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Centuries ago, the Scottish botanist Robert Brown became fascinated by the zigzag motion of fragments within pollen grains. In his pioneering observations, made with a primitive microscope, Brown had spotted this random jittery motion as early as 1827. What puzzled him was that this incessant movement did not arise from currents in the fluid, or from evaporation, or from any other clear-cut cause. He was aquiver with the idea that he had glimpsed an animating force \u2014\u201cthe secret of life.\u201d
Being a good scientist, he knew that he needed more evidence. At that time, Brown was well known and had been honored across Europe, gaining an honorary doctorate from Oxford in the same ceremony as the great physicist Michael Faraday and chemist John Dalton, pioneering the exploration of Australia, and even advising Darwin on what equipment he should take with him on his famous voyage of discovery aboard the Beagle. After observing the same kind of motion within mineral grains, which were obviously inanimate, Brown discarded the idea that he had seen the vital essence at work, with understandable disappointment.
Yet, in a certain sense, he had indeed glimpsed an animating force. The key step toward making sense of what Brown had actually witnessed came more than seventy-five years later, when Albert Einstein demonstrated how the tiny zigzagging particles were being buffeted about by the invisible molecules that made up the water around them. The existence of molecules was still rejected by some major figures in the scientific establishment of 1905. Einstein predicted that the random motions of molecules in a liquid putting pressure on larger, suspended particles would result in the particles\u2019 irregular motions, big enough to be directly observed under the gaze of a microscope. From this jittery motion, Einstein could even work out the dimensions of the molecules. Although Brownian motion did not turn out to be a vital force, Brown\u2019s observation paved the way for the understanding that we now use to explain early life.<\/p>\n\n\n\n