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Posts Tagged ‘Physics

“The distinction between past, present and future is only a stubbornly persistent illusion”*…

A dog dressed as Marty McFly from Back to the Future attends the 25th Annual Tompkins Square Halloween Dog Parade in New York October 24, 2015.
AFP PHOTO / TIMOTHY A. CLARY via Getty Images

“The past is obdurate,” Stephen King wrote in his book about a man who goes back in time to prevent the Kennedy assassination. “It doesn’t want to be changed.”

Turns out, King might have been onto something.

Countless science fiction tales have explored the paradox of what would happen if you do something in the past that endangers the future. Perhaps one of the most famous pop culture examples is Back to the Future, when Marty McFly went back in time and accidentally stopped his parents from meeting, putting his own existence in jeopardy.

But maybe McFly wasn’t in much danger after all. According a new paper from researchers at the University of Queensland, even if time travel were possible, the paradox couldn’t actually exist…

Find out why: “Paradox-Free Time Travel Is Theoretically Possible, Researchers Say.

* Albert Einstein

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As we ponder predestination, we might send cosmological birthday greetings to Enrico Fermi; he was born on this date in 1901.  A physicist who is best remembered for (literally) presiding over the birth of the Atomic Age, he was also remarkable as the last “double-threat” in his field:  a genius at creating both important theories and elegant experiments.  As recently observed, the division of labor between theorists and experimentalists has since been pretty complete.

The novelist and historian of science C. P. Snow wrote that “if Fermi had been born a few years earlier, one could well imagine him discovering Rutherford’s atomic nucleus, and then developing Bohr’s theory of the hydrogen atom. If this sounds like hyperbole, anything about Fermi is likely to sound like hyperbole.”

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Written by LW

September 29, 2020 at 1:01 am

“Evidently, the fundamental laws of nature do not pin down a single and unique universe”*…

For the World Is Hollow and I Have Touched the Sky Original printing of the Flammarion engraving, from 1888.
Artist unknown; from Camille Flammarion, L’Atmosphère: Météorologie Populaire

The name of the image—the “Flammarion engraving”—may not ring a bell, but you’ve seen it many times. It depicts a traveler wearing a cloak and clutching a walking-stick; behind him is a varied landscape of towns and trees; surrounding all is a crystalline shell fretted with countless stars. Reaching the edge of his world, the traveler pushes through to the other side and is dazzled by a whole new world of light and rainbows and fire.

The image was first published in 1888 in a book by French astronomer Camille Flammarion. (The original engraving was black and white, although colorized versions now abound.) He notes that the sky does look like a dome on which the celestial bodies are attached, but impressions deceive. “Our ancestors,” Flammarion writes, “imagined that this blue vault was really what the eye would lead them to believe it to be; but, as Voltaire remarks, this is about as reasonable as if a silk-worm took his web for the limits of the universe.”

The engraving has come to be seen as a symbol of humanity’s quest for knowledge, but I prefer a more literal reading, in keeping with Flammarion’s intent. Time and again in the history of science, we have found an opening in the edge of the known world and poked through. The universe does not end at the orbit of Saturn, nor at the outermost stars of the Milky Way, nor at the most distant galaxy in our field of view. Today cosmologists think whole other universes may be out there.

But that is almost quotidian compared to what quantum mechanics reveals. It is not just a new opening in the dome, but a new kind of opening. Physicists and philosophers have long argued over what quantum theory means, but, in some way or other, they agree that it reveals a vast realm lying beyond the range of our senses. Perhaps the purest incarnation of this principle—the most straightforward reading of the equations of quantum theory—is the many-worlds interpretation, put forward by Hugh Everett in the 1950s. In this view, everything that can happen does in fact happen, somewhere in a vast array of universes, and the probabilities of quantum theory represent the relative numbers of universes experiencing one outcome or another. As David Wallace, a philosopher of physics at the University of Southern California, put it in his 2012 book, The Emergent Multiverse, when we take quantum mechanics literally, “the world turns out to be rather larger than we had anticipated: Indeed, it turns out our classical ‘world’ is only a small part of a much larger reality.”…

If multiverses seem weird, it’s because we need to revamp our notions of time and space: “The Multiple Multiverses May Be One and the Same.”

