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Re: Causation in Physics: F=ma



On 11/14/2003 11:10 AM, Joseph Bellina wrote:

If we think of macroscopic objects, then there is a time delay
between the application of the force and the response of the object,
since the influence propogates at about the speed of sound.

so it seems to me appropriate to think of "force" as cause of change
in velocity.

Nice try, but it doesn't work that way.

In relativity we speak of the "light cone".
More generally it is the cone of causal propagation.
For material objects, it will be the *sound* cone.

When a disturbance propagates through the object,
points outside the cone will be subject to neither
a force nor an acceleration. If and when the force
arrives, there will be an acceleration, and vice
versa. So this example sheds no light on the
question of whether F causes ma, or vice versa, or
neither.

Other considerations still indicate that "neither"
is the right answer.