[Just thinking (OP)]

The two photons should be identical, so such a device cannot be built.

I think you may be correct that's why Bored chemist is thinking doppler but that may prove very difficult.

[Bored chemist]

We will have to manufacture a device that we will call a, new photon created light Spectrum analyzer machine I will leave that part for your very competent self to deliver.

The two photons should be identical, so such a device cannot be built.

Watch this space...

[Kryptid]

Watch this space...

Was I wrong? If so, I'm willing to be corrected.

[Bored chemist]

If the bulb is still and the mirror is moving and you get a doppler shift the light is coming from the mirror.

So, what's the difference between reflection- which changes the wavelength of the waves and  creation of a new photon- with a new wavelength?

[trevorjohnson32]

Light is a wave, no photon, that's just theory. A wave is a denser part of a medium spreading outward to a less dense part of that medium, so light has space-time as its medium, so light is space.

[Kryptid]

Light is a wave, no photon, that's just theory.

Ignoring the fact that "just a theory" is not a bad thing when it comes to science...

Photons are quite well documented. We can detect them. We know they are there.

[Just thinking (OP)]

So, what's the difference between reflection- which changes the wavelength of the waves and  creation of a new photon- with a new wavelength?

I find the question difficult to understand but I can say this if the mirror is moving towards the doppler detector and we get a blue shift it just means the light is being compressed and the opposite for the redshift. I think the big problem with using a mirror to detect any shift is that the mirror would have to be moving very fast to see any noticeable change in pattern.

[trevorjohnson32]

Light is a wave, no photon, that's just theory.

Ignoring the fact that "just a theory" is not a bad thing when it comes to science...

Photons are quite well documented. We can detect them. We know they are there.

what shape is a photon is it like a long french fry?

[Kryptid]

what shape is a photon is it like a long french fry?

As best as we can tell, it's shaped like either a wave or a point (depending on the measurement method).

[Bored chemist]

Light is a wave, no photon, that's just theory. A wave is a denser part of a medium spreading outward to a less dense part of that medium, so light has space-time as its medium, so light is space.

Be quiet; the grown ups are talking.

[Bored chemist]

So, what's the difference between reflection- which changes the wavelength of the waves and  creation of a new photon- with a new wavelength?

I find the question difficult to understand but I can say this if the mirror is moving towards the doppler detector and we get a blue shift it just means the light is being compressed and the opposite for the redshift. I think the big problem with using a mirror to detect any shift is that the mirror would have to be moving very fast to see any noticeable change in pattern.

It's pretty much a rhetorical question.
I don't think there is a way in which we could distinguish the way that modern physics treats the reflection of light from the idea of the photons conveying their  energy to the electrons and then the energy being re-emitted.

[Kryptid]

Be quiet; the grown ups are talking.

Mind your manners, please...

[Bored chemist]

I think the big problem with using a mirror to detect any shift is that the mirror would have to be moving very fast to see any noticeable change in pattern.

Well... radar speed traps work just fine.

It's also possible to accelerate a bunch of plasma to a very high speed, and reflect light off it.
You get a doppler shift.

[Just thinking (OP)]

Well... radar speed traps work just fine.

It's also possible to accelerate a bunch of plasma to a very high speed, and reflect light off it.
You get a doppler shift.

I think the speed camera is measuring the change in distance of the moving vehicle over time not the same type of shift. The plasma method may be the answer if that is possible.

[Bored chemist]

I think the speed camera is measuring the change in distance of the moving vehicle over time not the same type of shift.

https://en.wikipedia.org/wiki/Radar_speed_gun#Doppler_effect

[Just thinking (OP)]

Quote from: Just thinking on Today at 07:49:18

    I think the speed camera is measuring the change in distance of the moving vehicle over time not the same type of shift.

https://en.wikipedia.org/wiki/Radar_speed_gun#Doppler_effect

It seems to be the case if I am correct that would mean that the radar device can measure 1 billionth of the speed of light and if so that is sensitive enuff to detect a change of one kilometre per hour. My apology for douting.

[Just thinking (OP)]

The problem with measuring a return signal whether it is light of a mirror or radar of a target is that whether the return signal is a deflection or a newly created photon is that it will return with the same response either way so nothing can be learned by this method but if so how?

[Bored chemist]

The problem with measuring a return signal whether it is light of a mirror or radar of a target is that whether the return signal is a deflection or a newly created photon is that it will return with the same response either way so nothing can be learned by this method but if so how?

What you learn is that there is no difference.

[Just thinking (OP)]

What you learn is that there is no difference.

It sounds like it would be difficult if not impossible to confirm.

[Bored chemist]

If there is no way, even in principle, to tell the difference between two things then are they actually different?