Light also a form of energy, scattered in various directions when some
action take part between molecules or atoms. Matter is a concentrated spot of energy.
Light propagates the same way heat or Electro magnetism is radiated.
A spot of light emitted from a source will emit again itself in
all directions in the next step, resulting in diminished intensity.
Therefore, light spends while it propagates. It doesn't require a
medium to travel.
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 be considered as light anymore. Like any other form
of energy, light is also available within a certain frequency
range. Light is available within a spectrum of 380 Tetra Hertz
to 760 Tetra Hertz. Tetra hertz is One trillion periods per second.
Therefore, the light spectrum has 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 through
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 on the length, it has to travel
its' color changes from violet to red.
Likewise, 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. The theory
of relativity is 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
into the way light is generated and how it is propagated.
During jet propulsion, the backward emission of gasses has relatively
zero velocity. So that the exhaust gas remains stationary in the sky
and we see it as a smoke line drawn in the sky.
This phenomenon further derives from the maximum speed
a jet plane can achieve is the root mean square speed of exhaust gasses.s.