Theoretical Physics

Is Nature Unnatural?

Decades of confounding experiments have physicists considering a startling possibility: The universe might not make sense.

Is the universe natural or do we live in an atypical bubble in a multiverse? Recent results at the Large Hadron Collider have forced many physicists to confront the latter possibility. (Illustration: Giovanni Villadoro)

Illustration by Giovanni Villadoro

Is the universe natural or do we live in an atypical bubble in a multiverse? Recent results at the Large Hadron Collider have forced many physicists to confront the latter possibility.

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On an overcast afternoon in late April, physics professors and students crowded into a wood-paneled lecture hall at Columbia University for a talk by Nima Arkani-Hamed, a high-profile theorist visiting from the Institute for Advanced Study in nearby Princeton, N.J. With his dark, shoulder-length hair shoved behind his ears, Arkani-Hamed laid out the dual, seemingly contradictory implications of recent experimental results at the Large Hadron Collider in Europe.

“The universe is inevitable,” he declared. “The universe is impossible.”

The spectacular discovery of the Higgs boson in July 2012 confirmed a nearly 50-year-old theory of how elementary particles acquire mass, which enables them to form big structures such as galaxies and humans. “The fact that it was seen more or less where we expected to find it is a triumph for experiment, it’s a triumph for theory, and it’s an indication that physics works,” Arkani-Hamed told the crowd.

However, in order for the Higgs boson to make sense with the mass (or equivalent energy) it was determined to have, the LHC needed to find a swarm of other particles, too. None turned up.

Natalie Wolchover/Simons Science News

“The universe is impossible,” said Nima Arkani-Hamed, 41, of the Institute for Advanced Study, during a recent talk at Columbia University.

With the discovery of only one particle, the LHC experiments deepened a profound problem in physics that had been brewing for decades. Modern equations seem to capture reality with breathtaking accuracy, correctly predicting the values of many constants of nature and the existence of particles like the Higgs. Yet a few constants — including the mass of the Higgs boson — are exponentially different from what these trusted laws indicate they should be, in ways that would rule out any chance of life, unless the universe is shaped by inexplicable fine-tunings and cancellations.

In peril is the notion of “naturalness,” Albert Einstein’s dream that the laws of nature are sublimely beautiful, inevitable and self-contained. Without it, physicists face the harsh prospect that those laws are just an arbitrary, messy outcome of random fluctuations in the fabric of space and time.

The LHC will resume smashing protons in 2015 in a last-ditch search for answers. But in papers, talks and interviews, Arkani-Hamed and many other top physicists are already confronting the possibility that the universe might be unnatural. (There is wide disagreement, however, about what it would take to prove it.)

“Ten or 20 years ago, I was a firm believer in naturalness,” said Nathan Seiberg, a theoretical physicist at the Institute, where Einstein taught from 1933 until his death in 1955. “Now I’m not so sure. My hope is there’s still something we haven’t thought about, some other mechanism that would explain all these things. But I don’t see what it could be.”

Physicists reason that if the universe is unnatural, with extremely unlikely fundamental constants that make life possible, then an enormous number of universes must exist for our improbable case to have been realized. Otherwise, why should we be so lucky? Unnaturalness would give a huge lift to the multiverse hypothesis, which holds that our universe is one bubble in an infinite and inaccessible foam. According to a popular but polarizing framework called string theory, the number of possible types of universes that can bubble up in a multiverse is around 10500. In a few of them, chance cancellations would produce the strange constants we observe.

In such a picture, not everything about this universe is inevitable, rendering it unpredictable. Edward Witten, a string theorist at the Institute, said by email, “I would be happy personally if the multiverse interpretation is not correct, in part because it potentially limits our ability to understand the laws of physics. But none of us were consulted when the universe was created.”

“Some people hate it,” said Raphael Bousso, a physicist at the University of California at Berkeley who helped develop the multiverse scenario. “But I just don’t think we can analyze it on an emotional basis. It’s a logical possibility that is increasingly favored in the absence of naturalness at the LHC.”

What the LHC does or doesn’t discover in its next run is likely to lend support to one of two possibilities: Either we live in an overcomplicated but stand-alone universe, or we inhabit an atypical bubble in a multiverse. “We will be a lot smarter five or 10 years from today because of the LHC,” Seiberg said. “So that’s exciting. This is within reach.”

Cosmic Coincidence

Einstein once wrote that for a scientist, “religious feeling takes the form of a rapturous amazement at the harmony of natural law” and that “this feeling is the guiding principle of his life and work.” Indeed, throughout the 20th century, the deep-seated belief that the laws of nature are harmonious — a belief in “naturalness” — has proven a reliable guide for discovering truth.

“Naturalness has a track record,” Arkani-Hamed said in an interview. In practice, it is the requirement that the physical constants (particle masses and other fixed properties of the universe) emerge directly from the laws of physics, rather than resulting from improbable cancellations. Time and again, whenever a constant appeared fine-tuned, as if its initial value had been magically dialed to offset other effects, physicists suspected they were missing something. They would seek and inevitably find some particle or feature that materially dialed the constant, obviating a fine-tuned cancellation.

This time, the self-healing powers of the universe seem to be failing. The Higgs boson has a mass of 126 giga-electron-volts, but interactions with the other known particles should add about 10,000,000,000,000,000,000 giga-electron-volts to its mass. This implies that the Higgs’ “bare mass,” or starting value before other particles affect it, just so happens to be the negative of that astronomical number, resulting in a near-perfect cancellation that leaves just a hint of Higgs behind: 126 giga-electron-volts.

