1 I could not get my post !!!!!!!!

2 I could not get my post !!!!!!!!

Just about half of us, I estimate.

Dirk Vdm

3 I could not get my post !!!!!!!!

And you are, of course, aware that velocity is not absolute, yes?

And you are, of course, aware that the earth is moving about 30 km/sec in its orbit around the sun, not so?

And as an EE, you know that capacitors do not change their capacitance with the earth's orbital motion?

So you should be able to conclude that the speed of light is independent of the motion of its source. If this were not enough, experience with communication with spacecraft moving at up to 50 km/sec, demonstrates that this is so.

This should be quite sufficient for you to derive the Lorentz transform equations which refute your many unfounded assertions, so I don't see how you can deny actual experiments hen you claim actual experiments are what counts.

4 I could not get my post !!!!!!!!

>	As an EE, you are, of course, aware that c = 1/sqrt(mu0*epsilon0), right?

C in this case is the speed of electro magnetic radiation in vacuum.

>	And you are, of course, aware that velocity is not absolute, yes?

Speed/ velocity is equal to (r2-r1)/(t2-t1). What is the meaning of the claim that velocity is not absolute?

>	And you are, of course, aware that the earth is moving about 30 km/sec in its orbit around the sun, not so? And as an EE, you know that capacitors do not change their capacitance with the earth's orbital motion?

What is the meaning of this sentence?

>	So you should be able to conclude that the speed of light is independent of the motion of its source.

IMO the easiest(?) way to demonstrate this when you have two cars (one at at rest and one moving) which turn on their lights when they pass. You, in front of them at a certain distance, will observe these two events simultaneous (I expect) which demonstrates that the speed of light (photons) is not influenced by neither the emitter nor the receiver. (But in no way quantifies this speed.)

>	This should be quite sufficient for you to derive the Lorentz transform equations which refute your many unfounded assertions, so I don't see how you can deny actual experiments hen you claim actual experiments are what counts.

5 I could not get my post !!!!!!!!

Of course.

> >	And you are, of course, aware that velocity is not absolute, yes?

>	Speed/ velocity is equal to (r2-r1)/(t2-t1). What is the meaning of the claim that velocity is not absolute?

Velocity does NOT refer to some absolute reference point. It is, as your equation says, determined with respect to an arbitrary coordinate system.

> >	And you are, of course, aware that the earth is moving about 30 km/sec in its orbit around the sun, not so? And as an EE, you know that capacitors do not change their capacitance with the earth's orbital motion?

>	What is the meaning of this sentence?

That epsilon0 is NOT changed by your motion.

> >	So you should be able to conclude that the speed of light is independent of the motion of its source.

>

IMO the easiest(?) way to demonstrate this when you have two cars (one at at rest and one moving) which turn on their lights when they pass. You, in front of them at a certain distance, will observe these two events simultaneous (I expect) which demonstrates that the speed of light (photons) is not influenced by neither the emitter nor the receiver. (But in no way quantifies this speed.)

Not exactly an EE experiment, but okay :-)

> >	This should be quite sufficient for you to derive the Lorentz transform equations which refute your many unfounded assertions, so I don't see how you can deny actual experiments [w]hen you claim actual experiments are what counts.

>	The Lorentz factor by definition is mathematics. See: https://en.wikipedia.org/wiki/Lorentz_factor

So is (r2 -r1)/(t2 - t1). What's your point? Mathematics is just logical deduction from basic postulates.

>	The physical issue starts when you use this factor in order to describe time, length and mass for a moving object.

No. The "physical issue" starts with the postulates:
1. Principle of relativity
2. Invariance of the speed of light

There is also the assumption that space and time are isotropic, homogeneous and uniform. What this means is that a transformation from one inertial frame to another must be of the form:

x' = G*(x + H*t)
t' = A*(t + B*x)

Using the PoR, you can deduce that G must equal A. Also from the PoR, you can deduce that H = -v.

In the case of the Galilean transform, which assumes absolute time, A = 1 and B = 0. Thus G = 1 also. Using the second postulate, however, A is NOT unity and B is NOT zero.

