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Steve3007 wrote: ↑September 5th, 2018, 2:57 am If anyone's interested, here's a Relativistic description of the Sagnac effect that I'm currently in the process of reading:

http://www.physicsinsights.org/sagnac_1.html

I don't have any judgments on it yet because I haven't finished reading it.

I didn't find it very well explained. The effect seems intuitive (using classic explanation, not relativistic), but it took me a long time to glean the setup and thus to conclude that. The clocks are moving with the spinning disk, and they are at the same place as each other, so there is no synchronization issues.

The setup (clocks attached to disk in "Final case") is not shown until about 70% of the way through the article. Relativity doesn't significantly come into play, so the discussion in "peculiar case" is irrelevant (where they're syncing two linearly separated clocks in some frame).

If the signal is moving with the spinning disk, it must travel not just around the disk but the additional length to the clock that has moved away from the starting point. If signal is sent backwards, it meets the moving clock coming the other way. This effect far out-strips the relativistic effect of the clock running slow because it is moving in the frame of the disk. Similarly if I view a clock coming to me rapidly (linearly), the clock appears slowed due to dilation, but it speeds up due to Doppler effect, which is far more significant. The approaching clock appears to run fast, not slower. Receding clocks appear much slower because the two effects combine instead of cancel each other.

Some naive comments in the article: In fig 5, it says the two clocks are adjacent, and so "necessarily synced to each other when viewed from the lab frame". In fact, being adjacent at all times, they are necessarily synced to each other in any frame. They could be (and probably are) the same clock.

Another heading near the bottom announces: "Note that You Can't Synchronize the Clocks in a Rotating Frame"
Well you can if the clocks are adjacent, so this is irrelevant. There is no movement you can do to a pair of clocks to get them out of sync if they're always together.

Third paragraph from the top, the author seems to mistakenly take the wrong approach: "Throughout this page, I'm going to treat the effect using straight-line motion rather than circular motion as much as possible, which greatly simplifies the math."
In fact the math is unnecessary. I've described the effect by showing that the distance traveled by the signal is different one way than the other. I didn't need to express a formula to notice that.

Steve3007 wrote: ↑September 5th, 2018, 4:54 am In the interests of balance, here's another article about the Sagnac effect that appears, at a brief glance, to put the opposite point of view to the article I cited in my previous post:

http://www.conspiracyoflight.com/Sagnac ... ndRel.html

Where are you finding these amateur articles? This one is worse than the first one.

I got as far as the first picture showing the two 'observers' and the red (with spin)/blue(against) arrows.
The text around that states: "If we now rotate the disk clockwise at [linear] velocity v, we find that the blue beam arrives back at the detector before the red beam – in fact, the difference in the velocity of light turns out to be 2*v, because the blue beam travels at C+v and the red beam at C-v"

where "C" means 'c' (light speed) except they should have mentioned that it is actually what the first article labels 'k' which is light speed through whatever medium they're sending it. The author apparently assumes that the refractive index is 1 and c can be used.

Anyway, the signal does not travel at c+v. Light moves at constant velocity c in any frame. You can't send a signal to Mars quicker by signalling down a fast-moving fibop cable or by firing a flashlight from a canon. This author doesn't know his science. If the red signal travels at c+v and blue at c-v, why does the blue signal reach the target first?

In fact, v does play a role if the refraction index is high. If the index is high, the light moves far slower than c and the v comes into play, speeding one signal and slowing the other, but only by a fraction of v. In fact, if you have say Glass with a refraction index of 3 and you move that glass at 1/3c in some frame, a light signal traveling through it against that movement will be stationary in that frame. If it is on our disk, it will have to wait for the detector to make one full lap. The signal going with the spin would have to go around 3 times to lap the detector going around twice. All that is without relativistic consideration, and there would be some adjustments at that speed.

