Re: Motion Through Space Is Meaningful


2ndPostulateDude wrote:
> PD wrote:
> >2ndPostulateDude wrote:
> >>SR's "prediction" of one-way light speed invariance is
> >>fully circular because the "invariance" is given up front
> >>(via a mere definition), so it must be the "result."
>
> >That's correct. It is not a prediction at all and is
> >irrelevant to the set of predictions that SR makes.
>
> Then why did you use it below in your list of "SR
> predictions"?

It wasn't. It is a *postulate* from which the prediction is *derived*.
It is not a prediction.

> And why is it called Einstein's
> light postulate? (A postulate in physics is a
> prediction

The hell it is! Look up the word in a dictionary!
A postulate is something that is *assumed without proof*.
In mathematics, it is synonymous with "axiom", which is another word
you can look up.
One then checks whether the *consequences* of that assumption match up
with reality.

> - it is a claim that something should
> be that way

This again is plain wrong, and is fundamental to your misconceptions.
Einstein's light postulate is stated and taken as *an assumption* from
which testable consequences can be derived. If the consequences are
shown to be incorrect, *then* one can assume that the postulates are
incorrect. However, no one has shown that the consequences of those
assumptions are incorrect, and therefore there is no reason to believe
that the assumptions are incorrect.

> - and in this case, it was Einstein's
> prediction that light's speed between two clocks
> should be invariant.)
>
> >>SR's "prediction" of "clock slowing" does not pertain
> >>to actual or physical clock rhythms, so is trivial.
>
> >Define actual or physical clock rhythms. That is, define
> >*exactly how* you would measure the physical duration of
> >some process.
>
> You seem to think that this is problematic; it is not.
> Here is a very simple definition of "intrinsic clock
> rhythm":
>
> Given atomic clocks, let
>
> (1) internal atomic transition = (1) time unit.
>
> Given this definition, there can be no ambiguity re the
> physical meaning of "intrinsic clock rhythm" because we
> have the following simple physical identity:
>
> Readings = Rhythms
>
> That is, the above requirement directly relates a clock's
> current reading with its total number of atomic vibrations.
>
> And it's equally easy to measure the actual (physical)
> duration of a process:
>
> Measure light's passing speed using a pair of (absolutely
> or truly) synchronous clocks. Since, per the MMx, clocks
> run slow, and rods shrink in a known way, we can use the
> result to determine our speed through space. We can then
> tell if a given clock is really slowed, and by how much.

Let me give you an example. In one experiment where I am watching muons
decay, they live for an average of 2.2 usec. In another experiment, a
population of muons identical in every way except for their state of
motion lives on average 5.2 usec. In aother experiment, a population of
muons identical in every way except for their state of motion lives on
average 11.2 usec.

Show me specifically how you know the speed through space of either me
or the muons in each case.

By the way, the three cases given above are physically real.

>
> >You're right, since SR in fact says that physical clock
> >rhythms do not have any physical meaning outside of the
> >*measurement* made, then it makes no predictions at all
> >about any slowing of a physical clock rhythm, nor does
> >it pretend to.
>
> It doesn't pretend to address physical phenomena because
> it is not a scientific theory.
>
> >>And the same goes for SR's "predictions" of length
> >>"contractions" and "mass" "increases."
>
> >Define actual or physical lengths. That is, define
> >*exactly how* you would measure the physical length
> >of some object.
>
> No problem. You first determine your speed through space
> as given above, and then you will know by how much your
> ruler is physically contracted.

This tells me nothing about how I measure the length of a rod. Suppose
I don't know its speed, though I can see it flying by. How do I measure
its length?

>
> >>SR did not predict round-trip light speed invariance or
> >>isotropy - SR merely incorporated these as experimental
> >>results.
>
> >You're right, this was built in as an assumption, not as
> >a prediction. Gee, you really think that's all SR had to say?
>
> It wasn't a meant as mere assumption, but as an experimental
> fact (given by the MMx).
>
> >How about the following?
>
> >1. The measured spacetime interval ....
>
> The space-time interval has no physical meaning, so it is
> irrelevant to physics.

This is an assertion without basis. If I measure something that stays
invariant, regardless of observer, this is the customary flag for
physicists that it is physically significant. Energy and momentum would
not be considered to have physical meaning if it were not for the
observation that those quantities are locally conserved. But they are
and that's why they are physical quantities. The interval is
*experimentally* verified to be an invariant quantity and therefore it
is a quantity with presumably physical meaning.

>
> >2. The measured momenergy ....
>
> Since SR pertains not to any actual or intrinsic energy or to
> any intrinsic or absolute momentums, this, too, is irrelevant
> to physics.

See the above remark regarding interval.

How would you measure or even define an object's intrinsic or absolute
momentum?

>
> >3. Velocities do not add algebraically ....
>
> You apparently forgot that SR's composition of velocities
> equation is based entirely on Einstein's light postulate,
> which you yourself (above) agreed was a mere triviality
> as far as physics goes, and, indeed, was not even important
> to SR. Circularities and trivialities abound in SR!

The fact that it is based on a postulate does not mean that it is a
postulate itself. It is a nontrivial prediction that is experimentally
testable and in fact experimentally confirmed.

>
> >4. Applying a constant force to an object will produce a
> >steady increase in the momentum of the object, but not
> >a steady increase in the velocity of the object; the
> >momentum is not bounded, but the velocity is (by c).
> >This is directly testable.
>
> SR does not predict a real max velocity, only a measured
> max velocity, and this is due entirely to Einstein's
> light postulate. (It forces clocks to be unable to measure
> a speed >c.)

So perhaps you need to tell me how to measure a true and absolute
velocity that is free from this burden.

>
> >This is just a sample of some of the basics. You apparently
> >are not aware of what SR says and what it does not.
>
> Hmmmmm....
>
> --
> 2nd Postulate Dude

.

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