Re: Expelled: If you don't believe in holy physics dogma ; you're fired!

"Timo A. Nieminen" <timo@[EMAIL PROTECTED]
> wrote in message 
news:Pine.WNT.4.64.0806221102300.656@[EMAIL PROTECTED]
> On Sat, 21 Jun 2008, Bill Miller wrote:
>
>> One of the fundamental laws of mechanics is Newton's law of action and
>> reaction, usually stated as : "Whenever a body exerts a force (action)
on 
>> a
>> second body, the second body exerts an equal and opposite force 
>> (reaction)
>> on the first body."
>>
>> Suppose that a stationary mass is located in the gravitational field of
>> another, distant stationary mass.The two m***** exert equal and
opposite
>> forces on each other. (Action and reaction)  Let us now allow one mass
to
>> move under the action of the field of the other mass. ut the second
mass,
>> being far away, does not yet "know
>> that the first mass has moved. (gravity -- like light -- cannot
propagate
>> instantaneously.) The second body continues to experience the same
force 
>> as
>> before.
>>
>> In other words, the forces are now unequal in magnitude and direction
and
>> Newton's action/reaction law no longer holds! Further, this situation 
>> also
>> is in conflict with the very basic law of conservation of momentum.
>
> Hmm. Newton's 3rd law of motion (along with Newton 2, to relate force
and 
> transfer of momentum) is basically a statement that momentum is
conserved.

Correct. And as long as the interaction is of a contact nature, then 
eveything is OK. But when there is a delay between the action and the 
reaction, then *for that delay period* momentum is not conserved. But we 
know that momentum MUST be conserved, so we must look at Newton with an
eye 
to modifying it to deal with what amounts to a time dependency.

This is not a new idea. We have long recognized, for EM that electrostaic 
representations break down when time dependency is present.

Heaviside suggested this in 1893 but never took it all the way to its 
logical conclusion.
>
> Yes, if we consider two m***** as above (or two electric charges) to be 
> interacting with each other, we have exactly the problem you point out.
>
> Does this mean Newton 3 is wrong? Does this mean momentum is not 
> conserved? I would say that it means that we simply don't have a
situation 
> where there are two objects interacting at a distance, but two objects 
> each interacting with a field. Perhaps the interaction really is as 
> described by field theory, a local interaction between field and body,
and 
> we should throw away the classical mechanics idea of interaction at a 
> distance rather than Newton 3.

That's one way of dealing with it. I believe that a better way would be to

recognize that Newton's work is not applicable to time dependency. That's
no 
different, conceptually, from Maxwell's expansion of Ampere's Law to
include 
The rate of Change Of E field in order to deal with magnetic fields in a 
time-dependent environment.

Please note that Amoere's Law was not WRONG. It was simply not totally 
applicable to a time dependent environment. Same situation with Newton and

gravity.
>
> We know that a force is exerted on each mass. We know that in a static 
> case, the force is symmetric. We don't know that it is the other body
that 
> is actually exerting the force. The example you give strongly suggests 
> that it isn't.

Nope. It suggests (to me) that -- just like Maxwell's adaptation of
Ampere's 
Law -- we need an adaptation of Newton.
>
> It wasn't that long ago that I wrote a lot more about this, so I won't 
> repeat it here.
>
> But for an example of a "law" by Newton that we know is only an 
> approximation: Newton's law of universal gravitation.
>
> -- 
> Timo

Bill