Spooky action 10,000 times FTL. Yawn.

On the one hand, completely boring. Another test of QM is in complete agreement with theory.

On the other hand, this is almost as creepy now as it was when a 2007 Wired magazine article on a 1999 entanglement experiment casually noted that observer-independent reality was up against the possibility of free will. That set me off on my extended review of quantum mechanics; along the way free will seems to have come out ahead of reality.

Not quite as creepy though, because I'm getting used to living in a universe that's infinitely weirder than it seems. Here's the latest edition ...

Quantum weirdness wins again: Entanglement clocks in at 10,000 times faster than light: Scientific American Blog

No matter how many times researchers try, there's just no getting around the weirdness of quantum mechanics.

In the latest attempt, researchers at the University of Geneva in Switzerland tried to determine whether entanglement—the fact that measuring a property of one particle instantly determines the property of another—is actually transmitted by some wave-like signal that's fast but not infinitely fast.

Their test involved a series of measurements on pairs of entangled photons (particles of light) that were generated in Geneva (aerial view at left) and then split apart by optical fiber to two villages 18 kilometers (11 miles) apart where the team had set up photon detectors. (In 2007, researchers transmitted entangled light 144 kilometers between two of the Canary Islands.)

The idea in the new experiment is that the photons in each pair of entangled pair are hitting the distant detectors simultaneously, so there's no time for them to exchange a signal. By comparing results from the two detectors, the researchers determined whether the photons were entangled or not, using a test known as Bell's inequalities.

The photons were indeed entangled, the group reports in Nature. But in reality, no experiment is perfect, so what they end up with is a lower limit on how fast the entanglement could be traveling: 10,000 times the speed of light....

.. It's always conceivable that quantum mechanics might break down (read: show some signs of everyday normalcy) if experimenters could test it the right way. In a 2007 study, researchers in Vienna tested the idea that maybe the instantaneous-ness of entanglement (called nonlocality) was consistent with hidden "variables" that can explain the randomness of quantum measurements. But no dice for that idea...

... Rudolph says we're probably stuck with instantaneous entanglement, which seems impossible to us because we're stuck in everyday space and time. "We need to understand how quantum mechanics sees space and time," he says. "I think there's probably much deeper issues.

Yep, we're stuck.

I recommend Gribbin for a layperson explanation of how bad things are, though his preferred model for understanding entanglement is currently out of fashion (and incompatible with free will).

Three Shtetl-Optimized posts for livening the mind

I really need to study, so I'm noting these for future reading.

These are a set of Aaronson posts, found by tracing back from the latests, that taken together are very good reading in physics and philosophy:

• The relativity of originality
• His review of Wolfram (pdf)
• Newcomb's problem
• PHYS771 Free will

All the essays touch, more or less directly, on the question of whether "free will" (as Scott rigorously defines it) is possible. Note this is distinct from the concept of responsibility -- every reasonable thinker over the past few centuries has understood that "responsibility" is a social construction with no intellectual integrity.

By way of background scientists philosophers have gone back and forth on this since science was more or less born with Francis Bacon. Things looked particularly bad in the 20th century; in the absence of quantum mechanics general relativity seemed to predict a universe frozen in space-time, in which every moment occurred at once and invariably. Maybe this is where Vonnegut's Tralfamadorean determinism came from.

QM seemed to restore free will, but it introduced some disturbing predictions of its own. Physicists attempted to restore the concept of an observer-independent reality through the transactional interpretation, but that did in free will

More recently reality (or realism) seems to be out favor, so maybe free will is back.

Now you're prepped to read Aaronson.

PS. See also - Sean Carroll's favorite posts.

Bayes theorem and the anthropic principle

Years ago I used to teach Bayes theorem to informatics grad students.

I was reassigned to other lectures though. Truth is, I had a hard time focusing on the boring stuff we were doing with Bayes. It just seemed like there was a deep weirdness about the Bayesian model of probability, but I couldn't quite put my finger on it. I was sure someone who understood it deeply would justify my queasiness.

