From: schiller@prl.philips.nl (schiller c)
Newsgroups: sci.philosophy.tech
Subject: Re: Which theory before observation ?
Date: 11 Jan 93 08:43:06 GMT
Organization: Philips Research Laboratories Eindhoven, Netherlands

sasghm@theseus.unx.sas.com (Gary Merrill) writes:


>The fact that you put the question by requesting an example of how
>a theory is necessary to observe something indicates a lack of
>understanding and sensitivity to the real issues.  I don't need a
>theory to observe *something*.  But to say (in a coherent manner
>and with a clear intersubjective sense) that *what* I have observed
>is an *electron* requires substantial theoretical superstructure.


No. It requires only to show that what you see here is the *same*
as what you saw in your previous experiments. No theoretical structure
is necessary, just the list of jour previous observations.


>A couple of years ago one of my sons built a Wilson cloud chamber
>(for a science fair) and did several of the usual experiments.
>We all stood around and observed the alpha particles.  No, wait.
>I didn't actually see the *alpha particle*.  I saw a trail of vapor
>in the chamber. No, wait some more.  How do I know that it was
>*vapor* I saw?  What I saw was a white line against the black
>background of the chamber.
>Demonstrate this experiment to someone with no knowledge of *theory*
>and you won't (can't!) get them to say
>	I see a vapor trail.
>	I see an alpha particle.
>Now *you* can say
>	What they see is a vapor trail.
>	What they see is an alpha particle.
>but you say this (and *justify* these assertions) based on the *theory*
>that you know.  You can *say* that each of the following is a fact:
>	There is a white line of something in the chamber.
>	There is a vapor trail in the chamber.
>	There is the track of an alpha particle in the chamber.
>But there is an important *difference* among these "facts".  If you
>don't recognize that difference and how it plays a role in theory
>development, theory confirmation, theory acceptance and rejection;
>and if you simply lump all of these "facts" together and insist that
>they are all independent of theory; then you may call yourself a
>scientist, but you won't be a very good one.

Wow ! When a sientist pretends to "see" an alpha-particle, in a Wilson chamber,
what he says is an abbreviated form of the following:

We see a track. There is a ray of something producing a track. Now let's see if
one can describe this thing in more detail. Let's put the chamber in a magnet.
Ah, the track bends. Ah, the particle is positively charged. The mass over
charge ratio has a certain value. Then one measures the mass. One gets a
certain value. Ah, in the beginning of the century, particles with the same
properties had already been seen, and then such a particle, with that charge and
that mass, was named an "alpha particle". 

(This actually was the historical path.)

If somebody sees a vapour ray with the same properties again, and directly says
: "It is an alpha particle !" He just wants to say that what he has seen now is
the same thing he has seen 30 years ago.

No theory is involved. Just the idea that you see again what you had seen
before. Naturally, you need the concept of mass and charge, and of magnetic
field. But you can repeat the same reasoning for these concepts, just as done
for the concept "alpha particle".


			Christoph Schiller
Newsgroups: sci.philosophy.tech