We’ve talked a lot about great scientists on this show: people who solved mysteries that have been stumping lesser smarty-pants for centuries. Some of them even answered questions nobody had ever thought to ask before. But a lot of great minds have not been great explainers. Richard Feynman, the American physicist, most famous for pioneering the field of quantum electro-dynamics – while playing the bongos at a strip club – was one of the twentieth century’s great explainers. Feynman could take the most abstruse, mind-bending stuff and break it down like you wouldn’t believe: simple; elegant; and at times really moving. And he was also a great scientist. Not only did he share Nobel prize in 1965 for helping other physicists understand how light and matter interact, he’s considered one of the greatest physicists of all time. He invented Feynman diagrams, unsurprisingly, which changed physics forever back in the 1940’s. He made significant contributions to the fields of quantum computing, nanotechnology, and particle physics. Plus, he pretty much single-handedly figured out why, or at least very astutely explained why the space shuttle Challenger blew up in 1986. He was also a total character who liked the ladies, math, and playing bongos; and he didn’t really care what people thought of him. But perhaps most importantly, Richard Feynman believed that understanding the world was important to being a person, not just a scientist, which made him not only one of history’s greatest scientists, but also one of the greatest science teachers. Let’s say, hypothetically, that all scientific information on the planet was destroyed, except for what could be contained in just one sentence, and a bunch of fifth-graders were given the job of writing that sentence down. I think this would probably be the best that they could write: “All things are made of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another.” That’s how Richard Feynman described the universe. And I sometimes don’t even know why we do these videos when Feynman did it all already. But unlike some other great minds, Feynman’s genius wasn’t immediately obvious. He was smart and liked science from a very young age, but when he was a kid he wasn’t flagged as an over-the-top genius or anything. He was also an extrovert, and a kind of sassy one. But something that set little Ritty Feynman apart from all the other smart kids is that he was curious about everything. He liked thinking about stuff – math in particular. In fact, math became his hobby, and he became great at it. In 1935 he went to college at MIT, but his course of study wasn’t exactly what he wanted. He wanted to know about the physics of subatomic particles – light and other things – that, at the time, physicists were just beginning to realize didn’t follow the rules of physics. This was the very-new field of quantum mechanics. In the absence of classes about these things – they didn’t have those yet – he got all the books that he could find and started reading. By the age of 23, he had a grasp on theoretical physics, which uses math to explain and predict natural phenomena. His mad math chops got him into Princeton’s PhD program, which was a big deal because he was Jewish and in the 1930’s a lot of colleges had a limit on how many Jews they admitted. His talents were so apparent that, even before he graduated, he was offered a job to work on the Manhattan Project – the government program to develop the first atomic bomb. His job was to help calculate the magnitude of a nuclear explosion. Suddenly, Feynman found himself working alongside the pioneers of quantum mechanics like Einstein and Wolfgang Pauli. But even as a junior physicist, Feynman didn’t care who he crossed. If he didn’t agree with, say, Niels Bohr, he’d tell him. He flatly refused to wear safety goggles to the first test explosion of the atomic bomb. If he got bored, he’d go around Los Alamos – the super-secure lab in New Mexico, where the Manhattan Project was headquartered – causing trouble, picking locks on drawers, sneaking into the lab after-hours, pranking other physicists by leaving notes that made them think that their research had been stolen by spies. You know – funny stuff that only got him arrested occasionally. So he’s kind of annoying, but what made him annoying also made him a great scientist. He was tenacious and endlessly curious and didn’t much care if he was wrong. He just wanted to find the solution to a problem. If more people were like that, the world maybe would be pretty different, and probably better. After World War II, Feynman’s obsession with getting to the bottom of things got him into the thick of a math problem so tough it made other physicists want to make an atomic bomb just so they could blow their faces off. The problem was the theory of quantum electrodynamics, or QED – a theory that had been established but not completely resolved – that tried to explain how light interacts with matter at the very smallest possible level. But it was way more than that. By illuminating how particles behave at this level, QED had the potential to explain almost everything in the natural world: every color: weight; temperature; texture; sound. The difficulty scientists were having was simply in understanding light. You and I think of light in terms of visible light, but, really, all light is a form of electromagnetic radiation – the force that causes like charges to repel each other and opposite charges to attract. But light works differently under different circumstances. Visible light, for example, can be partly reflected by a window or more fully reflected in a mirror. Different colors of light can be separated when refracted through