*The following biographical article is about the genius Richard P. Feynman on the account of his birthday on the 11th of May. Wishing the great man a very happy birthday. *

It is different with the magicians. Even after we understand what they have done it is completely dark. Richard Feynman is a magician of the highest calibre. – Mark Kac

#### If it’s a boy, he’s going to be a scientist’

Richard Feynman (pronounced, appropriately, as ‘fine man’) was born to Melville and Lucille Feynman, on 11^{th} May, 1918 in Far Rockaway, New York. His parents had already predicted the future of their son he was going to be a scientist. By the end of high school and while in MIT for his bachelor degree in Physics, he was already fulfilling this prophecy. What they did not know was that their son would become one of the greatest of all times and lay down the groundwork for the most successful theory known to all of science. He would become to the second half of twentieth century physics what Einstein was to the first half.

#### The Feynman Algorithm

Later, people would wonder at the simple algorithm that Feynman used to follow for solving different problems in physics. Nobel Laureate Murray Gell-Mann, his rival at Caltech, outlined the Feynman algorithm:

- Write down the problem
- Think real hard (scratch your forehead a bit, if needed)
- Write down the solution

The only downside to this procedure is its limited use to most other people. Feynman himself said of his method: What one fool can do, another can too.

#### MIT, Marriage, Least Action, and his First Paper

In MIT, Feynman worked under the guidance of John Wheeler, a vibrant fearless man, only about 4 years older. Feynman enjoyed the talks they had and soon learned enough of mathematics to outdo Wheeler himself. They worked on an electromagnetic theory, worrying about the infinite self-energies of charged point particles, removing the entire field framework and replacing them by action-at-a-point mechanisms, an extremely bold step against the tide of modern physics. The Wheeler-Feynman theory was well received when it was presented by Feynman to an audience comprising illustrious personalities like Einstein, Pauli, von Neumann and Wigner. A decade later, the theory would be proved wrong, and Feynman would send a letter to Wheeler saying Guess we were wrong about the absorber theory’ and get no response from him.

In the meantime, he was introduced to a physical concept that would change the course of his life the Principle of Least Action. His mathematics teacher, Mr. Bader, noticing him to be fidgety in class, introduced the concept. Feynman fell in love with it and the marriage would last for the rest of his life. He had already fallen in love with a girl Arline Greenbaum and they would also be married in a few years, but that would end in tragedy.

The principle of least action is simple. Total energy for a system can be defined as the sum of kinetic and potential energies. If the system is isolated, the total energy remains constant.

A quantity, known as the Lagrangian, is defined as kinetic energy *minus* potential energy. This is not a constant quantity. In fact this depends on the path a particle takes. Action is defined as the sum of Lagrangian calculated at different points in the path over the entire path. (This continuous sum is referred to as an integral). Now, here’s the catch. You can calculate the action for many millions of paths. The least value of action will come from the path that the particle actually takes. In other words, a particle always takes the path of least action.

But, Feynman asked, is that the only path quantum particles take, or are contributions from other paths also important? Before he could answer this question, his country needed him. In a fit of patriotic fervor, he joined the Manhattan Project. He was also concerned about his fiancÃ©’s suddenly deteriorating health. She had Lymphatic Tuberculosis. Feynman took as much care of her as he could. They decided to get married, and, despite opposition from his parents, they did. Arline died just after the war ended. Feynman did not cry for her; he was prepared for this. Later, he would see a dress in London, and, thinking that Arline would have looked good in it, burst out. In his last letter to Arline, which he wrote after her death, he ends with the poignant “PS: Please excuse my not mailing this â€” but I don’t know your new address”.

#### The Manhattan Project

Feynman played a major part in the Manhattan Project his first brush with real calculations, throwing out the idealizations often made in theoretical physics. He amazed people with his math skills, entertained people by showing tricks he could do with a pencil and, most famously, by cracking safes! He felt no guilt or remorse about the bomb. Later, however, he would often mentally question the perceived futility of any architectural constructions. Didn’t they know that an atom bomb could instantly destroy all?

#### The Crowning Glory

After receiving his Ph.D. during the war, Feynman was free to develop the key ideas of his own theory. What if the electron followed all possible paths from a source to a destination? If the electron, or photon, went through both slits in a double-slit experiment or through all three slits in a triple-slit experiment, should it not go through all possible points in space, while propagating through free space? (Think about it: Free space means an infinite number of slits! It should go through all of them!) This led him onto a new approach to quantum mechanics, which modern physicists think is *THE* approach the path integral formulation. It’s quite technical, but the basic idea is the principle of least action. Contributions from all paths need to be considered, not just the path the particles take classically. The electron sniffs its way through space-time, as Feynman explained.

In order to do an integral, he invented diagrams, known as Feynman diagrams. Now these diagrams are ubiquitous in quantum field theory.

This revolutionary new idea led to a new more powerful formulation of Quantum Electrodynamics (QED) the quantum theory of electrons, light and their interaction. This is a jewel in the crown of physics, accurate to ten parts in a billion. As Feynman pointed out, this was like measuring the distance from New York to Los Angeles to the accuracy of the breadth of a single human hair.

As Caltech physicist Leonard Mlodinow notes, only Feynman could come up with such a prescription of following all paths, since he was himself like an electron. Freeman Dyson initially described Feynman as “half genius and half buffoon”, later updating it to “full genius and full buffoon”.

Feynman also dabbled’ in superfluidity, publishing a series of six classic papers.

#### Cancer, Challenger Disaster and Death

In 1978, Feynman was diagnosed with cancer. In 1986, he was called to be a panelist in the 12 member panel investigating the Challenger tragedy. His (third) wife had convinced him that

If you don’t do it, there will be 12 people, all in a group, going around from place to place together. But if you join the commission, there will be 11 peopleall in a group, going around from place to place together, while the twelfth one runs around all over the place, checking all kinds of unusual things.

Feynman forsook his self-imposed ban on participating in administrative matters and joined in. His exposure of the O-ring fallacy is now legendary (“Reality must take precedence over public relations; for Nature cannot be fooled”). Watch it here.

Cancer was, however, taking its toll. In 1988, 15^{th} February, after fighting with cancer for a decade, he finally lost. He came out of his coma, said I don’t want to die twice. Dying is boring. That was the last of his discoveries.

#### But he lives on…

Take a step back and think: It wasn’t about the Nobel Prize (1965, Physics); Feynman is a physicist’s physicist.

His contributions stretch from QED, to particle physics, to superfluidity and to even QCD (the physics of quarks). He was the most fun-filled character you’d ever encounter. He was a fabulous teacher; the three volumes of Feynman’s Lectures on Physics’ are classics. His lectures on QED, compiled in a book named QED: The Strange theory of light and matter’ can be enjoyed by anyone, with or without a physics major. Feynman was a larger than life figure, a giant in the physics community and a legend outside it. He was as popular and as beloved as scientists can possibly get. He was Elvis with the wonder of the voice transferred to the brain. Maybe, Feynman was greater.

#### Reading Recommendation:

*The author strongly urges the reader to go through a few books on Feynman in order to get to know him better. Here are a few suggestions:*

*1. Surely you’re joking, Mr. Feynman – Stories of Feynman*

*2. What do you care what other people think? – Stories of Feynman (sequel to above, has a lot of stuff on the Challenger investigation)*

*3. QED: The strange theory of Light and Matter -Feynman’s lectures on QED*

*4. “There’s plenty of room at the bottom” – Feynman’s lecture on nanotechnology (extremely imaginative and surprisingly prophetic) *

*5. Genius by James Gleick** *

*6. Some Time with Feynman – by Leonard Mlodinow** *

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