Good.
> Problem with the lightning stroke is that it is not a single event but
> a series of events and so it conveniently obliterates everything.
I beg your pardon. In what was proposed, a lightning stroke was
described as a momentary source with a single flash of light (radiating
to all observers), and which would leave evidence of its location by a
scorch mark. Why do you think of it as something other than as described?
> Right configuration would be pulses of light at A and B which are
> reflected by two mirrors at 45, in respective frames. Upper two should
> be half silvered and below them we should have transparent floor for
> the train. You may say that with this there are four separate events,
> but for the present conclusions they can be considered as two events.
>
> In Einstein�s gedanken, both conclude that the events are
> simultaneous.
In *Einstein's* gedanken? No they don't. Are you reading the same
material by Einstein that I've read?
> But K has to look at happenings in K� to arrive at the
> conclusion that events are not simultaneous in the frame K�.
No, you have not read and understood what Einstein said.
Here is what the gedanken says:
1. The three criteria of simultaneity (as we outlined them earlier) are
laid out.
2. M and M' both agree that criteria 3 is not met for M', and is met for
M. There can be no disagreement about actual observations.
3. For M, all three simultaneity criteria are met, and so the
*unambiguous* conclusion is that the flashes were simultaneous.
4. For M' the first two simultaneity criteria are met, but the third one
is not, and so the *unambiguous* conclusion is that the flashes are not
simultaneous.
At this point Einstein pauses and points out that there is no priority
given to either frame, so it's impossible to point to either frame and
say that one is right and the other is wrong. So it is a simple fact
that simultaneity is frame-dependent.
5. BUT, Einstein goes a step further and says, M and M' are both
thinking people, and they must be then puzzling over the result and they
go back to wondering how they go to this place. So they ask the
question, how is it that criteria 3 is met for M and not for M', which
leads to the inescapable conclusion?
6. Einstein shows that this result is perfectly understandable. M looks
at what's happening for M' and sees that *of course* the signals do not
arrive at the same time at M', because condition 2 doesn't hold for M'
in K. M' disagrees, of course, and says that of course condition 2 holds
-- he can measure that he stood exactly midway between the lightning
flashes, as evidenced by later measurements to the scorch marks on the
train. So there is a source of disagreement.
7. What Einstein did NOT talk about is how M' accounts for the fact that
M saw the signals at the same time, even though the flashes were not
simultaneous. This too is easy to understand, as M is not midway between
the two events in frame K', and it's easy to see how light from the
later lightning strike could arrive at M at the same time as light from
the earlier lightning strike. So this is how M' accounts for M receiving
the light at the same time.
8. The two observers think about this some more and are still flummoxed
by the inescapable conclusions about simultaneity based on the three
criteria, and then they ask, how is it that criterion 1 is satisfied by
both observers? If the signal speed is identical from both flashes for
M, shouldn't it be nonidentical for M', or vice-versa? But here is where
experiment comes in and says, no, it is confirmed experimentally that
the signal speed is identical from both flashes for M and also identical
from both flashes for M'. So condition 1 is satisfied for both, and
there is no escape from the simultaneity conclusions they made earlier.
It's a pity that you have misunderstood this gedanken so badly. Who
taught it to you? Or was it the case that no one taught it to you and
you attempted to learn it yourself without assistance?
> You
> should understand that I am talking about viewpoint of K. Light pulses
> can also trigger four guns and the events A� and A can be treated as a
> single event. Same with B and B�. In their respective frames, events