Brain Drain

September 10, 2009

It's rare that Sean and I argue over who gets to blog about a particular topic, but when our pal Jim Kakalios, author of The Physics of Superheroes, told us about the latest issue of The Incredible Hercules #133, oh, it was on! Because the new arch-villain(s) of the story arc are Boltzmann Brains -- or rather, "freak observers fluctuated out of thermal equilibrium."

So who would get to blog about it first? On the one hand, science and entertainment, including comic books and other aspects of pop culture, is pretty firmly my bailiwick, given that I wrote a book called The Physics of the Buffyverse and my current job is heading up the Science and Entertainment Exchange.

On the other hand, Sean has blogged extensively about entropy, quantum fluctuations and Boltzmann Brains, and just wrote an entire book about the arrow of time in which Boltzmann figures quite prominently -- so it's clearly his bailiwick as well. In the end I caved to his greater expertise: Sean's blog post about this exciting new trend in comics is here.

What exactly are Boltzmann Brains? I'll let Sean explain, since he really is the resident expert:

The Boltzmann Brain paradox is an argument against the idea that the universe around us, with its incredibly low-entropy early conditions and consequential arrow of time, is simply a statistical fluctuation within some eternal system that spends most of its time in thermal equilibrium. You can get a universe like ours that way, but you're overwhelmingly more likely to get just a single galaxy, or a single planet, or even just a single brain -- so the statistical-fluctuation idea seems to be ruled out by experiment.

Dennis Overbye wrote a very nice overview in The New York Times back in 2008 exploring the pro and con arguments surrounding Boltzmann Brains. I'm not sure I'm quite willing to accept that I'm nothing more than a "momentary fluctuation in a field of matter and energy out in space," popping into existence just long enough to look around and say, "Hey! There's a nifty universe here!" before annihilating back into the oblivion of thermal equilibrium. But it does make for an intriguing twist on Descartes' classic maxim: "I fluctuate, therefore I am... for a split second, anyway."

Schroedinger's Dog in Copenhagen

May 27, 2009

My bloggy buddy Chad Orzel, over at Uncertain Principles, has a new book coming out in December, called How To Teach Physics To Your Dog. The dog in question is Emmy, known to Chad's readers as "The Queen of Niskayuna," who has a tendency to browse Chad's physics books when she's bored. And oh, yes, fame will most certainly go to her head.

Chapter 3 deals with the "Copenhagen Interpretation" of quantum mechanics, specifically, the infamous thought experiment known as "Schroedinger's Cat." Back in 1935, physicist Erwin Schroedinger illustrated how ludicrously counter-intuitive the implications of quantum mechanics could be by suggesting one could place a cat in a closed box with a single uranium atom (a highly unstable element), right next to a Geiger counter. The uranium atom has a 50% chance of decaying and emitting an electron, and that tiny bit of radiation would set off the Geiger counter. To up the stakes, Schroedinger pictured a hammer rigged to smash a small vial containing cyanide, should the Geiger counter detect any radiation, instantly killing the poor kitty. (Emmy, not surprisingly, has no moral qualms about this.)

That's not the mind-bending part of the thought experiment. According to quantum mechanics, we have no way of knowing before we open the box whether the cat is alive or dead. And until we do so, the cat inhabits a bizarre superposition of states -- both alive and dead at the same time -- until we open the box and look for ourselves. This constitutes a "measurement" or observation, and the cat's wavefunction collapses into either an alive or dead state. So in that sense, observation determines reality.

"Preposterous!" you say. So did lots of people, including physicists, when the implications of quantum mechanics were first being debated. Albert Einstein was famously skeptical, once asking Niels Bohr if he truly believed that, say, the moon is not there when we don't happen to be looking at it.

Einstein had a point: quantum mechanics only applies to the subatomic world; on the macroscopic level, we don't see those bizarre effects. Cats are alive or dead, not both at the same time. That's because cats are macroscopic objects, made of billions of subatomic particles. And an "observation" doesn't necessarily imply a human (or canine) observer. Any interaction whatsoever within the system -- a particle in the air interacting with a single particle of the cat -- is sufficient to cause the wave function to collapse and destroy any superposition of states. The moon doesn't actually need us to look at it -- although why wouldn't you, on a nice clear night when it's hanging low in the sky?

