[From Bill Powers (931224.1030 MST)]

I recommend

Lindley, David; _The End of Physics: the myth of a unified

theory_. New York: BasicBooks, a division of Harper-Collins

(1993).

Lindley works for _Nature_.

Some of the next-to-last paragraph of the book is worth quoting:

The ideal theory of everything, in the minds of the

physicists searching for it, is a mathematical system of

uncommon tidiness and rigor, which may, if all works out

correctly, have the ability to accomodate the physical facts

we know to be true in our world. The mathematical neatness

comes first, the practical explanatory power second. Perhaps

physicists will one day find a theory of such compelling

beauty that its truth cannot be denied; truth will be beauty

and beauty will be truth -- because, in the absence of any

means to make practical tests, what is beautiful is declared

ipso facto to be the truth. (p. 255)

This book contains a long and careful analysis of the history of

physics -- how it got to be the way it is. Lindley emphasizes

periodically that the complexities of "fundamental" (i.e.,

particle) physics have never been invented for the fun of it;

physicists have always been trying to find the simplest

explanation they could find. The complexity of nature, says

Lindley, simply requires a complex theory. This is a very

charitable view, but I think it is open to question. I'm not sure

that Lindley meant it to be taken seriously.

One hint that he didn't comes in his observation that physicists

seem to treat the current state of particle theory as if it is

"ground zero" -- that is, to be taken as given without any

further attempt to explain why. This puts physics alone among the

sciences in declaring deeper questions to be out of bounds.

There were numerous places during the historical discussions

where I wished that physicists had spent more time asking why

before they settled on an official view. Starting with the

troubles that led to the special theory of relativity, some

physicists seemed to become suddenly impatient with the slow

march of progress; it's as though they wanted to leapfrog the

usual way of going, to skip all the explorations of simple

problems, to get on with it. This is when the theoretical

explorations began to develop their own life, with longer and

longer stretches of uninterrupted computation being used to

bridge longer and longer gaps between experimental

demonstrations. The world of observation and direct experience,

which is the only ultimate anchor for any theoretical framework,

began to fade into the background. A smaller and smaller

percentage of the critical assumptions were put to test; the

number and variety of actual phenomena involved got smaller and

smaller.

I wish, for example, that when the quantum nature of some

phenomena was discovered, physicists had taken more time to ask

how this kind of phenomenon might be generated in a continuous

universe, instead of instantly giving up on continuity. There are

many possibilities; think of standing waves in a string, which

occur only in whole-number ratios, yet are completely explainable

in terms of continuous relationships. Perhaps physicists were

still in shock from the discovery of the constancy of the speed

of light; perhaps those who were happy to see the old Newtonian

scheme collapse (something of an exaggeration) were just the sort

who would seize on other apparent breaks with tradition without

asking too closely whether they were also necessary.

On the surface, the ideas that came out of Copenhagen are very

much in line with PCT. We know only what we can observe; the

universe itself is unknowable. If we can't simultaneouly measure

position and momentum, then we must accept that our observed

universe is basically uncertain. If we are limited to the

calculation of probabilities, then the world we are given to

analyze is probabilistic.

The odd thing about this latter assumption is that the main tool

of quantum physics, the Schroedinger wave equation, is basically

a continuous equation, with continuous derivatives. A conscious

decision was made to treat it not as a description of a

continuous phenomenon, but as a description of a probability

distribution. All at once, physicists started wearing quantized

and probability-colored glasses, apparently unaware that the same

principle applied: you see the world that is constructed by human

perceptions. The view through these spectables quickly came to

dominate physics; it was accepted that the world was

fundamentally quantized, not Einsteinian.

Lindley notes one of the penalties for this decision: general

relativity (which is about a continuous if distorted universe)

and quantum mechanics remain at odds with each other. The Big

Bang, according to general relativity, would have had to start

with a singularity. Quantum mechanics can't allow that

singularity to exist: only a finite probability cloud could have

existed.

The way quantum mechanics gets around the problem of

singularities is to use a trick that has had to be used often

during its development. Well, the physicists say, we know that

there was no singularity at t = 10^-24 sec, so we'll just

normalize to that time and forget about what happened earlier.

This same problem arose in trying to describe the electron in

quantum-mechanical terms. When the equations were solved, more or

less, infinities immediately cropped up, both in modeling a

single electron and in modeling the distributions of multiple

electrons around the same atom. So someone decided that if the

wave function could be defined at some small distance from the

singularity, we could just forget about the infinities. This was

"renormalization."

In ordinary physics we have a similar problem. If a gravitation

field falls off as the inverse square of distance, what is the

gravitational field at the center of a mass? Infinity, of course.

For macro phenomena, the solution is easy: you recall that a

planet's mass is distributed, so when the distance shrinks to

less than the radius of the planet, the amount of mass

contributing to the field also shrinks and the field goes to zero

at the center of the planet. This leaves the description

believable all the way from infinite distance to zero distance.

But in quantum mechanics this solution was not available, or for

some reason was not considered. Since everything had to consist

of particles, infinities cropped up everywhere (until string

theories appeared), and one had to find an excuse for this

failing of the theoretical representation, or a way to ignore it.

This, I think, is where physics starting getting (a) sloppy, and

(b) mystical. Instead of admitting that there was a problem with

the model, physicists started drawing a veil of mathematics

across the scene. Renormalization was used basically because

without it, the theory failed. The Schroedinger wave equation was

transformed from a mathematical expression into an illuminated

script on an altar. At that level of analysis, all search for an

alternative description that would not bring up those ugly

infinities was halted. Nobody ever seemed to think that they

might have been created by the theory: by the Schoedinger

equation itself.

All these heretical ideas are mine, not Lindley's. Lindley does

not address the issue of what might have been or what the

critical decisions were in the development of fundamental

physics. In fact, Lindley doesn't speak about the influence of

the very early adoptions of premises in creating the difficulties

that physicists have had ever since. Nor does he remark on the

way in which the world of experimental quantum physics has shrunk

until all it seems concerned with is the discovery of a new

particle at longer and longer intervals.

He does point out that one of the latest gimmicks, supersymmetry,

seems to have put an end to experimental particle physics. As

soon as supersymmetry was invented, every known particle in

existence suddenly acquired an imaginary companion particle. The

least energetic of these new particles might possibly be

observable using a supercollider. Observing the rest of them

would require increasing the collision energy by a factor of

trillions. This means that supersymmetry will just have to remain

a figment of the imagination -- beautiful in the eyes of the

physicist, perhaps, but unverifiable. There is therefore nothing

left to prevent physicists from completing the grand unified

theory of everything. All that is now required is that it be

internally consistent, like any systematic delusion. Nature need

no longer be consulted.

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Best,

Bill P.