Explaining Rigid Body Movement with 15*3*10^8m Stick

[arunrajagopal]

Assume a stick
of length 15*3*10^8 metre.
One end points towards
me, at the other end we
place a ball very near to
the end of the stick. If i
push the end pointing
towards me with some
force, instantaneously the
ball will be moved(~). At
the same time, a light
beam emanating
alongside me would take
15 seconds to reach that
ball. How can i change the
information of a space
even before the light beam
reaches out to that place
(~)? This question appears
to be childish, pardon my
innocence, explain me
please. I've been baffled
by this question since my
childhood. I know this
question is a flaw or
immature way of
understanding a concept,
please find out the
misconception I've been
thinking of.

P.S: I'm NOT gonna
SHAKE, or BANG, or MAKE
VIBRATE the stick. This situation is slightly analogous to Newton's gravity model which contradicts with light's speed limit later overturned by einstein's general theory of relativity, but not completely i think.

(~)-Doubtful.

 

[Doc Al]

If i
push the end pointing
towards me with some
force, instantaneously the
ball will be moved(~).

When you push one end of the 'rigid' body, it takes time for the other end to move. It's not instantaneous.

 

[lyy1992]

When you push one end of the 'rigid' body, it takes time for the other end to move. It's not instantaneous.

That means the ball will move 15 seconds later after you pushed the rod? The force itself is also traveling at the speed of light?

 

[Fredrik]

No, at the speed of sound. DaleSpam posted a nice FAQ reply to this question yesterday.

https://www.physicsforums.com/showthread.php?t=536289

If you hit the surface closest to you so hard that it's forced to move faster than the speed of sound in the material, it will probably break. It will also create a disturbance that propagates faster than the speed of sound for a little while (but obviously never faster than the object that hit it), and eventually turns into a plain old sound wave when it has lost enough energy.