The Doppler ‘Mess’

Most educated people would have heard about Doppler Effect as this is part of the science curriculum from secondary school level. A change in the observed frequency of a wave due to relative motion between the source and observer is called Doppler Effect.

We all experience this phenomenon in our everyday life. For example when a police siren approaches us, we hear a high pitched (high frequency) sound and as the siren passes away from us, we hear a low pitched sound even though the siren produces the sound at the same frequency throughout. Even more familiar is the scenario of an approaching train. Also one experiences the same effect by moving towards or away from a stationary sound source. This is true with any type of waves including water waves and light waves.

So different observers note a different frequency for the same wave depending upon their relative motion with respect to the source.

But what is so special about this?

Imagine that a projectile is moving at 10meters/sec with respect to its source. An observer moving at 2meters/sec with respect to the source in the same direction, will measure the velocity of the projectile as only 8meters/sec. So while the ‘original’ velocity of projectile is 10meters/sec, the observer measures that as 8meters/sec.

Shall we call this velocity shift or change in the observed velocity as Doppler Effect or Einstein Effect? Obviously the velocity of any particle or projectile will be different to different observers depending upon their reference frames and we know that all reference frames are equally valid and there is nothing special about the reference frame of the source. Scientific folk knows this very well.

But what is not realised by the scientific folk is that like a particle’s velocity, a wave’s frequency is relative and is dependent upon the reference frame of the observer. Frequency by definition is the number of waves crossing a reference point per second or the number of waves received by a detector per second. So it is what an observer measures of a wave.

We don’t consider the velocity of a projectile with respect to its source as its actual velocity. Similarly if a source releases a wave at some particular frequency, that frequency doesn’t become its ‘actual’ frequency –the said frequency is only true in the reference frame of the source. The medium’s particles will experience a different frequency for the same wave if the source and medium are in relative motion. Some other observer may experience an even different frequency depending upon his relative motion. Just like the case with velocity, no one’s measurement of a wave’s frequency can be sworn upon as absolute to call others’ as apparent.

Not only are frequency and velocity frame dependent, same is also the case with energy because energy is dependent upon frequency and velocity.

Disentangling the Doppler ‘Mess’

Like with so many things in physics, physicists have messed up with Doppler Effect to such an extent that disentangling the entire mess is not an easy task and demands a separate volume for itself.

We know that it is the relative motion between the source and the observer that results in Doppler shift. And we also know that motion is a relative thing, so whether it is the source or the observer who is moving, things should remain the same for the observer in both the scenarios. In other words the observer will not be able to tell whether he is moving towards the source or the source is moving towards him because from his perspective both scenarios are identical. Why I am stressing this point is that the implications are enormous- in case if the observer is able to tell who is actually moving by looking at a particular wave or projectile released by the source, then that obviously goes against the basic premise that motion is relative.

Imagine that a stationary source fires a projectile towards a stationary observer at 10meters/sec. The observer here obviously sees the projectile approaching him at velocity 10meters/sec. Now imagine the following two scenarios-

1) the source moving at 10meters/sec towards the observer as it fires the projectile

2) the observer moving towards the source at 10meters/sec as the source fires the projectile

From the observer’s perspective he is always stationary and hence he notes no difference in the above scenarios- according to him, the source is approaching him at 10meters/sec and the projectile at 20meters/sec. He sees no difference in what he experiences and he will not be able to tell who is actually moving.

But how come an observer experiences a wave differently depending upon who is moving? Physicists preach that when the observer moves towards the stationary source, he receives waves with same wavelength but at a faster velocity. But when it is the source that moves towards the stationary observer, he receives waves of shorter wavelength travelling at the same velocity as before. Moreover, apparently the observer experiences a different frequency shift in both the scenarios. So the same wave will be noted to have a different frequency, wavelength and velocity depending upon whether the observer himself moves towards the source or the source moves towards the observer.

And our physicists have devised different formulae to calculate the observed frequency, wavelength and velocity of a wave depending upon who is ‘actually’ moving.

http://hyperphysics.phy-astr.gsu.edu/hbase/sound/dopp.html

http://www.phys.uconn.edu/~gibson/Notes/Section6_3/Sec6_3.htm

http://physics.bu.edu/~redner/211-sp06/class19/class19_doppler.html

So motion is not relative! What an awful science we have been religiously listening to and carrying on in our minds. On one hand physicists preach that motion is relative and on the other hand they preach weird formulae which imply that motion is not relative.

