Sabine Hossenfelder: "The speed of light is the same for all observers." https://bigthink.com/hard-science/special-relativity-existential-physics/

No it obviously isn't. Here are two observers, stationary and moving:

https://www.youtube.com/watch?v=bg7O4rtlwEE

The speed of the light pulses relative to the stationary observer is

c = df

where d is the distance between subsequent pulses and f is the frequency measured at the stationary observer. The speed of the pulses relative to the moving observer is

c'= df' > c

where f' > f is the frequency measured at the moving observer.

See more here: https://twitter.com/pentcho_valev

Pentcho Valev

On 2022-08-20 11:08:13 +0000, Pentcho Valev said:

> Sabine Hossenfelder: "The speed of light is the same for all observers."
> https://bigthink.com/hard-science/special-relativity-existential-physics/

True.

> No it obviously isn't.

It isn't obvious as light is so fast.

> Here are two observers, stationary and moving:

In order to avoid unnecessary complications the moving observer
should move (as observed by the stationary observer) directly
towards to or away from the light source.

> The speed of the light pulses relative to the stationary observer is
>
> c = df
>
> where d is the distance between subsequent pulses and f is the
> frequency measured at the stationary observer. The speed of the pulses
> relative to the moving observer is

c' = d'f'

> where f' > f is the frequency measured at the moving observer.
and d' < d is the distance between subsequent pulses as measured by
the moving observer.
Or f' < f and d' > d if the moving observer is moving to the opposite
direction.

Observations show that c' = c both when c' is directly measured and
when d' and f' are separately measured.

Mikko

Le 20/08/2022 à 13:20, Mikko a écrit :
> On 2022-08-20 11:08:13 +0000, Pentcho Valev said:
>
>> Sabine Hossenfelder: "The speed of light is the same for all observers."
>> https://bigthink.com/hard-science/special-relativity-existential-physics/
>
> True.
>
>> No it obviously isn't.
>
> It isn't obvious as light is so fast.
>
>> Here are two observers, stationary and moving:
>
> In order to avoid unnecessary complications the moving observer
> should move (as observed by the stationary observer) directly
> towards to or away from the light source.
>
>> The speed of the light pulses relative to the stationary observer is
>>
>> c = df
>>
>> where d is the distance between subsequent pulses and f is the
>> frequency measured at the stationary observer. The speed of the pulses
>> relative to the moving observer is
>
> c' = d'f'
>
>> where f' > f is the frequency measured at the moving observer.
> and d' < d is the distance between subsequent pulses as measured by
> the moving observer.
> Or f' < f and d' > d if the moving observer is moving to the opposite
> direction.
>
> Observations show that c' = c both when c' is directly measured and
> when d' and f' are separately measured.
>
> Mikko

Obserbal speed Vo, ie measurable in any given reference frame, the speed
of light, is invariant by change of reference frame.

The general equation of addition of relativistic velocities applies to all
OBJECTS, and to all PROPERTIES OF PHYSICS.

In particular at the observable speed of light (speed of transmission of
information).

Here is the general relativistic equation

<http://news2.nemoweb.net/jntp?6BPZ3Iuhq3OFI-j0E15aMMT4GUI@jntp/Data.Media:1>

R.H.
<http://news2.nemoweb.net/?DataID=6BPZ3Iuhq3OFI-j0E15aMMT4GUI@jntp>

"To state that the speed of light is independent of the velocity of the observer is very counterintuitive. Some people even refuse to accept this as a logically consistent possibility, but in 1905 Einstein was able to show that it is perfectly consistent if you are prepared to give up assumptions about the absolute nature of space and time." http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html

So Einstein vandalized space and time and the counterintuitive nonsense became "perfectly consistent" with the preposterous "spacetime". Yet the constancy of the speed of light remained obvious nonsense in the Doppler effect scenario. The motion of the observer cannot change the wavelength of the incoming light:

"Thus, the moving observer sees a wave possessing the same wavelength [...] but a different frequency [...] to that seen by the stationary observer." http://farside.ph.utexas.edu/teaching/315/Waveshtml/node41.html

"The wavelength is staying the same in this case." https://www.youtube.com/watch?v=MHepfIIsKcE

"Vo is the velocity of an observer moving towards the source. This velocity is independent of the motion of the source. Hence, the velocity of waves relative to the observer is c + Vo. [...] The motion of an observer does not alter the wavelength. The increase in frequency is a result of the observer encountering more wavelengths in a given time." http://a-levelphysicstutor.com/wav-doppler.php

Accordingly, if the speed of the observer relative to the light source is Vo, the speed of the light relative to the observer is c+Vo.

