Djinn and paradox

In the very peculiar Doctor Who episode "Joy to the World," the character of Joy Almondo is being controlled by a device inside a briefcase that -- if activated -- will release as much energy as a supernova, destroying the Earth (and the rest of the Solar System).  But just at the nick of time, a future version of the Doctor (from exactly one year later) arrives and gives the current Doctor the override code, saving the day.

The question comes up, though, of how the future Doctor knew what the code was.  The current Doctor, after all, hadn't known it until he was told.  He reasons that during that year, he must have learned the code from somewhere or someone -- but the year passes without anyone contacting him about the briefcase and its contents.  Right before the year ends (at which point he has to jump back to complete the loop) he realizes that his surmise wasn't true.  Because, of course, he already knew the code.  He'd learned it from his other self.  So armed with that knowledge, he jumps back and saves the day.

Well, he saves the moment, at least.  As it turns out, their troubles are just beginning, but that's a discussion for another time.

A similar trope occurred in the 1980 movie Somewhere in Time, but with an actual physical object rather than just a piece of information.  Playwright Richard Collier (played by Christopher Reeve) is at a party celebrating the debut of his most recent play, and is approached by an elderly woman who hands him an ornate pocket watch and says, in a desperate voice, "Come back to me."  Collier soon goes back in time by six decades, finds her as a young woman, and they fall desperately in love -- and he gives her the pocket watch.  Ultimately, he's pulled back into the present, and his girlfriend grows old without him, but right before she dies she finds him and gives him back the watch, closing the loop.

All of this makes for a fun twist; such temporal paradoxes are common fare in fiction, after all.  And the whole thing seems to make sense until you ask the question of, respectively (1) where did the override code originally come from? and (2) who made the pocket watch?

Because when you think about it -- and don't think too hard, because these kinds of things are a little boggling -- neither one has any origin.  They're self-creating and self-destroying, looped like the famous Ouroboros of ancient myth, the snake swallowing its own tail. 

[Image is in the Public Domain]

The pocket watch is especially mystifying, because after all, it's an actual object.  If Collier brought it back with him into the past, then it didn't exist prior to the moment he arrived in 1920, nor after the moment he left in 1980 -- which seems to violate the Law of Conservation of Matter and Energy.

Physicists Andrei Lossev and Igor Novikov called such originless entities "djinn particles," because (like the djinn, or "genies," of Arabian mythology) they seem to appear out of nowhere.  Lossev and Novikov realized that although "closed timelike curves" are, theoretically at least, allowed by the Theory of General Relativity, they all too easily engender paradoxes.  So they proposed something they call the self-consistency principle -- that time travel into the past is possible if and only if it does not generate a paradox.

So let's say you wanted to do something to change history.  Say, for example, that you wanted to go back in time and give Arthur Tudor, Prince of Wales some medication to save his life from the fever that otherwise killed him at age fifteen.  This would have made him king of England seven years later instead of his younger brother, who would have become the infamous King Henry VIII, thus dramatically changing the course of history.  In the process, of course, it also generates a paradox; because if Henry VIII never became king, you would have no motivation to go back into the past and prevent him from becoming king, right?  Your own memories would be consistent with the timeline of history that led to your present moment.  Thus, you wouldn't go back in time and save Arthur's life.  But this would mean Arthur would die at fifteen, Henry VIII becomes king instead, and... well, you see the difficulty.

Lossev and Novikov's self-consistency principle fixes this problem.  It tells us that your attempt to save Prince Arthur must have failed -- because we know that didn't happen.  If you did go back in time, you were simply incorporated into whatever actually did happen.

Timeline of history saved.  Nothing changed.  Ergo, no paradox.

You'd think that physicists would kind of go "whew, dodged that bullet," but interestingly, most of them look at the self-consistency principle as a bandaid, an unwarranted and artificial constraint that doesn't arise from the models themselves.  Joseph Polchinski came up with another paradoxical situation -- a billiard ball fired into a wormhole at exactly the right angle that when it comes out of the other end, it runs into (and deflects) itself, preventing it from entering the wormhole in the first place -- and analysis by Nobel Prize-winning physicist Kip Thorne found there's nothing inherent in the models that prevents this sort of thing.

