«

"Ron Adam" <> wrote in message
news:cTp4f.16180$. ..
> Christian Stapfer wrote:
>
>> This discussion begins to sound like the recurring
>> arguments one hears between theoretical and
>> experimental physicists. Experimentalists tend
>> to overrate the importance of experimental data
>> (setting up a useful experiment, how to interpret
>> the experimental data one then gathers, and whether
>> one stands any chance of detecting systematic errors
>> of measurement, all depend on having a good *theory*
>> in the first place). Theoreticians, on the other hand,
>> tend to overrate the importance of the coherence of
>> theories. In truth, *both* are needed: good theories
>> *and* carefully collected experimental data.
>>
>> Regards,
>> Christian
>
> An interesting parallel can be made concerning management of production vs
> management of creativity.
>
> In general, production needs checks and feedback to insure quality, but
> will often come to a stand still if incomplete resources are available.
>
> Where as creativity needs checks to insure production, but in many cases
> can still be productive even with incomplete or questionable resources.
> The quality may very quite a bit in both directions, but in creative
> tasks, that is to be expected.
>
> In many ways programmers are a mixture of these two. I think I and Steven
> use a style that is closer to the creative approach. I get the feeling
> your background may be closer to the production style.
>
> Both are good and needed for different types of tasks. And I think most
> programmers can switch styles to some degree if they need to.

Come to think of an experience that I shared
with a student who was one of those highly
creative experimentalists you seem to have
in mind. He had just bought a new PC and
wanted to check how fast its floating point
unit was as compared to our VAX. After
having done his wonderfully creative
experimenting, he was utterly dejected: "Our (old)
VAX is over 10'000 times faster than my new PC",
he told me, almost in despair. Whereupon I,
always the uncreative, dogmatic theoretician,
who does not believe that much in the decisiveness
of the outcome of mere experiments, told him
that this was *impossible*, that he *must* have
made a mistake...

It turned out that the VAX compiler had been
clever enough to hoist his simple-minded test
code out of the driving loop. In fact, our VAX
calculated the body of the loop only *once*
and thus *immediately* announced that it had finished
the whole test - the compiler on this student's
PC, on the other hand, had not been clever enough
for this type of optimization: hence the difference...

I think this is really a cautionary tale for
experimentalists: don't *believe* in the decisiveness
of the outcomes your experiments, but try to *understand*
them instead (i.e. relate them to your theoretical grasp
of the situation)...

Regards,
Christian

Christian Stapfer wrote:

> As to the value of complexity theory for creativity
> in programming (even though you seem to believe that
> a theoretical bent of mind can only serve to stifle
> creativity), the story of the discovery of an efficient
> string searching algorithm by D.E.Knuth provides an
> interesting case in point. Knuth based himself on
> seemingly quite "uncreatively theoretical work" (from
> *your* point of view) that gave a *better* value for
> the computuational complexity of string searching
> than any of the then known algorithms could provide.

are you talking about KMP? I'm not sure that's really a good example of
how useful "theoretical work" really is in practice:

- Morris had already implemented the algorithm (in 196 when Knuth "dis-
covered" it (1971 or later), so the "then known" part of your argument is
obviously bogus. "then known by theoretical computer scientists" might
be correct, though.

- (iirc, Knuth's first version wasn't practical to use; this was fixed by Pratt)

- (and iirc, Boyer-Moore had already been invented when Knuth published the
first paper on KMP (in 1977))

- for use cases where the setup overhead is irrelevant, Boyer-Moore is almost
always faster than KMP. for many such cases, BM is a lot faster.

- for use cases such as Python's "find" method where the setup overhead cannot
be ignored, a brute-force search is almost always faster than KMP.

- for use cases such as Python's "find" method, a hybrid approach is almost
always faster than a brute-force search.

in other words, the "better" computational complexity of KMP has turned out
to be mostly useless, in practice.

