If a charge vibrates at the speed of light and does not accelerate it cannot launch a wave in space. And when it accelerates it launches an electromagnetic wave in space. Let's call, v, the speed of the frame of reference of the charge. When the charge moves in the direction of the frame of reference it produces this well-known pattern of an electromagnetic wave and this, v, is in the De Broglie formula and the wavelength of the emitted photon is also in the De Broglie equation. Now when, v, is about equal to, c, we will no longer have the known shape of the wave but we will have almost a flat line instead of the ripples, in other words the charge will vibrate at a speed, c', lower than the speed of light, c, because of the very high speed, v, of the frame of reference. In other words when the charge accelerates and its speed is about, c, IT WILL NOT LAUNCH ANY MORE PHOTON INTO SPACE.

The question is when a light moving between two mirrors and this system of two mirrors is moving at a very high speed, v, the speed of light between the two mirrors decreases or not IF WE MAKE THE ANALOGY WITH THE EXAMPLE OF THE CHARGE.

We can link this to our preprint on RG whose title is "Time dilation as an intrinsic property of light explaining the constancy of the speed of light regardless of the frame of reference from which it is measured".