Of course Nature is neither stupid nor weird (unlike our physicists’ understanding of Her) to contradict Her own basic rules. The reason for the apparent discrepancy is that our physicists have not been careful about the various reference frames while preaching the above- they mess up with frequency, wavelength and velocity of a wave under study by viewing each of them from different reference frames i.e. they talk about frequency from the source/observer’s frame, wavelength from medium’s perspective and velocity from which ever frame that makes them comfortable. Often they don’t specify from whose perspective something is being discussed and instead they toggle between source to medium to observer even without realising.

For example in the scenario of an observer moving towards a stationary source, when physicists say frequency increases but wavelength remains the same, they are talking about frequency in the observer’s frame but wavelength from the medium’s frame. The truth is that when an observer approaches a stationary source, not only does the frequency increase but also the wavelength decreases if one measures the same from the observer’s frame. But how to measure the wavelength from the observer’s frame?

Let us analyse that. The observer hears an increase in the sound frequency because his tympanic membrane or ear drum vibrates more rapidly as he receives more waves per second while he approaches the sound source. These vibrations from the ear drum get conducted across the middle ear via three tiny interconnected bony structures called ossicles and reach the inner ear and from there signals go to the brain in the form of nerve impulses.

Of course one need not bother too much about the anatomic details of middle ear or on how the signals get transmitted from the inner ear to the brain. The point of interest is that the vibrations from the ear drum also get transmitted to the air column in the middle ear. The sound waves that get transmitted in this air column vibrate at the same frequency as the ear drum (which is obviously higher than the frequency of source) and will have a shorter wavelength compared to the waves that reach the ear drum via the external air medium.

 

IMG_1649[1]

So in the reference frame of the observer (represented by the air column in his middle ear), not only does the frequency of the sound increase, but also its wavelength decreases. So obviously physicists are wrong when they say that wavelength doesn’t change in the scenario of a moving observer.

So as the observed frequency increases, the observed wavelength correspondingly decreases for the moving observer. That implies that the observed velocity must remain the same (because Velocity = Frequency x Wavelength). But then how come the observed velocity of the sound is more when the observer moves towards the sound source? Well, physicists have a totally wrong concept about wavelength so they can’t obviously be correct with the velocity formula that incorporates ‘their’ wavelength! (Much of our misunderstanding in wave motion comes from that of the wavelength. Things will surely become clear as we talk about the fundamentals of wave motion but until then we will imagine wavelength as a measure of spatial spread or dispersion of the energy pocket in the medium)

The truth is – the thing which should ‘sit’ by the side of the frequency in the above velocity formula should be amplitude and not wavelength. So it is the frequency and the amplitude which will decide the velocity of propagation of a wave. And as shown in the picture above, while there is an increase in the observed frequency, the amplitude remains the same (of course the particles will oscillate at a ‘higher level’ i.e. in an excited state and I will be discussing this in a separate section) and thus we can explain the ‘apparent’ increase in the observed velocity without making things contradict each other.

(Of course physicists almost never talk about amplitude when they preach Doppler Effect – http://www.physicsforums.com/showthread.php?t=509032. They only talk about change in frequency and change in wavelength and only occasionally about change in velocity).

To conclude for now, whether it is the source or the observer that moves, what the observer feels will remain the same i.e. the observed frequency, wavelength, velocity and amplitude will remain the same in either scenarios. And it makes sense because we believe that motion is relative. (But of course there is a catch here and I will discuss that elsewhere)

Doppler Effect and EM waves

Physicists believe that in case of mechanical waves (sound waves and water waves), motion of the source doesn’t alter the observed velocity of the waves- that is whether a source is moving or stationary, the waves it produces reach the observer at the same velocity. And when it comes to the scenario of a moving observer and stationary source they teach that a wave’s velocity changes depending upon the observer’s motion. That means an observer sees the waves reaching him at a faster velocity when he moves towards the source and sees the same approaching him slower when he moves away from the source.