The discussion goes on into the observer A on the disk: "On the other hand, the observer at A who is rotating with the disk has observed that the source and detector are stationary from his perspective, as are the paths, so he can only conclude (assuming no foreknowledge that he is rotating) that the light has actually travelled at two different velocities around the disk, being C+v and C-v. Who is right?"
This is nonsense. Observer A doesn't need to look out of the window to detect that he is spinning and which way. He knows damn well that the source/detector is moving, in any frame. He should expect the Sagnac effect.

But I like to try to steer the conversation away from all the talk of clergy, and sheep and Einstein-worshippers, and "the establishment" and try to analyse arguments.

A worthy goal Steve.

Steve3007 wrote: ↑September 5th, 2018, 2:57 am If anyone's interested, here's a Relativistic description of the Sagnac effect that I'm currently in the process of reading:

http://www.physicsinsights.org/sagnac_1.html

I don't have any judgments on it yet because I haven't finished reading it.

I am unimpressed by the description. I had to go down 70% of the way to find the setup of the experiment. Nothing before that seemed to say that the clocks move with the spin. The effect can be explained with classic physics: The signal going with the spin has to go all the way around plus the additional distance to catch up with the moving clock. That takes longer than the reverse signal that meets the clock going the other way.

The articles goes into irrelevant linear cases with separated clocks, which would indeed bring relativity into play. Yes, at great enough speed, relativity would dilate the moving clock and alter the disk circumference, but that effect would pale against the classic effects of the different lengths traveled by each signal.

A naive comment near the bottom is a section stating: "Note that You Can't Synchronize the Clocks in a Rotating Frame". Well you can if they're in the same place. In fact the setup probably just uses one clock for both source and detector. There is nothing you can do to unsync a pair of clocks if they're always together.

Steve3007 wrote: ↑September 5th, 2018, 4:54 am In the interests of balance, here's another article about the Sagnac effect that appears, at a brief glance, to put the opposite point of view to the article I cited in my previous post:

http://www.conspiracyoflight.com/Sagnac ... ndRel.html

This one is worse than the first. Where do you find these amateur articles?

The author assumes a perfect refraction index of 1, so light travels at c (or C as he uses). I got as far as the first picture with the two observers. The text around that says:

If we now rotate the disk clockwise at velocity v, we find that the blue beam arrives back at the detector before the red beam – in fact, the difference in the velocity of light turns out to be 2*v, because the blue beam travels at C+v and the red beam at C-v.

Velocities don't add that way. Light (in a perfect medium) travels at c. If the red signal is going faster than c, why does it get to the detector after the blue signal? You can't send a signal to Mars faster if you send it through a fast moving fibop cable or fire a flashlight from a canon.
In fact, v comes into play if the refraction index is high. If you have a cable with a refraction index of 3 and spin it at 1/3c, the signal moving against the spin would be stationary and would have to wait for the detector to make one lap. The signal going with the spin would have to go around thrice to lap the detector that goes around twice.

Another nit is a description of rotating the disk at 'velocity v'. He means linear speed of the edge, not linear velocity. This author doesn't know the difference.

The discussion goes on to talk about the frame of the spinning observer A, which mistakenly asserts that the whole setup is stationary from his perspective. This is totally wrong. He doesn't need to look out of the window to detect that he is spinning, and which direction. Rotational reference frames are not equal. He should expect the Sagnac effect. The author ignores this and attempts to discredit relativity with: "Who is right? Well, the problem is this – from the point of view of special relativity, there are no preferred frames of reference, there are only relative frames of reference, so we can’t argue that frame B is better than frame A without defeating the underlying premise of the theory. In special relativity (SR), the position of the observer is supposed to be arbitrary. However, if we accept that perspective A is legitimate, we defeat the first postulate of SR, namely:

“that light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body”. – Einstein [7]"

Nevermind that SR doesn't cover accelerating things like our clock, or that this isn't really a case of empty space. The point is that in any inertial frame, the signal going with the spin has further to go than the signal against. This author is apparently treating a rotating reference frame as an inertial frame when assuming that the two signals are traveling the same distance.

