Physicists War Over a Unified Theory

beggs writes: "I was looking through the New York Times and came across an article which talks about a new front in the war to find a unified theory, but this one does not come from the particle physicists, it comes from the solid state physicists. Here is a little quote for wet your appetite: 'some solid-state physicists are trying to show that the laws of relativity, long considered part of the very bedrock of the physical world, are not platonic truths that have existed since time began.'"

Comments

We never really know anything

[KarmaBlackballed]

It is narrow thinking to propose that we ever have the "final" answer because there is no way to prove that something is right. We can only prove that things are wrong.

Newton thought he had it covered, and the world agreed. Then Einstein came along and shook our understanding in strange ways. People got comfortable, then Schroedinger and his damn cats show up and screw things up again. Then we get comfortable. Then scientist discover that we still do not have whole story yet again.

Don't you get it? The wonderfulness of it all is that we will never know it all. The beauty of creation is that we will always have something more to discover.

Re:We never really know anything

[tijnbraun]

This reminds me of pascal's image of knowledge...
Where knowledge is symbolized by the sphere's volume and the unknown by the sphere's surface. Therefore as knowledge grows, so does the unkown (although the volume grows faster than the surface, total wisdom will be never achieved.)

(or if the sphere is a balloon, science grows until it explodes :)

Re:We never really know anything

[Violet Null]

There is a man called Godel who proved that so.

1) Godel's proof only works in discrete systems that support (at least) a small number of operations. It is not, despite the occasional comment to the contrary, necessarily applicable to, say, human existance.

2) Godel's proof does not say that it is impossible to know everything. It says that in these discrete systems, it is either a) impossible to make some valid statements (an incomplete system), or b) possible to make some invalid statements (an incorrect system).

3) Godel's proof only works if you are using boolean logic (and, in fact, works only because boolean logic is so bad at handling self-referential statements). This does not mean that the universe works the same way.

Re:We never really know anything

[dragons_flight]

You are forgetting something. Before the great paradigm shifts in the history of physics (Newton, Einstein, Bohr, etc.), there was always evidence that something was wrong with prevailing theory. Scientists on the front lines weren't "comfortable", they noticed things like the "ultraviolet catastrophe" and the precise spectra of atoms and knew something was wrong.

Today we know that general relativity and quantum mechanics don't work together, but we aren't sure how to fix it (though string theorists try hard).

Eventually it's conceivable that we'll write down some basic laws and then millenia will pass without any evidence that something is still wrong. While you're right that it's impossible to prove that these laws are correct, scientists are very diligent about trying to find holes and if none are found, then everyone will believe we finally know the truth. And perhaps we actually will.

Re:We never really know anything

[dangermouse]

also, as a studying mathematician, i do believe that we can proove and disprove things absolutely. to think otherwise is incredibly naive given the relative success of humanity.

Mathematics is entirely artificial. It's based on rules and premises that we pretty much made up. You can prove things in math because it's a self-contained problem set, and you're looking at it from the outside with an omniscient view.

When you didn't invent the framework of the problem, it tends to be harder to prove a solution.

That said, you may never be able to prove a Unified Theory, because you can't ever be certain you've described every aspect of the problem set. But you can disprove a physical theory (or at least show it to be lacking) simply by finding a counterexample.

Re:We never really know anything

[blamario]

To quote (by memory) from the Hitchhikers' guide:

There's a theory saying that, if we ever figure out the Universe, it will be immediately replaced by something even more complicated. There's another theory saying that already happened.

Okay, Here It Is

[The Gardener]

December 4, 2001

Challenging Particle Physics as Path to Truth

By GEORGE JOHNSON

n science's great chain of being, the particle physicists place themselves with the angels, looking down from the heavenly spheres on the chemists, biologists, geologists, meteorologists -- those who are applying, not discovering, nature's most fundamental laws. Everything, after all, is made from subatomic particles. Once you have a concise theory explaining how they work, the rest should just be filigree.