</F>

On Sun, 16 Oct 2005 15:16:39 +0200, Christian Stapfer wrote:

> Come to think of an experience that I shared
> with a student who was one of those highly
> creative experimentalists you seem to have
> in mind. He had just bought a new PC and
> wanted to check how fast its floating point
> unit was as compared to our VAX. After
> having done his wonderfully creative
> experimenting, he was utterly dejected: "Our (old)
> VAX is over 10'000 times faster than my new PC",
> he told me, almost in despair.

Which it was. It finished executing his code in almost 1/10,000th of the
time his PC could do.

> Whereupon I,
> always the uncreative, dogmatic theoretician,
> who does not believe that much in the decisiveness
> of the outcome of mere experiments, told him
> that this was *impossible*, that he *must* have
> made a mistake...

It wasn't a mistake and it did happen. The VAX finished the calculation
10,000 times faster than his PC. You have a strange concept of "impossible".


> It turned out that the VAX compiler had been
> clever enough to hoist his simple-minded test
> code out of the driving loop.

Optimizations have a tendency to make a complete mess of Big O
calculations, usually for the better. How does this support your
theory that Big O is a reliable predictor of program speed?

For the record, the VAX 9000 can have up to four vector processors each
running at up to 125 MFLOPS each, or 500 in total. A Pentium III runs at
about 850 Mflops. Comparing MIPS or FLOPS from one system to another is
very risky, for many reasons, but as a very rough and ready measure
of comparison, a four processor VAX 9000 is somewhere about the
performance of a P-II or P-III, give or take some fudge factor.

So, depending on when your student did this experiment, it is entirely
conceivable that the VAX might have been faster even without the
optimization you describe. Of course, you haven't told us what model VAX,
or how many processors, or what PC your student had, so this comparison
might not be relevant.



> In fact, our VAX
> calculated the body of the loop only *once*
> and thus *immediately* announced that it had finished
> the whole test - the compiler on this student's
> PC, on the other hand, had not been clever enough
> for this type of optimization: hence the difference...

Precisely. And all the Big O notation is the world will not tell you that.
Only an experiment will. Now, perhaps in the simple case of a bare loop
doing the same calculation over and over again, you might be able to
predict ahead of time what optimisations the compiler will do. But for
more complex algorithms, forget it.

This is a clear case of experimentation leading to the discovery
of practical results which could not be predicted from Big O calculations.
I find it quite mind-boggling that you would use as if it was a triumph
of abstract theoretical calculation when it was nothing of the sort.


> I think this is really a cautionary tale for
> experimentalists: don't *believe* in the decisiveness
> of the outcomes your experiments, but try to *understand*
> them instead (i.e. relate them to your theoretical grasp
> of the situation)...

Or, to put it another way: your student discovered something by running an
experimental test of his code that he would never have learnt in a million
years of analysis of his algorithm: the VAX compiler was very cleverly
optimized.

The fact that your student didn't understand the problem well enough to
craft a good test of it is neither here nor there.



--
Steven.

