Why Haven't Two Clocks on a Table Been Used to Measure Light's One-Way Speed?

[Hurkyl]

And don't forget that everyday observation contradicts classical mechanics too! Inertia? Pthht! When I stop pushing something, it stops!

 

[outandbeyond2004]

In a previous post

v

is a dimensionless quantity representing a fraction of the speed of light. If you have a velocity in say meters/sec, divide it by c before plugging it into

v

. Sorry.


It's been fun, it made me think about issues I had not really thought about before, and I think I gained a better understanding of SR. Good mental exercise, too, from trying to convince a skeptic of the truth of SR. This is not necessarily my last post in this topic, but . . .

 

[Eyesaw]

Originally posted by Hurkyl
And don't forget that everyday observation contradicts classical mechanics too! Inertia? Pthht! When I stop pushing something, it stops!

Not true. Performing the ball rolling experiment by Galileo would show that the ball always tries to achieve a final height that is equal to its initial height, roughly demonstrating a conservation of energy. And probably by oiling the surface the ball rolled on, he and Newton were able to show friction as a force that slowed down the ball, so that in its absence, the previously demonstrated conservation of energy would require the ball to move for all time.
No contradictions at all. Galileo and Newton merely used inductive reasoning to arrive at the law of inertia.

On the other hand, Einstein's SR proposed a totally absurd and illogical notion that velocity of light can be an absolute constant for all observers, regardless of their velocities through space. This is trivially proven false by demonstrating that motion exists. Or more elegantly, like MM, that one ray of light cannot be everywhere at once.

 

[russ_watters]

Originally posted by Eyesaw
SR dogma...

Heh - so SR is 100 year old dogma while Newtonian physics is 500 year old...what?

Eyesaw and MM, asserting something to be true is not the same as proving it. You guys have made a lot of assertions but have provided only misunderstood interpetations as proof. SR is thoroughly proven. If you wish to overturn it, first learn it. Of course once you learn what it and the evidence for it actually says, you'll realize why it is accepted: it works.

Also, while arguments are welcome, attitudes are not. Lose the attitudes.

 

[Eyesaw]

Originally posted by Martin Miller

I have already presented one experimental proof of the variance of light's one-way speed. Here is yet another:

Given 2 people (P1 and P2) meeting in passing while steadily walking at different speeds as a single light ray approaches, as shown:

...P1....<~~~~ray
...P2

At the above critical point in the experiment, both the light ray's tip is at a single point, and the observers are at a single point; this proves to the observers that the ray is now equidistant from them; they can qualitatively label this distance X.

After the observers separate, the ray will reach one of them
first, as shown:

...P1<~~~~~~~~ray
P2

Since the tip of the light ray cannot be in two places at once,
the observers know that it reached them sequentially at absolutely
different times. (Here is a down-to-earth example: If I see the
real you in Texas and in New York, then this proves that I saw you
at absolutely different times because you cannot be in two places
at once.) They can qualitatively label these absolutely different
times T1 and T2.

The observers can now qualitatively compare one-way light speeds.
Here are their simple results:

Light's speed wrt P1 = X/T1

Light's speed wrt P2 = X/T2

This is a simple and direct experimental proof of the variance
of light's one-way speed.

How many more such proofs do you need? [/B]

You had the right idea but this experiment is flawed. The X distance the light traveled with respect to your thought experiment is different for p1 and p2. The experiment should be revised to
say that x marks the spot where p1 and p2 meet, who were traveling at different velocities so that when the light strikes the spot x, p1 and p2 would have traveled a different distance with respect to the light in the same amount of time. I.e.,

light's speed wrt P1 = (X + P1x)/T
light's speed wrt P2 = (X + P2x)/T

c for P1 not equal to c for p2- QED.

 

[outandbeyond2004]

Eyesaw, once again, it was not Einstein who first proposed that the speed of light was a constant. It was a theoretical consequence of Maxwell's equations for electrodynamics, which were based on decades of experiments. Was your computer designed using equations other than Maxwell's? You might as well as assert that it was.

