Jump to content


Photo
- - - - -

Light Speed, Photons And Redshift

Light speed

  • Please log in to reply
12 replies to this topic

#1 Mattzy

Mattzy

    Questioning

  • Members
  • PipPipPipPip
  • 116 posts

Posted 25 May 2019 - 07:29 PM

The photon wavelength of a receding star (moving away from the observer/receiver) has lengthened wavelength (redshift) at the observer/receiver. Light is emitted at light speed and - in this case red - wavelength, but the observer at the point of the photon arrival / detection can measure redshift. The speed also has to (seemingly but nonsensically) increase between the two points in order to make up for the speed of the source and arrive at light speed. How can photon wavelength and speed change between emission and arrival?

How can the Doppler effect apply when the speed of the arriving photon is the same as its emission speed? 

I hope this is a better phrased question than the last one which was a bit of a ramble.



#2 rhertz

rhertz

    Understanding

  • Members
  • PipPipPipPipPip
  • 303 posts

Posted 25 May 2019 - 09:39 PM

The photon wavelength of a receding star (moving away from the observer/receiver) has lengthened wavelength (redshift) at the observer/receiver. Light is emitted at light speed and - in this case red - wavelength, but the observer at the point of the photon arrival / detection can measure redshift. The speed also has to (seemingly but nonsensically) increase between the two points in order to make up for the speed of the source and arrive at light speed. How can photon wavelength and speed change between emission and arrival?

How can the Doppler effect apply when the speed of the arriving photon is the same as its emission speed? 

I hope this is a better phrased question than the last one which was a bit of a ramble.

 

Your confusion is understable, and is based on the clash of the classical theory of light being electromagnetic waves (Maxwell) and the quantum theory of light (Planck) as composed of "quantum of action", later called photons.

 

As Planck is the father of quantum physics, his explanation has to prevail in the explanation of the dual behavior of light: "Light travels as electromagnetic waves, but are emitted and absorpted by matter as quantum of action (photons)".

 

There has not been a better explanation in 119 years, since Planck's Law. There is not a theory that can unify classical and quantum theories, so scientists have to deal with this dual explanation (which has no solution at sight).

 

This is the best I can do for you now. You have to accomodate your doubts around the basic fact of the dual behavior of light using our mathematics.


Edited by rhertz, 25 May 2019 - 10:06 PM.

  • Mattzy likes this

#3 VictorMedvil

VictorMedvil

    The Human Shadow

  • Members
  • PipPipPipPipPipPipPip
  • 1342 posts

Posted 26 May 2019 - 12:25 AM

The photon wavelength of a receding star (moving away from the observer/receiver) has lengthened wavelength (redshift) at the observer/receiver. Light is emitted at light speed and - in this case red - wavelength, but the observer at the point of the photon arrival / detection can measure redshift. The speed also has to (seemingly but nonsensically) increase between the two points in order to make up for the speed of the source and arrive at light speed. How can photon wavelength and speed change between emission and arrival?

How can the Doppler effect apply when the speed of the arriving photon is the same as its emission speed? 

I hope this is a better phrased question than the last one which was a bit of a ramble.

 

Well to answer your question about redshift the wavelength of the light changes and when the wavelength of the photon changes it makes the photon redshift while the emission velocity is still C, the wavelength of the photon is different which causes this redshift even though the velocity of the photon doesn't change.

 

dopplerwaves.jpg

 

when the universe expands and a photon goes over the points expanded the photon itself expands too, which causes Redshift in photons traveling vast distance across the universe from a galaxy from moving objects which expanding too via Dark Energy Expansion of the universe.

 

Redshift-Galaxy.jpg


Edited by VictorMedvil, 26 May 2019 - 12:32 AM.

  • Mattzy likes this

#4 Mattzy

Mattzy

    Questioning

  • Members
  • PipPipPipPip
  • 116 posts

Posted 27 May 2019 - 12:44 AM

Many thanks Victor, I appreciate the effort and the diagrams! The problem of light arriving at the same speed regardless of the relative speed of its emitter is still unanswered though. I suspect the question probably goes to relativity. How can this change in frequency occur if light speed is constant? That is my question. How? 

rhertz is saying that the question is waiting for physics to come up with a unifying theory - I have no doubt that he is correct.

 

Re. the light speed question (without the redshift bit) - I will ask the question to the relativity guys and see what they say.

Thanks again Victor,

Mattzy



#5 VictorMedvil

VictorMedvil

    The Human Shadow

  • Members
  • PipPipPipPipPipPipPip
  • 1342 posts

Posted 27 May 2019 - 01:41 AM

Many thanks Victor, I appreciate the effort and the diagrams! The problem of light arriving at the same speed regardless of the relative speed of its emitter is still unanswered though. I suspect the question probably goes to relativity. How can this change in frequency occur if light speed is constant? That is my question. How? 

rhertz is saying that the question is waiting for physics to come up with a unifying theory - I have no doubt that he is correct.

 

Re. the light speed question (without the redshift bit) - I will ask the question to the relativity guys and see what they say.