Even the kindred discipline of solid-state physics, which is concerned with the mass behavior of particles -- what metals, crystals, semiconductors, whole lumps of matter do -- is often considered a lesser pursuit. "Squalid state physics," Murray Gell-Mann, discoverer of the quark, dubbed it. Others dismiss it as "dirt physics."

Recently there have been rumblings from the muck. In a clash of scientific cultures, some prominent squalid-staters have been challenging the particle purists as arbiters of ultimate truth.

"The stakes here are very high," said Dr. Robert B. Laughlin, a Stanford University theorist who shared a Nobel Prize in 1998 for discoveries in solid-state physics. "At issue is a deep epistemological matter having to do with what physics is."

Last year Dr. Laughlin and Dr. David Pines, a theorist at the University of Illinois and Los Alamos National Laboratory, published a manifesto declaring that the "science of the past," which seeks to distill the richness of reality into a few simple equations governing subatomic particles, was coming to an impasse.

Many complex systems -- the very ones the solid-staters study -- appear to be irreducible. Made of many interlocking parts, they display a kind of synergy, obeying "higher organizing principles" that cannot be further simplified no matter how hard you try.

Carrying the idea even further, some solid-state physicists are trying to show that the laws of relativity, long considered part of the very bedrock of the physical world, are not platonic truths that have existed since time began.

They may have emerged from the roiling of the vacuum of space, much as supply-and-demand and other "laws" of economics emerge from the bustle of the marketplace. If so, then solid-state physics, which specializes in how emergent phenomena occur, may be the most fundamental science of them all.

"We're in the midst of a paradigm change," Dr. Pines said. "Ours is not the prevailing view, but I think it will turn out to be the one that lasts."
Working in this vein, one of Dr. Laughlin's Stanford colleagues, Dr. Shoucheng Zhang, recently was co- author of a paper suggesting that elementary particles like photons and gravitons, the carriers of electromagnetism and gravity, might not be so elementary after all -- they might emerge as ripples in the vacuum of space, bubbling up from the quagmire in a way that can best be explained in terms of solid-state physics.

"The idea is of course crazy, thought provoking, and somewhat anti-establishment," Dr. Zhang said. "The main idea is to apply concepts from solid-state physics to answer some big questions of the universe."

The particle physicists insist that there is plenty of mileage left in their own approach. "I strongly believe that the fundamental laws of nature are not emergent phenomena," said Dr. David Gross, director of the Institute for Theoretical Physics at the University of California at Santa Barbara. "Bob Laughlin and I have violent arguments about this."

After hearing Dr. Zhang describe his theory at a seminar last month, Dr. Gross deemed it "an interesting piece of work." He said he found the mathematics "beautiful and intriguing, and perhaps of use somewhere."

That may sound like faint praise, but the particle physicists have reason to be wary. The squalid-staters are challenging them in a debate over how the universe is made and how science should be done.

Following the method of Plato, the particle physicists are inclined to see nature as crystallized mathematics. In the beginning was a single superforce, the embodiment of an elegant set of equations they call, only a bit facetiously, the theory of everything. Then along came the Big Bang to ruin it all.

The universe cooled and expanded, the single force splintering into the four very different forces observed today: electromagnetism and the weak and strong nuclear forces, which work inside atoms, are described by quantum mechanics and special relativity. The fourth force, gravity, is described by an entirely different theory, general relativity.

The particle physicists' ultimate goal is "grand unification" -- recovering the primordial symmetry in the form of a single law -- a few concise equations, it is often said, that could be silk-screened onto a T- shirt.

This approach, in which the most complex phenomena are boiled down to a unique underlying theory, is called reductionism.

The problem, the solid-staters say, is that many forms of matter -- ranging from the exotic like superconductors and superfluids to the mundane like crystals and metals -- cannot be described in terms of fundamental particle interactions. When systems become very complex, completely new and independent laws emerge. "More is different," as the Nobel laureate Philip W. Anderson put it in a landmark paper in 1972. To the solid-staters, it would take something the size of a circus tent to hold all the equations capturing the unruliness of the physical world.