Physicists have gone through three generations of particle accelerators searching for new particles, posited by a theory called supersymmetry, that would drive the Higgs mass down exactly as much as the known particles drive it up. But so far they’ve come up empty-handed.

The upgraded LHC will explore ever-higher energy scales in its next run, but even if new particles are found, they will almost definitely be too heavy to influence the Higgs mass in quite the right way. The Higgs will still seem at least 10 or 100 times too light. Physicists disagree about whether this is acceptable in a natural, stand-alone universe. “Fine-tuned a little — maybe it just happens,” said Lisa Randall, a professor at Harvard University. But in Arkani-Hamed’s opinion, being “a little bit tuned is like being a little bit pregnant. It just doesn’t exist.”

If no new particles appear and the Higgs remains astronomically fine-tuned, then the multiverse hypothesis will stride into the limelight. “It doesn’t mean it’s right,” said Bousso, a longtime supporter of the multiverse picture, “but it does mean it’s the only game in town.”

Thomas Lin/Simons Science News

Brookhaven Forum 2013 David Curtin, left, a postdoctoral researcher at Stony Brook University, and Alessandro Strumia, a physicist at the National Institute for Nuclear Physics in Italy, discussing Strumia’s “modified naturalness” idea, which questions longstanding assumptions about how to calculate the natural value of the Higgs boson mass.

A few physicists — notably Joe Lykken of Fermi National Accelerator Laboratory in Batavia, Ill., and Alessandro Strumia of the University of Pisa in Italy — see a third option. They say that physicists might be misgauging the effects of other particles on the Higgs mass and that when calculated differently, its mass appears natural. This “modified naturalness” falters when additional particles, such as the unknown constituents of dark matter, are included in calculations — but the same unorthodox path could yield other ideas. “I don’t want to advocate, but just to discuss the consequences,” Strumia said during a talk earlier this month at Brookhaven National Laboratory.

However, modified naturalness cannot fix an even bigger naturalness problem that exists in physics: The fact that the cosmos wasn’t instantly annihilated by its own energy the moment after the Big Bang.

Dark Dilemma

The energy built into the vacuum of space (known as vacuum energy, dark energy or the cosmological constant) is a baffling trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion times smaller than what is calculated to be its natural, albeit self-destructive, value. No theory exists about what could naturally fix this gargantuan disparity. But it’s clear that the cosmological constant has to be enormously fine-tuned to prevent the universe from rapidly exploding or collapsing to a point. It has to be fine-tuned in order for life to have a chance.

To explain this absurd bit of luck, the multiverse idea has been growing mainstream in cosmology circles over the past few decades. It got a credibility boost in 1987 when the Nobel Prize-winning physicist Steven Weinberg, now a professor at the University of Texas at Austin, calculated that the cosmological constant of our universe is expected in the multiverse scenario. Of the possible universes capable of supporting life — the only ones that can be observed and contemplated in the first place — ours is among the least fine-tuned. “If the cosmological constant were much larger than the observed value, say by a factor of 10, then we would have no galaxies,” explained Alexander Vilenkin, a cosmologist and multiverse theorist at Tufts University. “It’s hard to imagine how life might exist in such a universe.”

Most particle physicists hoped that a more testable explanation for the cosmological constant problem would be found. None has. Now, physicists say, the unnaturalness of the Higgs makes the unnaturalness of the cosmological constant more significant. Arkani-Hamed thinks the issues may even be related. “We don’t have an understanding of a basic extraordinary fact about our universe,” he said. “It is big and has big things in it.”

The multiverse turned into slightly more than just a hand-waving argument in 2000, when Bousso and Joe Polchinski, a professor of theoretical physics at the University of California at Santa Barbara, found a mechanism that could give rise to a panorama of parallel universes. String theory, a hypothetical “theory of everything” that regards particles as invisibly small vibrating lines, posits that space-time is 10-dimensional. At the human scale, we experience just three dimensions of space and one of time, but string theorists argue that six extra dimensions are tightly knotted at every point in the fabric of our 4-D reality. Bousso and Polchinski calculated that there are around 10500 different ways for those six dimensions to be knotted (all tying up varying amounts of energy), making an inconceivably vast and diverse array of universes possible. In other words, naturalness is not required. There isn’t a single, inevitable, perfect universe.

“It was definitely an aha-moment for me,” Bousso said. But the paper sparked outrage.

“Particle physicists, especially string theorists, had this dream of predicting uniquely all the constants of nature,” Bousso explained. “Everything would just come out of math and pi and twos. And we came in and said, ‘Look, it’s not going to happen, and there’s a reason it’s not going to happen. We’re thinking about this in totally the wrong way.’ ”

Life in a Multiverse

The Big Bang, in the Bousso-Polchinski multiverse scenario, is a fluctuation. A compact, six-dimensional knot that makes up one stitch in the fabric of reality suddenly shape-shifts, releasing energy that forms a bubble of space and time. The properties of this new universe are determined by chance: the amount of energy unleashed during the fluctuation. The vast majority of universes that burst into being in this way are thick with vacuum energy; they either expand or collapse so quickly that life cannot arise in them. But some atypical universes, in which an improbable cancellation yields a tiny value for the cosmological constant, are much like ours.

In the multiverse scenario a vast and diverse array of bubble universes fluctuate into existence inside a larger vacuum. A small fraction of the universes have physical properties conducive to life.

