Re: [asa] Trees don't lie

From: George Murphy <GMURPHY10@neo.rr.com>
Date: Sun Mar 22 2009 - 13:15:26 EDT

Glenn -

If it isn't too presumptuous (because you know far more about this than I
do), let me call attention to Hubbert's prediction in 1956 that oil
production in the lower 48 would peak around 1969. It did in 1970. Of
course that wasn't a precise prediction of the sort we can sometimes make in
physics but it was more than just some average guy on the street saying "I
think oil's going to start getting scarcer pretty soon." If you wish you
can fill in some details on how Hubbert made that prediction but I'm
guessing that it was with informed & intelligent extrapolation from data
about known reserves, likely finds of new fields, oil consumption, &c. It
wasn't by trying to solve some complicated set of equations.

& that prediction isn't unique. Political pollsters predict results of
elections & often are quite accurate. Las Vegas oddsmakers make (in effect)
statistical predictions about the likelihood of various teams winning the
NCAA tournament, the world series, Super Bowl, &c. Sometimes they're
wrong - not much of anyone expected Tampa Bay to be in the World Series or
the Cardinal in the Super Bowl - but if they give 100-1 odds against some
team winning, you're probably throwing your money away if you bet against
them.

I suppose we could debate whether or not these are "predictions." Maybe
they're just estimates or guesstimates, but they suggest that you need to
nuance your claims that complex phenomena are basically unpredictable. &
ditto for the idea that the experts don't know anymore than the average guy
on the street.

2d, & less important for the basic question, don't overemphasize the role of
nonlinearity in all this. Yes, many nonlinear systems display sensitivity
to initial conditions but not all do. As the most obvious counterexample, a
damped nonlinear oscillator will come to rest asymptotically, regardless of
initial conditions. & while some of the systems you list, & especially
those involving human beings, are very complex & it's in practice impossible
to predict their precise state at all future times, we in fact have no
differential equations, linear or not, that describe the dynamics of such
systems. (What are the equations of motion of a US presidential election?)
So while speaking of these systems as "nonlinear" may be a helpful metaphor
it's no more than that & risks giving a more reductionistic picture than is
appropriate.

Shalom
George
http://home.roadrunner.com/~scitheologyglm

----- Original Message -----
From: "Glenn Morton" <glennmorton@entouch.net>
To: "George Murphy" <GMURPHY10@neo.rr.com>
Cc: "asa" <asa@calvin.edu>
Sent: Saturday, March 21, 2009 10:42 PM
Subject: Re: [asa] Trees don't lie

>I would say that the climate, the weather, political systems,, economics,
>the oil markets etc, are all highly nonlinear. Tell me if it is going to be
>raining where you are 33 days from now. Tell me what the price of the stock
>market will close at on Monday. Tell me what the price of oil will be
>April 23. Tell me what country will be our biggest problem in 2010. All
>of these things involve nonlinearities.
>
> And I disagree that if one cant predict from them they won't be studied.
> They will be studied because they are the real equations that govern this
> universe and curiousity and hope that we can predict something will ensure
> their study
>
> ----- Original Message -----
> From: "George Murphy" <GMURPHY10@neo.rr.com>
> To: "Glenn Morton" <glennmorton@entouch.net>; "William Hamilton"
> <willeugenehamilton@gmail.com>; <mrb22667@kansas.net>
> Cc: "asa" <asa@calvin.edu>
> Sent: Saturday, March 21, 2009 7:34 PM
> Subject: Re: [asa] Trees don't lie
>
>
>> For a chaotic system one can't predict the future state of the system in
>> detail for any length of time. But you can often make (a) statistical
>> predictions & (b) thermodynamic predictions about the overall state of
>> the system. Of course these are related. If all nonlinear dynamics
>> could do was to say that we can't predict anything then people wouldn't
>> publish books &c on nonlinear dynamics.
>>
>> Shalom
>> George
>> http://home.roadrunner.com/~scitheologyglm
>>
>>
>> ----- Original Message -----
>> From: "Glenn Morton" <glennmorton@entouch.net>
>> To: "George Murphy" <GMURPHY10@neo.rr.com>; "William Hamilton"
>> <willeugenehamilton@gmail.com>; <mrb22667@kansas.net>
>> Cc: "asa" <asa@calvin.edu>
>> Sent: Saturday, March 21, 2009 3:05 PM
>> Subject: Re: [asa] Trees don't lie
>>
>>
>>> George wrote Saturday, March 21, 2009 10:11 AM
>>>
>>>> I agree that in some fields "expertise" is overrated. It's pretty
>>>> funny, in a gallow humors way, to hear the argument that financial
>>>> firms have to pay big bonuses in order to hold on to the people whose
>>>> "expertise" has driven the company, & maybe the country, into the
>>>> ground. OTOH there's a populist temptation to debunk the idea of
>>>> expertise because then "we're just as good as they are." & it's not
>>>> clear that being able to predict the future is always the best
>>>> criterion.
>>>
>>>
>>> There is no doubt that a physicist knows the equations and where it
>>> comes to deterministic systems, the physicist will do way better than
>>> anyone else. But, most systems we humans deal with are decidedly NOT
>>> linear or deterministic. They are non-linear. And one thing that should
>>> have been learned, but apparently hasn't been by many in the field of
>>> science, NO ONE can predict the state of a nonlinear system after a
>>> certain period of time. The physicist is as helpless as the plumber or
>>> homeless person and thus, all guesses will have the equivalent chance of
>>> success.
>>>
>>> that is why experts differ on what the stock market will do, what the
>>> weather will be like next week etc. And when it comes to global
>>> warming, everyone is absolutely sure that they know what this grand
>>> nonlinear system we call climate will do. They are acting as if it is a
>>> linear system when it is decidedly nonlinear.
>>>
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>

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Received on Sun Mar 22 13:15:53 2009

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