Q&A with David Rideout: Testing Reality in Space

Peter,

Your travelator scenario is irrelevant - it is not analogous to the Doppler frequency shift. The Albert Einstein Institute offers a nice scenario with animations - just analyse it (if you can) and see if the speed of the light pulses (relative to the receiver) is constant or not:

Albert Einstein Institute: "Here is an animation of the receiver moving towards the source:

stationary receiver

moving receiver

(...) By observing the two indicator lights, you can see for yourself that, once more, there is a blue-shift - the pulse frequency measured at the receiver is somewhat higher than the frequency with which the pulses are sent out. This time, the distances between subsequent pulses are not affected, but still there is a frequency shift: As the receiver moves towards each pulse, the time until pulse and receiver meet up is shortened. In this particular animation, which has the receiver moving towards the source at one third the speed of the pulses themselves, four pulses are received in the time it takes the source to emit three pulses."

Pentcho Valev

Pentcho,

if I start moving forwards led by a block of glass or lens material to intercept light, I can't measure the light until it does so. It is then propagating within the lens medium (eye ~n=1,38) at c/n wrt the lens state of motion.

That is the exact case for all measurements of light speed and frequency. Despite mainstream beliefs and intellectual failure the frequency doesn't change with the wavelength, its the speed of light that changes. But only the light that ARRIVES!

Peter

Peter,

Look at those animations Pentcho posted. The distance between wave crests is unchanged. However when the receiver moves with a velocity, v towards the source the crests hit him earlier than when stationary. The animation suggests, it is f that changes and not L.

There seems to be a misunderstanding what the argument about c is about. Take an observer between two equidistant points on Earth (East-West direction), then synchronously flash light ONCE from those points. Which light arrives the observer first? It is found that despite the Earth orbiting the Sun from West to East (as seen from the North as Georgina advises we specify), both flashes are seen at the same time. One is not red-shifted and the other blue-shifted, even though the observer moves some distance towards and away from the emitted and incoming flash.

Then repeat again, moving the equidistant points further out, say near the moon, and flash your light ONCE again. This time, one flash of light is seen before the other. The puzzle is why? That is the riddle.

Peter always says the light speed changes to a new LOCAL c on arrival. Why does it change to LOCAL c to preserve the postulates of SR, but refuses to change to LOCAL c on getting to the observer in the latter case?

Then, Peter what is your definition of Quantum Vacuum? I had earlier raised some issues with you on Why Quantum blog on Aug. 8, 2014 @ 15:18 GMT.

Regards,

Akinbo

*Pentcho, thanks for those animations. They clear a lot of fog.

Akinbo,

That over-simplified view has fooled everybody so far. Now upgrade it to faithfully model reality;

Put the essential measurement tool, a lens with non zero thickness, at the start of the blue detector. Then put a processor behind it, and a wire or optic nerve between them. (the 'Shannon channel') (There can be NO 'frequency' computed until the signal enters the 'processor' and it calculates against time).

It is the 'processor' that produces the "measurement" of frequency. So now study the wavelength in the lens and channel. THAT is the ONLY wavelength the processor has access to.

In the case of the emitter moving through a medium the wavelength has already changed on entering the medium to propagate at c!

DFM, QED.

Best wishes

Peter

Peter,

"Put the essential measurement tool, a lens with non zero thickness, at the start of the blue detector. Then put a processor behind it, and a wire or optic nerve between them. (the 'Shannon channel') (There can be NO 'frequency' computed until the signal enters the 'processor' and it calculates against time)."

This is irrelevant. You have killed many discussions so far by introducing things like that.

Pentcho Valev

Pentcho,

"That over-simplified view has fooled everybody so far."

It appears it will continue to fool you while you behave like mainstream by clinging to your beliefs and a narrow closed minded way of seeing things.

It's not "irrelevant". I suggest nothing is more accurate and relevant.

Peter

Peter, I must agree with Pentcho on this one. I have disagreed with him many times in the past so I am not taking sides. Pentcho's animation clarifies a puzzling situation regarding what changes when an observer moves, i.e. wavelength, frequency or speed, ALL three, TWO out of three or NONE? It is worthy to note that dimensionally, time is present in speed (Meter per second) and frequency (cycles per second) but absent in wavelength (Length)

The introduction of a processor, a wire, optic nerve or the 'Shannon channel' is unnecessary. A frequency measurer is merely a counter. Frequency being cycles per second, if you can count faster or slower by delaying or hastening light arrival by your movement, you can change the measured frequency (IMO).