Since then there's been a bit of a renaissance in thinking about Bayes. In Our Time even did a recent programme with a good bit of Bayes. Physicists are all over Bayes these days, and the Bayesian vs. Frequentist combat is out in the open (I knew this stuff was weird).

These days, I could assign students this essay to read:

PHYS771 Lecture 17: Fun With the Anthropic Principle

... So if Bayes' Theorem seems unobjectionable, then I want to make you feel queasy about it. That's my goal. The way to do that is to take the theorem very, very seriously as an account of how we should reason about the state of the world...

Of course that assignment might also shrink the class size ...

Quantum Computing: the lecture notes

From the professor (Scott Aaronson of Shtetl Optimized) who gave us his lectures on theoretical computer science, we now have PHYS771 Quantum Computing Since Democritus. Or at least, as of today, lectures 1-13.

We eagerly await 14-21, including "Free Will" (I really want that one) and "Cosmology and Complexity".

Hacking encryption keys: quantum and otherwise

A non-specialist has written a review of quantum computer factoring that matches what I've been reading from my physics blogs. Quantum computing, alas, isn't as impressive as it used to be. Even if we can make it work, quantum computing is not necessarily a qualitative improvement over conventional computation -- though it will explore some (truly) mind-boggling quantum physics.

I wanted to call out one small part of the post though:

... I went over to a site that will tell you how long a key you need to use, http://www.keylength.com/. Keylength.com uses estimates made by serious cryptographers for the life of keys. They make some reasonable assumptions and perhaps one slightly-unreasonable assumption: that Moore's Law will continue indefinitely. If we check there for how long a 4096-bit key will be good for, the conservative estimate is (drum roll, please) — the year 2060...

Most of us make do with AES 128 bit (Tiger disk image encryption) and AES 256 bit (Leopard disk image encryption) keys. I checked out the NIST 2007 recommendations on keylength.com and found:

• AES 128: > 2030
• AES 256: >> 2030

Another table (ENCRYPT) described 256 symmetric key (ie. AES) as "good protection against quantum cryptography". So most of us don't need to worry about 4096 bit keys unless we're protecting information that will be very valuable in 2040.

I'll be 80 then -- if I'm alive. I'm not too worried.

Of course Schneier et all are usually reminding us that the key length is generally the least of our worries. Weak passwords, dictionary attacks, attacks on keys in memory, etc are all bigger threats. The biggest threat of all, though, is security that either destroys our data (that's really secure!) or that is too onerous to easily implement.

PS. I was in the "quantum will get us" crowd, so I'm a bit humbled by the new wave of "quantum reality".

Mathematical universe: the softly spoken premise of string theory

Why are mathematical models so insanely good at making predictions about the physical universe?

Is this a testament to the general modeling power of mathematics to describe any internally consistent system, or is the universe in some sense fundamentally mathematical?

These are the sorts of questions that used to come up in my undergraduate days. I don't recall a good answer, though I was certainly on the dim side of that student body. It may be that the answers were simply over my head.

I wonder about those questions again as I, very slowly, read Brian Greene's The Fabric of the Cosmos (See also: BBC IOT - Theories of Everything With Brian Greene). It's a good book; I'll have more to say on it when I'm done - sometime in the spring of 2008. For now I will say I like the substantial non-string chapters better than the string theory portion.

There are a few reasons for this preference. Greene is a string theorist, and I think most specialists do best describing things outside of their core passion. It's easier to be neutral about things that you haven't poured your heart into. More interestingly, the old question, "Is the universe fundamentally mathematical?", plays a role as well.

Most new physics seems, to a hobbyist like me, to make a reasonable bet that the implausible success of mathematical models will hold in new domains. It's a bit like tossing a plank off the end of a pier, assuming that when one walks to the end of the plank a supporting pillar will be found.

