# Thread: Doppler Effect vs. Special Relativity

1. In 1842 Christian Doppler proposed that frequency of waves change for an Observer moving relative to Source. In case of light: f = f’(1+v/c)
f= frequency received by Observer
f’= frequency emitted by Source
v = relative velocity of Source and Observer

Doppler focused on frequency and didn’t take into consideration the cause of it, namely the change of the Time Frames of events relating to Observer moving relative to Source.

Real Doppler Effect depends on 4 factors: 1- Speed of waves mediating events in space; 2- Relative speed of Source in space; 3- Relative speed of Observer in space; 4 The length of Time Frame of the observed event (determines the angle of field Alfa for Observer for trigonometric calculations).

The Time frames of events emitted by Source change for the Observer by the next formula:
T = T’+ t – t’ = T’ + (x – x’)/c
- where T= Perceived Time frame of Observer for received event;
T’= Real Time frame of Source for emitted event
t’ = time needed by the first wave of event to reach observer;
t = time needed by the last wave of event to reach observer;
x and x’ = the distances covered by the last and first waves
D = T/T’ - where D = Real Doppler factor;

Trigonometric form for stationary Observer: D = 1 + Sv/c
-where ’S’ Sine factor = (sinGamma-sinBeta)/sinAlfa
v= relative velocity of Source and Observer; c = velocity of light
Beta = inner angle of movement of Source (- Theta used in classic Doppler effect);
Alfa= angle of event seen by Observer; Gamma=180-Alfa-Beta (see Doppler Effect vs. Special Relativity)
lim S = cosBeta; lim D = 1 + cosBeta v/c

Identities: lim (sinGamma-sinBeta)/sinA = cos Beta = cos(-Teta);
D = factor of Classic Doppler effect when Beta = 180 or 0 degree;
Because T’ cannot be zero the result of Classic Doppler effect is false when Source nears Observer in an angle.
D=Lorentz’s factor when Gamma=90 degree and Observer moves away from stationary Source and T=t;
D = 1/Lorentz’s factor when Beta = 90 degree and Source moves toward stationary Observer, and T ’ = t’

Identity Angle

When cosBeta = v’T’/2tc then Beta = Gamma S=0 and D = 1. At this angle T’=T .
In Real Doppler Effect the Identity Angle depends on Time frame, velocity of waves, velocity of Source and distance, while Classic Doppler Effect fix this angle as 90 degree because cos90 = 0.

The equations of Real Doppler Effect:
T =DT’ - where T= Time Frame of event measured by Observer; T’= Emitted Time Frame of Source
f = f’/D - where f= average frequency measured by Observer; f’=frequency emitted by Source
v = v’/D -where v = average speed of Source measured by Observer
l = Dl’ - where l = average wavelength measured by Observer, l’= wavelength measured by Source
L = L’+ v (t’ - t) - where L= length of Source measured by Observer in the direction of movement
L’= length of Source measured by Source;
t’- t = time difference of waves reaching Observer started from the front and from the back part of Source.

Main Differences to Special Relativity (SR)

Real Doppler Effect transforms events mediated by waves to the perception of Observers and to the realities of Sources, or calculates relative velocities by analysing frequency changes, while Special Relativity transforms the realities of Observers and Sources to the speed of light to keep it constant.

According Special Relativity the maximum reachable relative velocity is the constant speed of light.
Doppler effect doesn’t set a limit, even calculates by higher relative velocities when converting time or frequencies e.g. when observer moves toward Source: D= c/(v+c); T=DT’; f= f’/D = f’(c+v)/c.

Sandor Fofai  2.

3. Originally Posted by Sandor Fofai In 1842 Christian Doppler proposed that frequency of waves change for an Observer moving relative to Source.{long dissertation excised}

Main Differences to Special Relativity (SR)

RDE transforms events transmitted by waves to the realities of Observers and Sources, while SR transform the realities to the speed of light.
No, SR does not do that. Why do you think so?

According Special Relativity the maximum reachable velocity is the constant speed of light.
Close enough.

Real Doppler effect doesnt set a limit.
Then it fails to conform to experimental observations. This failure would seem to be a rather fatal problem for RDE.

Theoretically if an object would break light barrier, it would pop up abruptly in the space in a strong flash, than its doubled images would fast disappear in two opposite direction. Because the fastest forces are electromagnetic waves and they cannot accelerate objects over their own speed, this phenomenon has however little chance to happen.