There is also no need to introduce a medium in this case since both emitter, receiver and signal are in the same medium. "...the wavelength has already changed on entering the medium", has no meaning. Where was the wavelength before entering the medium?

There may be issues however for the case when the signal enters a new medium. In that case speed and frequency can certainly change. I am not sure yet whether in that case wavelength can change also. Pentcho may find us a reference or an animation depicting that.

Any answers to my poser, why a Doppler shift or difference in light arrival times is not observed in our spaceship called earth, but is observable for light coming from outside our spacecraft?

If what DFM says is that all light speed is reduced to 'local c', what is local, the observer or the spaceship? If it is observer, then how many local c's are in the ship?

In my pet theory, I think Galilean relativity holds the key as illustrated by Galileo's ship (see The proposal). Light within the ship is not influenced by the spacecraft or ship's motion. For sound, we have air. For light, do we have a possible matter medium (or 'ponderable' matter as Einstein may say) that can also be gravitationally bound to the moving Earth? I think we do.

As usual with these exchanges I discover something new here (relativityoflight.com) which I will read later. Looks interesting.

Regards,

Akinbo

Peter,

Consider Dopler shift (moving observer) for sound waves:

"Sound waves have speed c, and f and L are related by c=Lf. For an observer moving relative to medium with speed u, apparent propagation speed c' will be different: c'=c±u. Wavelength cannot change - it's a constant length in the medium, and same length in moving coordinate system (motion does not change lengths). Observed frequency has to change, to match apparent speed and fixed wavelength: f'=c'/L."

Do you accept this interpretation? If you do, you will probably understand how irrelevant your lens, processors, wires, optic nerves etc. are.

Pentcho Valev

Pentcho, let's not crucify Peter. If you look at page 5 of the lecture you linked. You will see how unfortunately teachers mislead their students. Peter may have attended one such lecture. In that Washington University, a lecturer taught his students that when source is moving, frequency remains constant and wavelength changes (Which is FALSE), but when observer is moving frequency changes and wavelength remains constant.

The correct position should be that frequency remains constant in BOTH cases, but it is 'Observed' frequency that changes in both scenarios consequent on change in relative speed, while wavelength is constant in the medium no matter whether it is source or observer that is moving.

When a source chases its own waves as the lecturer says, the emission frequency remains what it was when source was stationary BUT because the next wave is emitted in a different position than the previous, the 'observed' frequency changes as you showed in your animation.

Regards,

Akinbo

Akinbo,

"a processor, a wire, optic nerve or the 'Shannon channel' is unnecessary."

It'd be interesting to deprive an observer of those elements and see if he can obtain a 'frequency'.

It's not shocking or worrying that you think that way. It's the mainstream view, and in line with my 2010/11 '2020 Vision' essay, where I estimated it's be at least 2020 before any change in understanding.

I'd like to be proved wrong, but can't expect to be.

Best wishes

Peter

Peter,

"All observers made of matter constitute a 'medium' with it's own rest frame."

You obviously believe this is a great insight of yours that the world still does not understand. I think it is an obsession that has killed many discussions.

Pentcho Valev

Pentcho,

Do you disagree with the insight? If you research how a 'GRIN' lens works, then consider two in relative motion, you may perhaps find it to be an eye opener.

There's no hurry. But I suspect, and I hope, hidden truth will always 'kill' discussions straying far from it.

Best wishes

Peter

Peter,

All observers made of matter constitute a 'medium' with its own rest frame.

Yes. But we are considering the effect of the media in which the wave is substantially propagated. If you want to broaden that you might as well treat the lens, aqueous humor of the eye, retina and all their individual cells as constituting 'media', each with its own rest frame.

That lecturer was correct for the case I outlined above...

Cannot be. Consider a source and an observer in space. Both Galilean and Special relativity tell us that when they approximate each other, Velocity is relative and we cannot distinguish who is doing the moving, source or observer (there are however issues here concerning Absolute motion). Thus when a Doppler blue shift is observed, the equation should be equivalent whether it is the observer deemed to move or it is the source. But this is not the case as the equations are slightly different quantitatively by about v2/c2.

According to the lecturer,

f' = f(1 u/c) for observer deemed to move towards source

f' = f [1/(1- u/c)] for source deemed to move towards observer

Both f's are not equal.