* Alan Lightman, The Accidental Universe: The World You Thought You Knew

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As we find one in many, we might send relativistic birthday greetings to Victor Frederick “Viki” Weisskopf; he was born on this date in 1908. A theoretical physicist who contributed mightily to the golden age of quantum mechanics, Weisskopf did postdoctoral work with Werner Heisenberg, Erwin Schrödinger, Wolfgang Pauli and Niels Bohr. He emigrated from Austria to the U.S. in 1937 to escape Nazi persecution. During World War II he was Group Leader of the Theoretical Division of the Manhattan Project at Los Alamos, and later campaigned against the proliferation of nuclear weapons.

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Written by LW

September 20, 2020 at 1:01 am

“Biology gives you a brain. Life turns it into a mind.”*…

 

Mind

 

I have a confession. As a physicist and psychiatrist, I find it difficult to engage with conversations about consciousness. My biggest gripe is that the philosophers and cognitive scientists who tend to pose the questions often assume that the mind is a thing, whose existence can be identified by the attributes it has or the purposes it fulfils.

But in physics, it’s dangerous to assume that things ‘exist’ in any conventional sense. Instead, the deeper question is: what sorts of processes give rise to the notion (or illusion) that something exists? For example, Isaac Newton explained the physical world in terms of massive bodies that respond to forces. However, with the advent of quantum physics, the real question turned out to be the very nature and meaning of the measurements upon which the notions of mass and force depend – a question that’s still debated today.

As a consequence, I’m compelled to treat consciousness as a process to be understood, not as a thing to be defined. Simply put, my argument is that consciousness is nothing more and nothing less than a natural process such as evolution or the weather. My favourite trick to illustrate the notion of consciousness as a process is to replace the word ‘consciousness’ with ‘evolution’ – and see if the question still makes sense. For example, the question What is consciousness for? becomes What is evolution for? Scientifically speaking, of course, we know that evolution is not for anything. It doesn’t perform a function or have reasons for doing what it does – it’s an unfolding process that can be understood only on its own terms. Since we are all the product of evolution, the same would seem to hold for consciousness and the self.

My view on consciousness resonates with that of the philosopher Daniel Dennett, who has spent his career trying to understand the origin of the mind. Dennett is concerned with how mindless, mere ‘causes’ (A leads to B) can give rise to the species of mindful ‘reasons’ as we know them (A happens so that B can happen). Dennett’s solution is what he calls ‘Darwin’s dangerous idea’: the insight that it’s possible to have design in the absence of a designer, competence in the absence of comprehension, and reasons (or ‘free-floating rationales’) in the absence of reasoners. A population of beetles that has outstripped another has probably done so for some ‘reason’ we can identify – a favourable mutation which produces a more camouflaging colour, for example. ‘Natural selection is thus an automatic reason-finder, which “discovers” and “endorses” and “focuses” reasons over many generations,’ Dennett writes in From Bacteria to Bach and Back: The Evolution of Minds (2017). ‘The scare quotes are to remind us that natural selection doesn’t have a mind, doesn’t itself have reasons, but is nevertheless competent to perform this “task” of design refinement.’

I hope to show you that nature can drum up reasons without actually having them for herself. In what follows, I’m going to argue that things don’t exist for reasons, but certain processes can nonetheless be cast as engaged in reasoning…

Distinguished neuroscientist and psychiatrist Karl Friston argues that the special trick of consciousness is being able to project action and time into a range of possible futures: “The mathematics of mind-time.”

See also: “How the Brain Creates a Timeline of the Past” (source of the image above).

* Jeffrey Eugenides, Middlesex

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As we get our minds around our minds, we might spare a thought for Oliver Wolf Sacks; he died on this date in 2015.  A neurologist, naturalist, historian of science, and author, he had an active clinical practice, but is more widely-remembered for his writing, mostly case studies from his clinical experience and memoir in which which he treats himself as a clinical subject.  Awakenings, for example, recounted his experience treating post-encephalitic patients with a new drug (levodopa); it was a best seller that served as the basis of a BBC Discovery documentary and was adapted into a feature film.  Widely honored for his prolific work, Sacks was the recipient of the 2001 Lewis Thomas Prize for excellence in scientific writing.

250px-9.13.09OliverSacksByLuigiNovi source

 

Written by LW

August 30, 2020 at 1:01 am

“All poets write bad poetry. Bad poets publish them, good poets burn them.”*…

 

Thunderstorm with the Death of Amelia 1784 by William Williams active 1758-1797

Thunderstorm with the Death of Amelia, by William Williams, 1784. Photograph © Tate (CC-BY-NC-ND 3.0).