More here: https://twitter.com/pentcho_valev

Pentcho Valev

Mikko wrote:

> On 2022-08-20 11:08:13 +0000, Pentcho Valev said:
>> Sabine Hossenfelder: "The speed of light is the same for all observers."
>> https://bigthink.com/hard-science/special-relativity-existential-physics/
>
> True.
>
>> No it obviously isn't.
>
> It isn't obvious as light is so fast.

That is not a convincing reasoning.

That the speed of light is observer-independent was already indicated by
observations of Io by Ole Rømer in the 17th century:

When Terra was farther away from Jupiter, Io was “behind schedule”; when it
was closer to Jupiter, Io was “ahead of schedule”. Knowing approximately
the difference between those distances and the times allowed Rømer to make
the first estimate of the sped of light.

And often overlooked fact is that this measurement depend on whether Terra
was moving away from Io, was moving sidewards, or towards it. This proves
the initial statement.

Multiple observations were made following that which confirmed this fact to
increasingly better precision. By 1983 the speed of light in vacuum has
been measured so precisely that its value had been defined as a fundamental
natural constant in the SI rather than begin measured:

c₀ = 299'792'458 m/s.

<https://www.bipm.org/en/measurement-units>

Since special relativity rests on that assumption, and the predictions of
special relativity have all been confirmed to very high precision, no
credible scientist would, and no ocreedible scientist does, question that
the speed of light in vacuum is observer-indepedent:

<https://www.youtube.com/watch?v=Txv7V_nY2eg&list=PL41EYJuJ5YuAb924jH_kYW5vszLfNaPWI&index=3>

PointedEars
--
«Nec fasces, nec opes, sola artis sceptra perennant.»
(“Neither high office nor power, only the scepters of science survive.”)

—Tycho Brahe, astronomer (1546-1601): inscription at Hven

[Fixed some egregious typos]

Mikko wrote:

> On 2022-08-20 11:08:13 +0000, Pentcho Valev said:
>> Sabine Hossenfelder: "The speed of light is the same for all observers."
>> https://bigthink.com/hard-science/special-relativity-existential-physics/
>
> True.
>
>> No it obviously isn't.
>
> It isn't obvious as light is so fast.

That is not a convincing reasoning.

That the speed of light is observer-independent was already indicated by
observations of Io by Ole Rømer in the 17th century:

When Terra was farther away from Jupiter, Io was “behind schedule”; when it
was closer to Jupiter, Io was “ahead of schedule”. Knowing approximately
the difference between those distances, and the times, allowed Rømer to make
the first estimate of the speed of light:

<https://en.wikipedia.org/wiki/R%C3%B8mer%27s_determination_of_the_speed_of_light>

An often overlooked fact is that these measurements did not depend on
whether Terra was moving away from Io, was moving sidewards, or towards it.
This confirms the initial statement already.

Multiple observations were made following that which confirmed this fact to
increasingly better precision. By 1983 the speed of light in vacuum had
been measured so precisely that its value had been defined as a fundamental
natural constant in the SI rather than being measured:

c₀ = 299'792'458 m/s.

<https://www.bipm.org/en/measurement-units>

Since special relativity rests on that assumption, and the predictions of
special relativity have all been confirmed to very high precision, no
credible scientist would, and no credible scientist does, question that
the speed of light in vacuum is observer-indepedent:

<https://www.youtube.com/watch?v=Txv7V_nY2eg&list=PL41EYJuJ5YuAb924jH_kYW5vszLfNaPWI&index=3>

PointedEars
--
«Nec fasces, nec opes, sola artis sceptra perennant.»
(“Neither high office nor power, only the scepters of science survive.”)

—Tycho Brahe, astronomer (1546-1601): inscription at Hven

On 8/20/2022 6:00 PM, Thomas 'PointedEars' Lahn wrote:

[...]

