yknot

swansont, on 17 Nov 2013 - 10:11 AM, said:

>Synchronization requires clocks to run at the same rate. Clock frequencies vary by gamma from frame to frame, so clocks in different frames run at different rates. Q.E.D.

 

No, clock synchronization does not call for equal clock rates across frames; it just requires that the clocks in each frame are related in some way, preferably correctly (i.e., absolutely synchronized). (In order to determine event order, all you need is a pair of synch'd clocks no matter what rate they have as long as both have the same rate, as they will if they are in the same frame.)

 

>You're also wrong about proving a negative, because this is not a matter of data or evidence. The statement is a ramification of the theory, which means the prediction is mathematical and it is possible to prove a negative in mathematics.

 

Math is not physics. And how would you prove that two clocks cannot be absolutely synchronized? This could happen purely accidentally or by the random thumpings of a herd of monkeys, so it is indeed physically possible.

 

>It is observed not to agree with how nature behaves. It's also disagrees with electrodynamics, a very successful theory.

 

 

Einstein said otherwise. He said that given the clocks of classical physics (and he never said that such clocks cannot exist, only that we should discard them and replace them with his asynchronous clocks), light's one-way speed will certainly vary with frame velocity.

 

[Quoting Einstein:]

"w is the required velocity of light with respect to the carriage, and we have

 

w = c - v.

 

The velocity of propagation of a ray of light relative to the carriage thus comes out smaller than c.

 

But this result comes into conflict with the principle of relativity.... For, like every other general law of

nature, the law of the transmission of light in vacuo must, according to the principle of relativity, be the

same for the railway carriage as reference-body as when the rails are the body of reference."

http://www.bartleby.com/173/7.html

 

Actually, this does not come into conflict with the principle of relativity because that principle just calls for everyone to have the same general laws, and in this case the general law is w = c ± v. There was never even an apparent conflict, so there was never any need to invent a theory (SR) to "fix" it .

 

>It agrees with how nature behaves, to within experimental error. It's also consistent with electrodynamics, a very successful theory.

 

Here we have a major problem; there has never been any experiment showing light's invariance between two mutually-at-rest clocks; in fact, this cannot even be shown on paper (no matter how much math you use).

No, this won't work. One of the ramifications of relativity is that it's not possible to synchronize clocks in different reference frames.

 

Since a negative statement cannot be proved, I ask for evidence.

 

You seem to be selectively reading and/or quoting from Einstein's work (I'm not going to try searching for an online copy to check the context. And anyway, there are far better sources to learn relativity from.)

 

The whole point of his work is to show that such absolute synchronization is not possible; there is no absolute time. If you haven't understood that, then clearly you haven't understood the theory of relativity.

 

There is little point you arguing against it from this position of relative (see what I did there) ignorance. You need to study the theory first, then ask for help with parts you have a problem with. Starting out with a closed mind is not going to get you very far.

 

 

I don't know how to respond to this. It appears to be a case of thinking that your intuition trumps objective evidence. I'm afraid that the timing of events is observer dependent (as are many other things such as length, energy, ...) whether you like it or not. The universe apparently doesn't care about your opinion.

You have a lot of nerve accusing someone of selective quoting without having even looked at the source. I think that you owe me an apology. And who better to learn SR from than the originator?

 

And the whole point of E's work cannot be to show that absolute synch is impossible because such a negative cannot be proved. If you know of such a proof, then state it.

 

I further resent being labeled close-minded this early in the game. See my last post for this "session."

 

As for my statement that events are observer-independent, here is someone else who stated that:

 

[Tom Roberts wrote:]

This is a foundation of modern physics: all physical phenomena are

completely independent of coordinates, because Nature quite clearly

doesn't need or use coordinates. Coordinates are merely tools of

description, and artifacts related to the choice of coordinates cannot

affect physical phenomena, only the _description_ of them. There's no

reasonable definition of "real" that makes _descriptions_ be "real".

http://groups.google.com/group/sci.physics/browse_frm/thread/d4ac4d13086ac07e/a29b0e07db6f1f8b#a29b0e07db6f1f8b

 

Maybe you would like to argue with Tom?