String theory tosses a breathtakingly long plank. It's a daring bet indeed. If we're ever to find out that it holds (proof of those necessary 10 space dimensions?) then we do have to take seriously the old whimsy that the universe, at its heart, is purely mathematical.

Until that day, it sure does feel to the physics hobbyist more like an exercise in mathematical brilliance than even traditional theoretical physics ...

Physics Feast: Sean Carroll's favorite posts

Sean "Cosmic Varience" Carroll has indexed his personal favorite posts. A true feast for the physics fan.

Two dimensional string theory

Promotion has sapped the output of my favorite physics bloggers, so I'm grateful to FMH for my physics fix:

Shadow World: Science News Online, Nov. 17, 2007

....Since 1997, physicists have proposed countless variations on Maldacena's theme, all of which interpret a string as a swarm of particles living in a small number of dimensions. Perhaps the easiest case to visualize is when that number is two. In such a scenario, anything that takes place in your many-dimensional, stringy universe has a sort of shadow representation in terms of particles moving on that universe's 'sphere at infinity.' This esoteric-sounding concept is actually similar to the familiar celestial sphere of the night sky as seen from Earth: It's the two-dimensional surface spanning all possible directions one can point to infinitely far in space...

So this re-representation of string theory has been popular for 10 years -- but I don't recall reading about it.

Annoying.

Sciam did cover this in Nov 2005 ("The Illusion of Gravity"), but I wasn't a subscriber then. (SciAm is the only periodical I subscribe to does not give archival access to current print subscribers. It's their right, but I do hold it against them.)

Wikipedia presents the theory more technically:

Juan Martín Maldacena (born September 10, 1968) is a theoretical physicist born in Buenos Aires, Argentina. Among his many discoveries, the most famous one is the most reliable realization of the holographic principle - namely the AdS/CFT correspondence, the successfully tested conjecture about the equivalence of string theory or supergravity on Anti de Sitter (AdS) space, and a conformal field theory defined on the boundary of the AdS space.

and on AdS/CFT correspondence:

In physics, the AdS/CFT correspondence (anti-de-Sitter space/conformal field theory correspondence), sometimes called the Maldacena duality, is the conjectured equivalence between a string theory defined on one space, and a quantum field theory without gravity defined on the conformal boundary of this space, whose dimension is lower by one or more...

Now, as we all know one of the primary challenges of the last 80 or so years of physics has been quantizing gravity. So, as a hobbyist reading this, I'm thinking the mathematical trick is to make the problem more tractable (and perhaps more constrained?) by taking gravity out of the picture. Hence the SciAm title - the "illusion of gravity".

This might be a bit like the old polar vs. cartesian coordinate transformation in Physics 101. Neither is "truer" than the other, but in some problems solutions are much easier. Or maybe the the Maldacena view will turn out to be the "better" model of "reality" (whatever that slippery beast might be).

I'll have to look around for some other popular summaries ...

Particle vs. Field: which is truer

Today it seems that particles are merely secondary ....

Nonlocality of a Single Particle Demonstrated Without Objections

... The scientists note an interesting comparison of their result to a principle of Leibniz’s metaphysics, the identity of indiscernibles. According to the principle, a pair of entangled quantum particles must be indiscernible from a single particle, since both objects have in common all the same properties—this is the only stipulation of the principle, number being irrelevant. The single-state nonlocality demonstrated here reinforces the equivalence of a single state and an entangled state—giving more credence to the position that quantum field theory, where fields are fundamental and particles secondary, is a close representation of reality...

In knowledge modeling the debate is between the nodes (statements) and the arcs (relationships). The arcs are pulling ahead.

Relativity + QM + symmetry = QED

After a series of posts with only a marginal connection to physics, CV has returned with a nice discussion of the Higgs particle:

Higgs 101 | Cosmic Variance

...Here comes the miracle: if you impose upon our relativistic, complex, quantum-mechanical wavefunctions the requirement that they be invariant under these U(1) transformations, then you get electromagnetism. Conservation of electric charge. A massless photon. QED - quantum electrodynamics, in all its 12-digit precision glory. Electromagnetism is a simple consequence of the U(1) symmetry of any wavefunction....