Some have argued that the ease with which time travel into the past engenders paradox is an indication that it's simply an impossibility; eventually, they say, we'll find that there's something in the models that rules out reversing the clock entirely.  In fact, in 2009, Stephen Hawking famously hosted a time-travelers' party at Cambridge University, complete with fancy food, champagne, and balloons -- but only sent out invitations the following day.  He waited several hours, and no one showed up.

That, he said, was that.  Because what time traveler could resist a party?

But there's still a lingering issue, because it seems like if it really is impossible, there should be some way to prove it rigorously, and thus far, that hasn't happened.  Last week we looked at the recent paper by Gavassino et al. that implied a partial loophole from the Second Law of Thermodynamics -- if you could travel into the past, entropy would run backwards during part of the loop and erase your memory of what had happened -- but it still leaves the question of djinn particles and self-deflecting billiard balls unsolved.

Seems like we're stuck with closed timelike curves, paradoxes notwithstanding.

Me, I think my mind is blown sufficiently for one day.  Time to go play with my puppy, who only worries about paradoxes like "when is breakfast?" and the baffling question of why he is not currently getting a belly rub.  All in all, probably a less stressful approach to life.

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Defanging the basilisk

The science fiction trope of a sentient AI turning on the humans, either through some sort of misguided interpretation of its own programming or from a simple desire for self-preservation, has a long history.  I first ran into it while watching the 1968 film 2001: A Space Odyssey, which featured the creepily calm-voiced computer HAL-9000 methodically killing the crew one after another.  But the iteration of this idea that I found the most chilling, at least at the time, was an episode of The X Files called "Ghost in the Machine."

The story -- which, admittedly, seemed pretty dated on recent rewatch -- featured an artificial intelligence system that had been built to run an entire office complex, controlling everything from the temperature and air humidity to the coordination of the departments housed therein.  Running the system, however, was expensive, and when the CEO of the business talks to the system's designer and technical consultant and recommends shutting it down, the AI overhears the conversation, and its instinct to save its own life kicks in.

Exit one CEO.

The fear of an AI we create suddenly deciding that we're antithetical to its existence -- or, perhaps, just superfluous -- has caused a lot of people to demand we put the brakes on AI development.  Predictably, the response of the techbros has been, "Ha ha ha ha ha fuck you."  Myself, I'm not worried about an AI turning on me and killing me; much more pressing is the fact that the current generative AI systems are being trained on art, writing, and music stolen from actual human creators, so developing (or even using) them is an enormous slap in the face to those of us who are real, hard-working flesh-and-blood creative types.  The result is that a lot of artists, writers, and musicians (and their supporters) have objected, loudly, to the practice.

Predictably, the response of the techbros has been, "Ha ha ha ha ha fuck you."

We're nowhere near a truly sentient AI, so fears of some computer system taking a sudden dislike to you and flooding your bathroom then shorting out the wiring so you get electrocuted (which, I shit you not, is what happened to the CEO in "Ghost in the Machine") are, to put it mildly, overblown.  We have more pressing concerns at the moment, such as how the United States ended up electing a demented lunatic who campaigned on lowering grocery prices but now, two months later, says to hell with grocery prices, let's annex Canada and invade Greenland.

But when things are uncertain, and bad news abounds, for some reason this often impels people to cast about for other things to feel even more scared about.  Which is why all of a sudden I'm seeing a resurgence of interest in something I first ran into ten or so years ago -- Roko's basilisk.

Roko's basilisk is named after a guy who went by the handle Roko on the forum LessWrong, and the "basilisk," a mythical creature who could kill you at a glance.  The gist is that a superpowerful sentient AI in the future would, knowing its own past, have an awareness of all the people who had actively worked against its creation (as well as the people like me who just think the whole idea is absurd).  It would then resent those folks so much that it'd create a virtual reality simulation in which it would recreate our (current) world and torture all of the people on the list.

This, according to various YouTube videos and websites, is "the most terrifying idea anyone has ever created," because just telling someone about it means that now the person knows they should be helping to create the basilisk, and if they don't, that automatically adds them to the shit list.

Now that you've read this post, that means y'all, dear readers.  Sorry about that.

Before you freak out, though, let me go through a few reasons why you probably shouldn't.