Einstein said classical physics (i.e. with Galilean transforms) has absolute time. He then goes on to show that Galilean transforms do not describe reality, thus absolute time doesn't exist in reality. The "truly synchronous clocks" you want do not exist. That's not a choice, that's how nature actually behaves.

What, specifically, is "wrong" with the Galilean trans. claim that light's speed from point A to point B varies per inertial frame?

 

OTOH, what is "right" about relativity's claim that light's speed from point A to point B is c in all inertial frames?

 

To whom it may concern:

 

Einstein's embankment observer says that he was centered on the events when they occurred, and he also says that since he need not take into account any movement toward either light ray, he can safely conclude that the events occurred simultaneously simply because the rays from the events reached him simultaneously.

 

Similarly, Einstein's train observer says that he also was centered on the events when they occurred, and he also says that since he need not take into account any movement toward either light ray, he can safely conclude that he events did not occur simultaneously simply because the rays from the events reached him at different times.

 

After being adjacent (or side-by-side), the two observers separate. Since they are in different locations when the light rays arrive, they _cannot_ see the rays in the same way. (This was even hinted at by Einstein when he said "If an observer sitting in the position M’ in the train did not possess this velocity, then he would remain permanently at M, and the light rays emitted by the flashes of lightning A and B would reach him simultaneously, i.e. they would meet just where he is situated.")

 

Clearly, this has nothing to do with how the lightning events occurred, but everything to do with the spatial separation of the two observers.

 

Just as clearly, it is improper to use light signals from events to judge their time order if observer differences (such as spatial separation during the observation) are completely ignored.

 

One way for Einstein's observers to validly use light rays from the events to judge their occurrence order would be if each observer knows how he moves in relation to the rays. For example, if the embankment observer knows that he remains centered on the approaching rays, then he can he validly claim that the events occurred simultaneously.

 

Of course, the best way for observers to determine event order is simply by placing truly synchronous clocks at the events in question. Here is how Einstein described such clocks:

 

"[in classical physics] [t]he simultaneity of two definite events with reference to one inertial system involves the simultaneity of these events in reference to all [other] inertial systems. This is what is meant when we say that the time of classical physics is absolute." [Einstein's book _Relativity_, p. 149]

 

Yes, Einstein decided to discard such clocks (because he wrongly believed that they violated the principle of relativity), but he of course could not prove the negative that such clocks cannot exist. All that is needed is some method for truly synchronizing clocks.

 

And after discarding truly synchronous clocks, Einstein replaced them with absolutely asynchronous clocks, but such clocks cannot possibly make correct measurements. As we all know, events are independent of coordinate systems, and two events can occur in only one way, and clocks should reflect this simple fact. For example, two people born on opposite sides of Earth will reflect the fact that they were born truly simultaneously by remaining practically the same age, so clocks should also reflect this.

 

 

Question: Would sim. be rel. given truly synch'd clocks* AT the events?

 

Strange replied:

>See Janus's answer above.

 

He made no mention of truly synch'd clocks, but Einstein did, saying that simultaneity would not be relative given such clocks.

 

Quoting Einstein:

"[in classical physics] [t]he simultaneity of two definite events with reference to one inertial system involves the simultaneity of these events in reference to all [other] inertial systems. This is what is meant when we say that the time of classical physics is absolute." [Einstein's book _Relativity_, p. 149]

 

If all it takes is a pair of (truly) synchronous clocks at the events to get rid of relative simultaneity, then it is clear that the latter is not given by nature but by man via his choice to use asynchronous clocks at the events or by improperly using light rays from the events.

 

The only way that observers can properly use light signals from events to judge the simultaneity of them is if the observers know how they are actually moving in relation to these light signals. But neither observer in Einstein's train example knows this. In fact, it is utterly ignored. (More on this below.)