Christian Stapfer wrote:
> "Ron Adam" <> wrote in message
> news:cTp4f.16180$. ..
>
>>Christian Stapfer wrote:
>>
>>
>>>This discussion begins to sound like the recurring
>>>arguments one hears between theoretical and
>>>experimental physicists. Experimentalists tend
>>>to overrate the importance of experimental data
>>>(setting up a useful experiment, how to interpret
>>>the experimental data one then gathers, and whether
>>>one stands any chance of detecting systematic errors
>>>of measurement, all depend on having a good *theory*
>>>in the first place). Theoreticians, on the other hand,
>>>tend to overrate the importance of the coherence of
>>>theories. In truth, *both* are needed: good theories
>>>*and* carefully collected experimental data.
>>>
>>>Regards,
>>>Christian
>>
>>An interesting parallel can be made concerning management of production vs
>>management of creativity.
>>
>>In general, production needs checks and feedback to insure quality, but
>>will often come to a stand still if incomplete resources are available.
>>
>>Where as creativity needs checks to insure production, but in many cases
>>can still be productive even with incomplete or questionable resources.
>>The quality may very quite a bit in both directions, but in creative
>>tasks, that is to be expected.
>>
>>In many ways programmers are a mixture of these two. I think I and Steven
>>use a style that is closer to the creative approach. I get the feeling
>>your background may be closer to the production style.
>
>
> This diagnosis reminds me of C.G. Jung, the psychologist,
> who, after having introduced the concepts of extra- and
> introversion, came to the conclusion that Freud was
> an extravert whereas Adler an introvert. The point is
> that he got it exactly wrong...
>
> As to the value of complexity theory for creativity
> in programming (even though you seem to believe that
> a theoretical bent of mind can only serve to stifle
> creativity), the story of the discovery of an efficient
> string searching algorithm by D.E.Knuth provides an
> interesting case in point. Knuth based himself on
> seemingly quite "uncreatively theoretical work" (from
> *your* point of view) that gave a *better* value for
> the computuational complexity of string searching
> than any of the then known algorithms could provide.
>
> Regards,
> Christian


> (even though you seem to believe that
>> a theoretical bent of mind can only serve to stifle
>> creativity)

No, that is not at all what I believe. What I believe is, "The
insistence of strict conditions can limit creative outcomes."

The lack of those limits does not prevent one from using any resources
(including theoretical ones) if they are available.

You seem to be rejecting experimental results in your views. And the
level of insistence you keep in that view, leads me to believe you favor
a more productive environment rather than a more creative one. Both are
good, and I may entirely wrong about you, as many people are capable of
wearing different hats depending on the situation.

I think the gist of this thread may come down to...

In cases where it is not clear on what direction to go because the
choices are similar enough to make the choosing difficult. It is almost
always better to just pick one and see what happens than to do nothing.

Cheers,
Ron

"Fredrik Lundh" <> wrote in message
news:mailman.2137.1129475887.509.python-...
> Christian Stapfer wrote:
>
>> As to the value of complexity theory for creativity
>> in programming (even though you seem to believe that
>> a theoretical bent of mind can only serve to stifle
>> creativity), the story of the discovery of an efficient
>> string searching algorithm by D.E.Knuth provides an
>> interesting case in point. Knuth based himself on
>> seemingly quite "uncreatively theoretical work" (from
>> *your* point of view) that gave a *better* value for
>> the computuational complexity of string searching
>> than any of the then known algorithms could provide.
>
> are you talking about KMP?

Yes. I cannot give you the source of the story,
unfortunately, because I only have the *memory* of
it but don't know exactly *where* I happended to read
it. There, Knuth was said to have first analyzed the
theoretical argument very, very carefully to figure
out *why* it was that the theoretical bound was so
much better than all "practically known" algorithms.
It was by studing the theoretical work on computational
complexity *only* that the light dawned upon him.
(But of course, Knuth is "an uncreative dumbo fit
only for production work" - I am speaking ironically
here, which should be obvious.)

> I'm not sure that's really a good example of
> how useful "theoretical work" really is in practice:

Oh sure, yes, yes, it is. But my problem is to find
a good source of the original story. Maybe one
of the readers of this thread can provide it?

> the "better" computational complexity of KMP has
> turned out to be mostly useless, in practice.

Well, that's how things might turn out in the long run.
Still, at the time, to all appearances, it *was* a
case of practical creativity *triggered* by apparently
purely theoretical work in complexity theory.

More interesting than your trying to shoot down
one special case of the more general phenomenon of
theory engendering creativity would be to know
your position on the more general question...

It happens *often* in physics, you known. Einstein
is only one example of many. Pauli's prediction of
the existence of the neutrino is another. It took
experimentalists a great deal of time and patience
(about 20 years, I am told) until they could finally
muster something amounting to "experimental proof"
of Pauli's conjecture.

