Freethought & Rationalism Archive

Ted Hoffman · 05-16-2003, 05:47 AM

As I was reading Max Tegmarks' May 2003 paper on Parallel universes that was published in SCientific American, he mentioned in one section of his website that Martin Rees' Our Cosmic Habitat has cosmological evidence for multiverses.
Has anyone read the book - or is anyone aware of any empirical evidence that points to existence of multiverses?

I was arguing with Christopher Michael langan (he of the CTMU) at ISCID in this thread and the thread got closed before we could address the issue.

CMLs argument was that Tegmarkian parallel universes (which is divided to 4 levels) is consistent with CTMU and the link above shows my thoughts (Jacob Aliet) and others thoughts about that. Is the multiverse concept totally abstract and wholly based on isomorphisms or is there empirical evidence to bach it up?

As Karl D Stephan notes in his paper in the above link:

Quote:

The experimental tests he proposes for these theories really consist in making the philosophical presuppositions required for believing in the theories, and then verifying that the theories agree with already-known data about the present visible universe. So far from being a legitimate way to inflate probabilistic resources to defeat arguments in favor of intelligent design, Tegmark�s parallel universes represent an array of philosophical arguments disguised as science

Which partly, is how I described the CTMU.

But Max states:

Quote:

Is a multiverse theory one of metaphysics rather than physics? As emphasized by Karl Popper, the distinction between the two is whether the theory is empirically testable and falsifiable. Containing unobservable entities does clearly not per se make a theory non-testable. For instance, a theory stating that there are 666 parallel universes, all of which are devoid of oxygen makes the testable prediction that we should observe no oxygen here, and is therefore ruled out by observation....
The lesson to learn from this example is that multiverse theories can be tested and falsi ed, but only if they predict what the ensemble of parallel universes is and specify a probability distribution (or more generally what mathematicians call a measure) over it. As we will see in Section VB, this measure problem can be quite serious and is still unsolved for some multiverse theories.

So should you believe in parallel universes? Let us conclude with a brief discussion of arguments pro and con. First of all, we have seen that this is not a yes/no question rather, the most interesting issue is whether there are 0, 1, 2, 3 or 4 levels of multiverses. Figure 1 summarizes evidence for the different levels. Cosmology observations support Level I by pointing to a
at infinite space with ergodic matter distribution, and Level I plus inflation elegantly eliminates the initial condition problem. Level II is supported by the success of inflation theory in explaining cosmological observations, and it can explain apparent fine-tuning of physical parameters.
Level III is supported by both experimental and theoretical evidence for unitarity, and explains the apparent quantum randomness that bothered Einstein so much without abandoning causality from the bird perspective.
Level IV explains Wigner's unreasonable effectiveness of mathematics for describing physics and answers the question why these equations, not others?".

PS: Maxes level III is equivalent to Everetts multiverse in his MWI of the collapse of the universal wavefunction.

eh · 05-18-2003, 08:39 AM

If there is empirical evidence for a multiverse, it certainly was not presented in the recent Sci-American article. It seems Sci American published this sensationalist article aimed at selling magazines.

For example, you listed the claim that observational evidence is consistent with an infinite universe (level 1 multiverse), but the same evidence is consistent with a finite but very large universe. There is also the claim that observational evidence is consistent with inflation. So what? Is there any evidence whatsoever such an inflation event could produce a region of space with different laws of physics? I didn't think so.

But then, what magazine sales wouldn't benefit from claims that multiple universes have been proven?

Tenspace · 05-18-2003, 09:01 AM

How about the work of David Deutsch? He feels that interference patterns, such as the results of the "Two-Slit Experiment", are empirical proof of other universes. To quote, from his book, "The Fabric of Reality":

In interference experiments there can be places in a shadow-pattern that go dark when new openings are made in the barrier casting the shadow. This remains true even when the experiment is performed with individual particles. A chain of reasoning based on this fact rules out the possibility that the universe we see around us constitutes the whole of reality. In fact the whole of physical reality, the multiverse, contains vast numbers of parallel universes.

Thoughts?

Tenspace

Wounded King · 05-19-2003, 01:52 AM

Quote:

A chain of reasoning based on this fact rules out the possibility that the universe we see around us constitutes the whole of reality.

This doesnt neccessarily lead directly to his next statement. It certainly shows that the visible universe around us is not the whole of reality, but does it really exclude all other interpretations of QM except MW?

The many worlds interpretation certainly isnt wholly abstract though, there may be no proper empirical evidence as yet but it should be able to be falsified at least at some point in the future, or so my reading of the MWI faq leads me to believe.

The other models Tegmark puts forward certainly seem more like philosophy, especially given some of his assumptions.

excreationist · 05-19-2003, 09:59 AM

Quote:

Originally posted by Tenspace
How about the work of David Deutsch?....

A clearer explanation for what you quoted is at the bottom of this link:
http://www.newscientist.com/hottopic...sp?id=22994400

I think quantum computing is an area that MWI explains a lot better (from that above link)

Quote:

.....Perhaps the sceptics will be convinced by a practical demonstration of the multiverse. And Deutsch thinks he knows how. By building a quantum computer, he says, we can reach out and mould the multiverse.

"One day, a quantum computer will be built which does more simultaneous calculations than there are particles in the Universe," says Deutsch. "Since the Universe as we see it lacks the computational resources to do the calculations, where are they being done?" It can only be in other universes, he says. "Quantum computers share information with huge numbers of versions of themselves throughout the multiverse."

Imagine that you have a quantum PC and you set it a problem. What happens is that a huge number of versions of your PC split off from this Universe into their own separate, local universes, and work on parallel strands of the problem. A split second later, the pocket universes recombine into one, and those strands are pulled together to provide the answer that pops up on your screen. "Quantum computers are the first machines humans have ever built to exploit the multiverse directly," says Deutsch.

At the moment, even the biggest quantum computers can only work their magic on about 6 bits of information, which in Deutsch's view means they exploit copies of themselves in 2^6 universes-that's just 64 of them. Because the computational feats of such computers are puny, people can choose to ignore the multiverse. "But something will happen when the number of parallel calculations becomes very large," says Deutsch. "If the number is 64, people can shut their eyes but if it's 10^64, they will no longer be able to pretend."....

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05-18-2003, 08:39 AM	#2
eh Senior Member Join Date: Sep 2000 Location: Canada Posts: 624	If there is empirical evidence for a multiverse, it certainly was not presented in the recent Sci-American article. It seems Sci American published this sensationalist article aimed at selling magazines. For example, you listed the claim that observational evidence is consistent with an infinite universe (level 1 multiverse), but the same evidence is consistent with a finite but very large universe. There is also the claim that observational evidence is consistent with inflation. So what? Is there any evidence whatsoever such an inflation event could produce a region of space with different laws of physics? I didn't think so. But then, what magazine sales wouldn't benefit from claims that multiple universes have been proven?

05-18-2003, 09:01 AM	#3
Tenspace Junior Member Join Date: Apr 2003 Location: Florida, USA Posts: 69	How about the work of David Deutsch? He feels that interference patterns, such as the results of the "Two-Slit Experiment", are empirical proof of other universes. To quote, from his book, "The Fabric of Reality": In interference experiments there can be places in a shadow-pattern that go dark when new openings are made in the barrier casting the shadow. This remains true even when the experiment is performed with individual particles. A chain of reasoning based on this fact rules out the possibility that the universe we see around us constitutes the whole of reality. In fact the whole of physical reality, the multiverse, contains vast numbers of parallel universes. Thoughts? Tenspace

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