then there is no "outside" for a Copenhagen type observer. But partisans of MWI (e.g., Tipler), sometimes overstate the case & suggest that quantum cosmology _requires_ MWI.

It's also worth noting that the idea of a splitting worlds in MWI, like that of the collapse of the wave function in the more traditional approach, is a _postulate_, not something that is proven on the basis of other assumptions.

I'll mention again the paper on various parallel world ideas (including MWI) & theology that I gave at the 1987 ASA meeting. I'll be glad to send a copy to anyone who gives me a snailmail address, though at present delivery will be delayed somewhat.

As to the time travel issues discussed in the link James has given, I think that MWI is a solution to a non-problem. The so-called "grandfather paradox" really arises from the assumption that _if_ I could travel into the past I could kill my grandfather before my father was conceived. I.e., the idea of alternate worlds is taken for granted. But if the past is fixed then I just can't do it. I can't kill my grandfather because I didn't. Nahin's book _Time Machines_ provides a good discussion of this & other matters related to time travel. (Portions of this book, including - if I remember correctly - treatment of this "paradox," arae available on Google.)

Shalom
George
---- James Patterson <james000777@bellsouth.net> wrote:
> These three references here raise a question for me in regard to quantum
> physics...how popular and accepted is this "Many Worlds" concept? It appears
> to have been around for at least 50 years.
>
>
>
> 1. Wiki on Many-worlds <http://en.wikipedia.org/wiki/Many_worlds>
> interpretation "The many-worlds interpretation or MWI (also known as the
> relative state formulation, theory of the universal wavefunction, parallel
> universes, many-universes interpretation or just many worlds), is an
> interpretation of quantum mechanics.".
>
>
>
> 2. Parallel universe proof boosts time travel hopes
>
> By Roger Highfield - Last Updated: 10:46AM BST 24 Sep 2007
>
> "Parallel universes really do exist, according to a mathematical discovery
> by Oxford scientists that sweeps away one of the key objections to the mind
> boggling and controversial idea..." Read
> <http://www.telegraph.co.uk/scienceandtechnology/science/sciencenews/3307757
> /Parallel-universe-proof-boosts-time-travel-hopes.html> more
>
>
>
> 3. Also - a book by Frank Tipler - "The Physics of Christianity" - which I
> confess I can't understand all of - but he professes to be both a Christian
> and to believe in multiple universes.
>
>
>
> JP
>

To unsubscribe, send a message to majordomo@calvin.edu with
"unsubscribe asa" (no quotes) as the body of the message.
Received on Mon Feb 2 10:47:05 2009