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Author Topic: Why do photons have the same speed regardless of the velocity of their source?  (Read 12662 times)

Offline JoeBrown

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Yet - a Doppler shift cancelled the blueshift redshift frequencies between the 2 'static in motion' and 'constant in distance' locations... How did it do this?

They gravitational shifted the height of the tower.  -- errr.  Trying, to be  a wisenhymer.

They moved the light source and/or receiver, which produced doppler shift to cancel gravitational shift.  I don't believe they had to change the height of the tower to accomplish the feat.
 

Offline timey

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Joe - I can't believe I am actually dignifying your post of absolute and total ignorance with an answer... But here goes...

They did not 'move' the light source or the receiver.  They did not extend or shorten the 'distance' from the bottom of tower to the top of tower.

Why don't you read up on the subject 'before' commenting?

https://en.m.wikipedia.org/wiki/Pound–Rebka_experiment
 

Offline Colin2B

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.

There was no relative speed between the top of tower and bottom of tower in either instance. 
But there was, the source was mounted on a loudspeaker cone so it moved towards and then away from the receiver.
 

Offline timey

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Colin - they created a Doppler shift by vibrating the speaker at frequencies between 10 and 50 hertz to cancel out the redshift  blueshift frequencies.  The distance between the speaker and the receiver remained at 22.5 metres.  Therefore the distance between the emitter and receiver remained at 22.5 metres and the distance between the top of tower and bottom of tower remained at 22.5 metres.  The gamma rays travelled 22.5 metres 'only'.

When the Doppler shift canceled out the gravitational blueshift, the receiving sample absorbed gamma rays and the number of gamma rays detected by the scintillation counter dropped accordingly. The variation in absorption could be correlated with the phase of the speaker vibration, hence with the speed of the emitting sample and therefore the Doppler shift.

A Doppler shift in light was identified in this experiment whereas there was no relative motion between the emitter of the gamma rays and the receiver, and no contraction or expansion between the top of tower and bottom of tower.

How did it do this?

Clearly redshift is thought indicative of an expanding universe, whereby the light emitter and receiver are experiencing an expansion of distance between themselves, at an accelerated rate.

The Pound Rebka indicates that redshift from bottom of tower to top of tower shows no such thing!  The light source is not accelerating away. There is no expansion of distance.
 

Offline timey

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Therefore the only explanation for any relative motion is within the movement of the light!  But this is not possible, because the speed of light is constant.  The only other aspect in this instance that would affect relative motion is 'time', and I'm sorry, but a Doppler shift of time in accordance with redshift blueshift frequencies is entirely contrary to currently held theory!

This being my point...
 

Offline JoeBrown

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Perhaps they selectively applied cosmological shift to the tower?

The wiki article you linked to states:
Quote
By vibrating the speaker cone the gamma ray source moved with varying speed, thus creating varying Doppler shifts. When the Doppler shift canceled out the gravitational blueshift, the receiving sample absorbed gamma rays and the number of gamma rays detected by the scintillation counter dropped accordingly. The variation in absorption could be correlated with the phase of the speaker vibration, hence with the speed of the emitting sample and therefore the Doppler shift.

The vibration of the speaker caused a change in relative motion.  They weren't quite statically separated.

However, as you pointed out, shift has nothing to do with the subject.  So why are we beating this poor horse? To give it some cosmological shift?
 

Offline timey

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Yup - you are definitely a little on the dense side to be sure!

The definitive statement here being "When the Doppler shift canceled out the gravitational blueshift, the receiving sample absorbed gamma rays"

For the gravitational blueshift to be cancelled out by the phase of the speaker, the blueshift of the light would have to match the phase of the speaker.

Does this compute?
 

Offline JoeBrown

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Timey, I must be dense.

When a speaker vibrates, it is considered motion.  Motion causes doppler shift.

You indicated that doppler shift occurred without motion, when motion was clearly stated to be involved.

I have no idea what's supposed to compute. I calculate you have completely read past the word "motion"

--
I've read these sentences, completely ignoring the word motion.  Makes me kinda sea sick, like your argument, whatever that might be.
« Last Edit: 22/03/2016 01:52:13 by JoeBrown »
 

Offline timey

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Dense was perhaps too mild a term...

