Who would have thought it? A sockless patent clerk with an unexceptional academic record gave his name to posterity as a synonym for outstanding genius. You don't have to be an Einstein to name the most legendary scientist of the twentieth century. His legacy includes the only equation most of us have any purchase on, E= me2. Small enough to be piped on an iced bun, it states with exquisite succinctness that matter and energy are interchangeable and that matter is a very concentrated form of energy.

You can say of an object that its energy content E is equal to its mass m multiplied by the speed of light c (which is just less that 300,000 km per second) squared. If you work this through, the energy found within the most ordinary, minute object is found to be enormous. With alarming alacrity, Homo sapiens exploited this potential in Fat Boy, the bomb that fell on Hiroshima. A bitter illustration of two adages – ‘knowledge is power’ and 'power corrupts'.

Einstein overturned notions that remain deeply embedded in the consensus view of reality. Much of his work has not really percolated into the shared pool of 'common sense' knowledge in the way that the work of Galileo or Newton has. He stuck the knife in the Newtonian image of space and time. Whereas time was an absolute for Newton, Einstein introduced the notion of relativity.

His starting assumption - that the speed of light is constant - revealed curiosities in nature. He said that both time and position depend on the velocity of the observer relative to that being observed.

In our everyday experience common sense supports Newton's view entirely. Arranging to meet a friend, for example, if we synchronise our watches, agree the time and place, there should be no difficulty. Einstein's perception, that there is no absolute time or space, was both revolutionary and against the grain of intuition. The key to this insight is relative motion. Two observers moving past each other very fast measure the passage of time and distance differently. Each one sees time passing more slowly for the other than for him/ herself. They also see the other foreshortened in the direction of motion. This effect is always true but does not become noticeable until the relative speed approaches the speed of light.

Our lives occur in slo-mo compared with the speed of a light wave, so these oddities are outside our daily experience. Light is very special - the fastest little mover in the known universe. A key ingredient in Einstein's theory is the assumption that the speed of light has the same value for all observers, no matter how fast they are moving. Travelling at a constant speed (about 300,000 km / 186,000 miles per second), it sets the limit for the transmission of any information. Nothing moves faster than light.