In a paper posted last month to the physics preprint website arXiv.org, Bousso and a Berkeley colleague, Lawrence Hall, argue that the Higgs mass makes sense in the multiverse scenario, too. They found that bubble universes that contain enough visible matter (compared to dark matter) to support life most often have supersymmetric particles beyond the energy range of the LHC, and a fine-tuned Higgs boson. Similarly, other physicists showed in 1997 that if the Higgs boson were five times heavier than it is, this would suppress the formation of atoms other than hydrogen, resulting, by yet another means, in a lifeless universe.

Despite these seemingly successful explanations, many physicists worry that there is little to be gained by adopting the multiverse worldview. Parallel universes cannot be tested for; worse, an unnatural universe resists understanding. “Without naturalness, we will lose the motivation to look for new physics,” said Kfir Blum, a physicist at the Institute for Advanced Study. “We know it’s there, but there is no robust argument for why we should find it.” That sentiment is echoed again and again: “I would prefer the universe to be natural,” Randall said.

But theories can grow on physicists. After spending more than a decade acclimating himself to the multiverse, Arkani-Hamed now finds it plausible — and a viable route to understanding the ways of our world. “The wonderful point, as far as I’m concerned, is basically any result at the LHC will steer us with different degrees of force down one of these divergent paths,” he said. “This kind of choice is a very, very big deal.”

Naturalness could pull through. Or it could be a false hope in a strange but comfortable pocket of the multiverse.

As Arkani-Hamed told the audience at Columbia, “stay tuned.”

This article was reprinted on ScientificAmerican.com.

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  • Is natural/unnatural the best distinction to use here? If Einstein used natural, as your post describes, to refer to “sublimely beautiful, inevitable and self-contained,” then perhaps something along the lines of chaotic, random, or stochastic might fit. Unless one attributes everything to a super-natural phenomena, then everything is natural.

  • Naturalness is about setting some constant to zero or infinity and see if some extra symmetry structure appears while it is still a good approach to the current model. If we do a complete break of electroweak, the surviving QCD times EM is a Kaluza Klein theory in 9 dimensions, the compact manifold is CP2xS1, whose isometry group is SU(3)xU(1), and there is no problem with chirality, because neither colour not EM are chiral. And if we do a complete restoration of electroweak, we have a D=11 theory linked to a D=12 theory; the relevant 7-dimensional compact manifold is some quotient of S3xS5 by an action of U(1). Note that the group of isometries of S3xS5 has the same Lie Algebra that Pati-Salam theory. Most of this stuff is Nucl. Phys. B186 (1981) 412-428 by E. Witten.
    Recently, Alain Connes has found that the SM could impose a composite Higgs on Pati-Salam, explaining the link between them.

  • Our conceptions are products of our brains. Our brains evolved via selection pressures (conditions) for reproductive success on planet Earth. Psychophysical experiments easily demonstrate that what we perceive and conceive are useful illusions rather than ‘reality.’ There is no reason to surmise that the human brain (and mind) is capable of infinite, or even modest, acumen. It’s more likely that we are incapable of understanding the universe. A sage scientist once said that what we see is illusion and what we don’t see is reality. I suggest that we cannot see reality. In fact, the very idea of a ‘physical reality’ is itself an invention constrained by the limits of the human psyche.

  • For a great interview with Nima Arkani-Hamed check out his conversation with Ideas Roadshow (http://www.ideasroadshow.com/issues/nima-arkani-hamed-2013-03-22)

  • The experimental basis for Higgs is surely evidence of a natural and simple order to the universe. To define “unnatural” as the absence of complete informations, is to essentially say that everything will be unnatural until we know everything, which is in itself, as far as the recorded history of science, unnatural.

  • So what I’m trying to figure out is why the laws of physics have to stay the same in this universe if we are living in a multiverse. What mechanism is enforcing these laws? What happens if our universe collides with another universe? What laws are followed?

    Yeah, I agree that the universe is unnatural and appears fine tuned. I wonder why that is…

  • @Hominid + DrDave

    I believe you both are right, as, in my own humble opinion, a lot of the issues that arise from the nose-bleed edge of contemporary physics we can reduce to our epistemic limits. It seems like physicists, having all these cool new toys, over-zealously peer further than the human perspective can account for. And, while I do not believe that it’s an absurd task to attempt to understand the increasingly uncomprehensible aspects of our surroundings, we should keep in mind that our dealings will become less and less qualifiable the further we go along.

    We are on the precipice of our own position in reality. We wish to go further, but the universe is returning our pleas with directions we cannot easily or entirely put into terms as to handle them. Yet it appears that physicists do not acknowledge this fact, and they are embarking on a quest to find out how many angels fit on the head of a pin.

  • The more I read the article the more it makes a case for there being a fine-tuner of all of these factors.

  • All the consternation expressed in this article about incongruous experimental results is merely desperation of quantum theorists, whose ‘Golden Calf’ – Supersymmetry theory (SUSY) – now seems to be headed for the slaughterhouse. See https://www.quantamagazine.org/features/science-news/as-supersymmetry-fails-tests-physicists-seek-new-ideas/

    “The spectacular discovery of the Higgs boson in July 2012 confirmed a nearly 50-year-old theory of how elementary particles acquire mass, which enables them to form big structures such as galaxies and humans.”

    In fact, the finding of the Higgs boson confirms that any exchange of mass, through particle decay, for example, is mediated by the Higgs boson. The only rationale for confirming the entire hypothesis of the Higgs Mechanism (commonly thought to fill all of space – continuously imparting rest mass to all fundamental particles), is that the Higgs boson prediction was included. However, a mediating boson should be associated with any hypothesis of particle mass that is consistent with quantum theory – so it can certainly be argued that the process of fundamental particles’ acquisition of rest mass has not been confirmed at all! In fact, the inherent rest mass of fundamental particles accounts for less than about 1% of all atomic mass!

