Re: A little challenge for relativists.

Harry:
>"Bilge" <dubious@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
>news:slrndp055j.64k.dubious@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> Harry:
>> >
>> >"Bilge" <dubious@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
>>
>> >> Yes, it is. Absolute simultaneity defines a symmetry. That symmetry
>> >> defines the galilean group.
>> >
>> >Bilge, aeons ago I asked you to provide a real world example - which
>should
>> >be easy, if you talk experimental physics. Just specify a measurement
>that
>> >according to you can be done with SRT but can't be done if an absolute
>frame
>> >exists, say moving at 0.6c "absolute" towards Orion, and then what. Or,
>if
>>
>> Define the frame.
>
>Why don't you define it? OK I'll go ahead and do it: let's take a physical
>frame S, moving at 0.6c "absolute" towards Orion. At rest in this frame is
>an observer, let's call him Bilge. According to the theory he can't directly
>measure his speed, but he can measure other, related effects that are
>consequences of the theory.

That doesn't define the frame. To define a frame, and initialize the
data, you must specify the positions of the other objects in that
frame on a the line defined as t = 0 (Or some other definition which is
self consistent). The line t = 0, has no intrinsic meaning, so _you_
have to specify what it means. I'm not going to do it for you. Before
you take another stab at it, you might look up the commutation relations
for the poincare algebra.


>He can also observe what is happening in another physical frame S' that is
>moving in such a peculiar way (if I understood you correctly) that Bilge
>can't measure the relative speed between the two systems, in local units.

You not only didn't understand me, you aren't even on the same page.
The poincare group has ten killing vectors which define ten observables.
You cannot specify all ten when initializing your data. The choice
is up to you, but once you specify a complete set which commutes,
you cannot insist the rest be observables.

>> That means initialize the energy, momenta and
>> positions of everything relevent at the time t = 0 (i.e., now).
>> Since no observer can do that, you'll have to figure out what
>> you can define.
>
>What would be relevant for your example? You failed to explain where you
>think is a problem. But you give me the impression that according to you, if

It's _your_ example, not mine. I could care less if you manage to ever
specify an experiment that is self-consistent, so you'll have to go study
on your own. Here's a hint, though. The poincare group has ten killing
vectors which correspond to, (1) time and space translations, (2) 3 lorentz
boosts, (3) 3 spatial rotations. You also have the mass^2 as a casimir
operator. You'll need to pick the set that best suits the coordinates
in which you define t = 0.


>Bilge doesn't *know* his speed, that therefore he can't *have* a speed. If
>that's what you mean, then that's a logical error. But surely you can't mean
>that... right?

You're right. I can't mean that. In fact, I can't mean anything
close to that.


.

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