Symmetry, in this case the U(1) transformation invariance, is given a natural place in this discussion of the Higgs.

Nice summary!

Blah, blah, quantum entanglement, yawn, hacking reality, zzzzz

I'm almost caught up with modern physics, but it's taken a toll.

It's started my reading a few months ago when I realized I'd fallen hopelessly out of date, but I'm now only a few chapters from finishing Greenes latest tome. Alas, between Gribbin and Greenes, I'm a broken man. Modern physics is so consistently and cumulatively weird that a steady diet has eliminated my critical capacity. No wonder science fiction writers feel beaten down -- no work of fiction can be as mind-bending as today's physics. It's enough to make the idea that we're all living in a simulation seem comforting by comparison.

Which is to say that latest proof that the universe is every bit as weird as predicted is a bit of a yawner ...

'Spooky' science points to quantum internet - Internet - www.itnews.com.au

Physicists at the University of Michigan have demonstrated how two separate atoms can communicate with a sort of 'quantum intuition' ...

The scientists used light to establish an "entanglement" between two atoms, which were trapped one metre apart in separate enclosures...

... David Moehring, the lead author of the paper who performed the research as a University of Michigan graduate student, explained that the most important aspect of the experiment is the distance between the two atoms.

"The separation of the quantum bits [qubits] in our entangled state is the most important feature," he said.

"Localised entanglement has been performed in ion trap qubits in the past, but to build a scalable quantum computer network (or a quantum internet) the creation of entanglement schemes between remotely entangled qubit memories is necessary."

The researchers used two atoms to function as qubits storing a piece of information in their electron configuration. They then excited each atom, inducing electrons to fall into a lower energy state and emit one photon, or one particle of light, in the process.

The atoms, which were actually ions of the rare-earth element ytterbium, are capable of emitting two different types of photons of different wavelengths.

The type of photon released by each atom indicates the particular state of the atom. Because of this, each photon was entangled with its atom.

By manipulating the photons emitted from each of the two atoms and guiding them to interact along a fibre-optic thread, the researchers were able to detect the resulting photon clicks and entangle the atoms.

Professor Monroe explained that the fibre-optic thread was necessary to establish entanglement of the atoms. But the fibre could be severed and the two atoms would remain entangled, even if one were "carefully taken to Jupiter"...

I wasn't being entirely supercilious. My reading suggests this is a perfectly prosaic result, indeed anything different would have been shocking. The reason the paper was published is because of the experimental genius required, and perhaps because it suggests new ways to build a quantum computer.

Reality, perception, Hume, the red pill - and John Tierney

There's no way I have time to do this post justice, but I'll put something up anyway. Maybe I'll fill it in later.

What do these things have in common?

• Measurement in quantum mechanics and the "shut up and calculate" response to questions about reality and quantum mechanics
• Hume, Common Sense Philosophy and life in simulation (both of these are basically links to the end of a post, sorry, more below)
• How a digital picture taken of an analog photo can show more detail than is present in the analog original
• The output of the retina compared to the post-processed signals that become the fodder for perception
• The Red Pill and how to detect a VM

As a hint, here's a little bit more on the In Our Time programme on Common Sense Philosophy

• David Hume realized he couldn't "get out of his head". That is, he couldn't show that his "perceptions" were attached to an external truth, he had to simply assume there was an "out there". Thomas Reid responded with an 18th century version of "shut up and calculate", asserting that philosophy had to begin with the assumption of a physical reality and this could not be questioned. Reid was a deist, like Descartes he began with the assumption of a benign Principle Designer who wouldn't resort to trickery. Of course if one attributes more complex attributes to the PD then all bets are off ...
  

