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Many Worlds Roundup

By localroger in Culture
Sat Feb 23, 2002 at 10:15:19 AM EST
Tags: Books (all tags)
Books

In this article I will review three fictional treatments of the Many Worlds Interpretation of quantum mechanics (the "MWI"), which postulates that the Universe solves several quantum mechanical paradoxes by resolving all the possible end states of every quantum event, in separate parallel universes. It's interesting to see how attitudes toward the theory have morphed over the years. We will consider:

While "Many Worlds" get the physicist off the hook, the theory's suggestion that all possible worlds somehow "really exist" in parallel raises other issues more appropriately explored in fiction, where we can wonder how people will react to the news.


1.

All the Myriad Ways is arguably Larry Niven's best short work from his most productive period. Niven was one of my favorite writers when I was a lot younger than I am now; at his best he makes you look past his technical lapses and ham-handed characterization by dazzling you with brilliant flights of imagination. Myriad Ways is an uncharacteristically subdued work for Niven, lacking the FTL space drives and two-headed aliens and planetary-scale engineering works for which he's more commonly known. It isn't even set in his Known Space future history. And it works because of its laser-like simplicity.

Niven's story doesn't even display an awareness of the formal MWI. Instead of dragging out quantum mechanics and state vectors to establish the background, Niven has narrator Gene Trimble complain that he doesn't understand the theory himself, except that the upshot is that the Universe splits every time "someone makes a decision." A quantum physicist would pull his hair out at the vagueness of this, yet it's a reasonably accurate rendering of the MWI.

Niven takes a straightforward SFnal approach to his alternate universes. If you want to get somewhere, whether it's another world, another time, or another parallel universe, you do it by getting in a machine that takes you there. The people who run these machines are pilots, skilled people boldly going where no one from their timeline has gone before. The man on the street does not go to alternate universes. He reads about them in the newspaper, and marvels.

While Niven touches briefly on the technological wonders brought back from more advanced timelines ("and Crosstime held all the patents...") he also cleverly notices that ordinary things like staplers and butane lighters might be just as important as rocket engines and computers. At the time of the story, cross-time travel has only existed in Trimble's universe for eleven months. The wonders are still mostly in the papers, but the promise of enormous change hangs over everything.

For Trimble, the fly in the ointment is this epidemic of suicide and random crime he is investigating. The story is told in the form of a detective's meditation as he cleans his gun; he rambles a bit, recalling encounters and events of note as he tries to piece together a puzzle which, he feels in his gut, must somehow revolve around Crosstime exploration.

Trimble thought of a lonely woman making herself a drink at three in the afternoon. She thinks of myriads of alter egos with husbands, lovers, children, friends. Unbearable to think that all the might-have-beens are as real as herself. As real as this ice pick in her hand...
Trimble puts his gun together and wonders. At this moment he might have the flash of inspiration that solves the mystery. It might slip away, leaving him frustrated again. He might regard the gun curiously, thinking of the suicides. The gun might go off accidentally. He might dry-fire it at himself...

...and of course, he does all of those things, and more.

2.

As one might divine from the title, Frederich Pohl wrote The Coming of the Quantum Cats with quantum theory in mind. Pohl envisions a huge machine which doesn't go with you when you cross between universes; instead it gives you a push, and after awhile you tend to pop back unless you're well planted in your destination. As the story opens a belligerently militaristic version of the United States (yes, even worse than this one) is about to use the technology to mount an invasion in its own world by transporting the troops in another. Jerry Brown is President and Dominick DeSota is the major in charge of the invasion.

The invading world didn't invent the technology; they were contacted and stole it from a world in which Dominick DeSota was an important scientist on the project. In his world the President is Nancy, not Ronald, Reagan.

In the world being used for the invasion Senator Dominick DeSota and President Jack Kennedy are briefed by Dr. Dominick DeSota. Our own timeline is mentioned specifically, when Dr. DeSota mentions those lines where Ronald Reagan is President and Jack Kennedy was assassinated by some guy named Oswald.

An improbable North American Muslim theocracy is also involved, in which Nicky DeSota is a struggling mortgage broker. Nyla, the main female character, is alternately a concert violinist, a thumbless FBI agent, and Senator DeSota's mistress.

Pohl has great fun with the different politics and fates of his characters. There is also an ominous backdrop; between each chapter is a little vignette about some really weird out-of-place freak event. Eventually it becomes clear that these "rebound" events are a side effect of the dimensional travel. Just when the situation is looking really grim a Deus ex Machina intervenes -- a very advanced cartel of ten worlds which developed quantum travel early and cooperated.

The cooperative has discovered the nasty side effect of parallel-time travel; once vibrations are set up, they don't stop. Travel causes bizarre spontaneous crossing of timelines; freight trains appear out of nowhere in residential neighborhoods, buildings fade in and out of existence, weather systems do not arrive where they are expected. The cooperative doesn't like this. When they detect unauthorized experimentation, they haul everyone involved off to a conveniently empty world where the human race was wiped out by biological warfare. There, dozens of Dr. Dominick DeSotas compare notes as they ponder giving up quantum physics for farming.

Pohl has said in interviews that he is not a "hard-science" wonk; he takes his one idea and chases it, usually concentrating on the human side. Yet Quantum Cats is quite satisfying on the technical side. The few loose ends are left hanging deliberately, and one feels they belong as they are. There are no jarring failures of belief in the story background, which sounds no crazier than anything real scientists have been writing about lately.

Pohl, like Niven, is driven by the effect such technology will have on people; all their might-have-beens and what-ifs are now in their faces. He is wonderfully inventive at mixing up the details of history and experience to create basically similar yet shockingly different worlds and personalities. As with the technology, all his characters are believable and act naturally given their origins.

3.

James P. Hogan has a well-deserved reputation as a hard-science wonk and a history of working out marvelously complicated, yet beautifully consistent systems of physics to justify his fictional inventions. Yet Paths to Otherwhere is by far the weakest work in the roundup, a surprising disappointment which deserves forensic analysis.

The point-of-view world in Otherwhere is another militarized, paranoid American dystopia. Hogan being Hogan, he takes half the book to get us to Otherwhere; first we have to see how the "intuition amplifier" works, and endure a ponderous explanation of how DNA is a quantum antenna, cooperating across timelines to achieve rapid evolutionary change when it's appropriate without the intermediate forms which are so embarrassingly absent from the fossil record. Hogan remembers to mention this once or twice, but once it's explained it never becomes relevant to the story.

By page 80 or so the scientists have managed to discover that they can project their consciousness into nearby alternate timelines, and vice-versa. The evil paranoid government droids running the project see wonderful possibilities for spying, since the nearby universes are similar enough to ours to make espionage from them useful. But Hogan does several things here that ring false to me.

Firstly, while I can see the logic of forbidding matter transfers between universes, the way consciousness is projected is that your body in this universe goes limp, while you take over the body of your twin or "analog" in the alternate universe. Hogan depicts several dangerous and embarrassing results of this, none of which is remotely as creepy as the idea of "riding" your analog like some kind of voodoo god. The experimenters also seem to take it cheerfully in stride that they will occasionally zone out and play host to a visitor from some other parallel universe.

Wrapped up in all of this is a thread about Eastern religion, and how the quantum amplifiers somehow duplicate and enhance what spirituality accomplishes naturally, the direct experience of alternate quantum realities. It also seems to breezily assume mental dualism, that the mind is somehow separable from the brain and body it inhabits. Reading this in a James P. Hogan novel is like seeing Linus Torvalds in an advertisement for Microsoft Windows. I have the distinct feeling this book is a paen to all the folks he has pissed off over the years with his anti-religion rants, especially the Zambendorf character in Code of the Lifemaker.

Around page 100 a renegade group of non-fascist scientists begins an unauthorized exploration of "distant" worlds, against the wishes of the military project leaders who don't see the espionage uses of universes that don't resemble ours very much. Around page 180 they begin to figure out how to aim. Around page 200 they realize that if they project into an analog in an alternate universe, and don't go through the shutdown sequence, they'll stay in the alternate universe.

It strikes me as odd that they could learn enough to aim for a particular universe and deliberately cause and reverse these projections, yet not be aware that the projection is permanent unless deliberately reversed. This doesn't make sense, and Hogan obviously adopted it out of plot necessity; permanent projection makes it possible to emigrate.

Finally, around page 230, we meet the title of the book. In the Otherwhere universe World War I ended before it was well begun, WWII never happened, and the nations of the world have lived in mutually altruistic harmony ever since. In other words, it's the planet Charon from Voyage From Yesteryear, thinly transplanted to an alternate 20th century. Everyone who visits Otherwhere, including the fascist military leaders, loves the place.

In timelines as distant from ours as Otherwhere, not everyone has an analog and your analog might have a different name and occupation and live on a different continent than you do. Most of the rest of the book is devoted to the good and bad guys locating and positioning their analogs in Otherwhere so as to be ready to emigrate and, in the case of the bad guys, to kill the good guys' analogs on general principles so they can't emigrate. (Somehow, it appears that there is only one Otherwhere, something vaguely to do with attractors in the hoohah space of the temporal doubletalk fractal.)

The good guys devote all of two or three pages to the ethical problem of emigrating into a body which has a previous occupant, with his own history, memories, etc. Far along this is glossed over with a happy-feely explanation that, as you hang around, your personality merges with the one you've invaded into a gloriously blissful combination superior to either individual. Thus, when a couple of the good guys manage to emigrate and destroy the recall codes, leaving limp bodies in their home universe, we're supposed to see it as a triumph. (And what happens to the bodies? Nothing indicates that they die. The whole issue is swept under a rug in the last few pages.)

And I'm left with a really bad taste in my mouth over the analogs in Otherwhere, who (unlike the self-proclaimed "good guys") did not get a choice in the matter of whether to be invaded. Furthermore, we are given to understand that in some weird New Agey sense the machine itself tends to turn fascist military scum into touch-feely altruistic libertarians, offering a key to liberating the seemingly hopeless home universe. (How? By strapping all the leaders in and taking them for a ride?)

All in all it's a great big gushy nonsensical mess that takes 400 pages to reach an ethically unsatisfying and technically unbelievable conclusion which contradicts everything else Hogan has ever written. What in hell was he thinking?

I think part of the problem is that Hogan, like any sensible person, is uncomfortable with the MWI on a deep level. Both he and Pohl make an effort to limit the number of actual alternate universes; Pohl by fiat, Hogan by invoking fractals. This softens the impact and the strain on the imagination, turning what could be a deep philosophical question into a travelogue. (Larry Niven got this part best, looking the implications squarely in the face and making them the point of his story.)