The speaker phase consists of the motion of a Doppler shift.  The light matches the motion of a Doppler shift, proven by the phase of the speaker cancelling out the frequency of the light.  However, the light emitter and the light receiver are NOT in motion.  Neither does the distance between the light emitter and the receiver contract or expand.  Therefore the Doppler shift 'motion' identified by the experiment is due to a Doppler shift in the light itself.

On the basis that the premiss of the experiment has clearly gone over your head, never mind the point I'm making.  Legs on you, an egg wouldn't crack if it fell out of your arse!

I look forward to a proper physicists comments...
 

Offline JoeBrown

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I look forward to a proper physicists comments...

I fear you are incorrect.  You misunderstand what others comprehend, then argue a misguided point.  That does not make for "proper" comment of physics or anything in general.  Your posts are intentionally rude and ignorantly inappropriate.

I'm dense for trying to explain.  For that I apologize.

--

If you truly wish to prove your erroneous point:

Quote
the gamma ray source moved

Kindly explain how that phrase does not equate to motion.



Perhaps it isn't the word "moved" that's causing the issue.

The gamma ray source, is the light source that moved.
« Last Edit: 22/03/2016 06:14:58 by JoeBrown »
 

Offline alancalverd

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Colin - they created a Doppler shift by vibrating the speaker at frequencies between 10 and 50 hertz to cancel out the redshift  blueshift frequencies.  The distance between the speaker and the receiver remained at 22.5 metres.

Either the speaker was vibrating, in which case the distance between source and detector was varying, or it wasn't vibrating and the distance was constant.

Is that enough "proper physics"?
 
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Offline Colin2B

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Colin - they created a Doppler shift by vibrating the speaker at frequencies between 10 and 50 hertz to cancel out the redshift  blueshift frequencies.  The distance between the speaker and the receiver remained at 22.5 metres.

Either the speaker was vibrating, in which case the distance between source and detector was varying, or it wasn't vibrating and the distance was constant.

Is that enough "proper physics"?
Thanks Alan, my point exactly.
 

Offline timey

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Is that enough "proper physics"?

Oh fer goodness sake!!!

My answer:  No, not really!

Yes - the Doppler shift is created by the vibration of the speaker...but the speaker isn't creating the gravitational shift in the light that the vibration of the speaker cancels out.  The speaker cone fabric is moving back and forth, as speakers do, to create vibration, but neither the light source or the receiver are in relative motion with respect to each other, such as a natural light source and receiver.  The distance between the light source and the receiver, apart from this vibration of the speaker is 'static'.

What the experiment shows is that there is a Doppler shift in the motion of light that is not associated with an expanding distance, or an acceleration of the speed of travel of the light source.

How can there be 'relative motion' in light over a distance that is constant when the speed of light is constant?
 

Offline timey

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I fear you are incorrect.  You misunderstand what others comprehend, then argue a misguided point.  That does not make for "proper" comment of physics or anything in general.  Your posts are intentionally rude and ignorantly inappropriate.

Actually I am not incorrect.  And I am not being rude.  If you want to accuse someone of being a weisenhiemer, and make idiotic comments about cosmological shift, and intimate that the tower itself suffered a gravitational shift, without actually attempting to understand what the poster is in fact talking about, then you are fair game as far as I'm concerned.  Short legs being an apt description!
 

Offline McQueen

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Here is the quote on the location of the gamma ray source:

  A solid sample containing iron (57Fe) emitting gamma rays was placed in the center of a loudspeaker cone which was placed near the roof of the building. Another sample containing 57Fe was placed in the basement.

Since the gamma ray source was placed in the centre of the loudspeaker cone, I assume that the gamma ray source was moving up and down with the vibration of the speaker, causing the distance over which the light had to travel to vary. But in which case where does the doppler shift come in ? In order to establish validity (i.e., to prove that the gravitational blue shift would act as was supposed resulting in non-absorption of the gamma ray) shouldn't a test have been carried out without the speaker, or is that taken for granted ?
 

Offline puppypower

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Consider, as an analogy for a photon, a boat traveling on the water. The boat is analogous to the particle, while the wake created by the boat is analogous to the wave aspect of the photon. If we had two tunnels under the bridge, the boat; particle, can only go through one tunnel at a time, while the wake, if spread out, can go through both tunnels.

The boat needs a constant supply of energy to keep moving at velocity V. This energy is needed to overcome friction between the boat and water. If the boat cuts the engines, the particle will slow, coast and then stop, while the wake will decay and finally stop. The speed of light is needed to maintain the wake/wave of the photon particles.

The question becomes how does a photon move through the medium of space-time and not slow down or speed up? What is the source of the propulsion energy?

If we assume the speed of light is the ground state of the universe, this implies all inertial references will be at higher potential. In this case, the constant speed of light would be connected to photons being constantly induced into the ground state ay C. The photons are constantly induced to higher potential; less than C by inertial. They cyclically drop back to the ground state; speed of light, while the energy differential is given off; motor that generates the wake/wave. 

One analogous way to look at this is connected to a house with a variety of electrical circuits, all using the same ground; earth. The ground is common to all the circuits and is at lower potential than any voltage/current configuration we may use. The potential difference between the inertial states, and the ground, is the energy potential used to drive the particle, which creates an analogous wake in space-time. This wake can become modified with the medium of space-time; red and blue shift, but the ground never changes, so the particles are always moving at C.
 

Offline marzosia2

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MOD EDIT: please keep your replies clear ,concise and relevant. Large, multiple posts of diagrams and no explanation will be treated as spam and removed.
« Last Edit: 22/03/2016 12:47:29 by Colin2B »
 

Offline timey

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Consider, as an analogy for a photon, a boat traveling on the water. The boat is analogous to the particle, while the wake created by the boat is analogous to the wave aspect of the photon. If we had two tunnels under the bridge, the boat; particle, can only go through one tunnel at a time, while the wake, if spread out, can go through both tunnels.

The boat needs a constant supply of energy to keep moving at velocity V. This energy is needed to overcome friction between the boat and water. If the boat cuts the engines, the particle will slow, coast and then stop, while the wake will decay and finally stop. The speed of light is needed to maintain the wake/wave of the photon particles.

The question becomes how does a photon move through the medium of space-time and not slow down or speed up? What is the source of the propulsion energy?

If we assume the speed of light is the ground state of the universe, this implies all inertial references will be at higher potential. In this case, the constant speed of light would be connected to photons being constantly induced into the ground state ay C. The photons are constantly induced to higher potential; less than C by inertial. They cyclically drop back to the ground state; speed of light, while the energy differential is given off; motor that generates the wake/wave. 

One analogous way to look at this is connected to a house with a variety of electrical circuits, all using the same ground; earth. The ground is common to all the circuits and is at lower potential than any voltage/current configuration we may use. The potential difference between the inertial states, and the ground, is the energy potential used to drive the particle, which creates an analogous wake in space-time. This wake can become modified with the medium of space-time; red and blue shift, but the ground never changes, so the particles are always moving at C.

Fair enough PuppyPower... BUT... in Pound Rebka """Where"" in space time does this wave LENGTH exist if the distance between light source and receiver is held 'static', with respect to each other, on the basis that the oscillations of the speaker are creating a Doppler shift that cancels out the gravitational shift of the light?
 

Offline jeffreyH

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Maybe a little mathematics would clear things up... or maybe not.
 

Offline timey

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https://en.m.wikipedia.org/wiki/Doppler_effect

Quoted from link above:
"For waves that propagate in a medium, such as sound waves, the velocity of the observer and of the source are relative to the medium in which the waves are transmitted. The total Doppler effect may therefore result from motion of the source, motion of the observer, or motion of the medium. Each of these effects is analyzed separately. For waves which do not require a medium, such as light or gravity in general relativity, only the relative difference in velocity between the observer and the source needs to be considered."

???
 

Offline PmbNEP

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Quote from: NeT-HeaD
I learned that light travels at the same given speed no matter if a light source is static in a fixed place or the source is moving towards you in that same space.

What is it that decelarates a photon that is emitted from an object moving toward you with say half the speed of light to come back to exactly the fixed speed of light.
That's called the invariance of the speed of light. It's the second postulate of special relativity. It's referred to as a postulate because nobody knows why the speed of light is independent of the speed of source.

However you can think of the reason as due to the properties of spacetime. When you change from one frame of reference, e.g. the frame in which the source is at rest, to one in which the source is moving then you're changing to a frame where, as determined from the rest frame, distances parallel to the motion of the source are shorter and where time intervals are shorter, both in exact proportions so that the speed of light has the same speed in all inertial frames.
 

Offline timey

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That's called the invariance of the speed of light. It's the second postulate of special relativity. It's referred to as a postulate because nobody knows why the speed of light is independent of the speed of source.

However you can think of the reason as due to the properties of spacetime. When you change from one frame of reference, e.g. the frame in which the source is at rest, to one in which the source is moving then you're changing to a frame where, as determined from the rest frame, distances parallel to the motion of the source are shorter and where time intervals are shorter, both in exact proportions so that the speed of light has the same speed in all inertial frames.

Very good Pmb!!!

Now could you please tell me how, within the Pound Rebka experiment, a Doppler shift can be identified within the gravitational shift of light when there is no relative motion between the light source and the receiver other than the oscillations of the speaker cone... these oscillations of the speaker cone being the method of measuring the fact of the Doppler shift within the gravitational shift of light via cancellation of redshift blueshift frequencies... ???
« Last Edit: 22/03/2016 15:41:00 by timey »
 

Offline JoeBrown

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Now could you please tell me how, within the Pound Rebka experiment, a Doppler shift can be identified within the gravitational shift of light when there is no relative motion between the light source and the receiver other than the oscillations of the speaker cone... these oscillations of the speaker cone being the method of measuring the fact of the Doppler shift within the gravitational shift of light via cancellation of redshift blueshift frequencies... ???

The Pound Rebka experiment used MOTION produced by a speaker cone.  The gamma ray light source was mounted on a MOVING speaker cone, which induced doppler shift.

The argument that doppler shift occurred without motion is flawed.  There was movement.  It didn't require a lot of movement.  Since the distance was in nearly constant flux.  They recorded the phase of the speaker movement to account for doppler shift.

--

Now for my timely wizenhimer remark:  DOH
 

Offline NeT-HeaD

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Guy's
All your chatter about dopler dazzles me but . . .
it seems to me that only aplies to interaction between fotons emmited in a row one after another when emmited from moving source or observed by moving source. i wanted to keep the question simple by observing just the ONE photon and its behaviour when emmited form a source.

But hey. it's still very enlightning to follow your guys arguements :)
.
 

Offline timey

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The Pound Rebka experiment used MOTION produced by a speaker cone.  The gamma ray light source was mounted on a MOVING speaker cone, which induced doppler shift.

The argument that doppler shift occurred without motion is flawed.  There was movement.  It didn't require a lot of movement.  Since the distance was in nearly constant flux.  They recorded the phase of the speaker movement to account for doppler shift.

--

Now for my timely wizenhimer remark:  DOH

Joe - Again you entirely miss even the 'intended' purpose of the experiment itself.

For the last time -  A Doppler shift was created by mounting the light source in the centre of the speaker cone.  It is sooo obvious that the gamma ray source will move as per the vibration of the speaker that I thought it unnecessary of mention.  It's the entire premiss of the experiment!  They created the measuring Doppler effect using hertz and the subsequent vibration of the speaker in order to cancel out the blueshift redshift frequencies of the light undergoing gravitational shift.

Now then - listen very carefully...  For a Doppler shift in vibration to cancel out the frequencies of blueshift redshift, the frequencies of blueshift redshift must resemble exactly the vibration of the Doppler shift.  Therefore the 'motion' you insist is occurring for the light source, this motion 'actually being' the motion of the speaker, is resembled exactly 'in' the gravitational shift.  Note:  The gravitational shift distance in this experiment is 'static'.  There is no relative motion between the 'distance' of the gravitational shift and observation 'with respect' to the gravitational field, and therefore no """obvious"""" relative motion for a Doppler shift for light in this experiment in the gravitational field.

Redshift is synonymous with expanding distances, and blueshift with contracting distances, as per space time considerations!!!  Yet, as per Pound Rebka, we see a Doppler shift in the gravitational shift of light, measured by a vibration, caused by motion of a speaker receiving between 10 and 50 hertz, over a constant distance in the gravitational field between a light source and receiver that are experiencing no relative motion between themselves, other than the forward and 'backward' motion of a speakers vibration acting upon the light source.

How can there be a Doppler shift in the gravitational shift of light over a constant distance when the speed of light is constant?  What exactly is causing the 'motion' of this Doppler shift found within the gravitational shift of light in this instance?

P.S Net-Head, I'm sorry if we have digressed.  I'm not entirely sure what your interest is in one photon, but I'm pretty sure knowing about what happens to light in general can only help :)
« Last Edit: 22/03/2016 18:43:22 by timey »
 

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