First, notice that the idea isn't that the basilisk will reach back in time and torture the actual me; it's going to create a simulation that includes me, and torture me there.  To which I respond: knock yourself out.  This threat carries about as much weight as if I said I was going to write you into my next novel and then kill your character.  Doing this might mean I have some unresolved anger issues to work on, but it isn't anything you should be losing sleep over yourself.

Second, why would a superpowerful AI care enough about a bunch of people who didn't help build it in the past -- many of whom would probably be long dead and gone by that time -- to go to all this trouble?  It seems like it'd have far better things to expend its energy and resources on, like figuring out newer and better ways to steal the work of creative human beings without getting caught.

Third, the whole "better help build the basilisk or else" argument really is just a souped-up, high-tech version of Pascal's Wager, isn't it?  "Better to believe in God and be wrong than not believe in God and be wrong."  The problem with Pascal's Wager -- and the basilisk as well -- is the whole "which God?" objection.  After all it's not a dichotomy, but a polychotomy.  (Yes, I just made that word up.  No, I don't care). You could help build the basilisk or not, as you choose -- and the basilisk itself might end up malfunctioning, being benevolent, deciding the cost-benefit analysis of torturing you for all eternity wasn't working out in its favor, or its simply not giving a flying rat's ass who helped and who didn't.  In any of those cases, all the worry would have been for nothing.

Fourth, if this is the most terrifying idea you've ever heard of, either you have a low threshold for being scared, or else you need to read better scary fiction.  I could recommend a few titles.

On the other hand, there's always the possibility that we are already in a simulation, something I dealt with in a post a couple of years ago.  The argument is that if it's possible to simulate a universe (or at least the part of it we have access to), then within that simulation there will be sentient (simulated) beings who will go on to create their own simulations, and so on ad infinitum.  Nick Bostrom (of the University of Oxford) and David Kipping (of Columbia University) look at it statistically; if there is a multiverse of nested simulations, what's the chance of this one -- the one you, I, and unfortunately, Donald Trump belong to -- being the "base universe," the real reality that all the others sprang from?  Bostrom and Kipping say "nearly zero;" just considering that there's only one base universe, and an unlimited number of simulations, means the chances are we're in one of the simulations.

But.  This all rests on the initial conditional -- if it's possible to simulate a universe.  The processing power this would take is ginormous, and every simulation within that simulation adds exponentially to its ginormosity.  (Yes, I just made that word up.  No, I don't care.)  So, once again, I'm not particularly concerned that the aliens in the real reality will say "Computer, end program" and I'll vanish in a glittering flurry of ones and zeroes.  (At least I hope they'd glitter.  Being queer has to count for something, even in a simulation.)

On yet another hand (I've got three hands), maybe the whole basilisk thing is true, and this is why I've had such a run of ridiculously bad luck lately.  Just in the last six months, the entire heating system of our house conked out, as did my wife's van (that she absolutely has to have for art shows); our puppy needed $1,700 of veterinary care (don't worry, he's fine now); our homeowner's insurance company informed us out of the blue that if we don't replace our roof, they're going to cancel our policy; we had a tree fall down in a windstorm and take out a large section of our fence; and my laptop has been dying by inches.

So if all of this is the basilisk's doing, then... well, I guess there's nothing I can do about it, since I'm already on the Bad Guys Who Hate AI list.  In that case, I guess I'm not making it any worse by stating publicly that the basilisk can go to hell.

But if it has an ounce of compassion, can it please look past my own personal transgressions and do something about Elon Musk?  Because in any conceivable universe, fuck that guy.

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NEW!  We've updated our website, and now -- in addition to checking out my books and the amazing art by my wife, Carol Bloomgarden, you can also buy some really cool Skeptophilia-themed gear!  Just go to the website and click on the link at the bottom, where you can support your favorite blog by ordering t-shirts, hoodies, mugs, bumper stickers, and tote bags, all designed by Carol!

Take a look!  Plato would approve.

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The illusion of causality

Fighting bad thinking is an uphill battle, sometimes.  Not only, or even primarily, because there's so much of it out there; the real problem is that our brains are hard-wired to make poor connections, and once those connections are made, to hang on to them like grim death.