4.

"Many Worlds" sound like the basis of a great yarn, but when you get down to it there aren't many yarns you can tell, beyond the one Niven told, without imposing limitations of one sort or another. Rudy Rucker once alleged that the MWI multiverse actually contains no information; I think he overstates the case but it does seem pointless for the universe to exist at all if it never makes a decision. By analogy, when we run a simulated universe in a computer we do it because we are interested in the outcome, whether it's a game or a physical process simulation. The only reason to run all possible outcomes would be to draw a map, rather like the Mandelbrot Fractal, which indexes those outcomes in the way Mandelbrot indexes the space of Julia sets. One then has to ask what use such a map would be, and to whom, and why. It does not seem like the sort of thing that would arise on its own via an evolutionary process.

There might be a story in that idea. But so far nobody seems to be thinking much past the kewlness of other timelines where you might be rich, famous, and dating a supermodel. It seems like a theory as profound as the MWI would yield more fictional possibilities than the quick meditation on futility and the fun romp through alternate history. But the competent author who has written several of my favorite books turned in an embarrassing disappointment when he tried to use MWI as the basis for a drama. It remains to be seen if other authors will have better luck.

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Poll
The MWI is
o True 12%
o False 2%
o fun to think about 18%
o true and false at the same time 4%
o both true and false until its state vector collapses 25%
o ridiculous 2%
o I want to move to the world where I'm rich, famous, and dating a supermodel 33%

Votes: 71
Results | Other Polls

Related Links
o Many Worlds Interpretation
o All the Myriad Ways
o The Coming of the Quantum Cats
o Paths to Otherwhere
o Known Space
o Code of the Lifemaker
o Voyage From Yesteryear
o Mandelbrot Fractal
o Also by localroger


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Many Worlds Roundup | 96 comments (92 topical, 4 editorial, 0 hidden)
I'd recommend (5.00 / 4) (#1)
by medham on Sat Feb 23, 2002 at 12:05:54 AM EST

Greg Egan's Distress for another heady romp through this particular territory--one that takes the socially epistemological dimensions of "many world" speculation by the metaphysical nuts, as it were.

The real 'medham' has userid 6831.

Seconded (5.00 / 2) (#6)
by spiralx on Sat Feb 23, 2002 at 08:35:43 AM EST

Distress is an absolutely superb book which takes an idea and pushes it to its conceptual limits... well worth a read.

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

Quarantine and Teranesia (5.00 / 1) (#20)
by Scrymarch on Sat Feb 23, 2002 at 02:09:15 PM EST

... both also demolish the article's suggestion that not much interesting can be fictionally written about many-worlds quantum theory. Both are extraordinary books.

Quarantine (written before Distress) probably covers the many-worlds stuff most comprehensively. Some philosophical territory is shared with Distress; his first big three books all deal with concepts of how decisions and information might directly affect the fundamental physical world. He's moved away from this of late; the vein was pretty much mined.

"Metaphysics has been an experimental science since the 1980's"

Before I stop gushing I'd say Egan and Neal Stephenson are the finest writers in SF today.

[ Parent ]

I've read Teranesia (5.00 / 1) (#42)
by medham on Sun Feb 24, 2002 at 03:09:05 PM EST

And I'm not sure how applicable the many-worlds theory is to it. I found it the least interesting of his books that I've read (but better-written than Quarantine, certainly), though one of Egan's most commendable traits is a high degree of political awareness--famously absent or perverted in many authors with whom he is often compared (Niven *shudder*, Bear the American-style ultra-rightist libertarian, etc.)

The academic parody stuff in Distress is also a bit forced; we academics do a much better job of parodying ourselves (think Sokal, Lodge), and the outsider's satire is usually off-key.

The real 'medham' has userid 6831.
[ Parent ]

Many-worlds in Teranesia (Spoilers) (none / 0) (#48)
by Scrymarch on Mon Feb 25, 2002 at 08:12:47 AM EST

Spoilers.

As I recall the mechanism in Teranesia relied on a genetic computer that took advantage of evolutionary adaptations in alternate worlds. By contrast Distress relied on a wild variant of information cosmology and the implications of a Theory of Everything, with the quantum stuff peripheral. So from my dodgy memories Teranesia involves more quantum many-worlds stuff than Distress.

The academic parody stuff in Distress is also a bit forced; we academics do a much better job of parodying ourselves (think Sokal, Lodge), and the outsider's satire is usually off-key.

Well, to me it rang true, especially as a parody of "public intellectuals" like Germaine Greer. It was pretty squarely aimed at the humanities, too, not academics in general. Large chunks of the humanities do seem to be wrapped in a medieval non-empiricism of symbols and literary models; that's where the parody is aimed. (This dismays me; they are wonderful topics of study.) But I haven't read Sokal or Lodge, so I'll have to take your word there.

Have you read Cryptonomicon? Was your reaction to parody there similar?

[ Parent ]

Well (none / 0) (#59)
by medham on Mon Feb 25, 2002 at 03:19:55 PM EST

I thought that Teranesia was rushed and confused, and I'm not sure your account is the only way that can be made of it.

I think Fay Weldon is the main target of ridicule in Distress.

"Medieval non-empiricism of symbols and literary models" doesn't make any sense at all. "Empiricism" is an epistemological position, for starters, and one that is held by the vast majority of social constructionist academics.

And I just don't think Stephenson is very talented or smart. Sorry.

The real 'medham' has userid 6831.
[ Parent ]

Well (none / 0) (#84)
by Scrymarch on Wed Feb 27, 2002 at 01:22:16 PM EST

I thought that Teranesia was rushed and confused, and I'm not sure your account is the only way that can be made of it.

That's interesting, I thought it the slowest and most deliberate of Egan's books.

I think Fay Weldon is the main target of ridicule in Distress.

Apologies, I was thinking of Teranesia.

"Medieval non-empiricism of symbols and literary models" doesn't make any sense at all. "Empiricism" is an epistemological position, for starters, and one that is held by the vast majority of social constructionist academics.

I was basically alluding to vast metaphor overextension and disregard of the scientific method; I sympathise with Egan's concern and have despaired at public intellectuals missing the point. But I have no examples to hand, and I was promoting empiricism, so we'll have to let it slide.

And I just don't think Stephenson is very talented or smart. Sorry.

It's ok, I'm not related to him :). I'd be interested in which books so failed to impress you, though.

[ Parent ]

Iain M. Banks (none / 0) (#44)
by Pac on Sun Feb 24, 2002 at 07:23:58 PM EST

I would just like to second your list of finest SF writers, adding just this one name.

And Bain's Excession, although far simpler than Egan's Diaspora, touchs the many-universes theory from a very interesting point of view.

Evolution doesn't take prisoners


[ Parent ]
Also (5.00 / 1) (#34)
by Motor on Sun Feb 24, 2002 at 08:26:13 AM EST

Greg Egan's just had another book published - Schild's Ladder. I had it on pre-order and it arrived yesterday morning. For some reason, Amazon.co.uk is still listing it as not yet available though.

I haven't actually opened it yet (too busy), but the jacket blurb sounds like your typical mind-blowing Egan trip into physics. You can read the synopsis, and see his usual Java applet demonstrations of his ideas here.

[ Parent ]

some speculation (4.00 / 3) (#2)
by xriso on Sat Feb 23, 2002 at 06:08:18 AM EST

I'm not a scientist (yet) or anything, but could a valid explanation of quantum phenomena be that there are simple non-probabilistic laws underlying these quantum effects? The reason we would not be able to use (or perhaps know) these simple laws is because we are stuck in the same universe with what we are trying to apply the laws. The uncertainty principle could easily come out of such a set of laws as an effect of the ways that we observe things (eg. by detecting light that slammed into the particle).

In this model, quantum mechanics would serve as the practical theory of how we treat particle systems, taking into consideration the fact that we don't know all the information about said systems. If we knew the laws we would be able to (in "theory") simulate another universe that is very similar to ours on a macroscopic level, and we would know all the information contained in that universe. However, both the simulations and us would be unable to know the exact fine structure of our own universes, so we would both use quantum mechanics to make predictions about our own universes.

Correct me if I'm wrong, but I was under the impression that superstring theory would provide a set of laws that explains both quantum and relativistic effects.
--
*** Quits: xriso:#kuro5hin (Forever)

Hidden variables theories (5.00 / 1) (#9)
by spiralx on Sat Feb 23, 2002 at 10:31:46 AM EST

Dunno if it's quite what you meant but there is a class of quantum mechanical theories out there which involve "hidden variables" - things which we cannot see but are causal. The most well-known theory is the pilot-wave theory, however this brings its own problems (see section 5.5 here, although it is a little technical).

Correct me if I'm wrong, but I was under the impression that superstring theory would provide a set of laws that explains both quantum and relativistic effects.

Yes, it allows for gravity to be quantised without all the nasty problems that plague other methods of doing so. And it might even answer some of the questions we have about QM... but we can't say for sure yet.

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

The many interpretations interpretation (5.00 / 1) (#23)
by KWillets on Sat Feb 23, 2002 at 03:00:21 PM EST

Your intuition is correct, and Bohm's interpretation (derived from de Broglie) is a deterministic model for the underlying, unobservable portion of quantum theory. In short, "probability waves" are not in themselves a proof that the universe in nondeterministic, since a deterministic model can be slipped underneath them with full consistency.

It's similar to looking at a lot of baseball statistics and deciding whether baseball is deterministic or not. If we have evidence of people throwing balls and swinging bats we can conclude that baseball games consist of real physical acts leading to a known conclusion, but if we don't, we could conclude that it's random or non-causal. The fact that QM's low-level details are unobservable, but not necessarily non-existent, keeps the debate inconclusive.

A refinement of Bohm's model is based on the idea that ignorance of initial conditions (eg the exact position and momentum of a particle at the start of an experiment) leads to a commensurate uncertainty about later conditions. Even in a deterministic model, this uncertainty necessitates a probabilistic formulation, with a lot of inconclusive philosophizing as a side effect.



[ Parent ]
Baseball (none / 0) (#89)
by dennis on Wed Feb 27, 2002 at 06:57:07 PM EST

It's a little weirder than baseball statistics. Deterministic hidden variables only work if you abandon locality (which is what Bohm does). It's as if the baseball statistics for each game depend not only on the people throwing balls and swinging bats, but also on the movements of people in the stands, and the cars in the parking lot, and whether or not you bought a hot dog.