Not surprisingly, they don’t extend the same rules to the EM waves because doing so would destroy their wonderful but stupid theory of relativity which preaches that speed of light is constant irrespective of the motion of the source or the observer. I can understand their logic here- A major stupidity can’t be challenged or overthrown by a minor stupidity. Obviously physicists are only half stupid when they talk about mechanical waves but become totally stupid when they start talking about light and EM waves.

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Comments

  • hywel  On January 4, 2015 at 4:27 am

    Dr Srinivasa
    if a duck moves forward in a pond, the waves in front of him are more bunched up than behind him.
    if you circle the pond (observer) nothing changes: from every angle the above applies.
    the observer is irrelevant.
    if he jump in the pond and stands in the in front of the oncoming duck, he will have an effect on the waves, if he comes into contact with them: they will compress even more.
    the duck’s motion affects the wave, so to does the position of the observer – she has to be subjective/ in contact.
    we are told that emr waves are similar to water waves – transverse.
    the doppler effect proves that that the motion of the emitter has an effect on the wave, therefore how can light be a far field/ free from source.
    is this a sound argument to you?
    and why is amplitude of emr waves hardly ever discussed/

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    • drgsrinivas  On January 17, 2015 at 5:53 pm

      Actually every phenomenon that we observe of light waves can be explained from your ‘duck in the pond’ analogy. People, whose minds have been spoilt by modern science obviously find that difficult. If someone teaches that light waves behave differently from water waves, it just shows one’s ignorance about both types of waves.

      Whenever scientists use the term ‘field’, it usually means that they really don’t know what actually happens there. The term just helps them to hide their ignorance and to pose highly intelligent. When you strike the surface of water in a pond, it will result in water currents in the immediate vicinity and the same will lead to water waves a little far away. My guess is that the mass movement of medium particles near the source gives the so called ‘near field’ effect while the far away waves give the ‘far field’ effect. So it is the same fundamental mechanism that produces both the fields.

      BTW, as I have explained elsewhere, all waves are longitudinal waves and there aren’t anything called transverse waves. What we observe as transverse waves on the surface of a pond simply represent the surface manifestation of the underlying longitudinal water waves. So the belief that light waves are transverse waves is a myth.

      Why don’t they talk about the amplitude of EM waves? Well, our scientists’ understanding of EM waves is already wacky and if they start talking about amplitude, that will literally make us vomit. So better they don’t talk about that!

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  • monsieur42  On January 7, 2015 at 7:51 am

    Now I just lost all respects for your scientific opinion if you are not able to understand why the motion of the source or the motion of the observer makes a big difference in the case of the propagation of a sound wave in air. And it does not mean that motion is not relative. Quite the contrary, motion is still relative. But in the case being debated here, one has to consider the presence of air. And one could not differentiate between a case where the observer is moving toward the source in still air of if the mass of air is moving toward the observer. The relativity here apply to the source, the observer and the mass of air, not just the source and the observer. By the way, you can still express your scientific opinion without using the qualifier of stupid for those who have a different view. However, I must admit that I came very close to using it for your scientific explanation of the sound wave propagation.

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  • monsieur42  On January 9, 2015 at 7:59 am

    And just to make sure that the correct interpretation is clear for everyone, I will add:
    -1st scenario: The observer is moving towards the source at speed Vo. The source is fixed and so is the mass of air relative to the source. Therefore air and source are fixed and the observer moves relative to the air and the source.

    -2nd scenario: To be a relativist valid scenario, all the relative motions must be reversed, including the motion relative to the air. Therefore in this 2nd scenario, the observer becomes fixed and it is the source AND the air that will move towards the observer at speed Vo.

    The perceived wave velocity, wave length and wave frequency will be the same for those 2 scenarios, both from the point of view of the source and from the point of view of the observer. Where the “weird” (but correct) physicists need to use different formulas leading to different results depending on the point of view of the source or the observer is for cases where the air is fixed in both scenarios. In the 2 scenarios you presented, the results need to be different because in one case the observer moves relative to the air but in the 2nd case the air does not move relative to the observer and therefore the 2 cases are effectively not an example of relative motion. No need to invoke wave amplitude and internal ear anatomy to see clear on this one.

