Ricardo Jimenez <rickyjim@earthlink.net> wrote:

> I have been under the impression that it means:
> 1. Two inertial observers define the second in the same way as a
> certain number of vibrations of a cesium atom.
> 2. They define the meter in the same way as the distance light travels
> in a certain fraction of a second.
> 3. They both pick a pair of points at rest in their respective
> coodinate systems and measure the distance between them and the time
> light takes to go from one to the other.

Misunderstanding here: you cannot measure the distance
*and* the time it takes light to move between the points.
The distance between the points *is* the time
it takes light to travel between then, by definition.
(apart from a trivial numerical conversion constant)

> 4. When they divide their respective measurements in 3 of distance by
> their measurements of time, they get the same number.
>
> Is that it? No more, no less?

Less than less: It has nothing to do with it.
The definition of the meter in terms of the speed of light
has nothing to do with relativity
or with the constancy of the speed of light.
It must be made because it is the only way
to do accurate length measurements.
It is metrology, not relativity,

Jan

On Wednesday, 9 February 2022 at 14:27:01 UTC+1, J. J. Lodder wrote:

> Misunderstanding here: you cannot measure the distance
> *and* the time it takes light to move between the points.
> The distance between the points *is* the time
> it takes light to travel between then, by definition.
> (apart from a trivial numerical conversion constant)

JJ, poor halfbrain, definitions change, and you've
already shown you're rejecting the definitional
canon making the idiocy above true.

J. J. Lodder <nospam@de-ster.demon.nl> wrote:
> Ricardo Jimenez <rickyjim@earthlink.net> wrote:
>
>> I have been under the impression that it means:
>> 1. Two inertial observers define the second in the same way as a
>> certain number of vibrations of a cesium atom.
>> 2. They define the meter in the same way as the distance light travels
>> in a certain fraction of a second.
>> 3. They both pick a pair of points at rest in their respective
>> coodinate systems and measure the distance between them and the time
>> light takes to go from one to the other.
>
> Misunderstanding here: you cannot measure the distance
> *and* the time it takes light to move between the points.
> The distance between the points *is* the time
> it takes light to travel between then, by definition.
> (apart from a trivial numerical conversion constant)

Since the 1980s, yes. But before that, there was still a non-trivial claim.

However, it IS useful to pull in the Surveyor’s Parable here and note that
the difference in units for distance and time are more or less a historical
accident and without physical necessity. Then, converting to a more
sensible system of units (so-called “natural units”), the statement about
light speed is that the speed of light between any two events will always
be 1. Expressed this way, it seems a little less peculiar that it would
turn out that way.

>
>> 4. When they divide their respective measurements in 3 of distance by
>> their measurements of time, they get the same number.
>>
>> Is that it? No more, no less?
>
> Less than less: It has nothing to do with it.
> The definition of the meter in terms of the speed of light
> has nothing to do with relativity
> or with the constancy of the speed of light.
> It must be made because it is the only way
> to do accurate length measurements.
> It is metrology, not relativity,
>
> Jan
>
>
>
>
>

--
Odd Bodkin -- maker of fine toys, tools, tables

Odd Bodkin <bodkinodd@gmail.com> wrote:

> J. J. Lodder <nospam@de-ster.demon.nl> wrote:
> > Ricardo Jimenez <rickyjim@earthlink.net> wrote:
> >
> >> I have been under the impression that it means:
> >> 1. Two inertial observers define the second in the same way as a
> >> certain number of vibrations of a cesium atom.
> >> 2. They define the meter in the same way as the distance light travels
> >> in a certain fraction of a second.
> >> 3. They both pick a pair of points at rest in their respective
> >> coodinate systems and measure the distance between them and the time
> >> light takes to go from one to the other.
> >
> > Misunderstanding here: you cannot measure the distance
> > *and* the time it takes light to move between the points.
> > The distance between the points *is* the time
> > it takes light to travel between then, by definition.
> > (apart from a trivial numerical conversion constant)
>
> Since the 1980s, yes. But before that, there was still a non-trivial claim.

Yes, a non-trivial claim of low accuracy.

> However, it IS useful to pull in the Surveyor's Parable here and note that
> the difference in units for distance and time are more or less a historical
> accident and without physical necessity. Then, converting to a more
> sensible system of units (so-called "natural units"), the statement about
> light speed is that the speed of light between any two events will always
> be 1. Expressed this way, it seems a little less peculiar that it would
> turn out that way.

