So you might have an evil twin out there in the Multiverse...

[VarysTheSpider]

If some of the multiverse hypothesis are correct the hat universe exists.

An all hat universe seems impossible and begets paradox: what came first, the hipster or the hat?

[Larry of the Lawn]

An all hat universe seems impossible and begets paradox: what came first, the hipster or the hat?

The PBR soaked mustache actually precedes both.

[Sci-2]

From the link IHT mentioned:

Questions About the Multiverse (posted in 2011)

The [2011] August issue of Scientific American has the multiverse on the cover, with a skeptical feature article on the topic by George F. R. Ellis, Does the Multiverse Really Exist?, which argues that heavily promoted multiverse research isn’t really testable and can’t explain much of anything. Vilenkin and Tegmark respond with The Case for Parallel Universes.

I just took a look at some of the earliest postings on this blog about the multiverse from as far back as seven years ago (e.g. here and here). Things haven’t changed at all. One might be tempted to criticize Scientific American for keeping this alive, but they just reflect the fact that this pseudo-science continues to have significant influence at the highest levels of the physics establishment. The Perimeter Institute recently ran a conference on Challenges for Early Universe Cosmology, which was dominated by multiverse mania. Unlike the case at SciAm, multiverse skepticism didn’t get prominent play at Perimeter.

[Sci-2]

If It’s Possible, It Happened -> ‘Our Mathematical Universe’: A Case for Alternate Realities

...Our reality, in other words, is not just described by mathematics, it is mathematics.

The vision of a purely mathematical universe, one that can be understood solely through rigorous mathematical reasoning, is far from new. As far back as the sixth century B.C., the Pythagoreans declared that “all is number,” and in the 17th century A.D. Descartes tried to deduce the universe from first principles. Other 17th-century rationalists, including Hobbes and Leibniz, offered their own versions of the mathematical universe.

Such efforts to comprehend the world entirely through mathematical reasoning certainly had their triumphs, none more so than when Einstein upended our universe using nothing more than careful reasoning and mathematical calculations.

But the overall record for such attempts is decidedly mixed: The Pythagoreans, who insisted that everything was made of whole numbers and their ratios, foundered on the discovery of irrationals, and Descartes concluded that matter was simple extension in space, that a vacuum was impossible and that the planets swirled in vortexes of ether.

It is difficult to say whether Dr. Tegmark’s mathematical universe will ultimately be deemed an Einsteinian triumph or a Cartesian dead end. His conclusions are simply too far removed from the frontiers of today’s mainstream science, and there is little hope that conclusive evidence will emerge anytime soon.

[Sci-2]

Multiverse Controversy Heats Up over Gravitational Waves

The multiverse is one of the most divisive topics in physics, and it just became more so. The major announcement last week of evidence for primordial ripples in spacetime has bolstered a cosmological theory called inflation, and with it, some say, the idea that our universe is one of many universes floating like bubbles in a glass of champagne. Critics of the multiverse hypothesis claim that the idea is untestable—barely even science. But with evidence for inflation theory building up, the multiverse debate is coming to a head.

It seems to me there's at least two kinds of Multiverse being argued here - the one that comes from Everett's Many Worlds Interpretation and the one that is truly divergent universes with their own laws...

[Elder Sister]

I am 99% positive that I'm the evil twin. Am hoping that somewhere out there is a kindly, twinkly Elder Sister.

I don't really care about meeting up with her, though. She'd probably be a major drag.

[The Undead Martyr]

I prefer Futurama's vision of the multiverse: There's this universe, and then there's one other next door where everything's exactly the same, but we all wear hats.

Anything more complicated than that just gives me a headache. Also, I vaguely get the sense that all this stems from us not having a complete enough sense of math, and that one day humanity will discover some formula/equation/something that just clicks into place, explaining so much of what we don't know, and we'll look and laugh at how complicated we thought the universe was.

My calculus class had an interesting question- namely, if reality is quantized, how can calculus (which is not quantized, but assumes a continuous distribution) accurately model reality? It can, at best, be an "approximation" though of a potentially good order on the macro scale.

[Sci-2]

Hmm, this article might get IHT on the side of Multiverse hypsters seeing as the opposition is coming from the humanities ;) :

Physics’s pangolin: Trying to resolve the stubborn paradoxes of their field, physicists craft ever more mind-boggling visions of reality

Nothing in our experience compares to this unimaginably vast number. Every universe that can be mathematically imagined within the string parameters — including ones in which you exist with a prehensile tail, to use an example given by the American string theorist Brian Greene — is said to be manifest somewhere in a vast supra-spatial array ‘beyond’ the space-time bubble of our own universe.