Halc wrote:I didn't find it very well explained...Where are you finding these amateur articles? This one is worse than the first one...I am unimpressed by the description...This one is worse than the first. Where do you find these amateur articles?

As I said, I haven't had a chance to look at them yet. If they're no good, it's probably because I just quickly googled "Sagnac effect". Too lazy! Thanks for assessing them. If you can find better written articles and cite them here I reckon that would be useful.

Steve3007 wrote: ↑September 5th, 2018, 9:11 amAs I said, I haven't had a chance to look at them yet. If they're no good, it's probably because I just quickly googled "Sagnac effect". Too lazy! Thanks for assessing them. If you can find better written articles and cite them here I reckon that would be useful.

Well, the legit ones are not trying to discredit relativity, so there isn't going to be fallacious reasoning in them. I made a mistake myself here:

Halc wrote: ↑September 5th, 2018, 9:04 am In fact, v comes into play if the refraction index is high. If you have a cable with a refraction index of 3 and spin it at 1/3c, the signal moving against the spin would be stationary and would have to wait for the detector to make one lap. The signal going with the spin would have to go around thrice to lap the detector that goes around twice.

That was done using only classic physics to add speeds, which is something I dinged the author for. Poor form, right?

I think you can make the 'against' signal stand still this way, but the other direction adds .333c refraction to .333c spin which does not add up to .666c combined. It is in fact .6c, and so probably takes more than 2 rotations to be detected, and even then you have to take into account the dilation of the fairly fast moving clock and the length contraction of the disk.

An perpetual energy machine was described using this principle. Manufacture and infinitely rigid disk that is already spinning at high speed. Due to length contraction, the circumference would be less than diameter*pi since the middle of the disk moves slower than the points further out. This cannot change due to the rigidity of the disk, so any attempt to slow the disk will fail. Power a generator by the unstoppable disk.
Similarly, I can signal my comrade on Mars faster than light by poking him with a thin stick made of the same stuff. All kinds of fun things can be accomplished with materials with absurd properties. The sci-fi author Larry Niven is well known for these sorts of ideas.

'Hey did you just poke me faster than light?' the idea makes me chuckle, never heard that example before though after googling it it seems quite a common one

Eduk wrote: ↑September 5th, 2018, 10:03 am 'Hey did you just poke me faster than light?' the idea makes me chuckle, never heard that example before though after googling it it seems quite a common one

Such signals pass through a stick only at the speed of sound, which is bounded by light speed regardless of density or rigidity. That demonstrates that there is no such thing as an infinitely rigid material.

Steve3007 wrote: ↑September 4th, 2018, 5:14 amIf you're going to have to stop replying, no worries. No pressure.

I'll keep responding to each post in turn, but I can't keep up with the high speed they come in as I always have to put work first, but if I go slowly, it takes the pressure off everyone else too, so it's less stressful for everyone.

Conversations here (and in other similar environments) very often descend into mutual insults.

I reflect back at people what they give to me, so two of you are currently in absolutely no danger of coming under fire, while the other participant will get back what he throws. If I attack a position you hold, that is not an attack on you, but on that position.

So, bearing in mind the above advanced apology, I'd like to ask:

1. If I throw a ball upwards, neglecting air resistance, as soon as it has left my hand, is it:

a. Accelerating
b. Deccelerating
c. It depends on the coordinate system you're using

It could be a, or b, or b followed by a. The universe supports only one underlying reality and we should not be fooled into thinking it supports an infinite number of contradictory ones at the same time. (Even with quantum physics, the universe supports only one reality - something that's "in two places at the same time" is only half in each of those places at the same time, providing "provisional realities" which only solidify into more certain ones as things simplify down when/if supporting multiple options becomes unsustainable. The waves are only doing one thing.)

2. Do you appreciate the difference between an inertial and a non-inertial frame of reference?

One type's a genuine frame, while the other's a pseudo-frame which switches real frame continually.

3. Do you appreciate that velocity and acceleration are both vector quantities?

I don't see the significance. Acceleration accumulates energy, while deceleration loses energy. Anything that tries to make out that the two things are identical is a mathematical abstraction.

4. If an object is moving in a circle (rotating), like a stone on a string, a planet in a circular orbit or the apparatus in the Sagnac Effect experiments that you have mentioned, do you accept that the object is accelerating towards the centre of the circle and is therefore in a non-inertial reference frame?

It is in such a pseudo-frame, but everything it does maps to an inertial frame and it can be analysed just fine using inertial frames. I'm happy to go through the experiment with you using all the options though as using a non-inertial frames proves the same point.

5. Do you accept that, strictly speaking, the statement: "object A is moving at 5 m/s" has no physical significance because it does not correspond to anything that can be empirically confirmed or denied? Do you accept that in order to give it such physical significance I have to say something like: "object A is moving at 5 m/s relative to object B"?

From the universe's point of view, it has an absolute meaning. All we can do when assigning speed descriptions to things is provide conditional truths about speeds of objects (on the basis of a particular frame being the absolute one) or give their speed relative to other objects, but we are not banned from considering what the universe must be doing and the logical superiority of it doing one single thing rather than a plurality of magical, contradictory things.

Halc wrote: ↑September 4th, 2018, 8:24 am Velocity on the other hand is a vector quantity, and deceleration does not apply. p=mv (momentum = mass * velocity) and Newton's second law F=ma (force, mass, acceleration) use velocity and vector acceleration. There is no vector deceleration. Force is always added to a thing's velocity to accelerate it to a different velocity. Deceleration is a word only applying to a scalar value.

That explains what Steve was getting at, but if you're adding vectors, you're just hiding decelerations by passing them off as accelerations, so it is indeed just a mathematical abstraction.

An apple is green and another is red. That is incompatible by the way you are presenting your argument.
The same apple is green and red to different (objectively stationary if you want) observers if the apple is travelling quickly between them.

There is one underlying reality when it comes to the frequency of light coming off the apple, but you can't know what it is unless you can identify the absolute frame.

The train whistle is tuned to F sharp to one pedestrian, and to D to another.

Again there is only one truth underlying it - there is a set amount of energy involved, and measuring it from the wrong frame either overrepresents or underrepresents the amount of energy. If you pick an extreme frame, you can multiply the amount of energy asserted to be in the universe to infinite levels.

You are stationary in the frame of the floor under you. At the same time, you are moving at 30 km/sec relative to the sun.

For some reason, you have attributed that last statement to Einstein (it is about 4 centuries old), and decided that only that one is an incompatibility, and not the others.

They are all incompatible as soon as you assert that all frames are equally valid (and fail to spell out that you don't take them to be equally true).

The simulation (by your description) depicts a current state of the universe. SR has no such premise. The simulation as a whole does not represent Einstein's SR. It represents SR insofar as it shows which events are considered to be at a uniform amount of time away from one select event (X) relative to any chosen frame. In no frame does an event 'unhappen', so in reality, no unhappenings would be occurring.

If all frames are equally valid, you have no basis for not accepting all of them as being asserted to be equally correct. Mode 2 is the original SR model and it generates contradictions. You allow the universe to run events for a certain length of time, then you freeze it, and lo and behold: it can't make up its mind what's happened and what hasn't happened at the point of freezing. SR pretends that this problem doesn't exist by ignoring it - it is brushed under the carpet, and hordes of gullible people just swallow it without questioning the contradictions, but there are the contradictions playing out right before your eyes.

SR does not posit that
1) there is but one preferred frame
2) there is one current moment or event, AND
3) that the preferred frame changes arbitrarily.

SR claims that there is no absolute frame, and the result is contradictions. You can try to remove that claim from it (even though it is well established that that claim is part of SR), but leaving the door open by not committing to there either being or not being an absolute frame wouldn't make its position any better - one of those options leads to contradictions, and therefore the only viable option remaining is to jump to a magic block model or to accept that there is an absolute frame, which equates to capitulation to LET. SR also bans you from considering issues like simutaneity at a distance because that runs into contradictions, so it simply shuts off all discussion of it and plays silly games with time in an attempt to shut down logical thinking, but rational people should not let it off the hook on this point. If the real universe was halted and frozen at a single moment in time, it wouldn't be possible for it to freeze in such a way that event X has both happened and not happened yet at the point of freezing. There must be a strictly controlled unfolding of events that doesn't have such magical properties, and that means the clocks on some paths have to run slow under the governance of a superior time tied to one frame (or you must switch to a block model).

LET only posits the first of these three, and SR is mute about the first two. It denies the third, as does any theory I've ever encountered.

SR doesn't have a preferred frame to switch - it always has all frames at once, and that leads to it having to tolerate contradictions which invalidate it.

David Cooper wrote:I'll keep responding to each post in turn, but I can't keep up with the high speed they come in as I always have to put work first, but if I go slowly, it takes the pressure off everyone else too, so it's less stressful for everyone.

Yes. Putting work first. In theory, I should be doing that too.

I've tried in the past to keep answering posts in turn, but it's often just not possible.

Anyway, your answers:

1. If I throw a ball upwards, neglecting air resistance, as soon as it has left my hand, is it:

a. Accelerating
b. Deccelerating
c. It depends on the coordinate system you're using

It could be a, or b, or b followed by a. The universe supports only one underlying reality and we should not be fooled into thinking it supports an infinite number of contradictory ones at the same time. (Even with quantum physics, the universe supports only one reality - something that's "in two places at the same time" is only half in each of those places at the same time, providing "provisional realities" which only solidify into more certain ones as things simplify down when/if supporting multiple options becomes unsustainable. The waves are only doing one thing.)

That seems like an odd answer to me. The question of whether an object thrown upwards is regarded as accelerating or decelerating is not the same as the question of whether it is an apple or an orange. An object cannot be both an apple and an orange. But the answer is c. As soon as it leaves my hand its velocity vector is pointing away from the Earth and its acceleration vector is pointing towards the Earth. It is moving upwards but accelerating downwards. So, if we regard the positive direction of acceleration as up, it is decelerating.

2. Do you appreciate the difference between an inertial and a non-inertial frame of reference?

One type's a genuine frame, while the other's a pseudo-frame which switches real frame continually.

A non-inertial frame is one which is accelerating or is in a gravitional field. I don't know what you mean by "switches real frame continually".

3. Do you appreciate that velocity and acceleration are both vector quantities?

I don't see the significance. Acceleration accumulates energy, while deceleration loses energy. Anything that tries to make out that the two things are identical is a mathematical abstraction.

Again, an odd answer. You don't see the significance of the concept of a vector? Does that mean you do or don't appreciate that velocity and acceleration are both vector quantities? You must surely be aware of the basic mathematics of vectors? Vector addition? Vector (cross) and scalar (dot) products? Vactor calculus? All that kind of thing? Do you see the significance of scalars? Or of any mathematical concepts?

4. If an object is moving in a circle (rotating), like a stone on a string, a planet in a circular orbit or the apparatus in the Sagnac Effect experiments that you have mentioned, do you accept that the object is accelerating towards the centre of the circle and is therefore in a non-inertial reference frame?

It is in such a pseudo-frame, but everything it does maps to an inertial frame and it can be analysed just fine using inertial frames. I'm happy to go through the experiment with you using all the options though as using a non-inertial frames proves the same point.

But, to answer the question, you do understand the definitions of "vector", "speed", "velocity", "acceleration", and "circles" which lead to the fact that an object moving at constant speed in a circle is accelerating towards the centre of the circle, right? And you do appreciate that if an object is accelerating then a reference frame that is stationary relative to that object is non-inertial?

5. Do you accept that, strictly speaking, the statement: "object A is moving at 5 m/s" has no physical significance because it does not correspond to anything that can be empirically confirmed or denied? Do you accept that in order to give it such physical significance I have to say something like: "object A is moving at 5 m/s relative to object B"?

From the universe's point of view, it has an absolute meaning. All we can do when assigning speed descriptions to things is provide conditional truths about speeds of objects (on the basis of a particular frame being the absolute one) or give their speed relative to other objects, but we are not banned from considering what the universe must be doing and the logical superiority of it doing one single thing rather than a plurality of magical, contradictory things.

Another odd answer.

Maybe I'm misinterpreting you, but, based on these strange answers, and non-answers, to straightforward questions, I can't help thinking that you're confused about what some basic physical properties such as velocity and acceleration mean and thinking that this leads you to make category errors.

In order to start analyzing advanced theories of physics such as SR, GR and LET in sufficient depth to be able to decide that SR and GR are invalid, did you do the groundwork of studying physics and maths to the equivalent of GCSE, 'A' Level and first degree standard? I don't mean necessarily having to actually do those qualifications. I just mean studying the subjects in the depths that they are studied by people who do. If not, I honestly can't see how you can draw the conclusions that you have. In general, I don't see how it's possible to properly critique a subject unless you know what it's saying and the language in which it's saying it. I wouldn't myself. I wouldn't, for example, claim to have overturned the prevailing theories of economics (whatever they are) until I'd studied that subject in enough depth to appreciate what they say.

I want a go, without cheating and using Google.
1.c. it is accelerating downwards exactly as much as it is decelerating upwards.
2. Not off the top of my head. Too long ago since I did applied maths. Inertial means something like stationary or constant speed, as in no forces acting?

3. Yes

4. Yes an orbit is just a constant fall?

5. Yes.

Aww even though I posted after you Steve I didn't read your post with all the answers first.

Halc wrote:Velocity on the other hand is a vector quantity, and deceleration does not apply. p=mv (momentum = mass * velocity) and Newton's second law F=ma (force, mass, acceleration) use velocity and vector acceleration. There is no vector deceleration. Force is always added to a thing's velocity to accelerate it to a different velocity. Deceleration is a word only applying to a scalar value.

David Cooper wrote:That explains what Steve was getting at, but if you're adding vectors, you're just hiding decelerations by passing them off as accelerations, so it is indeed just a mathematical abstraction.

OK, backing up even further in the attempt to find some kind of common ground:

I am 5 feet 11 inches tall. That's 1.8 metres. Do you accept that I am both of those things? Or do you think it has to be one or the other?

(This is not some kind of trick question. The obvious answer will do.)

Eduk wrote:I want a go, without cheating and using Google.
1.c. it is accelerating downwards exactly as much as it is decelerating upwards.
2. Not off the top of my head. Too long ago since I did applied maths. Inertial means something like stationary or constant speed, as in no forces acting?

3. Yes

4. Yes an orbit is just a constant fall?

5. Yes.

To be fair, I suppose questions that begin with "do you appreciate..." or "do you accept..." are leading the witness a bit, aren't they. But, anyway, my only comments on your answers would be these:

2: A non-intertial reference frame has forces acting inside it, yes. You can measure those forces with an accelerometer. A.K.A. some object hanging from a spring with a ruler next to it. In a closed box that is stationary with respect to that reference frame, You can tell that you're either accelerating or you're in the presence of a uniform gravitational field. But no experiment you can do entirely within that box can tell you which it is.

4: If we say "a constant fall" I think it can be misleading because "fall" is a colloquial word that could be interpreted to mean "moving towards the surface of the Earth". I think it's better to stick to the more rigorously defined words and say that a circular orbit means that the magnitude of the acceleration vector is constant and the direction of that vector is towards the centre of the Earth.

Yes rather leading
Your reply to 4 is interesting, thanks for taking the time.