So, do we live in a simulation in a "real" world, or do we live in a simulation in a simulation?

Update 8/15/07: It must be something in the air. I just saw this: Tierney (NYT) interviews Nick Bostrum.

... The math and the logic are inexorable once you assume that lots of simulations are being run. But there are a couple of alternative hypotheses, as Dr. Bostrom points out. One is that civilization never attains the technology to run simulations (perhaps because it self-destructs before reaching that stage). The other hypothesis is that posthumans decide not to run the simulations...

Oh dear, it's getting harder to keep this blog on the fringes. I'll have to try harder. So, if we are (or I am) in a simulation run by ripples of space time in the infinite dying years of the endless universe, is this heaven, hell or are we (I) simply glitches in the software? Ok, now I'm back on the fringe ...

Or maybe not. Tierney, who was a miserable political columnist, is more imaginative than I could have imagined:

... My gut feeling is that the odds are better than 20 percent, maybe better than even. I think it’s highly likely that civilization could endure to produce those supercomputers. And if owners of the computers were anything like the millions of people immersed in virtual worlds like Second Life, SimCity and World of Warcraft, they’d be running simulations just to get a chance to control history — or maybe give themselves virtual roles as Cleopatra or Napoleon.

It’s unsettling to think of the world being run by a futuristic computer geek, although we might at last dispose of that of classic theological question: How could God allow so much evil in the world? For the same reason there are plagues and earthquakes and battles in games like World of Warcraft. Peace is boring, Dude...

Not bad really, though he's jumping to conclusions by assuming that whatever runs our purported simulation need have any similarity to us. This next bit I know Tierney got from a rather good science fiction story (I'll look it the story reference):

... There could be layer upon layer of simulations until you finally reached the architect of the first simulation — the Prime Designer, let’s call him or her (or it)...

and

...We’d start our simulation, expecting to observe a new virtual world, but instead our own world might end — not with a bang, not with a whimper, but with a message on the Prime Designer’s computer...

Darn, he took that one from me. I have to check if I ever seeded the meme that quantum computers would make us all dumber, since they'd suck the cycles that drive our simulations (hmm, is that testable? Probably not, the clock speed would simply drop.)

Next thing you know, Tierney will be onto the Fermi Paradox connection -- maybe after he recovers from the beating that he's about to receive from the general public.

I guess I can't stay on the fringe forever.

Update 8/15/07b: I remembered Reid's name and revised the post accordingly.

Update 1/18/08: See this later post on the same topic.

Quantum erasure and apple of the tree of knowledge

I skimmed the SciAM article on building a home "quantum eraser", but I didn't appreciate that the 1982 experiment is just one notch weirder than the what I'd read in Gribbin's 1997 book [1]. I realized how ++weird the result is upon reading Greenes description today [2].

As I dimly recall it, the "Aspect experiments" showed that the measured interference pattern that

• requires passage of a single photon through spatially separated paths simultaneously [3]

also

• requires no peeking after the photon has travelled the spatially separated paths
  

It's the "no-peeking after" part that made the experimental results so delicious. Causality (arrow of time), 1 dimensional time, and 3 dimensional space and "objective" reality all took big hits from the Aspect experiment. The discussion ever since has been which, if any, survived.

My weak understanding of Greenes' non-mathematical interpretation of the "erasure experiment was that the "no peeking after" clause is extended as follows:

and

• tricks that allow you to defer "peeking" until after the interference pattern ought to be formed don't work either (no surprise here, this is a variant of the Aspect experiment)
• if you set up a "deferred peeking" trick, but then undo it before you "peek", then the interference pattern can return. (surprise)
  

So it's the last bit that adds an additional note of sublime weirdness to the aspect experiment. It makes it just a bit easier to believe that the fundamental rule is really "no peeking". This is just something you can't know about.