Like Aristotle, they lean toward the notion that it is the equations that flow from nature instead of the other way around. Mathematics is just a tool for making sense of it all.

"For at least some fundamental things in nature, the theory of everything is irrelevant," declared Dr. Laughlin and Dr. Pines in the Jan. 4, 2000 issue of The Proceedings of the National Academy of Sciences. "The central task of theoretical physics in our time is no longer to write down the ultimate equations but rather to catalog and understand emergent behavior in its many guises, including potentially life itself."

There may not be a theory of everything, they say, just a lot of theories of things. This is exactly the kind of squalor the particle physicists abhor.

Dr. Grigori E. Volovik, a solid- state physicist at the Helsinki University of Technology in Finland, champions an idea he calls "anti- grand unification." In a review article last year (xxx.lanl.gov/abs /gr-qc/0104046), he ventured that the universe may have begun not in a state of pristine symmetry but in one of lawlessness. The laws of relativity and perhaps quantum mechanics itself would have emerged only later on.

The notion of emergent laws is not radical in itself. A flask of gas consists of trillions of molecules randomly colliding with one another. From this disorder, qualities like temperature and pressure emerge, along with laws relating one to the other.

So take that idea a level deeper. Physicists now believe that the vacuum of space is, paradoxically, not vacuous at all. It seethes with energy, in the form of "virtual particles" constantly flitting in and out of existence. So perhaps, Dr. Volovik suggests, even laws now considered fundamental emerged from this constant subatomic buzz.

Solid-state physics offers clues to how something like this might occur. The atomic vibrations that ripple through matter are, like all quantum phenomena, carried by particles -- called, in this case, phonons.

Just as photons carry light and gravitons carry gravity, phonons carry the subatomic equivalent of sound. Like bubbles in a carbonated beverage, phonons -- physicists call them "quasi particles" -- appear only when the medium is disturbed.

In the world of solid-state physics, quasi particles abound. In some substances, like the semiconductors used to make computer chips, the displacement of an electron leaves behind a "hole" that behaves like a positively charged particle. An electron and a hole can sometimes stick together to form a chargeless quasi particle called an exciton. Other such ephemera include magnons and polarons.

Evanescent though they are, quasi particles act every bit like elementary particles, obeying the laws of quantum mechanics. This has led some mavericks to wonder whether there is really any difference at all. Maybe elementary particles are just quasi particles -- an effervescence in the vacuum.

Particularly intriguing is a phenomenon, occurring at extremely low temperatures, called the fractional quantum Hall effect. In certain substances, quasi particles appear that act curiously like electrons but with one-third the normal charge. (Dr. Laughlin won his Nobel Prize for a theory explaining this.)

Quarks, the basic building blocks of matter, also carry a one-third charge, a coincidence that has fueled speculation that emergence may be somehow fundamental to the very existence of the physical world.

A stumbling block to carrying this idea further has been that the quantum Hall effect seems to work only in two-dimensions -- on the surface of a substance. But in a paper published in the Oct. 26 issue of Science, Dr. Zhang and his student Jiangping Hu showed how to extend the phenomenon. In their scheme, the physical world would be a three-dimensional "surface" of a four-dimensional "quantum liquid" -- an underlying sea of particles that can be thought of as the vacuum.

Analyzing the ripples that would appear in such a medium, the two scientists were surprised to find that they mathematically resembled electromagnetic and gravitational waves. But there are problems with the model. At this point, the hypothetical photons and gravitons that emerge from the equations do not interact with other particles, as they do in the real world.

"The coupling is zero, so apples are weightless, as is everything else," said Dr. Joseph Polchinski, a string theorist at the University of California at Santa Barbara, who recently discussed the model with Dr. Zhang.

And there is what the theory's inventors concede is an "embarrassment of riches" -- the equations predict hordes of exotic particles that do not exist.