You can say all of what I just said above, and watch your listeners' eyes glaze over in bafflement. Or you can take the humorous approach, like Chad, and try explaining it in the simplest possible terms to your dog. In the book, Emmy clearly stands in for the Everyman (or Everydog), asking the kind of basic "why is the sky blue" questions that most of us are reluctant to ask for fear of looking, well, stupid. Dogs don't have this hang-up. Here's Chad reading aloud from Chapter 3, with accompanying photos:

Stop Making Sense

February 24, 2009

I've been noticing a few flurries around the blogosphere about a new book by Michael Brooks, 13 Things That Don't Make Sense, discussing 13 controversial scientific anomalies that may (or may not) turn out to be revolutionary. The buzz caught my interest because I read and reviewed the book late last year for New Scientist; you can find my official take here.

Brooks has a physics background and is a careful, engaging writer, but his biases show pretty evidently in 13 Things: he's an unapologetic champion of the underdog scientist. That's all very well and good -- who doesn't like to root for the underdog now and then? -- but it's awfully tempting to lazily resurrect the tired old specter of rigid Establishment Science refusing to be open to new ideas, when in fact, that constant questioning and testing and slowness to accept new theories and results is part of the necessary rigor of the scientific process.

Chad Orzel over at Uncertain Principles summed up the problem with Brooks' tome quite neatly when he reviewed the book last month:

In the physics and astronomy sections, for example, the dark matter chapter makes a passing reference to the Bullet Cluster observations, and says a bunch of unkind things about how the authors were arrogantly ignoring modified gravity theories. It barely explains what the Bullet Cluster results were, though, and merely asserts that the whole thing can be explained by modified gravity, without explaining how.

As a fellow science writer, I'm sympathetic to the need to pare down the technical details when writing about esoteric theories for a general audience.  Describing just the basics of modified gravity in sufficient detail would take an entire chapter in and of itself and Brooks didn't have that luxury in a pop-sci book. Even the Wikipedia entry would make your eyes glaze over in seconds flat. (Thanks to XKCD, I am now hip to simple.wikipedia.org, which is teh awesome.)

Now, Brooks' fundamental premise is perfectly sound: if you want to find where the most exciting scientific breakthroughs are likely to occur, a good strategy is to look to the anomalies. And he does try to cover his chosen topics with care, while still keeping the prose accessible. But even I had the sense that the omissions in the book were carefully cherry-picked to make controversial theories/results more probable than current scientific consensus would warrant.

Why is that a problem? Well, the vast majority of the American public weren't exactly glued to their seats in fascination when the Bullet Cluster images first debuted, nor do they have more than a passing understanding of what dark matter is supposed to be. And that means they'll miss many subtle distinctions that would be immediately obvious to even a scientifically literate layperson like me. A recent review in the Times (UK) Online illustrates my point perfectly:

One of the great discoveries of 20th-century science was that our universe is expanding. The discovery, however, led straight to another puzzle. The puzzle is, there's nowhere near enough matter to prevent the expanding universe from blowing apart completely into a vast, sterile infinity of lifeless interstellar dust. So how come we live in a lumpy universe, one of the lumps being the planet on which we live? There must be more matter than we can see: the famous dark matter and, to go with it, something even more mysterious - dark energy.

To date, however, there's not a shred of evidence for either, even though teams of scientists have been looking for years. [emphasis mine]

Um, thanks for playing, Times Online, but that's a gross overstatement of the case. A simple Google search would yield countless articles and blog posts about all the experimental evidence accumulated thus far in support of both dark energy and dark matter. In fact, you can find an excellent in-depth but accessible analysis of the Bullet Cluster observations, and the ramifications for one popular modified gravity theory in particular called MOND, in the archives of Cosmic Variance, authored by my physicist spouse back in August 2006.

Sean has done his share of work on modified gravity; he's hardly the stereotypical closed-minded Establishment Scientist, willingly admitting that "in principle, it's absolutely possible that gravity could be modified, and it's worth taking seriously."  He actually thinks modified gravity would be really cool -- but only if it's born out by observation.

Personally, I would prefer to explain cosmological dynamics using modified gravity instead of dark matter and dark energy, just because it would tell us something qualitatively different about how physics works. ... We would all love to out-Einstein Einstein by coming up with a better theory of gravity. But our job isn’t to express preferences, it’s to suggest hypotheses and then go out and test them.