I've come to appreciate how hard it is for some people to accept the notion that the vacuum local speed of light is really a constant. I can't remember whether I started out disbelieving in its constancy before finally accepting it as a scientific fact, but I can't think of any table-top experiment that the average Joe or Joette can do. The GPS devices are good 'experiments,' but one still has to be told that their design requires GR. (I once told a friend that, and he showed amazement, if not disbelief.) I have toured several science fairs by now, and certainly nobody was demonstrating light-speed constancy, ha, ha.

Perhaps what Eyeshaw should do is to apply for a job as particle-accelerator designer. I would be totally staggered if he became one.

 

[Eyesaw]

Originally posted by russ_watters
Heh - so SR is 100 year old dogma while Newtonian physics is 500 year old...what?

Eyesaw and MM, asserting something to be true is not the same as proving it. You guys have made a lot of assertions but have provided only misunderstood interpetations as proof. SR is thoroughly proven. If you wish to overturn it, first learn it. Of course once you learn what it and the evidence for it actually says, you'll realize why it is accepted: it works.

Also, while arguments are welcome, attitudes are not. Lose the attitudes.

You are the one with the attitude. I would not waste my energy trying to explain something to a robot whose designers, running
out of AI chips, replaced with a NI chip- i.e., No Intelligence technology.

 

[Eyesaw]

Originally posted by outandbeyond2004
Eyesaw, once again, it was not Einstein who first proposed that the speed of light was a constant. It was a theoretical consequence of Maxwell's equations for electrodynamics, which were based on decades of experiments. Was your computer designed using equations other than Maxwell's? You might as well as assert that it was.

I've come to appreciate how hard it is for some people to accept the notion that the vacuum local speed of light is really a constant. I can't remember whether I started out disbelieving in its constancy before finally accepting it as a scientific fact, but I can't think of any table-top experiment that the average Joe or Joette can do. The GPS devices are good 'experiments,' but one still has to be told that their design requires GR. (I once told a friend that, and he showed amazement, if not disbelief.) I have toured several science fairs by now, and certainly nobody was demonstrating light-speed constancy, ha, ha.

Perhaps what Eyeshaw should do is to apply for a job as particle-accelerator designer. I would be totally staggered if he became one.

Once again, Maxwell's equations were formulated under the pretext of an ether- this is evident in the fact that the EM propagation equations were wave equations and not equations that describe motion of individual particles. Since Einstein disposed of the ether, he revokes his right to the Maxwell formulation of EM phenomena. So any fanatic of SR should be obligated to produce the derivation of a constant c in vacuum without the Maxwell equations. Show me then
how Einstein arrived at his postulate of a constant c without the
Maxwell equations.

Furthermore, the fact that c is a constant in Maxwell's equations
in no way implies the Galilean transformation for light to be invalid. This rather is a consequence of SR's illiteracy in logic. Nor does it require that c be independent of the velocity of source
or inertial frame. Einstein's two postulates in SR contradict each other and have never been proven by any experiment when they are simultaneously applied.

It's not that c being constant in vacuum is hard for people to believe (since if we are accustomed to the law of inertia alreadyyy and in the absence of any external force, there's no reason c should vary from place to place), but Einstein's illogical requirement that c be constant
for observers moving at a different velocity than the frame in which c was obtained, which resulted in the absurd notions of time dilation and space contraction, which ironically, if SR's logic was taken to its conclusions, could not even exist.

 

[Hurkyl]

Not true. Performing the ball rolling experiment by Galileo would show that the ball always tries to achieve a final height that is equal to its initial height, roughly demonstrating a conservation of energy. And probably by oiling the surface the ball rolled on, he and Newton were able to show friction as a force that slowed down the ball, so that in its absence, the previously demonstrated conservation of energy would require the ball to move for all time.
No contradictions at all. Galileo and Newton merely used inductive reasoning to arrive at the law of inertia.

If I roll a ball downhill (oiled or not), it stays downhill. It's totally illogical to think otherwise. And "friction" is just absurd; the ball slows down because there's nothing to keep it moving!

Law of Inertia! Hah! It is trivially proven false by demonstrating that an object will come to rest on its own!

I bet that you're going to tell me that feathers and bowling balls fall at the same speed too, aren't you?

