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Posts Tagged ‘quantum theory

“Physics is like sex: sure, it may give some practical results, but that’s not why we do it”*…

 

Feynman and Dirac

Two of Marek Holzman’s photographs of Feynman and Dirac together in Warsaw in 1962

 

Beloved late physicist Richard P. Feynman (1918–1988) first met his hero Paul Dirac (1902–1984) during Princeton University’s Bicentennial Celebration in 1946 and then again at least twice, in 1948 and 1962. Most notably, the two came to heads during the so-called Pocono Conference when Feynman gave a lecture on a nascent “Alternative Formulation of Quantum Electrodynamics”, reformulating the theory which had earned Dirac the Nobel Prize in Physics in 1933. A star-studded audience of 28 of the world’s leading physicists attended the conference, including J. Robert Oppenheimer, Niels Bohr, Eugene Wigner, John von Neumann, Enrico Fermi, Hans Bethe and of course, the inventor of the theory himself, Paul Dirac.

Feynman’s reformulation of Dirac’s theory was not well received at Pocono, as Bohr, Teller and Dirac all raised objections. Feynman’s disappointment from the audience’s reaction motivated him to write up his work for publication instead. He did so, and in the next three years went on to publish four major papers describing his now well-developed theory and its implications…

Feynman and Dirac [met for the last] time, at the International Conference on Relativistic Theories of Gravitation in Warsaw, Poland in 1962… Their conversation, as overheard by a nearby physicist, was so remarkable that he jotted it down:

F: I am Feynman.
D: I am Dirac.
(Silence)
F: It must be wonderful to be the discoverer of that equation.
D: That was a long time ago.
(Pause)
D: What are you working on?
F: Mesons.
D: Are you trying to discover an equation for them?
F: It is very hard.
D: One must try.

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Another of Holzman’s photographs from Warsaw

Feynman’s work earned him a share of the Nobel Prize in Physics in 1965.

Paul Dirac died in 1984 at the age of 82 years old. Two years later, Feynman was invited to give one of three Dirac Memorial Lectures. He did so, with a lecture entitled “Elementary Particles and the Laws of Physics”, which he opened as follows:

When I was a young man, Dirac was my hero. He made a new breakthrough, a new method of doing physics. He had the courage to simply guess at the form of an equation, the equation we now call the Dirac equation, and to try to interpret it afterwards.

 

How Paul Dirac, Richard Feynman’s hero-turned-opponent, motivated a life’s work which not only altered the trajectory of modern physics, but also erected Feynman’s legend as one history’s finest scientist: “When Feynman met Dirac.”

* Richard Feynman

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As we chase after clarity, we might send very tiny birthday greetings to Wolfgang Paul; he was born on this date in 1913.  A physicist, he developed the non-magnetic quadrupole mass filter which laid the foundation for what is now called an ion trap— a device (also known as a Paul trap) that captures ions and holds them long enough for study and precise measurement of their properties.  During the 1950s he developed the so-called Paul trap as a means of confining and studying electrons.  He shared the Nobel Prize in Physics in 1989 for his work.

He humorously referred to Wolfgang Pauli as his imaginary part.

220px-Wolfgang_Paul source

 

“Time … thou ceaseless lackey to eternity”*…

 

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Source art: Chronos and His Child by Giovanni Francesco Romanelli

 

The human mind has long grappled with the elusive nature of time: what it is, how to record it, how it regulates life, and whether it exists as a fundamental building block of the universe…

Quanta‘s fascinating timeline traces our evolving understanding of time through a history of observations in culture, physics, timekeeping, and biology: “Arrows of Time

* Shakespeare, The Rape of Lucrece

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As we try to Be Here Now, we might send amusingly insightful birthday greetings to Richard Philips Feynman; he was born on this date in 1918.  A theoretical physicist, Feynman was probably the most brilliant, influential, and iconoclastic figure in his field in the post-WW II era.

Richard Feynman was a once-in-a-generation intellectual. He had no shortage of brains. (In 1965, he won the Nobel Prize in Physics for his work on quantum electrodynamics.) He had charisma. (Witness this outtake [below] from his 1964 Cornell physics lectures [available in full here].) He knew how to make science and academic thought available, even entertaining, to a broader public. (We’ve highlighted two public TV programs hosted by Feynman here and here.) And he knew how to have fun. The clip above brings it all together.

– From Open Culture (where one can also find Feynman’s elegant and accessible 1.5 minute explanation of “The Key to Science.”)

 

Written by LW

May 11, 2020 at 1:01 am

“Real randomness requires an infinite amount of information”*…

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If you have ever tossed dice, whether in a board game or at the gambling table, you have created random numbers—a string of numbers each of which cannot be predicted from the preceding ones. People have been making random numbers in this way for millennia. Early Greeks and Romans played games of chance by tossing the heel bone of a sheep or other animal and seeing which of its four straight sides landed uppermost. Heel bones evolved into the familiar cube-shaped dice with pips that still provide random numbers for gaming and gambling today.

