Difference between relativistic doppler effect and classical one?

In summary, the conversation discusses the differences between Galilean Relativity (GR) and Einstein Relativity (ER) in describing a phenomenon, with a focus on the mathematical expressions for the Doppler effect. The question is raised whether the same mathematical approach used for describing sound can be applied to light, and whether there is any physical evidence that the Doppler effect for light is different from that of sound. The conversation also mentions the observation of transverse doppler in light, which is not accounted for in classic doppler theory.
  • #1
lightconstant
8
0
When I ask for differences I am not meaning mathematical ones since that it is obvious:
We have a phenomenon p, p can be described by Galilean Relativity (GR)
and by Einsten Relativity (ER).
ER(p)!=GR(p)
The math expression that describes this phenomenon is different.
Then the doppler effect will have another mathematical expression
ER(dp)!=GR(p)
Maybe someone wants to say that GR is like a subset of ER for small velocities in reality It is not It looks similar but It is not, well let us get to the point.
Sound can be described by the classical doppler effect GR(d_e) by addition and substration of velocities though we know the velocity is constant due to the medium.
My question can we do the same with light? can we explain it mathematically with the addition of c+v, c-v?
I hope I have expressed myself clearly, I know c is a constant and We can not add velocities, what am I asking is if by using galilean relativity the doppler effect of light can be explained adding velocities, after all sound has a constant velocity and we add it.
Let us put it another way, is there any physical not mathematical proof, evidence, observation, meaning... that the doppler effect of light is different than the sound one?
Or Is It just the way It is expressed mathematically.
Because I see this applet:
http://webphysics.davidson.edu/applets/applets.html
and the phenomenon looks the same.
 
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  • #2
lightconstant said:
When I ask for differences I am not meaning mathematical ones since that it is obvious:
We have a phenomenon p, p can be described by Galilean Relativity (GR)
and by Einsten Relativity (ER).
ER(p)!=GR(p)
The math expression that describes this phenomenon is different.
Then the doppler effect will have another mathematical expression
ER(dp)!=GR(p)
Maybe someone wants to say that GR is like a subset of ER for small velocities in reality It is not It looks similar but It is not, well let us get to the point.
Sound can be described by the classical doppler effect GR(d_e) by addition and substration of velocities though we know the velocity is constant due to the medium.
My question can we do the same with light? can we explain it mathematically with the addition of c+v, c-v?
I hope I have expressed myself clearly, I know c is a constant and We can not add velocities, what am I asking is if by using galilean relativity the doppler effect of light can be explained adding velocities, after all sound has a constant velocity and we add it.
Let us put it another way, is there any physical not mathematical proof, evidence, observation, meaning... that the doppler effect of light is different than the sound one?
Or Is It just the way It is expressed mathematically.
Because I see this applet:
http://webphysics.davidson.edu/applets/applets.html
and the phenomenon looks the same.

Much of what you say is not comprehensible. Classic doppler has no provision for transverse doppler (change in frequency of light emitted by a moving source exactly perpendicular to the receiver). This has been observed with light.

See: http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html#Tests_of_time_dilation
 
  • #3
Thank you PAllen I saw that somewhere but did not know it was only light related,
I guess the phenomenon It is not the same since one has transverse doppler and the other one does not.
Let me look at it and see what is about.
 

What is the relativistic Doppler effect?

The relativistic Doppler effect is a phenomenon in which the observed frequency of a wave, such as light or sound, is affected by the relative motion between the source of the wave and the observer. It takes into account the effects of special relativity, which states that the laws of physics are the same for all observers in uniform motion.

What is the classical Doppler effect?

The classical Doppler effect is a phenomenon in which the observed frequency of a wave is affected by the relative motion between the source of the wave and the observer. It is based on the principles of classical mechanics and does not take into account the effects of special relativity.

How do the formulas for relativistic and classical Doppler effect differ?

The formula for the relativistic Doppler effect includes a term for the relative velocity between the source and observer, as well as a factor for the speed of light. In contrast, the formula for the classical Doppler effect only includes a term for the relative velocity.

What are some examples of the relativistic Doppler effect?

Some examples of the relativistic Doppler effect include the redshift of light from distant galaxies, the blue shift of light from objects moving towards us, and the time dilation of clocks in motion. It also applies to other types of waves, such as sound waves.

Why is the relativistic Doppler effect important in modern physics?

The relativistic Doppler effect is important in modern physics because it helps us understand and predict the behavior of waves in situations involving high speeds or strong gravitational fields. It is a crucial factor in many theories, such as general relativity and the Big Bang theory.

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