 

[Eyesaw]

Originally posted by Hurkyl
If I roll a ball downhill (oiled or not), it stays downhill. It's totally illogical to think otherwise. And "friction" is just absurd; the ball slows down because there's nothing to keep it moving!

Law of Inertia! Hah! It is trivially proven false by demonstrating that an object will come to rest on its own!

Actually I like your notion of inertia better (I thought the same myself). But I think Galileo and Newton's law of inertia are made consistent with observation by the different assumptions they make about motion. In G and N's model, motion is carried out by tireless donkeys so that the only way to slow the carriage down is by forcefully removing the donkeys or attaching to the carriage donkeys that move in the opposite direction until the forces are balanced ("force" here having a different meaning than that in F=ma). In your model, the carriage is a Honda Civic, a Lumina, Maxima, e.gs., that requires gas to run and only gives you miles to the gallon.

Otoh, I can't see how Einstein's SR can be made consistent with logic and daily observations. It seems to require that there be an infinite number of predetermined universes.

I bet that you're going to tell me that feathers and bowling balls fall at the same speed too, aren't you?

As a matter of fact, I don't believe they do. And there's an usenet poster with a very high IQ that is currently trying to dispute this notion:

http://www.mazepath.com/uncleal/qz.pdf

 

[outandbeyond2004]

Originally posted by Eyesaw
Once again, Maxwell's equations were formulated under the pretext of an ether-

To be sure, the aether idea was raised and debated long before Maxwell, but I learned electrodynamics without its aid.

Originally posted by Eyesaw
this is evident in the fact that the EM propagation equations were wave equations and not equations that describe motion of individual particles.

What about the Lorentz force law?

Originally posted by Eyesaw
Since Einstein disposed of the ether, he revokes his right to the Maxwell formulation of EM phenomena.

A kind of Yogi Berraism is a saying that makes you want to reply to it, but you just can't think of something good to say, it's so illogical and/or irrelevant. You'd open your mouth to reply then think better of it. And then one minute later you again want to reply but again decide not to. And so on.

Originally posted by Eyesaw
So any fanatic of SR should be obligated to produce the derivation of a constant c in vacuum without the Maxwell equations. Show me then
how Einstein arrived at his postulate of a constant c without the
Maxwell equations.

Who, me? Nay, nay, rather ask God to transport you back to the time when Einstein was pondering such matters on his way to his 1905 SR paper.

Originally posted by Eyesaw
Furthermore, the fact that c is a constant in Maxwell's equations
in no way implies the Galilean transformation for light to be invalid. This rather is a consequence of SR's illiteracy in logic. Nor does it require that c be independent of the velocity of source
or inertial frame. Einstein's two postulates in SR contradict each other and have never been proven by any experiment when they are simultaneously applied.

Eyesaw, what the boys in white ought to do is to take you in a straitjacket off to one of these particle smashers and make you a nice plumb juicy target for these wee lil beasties to smash into and produce lovely data to wow the world and lead us into peace and joy forever.

 

[Nereid]

Eyesaw, in another thread in this very same sub-forum, I post two links to lists (with references) of tests of SR and GR. Your reply to my post was (excerpts): "Yes, I have looked at that webpage before. But before we go over these experiments, I'd still like an answer to how any test can be claimed to have confirmed SR ..."

In a nutshell, the answer to your question is 'you can make quite specific predictions from SR; you can do the experiments and make the observations; when you do, you find that the predictions are correct, to within the experimental/observational errors'. IMHO, that's all you can ask of a theory.

So, let's go look at the experiments on the lists:
1) was a specific prediction from SR made?
2) was that prediction made correctly (e.g. no screw-up in the math)?
3) did the researchers do the experiment/make the observation?
4) were the results consistent with the prediction?

Please tell us which of the experiments, in your mind, have "NO" as the answer to any question.

 

[outandbeyond2004]

I would like to suggest that anybody try to design a system like the GPS withOUT GR (at least the low-velocity, low-stress, weak-gravity version or the Parameterized Post-Newtonian formalism). It can be done, I think. I won't try it myself; I trust GR and suspect it would be a well-nigh impossible feat to pull off. However, if Eyesaw, MM, or someone else actually pulls it off, I may decide to abandon GR, especially if the mathematics is simpler.

