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Posts Tagged ‘atomic bomb

“It can be argued that in trying to see behind the formal predictions of quantum theory we are just making trouble for ourselves”*…

Context, it seems, is everthing…

… What is reality? Nope. There’s no way we are going through that philosophical minefield. Let’s focus instead on scientific realism, the idea that a world of things exists independent of the minds that might perceive it and it is the world slowly revealed by progress in science. Scientific realism is the belief that the true nature of reality is the subject of scientific investigation and while we may not completely understand it at any given moment, each experiment gets us a little bit closer. This is a popular philosophical position among scientists and science enthusiasts.

A typical scientific realist might believe, for example, that fundamental particles exist even though we cannot perceive them directly with our senses. Particles are real and their properties — whatever they may be — form part of the state of the world. A slightly more extreme view is that this state of the world can be specified with mathematical quantities and these, in turn, obey equations we call physical laws. In this view, the ultimate goal of science is to discover these laws. So what are the consequences of quantum physics on these views?

As I mentioned above, quantum physics is not a realistic model of the world — that is, it does not specify quantities for states of the world. An obvious question is then can we supplement or otherwise replace quantum physics with a deeper set of laws about real states of the world? This is the question Einstein first asked with colleagues Podolski and Rosen, making headlines in 1935. The hypothetical real states of the world came to be called hidden variables since an experiment does not reveal them — at least not yet.

In the decades that followed quantum physics rapidly turned into applied science and the textbooks which became canon demonstrated only how to use the recipes of quantum physics. In textbooks that are still used today, no mention is made of the progress in the foundational aspects of quantum physics since the mathematics was cemented almost one hundred years ago. But, in the 1960s, the most important and fundamental aspect of quantum physics was discovered and it put serious restrictions on scientific realism. Some go as far as to say the entire nature of independent reality is questionable due to it. What was discovered is now called contextuality, and its inevitability is referred to as the Bell-Kochen-Specker theorem.

John Bell is the most famous of the trio Bell, Kochen, and Specker, and is credited with proving that quantum physics contained so-called nonlocal correlations, a consequence of quantum entanglement. Feel free to read about those over here.

It was Bell’s ideas and notions that stuck and eventually led to popular quantum phenomena such as teleportation. Nonlocality itself is wildly popular these days in science magazines with reported testing of the concept in delicately engineered experiments that span continents and sometimes involve research satellites. But nonlocality is just one type of contextuality, which is the real game in town.

In the most succinct sentence possible, contextuality is the name for the fact that any real states of the world giving rise to the rules of quantum physics must depend on contexts that no experiment can distinguish. That’s a lot to unpack. Remember that there are lots of ways to prepare the same experiment — and by the same experiment, I mean many different experiments with completely indistinguishable results. Doing the exact same thing as yesterday in the lab, but having had a different breakfast, will give the same experimental results. But there are things in the lab and very close to the system under investigation that don’t seem to affect the results either. An example might be mixing laser light in two different ways.

There are different types of laser light that, once mixed together, are completely indistinguishable from one another no matter what experiments are performed on the mixtures. You could spend a trillion dollars on scientific equipment and never be able to tell the two mixtures apart. Moreover, knowing only the resultant mixture — and not the way it was mixed — is sufficient to accurately predict the outcomes of any experiment performed with the light. So, in quantum physics, the mathematical theory has a variable that refers to the mixture and not the way the mixture was made — it’s Occam’s razor in practice.

Now let’s try to invent a deeper theory of reality underpinning quantum physics. Surely, if we are going to respect Occam’s razor, the states in our model should only depend on contexts with observable consequences, right? If there is no possible experiment that can distinguish how the laser light is mixed, then the underlying state of reality should only depend on the mixture and not the context in which it was made, which, remember, might include my breakfast choices. Alas, this is just not possible in quantum physics — it’s a mathematical impossibility in the theory and has been confirmed by many experiments.

