Posts Tagged ‘quantum physics’
“I have not yet lost a feeling of wonder, and of delight, that the delicate motion should reside in all the things around us”*…
The proton, the positively charged particle at the heart of the atom, is an object of unspeakable complexity, one that changes its appearance depending on how it is probed…
“This is the most complicated thing that you could possibly imagine,” said Mike Williams, a physicist at the Massachusetts Institute of Technology. “In fact, you can’t even imagine how complicated it is.”
The proton is a quantum mechanical object that exists as a haze of probabilities until an experiment forces it to take a concrete form. And its forms differ drastically depending on how researchers set up their experiment. Connecting the particle’s many faces has been the work of generations. “We’re kind of just starting to understand this system in a complete way,” said Richard Milner, a nuclear physicist at MIT.
As the pursuit continues, the proton’s secrets keep tumbling out. Most recently, a monumental data analysis published in August found that the proton contains traces of particles called charm quarks that are heavier than the proton itself.
The proton “has been humbling to humans,” Williams said. “Every time you think you kind of have a handle on it, it throws you some curveballs.”
Recently, Milner, together with Rolf Ent at Jefferson Lab, MIT filmmakers Chris Boebel and Joe McMaster, and animator James LaPlante, set out to transform a set of arcane plots that compile the results of hundreds of experiments into a series of animations of the shape-shifting proton…
Charlie Wood (and Merrill Sherman) have incorporated that work into an attempt to unveil the particle’s secrets: “Inside the Proton, the ‘Most Complicated Thing You Could Possibly Imagine’,” from @walkingthedot in @QuantaMagazine.
* Edmund Burke
###
As we ponder presumptive paradoxes, we might send insightful birthday greetings to David Schramm; he was born on this date in 1945. A theoretical astrophysicist, he established the field of particle astrophysics, a branch of particle physics that studies elementary particles of astronomical origin and their relation to astrophysics and cosmology. He was particularly well known for the study of Big Bang nucleosynthesis and its use as a probe of dark matter and of neutrinos. And he made important contributions to the study of cosmic rays, supernova explosions, heavy-element nucleosynthesis, and nuclear astrophysics generally.
“Why, sometimes I’ve believed as many as six impossible things before breakfast”*…
Imaginary numbers were long dismissed as mathematical “bookkeeping.” But now, as Karmela Padavic-Callaghan explains, physicists are proving that they describe the hidden shape of nature…
Many science students may imagine a ball rolling down a hill or a car skidding because of friction as prototypical examples of the systems physicists care about. But much of modern physics consists of searching for objects and phenomena that are virtually invisible: the tiny electrons of quantum physics and the particles hidden within strange metals of materials science along with their highly energetic counterparts that only exist briefly within giant particle colliders.
In their quest to grasp these hidden building blocks of reality scientists have looked to mathematical theories and formalism. Ideally, an unexpected experimental observation leads a physicist to a new mathematical theory, and then mathematical work on said theory leads them to new experiments and new observations. Some part of this process inevitably happens in the physicist’s mind, where symbols and numbers help make invisible theoretical ideas visible in the tangible, measurable physical world.
Sometimes, however, as in the case of imaginary numbers – that is, numbers with negative square values – mathematics manages to stay ahead of experiments for a long time. Though imaginary numbers have been integral to quantum theory since its very beginnings in the 1920s, scientists have only recently been able to find their physical signatures in experiments and empirically prove their necessity…
Learn more at “Imaginary numbers are real,” from @Ironmely in @aeonmag.
* The Red Queen, in Lewis Carroll’s Through the Looking Glass
###
As we get real, we might spare a thought for two great mathematicians…
Georg Friedrich Bernhard Riemann died on this date in 1866. A mathematician who made contributions to analysis, number theory, and differential geometry, he is remembered (among other things) for his 1859 paper on the prime-counting function, containing the original statement of the Riemann hypothesis, regarded as one of the most influential papers in analytic number theory.
Andrey (Andrei) Andreyevich Markov died on this date in 1922. A Russian mathematician, he helped to develop the theory of stochastic processes, especially those now called Markov chains: sequences of random variables in which the future variable is determined by the present variable but is independent of the way in which the present state arose from its predecessors. (For example, the probability of winning at the game of Monopoly can be determined using Markov chains.) His work on the study of the probability of mutually-dependent events has been developed and widely applied to the biological, physical, and social sciences, and is widely used in Monte Carlo simulations and Bayesian analyses.
“The threat of a pandemic is different from that of a nerve agent, in that a disease can spread uncontrollably, long after the first carrier has succumbed”*…
We were, of course, warned. As we do our best to digest the news of emergent new strains of the COVID-19 virus, a look back at Annie Sparrow‘s 2016 New York Review of Books essay on pandemics…
Pandemics—the uncontrolled spread of highly contagious diseases across countries and continents—are a modern phenomenon. The word itself, a neologism from Greek words for “all” and “people,” has been used only since the mid-nineteenth century. Epidemics—localized outbreaks of diseases—have always been part of human history, but pandemics require a minimum density of population and an effective means of transport. Since “Spanish” flu burst from the trenches of World War I in 1918, infecting 20 percent of the world’s population and killing upward of 50 million people, fears of a similar pandemic have preoccupied public health practitioners, politicians, and philanthropists. World War II, in which the German army deliberately caused malaria epidemics and the Japanese experimented with anthrax and plague as biological weapons, created new fears…
According to the doctor, writer, and philanthropist Larry Brilliant, “outbreaks are inevitable, pandemics are optional.”
…
Much of human history can be seen as a struggle for survival between humans and microbes. Pandemics are microbe offensives; public health measures are human defenses. Water purification, sanitation, and vaccination are crucial to our living longer, better, even taller lives. But these measures of mass salvation are not sexy. While we know prevention is better and considerably cheaper than cure, there is little financial reward or glory in it. Philanthropists prefer to build hospitals rather than pay community health workers. Pharmaceutical companies prefer the Western market to the distant and poor Global South where people cannot afford to buy treatments. Education is a powerful social vaccine against the ignorance that enables pathogens to flourish, but insufficient to overcome the corruption of public goods by private interests. The current enthusiasm for detecting the next panic-inducing pathogen should not divert resources and research from the perennial threats that we already have. We must resist the tendency of familiarity and past failures to encourage contempt and indifference…
An important (and in its time, sadly, prescient) read: “The Awful Diseases on the Way,” from @annie_sparrow in @nybooks.
See also “6 of the Worst Pandemics in History” (source of the image above) and “A history of pandemics.”
[TotH to MK]
###
As we prioritize preparation, we might recall that it was on this date in 1935 that physicist Erwin Schrödinger published his famous thought experiment– now known as “Schrödinger’s cat“– a paradox that illustrates the problem of the Copenhagen interpretation of quantum mechanics.
“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
###
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.
You must be logged in to post a comment.