[ Parent ]
Greg Egan is a Geek God (5.00 / 2) (#4)
by TheophileEscargot on Sat Feb 23, 2002 at 06:33:16 AM EST

The best Many-Worlds thing I read was a short story "The Infinite Assassin" by Greg Egan; which actually uses real set theory to drive the plot. An Infinite Assassin has to go through infinite universes, but unfortunately some infinities are bigger than others...

Can I state for the record that Greg Egan is God? He's an SF writer, and a professional programmer, so you can go to his home page and see animations and simulations of the physics of his setups. How cool is that?
----
Support the nascent Mad Open Science movement... when we talk about "hundreds of eyeballs," we really mean it. Lagged2Death

Thanks (5.00 / 2) (#7)
by localroger on Sat Feb 23, 2002 at 08:54:23 AM EST

It's worth noting that Egan has a much more newbie-friendly introduction to quantum mechanics than the FAQ I linked.

I can haz blog!
[ Parent ]

I don't know what your definition of ... (none / 0) (#12)
by Rk on Sat Feb 23, 2002 at 11:42:17 AM EST

newbie friendly is, but I did not find that newbie-friendly. It would hvae been better to explain the concepts, rather than to list every relevant equation. Doing so makes it very difficult to understand.

[ Parent ]
Unfortunately... (5.00 / 1) (#16)
by localroger on Sat Feb 23, 2002 at 12:30:09 PM EST

...it's almost impossible to really understand the concepts without some of the math. Egan does a good job of distilling it, but it does require some thought to follow.

The key is understanding that the Heisenberg Uncertainty Principle isn't about measurement accuracy; there are sound mathematical reasons for understanding that the particle is really in more than one place at the same time. Egan's is the simplest exposition of that which I've ever seen.

Of course you can always understand it in Larry Niven's terms, but that doesn't give you an idea of why serious scientists are suddenly showing an interest in the MWI after years of thinking it ridiculous.

I can haz blog!
[ Parent ]

And Greg Egan actually knows what he's talking abo (5.00 / 1) (#13)
by SIGFPE on Sat Feb 23, 2002 at 12:03:52 PM EST

...unlike a writer like Larry Niven who's about as close to completely ignorant of science as a science fiction writer can get. Teranesia is also a bit of a Many Worlds influenced story by Egan.
SIGFPE
[ Parent ]
Niven (none / 0) (#64)
by Legion303 on Mon Feb 25, 2002 at 09:59:59 PM EST

How is Niven (who has a degree in mathematics) ignorant of science? Details?

-Legion

[ Parent ]

He just doesn't know much science... (none / 0) (#96)
by SIGFPE on Mon Mar 11, 2002 at 02:26:44 PM EST

...beyond what's in pop science magazines - in fact I think he knows less. My first experience of Niven, many years ago was Neutron Star (I think that's the name). A whole story based on the premise that scientists in the far future have forgotten about the tidal effects of gravity. It's just about the most stupid premise for a story I've ever read! My experiences later (Mote in God's Eye, Ringworld) were negative enough to make me give him up completely.
SIGFPE
[ Parent ]
Greg Egan wrote Quarantine, the perfect MW novel (5.00 / 1) (#28)
by Will Sargent on Sat Feb 23, 2002 at 03:46:28 PM EST

It's obvious the reviewer has never read Quarantine, otherwise it would be at the head of the list.

Quarantine is a story which revolves around the plot device that you can actually use quantum instability to choose your possible future -- your quantum self examines all the possibilities and picks from them the best one.

The freaky thing is that you get to read about some of the worlds which have been "discarded". This adds an extra frission as you realize what the quantum paths reveal about humanity's impact on the future (hint: it's in the title).
----
I'm pickle. I'm stealing your pregnant.
[ Parent ]
Another good book (none / 0) (#10)
by spiralx on Sat Feb 23, 2002 at 10:36:09 AM EST

Well a great one actually is Stephen Baxter's authorised followup to The Time Machine by HG Wells called The Time Ships. Although I have to say the USian cover is pretty damn nasty ;)

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey

don't forget... (5.00 / 2) (#11)
by sesquiped on Sat Feb 23, 2002 at 11:15:02 AM EST

"The Garden of Forking Paths," by Jorge Luis Borges. (I'd link somewhere, but nothing I found via google was very informative.) It's not SF (the best categorization would be magical realism), but it does allude to MWI in a few ways, and makes some connections to Eastern religion.

I won't go into the plot here, but I'll just describe a thought or two: The meat of the story seems to be in the dialogue that occupies the later two thirds (which features some discussion about MWI and the nature of time), but I was a little disappointed when there seemed to be one single concrete (but quite cool) conslusion upon reaching the end. Given the themes in the body of the story, I would have expected something more interesting, or at least more ambiguous.

I found and url (none / 0) (#30)
by vsoto on Sat Feb 23, 2002 at 09:44:45 PM EST

Here is an url I found:

http://www.nachomarquez.com.ar/Borges/Ficciones/el_jardin_de_los_senderos_que_se_bifurcan.htm

sorry, Borges' native language was spanish.

[ Parent ]
you didn't accomplish your thesis. (none / 0) (#14)
by Maniac_Dervish on Sat Feb 23, 2002 at 12:15:04 PM EST

you say, in the introduction, that you're going to "raise other issues" - the three sections about the novels don't do much with this, and your section 4 doesn't tie it all together very well.... i'd like to see a re-write of this with some structural revisions.... the majority of the content in sections labeled 1,2, and 3 seems to be plot summary. as an english teacher, that disturbs me :)

~dervish

You misunderstood (5.00 / 2) (#15)
by localroger on Sat Feb 23, 2002 at 12:26:14 PM EST

I didn't say I was going to raise other issues -- I said the MWI raises other issues. This is basically a comparative review of how three authors explored those issues.

What I found interesting, and what spurred me to write this, is that the writer with the best (and well-earned) reputation for solid "hard" SF fell flat on his face trying to confront the MWI, while authors known more for character development and uneducated flights of fancy made a much better showing.

"What other issues?" Niven points out a psychological effect which, like most brilliant ideas, is obvious only once pointed out. Pohl asks if interdimensional travel might have unwanted side effects, like many other human activities; and also places us solidly on the other side of the universe that didn't invent MWI travel but got invaded by the one that did. Hogan, the hard scientist, spends > 100 pages wonking us with theory and fails to deliver a satisfying story -- breezing over the points Niven and Hogan explored, and failing to serve up anything else believably worthwhile.

If you expect much more than that in a review this length of over 800 pages of source material, I'm glad I'm not one of your English students.

I can haz blog!
[ Parent ]

What about Baron Gottfried Wilhelm von Leibniz? (5.00 / 1) (#17)
by shinshin on Sat Feb 23, 2002 at 12:51:36 PM EST

How could anyone do a study of the various "many universes" dicourses without even a passing mention of that 17th century whack job Baron Gottfried Wilhelm von Leibniz, last of the great Continental Rationalists and who vies with Newton for the title "the father of calculus", who proposed solething like this:

God (alone) exists necessarily, and everything else flows from the divine nature. Limited only by contradiction, god first conceives of every possible world--the world with just one monad; the worlds with exactly two monads; those with three, with seventeen, with five billion, etc. Then god simply chooses which of them to create.

Of course even god must have a sufficient reason for actualizing this world rather than any other. The most direct advantage of this world is that (as the plenum principle requires) it is the fullest. That is, more things exist and/or more events actually take place in this world than in any other consistent set of interrelated monads. In a more lofty tone, Leibniz declared that a benevolent god would choose to create whatever possible world contained the smallest amount of evil; hence (in a phrase that would later be mocked by Voltaire) this is "the best of all possible worlds," according to Leibniz. Nothing about it could be changed without making things worse rather than better on the whole.

Similarly, the existence of a benevolent god can be used to account for the smooth operation of a universe that consists of indefinitely many distinct individual substances, none of which have any causal influence over any other. (Monadology 51 ) A crucial element of god's creative activity, Leibniz held, is the establishment of a "pre-established harmony" among all existing things. Like well-made clocks that have been synchronized, wound, and set in motion together, the monads that make up our world are independent, self-contained, purely active beings whose features coincide without any genuine interaction among them.

One special case of this pre-established harmony, of course, accounts for the apparent interaction of mind and body in a human being as nothing more than the perfect parallelism of thier functions. In fact, the human mind is just the dominant member of a local cluster of monads which collectively constitute the associated human body. (Monadology 63) Neither has any real effect on the other, but these monads are most clearly reflected in each others' foreground. Thus, in both sensation and volition, the divinely-ordained coincidence of bodily movements and mental thoughts creates an illusion of genuine causal influence.

Synchronicity (none / 0) (#18)
by dennis on Sat Feb 23, 2002 at 01:02:12 PM EST

As you mention, Hogan's book starts with a speculation that many-worlds is the basis for human intuition about the future.

Which now gives me a bit of a funny feeling, because as it happens, just last night I picked up his book!

Consequently I've avoided reading your review until I'm done with the book, will post more later...

I would not take many worlds too seriously (3.50 / 4) (#19)
by Weezul on Sat Feb 23, 2002 at 01:48:21 PM EST

There are three compeating notions for what quantum mechanics "means," the first is the classical copenhagen interpretation, the second is many words, and the third is bomian mechanics (the world really dose work like little balls, but it works that way in a higher dimentional phase space). Whatever people tell you none of these has been disproved and none of them are reall diffrent when it comes down to the experemental level. They all use the wave euation. They all have spooky action at a distance which is not really spooky since it dose not communicate any information If you want to understand quantum mechanics you need to understand the wave equation and forget about all the p[hilosophical bagage. The philosophical bagage is not science, it's only wild speculation. Now there are good physicists who believe these theories, but that dose not mean this baggage necissary.

"Fascism should more appropriately be called Corporatism because it is a merger of state and corporate power." - Benito Mussolini
Appropriate typo... (4.50 / 2) (#21)
by FreeBarking on Sat Feb 23, 2002 at 02:11:53 PM EST

You wrote:

There are three competing notions for what quantum mechanics "means," ... , the second is many words, ...

Indeed, most physicists would agree that all of these interpretations are "many words" without a lot of real content.

