Question

Why does light travels with such a great speed?

Answer 1

Light travels so fast because it has no mass. The particles that make up electromagnetic radiation are called photons. ... According to the General Theory of Relativity anything with zero mass must travel through space at precisely the fundamental constant speed of which we know as "the speed of light (in a vacuum)"

Einstein's theory of relativity. According to this theory if any body travels faster than the velocity of light it's mass is assumed to be infinite.
So according to the equation E=mc² energy needed is infinite.
So light travels with a high speed