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Talking of Yawning Gaps as I was yesterday, the most celebrated Gap in Physics is the chasm between Classical and Quantum Physics over which no army of Lord Raam has yet succeeded in casting a bridge that is pucca and beautiful.
The Collapse Hypothesis, Entanglements of all sorts, a rigorous link between the deterministic ideas of one and the probabilistic interpretation of the other are just a few of the troubles. I read in 'The Dreams of a Final Theory' that Weinberg (?) while going up an elevator with a colleague happened to ask a Research Scholar in the lift what his thesis problem was. And on being told: "Foundations of Quantum Mechanics" he remarked sotto voce to his colleague: "This thesis will never see light of the day" like Pauli told Feynman that his Guide Wheeler will never give that talk on the QM version of the half-delayed-half-advanced theory.
Anyway two of the most celebrated heroes of QM are Dirac and Feynman whose personalities were poles apart. And Dirac's Principles of QM is as delightful to read as Feynman's slim book of lectures titled QED.
So, I thought I would compile a few tidbits about these two gleaned from James Gleick's tome Genius and take rest from original work for tonight like the copy cats of PAN Loop 30 years ago (Rinkujee, the elder daughter of RSS came to me with the Champak riddle: "In a boat carrying nine cats, one of them jumps into the water, and then all the other eight follow her; WHY?" Answer: They were copycats)
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Feynman was drawing unfamiliar diagrams on the blackboard. He showed a particle of antimatter going backward in time. This mystified Dirac, the man who had first predicted the existence of antimatter. Dirac now asked a question about causality: "Is it unitary?" Unitary! What on earth did he mean?
"I'll explain it to you," Feynman said, "and then you can see how it works, then you can tell me if it's unitary." He went on, and from time to time he thought he could still hear Dirac muttering, "Is it unitary?"
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Oppenheimer warned (Berkeley) that Feynman was sure to have other job offers, because "a not inconsiderable number of 'big shots' " had already noticed him. He quoted two of the big shots. Bethe, according to Oppenheimer, had said bluntly that he would sooner lose any two scientists than lose Feynman. And Wigner of Princeton had made what was, for a physicist's physicist in the 1940s, perhaps the ultimate tribute.
"He is a second Dirac," Wigner said, "only this time human."
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"Feynman looked out the window and saw Dirac lolling on a patch of grass and gazing at the sky. He had a question that he wanted to ask Dirac since before the war. He wandered out and sat down. A remark in a 1933 paper of Dirac's had given Feynman a crucial clue towards his discovery of a quantum-mechanical version of the action in classical mechanics. "It is now easy to see what the quantum analogue of all this must be," Dirac had written, but neither he nor anyone else had pursued this clue until Feynman discovered that the "analogue" was, in fact, exactly proportional. There was a rigorous and potentially useful mathematical bond. Now he asked Dirac whether the great man had known all along that the two quantities were proportional.
"Are they?" Dirac said. Feynman said yes, they were. After a silence he walked away.
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Despite what he told Bethe, he did make a connection between the axial wobble of a cafeteria plate and the abstract quantum-mechanical notion of spin that Dirac had so successfully incorporated in his electron.
Many years later Feynman and Dirac met one more time. They exchanged a few awkward words --- a conversation so remarkable that a physicist within earshot immediately jotted down the Pinteresque dialogue he thought he heard drifting his way:
I am Feynman.
I am Dirac. (Silence.)
It must be wonderful to be the discoverer of that equation.
That was long time ago. (Pause.) What are you working on?
Mesons.
Are you trying to discover an equation for them?
It is very hard.
One must try.
More than anyone else, Dirac had made the mere discovery of an equation into a thing to be admired. To aficionados the Dirac equation never did quite lose its rabbit-out-of-a-hat quality.
*******************************************************************************************************
P.S. This copycat (gps) just looked up the Index for 'Feynman and Dirac' and topoed feverishly.
