Age of Universe relative to what?

[TrickyDicky]

Yes, it is: "In the real world, there exists no such state of absolute rest. That's the content of the so-called principle of relativity, which is one of the basic postulates of the special theory of relativity."
http://www.einstein-online.info/elementary/specialRT/RelativityPrinciple

Here your troll soul shines at its brightest, you ignore my previous post that settled the argument by giving it context, then you quote some words as if they were from the first postulate when in fact are taken from some website for kids, which suggests you haven't even read the original postulates. And finally you take a couple of sentences out of context and put them together for effect:as I said pure trolling. I must admit I had a good laugh too.

 

[Dale]

And finally you take a couple of sentences out of context and put them together for effect.

The quotes were deliberately brief, for effect as you mention, but hardly taken out of context. Or are you honestly going to try to claim that your posts 18, 22, 26, and 27 didn't all try to promote the idea of absolute rest?

Look, I'm glad you changed your mind, but don't try to pretend that I took something out of context when it was clearly in line with what you had been repeatedly saying in multiple posts.

 

[phinds]

Here your troll soul shines at its brightest, you ignore my previous post that settled the argument by giving it context, then you quote some words as if they were from the first postulate when in fact are taken from some website for kids, which suggests you haven't even read the original postulates. And finally you take a couple of sentences out of context and put them together for effect:as I said pure trolling. I must admit I had a good laugh too.

TrickyDicky, you are indeed living up to your name. "Out of context" ? Please.

 

[DaveC426913]

TrickyDicky, members of 6 years with 9000+ posts are not trolls, pretty much by definition, but regardless, we don't use that word here; it is an infractible offense and a personal attack.

If you have a beef with the argument, attack the argument, not the arguer. You'll notice right up until your trolling comments, everyone else was doing you the courtesy targeting your arguments, not you personally. Let's keep it that way.

 

[Dale]

It's OK, I understand his irritation with me, and I don't take offense at it. He changed his mind to agree with me, but instead of accepting it graciously and allowing him to save face I emphasized it and laughed at him. I provoked him, and I hope no infractions result.

 

[Snip3r]

You can only measure the round-trip speed of light

a quick question why can't 1-way speed of light be measured?

 

[Dale]

a quick question why can't 1-way speed of light be measured?

In order to measure the one-way speed of light requires two synchronized clocks. In order to synchronize the clocks you have to adopt some synchronization convention. Your measurement of the one-way speed of light then depends on the synchronization convention you have chosen, so you measure whatever number you chose to measure.

 

[TrickyDicky]

It's OK, I understand his irritation with me, and I don't take offense at it. He changed his mind to agree with me, but instead of accepting it graciously and allowing him to save face I emphasized it and laughed at him. I provoked him, and I hope no infractions result.

If it makes you happy to think that...lol oh, you enjoy provoking people eh noughty boy?, yeah, you got such power to make me change my mind to agree with you whenever you want.
Anyway why should you take offence if I just described your behaviour wrt a particular post, no personal attack involved at all. I'm sure you and your defenders are honourable men. (well maybe honourable dog in phinds case).

 

[Dale]

If it makes you happy to think that...lol oh, you enjoy provoking people eh noughty boy?, yeah, you got such power to make me change my mind to agree with you whenever you want.

Are you saying you didn't change your mind from

there has to be some absolute rest

in post 18 and emphasized in posts 22, 26, and 27 to

there is obviously no absolute rest

in post 31?

 

[TrickyDicky]

Do you mean you didn't read #34 yet?

And why don't you quote the complete phrase?

You are getting boring, I won't respond to any more of your instigations, don't find it fun anymore.

 

[Dale]

Do you mean you didn't read #34 yet?

If you had just posted 18 and 34 then I would have chalked it up to miscommunication, that from the beginning you had meant "it appears natural but it is wrong".

But in your followup posts (especially 22 and 26) you went far beyond that and explicitly stated that it didn't just "appear natural" but that logically "one implies the other" and "it is in the postulates". If anything your emphasis of the "seems natural" comment is out of context wrt the rest of your comments.

And why don't you quote the complete phrase?

For effect, as you already realized and I already agreed. It isn't misrepresenting your comments in any way, so I picked the most effective quotes.

I won't respond to any more of your instigations, don't find it fun anymore.

I am not surprised you don't find it fun anymore. I wouldn't either if I were in your position. But that is why, when I make a mistake or change my mind during a discussion, I usually admit it unambiguously. I do that to preempt anyone who would point out the change at my expense.

 

[phinds]

DaleSpam, your patience and equanimity amaze me. Thanks for setting a good example.

 

[Dale]

Thanks, although if I were really to be a good example I do feel like I shouldn't have rubbed it in his face in post 35. I am sad that he was banned or quit; I hope it is temporary.

 

[phinds]

Thanks, although if I were really to be a good example I do feel like I shouldn't have rubbed it in his face in post 35. I am sad that he was banned or quit; I hope it is temporary.

See that's why you're a good example. You're sad he was banned. I found him so offensive I'm glad he was banned. I just have no patience with his kind of behavior even though I sometimes have to struggle to keep myself from doing similar things, although I don't think even in my worst moments I'd call another forum member a dog, and I have no difficulty in admitting when I'm wrong.

 

[my_wan]

I didn't take TrickyDicky's quoted text to be contradictory in the context given. It seemed to me that if you take the quotes in the context given as contradictory implies relativity is contradictory. In fact I'll search up a quote from Einstein's book making a major point of saying that in the context of GR the constancy of light cannot be considered an "absolute" constant. Simply choosing to apply "absolute" in the sense certain fringe interpretations use it as a beating stick on relativity isn't necessarily valid. The speed of light is itself not an absolute constant, it is an observationally bound constant.

It is also possible to measure the one way speed of light, though I know of no explicit examples of it actually being done. Simply take a rotating hollow disk with holes on opposite side and note the RPM ranges in which a very short flash of light makes it through the disk to be detected, or some variation thereof.

 

[ghwellsjr]

It is also possible to measure the one way speed of light, though I know of no explicit examples of it actually being done. Simply take a rotating hollow disk with holes on opposite side and note the RPM ranges in which a very short flash of light makes it through the disk to be detected, or some variation thereof.

So you think a mechanical device can instantly transmit time information over a long distance? Sorry, that won't work.

 

[Dale]

It is also possible to measure the one way speed of light, though I know of no explicit examples of it actually being done. Simply take a rotating hollow disk with holes on opposite side and note the RPM ranges in which a very short flash of light makes it through the disk to be detected, or some variation thereof.

This seems similar to yuiop's proposal discussed in detail here:
https://www.physicsforums.com/showthread.php?t=461274

 

[my_wan]

So you think a mechanical device can instantly transmit time information over a long distance? Sorry, that won't work.

The device doesn't need to transmit time information. The distance between the two holes determine the timing, not clocks. The only variable involving a clock is the RPM of the disk. Are you saying I can't know the RMP of the disk over long distances? Even setups that have the light source on full time can work and the only thing measured is RPM and what RPM ranges did the light get through.

I can think of a few more approaches using a CCD, since you can actually tell where on a CCD the light hit and even position shifts of a frequency variance over the CCD. Creating a light source with a frequency spread like this is easy enough.

Never really cared much but I'll look over the links.

 

[Passionflower]

So you think a mechanical device can instantly transmit time information over a long distance? Sorry, that won't work.

We can always use subspace transmission to send a message really fast! ;)

 

[my_wan]

I see that thread still involved clocking flashes. There is no need. You have a rotating hollow pipe of a given length with an always on light source at one end, such that when the pipe points at the light source it goes through the pipe and detected at the other end. If the RPM is large enough the light never makes it through the pipe to be detected. The RPM is the only effective clock.

 

[my_wan]

It wouldn't even have to be a binary result, such that light was either detected or not. Since as the RPM increased the effective size of the hole is reduced which reduces the intensity of light as a result of a finite C. Neither would the relativity of rigidity play a role, since we know the the end results are always the same as if we presumed the relativity of rigidity played no role.

So here we have variation in both intensity and duration, where duration is not too significant in terms of the speed C, mostly just the effect of RPM alone, but intensity is. This would allow measurements with a finer grained variation in RPM and testable over a greater range of RPM.

 

[ghwellsjr]

Could you explain your experiment in more detail? I can't figure out what you are proposing. You started with a "rotating hollow disk with holes on opposite side" and now you're talking about a "rotating hollow pipe". Please describe the orientation of these rotating devices and where the holes are and how the light propagates, etc. I'm sure it's clear in your mind but it's not in mine.

 

[Dale]

I see that thread still involved clocking flashes. There is no need. You have a rotating hollow pipe of a given length with an always on light source at one end, such that when the pipe points at the light source it goes through the pipe and detected at the other end. If the RPM is large enough the light never makes it through the pipe to be detected. The RPM is the only effective clock.

The key objection, which applies to your idea, is this one:
https://www.physicsforums.com/showpost.php?p=3069207&postcount=14
with some follow-up here:
https://www.physicsforums.com/showpost.php?p=3070985&postcount=21
and here:
https://www.physicsforums.com/showpost.php?p=3075250&postcount=33

Your device let's through light at a specific speed due to its geometry. However, in theories with non-isotropic 1-way speeds of light (i.e. non-Einstein synchronization conventions) the length contraction is no longer isotropic and the device is geometrically distorted such that the light passes.

You simply cannot measure the one-way speed of light without assuming it.

 

[my_wan]

In the configuration it really makes no difference whether the pair of holes the light must pass through is a pair of holes on a surface of a cylinder or a hollow pipe in which the light must pass.

DaleSpam brings up a bigger issue. In the context of standard relativity the relativity of rigidity, as I've noted, makes no difference to the outcome. If "theories with non-isotropic 1-way speeds of light" are merely a different choice of synchronization then this is in principle perfectly allowed by relativity. Relativity only chose the synchronization procedure to match the maximal rate at which a given observer could obtain information about global coordinates as it was mathematically expedient, and only restricted it in such a way that effects could not precede causes. Choosing a different synchronization procedure in principle is no more physically significant than selecting a different coordinate choice. Trying to attach 'real' physical meaning to that is no different that arguing over which clock is really going slower, or which of two meteors the relational kinetic energy is 'really' located at.

Therefore, simple choosing a differing synchronization procedure which gives differing mathematical conditionals of space and time, has no physical meaning. Trying to require it to be measurable is like trying to measure the difference between 1 inch and 2.54 cm.

If the actual physics differs, outside of what is effectively a coordinate choice, then the anisotropy measuring procedure stands. That's why I mentioned my lack of real interest, because the only reasonable anisotropic C theories I seen are nothing more than an effectively different coordinate choice. Which might still provide some interesting numerical solutions to difficult problems and/or interesting perspectives.

We already know from GR that light speed does not constitute an absolute constant, only a relational constant.

The only people a measurable anisotropic C has any bearing on is the Einstein is wrong crowd. The people looking for some kind of absolute coordinate choice as if it is a physically real thing.

 

[ghwellsjr]

Could you explain your experiment in more detail? I can't figure out what you are proposing. You started with a "rotating hollow disk with holes on opposite side" and now you're talking about a "rotating hollow pipe". Please describe the orientation of these rotating devices and where the holes are and how the light propagates, etc. I'm sure it's clear in your mind but it's not in mine.

In the configuration it really makes no difference whether the pair of holes the light must pass through is a pair of holes on a surface of a cylinder or a hollow pipe in which the light must pass.

If you are going to claim that your method of measuring the one-way speed of light works, then you must have a way of measuring how long it takes for light to traverse some measured distance. Just saying that you have a rotating object with holes in it does not communicate what you have in mind.

If you have lost interest in defending your claim, I would at least urge you to read the wikipedia article on "one-way speed of light" to see that several attempts at measuring it have proved to be failures.

 

[my_wan]

If you are going to claim that your method of measuring the one-way speed of light works, then you must have a way of measuring how long it takes for light to traverse some measured distance. Just saying that you have a rotating object with holes in it does not communicate what you have in mind.

If you have lost interest in defending your claim, I would at least urge you to read the wikipedia article on "one-way speed of light" to see that several attempts at measuring it have proved to be failures.

My lack of interest only extends to my personal desire to developing such proposals. Answering the questions here is not an issue.

I'll try to outline it more clearly, using the pipe version. It is very similar to what yuiop suggested here, but does not require flashing a light. The light can be on full time. Whether it makes it to the detector, and how much, is what is measured. I also reiterate why the Relativity of Simultaneity (RoS) is not and issue, as brought up in the previous thread, and how it is timed.

Consider a radial arm of length r with a 1 cm square hole down the length of it. At one end there is a 1 cm^2 CCD used to detect the light intensity. The only way for light to get to this CCD is through the hole down the full length of the pipe. This pipe is then given an axis of rotation at r/2, with the open end of the pipe passing the light source. Hence at any given non-zero RPM the light only has a certain amount of time to get to the CCD before before it hits the pipe rotating into its line of travel. Knowing the RPM is the only clocked variable needed. If the pipe is 1 m long then the light must travel 1 meter minimum before the end of the rotating pipe moves 1 cm. If the photons is less than optimally aligned with the hole at entry it will have to move even faster to get to the detector.

1) The only clock is the RPM and length of the pipe.
2) The light is on constantly.
3) If the open end of the pipe travels at least 1 cm (defined by pipe length and RPM) before the light travels r then no light will ever make it to the detector.
4) No other clocks or timing mechanisms needed other than 1), such that no synchronization is required.
Synchronization is provided as a function of geometry, so I'll deal with the RoS issues again.

RoS:
SR clearly predicts that the experimental results of any effects of RoS exactly matches the experimental results to be expected if you never bothered with the mathematics of RoS to begin with. Hence expected results per SR need not mathematically bother with the rigidity issue in SR. Such issues are only relevant to appearances from differing frames, all of which agree on what end results both should be and are if SR holds. It's a waste of time to bring it up, unless some other theory attaches some real physical and differing meaning to this rigidity issue beyond a simple coordinate choice.

Measuring Results:
At 0 RPM with the open end of the pipe facing the light source you will get a maximal light intensity on the detector. Even a small RPM will prevent some minute percentage of the photons from reaching the detector, lowering the light intensity. Note that the time interval in which light reaches the detector is not what we are trying to measure, only the change in average intensity at a given instant. Though it is perfectly fine to average over the intensity for each rotation, if you curve fit against the expected drop in average intensity resulting from reduced duration with increased RPM.

What we are then looking for is a deficit in light intensity, compared to the expectation curve if the speed of light was assumed infinite. Tracking this over a large range of RPMs then let's us compare not only the expectation of single points, but track the expectations curves over a large range of expected curves. This allows us to remove a large amount of noise in the data, much like with an interferometer can obtain a partial wavelength resolution.

Results:
If an alternative physical interpretation involves a differing relative ratio between geometry and clocks, such that they covary in different ways, then this setup should measure if if it is within range of the resolution provided by the setup. If the covariance between clock and geometry does not differ then the alternative model is only arguing about a non-physical coordinate choice rather than any physically meaningful effect. This is because the only clock in operation here is the RPM requiring the geometry predicted by SR to be meaningful in relation to that RPM clock. Hence this only synchronizes a clock with geometry, not any other clock. In SR and GR geometry is a type of clock, and a clock is a type of geometry in which any physically differing theory must disagree on how they covary in some way.

 

[ghwellsjr]

I'm sorry but I still have trouble with what you are describing. Let me ask some questions and if you already answered them, then please quote where you did:

1) Is the CCD fixed to the end of the pipe and rotating with it?

2) Is the light source not spinning with the pipe?

3) Is the pipe spun at its center like a two-bladed propeller?

If you answer all the questions with "yes", then how does any light get down through the pipe when it is spinning at a high speed? It seems like the CCD will only pick up light when the pipe is stopped and aligned with the light source and as soon as you start accelerating it, the light will immediately drop off and never be detected again. I can't see any RPM that would let the light travel down the pipe. What am I missing?

 

[my_wan]

I'm sorry but I still have trouble with what you are describing. Let me ask some questions and if you already answered them, then please quote where you did:

1) Is the CCD fixed to the end of the pipe and rotating with it?

2) Is the light source not spinning with the pipe?

3) Is the pipe spun at its center like a two-bladed propeller?

1) Ideally yes, but so long as the light only reaches it through the pipe hole it makes no difference.

2) No. It is fixed with the pipe hole pointing directly at it once per revolution.

3) Yes, that is best for balance and maximal length for the torque involved.

If you answer all the questions with "yes", then how does any light get down through the pipe when it is spinning at a high speed? It seems like the CCD will only pick up light when the pipe is stopped and aligned with the light source and as soon as you start accelerating it, the light will immediately drop off and never be detected again. I can't see any RPM that would let the light travel down the pipe. What am I missing?

So are you saying 1 revolution per hour is enough to stop light from getting through?

The more sensitive the light intensity (not duration) variation is to RPM the better. Yet it's not binary where just any speed will completely shut off the light getting through during the time the hole faces the light source. The light has to be slow enough that it falls to get to the detector before the pipe rotates into it, such that the photons collide with the walls inside the hole. If the expected light duration drops too fast to provide enough detection simply increasing the intensity of the light source is sufficient. This is because it is not absolute intensities that are being measured. Rather it is the relative drop rate in the intensity curve above the expectations when C is assumed infinite that you are comparing the entire range of RPMs against.

