If you were to make a list of the top five scientists who ever lived, who would you choose? People are asking the question (also, here, here). So far, it hasn't been all that interesting. All the lists have two or three names in common, and throw in two or three unexpected names for balance. Physics is highly overrepresented, either because people are easily impressed, or because they've watched Cosmos one too many times. Don't get me wrong, I like physics as much as anybody. But once your list includes Newton, Einstein, and Maxwell, and then you throw in Galileo, well there's not much room for anything else. None at all if you take Darwin as a given.
So I decided to do something a little different: What five scientists have had the greatest impact on human life? Yes, Newton was great, but gravity goes on without him. Many later discoveries stood on his shoulders, but Newton's achievements were far more intellectual than practical. I'm looking for people whose accomplishments saved lives, prevented wars, stopped hunger, or released people from endless drudgery. This isn't a list of inventors -- if it were, there would be a lot of ancient inventions like the moldboard plow that deserve more attention than anything modern. It's a list of scientists whose impact stretched across many fields, and without whom life today would likely be worse.
1. R. A. Fisher. His work in population genetics laid the foundations for the vast productivity increases of twentieth-century agriculture. He was far from alone in this, but he stood apart from his contemporaries by inventing many of the statistical methods that would come to define scientific hypothesis testing. Without Fisher's innovations in statistics, large-scale medical research studies would be meaningless. All this after he established the basis for Mendelian inheritance of continuous characters.
2. Louis Pasteur. Everyone knows that he kept milk from souring. His work established the germ theory, with immense effects on human medicine, food (and beer) production, and the care of crops and domesticated animals. Less well known is his early research on crystallography, which discovered the chirality of organic molecules and made use of methods that would later be essential to determine the structure of DNA. And, oh yeah, he developed the first man-made vaccines, curing the otherwise incurable rabies.
3. Leo Szilárd. How good can a physicist be and still be virtually unknown? Szilárd may set the bar. In his early career, he set out the mathematical connection between physical entropy and information, and was the first to conceive and (with Fermi) carry out a nuclear chain reaction. Most of the important physicists of his day were involved in the Manhattan Project, but Szilárd initiated it, drafting the famous letter from Einstein to Roosevelt. He organized pre-war efforts to keep atomic research secret, and founded post-war efforts to promote arms control. Then, he became a biologist: discovering that UV light kills bacteria, and inventing the chemostat. He made the atomic bomb and nuclear power possible, did everything possible to keep them from the Axis, and laid the groundwork for molecular biology. All this from a man who set out with his partner to invent a refrigerator with no moving parts. The partner: Albert Einstein.
4. John von Neumann. The indispensable mathematician, he did more than anyone else to create the postwar world. His developments in game theory shaped the Cold War, his work in formal logic led to Gödel's famous incompleteness theorem, and his early work with computers paved the way to the information revolution. He brought computers into the Manhattan Project, helped develop the hydrogen bomb, and developed new simulation methods essential to building efficient jet and rocket engines, and ultimately modeling all kinds of scientific problems.
5. This one is for you. Who else belongs on this list?