At 05:29 PM 10/15/00 -0400, Ludwik Kowalski wrote:
a) Is nature governed by laws,
Yes and no. Mostly yes.
I say mostly yes, even though
-- There are parts of physics where God evidently does play dice. We
have no law to predict the outcome of any particular dice-roll.
-- There are parts of physics that we don't understand.
-- I suspect there will always be parts of physics we don't understand.
I say mostly yes, because there is a huge amount of stuff we do
understand. We can construct macroscopic technology that averages out the
dice-rolls and performs all sorts of wonderful predictable actions.
b) Are these laws causal?
That's an interesting question, but the wording is a bit ambiguous. Let's
break it into less-ambiguous sub-questions:
1) If we take all the laws of physics collectively, do they express
causality principles? Answer: Yes.
2) If we take one of the laws of physics individually, is that law
consistent with the overall causality principles? Answer: Yes. It would
be very bad to have one of the laws contradict the others.
3) If we take one of the laws of physics individually, does that law by
itself encode everything we know about causality? Answer: In most cases,
no.
In particular, the law F=ma does not encode _any_ of what we know about
causality.
-- F=ma does not encode any of what we know about the arrow of time in
thermodynamics.
-- F=ma does not encode any of what we know about light-cones in special
relativity.
-- F=ma does not encode any of what we know about neutral Kaon decay.
Summary: F=ma doesn't violate causality, but it doesn't enforce it,
either. It just goes along for the ride.
We have exhibited cases where it is more natural to calculate acceleration
in terms of F/m, and vice versa (F in terms of m*a); no law of mechanics
favors one over the other.