State Einstein's special theory of relativity and provide the mass-energy equivalence formula.

(N/A) Einstein's special theory of relativity is based on two fundamental postulates:
$1$. The laws of physics are the same in all inertial frames of reference.
$2$. The speed of light in a vacuum is constant for all observers,regardless of the motion of the light source or the observer.
As a consequence of this theory,Einstein proposed the mass-energy equivalence formula,which states that mass and energy are interchangeable. The formula is given by:
$E = mc^2$
Where:
$E$ is the energy equivalent of the mass,
$m$ is the mass of the object,
$c$ is the speed of light in a vacuum (approximately $3 \times 10^8 \ m/s$).