Let me apologize to Eyesaw. I thought for a moment that he was kidding. I didn't intend to start a flame war.


The Galilean velocity addition theory HAS been tested -- and found to be wrong for particles traveling at high speeds. I mean if in a frame another frame is traveling at speed v and in the second frame an object is traveling at speed w, then the object is predicted to travel at speed w + v wrt the first frame (that's only if the respective velocities are parallel). Is that what MM, Eyesaw, etal. have in mind, the Galilean velocity addition theory?

 

[Hurkyl]

Otoh, I can't see how Einstein's SR can be made consistent with logic and daily observations.

It can't! SR is indistinguishable from Newton when low velocities are involved, and we already see that Newton is inconsistent with logic and daily observations.

You know, we might have a lot more competent engineers if we drop science from their cirriculum, so we don't lead them astray from the obvious facts of everyday experience!

Furthermore, the fact that c is a constant in Maxwell's equations
in no way implies the Galilean transformation for light to be invalid.

We don't need Maxwell to prove them invalid! We just have to toss a ball straight up while running very fast - it lands behind me, not in my hand!

 

[Eyesaw]

Originally posted by Nereid
Eyesaw, in another thread in this very same sub-forum, I post two links to lists (with references) of tests of SR and GR. Your reply to my post was (excerpts): "Yes, I have looked at that webpage before. But before we go over these experiments, I'd still like an answer to how any test can be claimed to have confirmed SR ..."

In a nutshell, the answer to your question is 'you can make quite specific predictions from SR; you can do the experiments and make the observations; when you do, you find that the predictions are correct, to within the experimental/observational errors'. IMHO, that's all you can ask of a theory.

So, let's go look at the experiments on the lists:
1) was a specific prediction from SR made?
2) was that prediction made correctly (e.g. no screw-up in the math)?
3) did the researchers do the experiment/make the observation?
4) were the results consistent with the prediction?

Please tell us which of the experiments, in your mind, have "NO" as the answer to any question.

That webpage provides references to the literature of the experiments, without details to any of them so not much for discussion there. And it's obvious from the author's commentaries on the experiments that he holds a clear bias for SR results- it's like reading a report on the effects of smoking from the tobacoo companies. If you have details on a specific experiment in mind,
I'm sure we would find some flaw in it since it's clearly impossible for SR's postulates to be correct.

The speed of light being source independent and a constant c relative to the vacuum, yes. That physics is the same in all inertial frames, maybe. That both are true simultaneously- no.

 

[Eyesaw]

Originally posted by Hurkyl
It can't! SR is indistinguishable from Newton when low velocities are involved, and we already see that Newton is inconsistent with logic and daily observations.

Impossible. The classical interpretation of SR requires different
inertial frames to be living in different space and time zones- the resulting time dilation and space contraction effects is what allows the c from a stationary frame to be observed as c from a moving frame. That was the whole purpose for the Lorentz transformation. Thus, metaphysically, SR is not indistinguishable from Newton at any velocity.


Nor have you demonstrated how Newtonian mechanics is inconsistent with logic and daily observations to support your other remark.

We don't need Maxwell to prove them invalid! We just have to toss a ball straight up while running very fast - it lands behind me, not in my hand!

Here you are introducing gravity which isn't even covered by SR. Even so, when you toss the ball straight up, you did not apply horizontal velocity to it so the ball ends up in a different inertial frame than you, when horizontal velocities are compared. This result is in complete agreement with Galilean transformation
whereby the ball's velocity in the horizontal direction is c +/- v as observed by the running person, with c being 0 in this particular case. So, wrong again. Once again, the addition of velocities in different inertial frames is a fundamental statement about motion, space and time- one cannot make a reality based on absolute time and space consistent with one that requires a relative space and time- but this is not to say that SR is even correct in the latter respect.
Try analyzing the motion of the ball using SR with respect to the runner- you run into the scenario I brought up awhile ago of having 3 dimensions for time in SR. Ridiculous.

 

[Martin Miller]

ahrkron wrote:
"Once you have the two clocks' terminal connected to the same source,
you just send the signal. Each will receive half the current, but
they will start prompted by the same pulse."

