I need help with Doppler's effect understanding

[frostysh]

11 hours ago, Mordred said:

In Galilean relativity the primary differences is that the speed of light had no speed limit. Time itself is absolute. The principle of invariance however remains the same. The definition of an inertial frame is also identical.

We know today that Newtonian/ Galilean physics is wrong on two major points. The speed of light is limited and so is all information exchange by the constant c.

We also know that time is not absolute and that the absolute frame does not exist. An Eather has medium like properties that if it did exist would cause directional drag aka the one way speed of light tests. All tests on c show there is no directional difference in the speed of light between two observers.

In Lorentz transformations you have both length contraction and time dilation however in each reference frame the laws of physics such as Pythagoras theorem remain the same (per the reference frame) this is the same within the reference frame for Galilean relativity. 

 Conjecturing some medium or Eather is very commonly done by far more posters than you realize you'd be amazed how often it crops up.

Now two observers that see different densities do apply in gravitational redshift but why would the two observers see different densities in non relativistic Doppler ?

Here is the details for the Michelson Morley test for an Eather

https://www.google.com/url?sa=t&source=web&rct=j&url=https://faculty.etsu.edu/gardnerr/5310/5310pdf/dg2-2.pdf&ved=2ahUKEwjWksX-tuLjAhUFj54KHVpeBC0QFjAAegQIAhAB&usg=AOvVaw3fVRCzr82fWGmyXI9J2AD3

Ok let's try this we will stick to sound waves for now and show why  moving relative to the wavefronts changes the wavelength.

First you have a wave that emits a wavelength λ this wavelength emits a continuous sequence of wavefronts given at a rate of 1ν which is it's given frequency so let's say the source is moving slowly towards you the observer at speed μ now each time the source transmits it's signal it has moved a distance μt this changes the distance of the frequency wavefronts from 

1ν

Which now becomes 

λ=cv−μt=cν−μν=cν(1−β)

It's apparent frequency becomes

ν´=csν=ν1−β

There you have it the source is moving so each time it emits a frequency wave pulse its position is different thus changing the frequency. You do not require any medium to get this effect nor does this in any way violate Galilean relativity (however sound waves itself required a medium) the effect itself doesn't require a medium  if the density of the two emitters location differs from the observer location the speed of sound will vary on route and you will need to account for that seperately.

However the generalized Doppler effect is based on the medium density being the same between the observer and emitter and the only cause is from a moving source.

In essence it is simply addition of velocities for classical physics.

 

1) The principe of invariance is not the same, invariant related to Galilean transformation is not the same as invariant related to Lorentz's transformation. At least I heard so, but my poor present knowledge of classical mechanics, and much, much more poor knowledge of relativistic kinematics. It's remarkably that formulas Doppler effect derived from Galilean transformation (as I have showed up above) is not the same as formula derived from Lorentz's transformation when speed is much more less the speed of light propagation in vacuum. If you think that invariances is the same and you can prove it?

2) Relativistic and Classical difference major is not in the speed of light finitiality, I think you are mistaken again. It's laying in two different groups of transformation Galilean and Lorentz's for an example. The branch of mathematics which is describing this difference called 'The Group Theory'. At least I have heard it in my University when study long ago.

3) I think you are not clearly understanding the formulas which you are typing (but of course I can be wrong), especially you are mistaken about physical meanings of that. It is a many works and articles in which is explained what I am trying to understand (and where you are totally mistaken, as I think), but the problem is me is in rural area, no job with money and I have no time to study so difficult to me subject for now, but I can provide you with some (there is actually a lot of) articles which can help, this one from google but in the large books is too lot on subject typed — On The Galilean and Lorentz Transformations (2013). (So horribly small pictures in the article.) Also there is some 'paradoxes' appears in relativistic Doppler Effect, and it cannot be so trivially described that you have tried.

P. S. HOW to enlarge formulas on this forum? Like \large in Latex or something? It's looks not very cool and too small... Also in quotes is not good formulas representing, how choose so awful mathematics support for the scientific forum? *facepalm*

Edited August 2, 2019 by frostysh

[Mordred]

I suggest you Google Galilean invariance. Which states the laws of physics are the same in all reference frames. 

That is identical to premise 1 of the Lorentz transforms.

Secondly those formulas I gave are not in error. Doppler shift simply applies velocity addition to moving sources when dealing with wave front pulses.

Either the source or observer is moving so you must account for the movement on pulse arrival  times.

[frostysh]

5 hours ago, Mordred said:

I suggest you Google Galilean invariance. Which states the laws of physics are the same in all reference frames. 

That is identical to premise 1 of the Lorentz transforms.

Secondly those formulas I gave are not in error. Doppler shift simply applies velocity addition to moving sources when dealing with wave front pulses.

Either the source or observer is moving so you must account for the movement on pulse arrival  times.

I am sorry, but my mission, at least for now, is not explaining fundamentals of classical and relativistic kinematics on science-popular level like a 'computer program' to the peoples that can only understand computer programs, but to understand some of this very fundamentals by myself. So corresponding to the present goal of my mission, I will not follow your suggestion and better will search the answer in some other places. But anyway, thank you, at least I have remind to myself some things when explaining it to you and to the forum users. 

Edited August 2, 2019 by frostysh

[Amazing Random]

Try to think sound as waves and each wave is a circle . Ok let's take a source of sound or sound waves . The source emmits sound waves at a certain frequency . Ok? When the source is immobile the receiver receives the sound waves with the same frequency emmited from the source.When the source is moving however the distance between two waves changes (due to the moving source) so since the distance between the waves is increased the next wave takes more time to be arrived so the frequency received by the receiver is changed.

[Mordred]

Mathematically by ratio it's much the same as moving toward a moving train. Think of the beginning and end of the individual train cars. If your approaching each other the rate each car goes by will be increased.

Now replace the train with a signal then look at the leading edge and falling edge.

Both scenarios use vector addition rules 

[George Dowell]

On 8/2/2019 at 12:32 PM, Amazing Random said:

Try to think sound as waves and each wave is a circle . Ok let's take a source of sound or sound waves . The source emmits sound waves at a certain frequency . Ok? When the source is immobile the receiver receives the sound waves with the same frequency emmited from the source.When the source is moving however the distance between two waves changes (due to the moving source) so since the distance between the waves is increased the next wave takes more time to be arrived so the frequency received by the receiver is changed.

If I may add a practical example to verify the quoted above:

As a Ham Radio operator, one of the many aspects that fascinated me was E.M.E.- That is a radio path which originates on the earth (me) travels to the moon, is reflected, a portion of that comes back to the earth. This happens on 144 MHz.

When I listed to my own radio signal coming back, 2.7 +/- seconds later, it is on a different frequency at my location than the original frequency. The difference frequency is constantly changing due to the constant orbital motion, and will be above or below the transmitted frequency depending is the moon is advancing or receding relative to my position. We use this path to 2-way communicate with other radio stations scattered all over the world. This is Doppler shift and shows both + and - , or in light would be blue and red shift.

The other earthly example is Police Speed Radar- they used continuous transmission 10 GHz when I worked on them, the signal hit a car and bounced back to the duplex antenna at the transmitter, where a tiny portion of the transmitting signal was mixed with the received signal, yielding a difference frequency equal to the Doppler shift caused by the vehicles velocity. This was in the audio range and could be accurately counted, the frequency being displayed in MPH for the operator to see.

Both these are relativistic examples, and I believe the formulas  some mentors mentioned were the same ones we applied to radio frequency Doppler shift.

 

Geo>K0FF

K0EME