Why Mass Equals Energy?

"Energy equals mass times the speed of light squared." On the most basic level, the equation says that energy and mass (matter) are interchangeable; they are different forms of the same thing. Under the right conditions, energy can become mass, and vice versa.

Why is E mc2?

Although we say E = mc^2, Einstein first wrote it this other way, assigning an energy-equivalent-mass to massless particles. ... Conserving energy and momentum both seems to be something our Universe requires, and that's why E = mc^2.

Why is energy proportional to mass?

Kinetic energy is directly proportional to the mass of the object and to the square of its velocity: K.E. = 1/2 m v². ... If the mass has units of kilograms and the velocity of meters per second, the kinetic energy has units of kilograms-meters squared per second squared.