 

Readers may recall an earlier nod to William Topaz McGonagall, widely considered to be the worst published poet in British history.  McGonagall, best known for his widely-excoriated verse recounting of “The Tay Bridge Disaster,” distributed his poems, often about momentous events, on handbills and performed them publicly (often, it is reported, to cat calls and thrown food).  And he collected his verse into volumes including Poetic Gems, More Poetic Gems, Still More Poetic Gems, Further Poetic Gems, and Yet Further Poetic Gems.  Imagine your correspondent’s surprise and delight to find a learned appreciation of McGonagall’s place in poetic history:

Not unjustly, McGonagall is rarely mentioned without an epithet: some version of “the worst poet in the English language.” And by any reasonable account, any judgment based on the most universally shared values of poetics, prosody, and taste, there is little to admire in McGonagall. The rest of his corpus shares—replicates, really—the faults of “The Tay Bridge Disaster”: its lapses into bathos, its involuted syntactical structures, its rhymes so slanted as to be more or less horizontal.

There have been worse poets, of course, and as such it would be more accurate to describe McGonagall as the worst famous poet in the English language, a testament in part to the man’s powers of self-promotion and the caprices of literary history. But McGonagall’s notoriety still owes much to the singularly strange power of his own badness. There’s something, I think, in poems like “The Tay Bridge Disaster”—as well as McGonagall’s many poems on his great themes of death and destruction—that is worth examining; something that might redeem him, ever so slightly, from the annals of amusing semi-obscurity; something unsettling about his ostensibly blinkered artistic vision that might help to account for why he lingers as the patron saint of misbegotten verse…

On William Topaz McGonagall, the worst famous poet in the English language: “The Disaster Poet.”

(Readers will find a selection of McGonagall’s poems here.)

* Umberto Eco

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As we bathe in bathos, we might spare a thought for the decidedly more-accomplished poet (and playwright, artist, biologist, theoretical physicist, and philosopher) Johann Wolfgang von Goethe; he died on this date in 1832.  Probably best remembered these days for Faust, he was “the master spirit of the German people,” and, after Napoleon, the leading figure of his age.

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Written by LW

August 28, 2020 at 1:01 am

“If you are not completely confused by quantum mechanics, you do not understand it”*…

 

uchicagoscie

 

If we can harness it, quantum technology promises fantastic new possibilities. But first, scientists need to coax quantum systems to stay yoked for longer than a few millionths of a second.

A team of scientists at the University of Chicago’s Pritzker School of Molecular Engineering announced the discovery of a simple modification that allows quantum systems to stay operational—or “coherent”—10,000 times longer than before. Though the scientists tested their technique on a particular class of quantum systems called solid-state qubits, they think it should be applicable to many other kinds of quantum systems and could thus revolutionize quantum communication, computing and sensing…

Down at the level of atoms, the world operates according to the rules of quantum mechanics—very different from what we see around us in our daily lives. These different rules could translate into technology like virtually unhackable networks or extremely powerful computers; the U.S. Department of Energy released a blueprint for the future quantum internet in an event at UChicago on July 23. But fundamental engineering challenges remain: Quantum states need an extremely quiet, stable space to operate, as they are easily disturbed by background noise coming from vibrations, temperature changes or stray electromagnetic fields.

Thus, scientists try to find ways to keep the system coherent as long as possible…

“This breakthrough lays the groundwork for exciting new avenues of research in quantum science,” said study lead author David Awschalom, the Liew Family Professor in Molecular Engineering, senior scientist at Argonne National Laboratory and director of the Chicago Quantum Exchange. “The broad applicability of this discovery, coupled with a remarkably simple implementation, allows this robust coherence to impact many aspects of quantum engineering. It enables new research opportunities previously thought impractical.”…

Very big news at a very small scale: “Scientists discover way to make quantum states last 10,000 times longer.”

*John Wheeler

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As we strive for stability, we might send calculated birthday greetings to Brook Taylor; he was born on this date in 1685.  A mathematician, he is best known for his work in describing and understanding oscillation.  In 1708, Taylor produced a solution to the problem of the center of oscillation.  His Methodus incrementorum directa et inversa (“Direct and Indirect Methods of Incrementation,” 1715) introduced what is now called the calculus of finite differences.  Using this, he was the first to express mathematically the movement of a vibrating string on the basis of mechanical principles.  Methodus also contained Taylor’s theorem, later recognized by Joseph Lagrange as the basis of differential calculus.

A gifted artist, Taylor also wrote on the basic principles of perspective, including the first general treatment of the principle of vanishing points.

220px-BTaylor source

 

 

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