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    • drgsrinivas  On January 13, 2015 at 10:14 am

      My apologies for the late reply and leaving your split mind unattended but it has been a busy time for me. If your religious scientific mind had been little more critical, it would have asked me about the ‘catch’ that I had mentioned and that would have saved you from exposing your split mindset.

      Let me confess that your scientific cult is not actually stupid. Rather you have a split mindset. On one side you have an ‘innate intelligent mind’, by virtue of which you are actually capable of intelligently analysing and interpreting things rationally. But on the other hand you have a more dominant ‘acquired stupid religious scientific mind’ which is conditioned and controlled by the mythical theories of your stupid science religion. By virtue of this, you are ‘protected’ from understanding anything that goes against the teachings of your stupid religion but you readily ‘understand’ and embrace all the weird and illogical conclusions made by your pastors. While the fact that you were able to point the out the ‘flaw’ in my above presentation proves your ‘innate’ intelligent mind, your failure to appreciate the fact that wave motion has been revamped in Toto and that many scientific myths (including your wave particle duality) have been demystified proves your ‘acquired’ stupid religious mind.

      It made me laugh when I read that you have lost respect in my scientific opinion- that suggests as if you had some respect in my scientific views before but which you had never conveyed. I wondered what made you to have respect in the first instance and what prevented you from expressing the same. How come you are only conveying your disrespect? But anyhow, true scientific minds don’t bother about being respected. It is respect that people paid to scientists which converted your science into a religion. Most people don’t feel comfortable disagreeing with someone whom they respect. May be it is not difficult for people with split minds like your crowd, but split minds are not the best minds to judge things and to teach correct science.

      It is not just difference of opinion that I have called as stupid. When I called some crowd stupid, I meant they are stupid by all means. For example, time dilation, particle travelling in multiple paths simultaneously, something present at multiple places at the same time, bending of spacetime, a cat that is both dead and alive etc.

      I was originally not that hostile towards the scientific community. I was much softer and polite when I first presented my arguments in science forums. But the crowd was so hostile, abusive and humiliating to me that it was not possible to continue any rational discussion. It was like talking about morals with religious extremists and terrorists! Is it possible for anybody to be polite towards such extremists for any length of time?

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    • drgsrinivas  On January 13, 2015 at 10:17 am

      Now coming to the ‘flaw’ that your split religious mind is proud of pointing out, and the ‘catch’ that I have mentioned but have forgotten to elaborate on (BTW, I am thankful to your split mind for reminding me of my unfinished job):-

      Yes, you are right in the sense that if we don’t ignore the existence of medium, the two scenarios become asymmetric. And this is exactly what I am going to make use of to argue against your long held scientific superstition that motion is relative. So according to me motion is not relative, though I have argued earlier in favour of your religious belief! (And this is what the ‘catch’ that I have mentioned above).

      As you have rightly pointed out, the scenario of an observer moving towards a stationary source (scenario 1) and the scenario of the source moving towards the stationary observer are not really symmetric (scenario 2). But that can’t be an argument to religiously swear by what your religious pastors preached and believe that the observed wavelength will be different between the two scenarios.

      Even in the scenario of the observer moving towards a stationary source, it is clearly shown by the middle ear analogy that the wavelength actually shortens if one looks at things carefully from the perspective of the observer. But it is understandable why you don’t get that point: as explained before, your acquired religious mind, which dominates your innate intelligent mind, ‘protects’ you from understanding anything that goes against the religious teachings of your stupid religion. So I don’t expect you to understand what I am going to discuss here. And don’t think that I am explaining all this to your ‘protected’ minds even if you feel so.

      Only spilt minds like you will imagine the medium as lying absolutely still whenever some object (whether it is the source or the observer) moves inside a medium. Really critical minds, unspoilt by your religion, will know that whenever some object moves inside a fluid medium, the object drags the fluid with it. In other words, the motion of a body (eg. source) will cause the medium to flow in the same direction (see foot note). So another body in the vicinity (observer) feels that both the source and the medium are moving towards it.

      And that is also what actually happens when the observer moves towards a stationary source. So the two scenarios are symmetrical in a sense i.e. whether it is the observer which moves towards a stationary observer or the source that moves towards the stationary observer, what the observer feels remains more or less the same. This is especially true when the source and the observer are close to each other (‘near field’).

