Many Worlds Theory

Could someone explain it to me? I’d be most grateful.

Please keep any explanations dirt simple, thanks.

I’m generally happy just to do the math myself and leave the interpretations to the philosophers, but the basic idea behind the many worlds interpretation of quantum mechanics is that whenever there are multiple possibilities for some event (particle decays or does not decay, spin is measured up or down, etc.), rather than having the wavefunction “collapse” to one state or the other, each possibility exists in some world, and we just see one of them, while the other goes off in its own world that never intersects with this one again.

And how’s that for a run-on sentence?

Until someone more knowledgable shows up, if you just put “many worlds interpretation” in your favorite search engine, it should turn up several lay explanations.

The many-worlds model was developed by Hugh Everett and John A. Wheeler in the 1950s. It is opposed to the more widely accepted “Copenhagen Interpretation” (whereby some of the possibilities collapse as Philbuck stated).

The difficulty with the many-worlds model is that, as far as I know, it makes exactly the same predictions that the Copenhagen interpretation does. So there is no particular benefit to accepting the many-worlds model, unless you write science fiction (as I do). There are some physicists who believe the many-worlds model does a better job at interpreting the EPR paradox (discussed in another thread today), but frankly that is beyond my understanding.

I just read Michael Chrichtons’ Timeline
It explains the Many Worlds Theory as best he can.
If you are interested, give it a read.

This is my 100th post - all right!

An interesting, if somewhat technical, explanation of the many-worlds interpretation of QM can be found here.


If you want a metaphysical explanation read Jane Roberts “The Unknown Reality” in two volumes.

There is a very good FAQ about the Many-Worlds Theory available at . Unfortunately, it has a font problem due to an HTML error, and no one has replied to my emails pointing out the error and how to fix it.

In case you’re interested in fixing a saved copy on your own, a line near the beginning of the document reading:

<h2 align=center>© Michael Clive Price, February 1995</a>

needs to be changed to:

<h2 align=center>© Michael Clive Price, February 1995</h2>
An interesting point made by the FAQ is that, in the opinion of many physicists, the Many-Worlds Interpretation is the default interpretation of quantum mechanics. By that, I mean that the theory follows logically if the equations describing quantum phenomena are read as directly describing the universe. The mainstream Copenhagen interpretation, in their point of view, requires an additional physical process to “collapse” the universe into a single outcome—a process which is mathematically and conceptually very difficult to reconcile with the rest of physics as well as being completely unnecessary to predict the outcome of any experiment.

It should also be noted that the theory, as described in this FAQ, does not involve the physical “division” or “duplication” of the universe—it merely describes the fact that components of the universal wave function corresponding to different experimental outcomes do not interact with each other.

I just wanna say a big thanks to everyone who replied. I’m much clearer on this theory than I was before.

My favorite quote on the subject (for whom I am unable to remember the author) is “If you believe in the many-worlds model, then you should play Russian roulette for high stakes, because somewhere, you’re going to make a lot of money”.

The matter of the many-worlds interpretation would leave the realm of philosophy and become part of practical science, should time travel (in the science-fiction sense of the word, not just the ordinary “one second per second” sort) ever be developed, as it is often used to explain away the potential paradoces assosciated with such travel. Personally, I don’t buy it, thanks to Occam’s Razor, but I’ll have to wait until I invent time travel to prove it.

Chronos, beat me to the punch. I love paradox’s, like this classic:
“What happens if i go back in time and kill my father before he’s my father?”
Well, easy, you don’t exist. Only, you do. Thanks to our many-worlds theory, you, as you know yourself to be, will return to whenever you return to and still have your father to deal with. However, in another world, there exists neither you nor your father, and possibly more or less people depending on other repercussions.
Sometimes I like to watch movies/TV shows on time travel and comment on how certain things wouldn’t work how they described (at least, not according to current QM theories.)
Of course, that’s because most plots dealing with time travel don’t use a flux capicitor, which, as we all know, makes time travel possible (but requires 1.21 GW to power (that’s a downer.))

but its easier than finding a DeLorean in working order :slight_smile: