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

  • Thread starter Thread starter Martin Miller
  • Start date Start date
  • Tags Tags
    Sr
Click For Summary
The discussion centers on the challenge of measuring the one-way speed of light using two clocks placed on a table, questioning why this straightforward experiment has not been conducted. Participants argue that existing methods, like GPS, assume light speed invariance without directly testing it. The conversation highlights the synchronization issues inherent in using spatially separated clocks, with some asserting that absolute simultaneity is necessary for accurate measurements. Critics of special relativity (SR) express skepticism about the validity of current theories, suggesting that Einstein's framework relies on unproven assumptions. Ultimately, the thread emphasizes the need for a clean, direct experiment to resolve these fundamental questions about light's speed and the nature of simultaneity.
  • #61
Originally posted by Hurkyl
*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?

Only if you threw the ball up while standing still. If you threw the ball up then ran away from it, it will obviously fall away from you since you gained velocity in the horizontal direction with respect to the Earth frame while the ball did not.

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.

The ball will not land behind you if never ran away from it. GAlilean relativity most definitely does not predict the ball to fall behind you if you threw it while standing still with respect to the Earth frame. This simple motion of the ball on the other hand cannot be analyzed by SR since the ball is in an accelerated frame with respect to you and is also moving in a direction perpedicular to your motion so that you end up with time dilation and space contraction in two different directions. Absurd.
 
Physics news on Phys.org
  • #62
Originally posted by 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.

The postulate Galilean relativity and SR have in common is the one that says that physics is the same in all inertial frames. I don't think GAlileo every mentioned about transforming events from one inertial frame to another but if one were to do so then obviously something moving at c, y, m, l, j, a, b, d, e, x, n, s, q, et al in a "rest" frame would have a velocity of c +/- v after transforming coordinates. This is the logical consequence of the addition or subtraction of velocity to the rest coordinates.

The relevant point here is that after transforming coordinates by Galilean relativity, the c, representing a physical constant maybe,
can remain a constant only if we make the additional assumption of source dependency. This c could be the speed of light for example as measured in an inertial frame.

SR on the other hand introduces a postulate that contradicts the first postulate. That's why any attempts at physical interpretation led to paradox.
 
Last edited:
  • #63
Only if you threw the ball up while standing still.

While running, I am still in the inertial reference frame centered on me.


This is the logical consequence of the addition or subtraction of velocity to the rest coordinates.

And why should we believe in addition/subtraction of velocity to the rest coordinates? It is this assumption that SR contradicts.


Shall I remind you that the assumption that "All physical laws are the same in all inertial reference frames" implies that the speed of an electromagnetic wave is the same in every reference frame, ala Maxwell's theory of Electrodynamics?
 
  • #64
Eyesaw, perhaps you have a techie friend who would enjoy cobbling together a tabletop Michelson-Morley interferometer using spare parts. He could then demonstrate for you personally that the postulate of linear velocity addition is not natural, contrary to what you think is logical.
 
  • #65
Originally posted by Hurkyl
While running, I am still in the inertial reference frame centered on me.

No, Inertial frames are distinguished by the difference in velocity they have between them. When you start running, you change your inertial frame. Thus if you threw the ball upwards while standing and afterwards proceeded to run horizontally away from it, you and the ball end up in different inertial frames, whether under Galilean Relativity or SR. Only if you threw the ball while running, at constant velocity, will it be in the same inertial frame as you
and therefore fall down to bonk you- of course such an experiment
is difficult to perform because of the difference in air drag e.g.


And why should we believe in addition/subtraction of velocity to the rest coordinates? It is this assumption that SR contradicts.

Because 1+1 = 2. Because 2+2 = 4. Because 3+3=6. Because 5+5=10. Because if J is moving at c relative to M, and L is moving at v relative to M, then J must be moving at c +/- v relative to L or else we arrive at the contradiction that L is not moving relative to M.


Shall I remind you that the assumption that "All physical laws are the same in all inertial reference frames" implies that the speed of an electromagnetic wave is the same in every reference frame, ala Maxwell's theory of Electrodynamics?

And as I already explained in response to self-adjoint, any physical law can be made constant in Galilean relativity by assuming source dependency. SR assumed source independency, that's what resulted in contradiction. You can logically assume source independency only if physical laws are frame dependent.
 
Last edited:
  • #66
Only if you threw the ball while running, at constant velocity, will it be in the same inertial frame as you
and therefore fall down to bonk you- of course such an experiment
is difficult to perform because of the difference in air drag e.g.

This is the point I was trying to make that got lost in the parody.

Experience "proves" Galilean relativity wrong because of air drag. If I'm running and I throw a ball up, it falls behind me, which seems to contradicts Galilean relativity. However, if you were the type who didn't want to believe in Galilean relativity, you could easily use this scenario to rationalize your belief that Galilean relativity is false.


Because if J is moving at c relative to M, and L is moving at v relative to M, then J must be moving at c +/- v relative to L or else we arrive at the contradiction that L is moving relative to M.

What's the contradiction? Are you assuming that if M measures the distance between J and L, then L simultaneously measures the same distance?


And as I already explained in response to self-adjoint, any physical law can be made constant in Galilean relativity by assuming source dependency.

Funny, I've never seen a consistent version of Maxwell's equations that has source dependancy.
 
  • #67
Originally posted by Eyesaw

Because 1+1 = 2. Because 2+2 = 4. Because 3+3=6. Because 5+5=10. Because if J is moving at c relative to M, and L is moving at v relative to M, then J must be moving at c +/- v relative to L or else we arrive at the contradiction that L is moving relative to M.

Do you have an analysis of the Michelson-Morley interferometer experiment?

Also, how do you explain this experiment with a magnetometer at rest wrt a electrically charged ball: The magnetometer registers zero, but if it moves at speed v wrt the ball, it registers the strength of a magnetic field in proportion to v?
 
  • #68
Originally posted by outandbeyond2004
Do you have an analysis of the Michelson-Morley interferometer experiment?

Some descriptions of the Michelson Morley experiments differ from others- I shall use this one for my answer :http://galileoandeinstein.physics.virginia.edu/lectures/michelson.html

Using Galilean relativity, the null result can be explained either assuming the light is source dependent or not, weird as it seems. In the case of source independence, the horizontal path (assuming this is the direction of motion of the Earth through space) traveled by the light would be L+v in the direction of the Earth's motion and L-v going back for a round trip distance of 2L. In the vertical path, the distance is just L up and L down for a roundtrip of 2L. Since both vertical and horizontal paths are equal, a null result is obtained. The argument applies even when the apparatus is turned.

In the case of source dependence, the time traveled for the light would be (M+v) - v in the direction of Earth motion and (M-v) + v going back for a roundtrip time of 2M. Vertically, the time of flight would be (M+( hypotenuse displacement of light)) - ((hypotenuse displacement of velocity of source)) upwards and the same back down for a roundtrip time of (M+N) - N + (M+N) -N = 2M. Since both times are equal, the result is again a nullshift.

It seems a little strange that both assumptions lead to a null result so feel free to double check my calculations.

OTOH, interpreting the MMX using SR results in a contradiction. Taking the detector as the inertial frame (which would include the whole apparatus), it would say the apparatus is in a frame that is both time dilated and not time dilated , space contracted and not space contracted - since it would need time dilation and length contraction to explain the light traveling at c in a frame that is moving relative to a frame that is not moving with respect to the EArth. But this is no surprise since the theory uses two contradicting postulates.

If anything the MMX disproves SR, as any real experiment should. The weird result obtained for Galilean relativity is because we used the roundtrip speed of light and also because we assumed there is no stationary ether that can drag the light. That's about the only thing MMX proves- that light is not being dragged by a stationary ether.
 
Last edited:
  • #69
outandbeyond2004 wrote:
"... 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 noted:
"For synchronizing clocks in different reference frames, we use
SR and GR: again, like they do with GPS."

russ_waters also wrote the following in a slightly earlier post:
"At the risk of sounding like a broken record, GPS also requires
precise time signal synchronization - to within just a few nanoseconds."

----

MM replies (sans any hope of really getting thru, so it's basically
just for the record):
Empty claims of absolute synchronization (as in the above cases)
are not proofs of it.

FYI: There is only one way to prove absolute synchronization,
and that is by showing step-by-step how it can be done. (This
involves the necessary step of providing the verification
process.)

I would add that anyone who claims to be able to absolutely
synchronize clocks should also show what happens to light's
one-way speed when it is measured by said clocks.

Also, I should add that anyone who finds a way to absolutely
synchronize clocks will thereby disprove special relativity,
which of course has only relative simultaneity. (This includes
the scientists involved in the GPS system, but none of them has
publicly claimed to have found absolute synchronization.)

My prediction re the above is that no one in this forum will
ever show the required step-by-step proof of absolute clock
synchronization. (In fact, if I were wealthy, I would bet
big bucks on it!)
 
  • #70
Originally posted by Hurkyl
This is the point I was trying to make that got lost in the parody.

Experience "proves" Galilean relativity wrong because of air drag. If I'm running and I throw a ball up, it falls behind me, which seems to contradicts Galilean relativity. However, if you were the type who didn't want to believe in Galilean relativity, you could easily use this scenario to rationalize your belief that Galilean relativity is false.

