[ExI] QT and SR

[Jeff Davis]

John,

I've been thinking about this on and off for the last week, and am
more or less ready to respond.   However, it won't do any good if I
don't understand your approach, and I'm puzzled...

You write:

> An instant after you start moving you receive a report from
the fellow at the other end of the string saying he hasn't started moving yet.

I don't understand.  According to the setup both acceleration profiles
are identical.  You and your counterpart at the other end of the
string know this.  So why then would you get such a message, absent a
failure in the pre-programmed implementation of the two acceleration
profiles?  I'm guessing that you're suggesting a simultaneity issue.
But before addressing the matter I'd like to be clear.
And those follow on actions (quoted below) taken in response to and
following the initial message , appear to be uncoordinated with the
other ship, and to thoroughly deviate from the originally-planned
acceleration profile, and APPEAR to contradict the problem setup.

Anyway, can you help me out here?

Jeff

> Because of this you predict that when you make the next distance measurement you will find that the distance has decreased, but when the next LASER pulse arrives you find
that the distance is just the same. You can only conclude that
sometime after the last report the other fellow started to accelerate
and did so faster than you did.
>
> When he sends his next report you find he has indeed started to move but he still isn't moving as fast as you are, and yet the distance is the same as before.  The fellow at the other end of the string must still be accelerating faster than you and in fact he always will be.
> Of course an observer at the other end of the string could make similar observations and conclude that you are accelerating faster than he is. The two observers disagree
on who started moving first, but both agree that the other
end of the string is accelerating faster than their end; and that
pulls the string apart.

On Sat, Aug 9, 2008 at 10:43 PM, John K Clark <jonkc at bellsouth.net> wrote:
> "Jeff Davis" <jrd1415 at gmail.com>
>
>> Such an observer would see the entire assembly shrink
>> proportionately along its length.  No breakage.
>
> I am absolutely positively 100% certain the string will
> break, I might even be correct; at least that's what my
> intuition insists is true.
>
> Look at it from the point of view of an observer at one end
> of the string. Suppose a fellow at the far end of the string
> has a clock and sends a pulse of LASER light to you every 10 seconds and
> suppose you also have a clock and it's synchronized with his, so you know
> how long it took the light to reach you, hence you know how far away the
> other end of the string is. The other fellow also reports from time to time
> on how fast he is moving relative to some fixed point that both of you can
> both see.
>
> An instant after you start moving you receive a report from
> the fellow at the other end of the string saying he hasn't started moving
> yet. Because of this you predict that when you make the next distance
> measurement you will find that
> the distance has decreased, but when the next LASER pulse arrives you find
> that the distance is just the same. You can only conclude that sometime
> after the last report the other fellow started to accelerate and did so
> faster
> than you did.
>
> When he sends his next report you find he has indeed started to move but he
> still isn't moving as fast as you are, and yet the distance is the same as
> before.  The fellow at the other end of the string must still be
> accelerating faster than you and in fact he always will be.
>
> Of course an observer at the other end of the string could
> make similar observations and conclude that you are accelerating faster than
> he is. The two observers disagree
> on who started moving first, but both agree that the other
> end of the string is accelerating faster than their end; and that pulls the
> string apart.
> John K Clark
>
>
>
>
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