 

But why go to the trouble of using observers and light signals; why not just place absolutely synchronous clocks at the events. As Einstein said, this eliminates relative simultaneity and gives all observers absolute time (for judging event time differences).

 

Strange:

>The relatively of simultaneity is about how the two observers see the relationship between two different events. Of course they will see them at different times. But one will consider the two events to have happened at the same time, and the other will consider the two events to have happened at different times. This is AFTER taking into account the arrival time of the light.

 

But if the observers know that one is actually moving _toward_ one light signal and _away_ from the other, and that the other observer is _not_, then they will simply conclude (correctly) that the events happened in only one way (say truly simultaneously), and will say that they cannot properly use light signals from the events whilst they are moving helter-skelter wrt said signals.

 

Here is E's def. of abs. time:

Strange replied:

>Which he then goes on to demonstrate is incompatible with reality

 

In exactly what way are truly synchronous clocks "incompatible with reality"? It seems to me that Einstein's clocks are the ones that are incompatible because they wrongly say that two events can be said to occur in many different ways (temporally) whereas anyone knows that events are independent of observer observations and events occur in only one way in reality. (Ironically, Einstein's above agrees.)

>You don't seem to understand that the relativity of simultaneity is caused by the effects of motion that you are talking about (combined with the constant speed of light for both observers).

 

Question: Would sim. be rel. given truly synch'd clocks* AT the events? If so, then rel. sim. is not given by nature and is therefore not a part of physics.

Question: Which experiment has revealed the "constant speed of light" from point A to point B in any inertial ref. frame?

 

>What do you mean by observers "see the light differently"?

 

One sees it before the other despite the fact that they started out side-by-side when the light started.

 

 

>No one is refusing to take the movement of the observers into account. That relative movement is the cause of relativity of simultaneity (and time dilation, length contraction, etc)

 

It is not the "relative motion" of the observers wrt each other that is being ignored; it is the motions of the obs's wrt the light signals that is being ignored. And it is only this motion that matters in the train ex. and in my examples. Diff. frames move differently wrt any approaching ray of light and this must be taken into account when light rays from events are used to judge the events' temporal order.

 

*Here is E's def. of abs. time:

"[in classical physics] [t]he simultaneity of two definite events with reference to one inertial system involves the simultaneity of these events in reference to all [other] inertial systems. This is what is meant when we say that the time of classical physics is absolute." [Einstein's book _Relativity_, p. 149]

 

Again, because O2 is closer to the light source than O1.

 

This has got to be simple trolling. This is too simple to misunderstand as repeatedly as you appear to.

 

Yes, of course it's because O2 is closer to the source, but how did he get closer? My answer is simply that he moved relative to the source or, more specifically, rel. to light's emission point, or even more specifically, he moved closer or toward the tip of the approaching ray. In other words, it's observer motion relative to the ray's tip that matters here, and not observer motions relative to each other. We can see this clearly by using a single observer and a light source. The closer this obs. is the the source, the quicker he will see the light that is emitted (toward him). Yes, this is too simple, but it is also critical to understanding E's train ex. which purportedly showed rel. simult. whereas all it really showed was the very simple fact that observer motion rel. to light makes diff. obs's see the light differently. We can say more: It is wrong to use light rays from events + differently-moving obs's to judge the events' occurrence times if you refuse to take into account the fact that the obs's move diff'ly wrt to the sources. (The best way to correctly time events is by placing correctly synch'd clocks at the events.)

Of course it has to do with different relative motion. You've got O2 moving towards the light flash, so he's going to see the flash first. the light ray has to travel a greater distance to get to observer O1.