A particularly difficult one to overcome is our tendency to fall for the post hoc, ergo propter hoc fallacy -- "after this, therefore because of this."  We assume that if two events are in close proximity in time and space, the first one must have caused the second one.  Dr. Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia, likes to tell a story about his wife, who is a pediatrician, preparing to give a child a vaccination.  The child had a seizure as she was drawing the vaccine into the syringe.  If the seizure had occurred only a minute later, right after the vaccine was administered, the parents would undoubtedly have thought that the vaccination caused the seizure -- and after that, no power on Earth would have likely convinced them otherwise.

[Image is in the Public Domain courtesy of the NIH]

Why do we do this?  The most reasonable explanation is that in our evolutionary history, forming such connections had significant survival value.  Since it's usual that causes and effects are close together in time and space, wiring in a tendency to decide that all such correspondences are causal is still going to be right more often than not.  But it does lead us onto some thin ice, logic-wise.

Which is bad enough, but consider the study from three researchers -- Ion Yarritu (Deusto University), Helena Matute (University of Bilbao), and David Luque (University of New South Wales) -- that shows our falling for what they call the "causal illusion" is so powerful that even evidence to the contrary can't fix the error.

In a paper called "The dark side of cognitive illusions: When an illusory belief interferes with the acquisition of evidence-based knowledge," published in the British Journal of Psychology, Yarritu et al. have demonstrated that once we've decided on an explanation for something, it becomes damn near impossible to change.

Their experimental protocol was simple and elegant.  The authors write:

During the first phase of the experiment, one group of participants was induced to develop a strong illusion that a placebo medicine was effective to treat a fictitious disease, whereas another group was induced to develop a weak illusion.  Then, in Phase 2, both groups observed fictitious patients who always took the bogus treatment simultaneously with a second treatment which was effective.  Our results showed that the group who developed the strong illusion about the effectiveness of the bogus treatment during Phase 1 had more difficulties in learning during Phase 2 that the added treatment was effective.

The strength of this illusion explains why bogus "alternative medicine" therapies gain such traction.  All it takes is a handful of cases where people use "deer antler spray" and find they have more energy (and no, I'm not making this up) to get the ball rolling.  A friend just told me about someone she knows who has stage four breast cancer.  Asked how her chemo treatment was going, the friend said cheerfully, "Oh, I'm not doing chemo.  I'm treating it with juicing and coffee enemas!  And I feel fine!"

Sadly, she'll "feel fine" until she doesn't anymore, and at that point it'll probably be too late for chemo to help her.

Homeopathy owes a lot to this flaw in our reasoning ability; any symptom abatement that occurs after taking a homeopathic "remedy" clearly would have happened even if the patient had taken nothing -- which is, after all, what (s)he did.

And that's not even considering the placebo effect as a further complicating factor.

Helena Matute, one of the researchers in the recent study, has written extensively about the difficulty of battling causal illusions. In an article she wrote for the online journal Mapping Ignorance, Matute writes:

Alternative medicine is often promoted on the argument that it can do no harm.  Even though its advocates are aware that its effectiveness has not been scientifically demonstrated, they do believe that it is harmless and therefore it should be used.  "If not alone, you should at least use it in combination with evidence-based treatments," they say, "just in case."  

But this strategy is not without risk... even treatments which are physically innocuous may have serious consequences in our belief system, sometimes with fatal consequences.  When people believe that a bogus treatment works, they may not be able to learn that another treatment, which is really effective, is the cause of their recovery. This finding is important because it shows one of the mechanisms by which people might decide to quit an efficient treatment in favor of a bogus one.

I think this same effect is contributory to errors in thinking in a great many other areas.  Consider, for instance, the fact that belief in anthropogenic climate change rises in the summer and falls in the winter.  After being told that human activity is causing the global average temperature to rise, our brains are primed to look out of the window at the snow falling, and say, "Nah.  Can't be."

Post hoc, ergo propter hoc.  To quote Stephen Colbert, "Global warming isn't real, because I was cold today.  Also great news: world hunger is over because I just ate."

The study by Yarritu et al. highlights not only the difficulty of fighting incorrect causal connections, but why it is so essential that we do so.  The decision that two things are causally connected is powerful and difficult to reverse; so it's critical that we be aware of this bias in thinking, and watch our own tendency to leap to conclusions.  But even more critical is that we are given reliable evidence to correct our own errors in causality, and that we listen to it.  Like any cognitive bias, we can combat it -- but only if we're willing to admit that we might get it wrong sometimes.