There are only two problems with this, namely, you have yet to
prove that the pulses travel at equal speeds wrt the clocks, and
you have yet to provide a means of verifying absolute synchronicity.

And, as I said, but as you seemingly ignored, _if_ you had actually
discovered a means of absolutely synchronizing clocks, then you
would be the first.
[Ref: for some others who have tried, see the following:
"Conventionality in Distant Simultaneity," wherein three
proposals for absolute synch are shot down.
Peter Ohrstrom, Found. Phys. 10, 333 (1978).]

 

[Nereid]

Originally posted by Eyesaw
That webpage provides references to the literature of the experiments, without details to any of them so not much for discussion there.

Yes, there are a lot of them, aren't there? Which ones have you performed?

Originally posted by Eyesaw : And it's obvious from the author's commentaries on the experiments that he holds a clear bias for SR results- it's like reading a report on the effects of smoking from the tobacoo companies. If you have details on a specific experiment in mind,

It's not a question of 'bias', it's a question of results. You're the one proposing that SR is invalid (in some way), I'm challenging you to tell us which of the dozens of experiments which are consistent with SR are, in fact, not.

Originally posted by Eyesaw : I'm sure we would find some flaw in it since it's clearly impossible for SR's postulates to be correct.

That's precisely what I'm asking* you to do, show us the flaws in the experiments.

Originally posted by Eyesaw : The speed of light being source independent and a constant c relative to the vacuum, yes. That physics is the same in all inertial frames, maybe. That both are true simultaneously- no.

Experimental or observational results which show this, please!

*For the avoidance of doubt (and at the risk of being painfully repetitious), please look at the experiments on the lists, and for each *you* answer these questions:
1) was a specific prediction from SR made?
2) was that prediction made correctly (e.g. no screw-up in the math)?
3) did the researchers do the experiment/make the observation?
4) were the results consistent with the prediction?

Having done that, please tell us which of the experiments, in your mind, have "NO" as the answer to *any* question.

 

[Eyesaw]

Originally posted by outandbeyond2004
I would like to suggest that anybody try to design a system like the GPS withOUT GR (at least the low-velocity, low-stress, weak-gravity version or the Parameterized Post-Newtonian formalism). It can be done, I think. I won't try it myself; I trust GR and suspect it would be a well-nigh impossible feat to pull off. However, if Eyesaw, MM, or someone else actually pulls it off, I may decide to abandon GR, especially if the mathematics is simpler.

Let me apologize to Eyesaw. I thought for a moment that he was kidding. I didn't intend to start a flame war.


The Galilean velocity addition theory HAS been tested -- and found to be wrong for particles traveling at high speeds. I mean if in a frame another frame is traveling at speed v and in the second frame an object is traveling at speed w, then the object is predicted to travel at speed w + v wrt the first frame (that's only if the respective velocities are parallel). Is that what MM, Eyesaw, etal. have in mind, the Galilean velocity addition theory?

No need for apologies, I don't take flames very seriously anyways and think it's healthy. Sticks and stones... Anyways, please provide the experiments demonstrating the Galilean velocity addition to be incorrect.

 

[Martin Miller]

outandbeyond2004 noted:
"Oh, sorry, I see now that you ARE asserting anisotropy . . . are you? I feel a little confused."

That's funny, I would have bet good money that I said
"In other words, experiment shows that light's one-way
speed varies with frame velocity" in a prior post of
3-16-2004.

outandbeyond2004 noted:
Your P1-P2-light ray does not prove that. It is only a thought experiment;

Name one reason why it cannot be actually done;
in fact, it is done every day by people walking
toward light from the sun or even car headlights.
Not to mention the fact that all of SR is based
on thought experiments.

outandbeyond2004 continued:
... and, more important, your analysis is mistaken or inadequate.
The light ray is going in one direction only. To prove anisotropy
you need to show that speeds in other directions are different.

You are the one who brought up anisotropy; my experiment
disproves Einstein's invariance.

And you have yet to prove either invariance or isotropy.

You also have yet to prove that Einstein's clocks are
correctly synchronized.

You have also yet to present a single piece of experimental
evidence for SR that is untainted by Einstein's clocks.

But I can fully understand why, so don't sweat it.

