Re: Evil Twin Paradox

On Wed, 8 Aug 2007 06:08:35 -0700, "N:dlzc D:aol T:com \(dlzc\)"
<dlzc@xxxxxxx> wrote:

Dear David:

"David" <dseppala@xxxxxxxxxxxxx> wrote in message
news:3g9jb3d02c9bbq31e126aqkjirneu6jf4m@xxxxxxxxxx
On Tue, 7 Aug 2007 20:50:55 -0700, "N:dlzc D:aol T:com
\(dlzc\)"
<dlzc@xxxxxxx> wrote:
"David" <dseppala@xxxxxxxxxxxxx> wrote in message
news:djeib3d29fuqhf6jqphp86197mqe13mhbe@xxxxxxxxxx
...
In this problem as I stated relative to each spaceship
the projectile travels perpendicular to the ship.

Then the bullet is *much* narrower than the gap in the wall,
and
there is no paradox.

That is the rest frame view (good twin's frame).

No, it is (based on your geometry) the frame of the good twin
*and* that of the bullet. The bullet is travelling at right
angles to the path of the evil twin, so the opening in the wall
is 10 ly wide.

In the evil twin's frame, the bullet is also narrower (upon
firing) than the opening in the wall.

No paradox.

David A. Smith
I don't see how to view things from the moving frame (evil twin's
frame). In this frame the evil twin is firing a 100 millimeter
projectile along the y axis. If the steel wall along the x axis was
stationary as measured in his frame, the gap in the wall would have to
be at least 100 millimeters wide for the bullet to pass through
without hitting the steel wall.
Now let's look at the problem with a very low velocity for the steel
wall and for the projectile as viewed in the evil twin's frame.
If the 100 millimeter projectile takes one second to cross the
x-axis as it travels along the y-direction, and if the steel wall is
moving at V=10 m/s along the x-axis, the gap in the wall must be far
larger than 100 millimeters for the projectile to pass through without
hitting the walls - the gap would have to be around 10.1 meters wide
for the projectile to pass.
Now here's what I don't follow. In the moving frame (the evil
twin's frame) what does he measure the size of the gap to be? When I
apply the simple formula L' = L * (SQRT(1-V**2/c**2)) and I let V get
sufficiently close to c, I find that L' (the length of the gap in the
moving frame) is less than 100 millimeters. How does the moving frame
observer (evil twin) measure the gap so that its larger than 100
millimeters required for the projectile to pass through?
Thanks,
David

.

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