But I also tend to agree with Sidney Coleman, and others like him, who say that since quantum mechanics is the theory that best describes our observations of the world, it's not quantum mechanics that we need to "interpret", it's classical mechanics. What he and others call the "take quantum mechanics seriously" interpretation ends up looking very much like what some call "many-worlds". The Copenhagen Interpretation assumes the existence of a classical experimental apparatus making measurements on a quantum-mechanical system. But if everything obeys the laws of quantum mechanics, the Copenhagen interpretation becomes an approximation to the purely quantum-mechanical reality, which some like to call many worlds...

[ Parent ]

ok (none / 0) (#27)
by Weezul on Sat Feb 23, 2002 at 03:33:41 PM EST

But the Copenhagen interpretation *is* the story of why quantum mechanics exists. I would not expect this to necissarily be the whole story, but I would expect it to have a measure of "sanity" or "rigour." Sidney Coleman may very well be correct if he is claiming that this level of rigour is unessicary for physics, as it was never demanded of classical mecahincs (or realitivity might have been discovered half a century eariler). Still, we have a theory with that level of "philosophical precission," so the other interpretations need to produce experementally verifiable results which the Copenhagen interpretation dose not produce.

btw> I don't know the details, but I would suspect that Bomian mecahnics might meet Coleman's criteria for "taking classical mecahincs seriously" too.

"Fascism should more appropriately be called Corporatism because it is a merger of state and corporate power." - Benito Mussolini
[ Parent ]
quantum-mechanical reality (none / 0) (#51)
by kubalaa on Mon Feb 25, 2002 at 10:20:50 AM EST

So far, I'm not really sure that "many worlds" has any inherent meaning, any more than "the matrix" philosophy. If worlds cannot interact, then they may as well not exist. If they can interact, then they may be considered part of the same world. I have yet to hear anyone seriously explain what "many worlds" has to do with quantum mechanics, other than a vague popular-science notion of quantum mechanics as having to do with cats which are both alive and dead or "probability waveforms."

[ Parent ]
Understanding the wave equation (5.00 / 2) (#22)
by bodrius on Sat Feb 23, 2002 at 02:26:18 PM EST

The problem is that for some people, myself included, it is almost impossible to "understand" the wave equation without an idea of what it talks about.

By "understand" I don't mean we can't use it. I mean we don't "get it" in the fundamental level that allows us to use it as part of our language and our view of the world.

Perhaps my problem can be put this way: for me, an equation does not a theory make.

A vital part of the theory, yes, but without the explanation I find it hard to digest that there is a difference between Schrodinger's equation and some arbitrary correlation that just happens to work.

It seems to me that the philosophical baggage is a great part, perhaps the greatest part, of the benefit a new physics framework provides, because it percolates to other areas of science and culture.

It seems to me that disregarding the philosophical baggage is condemning most people, including some who actually work with these equations, to keep a worldview that is fundamentally wrong, and whose axioms do not let them doubt things that should be doubted.
Freedom is the freedom to say 2+2=4, everything else follows...
[ Parent ]
There's a fourth (none / 0) (#55)
by epepke on Mon Feb 25, 2002 at 12:28:28 PM EST

This is that probability itself breaks down. I only mention it because a physicist with whom I used to work (Saul Youssef) liked this one. Personally, I couldn't care less.


The truth may be out there, but lies are inside your head.--Terry Pratchett


[ Parent ]
And also... (none / 0) (#67)
by spiralx on Tue Feb 26, 2002 at 05:36:04 AM EST

The Transactional Interpretation, based on Wheeler-Feynmann absorber theory.

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

MWI and Theodicy (5.00 / 1) (#24)
by aminorex on Sat Feb 23, 2002 at 03:06:12 PM EST

The most interesting aspect of the MWI, from my point of view, is its relationship to the Problem of Evil. Consider a God who defines truth and falsehood by fiat, no less for deontic than for propositional modalities. The set of universes that exist are then simply those the existence of which is morally superior to their non-existence, i.e. the net wins. Sure evil exists, but only up to the point where it wins. Any transcendent resolution of the divergence of the underlying metaphysical reality thus constitutes a victory of good over evil.

This is considerably easier to swallow than Liebniz's "best of all possible worlds"; very few of us lack the imagination to concieve of worlds better than the world of our experience.

Sliders (none / 0) (#25)
by X3nocide on Sat Feb 23, 2002 at 03:33:24 PM EST

I think that was the premise behind the FOX scifi series Sliders. There was some math and equations stated in the beginning few episodes, but I was far too young at the time to really comprehend anything; I figure'd it was just gibberish technobabble like on star trek, to lend a little suspension of disbelief. Maybe someone else remembers better than I?

pwnguin.net
re: Sliders (5.00 / 1) (#32)
by Corwin on Sun Feb 24, 2002 at 12:51:27 AM EST

In Sliders they kept making mention of the Einstein-Rosen-Podolsky bridge.

I, too, pretty much ignored it and enjoyed the show without thinking too much of the science. :)

But a search on Google comes up with some interesting things. Go have a looksee.

The only thing that I find with all three of those names is a thought-experiment, but the Einstein-Rosen bridge describes wormholes through rotating black holes.

---
I'm in search of myself. Have you seen me anywhere?
[ Parent ]
MWI and Death (5.00 / 1) (#26)
by cyberformer on Sat Feb 23, 2002 at 03:33:30 PM EST

The Many Worlds theory means that we will all live forever, or at least much longer than most other people.

At the moment of your death in one reality, the Universe splits, and in another reality you survive. Assuming that there isn't a non-physical afterlife (in which case we already living forever anyway), you aren't aware of being dead, only of being alive. So, subjectively, we never die, though we will witness the deaths of everyone we know and love, and will eventually become so old and frail that our eternal life is one of unending pain.

Really? (none / 0) (#33)
by qpt on Sun Feb 24, 2002 at 03:20:49 AM EST

That assumes that it is physically possible to live forever, which I think is doubtful.

The problem is this assertion:

At the moment of your death in one reality, the Universe splits, and in another reality you survive.

That is only true if it is physically possible for you to survive and your death was caused by an indeterminate event. This is often not the case.

Domine Deus, creator coeli et terrae respice humilitatem nostram.
[ Parent ]

Actually it is always physically "possible&qu (none / 0) (#87)
by MickD on Wed Feb 27, 2002 at 06:01:42 PM EST

The neat thing though is that the "Many" in the many worlds interpratation is a huge number in fact it is infinite, I believe even duplicate worlds fall out of the interpretation. All possible worlds exist.

If I fall out a window it is possible that all the air molecules near me will pile up underneath me and stop me from squishing into the pavement. It sure isn't likely, (read Probable) but the laws of physics and especially quantum physics work on probabilities and as long as the probability isn't zero.zero-bar that is all you need to keep on living.

That's the theory anyway. But so far it has stood up to 100% of the testing I have done. :)

I have thought about standing at ground zero of a nuclear test for a definitive proof, but I like my body too much the way it is now. And the failure of the proof would kinda suck
Is this the end yet? how 'bout now?..how 'bout now?..how 'bout now?..
[ Parent ]
But then on the other hand... (none / 0) (#57)
by epepke on Mon Feb 25, 2002 at 02:26:37 PM EST

We'd also already be dead.


The truth may be out there, but lies are inside your head.--Terry Pratchett


[ Parent ]
Niven's story resonated intuitively with me. (4.00 / 1) (#29)
by la princesa on Sat Feb 23, 2002 at 06:32:29 PM EST

Long ago I read it (wrote about it months ago, but had forgotten the author/title and your description of the plot restored them to memory) and it solidified a hazy idea I've always had since childhood-- that there may well be other concurrent worlds where one has fulfilled or explored different possibilities than in one's current world. And of course the idea of suicide because one can't possibly have a life as cool as that of one's alternate selves at the same age does crop up, as does the possibility of having the coolest life of all of them. My view of the Many Worlds concept isn't quite the same as the scientific one, but it has enough similarities to some theories to make me feel like my early intuitions might be accurate in certain (possibly unprovable) respects. Gracias for restoring to memory a tale I'd forgotten except for plot and gracias again for an interesting discussion of other writers' takes on this idea.

Timeline (none / 0) (#31)
by labradore on Sat Feb 23, 2002 at 10:53:02 PM EST

Michael Crichton's Timeline was a book that dealt sparingly with quantum mechnanics. I didn't understand the premise very well but appearantly time travel was supposed to be possible using quantum computers. The idea seemed to be that one could travel to another universe that was younger than our own therefore it would be time traveling. Has anyone else read this book? I listened to it on tape on a long trip and though the history and the characters were interesting, the science seemed to be bunk.



Crichton's Timeline (none / 0) (#35)
by localroger on Sun Feb 24, 2002 at 08:31:46 AM EST

Timeline is another interesting failure of imagination; Crichton uses the full-blown MWI to justify simple linear time travel. I found it unbelievable that characters who had put the investment in resources into the apparatus Crichton described, with all its vast implications, would be using it mainly to run around 14th century France, for cryin' out loud.

Obviously, having decided to write a medieval time travel story, Crichton needed a SFnal excuse to get his people there. The course he chose was a classic example of Mr. Cockroach, meet Mr. Atomic Bomb.

I can haz blog!
[ Parent ]

MWI (5.00 / 3) (#36)
by Matrix on Sun Feb 24, 2002 at 08:33:19 AM EST

Unfortunately, while MWI proposes the possible existance of other "world-lines", it says nothing about two things:

  1. Travelling between them.
  2. Lines merging back together.

These two combined put SF books that involve travel between alternate worlds without accounting for certant things on rather shaky ground. I'll deal primarily with the first, as its the one anyone reading these books should have noticed.

Now, first, we have to assume one thing. That any action which could possibly have more than one outcome will result in a split into one or more parallel universes. Limiting it to human actions, as many authors do, requires one to explain why humans are so special. Few, or none, that I've read do this satsifactorily.

With that said, assume I start working on inventing a machine to travel between these universes. Of course, there's multiple ways I can go about this, and even more ways I can fail. So we'll be conservative, and assume that, in one hundred closely linked universes, I wind up with a machine to let me move between universes. Now, where can I go? The usual explanation is "the closest universes", but that doesn't make sense. Then I'd just wind up in these other close-by universes where there aren't many differences other than my machine. (This is, of course, a vast simplification, but we'll ignore that for now.)

