(Roughly) Daily

Posts Tagged ‘reality

“‘Space-time’ – that hideous hybrid whose very hyphen looks phoney”*…

Space-time curvature [source: ESA]

Space and time seem about as basic as anything could be, even after Einstein’s theory of General Relativity threw (in) a curve. But as Steven Strogatz discusses with Sean Carroll, the reconciliation of Einstein’s work with quantum theory is seeming to suggest that space and time might actually be emergent properties of quantum reality, not fundamental parts of it…

… we’re going to be discussing the mysteries of space and time, and gravity, too. What’s so mysterious about them?

Well, it turns out they get really weird when we look at them at their deepest levels, at a super subatomic scale, where the quantum nature of gravity starts to kick in and become crucial. Of course, none of us have any direct experience with space and time and gravity at this unbelievably small scale. Up here, at the scale of everyday life, space and time seem perfectly smooth and continuous. And gravity is very well described by Isaac Newton’s classic theory, a theory that’s been around for over 300 years now.

But then, about 100 years ago, things started to get strange. Albert Einstein taught us that space and time could warp and bend like a piece of fabric. This warping of the space-time continuum is what we experience as gravity. But Einstein’s theory is mainly concerned with the largest scales of nature, the scale of stars, galaxies and the whole universe. It doesn’t really have much to say about space and time at the very smallest scales.

And that’s where the trouble really starts. Down there, nature is governed by quantum mechanics. This amazingly powerful theory has been shown to account for all the forces of nature, except gravity. When physicists try to apply quantum theory to gravity, they find that space and time become almost unrecognizable. They seem to start fluctuating wildly. It’s almost like space and time fall apart. Their smoothness breaks down completely, and that’s totally incompatible with the picture in Einstein’s theory.

s physicists try to make sense of all of this, some of them are coming to the conclusion that space and time may not be as fundamental as we always imagined. They’re starting to seem more like byproducts of something even deeper, something unfamiliar and quantum mechanical. But what could that something be?….

Find out at: “Where Do Space, Time and Gravity Come From?, ” from @stevenstrogatz and @seanmcarroll in @QuantaMagazine.

* Vladimir Nabokov

###

As we fumble with the fundamental, we might send far-sighted birthday greetings to Jocelyn Bell Burnell; she was born on this date in 1943. An astrophysicist, she discovered the first pulsar, while working as a post-doc, in 1957. She then discovered the next three detected pulsars.

The discovery eventually earned the Nobel Prize in Physics in 1974; however, she was not one of the prize’s recipients. The paper announcing the discovery of pulsars had five authors. Bell’s thesis supervisor Antony Hewish was listed first, Bell second. Hewish was awarded the Nobel Prize, along with the astronomer Martin Ryle.

A pulsar— or pulsating radio star– a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. The precise periods of pulsars make them very useful tools. Observations of a pulsar in a binary neutron star system were used to  confirm (indirectly) the existence of gravitational radiation. The first extrasolar planets were discovered around a pulsar, PSR B1257+12.  And certain types of pulsars rival atomic clocks in their accuracy in keeping time.

Schematic rendering of a pulsar

source

Jocelyn Bell Burnell

source

Written by (Roughly) Daily

July 15, 2022 at 1:00 am

“The truth is rarely pure and never simple”*…

For a century, the idea of truth has been deflated, becoming terrain from which philosophers fled. Crispin Sartwell argues that they must return – urgently…

It is often said, rather casually, that truth is dissolving, that we live in the ‘post-truth era’. But truth is one of our central concepts – perhaps our most central concept – and I don’t think we can do without it. To believe that masks prevent the spread of COVID-19 is to take it to be true that they do. To assert it is to claim that it is true. Truth is, plausibly, central to thought and communication in every case. And, of course, it’s often at stake in practical political debates and policy decisions, with regard to climate change or vaccines, for example, or who really won the election, or whom we should listen to about what.

One might have hoped to turn to philosophy for a clarification of the nature of truth, and maybe even a celebration of it. But philosophy of pragmatist, analytic and continental varieties lurched into the post-truth era a century ago. If truth is a problem now for everyone, if the idea seems empty or useless in ‘the era of social media’, ‘science denialism’, ‘conspiracy theories’ and suchlike, maybe that just means that ‘everyone’ has caught up to where philosophy was in 1922…

[Sartwell sketches the last 100 years of philosophy, and it’s undermining of the very idea of truth.]

I don’t think, despite all the attacks on the notion by all sorts of philosophers for a good century, that we’re going to be able to do without truth. In a way, I don’t think all those attacks touched truth at all, which (we’re finding) is necessary, still the only possible cure…

As a first step… we might broaden the focus from the philosophical question of what makes a sentence or proposition true or false to focus on some of the rich ways the concept of truth functions in our discourse. That love is true does not mean that it is a representation that matches up to reality. It does not mean that the love hangs together with all the rest of the lover or lovee’s belief system. It doesn’t mean that the hypothesis that my love is true helps us resolve our problems (it might introduce more problems). It means that the love is intense and authentic, or, as I’d like to put it, that it is actual, real. That my aim is true does not indicate that my aim accurately pictures the external world, but that it thumps the actual world right in the centre, as it were.

Perhaps what is true or false isn’t only, or even primarily, propositions, but loves and aims, and the world itself. That is, I would like to start out by thinking of ‘true’ as a semi-synonym of ‘real’. If I were formulating in parallel to Aristotle, I might say that ‘What is, is true.’ And perhaps there’s something to be said for Heidegger’s ‘comportment’ after all: to know and speak the real requires a certain sort of commitment: a commitment to face reality. Failures of truth are, often, failures to face up. Now, I’m not sure how much that will help with mathematics, but maths needs to understand that it is only one among the many forms of human knowledge. We, or at any rate I, might hope that an account that addresses the traditional questions about propositional truth might emerge from this broader structure of understanding. That is speculative, I admit.

