I finished reading Three Roads to Quantum Gravity (2001), by Lee Smolin, a theoretical physicist whose general sensibility I’ve always appreciated. I don’t always agree with his ideas, but I like the thoughtful way he expresses them. Smolin brings some philosophical thinking to his physics.
While he added a lengthy Postscript to the 2017 edition, the book is outdated both by time and by Smolin. In 2006 he published The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next, which explored issues in the practice of theoretical physics. But in 2001 he still thought string theory was (at least part of) The Answer.
Almost none of which is the subject of this post.
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15 Comments | tags: black hole, Lee Smolin, Loop Quantum Gravity, quantum gravity | posted in Books, Brain Bubble
Oh, look! Dancing Pixies!
In the last two posts I’ve explored some ideas about what a computer is. More properly, what a computation is, since a computer is just something that does a computation. I’ve differentiated computation from calculation and, more importantly, evaluation. (This post assumes you’ve read Part I and Part II.)
I’ve also looked at pancomputationalism (the idea everything computes). The post hoc approach of mapping of random physical states to a computation seems especially empty. The idea of treating the physical dynamics of a system as a computation has more interesting and viable features.
That’s where I’ll pick things up.
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4 Comments | tags: analog computer, computation, computationalism, digital computer | posted in Computers, Science
Computer cluster?
Last time I began exploring what we mean by the terms “computer” or “computation.” Upon examination, these turn out to be not entirely obvious, so some resort to the edge cases: Computers are Turing Machines; or Everything is a computer.
Even then the situation remains stubbornly not obvious. Turing Machines are abstractions quite different from what we typically call computers. Saying everything computes creates such a broad umbrella that it renders the notion of computation nearly useless.
This series explores the territory between those edge cases.
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7 Comments | tags: analog computer, computation, digital computer | posted in Computers, Science
Two computers?
Earlier this year I wrote a trilogy of posts exploring digital dualism — the notion that a (conventional) computer has a physical layer that implements a causally distinct abstract layer. In writing those posts I found my definition of computation shifting slightly to embrace the notion of that dualism.
The phrase “a (conventional) computer” needs unpacking. What is a computer, and what makes one conventional? Computer science offers a mathematical view. Philosophy, as it often does, spirals in on the topic and offers a variety of pancomputation views.
In this series I’ll explore some of those views.
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5 Comments | tags: analog computer, computation, digital computer | posted in Computers, Science
Flat Earth!
To describe how space could be flat, finite, and yet unbounded, science writers sometimes use an analogy involving the surface of a torus (the mathematical abstraction of the doughnut shape). Such a surface has no boundary — no edge. And despite being embedded in three-dimensional space, the torus surface, if seen in terms of compensating surface metric, is indeed flat.
Yet a natural issue people have is that the three-dimensional embedding is clearly curved, not flat. It’s easy to see how wrapping a flat 2D sheet into a cylinder doesn’t distort it, but hard to see why wrapping a cylinder around a torus doesn’t stretch the outside and compress the inside.
In fact it does, but there are ways to eat our cake (doughnut).
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43 Comments | tags: 2D space, 3D space, cosmology, flat space, Flatland, space, torus | posted in Math
Speaking of Bell tests, I’ve noticed that science writers often struggle to find a good metaphor that illustrates just what’s so weird about the correlation between entangled particles. Bell tests are complex, and because they squat in the middle of quantum weirdness, they’re hard to explain in any classical terms.
I thought I had the beginnings of a good metaphor, at least the classical part. But the quantum part is definitely a challenge. (All the more so because I’m still not entirely clear on the deep details of Bell’s theorem myself.)
Worse, I think my metaphor fails the ping-pong ball test.
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35 Comments | tags: Bell's Theorem, particles, quantum mechanics | posted in Brain Bubble, Physics
Last time I explored the quantum spin of photons, which manifests as the polarization of light. (Note that all forms of light can be polarized. That includes radio waves, microwaves, IR, UV, x-rays, and gamma rays. Spin — polarization — is a fundamental property of photons.)
I left off with some simple experiments that demonstrated the basic behavior of polarized light. They were simple enough to be done at home with pairs of sunglasses, yet they demonstrate the counter-intuitive nature of quantum mechanics.
Here I’ll dig more into those and other experiments.
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10 Comments | tags: Bell's Theorem, photons, QM101, quantum mechanics | posted in Physics
Earlier in this QM-101 series I posted about quantum spin. That post looked at spin 1/2 particles, such as electrons (and silver atoms). This post looks at spin in photons, which are spin 1 particles. (Bell tests have used both spin types.) In photons, spin manifests as polarization.
Photon spin connects the Bloch sphere to the Poincaré sphere — an optics version designed to represent different polarization states. Both involve a two-state system (a qubit) where system state is a superposition of two basis states.
Incidentally, photon polarization reflects light’s wave-particle duality.
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8 Comments | tags: Bell's Theorem, photons, QM101, quantum spin, wave-function, wave-particle duality | posted in Physics
This post’s fill-in-the-blank title (given the “season” clue that we’re talking about television shows) might refer to any of at least three series, all coincidentally from Amazon Prime studios. In fact it refers to all three, although this post is only about two because I already wrote about Upload. As it turns out, I liked it best of the three U___ shows.
The other two are Undone and Utopia (the new one). I’d tried the former last year but wasn’t grabbed. This time I liked it better and binge-watched the whole season. The latter was dark and very murder-y. Both of them were… okay. I don’t quite recommend either, though.
What I do recommend (highly!) is the anime movie, Penguin Highway.
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37 Comments | tags: Amazon Prime, anime, Japanese anime, Penguin Highway, science fiction TV, SF, SF TV, Undone (TV series), Utopia (TV series) | posted in Sci-Fi Saturday, TV
I finished The Quantum Labyrinth: How Richard Feynman and John Wheeler Revolutionized Time and Reality (2017), by Paul Halpern. As the title implies, the book revolves around the careers and lives of John A. Wheeler (1911–2008) and Richard Feynman (1918–1988). After Feynman graduated from MIT he became Wheeler’s teaching assistant at Princeton. The two men, despite very different personalities, became life-long friends and collaborators.
One of Wheeler’s many claims to fame is his promotion of Hugh Everett’s PhD thesis, The Theory of the Universal Wave Function. That paper, of course, is the seed from which grew the Many Worlds Interpretation of Quantum Mechanics.
The thing is, there are two major versions of the MWI.
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3 Comments | tags: Many Worlds Interpretation, MWI, Paul Halpern, quantum mechanics, Sabine Hossenfelder | posted in Brain Bubble, Physics
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