So, instead, lets assume I can travel anywhere I like. So I hop in my machine and whiz off to ubertopia. Whoops! My arrival there, being an event, causes the universe to divide. Again, we'll be conservative, and imagine a hundred divisions. In some, I botch my arrival and die. In others, I'll arrive safely, have a similar but slightly different series of adventures, then hop in my machine again and whiz back home. As you can see, this would create a big problem for any Evil Organization Lackies following me. Not only does their arrival in a universe split it up, but they might arrive in one I never arrived in at all!

Now, after eluding my pursuers and heading back home, we've got another problem. Where exactly is "home"? While I've been away, my universe has been merrily dividing away. So I've got quite a lot of choices. Assuming I pick randomly, we'll be fine, right? Every me will wind up in a different universe.

Whoops. Logical inconsistancy. Since I'm choosing randomly, I cause a split in which I make every possible choice. (Simplified things a little, again) Which means that every universe I had to choose between winds up with a copy of all the "me"s that arrived and departed safely. In fact, we wind up with quite a lot of them, once we consider all the random choices I've had to make so far. In some universes, yes, only one will arrive safely. In many, they get the full set.

So while it can be fun to consider, SF involving travel between alternate world-lines ultimately winds up in the same category as SF involving time travel. Namely, fantasy based loosely on science. (See Niven's assorted writings on time machines)


Matrix
"...Pulling together is the aim of despotism and tyranny. Free men pull in all kinds of directions. It's the only way to make progress."
- Lord Vetinari, pg 312 of the Truth, a Discworld novel by Terry Pratchett

To play Devil's Advocate... (5.00 / 1) (#37)
by localroger on Sun Feb 24, 2002 at 08:56:02 AM EST

While there are plenty of objections, in fairness to the SF authors who have trodden this path I think it's worth pointing out that you can't dismiss the whole idea quite this breezily.

Limiting it to human actions, as many authors do, requires one to explain why humans are so special. Few, or none, that I've read do this satsifactorily.

Unfortunately, they've been working with what quantum physicists give them, and there is a school of thought that consciousness has some fundamental bearing on the matter. If you read the section of the FAQ I linked you'll see that the issue of decoherence is one of the hot topics in this area. Noting all the flapdoodle about quantum computers, I tend to think decoherence is forced when the computational overload lights start blinking on the Big Computer, and consciousness is just particularly adept at forcing that to happen.

My arrival there, being an event, causes the universe to divide.

Not necessarily; the correspondence between you and the receiving universe could involve either a single instance or one of several flavors of infinity on either side of the colon. It is quite reasonable to assume aleph-null:aleph-null, in which case each singular you can enter a singular receiving universe safely. (This is of course an unfounded SFnal assumption, but the point is that it is a reasonable SFnal assumption.)

As you can see, this would create a big problem for any Evil Organization Lackies following me. Not only does their arrival in a universe split it up, but they might arrive in one I never arrived in at all!

I believe someone else mentioned that Greg Egan uses this as a plot device in The Infinite Assassin. I'm gonna have to read that...

Whoops. Logical inconsistancy. Since I'm choosing randomly, I cause a split in which I make every possible choice.

The number of possible choices may not be infinite. In Otherwhere Hogan's scientists use random numbers generated from radioactive decay to create ID markers for their home universe. While you will get every possible result, there are a finite number of possible results. Since the number of things causing the universe to split is much larger than the number of choices in homing beacon, it seems the real problem is that most universes that remember sending out a traveller will never get one back.

My point is not to argue that crosstime travel is possible -- it's clearly very unlikely -- but unlike time travel and non-instantaneous FTL travel, there are still reasonable ways to talk around it without violating established principles. (This is undoubtably why Crichton chose MWI to prop up his time travel scenario in Timeline.) Of course one day we'll get this all sorted out and then you'll probably be proven right. But remember it wasn't all that long ago that going at the "ridiculous speed" of 40 miles per hour, or travelling to the Moon, were also considered impossible.

I can haz blog!
[ Parent ]

Breif Reply (5.00 / 1) (#38)
by Matrix on Sun Feb 24, 2002 at 10:00:21 AM EST

I don't have much time now, but for the sake of discussion, I'll answer one or two of your points.

Not necessarily; the correspondence between you and the receiving universe could involve either a single instance or one of several flavors of infinity on either side of the colon. It is quite reasonable to assume aleph-null:aleph-null, in which case each singular you can enter a singular receiving universe safely. (This is of course an unfounded SFnal assumption, but the point is that it is a reasonable SFnal assumption.)

Not quite. There are two outcomes. Either everything goes well and I arrive, or something in my machine screws up and I don't arrive. That's a split in two right there. Even assuming that doesn't occur, splits start happening as soon as I arrive. How long do I spend checking readings before climbing out? Which way do I turn when I do step out? What's the first thing I go to do? There's a number of changes right there. This is normal, but it also results in X universes where I exist with a universe-hopping machine.

Hogan's theory merely further complicates things. Yes, the radioactive decay could be different in each branch. But it also (I think, its been a while since I did any physics for radioactive decay) increases the likelihood of the many travellers from different branches of the target universe returning to the same branch of their departure universe. And it doesn't address the problem of departure - a hundred mes, each randomly or pseudo-randomly choosing an alternate universe to jump to seems very likely to result in several deciding to jump to the same place.

As for non-instant FTL travel... It depends. I think that even most space opera authors now use wormholes of one kind or another. Some speculation (like David Weber's) can stand up to cursory evaluation, though is obviously impossible based on what we now know. Of course, one thing to remember is that little of our science now is absolutely right. Its just less wrong than anything before. Einstein, like Newton, will eventually be (partially) disproved. Based on what we know now, both cross-timeline and FTL travel are impossible. Who knows what we'll know a hundred years from now?

The most blatant example is the recent lack of discovery of a flavour of elementry particle where theories predicted it should. Last I heard, this was going to require a substantial overhaul of large parts of theory that depended on this particle's existance at these wavelengths/energy levels.


Matrix
"...Pulling together is the aim of despotism and tyranny. Free men pull in all kinds of directions. It's the only way to make progress."
- Lord Vetinari, pg 312 of the Truth, a Discworld novel by Terry Pratchett
[ Parent ]

Quick question (5.00 / 1) (#40)
by Amesha Spentas on Sun Feb 24, 2002 at 12:04:02 PM EST

Now, first, we have to assume one thing. That any action which could possibly have more than one outcome will result in a split into one or more parallel universes. Limiting it to human actions, as many authors do, requires one to explain why humans are so special. Few, or none, that I've read do this satsifactorily.

Am I missing something? Most of the discussions I've seen are relating to MW being created based on human decisions. Is the MWI Theory based on Richard Feynman's "Multiple Histories" or "sum-over-histories" theory or is the MWI based on something else entirely? If it is based on the "Multiple Histories" Theory then my understanding of "Multiple Histories" is that for each possible Quantum path a particle can take it instead takes every possible path. However it still ends up arriving at the same destination. Can someone point me to a complete description of the MWI theory?

Registered to die for the government at 18, and had to pay postage on the registration form - AnalogBoy
[ Parent ]

FAQ (none / 0) (#43)
by Matrix on Sun Feb 24, 2002 at 03:29:07 PM EST

See the FAQ linked to up at the top of the story. It seems to know what its' talking about. Most of the SF books I've read involve alternate realities based on primarily human decisions, though.


Matrix
"...Pulling together is the aim of despotism and tyranny. Free men pull in all kinds of directions. It's the only way to make progress."
- Lord Vetinari, pg 312 of the Truth, a Discworld novel by Terry Pratchett
[ Parent ]

Schrodinger's Cat (3.00 / 1) (#39)
by S_hane on Sun Feb 24, 2002 at 10:46:14 AM EST

What about the Schrodinger's Cat trilogy, by Robert Anton Wilson? Certainly one of the stranger MW reads out there, and maybe one of the first modern ones too (written in 1979).

Having read it quite a while ago, I can't remember a great deal of what happened, but a combination of this series and "Illuminatus!" (not MW, but very...odd) really blew my mind at the time.

From memory, Wilson doesn't place any restrictions on the multiple worlds, and doesn't even deal with explicit traversal between them. Instead, the stor(y/ies?) takes place many times, with many different outcomes, all woven into a wonderfully confusing tapestry.

Great stuff, anyway. Random quotes can be found here

    -Shane Stephens


The future & the past... (5.00 / 1) (#45)
by univgeek on Sun Feb 24, 2002 at 07:56:25 PM EST

Isaac Asimovs 'The End of Eternity' also comes under the same category I suppose. The book deals with a society which has found time-travel, but which does not realise that they are dealing with an infinite number of realities. They are then stopped by a future civilisation. The future civ does this in order that humans expand outside the Earth.

With my limited understanding of the MWI theory let me state a question I have. Compare the infinite universes to the infinite number of points on a real number line. Of course the probabilities associated with any one of these points has to be zero. But is the probability associated with a group of possible universes finite? This is probably what Asimov explores in his book.

My question, Is something able to influence these probabilities?

Of course all this is pulled straight out of my a$$... ;-))

On a lighter note, in my nth re-reading of HHGTG, Douglas Adams' MWI interpretation seems to be pretty good too. His take on what would happen with cheap time-travel - 'I've been to the future, its the same as here - except faster' Ford Prefect. (not an exact quote).

I've always thought that Douglas Adam's version of the universe is going to be the One True Universe (tm). Seems to be much more likely than a human-only universe (a la Foundation). And the plural universes concept, with discontinuities is interesting too.

Nice article!!!
Arguing with an Electrical Engineer is liking wrestling with a pig in mud, after a while you realise the pig is enjoying it!

My favorite use (abuse?) of Many Worlds (3.66 / 3) (#46)
by hardburn on Mon Feb 25, 2002 at 12:15:45 AM EST

I discovered this one from its entry in the Jargon file under "bogo-sort". A "bogo-sort" is the very Worst Possible algorithm you can use in a program (as opposed to a "bubble-sort", which is mearly naive). Sorting a deck of cards using a bogo-sort is done by throwing the cards up in the air, picking them up, and checking if they're sorted. If they're not, throw them up in the air again. Repeat until the cards are sorted.

Later, someone figured out that, if the "Many Worlds" interpretation of Quantum Physics is true, you can actualy do a bogo-sort in about O(n) time. You first randomly sort the array using a quantum algorithm. Then you check if it's sorted (this is the part that takes O(n) time). If it's not sorted, destroy the universe.

That last step is left as an exercise to the reader.