>

The document https://sites.google.com/view/realscience/first-article above paragraph 4 reads: "When v > c, t’1 becomes an imaginary number to the outside observer." and: "Here, at v = c , the vehicle length will seem to be zero to the outside observer which makes the vehicle invisible to the outside observer, but inside the vehicle all is as usual." The problem is that from a mathematical point you can do that but not from a physical point when you perform an actual experiment which tries to validate one of these three equations. The biggest problem are the definition of the parameters v and c. This same problem is also discussed in: "Re: Speed of light in vacuum, what definition?" of 27 June https://groups.google.com/forum/?fromgroups=#!topic/sci.physics.relativity/qHMbZeyXWmI The central question is does a super nova (its remnant) always stays at the center of its own photon sphere?

That's NOT a "central" question. The central question is, Are the postulates consistent with experimental evidence? This question can, and has been, answered ... by experiment.

>	IMO it does not.

“All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others.”
-- Douglas Adams

"You are not entitled to your opinion. You are entitled to your informed opinion. No one is entitled to be ignorant." — Harlan Ellison

>	Its position can vary and has a speed relatif to the center this sphere. That means from its own point of view physical the speed of light in both directions is not the same. The speed is only the same for the point at the center of this sphere. Nicolaas Vroom.

Opinions are worthless without REAL evidence to back them up. The REAL evidence comes from experimental results and correct deduction from them.

If you use the Lorentz transform (which is logically deduced from the postulates which have been verified experimentally), you can answer your non-central question. And the answer may surprise you (I did me when I first considered it).

6 I could not get my post !!!!!!!!

>>	What is the meaning of this sentence?

>	That epsilon0 is NOT changed by your motion.

This would be an interesting topic to investigate. Permittivity and Permeability are both about consistency. Or is something you don't really know.

7 I could not get my post !!!!!!!!

> >	The central question is does a super nova (its remnant) always stays at the center of its own photon sphere?

>	That's NOT a "central" question. The central question is, Are the postulates consistent with experimental evidence? This question can, and has been, answered ... by experiment.

Still the question remains: Does the neutron star stay at the center of the sphere. A different question is: What can we say about the moment of "collision" of the two spheres.

> >	IMO it does not.

-- IMO

>	“All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others.” -- Douglas Adams

IMO

>	"You are not entitled to your opinion. You are entitled to your informed opinion. No one is entitled to be ignorant." — Harlan Ellison

There is nothing wrong when someone has his or her own opinion. The next step is to challenge this opinion by yourself and by others.

> >	Its position can vary and has a speed relatif to the center this sphere. That means from its own point of view physical the speed of light in both directions is not the same. The speed is only the same for the point at the center of this sphere. Nicolaas Vroom.

>	Opinions are worthless without REAL evidence to back them up.

The same is true for people who don't agree with someone's opinion.

>	The REAL evidence comes from experimental results and correct deduction from them.

There are two possiblities: You can start from a set of postulates and make predictions. The evidence comes from experiments or observations which agree with these predictions. A different route is you make observations and you define the laws which describe these observations, Next you make new predictions. Also here: The evidence comes from experiments or observations which agree with these new predictions.

>	If you use the Lorentz transform (which is logically deduced from the postulates which have been verified experimentally), you can answer your non-central question. And the answer may surprise you (I did me when I first considered it).

This issue is discussed separately in the thread: "Time dilation in Wikipedia"

Nicolaas Vroom

8 I could not get my post !!!!!!!!

If the star is moving inertially, then it remains at the center of the light sphere as seen in its rest frame; it does NOT remain at the center of the light sphere seen in any other inertial frame. If it is not moving inertially, it does NOT remain at the center of any inertial frame's sphere.

Note that relative to essentially all non-inertial coordinates there is no light sphere [#]. Note also that if there is gravitation from sources other than the neutron star itself, or if the neutron star is itself not spherically symmetric, then there are no light spheres at all (and of course no inertial frames, only locally-inertial frames).

[#] Exercise for the reader: construct non-inertial coordinates on flat spacetime relative to which there is a light sphere from a single pulsed light source. Hint: consider the relationship between such coordinates and some inertial frame. Hint2: Consider the symmetry of the physical situation.

Tom Roberts

9 I could not get my post !!!!!!!!

No, that question DOESN'T remain. The LT is derived from the postulates which have been verified experimentally; therefore, the LT answers your question.