      But when the observer and the source are far away from each other, the scenarios become less symmetrical, the reason being that the ‘currents’ induced by the moving source becomes attenuated as one moves away from the source especially in an ‘open’ environment. (Of course this attenuation is minimal in a closed environment i.e. when the source, medium and observer are inside a rigid cylinder). So a stationary observer may not sense fluid currents induced by the moving source if the latter is far away. But in the scenario of the observer himself moving towards the stationary source, the observer would always feel the relative motion of the medium irrespective of whether the source is far away or near. But whether it is the observer who moves or the source that moves, the observer would notice the same frequency shift and wavelength shift for the sound waves generated by the source as has been explained in the page above.

      Now imagine that the observer is only capable of sensing the sound waves but is insensitive to feel the currents in the medium. Obviously this observer will not be able to say whether he is moving towards the source or the source is moving towards him. So he might argue that motion is relative. But this is only because the observer is unable to sense the differences between the two scenarios.

      Similarly when a train passes by our stationary train, we get the illusion that we are moving. It may not be possible for us to tell which train is actually moving. And from that we might argue that motion is relative. Again that is because of our inability to sense the differences in the air winds between the two scenarios. Obviously one’s inabilities can’t be argued as laws of Nature (unlike what your quantum pastors do).

      Same is the case when two objects in outer space move relative to one another. Each object will notice the same frequency shift in the light signals from the other object irrespective of who actually moves. But the two scenarios are not really identical: the object which actually moves feels more resistance from the Ether medium than the stationary object. Hence it is wrong to propose that motion is relative.

      I know that your stupid religious scientific crowd don’t believe in Ether and hence may continue to chant that motion is relative. But I can show you that motion is not relative using your own religious myths viz. microwave background radiation and gravitational waves.

      Imagine that we are in the outer space and are looking at a distant star. Let’s now see how we could differentiate between the following two scenarios and tell who is actually moving.

      Scenario 1: We are stationary and the star moves towards us: We will obviously notice an increase in the frequency of the light coming from the star. Also, if we have a ‘radio-telescope’ with us, we will be able to sense the ‘gravitational waves’ generated by the motion of the star.

      Scenario 2: We are moving towards the star which is stationary: Again we will note an increase in the frequency of the light from the star. This time, our radio- telescope will not pick up any gravitational waves. Rather we record little blue shifting in the cosmic microwave background radiation. In the first scenario, this blue shifting of CMBR doesn’t occur.

      I know it is beyond your religious ‘scientific’ mind to grasp why that happens! But have a try!

      Note: The same phenomenon of fluid drag explains the so called gravitational waves, space contraction myth etc preached in your religion and also why the velocity of a wave, whether it is a water wave or light wave or a sound wave, remains unaltered by motion of the source or the observer, but I don’t want to burden your religious mind with all that now!

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  • Grandon13  On January 14, 2015 at 6:51 am

    Hi, I just stumbled upon your site and I’m very pleased to find some people on the rational side. I found this site looking for some exhaustive refutation of Jean-Pierre Garnier Malet’s theories, but so far I have found NOTHING. Some friends told me about him and encouraged me to find out about his theories as they are “scientifically sound” according to them. Have you heard about him?
    Thanks in advance for your time.

    Like

    • drgsrinivas  On January 15, 2015 at 6:58 pm

      Sorry, I am hearing that for the first time.
      Just googled- My first impression is that his doubling theory makes little sense to me.

      Like

  • Alan VanMeter  On October 22, 2017 at 11:15 pm

    Hello sir. I just was hoping to get your take on an observation I had experienced concerning the Doppler effect of waves. I was in the desert at a gas station on a very windy day, and then heard some motor cycles which sounded by Doppler effect to be headed away from me. I looked in the direction the sound appeared to be originating from, but saw nothing. Then two motor cycles came riding past from the opposite direction, and it befuddled me, as no matter which direction they rode, they sounded to be heading away from me. I know the wind was causing this strange effect, as it was very windy. Later I remembered this as I was thinking of Red Shift, and wondered if space-time were perhaps moving like a fluid, like the wind, perhaps it may cause a similar effect with respect to light waves. It also made sense to me concerning Olber’s paradox. I am not a scientist, just a curious person.

    Like

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