Regards,
Christian
--
"Experience without theory is blind,
but theory without experience is mere
intellectual play."
- Immanuel Kant

»Experience remains, of course, the sole criterion
of the *utility* of a mathematical construction.
But *the*creative*principle* resides in mathematics.«
- Albert Einstein: ‘The World As I See It’

»The astronomer Walter Baade told me that, when he
was dining with Pauli one day, Pauli exclaimed,
"Today I have done the worst thing for a theoretical
physicist. I have invented something which can never
be detected experimentally." Baade immediately offered
to bet a crate of champagne that the elusive neutrino
would one day prove amenable to experimental discovery.
Pauli accepted, unwisely failing to specify any time
limit, which made it impossible for him ever to win
the bet. Baade collected his crate of champagne (as
I can testify, having helped Baade consume a bottle of it)
when, just over twenty years later, in 1953, Cowan and
Reines did indeed succeed in detecting Pauli’s particle.«
- Fred Hoyle: ‘Astronomy and Cosmology’

Christian Stapfer wrote:

> It turned out that the VAX compiler had been
> clever enough to hoist his simple-minded test
> code out of the driving loop. In fact, our VAX
> calculated the body of the loop only *once*
> and thus *immediately* announced that it had finished
> the whole test - the compiler on this student's
> PC, on the other hand, had not been clever enough
> for this type of optimization: hence the difference...
>
> I think this is really a cautionary tale for
> experimentalists: don't *believe* in the decisiveness
> of the outcomes your experiments, but try to *understand*
> them instead (i.e. relate them to your theoretical grasp
> of the situation)...
>
> Regards,
> Christian

True understanding is of course the ideal, but as complexity increases
even theoretical information on a complex system becomes incomplete as
there are often other influences that will effect the outcome.

So the you could say: don't *depend* on the completeness of your
theoretical information, try to *verify* the validity of your results
with experiments.

Cheers,
Ron

"Ron Adam" <> wrote in message
news:jYv4f.152052$ m...
> Christian Stapfer wrote:
>> "Ron Adam" <> wrote in message
>> news:cTp4f.16180$. ..
>>
>>>Christian Stapfer wrote:
>>>
>>>
>>>>This discussion begins to sound like the recurring
>>>>arguments one hears between theoretical and
>>>>experimental physicists. Experimentalists tend
>>>>to overrate the importance of experimental data
>>>>(setting up a useful experiment, how to interpret
>>>>the experimental data one then gathers, and whether
>>>>one stands any chance of detecting systematic errors
>>>>of measurement, all depend on having a good *theory*
>>>>in the first place). Theoreticians, on the other hand,
>>>>tend to overrate the importance of the coherence of
>>>>theories. In truth, *both* are needed: good theories
>>>>*and* carefully collected experimental data.
>>>>
>>>>Regards,
>>>>Christian
>>>
>>>An interesting parallel can be made concerning management of production
>>>vs
>>>management of creativity.
>>>
>>>In general, production needs checks and feedback to insure quality, but
>>>will often come to a stand still if incomplete resources are available.
>>>
>>>Where as creativity needs checks to insure production, but in many cases
>>>can still be productive even with incomplete or questionable resources.
>>>The quality may very quite a bit in both directions, but in creative
>>>tasks, that is to be expected.
>>>
>>>In many ways programmers are a mixture of these two. I think I and
>>>Steven
>>>use a style that is closer to the creative approach. I get the feeling
>>>your background may be closer to the production style.
>>
>>
>> This diagnosis reminds me of C.G. Jung, the psychologist,
>> who, after having introduced the concepts of extra- and
>> introversion, came to the conclusion that Freud was
>> an extravert whereas Adler an introvert. The point is
>> that he got it exactly wrong...
>>
>> As to the value of complexity theory for creativity
>> in programming (even though you seem to believe that
>> a theoretical bent of mind can only serve to stifle
>> creativity), the story of the discovery of an efficient
>> string searching algorithm by D.E.Knuth provides an
>> interesting case in point. Knuth based himself on
>> seemingly quite "uncreatively theoretical work" (from
>> *your* point of view) that gave a *better* value for
>> the computational complexity of string searching
>> than any of the then known algorithms could provide.
>>
>> Regards,
>> Christian
>
>
>> (even though you seem to believe that
>>> a theoretical bent of mind can only serve to stifle
>>> creativity)
>
> No, that is not at all what I believe. What I believe is, "The insistence
> of strict conditions can limit creative outcomes."

