The Photon Shift

 

The nature of the photon shift will be discussed in a bit more detail. Two RFs, S and S’, will be considered, with S’ is moving at some velocity v relative to S. A flash of light is emitted from the center of S’. So what happens when the light leaves S’ to travel in S? The light traveling forward decelerates and the light traveling the opposite direction accelerates so that its speed in S relative to S is c and –c respectively in the forward and rear directions. However, because of the momentum of the light, a certain amount of the velocity of the source (or momentum imparted by the source) is retained by the photons. This causes the photons that are not at 0 or 180 degrees with respect to v to shift toward the front (the direction of v) of the spherical wave. Depending upon how fast the source was traveling, there might be only a limited percentage of the total emitted light that travels back for an observer to see from behind the source.

 

The following is a brief look at the details of the velocity vectors causing this shift. Figure 1 shows the relationship of the velocity imparted by the source and the direction of travel of a particular photon. The vector v_source is the velocity of the source. Figure 1 shows both a forward and a backward traveling photon. The backward component v_-r would actually be on the photon vector, but is offset for visibility. The photon velocity in S’ is labeled c.

 

Figure 1

 

After leaving S’, the time gradient (TG) associated with S will control the radial speed of the photon which will eliminate the imparted velocity component in the direction of the photon vector (v_r). This will change the vector magnitude in the direction of  to . This will result in a tangential velocity of . The angle of the light vector with respect to v will be generalized to  for the following discussion. The tangential imparted velocity is . The tangential velocity magnitude will be 0 at angles of 0 and 180 degrees to v, and will be equal to the magnitude of v at angles of 90 and 270 degrees to v.

 

Note that if the absolute value of the sine is used, then . This is equivalent to , which is equivalent to  in terms of the Lorentz transformation coefficients. The tangential velocities cause the photon vectors to shift their angles closer to v[1] and the photon velocity will conform to the clock rate in S as discussed in the previous section on velocity addition.

 

Thus it appears that the original angle of exit of a photon from an emitter moving relative to an observer is not the angle that will be determined by an observer. The original angle by which the photon leaves the emitter will determine the change in forward velocity that the external time gradient imposes. This will determine the effective wavelength of the photon, and any change of direction caused by the tangential velocity would not seem to change that wavelength. Thus the observed angle has to be increased to relate the wavelength shift to the original angle of exit. This is apparently what the ‘relativistic correction’ does. Multiplying the classical formula for displaced lines by g apparently removes the effect of the tangential velocity so that the shift reflects that for the actual angle that the photon velocity had with respect to v when it was emitted by the source. An example of this is the experiment by Ives on hydrogen canal rays[2].

 

As a result of the photon shift the light from a star moving toward us with a high velocity should appear brighter than when it is moving away from us. This is because the photons shift toward the direction of motion. Since the original direction of each photon determines the extent of its deceleration, and this determines what the wavelength will be, the spectrum of a star moving rapidly toward us should show broadened spectral lines. This broadening would probably be on the shorter wavelength side with respect to the position that we consider normal for any particular line, unless the star was going very, very fast toward us. In that case some broadening might also be expected on the longer wavelength side if the photons originally emitted with angles greater than 90 degrees to the velocity vector of the star shift far enough forward to be included in the light we see. There are stars that show a periodic change in brightness, and this may be the result of the photon shift in some cases where another cause is not apparent.

 

The action of a TG on the light, as seen above, can be considered in terms of some force acting on the light. Force acting on a physical entity can alter the momentum of that entity. Is the momentum of the light changed by this action? If so, where does the energy for the change come from or go to? The momentum of light is considered to be the energy of the light divided by the speed of the light .  The energy of light when emitted is Plank’s constant times the frequency, . The change in the velocity of the light does not alter the frequency, so the energy should remain the same. This suggests that the momentum should change when the speed changes. However, these formulas are based on the assumption that the speed of light does not change. It is possible that the value of Plank’s constant changes depending on the reference frame that it is calculated relative to. In which case, perhaps the momentum (or energy) of the light might not change. Note that if the wavelength were measured outside of the emitter RF, where the speed of light might be different, then the energy would appear to have changed. But has it? For the present, the particular considerations in this paragraph remain open questions, as does the specific definition of momentum, energy, etc. when calculations are subject to changes in clock rate and a variable speed of light. Some of this is discussed further in a separate section on Light and Energy.

