Re: relativity of simultaneity - real or perceived?


"Curious" <anthonyroseuk-curious@xxxxxxxxxxx> wrote in message
news:1116190979.926969.33500@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Martin Hogman wrote:
> >The equations of special relativity (SR) tell us
> >where the particle actually is not where it is
> >seen to be.
>
> >Events which are simultaneous in one frame of
> >reference may ('really') not be so in another. This is
> >one of the most important points to understand
> >in SR.
> >> Would you agree with Paul that they are EITHER simultaneous events
> OR
> >> not?
> >This is wrong. Paul is one of the regular 'aether
> >theorists' on this group.
> >>Or do you go for the 'there is no absolute reality, we can only
> >> know what we measure' view shared by Dave A. Smith, and believe that
>
> >> they are both simultaneous AND non-simultaneous?
> >That is not put very well. Events themselves are the
> >absolute reality in SR. Whether they are simultaneous
> >or not depends on your frame of reference.
> >> Or do you say that this is where the evidence leads, despite that
> fact
> >> that it is beyond us to understand the multiple 'realities'?
> >Multiple realities are not part of SR; measurements
> >(allowing for the transit time of light) made in different
> >frames of reference are.
> >> If the box was a bomb that blew up instantly when two photons hit it
>
> >> simultaneously at both ends, would an observer in frame 1 see it
> >> explode but an observer in frame 2 see it remain unexploded?
> >No, this never happens. The final result is always
> >the same in both frames.
> Straight talk - refreshing - but appears to me to be contradictory.
> I will buy a textbook if I have to but at this stage I'm just a layman
> with a question which I believe doesn't need great maths to answer - if
> you tell me it does, ok, I'll accept that at face value for now.
> But the question is this:
> If in frame 1, the two photons are calculated (not perceived) to arrive
> at each end of the box simultaneously, but per frame 2 there is no
> point in time at which they will arrive at the ends of the box
> simultaneously, then we have two MUTUALLY EXCLUSIVE versions of events.

That is the error in your logic. They are not mutually exclusive. If
events in one frame are simultaneous there is no a-priori reason for it to
be simultaneous in another frame. You are caught in the clutches of you own
preconceptions similar to those in Gauss's time who could not comprehend non
Euclidian geometry - they thought Euclidean geometry was a-priori true.

> Either they DO hit the ends of the box simultaneously, or they do NOT.

True - but that can only be said for a measurement taken at a point, at a
specific time, and in a specified frame. SR says it depends on your frame
of reference. Logic forces us to conclude in an inertial frame if an event
is simultaneous in that frame then it is simultaneous for all observers in
that frame - this follows from the homogeneity property of an inertial
frame. But there is no logical reason to conclude it must be simultaneous
in other frames. In SR you must throw you intuition out the window and
challenge your usual assumptions.

> Either one or both of the descriptions of events must be claimed to be
> due to perception - for a logical contradiction cannot be truth.

Since there is no logical contradiction there is no problem.

> (Unless you believe that the observer's presence affects reality.)

In SR the presence of observers affects nothing.

> If you claim that whether they are simultaneous or not depends on the
> frame, then you are having your cake and eat it.
> Going back to the bomb, never mind the mechanism, but the trigger is
> that two photons arrive simultaneously. Will an observer in frame 1 see
> the bomb blow up? Yes, of course. Will an observer in frame two see the
> bomb blow up? No, of course not.

The detection of the simultaneous arrival of the photons is determined by
some kind of detector - obviously. That detector must be at rest in some
frame. It is what is simultaneous in that frame that determines what the
detector will register and if the bomb blows up. No logical contradiction
arises if detectors or observes in other frames do not detect or measure the
same two events as simultaneous.

> Correct?
> Now don't make me catch a fish with my bare hands like Jon again!

I am sure if you think about it clearly you will see there is no problem.

Thanks
Bill


.

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