Advanced information on the Nobel Prize in Physics, 5 October 2004

We know of two fundamental forces on the macroscopic scale that we experience in daily life: the gravitational force that binds our solar system together and keeps us on earth, and the electromagnetic force between electrically charged objects. Both are mediated over a distance and the force is proportional to the inverse square of the distance between the objects. Isaac Newton described the gravitational force in his Principia in 1687, and in 1915 Albert Einstein (Nobel Prize, 1921 for the photoelectric effect) presented his General Theory of Relativity for the gravitational force, which generalized Newton’s theory. Einstein’s theory is perhaps the greatest achievement in the history of science and the most celebrated one. The laws for the electromagnetic force were formulated by James Clark Maxwell in 1873, also a great leap forward in human endeavour. With the advent of quantum mechanics in the first decades of the 20 century it was realized that the electromagnetic field, including light, is quantized and can be seen as a stream of particles, photons. In this picture, the electromagnetic force can be thought of as a bombardment of photons, as when one object is thrown to another to transmit a force. In a similar way the gravitational force is believed to be transmitted by particles called gravitons, but since the gravitational force is some 10 times weaker than the electromagnetic force, they have not yet been detected.