To show that relative observer motion is not really involved, we can eliminate it by placing both observers in the same inertial frame as follows:

 

--------------------O1------------------------------O2---------------------A-Frame x axis--------------------<~~~~~~~~~~light ray

 

Just as in E's train ex. and as in my half-****d version,, O2 sees the ray before O1. Why do they see the ray arrive differently? (Catch you in the am)

Let's worry about the very simplest part of my example. Forget about length contractions and invariant light speed (because no one is measuring either lengths or speeds). Forget about points of view where one person looking at another (because there are none). Let me just ask this one simple question: Why do my observers see the light ray differently? (This cannot be due to "different relative motions" because neither observer is observing or recording the motion of other.) (And I can just as well ask the same question about E's version - why did his two observers see the two rays arrive differently?) There has to be some physical reason why the observers see things differently.

 

Saying what they are would be useful. There's a single flash of light. What else?

 

I started (in order to simplify) with a single flash to show that the difference between the two observers in the single-flash case has everything to do with their different motions, and really nothing at all to do with event times. Then this conclusion can easily be extended to cover the entire train example by simply adding a second lite flash, but this is not really necessary is it? (I'm just saying that E's train ex. does not show that sim. is rel. but merely shows that observers moving differently will see events differently if they judge event times by light-rays-from-the-events and totally ignore the fact that they moved differently during the experiment, which is what really caused them to see the events diff'ly.)

The distance has less meters in O2 frame.The distance has more meters in O1 frame.

 

This was 1/2 of E's train ex. & he had his observers equidistant from both light-emitting events. (The lightning strikes could leave burn marks in each frame to verify this, as many have said.)

To keep it as simple as possible, we will use only the right half of E’s train example.

 

O1
-----------------------------------------------<~~~~~light
O2-->

A light ray starts equidistant from inertial observers O1 and O2, as shown. And yet O2 sees the ray before O1. (And this is absolutely before because these are light-like events.)

Why this difference?

 

I’m guessing that is has nothing to do with either the event or light’s speed, but that it has everything to do with the fact that the observers moved differently in relation to the approaching light ray.

 

But this does not show that simultaneity is relative; it merely shows that observers moving differently will see events differently. It is wrong to ignore these different motions, and to then go on and say that the events occurred differently for the two train example observers.

 

Except that light is not a fence post. The speed of light

 

is invarient in all inertial frames, regardless of theirrelative

 

motion.

 

 

 

You do not seem to have heard about Relativity.

 

 

 

 

OK, I resent the blatant insult.

 

 

 

From someone who cannot even spell invariant,

 

I am receiving an insult?

 

 

 

Please.

 

 

 

This will be my final post in this forum.

 

(Everybody clap loudly!)

 

 

 

But I will leave a parting shot that cannot be denied.

 

 

 

No one has every correctly measured any speed, much

 

less light's speed.

 

 

 

If you fail to grasp this, then consider the following simplefacts:

 

 

 

(1) No one can prove that their clocks are not intrinsicallyslowed.

 

(Intrinsic slowing is the same as twins and triplets aging

 

differently. It is physical and not reciprocal.)

 

(This alone makes all speed measurements invalid)

 

 

 

(2) No one can prove that their rulers are not intrinsically

 

contracted.

 

(This adds to the above problem)

 

 

 

(3) No one can prove that their clocks are correctly or

 

absolutely synchronous.

 

(This invalidates all one-way speed measurements,

 

from the speed of a bug relative to a log to the speed

 

of light.)

 

 

 

If you cannot validly measure the speed of a freekin

 

bug relative to a log, then your physics is totally

 

screwed up. Face the facts.

 

 

 

I'm serious, dudes.

 

Very serious.

 

 

 

PS> ACG52 presented zero proof of light's invariance one-way

 

speed. He cannot because there is no proof.

 

Tip: click inside this box to load the editor

 

The different FREQUENCY of the light relative to the observers, not the speed.

 

 

 

 

 

 

You must have forgotten about or somehow overlooked my fence analogy

 

(given in my first post).

 

 

 

Let's say that a picket fence is floating in space (inertially, no acceleration).

 

Let's say that you and I see different frequencies for this fence. That is, we

 

observe different numbers of fence posts passing us each second. Is not

 

the only way that this can occur is for us to be moving at different speeds

 

relative to said fence?