What is so epistemologically daring here is that the equations are taken to be the fundamental reality. The fact that the mathematics allows for gazillions of variations is seen to be evidence for gazillions of actual worlds.

This kind of reification of equations is precisely what strikes some humanities scholars as childishly naive. At the very least, it raises serious questions about the relationship between our mathematical models of reality, and reality itself. While it is true that in the history of physics many important discoveries have emerged from revelations within equations — Paul Dirac’s formulation for antimatter being perhaps the most famous example — one does not need to be a cultural relativist to feel sceptical about the idea that the only way forward now is to accept an infinite cosmic ‘landscape’ of universes that embrace every conceivable version of world history, including those in which the Middle Ages never ended or Hitler won.

[Anatúrinbor]

Does this mean that there is a universe with a version of me that's, let's say, a murderer? Or worse, a universe where my enemies are winning? Because those are some really disturbing thoughts.

[Ser Scot A Ellison]

TGR,

Yes, And if the Universe is open and infinite there is an infinite number of you and me reading and posting on this board right now.

[Sci-2]

TGR,

Yes, And if the Universe is open and infinite there is an infinite number of you and me reading and posting on this board right now.

IIRC there's also universes where people have become convinced that one of the other interpretations of the Measurement Problem are correct because the results work out perfectly for the "erroneous" intepretation.

[Sci-2]

This might be applicable to the Religion thread but it seemed to fit better here:

Pseudophysics: The New High Priesthood

Five years after Erwin Schrödinger's talk, in 1957, the American physicist Hugh Everett III proposed the "many-worlds interpretation" of quantum mechanics, which pretty much does what Schrödinger had suggested. According to Everett, every time a quantum event is observed, all its other possibilities implicit in its "wave function" also take place -- but in other worlds. Deutsch is supportive of this interpretation, and of the theory that a multiverse exists. The same year that Deutsch's book came out, 2011, Brian Greene published an entire book about the possibility of a multiverse, titled The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos. Greene is lukewarm about "many worlds" but supportive of how a multiverse might emerge out of the equations of string theory. String theory uses mathematical equations that rely on the existence of additional dimensions of spacetime (as many as six or seven new dimensions), and these dimensions, according to Greene, can hide other universes to give us a multiverse. He describes a few other theoretical gateways to a multiverse -- but not a single one has any experimental or observational evidence to support it. Can such wholly unsupported speculations really be called science? It should be noted that at the Large Hadron Collider scientists have not only searched (and found) the Higgs particle but actively looked for evidence of hidden dimensions of spacetime -- and they've found absolutely nothing! And while cosmic inflation is indeed a very plausible theory, if inflation acts on different parts of our universe, inflating each one at a time, this does not make a multiverse; it simply creates inaccessible parts of the same, single universe.

[Sci-2]

Quantum Mechanics (an embarrassment) - Sixty Symbols

Carroll argues for the Multiverse in this video. Seems kinda weak to me in light of IHT's criticisms, but I'm just a layperson with some passing interest.

Even the professional understanding of quantum mechanics is "embarrassing", says cosmologist Sean Carroll.
Read Sean's blog on this subject at http://bit.ly/V1SUpV and the full paper at http://arxiv.org/abs/1301.1069

We filmed with Sean during his visit to the University of Nottingham and will have more videos with him coming soon.

[Sci-2]

Is the Search for Immutable Laws of Nature a Wild-Goose Chase?

Four iconoclastic thinkers are challenging the assumption of scientists from Newton to Einstein: That there is one set of laws that perfectly describe the universe for all time.

“I called it the clock ambiguity,” Albrecht says. “Basically, different choices of a clock lead to different kinds of physics. I got entirely different kinds of universes depending on the clock I chose.”

This is not what Albrecht was expecting or hoping for. He had expected quantum cosmology to tell him exactly why the universe we live in looks the way it does. The discovery of the clock ambiguity seemed to block that path. It looked to him as if quantum cosmology would never predict the course of history through the universe because the laws determining that history could never be specified beforehand. A few physicists have challenged this radical idea, but many share their colleague’s befuddlement. “What I was finding seemed crazy,” he says. “It meant that the fundamental physical laws were not fundamental.”

Neither string theory nor the multiverse theory explain nature’s mysteries so much as explain them away, Unger concludes. “When we imagine our universe to be just one out of a multitude of possible worlds, we devalue this world, the one we see, the one we should be trying to explain,” he says. “The scientist should treasure the riddles he can’t solve, not explain them away at the outset.”

