Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.

Saturday, August 25, 2018

Cart both before and after the horse

Let's end the week on a happy, if surreal, note with a new experiment in quantum physics that calls into question the arrow of time.

The "arrow of time" has bedeviled physicists for decades -- why time only flows one direction, while in the three spatial dimensions you can move any way you like (up/down, backwards/forwards, right/left).  But with time, there's only one way.


The causality chain -- that events in the past cause the ones in the future -- certainly seems rock-solid.  It's hard to imagine it going the other way, Geordi LaForge's weekly rips in the space/time continuum notwithstanding.  Although I must admit I riffed on the idea myself in my short story "Retrograde," about a woman who perceives time running backwards.  It's going to be in a short story collection I'm releasing next year, but you can read it for free on my fiction blog.

But in real life, we take the arrow of time for granted.  It's why no one was especially surprised when Stephen Hawking threw a champagne party in 2009 for time travelers, but mailed the invitations after the event was over... and no one showed up.

In any case, the arrow of time and causality chains would seem to make it certain that if there are two events, A and B, either A preceded B, A followed B, or they occurred at the same time.  (I'm ignoring the wackiness introduced by relativistic effects; here, we're simplifying matters by saying the observation and both events occurred in the same frame of reference.)

So far, so good, right?  The order of two events is a sure thing.

An experiment performed at the University of Queensland (Australia) has just proven that to be wrong.

In a paper called "Indefinite Causal Order in a Quantum Switch" that appeared last week in Physical Review Letters, by Kaumudbikash Goswami, Christina Giarmatzi, Michael Kewming, Fabio Costa, Cyril Branciard, and Andrew G. White, we find out about research that blows away causality by creating a device where a beam of light undergoes two operations -- but in our choices of A following B or B following A, what actually happens is...

... both.

[Image is in the Public Domain}

The setup is technical and far beyond my powers to explain in a way that would satisfy a physicist, but the bare bones are as follows.

Light has a property called polarization.  In effect, that means it vibrates in a particular plane.  As an analogy, think of someone holding a long spring, with the other end tied to a post.  The person is jiggling it to create a wave in the spring.  Are they waving it up and down?  Side to side?  Diagonally?

That's polarization in a nutshell.

(An interesting side-note: this is why polarized sunglasses work.  Light reflecting off a surface gets polarized in the horizontal direction, so if you have a material that blocks horizontally-polarized light, it significantly reduces glare.)

Anyhow, what Goswami et al. did was to rig up a device wherein a horizontally-polarized photon goes down a path where it experiences A before B, while a vertically-polarized one a path where it experiences B before A.  But here's where it gets loony; because of a phenomenon called quantum superposition, in which a photon can be in effect polarized in both directions at the same time, when you pass it through the device, event A happens before event B, and B happens before A, to the same photon at the same time.

Okay, I know that sounds impossible.  But in the quantum realm, seriously weird stuff happens.  It's counterintuitive -- even the eminent Nobel laureate Niels Bohr said, "[T]hose who are not shocked when they first come across quantum theory cannot possibly have understood it."  Thus we have not only loopy ideas like Schrödinger's Cat, but experimentally-verified claims such as entanglement (what Einstein called "spooky action at a distance"), an electron being in two places at once, and the fuzziness of the Heisenberg Uncertainty Principle (that the more you know about an object's velocity, the less you know about its position -- and vice versa).

Which is a deliberate setup for my favorite joke of all time.  Ready?

Schrödinger and Heisenberg are going down the highway in Schrödinger's car, Heisenberg at the wheel, and a cop pulls them over.

"Buddy," the cop says, "do you know how fast you were going?"

Heisenberg says, "No idea.  But I can tell you exactly where I was."

The cop says, "Okay, if you're gonna be a smartass, I'm gonna search your car."  When the cop opens the trunk, there's a dead cat inside.

The cop says, "Did you know there's a dead cat in your trunk?"

Schrödinger says, "Well, there is now."

Ba-dump-bump-kssh.  Ah, nerd humor is a wonderful thing.

But I digress.

As impossible as quantum mechanics sounds, it seems to be true.  John Horgan, in his book The End of Science, writes, "Physicists do not believe quantum mechanics because it explains the world, but because it predicts the outcome of experiments with almost miraculous accuracy.  Theorists kept predicting new particles and other phenomena, and experiments kept bearing out those predictions."

Which is a nicer way of saying that if your common sense rebels when you hear this stuff, sucks to be you.

So as bizarre as it is, we're forced to the conclusion that the universe is a far weirder place than we thought.  Myself, I think it's kind of cool.  Despite my B.S. in physics -- and let me tell you, I was no great shakes as a physics student, and I'm convinced some of my professors passed me just so I wouldn't have to retake their courses -- my mind is overwhelmed with awe every time I read about this stuff.  I wonder, though, if it's even possible for the human mind to truly conceptualize how quantum mechanics works; we are so locked into our ordinary, classical, three-dimensional world, where first you turn the key in the ignition and then your car starts, we're completely at sea even trying to think about the fact that on some level, we can't take any of those things for granted.

So this is looking like opening up a whole new area of study.  Very exciting stuff.  And it may be naive of me, but I'm still hoping it's going to lead to a time machine.

First thing I'm going to do is crash Stephen Hawking's party, temporal paradox or no.  It may cause the universe to end, but that's a risk I'm willing to take.


This week's Skeptophilia book recommendation is a classic, and especially for you pet owners: Konrad Lorenz's Man Meets Dog.  In this short book, the famous Austrian behavioral scientist looks at how domestic dogs interact, both with each other and with their human owners.  Some of his conjectures about dog ancestry have been superseded by recent DNA studies, but his behavioral analyses are spot-on -- and will leaving you thinking more than once, "Wow.  I've seen Rex do that, and always wondered why."

[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]

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