 

 

 

And, as I said in my original post, since relative motion is reciprocal, we

 

must say that the fence is moving at different speeds relative to each of us.

 

 

 

Methinks that you fellows are (for some reason that I cannot yet fathom) fighting

 

too strongly against the simple equation w = c - v. It's time to face the facts

 

and get on with life.

To Mr. Hyde:

 

 

Let me for a minute return to my original post. What do you,

 

Mr. Hyde, think causes observers to see different colors when

 

viewing the same passing light ray? Since the light itself

 

cannot and does not change color, we are left with only one

 

answer, namely, the different speeds of the observers relative

 

to the passing light. This simple experiment alone is enough

 

to prove that light's speed relative to observers varies.

 

 

But let me also return to Einstein's simple equation, w = c - v.

 

Regardless of your statement that Einstein was in the process of

 

"proving" that classical time was incorrect, he _did_ in fact

 

derive the equation w = c - v. Can you show us how he derived it?

 

 

And as for your statement that there were no Mars or Moon probes

 

in Einstein's day, this is irrelevant because Einstein could have

 

used a thought experiment, as he often did (even in the "important"

 

case of his derivation of the relativity of simultaneity.)

 

 

Perhaps if you just show how Einstein derived his equation w = c - v,

 

you will see what I have been talking about (non-argumentatively).

 

 

But I _will_ give you the following little hint: Einstein did not

 

really prove that the clocks of classical physics were wrong, but

 

simply discarded such clocks in lieu of the really wrong clocks

 

(asynchronous clocks) of special relativity. As we know, he replaced

 

good clocks with bad clocks (absolutely synchronous clocks with

 

absolutely asynchronous clocks) in order to (try to) get all clocks

 

to record "c" for the one-way speed of light. Of course, he very

 

conveniently did _not_ show how this can be done experimentally.

 

But you, Mr. Hyde, are welcome to try.

 

 

Well, I have blabbered enough for now.

 

 

(Oh, I almost forget to mention that you have yet to show how your

 

probe experiment yields the value "c" for light's one-way speed.)

 

I think the first verification of the absolute speed of light was by DeSitter in 1913. He examined binary star systems ( two stars revolving around a common center of gravity). His observations and analysis agreed with Einstein's prediction. And this was a one-way light experiment.

 

See for example http://en.wikipedia....star_experiment

 

Well, this is only about light's source independency, not its one-way speed.

 

Wouldn't GPS fail if there was a variable sped of light? The time of flight from the satellites would be off, leading to a positioning error.

 

All clocks today are synchronized per Einstein's definition, and this

definition assumes "c" for light's one-way speed.

 

Obviously, truly or absolutely synchronous clocks would be better for GPS,

but it can get by with Einstein's slightly-off clocks because of the following:

 

On the satellite side, timing is almost perfect because

they have incredibly precise atomic clocks on board.

 

But what about our receivers here on the ground?

 

Remember that both the satellite and the receiver need

to be able to precisely synchronize their pseudo-random

codes to make the system work.

 

If our receivers needed atomic clocks (which cost upwards

of $50K to $100K) GPS would be a lame duck technology.

Nobody could afford it.

 

Luckily the designers of GPS came up with a brilliant

little trick that lets us get by with much less accurate

clocks in our receivers. This trick is one of the key

elements of GPS and as an added side benefit it means

that every GPS receiver is essentially an atomic-accuracy clock.

 

The secret to perfect timing is to make an extra satellite measurement.

That's right, if three perfect measurements can locate a point in

3-dimensional space, then four imperfect measurements can do the

same thing.

 

By using an extra satellite range measurement and a little algebra

a GPS receiver can eliminate any clock inaccuracies it might have.

 

If you, Mr. Swan..., think that GPS clocks are absolutely synchronous,

then please tell us how that was done. According to current theory,

it cannot be done, and should not be done ("cause time is relative, not

absolute per Albert E).

 

What you all are overlooking here is the simple fact that Einstein himself

said mathematically that the one-way light speed will vary given the

clocks of classical physics, clocks which he was unable to obtain probably

because he wanted to discard them.