>	A different question is: What can we say about the moment of "collision" of the two spheres.

GR must be employed for that.

> > >

IMO it does not.

>

-- IMO

> >	“All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others.” -- Douglas Adams

>

IMO

> >	"You are not entitled to your opinion. You are entitled to your informed opinion. No one is entitled to be ignorant." — Harlan Ellison

>	There is nothing wrong when someone has his or her own opinion. The next step is to challenge this opinion by yourself and by others.

That's when you find out your opinion is uninformed.

> > >

Its position can vary and has a speed relatif to the center this sphere. That means from its own point of view physical the speed of light in both directions is not the same. The speed is only the same for the point at the center of this sphere. Nicolaas Vroom.

> >	Opinions are worthless without REAL evidence to back them up.

>	The same is true for people who don't agree with someone's opinion.

And I presented such backup. You have not.

> >	The REAL evidence comes from experimental results and correct deduction from them.

>	There are two possiblities: You can start from a set of postulates and make predictions. The evidence comes from experiments or observations which agree with these predictions.

Yes. Always. You can also test the postulates.

>	A different route is you make observations and you define the laws which describe these observations, Next you make new predictions. Also here: The evidence comes from experiments or observations which agree with these new predictions.

Of course, but you are asking questions that cannot be tested experimentally. So the ONLY course is to test the postulates. If they are verified, and the mathematical derivation from them is valid, you can rely on the what the derivation predicts.

> >	If you use the Lorentz transform (which is logically deduced from the postulates which have been verified experimentally), you can answer your non-central question. And the answer may surprise you (I did me when I first considered it).

>	This issue is discussed separately in the thread: "Time dilation in Wikipedia" Nicolaas Vroom

You expect everyone to go off and read that? I don't remember it, so it was most likely quite unmemorable.

10 I could not get my post !!!!!!!!

(The stars in a galaxy are not moving inertially, as such you have answered my original question)

This leads to the following remark:
What is the purpose of an inertial frame?
But there is more: Apperently there are light spheres and each of these light spheres have a center i.e. a point of origin. Is it not true that all these points of origin together define an inertial frame? (a coordinate system)

>	Note that relative to essentially all non-inertial coordinates there is no light sphere [#].

?

>	Note also that if there is gravitation from sources other than the neutron star itself, or if the neutron star is itself not spherically symmetric, then there are no light spheres at all.

That is too strict. There is always something that resembles a light sphere. The largest cause of any asymmetry is in the source. Gravitation from other objects is also a cause of deformation.

>	(and of course no inertial frames, only locally-inertial frames).

?

>	[#] Exercise for the reader: construct non-inertial coordinates on flat spacetime relative to which there is a light sphere from a single pulsed light source. Hint: consider the relationship between such coordinates and some inertial frame. Hint2: Consider the symmetry of the physical situation.

Why this exercise?

Nicolaas Vroom

11 I could not get my post !!!!!!!!

You delude yourself. by "inertially" you apparently mean "in straight line." but stars move approximately that way. So your attempt to belittle Tom Robert's lesson is pretence.

>	This leads to the following remark: What is the purpose of an inertial frame?

To simplify explanation of how the universe works.

>	But there is more: Apperently there are light spheres and each of these light spheres have a center i.e. a point of origin. Is it not true that all these points of origin together define an inertial frame? (a coordinate system)

> >	Note that relative to essentially all non-inertial coordinates there is no light sphere [#].

>

?

That is, they aren't spheres to accelerated observers.

> >	Note also that if there is gravitation from sources other than the neutron star itself, or if the neutron star is itself not spherically symmetric, then there are no light spheres at all.

>	That is too strict. There is always something that resembles a light sphere. The largest cause of any asymmetry is in the source. Gravitation from other objects is also a cause of deformation.

Sure, but it's not too strict if the gravitation is strong.

12 I could not get my post !!!!!!!!

Yes. Don't we all mean that?

>	but stars move approximately that way.

Yes. But on the long run (as in a galaxy) they move in a circle.

>	So your attempt to belittle Tom Robert's lesson is pretence.

?