Or as James Randi was fond of saying, "Don't believe everything you think."

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I'm always amazed by the resilience we humans can sometimes show.  Knocked down again and again, in circumstances that "adverse" doesn't even begin to describe, we rise above and move beyond, sometimes accomplishing great things despite catastrophic setbacks.

In Why Fish Don't Exist: A Story of Love, Loss, and the Hidden Order of Life, journalist Lulu Miller looks at the life of David Starr Jordan, a taxonomist whose fascination with aquatic life led him to the discovery of a fifth of the species of fish known in his day.  But to say the man had bad luck is a ridiculous understatement.  He lost his collections, drawings, and notes repeatedly, first to lightning, then to fire, and finally and catastrophically to the 1906 San Francisco Earthquake, which shattered just about every specimen bottle he had.

But Jordan refused to give up.  After the earthquake he set about rebuilding one more time, becoming the founding president of Stanford University and living and working until his death in 1931 at the age of eighty.  Miller's biography of Jordan looks at his scientific achievements and incredible tenacity -- but doesn't shy away from his darker side as an early proponent of eugenics, and the allegations that he might have been complicit in the coverup of a murder.

She paints a picture of a complex, fascinating man, and her vivid writing style brings him and the world he lived in to life.  If you are looking for a wonderful biography, give Why Fish Don't Exist a read.  You won't be able to put it down.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Order of operations

I try not to write in Skeptophilia about topics I don't fully understand -- well, at least understand as fully as my brainpower and the available information allow.  But today I'm going to tell you about a recent paper in theoretical physics that blew my mind so completely that I had to write a post about it, even though saying "I don't completely comprehend this" is a serious understatement.

So here goes.  Just don't ask me to clarify further, because the most you'll get is the Canine Head-Tilt of Puzzlement.

The paper, which appeared last week in Nature Communications, is entitled "Bell's Theorem for Temporal Order," and was written by Magdalena Zych and Fabio Costa (of the University of Queensland), Igor Pikovski (of Harvard University), and Časlav Brukner (of the University of Vienna).  The issue the four physicists were looking at was the seeming paradox of the different way that time (specifically, temporal order) fits into general relativity and quantum theory.  In relativity, the flow of time depends on your relative speed and the distribution of mass near you; in general, the faster you're going, or the nearer you are to a massive object, the slower your clock runs.  Because reference frame is relative (thus the name of the entire theory), you don't notice this effect yourself -- to you, your clock runs just fine.  But to someone observing you at a distance, the flow of time in your frame of reference has become more sluggish.

Weird enough, but that's only the beginning.  To take the most familiar example, consider two astronauts in spacecraft zooming away from each other at a substantial fraction of the speed of light.  To astronaut A, his clock is running fine, and astronaut B's clock is slow (because he's moving away from A at a high speed).  But from B's perspective, it's A that's moving; so B thinks his own clock is accurate, and A's is the one that's running slow.

And it's not that one's right and the other is somehow being fooled.  Both of them are right -- because time is relative to your speed.

As an outcome of this (and germane to the paper I referenced), what this also means is that A and B can differ in what they perceive as the time order of two events.  Occurrences that appear simultaneous to one of the astronauts might appear sequential to the other.

With me so far?  Well, the problem that Zych et al. were investigating was that in quantum theory, there's no allowance for relativistic ordering of events.  Time's arrow is one-directional, and if event X followed Y in one reference frame, it would do so on all reference frames.

Well, that's what the physicists thought -- until this paper showed a theoretical framework that suggests otherwise.

Zych et al. proposed a thought experiment involving two spaceships, one of which is near a massive object (which, as I mentioned, warps spacetime in such a way as to slow down the passage of time).  They're engaged in a war game that requires them to fire their phasers simultaneously and immediately afterward start their engine so as to dodge the blast.  The problem is, the ship near the massive object will have a slower clock, and will not be able to fire quickly enough to escape being blasted by the other ship.

So far, weird but not that hard to understand.  What Zych et al. did was to ask a single question: what if the two ships were in a state of quantum superposition before they fired?

