• There is an upper limit and a lower limit of light spectrum. Above upper limit energy emission as light, will stop and it turns to a different form of energy,  that cannot consider as light anymore. Like any other form of energy, light  also available within a certain frequency range. Light is available within a spectrum 380 Tetra Hertz to 760 Tetra Hertz. Tetra hertz is One trillion periods per second. Therefore light spectrum is having different speeds. "Look at the Rainbow."

• We can imagine what will happen if we travel at speeds closer to speed of light, assuming how we experience Dopler effect. If we reach towards the speed of light, the color of objects we see will be turning from blue color to red color. We will see straight objects getting concaved.

  We have experienced that we can change the speed of light with laboratory experiments, (See Fig.2) by letting it pass though different mediums. When we change the speed of light in a laboratory experiment by passing it through a prism its velocity reduces through the glass medium. Depending the length it has to travel its' color changes from violet to red.

  Like wise it is not possible to derive theories assuming the speed of light is invariant. By making a wrong assumption at this stage we may end up with alarming mathematical results. Theory of relativity based on the assumption that the speed of light is invariant to all observers. Like any other power or particle, light also has to initiate from some source. Also we should look in to the way how light is generated and how it is propagated.

During jet propulsion the backward emission of gasses having relatively zero velocity. So that the exhaust gas remain stationary on sky and we see it as a smoke line drawn in sky.

This phenomena further derives: that the maximum speed that a jet plane can achieve is the root mean square speed of exhaust gasses.