Subject: Why is the speed of light considered the highest speed ?

Why is the speed of light considered the highest speed possible.  You 
said (in message 844422175.Ph) :

"Actually, the *SUPPOSITION* that the speed of light is the
ultimate speed limit was at the heart of the equations that
Albert Einstein (and others) developed during their work on
the general and special theories of relativity."

Because it was a supposition and unproven, we must separate the ideas 
of the speed of light and the fastest possible speed to prove that 
they are equal.  In relativity equations, we must assume that c means 
the highest possible speed, not the speed of light.

Light will slow down when entering an optically dense medium.  While 
travelling in the medium, the light still exists.  Therefore, the 
light has energy.  Because of e[equ]mc˛, light has mass.  So, when light 
travels at less than c, it has mass.

If the speed of light in a vacuum truly is equal to c, then when the 
light reenters the vacuum, it will speed up to c.  However, it has 
mass at a speed slower than c.  To speed up to c would require 
infinite energy.  Photons have a finite amount of energy and cannot 
reach c.

According to this reasoning the speed of light is not c, although it 
might be remarkably close to c.

Re: Why is the speed of light considered the highest speed ?