Einstein’s famous equation has grown into one of the great symbols of the 20th century. It is the one equation in science that people recognize, if any is. It has a kind of iconic status and dual connotations: the brilliance and insight of Einstein and the darkness of atomic bombs. Images.
The basic idea behind the formula E=mc2 is easy to state. Mass and energy are really just the same thing. At first that seems impossible.
• Mass is a measure of the quantity of stuff and manifests as a resistance to acceleration. A body with little mass, like a pebble, is easy to set in motion.