Sandor Fofai
The "little chance" is rather due to the fact that SR holds, rather than RDE.

Along with your passionate embrace of push gravity, you seem to be fond of ideas that "make sense" to you personally, without regard to the vast body of experimental evidence aligned against your ideas.  4. In this article I tried to show that the factor of classic Doppler effect cannot give correct solution when there is an angle of movement of Source toward Observer, because this case the frequency changes continuously, so the time-length of the examined effect have a role which can be expressed by Time Frames. By transforming time Doppler Effect contradict Special Relativity not because my passion but because two different law cannot coexist for long.

SR is based on the experiment of Michelson-Morley where they tried to detect the effect of movement on light, but didn’t moved their apparatus. (Sagnac moved his apparatus and find the difference)
Yes, I’m skeptical about the result of their experiment and the theory built on it, and I’m not alone.
“Observational data that is taken as evidence for dark energy and dark matter could indicate the need for new physics” – Wikipedia
A century went, but the “vast body of experimental evidence” are still missing. Answers given by Special Relativity are not enough, alternative theories are labeled pseudo – that’s the trap of 22.  5. Originally Posted by Sandor Fofai In this article I tried to show that the factor of classic Doppler effect cannot give correct solution when there is an angle of movement of Source toward Observer, because this case the frequency changes continuously, so the time-length of the examined effect have a role which can be expressed by Time Frames. By transforming time Doppler Effect contradict Special Relativity not because my passion but because two different law cannot coexist for long.
No.

SR is based on the experiment of Michelson-Morley where they tried to detect the effect of movement on light, but didn’t moved their apparatus.
No. Your knowledge of the literature is as if you hadn't read anything written about SR in the last 100 years. I suggest you repair that deficiency first. See, e.g., http://en.wikipedia.org/wiki/Tests_o...ial_relativity for a start. You cannot hope to overturn a theory you clearly do not even understand.

Yes, I’m skeptical about the result of their experiment and the theory built on it, and I’m not alone.
That's fine, but also empty. Anyone can state that they are skeptical of anything. So what? It's a useless position unless one can articulate a reason. Thus far, you have failed rather spectacularly to make your case.

“Observational data that is taken as evidence for dark energy and dark matter could indicate the need for new physics” – Wikipedia
Argument by quotation is regarded as feeble. I could just as well quote Sagan: "They also laughed at Bozo the Clown." Aside from proving that we've both mastered the art of cut-and-paste, not much of relevance has been established.

A century went, but the “vast body of experimental evidence” are still missing. Answers given by Special Relativity are not enough, alternative theories are labeled pseudo – that’s the trap of 22.
You don't seem to be aware of that vast body of experimental evidence, yet you feel confident in asserting that something is missing. Be specific. Handwaving only makes you seem like a smug poser. That doesn't get you far here, in a science forum.  6. First off, the classic Doppler effect relies on a medium through which the medium is propagated. Since light does not use a medium, it does not hold for light.

Instead, we use the Relativistic Doppler effect equation. where v is positive when the source is receding.

And even this is just the special case of the formula where theta is the angle between the direction the observer sees the light coming from and the direction the source is from the observer when the light was emitted.

The first equation is what the second equation reduces to when theta equals 0.

So, we do not use the classical form of Doppler shift when dealing with light, and the general form we do use does take into account differences between the angle of the incoming light and the path of the source.  7. Originally Posted by Janus First off, the classic Doppler effect relies on a medium through which the medium is propagated. Since light does not use a medium, it does not hold for light.

Instead, we use the Relativistic Doppler effect equation. .
You may want to correct the above to read:   8. Originally Posted by Howard Roark  Originally Posted by Janus First off, the classic Doppler effect relies on a medium through which the medium is propagated. Since light does not use a medium, it does not hold for light.

Instead, we use the Relativistic Doppler effect equation. .
You may want to correct the above to read: Thanks. Edited.  9. -  10. -  11. Originally Posted by Janus  Originally Posted by Howard Roark  Originally Posted by Janus First off, the classic Doppler effect relies on a medium through which the medium is propagated. Since light does not use a medium, it does not hold for light.

Instead, we use the Relativistic Doppler effect equation. .
You may want to correct the above to read: Thanks. Edited.
You are welcome. (but the edit is still incorrect). Now, it is correct :-)  12. -  13. -  Bookmarks
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