> Since special relativity rests on that assumption, and the predictions of
> special relativity have all been confirmed to very high precision, no
> credible scientist would, and no credible scientist does, question that
> the speed of light in vacuum is observer-indepedent:

While the general appearance of the text in your paragraph above appears
to be simple, I can't think of a more confusing presentation to the
point that it is misleading. But then this is your general approach
in these newsgroups. I'll not involve myself with further discussion
with you based on your past performance because you are disingenuous.

On Sunday, 21 August 2022 at 00:41:19 UTC+2, Thomas 'PointedEars' Lahn wrote:
> Mikko wrote:
>
> > On 2022-08-20 11:08:13 +0000, Pentcho Valev said:
> >> Sabine Hossenfelder: "The speed of light is the same for all observers.."
> >> https://bigthink.com/hard-science/special-relativity-existential-physics/
> >
> > True.
> >
> >> No it obviously isn't.
> >
> > It isn't obvious as light is so fast.
> That is not a convincing reasoning.
>
> That the speed of light is observer-independent was already indicated by
> observations of Io by Ole Rømer in the 17th century:

Only such an idiot can believe such an impudent lie.

whodat wrote:

> On 8/20/2022 6:00 PM, Thomas 'PointedEars' Lahn wrote:
>> Since special relativity rests on that assumption, and the predictions of
>> special relativity have all been confirmed to very high precision, no
>> credible scientist would, and no credible scientist does, question that
>> the speed of light in vacuum is observer-indepedent:
>
> While the general appearance of the text in your paragraph above appears
> to be simple, I can't think of a more confusing presentation to the
> point that it is misleading. But then this is your general approach
> in these newsgroups. I'll not involve myself with further discussion
> with you based on your past performance because you are disingenuous.

I am sorry if my explanations are too complex or large for your puny mind to
comprehend, but that is *your* problem.

PointedEars
--
Q: What did the nuclear physicist post on the laboratory door
when he went camping?
A: 'Gone fission'.
(from: WolframAlpha)

On 2022-08-20 22:14:07 +0000, Pentcho Valev said:

> "Thus, the moving observer sees a wave possessing the same wavelength
> [...] but a different frequency [...] to that seen by the stationary
> observer."
> http://farside.ph.utexas.edu/teaching/315/Waveshtml/node41.html

True only in non-relativistic situations, i.e. for speeds much less
than the speed of light, as noted on the same page.

Mikko

On 2022-08-20 23:00:11 +0000, Thomas 'PointedEars' Lahn said:

> [Fixed some egregious typos]
>
> Mikko wrote:
>
>> On 2022-08-20 11:08:13 +0000, Pentcho Valev said:
>>> Sabine Hossenfelder: "The speed of light is the same for all observers."
>>> https://bigthink.com/hard-science/special-relativity-existential-physics/
>>
>> True.
>>
>>> No it obviously isn't.
>>
>> It isn't obvious as light is so fast.
>
> That is not a convincing reasoning.

Pencho Valev's reasoning never is.

Mikko

On August 20, Thomas 'PointedEars' Lahn wrote:
> That the speed of light is observer-independent was already indicated by
> observations of Io by Ole Rømer in the 17th century:
> When Terra was farther away from Jupiter, Io was “behind schedule”; when it
> was closer to Jupiter, Io was “ahead of schedule”. Knowing approximately
> the difference between those distances, and the times, allowed Rømer to make
> the first estimate of the speed of light:
>
> An often overlooked fact is that these measurements did not depend on
> whether Terra was moving away from Io, was moving sidewards, or towards it.
> This confirms the initial statement already.

Not quite.

Rømer established that light speed is finite. However, his observations don't
test for observer independence, because his estimates of Jupiter's distance
DEPENDS (assumes) constant c, regardless of Earth's motion. Hence it's
circular, a fallacy, to claim that he demonstrated such a result.

> Multiple observations were made following that which confirmed this fact to
> increasingly better precision. By 1983 the speed of light in vacuum had
> been measured so precisely that its value had been defined as a fundamental
> natural constant in the SI rather than being measured:
> c₀ = 299'792'458 m/s.
>
> Since special relativity rests on that assumption, and the predictions of
> special relativity have all been confirmed to very high precision, no
> credible scientist would, and no credible scientist does, question that
> the speed of light in vacuum is observer-indepedent:

Since c is now a DEFINED constant, rather than measured, it is tautological
that it's observer independent. It's a matter of logic, not science.