And as the rest of the post makes clear, one of the best tests scientists have devised to date to probe for evidence of dark matter shows very clearly that the stuff exists. Even then, Sean is far too good a scientist to assume that's the end of the matter:

So is this the long-anticipated (in certain circles) end of MOND? What need do we have for modified gravity if there clearly is dark matter? Truth is, it was already very difficult to explain the dynamics of clusters (as opposed to individual galaxies) in terms of MOND without invoking anything but ordinary matter. Even MOND partisans generally agree that some form of dark matter is necessary to account for cluster dynamics and cosmology. It’s certainly conceivable that we are faced with both modified gravity and dark matter. If the dark matter is sufficiently “warm,” it might fail to accumulate in galaxies, but still be important for clusters. Needless to say, the picture begins to become somewhat baroque and unattractive.

But the point is not whether or not MOND remains interesting; after all, someone else might come up with a different theory of modified gravity tomorrow that can fit both galaxies and clusters. The point is that, independently of any specific model of modified gravity, we now know that there definitely is dark matter out there. It will always be possible that some sort of modification of gravity lurks just below our threshold of detection; but now we have established beyond reasonable doubt that we need a substantial amount of dark matter to explain cosmological dynamics.

I hope the Times Online reviewer is taking notes...

Image: XKCD.

Paging Professor Frodo

August 19, 2008

Over the course of my Internet wanderings a couple of weeks ago, I stumbled across a fascinating abstract in the arXiv by one Alejandro Gangui on the 13th century cosmology of Dante's Divine Comedy. To my chagrin, the paper is in Spanish, so I was unable to peruse this unusual academic offering in-depth, although I'm guessing it focuses on the (pre-Copernican) Ptolemaic model of the heavens -- as, indeed, did much of medieval and Renaissance art and literature.

It also reminded me of an intriguing talk a few years ago at an APS meeting in Montreal on teaching astronomy through the works of J.R.R. Tolkien. (I can hear Lord of the Rings fans perking up this very moment.) This unique approach is the brainchild of Kristine Larsen, a professor of physics and astronomy at Central Connecticut State University who is known for her quirky creative approach to classroom instruction.  Larsen is also a hardcore Tolkien fan, so it was a natural choice to fuse her passion for Middle-Earth with her love for astronomy, writing academic papers and designing classroom activities exploring the science embedded in the LOTR trilogy.

Science fiction and fantasy relies upon world-building: the more "believable" you can make your fictional universe, the easier it is for the reader to become lost in that world. Star Trek, Star Wars, even Buffy the Vampire Slayer have carefully crafted "universes" with rules, origin myths, elaborate histories, geography, and the like. And those worlds are internally consistent, within reason. But Tolkien created one of the most elaborate worlds yet with Middle-Earth, complete with its own Elvish language (loosely based on ancient Anglo-Saxon) and -- according to Larsen -- its own cosmology. Tolkien, it seems, loved astronomy as well as story-telling.

He invented constellations, for example, some of which correspond to actual star groupings. For instance, in The Fellowship of the Ring, there are detailed references to specific stars: Remmirath, Borgil, and Menelvagor -- the latter described as the "Swordsman of the Sky... with his shining belt." This is an obvious reference to Orion. Larsen says Remmirath corresponds to the Pleiades. The identity of Borgil is less clear, but Larsen believes it corresponds to Aldebaran.

Tolkien painstakingly timed the internal chronology of the trilogy's events to the cycle of lunar phases. It gave him no end of grief, judging by letters to his son Christopher. In one dated May 14, 1944, for example, he laments his continued "trouble with the moon. By which I mean that I found my moons ... were doing impossible things, rising in one part of the country and setting simultaneously in another."

The extraordinary precision with which Tolkien mapped all this out makes for a terrific classroom exercise, according to Larsen. Her students study the cycle of the phases of the moon, and the times of day (or night) they are visible, using Discovery's online moon phase locator. Then they use what they've learned to analyze several passages from The Fellowship of the Ring, when Sam is asking Frodo how much time has elapsed on their journey ("What day is it, Mr. Frodo?").

Larsen even found evidence in The Silmarillion that the mythological origin for the moon in Middle-Earth  closely mirrored the "fission theory" of one G.H. Darwin that was popular at the time Tolkien was writing LOTR. I can't believe she managed to plow all the way through The Silmarillion, never mind make such an in-depth analysis. It's not Tolkien's most riveting work.

In fact, Larsen shares a bit of Tolkien's obsessive attention to detail, as well as his patience, poring over letters, manuscripts, notes and so forth to glean every last scrap of information about the author's creative process -- he was refining his fictional world right up until he died. But she still finds time for a bit of humor now and then, like this tongue-in-cheek scientific "paper" by one P. Legolas of the Mirkwood Academy of Sciences -- complete with elaborate footnotes -- proposing the existence of a new element ("Orodruinium") with unique properties used to create the One Ring. The abstract drily observes, "[T]his priceless antiquity was destroyed in an unfortunate ledge-dancing incident... which also claimed the life of one S. Gollum."