If however, you want to argue that they are not meant not to be equal, then this again negates the SR postulate that an observer cannot determine his state of motion by observation of light (electromagnetic phenomena).

I ask again, why is a Doppler shift not observed on Earth for light flashed terrestrially despite Earth moving in a direction towards or away from the flash? Any suggested answer? For sound, we don't observe a Doppler shift due to Earth motion no matter the direction of the sound because the sound medium itself is in motion with the Earth (i.e. in our spaceship). Note that Doppler shift of light is observed due to Earth motion from distant light sources.

Regards,

Akinbo

Akinbo,

"why is a Doppler shift not observed on Earth for light flashed terrestrially despite Earth moving in a direction towards or away from the flash?"

Because Earth, it's atmosphere and it's ionosphere clearly represent an "Inertial system" (mass all in one definable state of motion; orbiting the sun at a velocity v), which gives a 'discrete field' model (DFM). The ('near/far field') BOUNDARY is the outer ionosphere/plasmasphere. As we know, all moving bodies have this electron 'surface' fine structure.

The logic of TWO cases of emitter/observer motion is simply described by analogy with sound. You and I are 100m apart with a sound recorder (R) at rest between us. You beep your horn while at rest for 'control' data. In case 1) you drive towards me and beep your horn. Both I and (R) hear the sound Doppler shifted to a higher pitch (shorter wavelength and higher frequency, ok? standard stuff.

In case 2) I drive towards you (and (R). Now the sound is approaching me at s+v wrt MY rest frame. I still hear your horn Doppler shifted to a higher pitch. but DOES (R)!? NO! Of course not.

As propagation speed past (R) remains the speed of sound in air that means both wavelength AND 'f' ARE different, as the lecturer correctly identified.

The problem is that doesn't n meet with your long held assumptions. But that doesn't make it false. It was your old assumptions that were false!

But you ask; "as it left the car it was doing c wrt the car, so where did it change speed!?" Very simple; It was at the 'extinction distance' in air, which started immediately the sound waves hit the medium.

What's shocking and unfamiliar is that light from your headlights does precisely the same. In terms of Maxwell's equations that 'transition zone' IS the Maxwell near/far field transition zone (TZ). It's well known to all antenna engineers (except they'll give you various different formulae as it's wavelength dependent). For light it's just under 1 micron. Google it. Fresnel refraction and Snells law fail at the TZ! (ever heard of 'Fraunhoffer' refraction? It's the 'other' side of the TZ, where 'virtual electrons' live (really real but move at c+/-v) and has never been theoretically rationalised.

As your car heads towards me the light from the bulb travels to the lens and through the glass at c/n in the glass rest frame (a local 'discrete field'). On re-emission into the air it's re scattered to c in and wrt the air, and propagates at c wrt the AIR rest frame. The wavelength is then reduced, so I and (R) see it blue shifted. All PRECISELY as found in every optical experiment carried out. (Thus the theoretical 'anomalies')

But I suggest you'll certainly qualify to apply for Mensa if you rationalise, apply and REMEMBER all that! (As I told you, the table I gave you is an 'aide memoir')

Best wishes

Peter

Peter,

"Do you disagree with the insight?"

It is flagrantly irrelevant. A discussion of the Doppler effect can have nothing to do with a discussion of the eye, retina and optic nerve.

Pentcho Valev

Pentcho,

Very relevant. Just not commonly understood. The lens of the eye is a medium, as all lenses, with 'fine structure' surface electrons.

The Doppler effect is the delta wavelength at a change in propagating medium. The delta has 2 elements; relative refractive index n, and relative velocity v!

You will of course find that entirely unfamiliar, but test it in application and you'll find it shows 'relative' c+v as well as 'propagation' c/n and resolves every anomaly and paradox under the sun and beyond.

Optical science evidence all agrees. And as my old physics teacher used to a say; whatever you may believe; "the proof of the pudding is in the eating".

Best wishes

Peter

Peter,

"why is a Doppler shift not observed on Earth for light flashed terrestrially despite Earth moving in a direction towards or away from the flash?". Because Earth, it's atmosphere and it's ionosphere clearly represent an "Inertial system" (mass all in one definable state of motion; orbiting the sun at a velocity v),...

