Re: Newton's 3rd law? was Re: inertial forces (definition)

[Robert Carlson <Raacc@AOL.COM>]

David,

Can you show me how you would calculate the period of the space shuttle at an
altitude of 200 miles above the Earth's surface?

Bob Carlson

In a message dated 10/18/99 10:24:48 PM Central Daylight Time,
David_Bowman@GEORGETOWNCOLLEGE.EDU writes:

> Newton's 3rd law implies and is consistent only with instantaneous
>  interaction at a distance.  It is inconsistent with the retarded
>  causation of relativity--both special and general.  The only kind of
>  Newton's 3rd law that can survive when relativity is taken into account
>  is for a zero distance contact force between particles.  Unfortunately we
>  don't know of any such forces in real life.  The closest to a real
>  contact force we can come up with is for the weak interaction whose range
>  is about 2 x 10^(-18) m.  All realizable forces are carried through the
>  intermediary of a field of some kind.  Such a field propagates changes no
>  faster than c.  This means that Newton's third law can't hold for any two
>  spatially separated objects interacting via the field because they can't
>  keep in instantaneous communication with each other so they can exert
>  their respective forces on each other in a way that can be precisely
>  synchronized as exactly "equal & opposiite".  Of course, this does not
>  mean that Newton's third law is not an excellent *approximation* in many
>  important instances.  In the case of gravitation it is an even better
>  approximation than it is for electromagnetism because gravitational
>  interactions tend to have the effect of their actual retarded interaction
>  cancel out in the near field to a higher order in 1/c^2 than they do for
>  electromagnetic forces.