It invariably reminds anyone taught by nuns of the "apple of the tree of knowledge" -- "but from the tree of the knowledge of good and evil you shall not eat, for in the day that you eat from it you will surely die.".

The universe seems to be telling us we can't watch some things too closely. Naturally, that only increases our appetite ....

[1] I really don't think Gribbin discussed this experiment, even though it was old when he wrote the book. It doesn't show up here either. I wonder why not ...

[2] Greenes is a cosmologist at heart, and he tends to shy away from the quantum weirdness Gribbin and others embrace, but he did a good job describing erasure.

[3] Paradox puzzles often require one to think carefully about what words mean, so I italicized a few of the interesting ones. Spatial separation, for example, has been shown not to mean what we thought it meant. Two entangled photons a universe apart are, by some measures, not separated at all.

Nature: 5 July 2007 - the quantum mechanics and science fiction issue

Nature, one of the two preeminent journals of science has dedicated a "science fiction" issue to examination of the multiverse and other QM interpretations. Of course nothing is available for viewing online, you have buy the issue. I'll see if I can get access through my U MN account. More later.

Update: I was too quick. The many worlds essay is available, some others may be too.

Cosmic Variance's Sean Carroll on the arrow of time

I've been reading Sean Carroll's posts on Cosmic Variance, not realizing until now that he's a research associate at my alma mater. I guess blogs really are infested by amateurs destroying our culture of knowledge ...

Sean's presentation is pretty readable for the interested layperson ...

Sean Carroll: Why Is the Past Different From the Future?

... In such a universe, everything we think we "remember" ... about the past is ... a mistake.

Dinosaur skeletons arose spontaneously out of dirt.

It's been a busy road to reading material like Sean's. It started when I came across this comment in Wired  last February:

Even the best theories to explain how entanglement gets around this problem seem preposterous. One, for example, speculates that signals are shot back through time. Ultimately, the answer is bound to be unnerving: According to a famous doctrine called Bell’s Inequality, for entanglement to square with relativity, either we have no free will or reality is an illusion. Some choice.
- Lucas Graves, New York City-based writer

As near as I can tell Lucas was simplifying a bit. The complete absence of free will (aka. life in God's movie or the Tralfamadorian perspective) goes back originally to Newton (determination by mechanics) then to Einstein (determination by time slice perspectives) and returned with the transactional interpretation of QM. The good news for the non-Calvinists among us is that the evidence (as I read of it) favors the non-existence of independent reality over the kind of absolute determinism where not only dinosaurs arise from dirt, but all of space and time arise spontaneously and (seemingly) coherently.

So what does all this have to do with Carroll's talk? Well, it seems plausible that the "arrow of time" has something to do with predetermination or non-determination and that it should also have equivalences in both cosmology and quantum mechanics. Here's Carroll's conclusion about where time comes from in the view cosmology - it involves the infinite multiverse ...

...If the universe lasts forever but has no equilibrium
state, we naturally obtain an arrow of time.

It’s crucial that the way in which the multiverse
creates more entropy is to make universes like ours...

Further I cannot go! So where does the arrow of time come from in QM? I'm imagining at the moment that it comes from decoherence...*

* Ok, how did I know that "Decoherence, Quantum Measurement and the Arrow of Time" existed? I didn't, of course. I hypothesized that the arrow of time emerges as a universe of infinite possibilities collapses as the past interacts with it -- an idea that's appeared in at least one science fiction story I've read. I knew decoherence is the technical term used for the interpretation of QM most consistent with this model, so I searched on "decoherence" and "arrow of time". Easy. (The alternate explanation, of course, is that the conference didn't really exist until I thought of it, which led the quantum chaos of the past to collapse.... :-)

Pursuing the evolution of the philosophy of quantum physics

This post is partly a pursuit of my ongoing interest in the philosophical interpretations of quantum reality, but it's mostly a story of how radically the world is changing. I still remember paging through volumes of the Index Medicus in our library -- a task as far removed from today's world as using a book to look up a logarithm (yes, I learned that too ...).

Recently, when searching for post of mine on a related topic, I came across one from 2004 about a research paper on the "emergence" of consensus reality as a result of multiple observations selecting for a "pointer" (stable) macro state. (Quantum Darwinism.)

It's interesting stuff, but how do I pursue it further? Turns out, it's not so hard.

My blog post pointed to the Nature article. That pointed to a PubMed (med?!) citation, and related articles, including one on quantum coherence in biological systems. (Is the human brain a quantum computer? It's fun to ask such questions, though I suspect it is not.) Note that these PubMed queries have an RSS feed, so I can track activity via Bloglines.

Next I took the title from the PubMed citation and plugged it into Google Scholar; this produces an interesting result set with links to yet more related articles.

Today most of the endpoints are dead-ends (pay-per-view journals), but more and more science is being published in open journals. We're not far from a world in which the queries I did (they took far less time to do than to describe) will end in readable journal articles, such as D Poulin's 2004 Physics thesis. (PDF btw, Google tries to render an HTML version, but it chokes on the equations).

Incidentally, it does appear that realism (observer-independent reality) has joined locality ("things" are bounded by space) in the dustbin of history. Our university is deeply quantum, and the seeming persistence of everyday reality is an emergent result ...

PS. There's a wee bit of whackiness in some of the results I found.

The single speed universe

For the photon, there is neither time nor distance. Every destination takes no time at all to reach, which is, of course, also true of non-local "transmission" of non-meaning. I've retained that much from Gribbin and my recent readings of popular works on cosmology and quantum physics.

So does that mean that there's only one "space-time speed" for everything, namely to be as motionless as a photon?

After all, the more gravity one feels, and the more history of acceleration one has, the more one moves through time rather than space alone. in other words, as one gets closer to the speed of light the energy input of an accelerating force is diverted into time travel rather than space travel.

So, if one thinks of speed as movement through space and time, is it true to say that everything in the universe has the same "speed"?

I did a quick google on the topic, and found this article. So maybe that is the way physicists think about spacetime velocity. BTW, the article claims that one interpretation of general relativity is consistent with both the transactional interpretation of QM and Tralfamadorian philosophy.

Truly, all of modern physics is an attempt to understand the photon ...

Update 5/15: Turns out I was remembering chapter one (relativity theory) of Greene's overview of cosmology and theoretical physics! I'd skimmed the chapter a few weeks ago and I was basically recalling what he'd written, though the Tralfamadorian bit is mine. Nice to know I wasn't just spouting off! Even Greene mentions how alien and astounding special and general relativity theory feel when he reviews the concepts -- and that's his profession. These are concepts so beyond our everyday existence that they easily slip out of my feeble mind ...

I'm now taking a leisurely slow read through the book and will doubtless have further related comments ..

Gingrich's Amazon reviews

I was reviewing Gribbin's "Kittens" book, when I came across a reasonable review written by Newt Gingrich. It wasn't an in-depth review, but it's likely he at least skimmed the book. It's not an easy book.

Gingrich was profoundly wrong headed and laid the way for Rove, but it's a measure of Rove/Cheney/Bush's incompetence and willful ignorance that nowadays Gingrich looks much the lesser evil ...

Time, entropy and baby universes

CV talks about manufacturing universes that vanish as an evaporating black hole....

How Did the Universe Start? | Cosmic Variance

... The baby-universe idea at least has the chance to give rise to a spontaneous violation of time-reversal symmetry and explain the arrow of time. If we start with empty space an evolve it forward, baby universes can (hypothetically) be born; but the same is true if we run it backwards. The increase of entropy doesn’t arise from a fine-tuning at one end of the universe’s history, it’s a natural consequence of the ability of the universe to always increase its entropy. We’re a long way from completely understanding such a picture; ultimately we’ll have to be talking about a Hilbert space of wavefunctions that involve an infinite number of disconnected components of spacetime, which has always been a tricky problem. But the increase of entropy is a fact of life, right here in front of our noses, that is telling us something deep about the universe on the very largest scales.