a prism. Lenses can focus beams of light. In each of these phenomena, light is interacting with matter differently on a subatomic level. By the time Feynman started working on QED, physicists had realized that these phenomena could be explained by electrons exchanging photons – temporary virtual packets that conveyed the electromagnetic force that we know as “light” with each other and with other fundamental particles. The thing about virtual particles like photons is that they just briefly pop into existence. That is, they acquire mass from energy, then do their job, and then disappear again. So when physicists got stuck – and what Feynman wanted to figure out – was how to predict how photons and electrons would behave under different circumstances. It all had to do with probabilities – the likelihood that a group of these particles would act a certain way in a certain situation. Feynman likened it to predicting a game of checkers. It’s not so hard to keep track of probability in checkers when you’re playing on a normal board. But say the checkers board was a hundred times bigger or a thousand or a million times bigger! Then the probabilities become much harder to sort out because there are so many checkers – or electrons or other subatomic particles. So when physicists tried to calculate how any given particle in an interaction would behave, the answer was basically infinity. The electron could scatter in infinite directions in infinite states of energy with a mass that was utterly unknowable. And, you know, these physicist weren’t born yesterday; they knew that couldn’t be right. So Feynman and a couple of his coleagues dug into the math, untangling the super-difficult algebra that came with tying in more and more bigger checkerboards as it were. Which is where Feynman’s Diagrams came in. Feynman initially started using diagrams as shorthand in his notes. But soon he figured out that they could be really useful in sorting out the math of QED. Because the particles he was pondering were doing all sorts of things: travelling through space; swapping other particles; appearing and disappearing; and sometimes coliding – which would turn them into totally different particles – and because he was dealing with probabilities, he could never really know for sure what was happening when or in what order. So in 1948 he marched into a meeting of physicists in Pennsylvania and drew a simple diagram on the blackboard. It showed two electrons moving through space, with one electron emitting a photon that’s absorbed by the other, and then both moving off in different directions. So he plotted this interaction against time, so the same diagram showed that the photon could be absorbed earlier, allowing for the uncertainty of time at the quantum level. Then he annotated the diagram with all the parts of the mathematical formula that reflected this interaction; and suddenly, it became clear: he had just written out the hardest math of the century – in a picture. The diagrams allowed for flexibility in terms of what was happening and when. You could extrapolate, from one basic interaction, a whole multitude of possible other interactions. With each event branching off into other possible events, the world of quantum electrodynamics could just unfold right in front of you like an episode of Scooby-Doo. For these diagrams and the incredibly complex – and, in the end, accurate – formulations that they helped represent, Feynman was awarded the Nobel Prize for Physics in 1965. And because of his willingness to tackle and help sort out the toughest algebra problem in history, other physicists were able to go on and gradually untangle the giant, unholy math-knot that was QED. Feynman gave physicists a way to depict a world that nobody had been able to describe before let alone observe, which is arguably one of the greatest contributions to science any single person has ever made. From there, Feynman kept doing math that nobody else understood on topics like quantum gravity, quantum computers, and nanotechnology. And he kept getting a kick out of it even though every problem he put his mind to was fantastically-tough. He once said in a lecture, “I’m going to have fun telling you about this absurdity, because I find it delightful.” Aside from being a great scientist and a great teacher, Richard Feynman was just a kooky and curious guy: he reportedly did a lot of math in strip clubs; he was an awesome bongo player and a painter; and he spent years negotiating with the Soviet government trying to get into Tuva, a remote country in Asia where he wanted to learn the native style of throat singing. Sadly, a letter clearing him for travel to Tuva arrived the day after he died. Feynman was also on the committee appointed to investigate the explosion of the space shuttle Challenger in 1986. At a televised hearing, Feynman asked for a glass of ice water and put one of the seals from the shuttle’s rocket booster – called an “O-ring” – in the water. Then he interrupted the hearing to demonstrate that it became less-resilient when it got cold, which proved to be the cause of the disaster. So I wish Richard Feynman was still around because he was awesome and I want to meet him and be his best friend. But, after a long battle with two different types of cancer, he died in 1988. His last words were, “I’d hate to die twice; it is so boring.” Hail Richard Feynman, King of Physics and my heart. Thank you for watching this episode of SciShow. If you have any questions or comments, you can find us on Facebook or Twitter or, of course, down in the comments below. And if you want to keep getting smarter with us here at SciShow, you can go to youtube.com/scishow and subscribe.