Physics Form 5: Chapter 5 - Einstein Equation, Mass-Energy Equivalence

In 1905, Albert Einstein published his theory of Special Relativity. In this paper, Einstein took his readers through the thought process which led him to the most famous equation, E = mc².

Introduction to mass and energy
Mass is a measurement of how much quantity of matter inside of an object. Mass is also a measure of inertia - the more mass an object has, the harder it is to move and once it is moving, the harder it is to stop it. On the hand, energy is the ability to do work. Mass and energy can be neither created nor destroyed. While they can be converted into different forms (mass can turn from solid to liquid to gas, and can be cut up or turned to dust, while kinetic energy can be transferred to potential energy or sound energy or heat energy), there will always remain the same amount in our universe.

Einstein's way to explain mass and energy

Einstein began, it is said, by looking at the equation for finding an object’s kinetic energy:

Einstein was able to take this equation, combine it with other known equations, do a little bit of math, and come up with the following:

 

The equation most people are familiar with, E = mc², can be obtained by assuming that the “object” in question has a speed of zero. If an object is perfectly still, the entire right half of the equation cancels out, and we are only left with the familiar equation.

This equation shows that Mass and Energy are not just similar – they are the same thing, but in different forms, with the ability to be converted into one another. Mass can be turned into energy, and energy can be turned into mass. Further, this equation shows us that a tiny bit of mass can be turned into a lot of energy (the equivalent of the amount of mass times the speed of light squared!), while a lot of energy can only be turned into a little bit of mass.

The equation truly was a revolutionary one, though no one knew just how much so until it was realized that it would be possible, using radioactive elements, the atomic bomb, and later atomic energy.

It is Einstein’s equation which helped scientists predict just what would happen when that first nuclear explosion was triggered, and it is what tells particle physicists what will happen when they smash two beams of particles together in an accelerator.