My apologies ...
 

... for not posting a political thread, but I found this interesting.

Bot

Theory in particle physics: Theological speculation versus practical knowledge

Burton Richter
October 2006, page 8


To me, some of what passes for the most advanced theory in particle physics these days is not really science. When I found myself on a panel recently with three distinguished theorists, I could not resist the opportunity to discuss what I see as major problems in the philosophy behind theory, which seems to have gone off into a kind of metaphysical wonderland. Simply put, much of what currently passes as the most advanced theory looks to be more theological speculation, the development of models with no testable consequences, than it is the development of practical knowledge, the development of models with testable and falsifiable consequences (Karl Popper's definition of science). You don't need to be a practicing theorist to discuss what physics means, what it has been doing, and what it should be doing.

When I began graduate school, I tried both theory and experiment and found experiment to be more fun. I also concluded that first-rate experimenters must understand theory, for if they do not they can only be technicians for the theorists. Although that will probably get their proposals past funding agencies and program committees, they won't be much help in advancing the understanding of how the universe works, which is the goal of all of us.

I like to think that progress in physics comes from changing "why" questions into "how" questions. Why is the sky blue? For thousands of years, the answer was that it was an innate property of "sky" or that the gods made it so. Now we know that the sky is blue because of the mechanism that preferentially scatters short-wavelength light.

In the 1950s we struggled with an ever-increasing number of meson and baryon resonances—all apparently elementary particles by the standards of the day. Then Murray Gell-Mann and George Zweig produced the quark model, which swept away the plethora of particles and replaced them with a simple underlying structure. That structure encompassed all that we had found, and it predicted things not yet seen. They were seen, and the quark model became practical knowledge. Why there were so many states was replaced with how they came to be.

A timelier example might be inflation. It is only slightly older than string theory and, when created, was theological speculation, as is often the case with new ideas until someone devises a test. Inflation was attractive because if it were true it would, among other things, solve the problem of the smallness of the temperature fluctuations of the cosmic microwave background radiation. Inflation was not testable at first, but later a test was devised that predicted the size and position of the high angular harmonic peaks in the cosmic microwave background radiation. When those were found, inflation moved from being theological speculation to a kind of intermediate state in which all that is missing to make it practical knowledge is a mathematically sound microscopic realization.

The general trend of the path to understanding has been reductionist. We explain our world in terms of a generally decreasing number of assumptions, equations, and constants, although sometimes things have gotten more complicated before they became simpler. Aristotle would have recognized only what he called the property of heaviness and we call gravity. As more was learned, new forces had to be absorbed—first magnetic, then electric. Then we realized that the magnetic and electric forces were really the electromagnetic force. The discovery of radioactivity and the nucleus required the addition of the weak and strong interactions. Grand unified theories have pulled the number back down again. Still, the general direction is always toward the reductionist—understanding complexity in terms of an underlying simplicity.

The last big advance in model building came a bit more than 30 years ago with the birth of the standard model. From the very beginning it, like all its predecessors, was an approximation that was expected to be superseded by a better one that would encompass new phenomena beyond the standard model's energy range of validity. Experiment has found things that are not accounted for in it—neutrino masses and mixing and dark matter, for example. However, the back-and-forth between experiment and theory that led to the standard model ended around 1980. Although many new directions were hypothesized, none turned out to have predicted consequences in the region accessible to experiments. That brings us to where we are today, looking for something new and playing with what appear to me to be empty concepts like naturalness, the anthropic principle, and the landscape.

More at: http://www.physicstoday.org/vol-59/iss-10/p8.html

Hey Bot,
Some reading I have done in more or less popular literature on hyperspace and such leads to me understand that mathematicians can prove, or demonstrate the existance of more then the 3 or 4 dimensions we experience. Something about some extremely complex equations explaining behaviors in our universe become very simple in 5 or 6 dimensions.
Can you explain it any simpler than the books i read?
How many dimensions really might exist? Can you even imagine how to think what 5 or 6 or more dimension might be like? I admit it; I am a creaure in 3 or 4 dimensions ( time may, or may not be the 4th). I can imagine a 2 dimensional world ( stick figures on a sheet of paper) but I can't even imagine more than I have experienced.