Thanks again Victor,

Mattzy

 

The speed of light doesn't need to change as the size of the packets themselves change which would both arrive at the same time as the moving object does not dictate the velocity of light just as when you move a laser pointer next to a lamp the lamp's light doesn't arrive before the moving laser pointer's light. The Frequency doesn't change the wavelength does as described by the red-shift equations.

 

Relativistic-Redshift.gif

 

redshift.gif

 

Same Frequency different wavelength, In the thread(http://www.sciencefo...velocity/page-2) that is how I received a max velocity of a photon of C + VD or  C + H during photon emission from a Dark Energy expanding source that is moving toward you or C - VD or C - H from a Dark Energy expanding Source that is moving away from you, so possibly very slightly would the timing be different by a factor of VD or H which mind you would show up as the object being red-shifted or blue-shifted not a different velocity as light cannot travel faster than light.


Edited by VictorMedvil, 27 May 2019 - 01:55 AM.

  • Mattzy likes this

#6 Mattzy

Mattzy

    Questioning

  • Members
  • PipPipPipPip
  • 116 posts

Posted 28 May 2019 - 02:18 AM

Thanks Victor, OK, the lazer pointer is emitting a single wavelength at emission, many of the wavelengths coming from the lamp are different but they all travel at the same speed, agreed. But what's baffling is that there seems to be some mysterious force that determines the change in wavelength (stretches the packets) just for those packets that arrive at the detector! All the packets emitted from (say a star) in all directions are not redshifted. But those that hit the observer are! ,Packets traveling alongside those that hit the detector but don't hit the detector must be identical during their journey! .Am I missing something?

As rafcis is saying, the solution must only be in the concept of time - as realised by Einstein of course - and not understood by me!



#7 VictorMedvil

VictorMedvil

    The Human Shadow

  • Members
  • PipPipPipPipPipPipPip
  • 1342 posts

Posted 28 May 2019 - 02:35 AM

Thanks Victor, OK, the lazer pointer is emitting a single wavelength at emission, many of the wavelengths coming from the lamp are different but they all travel at the same speed, agreed. But what's baffling is that there seems to be some mysterious force that determines the change in wavelength (stretches the packets) just for those packets that arrive at the detector! All the packets emitted from (say a star) in all directions are not redshifted. But those that hit the observer are! ,Packets traveling alongside those that hit the detector but don't hit the detector must be identical during their journey! .Am I missing something?

As rafcis is saying, the solution must only be in the concept of time - as realised by Einstein of course - and not understood by me!

 

It depends on the direction of movement whether the packets are red-shifted or blue-shifted, it is not like there is some magical force that seems to shift it for the observer, The packets are shifted during transmission from the source due to the movement of the source, all the packets are indeed shifted by some amount, if the object is moving in a direction during transmission. Dark Energy or what is called expansion of the universe shifts the wavelength of the packets or the movement of the object. The observer can be in any direction from the source and depending on the direction of the observer from the moving object they will read different red-shifts or blue-shifts depending on the movement of the source from their position.


Edited by VictorMedvil, 28 May 2019 - 02:46 AM.


#8 Mattzy

Mattzy

    Questioning

  • Members
  • PipPipPipPip
  • 116 posts

Posted 28 May 2019 - 03:58 AM

Thanks Victor for going along with me. I'm not sure about "the object is moving in a direction during transmission". We can say that all stars are moving in relation to others and to all other objects, but light is being emitted in all directions from each star and the packets are emitted without change from any hemisphere with respect to any perceived directional movement.

The light always arrives at the detector/observer at the same speed (light). That's the conceptual problem. I think it must go to relativity.

I stand to be corrected but I don't think we can say that stars are moving through space with compressive waves of photons in front of them and stretched waves behind them. I think we can only talk about relativity - which I am admittedly trying to comprehend.

As I said, imagine two photons traveling in parallel from a star. They have identical characteristics. If one hits a detector moving towards the source and the other hits an detecor moving away from the source they will record different blue/red shifts and both arrive at the same speed. Can you tell me where on their journeys the wavelengths changed?

Best regards, Mattzy.



#9 VictorMedvil

VictorMedvil

    The Human Shadow

  • Members
  • PipPipPipPipPipPipPip
  • 1342 posts

Posted 28 May 2019 - 04:07 AM

Thanks Victor for going along with me. I'm not sure about "the object is moving in a direction during transmission". We can say that all stars are moving in relation to others and to all other objects, but light is being emitted in all directions from each star and the packets are emitted without change from any hemisphere with respect to any perceived directional movement.

The light always arrives at the detector/observer at the same speed (light). That's the conceptual problem. I think it must go to relativity.

I stand to be corrected but I don't think we can say that stars are moving through space with compressive waves of photons in front of them and stretched waves behind them. I think we can only talk about relativity - which I am admittedly trying to comprehend.

As I said, imagine two photons traveling in parallel from a star. They have identical characteristics. If one hits a detector moving towards the source and the other hits an detecor moving away from the source they will record different blue/red shifts and both arrive at the same speed. Can you tell me where on their journeys the wavelengths changed?

Best regards, Mattzy.