But now we also have more sophisticated random number generators, the latest of which required a lab full of laser equipment at the U.S. National Institute of Standards and Technology (NIST) in Boulder, CO. It relies on counterintuitive quantum behavior with an assist from relativity theory to make random numbers. This was a notable feat because the NIST team’s numbers were absolutely guaranteed to be random, a result never before achieved.

Why are random numbers worth so much effort? Random numbers are chaotic for a good cause. They are eminently useful, and not only in gambling. Since random digits appear with equal probabilities, like heads and tails in a coin toss, they guarantee fair outcomes in lotteries, such as those to buy high-value government bonds in the United Kingdom. Precisely because they are unpredictable, they provide enhanced security for the internet and for encrypted messages. And in a nod to their gambling roots, random numbers are essential for the picturesquely named “Monte Carlo” method that can solve otherwise intractable scientific problems…

Using entanglement to generate true mathematical randomness– and why that matters: “The Quantum Random Number Generator.”

* Tristan Perich

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As we leave it to chance, we might send learned birthday greetings to Athanasius Kircher; he was born on this date in 1602.  A scholar, he published over 40 works. perhaps most notably on comparative religion, geology, and medicine, but over a range so broad that he was frequently compared to Leonardo Da Vinci (who died on the date in 1519) and was dubbed “Master of a Hundred Arts.”

For a look at one of his more curious works, see “Wonder is the beginning of wisdom.” And his take on The Plague (through which he lived in Italy in 1656), see here.

220px-Athanasius_Kircher_(cropped) source

“Every why hath a wherefore”*…

 

causalitymain

 

Physicists have started to realise that causality might not be as straightforward as we thought. Instead of cause always preceding effect, effects can sometimes precipitate their causes. And, even more mindbogglingly, both can be true at once. In this version of events, you would be opening the fridge because the butter was already on the table, and your toast would be perfectly golden both before and after you put it in the toaster. You wouldn’t just be making breakfast – your breakfast would also be making you.

Playing fast and loose with causality does more than make for confusing mornings. It could shake physics to its very foundations. No longer having a definite order of events goes against the picture of the universe painted by general relativity, and even hints at a reality beyond quantum mechanics, the best model we have of the subatomic world. Allowing causality to operate in both directions could allow us to combine these two theories into a single framework of quantum gravity, a goal that has eluded us for over a century. The end of causality as we know it …

In everyday life, causes always precede effects.  But new experiments suggests that things might be different when things get very, very tiny: “In the quantum realm, cause doesn’t necessarily come before effect.”

* Shakespeare, Comedy of Errors

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As we get small, we might recall that it was on this date in 1564 that results of the Council of Trent (Concilium Tridentinum) were published, condemning what the Catholic Church deemed to be the heresies of Protestants.  The embodiment of the Counter-Reformation, it established a firm and permanent distinction between the two practices of faith.

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Council of Trent (painting in the Museo del Palazzo del Buonconsiglio, Trento)

source

 

Written by LW

January 26, 2020 at 1:01 am

“I’ve developed a new philosophy. I only dread one day at a time.”*…

 

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Starting [last] month, the very talented Adam Koford, the creator of Laugh-Out-Loud Cats webcomic, started posting these wonderful bootleg Peanuts comics to his Twitter account, and continued almost every day since.

Loose and sketchy, they capture the essence of Charles Schultz’ Peanuts so well: sweet and sad, combining childlike wonder and existential dread. As he went on, they started evolving a unique style of their own, distinct from the Peanuts characters but still recognizable….

Via Andy Baio‘s wonderful site Waxy.  The “Peanuts” panels are strewn through Adam’s Twitter feed; as a gift to us all, Baio collected a bunch of them into a Twitter “Moment.”

Enjoy… and don’t mention it to the Schultz estate.

* Charlie Brown

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As we ruminate on reality, we might recall that today’s a relative-ly good day for it, as it was on this date in 1900 that German physicist Max Planck presented and published his study of the effect of radiation on a “black-body” substance (introducing what we’ve come to know as the Planck Postulate), and the quantum theory of modern physics– and for that matter, Twentieth Century modernity– were born.

Planck study demonstrated that in certain situations energy exhibits the characteristics of physical matter– something unthinkable at the time, when energy was thought to exist only in wave form– and suggested that energy exists in discrete packets, which he called “quanta”… thus laying the foundation on which he, Einstein, Bohr, Schrodinger, Dirac, and others built our modern understanding.

220px-Max_Planck_1933Max Planck

 

Written by LW

December 14, 2019 at 1:01 am

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