[alancalverd]

No problem (to a physicist, though the mechanical workshop might grumble) spinning a 10m axle at 50,000 rpm. Fizeau used an 8000 m path length and 1500 rpm so we just need a lot more cogs on our wheels. Could be a neat experiment to do in orbit!

Fortunately the advent of lasers allows us to use higher beam intensity, with negligible divergence, than was available to Fizeau.

[hamdani yusuf]

Using toothed wheel may suffer from diffraction. That's why Foucault and Michelson used rotating mirror to get more accurate results.
Mechanical axles have problem with elasticity. Slight imperfection may affect the timing differences, which in turn leads to inaccurate results. Multiple cogs may introduce problem with synchronicity.

[alancalverd]

Accuracy isn't the primary concern here: what matters is whether you get the same result with the beam travelling in either direction. If you are worried about loss of synchronism (which I have minimised by driving the system symmetrically from the center of the axle) you can try spinning it clockwise and anticlockwise and take the mean.

A bit of diffraction isn't a problem. We are only looking for the maximum of intensity versus speed of rotation, not an absolute value of intensity.

[hamdani yusuf]

Accuracy isn't the primary concern here: what matters is whether you get the same result with the beam travelling in either direction. If you are worried about loss of synchronism (which I have minimised by driving the system symmetrically from the center of the axle) you can try spinning it clockwise and anticlockwise and take the mean.

A bit of diffraction isn't a problem. We are only looking for the maximum of intensity versus speed of rotation, not an absolute value of intensity.

It matters because slight imperfection in the material of the axle can introduce errors  larger than the signal you try to detect. I'm not talking about the intensity. It's about the timing.
In the end, the question is how much speed difference can be detected by your experimental setup?

[alancalverd]

In principle, any speed difference will be detectable.

As we approach the first maximum transmission, we hold the speed of rotation steady. If the slits are out of phase due to an imperfection in the axle, the maximum transmission will be less than 100% but still a maximum. The only measurements required to determine c are the length of the axle and the rate of rotation that produces the first maximum signal.

Now fire the beam from B to A. if the speed of light is invariant with direction, maximum transmission will occur at the same rate of rotation but may be brighter or dimmer than the AB value depending on the phase difference between the wheels.

[hamdani yusuf]

In principle, any speed difference will be detectable.

Small speed difference produces small signal to noise ratio, thus requires higher precision experimental setup, which typically has larger size.

[hamdani yusuf]

Now fire the beam from B to A. if the speed of light is invariant with direction, maximum transmission will occur at the same rate of rotation but may be brighter or dimmer than the AB value depending on the phase difference between the wheels.

Do you think earth rotation has an effect?

[alancalverd]

Not if you do the experiment in space. Nor if you align the apparatus north-south. If you get the same answer east-west, you have proved the nonexistence of aether.

[hamdani yusuf]

Not if you do the experiment in space. Nor if you align the apparatus north-south. If you get the same answer east-west, you have proved the nonexistence of aether.

Do you consider Sagnac effect?

[alancalverd]

The "space" machine does not rotate about any axis perpendicular to the main axle.  If we do the experiment on the earth's surface with north-south orientation, we can measure c in both directions with equal (if any) Sagnac shifts.

[hamdani yusuf]

The "space" machine does not rotate about any axis perpendicular to the main axle.  If we do the experiment on the earth's surface with north-south orientation, we can measure c in both directions with equal (if any) Sagnac shifts.

If we do the experiment on the earth's surface with east-west orientation, will we measure different value of c in opposing directions?

[alancalverd]

Hopefully not, but you'd expect a change in wavelength.

[hamdani yusuf]

Hopefully not, but you'd expect a change in wavelength.

That would imply that the wavelengths are different. It should be detectable using an experimental setup that produces standing wave, like a microwave transmitter in front of a reflector.

[alancalverd]

The Pound-Rebka experiment was a neat demonstration, using Mossbauer as a very fine notch filter.  You'd be hard pressed to detect the wavelength shift with microwaves.

[mxplxxx]

This is horribly simplistic I know but I have tried and can't find an answer. What waves in wave/particle duality? Surely it is the particle, in which case, why is there a problem?

[alancalverd]

If you think wave/particle duality is meaningful, you are barking up a tree that was felled a century ago.

[mxplxxx]

If you think wave/particle duality is meaningful, you are barking up a tree that was felled a century ago.

Tell me more - I thought it was one of the cornerstones of Quantum Theory.

[mxplxxx]

If you think wave/particle duality is meaningful, you are barking up a tree that was felled a century ago.

From Copilot "It?s important to note that while the language used to describe quantum phenomena has advanced, the underlying principles that led to the concept of wave-particle duality are still valid and essential for understanding the quantum world. The concept has been refined rather than refuted, and it remains a cornerstone of quantum mechanics, albeit with a deeper and more complex interpretation than a century ago."

[alancalverd]

the underlying principles that led to the concept of wave-particle duality are still valid and essential for understanding the quantum world.

That statement is about as wrong as it can be, and underlies about half of the misapprehensions that find their way into this forum.

[mxplxxx]

the underlying principles that led to the concept of wave-particle duality are still valid and essential for understanding the quantum world.

That statement is about as wrong as it can be, and underlies about half of the misapprehensions that find their way into this forum.

Then how about giving us the benefit of your boundless wisdom and tell us what we need to know about wave/particle duality. 😎