Doppler shift

 

Consider a star (or any light source) that is moving at some velocity through the surrounding space. The time gradient (TG) associated with the star determines the forward speed of the emitted light relative to the star. The TG moves with the star, and the light expands from the star forming a sphere of light with the star at its center. When the light leaves the star’s TG and enters the TG of the surrounding space[1], the light will continue expanding as a sphere, but the star will no longer be centered within that sphere. The star will move off center in the direction of the star’s velocity. The space’s TG will then determine the forward speed of the light. Thus the light accelerates when leaving a moving body in a direction opposite to the velocity (red shift), and decelerates when leaving in the same direction as the velocity (blue shift). The extent of this is dependent on the star’s velocity and the angle of exit with respect to the velocity vector. A reverse acceleration or deceleration occurs as the light reaches the observer’s location if that location is also in motion. While the emitting star’s TG controls the light speed, the increase in velocity as it travels outward from the star can be considered as a gravitational shift. Any change in forward speed as a result of the transition from the star’s TG to the space’s TG and then to the observer’s TG is usually referred to as a ‘Doppler shift’. Thus the ‘Doppler shift’ occurs as a result of the effect of time gradients on the speed of a photon. There is an inverse gravitational shift as the light travels through the time gradient at the observer’s location to the observer.

 

The usual explanation for the ‘Doppler shift’ with light would seem to relate the shift to the rate at which photons reach the detecting apparatus, which is highly unlikely[2]. Light is emitted when a single transition occurs such as an electron going from one orbital state to another, and an energy quantum, or photon, is emitted. The properties of that photon would not seem to depend upon when any other photons are emitted. This is different than the production of sound or anything else that depends upon a continuous oscillation. In that case, the movement of the emitter toward or away from an observer would alter the frequency that is detected by the observer. This is unlikely to occur with photons, which are unlikely to travel from the emitter to the detector in a continuous wave generated by a continuous oscillation at the emitter. See illustration 2 at the end of this section. Actually, the fact that wavelength shifts are detected would appear to be a persuasive observational indication that the speed of light is variable, at least for higher energy radiation. The situation with the lower energy radiation is considered in the section Implications – Radar.

 

The consideration of light in terms of continuous waves provides a means of mathematically describing many aspects of the behavior of light. But viewing the physical nature of light as continuous waves may not be justified. For instance, the diffraction of light by a grating is generally described in terms of continuous waves that are all in phase passing through the grating. By considering the interference effects on the light at different angles after passing through the grating, the grating formula can be easily derived. On the other hand, experiments with single photons passing through two slits show that diffraction will occur with single photons. The process normally used to derive the grating equation does not easily explain this. Perhaps the observed diffraction pattern is actually the sum of the results of each photon taking their individual paths beyond the grating without the interactive interference process with the other photons being a major factor. Considering the results on the basis of continuous waves may provide correct results but may not represent the actual physical process, which may not be truly understood yet. Although it is clear that photons can behave like waves and/or particles during the interaction and detection phase of their life, it is not clear what they are like after being generated and during the transit phase.

 

It does not seem unreasonable to expect that any explanation of the behavior or light should apply with equal validity to a group of photons or to a single photon. The diffraction formula as applied to light interacting with a grating would seem to depend upon an orderly (in phase and coordinated, or coherent) approach of the photons to the grating, or upon the grating somehow regulating their interaction to produce the appropriate positioning and phasing for the formula to apply. It is difficult to see how this can actually occur with most light sources. Thus the discussions about the ‘Doppler shift’ in this site are oriented toward considering the behavior and properties of individual photons, or energy quanta.

 

A photon leaving an emitter would pass through the time gradient associated with the emitter with increasing velocity as the clock rate decreased. After passing from the influence of the emitter into the surrounding space it would travel at a velocity determined by the clock rate in that space. Upon reaching an observer, the speed would decrease according to the time gradient associated with the observer. If either the emitter or observer were in motion, there would also be an acceleration or deceleration upon moving from one time gradient to another that would depend upon the velocities of the emitter and observer. The observed wavelength shift would also be sensitive to any velocity change while traveling through the space between the time gradients associated with the emitter and observer.

 

This suggests an interesting possibility. If the universe is expanding, then the matter within it must have been denser in the distant past. This might have resulted in the speed of light through space being slower than it is today. As the universe expanded, the density of matter in the light path would become less and the speed of light would increase. This could result in a greater red shift than would have been the case otherwise. This could mean that a greater red shift for more distant emitters might not be solely due to the relative velocity of the emitter and observer and gravitational shifts, but to the change in the speed of light as it traveled through space over the time it has taken for the light to reach the observer.

 

The following illustration shows the effect of the time gradient associated with a star and the star’s velocity on the wavelength of an emitted photon. The increase in speed is essentially the same in all directions while the photon is within the star’s time gradient, and thus the increase in wavelength is also the same. When the time gradient in the space around the star becomes the predominant one, the speed of the photon and its wavelength will change according to the direction in which it leaves the star. The wavelength changes are somewhat exaggerated so that the specific direction of any changes are apparent. Directional changes due to any possible ‘photon shift’ are not shown.

 

 

Illustration 1

 

The following animated illustration shows the emission of sound and light from a source. Continuous movement of the sound source (speaker diaphragm) to the right would cause the sound waves to be closer together, thus making the pitch higher to an observer on the right. Continuous movement of the atom emitting the photons to the right would not have a similar effect on the photons, since the spacing of the photons presumably has no effect on observations of the wavelength associated with the photons. The emission of light does not occur as a result of oscillations but of transitions from one energy state to another. These transitions do not occur with any particular or regular frequency. Of course the actual travel of the photons would be much faster relative to the sound waves than shown in the illustration.

 

 

Illustration 2