Using this insight, and some associated mathematics, Einstein was able to accurately calculate the average distance an immersed visible particle would travel in a given time. So, if the concentration of large particles varies, they too flow to even out their concentration just like the atoms and molecules in which they are immersed. What was required, in short, was Einstein's realization that even though observable particles are much larger, they still generate pressure the same way as the invisible molecules in which they are immersed. Measuring this motion, however, and explaining it mathematically had proven extremely difficult. The jittery motion of tiny observable particles had been described by botanist Robert Brown as early as 1827, and was not surprisingly known as Brownian motion. A visible object, immersed among these invisible, randomly jostling molecules, wouldn't move much most of the time, since it would normally be buffeted from all sides evenly-but then occasionally it could be "pushed" in one direction and then moments later pushed in a different direction, showing a "zigzag" motion. Then, another nearby group of molecules could for a moment move mostly in a different direction. But Einstein realized that this random chaos of jostling, invisible molecules would produce statistical fluctuations-for example, once in a while a small group of invisible molecules could, just for a moment, move in mostly the same direction. The average behavior of these molecules produces the overall properties of any liquid that we observe. Furthermore, these molecules are always in random, ceaseless motion. Einstein also in 1905 mathematically proved the existence of atoms, and thus helped revolutionize all the sciences through the use of statistics and probability.Ītomic theory says that any liquid is made up of molecules (invisible in 1905). Yet these were not sufficient world-changing, revolutionary advances in physics for a single year. Einstein in 1905 also explained the equivalency of mass and energy, expressed by the famous equation e=mc 2. He published his Special Theory of Relativity, which later led to the General Theory of Relativity, which led to his designation as "the father of modern physics." Einstein also in 1905 proposed that light energy can be absorbed or emitted only in discrete packets called quanta, a provocative contradiction of the then-prevalent wave theory of light-and this led to Einstein's winning of the Nobel Prize. While working at the patent office in Bern, Switzerland, he completed his PhD dissertation. The year 1905 was a good year for 26-year-old Albert Einstein. Was the idea of atoms actually "real?" Or was something else, perhaps something unexpected, going on? When Einstein was a young man, atoms had never been observed. The idea of atoms as a shortcut for thinking about how matter worked seemed quite useful even more than a century ago-but then again, so did ideas like a stationary earth at the center of the universe. This sounds obvious enough to us today, but not very long ago, relatively speaking, chemists and physicists were known to debate this idea fiercely. When you really get down to it, "atomic theory" begins with a claim that matter is made of atoms. As a slightly overdue commemoration of Albert Einstein's 133 nd birthday, I would like to make a quick note of his most "elemental" contribution to atomic theory-he was the first person to show a way to prove the existence of atoms-using an ordinary microscope!
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