Re: What are relativists?

jem wrote: 
Baugh wrote:

Pentcho Valev wrote:

Bryan Wallace http://www.ekkehard-friebe.de/wallace.htm :

"The true scientist must have faith and believe in the scientific
method of testing theories, and not in the theories themselves.



It isn't a faith it is a dicipline.


It isn't a dicipline, it's a discipline. :) 
Thanks, I've got to spell check more often.  My keyboard
spelling is very bad.  (Type too fast and don't spell things out, just
type the "whole word" as per habit).

Good post, but does a relativist take the position that "absolute quantities cannot be defined"? Doesn't any invariant quantity qualify as an absolute quantity? 

What? Like c?  That is a relation between our chosen units for measuring
 spatial distance and our chosen units for measuring time.  It is
comparable to "12 inches per foot".

Consider the mass of the electron?  Again mass is relative to our chosen
common units of space-time, i.e. relative to scale.

But this is I think getting off the point.  Relativists view any
observable, any variable, as relative to the method of determination.
Relative position, relative momentum, relative "state" in QM.

Those quantities such as total spin, or rest energy are not so much
observed as fixed by convention or by assumption.  E.g. total spin
say of an electron is based on the convention of measuring total angular
momentum about a specific point.  (like rest mass is energy in a
specific inertial frame).

What actually goes on in the laboratory is that we note that the
components of total angular momentum of a "spin-1/2" particle
may change by units of hbar/2 rather than say hbar as for "spin-1"
particles.  One then in preparing the beam of electrons which will
travel through the Stern-Gerlach magnet so that their total
angular momentum about some point does not vary by more than one unit
and so you see two output beams reflecting electrons whose total angular
momentum in the x-y plane about any point differ by one half unit.

Remember that to set up an spin measurement the width of the beam (delta
x) needs to be small *and* the spread in the momentum of the beam (delta
P_y) needs to be small.  It is when you idealize an electron as a
classical point particle that you get the illusion that spin is
"intrensic" and thus total spin is an absolute quantity of the electron.

Finally let me say I don't speak for "all relativists"
only for myself with regard to your question.  To answer
your question directly, I don't know.  I would never say
never but give me an example and I'll parse the definition
and see if it is truely "absolute" or if its "absoluteness"
is a matter of convention or restriction in cases.

Being "a relativist" may itself be "relative" in that
we must, in able to communicate adopt some absolutes
at least as a common convention.  At the same time
we must acknowledge that some quantities when examined
in their fundamental meaning are defined only relative to
one another.  If you want a a definition of "a relativist"
lets say we don't a priori assume absoluteness and look
to see if there are implicit non-physical conditions or
assumptions which fix the scale and center for a set
of possible observations.

In both theory and experiment it is important to sniff out
these a priori assumptions and make them explicit.


Regards,
James Baugh



Regards,
James Baugh






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  • Re: What are relativists?
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