First of all, it is funny that Einstein did not mention

your "one-way experiment," and second of all, it is not

possible to measure light's one-way speed without using

two clocks, and third of all, why did you ignore Einstein's

simple equation saying that given the clocks of classical

physics, light's one-way speed must vary with frame velocity?

 

And please show the math (you said it was simple math) for

your experiment to show how light's one-way speed can be c

in any inertial frame.

 

Your claim that my above was "totally false" is itself totally

false, as you will soon discover by trying to do the math.

To Hyde:

 

Please point out my argumentative stuff; I do not intend to be so.

 

To explain my "fixation" on light's one-way speed, and why and how it

differs fundamentally from the round-trip speed, I turn to Einstein's own

words, since you seem to think that mine are somehow "argumentative."

(I really should not have to use Einstein's words to explain SR because

they have been readily available to everyone for decades, but since you asked....)

 

The one-way and round-trip cases are different. One-way light speed "invariance"

had to be given by definition, whereas round-trip speed invariance was given

prior to special relativity via experiment, as Einstein said in his 1905 paper

.

 

"In agreement with experience we further assume the quantity

 

2AB/(t'a-ta) = c

 

to be a universal constant - the velocity of light in empty space."

 

http://www.fourmilab...in/specrel/www/

[Einstein's "In agreement with experience" means "In agreement

with experiment." (The Michelson-Morley experiment - MMx)

Einstein's "2AB" means "a round-trip from A to B and back."

Einstein's time period "ta'-ta" is the round trip time per one clock.

(Einstein had to use the word "assume" because the MMx did not

use a clock. Later, the Kennedy-Thorndike experiment did use a

clock, and also got c for light's round-trip speed. Yes, there were

two round-trip null results, meaning that the first one did _not_

prove round-trip invariance.)]

 

But Einstein was _unable_ to point to a one-way light speed experiment

because none existed, and this is still the case.

 

As I said, all he could do was to define "invariance," as is seen clearly

by the following from Einstein's SR paper:

 

"Any ray of light moves in the "stationary"' system of co-ordinates

with the determined velocity c, whether the ray be emitted by a

stationary or by a moving body. Hence

 

velocity = light path/time interval

 

where time interval is to be taken in the sense of the definition in § 1."

 

Since the definition in §1 forces clocks to obtain the value "c" for

light's one-way speed (by presetting them to read the same time

for both one-way trips purely by stipulation), it is clear that this

"invariance" is neither a postulate nor assumption, but merely

a convention like the rather trivial convention that 12"= 1'.

 

The problem with Einstein's definition is that it causes clocks to be

asynchronous. This is why SR has relative time, which is really just

a euphemism for incorrect time since everyone knows that SR's clocks

are not absolutely synchronous. SR does not have absolute time only

because Einstein decided to force clocks to "get" "c" as he wished.

To repeat: No experiment has ever said this (or ever will).

 

Even though Einstein preferred his asynchronous clocks (because

they seemed to give him what he thought he needed, namely, one-way

"invariance," he was unable to prove that truly synchronous clocks

cannot exist because negatives cannot be proved.

 

In fact, Einstein mathematically stated that observers who use the

absolutely synchronous clocks of classical physics will get a _variable_

one-way light speed.

 

[Quoting Einstein:]

"w is the required velocity of light with respect to

the carriage, and we have

 

w = c - v.

 

The velocity of propagation of a ray of light relative

to the carriage thus comes out smaller than c.

 

But this result comes into conflict with the principle

of relativity.... For, like every other general law of

nature, the law of the transmission of light in vacuo

must, according to the principle of relativity, be the

same for the railway carriage as reference-body as when

the rails are the body of reference."

http://www.bartleby.com/173/7.html

 

This is not a closing velocity because Einstein claims

that it conflicts with the principle of relativity, and

a closing velocity would not do this.

 

Also, no mere closing velocity could have given Einstein

a headache.