----
while($story = K5::Story->new()) { $story->vote(-1) if($story->section() == $POLITICS); }


"unscientific", defined (3.50 / 2) (#47)
by streetlawyer on Mon Feb 25, 2002 at 02:29:32 AM EST

I've never understood whypeople don't see the Many Worlds Interpretation for what it is -- an unscientific "Just So Story" for people who don't want to get to grips with the realities of quantum mechanics. I'm also not aware of any physicist worth a lick who takes it seriously; even one of its inventors (Wheeler) gave up on it, particularly when he saw some of the uses to which it was being put.

It is the absolute paradigm case of a non-scientific, untestable assertion, which isn't even testable in principle! This makes it far less of a scientific hypothesis than, say, astrology or creationism, each of which could in principle be subject to falsification.

I'm pretty sure that future historians of science will regards the MWI as evidence of how much otherwise reputable physicists were prepared to ignore science and logic in order to preserve a worldview which didn't have any space for mind. With any luck, some future genius will be able to work out why this was so important to them, because it beats me.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever

All QM interpretations are unscientific (4.00 / 1) (#49)
by epepke on Mon Feb 25, 2002 at 08:24:29 AM EST

There is no known way to distinguish between the various interpretations of QM by experiment, so any assertion that one is right is unscientific. I once saw a suggestion of an experiment based on reversible quantum computers, but it was wrong. The fun is in figuring out why it is wrong. (Hint: erasing a bit involves thermodynamics.)

However, interpretations are enjoyable. Even physicists need something to talk about when they're having a beer. Besides, the mentioned stories and novels are fiction. They should not pose any problems for anyone who understands the first principle of fiction, namely, that it isn't true.

In my experiencer, people seem to have a certain prejudice against the Many Worlds interpretation that they don't have for, say, the Copenhagen interpretation. When you single out MW for being unscientific, though, the very act of singling it out is itself unscientific.


The truth may be out there, but lies are inside your head.--Terry Pratchett


[ Parent ]
I see your point but disagree (none / 0) (#50)
by streetlawyer on Mon Feb 25, 2002 at 08:33:54 AM EST

The Copenhagen Interpretation is more scientific, however, because it does not postulate vast numbers of metaphysical entities. It also has a comendable Kantian modesty, in that it talks about descriptions rather than things. For this reason, I tend to find that Copenhagenists are better physicists and more mature people than MWI-theorists, because they don't have this need to keep talking about a "thing-in-itself" which goes beyond what they know.

Just as an observation, I've never yet read a MWI-ist who didn't at some point or another try to spatialise time.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

Unfortunately (none / 0) (#52)
by spiralx on Mon Feb 25, 2002 at 11:29:12 AM EST

The Copenhagen Interpretation falls down because it claims that an act of observation is required for the collapse of the wavefunction to occur without specifying what such an observer entails. Hand-waving arguments about consciousness don't really do it for me either, because then you can easily set up an infinite regress of necessary observers.

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

so what? (none / 0) (#53)
by streetlawyer on Mon Feb 25, 2002 at 11:54:24 AM EST

Yes, but why is this an objection? Properly understood (ie: as understood by Bohr, Heisenberg often seems to screw it up IIRC), all this is saying is that an event of observation collapses the probability waveform. Bohr never claimed that this is some metaphysical event whereby the electron jumps from one slit to the other. The act of observing "creates" an event of observation in the same way that sitting down "creates" your lap. The dependence is logical, not metaphysical. Bohr is very clear on this; he's talking about the epistemology and steadfastly refusing to say anything about what he fundamentally views as unanswerable questions. It's that bloody cat that makes people think differently about this. We ought to teach the cat to speak Chinese and do away with two confusing thought experiments at once.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]
No, not that (none / 0) (#60)
by spiralx on Mon Feb 25, 2002 at 03:23:40 PM EST

I don't have a problem with what you're saying, although some people do as it implies that quantum mechanics is inherently non-local. It's the precise meaning of what an "act of observation" entails that bothers me. By following the CI strictly you end up with Wigner's Paradox and require consciousness to have some kind of priviliged role, something I find too anthropocentric to be true.

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

nononono (none / 0) (#62)
by streetlawyer on Mon Feb 25, 2002 at 06:28:07 PM EST

Look, Wigner's paradox is a confusion. There's nothing paradoxical in consciousness having a role in observation; the fact that observations require observers isn't a kind of anthropocentrism which should worry us, because. The problem comes in when you start assuming that "collapsing the probability waveform" has some incredible significance above and beyond marking the point in space-time when observer A made observation B. Which is what the Copenhagen Interpretation specificaly tells us not to do.

In a way, Wigner is underlining the whole point of the CI, which is that we should only be talking about observations and what we can observe, and not pretending to describe Ultimate Reality. And if you look at it that way, it's obvious that it has to be an anthropocentric concept.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

So do I (none / 0) (#54)
by epepke on Mon Feb 25, 2002 at 12:24:58 PM EST

It might be, well, more scientisty, but it isn't any more scientific.

My unscientific interpretation is this: Wavefunctions don't collapse. Physicists do.


The truth may be out there, but lies are inside your head.--Terry Pratchett


[ Parent ]
You should read some technical stuff on MWT... (none / 0) (#61)
by SIGFPE on Mon Feb 25, 2002 at 03:43:52 PM EST

In the MW interpetation there is one wavefunction that satisfies one wave equation at all times. In the Copenhagen interpretation there are observers and there are systems described by wave functions. When an 'observer' (whatever that means) observes (whatever that means) a system described by a wavefunction (whatever makes it of that special class) it stops satisfying the wave equation for a moment, collapses into an eigenfunction and then proceeds with obeying the wave equation. Whether one considers metaphysical entities to be multiplied in either case is merely a function of one's prejudices.

As for your comments about 'mature' physicists - it goes to demsontrate the old adage about how a revolution in physics isn't over until the previous generation have all died off.
SIGFPE
[ Parent ]

Jebus (5.00 / 1) (#63)
by streetlawyer on Mon Feb 25, 2002 at 06:35:53 PM EST

Why is it that people keep telling me to "read some of the technical works" which I've obviously read, simply because I disagree with their pet theory?

The Copenhagen interpretation restricts itself to talking about observations made by observers. We know that there are such things as observations, because we make them, and we know that there are such things as observers, because we are them. Despite your scare-quotes and spiralx's (vastly more erudite) comments about paradox, there is nothing imprecise or unrigorous about Niels Bohr's concept of an observer. Bohr's theory describes perfectly the empirical evidence without needing to suppose the existence of anything that we don't already know exists. The Many Worlds Interpretation postulates an infinity of parallel physical entities which do not interact causally with anything we can ever measure. It's an unfalsifiable existence claim about metaphysical entities, which makes it less metaphysically parsimonious than the CI, which is purely a mathematical description of available sense-data.

The only merit in MWI that I can see is that it makes the universe safe for materialism again, because it ignores the fact that experimental observations (like all other sense-data) are intrinsically subjective. Which sounds to me like a bad thing about materialism rather than a good thing about the MWI.

To adapt a common (and uncommonly stupid) argument of the atheists, why shouldn't I believe that MWWIPU (Many Worlds With Invisible Pink Unicorns) Hypothesis, which is equivalent to MWI plus the assertion that all universes other than our own are chock full of invisible pink unicorns?

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

There's a reason why people ask you the same thing (none / 0) (#65)
by SIGFPE on Mon Feb 25, 2002 at 10:53:22 PM EST

You're being very silly when you talk about parsimony. You're using Occam's razor like a child with a new toy without the slightest regard for what it really means and what use it serves. Applying Occam's razor does not mean simply counting up how many entities you have in your physical system and picking the one with the fewest. If you're going to play silly buggers like that then I'm going to claim that every wavefunction collapse is a an extra metaphysical entity and that the Copenhagen interpretation multiplies entities needlessly whereas MWT has one seamless universe. You're playing disingenously - even the Copenhagen interpretation postulates a wavefunction for unobserved particles that is a sum of an infinity of eigenfunctions but you seem to forget this. MWT merely extends this to include observers by removing an arbitrary distiction (more metaphysical mutiplication) betwen observers and the observed.

MWT is derived by taking the two postulates of the Copenhagen interpetation and deleting one.

Occam's razor is about finding the simplest description. It's about solving problems with the least effort and with the simplest principles. Simpler equations and the fewer postulates.

And that stuff about the concept of an observer being rigorous is a damnable lie. The Copenhagen interpretation is completely unable to say anything about useful about observers. Nothing whatsoever except that they cause wavefunction collapse (by some mysterious indescribable mechanism). It can say nothing about how observers work. There are no criteria for determining if something is an observer (except...uh...well...it looks like one so maybe it is one). It can't even begin to explain why an observer, sitting in a car say, should move with the rest of the car. Why should the car engine ultimately push the observer? In the Copenhagen interpretation an observer is some ineffeable thing and yet forces somehow magically can act on it. The fact that you can look out the window and recognise some observers says absolutely nothing about the rigorousness of the concept and I can't believe you claim it does. I can recognise simultaneity when I see it - maybe I should reject special relativity. The Copenhagen interpretation isn't even an 'interpretation' - it doesn't have enough coherence to even be thought of as a theory of anything. It's like a broken old calculator. You can get calculations done with it as long as you restrict what buttons you press and don't do stuff with really big numbers - but if you need to do anything sophisticated you need to graduate to a real man's tool.

I'm not even going to reply to the nonsense about pink unicorns.

Maybe I'll give up the atomic theory. Surely having 10^23 atoms in every mole is multiplying entities far beyond believing in a continuum and far worse than the benefits to be brought by the simplification of theory.

Oh yeah...and as for that stuff about "better physicists" not being supporters of MWT, it's a lie too. MW theorists include Hawking, Feynman and many others. The only poll I know of actually had MWT as the most popular theory. Among quantum cosmologists it's nearly universal. Among experimentalists it's less popular - not surprising because they don't need it - just as a car mechanic doesn't need to understand Newton's laws to fix an engine.
SIGFPE
[ Parent ]

Idiot (none / 0) (#66)
by streetlawyer on Tue Feb 26, 2002 at 02:31:47 AM EST

First up, I will extend the principle of charity by assuming that you're wrong about Feynman and Hawking because you don't know the difference between the sum-over-histories interpretation and "Many Worlds", rather than out of more sinister motives.

Second, you don't understand the Copenhagen interpretation, so I don't propose to discuss it any further with you. The observer creates the observation in the same way that the act of sitting creates your lap, or an act of marriage destroys a bachelor. It's a simple logical independence, and when someone tries to claim that there's something "Ineffable" about it, it's a clear sign that they don't understand it.