CORRECT, thy mouth sayeth it, but using so many words. Lesson to take away: With an earth-bound medium (whatever pet medium individuals come up with), the Michelson-Morley experiment on earth surface will not reveal the earth's motion by using light. No need for length contraction and time-dilation. No need to continue your romance with SR. (It is important to note however that the pet medium must exist in the terrestrial 'vacuum' since the M-M experiment gives same result).

On the analogy of 'TWO cases of emitter/observer motion' is simply described by analogy with sound.

In case 1) you drive towards me and beep your horn. Both I and (R) hear the sound Doppler shifted to a higher pitch (shorter wavelength, NO and higher observed frequency, YES.

In case 2) I drive towards you (and (R). Now the sound is approaching me at s+v wrt MY rest frame. I still hear your horn Doppler shifted to a higher pitch. but DOES (R)!? YES, R will also still hear my horn at same higher pitch, but you will hear at a higher pitch than the higher one you heard in case 1).

But you ask; "as it left the car it was doing c wrt the car, so where did it change speed!?"

I am not sure I get your meaning here. The sound waves DID NOT EXIST somewhere before hitting the medium. The waves are a disturbance in the medium. Very simple, so "no 'extinction distance' in air, which started immediately the sound waves hit the medium".

On the frequent use/ abuse of absorption and re-emission,...

Perhaps you don't take cognizance that if things happen that way, when an electron or whatever particle absorbs the light, the re-emission will be in ALL directions and not necessarily in the direction of initial propagation. If we are to believe this, then a light ray sent on a message to deliver a certain amount of energy to a receptor will have almost all its energy re-emitted and sent to different unintended destinations. I don't think that is what is observed. Lasers tell us this and you can take this as a guided missile against this part of DFM! What is observed is that some of the encounters on the way may retain only some of the energy, if it is matter. Most of it gets delivered to destination if it is in empty space.

Finally, the correct and universal Doppler equation would have to be

f' = f(1 + u/c), where u is the relative velocity of observer and source to each other, with + or - sign being applied appropriately. Without this an observer will be able to tell who is doing the moving between source or receptor because f(1 + u/c) is not equal to f [1/(1- u/c)]. There is a difference of u22/c2 as I pointed out.

Best wishes,

Akinbo

*Laptop battery running low...

Akinbo,

"you drive towards me and beep your horn. Both I and (R) hear the sound Doppler shifted to a higher pitch (shorter wavelength, NO"

I'm rather dumbfounded that you seriously suggest that with a known medium propagation speed, static medium and a source moving ever closer to the observer with each emission (wave OR particle) that the wavelength (distance) between them will not be less than the distance if the emitter was not in motion?

And do you insist light waves do not exist between the bulb and lens of a car headlight before hitting the moving air?

If so I fear you may be truly a lost cause to nature Akinbo. But I'm sure you'll get on fine with 'physics'.

Best wishes

Peter

Peter,

"you drive towards me and beep your horn. Both I and (R) hear the sound Doppler shifted to a higher pitch

Higher observed frequency YES, Higher resultant speed, YES, shorter wavelength, remains NO. In this regard, our lecturer was correct in saying, "Wavelength cannot change - it's a constant length in the medium, and same length in moving coordinate system (motion does not change lengths)".

I'm rather dumbfounded that you seriously suggest that with a known medium propagation speed, static medium and a source moving ever closer to the observer with each emission (wave OR particle) that the wavelength (distance) between them will not be less than the distance if the emitter was not in motion?

By the principle of equivalence or relativity, whereby what is moving towards the other can be relative, why should wavelength be unchanged in one scenario and change in the other. Throwing the boomerang back at you, do you suggest that when the observer moves ever closer to the source with each emission (wave OR particle) that the wavelength (distance) between them will not be less than the distance if the observer was not in motion?

And do you insist light waves do not exist between the bulb and lens of a car headlight before hitting the moving air?

No, light waves exist between the bulb and the lens of a car before hitting the air. But light waves DO NOT EXIST in the bulb before emission.

Lastly, what is your take on the lecturer's observed blue Doppler frequency shift for the case of an observer moving with a velocity, u towards a stationary source being quantitatively different from that when the source moves with SAME velocity, u towards a stationary observer? I don't think there should be a difference in the blue shift. But if there is, this appears to violate the relational view of space and there may then be something in it for Newton's 'Absolute Motion', i.e. a means of experimentally determining which object is doing the moving.

Regards,

Akinbo