 

[ahrkron]

Originally posted by Martin Miller
There are only two problems with this, namely, you have yet to
prove that the pulses travel at equal speeds wrt the clocks,

If both clocks are identical, there is no reason to expect otherwise. Anyway, this potential problem is easy to overcome: just reduce the length of the "Y" branches as much as possible. Clearly, there is no reason why this coudln't be zero. Ultimately, you can even attach the two clocks to, say, both sides of the same circuit board, so that they share the exact same input lines (so there are not two pulses).

and you have yet to provide a means of verifying absolute synchronicity.

I did. You just need to let the two clocks run for, say, a day, and then send the stop signal. At that moment, both clocks are programmed to store their final times in memory devices, and both are displayed in a screen. If both show the same number, you know that they are in sych down to one count in a day worth of counts.

As an example, say that they count once per nanosecond (ns) (which is not much; the computer I'm working on has a 2GHz clock, i.e., its clock ticks twice every nanosecond). In a day, you have a total of 86400 seconds, which makes 8.64x10^13 ns. Adjust anything you need until, after a day, you get the two clocks to get the same count. Then you know that they are syncronized to one part in 8.64x10^13. Not bad at all, and good enough to make the measurement for the speed of the space shuttle (8 km/s, which gives a time dilation difference of the order of 10^-9; i.e., the potential experimental error is four orders of magnitude smaller than the difference you want to measure! that allows for a very good measurement)

And, as I said, but as you seemingly ignored, _if_ you had actually
discovered a means of absolutely synchronizing clocks, then you
would be the first.

Time synchronization is not the problem you make of it. There are high speed networks all around us these days. In order for them to work properly, transmitters and receivers need to have similar speeds and to exchange signals at the right times.

 

[outandbeyond2004]

I googled "Michelson-Morley interferometer ("table-top" OR tabletop)"

Guess what, some authors actually propose that a MM interferometer mounted on a table can measure the Milky Way Galaxy mass. Why don't MM, Eyesaw, et. al. construct their own interferometers and try to verify the predictions in the following paper:

Weighing the Milky Way

If one is all thumbs, surely one has techie friends who could help. I am going to send my nephew the URL. Maybe at the next science fair he will wow people.

 

[Nereid]

ahrkron wrote: Time synchronization is not the problem you make of it. There are high speed networks all around us these days. In order for them to work properly, transmitters and receivers need to have similar speeds and to exchange signals at the right times.

To amplify on ahrkron's comment: modern telecoms networks - whether a large office one, or the China Telecom's phone network (>150 million circuits), or anything in between - rely heavily upon accurate synchronisation.

The problem of 'distributing the clocks' is an old one in telecoms, and was solved (from an engineering perspective) a long time ago. There are commercial solutions - http://www.empowerednetworks.com/solution/products/symmetricom.htm -widely available. If you google on 'distributing clock telecom network' (or similar) you'll find a large number of good sites; some of the vendors have extensive product data sheets describing clock synchronisation in much detail.

 

[russ_watters]

Originally posted by Nereid
To amplify on ahrkron's comment: modern telecoms networks - whether a large office one, or the China Telecom's phone network (>150 million circuits), or anything in between - rely heavily upon accurate synchronisation.

At the risk of sounding like a broken record, GPS also requires precise time signal synchronization - to within just a few nanoseconds.

 

[Martin Miller]

ahrkron wrote:
"Time synchronization is not the problem you make of it. There
are high speed networks all around us these days. In order for
them to work properly, transmitters and receivers need to have
similar speeds and to exchange signals at the right times."

It is not my problem - it is SR's and Einstein's problem.
It was Einstein who claimed that he did not possesses the
"means of measuring time." (his words, not mine) Also,
did you not look at the peer-reviewed physics article to
which I referred?

Anyway, let's see if we can clear up this matter via the
following simple question:

Would you please show at least two inertial coordinate
systems' observers using your "synchronized" clocks to
measure light's one-way speed - in full numerical detail?
(I want to see times on all clocks used.)

Although my query just given should be sufficient, I will,
nonetheless, continue to address your reply.

ahrkron wrote:
"If both clocks are identical, there is no reason to expect otherwise.
Anyway, this potential problem is easy to overcome: just reduce the
length of the "Y" branches as much as possible ..."