Nicolaas Vroom

13 I could not get my post !!!!!!!!

>>>	(The stars in a galaxy are not moving inertially, as such you have answered my original question)

>>	You delude yourself. by "inertially" you apparently mean "in straight line."

>	Yes. Don't we all mean that?

No. we do not.

By "inertially", it means without acting external net force.

It is straight line in context of Newtonian mechanics.
It is straight line in context of SR and negligible gravity.

In GR context, it is geodesics in non local scale, OR, is is approximately a straight line in locally inertial frame.

>

>>	but stars move approximately that way.

>	Yes. But on the long run (as in a galaxy) they move in a circle.

Orbits are considered as inertial motion in GR context, as gravity is not considered as a force.

-- Poutnik Guard the words you use speaking about others, as they speak about you.

14 I could not get my post !!!!!!!!

>	In GR context, it is geodesics in non local scale, OR, is is approximately a straight line in locally inertial frame.

Fine. Now define your straight line.

15 I could not get my post !!!!!!!!

You seem to be straining at gnats. Do you also swallow camels?

16 I could not get my post !!!!!!!!

When Tom Roberts writes: "If it is not moving inertially, it does NOT remain at the center of any inertial frame's sphere." Immediate my next question is: Are there frames (coordinate systems) in which the origin stays at the center of such a light sphere.

Consider a Lightsource LS1 which moves in a certain direction. Consider a second Lightsource LS2 which moves with a different speed in a different direction. (They are not exactly at collision course) When they almost meet at closest distance each LS generates an explosion which creates a light sphere.
At that moment and position you can assign for each LS an inertial frame which the LS as origin and the x axis in the direction of movement.
The question is will the LS stay at the center of the light sphere? Outside observers will claim that when they see a flash from the first LS they also see a flash from the second LS i.e. light sphere. This means the light spheres are almost one and the same.

The question is which inertial frame is at the center of this light sphere?
Ofcourse you could claim that the inertial frame of LS1 is at the center of the light sphere. But so can LS2. They can not be both, because the two inertial frames have different speeds and directions.
That means neither. This leaves the possibility open that there is a different coordinate system with the origin at the center and with stays at the center.

Nicolaas Vroom

17 I could not get my post !!!!!!!!

He answered that: in the frame where the source is stationary.

That should answer ALL your questions.

18 I could not get my post !!!!!!!!

To make calculation simpler, because inertial frames reflect a local symmetry of the world we inhabit.

>	But there is more: Apperently there are light spheres and each of these light spheres have a center i.e. a point of origin. Is it not true that all these points of origin together define an inertial frame? (a coordinate system)

No. First, the light sphere is only approximate: light is affected by gravity, and in a region where gravity is large, an omnidirectional pulsed light source does not emit a sphere of light.

An inertial frame is a 4-d REGION, not just a point. If you have light spheres, each will only identify its center as a point, not a region.

>>	Note that relative to essentially all non-inertial coordinates there is no light sphere [#].

>

?

If you are accelerating (i.e. non-inertial) in a region with negligible gravity, the light will form spheres relative to inertial frames, but not relative to you. This is related to simultaneity, and the lack of it in non-inertial coordinates.

>

Consider a Lightsource LS1 which moves in a certain direction. Consider a second Lightsource LS2 which moves with a different speed in a different direction. (They are not exactly at collision course) When they almost meet at closest distance each LS generates an explosion which creates a light sphere.

I assume they come very close, so one cannot distinguish their locations at the time of the TWO explosions.

>

At that moment and position you can assign for each LS an inertial frame which the LS as origin and the x axis in the direction of movement. The question is will the LS stay at the center of the light sphere? Outside observers will claim that when they see a flash from the first LS they also see a flash from the second LS i.e. light sphere. This means the light spheres are almost one and the same.

There is not one light sphere, there are two: LS1 remains at the center of the light that it emitted at its explosion, and LS2 remains at the center of the light that it emitted at its explosion.

Any pointlike observer will see both light spheres simultaneously, but the redshifts of the two light spheres will differ (except at certain special locations).

>	The question is which inertial frame is at the center of this light sphere? Ofcourse you could claim that the inertial frame of LS1 is at the center of the light sphere. But so can LS2.

There are TWO light spheres, not just one. Recognizing this resolves all your confusion.

Tom Roberts