If C was infinite then the curves exactly match. There would never be an intensity drop during that time, no matter how short, that the hole was aligned with the light source. The slower the finite speed the greater the deviation from the reference curve, and the more rapidly it deviates from this reference curve with higher RPM.

I'm not sure what the difficulty is in the description. CCD detectors can essentially detect down to single photons getting through. Obviously you want a more intense light source than that.

 

[DrGreg]

my_wan,

DaleSpam has already suggested the flaw in this experiment in post #58. To calculate the speed of light from the measured radius and angular velocity, you need to compute the linear velocity of both ends of the rod, relative to an inertial frame in which the centre of rotation is at rest.

If you assume Einstein synchronization, this is easy enough, and the two velocities are equal and opposite. But with some other synchronization, the two velocities need not be equal in magnitude, so you have insufficient information to calculate them without knowing the synchronization convention.

Your method implicitly assumes Einstein synchronization, i.e. that the one-way speed of light equals the two-way speed, so it is actually measuring the two-way speed.

 

[Dale]

In the context of standard relativity the relativity of rigidity, as I've noted, makes no difference to the outcome.

What is "the relativity of rigidity"? I have never heard of that.

 

[my_wan]

What is "the relativity of rigidity"? I have never heard of that.

Basically Born rigidity as he was the first to introduce the notion. Though a lot of other cases have been added since, such as Rindler's rod and hole paradox [Am. J. Phys. 29 365–6 (1961)], the pole and barn or ladder and barn paradox, etc. Basically anything that involves the Herglotz-Noether theorem [J. Math. Phys. 8, 919 (1967)]. Recently Ziyang Hu offered a proof of Herglotz-Noether theorem in all dimensions in a preprint: http://arxiv.org/abs/1004.1935

my_wan,

DaleSpam has already suggested the flaw in this experiment in post #58. To calculate the speed of light from the measured radius and angular velocity, you need to compute the linear velocity of both ends of the rod, relative to an inertial frame in which the centre of rotation is at rest.

These I have responded to. In effect my solution was to simply accept the Herglotz-Noether theorem. I'll reiterate below, but you can also put the detector at the center of the pipe for the same general measurement. If differing linear velocities was physically meaningful beyond what the Herglotz-Noether theorem entails then the results will differ from an expectation curve. That's why instead of data points from a singular linear velocity giving a speed C, we also want a continuous range of RPMs to compare the variations over.

If you assume Einstein synchronization, this is easy enough, and the two velocities are equal and opposite. But with some other synchronization, the two velocities need not be equal in magnitude, so you have insufficient information to calculate them without knowing the synchronization convention.

Naturally I take the Einstein synchronization to compute the expectation curve. When you speak of "equal in magnitude" in the manner suggested then you must implicitly attach some form of absolute meaning to a magnitude for this to be relevant. This implied absolute magnitude includes both space and time such that absolute simultaneity is implied. If not then relativity does not preclude, nor deny the validity of, alternative synchronization methods which provide differing magnitudes of time and distance so long as the consequences are the same. In this respect differing synchronization procedures are effectively no different than a non-physical coordinate choice.

Hence the only real question is how do such differing models differ physically, beyond what is effectively a coordinate choice. If they do then you can get effects like Bell's spaceship paradox where they shouldn't be. Anything less and relativity makes no claims of it being wrong, in which case the only question is of what mathematical value is it for solving certain problems.

Your method implicitly assumes Einstein synchronization, i.e. that the one-way speed of light equals the two-way speed, so it is actually measuring the two-way speed.

In effect what you are saying is that if relational quantities do not differ, but theory X wants to attach an absolute value in some degree to one of the relational variables in a manner that doesn't contradict relational values then this is somehow a physically differing theory? I did not assume Einstein synchronization was uniquely valid. I do not assume that relativity claims that Einstein synchronization is uniquely valid. I only assume it is one of an unknown number of equally valid solutions. If you want a differing theory that is physically meaningful beyond what is effectively a coordinate choice either show the physical effects or explain which of two meteors with x relational (kinetic) energy the energy is located at.

