Einstein's century

Picture / Rod Emmerson

Albert Einstein began working at the patent office in Bern, Switzerland, a little more than a century ago, with an undistinguished academic record. He had flunked the entrance exam for the Swiss Federal Institute of Technology and took the job evaluating inventions because it paid a regular salary.

Yet in 1905 he made discoveries that dwarfed anything passing through the patent office. Between March and September, he published five papers, any one of which would have won the Nobel Prize. They revolutionised our understanding of the cosmos. He was 26.

This year has been designated Einstein year to mark the centenary of the physicist's annus mirabilis of achievement. No one else has produced so many works of such importance and originality in so short a time. He demonstrated, merely by thinking about it, that the universe was not as it seemed.

Today, Einstein is venerated as an intellectual colossus who bestrode the 20th century like no other. With his mane of wild hair, he embodied the eccentric professor, instantly recognisable by millions. But if most people can put a name to the face, few outside the world of science can explain his discoveries.

The theory of relativity is the discovery for which Einstein is most famous but, even for experts, it was difficult to grasp. Sir Arthur Eddington, the British astrophysicist who proved the theory in 1919 by demonstrating that light from the stars was bent by the sun during a solar eclipse, was once asked if it was true that only three people understood relativity. He paused before his celebrated wisecrack: "I am still trying to think who the third person is."

Einstein's ideas, despite their difficulty, reverberated beyond science, influencing the worlds of art, literature and poetry. He seemed to pull the rug from under reality in a way that resonated with artists, scientists and the ordinary people at a time of unprecedented upheaval in the social order, winning him worldwide fame.

But a century ago he was an anonymous clerk unknown beyond his immediate circle. He had no research post, no university department, no library. He described his friend, Michele Besso, with whom he walked home from the patent office every day, as "the best sounding-board in Europe" for scientific ideas. With other friends in Bern, all outside the academic world, they established a group to discuss science and philosophy, calling themselves the Olympia Academy, in mockery of the official bodies that then dominated science.

At the time of Einstein's birth in Ulm, Germany, in 1879, the theories of classical physics had accounted for most of the phenomena of the universe. Newton's laws described the motion of objects as small as a pin or as large as a planet and Faraday had shown how to generate electricity.

But some problems were exercising scientific minds when Einstein entered his 20s. One involved light, which was thought to be a smoothly oscillating electromagnetic wave. But what was the mysterious ether through which it passed? And how did it explain heat radiation?

Another involved gravity. How did the force described by Newton, which accounted for his collision with the apple, exert its effect at a distance?

Einstein's first insight came in March, 1905, with the publication in Annalen der Physik, the leading German physics journal, of a new idea he had about the structure of light. Light was not a wave, he suggested, but a particle, in some ways like the particles of a gas. Its energy was not distributed evenly but concentrated in discrete packets. These packets of energy, which he called light quanta, were "localised in points in space, move without dividing and can be absorbed or generated only as a whole".

The theory eliminated the problem of the ether but also explained a phenomenon then puzzling experimental physicists: how, when light falls on a metal, electrons are ejected from its surface. The paper, which Einstein regarded as the most revolutionary, provided the first account of the photoelectric effect and gave birth to quantum theory, which has since dominated physics.

A month later, in April, Einstein submitted his much-delayed doctoral dissertation to the University of Zurich showing that the size of molecules in a liquid could be measured by its viscosity.

He used sugar dissolved in water to demonstrate the theory, which provided a measure of the real size of molecules, making them harder to dismiss as useful fictions.

In May came a paper explaining "Brownian motion", a mystery in biology, which provided an experimental test for the theory of kinetic energy, which says that heat is produced by the agitated motion of atoms.

When particles are suspended in a liquid they perform a random, jittery dance visible under the microscope, known as Brownian motion. Such a random dance would be predicted by the irregular bombardment of the particles by the liquid's invisible atoms, Einstein said. A failure to observe the effect would refute the theory of kinetic energy. His paper in Annalen der Physik reinforced the kinetic theory, creating a powerful tool for studying the movement of atoms.

Then in June came the bombshell that was to transform the world of physics. Einstein sent Annalen der Physik a paper on electromagnetism and motion which disputed the absolute nature of space and time, claiming both could be modified by circumstances, and that the only fixed point in a relative universe was the speed of light.

The kernel of the theory was that space and time are relative to the observer and to the thing being observed, and the faster one moves the more pronounced these effects become. An observer can never accelerate to the speed of light but the faster one goes the more distorted objects will appear.

Bertrand Russell, the philosopher, tried to explain the idea in his book, The ABC of Relativity, by using the example of a train 100 yards (91.4m) long travelling at 60 per cent of the speed of light. To someone standing on a platform as the train passed, it would appear to be only 80 yards (73m) long and everything on it would be similarly compressed. The voices of the passengers would sound slurred and their movements would appear ponderous. Even the clocks on the train would appear to be running slow.

The crucial point is that the train passengers would be unaware of these distortions. To them, everything would appear normal. It would be the people on the platform who would seem weirdly compressed and slowed. It all depends on the observer's position relative to the moving object.

Einstein had long been convinced that the principle of relativity must apply to all phenomena, including light. His stroke of genius was to find a way of explaining this by devising a novel concept of space and time, called spacetime. The theory was called the Special Theory of Relativity. It became the General Theory of Relativity when Einstein, more than a decade later, included a new idea about gravity.

Any object distorts the fabric of spacetime. Just as a large ball placed on a taut piece of elasticated cloth stretches the fabric and causes it to sag, planets and stars stretch space-time, which is known as the geodetic effect.

This was a crucial insight. Gravity was not, as Newton had claimed in 1687, a force that attracted bodies together but the product of warped spacetime. Thus the planets orbiting the sun are not being pulled by the sun: they are following the curved spacetime deformation caused by the sun.

That extension of the theory did not come until 1916, but in September 1905 Einstein followed his initial insight with a short note reporting a remarkable consequence of his special theory of relativity: if a body emits a certain amount of energy, its mass must decrease by a proportionate amount. The observation yielded the iconic equation E=MC2, where C is the speed of light.

Einstein wrote to a friend at the time: "The relativity principle in conjunction with the Maxwell equations demands that the mass is a direct measure for the energy contained in bodies; light transfers mass ... This thought is amusing and infectious but I cannot possibly know whether the good Lord does not laugh at it and has not led me up the garden path."

The good Lord, it turned out, had not led him astray. One effect the theory predicted was that when a ray of light passed near a massive body it would be bent. In May, 1919, Sir Arthur Eddington, made the necessary measurements. They showed exactly what Einstein predicted. Later, the truth of the equation E=MC2, was confirmed over Hiroshima in 1944 when a handful of matter was converted into enough energy to destroy a city.

Einstein was not involved in the development of the atom bomb but he became associated with it. In 1946, Time portrayed him as a tragic figure, sad-eyed and dishevelled, with a mushroom cloud rising behind him on which the equation was emblazoned.

The fifth paper was published in September of that year and Einstein's burst of creativity was over. He never again matched the extraordinary whirlwind of original thought. He later said, "A storm broke loose in my mind."

In March last year, 99 years after Einstein published his first ideas about relativity, Gravity Probe B blasted into orbit. The US$700 million ($998 million) mission uses four perfect spheres inside the world's largest vacuum flask to detect minute distortions in the fabric of the universe. The aim is to demonstrate Einstein's theory of relativity with unprecedented precision.

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