======================================================================
Talking of Yawning Gaps as I was yesterday, the most celebrated Gap in Physics is the chasm between Classical and Quantum Physics over which no army of Lord Raam has yet succeeded in casting a bridge that is pucca and beautiful.
The Collapse Hypothesis, Entanglements of all sorts, a rigorous link between the deterministic ideas of one and the probabilistic interpretation of the other are just a few of the troubles. I read in 'The Dreams of a Final Theory' that Weinberg (?) while going up an elevator with a colleague happened to ask a Research Scholar in the lift what his thesis problem was. And on being told: "Foundations of Quantum Mechanics" he remarked sotto voce to his colleague: "This thesis will never see light of the day" like Pauli told Feynman that his Guide Wheeler will never give that talk on the QM version of the half-delayed-half-advanced theory.
Anyway two of the most celebrated heroes of QM are Dirac and Feynman whose personalities were poles apart. And Dirac's Principles of QM is as delightful to read as Feynman's slim book of lectures titled QED.
So, I thought I would compile a few tidbits about these two gleaned from James Gleick's tome Genius and take rest from original work for tonight like the copy cats of PAN Loop 30 years ago (Rinkujee, the elder daughter of RSS came to me with the Champak riddle: "In a boat carrying nine cats, one of them jumps into the water, and then all the other eight follow her; WHY?" Answer: They were copycats)
********************************************************************************************************
Feynman was drawing unfamiliar diagrams on the blackboard. He showed a particle of antimatter going backward in time. This mystified Dirac, the man who had first predicted the existence of antimatter. Dirac now asked a question about causality: "Is it unitary?" Unitary! What on earth did he mean?
"I'll explain it to you," Feynman said, "and then you can see how it works, then you can tell me if it's unitary." He went on, and from time to time he thought he could still hear Dirac muttering, "Is it unitary?"
**********************************************************************************************************
Oppenheimer warned (Berkeley) that Feynman was sure to have other job offers, because "a not inconsiderable number of 'big shots' " had already noticed him. He quoted two of the big shots. Bethe, according to Oppenheimer, had said bluntly that he would sooner lose any two scientists than lose Feynman. And Wigner of Princeton had made what was, for a physicist's physicist in the 1940s, perhaps the ultimate tribute.
"He is a second Dirac," Wigner said, "only this time human."
********************************************************************************************************
"Feynman looked out the window and saw Dirac lolling on a patch of grass and gazing at the sky. He had a question that he wanted to ask Dirac since before the war. He wandered out and sat down. A remark in a 1933 paper of Dirac's had given Feynman a crucial clue towards his discovery of a quantum-mechanical version of the action in classical mechanics. "It is now easy to see what the quantum analogue of all this must be," Dirac had written, but neither he nor anyone else had pursued this clue until Feynman discovered that the "analogue" was, in fact, exactly proportional. There was a rigorous and potentially useful mathematical bond. Now he asked Dirac whether the great man had known all along that the two quantities were proportional.
"Are they?" Dirac said. Feynman said yes, they were. After a silence he walked away.
*********************************************************************************************************
Despite what he told Bethe, he did make a connection between the axial wobble of a cafeteria plate and the abstract quantum-mechanical notion of spin that Dirac had so successfully incorporated in his electron.
Many years later Feynman and Dirac met one more time. They exchanged a few awkward words --- a conversation so remarkable that a physicist within earshot immediately jotted down the Pinteresque dialogue he thought he heard drifting his way:
I am Feynman.
I am Dirac. (Silence.)
It must be wonderful to be the discoverer of that equation.
That was long time ago. (Pause.) What are you working on?
Mesons.
Are you trying to discover an equation for them?
It is very hard.
One must try.
More than anyone else, Dirac had made the mere discovery of an equation into a thing to be admired. To aficionados the Dirac equation never did quite lose its rabbit-out-of-a-hat quality.
*******************************************************************************************************
P.S. This copycat (gps) just looked up the Index for 'Feynman and Dirac' and topoed feverishly.
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