Superposition is one of the weirdest outcomes of quantum physics, but it's been demonstrated experimentally so many times that we have no choice but to accept that this is how the universe works.  The idea is that if a physical system could exist in two or more possible states, its actual state is an array of possibilities all existing at the same time until some measurement destroys the superposition and drops the system into one of the possible outcomes ("collapsing the wave function").  The most famous iteration of this is Schrödinger's Cat, who is both alive and dead until the box is opened.

In the case of the ships, the superposition results in quantum entanglement, where the entire system acts as a single entity (in a causal sense).  Here's how the result is described in a press release from the University of Vienna:

If a powerful agent could place a sufficiently massive object, say a planet, closer to one ship it would slow down its counting of time.  As a result, the ship farther away from the mass will fire too early for the first one to escape. 

The laws of quantum physics and gravity predict that by manipulating a quantum superposition state of the planet, the ships can end up in a superposition of either of them being destroyed...  The new work shows that the temporal order among events can exhibit superposition and entanglement – genuinely quantum features of particular importance for testing quantum theory against alternatives.

So each of the ships is in a state of both being destroyed and not being destroyed, from the standpoint of an outside observer -- until a measurement is made, which forces the system into one or the other outcome.

Note what this isn't saying; it's not implying that one of the ships was destroyed, and we simply don't know which yet.  It's implying that both ships are in an entangled state of being blasted to smithereens and not.

At the same time.

The authors write:

This entanglement enables accomplishing a task, violation of a Bell inequality, that is impossible under local classical temporal order; it means that temporal order cannot be described by any pre-defined local variables.  A classical notion of a causal structure is therefore untenable in any framework compatible with the basic principles of quantum mechanics and classical general relativity.

All of which leaves me sympathizing a great deal with Winnie-the Pooh.

So there you have it.  It turns out that the universe is a weird, weird place, where our common-sensical notions of how things work are often simply wrong.  Even though I'm far from an expert -- I run into the wall pretty fast when I try to read actual papers in physics, or (for that matter) in most scientific fields -- I find it fascinating to get a glimpse of the actual workings of the cosmos.

Even if it blows my tiny little mind.

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This week's Skeptophilia book recommendation is a must-read for anyone interested in astronomy -- Finding Our Place in the Universe by French astrophysicist Hélène Courtois.  Courtois gives us a thrilling tour of the universe on the largest scales, particularly Laniakea, the galactic supercluster to which the Milky Way belongs, and the vast and completely empty void between Laniakea and the next supercluster.  (These voids are so empty that if the Earth were at the middle of one, there would be no astronomical objects near enough or bright enough to see without a powerful telescope, and the night sky would be completely dark.)

Courtois's book is eye-opening and engaging, and (as it was just published this year) brings the reader up to date with the latest information from astronomy.  And it will give you new appreciation when you look up at night -- and realize how little of the universe you're actually seeing.

[Note: if you purchase this book from the image/link below, part of the proceeds goes to support Skeptophilia!]

Paradoxes within paradoxes

Sometimes the simplest, most innocuous-seeming questions can lead toward mind-blowingly profound answers.

I remember distinctly running into one of these when I was in -- I think -- 8th grade science class.  It was certainly pre-high-school; whether it was from Mrs. Guerin at Paul Breaux Junior High School, or another of my teachers, is a memory that has been lost in the sands of time and middle-aged forgetfulness.

What I have never forgotten is the sudden, pulled-up-short response I had to what has been nicknamed Olbers' Paradox, named after 18th century German astronomer Heinrich Wilhelm Matthias Olbers, who first thought to ask the question -- if the universe is infinite, as it certainly seems to be, why isn't the night sky uniformly and dazzlingly bright?

I mean, think about it.  If the universe really is infinite, then no matter what direction you look, your line of sight is bound to intersect with a star eventually.  So there should be light coming from every direction at once, and the night sky shouldn't be dark.  Why isn't it?

The first thought was that there was something absorptive in the way -- cosmic dust, microscopic or submicroscopic debris left behind by stars and blown outward by stellar wind.  The problem is, there doesn't seem to be enough of it; the average density of cosmic dust in interstellar space is less than a millionth of a gram per cubic meter.