    “… The Higgs boson has a mass of 126 giga-electron-volts, but interactions with the other known particles should add about [10^18] giga-electron-volts to its mass. This implies that the Higgs’ “bare mass,” or starting value before other particles affect it, just so happens to be the negative of that astronomical number, resulting in a near-perfect cancellation that leaves just a hint of Higgs behind: 126 giga-electron-volts.

    This apparently mystifying conception seems to presume that fundamental particles must continuously interact with a Higgs field to reacquire their inherent mass. Since quarks, for example, were only produced in the exceedingly dense conditions of the very early universe, it alternatively seems most likely that they must have permanently acquired their inherent, invariable rest mass at that time (perhaps from a hyperdense Higgs field)! Nowadays, essentially all quarks are bound within nuclei, the confinement of their kinetic propagation energy by the strong force accounts for the vast majority of atomic mass in the universe. There seems to be no possibility that quarks could be dynamically interacting with a Higgs field – thus invalidating the enormous additional mass requirements expected for the Higgs boson (above).

    The only link between the apparently impending SUSY failure and the multiverse concept seems to be some desperate reasoning such as ‘if we can’t find the supermassive versions of standard model particles, then they must be hiding in dimensions we can’t access.’ Please!

    “If no new particles appear and the Higgs remains astronomically fine-tuned, then the multiverse hypothesis will stride into the limelight. “It doesn’t mean it’s right,” said Bousso, a longtime supporter of the multiverse picture, “but it does mean it’s the only game in town.””

    Very briefly, one of the primary justifications for supersymmetry and most interpretations of astronomical observations has been the long held belief in misperceived requirements for dark matter in the universe. See a video simulation of two large spiral galaxies merging to form a large elliptical galaxy: http://news.sciencemag.org/sciencenow/2013/05/video-two-galaxies-on-a-collisio.html

    The research report is freely available in preprint form (as accepted by the publisher) – see:
    “The rapid assembly of an elliptical galaxy of 400 billion solar masses at a redshift of 2.3,” http://arxiv.org/abs/1305.4930

    The report does not mention dark matter, so its unclear if any was included in the simulation illustrated by the video. However, large spiral galaxies are commonly considered by astrophysicists to contain up to 10x more dark matter than ordinary matter. Conversely, there is no compelling evidence for the existence of dark matter in large elliptical galaxies – if they are formed from spiral galaxies, where could their supposed dark matter have gone?

    Perhaps the gravitational evaluation of spiral galaxies produces incorrect results… Please see: “Inappropriate Application of Kepler’s Empirical Laws of Planetary Motion to Spiral Galaxies…” http://fqxi.org/data/essay-contest-files/Dwyer_FQXi_2012__Questionin_1.pdf

    Also see: Pierre Magain, Virginie Chantry, (2013), “Gravitational lensing evidence against extended dark matter halos” http://arxiv.org/abs/1303.6896

    Many of the justifications for dark matter’s existence should be reevaluated. If there were no requirement for dark matter, we’d suddenly find ourselves much closer to understanding the fundamental nature of the universe…

    Also, see: “Higgs Boson Positively Identified,”
    http://news.sciencemag.org/sciencenow/2013/03/higgs-boson-positively-identifie.html

  • What I believe the laymen (people like me) find so fascinating here is that each door we unlock opens to another room far more complicated than we could have imagined. Each answer generates thousands of new questions. The bigger the answer the more likely it will call into question the very substance of our original theories regarding who we are and how this all works.

    I wish that I was better at math

  • It occurs to me that many valid calculations were made about astronomical phenomena when the view of the solar system was that it was geocentric. It wasn’t until scientists expanded their sphere of study that the heliocentric model was demanded and shown to be correct. Could it be that we are operating with a naïveté similar to Ptolemy but because of our many successes, we are missing something crucial—some element that we cannot conceive of or fathom at this time? We may just be waiting for a new Galileo Galilei.

  • Dizzy Hunter: that’s like saying because your lottery ticket won, there must have been an invisible hand guiding the winning numbers to match your ticket. No inviible hand needed, dude – as Joni Mitchell sang, it’s all luck, it’s just luck.

  • I find the use of the term “lack of naturalness” to be misleading and inappropriate. Whatever is out there is by definition in accordance with natural laws. Just because the equations that physicists are using don’t quite add up yet, and are showing unexpected discrepancies that may indicate a multiverse, doesn’t mean the universe is unnatural. It means that it is subject to even higher laws of nature that we didn’t even know were there.

  • Multiverse? How can physically impossible objects arise? How can you have a alternate parameters for the laws of “Nature” and come up with anything. This multiverse idea needs to go down for the fact that it for 1.) is unknowable, 2.) is untestable, and 3.) It takes way more faith than belief in God. (Terry Collman who posted here previously must be commended for his immense amount of faith in the multiverse theory, and a song lyric) I suppose anything is plausible but Hey! This is where we live!. We live in an actual working model of reality right here folks!!!. (Somebody quote me on that) And it looks just like things are quite orderly here. So orderly it has all science scratching their heads. “What could it be? It can’t be god, there must be some “natural” explanation” Violla! we must live in a multiverse where anything is possible. Yeah that’s it. Ahh, the great and powerful Multiverse”

    Postulate about some unknowable hypothetical object that is way too far away to ever observe all you want. Theoretics can only push you toward observation. If observation is impossible then the theory will just remain a theory. And so science and faith collide.