That's agreed. But going off *blindly*experimenting*
without trying to relate the outcome of that experimenting
back to ones theoretical grasp of the work one is doing
is *not* a good idea. Certainly not in the long run.
In fact, muddling-trough and avoiding the question
of suitable theoretical support for one's work is
perhaps more typical of production environments.

> The lack of those limits does not prevent one from using any resources
> (including theoretical ones) if they are available.
>
> You seem to be rejecting experimental results in your views.

Not at all. You must have mis-read (or simply not-read)
my posts in this thread and are simply projecting wildly,
as psychoanalysts would call it, that is all.

> And the level of insistence you keep in that view,

A view that I do not really have: you are really projecting
indeed.

> leads me to believe you favor a more productive environment
> rather than a more creative one.

You are mistaken. Although I have some "practical background"
(originally working as a "self-taught" programmer - although,
ironically, for a "development and research department"),
I went on to study mathematics at the Federal Institute
of Technology here in Switzerland. Do you want to say that
having been trained as a mathematician makes one uncreative?
- But it is true that mathematicians are socialized in such
a way that they tend to take over rather high standards of
precision and theoretical grounding of their work.

> Both are good, and I may entirely wrong about you,

... you are at least *somewhat* wrong about me,
that I am quite sure of...

> as many people are capable of wearing different hats depending on the
> situation.
>
> I think the gist of this thread may come down to...
>
> In cases where it is not clear on what direction to go because the choices
> are similar enough to make the choosing difficult. It is almost always
> better to just pick one and see what happens than to do nothing.

As it appears, not even my most recent post has had
*any* recognizable effect on your thoroughly
misapprehending my position.

Regards,
Christian

"Steven D'Aprano" <> wrote in message
newsan.2005.10.16.16.01.43.591166@REMOVETHIScybe r.com.au...
> On Sun, 16 Oct 2005 15:16:39 +0200, Christian Stapfer wrote:
>
>> Come to think of an experience that I shared
>> with a student who was one of those highly
>> creative experimentalists you seem to have
>> in mind. He had just bought a new PC and
>> wanted to check how fast its floating point
>> unit was as compared to our VAX. After
>> having done his wonderfully creative
>> experimenting, he was utterly dejected: "Our (old)
>> VAX is over 10'000 times faster than my new PC",
>> he told me, almost in despair.
>
> Which it was. It finished executing his code in almost 1/10,000th of the
> time his PC could do.
>
>> Whereupon I,
>> always the uncreative, dogmatic theoretician,
>> who does not believe that much in the decisiveness
>> of the outcome of mere experiments, told him
>> that this was *impossible*, that he *must* have
>> made a mistake...
>
> It wasn't a mistake and it did happen.

Yes, yes, of course, it was a mistake, since
the conclusion that he wanted to draw from
this experiment was completely *wrong*.
Similarly, blind experimentalism *without*
supporting theory is mostly useless.

> The VAX finished the calculation
> 10,000 times faster than his PC.
>You have a strange concept of "impossible".

What about trying, for a change, to suppress
your polemical temperament? It will only lead
to quite unnecessarily long exchanges in this
NG.

>> It turned out that the VAX compiler had been
>> clever enough to hoist his simple-minded test
>> code out of the driving loop.

But, mind you, his test was meant to determine,
*not* the cleverness of the VAX compiler *but*
the speed of the floating-point unit. So his
experiment was a complete *failure* in this regard.

