The point isn't "what is the true meaning of N1", I'll be the first one to
say that the idea of an inertial frame is intimitely wrapped up in N1 and
its existence may be the real meaning of N1, (although I think the idea of
inertia is also an important idea with N1).
One common phrasing of N1 is: "An object continues in a state of uniform
motion continues in a state of uniform motion unless acted upon by outside
forces." To understand such a statements requires me to imagine an object
moving without outside forces influencing its motion; since I've never
actually seen such a situation. This is a form of "gedankening", and I
think it was a necessary part of the process of coming up with N1, probably
even for Newton; certainly for me.
Joel
----------
From: JACK L. URETSKY (C) 1996; HEP DIV., ARGONNE NATIONAL LAB, ARGONNE, IL
60439
To: QuistO; RAUBERJ; phys-l
Cc: JLU
Subject: RE: Gedankening
Date: Tuesday, October 28, 1997 8:41PM
Hi all-
Joel Rauber writes:
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Hey Gang,
a new thread for discussion; I'll try to start it by being a lightening rod!
I rather like Gedankening myself and consider it indispensable. I believe
Newton's first law came from Gedankening; didn't he have to imagine what
would be the case if you were able to remove all resistive forces, "make the
friction on the hockey puck less and less by better polishing the surface
upon which it slides".
Actually this is precisely the tension present in any beginning introductory
class; basic principles vs the "real world". Is it better to discuss
situations in a Gedanken sort of way, where you've removed "real world"
complications from the disucussion; in order to bring out the basic
principles clearly and unambigously. Or is it better to talk about the
"real world" with all its complications?
Joel
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Sorry, Joel, but I don't agree with your characterization of
Newton's first law (N1). I think that the real meaning of N1 is
"there exist inertial frames". That is not a proposition that can be
demonstrated by experiment, because it is a definition.
You could sharpen the discussion by picking a different example.