  • Well, I think a lot of times people think “mechanics” when they think physics. And it seems that much of the history of physics has just been a scientific investigation into mechanics. But I think the mechanical aspect of our physical universe is very base and distracting because it is what is most easily apparent.

  • What’s the point of a Multiverse if we can’t go to other universes? That’s no fun.

    I don’t see why we’d assume that a Multiverse would be unobservable, though. If it exists, it might very well have physical laws of its own, even if they aren’t our own laws. These physical laws would probably have to be something like “a ruleset for creating rulesets” (otherwise how would different sets of physical laws even exist in a Multiverse?) and thus these laws can probably be exploited or used in some way.

    After all, if our Universe isn’t perfect, then there’s no reason to believe that the barrier between the Universe and the outside Multiverse is somehow impassible. It -could- be impassible, but it could just as easily be something that can be passed if you find the right loophole or physical law to exploit.

    If the Multiverse exists, then it might be something we can use to modify our own Universe or even create new ones, and I don’t really know why people would pass it off as unobservable even if it’s incredibly different from our own Multiverse. Even if we can’t fully understand it, we could probably model at least some of it logically or mathematically.

  • Mike, you’re mistaking pursuit of a theory with faith.
    The main difference is of course the continued search for evidence.
    A certain amount of reasonable possibility must exist to go down an avenue of research. A good scientist will never claim to be “right” per se, but rather that the evidence seems to support the hypothesis. The more evidence that supports the theory, the more it can be relied on to be true.
    “Faith”, as you use the term, I assume you to use the term in the colloquial definition of the supernatural, or intelligent designer. The purpose of faith is not to quest for proof, evidence, or even to question at all. Whereas science is a continually searching, self correcting endeavour.
    If perhaps the research coming from the LHC points to a different direction, then any physicist worth his salt will go with it.
    All the while, new theories will be imagined, tested (realizing new ways to test them being an integral part of the process), proven, and discarded. While faith will continue to stand in place, and ask us to accept without question.

    BTW, just because these theories can’t be proven with the available data at the moment, doesn’t automatically lend any credibility to any supernatural possibilities.

  • @Dizzy Hunter I’m totally unsure about the concept of a ‘fine tuner’ being needed to fill gaps in knowledge. My feeling is that at this level of enquiry the tools we use are simply not capable of providing full answers.

  • You cannot calculate the mass of an important fundamental entity like the Higgs without even having a basic understanding of what dark matter is and how its initial misinterpretation has negatively affected our calculations of the cosmological constant.
    Dark matter is not even matter and does not produce gravity, but rather creates a “pooling” effect much like an ocean wave gathers and carries flotsam along with it at it’s crest. These “waves” were formed from a collision of massive bubbles 14 billion years ago. Dark energy is the gradual relaxation of these dark matter waves spreading everything apart.

  • I actually find what Jared B. said quite interesting. I do think that we have been quite distracted by the mechanical aspect of our universe because it is what is most apparent. There is so much that lies beneath and supports our physical reality. I think as more research is done, the realization that the Higgs field is actually the construct of spacetime itself will become apparent and everything will finally make sense.

  • Yes, the scientific community can continue to devise new theories, test them, discard them, postulate new theories, etc, ad.nauseum, until our Sun burns out. Yet, they will be no closer to the truth than we are today. Is there no point in this process when we can all conclude that, “Yes, this is unnatural and beyond our human capabilities to comprehend?”

  • I remember a physicist once said that the universe began with the breaking of the absolute symmetry of absolute emptiness. No matter, no energy, no space, no time, in that in a state of the absolute symmetry of absolute emptiness there can be no way to mark time or distance or anything else for that matter. Therefore the tiniest burst of energy for the most infinitesimally short fraction of a second would be a VERY big bang indeed. I truly admire the tenacity of those that wish to find their way back to this spark, to find the origin of everything. Unfortunately, this will never happen. It seems as if the Multiverse theory will be proven if not correct than at least most likely. If this is the case, and there are an infinite number (or damn near infinite anyway) of universal bubbles out there to choose from, we will never know which was the first to start things off.
    Beyond all of that complexity it seems to me to be the ultimate in hubris to think that we or any other physical form need be the only source of intelligence in all of this existence. Perhaps there was an initial spark of non-corporeal thought that began all of everything. I am not saying that I am advocating for the existence of what we have come to think of as some form of deity, just that we simply do not know. What if the breaking of the absolute symmetry of absolute emptiness was akin to one waking up suddenly from a dreamless sleep into a state of shocked awareness? I am sure we have all experienced this at one time or another so the analogy is simple enough to understand. What if all of existence stems from a single, tiny, burst of thought amounting to “what the …!” which rolled itself into everything that there is in an attempt to answer what is inherently unanswerable? It does seem to be the one universal question we all ask isn’t it? Who am I? How did I get here? I think the universe (multiverse) exists to answer that very question and since it does not know the answer, we are doomed to fail in attempting to find that answer ourselves; but hey, happy hunting!

  • The article describes a tapping of a consensus, I believ. It would have been even better if one could get a sense of the balance here, for example how many papers are done on multiverses vs naturalness. I think the latter would be very many, within particle theory.

    “Parallel universes cannot be tested for;”.

    I wish people stopped claiming that, since it is palpably untrue in the sense of testing hypotheses. If Weinberg’s result is taken to be derived from multiverse theory, it passed a hypothesis test.

    In this sense, claiming that parallel universes can’t be tested for is the same as claiming that neutrinos can’t be tested for because all we can ever see is missing momentum et cetera.