 

During the entire journey if it is Dark Energy doing it as it passes each point of space, if the object is moving at the beginning of the journey when it was released.


Edited by VictorMedvil, 28 May 2019 - 04:07 AM.


#10 exchemist

exchemist

    Creating

  • Members
  • PipPipPipPipPipPipPip
  • 2711 posts

Posted 28 May 2019 - 09:23 AM

Thanks Victor for going along with me. I'm not sure about "the object is moving in a direction during transmission". We can say that all stars are moving in relation to others and to all other objects, but light is being emitted in all directions from each star and the packets are emitted without change from any hemisphere with respect to any perceived directional movement.

The light always arrives at the detector/observer at the same speed (light). That's the conceptual problem. I think it must go to relativity.

I stand to be corrected but I don't think we can say that stars are moving through space with compressive waves of photons in front of them and stretched waves behind them. I think we can only talk about relativity - which I am admittedly trying to comprehend.

As I said, imagine two photons traveling in parallel from a star. They have identical characteristics. If one hits a detector moving towards the source and the other hits an detecor moving away from the source they will record different blue/red shifts and both arrive at the same speed. Can you tell me where on their journeys the wavelengths changed?

Best regards, Mattzy.

They don't change at any point on their journey, obviously. The wavelength just looks different to someone moving with the emitter, compared to someone moving with either of the detectors. And they will therefore also disagree about the energy and momentum carried by the light as well (as they also would if it were the Newtonian kinetic energy and momentum of a stream of classical particles).     


Edited by exchemist, 28 May 2019 - 09:23 AM.


#11 Mattzy

Mattzy

    Questioning

  • Members
  • PipPipPipPip
  • 116 posts

Posted 29 May 2019 - 01:18 AM

Thanks as always Victor. My question is still wanting an explanation. I think it's clear that there isn't a simple explanation - an perhaps no proof either!

Any of the facts that you state are the same facts that I began with in the opening question. I'm just trying to make sense of it all.

You agree that the wavelength does not change during the journey.  A spectrograph actually measures the redshift or blueshift at point of detection without any sense of perspective!

How can one possibly argue from the perspective of a person moving with an emitter that sees changes in wavelength? The eye can't do that. It does not seem scientific to state that the wavelength "just looks different" and "they will therefore disagree about energy". I recognise that you may be quoting from relativity theory but I was hoping for an explanation - I think you will agree that I will have to follow the suggested links and threads from rhertz and ralfcis and do some serious study.

Mattzy



#12 Mattzy

Mattzy

    Questioning

  • Members
  • PipPipPipPip
  • 116 posts

Posted 29 May 2019 - 03:17 AM

Well to answer your question about redshift the wavelength of the light changes and when the wavelength of the photon changes it makes the photon redshift while the emission velocity is still C, the wavelength of the photon is different which causes this redshift even though the velocity of the photon doesn't change.

 

dopplerwaves.jpg

 

when the universe expands and a photon goes over the points expanded the photon itself expands too, which causes Redshift in photons traveling vast distance across the universe from a galaxy from moving objects which expanding too via Dark Energy Expansion of the universe.

 

Redshift-Galaxy.jpg

Victor, I'm just going over what you sent me here. This is saying that there really is compressive and expansive waves in front of and behind stars that are moving seemingly outwards from some central point in the universe (the big bang). I see your point. But I don't think this applies in my question on relativity between given objects, unless redshift is only evident in cosmic expansion! Maybe I should post that question!

 I'm just trying to get to a basic understanding. I read that I will have to accept that measures of distance and time are motion dependent and that light has momentum and energy despite being massless. Ref. ralfcis on this site. I'm starting to get a headache! 



#13 VictorMedvil

VictorMedvil

    The Human Shadow

  • Members
  • PipPipPipPipPipPipPip
  • 1342 posts

Posted 31 May 2019 - 09:52 AM

They don't change at any point on their journey, obviously. The wavelength just looks different to someone moving with the emitter, compared to someone moving with either of the detectors. And they will therefore also disagree about the energy and momentum carried by the light as well (as they also would if it were the Newtonian kinetic energy and momentum of a stream of classical particles).     

 

Exchemist I wanted to say that the light obviously changes at points during its journey due to Dark Energy Expansion which is not just local to the source but effects the entire universe, even during its time in transit to the location Dark Energy slightly effects the Wavelength of the photon, The Longer the photon travels the more Dark Energy will effect the light particle, otherwise you wouldn't have Redshift from gravity sources either which as the light particle passes near large gravity sources is redshifted too passing near them, but if it is only the object moving then it only at the source is redshifted due to the Doppler effect. This is also why galaxies seem to be moving faster than light which aren't, because Dark Energy effects the photon in transit from a distant location.

 

https-blogs-images-forbes-com-startswith

 

red-shift-02.jpg

 

h0-gw-equation-v2-300x220.png

 

There is always a distance to take in account the larger the distance the more space the Hubble Constant takes effect on the photon which is why galaxies moving faster than light is bullshit.


Edited by VictorMedvil, 31 May 2019 - 10:08 AM.




Also tagged with one or more of these keywords: Light speed