If you are going to post a non-political thread, lets make it a doosey.

I read the section posted, but not the whole piece yet, but I need to. It seems to me that he is pointing to an inherent problem as theory gets more and more universal, general and abstract. If the theory is correct and explains all events then the theory will not in fact be falsifiable because all events will verify it. This is precisely the problem he seems to find in theology and to a large degree he is correct, but not completely. If theology responds with a modification to its theory in order to accomodate problems that have been raised in testing the theory, then theology is doing a very similar thing to what physicists do. The reason that the problem is more apparent in theology is that concepts of God are always universal with all encompassing implications, whereas in physics, hypotheses often deal with very specific events and explanations and aren't attempting to generate a grand universal theory. When physics does turn to universal grand theory there isn't a sharp line of demarcation between physics and theology. The sharp line of demarcation is largely sociological and cultural, not theoretical. The line is made because theologians are often just interested in preserving a tradition and physicists are often just interested in revising traditions. The best example I can think of in a modern thinker who blurred the distinction is A. N. Whitehead

Time is most definitely a dimension (no 'may, or may not be'), and mathematicians can certainly not prove the existence of unseen physical dimensions. M-Theory, which has broad support from physicists, requires at least 11 dimensions, but the existence of those dimensions remains the single biggest detractive factor from M-Theory support.

For a long time I've had similar feelings about the frontiers of quantum physics and cosmology. I have no college education so cannot comment on the mathamatics involved but I think that it is so advanced that it has long superceded the ability of spoken languages to translate it into concepts of which the great unwashed can achieve a meaningful understanding.

This is something I've often discussed with an old high school friend of mine who is now a professor of astrophysics at UCLA. Himself very much a theorist. I wonder if in fact much of the most advanced theories are inherently understandable outside of pure mathamatics. If not, then how does one differentiate them from the morass of metaphysical philosophy?

- Peter.

Actually, one of the greatest leaps of string theory is it's differentiation from pure mathematics. This may seem silly, but pre-string theory quantum physics treated "particles" as mathematical points, ignoring their capacity to occupy space. This distinction has profound ramifications and solves many of the problems quantum physics had previously presented. For example, while you can plot an infinite number of mathematical points on the surface of a sphere, there is a finite limit to the number of strings that can occupy that same space.

pj67coll explains my own beliefs pretty succinctly. From my perspective, believing that some theoretical physical model is better than some other is like me opining that Shintoism is better than Catholicism. I do not have enough understanding to make more than a faithful guess. My study of physics ended with intro physics for science majors. I made excellent grades and it was a wonderful course, quite rigorous, and gave me a valuable lesson in humility. It stood athwart a elegantly structured bridge across a vast canyon and stared me down like Gandalf, "Though shall not pass." I made a bargain, give me a good grade in this class and I promise never to venture into your landscape again.

Anyway, here's the section of that essay that concerns itself with String Theory, to which I believe you were alluding.

Bot

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String theory was born roughly 25 years ago, and the landscape concept is the latest twist in its evolution. Although string theory needed 10 dimensions in order to work, the prospect of a unique solution to its equations, one that allowed the unification of gravity and quantum mechanics, was enormously attractive. Regrettably, it was not to be. Solutions expanded as it was realized that string theory had more than one variant and expanded still further when it was also realized that as 3-dimensional space can support membranes as well as lines, 10-dimensional space can support multidimensional objects (branes) as well as strings. Today, there seems to be nearly an infinity of solutions, each with different values of fundamental parameters, and no relations among them. The ensemble of all these universes is known as the landscape.

No solution that looks like our universe has been found. No correlations have been found such as, for example, if all solutions in the landscape that had a weak coupling anywhere near ours also had a small cosmological constant. What we have is a large number of very good people trying to make something more than philosophy out of string theory. Some, perhaps most, of the attempts do not contribute even if they are formally correct.

