Re: About frames moving at constant velocity with respect to inertial ones

On Aug 9, 5:59 pm, Eric Gisse <jowr...@xxxxxxxxx> wrote:

On Aug 9, 2:00 pm, va...@xxxxxxxxxxx wrote:



You are suggesting that the definition of "inertial system" is "one
moving at constant velocity with respect to...an inertial system? A
little funny, isn't it?

Uh, no.

An inertial frame, by definition, is one moving with constant
velocity.


Not so!

The *definition* of an inertial frame was one in which Newton's first
and second laws of motion hold true.

In SR, this is might also be the case, but only if we use relativistic
mass when formulating Newton's Second Law.

If we wish to avoid the use of relativistic mass, then the defintion
gets amended and an inertial frame is defined as one in which Newton's
First Law holds true.


If another frame is moving with constant velocity with
respect to /another/ frame moving with constant velocity, it shouldn't
come as a great shock that it too is an inertial frame.


Now you're touching on the principle of relativity, which did come as
a great shock, even when expressed in its Galilean form.

Another great shock is that it's far from clear that inertial frames
can even exist except as local approximations.

An even greater shock comes when we realise that these "approximate"
inertial frames do not, in general, have constant relative velocities.


If I need to expand on this further, you might want to consider not
posting in a physics newsgroup.


Good advice for us all!

In any case, we are considering here Einstein's 1905 Relativity. Only
what Einstein wrote in 1905 is relevant here.

"We" are considering nothing.

It shows!

Love,
Jenny

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