Truth may not be the eternal unchanging Form that Plato thought it was, but that doesn’t mean it can be destroyed by a few malevolent politicians, tech moguls or linguistic philosophers, though the tech moguls and some of the philosophers (David Chalmers, for instance) might be trying to undermine or invent reality, as well. Until they manage it, the question of truth is as urgent, or more urgent, than ever, and I would say that despite the difficulties, philosophers need to take another crack. Perhaps not at aletheia as a joy forever, but at truth as we find it, and need it, now…

On why philosophy needs to return of the question of truth: “Truth Is Real,” from @CrispinSartwell in @aeonmag.

Source of the image above, also relevant: “The difference between ‘Truth’ and ‘truth’.”

* Oscar Wilde

###

As we wrestle with reality, we might recall that it was on this date in 1986 that Geraldo Rivera opened “Al Capone’s Vault”…

Notorious and “most wanted” gangster, Al Capone, began his life of crime in Chicago in 1919 and had his headquarters set up at the Lexington Hotel until his arrest in 1931. Years later, renovations were being made at the hotel when a team of workers discovered a shooting-range and series of connected tunnels that led to taverns and brothels making for an easy escape should there be a police raid. Rumors were spread that Capone had a secret vault hidden under the hotel as well. In 1985, news reporter Geraldo Rivera had been fired from ABC after he criticized the network for canceling his report made about an alleged relationship between John F. Kennedy and Marilyn Monroe. It seemed like a good time for Rivera to scoop a new story to repair his reputation. It was on this day in 1986 that his live, two-hour, syndicated TV special, The Mystery of Al Capone’s Vault aired. After lots of backstory, the time finally came to reveal what was in that vault. It turned out to be empty. After the show, Rivera was quoted as saying “Seems like we struck out.”

source

source

Written by (Roughly) Daily

April 21, 2022 at 1:00 am

“My work consists of two parts; that presented here plus all I have not written. It is this second part that is important.”*…

Ludwig Wittgenstein’s wooden cabin in Skjolden, Norway

On the occasion of it centenary, Peter Salmon considers the history, context, and lasting significance of Wittgenstein‘s revolutionary first work…

One hundred years ago, a slim volume of philosophy was published by the then unknown Austrian philosopher Ludwig Wittgenstein. The book was as curious as its title, Tractatus Logico-Philosophicus. Running to only 75 pages, it was in the form of a series of propositions, the gnomic quality of the first as baffling to the newcomer today as it was then.

1. The world is all that is the case.
1.1 The world is a totality of facts not of things.
1.11 The world is determined by the facts, and by their being all the facts.
1.12 For the totality of facts determines what is the case, and also whatever is not the case.
1.13 The facts in logical space are the world.

And so on, through six propositions, 526 numbered statements, equally emphatic and enigmatic, until the seventh and final proposition, which stands alone at the end of the text: “Whereof we cannot speak, thereof we must remain silent.”

The book’s influence was to be dramatic and far-reaching. Wittgenstein believed he had found a “solution” to how language and the world relate, that they shared a logical form. This also set a limit as to what questions could be meaningfully asked. Any question which could not be verified was, in philosophical terms, nonsense.

Written in the First World War trenches, Tractatus is, in many ways, a work of mysticism…

Ludwig Wittgenstein’s Tractatus is as brilliant and baffling today as it was on its publication a century ago: “The logical mystic,” from @petesalmon in @NewHumanist.

* Ludwig Wittgenstein

###

As we wrestle with reason and reality, we might recall that it was on this date in 1930 that Dashiell Hammett‘s The Maltese Falcon— likely a favorite of Wittgenstein’s— was published. In 1990 the novel ranked 10th in Top 100 Crime Novels of All Time list by the Crime Writer’s Association. Five years later, in a similar list by Mystery Writers of America, the novel was ranked third.

source

“Reality is frequently inaccurate”*…

Machine learning and what it may teach us about reality…

Our latest paradigmatic technology, machine learning, may be revealing the everyday world as more accidental than rule-governed. If so, it will be because machine learning gains its epistemological power from its freedom from the sort of generalisations that we humans can understand or apply.

The opacity of machine learning systems raises serious concerns about their trustworthiness and their tendency towards bias. But the brute fact that they work could be bringing us to a new understanding and experience of what the world is and our role in it…

The world is a black box full of extreme specificity: it might be predictable but that doesn’t mean it is understandable: “Learn from Machine Learning,” by David Weinberger (@dweinberger) in @aeonmag.

(image above: source)

* Douglas Adams, The Restaurant at the End of the Universe

###

As ruminate on the real, we might send carefully-computed birthday greetings to Grace Brewster Murray Hopper.  A seminal computer scientist and Rear Admiral in the U.S. Navy, “Amazing Grace” (as she was known to many in her field) was one of the first programmers of the Harvard Mark I computer (in 1944), invented the first compiler for a computer programming language, and was one of the leaders in popularizing the concept of machine-independent programming languages– which led to the development of COBOL, one of the first high-level programming languages.

Hopper also found and documented the first computer “bug” (in 1947).

She has both a ship (the guided-missile destroyer USS Hopper) and a super-computer (the Cray XE6 “Hopper” at NERSC) named in her honor.

 source

“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.

source

%d bloggers like this: