Does My Wrist Watch Physically Beat Slower?

[Tomahoc]

The Earth and the missile are both moving in the ether frame, so t = 30 seconds in the ether frame is *not* t' = 30 seconds in the Earth frame or the missile frame. You keep on switching numbers around so I'm not sure which numbers you are thinking of for this example, but if we take 0.9999c as the speed of the Earth and the missile in the ether frame, then gamma is about 71, so t = 30 seconds in the ether frame corresponds to t' = 30/71 seconds, or about t' = 0.42 seconds in the Earth frame or the missile frame. So a tachyon that travels instantaneously in the ether frame, and is launched at t = 30 seconds in the ether frame, will hit the Earth (or the missile) when the Earth's clock (or the missile's clock) reads about 0.42 seconds.

Oh I thought the time in the Earth frame and aether frame is the same. How do you compute for time in the aether frame. For example. The instantaneous tachyons moving with fixed velocity in the aether frame is launched at t = 30 seconds in the Earth frame to the missile..

What would be the corresponding time in the aether frame?

 

[PeterDonis]

Oh I thought the time in the Earth frame and aether frame is the same.

You said quite a few posts ago that you wanted to have the aether frame be different from the Earth frame, so that's what I was assuming.

How do you compute for time in the aether frame.

You have to first know which frame it is. If you know which frame is the aether frame, you can just use the Lorentz transformation to find any times or distances you like in that frame, if you know them in some other frame (like the Earth frame).

The instantaneous tachyons moving with fixed velocity in the aether frame is launched at t = 30 seconds in the Earth frame to the missile..

What would be the corresponding time in the aether frame?

It depends on which frame is the aether frame; see above. Since nobody has an actual physical theory that says which frame is the aether frame, there's no way of really answering these questions. I've said that repeatedly already.

 

[bobc2]

OK, then the conversation should really be concluded. Since they both use the LT for all of their experimental predictions then all of their experimental predictions must be identical. Since all of their experimental predictions must be identical there can be no experiment which could distinguish between the two.

Do you disagree in any way with that chain of reasoning? If so, please explain.

Given the assumptions you've been making, your logic seems valid. While my intuition tells me that too much significance is given to the Lorentz ether theory, I still haven't performed the due diligence in digging through the sequence of papers by Lorentz, Poincare', Heaviside, and others that would be required to correctly assess the basis for LET in its final form. I'm not sure Lorentz's original rationale for advancing the stationary ether (with the electric field states) was carried through with all of the revisions of the theory that occurred over some 10 or 15 years.

Perhaps this means I should yield the point to you for now. I don't think my colleague Vandam would back away so easily. I can understand how he would be so tenacious in discounting LET (remember his citing Lorentz's own resignation) and affirming the 4-dimensional universe as physical reality.

I realize that the attempt to distinguish between LET and Einstein-Minkowski is considered a philosophical endeavor, but this is where I disagree. My intuition is that physicists have not performed the due diligence on the physics side in identifying the correct theory. I'm not sure that the search for an experimental program yielding the distinction has been fully explored. I've cited the results of entanglement experiments, but it is clear that respondents here have not understood the thrust of my argument.

Anyway, this is a good point to let this discussion take a rest.

 

[Tomahoc]

You said quite a few posts ago that you wanted to have the aether frame be different from the Earth frame, so that's what I was assuming.



You have to first know which frame it is. If you know which frame is the aether frame, you can just use the Lorentz transformation to find any times or distances you like in that frame, if you know them in some other frame (like the Earth frame).



It depends on which frame is the aether frame; see above. Since nobody has an actual physical theory that says which frame is the aether frame, there's no way of really answering these questions. I've said that repeatedly already.

If the aether frame is the common origin where both Earth and missile left at 0.9999c then we can use your gamma factor of 71 and aether t = 30/71 seconds, or about aether t = 0.42 seconds, do you agree?

If the aether frame is elsewhere. Do you believe it is still possible to consider it as a common origin?

About aether as a concept. Do you think Aether is connected with physical interpretation of everything. So if there is aether, then particles have definite positions before measurements and the universe is really solid? Does aether signify or stand for gross physicality?

 

[PeterDonis]

My intuition is that physicists have not performed the due diligence on the physics side in identifying the correct theory. I'm not sure that the search for an experimental program yielding the distinction has been fully explored.

I'm not sure where one would start, particularly since, as you have already pointed out in this thread, nobody is seriously pursuing LET as an alternative theory. The math of SR has been extremely well confirmed by experiment, within its domain of validity, and in so far as an "interpretation" is required at all, everybody in the field seems to be using the Einstein-Minkowski interpretation. That's not to say that everybody in the field would agree with the strong claims about the "block universe" that some have made; but I think everybody in the field (or at least almost everybody) would agree with the weaker claim that 4-D spacetime is a good model at an appropriate level of approximation.

I've cited the results of entanglement experiments, but it is clear that respondents here have not understood the thrust of my argument.

This probably deserves its own thread, possibly in the quantum physics forum instead of this one.

 

[PeterDonis]

If the aether frame is the common origin where both Earth and missile left at 0.9999c then we can use your gamma factor of 71 and aether t = 30/71 seconds, or about aether t = 0.42 seconds, do you agree?

I think I understand what you mean here, but your way of phrasing it can be misleading. A frame is more than just an "origin". What I think you mean is: the aether frame is a frame whose origin is the event on the Earth's worldline at which the missile is fired, and in which the Earth is moving in one direction at 0.9999c and the missile is moving in the opposite direction at 0.9999c.

If the aether frame is elsewhere. Do you believe it is still possible to consider it as a common origin?

This is why I think your way of phrasing things above can be misleading. The "common origin" of the Earth and the missile is an invariant; it's the event on the Earth's worldline at which the missile is fired. The definition of that event doesn't depend on which frame you're in.

As far as where you place the origin of the aether frame, I don't think it matters, since a translation in space and/or time (which just shifts the origin without doing anything else) doesn't change any of the physics. But of course taking that attitude to its logical conclusion would lead you to discard the aether frame altogether and just use standard SR, since Lorentz transformations also don't change any of the physics.

About aether as a concept.

I don't think "aether" is a single well-defined concept; various people use it to refer to different ideas. As I've said before, I'm not aware of any currently viable physical theory that uses the concept, so I don't think your questions about it as a concept can be answered.

 

[Tomahoc]

I think I understand what you mean here, but your way of phrasing it can be misleading. A frame is more than just an "origin". What I think you mean is: the aether frame is a frame whose origin is the event on the Earth's worldline at which the missile is fired, and in which the Earth is moving in one direction at 0.9999c and the missile is moving in the opposite direction at 0.9999c.



This is why I think your way of phrasing things above can be misleading. The "common origin" of the Earth and the missile is an invariant; it's the event on the Earth's worldline at which the missile is fired. The definition of that event doesn't depend on which frame you're in.

As far as where you place the origin of the aether frame, I don't think it matters, since a translation in space and/or time (which just shifts the origin without doing anything else) doesn't change any of the physics. But of course taking that attitude to its logical conclusion would lead you to discard the aether frame altogether and just use standard SR, since Lorentz transformations also don't change any of the physics.

You mean someday a billion years from now if it was discovered that tachyons really use the aether frame and its velocity is fixed to it and we can contract Andromeda instantaneously. It doesn't matter where the aether frame is? (you described that "a translation in space and/or time (which just shifts the origin without doing anything else) doesn't change any of the physics)? Is it valid here?

I don't think "aether" is a single well-defined concept; various people use it to refer to different ideas. As I've said before, I'm not aware of any currently viable physical theory that uses the concept, so I don't think your questions about it as a concept can be answered.

 

[PeterDonis]

You mean someday a billion years from now if it was discovered that tachyons really use the aether frame and its velocity is fixed to it and we can contract Andromeda instantaneously. It doesn't matter where the aether frame is?

It would matter in that case, yes (more precisely, it would matter what state of motion the aether frame was in--i.e., what its speed was relative to other frames like the Earth frame--see further comments below). But if we made such discoveries it would not just be an addition to our current theories; it would falsify them, because it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that.

(you described that "a translation in space and/or time (which just shifts the origin without doing anything else) doesn't change any of the physics)? Is it valid here?

A translation (moving the origin of a frame without changing anything else) doesn't change the speed of anything relative to any frame, nor does it change the meaning of "instantaneously".

 

[Tomahoc]

It would matter in that case, yes (more precisely, it would matter what state of motion the aether frame was in--i.e., what its speed was relative to other frames like the Earth frame--see further comments below). But if we made such discoveries it would not just be an addition to our current theories; it would falsify them, because it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that.



A translation (moving the origin of a frame without changing anything else) doesn't change the speed of anything relative to any frame, nor does it change the meaning of "instantaneously".

You said earlier above it would matter, then below.. you said it doesn't change anything. So why does it matter? Maybe to synchronize the tachyon stations on Earth and Andromeda?

Right now. If one of the public speaks about tachyons or FTL... scientists would immediately yell.. "Relativity forbids it"... inquiring further.. you will hear the reasoning... "because FTL can violate causality"... not many of the public can argue ".. but the tachyons velocity is fixed relative to Aether frame so no causaity violated and instantaneous signal across the universe possible"... anyway.. how many percentage of physicists are familiar with this reasoning that "if the tachyons velocity is fixed relative to aether, instantaneous signalling is possible without causality violation?", all of them? or are there portions who haven't heard or thought of the possibility?

 

[PeterDonis]

You said earlier above it would matter, then below.. you said it doesn't change anything.

No, I said that whether "it" matters depends on what "it" is. You have asked about a number of different things in different scenarios; there isn't one single answer that applies to all of them. I have said that repeatedly.

In the particular post you quoted, I even stated explicitly what matters: the *speed* of the aether frame, relative to other frames of interest (like the Earth frame) matters. The *placement of the origin* of the aether frame does not matter.

but the tachyons velocity is fixed relative to Aether frame so no causaity violated

No, that's not correct. You even quoted my statement of why it's not correct: "it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that." Please read what I post more carefully before asking questions or raising issues that I've already addressed.

What fixing the tachyon speed relative to an aether frame *does* avoid is having closed causal loops. But avoiding closed causal loops is not sufficient to avoid violating causality period.

how many percentage of physicists are familiar with this reasoning

I don't know how many physicists have spent time thinking in detail about these things, but nothing I've said in this thread would be at all difficult for physicists in the field to understand. There have been a number of physics papers published on tachyons, so they are not an unfamiliar concept.

As far as what I said above about causality, the principle I gave--that spacelike separated events cannot be causally connected--is used everywhere that relativity is used in physics. Violating that principle would be a *huge* issue; all sorts of things in various fields depend on it.

 

[Tomahoc]

No, I said that whether "it" matters depends on what "it" is. You have asked about a number of different things in different scenarios; there isn't one single answer that applies to all of them. I have said that repeatedly.

In the particular post you quoted, I even stated explicitly what matters: the *speed* of the aether frame, relative to other frames of interest (like the Earth frame) matters. The *placement of the origin* of the aether frame does not matter.



No, that's not correct. You even quoted my statement of why it's not correct: "it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that." Please read what I post more carefully before asking questions or raising issues that I've already addressed.

What fixing the tachyon speed relative to an aether frame *does* avoid is having closed causal loops. But avoiding closed causal loops is not sufficient to avoid violating causality period.

Causality is related to time ordering, correct? Events at spacelike is not causality connected because it takes time for light to travel. This is why I think causality can be violated if they are connected at spacelike. But our tachyons moving fixed to aether frame changed that. Isn't it tachyons can connect events that are spacelike separated, this is the context of what I mean tachyon would avoid causality violation. Why, how do you define or what is the context of your "causality violation"?

I don't know how many physicists have spent time thinking in detail about these things, but nothing I've said in this thread would be at all difficult for physicists in the field to understand. There have been a number of physics papers published on tachyons, so they are not an unfamiliar concept.

As far as what I said above about causality, the principle I gave--that spacelike separated events cannot be causally connected--is used everywhere that relativity is used in physics. Violating that principle would be a *huge* issue; all sorts of things in various fields depend on it.

 

[PeterDonis]

Causality is related to time ordering, correct?

Yes; on our current understanding, the time ordering of causally connected events must be invariant--i.e., it must be the same in every frame.

Events at spacelike is not causality connected because it takes time for light to travel.

No; they can't be causally connected because their time ordering can be different in different frames. Adding tachyons doesn't change that.

 

[Tomahoc]

Yes; on our current understanding, the time ordering of causally connected events must be invariant--i.e., it must be the same in every frame.



No; they can't be causally connected because their time ordering can be different in different frames. Adding tachyons doesn't change that.

Do you mean "adding tachyons does change that" or "doesn't change that"? Because earlier you stated "But if we made such discoveries it would not just be an addition to our current theories; it would falsify them, because it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that".

So adding tachyons does change that. So your "doesn't" was a typo?

 

[PeterDonis]

Do you mean "adding tachyons does change that" or "doesn't change that"?

Adding tachyons doesn't change the fact that the time ordering of spacelike separated events is not frame invariant.

Because earlier you stated "But if we made such discoveries it would not just be an addition to our current theories; it would falsify them, because it would allow causal connections between events that are spacelike separated. Our current understanding of causality does not allow for that".

Allowing spacelike separated events to be causally connected would force us to modify all of the theories we have (which, as I said, is a lot of them) that assume that the time ordering of causally connected events must be frame invariant.

To see how drastic this would be, consider a commonplace causal phenomenon: I throw a baseball that breaks a window. If the baseball were made of tachyons, then in some frames those events would be in reverse order: to observers at rest in such frame, it would look like the window spontaneously reassembled itself as the baseball moved through it towards my hand.

 

[Tomahoc]

Adding tachyons doesn't change the fact that the time ordering of spacelike separated events is not frame invariant.



Allowing spacelike separated events to be causally connected would force us to modify all of the theories we have (which, as I said, is a lot of them) that assume that the time ordering of causally connected events must be frame invariant.

To see how drastic this would be, consider a commonplace causal phenomenon: I throw a baseball that breaks a window. If the baseball were made of tachyons, then in some frames those events would be in reverse order: to observers at rest in such frame, it would look like the window spontaneously reassembled itself as the baseball moved through it towards my hand.

But remember ordinary matter including light is frame dependent. Only the tachyons are not. So ordinary matter are not affected. Ordinary matter time ordering of causally connected events are still frame invariant even if there are tachyons.

If you still mean it. Try giving an example where baseball and tachyons are separate entities and how the former can be affected. All I know is that only tachyons emission and detection would have this time ordering affected.. not the ordinary matter.

 

[PeterDonis]

But remember ordinary matter including light is frame dependent. Only the tachyons are not. So ordinary matter are not affected. Ordinary matter time ordering of causally connected events are still frame invariant even if there are tachyons.

Yes. So what? If tachyons are allowed, then there are still going to be causally connected events that are spacelike separated. It doesn't matter that not *all* causally connected events are spacelike separated; having *any* of them be so is enough.

Try giving an example where baseball and tachyons are separate entities and how the former can be affected.

If tachyons can't affect objects that aren't tachyons, and vice versa, then tachyons effectively don't exist; there's no way to detect them and no way to affect them, because we and all of our scientific instruments aren't made of tachyons, we're made of ordinary matter. There's no point in discussing tachyons if they can't interact with ordinary matter; we can simply ignore them.

 

[Tomahoc]

Yes. So what? If tachyons are allowed, then there are still going to be causally connected events that are spacelike separated. It doesn't matter that not *all* causally connected events are spacelike separated; having *any* of them be so is enough.



If tachyons can't affect objects that aren't tachyons, and vice versa, then tachyons effectively don't exist; there's no way to detect them and no way to affect them, because we and all of our scientific instruments aren't made of tachyons, we're made of ordinary matter. There's no point in discussing tachyons if they can't interact with ordinary matter; we can simply ignore them.

Even without tachyons there are some problems with inconsistency. Going to the train example and 2 lightnings hitting both ends. It is said in:

http://www.rafimoor.com/english/SRE.htm

"Suppose we put two photoelectric cells at point P on the train where the two flashes of light meet in the man’s frame. One of the cells is directed to the front of the train and the other to the back. Now we connect the cells to a bomb in a way that if the two cells are illuminated simultaneously the bomb explodes. In the man’s frame the bomb will explode. In the woman’s it will not since in her frame the flashes meet by her and not at point P."

The woman is the one sitting on the moving, the man on the station at point P. The website didn't answer if the woman is dead or not. So do you think it explodes? The website didn't give details of what happen at the end. Just look at the illustration as the lightning and train example is classic. So there are some frames it explodes and some frames it doesn't? If not.. does it explode or not?

 

[Dale]

Even without tachyons there are some problems with inconsistency. ... So there are some frames it explodes and some frames it doesn't?

No, there are no problems with inconsistency, and there are no disagreements between frames on whether or not it explodes.

Similar problems are often given as homework in introductory relativity classes.

 

[PeterDonis]

Now we connect the cells to a bomb in a way that if the two cells are illuminated simultaneously the bomb explodes.

The word "simultaneously" is being used here in a different sense than you are interpreting it; it does not refer to two spacelike separated events, but to a single event--a single point in spacetime--at which two things happen (each cell receives a flash). A better way of phrasing how the cells are connected would be: "if the two cells receive light beams at the same spacetime event, the bomb explodes". That phrasing makes it clear that whether or not the bomb explodes is frame-invariant. See further comments below.

In the man’s frame the bomb will explode. In the woman’s it will not since in her frame the flashes meet by her and not at point P."

No, this is not correct. The two flashes do *not* meet by the woman; the woman sees the flash from in front of her *before* she sees the flash from behind her. The two flashes meet at point P even in the woman's frame; the difference is that in the woman's frame, point P is moving, whereas in the man's frame, point P is at rest.

does it explode or not?

It explodes.

 

[Tomahoc]

The word "simultaneously" is being used here in a different sense than you are interpreting it; it does not refer to two spacelike separated events, but to a single event--a single point in spacetime--at which two things happen (each cell receives a flash). A better way of phrasing how the cells are connected would be: "if the two cells receive light beams at the same spacetime event, the bomb explodes". That phrasing makes it clear that whether or not the bomb explodes is frame-invariant. See further comments below.



No, this is not correct. The two flashes do *not* meet by the woman; the woman sees the flash from in front of her *before* she sees the flash from behind her. The two flashes meet at point P even in the woman's frame; the difference is that in the woman's frame, point P is moving, whereas in the man's frame, point P is at rest.



It explodes.

Not so fast. Prior to the paragraph. It is said that "That is, while the man measures the light from the front getting to the woman before the light from the back, the woman sees the light from both sides simultaneously.".

The website especially mentioned that the woman sees the light from both sides simultaneously. So dead or alive, that is the question.

 

[PeterDonis]

Prior to the paragraph. It is said that "That is, while the man measures the light from the front getting to the woman before the light from the back, the woman sees the light from both sides simultaneously.".

Please read more carefully. The statement in quotes is a *hypothetical*, which the author later shows to be false. He is *not* stating it as an actual conclusion of relativity.

[Edit: The same is true of the statement I said was incorrect: "in the woman's frame it will not since in her frame the flashes meet by her and not at point P"--it is also part of the hypothetical, which the author later shows to be false.]

 

[Tomahoc]

Please read more carefully. The statement in quotes is a *hypothetical*, which the author later shows to be false. He is *not* stating it as an actual conclusion of relativity.

[Edit: The same is true of the statement I said was incorrect: "in the woman's frame it will not since in her frame the flashes meet by her and not at point P"--it is also part of the hypothetical, which the author later shows to be false.]

Ok. I'll look into them. For now. I'm looking for web sites that illustrates what you mentioned that "If tachyons are allowed, then there are still going to be causally connected events that are spacelike separated. It doesn't matter that not *all* causally connected events are spacelike separated; having *any* of them be so is enough.".

Know any such website with spacetime diagrams of tachyons and effects on causality to get me busy this weekend.

Or maybe an actual example you already knew. If the baseball is made up of normal matter and throws into a windows. If no tachyons, there is no frames where the order is reverse? If there are tachyons flying alongside.. how come it can be reverse? I get the essence, but want exact details of how the worldline details work that can make the ordering reverse or chaotic. Thanks.

 

[PeterDonis]

For now. I'm looking for web sites that illustrates what you mentioned that "If tachyons are allowed, then there are still going to be causally connected events that are spacelike separated.

This follows from the definition of tachyons: they travel faster than light. That means they travel on spacelike worldlines, so successive events on a tachyon's worldline are spacelike separated.

If the baseball is made up of normal matter and throws into a windows. If no tachyons, there is no frames where the order is reverse?

If the baseball is made of normal matter, then it travels on a timelike worldline. The time ordering of events on a timelike worldline is frame invariant. (The same is true of the ordering of events on a lightlike worldline, so a "baseball" made of photons would be the same in this respect as a baseball made of normal matter.)

