Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-L] nature +- observations +- models



There certainly is a reality underneath it all, Bob, but all we can do is
approach it incrementally with better and better models. Our theoretical
insights enable us to interpret experimental data, such that we are better
and better able to model the workings of the universe that is in fact there
to be discovered - but the model is never "reality"... it is only a
description thereof that is to some degree or another an accurate
description. I think that's all Dyson is getting at.

On Tue, Aug 23, 2016 at 9:06 AM, LaMontagne, Bob <RLAMONT@providence.edu>
wrote:

I've never been a Dyson fan. At some level, there has to be a 'reality"
beneath it all. I certainly have a deeper understanding of the world around
me than my cats. I would hope that somewhere in the far future our
exponentially expanding knowledge will expose that reality. I don't believe
that humans are restricted to their senses and wiring at birth the way a
cat is.

Bob at PC
I have returned from retirement to teach a General Physics course for our
Biology students. Of all the majors, they were the most fun to be in a
classroom with.

________________________________________
From: Phys-l <phys-l-bounces@www.phys-l.org> on behalf of Bob Sciamanda <
treborsci@verizon.net>
Sent: Tuesday, August 23, 2016 8:02 AM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] nature +- observations +- models

I am reminded of a remark of Freeman Dyson (Here paraphrased from faulty
memory) ==>

"I have great respect for Stephen Hawking, but he is wont to confuse the
model for the reality."

We have only models. By experiment we can test the model against reality,
but this can only lead to more useful models - not to "reality".

-----Original Message-----
From: John Denker
Sent: Sunday, August 21, 2016 12:12 AM
To: Phys-L@Phys-L.org
Subject: [Phys-L] nature +- observations +- models

. . . snip . . .
I mention this because on 08/20/2016 07:44 PM, Derek McKenzie wrote:

I would need a lot more convincing that a reasonably clear and useful
distinction can be made between questions about *physics* versus
questions about *models*.

Fair enough.

Beware that the word physics, as I use it, is ambiguous.
-- There is the physics that physicists do, which involves a great
deal of observing, plus a great deal of model-building and model-using.
-- There is the physics that Mother Nature does. She does whatever
she pleases, whether we observe it or not, whether we model it or not.

I used the word earlier today in ways that were not very clear, for
which I apologize. I should have said there is a distinction between
Mother Nature and our models thereof. Even after we clarify the
terminology, it's a tricky concept.

The distinction between Mother Nature and observations thereof goes
back more than 2300 years.
-- The word that can be spoken is not the true word.
The way that can be trodden is not the true way.
Laozi, _Tao Te Ching_

-- What you observe on the wall of the cave may be only a
distorted shadow of some deeper physical reality.
Plato, _The Republic_ book VII


We build models to fit the observations. This is not an exact science,
for two reasons:
*) The models never fit the observations exactly, and
*) The observations were never exactly right to begin with.


Here are some examples of what I'm talking about:

*) For thousands of years, people have used a geocentric model of the
universe. It is still in use for some purposes, even today, even in
the hands of serious people. For example, the US government will
happily tell you the time of sunrise and sunset, and I see no reason
to complain about this.
http://www.weather.gov/box/sunmoon

The laboratory reference frame, which is absolutely standard for
most purposes in the introductory physics course, implicitly
assumes a geocentric model.

At some point the geocentric model of the universe was "replaced"
by a better model, namely the heliocentric model. But it wasn't
really replaced, was it?

Furthermore, the heliocentric model wasn't exactly right, either.

*) For thousands of years, people were sure that the universe was
three dimensional. Surely if there was another dimension somebody
would have noticed, they told themselves. Then Minkowski comes
along and provides a much more powerful model, a four-dimensional
model.

*) Superfluidity was a complete surprise when it was first observed.
It was many many years before we had anything resembling a microscopic
model of what was going on.

*) Et cetera.

Some guy named Kuhn wrote a book about this sort of thing:
_The Structure of Scientific Revolutions_.

Conclusion:

Sometimes Mother Nature does stuff that surprises us, i.e. stuff
that is wildly inconsistent with pre-existing models.

Sometimes we maintain multiple inequivalent models of the same underlying
physics, i.e. the same underlying natural phenomena.

Mother Nature does what she pleases, whether we observe it or not,
whether we model it or not.

_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l

Bob Sciamanda
Physics, Edinboro Univ of PA (Em)
treborsci@verizon.net
www.sciamanda.com

_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l
_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l




--
Todd K. Pedlar
Associate Professor of Physics
Luther College, Decorah, IA
pedlto01@luther.edu