No, what it shows is that you can continue burning calories to overcome airdrag to keep at a constant velocity while the ball cannot because it doesn't have a digestive system for one. I don't think you've even tried this experiment yourself by the way. I'm in my office right now, which can be considered an inertial frame since everything in it are stationary. While standing in one place, I throw a ball in the air and it falls down in my hand. If I throw it upwards and then run away from the ball, it falls behind me. I then started running with the ball in my hand and after I throw it- as vertically as possible- it falls in my hand, not behind me.

But there are much better illustrations then your experiment that clearly demonstrates the validity of Galilean relativity and the Galilean addition law. In a car moving at 25 miles per hour with the windows rolled up while seated, throw a ball vertically and see if it flies to the back or lands in your hand.

I still think you are joking because I've never heard anyone dispute the validity of Galilean relativity in every day observations because it's so easily verified.
What's the contradiction? Are you assuming that if M measures the distance between J and L, then L simultaneously measures the same distance?

The contradiction is that we started out assuming there is velocity between M and L, then using J as a standard by which the velocity between M and L are to be determined. The only way J can have the same value for both M and L then is if there is no velocity between them, contradicting our starting assumption that there was. This is a reductio absurdum.

Funny, I've never seen a consistent version of Maxwell's equations that has source dependancy.
The postulate of physics being the same in all inertial frames makes any transformation equation redundant. Since the postulate is a statement about physics inside an inertial frame, of what relevance is it to transform an event into a different inertial frame? And this postulate is definitely not specific to the Lorentz Transformations since one can just as well transform the value C in one inertial frame using the Galilean transformation then adding or subtracting v to the c-value in the new frame to obtain the universal constant C, i.e. by assuming source dependency. The main difference is that the Lorentz Transformation starts out by assuming absolute space-time but then rejects it in the same equations in order to make C a universal constant- i.e. it results in physical and logical nonsense.
 
Last edited:
  • #71
Was Einstein really a genius?

Nereid noted:
"Einstein's theories ... have been tested in the
crucible of experiment and observation, and have
passed with flying colours."

Sorry to burst your bubble, "Mr. Nereid," but as
far as Einstein's special relativity goes, your
above is purely an urban legend.

There have been exactly zero tests of SR.

For example, the very basis of SR, Einstein's
light postulate (i.e., one-way, two-clock light
speed invariance) has not been tested.

(To explain: No one has ever used two clocks in
one frame to measure light's one-way speed.)
(In fact, no one has ever even shown on paper
how this could be done!)

For another example, actual time dilation effects
were not predicted by SR, so these effects do not
test or support SR.

(To explain: It is easy to prove that SR does not
pertain to actual or intrinsic time dilation {or to
an atomic clock's internal rhythm} -- all that needs
be done is to point out the very simple facts that [1]
any inertially-moving atomic clock always has only
_one_ atomic rhythm, and yet [2] Einstein's observers
in various frames find _many_ "rhythms" for one and the
same passing clock; these facts prove that SR can't
pertain to intrinsic clock rhythms.)

(And of course the same argument applies to the
"mass increase" and "length contraction" cases.)

Please check the historical record before posting
any more silly urban myths.

And as for Einstein's genius, he was indeed a very
brilliant person, a genius even, but he did not win
the Nobel for SR. Also, it is not genius-like to say
"I am merely stipulating one-way invariance purely
by definition" out of one side of one's mouth whilst
stating the exact opposite out of the other side (i.e.,
claiming that one-way invariance is a prediction or
a postulate or a law of physics per experiment).
 
  • #72
Originally posted by Martin Miller

I would add that anyone who claims to be able to absolutely
synchronize clocks should also show what happens to light's
one-way speed when it is measured by said clocks.

Also, I should add that anyone who finds a way to absolutely
synchronize clocks will thereby disprove special relativity,
which of course has only relative simultaneity. (This includes
the scientists involved in the GPS system, but none of them has
publicly claimed to have found absolute synchronization.)

My prediction re the above is that no one in this forum will
ever show the required step-by-step proof of absolute clock
synchronization. (In fact, if I were wealthy, I would bet
big bucks on it!)

I must admit that I have come into this discussion a bit late, but I have read through the entire thread. The discussion seems to be focused on clock synchronization, so my question is on the meaning of clock synchronization. I just want to be sure we all agree on the meaning of "synchronization".

MEANING OF CLOCK SYNCHRONIZATION

We have two clocks, clock A and clock B. Let them be of identical construction, therefore if they are both in inertial reference frames, they tick at the same rate. Let us suppose that the two clocks are at the ends of an absolutely rigid rod, therefore if one clock is in an inertial reference frame, then so is the other. Let us suppose then, that the clocks are in an inertial reference frame (hence the rod isn't rotating), now focus on the meaning of synchronization. To say that the clocks are 'synchronized' means that when clock A reads zeta, clock B simultaneously reads zeta. So, for example, if one clock currently read 17, and the other clock simultaneously reads 9929, then the two clocks aren't synchronized. Do we all agree that this is the meaning of synchronization?

Thank you.
 
Last edited:
  • #73
Martin Miller wrote:[n] Nereid noted: "Einstein's theories ... have been tested in the crucible of experiment and observation, and have passed with flying colours."

Sorry to burst your bubble, "Mr. Nereid," but as far as Einstein's special relativity goes, your above is purely an urban legend.

There have been exactly zero tests of SR.
That's Ms Nereid to you Martin.

Do you have a copy of Y.Z.Zhang, Special Relativity and its Experimental Foundations, World Scientific (1997)? If so, please tell us which of the tests discussed in this book failed?

If you don't, please check this page, and tell us which tests failed.

Please note that I am interested FIRST in 'pass/fail' in the following sense:
1) was there a specific, objective prediction made from SR?
2) did the experiment or observation produce a clear, unambiguous result?
3) was the result the same as that predicted by SR (within the errors of the observation)?

For the avoidance of doubt, I'm not interested (at this stage) in whether you feel there may or may not be inconsistencies in SR.
 
  • #74
Eyesaw, you assumed that if source-independent light goes out at L+v and comes back at L-v, then the trip time would be the same as though we have average (L+v plus L-v)/2 = L. Nay, nay, not so fast.

Going out, the half-trip time is D/(L+v) (assuming of course that D is not contracted or expanded). Coming back, the halftrip time is D/(L-v).

The total trip time is then D (1/(L+v) + 1/(L-v)) = D\frac{2L}{(L^2 - v^2)} = (2D/L)\frac{1}{1 - (v/L)^2}

If v is a substantial fraction of L, then there would be a rather obvious difference. Anyway, the MMXI should be able to detect interference from very small fractions of light.

I will look at the rest of your post hoping to catch more errors.
 
Last edited:
  • #75
Originally posted by outandbeyond2004
Eyesaw, you assumed that if source-independent light goes out at L+v and comes back at L-v, then the trip time would be the same as though we have average (L+v plus L-v)/2 = L. Nay, nay, not so fast.

Going out, the half-trip time is D/(L+v) (assuming of course that D is not contracted or expanded). Coming back, the halftrip time is D/(L-v).

The total trip time is then D (1/(L+v) + 1/(L-v)) = D\frac{2L}{(L^2 - v^2)} = (2D/L)\frac{1}{1 - (v/L)^2}

If v is a substantial fraction of L, then there would be a rather obvious difference. Anyway, the MMXI should be able to detect interference from very small fractions of light.

I will look at the rest of your post hoping to catch more errors.

Actually, the v I used represents a distance- i.e. the displacement through space of the moving apparatus as a result of its velocity v. Thus, it's clear that in the direction of motion, the light travels an extra distance of +v while in the round trip, the lesser distance traveled is -v. Even so, there is an error in your formula for time of flight since the time of flight of the light cannot be D/c+v and D/c-v if the distance back and forth for the light is not the same. Your usage of c+v and c-v is also in error since we are assuming the speed of light as source independent. The actual time of flight should be D+Q/c + D-Q/c = 2D/c. That is, the roundtrip distance is 2D or 2L or 2M or 2 and any other alphabet.
 
  • #76
We need to do this problem more carefully, at least I do. I made at least two mistakes in my last post.

Okay, let's assume light independence.

Shall we assume that the interferometer is moving at velocity v wrt the ether or the distant stars? To an observer moving with the interferometer, for light moving in the direction of the velocity, it appears to be moving at speed c - v? For light moving in the opposite direction, the observed speed is -c-v?
 
  • #77
Originally posted by Martin Miller
FYI: There is only one way to prove absolute synchronization,
and that is by showing step-by-step how it can be done. (This
involves the necessary step of providing the verification
process.)
Except for the word "absolute" (it doesn't exist in science), you can prove quite easily that GPS clocks are synchronized to within nanoseconds: stand over a benchmark with a gps reciever and compare the positions.
MEANING OF CLOCK SYNCHRONIZATION
Good point: since MM hasn't defined what he means by it, we can only make assumptions and he can flippantly reject any attempt to guess his intent. To most people, "synchronized" isn't a binary situation: clocks are synchronized to within a certain arbitrary precision. For my example of GPS clocks, they are synchronized to within a few nanoseconds of each other.

So, MM, perhaps you could precisely define what you mean by "synchronized."
The postulate of physics being the same in all inertial frames makes any transformation equation redundant. Since the postulate is a statement about physics inside an inertial frame, of what relevance is it to transform an event into a different inertial frame? [emphasis added]
I'm sorry, but that statement by being self contradictory displays a fundamental misunderstanding of what Einstein's Relativity says. The key word there is "in," not "between." If the rules worked the same between different frames, there would be no need for transformations. But since they only work the same in different frames, you need to do transformations to go between them.

And different frames are still related. By knowing how they are related you can make the appropriate transformations.
 
Last edited:
  • #78


quote:
--------------------------------------------------------------------------------
The postulate of physics being the same in all inertial frames makes any transformation equation redundant. Since the postulate is a statement about physics inside an inertial frame, of what relevance is it to transform an event into a different inertial frame? [emphasis added]
--------------------------------------------------------------------------------


I'm sorry, but that statement by being self contradictory displays a fundamental misunderstanding of what Einstein's Relativity says. The key word there is "in," not "between." If the rules worked the same between different frames, there would be no need for transformations. But since they only work the same in different frames, you need to do transformations to go between them.

And different frames are still related. By knowing how they are related you can make the appropriate transformations.

If physics is the same in all inertial frames, why do you need to transform anything? You can just use any arbitrary set of coordinates as long as it is an inertial frame. The only reason to transform coordinates is if physics is not the same in different inertial frames. But if you are going to use one inertial frame to view the events in another inertial frame, it's a contradiction to say first there is velocity between them and then say there is no velocity between them. Transforming coordinates to make the laws of physics the same in all inertial frames can be done many ways- doing it by the Lorentz Transformation results in contradiction. The better way to do it is to decide on source dependency from the getgo (through experimentation) and then decide whether the laws of physics are the same or not inside inertial frames. If experiments show source independency then the laws of physics can't be the same in different inertial frames; if the show source dependency then they can. That's inertial frame physics in a nutshell.
 
Last edited:
  • #79
russ_watters wrote (in part):
"So, MM, perhaps you could precisely define what you mean
by "synchronized."

"Originally posted by Martin Miller
FYI: There is only one way to prove absolute synchronization,
and that is by showing step-by-step how it can be done. (This
involves the necessary step of providing the verification
process.)"

"Except for the word "absolute" (it doesn't exist in science),
you can prove quite easily that GPS clocks are synchronized to
within nanoseconds: stand over a benchmark with a gps reciever
and compare the positions."

MM replies:
Please pardon my protest, but the word "absolute" does exist in
science; indeed, it is simply the opposite of "relative," so if
"relative" exists, then so does "absolute." For example, since
Einstein's clocks are based on relative simultaneity, all I have
to do to define absolutely synchronous clocks is to say that they
are the opposite of Einstein's. And as I mentioned earlier, even
Einstein stated mathematically that the absolutely synchronous
clocks of classical physics yield a variable one-way light speed.
Here is the relevant Einsteinian quote (repeated):

"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." (_Relativity_ Chap. VII)

Furthermore, every physicist agrees that two touching clocks
can be absolutely synchronized.

And this last fact provides us with the following simple way of
defining absolute synchronization for separated clocks:

Begin with two unstarted atomic clocks which are inertially moving
along one's frame's x axis. As the clocks meet in passing, absolutely
synchronize them by letting one start the other on touching. Then
assume (as did Einstein) that these clocks have identical internal
atomic rhythms. Given this, we know that they will remain absolutely
synchronous forever, no matter how far apart in space they may be.

Here is yet another definition of absolute clock synchronization:
Begin with two unstarted clocks located on one's frame's x-axis
at some distance apart. Cut a rod to fit precisely between these
two clocks. Remove the rod, place it somewhere else on the x axis,
and then slide it (inertially) toward the clocks. If we assume
(as did Einstein) that this rod's physical (or intrinsic) length
does not really vary with rod speed, then the rod will absolutely
synchronize the clocks if the former's ends are used to start the
latter.

And here is a simple image-based definition of absolute clock
synchronization: Picture two clocks which are running and which
are 50 light-years apart. One of them is on your desk very close
to your eyes. You are to reach out and touch the face of this
nearby clock with your index finger. If, at this exact moment,
the distant clock happens to read the same time as your near
clock, then the two clocks are (very, very nearly) absolutely
synchronous. (Disclaimer: I am of course _not_ saying here
that we can somehow _know_ what the distant clock is reading
when you touch the near clock; all I am doing here is providing
a graphical image of absolute synchronization which anyone can
fully understand instantly.)

Here is a pretty good indication of absolute synchronization:
If there is no theoretical or empirical reason for the failure
of one's chosen method for absolute synchronization.

Here are two almost-certain indications of absolute synchronization:
[1] Light's one-way, two-clock speed would vary with frame velocity.
[2] Observers in all frames would find the same times for any given
set of events.

Finally, here is a mathematically-certain indication of absolute
synchronization: Clocks in all frames are absolutely synchronous
IFF any given frame's observer's self-measured speed is the same
as that as determined by any other frame's observer. (A self-
measured speed is found by using one's two supposedly synchronous
clocks to measure the one-way speed of a passing light ray; as
Einstein himself noted, this speed should vary with frame velocity.)

I have repeatedly asked for a step-by-step description of some
means of absolutely synchronizing two clocks; so far, none has
appeared. I am of course speaking of dead-on synchronization
for clocks located anywhere in space, and not just close (i.e.,
within nanoseconds) of closely-located clocks. I am also talking
about proper verification of the claimed absolute synchronization.
 
  • #80
Here are two almost-certain indications of absolute synchronization:
[1] Light's one-way, two-clock speed would vary with frame velocity.
[2] Observers in all frames would find the same times for any given
set of events.

So in other words this clocks don't exist in a world ruled be GR.
In GR it is impossible to say if two clocks are synchronizated when they are at a certain distance. The time dilitation ( = a measure of non synchronisity)depends of the path the information takes to come to us.

There is only one way to prove absolute synchronization,
and that is by showing step-by-step how it can be done. (This
involves the necessary step of providing the verification
process.)"

Since this absolute synchronization is a proof of the incorrectness of GR, it 's up to you (who claimed the whole academic world is wrong) to proof of an existing absolute synchronizated set of clocks.

Begin with two unstarted atomic clocks which are inertially moving
along one's frame's x axis. As the clocks meet in passing, absolutely
synchronize them by letting one start the other on touching. Then
assume (as did Einstein) that these clocks have identical internal
atomic rhythms. Given this, we know that they will remain absolutely
synchronous forever, no matter how far apart in space they may be.
moving

we know that= Martin Miller assume that
What reason do you have that two clocks must stay synchronous forever

If we assume
(as did Einstein) that this rod's physical (or intrinsic) length
does not really vary with rod speed, then the rod will absolutely
synchronize the clocks if the former's ends are used to start the
latter.

The poor man can't defend himself, so don't put words in hi mouth he didn't mend to say
 
  • #81
Eyeshaw:

I got lost at the L-M step. What is wrong with the following analysis?

upleg travel time t_u can be found from this equation:

c = \frac{L + vt_u}{t_u}

Equation to find roundtrip travel time (downleg travel time t_d):

c = \frac{L + vt_u + L - vt_d}{t_u + t_d}

Eliminating t_u and solving for t_d, I got

round trip time = \frac{L}{c-v} + \frac{L}{c+v}

That is not the same as \frac{2L}{c}, as we can see when we transform the equation just above:

roundtrip time = (\frac{2L}{c})\frac{1}{1-(\frac{v}{c})^2}
 
Last edited:
  • #82
For example, the very basis of SR, Einstein's
light postulate (i.e., one-way, two-clock light
speed invariance) has not been tested.

(To explain: No one has ever used two clocks in
one frame to measure light's one-way speed.)
(In fact, no one has ever even shown on paper
how this could be done!)

For another example, actual time dilation effects
were not predicted by SR, so these effects do not
test or support SR.

Very true, but don't forget Roland DeWitte's experiment - two clocks and an electrical pulse (similar to the one-way light speed test). His results showed SR to be false.

And the physical cause of moving clocks running slow (time dilation)can be explained outside of SR using ether concepts.
 
  • #83
Originally posted by Martin Miller

I have repeatedly asked for a step-by-step description of some
means of absolutely synchronizing two clocks; so far, none has
appeared. I am of course speaking of dead-on synchronization
for clocks located anywhere in space, and not just close (i.e.,
within nanoseconds) of closely-located clocks. I am also talking
about proper verification of the claimed absolute synchronization.

Martin, I do not understand why clock synchronization is so important to you, since actual clock readings fall out of the mathematical analysis. In SR all that matters is how the "amount of time of an event" in one inertial reference frame relates to the amount of time of the same event viewed in a different inertial frame. My point is fairly simple to understand:

1. Let us stipulate that we have two clocks of identical construction, and that the clocks are attached by a rigid rod.

2. Let it be stipulated that the clocks are in an inertial reference frame.

Therefore, the clocks will tick at the same rate.

Thus, if they are in sync then they remain in sync, and if they are out of sync, then the difference in their readings is constant.

For example, suppose that when one clock reads 4, the other clock simultaneously reads 7. Since the readings of the two clocks differ, the clocks aren't synchronized. The difference in readings is:

7-4=3

Thus, the clocks are not in sync by 3 units.

If the readings had been equivalent, then the two clocks would be truly synchronous.

So here is my point though. The difference in readings is constant, and falls out of the mathematical analysis. In other words, relativity talks about how an amount of time in one inertial system "transforms" into a different inertial system.

For example, suppose that some event lasts \Delta t seconds measured by clock A, which is in an inertial reference frame. Now, suppose that clock B is moving relative to clock A, at a constant speed of v. According to SR, the time of the event will not be \Delta t seconds, according to clock B. Instead, the time measured by clock B will be delta t times gamma.

My point is that it is the difference in readings that matters, not the actual readings themselves. So, I don't see why clock synchronization is an issue.

I think your real question isn't being addressed. The issue shouldn't be how do you make two clocks synchronous, I think the real issue is, how does one determine the absolute difference in clock readings.

For example, suppose that one clock reads X, and another clock simultaneously reads Y. The difference in clock readings is defined as follows:

X-Y

If X=Y then the clocks are synchronized.
if not (X=Y) then the clocks aren't synchronized.

I think the real question for you is, "can one empirically determine the value of X-Y?" You seem to be hung up on empirically determining that X-Y=0. Wouldn't it be just as good to empirically determine "X-Y"? For example, suppose you already determined that X-Y = 52. Thus, the reading of clock X always exceeds the reading of clock Y by 52 units. Thus, if you are stationed at clock Y, and your clock currently reads 733, then you know that clock X reads 733+52=785.

So I guess my question is, "why do you need us to show that two clocks cannot be brought into synchronization?"
 
Last edited:
  • #84
Originally posted by Nereid
That's Ms Nereid to you Martin.

Do you have a copy of Y.Z.Zhang, Special Relativity and its Experimental Foundations, World Scientific (1997)? If so, please tell us which of the tests discussed in this book failed?

If you don't, please check this page, and tell us which tests failed.

Please note that I am interested FIRST in 'pass/fail' in the following sense:
1) was there a specific, objective prediction made from SR?
2) did the experiment or observation produce a clear, unambiguous result?
3) was the result the same as that predicted by SR (within the errors of the observation)?

For the avoidance of doubt, I'm not interested (at this stage) in whether you feel there may or may not be inconsistencies in SR.


Hello Ms. Nereid, I believe Martin said ALL of them.

:)
 
  • #85
It is not so much that clock A must show the same time as clock B, but simply that they have the same rate. Suppose A reads 10:00 and we can somehow simultaneously determine that B reads 10:30 PM. We wait about one hour, and check the clocks again. If we still can read them simultaneously and clock A reads 11:01 & B reads 11:31, then their rates are the same. Either we adjust one of the clocks so that they read the same, or simply take note of the initial times and take the time differences. For example we note Ta0 = 10:21, Tb0 = 10:31 and later Ta1 = 12:01 and Tb1 = 12:31. The time differences, deltaTa = Ta1 - Ta0 and deltaTb1 = Tb1 - Tb0 are still the same. Would this not be good enough?

Note that many physical processes can serve as relative clocks and cannot be adjusted to give absolute time. You can't look at me and exclaim, "Omy! 10:34 AM! I'm late!" Yet, some physicist might regard my beating heart as a sort of clock. How does anyone synchronize my heart with Greenwich mean time? My heart does beat at about 1 beat per second, sometimes, but I'll be darned if I am going to carry around a time read-out device for my heart.

How do you adjust the rate of all those binary pulsar systems out there? Can you attach a time-readout device to any of them? No, SR and GR really only work with time differences, not absolute time like Greenwich Mean Time or Universal Time.
 
Last edited:
  • #86
Since the interferometer went a distance of +v with respect to the vacuum, the light traveled L+M in the direction of motion and L-M back for a round trip distance of 2L.


Impossible. Did you even try to do the math on this one?

Suppose the interferometer lies on the x-axis and is traveling in the direction of the positive x-axis with a speed of v.

Suppose we emit a photon from the left edge of the interferometer at time 0 when the left edge of the interferometer is at x-coordinate 0. (So the right edge has coordinate L).

