rays came from. The chance discovery of radioactivity finally signaled the beginning of a new era in physics. As the element polonium, identified by Polish-born Marie Curie in 1898, emits radiation it changes spontaneously into lead. This discovery shattered the belief inherited from the Greeks that the elements are immutable and their atoms indestructible. What causes atoms to decay?What are they made of?What forces are at work inside them? Such questions were new to physics, and were to remain at its cutting edge throughout the twentieth century. The answers would affect our lives in ways no one could imagine in the year of 1900. The twentieth century began with a flurry of innovations such as the airplane, the mass-produced automobile, and transatlantic radio communication. They transformed the world, but the changes sweeping over physics at the same time were far more radical. Those brought about not just different lifestyles, but new ways of thinking. Modern physics grew out of classical physics and rest of three pillars: the quantum theory, which describes atoms and their nuclei, Special Relativity, which deals with the relationship between space and time and General Relativity, which explains gravity. The latter two were the sole creations of Albert Einstein and even the former received a crucial early contribution from him. Einstein's miracle year came in 1905 he was 26 years old and working as a patent examiner in Bern, Switzerland. In March he submitted a paper in which he proposed that light, which was classical physics treats as a wave phenomenon, could also be thought of as consisting of discrete bits of energy he called quanta. The implied wave/particle duality of light became the cornerstone of the new quantum theory. In May, Einstein explained the erratic motion of pollen suspended in water as due to the jostling of innumerable invisible molecules. When this theory was verified in the laboratory, even t...
