Memo 21.4
The Relativity Of Light…Described

Contrary to Einstein’s assertions, the propagation velocity of a light ray is not the same for all observers in all reference frames. In Figure 21.3, the tip of the light ray L1 is:

1. Propagating at the absolutely constant transmission velocity of c relative to its medium from point “a” in space to point “b” in space, regardless of the velocity v of its light source.

2. But relative to moving carriage A, it is also propagating at the relative velocity of c – v; and relative to carriage B it is also propagating at the relative velocity of c + v1.

3. Relative to the man (m1), it is also propagating at the relative velocity of c – v – w.

4. Relative to the rails directly below, it is also propagating at the relative velocity of c, plus or minus the velocity of the Earth through the Cosmos.

5. Relative to the light rays L2 and L4, it is also propagating at the relative velocity of 0 km/s.

6. Relative to the rocket ship, it is also propagating at the relative velocity of c + v2; and relative to the airplane it is also propagating at the relative velocity of c – v3.

7. Relative to the tip of light ray L3, it is also propagating at the relative velocity of c + c.

Just because the tip of each light ray transmitting at c is also propagating at various other velocities relative to moving material objects and other light rays, does not mean that we need other different transmission speeds for light.

Nor do we need to artificially do away with all such relative velocities of light propagation and mathematically (with the aid of the Lorentz transformation) and artificially make all relative velocities of light the same for all observers in all frames of reference.

An observer’s measurement of the relative velocity of anything that is moving, including the tip of a light ray, depends upon the relative velocity and direction of that which is moving…and the relative velocity and relative direction of the observer’s motion.

In Figure 21.3, the man m1

1. Measures the transmission velocity of the light ray L1 directly above him at c.

2. Measures the relative velocity of the tip of L2 at c – v – w.

3. Measures the relative velocity of the railway embankment at 0 – v – w.

4. Measures the relative velocity of the front of the carriage at 0 – w.

5. Measures the relative velocity of the man (m2) at 0.

6. Measures the relative velocity of the rocket ship at w + v + v2.

7. Cannot measure the transmission velocity of light ray L3, nor the relative velocity of the tip of light ray L3, because light ray L3 has not yet reached him.

An observer on the tip of light ray L1

1. Would measure the transmission velocity of L2 at c.

2. Would measure the relative velocity of L2 at 0 km/s.

3. Would measure the relative velocity of L3 at c + c.