"The hope is that some modification of the theory, not yet specified in detail, will remove the extra fields and turn on the coupling," Dr. Polchinski said. "Whether this can be done is at this point a guess. Overall my attitude now is interest with a high degree of skepticism."

If the theory can be made to work, it may point to a new way of unifying quantum mechanics and relativity. But Dr. Zhang is careful not to oversell what he considers a work in progress.

"Our work only made a tiny step toward this direction," Dr. Zhang said, "but it seems to indicate that the goal may not be impossible to reach." At the very least, he said, his work may inspire more collaboration between particle physicists and solid-staters.

Ultimately, though, the two sides know that they are talking across a divide. Taken to its extreme, emergence suggests that all the fundamental laws, even quantum mechanics, may be secondary -- that at the base of reality is random noise.

Dr. Polchinski said he found that idea discouraging.

"To me, the history of science seems to be a steady progression toward simpler and more unified laws, and I expect to see this continue and to contribute to it. Things may take many surprising twists and turns," he said, "but we reductionists are still quite happily and busily reducing."

Re:Okay, Here It Is

[Beryllium Sphere(tm)]

This is really a philosophical argument, not a scientific one. But it may be a productive one. And I bet computers have caused the argument.

For a long time humans lived in a world with cats and cookware. Human-made items like cookware were trivial to understand, and nobody hopes to understand a cat :-)

Then we got a little more sophisticated and had cats and clocks. We studied clocks because we could understand them. We learned about energy conservation, simple harmonic motion, and all sorts of classical physics. Reductionists can learn to understand a clock.

Then we had computers and cats. A computer looks like an elaborate clockwork but practical people don't try to manage them through first principles. They use heuristics like "it gets unstable when low on memory". Now we've got human-made artifacts, which we feel entitled to understand, which reductionism has increasing trouble explaining.

The promise here is that if we apply the same brainpower and effort to defining the laws of complex systems, maybe we'll gain some useful insights into economics, sociology, psychology and other fields of study which directly affect our lives.

I will not hold my breath waiting for a definitive theory of cats.

This Makes Me Nervous...

[Embedded Geek]

I am I the only one, but is anyone else worried that when they finally find the unified theory, "The Theory that Explains Everything," that it'll wind up being Murphy's Law?

Re:This Makes Me Nervous...

[(void*)]

Pardon me, that's the Meta-Murphy law, which has yet to be proven.

One law at a time, one law at a time.

Not Really

[nahtanoj]

Speaking as part of the community, the physics world is not at all portrayed accurately in this article. Nearly every physicist sees value in every subset of physics. Think nuclear physics is dead? I happen to know a few nuclear physicists who are still active in research. No-one I know refers to solid-staters as "squalid-staters". There is worthwhile research still in every discipline of physics, even solid state and particle physics.

I think what we have here is a case of journalistic hype used to make the a mountain out of a molehill. I do not think that anyone can deny that there has not been advances in the understanding of any field.

Ciao

nahtanoj

Re:natural laws hold true, but values do not

[Anonymous Coward]

This isn't quite correct. You are right that in changing the speed of light you are only redefining the time unit. (One second is how long a photon takes to travel a certain distance.) In everyday work, (yes- I am a physicist) I choose units where c is one. It makes things so much easier.

What the physicists are measuring isn't the speed of light - it is the dimensionless constant alpha. Since alpha is dimensionless, you cannot renormalise changes in it by changing the size of your units. (Alpha is a measure of the strength of the electromagnetic (and electroweak) force.)

Quantum mechanics is the thing we know least about. We have tested general relativity to fourteen decimal places, but QED (quantum electrodynamics) has only been tested to ten decimal places. Quantum is a theory filled with ad-hoc rules. GR is increadibly simple. It wouldn't surprise me at all if quantum field theory was shown to be a suitable limit of what happens to gravational waves once non-linear effects become important, and once you start running into the effects of compactified dimensions.

