Is it feasible to measure one way speed of light this way?

[kostarak]

TL;DR Summary

I know that this subject is pretty saturated even thought i waited a few days.Its a generalized theoretical expiremental set up to try and measure one way speed of light,i just want any input on this but beware it will require a few minutes of your spare time.Thanks in advance.

Theoretical experiment for measuring one way speed of light

From 1905 to this day we have not experimentally measured the one way speed of light between a source to the detector only the roundtrip from the source to the detector and back again. We just assume that the speed of light is the average speed and it’s the same at all directions equal to c. But I think it is important to point out that this is just a convention not an empirically verified fact. The aim of this paper is to provide a general methodology using a theoretical experiment that aims, if it gets implemented, to prove or disprove that the speed of light is equal at least in two directions along the horizontal axis. It’s not meant to provide specific technical details and it will require some modifications if it ever gets attempted.
We can start setting up our theoretical experiment now, which I call “The Weight Race Experiment/Method”. First of all we need some kind of containment or room to experiment. For simplicity’s sake we will go with the room. So now we take an optical fiber of certain length and cut it exactly in half. We use a laser that can shoot a vertical light beam in two angled and connected mirrors that split the beam and redirect them into the two out of the four non connected ends of the fibers we just cut respectively. Now we attach a rigid rod above the optic fiber and also make the system able to rotate (except the laser and the mirrors) around its center of gravity which would be near the center of our fiber. Also our system will be supported by the wall in a way that the two spheres are facing downwards. We now attach at the two edges of the fiber two special identical in every way clamps that each hold two also identical in every way spheres(also when light hits the special clamps they move to the open position at exactly the same time). Keep in mind that we still try to make everything be level. Last step is to remove as much air we can from the room and get it as close to a vacuum as possible.

Once the whole system is at rest and the two weights are balancing each other out we start by shooting two simultaneous light beams at each edge of the fiber optic. If the speed of light is the same in all directions then the whole system will remain at the same position and not rotate. If it’s not then the center of gravity will shift for a very small amount of time and it will make the (fiber/device/rod) system rotate and depending on how different the speed of light is in each direction the angle will increase in value relative to the original rest position of the whole system. That means that the difference between the different speeds of light and the angle created are analogous. Larger difference results in larger angle, which we can measure using an already built in sensor before the experiment even start.

 

[bob012345]

Summary:: I know that this subject is pretty saturated even thought i waited a few days.Its a generalized theoretical expiremental set up to try and measure one way speed of light,i just want any input on this but beware it will require a few minutes of your spare time.Thanks in advance.

Theoretical experiment for measuring one way speed of light

From 1905 to this day we have not experimentally measured the one way speed of light between a source to the detector only the roundtrip from the source to the detector and back again. We just assume that the speed of light is the average speed and it’s the same at all directions equal to c. But I think it is important to point out that this is just a convention not an empirically verified fact. The aim of this paper is to provide a general methodology using a theoretical experiment that aims, if it gets implemented, to prove or disprove that the speed of light is equal at least in two directions along the horizontal axis. It’s not meant to provide specific technical details and it will require some modifications if it ever gets attempted.
We can start setting up our theoretical experiment now, which I call “The Weight Race Experiment/Method”. First of all we need some kind of containment or room to experiment. For simplicity’s sake we will go with the room. So now we take an optical fiber of certain length and cut it exactly in half. We take a special device that can shoot two light beams from two opposing holes located at each side of the machine simultaneously and we attach the two out of the four non connected ends of the fibers we just cut in the two holes accordingly. Now we hang our system of [fiber-device-fiber] from the ceiling of the room and try to make it as level as possible. We now attach at the two edges of the cable two special identical in every way clamps that each hold two also identical in every way spheres(also when light hits the special clamps they move to the open position at exactly the same time). We also add two more identical clamps/spheres in the center points between the exposed ends of the fiber and the ends in which our special device is placed [clamp-fiber-clamp-fiber-device-fiber-clamp-fiber-clamp]. Keep in mind that we still try to make everything be level so we might also have to use strings to support the optic fiber to prevent from bending. Last step is to remove as much air we can from the room and get it as close to a vacuum as possible.
Now we can start our experiment. At a predetermined time the device shoots simultaneously two light rays to the left and to the right edge of the fiber respectively. If the speed of light is constant to all directions then the light beams will reach the first clamps in each direction at the same time thus releasing the first two spheres at exactly the same moment while the next two at an expected defined delay. If that’s not true and the speed of light is different at different directions then we would notice a difference in the value of that delay at both pairs, from which we could calculate the speed of light in each direction. If we can get the pair of spheres close enough we can use something simple like a camera to record them free falling.
There is another variation of this experiment that provides similar results but it does not require collecting any info in real time.