Where entropy increases, there goes time. Or so it goes.

Update 4/28/07: Infinitely expanding universes birthing within infinitely expanding universes. Requirements for human observation to collapse probability waves. All interpretations of self-consistent mathematics, but way beyond bizarre. Which leads to the scary thought. Could he be right? Brrrr.

The cat is undead until you open the box ...

A week or so ago I commented on recent research that both affirmed instantaneous non-local correlation of entangled quantum entities and attacked "realism". I couldn't however, really tell from the article what was meant by "realism".

This summary from a physics journal fills the gap. "Realism" is a way of saying that the "way of things" is not altered by the act of our observing them. The research seems to affirm an interpretation of quantum mechanics that gives special power to the act of perceiving, namely the power to collapse a wave function .... (emphases mine)

Quantum physics says goodbye to reality (April 2007) - News - PhysicsWeb

... Some 40 years ago the physicist John Bell predicted that many hidden-variables theories would be ruled out if a certain experimental inequality were violated – known as "Bell's inequality". In his thought experiment, a source fires entangled pairs of linearly-polarized photons in opposite directions towards two polarizers, which can be changed in orientation. Quantum mechanics says that there should be a high correlation between results at the polarizers because the photons instantaneously "decide" together which polarization to assume at the moment of measurement, even though they are separated in space. Hidden variables, however, says that such instantaneous decisions are not necessary, because the same strong correlation could be achieved if the photons were somehow informed of the orientation of the polarizers beforehand. [jf: In the transactional interpetation the "informing" can occur by meaning-free "messages" that travel back in time.]

Bell's trick, therefore, was to decide how to orient the polarizers only after the photons have left the source. If hidden variables did exist, they would be unable to know the orientation, and so the results would only be correlated half of the time. On the other hand, if quantum mechanics was right, the results would be much more correlated – in other words, Bell's inequality would be violated.

Many realizations of the thought experiment have indeed verified the violation of Bell's inequality. These have ruled out all hidden-variables theories based on joint assumptions of realism ... [reality exists when we are not observing it].... and locality ... [separated events cannot influence one another instantaneously]. But a violation of Bell's inequality does not tell specifically which assumption – realism, locality or both – is discordant with quantum mechanics.

Markus Aspelmeyer, Anton Zeilinger and colleagues from the University of Vienna, however, have now shown that realism is more [?] of a problem than locality in the quantum world. They devised an experiment that violates a different inequality proposed by physicist Anthony Leggett in 2003 that relies only on realism, and relaxes the reliance on locality. To do this, rather than taking measurements along just one plane of polarization, the Austrian team took measurements in additional, perpendicular planes to check for elliptical polarization.

They found that, just as in the realizations of Bell's thought experiment, Leggett's inequality is violated – thus stressing the quantum-mechanical assertion that reality does not exist when we're not observing it. "Our study shows that 'just' giving up the concept of locality would not be enough to obtain a more complete description of quantum mechanics," Aspelmeyer told Physics Web. "You would also have to give up certain intuitive features of realism."

This article is the best so far, but there were a few awkward phrases. I've tried to edit it minimally to clarify.

My current (weak) understanding is that locality fell a while ago. There was still hope of preserving realism, but now realism is at least partly gone. We're well into the realm of Schrodinger's "cat" being both alive and dead until an "observer" inspects the cat. I think this result may favor the "decoherence" interpretation of QM, and goes against the "transactional" interpretation favored by (among others) Gribbin.

Alternatively, there's always the reassuring possibility that mathematics is a less trustworthy guide to reality than commonly thought...

Update 5/26/2007: It turns out that in 2004 I posted on a fascinating discussion about how reality can be emergently structured that seems to fit very well with this experiment. I need to find more along the lines of that 2004 post!