Yes, that is instructive, for geometry, but obsolete for physics.
There is no longer a separate unit of length,
for reasons that have nothing to do with relativity.

Jan

Ricardo Jimenez <rickyjim@earthlink.net> wrote:
> On Wed, 9 Feb 2022 14:26:57 +0100, nospam@de-ster.demon.nl (J. J.
> Lodder) wrote:
>
>> Ricardo Jimenez <rickyjim@earthlink.net> wrote:
>>
>>> I have been under the impression that it means:
>>> 1. Two inertial observers define the second in the same way as a
>>> certain number of vibrations of a cesium atom.
>>> 2. They define the meter in the same way as the distance light travels
>>> in a certain fraction of a second.
>>> 3. They both pick a pair of points at rest in their respective
>>> coodinate systems and measure the distance between them and the time
>>> light takes to go from one to the other.
>>
>> Misunderstanding here: you cannot measure the distance
>> *and* the time it takes light to move between the points.
>> The distance between the points *is* the time
>> it takes light to travel between then, by definition.
>> (apart from a trivial numerical conversion constant)
>>
>>> 4. When they divide their respective measurements in 3 of distance by
>>> their measurements of time, they get the same number.
>>>
>>> Is that it? No more, no less?
>>
>> Less than less: It has nothing to do with it.
>> The definition of the meter in terms of the speed of light
>> has nothing to do with relativity
>> or with the constancy of the speed of light.
>> It must be made because it is the only way
>> to do accurate length measurements.
>> It is metrology, not relativity,
>>
>> Jan
>>
>>
> OK, so what do you think speed of light constancy means? However you
> set up making time and length measurements in one inertial system, you
> have to make some sort of assumption as how they compare when doing
> the same in another inertial systems. I guess you are saying that the
> latter is relativity while the former is metrology.
>

There are a couple things being noted in this thread.

Jan’s point, as I understand it (and it’s true) is that speed of light
constancy is a fait accompli at this point, well established enough that
the speed of light is now ASSUMED to be a constant, and in fact a constant
of conversion as straightforward as 2.54 cm/in. In this sense, there’s
nothing to test about that claim whatsoever anymore. This is so true that
the standard meter is DEFINED as that constant times a standard second.
That’s why it’s now metrology.

Before this was taken to be an accepted fact, however, the claim really had
to do with the rate that a SINGLE LIGHT RAY would be measured to propagate
at, as measured in two different reference frames. This is why I made the
distinction from the case you mentioned which is just taking a light ray
measured in one frame and a different light ray measured in a different
frame and comparing the results of each.

--
Odd Bodkin -- maker of fine toys, tools, tables

On Wednesday, 9 February 2022 at 17:56:11 UTC+1, bodk...@gmail.com wrote:
> Ricardo Jimenez <rick...@earthlink.net> wrote:
> > On Wed, 9 Feb 2022 14:26:57 +0100, nos...@de-ster.demon.nl (J. J.
> > Lodder) wrote:
> >
> >> Ricardo Jimenez <rick...@earthlink.net> wrote:
> >>
> >>> I have been under the impression that it means:
> >>> 1. Two inertial observers define the second in the same way as a
> >>> certain number of vibrations of a cesium atom.
> >>> 2. They define the meter in the same way as the distance light travels
> >>> in a certain fraction of a second.
> >>> 3. They both pick a pair of points at rest in their respective
> >>> coodinate systems and measure the distance between them and the time
> >>> light takes to go from one to the other.
> >>
> >> Misunderstanding here: you cannot measure the distance
> >> *and* the time it takes light to move between the points.
> >> The distance between the points *is* the time
> >> it takes light to travel between then, by definition.
> >> (apart from a trivial numerical conversion constant)
> >>
> >>> 4. When they divide their respective measurements in 3 of distance by
> >>> their measurements of time, they get the same number.
> >>>
> >>> Is that it? No more, no less?
> >>
> >> Less than less: It has nothing to do with it.
> >> The definition of the meter in terms of the speed of light
> >> has nothing to do with relativity
> >> or with the constancy of the speed of light.
> >> It must be made because it is the only way
> >> to do accurate length measurements.
> >> It is metrology, not relativity,
> >>
> >> Jan
> >>
> >>
> > OK, so what do you think speed of light constancy means? However you
> > set up making time and length measurements in one inertial system, you
> > have to make some sort of assumption as how they compare when doing
> > the same in another inertial systems. I guess you are saying that the
> > latter is relativity while the former is metrology.
> >
> There are a couple things being noted in this thread.
>
> Jan’s point, as I understand it (and it’s true) is that speed of light
> constancy is a fait accompli at this point, well established enough that
> the speed of light is now ASSUMED to be a constant, and in fact a constant
> of conversion as straightforward as 2.54 cm/in. In this sense, there’s
> nothing to test about that claim whatsoever anymore. This is so true that
> the standard meter is DEFINED as that constant times a standard second.
> That’s why it’s now metrology.