Sensationalist article, but neat idea

[ErfC]

I found the article kind of sensationalist. I mean, I'm sure there are physicsists who act like that, and I'm not surprised these are the ones that make it into newspaper articles. But I don't think most physicists are so violently opposed to each other's ideas.

I mean, okay, most of us are at least a little arrogant. We're revealing the secrets of the Universe -- how could our heads not swell, at least a little? But for most of us it's a little tongue-in-cheek, too.

Now the ideas in the article intrigue me. I'm in Particle Physics, and I was indeed under the impression that fundamental particles are, well, fundamental. The idea that this could all be quasi-particles ("effervescence in the vacuum" as the article puts it) like phonons (the sound equivalent of photons) in matter, is really cool.

I will agree with this much: there isn't enough discussion between the various disciplines. Scientists in general need to talk to each other more.

Re:natural laws hold true, but values do not

[gowen]

In everyday work, (yes - I am a physicist) I choose units where c is one. It makes things so much easier.

At my old university, we simply referred to these as "God's Units". Of course, I'm in a maths department now, so we just write c and leave all the fiddling about with actual numbers to the physicists.

L.E.J. Brouwer's "Life, Art, and Mysticism"

[Jagasian]

Here is a quote from the famous mathematician L.E.J. Brouwer, who saw the sciences as flawed due to their underlying philosophical foundations, which I think applies to the "Physicists War Over a Unified Theory":

Every branch of science will therefore run into ever deeper trouble; when it climbs too high it is almost completely shrouded in even greater isolation, where the remembered results of that science take on an independent existence. The "foundations" of this branch of science are investigated, and that soon becomes a new branch of science. One then begins to search for the foundations of science in general and knocks up some "theory of knowledge." As they climb higher and higher confusion grows until they are all completely deranged. Some in the end quietly give up; having thought for a long time about the elusive link betwen the intuiting consciousness (which develops from the perceptional world) and the perceptional world itself (which in turn only exists through and in the forms of the intuiting consciousness) - a confusion which arose from their own sin of constructing a perceptional world - they then plug the hole with the concept of the ego, which was self-created with and at the same time as their perceptional world; and they say, "Yes, of course, something must remain incomprehensible, and that something is the ego that comprehends."

But there are others who do not know when to stop, who keep on and on until they go mad: they grow bald, shortsighted, and fat; their stomachs stop working properly; and moaning with asthma and indigestion they fancy that equilibrium is within reach - and almost reached. So much for science, the last flower and ossification of culture.

G.U.T. is WAR!

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Getting rid of causality?

[sab39]

I remember reading an article some time ago in which a scientist proposed that Quantum Physics could actually be a natural corollary of General Relativity (where each particle is some kind of "ripple" in the space-time continuum), and that the mathematics of this could make sense if the requirement for Causality ("cause must happen before effect") were dropped from General Relativity.

His proposal suggested that quantum coupling (where two particles can become intertwined based on an earlier interaction) was caused by some kind of ripple-effect going back in time from the observed particle to the time that the original interaction happened.

He was able to explain many other aspects of Quantum Physics the same way, although he claimed that the mathematics was so complex that only the simplest of interactions had been formally proved to match between his model and QP - most of his theory, including the explanation of coupling, was hand-waving.

I always thought that this theory seemed one of the most elegant I've ever heard - no need to introduce new hypothetical particles like Strings, no need to assume that all the complexities of the Standard Model are fixed, absolute and arbitrary. Just take General Relativity, drop Causality, and look at what emerges.

I've often wondered whether this guy's theory ever went anywhere. It seems to have something in common with the theory proposed in this article - that QP is just an "emergent behavior" from GR. The difference is that the article seems to propose that there is no underlying rule at all except chaos and GR itself emerged from that; this guy proposed that GR was fundamental and QP was the emergent behavior.

Anyone know anything about this theory or know where the original article might be? Did this guy have any success or get any recognition? Has his theory been actually disproved, or simply ignored?