>
> Optimizations have a tendency to make a complete mess of Big O
> calculations, usually for the better. How does this support your
> theory that Big O is a reliable predictor of program speed?

My example was meant to point out how
problematic it is to assume that experimental
outcomes (without carefully relating them
back to supporting theory) are quite *worthless*.
This story was not about Big-Oh notation but
a cautionary tale about the relation between
experiment and theory more generally.
- Got it now?

> For the record, the VAX 9000 can have up to four vector processors each
> running at up to 125 MFLOPS each, or 500 in total. A Pentium III runs at
> about 850 Mflops. Comparing MIPS or FLOPS from one system to another is
> very risky, for many reasons, but as a very rough and ready measure
> of comparison, a four processor VAX 9000 is somewhere about the
> performance of a P-II or P-III, give or take some fudge factor.

Well, that was in the late 1980s and our VAX
certanly most definitely did *not* have a
vector processor: we were doing work in
industrial automation at the time, not much
number-crunching in sight there.

> So, depending on when your student did this experiment, it is entirely
> conceivable that the VAX might have been faster even without the
> optimization you describe.

Rubbish. Why do you want to go off a tangent like
this? Forget it! I just do not have the time to
start quibbling again.

> Of course, you haven't told us what model VAX,

That's right. And it was *not* important. Since the
tale has a simple moral: Experimental outcomes
*without* supporting theory (be it of the Big-Oh
variety or something else, depending on context)
is mostly worthless.

> or how many processors, or what PC your student had,
> so this comparison might not be relevant.

Your going off another tangent like this is
certainly not relevant to the basic insight
that experiments without supproting theory
are mostly worhtless, I'd say...

>> In fact, our VAX
>> calculated the body of the loop only *once*
>> and thus *immediately* announced that it had finished
>> the whole test - the compiler on this student's
>> PC, on the other hand, had not been clever enough
>> for this type of optimization: hence the difference...
>
> Precisely. And all the Big O notation is the world will not tell you that.
> Only an experiment will. Now, perhaps in the simple case of a bare loop
> doing the same calculation over and over again, you might be able to
> predict ahead of time what optimisations the compiler will do. But for
> more complex algorithms, forget it.
>
> This is a clear case of experimentation leading to the discovery
> of practical results which could not be predicted from Big O calculations.

The only problem being: it was *me*, basing
myself on "theory", who rejected the "experimental
result" that the student had accepted *as*is*.
(The student was actually an engineer, I myself
had been trained as a mathematician. Maybe that
rings a bell?)

> I find it quite mind-boggling that you would use as if it was a triumph
> of abstract theoretical calculation when it was nothing of the sort.

This example was not at all meant to be any
such thing. It was only about: "experimenting
*without* relating experimental outcomes to
theory is mostly worthless". What's more:
constructing an experiment without adequate
supporting theory is also mostly worthless.

>> I think this is really a cautionary tale for
>> experimentalists: don't *believe* in the decisiveness
>> of the outcomes your experiments, but try to *understand*
>> them instead (i.e. relate them to your theoretical grasp
>> of the situation)...
>
> Or, to put it another way: your student discovered

No. You didn't read the story correctly.
The student had accepted the result of
his experiments at face value. It was only
because I had "theoretical" grounds to reject
that experimental outcome that he did learn
something in the process.
Why not, for a change, be a good loser?

> something by running an experimental test of his code
> that he would never have learnt in a million
> years of analysis of his algorithm: the VAX compiler
> was very cleverly optimized.

Ok, he did learn *that*, in the end. But he
did *also* learn to thoroughly mistrust the
outcome of a mere experiment. Experiments
(not just in computer science) are quite
frequently botched. How do you discover
botched experiments? - By trying to relate
experimental outcomes to theory.

