PAGE 1 Churinga Publishing v
Books and publications on the interaction of systems in real time by A. C. Sturt
Economics, politics, science, archaeology. Page uploaded 21 March 2002. Minor edit 1 July 2004.

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Light and Mass
III. The Doppler Effect - Sound and Light

by A. C. Sturt cont.

PART III. The Doppler Effect - Sound and Light

2. The Analogy of Light with Sound

3. Wavelength change at the Locus of the Atom

4. Wavelength Shift at the Observer

5. Wavelength Shift in Transit - the Hypothesis of the Universal Medium

6. Harmonic Effects

7. the Nature of the Universal Medium

8. Microwave Radiation

9. Wavelength Shift from Rotation

10. Conclusions

PART I. Universal Units

PART II. Atomic Clocks on the Move

The principle of the Doppler effect is conventionally applied to light in the same way as to sound, in spite of the differences of the two phenomena. Light from stars is thought to have a redshift because they are moving away from Earth, and this in some way stretches the wavelength. But light has the unique characteristics that it propagates through empty space, its velocity is constant and in the visible range it relates to energy changes within individual atoms. This paper suggests that these should lead to a fundamentally different interpretation.

1. Sound Relationships

Sound is propagated through a continuous medium, for example air, and so it is a bulk property. Suppose sound from a source S located at A propagates through the air with velocity c in the direction of B, and an Observer observes what is happening from a position somewhere between them, as below:

Location B
at Location A Observer

Suppose A, the Observer and B are stationary with respect to the medium and therefore each other. The sound waves from S pass the Observer with a velocity c and arrive at B with a velocity c, all relative to the medium. If the sound wave leaves A with a wavelength lambda, the wavelength stays at lambda throughout.

If the source S now moves towards the Observer and B with a velocity v, the Observer sees that as soon as it emits a sound wave, S moves towards the wavecrest with velocity v. When it emits the next wave, S will be only a distance lambda . (c - v) / c away from the previous wavecrest, and so the wavelength will be reduced by, say, delta lambda. As S passes the Observer, the situation is reversed. The wavelength of sound coming back to the observer is increased as the source moves away from the wavecrest which it has just emitted.

The reduced wavelength (lambda - delta lambda) persists all the way to B, because B is in the direction of the velocity v. In fact the velocity of the source S has been defined in terms of the medium and the direction of B. But the sound will still arrive at B at velocity c. It will not be possible to determine the original wavelength lambda from the sound which arrives at B, because that information is not contained within the wavelength observed at B. Extrapolation back to the wavelength at the source S requires additional information.

The most that can be determined at B is the wavelength as it arrives. What interpretation is put on the wavelength at B depends on the nature of the detector at B.

This is all more readily expressed in equations than in words, but equations may gloss over some of the relationships which are necessary to the method.


unique properties of light

propagation of sound through air

ŠA.C.Sturt 2002

continued on Page 10
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