Stuart.

Re:Creationists...We've been here before

[darkPHi3er]

In the late 19th century, Albert A Michelson, according to many the "Greatest" physicist of his time (and winner of the first Nobel prize in Physics (1907), decided to measure the speed of light...in 1878, he did so accurately for the first time, he was using about $10.00 of lab equipment, btw...his passion for accuracy and precision led to his teaming up with Edward W. Morley, in 1878 to prove the existence of the cosmic "ether", through the....

Michelson-Morley Experiment. Michelson's career had been golden, and he was widely regarded as the best physicist of the 19th century. So, everyone "knew" that he would successfully prove the existence of the cosmic "ether", which would be the finally block in the edifice of Classical Newtonian physics...

instead, the experiment went completeley wrong, conclusively proved the lack of the cosmic ether, and Newton was kicked to the gutter (as an explanation for sub-macroscopic events)...

here's a link to a pretty good, non-technical account of this from U of Va....http://galileoandeinstein.physics.virginia.e du/lectures/michelson.html.....there's also a great page on Michelson here;....http://hum.amu.edu.pl/~zbzw/ph/sci/aam.ht m

In the 1950's, in the particle chambers of UCLA, strange traces were seen on the photograpic plates of particle collisions....physics of the time couldn't account for this particle, so the postdocs and the grad students waggishly nicknamed the unknown particle the "what-on", and many ignored it for over 20 years...

as instumentation and our undestanding of sub-nuclear particles became better, some other grad students, looking for new frontiers (and new dissertation topics), started researching the "what-on"...it has become....

The Quark and is now the center of the posh new "String Theory", which is yet another attempt to explain overall particle to particle interaction,and from the standpoint of "Classical Quantum Dynamics", Superstring theory kicks QD to the curb....here we go again.....

here's a good page on String Theory
http://superstringtheory.com/

the point being...these things we are discussing are so far beyond our abilities to directly sense or measure them, it's like the old story of the scientists examining an elephant in a lightless, closed room...

one scientist grabs the tail and thinks its a thin, long snake, another scientist grabs a tusk and thinks its a rhino, another grabs the trunk and thinks its a python...

since we have no ability to directly "view" or "measure" these things, we are using inference and deduction to provide us with our theories, yet as every generation of instrumentation improves and gives us new "information" we take that info and rework it...

face it, we could come up with a "Unified Theory" that completely explains our current "knowledge" about physics, to the satisfaction of 99% of the scientists on the face of the earth and....

it could be kicked over by some new experiment, just the way that Michelson-Morely kicked over "Classical" Physics...

Un Anticipated Consequences

[Alien54]

This all seems to be fall out and unanticipated consequences of various things:

1) the various quantum tunneling experiments, where the Mozart 40th Symphony was transmitted through solid metal at several times the speed of light. There is a good link here. There was even a NOVA special or something on that (see that transcript here, - info about 2/3rds into the material)

2) maybe something involving the research of Steven Wolfram (developer of Mathematica), as seen in his forth coming book A New Kind of Science, which is very geeky, very bizarre, and right up this alley, and is supposed to be a rethinking of the very fundamentals of how science works. My head hurts already. This book is due for publication in January 2002, and is well worth pre-ordering.

Re:a breath of fresh air

[Some guy named Chris]

i never liked the big bang theory. it stinks of creationism. ... i'm no cosmologist. but the big bang stinks of creationism to me ...

So, let me get this straight. You are rejecting a reasonable theory which fits the observed behaviours simply because it conflicts with your religious (or anti-religious) beliefs?

Isn't that what people accuse religious folks of daily?

You aren't being logically consistant. You rail against anything with any hint of taint from our human experience, but at the same moment your rejection is based in how you feel about the existing theories. Stinks of creationism is a very visceral reaction to what you insist should be a completely rational debate.

Face it. You have a philosophy guiding your argument as well. That philosophy is Nihilism and your post stinks of it.