    What people mean is that it is not conclusive, as long as naturalness can’t be excluded. An analogous situation would be gene selection vs group selection, say. They predict the same results, but group selection is both unlikely and as of yet unobserved. But it can’t be excluded as of yet.

  • @Hominid: Biologists like Coyne points out, since your’s is a popular idea among creationists aka denialists of biology, that evolution has resulted in senses that makes useful, correlated images of reality.

    In other words, a solid surface is mostly vacuum. we don’t observe it with our senses but we have learned that from observation through using our senses in experiments. As Sean Carroll says, the laws underlying the physics of everyday life are completely understood. [ http://blogs.discovermagazine.com/cosmicvariance/2010/09/23/the-laws-underlying-the-physics-of-everyday-life-are-completely-understood/ ]

    @Jason Thompson, Dizzy Hunter: If you don’t get from the article that the simplest explanation for many laws may be randomness as opposed to the complications of fine-tuning of parameters et cetera, you have read poorly.

    @mike: The multiverse is no more physically impossible than one universe. In fact, it is apriori more likely because we never see just one object in physics, we have one electron field yes but we see many electrons et cetera. It would take enormous coincidence or forcing to have just one universe pop out of physical law, even if it would be finetuned to just one set of parameters.

    As for unknowable, the article shows that it is nonfactual, and as for non-testable my previous comment (if it gets out of moderation) comments how it too is palpably nonfactual. (Eg Weinberg’s calculation is a hypothesis test of multiverse theory. It’s just not conclusive, but so are many other such tests. The point is to see if a theory is testable and survives test or is erroneous. Convergence to just one surviving theory is a boon, but never guaranteed.)

    This is physics, concerning what we can observe. Your magical beliefs have failed in comparison.

    @ Mike J: “Dark matter is not even matter”. Well, it is, even a layman as me can see that from Susskind’s youtube lectures, say. The microwave background acoustic peaks tells us it is matter and that it exists, and so does cluster collisions et cetera. Other theories have failed to predict the observations.

  • Well, many astrophysicists and others have never liked the idea of the Big Bang because it obviously implies a “moment” of creation, which in turn implies an outside agency, that agency being God.

    So, when multiverse theory came about around 1987 as the above wonderfully intellectually entertaining article reports, physicists loved the idea, since multiverse theory suggests that ours is just one of an infinite number of bubble universes, and that only some of those universes will by chance have the right forces at the right magnitudes for life to arise and evolve in them. And thus, no divine fine-tuning is necessary.

    But Wow! What a mystery it will always be. As at least one poster mentioned above, the more we know, the more we discover that we don’t know. What a fantastic existence this is for all of us, for all living things, and all things, in our own “little” Universe. And if we ever figure out not only the “what”, “how”, “where” and even the “why” questions (which I doubt we ever will), I think we would become bored with it all. So it’s good that ultimate existence of reality, time, and everything will never be fully understood by humankind, or any of the billions of other sentient kinds that are most assuredly “out there”.

    When thinking about cosmology? I think “supercosmology” would be a more apt term for this level of pondering and speculation (and theoretical science). But I’ll tell you all this, in my view, if God exists, well, that’s a fantastic and amazing thing. But it’s even more amazing and fantastic if He DOESN’T exist! As another poster said above, “happy hunting”!

  • At a deeper level; the “other side” of the hologram, I believe our universe began with two massive bubbles colliding in a true vacuum. The membranes of these bubbles is where the strings of String Theory reside, the collision imparted enough energy to the short-lived virtual strings and to the membrane to create a nearly permanent reality. This collision would push the bubbles flat where they make contact, which would result in violent, random wrinkling and contracting of the membrane. These wrinkles are dark matter…huge distortions of space, not particulate in nature which is why we can’t find them! In between these wrinkles, are the open flat expanses where matter annihilated it’s counterpart on the impacting bubble, so nothing exists in these voids. The edges of these “wrinkles” is where matter found refuge from annihilation, which also explains why matter won in the end but only a fraction of a percent survived. To this day it is where all matter still is, along these wrinkles of “dark matter” spread throughout the observable universe in massive, random, web-like patterns. The dark matter skeleton of the universe is where all matter exists because they were created simultaneously from the same massive, lower-dimensional collision and matter is trapped within these structures, leading to the illusion that there is a gravitational influence. Dark energy, on the other hand is merely the gradual relaxation of these massive wrinkles, pushing everything apart.

  • Just a drive-by from a non-scientist…….

    @Hominid: Lovely restatement of the philosophy of Immanuel Kant there. Died in 1804 and still right. Also that of Schopenhauer, who was arguing like a modern evolutionary psychologist shortly afterwards.
    @Larsson: I don’t see what is creationist about that. Kant was the original killer of God, before Nietzsche.
    @Nausea: Are you named for the book in which Sartre said that Nature has no laws, only habits? I do so wonder what damage has been done by the choice of the word “law” to describe observed regularities. It inclines us to envisage a legislator. Naughty.

  • Of course we have the infinite worlds hypothesis in which we could have an exact copy of myself only perhaps instead of living the life I do here, I could be a plumber, which I am not, and maybe in one of them I could be the Pope, which leads me to wonder what in the world I am doing in this one when I could be the Pope in the other.