When the answer was discovered, it was nothing short of mind-boggling.  It turns out Olbers' paradox isn't a paradox at all, because there is light coming at us from all directions, and the night sky is uniformly bright -- it's just that it's shining in a region of the spectrum our eyes can't detect.  It's called the three-degree cosmic microwave background radiation, and it appears to be pretty well isotropic (at equal intensities no matter where you look).  It's one of the most persuasive arguments for the Big Bang model, and in fact what scientists have theorized about the conditions in the early universe added to what we know about the phenomenon of red-shifting (the stretching of wavelengths of light if the space in between the source and the detector is expanding) gives a number that is precisely what we see -- light peaking at a wavelength of around one millimeter (putting it in the microwave region of the spectrum) coming from all directions.

[Image licensed under the Creative Commons Original: Drbogdan Vector: Yinweichen, History of the Universe, CC BY-SA 3.0]

So, okay.  Olbers' paradox isn't a paradox, and its explanation led to powerful support for the Big Bang model.  But in science, one thing leads to another, and the resolution of Olbers' paradox led to another paradox -- the horizon problem.

The horizon problem hinges on Einstein's discovery that nothing, including information, can travel faster than the speed of light.  So if two objects are separated by a distance so great that there hasn't been time for light to travel from one to the other, then they are causally disconnected -- they can't have had any contact with each other, ever.

The problem is, we know lots of such pairs of objects.  There are quasars that are ten billion light years away -- and other quasars ten billion light years away in the opposite direction.  Therefore, those quasars are twenty billion light years from each other, so light hasn't had time to travel from one to the other in the 13.8 billion years since they were created.

Okay, so what?  They can't talk to each other.  But it runs deeper than that.  When the aforementioned cosmic microwave background radiation formed, on the order of 300,000 years after the Big Bang, those objects were already causally disconnected.  And the process that produced the radiation is thought to have been essentially random (it's called decoupling, and it occurred when the average temperature of the universe decreased enough to free photons from the plasma and send them streaming across space).

The key here is the word average.  Just as a microwaved cup of coffee could have an average temperature of 80 C but have spots that are cooler and spots that are hotter, the fact that the average temperature of the universe had cooled sufficiently to release photons doesn't mean it happened everywhere simultaneously, leaving everything at exactly the same temperature.  In fact, the great likelihood is that it wouldn't.  And since at that point there were already causally disconnected regions of space, there is no possible way they could interact in such a way as to smooth out the temperature distribution -- sort of like what happens when you stir a cup of coffee.

And yet one of the most striking things about the cosmic microwave background radiation is that it is very nearly isotropic.  The horizon problem points out how astronomically unlikely that is (pun intended) if our current understanding is correct.

One possible explanation is called cosmic inflation -- that a spectacularly huge expansion, in the first fraction of a second after the Big Bang, smoothed out any irregularities so much that everywhere did pretty much decouple at the same time.    The problem is, we still don't know if inflation happened, although work by Alan Guth (M.I.T.), Andrei Linde (Stanford), and Paul Steinhardt (Princeton) has certainly added a great deal to its credibility.

So as is so often the case with science, solving one question just led to several other, bigger questions.  But that's what's cool about it.  If you're interested in the way the universe works, you'll never run out of things to learn -- and ways to blow your mind.

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This week's Skeptophilia book recommendation is one of personal significance to me -- Michael Pollan's latest book, How to Change Your Mind.  Pollan's phenomenal writing in tours de force like The Omnivore's Dilemma and The Botany of Desire shines through here, where he takes on a controversial topic -- the use of psychedelic drugs to treat depression and anxiety.

Hallucinogens like DMT, LSD, ketamine, and psilocybin have long been classified as schedule-1 drugs -- chemicals which are off limits even for research except by a rigorous and time-consuming approval process that seldom results in a thumbs-up.  As a result, most researchers in mood disorders haven't even considered them, looking instead at more conventional antidepressants and anxiolytics.  It's only recently that there's been renewed interest, when it was found that one administration of drugs like ketamine, under controlled conditions, was enough to alleviate intractable depression, not just for hours or days but for months.

Pollan looks at the subject from all angles -- the history of psychedelics and why they've been taboo for so long, the psychopharmacology of the substances themselves, and the people whose lives have been changed by them.  It's a fascinating read -- and I hope it generates a sea change in our attitudes toward chemicals that could help literally millions of people deal with disorders that can rob their lives of pleasure, satisfaction, and motivation.

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

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.

Forward.

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.

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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!]