That is, today, if light speed was measured as variable, depending on
velocity, the physicist would re-calibrate his instruments (of distance
and time), such that c always appears constant.

--
Rich

Mikko wrote:

> On 2022-08-20 23:00:11 +0000, Thomas 'PointedEars' Lahn said:
>> Mikko wrote:
>>> On 2022-08-20 11:08:13 +0000, Pentcho Valev said:
>>>> Sabine Hossenfelder: "The speed of light is the same for all
>>>> observers."
>>>> https://bigthink.com/hard-science/special-relativity-existential-physics/
>>>
>>> True.
>>>
>>>> No it obviously isn't.
>>>
>>> It isn't obvious as light is so fast.
>>
>> That is not a convincing reasoning.
>
> Pencho Valev's reasoning never is.

Check the quotation levels: I was referring to *your* reasoning.

(I have killfiled them.)

PointedEars
--
A neutron walks into a bar and inquires how much a drink costs.
The bartender replies, "For you? No charge."

(from: WolframAlpha)

On 2022-08-23 23:17:27 +0000, Thomas 'PointedEars' Lahn said:

> Mikko wrote:
>
>> On 2022-08-20 23:00:11 +0000, Thomas 'PointedEars' Lahn said:
>>> Mikko wrote:
>>>> On 2022-08-20 11:08:13 +0000, Pentcho Valev said:
>>>>> Sabine Hossenfelder: "The speed of light is the same for all
>>>>> observers."
>>>>> https://bigthink.com/hard-science/special-relativity-existential-physics/
>>>>
>>>> True.
>>>>
>>>>> No it obviously isn't.
>>>>
>>>> It isn't obvious as light is so fast.
>>>
>>> That is not a convincing reasoning.
>>
>> Pencho Valev's reasoning never is.
>
> Check the quotation levels: I was referring to *your* reasoning.
>
> (I have killfiled them.)

What in my message do you call "reasoning" ?

Mikko

Mikko wrote:

> On 2022-08-23 23:17:27 +0000, Thomas 'PointedEars' Lahn said:
>> Mikko wrote:
>>> On 2022-08-20 23:00:11 +0000, Thomas 'PointedEars' Lahn said:
>>>> Mikko wrote:
>>>>> On 2022-08-20 11:08:13 +0000, Pentcho Valev said:
>>>>>> Sabine Hossenfelder: "The speed of light is the same for all
>>>>>> observers."
>>>>>> https://bigthink.com/hard-science/special-relativity-existential-physics/
>>>>>
>>>>> True.
>>>>>
>>>>>> No it obviously isn't.
>>>>>
>>>>> It isn't obvious as light is so fast.
>>>> That is not a convincing reasoning.
>>> Pencho Valev's reasoning never is.
>> Check the quotation levels: I was referring to *your* reasoning.
>>
>> (I have killfiled them.)
>
> What in my message do you call "reasoning" ?

You argued that it would not be obvious that “the speed of light is the same
for all observers” because it would be “so fast”.

However, I have shown that with only 17th century astronomy it was already
possible to estimate the speed of light in (interplanetary) vacuum, and to
show that it does not depend on the motion of the observer relative to the
source.

That refutes your argument.

PointedEars
--
Q: Why is electricity so dangerous?
A: It doesn't conduct itself.

(from: WolframAlpha)

On Saturday, August 20, 2022 at 4:08:14 AM UTC-7, Pentcho Valev wrote:
> Sabine Hossenfelder: "The speed of light is the same for all observers." https://bigthink.com/hard-science/special-relativity-existential-physics/
>
> No it obviously isn't. Here are two observers, stationary and moving:
>
> https://www.youtube.com/watch?v=bg7O4rtlwEE
>
> The speed of the light pulses relative to the stationary observer is
>
> c = df
>
> where d is the distance between subsequent pulses and f is the frequency measured at the stationary observer. The speed of the pulses relative to the moving observer is
>
> c'= df' > c
>
> where f' > f is the frequency measured at the moving observer.
>
> See more here: https://twitter.com/pentcho_valev
>
> Pentcho Valev

There is No absolute rest for light or atom. Everything moves with respect to everything else.
The atom has its absolute motion in space toward or away from light's c speed in space.
There is a motion black hole where the atom moves fast enough ahead of light...