IOW, at time 0:
The left edge has x-coordinate 0
The right edge has x-coordinate L
The photon has x-coordinate 0

Now, let's find at what time the photon strikes the right edge:
The formula for the photons position is

x = 0 + ct

The formula for the right edge's position is

x = L + vt

Setting the x-coordinates equal gives:

L + vt = ct

or

t = L / (c - v)


So, at time t = L / (c - v):
The left edge is at x-coordinate L v / (c - v)
The right edge is at x-coordinate L c / (c - v)
The photon is at x-coordinate L c / (c - v)

Now, let's find out when the photon strikse the left edge again.

The formula for the position of the left edge is

x = v t

The formula for the position of the photon is

x - L c / (c - v) = -c (t - L / (c-v))
simplifying:
x - L c / (c - v) = -c t + L c / (c - v)
x = 2 L c / (c - v) - ct

Setting the x-coordinates equal and solving gives:

vt = 2 L c / (c - v) - ct
t = 2 L c / ( (c - v) (c + v) ) = 2 L c / (c^2 - v^2)


So the photon travels for time 2 L c / (c^2 - v^2). In that time, it travels a distance of 2 L c^2 / (c^2 - v^2). Funny, but that seems to be inequal to 2 L.


And you get an even different distance if the inferometer is moving in a different direction!
 
  • #87
If physics is the same in all inertial frames, why do you need to transform anything?

Practically, one very useful reason to transform anything is because computation may be simpler in another frame.


Conceptually, careful application of the transform laws help one work through errors in their understanding.
 
  • #88


Originally posted by Eyesaw
If physics is the same in all inertial frames, why do you need to transform anything?
I'm not sure where you're getting this idea from, but the whole point of "relativity," a concept which predates Einstein's version, is that the laws are the same in all reference frames. Under classical (also called Galilean) relativity, the fundamental postulate is the same as in Einstein's: The laws of the universe are the same for all observers regardless of inertial frame of reference.

This does not and never did imply that two observers in different frames would see the same thing - transformations are needed even under classical relativity. This should be self-evident from the commonly cited thought experiment with a man walking on a train:

A man is walking forward on a train at 1m/s relative to the train. The train is moving forward at 10m/s relative to the station. To a man standing on the platform, how fast is the man on the train moving? To a man sitting on the train, how fast is the walking man moving.

Clearly, the man sitting on the train and the man standing on the platform will not agree on the speed of the man walking unless they have a transformation equation by which to relate the two different frames of reference.
 
Last edited:
  • #89
One can indeed assert that physics is the same from frame to frame, in the sense that the laws of physics are the same in all frames. Yet, someone in free fall is not the same as someone lying on the ground. Nevertheless, we ought to be able to apply the _same_ laws to both persons' experiences. Transforming the laws from frame to frame is a necessity, because physics do differ from frame to frame, at least in evidence or observations.
 
  • #90
Originally posted by wisp
Very true, but don't forget Roland DeWitte's experiment - two clocks and an electrical pulse (similar to the one-way light speed test). His results showed SR to be false.
If true, it would be relatively (no pun intended) trivial to duplicate his results. From what I have heard, his results aren't accepted as credible by the scientific community.
And the physical cause of moving clocks running slow (time dilation)can be explained outside of SR using ether concepts.
That's true, but it is never preferable in science to add unsupported assumptions to a theory in order to make it fit some preconcieved notion of how the universe "should" work. So until someone finds real, scientific, positive evidence to show that there is an ether, we cannot assume there is one. At the very least, ether theory fails on those grounds.
Hello Ms. Nereid, I believe Martin said ALL of them.
That's nice, but I say all of them are valid. Do we have a Mexican standoff now, or should we practice some science by explaining why?
 
Last edited:

Similar threads

B One way speed of light in one reference frame measurement
  • · Replies 5 ·
Replies
5
Views
2K
I SR flat Lorentzian manifold and Anderson simultaneity convention
  • · Replies 16 ·
Replies
16
Views
2K
I Conventionality of the One-Way Speed of Light
  • · Replies 6 ·
Replies
6
Views
692
A 1-Way Speed of Light
  • · Replies 42 ·
2
Replies
42
Views
1K
I Is the concept of a one-way speed of light meaningful and measurable?
  • · Replies 25 ·
Replies
25
Views
4K
I Why is Rømer's light speed measurement not one-way?
  • · Replies 42 ·
2
Replies
42
Views
3K
B One-Way Speed of Light
  • · Replies 93 ·
4
Replies
93
Views
5K
B Finding One-Way Speed of Light: Use One Clock
  • · Replies 14 ·
Replies
14
Views
2K
I Standing light waves if the one-way speed of light were not constant?
  • · Replies 36 ·
2
Replies
36
Views
3K
I Synchronizing clocks at different locations to measure speed of light
  • · Replies 58 ·
2
Replies
58
Views
4K