I still read theory papers and I even understand some of them. One I found particularly relevant is by Stephen Hawking and Thomas Hertog. Their recent paper "Populating the Landscape: A Top-down Approach" starts with what they call a "no boundary" approach that ab initio allows all possible solutions.3 They then want to impose boundary conditions at late times that allow our universe with our coupling constants, number of noncompact dimensions, and so on. This approach can give solutions that allow predictions at later times, they say. That sounds good, but it sounds to me a lot like the despised fine-tuning. If I have to impose on the landscape our conditions of three large space dimensions, a fine structure constant of 1/137, and so on, to make predictions about the future, there would seem to be no difference between the landscape and effective field theory with a few initial conditions imposed.

Although the Hawking and Hertog paper sometimes is obscure to me, the authors seem to say that their approach is only useful if the probability distribution of all possible alternatives in the landscape is strongly peaked around our conditions. I'll buy that.

To the landscape gardeners I say: Calculate the probabilities of alternative universes, and if ours does not come out with a large probability while all others with content far from ours come out with negligible probability, you have made no useful contribution to physics. It is not that the landscape model is necessarily wrong, but rather that if a huge number of universes with different properties are possible and equally probable, the landscape can make no real contribution other than a philosophic one. That is metaphysics, not physics.

We will soon learn a lot. Over the next decade, new facilities will come on line that will allow accelerator experiments at much higher energies. New non-accelerator experiments will be done on the ground, under the ground, and in space. One can hope for new clues that are less subtle than those we have so far that do not fit the standard model. After all, the Hebrews after their escape from Egypt wandered in the desert for 40 years before finding the promised land. It is only a bit more than 30 since the solidification of the standard model.

There is another significant distinction. Science is 90% exploration and 10% explanation. It is a discipline that attempts to discover the truths around us. Western theology OTOH, is 0% exploration, and 100% explanation. You cannot modify "the truth" -- it is either the truth or it isn't. Any modification whatsoever, proves that it isn't. One cannot debunk science, theology tends to debunk itself.

?? Vice Versa? I see theology as more of a creative discipline not unlike science. The institutions of religion are conservative and seek to ossify theology but the theologians themselves have very often been very creative thinkers. Science does not have the same institutional hierarchy committed to the preservation of tradition so it is more open to change. Conflicts between competing theologies in the world's religions which are obvious to everyone as a result of modern communication may push theology back into a creative phase.

You're right, I was confusing theological discipline with presentation. I cannot recall the presentation of western religious dogma as "theory". Theories grow, change, fall by the wayside, but the presentation of the word of god does not typically allow for such disparities. If the word of god is exactly that, there is no allowance for error, therefore no room for modification.

One day some mathematician is going to have a solution that states that we do not exist - then, we'll be in real trouble!



Or....maybe not....since there are an infinite number of parallel universes (and these are infinitely "close" to one another), we might not even notice the loss of a few million. Just by thinking of the possibility, I just killed of a few hundred thousand, and the more I think of it, the more go. And now that you have just read this, a few more hundred thousand just dissappeared. This is turning into genocide. :eek:

I must have missed something in that essay that you folks found. The way I read it the essayist has divided physics theoreticians into two groups, one of which is what he terms, theological" in the sense that they have a sort of faith, rather than experimental observations, that theories will work out. He then proceeds to describe several instances of what he believes are examples of that sort of thinking.

B

the "sort of faith", sounds like intuition to me.

Then again... why not use intuition? I would think that (as a theorist/physicist of many years) after a while, you develop some sort of sense if something will work or not; or in the least, if there is the need for further exploration.
I bet that many of us use intuition on a daily basis - I know I use it for something as simple as predicting what highway lane will be most advantageous. Often times I have to use it to figure out the intent of a post here in the forum.

So.. yea...let them use intuition....betcha they are alot better at it than most of us. (As long as they don't think us out of existance)

No, we just went off on a brief tangent. The author is undoubtedly correct, and the reason is simple. Our thirst for knowledge has exceeded our ability to acquire it.