  • Multiverse as a mathematical concept is one thing, but to say there are infinite numbers of universes with all possible constants another.
    Let us consider a simple scenario of vibrations in a one dimensional string universe. Even in a one dimensional string, from a purely mathematical view point, you can have infinite possible values for resonances (particles). But if you take a real world string, the values are limited by the length of the string and the material properties of the string. The length of the string and the material properties of the string are environmental. While mathematically, there are infinite number of possible configurations of lengths and other numbers, real world possibilities are limited (though large) by the material world.
    While the mathematics of the abstract standard model (minus Higgs mechanism), has beautiful symmetries and perfection, chinks come when it collides with reality.
    The environmental variable that we cannot know is the *material* (if we can call it that) properties of the quantum (or standard model) vacuum. We are perceiving them through the Higgs mechanism and gravity which are peeking at us from a world deeper than the standard model.
    Multiverse might be true in so far as there might be more than one or many configurations for the universe.
    But taking solace in infinite possibilities (like the Library of Babel story by Jorge Luis Borges) and stopping there is like end of science.

  • I’m no physicist, and by no means qualified to speak for or against either of these arguments, but what denotes a natural or unnatural universe? I guess what I’m trying to ask is, does an unnatural universe imply that there is a consciousness at work doing the fine tuning, if that is in fact the case. Or would it point rather to a distinct anomaly in the creation of our own universe, and others like It, in a multiverse scenario. I suppose that is another way of asking the same questions that are currently perplexing reputable professionals today. Do classical and modern physics provide a false bubble of understanding in fine tuned universe, in which our perception is an illusion, and not meant to be fully understood by nature? Be kind, I’m attending a physics class for poets).

  • It is a while since I published anything in Theoretical Physics but I judge now that the time is ripe. We are most definitely at Peak Nonsense in Theoretical Physics. There are, in point of fact, a host of alternative explanations for most every “vexing puzzle” in physics today. The essential features of those explanations are three-fold: 1) they are simple and not very complicated and therefore do not garner their authors great attention; 2) they have a heritage in the physics and mathematics of the last two centuries (i.e. they are in no way radical); and 3) they involve nonlinear field theories which are in direct opposition to the prevailing statistical paradigm of linear field theories with point-particles and a mythical quantum observer. Now is a good time to make progress.

  • Ed Witten said, “I would be happy personally if the multiverse interpretation is not correct.”

    A scientist should never be happy or sad about a hypothesis

  • If most existing physicists would prefer to live in a ‘natural’ universe, this is probably because the thing that lured them into the world of physics was its naturalness. Now that we have new theories, new physicists will emerge who prefer chaos, multiplicity, etc.

  • I’ve never understood why theorists see the universe as “tuned” for life. Why can’t the universe simply be one of a million zillion possibilities – all equally unlikely? The only reason to speculate about how special this all is is if you think of life as something “special”. To us, it is. But if things came out differently and there was nothing in the universe but azure colored grapes, maybe they would be wondering who tuned the universe for azure colored grapes?

    I don’t mean this literally, incidentally. I fully understand that a miniscule change to any of 20 constants would rule out ALL life. If you prefer, substitute quantum flashes for the grapes. I give you full poetic license since it’s impossible to imagine a world with a different physics. The point is that any particular outcome seems weird after the fact. Probability doesn’t work backwards. You can’t say that the fact that you have the longest thumb in the world is a “miracle” because SOMEBODY has to have that silly thumb. It might as well have been you.

    I hope I’m making my point clear.

  • Humanity had to wait about 150 years from the death of Isaac Newtown to the birth of Albert Einstein. The universe did not change in that century and a half. Instead Einstein’s insights changed our understanding of our universe. The unnaturalist argument risks intellectual complacency, and lazy science. It’s historically ridiculous to suggest that a few decades of fruitless research represents a dead end. Just because we don’t understand something does not mean there is nothing to understand. It’s worth remembering that Ptolemy’s 2nd Century work Almagest, or “The Great Treatise,” was accepted as Gospel for 1,200 years, until Copernicus knocked it on its ear. It turns out the sun was at the center of our system, not the earth.

  • Personally, I’m comfortable with the notion of a universe without time, drowining in chaos and multiplicity, mostly full of dark matter and black holes, floating in a formless void of Lovecraftian horror.
    Makes sense to me.

  • I’m uncomfortable with the concept (or reality) of a multiverse but I know that is simply an irrational emotional prejudice. It’s just the next step in “the earth is the center of the universe, oops the sun is, oops our galaxy is, now oops the universe is the center of all of reality”.

    I not only can’t give a good reason for denying the multiverse, I must instead say “it certainly is a good and traditional liklihood”. Besides, in those 10^500th universes there might be some EXTREMELY interesting things well beyond our imagination.

    As the bard put it so well, “there are more things under the sun Horatio than are dreamt of in your philosophy. Anyone for the hyper universe?

  • Multiverses do make some sense to me. We seem to spend so much time looking for smaller and smaller things, particles. Call me crazy but lets just say the multiverse theory is in effect accurate, than we, our universe, might be like a cell in some cosmically large living thing. Basically I’m saying we should try looking at the other end of the spectrum; the extremely large as opposed to the extremely small.

  • Multiverse theory can be very well true. But it seems to me that it’s rather contraproductive. We shouldn’t assume about anything that it’s fine tuned and stop looking for any other reason. It might be fine tuned by accident or we might just not understand underlying laws.

  • While very large, the string theory estimate of the number of universes (10 ^500 ) is STILL a countable number. Many of the fundamental constants of our Universe are not countable. The odds of getting our Universe from the countable set is zero.

  • If there are other universes with different constants, they don’t have to fit into our imagination in order to support life. Our imagination is very much limited to our own universe. We cannot even comprehend a 4D universe, let alone different fundamental constants. And last but not least, what is life? When a star is formed until it dies, it has some planets orbiting it, it orbits around galactic centre which all resembles a living creature. Maybe we should redefine “Life”.