Mitchell Raemsch

On Sunday, 28 August 2022 at 01:12:20 UTC+2, Thomas 'PointedEars' Lahn wrote:

> However, I have shown that with only 17th century astronomy it was already
> possible to estimate the speed of light in (interplanetary) vacuum, and to
> show that it does not depend on the motion of the observer relative to the
> source.

Unforynately, only such an idiot can believe such a
nonsensical lie.

On 2022-08-27 23:12:16 +0000, Thomas 'PointedEars' Lahn said:

> However, I have shown that with only 17th century astronomy it was already
> possible to estimate the speed of light in (interplanetary) vacuum, and to
> show that it does not depend on the motion of the observer relative to the
> source.
>
> That refutes your argument.

If it were obvious in that the speed of light is independent of the
motion of the observer there would have been no point in Michelson-Morley
experiment.

Even now it is not obvious that the speed of light is the same
to all observers. In order to test it one needs instruments
that most people don't have.

Mikko

On Sunday, 28 August 2022 at 10:54:51 UTC+2, Mikko wrote:

> If it were obvious in that the speed of light is independent of the
> motion of the observer there would have been no point in Michelson-Morley
> experiment.
>
> Even now it is not obvious that the speed of light is the same
> to all observers.

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

Thomas 'PointedEars' Lahn <PointedEars@web.de> wrote:

> Mikko wrote:
>
> > On 2022-08-23 23:17:27 +0000, Thomas 'PointedEars' Lahn said:
> >> Mikko wrote:
> >>> On 2022-08-20 23:00:11 +0000, Thomas 'PointedEars' Lahn said:
> >>>> Mikko wrote:
> >>>>> On 2022-08-20 11:08:13 +0000, Pentcho Valev said:
> >>>>>> Sabine Hossenfelder: "The speed of light is the same for all
> >>>>>> observers."
> >>>>>> https://bigthink.com/hard-science/special-relativity-existential-physic
s/
> >>>>>
> >>>>> True.
> >>>>>
> >>>>>> No it obviously isn't.
> >>>>>
> >>>>> It isn't obvious as light is so fast.
> >>>> That is not a convincing reasoning.
> >>> Pencho Valev's reasoning never is.
> >> Check the quotation levels: I was referring to *your* reasoning.
> >>
> >> (I have killfiled them.)
> >
> > What in my message do you call "reasoning" ?
>
> You argued that it would not be obvious that "the speed of light is the same
> for all observers" because it would be "so fast".
>
> However, I have shown that with only 17th century astronomy it was already
> possible to estimate the speed of light in (interplanetary) vacuum, and to
> show that it does not depend on the motion of the observer relative to the
> source.
>
> That refutes your argument.
>
>
> PointedEars

Yes, but your argument is just plain wrong.
Roemer could only observe the zeroth order effect.
(time = distance/c)
No way that he could have observed the first order effect
c' = c_0 + v_source,

Jan

On Sunday, 28 August 2022 at 15:30:09 UTC+2, J. J. Lodder wrote:
> Thomas 'PointedEars' Lahn <Point...@web.de> wrote:
>
> > Mikko wrote:
> >
> > > On 2022-08-23 23:17:27 +0000, Thomas 'PointedEars' Lahn said:
> > >> Mikko wrote:
> > >>> On 2022-08-20 23:00:11 +0000, Thomas 'PointedEars' Lahn said:
> > >>>> Mikko wrote:
> > >>>>> On 2022-08-20 11:08:13 +0000, Pentcho Valev said:
> > >>>>>> Sabine Hossenfelder: "The speed of light is the same for all
> > >>>>>> observers."
> > >>>>>> https://bigthink.com/hard-science/special-relativity-existential-physic
> s/
> > >>>>>
> > >>>>> True.
> > >>>>>
> > >>>>>> No it obviously isn't.
> > >>>>>
> > >>>>> It isn't obvious as light is so fast.
> > >>>> That is not a convincing reasoning.
> > >>> Pencho Valev's reasoning never is.
> > >> Check the quotation levels: I was referring to *your* reasoning.
> > >>
> > >> (I have killfiled them.)
> > >
> > > What in my message do you call "reasoning" ?
> >
> > You argued that it would not be obvious that "the speed of light is the same
> > for all observers" because it would be "so fast".
> >
> > However, I have shown that with only 17th century astronomy it was already
> > possible to estimate the speed of light in (interplanetary) vacuum, and to
> > show that it does not depend on the motion of the observer relative to the
> > source.
> >
> > That refutes your argument.
> >
> >
> > PointedEars
> Yes, but your argument is just plain wrong.
> Roemer could only observe the zeroth order effect.
> (time = distance/c)
> No way that he could have observed the first order effect
> c' = c_0 + v_source,

Especially if it was gedanken/fabricated.