Photo: The Pleiades. Source: NASA/ESA/AURA/Caltech. Via Wikimedia Commons (public domain).

Astronomy by the Book

June 27, 2008

So much of what we now attribute to science used to be chalked up to the supernatural. Take the total solar eclipse, for example, which must have seemed like the wrath of the gods, or a frightening portent of doom, to many ancient cultures. It's still an awe-inspiring sight, even though we know it's a natural phenomenon that occurs whenever the Moon passes between the Sun and the Earth such that the Sun is entirely obscured. (You can watch a video of the 2006 total solar eclipse here.) Darkness unexpectedly falls, right in the middle of the day.

Frankly, it's a wee bit freaky, even if you're expecting it every 18 months or so. So imagine how even more spectacular it must have seemed to the Assyrians on June 15, 763 BC. Wikipedia tell me this is the earliest known total solar eclipse (known as the eclipse of Bur Sagale) described in an historically verified document (in this case, an ancient Assyrian text).

Until now, that is! Maybe. I guess it depends on whether you consider Homer's Odyssey (circa 800 BC) to be an historically verified document. A pair of biophysicists at Rockefeller University made science news headlines this week when they published a paper in Proceedings of the National Academy of Sciences USA claiming that Homer's epic poem describes a solar eclipse that occurred in 1178 BC.

According to Constantino Baikouzis and Marcelo Magnasco, the critical line appears towards the end of the epic saga, when the seer Theoclymenus foretells the imminent demise of Penelope's unwanted suitors, who've been pestering her to marry one of them, assuming Odysseus is dead. Depending on which translation you have on hand, Theo predicts the suitors will soon enter Hades, intoning (no doubt with appropriate gravitas), "The Sun has been obliterated from the sky, and an unlucky darkness invades the world." Unlucky indeed, for the suitors, who are quickly dispatched a few passages later by a vengeful Odysseus, who was the hot-tempered jealous sort. Either that, or he was very cranky after 10 years of wandering.

Even closer analysis of the text revealed other astronomical references. For instance, Odysseus navigates his little ramschackle survivor's raft by monitoring the constellations Pleiades and Bootes, and arrives home in Ithaca as Venus rises in the sky, just before dawn. Pleiades and Bootes only appear together in the sky twice a year, the scientists say, in March and September, while Venus rising before dawn would occur about one-third of the time during new moons. There's even a reference to the god Hermes flying west to the island of Ogygia, which Baikouzis and Magnasco interpret as representing the planet Mercury (the Roman name for Hermes). Mercury reverses course from west to east every 116 days. It's a bit flimsy, but some scholars believe that the Greeks used tales of their gods as a way to remember astronomical events, says Magnasco.

This suggests, among other things, that Homer had a much more detailed knowledge of astronomy than historians have given him credit for to date -- indeed, there's little historical evidence that any of the ancient Greeks tracked the movements of stars and planets in detail. In their defense, they didn't have access to a computer. The Rockefeller scientists were able to use commercial software to scan all the new moons (1,684 in all) between the years 1250 and 1125 BC, looking for the astronomical conditions described in the Odyssey.

They were able to narrow it down pretty well, since that combination only occurs about once every 2000 years. Through a process of elimination, they concluded that the eclipse Homer described occurred on April 16, 1178 BC, which does seem to coincide with the historical events in the epic poem. Granted, this is nearly 300 years before Homer actually wrote his masterpiece, but that's the ancient Greek oral tradition for you. The description is pretty vague, like something people had heard described through generations, rather than a firsthand account.

Baikouzis and Magnasco's paper has met with it share of skepticism. But it's fun little twist on ancient star-gazing. The next total solar eclipse rolls around on August 1. You'll have to travel to places like Greenland or western Mongolia to properly see it, but for diehard skywatchers with ample discretionary funds, it'd be well worth the trip. The rest of us can just sit back in our armchairs and engage in this hot new trend of literary astronomy -- a.k.a., astronomy by the book.

Images: (top) The 1999 total solar eclipse, photo by Luc Viatour. (bottom) "Odysseus Overcome by Demodocus' Song," painting by Francesco Hayez. Both via Wikimedia Commons.