Even some of The Shit's priests, like JJ Lodder, are rejecting
your idiotic definitions. Not even talking about serious people.

Ricardo Jimenez <rickyjim@earthlink.net> wrote:
> On Wed, 9 Feb 2022 16:56:07 -0000 (UTC), Odd Bodkin
> <bodkinodd@gmail.com> wrote:
>
>> There are a couple things being noted in this thread.
>>
>> Jan’s point, as I understand it (and it’s true) is that speed of light
>> constancy is a fait accompli at this point, well established enough that
>> the speed of light is now ASSUMED to be a constant, and in fact a constant
>> of conversion as straightforward as 2.54 cm/in. In this sense, there’s
>> nothing to test about that claim whatsoever anymore. This is so true that
>> the standard meter is DEFINED as that constant times a standard second.
>> That’s why it’s now metrology.
>>
>> Before this was taken to be an accepted fact, however, the claim really had
>> to do with the rate that a SINGLE LIGHT RAY would be measured to propagate
>> at, as measured in two different reference frames. This is why I made the
>> distinction from the case you mentioned which is just taking a light ray
>> measured in one frame and a different light ray measured in a different
>> frame and comparing the results of each.
>
> I'm still missing something. I understand that nowadays 2 different
> inertial observers set up metrology in their respective coordinate
> systems by assuming speed of light constancy in their own system. I
> don't see how you can conclude that the 2 different observers will
> come up with the same number for the interval between 2 events unless
> you make some additional assumption.
>

Well, look at it this way. Suppose the speed of light were NOT constant
from frame to frame, and that it depended on the speed of the source
relative to the receiver (say). Then c is not really a worthwhile constant
at all.

So FIRST the claims of relativity need to be tested well, including the
frame-independence of that speed. (Or if you like, experimentally testing
that v’ = (v+u)/(1+uv/c^2).) That in fact was done and to sufficient
quality that the constancy of c is not in doubt. When that got established,
then saying, “Well it’s just a constant then” allows the metrology
decision.

--
Odd Bodkin -- maker of fine toys, tools, tables

On Wednesday, 9 February 2022 at 19:08:57 UTC+1, bodk...@gmail.com wrote:

> So FIRST the claims of relativity need to be tested well, including the
> frame-independence of that speed. (Or if you like, experimentally testing
> that v’ = (v+u)/(1+uv/c^2).) That in fact was done and to sufficient
> quality that the constancy of c is not in doubt.

And while an idiot woodworker has no doubts, forbidden by his
moronic religion TAI keep measuring t'=t, just like all serious
clocks always did.
Even your idiot guru, BTW, was unable to insist on such an idiocy
for a long time, and his GR shit had to withdraw from it.

Ricardo Jimenez <rickyjim@earthlink.net> wrote:

> On Wed, 9 Feb 2022 14:26:57 +0100, nospam@de-ster.demon.nl (J. J.
> Lodder) wrote:
>
> >Ricardo Jimenez <rickyjim@earthlink.net> wrote:
> >
> >> I have been under the impression that it means:
> >> 1. Two inertial observers define the second in the same way as a
> >> certain number of vibrations of a cesium atom.
> >> 2. They define the meter in the same way as the distance light travels
> >> in a certain fraction of a second.
> >> 3. They both pick a pair of points at rest in their respective
> >> coodinate systems and measure the distance between them and the time
> >> light takes to go from one to the other.
> >
> >Misunderstanding here: you cannot measure the distance
> >*and* the time it takes light to move between the points.
> >The distance between the points *is* the time
> >it takes light to travel between then, by definition.
> >(apart from a trivial numerical conversion constant)
> >
> >> 4. When they divide their respective measurements in 3 of distance by
> >> their measurements of time, they get the same number.
> >>
> >> Is that it? No more, no less?
> >
> >Less than less: It has nothing to do with it.
> >The definition of the meter in terms of the speed of light
> >has nothing to do with relativity
> >or with the constancy of the speed of light.
> >It must be made because it is the only way
> >to do accurate length measurements.
> >It is metrology, not relativity,
> >
> >Jan
> >
> >
> OK, so what do you think speed of light constancy means? However you
> set up making time and length measurements in one inertial system, you
> have to make some sort of assumption as how they compare when doing
> the same in another inertial systems. I guess you are saying that the
> latter is relativity while the former is metrology.

