Re: What are relativists?

jem:
>Bilge wrote:
>
>> jem:
>> >
>> >I.e. the constants are dependent on which model is chosen to represent
>> >Nature. So are you distinguishing a relativist as someone who believes
>> >Nature can be represented by multiple models, whereas a non-relativist
>> >believes there is just one "true" model?
>>
>> The term, ``relativist,'' is what the kooks on this newsgroup
>> use to refer to anyone who considers relativity to be a real theory,
>> so they avoid physics and deal in semantics. Relativity has nothing
>> to do with relative quantities.
>
>OK, so what was the reason that "Relativity" was chosen as the name of
>the theory?

Who knows? Who cares? The muon was and on occasion is probably still
called a mu meson, even though nobody who is sane would consider it
a meson. The liquid drop model of the nucleus doesn't imply that a
nucleus is a drop of liquid. What counts it the content of the theory,
not the name. The content of relativity is invariance. It's a theory
based upon invariants.

>> >If not, how about giving an example of a hypothetical situation in which
>> >an "absolute quantity" would be definable.
>>
>> The asymptotic limit of the electromagnetic coupling constant, \alpha.
>> The weinberg angle. Spin. The planck length.
>
>Why do you think these are "absolute quantities"? Is it because they
>are fundamental entities of a theory?

No, it's because those are quantities we associate with the ``things''
we define as the objects that produce signals in detectors. Like electrons
and muons. We distinguish between them based on the properties we assign
them, like spin and mass, which allows us to define them the same way
regardless of what time of the day it is or where we are located. You are
free to try and define different things which do depend on what time of
day it is, but it's not really very clear how you would go about it,
or what those new particles would mean, physically.

The planck length however, seems to be rather special, since the
planck area defines a surface beneath which it is impossible, even
in principle, to contain more than a finite amount of information,
regardless of how you try to redefine it (assuming quantum mechanics
is correct). Reformulating quantum mechanics won't permit you obtain
anything but a different definition of the same limit. For additional
background on this, which is quite interesting in its own right,
search on the terms bekenstein, information, black holes, entropy.

>If so, is it the case for every theory, or only the consensus
>favorite at any particular time?

Depends on whether you want to give up the idea that a ``thing''
like an electron is an electron as measured by our instruments.
You can always define whatever you want within the limits of
self-consistency, but once you define some quantities, you are
forced to accept the consequences for self-consistency. If you
define the ``relativistic mass'' to be the property of an object,
then you have a great deal of physics to change in terms of what you
call an object, for example.

.

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