So, does this mean the universe cares about what I have for breakfast? Not necessarily. But, to believe the universe doesn’t care what I had for breakfast means you must also give up reality. You may be inclined to believe that when you observe something in the world, you are passively looking at it just the way it would have been had you not been there. But quantum contextuality rules this out. There is no way to define a reality that is independent of the way we choose to look at it…

Why is no one taught the one concept in quantum physics which denies reality?” It’s called contextuality and it is the essence of quantum physics. From Chris Ferrie (@csferrie).

* “It can be argued that in trying to see behind the formal predictions of quantum theory we are just making trouble for ourselves. Was not precisely this the lesson that had to be learned before quantum mechanics could be constructed, that it is futile to try to see behind the observed phenomena?” – John Stewart Bell

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As still we try, we might relatively hearty birthday greetings to Sir Marcus Laurence Elwin “Mark” Oliphant; he was born on this date in 1901. An Australian physicist who trained and did much of his work in England (where he studied under Sir Ernest Rutherford at the University of Cambridge’s Cavendish Laboratory), Oliphant was deeply involved in the Allied war effort during World War II. He helped develop microwave radar, and– by helping to start the Manhattan Project and then working with his friend Ernest Lawrence at the Radiation Laboratory in Berkeley, California, helped develop the atomic bomb.

After the war, Oliphant returned to Australia as the first director of the Research School of Physical Sciences and Engineering at the new Australian National University (ANU); on his retirement, he became Governor of South Australia and helped found the Australian Democrats political party.

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“As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.”*…

 

quantum computing

Quantum computing is all the rage. It seems like hardly a day goes by without some news outlet describing the extraordinary things this technology promises. Most commentators forget, or just gloss over, the fact that people have been working on quantum computing for decades—and without any practical results to show for it.

We’ve been told that quantum computers could “provide breakthroughs in many disciplines, including materials and drug discovery, the optimization of complex manmade systems, and artificial intelligence.” We’ve been assured that quantum computers will “forever alter our economic, industrial, academic, and societal landscape.” We’ve even been told that “the encryption that protects the world’s most sensitive data may soon be broken” by quantum computers. It has gotten to the point where many researchers in various fields of physics feel obliged to justify whatever work they are doing by claiming that it has some relevance to quantum computing.

Meanwhile, government research agencies, academic departments (many of them funded by government agencies), and corporate laboratories are spending billions of dollars a year developing quantum computers. On Wall Street, Morgan Stanley and other financial giants expect quantum computing to mature soon and are keen to figure out how this technology can help them.

It’s become something of a self-perpetuating arms race, with many organizations seemingly staying in the race if only to avoid being left behind. Some of the world’s top technical talent, at places like Google, IBM, and Microsoft, are working hard, and with lavish resources in state-of-the-art laboratories, to realize their vision of a quantum-computing future.

In light of all this, it’s natural to wonder: When will useful quantum computers be constructed? The most optimistic experts estimate it will take 5 to 10 years. More cautious ones predict 20 to 30 years. (Similar predictions have been voiced, by the way, for the last 20 years.) I belong to a tiny minority that answers, “Not in the foreseeable future.” Having spent decades conducting research in quantum and condensed-matter physics, I’ve developed my very pessimistic view. It’s based on an understanding of the gargantuan technical challenges that would have to be overcome to ever make quantum computing work…

Michel Dyakonov makes “The Case Against Quantum Computing.”

* Albert Einstein

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As we feel the need for speed, we might recall that it was on this date in 1942 that a team of scientists led by Enrico Fermi, working inside an enormous tent on a squash court under the stands of the University of Chicago’s Stagg Field, achieved the first controlled nuclear fission chain reaction… laying the foundation for the atomic bomb and later, nuclear power generation.

“…the Italian Navigator has just landed in the New World…”
– Coded telephone message confirming first self-sustaining nuclear chain reaction, December 2, 1942.