You don't reply to the "nonsense" about pink unicorns because it destroyed your pet theory, years ago, which is why anyone who wants to be intellectually respectable moved on to a sum-over-histories interpretation at about that time.

And you are utterly confused about what metaphysical claims the Copenhagen interpretation makes (in fact, you don't seem to know what a metaphysical claim is). The wave function for the Copenhagen interpretation is a mathematical description of observations. It restricts itself to talking about data we know we have. It does not postulate anything beyond its evidence (the fact that you think that the Copenhagen interpretation postulates hidden variables shows how poorly you have learned it, by the way).

And of course, many worlds can't handle the Bell's Theorem experiments other than by postulating a massive coincidence.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

Stuff (none / 0) (#68)
by spiralx on Tue Feb 26, 2002 at 05:53:46 AM EST

First up, I will extend the principle of charity by assuming that you're wrong about Feynman and Hawking because you don't know the difference between the sum-over-histories interpretation and "Many Worlds", rather than out of more sinister motives.

I believe he's talking about a poll done by L David Raub in which 58% of cosmologists and field theorists asked said they thought the MWI was true. This did include Hawking and Feynman, although Hawking expressed reservations about the name "many worlds".

The sum-over-histories thing is not an interpretation, it is a formalism, a way of calculating transition amplitudes just like Schrodinger's wave equation does or Heisenberg's matrix mechanics do. That's all it is. However, it does seem well-suited to the MWI interpretation.

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

Feynman (none / 0) (#69)
by streetlawyer on Tue Feb 26, 2002 at 06:34:50 AM EST

Was not asked in that poll, for the pretty decent reason that he was dead, IIRC. And while I don't claim to fully understand what Hawking means, I think his position is that the Schrodinger equations describe a physical reality, but not a multiverse (ie, a no-collapse theory, but not necessarily a full-on Everett MWI of the kind that David Deutsch and seemingly nobody else believes in). Penrose disagrees with him, whatever he thinks.

In general, Feynman is a pretty bad authority on lots of things. Contemporaries said that after reading his work on QED and then reading him on almost any other subject, they got the kind of feeling that Salieri must have experienced on meeting Mozart in person.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

Hawking and Feynman (none / 0) (#70)
by spiralx on Tue Feb 26, 2002 at 06:47:15 AM EST

Well I can't find a date for that survey, but all the links seem convinced it took place before 1988...

As for Hawking his cosmological theories involve a lot of talking about the wave-function of the entire Universe and how it branches off... his papers have referenced Everett's papers on many-worlds.

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

hrrrm (none / 0) (#71)
by streetlawyer on Tue Feb 26, 2002 at 07:16:08 AM EST

All the links I kind find are to the "Everett FAQ", a document I have to say I regard as disingenuous as it mentions the words "probability measure" precisely once and then in a context which suggests that a probability measure over worlds is a completely unproblematic thing. Its treatment of Bell's theorem is also a little bit ... odd, too. The document "presumes" that the poll was conducted before 1988 in order to assume that Feynman is included in it, but its date of publication was 1995.

Hawking references Everett, but he doesn't seem to believe in a splitting and branching multiverse. The reference appears to be to a 1976 paper on a different subject; I don't see why he would have nailed his colours to the mast in such a way. His book with Penrose (which I bought last week; it's really good) seems to have him postulating a realist theory of the probability waveform; this implies that there is a sense in which there is an existence for unactualised possibilities, but I don't think it commits him to a splitting, branching multiverse a la Wheeler. And as I said earlier, Penrose thinks its crap.

Do you not think that the Bell experiments make it much harder to believe in MWI? Is locality really so important to preserve?

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

*shrug* (none / 0) (#72)
by spiralx on Tue Feb 26, 2002 at 08:51:15 AM EST

Are you talking about the nature of space and time book? That was very good; serious discussions of quantum cosmology that actually had more beef than most such books. OTOH, it's been a while since I read it so my knowledge of the details is sketchy.

Do you not think that the Bell experiments make it much harder to believe in MWI? Is locality really so important to preserve?

Well I'm not a many-worlds person myself, so no. I don't think locality is essential or even likely. Personally I go more for the transactional interpretation, but I think a deeper understading may have to wait for deeper knowledge of the Universe.

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

yeh (none / 0) (#73)
by streetlawyer on Tue Feb 26, 2002 at 09:12:54 AM EST

Are you talking about the nature of space and time book?

Yeh, that's the one; I'm progressing through it rather glatially, mainly because I've also bought another incredibly nerdy economics book. But it does look very good.

I've never really understood the transactional interpretation, but Robert Anton Wilson thinks it's incredibly important.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

TI (none / 0) (#74)
by spiralx on Tue Feb 26, 2002 at 09:28:25 AM EST

The paper is here if you're interested. It's not unreasonably technical either, and contains several critiques of other interpretations as well as how the TI can be used to model things like the double-slit experiment and so on.

Alternatively, it's discussed quite nicely in John Gribbin's book Schrodinger's Kittens.

You're doomed, I'm doomed, we're all doomed for ice cream. - Bob Aboey
[ Parent ]

The poll was also reported in Scientific... (none / 0) (#76)
by SIGFPE on Tue Feb 26, 2002 at 12:38:32 PM EST

American a while back. The same article discussed Feynman's position.
SIGFPE
[ Parent ]
Yes and no (none / 0) (#77)
by SIGFPE on Tue Feb 26, 2002 at 12:56:45 PM EST

The sum-over-histories thing is not an interpretation, it is a formalism
Yes and no. In the sum-over-histories formalism you write the state of a system as a superposition of an infinity of different paths. This is implicitly a sum over universes so in fact sum-over-histories implies many worlds. However Copenhagen followers like to play a shell game where they hide that deduction under a shell and then declare, by fiat, that you're not allowed to look there. Nonetheless if you're looking for consistency many worlds is completely implicit in the Schrodinger equation.

It's not implicit if you bring in extra hypotheses to kludge your theory. Various hypotheses that Copenhagen interpretations try to use to patch up their theory include denying that QM works for large systems. In QM, if you have two quantum systems with state spaces S1 and S2 then the state space of the union of the two systems is the tensor product of S1 and S2. Copenhageners deny this applies to observers (arbitrarily) nonetheless it must apply to the rest of the universe (a product of lots of subsystems Si) so we have a state for the whole of the universe minus observers. Expanding out bases for each of these Si spaces we can form a basis for the tensor product space. Each basis element is effectively a universe (minus observers) and each state is a linear combination of these. So the Copenhagen interpretation predicts, guess what, a plurality of universes minus observers. One get out is to arbitrarily decide the tensor product rule fails after a point.

When Feynman was asked about Many Worlds he was reluctant to give it his assent. But when actually questioned in terms of individual propositions rather than merely an ideology he was clearly a many-worldsist. Many physicsts in fact don't like to give assent to any kind of ideology and simply get on with using the Schrodinger equation knowing that it predicts observer superposition states. They are effectively many-worldsists but don't call themselves such and it's from one such physicist that I first learnt about the idea.
SIGFPE
[ Parent ]

that's an outright fib (none / 0) (#85)
by streetlawyer on Wed Feb 27, 2002 at 03:38:20 PM EST

However Copenhagen followers like to play a shell game where they hide that deduction under a shell and then declare, by fiat, that you're not allowed to look there.

No, they simply point out that if you do look there then you have looked there. The Schrodinger equations are a mathematical model, that's all. Or perhaps you believe that Newton's calculus commits you to believing in infinitesimals?

Your statements about the interpretation of state space tensor products are simply false. Your "plurality of universes without observers" are simply potential observations which were not made; it's a fancy version of the Schrodinger's Cat paradox.

Any progress on finding a probability measure over possible worlds?

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

Well... (none / 0) (#92)
by SIGFPE on Wed Feb 27, 2002 at 09:59:36 PM EST

Any progress on finding a probability measure over possible worlds?
There's a perfectly good measure - it's pretty much the same one that members of the Copenhagen school use as you surely know. The one that's compatible with the Hilbert space structure on the space of 'universes'.

Your statements about the interpretation of state space tensor products are simply false
Which bit's false? That the state space of the union of two systems has a state space that is the tensor product? (After all many Copenhageners do deny that for large enough systems). That you can write a basis for the tensor product as all of the tensor products of the basis elements of the individual subspaces? That the state of the (universe minus observers) is a linear combination of said states?

Nice sig BTW!
SIGFPE
[ Parent ]

Misunderstood (none / 0) (#93)
by SIGFPE on Wed Feb 27, 2002 at 10:24:17 PM EST

Any progress on finding a probability measure over possible worlds?
If you're talking about some kind of measure on the space of possible entire worlds that's a different matter - I'm not sure what possible interest that has because I'm only interested in relative states. I thought you were talking about the old problem that MWers have with where the probabilities of relative states come from. Some people have tried to deduce the probabilities from the Schrodinger equation directly - but that always fails (and I think it always will). Otherwise you have to add some kind of extra postulate to the Schrodinger equation to get probabilities out. I'm happy to do that and in effect the measure I use turns out to be the same as that of members of the Copenhagen school.
SIGFPE
[ Parent ]
which bit's false? (none / 0) (#94)
by streetlawyer on Thu Feb 28, 2002 at 06:22:02 AM EST

Which bit's false?

The idea that this piece of mathematics would cause any problems at all to a Copenhagenist who hadn't been smoking weed recently. The base elements of the product space aren't "universes"; they're partial descriptions of the probability waveform. If you're going to interpret these base elements as representing physical reality, then you might have a problem if you also wanted to maintain the Copenhagen interpretation, but I really don't see why anyone would want to do this.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]

You know about this stuff don't you... (none / 0) (#95)
by SIGFPE on Fri Mar 01, 2002 at 11:03:09 AM EST

Interaction Free Measurement. That's not my favourite exposition but for some reason I don't seem to be able to get a hit on the preprint I originally read even though I'm using all the right keywords.
SIGFPE
[ Parent ]
Good. (none / 0) (#78)
by SIGFPE on Tue Feb 26, 2002 at 12:57:42 PM EST

in fact, you don't seem to know what a metaphysical claim is
Good. I'll leave the metaphysics and sophistry to you then.
SIGFPE
[ Parent ]
proud of your ignorance (none / 0) (#79)
by streetlawyer on Tue Feb 26, 2002 at 01:01:39 PM EST

Please, in that case, don't presume to start arguments with people who aren't ignorant on a subject in future.

