Einstein's Theory of Relativity Revisited

Einstein used "mind experiments" to develop
 

His Theory of Relativity.

He understood that "Energy is Mass and Mass is Energy
Neither can be created nor destroyed."

To quantify his formula
 

E=M
 

He chose the fastest speed known.

The Speed of Light

A better choice would have been

TIME

That would have made the formula

M=Et

This more closely reflects reality