Re: Relativists cannot count to three.

From: Androcles (dummy_at_dummy.net)
Date: 12/27/04 

Date: Mon, 27 Dec 2004 17:14:08 GMT

"Tom Capizzi" <tom.capizzi@verizon.net> wrote in message
news:B5Xzd.13240$152.549@trndny01...
>
> "Dirk Van de moortel" <dirkvandemoortel@ThankS-NO-SperM.hotmail.com>
> wrote in message news:7BWzd.11539$Os.754822@phobos.telenet-ops.be...
>>
>> "Androcles" <dummy@dummy.net> wrote in message
>> news:OcVzd.60125$ef5.15664@fe1.news.blueyonder.co.uk...
>>> If I stand before a vertical surface and throw a ball 'o' with
>>> speed
>>> 'u', catching it as it returns, I need a minumum of two coordinates
>>> to describe the events of emission, reflection and reception.
>>> Ao----------(+u - >)------------* emission
>>> *--------------------------------oB reflection
>>> Ao----------( -u <- )------------* reception
>>>
>>> In agreement with experience it is clear that the time for the ball
>>> to reach the wall and back again is given by 2AB/(t'A-tA) = u,
>>> the velocity of the ball.
>>>
>>>
>>> If I do this whilst riding a moving platform travelling at velocity
>>> v,
>>> the wall also moving, I need a minimum of three coordinates
>>> for a stationary observer to evaluate the events.
>>>
>>> Ao----------(v+u)-----------* emission
>>> *---------------------------oB reflection
>>> Co---------(v-u)------------* reception
>>>
>>> In the frame of the observer, the ball travels from A to B'
>>> at v+u and returns from B' to C at v-u.
>>>
>>> Einstein only uses two cordinates, A = C = (0,0,0) and B = (x',0,0).
>>
>> *You*
>> *do*
>> *not*
>> *understand*
>> *the*
>> *concept*
>> *of*
>> *coordinates*.
>
> Is it not true that SR only requires the origin of the moving
> observer's coordinate
> system and the stationary observer's coordinate system to be
> coincident at a
> single instant? After that both observers see the other's origin
> shifting position.

Correct. Dinky the spermless can't count to three either.
>
> In any case this model is useless for evaluating SR. The velocities
> are miniscule
> compared to the speed of light, and the velocity composition is linear
> here,
> unlike the requirement of SR.

This is not about "evaluating" SR, v can have any value.

 If you used the relativistic velocity
> composition
> formula and then examined the results as one of the velocities
> approached c,
> then it might be meaningful.

Sure thing.

c = (c+v)/(1+v/c),

giving
½[tau(0,0,0,t)+tau(0,0,0,t+x'/c+x'/c)] = tau(x',0,0,t+x'/c)
instead of
½[tau(0,0,0,t)+tau(0,0,0,t+x'/(c-v)+x'/(c+v))] = tau(x',0,0,t+x'/(c-v))
so now derive the Lorentz Transforms from that and then derive the
composition of velocities from the Lorentz Transforms.
Reference :
http://www.fourmilab.ch/etexts/einstein/specrel/www/

Androcles.

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