The 'landscape' he refers to has M-Theory in the middle, and a half dozen variants of string theory along the periphery of a metaphysical cytoplasmic blob. They overlap and offer bizarre inverse relationships with each other. The idea is that each theory is correct from it's particular perspective, but that we presently lack the additional perspectives required to piece them together into a cohesive truth.

The fact that this is undoubtedly wishful thinking doesn't automatically disqualify it, especially since nothing more attractive has come along. In the meantime, I have no doubt that important advancements have come from string theory, whether it ultimately pans out or not. At the very least, string theory and its variants will prove wildly useful tangents that may one day lead us to the desperately sought after GUT.

I saw a program once on String and M-theory. It takes a while before you can wrap your mind around it. If anything, it makes you realize how small and insignificant you could be.
It also makes me postulate that all those theories are merely puzzle pieces to a big picture (if you will), and I wonder if we as humans are actually equipped enough to wrap our minds around it. I'm thinking that the more removed it is from the dimensions that we are a part of/are familiar with, the more difficult it is to completely understand (grok) those dimensions.

The way I see it, the universe is so large and time so great, that even if there is only the one universe and only the one time, it will never be possible for man to fully understand it. That problem multiplies with each additional universe that is "real." If there is an infinity of universes, well then, we have an infinity of undefinability, whatever that means. I am reminded of Tom Hank's character in "Joe vs the Volcano," hallucinating while looking at the sky and saying, "I didn't know it was so big."

At the same time, I believe that it is possible to understand any given aspect of it. For example, we may gain a GUT understanding, but that is hardly the last word in complexity. Rather, it is the first step in understanding the universe from it's most fundamental processes. Maybe what I am saying is some sort of corollary of the Uncertainty Principle, in which it is possible to understand some process or other in its entirety or grasp the complexity of the whole problem, but never both at once.

Finally, if the universe is too complex to ever be understood by the mind of man, how is that different from theology?

I defer to our doctor of divinity in regard to your question, who is infinitely more qualified than I to provide a thoughtful response.

[lysergicism]Would the acquisition of all knowledge mean the death of science? Would the acquisition of all knowledge mean the death of theology? Does the answer to each question depend on the nature of that knowledge? [/lysergicism]

Do you mean 'photon' rather than 'electron'?

De Broglie Waves.

http://hyperphysics.phy-astr.gsu.edu/hbase/debrog.html

One day Rene Descartes was eating lunch in a small cafe at the side of the road. After he had finished the waiter approached and asked, "Msr. Descartes, have you had enough today? Would you like anything else?".

Descartes replied, "Thank you, I think not."


And promptly dissappeared.

**

There's a quote from someone, can't remember who or exactly how it goes. The gist is that "when science finally crests the hill of exploration and finds the ultimate truth it will meet face to face with religion". Anyone able to ID that quote? Source/text?

Don't know the source of that quotation, but got a good laugh over the Descartes story. Thanks.

Like the guy who preferred philosophy to Latin: Put Descartes before the Horace.

Or the veterinarian who tried to teach philosophy to a horse. Didn't work. Can't put Descartes before the horse.

Government grant?

I prefer mnemonics to help me remember my philosophers...

Immanuel Kant was a real pissant
Who was very rarely stable.

Heidegger, Heidegger was a boozy beggar
Who could think you under the table.

David Hume could out-consume
Wilhelm Friedrich Hegel,
And Wittgenstein was a beery swine
Who was just as schloshed as Schlegel.

There's nothing Nietzsche couldn't teach ya
'Bout the raising of the wrist.
Socrates, himself, was permanently pissed.

John Stuart Mill, of his own free will,
On half a pint of shandy was particularly ill.

Plato, they say, could stick it away--
Half a crate of whisky every day.

Aristotle, Aristotle was a bugger for the bottle.
Hobbes was fond of his dram,

And René Descartes was a drunken fart.
'I drink, therefore I am.'

