The Apparent Incompatibility Of The Law Of Propagation Of Light with Relativity

The simplest law in physics is the one that says how light travels in empty space in straight lines with a velocity of 300,000 km/sec.

This velocity is the same for all colours, because if this were not the case, the minimum of emission would not be observed simultaneously for different colours during the eclipse of a fixed star by its dark neighbour.

The Dutch astronomer De Sitter observed double stars and showed that:

• the velocity of starlight cannot depend on the velocity of motion of its star [light-emitter]
• it is improbable that this velocity of starlight is dependent on the direction in space

This simple law has plunged me into the greatest intellectual difficulties.

All processes happen in a rigid space or coordinate system. The embankment is our space.

• Remove the air
• Send a ray of light along the embankment
• The tip of the ray will be transmitted with the velocity c relative to the embankment.
• Our train is travelling with the velocity v
• Its direction is the same as that of the ray of light, but slower

What is the velocity of this ray of light relative to the carriage?

We apply Section 6 [addition of velocities] since the ray of light is like a man walking forward in the train:

• the velocity W of the man relative to the embankment is here replaced by the velocity of light relative to the embankment
• w is the required velocity of light with respect to the carriage

Thus:

w = c − v

The velocity of a ray of light relative to the carriage thus comes out smaller than c. But this conflicts with the principle of relativity in Section 5. This is because my theory of relativity says that the speed of light in a vacuum must be the same for:

• the railway carriage as reference-body 1
• the rails as reference-body 2

But Section 6 [Classical addition of velocities] makes this impossible [since it makes the light move faster than the speed of light].

All light travels relative to the embankment with the velocity c. This means that another law of propagation of light takes place with respect to the carriage. This is contradictory to the principle of relativity.

This means we must abandon either:

• my principle of relativity, or
• the speed of light in a vacuum

Those who have read my reasoning from Sections 1 to here would side with my principle of relativity because it is so natural and simple. This means that the speed of light in a vacuum must be replaced by a more complicated law that conforms to my principle of relativity.

The theoretical physics, however, shows that we cannot do that because H. A. Lorentz had shown a theory of electromagnetic phenomena which necessarily leads to the constancy of the speed of light in a vacuum.

Prominent theoretical physicists therefore reject my principle of relativity, even if no empirical data has disproven it.

The principle of relativity and the speed of light must be perfectly compatible. I arrive at this by analyzing the physical conceptions of space and time. I call this Special Relativity to distinguish it from General Relativity*.