## A century of progress – are you sure?

A century has passed since 1905, a watershed for physics. In that year, the quantum theory of light was first described in a paper dealing with the photoelectric effect. A subsequent flurry of investigation on this theme—with considerable input by the same author—led to the revolutionary development of quantum mechanics.

Also in 1905 a paper was published that dealt with the mechanics of Brownian motion and—along with another paper detailing a method for counting and determining the size of atoms and molecules—proved that atoms do actually exist, ending a debate that had raged for centuries.

But hold on to your hat—yet another paradigm-shifting theory of physics appeared in 1905, this time dealing with the nature of the cosmos. Dispensing with the idea of a luminiferous ether, the special theory of relativity demonstrated that space and time are not absolute and that measurements of time and distance vary systematically according to the relative motion of all things. Later in 1905, this theory was further embellished when the relationship between energy and mass was determined and the most famous equation in physics was formulated: E=mc^{2}.

Remarkable as all this activity was in a year that historians call the *annus mirabilis*, even more astounding was the fact that every one of these revolutionary ideas had the same author, Albert Einstein. And it was just the start of his 20-year purple patch, which would yield yet more amazing insights, including his *pièce de résistance*, general relativity: a theory of gravity. General relativity reveals the intimate relationship between space, time, matter and energy, whereby matter tells space-time how to curve and curved space tells matter how to move.

One hundred years later it is interesting to reflect on an explosion of scientific discovery that took place in the midst of our grandmothers, great-grandmothers or great-great-grandmothers. But how many of us actually understand any of Einstein’s work, even the hundred-year-old stuff? How many of us have an even remotely up-to-date knowledge of the world around us? The model of the atom taught at school level is a prequantum-mechanical model, predating 1926, and very few students progress to university-level physics, which presents a more accurate model.

If physics were the only field in which general knowledge lagged behind the state of the art by a hundred years, then this situation might be excusable, but there are plenty of others. How many of us know anything at all about music composition more recent than, say, Wagner (who died in 1883) or Tchaikovsky (1893)? Can you name a single work by Toru Takemitsu or Luciano Berio?

And how about art? Have you embraced the Stuck-ism and Thinkism movements of the 21st century? Are you one of the many that crowd the Louvre, or one of the few that waft through the Centre Pompidou?

One can of course argue that information gathering proceeds at a rate far greater than any single person might hope to keep up with, that advances in any field can only come about by narrowing the panorama and ignoring the background chatter. But I wonder if this accepted wisdom is truly wise.

Scientists after Newton called him lucky, in that there was only one Universe to discover and he discovered it. After him, it seemed, there was little left for physicists to do beyond crossing Newton’s t’s and dotting his i’s. But Einstein proved that concept wrong. When you examine Einstein’s methodology, the thing that impresses most is the attention he paid to seemingly unrelated ideas, which, as it turned out, were intrinsically related.

Whereas Newton’s approach was to determine how things worked, Einstein seemed more interested in why. Newtonian physics provides a mathematical calculation for the mystical force of gravity. Einstein demystifies, describing a universe where gravity is necessary: it is the direct line through curved space, a compelling consequence of the shape of the cosmos.

It is striking that the problem Einstein was grappling with when he died 50 years ago, identifying an underlying geometry that would unify classical and quantum physics, is still unresolved today. We like to look back a hundred years and think that we are smarter and more sophisticated than our predecessors, but perhaps this is conceit. If history is anything to go by, then our times are really inhabited by only a handful of pioneers, while the rest of us occupy a world that would have been rather more familiar to Newton, who died in 1727.