Mikko wrote:

> On 2022-08-27 23:12:16 +0000, Thomas 'PointedEars' Lahn said:
>> However, I have shown that with only 17th century astronomy it was
>> already possible to estimate the speed of light in (interplanetary)
>> vacuum, and to show that it does not depend on the motion of the observer
>> relative to the source.
>>
>> That refutes your argument.
>
> If it were obvious in that the speed of light is independent of the
> motion of the observer there would have been no point in Michelson-Morley
> experiment.

The Michelson–Morley experiment sought to investigate the properties of the
luminiferous aether (under the assumption that it exists), not to determine
the speed of light (relative to an observer).
> Even now it is not obvious that the speed of light is the same
> to all observers. In order to test it one needs instruments
> that most people don't have.

Questionable at best.

PointedEars
--
«Nec fasces, nec opes, sola artis sceptra perennant.»
(“Neither high office nor power, only the scepters of science survive.”)

—Tycho Brahe, astronomer (1546-1601): inscription at Hven

On 8/28/22 3:54 AM, Mikko wrote:
> If it were obvious in that the speed of light is independent of the
> motion of the observer there would have been no point in Michelson-Morley
> experiment.

It is not obvious, even though it appears to be true in the world we
inhabit.

> Even now it is not obvious that the speed of light is the same
> to all observers.

Yes, it is not obvious, even though it appears to be true in the world
we inhabit.

> In order to test it one needs instruments
> that most people don't have.

Doesn't matter, because "most people" don't do precision metrology.

Note that in the year or so leading up to the redefinition of the meter
in 1983, there were many high-precision measurements of the speed of
light, performed in the many locally-inertial frames occupied by
laboratories on the rotating and orbiting earth. They all obtained
answers consistent with the value that was ultimately chosen, many with
errorbars less than 1 m/s -- earth's orbital speed is ~ 30,000 times
larger than that.

Tom Roberts

On Tuesday, 30 August 2022 at 03:32:26 UTC+2, tjrob137 wrote:
> On 8/28/22 3:54 AM, Mikko wrote:
> > If it were obvious in that the speed of light is independent of the
> > motion of the observer there would have been no point in Michelson-Morley
> > experiment.
> It is not obvious, even though it appears to be true in the world we
> inhabit.

Unfortunately, the world you inhabit is the world of
your insane delusions, where everyone is FORCED
to obey idiots like you and their THE BEST WAY.

> Note that in the year or so leading up to the redefinition of the meter
> in 1983, there were many high-precision measurements of the speed of
> light, performed in the many locally-inertial frames occupied by

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

Mikko <mikko.levanto@iki.fi> wrote:

> On 2022-08-27 23:12:16 +0000, Thomas 'PointedEars' Lahn said:
>
> > However, I have shown that with only 17th century astronomy it was already
> > possible to estimate the speed of light in (interplanetary) vacuum, and to
> > show that it does not depend on the motion of the observer relative to the
> > source.
> >
> > That refutes your argument.
>
> If it were obvious in that the speed of light is independent of the
> motion of the observer there would have been no point in Michelson-Morley
> experiment.

It is not only not obvious, it is extremely counter-intuitive.
So counter-intuitive in fact
that no one ever even thought of the possibility
of a universe with an absolute prefered velocity,
not even as an obviously untrue 'what if' excercise.
It took Einstein's genius to see that it must be true.
It is obvious only in retrospect.

> Even now it is not obvious that the speed of light is the same
> to all observers. In order to test it one needs instruments
> that most people don't have.

It can no longer be tested directly,
because the speed of light can no longer be measured directly.
All testing of it must be indirect,
from the consequences for other kinds measurements,
(such as calibrations of meter standards)

Jan