Yes, Socrates, himself, is particularly missed,
A lovely little thinker,
But a bugger when he's pissed.

With thanks to Monty Python.

Golly, I don't remember that skit. Kerry, can you name it? I'd like to see it.

B

Excellent, thanks!

I remember it from Live at the Hollywood Bowl, sung by "Bruce" the Aussie with the cork hat.

Geometry is all
Nov 22nd 2007
From The Economist print edition

A shape could describe the cosmos and all it contains

ONE of the mysteries of the universe is why it should speak the language of mathematics. Numbers and the relationships between them are, after all, just abstract reasoning. Yet mathematics has shown itself to be particularly adept at describing both the contents of the universe and the forces that act on them. Now comes a paper which argues that one branch of the subject—geometry—could form the basis of all the laws of physics.

Physicists are an overbearing bunch. They have long sought a “theory of everything”. Such an opus would unite the fundamental forces—gravity, electromagnetism and the two forces that become apparent only at the atomic scale—with the matter on which they act, in a single, overarching framework. It would describe the universe as it existed at the moment of its creation in the Big Bang.


The nearest thing they have to this—the Standard Model of particle physics—is messy in places and partial, because it omits gravity. Three decades of effort have been expended on string theory, which includes gravity but at the expense of having the universe inelegantly sprout hidden dimensions. Other potential avenues, such as loop quantum gravity, are also proving untidy. That a theory of everything might emerge from geometry would be neat, but it is a long shot.

Nevertheless, that is what Garrett Lisi is proposing. The geometry he has been studying is that of a structure known to mathematicians as E8, which was first recognised in 1887 by Sophus Lie, a Norwegian mathematician. E8 is a monster. It has 248 dimensions and its structure took 120 years to solve. It was finally tamed earlier this year, when a group of mathematicians managed to construct a map that describes it completely.

Dr Lisi had been tinkering with some smaller geometries. Soon after reading about this map, however, he realised that the structure of E8 could be used to describe fully the laws of physics. He placed a particle (including different versions of the same entities, and using particles that describe matter and those that describe forces) on most of the 248 points of E8. Using computer simulations to manipulate the structure, he was able mathematically to generate interactions that correspond to what is seen in reality.

Using geometry to describe the world is not new. Murray Gell-Mann performed a similar trick 50 years ago in an attempt to make sense of the plethora of particles that was then emerging from experiments. He placed these on the points of a geometric structure known as SU(3), and found that, by manipulating the structure, he was able to reproduce the interactions of the real world. Dr Gell-Mann also identified points that had no known particles associated with them—and predicted the existence of particles that would fill those gaps. He was awarded the Nobel prize after they were detected. Interestingly, some 20 gaps remain in Dr Lisi's model. That suggests that 20 particles (or, at least, 20 different identities of particles) have yet to be discovered. If Dr Lisi can calculate the masses of these, he will have made predictions that can be tested experimentally.

The particles must be relatively massive, because they would otherwise have been discovered already. Detecting massive objects takes energy. (Einstein's famous equation, E=mc2, outlines how energy is equivalent to mass times the square of the speed of light.) When it is completed, the Large Hadron Collider, a machine being built at CERN, the European particle physics laboratory near Geneva, will create particles with greater masses than have yet been seen. It is due to start its scientific work in the summer of 2008, so a test of Dr Lisi's theory could come soon.

Although some famous physicists are championing the idea, Dr Lisi, who spends his time surfing and snowboarding and is not employed by a university or research institute, has by no means won the acceptance of all physicists. His work, which has been posted on the internet, has not yet been accepted for publication in any journal, although he has presented his ideas at research institutes and the work on which his paper is based was funded by a grant from a charitable foundation.

Certainly, there are glitches with Dr Lisi's analysis and some of the truly fundamental problems that plague more conventional work remain. Yet the theory has several appealing facets. It is elegant. It is expected to make testable predictions. Unlike some of the more complicated efforts to devise a theory of everything, this one should either succeed relatively rapidly or fail spectacularly. And that is more than can be said for three decades of work by other physicists.