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From: Peter Webb on 17 Jun 2010 22:55

"Me, ...again!" <arthures(a)mv.com> wrote in message
news:Pine.BSF.4.61.1006172128240.1906(a)osmium.mv.net...


On Thu, 17 Jun 2010, PD wrote:

> On Jun 17, 3:06 pm, "Me, ...again!" <arthu...(a)mv.com> wrote:
>> On Thu, 17 Jun 2010, PD wrote:
>>> On Jun 14, 5:15 pm, kenseto <kens...(a)erinet.com> wrote:
>>>> On Jun 2, 1:05 am, PD <thedraperfam...(a)gmail.com> wrote:
>>
>>>>> On Jun 1, 10:59 pm, "Me, ...again!" <arthu...(a)mv.com> wrote:
>>
>>>>>> On Wed, 2 Jun 2010, Peter Webb wrote:
>>>>>>> I gather from the context that you believe that Einstein's Special
>>>>>>> and
>>>>>>> General Theory of Relativity are wrong.
>>
>>>>>>> What do you think of Einstein's explanation of the photoelectric
>>>>>>> effect
>>>>>>> (which was instrumental in thedevelopment of Quantum Mechanics, and
>>>>>>> for which
>>>>>>> he earned a Nobel prize), and Einstein's modelling of Brownian
>>>>>>> motion (which
>>>>>>> virtually created the whole field of statistical mechanics) ?
>>
>>>>>>> Was he wrong about them as well?
>>
>>>>>> Was Einstein right or wrong?
>>
>>>>>> What we have are two schools of thought: i) Einstein did something,
>>>>>> vs.
>>>>>> ii) a bunch of experts/skeptics who think Einstein made a lot of
>>>>>> noise,
>>>>>> more heat than light, and fooled a lot of people.
>>
>>>>> I really don't care much for schools of thought. After all, there is
>>>>> still a substantial school of thought that the earth is 6600 years
>>>>> old, but that doesn't mean its existence automatically earns it any
>>>>> credibility.
>>
>>>>> I'm much more interested in understanding WHY those people in the
>>>>> anti-
>>>>> Einstein school of thought feel that way.
>>>>> Some candidate ideas:
>>>>> - The theory is wrong, because it makes no sense to these people, and
>>>>> these people firmly believe that unless a theory makes sense, it
>>>>> cannot possibly be considered right.
>>
>>>> No the theory calls the absolute rest frame as an inertial frame and
>>>> then turn around and deny the existence of an absolute rest frame.
>>
>>>> Ken Seto
>>
>>> It does no such thing. It says the properties of the inertial frame
>>> are identical to what YOU think the properties of an absolute frame
>>> has. But YOU are the ONLY one that believes the absolute frame is the
>>> one frame that has those properties. It is the mixing of what you have
>>> heard about SR with what you make up from your own head that makes you
>>> confused.
>>
>> OK, here is a "thought experiment" for you E/R whips: we have a large
>> volume of space (say light-year volumes), and two populations of
>> "particles" N1 and N2. N1 = N2 in number, size, mass distribution, and
>> in radial root mean square distance distribution from each other, and
>> also with light year distances from each other. Only difference is N1
>> is moving as a "flock" in direction different from N2, and both are
>> in the same large space. All the particles are stars and orbiting cool
>> bodies. And, there are no other N systems for tens of thousands of
>> lightyears in any direction. After time, T, the movement reverses, and
>> for
>> an identical duration. One of two identical twin brothers, who traveled,
>> at the time, to nearbly purple cool orbiting body is reunited with other
>> brother on red cool orbiting body.
>>
>> Is one older/younger than the other? Why?
>
> If the motion is symmetric -- that is, both N1 and N2 reverse their
> motion -- then no, one is not older or younger than the other.
>
> It is only when there is an asymmetry in the motion that there is an
> asymmetry in the aging.
>
> One way this can be explained, with a bit more background, is that one
> of the worldlines is straighter than the other, and the more crooked
> the wordline the less proper time will elapse.

Yeah, but I was trying to concoct a "thought experiment" where the
asymmetry would be very hard to _measure_. But, if what you said in your
first sentence is true, then ...OK... the symmetry issue must be
specified. But, then, I'm thinking, the effects depend on reference frame
specification that N1 vs N2 spatial mass distribution must be vastly
different (i.e. a small rocket vs whole planet or planetary system not
undergoing linear accelleration). Still seems odd. Its like the double
slit experiment for the wave-particle ambiguity: the small rocket must
"sense" the whole rest of the solar system as being "at rest" in its own
reference frame for the asymmetry effect to work.

Am I making any sense?

_______________________________________________
Yes and no. There is no requirement for the particles to "know" anything
about what is happening to the other particles, it is completely irrelevant
to the maths.

PD introduced the "proper" term, which is "proper time". This is the amount
by which a a particle/object/rocket ages in a journey. It can be thought of
as "wristwatch time", its the time duration recorded by a wristwatch
travelling with the object.

Proper time is an invariant in SR. That is, anybody can look at some other
rocket with a telescope and see what time is shown on their wristwatch when
they (say) land on another planet, or fire their thrusters, etc.

The twins paradox, and your question above, concerns proper time.

The proper time for N1 and N2 particles will be the same. There are several
ways in which to prove this, from easiest to hardest:

1. By symmetry, as you have done.

2. By noticing that the equations for time dilation use v^2. The only
difference between N1 and N2 is that one set used v^2, and the other set
uses (-v)^2, but (-v)^2 = v^2 so the same answer will pop out.

3. The above does the Lorentz transform relative to a frame that has the two
particles moving in opposite directions at the same speed, so you are
comparing speeds of v and -v. You can do the calculation in any other
intertial reference frame, in which case the two speeds are v+s and -v+s
where s is the speed of the frame relative to some other chosen frame. The
same answer will drop out, as the Lorentz equations are designed to have
this property. Proper time has to be an invariant, and this is one way of
deriving the Lorentz equations.

In general, a lot of people who doubt SR make more and more complex
scenarios to see if they can somehow break SR. This is unneccesary. We can
analyse each object one at a time to see what happens. The fact hat there
are several or many other objects in the thought experiment is irrelevant -
each one can be analysed separately, and as long as there are no collisions
or gravity or other interactions between the different particles they are
independent. Adding more particles just means you are doing the same sorts
of calculations multiple times, it doesn't alter the arguments.



> PD
>

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