Re: The first postulate is a truism.

On Sat, 21 Jun 2025 22:31:48 +0000, Python wrote:

Le 21/06/2025 à 23:14, clzb93ynxj@att.net (LaurenceClarkCrossen) a écrit
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On Sat, 21 Jun 2025 10:19:43 +0000, Mikko wrote:
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On 2025-06-20 18:55:34 +0000, LaurenceClarkCrossen said:
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On Fri, 20 Jun 2025 9:06:49 +0000, Mikko wrote:
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On 2025-06-19 17:37:29 +0000, LaurenceClarkCrossen said:
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Perplexity:
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"The First Postulate of Special Relativity
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Statement of the First Postulate
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The first postulate of special relativity, also known as the principle
of relativity, states:
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The laws of physics are the same in all inertial frames of
reference."
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"truism
/ˈtrˌizƏm/  n. a statement that is obviously true and says nothing new
or interesting. —truistic/trˈistik/ adj." -Oxford American.

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The first postulate is not a truism. It is possible to imagine a world
where it is not true and to believe that we actually live in a such
world.

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Your reply does not explain how it is not obviously true and nothing new
that wasn't already known long before Einstein.

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I did explain. And what I said was indeed known long before Einstein.
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If the first postulate were a truism nobody would ever have believed
otherwise. But ancinet literature shows that the opposite belief was
common.

So, Einstein added nothing new. How does that provide a basis for his
new theory? That he accepted the consensus view since Newton?

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Read paragraph I.1. in Einstein paper. This is the main point : the
meaning of the time coordinate  in an inertial frame.
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Up to Einstein (well, it started before with Poincaré and others) it was
taken for granted that you don't have to care about the time label of a
given event, without justification but the prejudice of existence of
some
"universal time". Einstein asked for the time coordinate to be defined
physically and proposed a procedure (the same one Poincaré proposed
before) and he proved that such a procedure is in conflict with absolute
simultaneity. Moreover it provides a way to treat space-time as a
geometric object (i.e. independent of coordinates), then comes
Minkowski,
GR, etc.
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Einstein expressed for space-time what Pythagoras theorem expressed for
space: a coordinate-free invariant.

So the first postulate says the physics formulas are the same in all
inertial frames, and Einstein concludes that the time coordinate is
different?