 

Some possible considerations that might modify what has been discussed above should now be mentioned.

 

The photons leaving the source at an angle greater than 90 degrees to v will essentially have the imparted radial velocity component reversed. The question arises as to whether or not there is some specific angle beyond which the tangential velocity component is also reversed. This does not seem likely, but may occur. If so, then the rearward emitted photons beyond this angle would shift to the rear, which might make the emitter seem brighter when going away from an observer as well. Another consideration is whether or not there may be an inherent resistance by the photon to the tangential velocity component. This is probably not the case, since the correction for this seems to provide reasonable results for wavelength shifts.

 

Photon Shift Experiment

 

The following experiment may help resolve some of the questions raised in considering the photon shift.

 

Two light emitting devices are affixed on opposite sides of the outer rim of a circular carrier that can be rotated rapidly about its center. These devices must emit light in the forward and backward direction. Two light sensors capable of measuring light intensity are placed facing the carrier in such a way that one is receiving the light from an emitter traveling toward it, and the other is receiving the light from the other emitter traveling away from it at the same time. Thus each sensor will be receiving light once every half revolution of the carrier. It would be beneficial if each emitter could be adjusted so that the sensors read the same light intensity from each from each side when the carrier is not moving. The sensor outputs could be attached to a dual recorder or equivalent for convenience.

 

The carrier is now rotated and the rotational velocity is slowly increased while the sensor output is monitored. Provided the carrier can be rotated fast enough, the sensor outputs should gradually change (assuming that the photon shift is real). If the photons are all shifting to the front, then the sensor reading the forward moving emitter should increase while the other one should decrease. If the forward moving photons shift to the front and the backward moving photons shift toward the rear, then both sensor reading should increase. If there were some specific angle other than 90 or 270 degrees where the rearward photons start shifting to the rear, the sensors would probably increase at different rates.

 

Figure 2 shows the layout of the equipment for the experiment.

 

Figure 2

 

Some experimentation with lenses and apertures on the lights will probably be needed to maximize any changes in intensity. The maximum shift would presumably be experienced by photons leaving the source in directions that are nearly perpendicular to the direction of travel of the source. Thus the lenses should be capable of directing as much of that light as possible to the detectors. It is possible that blocking part of the central area of the lens, with the light passing through an annulus, might be helpful in increasing the relative difference in intensities between the stationary and rotating sources.

 

The ability to actually observe any photon shift would depend upon the actual velocity of the lights. The further apart the light are, the greater their velocity for a given rotational speed. It is not clear whether or not sufficient velocity can be obtained with mechanical equipment.  Perhaps a means could be devised for conducting the experiment using a semi-mechanical approach that would allow greater velocities to be obtained.

 

Another problem might be the response speed of the detectors and the relationship of that to the rotational speed of the lights. This alone could cause changes in apparent intensity as the rotational speed was changed.

 

Photon Shift Experiment 2

 

This experiment to detect the photon shift is based on the possibility that ‘secondary emitters’ may also impart their velocity to photons. A secondary emitter is basically anything that reflects light, or anything that light temporarily transfers energy to and which then ‘sends’ the light energy on its way again.

 

Figure 3 illustrates the basic setup. It consists of a light source and detector in the center, and a circular mirror that can be rotated very rapidly around them.

 

 

Figure 3

 

Figure 4 shows the details of the alignment of the source and detector, and how the shift is detected. Basically, the light source and detector require the light to pass through a long small bore tunnel on the way out and back, with the tunnels aligned so that the light returns from the stationary mirror and passes through the detector tunnel so that it can be detected. When the mirror is rotated fast enough and if it imparts its velocity to the reflected photons, then the reflected light will return at a different angle and will not be able to pass through the return tunnel. This would be observed by a decrease in the light intensity as seen by the detector.

 

 

Figure 4

 

As with the first suggested experiment, the rotation must be very fast so that the circumference velocity reaches some appropriate fraction of the speed of light. Since this might require a very large radius, a purely mechanical arrangement as might be set up on a tabletop may not be adequate. Perhaps reflecting light from a particle whizzing around in an accelerator might be suitable provided such an arrangement could be accomplished.