If there are tachyons flying alongside.. how come it can be reverse?

Please read carefully. I didn't say "a baseball with tachyons flying alongside it"; I said "a baseball *made of* tachyons". That means the baseball itself is moving faster than light.

I get the essence, but want exact details of how the worldline details work that can make the ordering reverse or chaotic. Thanks.

See above. The time ordering of events on a spacelike curve is frame-dependent. That's just a basic fact about spacelike curves.

 

[Tomahoc]

Adding tachyons doesn't change the fact that the time ordering of spacelike separated events is not frame invariant.



Allowing spacelike separated events to be causally connected would force us to modify all of the theories we have (which, as I said, is a lot of them) that assume that the time ordering of causally connected events must be frame invariant.

To see how drastic this would be, consider a commonplace causal phenomenon: I throw a baseball that breaks a window. If the baseball were made of tachyons, then in some frames those events would be in reverse order: to observers at rest in such frame, it would look like the window spontaneously reassembled itself as the baseball moved through it towards my hand.

Ah. As long as closed causal loop is solved by tachyons moving fixed in aether frame. There is no problem about reverse order. I mean. When you rewind your video tape or fast forward them. It is just in the function. One knows that window doesn't spontaneously reassemble. So if a frame shows that. We can say "Ah, it's just an artifact"... unless you want to argue that what happens in a frame actually happens such that the window spontaneously reassemble? But then we can just say to ignore it... and just treat the normal ordering as actual with the reverse order virtual like virtual particles.. just an artifact effect.

 

[Dale]

Given the assumptions you've been making, your logic seems valid.

Good, I am glad that you agree with that much at least.

While my intuition tells me that too much significance is given to the Lorentz ether theory

Honestly, I don't place any significance on LET, it is merely the most well-known counter example to the Vandam's false claim that the experimental evidence we have to date can only be interpreted as a block universe and not as any other interpretation as well as his other false claim that the relativity of simultaneity implies a block universe.

I can understand how he would be so tenacious in discounting LET (remember his citing Lorentz's own resignation)

Lorentz's disavowal of LET is historical trivia and not relevant to the question of whether or not the evidence supports it. Science isn't a popularity contest, the only vote that counts is nature's.

I'm not sure that the search for an experimental program yielding the distinction has been fully explored.

If you wish to continue the search then this is where you need to focus your efforts. The task is fairly clear: find an experiment where LET predicts X and block-universe predicts Y with X≠Y. I don't believe the task is possible, for the reasons stated above, but at least it is clear.

What you can say that is not overstepping is that the evidence is consistent with a 4D universe. You can also talk about the many aesthetic, practical, and philosophical advantages of the block-universe approach over other approaches, like LET. If you don't claim that the block universe is the only interpretation supported by the evidence then your drawings and explanations would be quite beneficial, I think. And there is certainly nothing wrong with simply stating that it is your clear personal preference.

 

[PeterDonis]

One knows that window doesn't spontaneously reassemble.

But how do we know that? Because we always see the events in the same order: throw baseball, then window breaks. If baseballs made of tachyons were commonly observed, and we commonly saw the events in the opposite order, we might not be so confident that we knew which order was the "right" one.

unless you want to argue that what happens in a frame actually happens such that the window spontaneously reassemble?

Part of the standard physical interpretation of a frame is that "what happens in a frame actually happens", yes. There is no room in the standard interpretation for some observations made in a frame to be "artifacts".

and just treat the normal ordering as actual with the reverse order virtual like virtual particles

Since you mention virtual particles, it's worth bringing up the point that if we include quantum mechanics, we can no longer say that tachyons can actually transmit information or causal influences faster than light. See here:

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html

The same is actually true of virtual particles: virtual particles in quantum field theory can travel faster than light, but they can't be used to transmit information or causal influences faster than light, for the same sorts of reasons as tachyons can't be used that way as explained in the article above.

 

[jk22]

I think there are experiments checking the constancy of the speed of light no matter what the motion of the observer is in the so called emission theory (see Wikipedia), for example by measuring the speed of sun light during spring and autumn or from binary star systems and no significant difference could be found.
Another way to test it is the Sagnac interferometer that uses rotating mirrors.