  • If the possibility that our universe was created by design is ruled out, would it be true to say our universe was created naturally? If so, has nature ever created one of anything?

  • If it takes x universes it takes to get one like ours then there are x universes. That seems completely natural and obvious. No deities or designers required, just the law of large numbers. Unfortunately such an idea appears untestable.

  • We all of us risk falling in love with our own understanding of things, specially when tying to understand the nature of everything, us included. We find a pattern, follow it enthusiastically to the point of imposing it on reality. The first group I can think of who did this were the Pythagoreans, who were utterly convinced that the universe was ruled by number, which for them could be nothing other than the (positive) integers. When the discovery was made, while thinking about the length of the hypotenuse of a right triangle with the other two sides of unit length, that there had to be what are now (rather confusingly) termed ‘irrational’ numbers, an entire world view went into eclipse. Surely, reality itself had mandated the integers. There must be an error somewhere. In consequence, geometry was developed at the expense of (what we now term) algebra. which the Greeks failed to develop – as they could have – because they preferred their beloved (but wrong) assumption that integers alone would suffice. Another far more recent love-object which seemed also to have compelling reason to exist, was the ‘luminiferous ether’ – the light-carrying (luminiferous) substrate of space, which had to be the medium through which light propagated. A whole passel of apparently reasonable, but still wrong, assumptions. And the modern equivalent? Stay tuned!

  • Ed Witten said, “I would be happy personally if the multiverse interpretation is not correct.”

    A scientist should never be happy or sad about a hypothesis

  • If we accept that a fine tuned higgs boson will bring the answer, then why not understand that something could have ‘fine tuned’ it…?

  • James T. Dwyer you nailed it…

    “Many of the justifications for dark matter’s existence should be reevaluated. If there were no requirement for dark matter, we’d suddenly find ourselves much closer to understanding the fundamental nature of the universe…”

  • Twenty five hundred years ago, there was this fellow in India who said, that everything was basically mind. Max Tegmark thinks the universe is fundamentally information, and Seth Lloyd believes it is a quantum computer. Maybe they’re on to something?
    Maybe we should give up our mechanistic 19th. Century model of things?

  • For parallel universes to exist, there must be at least 1 hidden dimension of space beyond the ordinary 3. And the same searches that have failed to find new particles have ALSO failed to find evidence of such hidden dimensions. In short, to have the kind of multiverse these people are appealing to, you have to have somewhere to PUT it.

    As for their ‘anthropic’ twaddle, it isn’t science under any respectable definition of the term. Think about it: You start with a failure of imagination, namely that of explaining our own world’s physics. So, you then ‘explain’ it by invoking a grander, more crass failure of imagination- the utterly unsubstantiated assertion that sentient life couldn’t arise under laws of physics substantially different than our own. Not only is this idea not testable, it isn’t even logically falsifiable. It fails the test of being a scientific hypothesis in the most basic, brutal way you can fail. As somebody like Pauli might put it, it isn’t even wrong.

    Instead of that mental dead-end, I think we should revisit time. We already know that events in the future can affect events in the past- it is the only way to coherently explain many quantum effects like ‘delayed choice’. So what if things like particle masses are really dynamic quantities, with the entirety of space & time from the Big Bang to the ends of creation acting as a cosmic tuning fork? By considering the potential feedback mechanisms this opens up, you might be able to provide what is really needed- natural fine-tuning. And do so without having to claim that 90% of the universe is deliberately hiding from our instruments.

  • To induct or to deduct a understanding of the universe is not possible. The path to the realization of that understanding is difficult to find.

  • The LHC's second run is not a "last ditch" search for answers. If the universe is "unnatural" in the sense this article uses, then it doesn't follow that other universes must exist. It only means present understanding is incomplete. So, unnaturalness doesn't give a "huge lift" to the multiverse ideas. This article comes to the wrong conclusions about the absence of SUSY. If nature is not super-symmetric then superstring theory is wrong and so those 10^500 different vacuum states cannot physically exist. In other words, that works against a multiverse not for a multiverse. So the multiverse ideas have no rational basis to "stride into the limelight". The dream of uniquely predicting the constants of nature is still very much alive because either it or a multiverse is a false dichotomy. For example, Lawrence Krauss put forward an elegant Higgs-saw mechanism as a source for dark energy via a new scalar field. It doesn't solve the cancellation problem but the cancellation problem suggests there are yet to be discovered physical principles of quantum gravity which would explain it. People need to get rid of the naturalness or multiverse false dichotomy.

  • To be complete we should also consider a Creator God outside of space and time as the architect of this unnatural universe– that is specifically designed to contain life. This is no less scientific than the other non-testable theories such as the multiverse. Choose your miracle: God or the multiverse…

  • I 'm lost as to why "unnatural" is invoked. Even if you had 10 to the 500 power universes and as a chance cancellation you get this universe that still begs the question where were the rules established that dictated the laws of string theory to yield the "unnatural universe". You haven't got out of explaining the fine tuning parameters , you have only pushed back the question to a larger landscape. The emergent effects that produce the universe we see can't be explained by naive reduction. The structure that allows the chance occurrences to exist has to also account for the laws and rules that enable the emergent universe to exist in its present form. It's like when you see your cat or dog chasing it's tail. Trying to say you can explain the universe using a multiverse is doing the same thing. That does not say multiverse is not true anymore that the dog's tail is not there. It just means you are chasing your tail if you think you can explain fine tuning using a multiverse ides. Cute , nice try. But in the end my bet is you will keep coming up with more finely tuned parameters until the 10 to the 500 power will be insufficient to explain it.

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