I agree with you that very closely-spaced clocks can be nearly
absolutely synched, but I was speaking of absolute synchronization
in theory. That is, you must tell us how to absolutely synchronize
two clocks which may be 10,000 light-years apart.

quote:
and you have yet to provide a means of verifying absolute synchronicity.

ahrkron wrote:
"I did. You just need to let the two clocks run for, say, a day, and
then send the stop signal."

How do you know that the stop signal travels at equal speeds
wrt the clocks?

ahrkron wrote:
"... Then you know that they are syncronized to one part in 8.64x10^13.
Not bad at all, ..."

No, not bad for use on Earth, but try it for two clocks which are
moving at 90% light speed and are 10 light-years apart.

Please remember that all physicists and all other scientists
have only **one** definition of clock synchronization, namely,
Albert Einstein's, and it merely assumes one-way light speed
isotropy and invariance, and does not prove it. (Actually,
it is not really an assumption because it cannot be proved
because there is nothing to be proved -- it is a merely a
mandate that forces clocks to obtain one-way invariance and
isotropy. If anyone believes otherwise, then let her or him show
on paper how it can be proved or tested experimentally.)

 

[Martin Miller]

Eyesaw noted:
"You had the right idea but this experiment is flawed.
The X distance the light traveled with respect to your
thought experiment is different for p1 and p2. ..."

The experiment was designed to fit within the
context of SR, which involves measurements wrt
inertial coordinate systems.

To explain further:
Let's say that you and I are in different frames whose
x axes are parallel. I am at my frame's origin, and
you are at your frame's origin. At the moment that
these two origins meet in passing, suppose an explosive
event occurs some distance away near our frames' x axes.
Suppose this explosion burns spots on both axes. All
SR proponents will say that we will each measure the
_same_ distance from our origin to the burn mark on our
x axis. This is why I said that the approaching light
ray traveled the _same_ distance wrt the observers.

 

[outandbeyond2004]

Well, Martin Miller does have a good point, in a way. We can synchronize nearby clocks all we want, but what about events say 10 LY distant? We can't transport any clock there in any practical way; and even if we use FTL transport, how do we know that the transported clock stays synchronized?

Well, I hate to admit it, but we just assume that an hydrogen molecule there acts like an hydrogen molecule in the lab. Synchronization between a distant hydrogen molecule and a lab hydrogen molecule? You win

Indeed, a dirty secret in science is that astrophysics is done on the assumption that whatever happens in the lab also applies in a general way to what happens out there. That's all it is, just an assumption. The laws of physics on Earth are the same in distant places of the universe, I hope.

But, Martin, are you going to reject everything just because it is based on assumptions like the above? If you do, why are they so unreasonable? They are not proven and may never be, but are they really unreasonable?

 

[russ_watters]

Originally posted by outandbeyond2004
Well, Martin Miller does have a good point, in a way. We can synchronize nearby clocks all we want, but what about events say 10 LY distant? We can't transport any clock there in any practical way; and even if we use FTL transport, how do we know that the transported clock stays synchronized?

For synchronizing clocks in different reference frames, we use SR and GR: again, like they do with GPS.

 

[Hurkyl]

Even so, when you toss the ball straight up, you did not apply horizontal velocity to it so the ball ends up in a different inertial frame than you

*boggle*

You do realize that Galilean relativity says that if I throw a ball straight up (by my reckoning), it should come straight down and bonk me on the head, don't you?


It, of course, doesn't happen, because the ball will land behind me; I have to throw it slightly forward in order for it to bonk me on the head.

 

[selfAdjoint]

The first postulate of SR is that an inertial observer sees all physics the same as he would if at rest. Including the effects of local gravity, to a high degree of approximation. This is Galilean relativity. If you stand still on the surface of an airless, rotating planet and throw up a ball, it will have the same tangential speed as you do and will rise and fall, from your point of view, just as if you were at rest. And it will come down and bonk you.

Now if you project the ball very hard, so that it soars high, then maybe tidal effects will have some effect, but that is very very small. Basically Galilean relativiy rules, and your theories of what happens are wrong.