"Bill Hobba" wrote in message
...
| Bilge correctly wrote:
| Einstein could not have made a statement about "inertial frames"
| at all without appealing to newtonian mechanics. In fact, special
| relativity suffers from the defect of being unable to adequately
| define an inertial frame, newton or no newton. If einstein can rely
| on classical mechanics to help define the meaning of "inertial",
| then it's certain;y reasonable to use the first postulate and
| the fact that one cannot turn around in the time direction to rule
| out a euclidean metric.
|
| Just so people understand the problem with inertial frames comes when you
| examine then closely - normal simple definitions found in textbooks are ok
| if you don't examine then really carefully. In fact in Lagrangien
mechanics
| you define an inertial reference frame before you introduce any axioms.
| Actually it is also encoded is Newton's first law which should really read
| inertial reference frames exist ie frames in which free particles move
with
| constant velocity. Less someone objects that that is a circular argument
| (ie a free particle is one that has no force acting on it which implies it
| moves at constant velocity) a free particle can be defined as a particle
| that moves as if they were the only thing in an inertial frame. The
| problems with inertial frames comes when you examine closely exactly how
you
| specify a coordinate system and ensure clocks are synchronized. Just a
| question for Bilge though. Exactly how you rigorously define an inertial
| reference frame is not really something I have gone into detail about but
my
| understanding is it can be rigorously defined, it just requires a lot of
| care, or am I wrong?

I like the way Griffiths described an inertial frame in "Introduction to
Electrodynamics".

"To avoid this trap we define an inertial frame formally as one in which
Newton's first law holds. If you want to know whether you're in an inertial
frame, throw some rocks around---if they travel in straight lines at
constant speed, you've got yourself an inertial frame, and any frame moving
at constant velocity with respect to you will be another inertial frame."

I don't see that it has to be any more complicated than this.

FrediFizzx