Re: Help with SR time dilation
From: Ben Rudiak-Gould (br276deleteme_at_cam.ac.uk)
Date: 02/08/05
- Next message: Ken S. Tucker: "Re: GR -> Black Holes Can't Form... Take 2"
- Previous message: Bilge: "Re: Time Dilation Model, NO ONE can point out what's wrong"
- In reply to: dseppala_at_austin.rr.com: "Re: Help with SR time dilation"
- Next in thread: DavidBowman: "Re: Help with SR time dilation"
- Messages sorted by: [ date ] [ thread ]
Date: Tue, 08 Feb 2005 01:10:02 +0000
dseppala@austin.rr.com wrote:
> To help you visualize things. Let's make the moving trough (in Frame
> B) one-light year long. It is looks like a horse trough, which is
> basically a rectangular wooden box (or some other material) with no
> top. And lets say it is filled with water. Let this trough move past
> the pump in Frame A. The pump simply sprays water into the trough as
> the moving trough and water pass by. I don't see why one will need an
> indefinitely extending flexhose of some sort as you suggest.
Indeed not; this is a perfectly legitimate problem from an abstract SR
perspective, though still a bit iffy from an engineering perspective.
Considering an inertial frame in which the troughs move with equal and
opposite velocities, it's clear by symmetry that they will end up with equal
amounts of water after passing each other. In terms of A's rest frame, B
will be shorter (by a factor of gamma), meaning that the amount of time that
B's pump will be directly over some part of A will be larger (by a factor of
gamma) than the amount of time that A's pump will be directly over some part
of B. This is just enough to compensate for the fact that B's pump goes more
slowly (by the same factor of gamma). In terms of B's rest frame, the
description is the same, but with A and B reversed.
> Now if
> you want to include an argument that the length of the trough and the
> time constants assoicated with pumping out the water happen at
> different points in space, then instead of a single pump in the Frame
> A, we can have a series of pumps in frame A, and cycle them on and off
> as the single pump B of the moving frame is in their vicnity.
Note that by doing this you destroy the symmetry between A and B; i.e.
there's no longer any reason to expect from a symmetry argument that neither
trough will overflow. In fact in this case there will be a net increase in
the amount of water in trough B (though it won't overflow because the two
troughs will pass each other completely first). With respect to A's rest
frame, this is because the pump in trough B pumps more slowly. With respect
to B's rest frame, this is because there is overlap between the times that
the pumps in trough A are switched on. I'm assuming here that you wanted the
"pump switchover" to be instantaneous with respect to A's rest frame. If you
had a different synchronization method in mind then the analysis will be
different.
-- Ben
- Next message: Ken S. Tucker: "Re: GR -> Black Holes Can't Form... Take 2"
- Previous message: Bilge: "Re: Time Dilation Model, NO ONE can point out what's wrong"
- In reply to: dseppala_at_austin.rr.com: "Re: Help with SR time dilation"
- Next in thread: DavidBowman: "Re: Help with SR time dilation"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