Yes, metrology is about doing physics in one inertial system,
in particular in a standards lab.
Relativity is the postulate that all of physics is the same
in all inertial systems.
It is backed by all the experience that we have.

Einstein's breakthrough was the realisation
that 'all of physics' includes electromagnetism,
hence the speed of light.

What is 'new' is the precision revolution,
made possible by basing all of physics
on the measurement of time alone.
(hence abolishing all other primary standards)

Jan

Ricardo Jimenez <rickyjim@earthlink.net> wrote:
> What I think now is that:
> 1. There is a observer helper at each point of an inertial system
> having the same kind of cesium clock and as a result the clocks can be
> synchronized by sending light signals back and forth between them.
>
> 2. Then the chief inertial observer will get a non-contradictory
> definition of distance between any two spatial points in terms of
> sending and receiving of a light signal between them. In particular,
> the Pythagorean theorem will hold.
>
> 3. Then you assume that the speed of light between a send/receive
> pair of events will be the same regardless of in which inertial system
> the measurement is made.
>
> 4. 1,2,3 are enough to derive the Lorentz transformation and the rest
> of special relativity and you need all three.
>

Hmm. I’m not sure 4 follows from 1-3.

For example, the clocks you synchronized in 1 will not be synchronized in
any other inertial frame.

--
Odd Bodkin — Maker of fine toys, tools, tables

On Wednesday, 9 February 2022 at 22:31:36 UTC+1, bodk...@gmail.com wrote:

> For example, the clocks you synchronized in 1 will not be synchronized in
> any other inertial frame.

Unless, of course, they're improper, Like TAI, GPS, UTC
or any serious clocks made by serious people.

On Wednesday, 9 February 2022 at 22:31:25 UTC+1, J. J. Lodder wrote:

> Yes, metrology is about doing physics in one inertial system,
> in particular in a standards lab.
> Relativity is the postulate that all of physics is the same
> in all inertial systems.
> It is backed by all the experience that we have.

In the meantime in the real world, however, forbidden
by your moronic religion TAI keep measuring t'=t,
just like all serious clocks always did.

Ricardo Jimenez <rickyjim@earthlink.net> wrote:
> On Wed, 9 Feb 2022 21:31:29 -0000 (UTC), Odd Bodkin
> <bodkinodd@gmail.com> wrote:
>
>> Ricardo Jimenez <rickyjim@earthlink.net> wrote:
>>> What I think now is that:
>>> 1. There is a observer helper at each point of an inertial system
>>> having the same kind of cesium clock and as a result the clocks can be
>>> synchronized by sending light signals back and forth between them.
>>>
>>> 2. Then the chief inertial observer will get a non-contradictory
>>> definition of distance between any two spatial points in terms of
>>> sending and receiving of a light signal between them. In particular,
>>> the Pythagorean theorem will hold.
>>>
>>> 3. Then you assume that the speed of light between a send/receive
>>> pair of events will be the same regardless of in which inertial system
>>> the measurement is made.
>>>
>>> 4. 1,2,3 are enough to derive the Lorentz transformation and the rest
>>> of special relativity and you need all three.
>>>
>>
>> Hmm. I’m not sure 4 follows from 1-3.
>>
>> For example, the clocks you synchronized in 1 will not be synchronized in
>> any other inertial frame.
>
> Yes, of course. 1 means that each inertial system has its own cllocks
> synchronized. What else is needed to derive 4?
>

I do not think it is sufficient to just use the second Einstein postulate
(the frame invariance of the speed of light) to derive the Lorentz
transforms. At least, I’ve never seen it successfully done.

--
Odd Bodkin -- maker of fine toys, tools, tables