The variation of this experiment first of all is missing the first set of clamps so the only clamps it has are located at the exposed ends of the fiber respectively. Now we attach a rigid rod above the optic fiber and also make the system able to rotate around its center of gravity which would be near the center of our special device. Also our system will be supported by the wall and not from the ceiling in a way that the two spheres are facing downwards. Once the whole system is at rest and the two weights are balancing each other out we just repeat the same process as before by shooting two simultaneous light beams at each edge of the fiber optic. If the speed of light is the same in all directions then the whole system will remain at the same position and not rotate. If it’s not then the center of gravity will shift for a very small amount of time and it will make the (fiber/device/rod) system rotate and depending on how different the speed of light is in each direction the angle will increase in value relative to the original rest position of the whole system. That means that the difference between the different speeds of light and the angle created are analogous. Larger difference results in larger angle, which we can measure using an already built in sensor before the experiment even start.

First you should estimate what kind of difference in the speed of light you think you might observe. Then ask how that difference would be detected in the systems you are proposing and see if those detection schemes make sense. For example, if the difference amount to 1ns or one billionth of a second, could your system detect a 1ns difference in the falling weights or would such a small difference be swamped by experimental error?

 

[kostarak]

That depends a lot at specific technical details of the expirement,how exactly is set up,whats the accurancy of our measuring devices etc etc.Do not get stuck too much in technical details,try to think how feasible the general methodology is.

 

[bob012345]

That depends a lot at specific technical details of the expirement,how exactly is set up,whats the accurancy of our measuring devices etc etc.Do not get stuck too much in technical details,try to think how feasible the general methodology is.

Draw a schematic of your proposed setup please. But in general the feasibility depends of the details of the measurements. Thanks.

 

[phyzguy]

How do you expect to see the falling weights? Using light I suppose, which needs to propagate back to where you started. So how is it a one-way measurement?

 

[kostarak]

You will see them vertically to the optic fiber,so its a two way trip from you to the weights and back.I will try to draw it really quick

 

[Vanadium 50]

Before jumping in, is there any argument whatsoever that would convince you that you are wrong?

 

[kostarak]

Yes that's what i am looking for.If you have it i am actually glad to hear it.

 

[Dale]

Summary:: I know that this subject is pretty saturated even thought i waited a few days.Its a generalized theoretical expiremental set up to try and measure one way speed of light,i just want any input on this but beware it will require a few minutes of your spare time.Thanks in advance.

If we can get the pair of spheres close enough we can use something simple like a camera to record them free falling.

And what do you think happens to the recording on a camera if the one-way speed of light is anisotropic?

There is simply no possible experiment that can measure the one way speed of light independently of your synchronization convention

 

[kostarak]

Dale can you please explain more the problem with the camera please? I am imagining using the camera from the side view like i posted above.

 

[Devin-M]

Is this paper relevant?

“we also can reproduce the allowed light speed anisotropy appearing in the azimuthal distribution of the GRAAL experimental data”

https://www.sciencedirect.com/science/article/abs/pii/S0927650512000989

 

[Dale]

Dale can you please explain more the problem with the camera please? I am imagining using the camera from the side view like i posted above.

Really? If you think that you understand this stuff so well that you can propose an experiment which eluded the most brilliant minds of the last century then shouldn’t you be able to do this analysis in exact mathematical detail yourself?

I am sorry, but ever since that silly Veritasium video we have had a deluge of people doing exactly what you are doing. I was patient for the first several and had hoped that the phase had past. But frankly I am annoyed by it.

It is impossible! It is not a matter of clever experimental design, it is a matter of definition.

 

[Vanadium 50]

We take a special device that can shoot two light beams from two opposing holes located at each side of the machine simultaneously

(emphasis mine)

There's your problem. How do you ensure these events at different places are simultaneous.

 

[kuruman]

The Aspect experiment was designed to look at violations of Bell's inequalities but it relied on the isotropy of the speed of light. Two detectors were placed at equal distances from a source that generated two correlated photons moving in opposite directions. A coincidence circuit ensured that only simultaneous counts by the detectors were accepted. Simultaneous events were detected and accepted. What do you think this means?

 

[kostarak]

First of all i do not think this a magic or clever expiremental set up that will measure the one way speed of light,as you said the most brilliant minds of the last century tackled this problem and failed.I do not try to prove anything its just an idea (that yes originated by the Veritasium video) in which i wish input exactly because of my almost certainty that there is a problem which i am unable to find.

Also,if you are annoyed or frustrated by this no one forces you to read it or reply to it.Where else is better to get feedback than from a forum.

 

[kostarak]

Thats the problem that starts to be uncovered and by other frums vanad. Its not about leaving the holes at the same time more of starting at the same time from a single point. I am not knowledgeable enough to know such a device so i assumed that there has to be way to produce two opossing light beams at the same time with some process.

That assumption that slipped by is probably the problem.

 

[anorlunda]

Watch this video by Veritasium. I think your idea is one of the rejected methods discussed in the video. Pay close attention to the concept of simultaneity; that's where most people go wrong.

 

[Dale]

First of all i do not think this a magic or clever expiremental set up that will measure the one way speed of light

You certainly did not express that in your OP, which reads very much as though you believe that your “general methodology” will work.

i wish input exactly because of my almost certainty that there is a problem which i am unable to find.

Then I am glad I helped you find it.

A camera records light coming from different directions. If the one way speed of light is anisotropic then the image will be distorted due to the anisotropic delays compared to isotropic delays.

 

[kostarak]

Thanks dale now i see the problem,also i should explain more my intentions because of all this Veritasium surge.

Since its useless i edited out the first part and left the second in which i still have not gotten feedback.I slightly modified the special device i was using in hopes of not triggering any simultaneity problems (i will) but i am more interested if such a measumerent could be done using shifting of the center of mass.

 

[Dale]

hopes of not triggering any simultaneity problems

It is not possible to not trigger simultaneity. The one way speed of light is DEFINED as the time it takes for light to travel a fixed distance according to a pair of synchronized clocks. There is no way around the issue because it is part of the definition of the thing you are trying to measure.

In the second setup if the speed of light is anisotropic then so will the speed of sound be.

 

[kostarak]

Ok then if that's the problem then indeed there is no way arround.I will delete any comments that are not needed.

 

[PeroK]

Yes that's what i am looking for.If you have it i am actually glad to hear it.

The main argument is that this is not really an experiment problem, as such, but the definitions in modern physics do not allow a one-way speed to be unambiguously defined (and, if it cannot be defined, it cannot be measured). Physics is not perhaps as clear cut as mathematics, but you may as well try to prove that $1$ is not a prime number.

It really doesn't matter how clever your experiment is, the impossibility of a one-way measurement is embedded in the modern notions and definitions of time, space and speed.

 

[A.T.]

It is not possible to not trigger simultaneity. The one way speed of light is DEFINED as the time it takes for light to travel a fixed distance according to a pair of synchronized clocks.

Maybe it would help to talk about "speed in general", not "speed of light" here. This would avoid the misconception, that there is something special about light in this context.

 

[Vanadium 50]

Since its useless i edited out the first part

Please don't do that. Changing the question after it has received answers is not conducive to communication.

 

[PeroK]

Please don't do that.

