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

On Aug 10, 9:35 am, Tom Roberts <tjroberts...@xxxxxxxxxxxxx> wrote:

Yuan...@xxxxxxxxx wrote:

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

And third. The translator added the footnote "to lowest order in v/c",
which is relevant.


Of course, as you say, the footnote was added by the translator - many
years later.

What Einstein actually wrote, in 1905, translates as " ...a system of
coordinates in which Newtonian mechanics holds good".

What Einstein essentially did was to introduce additional postulates
which show that (the laws of) Newton's mechanics do not hold good in a
system in which Newtonian mechanics holds good.

Being as this is a contradiction, translators felt obliged to
"correct" Einstein by inserting footnotes such as "to lowest order in
v/c" or "to a first approximation".

(The earliest such note that I have seen is dated 1923 - 18 years
after the original.)

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

That was not a "shock" at all in 1905. Einstein was consolidating
Maxwell's equations into the wider realm of theoretical physics at the
time, of which the PoR was a founding principle.

IMHO this is the major reason why Planck and others
"jumped on the relativity bandwagon" so quickly.


Not a shock at all to those who already know about it - by 1905 the
principle of relativity was several hundred years old.

But the PoR always "come(s) as a great shock" - it just doesn't
"return as a shock" e.g to "Planck and others" who already know it.


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.

Well this is irrelevant to SR, and none of these were "shocks" in 1905
-- back then it was "obvious" and unquestioned that inertial frames
covered all of space. Today we know about your points because of GR and
a much wider theoretical knowledge of differential geometry.

It's not "irrelevan to SR", which is precisely why the translators
point out that Einstein's "stationary frame" is Newtonian only "to
lowest order in v/c" or "to a first approximation".

If it were irrelevant to SR, they would not have inserted the caveat.

Note my point that "it's far from clear that that inertial frames can
ven exist except as local approximations." Which is precisely the
point to which the translator was alluding.

It's not necessary to understand GR or differential geometry to
question, as I did, the existence of these "ideal" inertial frames or
their constant relative velocities.

They are as undetectible as the aether.

Love,
Jenny


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