If there is such a physical difference it will either show up as an isotropy in C at some RPM, the divergence in the curves as the RPM increases, or incongruence in the same curve fitting data over one or more linear velocities when the detector is placed at the center of the pipe. It's certainly possible to find some effect in the same way Bell's spaceship paradox results in a real effect when the spaceships use their respective Einstein synchronizations in an accelerated frame. Otherwise the whole point is of arguing the differing claim in the two models is effectively nothing more than a debate over which spaceships clock is really going slower.

 

[ghwellsjr]

1)So are you saying 1 revolution per hour is enough to stop light from getting through?

Yes, for about 59 minutes out of the hour.

I'm still not comprehending how RPM can determine the one way speed of light. It seems to me that if you spin the apparatus at some high RPM, no light will get through. If you slow it down, eventually some light will start to get through, but you said you want to maximize the intensity of the light, so as you continue to slow it down, more light will get through in bursts until finally the maximum light gets through at a very slow RPM and then if you continue spinning in the opposite direction, you will start minimizing the intensity. Don't you agree that the maximum intensity is when the pipe is stopped with the light shining through it? How can there be an increase in intensity beyond that point at any RPM?

 

[my_wan]

Yes, for about 59 minutes out of the hour.

I'm still not comprehending how RPM can determine the one way speed of light. It seems to me that if you spin the apparatus at some high RPM, no light will get through. If you slow it down, eventually some light will start to get through, but you said you want to maximize the intensity of the light, so as you continue to slow it down, more light will get through in bursts until finally the maximum light gets through at a very slow RPM and then if you continue spinning in the opposite direction, you will start minimizing the intensity. Don't you agree that the maximum intensity is when the pipe is stopped with the light shining through it? How can there be an increase in intensity beyond that point at any RPM?

And during that 1 minute the detectors receives x light which is x/60s light intensity. In this way intensity is expressed in terms of an intensity moment. Now you increase the RPM slightly such that some later data point only gives 30 seconds of light. Thus the intensity moment becomes x/30s. Now compare the theoretical curve that plots hundreds of data points at hundreds of RPM and compare it to experimental curves. In this way the absolute intensity of the light makes no difference so long as it is constant. However, if you want to assume this absolute intensity is physically meaningful, or that the transition across the pipe midpoint is somehow equivalent to a return path, plot similar data for small increments as the detector is moved increasing closer to the pipes midpoints.

In effect you can completely map all variables of the space relationally. If the relational variables are consistent then whatever model you choose that is consistent with it is fine. Relativity makes no claims of the validity, or lack of, concerning the physical status of such a model. Relativity only tells us about what the relational variables must be, not what physical model you can and cannot model these relational variables with.

 

[ghwellsjr]

OK, well, I overlooked the fact that two times per revolution the light will be able to travel down the pipe but I still don't see how it can get through with more intensity than if the pipe were stopped with the pipe letting the light through.

And what's this about moving the detector closer to the pivot point? I must have a completely wrong idea about what you are talking about. Can you draw a picture?

 

[my_wan]

OK, well, I overlooked the fact that two times per revolution the light will be able to travel down the pipe but I still don't see how it can get through with more intensity than if the pipe were stopped with the pipe letting the light through.

The description I give did not include detecting the light twice per revolution, though I see no problem with including that scenario if it helps anything. I think you are having trouble with the notion of an intensity "moment" as opposed to variations in absolute intensity. So I'll describe it without the logic of "moments".

It does not get through with "more" intensity. If the speed of light is infinite then the total amount of light getting through on each revolution drops as the RPM increases. If the speed of light is finite the amount of light getting through on each revolution drops even faster. So the "more" is not an increases of intensity. It is merely more of a decrease than what you would get with an infinite light speed. How much more is determined by the actual speed of light.

The infinite light speed curve to be calculated is the reference curve saying how fast the total light detected per revolution should decrease. The experimental results, given a finite light speed, should be even less light getting through. We can now compare, not just two data points, but the entire RPM curve to factor out noise. Both curves are less (not more) light per revolution, but one curve is still more than the other curve. How much gives the speed of light.

And what's this about moving the detector closer to the pivot point? I must have a completely wrong idea about what you are talking about. Can you draw a picture?

I only added the movable detector to respond to criticisms, much like your issue with light being detected twice per revolution, which I don't see any effective difference. Yet both are perfectly valid variations of the same test. I can draw a picture but it still needs understood that "more" does not mean more light. More is only relative to how much more one value drops compared to another when both are decreases. The actual implementation details can vary without effectively changing the test.