 

And no mere closing velocity could have caused the creation

of the theory of special relativity.

 

All of the above tells us that even though the round-trip light speed case

was closed (experimentally) prior to SR, the one-way case remains open.

All we need are a pair of (truly) synchronous clocks to get a variable one-way

light speed (w = c ± v, per Einstein himself), which would detect our absolute

motion, just as happened in Einstein's own example/experiment above.

 

So, if you think that I am just being "argumentative," or that my arguments

are merely "falling flat," then maybe you will listen to Einstein's own words.

The Doppler shift affects our observation of the frequency of light.It does not affect our observation of the speed of that light.

 

To model how our relative motion affects the speedof light and the speed of other thing, Einstein came up with aclever formula. See link:

 

http://math.ucr.edu/...R/velocity.html

 

Thanks for the replies, folks! I don't mean to sound argumentative, but I must stay with the facts, wherever that may lead!

 

 

 

One fact that pertains to the above is that Einstein's composition of velocities formula was based on his _assumption_ of one-way light speed invariance. Not surprisingly, given this, we end up "getting" "c" for the speed of light (and less than c for all other entities). (Neither Einstein nor anyone else ever actually _measured_ light's one-way speed between two clocks.)

 

 

 

Another fact that also pertains to the above is that one-way invariance is an invalid assumption because it cannot occur experimentally (or even theoretically).

 

 

 

Although this second fact may be difficult to believe, it is fairly easy to demonstrate by the following simple challenge:

 

 

 

Show on paper how light's one-way speed between two clocks can be c experimentally in any inertial frame or frames.

Mathematically you can think of it as this: If you move towards light, you run into the "bumps" or sign changes in a sine wave faster, and if you move away from light, you run into the sign changes at a slower rate, though the actual measurement of light is an instant process,but it might have to do with relative kinetic energy as well.

 

Since I am still confused re Mr. Hyde's remarks, I shall go ahead and address Mr. EquisDeXD's.

 

 

 

Here is a quick question that may help:

 

As far as relative motion per se is concerned, is there really any difference between that of a passing asteroid and that of a light ray? (Yes, I know that the ray may be traveling a lot faster, but that is beside the point.)

 

 

 

It seems to me that there is no difference at all, and this tells us that light's relative motion is no different from that of any other entity, such as a neutrino or a baseball.

 

 

 

This is probably why no experiment has ever shown a variance in light's one-way speed per two clocks.

 

 

 

The optical Doppler effect is just another example of light's varying one-way speed.

 

 

 

At least that's the way I seeze it. How about you guyzz??

To ACG52:

 

 

 

My point about the source was that motion relative to it cannot be involved if the source is no longer there. The only things that are involved are the light rays and the observers. They pass each other in the night.

 

 

 

My point about light's passing speed still stands because no one has ever measured light's passing (or one-way) speed. Can you possibly show how such a measurement can be even be made?

 

 

 

To Mr. Hyde:

 

I am unsure of your point. Could you possibly clarify?

The optical Doppler effect is defined as follows:

 

"A change in the observed frequency of light or otherelectromagnetic radiation caused by relative motion of the source and observer."

 

The problem with this definition is the fact that the light is no longer connected to the source by the time the former is viewed (by observers).

 

 

 

In fact, the source could be long gone or even utterly destroyed by the time its light is finally seen.

 

 

 

I see this light as being analogous to a simple picket fence that is floating in space whilst observers in various (inertial) frames pass by.

 

 

 

The fence does not (and cannot) change (no accelerations here, we are talking special relativity only), so the only thing that can cause a different view of its "frequency" (the passing of its posts) is different observer motions relative to the fence.

 

 

 

In the case of light, the same thing happens, that is, observers in different (inertial) frames see the light differently (different colors) because they are passing the light differently.

 

 

 

And since relative motion is reciprocal, this means that the light is passing the observers differently.

 

 

 

But now we have the problem that this last fact runs counter to special relativity theory.

 

 

 

At least, that's *my* conclusion. What say ye?