Illustration depicting the scene on Dec. 2, 1942 (Photo copyright of Chicago Historical Society)

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Indeed, exactly 15 years later, on this date in 1957, the world’s first full-scale atomic electric power plant devoted exclusively to peacetime uses, the Shippingport Atomic Power Station, reached criticality; the first power was produced 16 days later, after engineers integrated the generator into the distribution grid of Duquesne Light Company.

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Written by (Roughly) Daily

December 2, 2018 at 1:01 am

“Care keeps his watch in every old man’s eye / And where care lodges, sleep will never lie”*…

 

 xkcd

See also

* Shakespeare, Romeo and Juliet

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As we keep a stiff upper lip, we might recall that it was on this date in 1952 that Britain became the third country to conduct an atomic bomb test.  Its “Operation Hurricane” was carried out at Monte Bello, Australia, using an improved plutonium implosion bomb similar to the U.S. “Fat Man” (detonated over Nagasaki).  To test the effects of a ship-smuggled bomb (a threat of great concern at the time), Hurricane was exploded inside the hull of the HMS Plym (a 1,450 ton frigate) which was anchored in 40 feet of water 400 yards off shore.  The explosion, 9 feet below the water line, left a saucer-shaped crater on the seabed 20 feet deep and 1,000 feet across.

Hurricane’s mud-laden explosion

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Written by (Roughly) Daily

October 3, 2017 at 1:01 am

“Librarians are the secret masters of the world”*…

 

Interior view of the Manhattan Project’s Los Alamos scientific library

If library work was among the most tedious [at Los Alamos], the award for the most unenviable job likely belonged to its head librarian: Charlotte Serber, a University of Pennsylvania graduate, statistician, and freelance journalist who at one point interviewed Frank Lloyd Wright for The Boston Globe.

In 1942, J. Robert Oppenheimer selected Serber to spearhead the project in part because of her lack of librarian experience. He wanted someone who would be willing to bend the rules of cataloguing.

Her appointment was a victory for the women on the Hill. Though women were integral to the success of the Manhattan Project—scientists like Leona Woods and Mary Lucy Miller played central roles in the creation of the bomb—none occupied leadership positions.

In this respect, Serber stood alone. As the head of the scientific library, she became the Manhattan Project’s de facto keeper of secrets, a position that soon saw her targeted for an FBI probe—and almost ended in her being fired from the project…

The remarkable true tale of the woman who dodged accusations of communism, and made the atomic bomb possible: “The Librarian Who Guarded the Manhattan Project’s Secrets.”

* Spider Robinson

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As we check it out, we might recall that it was on this date in 1687 that Philosophiæ Naturalis Principia Mathematica (Latin for Mathematical Principles of Natural Philosophy),  was published.  Often referred to as simply the Principia, the three-volume work outlines Newton’s laws of motion, forming the foundation of classical mechanics; Newton’s law of universal gravitation; and a derivation of Kepler’s laws of planetary motion (which Kepler first obtained empirically).  This first edition was written in Latin, the universal language of scholarship at the time; an English edition was published in 1728.  It remains one of the most important works in the history of science.

Title page of the first edition

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Written by (Roughly) Daily

July 5, 2017 at 1:01 am

“If lightning is the anger of the gods, then the gods are concerned mostly about trees”*…

 

Lightning strikes around the world– in real time.

* Lao Tzu

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As we reach for our rods, we might recall that it was on this date in 1957 that the U.S. detonated an atomic weapon on a test range in the Yucca Flats in Nevada-a  test of the Air Force’s AIR-2 Genie missile with a nuclear warhead, part of the Plumbbob series, the biggest, longest, and most controversial test series in the continental United States: 29 tests, of which only two failed to detonate.  Exactly seven years later– on this date in 1964– the Soviet Union performed a nuclear test in Eastern Kazakh.

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Written by (Roughly) Daily

July 19, 2014 at 1:01 am

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