--
Just because things have been nonergodic so far, doesn't mean that they'll be nonergodic forever
[ Parent ]
Well if you want to discuss... (none / 0) (#80)
by SIGFPE on Tue Feb 26, 2002 at 01:26:25 PM EST

...theology why don't you raise the topic in a comment to a more suitable story.
SIGFPE
[ Parent ]
Good, a nice academic flame war (none / 0) (#75)
by epepke on Tue Feb 26, 2002 at 12:36:58 PM EST

However, since you didn't respond to this separately, I'm going to try to inflict my QM interpretation on you once again:

Wavefunctions don't collapse. Physicists do.

Think about it. Despite the aphoristic style, I am not being flippant.


The truth may be out there, but lies are inside your head.--Terry Pratchett


[ Parent ]
Sounds interesting (none / 0) (#81)
by SIGFPE on Tue Feb 26, 2002 at 03:04:20 PM EST

I've thought about it but can't imagine any formalism (yet) that would capture such an event.

PS To be academic both parties actually have to know what they're talking about.
SIGFPE
[ Parent ]

Nor I (none / 0) (#82)
by epepke on Tue Feb 26, 2002 at 06:57:42 PM EST

I've reversed your two paragraphs; I hope you don't mind.

PS To be academic both parties actually have to know what they're talking about.

Ah, yes, but notice I said academic, not scientific. Fortunately, with metaphysics, you don't need to know what you're talking about in order to have fun. In fact, it can get in the way.

I've thought about it but can't imagine any formalism (yet) that would capture such an event.

Nor I. But you see what I'm getting at, I hope, or at least as well as I do, which is not much. Anyway, probably some people don't, so I'll explain it as well as I can, which is probably not very well.

What do we know, at least as well as we know anything? I can think of two things:

1. The math works.

It seems to work out for what people have tried, well enough, and it hasn't been knocked down, which is about the best you can say.

2. The math gets really hard, really fast.

Coming up with QED wasn't easy, but it was doable. Coming up with subsequent ideas, including but not limited to QCD, took several decades and very fast computers. Even then, it's hard. It's hard just to draw Feynman diagrams for nontrivial interactions. I spent a lot of time at FSU trying to write a program to do it, and it's hard. You'd need a real nondeterministic Turing-machine to do a cat, and it would help a lot if it were an oracle machine. You just have to make approximations.

Several years ago, I thought I had the Copenhagen interpretation licked, at least in the context of quantum reversable computers and information theory, by saying that a wavefunction collapsed when a thermodynamically irreversible event happened. Then a few minutes later I came to my senses, realizing, of course, that thermodynamic irreversibility is itself just statistical, and the ground wasn't solid any more.

Now for the metaphysical part that I don't know anything about but will talk about anyway. All of the QM interpretations, to me, carry the flavor or miasma of a deus ex machina. All the little amplitudes are running around on stage, and it's a big mess, and nobody is sure who is what, and then a god comes from the ceiling and sorts it all out. Phew! I was worried for a while, but the wavefunction collapsed. An event occurred. The universe split. Or something else happened. But whatever happened, it finally, definitely happened.

I'm suggesting that quantum interpretations live in that little area between a very good approximation and certainty, and that they serve a psychological goal of keeping pysicists sane by enabling them to go back to a world that they can pretend is, basically, classical, where you can use angles to calculate your pool shots while you're at the pub.

However, what I'm also suggesting is that maybe nothing really happens beyond the fact that the math gets too hard to think about. No wavefunction collapses; that just fits the desire to go home at the end of the day. There are no two or four or whatever universes (or even one); that just fits the desire to count things. Amplitudes continue running around in their merry way. It's the physicist who collapses.

Of course, this would mean that saying that there is one (or two or twenty-seven or whatever) universes or saying that the plate you're looking at definitely shows a Gabor-like scattering pattern represents some sort of fundamental misunderstanding that is still good enough an approximation to get you through the day. This makes one's brain hurt, but it doesn't make it hurt much more than thinking that the Earth is accelerating outward, and that's why you can feel the chair on your butt.

All of this is totally useless, of course, but it might be good for a short story, as long as one stays away from that hackneyed Eastern stuff.


The truth may be out there, but lies are inside your head.--Terry Pratchett


[ Parent ]
I'm all for avoiding the Eastern stuff... (none / 0) (#83)
by SIGFPE on Tue Feb 26, 2002 at 07:27:46 PM EST

Sometimes I wish people would just be honest and use the words they really mean - s/observer/soul/.

Anyway...

saying that a wavefunction collapsed when a thermodynamically irreversible event happened. Then a few minutes later I came to my senses, realizing, of course, that thermodynamic irreversibility is itself just statistical, and the ground wasn't solid any more.
But that's exactly it. Just as irreversibility is a statistical thing so is wavefunction collapse. A system interacts with its environment and the combined system-environment wavefunction becomes teased apart into a sum of tensor products of collapsed wavefunctions and modified environments through decoherence. The different collapsed wavefunctions no longer interefere with each other for simple statistical reasons because the wavefunctions of the environments they become coupled to are likely to become too different to interfere again - except in the unlikely event of an irreversible phenomenon being reversed. So apparent wavefunction collapse is also a statistical phenomenon.
SIGFPE
[ Parent ]
what are observers then? (none / 0) (#86)
by Hightc on Wed Feb 27, 2002 at 05:51:58 PM EST

The problem with the copenhagen interpretation, as I understand it, is that it does not specify what an 'observer' is, or make any statement about what constitutes an 'observation'.

This is important though, becuase in CI, it makes a HUGE difference to the time evolution of a system depending on whether an observer is present. For example, (I think this question originally came from Bohm?), why is Mars appearing in a single location, and not in a linear superposition of every possible point in its orbit? The CI answer is because we 'observe' it and therefore collapse the wavefunction.

But what about before there humans on this planet? Does this mean that the dynamics of the solar system changed radically as soon as the first human (or some object capable of making an 'observation') looked into the sky?

So, I think CI is a cop-out. Surely 'wave-function collapse' is some kind of dynamical effect? MWI says that its basically an emergent phenomena arising from the large dimension of the Hilbert space. Penrose's theory is that there is a specific dynamical law for wavefunction collapse, which is associated with gravity. But the actual dynamical law is not (yet) known.

[ Parent ]

Philosophies (none / 0) (#90)
by dennis on Wed Feb 27, 2002 at 07:13:08 PM EST

I think the point is, you're dealing with two different philosophies of science. In one, you know you have observations, you do your best to predict what you're going to observe, and you leave it at that. Observations are what matter. In another, you're trying to figure out the metaphysics, and ask questions like "what is an observer," because you're trying to talk about what is, not what is observed.

[ Parent ]
Re:Jebus (none / 0) (#88)
by Hightc on Wed Feb 27, 2002 at 06:17:46 PM EST

To adapt a common (and uncommonly stupid) argument of the atheists, why shouldn't I believe that MWWIPU (Many Worlds With Invisible Pink Unicorns) Hypothesis, which is equivalent to MWI plus the assertion that all universes other than our own are chock full of invisible pink unicorns?

Because MWI consists of precisely one postulate: that the universe evolves according to the Schrodinger equation. Anything layered on top of that (ie metaphysics, multiple universes etc) is not part of the theory itself.

The MWWIPU theory requires a second postulate, which is unnecessary and violates Occam's Razor.

[ Parent ]

I disagree (none / 0) (#58)
by SIGFPE on Mon Feb 25, 2002 at 03:16:12 PM EST

There is no known way to distinguish between the various interpretations of QM by experiment
This is a false statement. If all the interpretations made the same predictions nobody would care and discussions of the interpretations of QM would be confined to the people who like to discuss things that don't matter - philosophers. Physicists aren't that stupid.

The interpretetaion of QM does matter. The differences between MWT and Copenhagen aren't small either. The problem is that where they differ is in large and complex systems. This means that we can't actually write down the full set of equations describing the system so it's hard to compare reality and theory. For example we can't right now write down the Schrodinger equation for an entire person. But Copenhagen and MWT make entirely different predictions about the behaviour of a person. In fact the interpretations are so different that quantum cosmologists tend to be MWTists because some find can't actually describe their systems within the context of the Copenhagen 'interpretation'.
SIGFPE
[ Parent ]

All-night burgers (none / 0) (#56)
by Kyle on Mon Feb 25, 2002 at 02:02:42 PM EST

I read All the Myriad Ways ages ago when I was reading my dad's shelf full of Niven. Another MWI story that stands out in my mind I can't remember the full title to. It was something like "Why I Left Blah Blah's All-Night Burgers". In it, a boy working at a burger joint in the middle of nowhere encounters a lot of MWI travelers. He decides he wants to try world traveling himself, but one of the travelers tells him, basically, "just go see the world you have; you don't need to skip universes to see wonders."

I liked the point of that. It runs counter to the usual MWI theme, saying that the other worlds aren't that great. Our own world is plenty interesting if you just go have a look at it.

Hogan (none / 0) (#91)
by dennis on Wed Feb 27, 2002 at 07:30:03 PM EST

I'm glad I finished reading Hogan's book before reading your review, since you gave away the entire plot! But you seem to have summed up your violated expectations more than the book itself. You complain that he's gotten new-agey when you expect him to give you pure hard science, etc.

But so far nobody seems to be thinking much past the kewlness of other timelines where you might be rich, famous, and dating a supermodel.

But Hogan does think of a lot of other things. There have been an awful lot of "alternate universe" SF books inspired by MWI, but fewer that really explore the quantum possibilities, without going too far afield from we know about physics. Hogan's book does that - transferring matter between worlds has no justification in QM, but consciousness is enough of a nebulous area, and has been speculated about by enough prominent physicists, that playing games with that is plausible. Beyond that, Hogan's book is packed with nifty ideas:

The self-correcting typewriter, for example. You and a bunch of near copies all type into a machine, which takes the average of all your keystrokes for its output. Since you'll all make mistakes at different random locations, the output is perfect.

The idea of human intuition coming from summing the results of different future worlds is something I haven't seen suggested elsewhere. But it's a very cool idea - it provides a mechanism for accurate foresight without violating causality.

I found this to be a concise, fast-moving book, and I'm surprised you thought it ponderous. But more than that, I think Hogan deals with some fairly deep issues here, and you've missed them entirely, just because you react so strongly against the kinds of ideas you think he's expressing.

Many Worlds Roundup | 96 comments (92 topical, 4 editorial, 0 hidden)
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