Regards,
Christian

"Steven D'Aprano" <> wrote in message
newsan.2005.10.16.18.52.56.797555@REMOVETHIScybe r.com.au...
> On Sun, 16 Oct 2005 19:42:11 +0200, Christian Stapfer wrote:
>
>> Pauli's prediction of
>> the existence of the neutrino is another. It took
>> experimentalists a great deal of time and patience
>> (about 20 years, I am told) until they could finally
>> muster something amounting to "experimental proof"
>> of Pauli's conjecture.
>
> Pauli's conjecture was the result of experimental evidence that was
> completely inexplicable according to the theory of the day:

So was it mere experiment or was it the relation
between experiment and theory that provided
the spur for creative advancement? My position
is the latter. Mere experiment does not tell you
anything at all. Only experiment on the background
of suitable theory does that.

> energy and
> spin was disappearing from certain nuclear reactions. This was an
> experimental result that needed to be explained, and Pauli's solution was
> to invent an invisible particle that carried that energy and spin away.

Pauli's creativity lay in proposing *this*
particular solution to the puzzle. And, surely,
if it had not been for Pauli's characterization
of that hypothetical particle, experimentalists
like Cowan and Reines would not have *anything*
to aim for in the first place.

But I'm not going to argue Pauli's case any futher
in this NG, because this is, in the end,
not a physics NG...

> (When I put it like that, it sounds stupid, but in fact it was an elegant
> and powerful answer to the problem.)
>
> The neutrino wasn't something that Pauli invented from theoretical first
> principles. It came out of hard experimental results.
>
> Physics of the last half century is littered with the half-forgotten
> corpses of theoretical particles that never eventuated: gravitinos,
> photinos, tachyons, rishons, flavons, hypercolor pre-quarks, axions,
> squarks, shadow matter, white holes, and so on ad nauseum.
>
> Neutrinos and quarks are exceptional in that experimental predictions of
> their existence were correct, and I maintain that is because (unlike all
> of the above) they were postulated to explain solid experimental results,
> not just to satisfy some theoretical itch.
>
> So yet again, your triumph of theory is actually a victory for experiment.

Well, I might tell now the story of Maxwell,
sitting in his garden - and deducing, from
his equations (which, admittedly, were inspired
by earlier experimental work by Faraday),
something really quite shockingly *new*:
the existence of electromagnetic waves.

Regards,
Christian
--
»From a long view of the history of mankind -
seen from, say, ten thousand years from now
- there can be little doubt that the most
significant event of the nineteenth century
will be judged as Maxwell's discovery of the
laws of electrodynamics. The American Civil
War will pale into provincial insignificance
in comparison with this important scientific
event of the same decade.«
- Richard P. Feynman: "The Feynman Lectures"

On Sun, 16 Oct 2005 19:42:11 +0200, Christian Stapfer wrote:

> Pauli's prediction of
> the existence of the neutrino is another. It took
> experimentalists a great deal of time and patience
> (about 20 years, I am told) until they could finally
> muster something amounting to "experimental proof"
> of Pauli's conjecture.

Pauli's conjecture was the result of experimental evidence that was
completely inexplicable according to the theory of the day: energy and
spin was disappearing from certain nuclear reactions. This was an
experimental result that needed to be explained, and Pauli's solution was
to invent an invisible particle that carried that energy and spin away.

(When I put it like that, it sounds stupid, but in fact it was an elegant
and powerful answer to the problem.)

The neutrino wasn't something that Pauli invented from theoretical first
principles. It came out of hard experimental results.

Physics of the last half century is littered with the half-forgotten
corpses of theoretical particles that never eventuated: gravitinos,
photinos, tachyons, rishons, flavons, hypercolor pre-quarks, axions,
squarks, shadow matter, white holes, and so on ad nauseum.

Neutrinos and quarks are exceptional in that experimental predictions of
their existence were correct, and I maintain that is because (unlike all
of the above) they were postulated to explain solid experimental results,
not just to satisfy some theoretical itch.

So yet again, your triumph of theory is actually a victory for experiment.


--
Steven.