That's the polite way to put it. If you were from Glasgow you could say:

"Gonna no dae that".

https://www.eathaggis.com/product/gonne-no-dae-that-mug

I was going to suggest you could put that mug on your Christmas present list, but they're sold out!

 

[FactChecker]

Your experiment might work as an idealistic thought experiment to detect a difference in the speed of light in different directions. (EDIT: But it won't work even for that.) I assume that you realize that there are so many difficulties that it is not a practical experiment. In addition to that, relativity theory has a lot of complications, such as the apparent rotation of a moving object. With all the complications, what could you really conclude (with enough evidence to convince skeptics) when the result inevitably shows no difference in speed? The beauty of the experiments that used light going in a "round-trip" is that they remove so many of the practical complications. They were so convincing that even the most skeptical people had to take the bizarre results (that the speed of light and the speed of the platform do not add) seriously.

 

[bob012345]

Really? If you think that you understand this stuff so well that you can propose an experiment which eluded the most brilliant minds of the last century then shouldn’t you be able to do this analysis in exact mathematical detail yourself?

I am sorry, but ever since that silly Veritasium video we have had a deluge of people doing exactly what you are doing. I was patient for the first several and had hoped that the phase had past. But frankly I am annoyed by it.

It is impossible! It is not a matter of clever experimental design, it is a matter of definition.

Not everyone knows what you are referring to and why you are upset. What video was that? What exactly is impossible? Thanks.

 

[Ibix]

Your experiment might work as an idealistic thought experiment to detect a difference in the speed of light in different directions.

No it won't. Any "one way speed measurement" either depends on clock synchronisation (which involves an assumption of the one way speed of light) or is a disguised two-way measurement. This one depends on the speed of light in one direction and the speed of sound in the other, so is of the "disguised two-way measurement" variety.

 

[FactChecker]

No it won't. Any "one way speed measurement" either depends on clock synchronisation (which involves an assumption of the one way speed of light)

I agree, but I think that the experiment described is really to detect any difference in speed, not to measure the speed. Even for that use, I don't think that the experiment described is worth figuring out the details. That is why I said "might work" because I don't want to quibble about all the reasons that it would not work.

 

[Ibix]

I agree, but I think that the experiment described is really to detect any difference in speed,

How is that different from measuring the one-way speeds? If I know the two way speed then I know the average one-way speed. Knowing that and the difference gets me the one way speeds - which are conventional, hence implying that the difference is conventional too.

 

[bob012345]

No it won't. Any "one way speed measurement" either depends on clock synchronisation (which involves an assumption of the one way speed of light) or is a disguised two-way measurement. This one depends on the speed of light in one direction and the speed of sound in the other, so is of the "disguised two-way measurement" variety.

How is the speed of sound involved?

 

[Ibix]

How is the speed of sound involved?

That's how the release of the weights is communicated through the apparatus. It can't be perfectly rigid because that would imply an infinite speed of sound in the apparatus. So the apparatus flexes rather than tipping, at least until the mechanical waves from the two releases meet.

 

[FactChecker]

How is that different from measuring the one-way speeds? If I know the two way speed then I know the average one-way speed. Knowing that and the difference gets me the one way speeds - which are conventional, hence implying that the difference is conventional too.

I would prefer that the OP realize how clever the Michelson-Morley experiment was than worry about the details of his deceptively complicated experiment. I would rather delete my post than divert this thread.

 

[bob012345]

No it won't. Any "one way speed measurement" either depends on clock synchronisation (which involves an assumption of the one way speed of light) or is a disguised two-way measurement. This one depends on the speed of light in one direction and the speed of sound in the other, so is of the "disguised two-way measurement" variety.

How does clock synchronisation assume the one way speed of light when two atomic clocks can be synchronised while together and then moved a distance apart for the experiment?

 

[Ibix]

How does clock synchronisation assume the one way speed of light when two atomic clocks can be synchronised while together and then moved a distance apart for the experiment?

Look up "slow clock transport". In short, time dilation is only negligible (for measurements of the speed of light) in the limit of small transport velocity when the speed of light is assumed to be isotropic.