Unger and Smolin want to shift the emphasis in physics away from these possible worlds and back to the one real world—our world, which is saturated with time. They urge their colleagues to abandon the search for timeless truths like string theory.

More broadly, they argue that physics should refrain from spinning any theories that require the existence of things that could never be disproved, such as multiverses. And it should recognize that there is no ideal realm of perfect, timeless mathematical forms that embody the laws of physics. Time is inherent in the universe, and nothing exists outside of time. Smolin thinks that Albrecht’s clock ambiguity is a symptom of the larger problem with the current approach to physics.

Kauffman has no qualms about abandoning an idea that has dominated the sciences since the days of Galileo: that a set of physical laws is all that is needed to predict the unfolding of reality. The name for this idea is reductionism—the belief that the whole can be understood by the predictable behavior of the parts. It is the philosophical underpinning of the physicist’s conviction that timeless, eternal laws rule the universe from the bottom up. Understand quarks, the thinking goes, and everything else follows.

“The dream of reductionism,” Kauffman says, “is that when all is said and done, science will provide us with a linked set of laws that begin with particle physics and take us through life all the way to social systems.” Albrecht’s clock ambiguity and Smolin’s critiques of string theory expose chinks in the armor of reductionism. Kauffman has come to believe that reductionism can take us just so far. Only by moving beyond it will we be able to see the universe’s hidden creativity.

[Sci-2]

Multiverse takes a hit:

Planck's Mystery Cosmic 'Cold Spot' May Be an Error

One of the more exotic explanations for the cold spot is that it could be observational evidence for the "multiverse"— a hypothesis with roots in superstring theory where our universe exists in an ocean of other universes — and the cold spot is caused by a neighboring universe pushing up against ours. Unfortunately, the feature might not even be real.

"Using new techniques to separate the foreground light from the background, and taking into account effects like the motion of our Galaxy, we found that most of the claimed anomalies we studied, like the cold spot, stop being problematic," said lead researcher Anaïs Rassat, of the Ecole Polytechnique Fédérale de Lausanne, Switzerland.

[Sci-2]

When parallel worlds collide … quantum mechanics is born

Our new theory also involves many worlds but there the similarity to the standard MWI ends.

First, we postulate a fixed, although truly gigantic, number of worlds. All of these exist continuously through time – there is no “branching”.

Second, our worlds are not “fuzzy” – they have precisely defined properties. In our approach, a world is specified by the exact position and velocity of every particle in that world – there is no Heisenberg uncertainty principle that applies to a single world. Indeed, if there were only one world in our theory, it would evolve exactly according to Newtonian mechanics, not quantum mechanics.

Third, our worlds do interact and that interaction is the source of all quantum effects. Specifically, there is a repulsive force of a very particular kind, between worlds with nearly the same configuration (that is, having nearly the same position for every single particle). This “interstitial” force prevents nearby worlds from ever coming to have the same configuration, and tends to make nearby worlds diverge.

Fourth, each one of our worlds is equally real. Probability only enters the theory because an observer, made up of particles in a certain world, does not know for sure which world she is in, out of the set of all worlds. Hence she will assign equal probability to every member of that set which is compatible with her experiences (which are very coarse-grained, because she is a macroscopic collection of particles). After performing an experiment she can learn more about which world she is in, and thereby rule out a whole host of worlds that she previously thought she might be in.

Putting all of the above together gives our theory – the Many Interacting Worlds approach to quantum mechanics. There is nothing else in the theory. There is no wavefunction, no special role for observation and no fundamental distinction between macroscopic and microscopic.

Nevertheless, we argue, our approach can reproduce all the standard features of quantum mechanics, including twin-slit interference, zero-point energy, barrier tunnelling, unpredictability and the Bell correlations mentioned above.

[Serious Callers Only]

Having a good twin would be more unsettling than a evil twin. Someone who is you, but undeniably better in all respects.

[Weeping Sore]

Having a good twin would be more unsettling than a evil twin. Someone who is you, but undeniably better in all respects.

There's a movie out now with a similar premise, The One I Love with Elizabeth Moss.

[Mlle. Zabzie]

Just further co option of what once was religion, then became philosophy and is now science. Humans have a need for the ineffable. Which is kinda funny for some monkeys with delusions of grandeur of you stop to think about it.

[Castel]

Just further co option of what once was religion, then became philosophy and is now science. Humans have a need for the ineffable. Which is kinda funny for some monkeys with delusions of grandeur of you stop to think about it.

Are you driving a Lincoln with Woody Harrelson in the passenger seat right now by any chance?