The primary goal of the European Space Agency’s Planck satellite is to provide a map of the cosmic microwave background with unprecedented precision. But along the way, you have to take into account that there is stuff in between us and the farthest edges of the universe — in particular, there’s all sorts of dust here in our home galaxy. You can even become famous just studying dust; one of the most highly cited papers in all of astrophysics is a 1997 map of galactic dust.

Dust isn’t only an annoyance — it’s also pretty. Planck hasn’t released any data about the CMB yet, but they just released a map of the cold dust in our local vicinity, looking for all the world like an abstract expressionist painting. (I want to suggest a particular artist, but my mind is blanking.) Click to embiggen.

It’s a false-color image, of course; the dust is very cold (tens of degrees above absolute zero), and the image is constructed from microwaves, not from visible light. You can see the plane of the galaxy, and the filamentary structures arising from all the churning of the interstellar medium from supernovae, star formation, magnetic fields, and so on.

Okay, pretty time is over. Let’s see the CMB.

Very lovely time lapse video from Mauna Kea, home to many of the world’s best optical telescopes:

The White Mountain from charles on Vimeo.

For me, it really captures the best parts of how observing feels.

It misses the not-so-good parts, where the instrument breaks, or you’re shut down for wind in perfectly clear weather, or you’re trying desperately to stay awake on a diet of nothing but reheated bagel dogs.

I suppose I’m feeling rather maudlin about it, because its now been years and years since I’ve set foot at an observatory. During the past decade, almost all of my data has been ordered up from satellites or the observing queue, in contrast to my years at Carnegie, where I was observing for more than a month each year. My scientific life is much more “family friendly” as a result, but I still do miss the cold nights and big skies.

(h/t Andrew Sullivan)

Welcome to this week’s installment of the From Eternity to Here book club. This is a fun but crucial part of the book: Chapter Ten, “Recurrent Nightmares.”

Excerpt:

Fortunately, we (and Boltzmann) only need a judicious medium-strength version of the anthropic principle. Namely, imagine that the real universe is much bigger (in space, or in time, or both) than the part we directly observe. And imagine further that different parts of this bigger universe exist in very different conditions. Perhaps the density of matter is different, or even something as dramatic as different local laws of physics. We can label each distinct region a “universe,” and the whole collection is the “multiverse.” The different universes within the multiverse may or may not be physically connected; for our present purposes it doesn’t matter. Finally, imagine that some of these different regions are hospitable to the existence of life, and some are not. (That part is inevitably a bit fuzzy, given how little we know about “life” in a wider context.) Then—and this part is pretty much unimpeachable—we will always find ourselves existing in one of the parts of the universe where life is allowed to exist, and not in the other parts. That sounds completely empty, but it’s not. It represents a selection effect that distorts our view of the universe as a whole—we don’t see the entire thing, we only see one of the parts, and that part might not be representative. Boltzmann appeals to exactly this logic.

After the amusing diversions of the last chapter, here we resume again the main thread of argument. In Chapter Eight we talked a bit about the “reversibility objection” of Lohschmidt to Boltzmann’s attempts to derive the Second Law from kinetic theory in the 1870’s; now we pick up the historical thread in the 1890’s, when a similar controversy broke out over Zermelo’s “recurrence objection.” The underlying ideas are similar, but people have become a bit more sophisticated over the ensuing 20 years, and the arguments have become a bit more pointed. More importantly, they are still haunting us today.

One of the fun things about this chapter is the extent to which it is driven by direct quotations from great thinkers — Boltzmann, of course, but also Poincare, Nietzsche, Lucretius, Eddington, Feynman. That’s because the arguments they were making seem perfectly relevant to our present concerns, which isn’t always the case. Boltzmann tried very hard to defend his derivation of the Second Law, but by now it had sunk in that some additional ingredient was going to be needed — here we’re calling it the Past Hypothesis, but certainly you need something. He was driven to float the idea that the universe we see around us (which, to him, would have been our galaxy) was not representative of the wider whole, but was simply a local fluctuation away from equilibrium. It’s very educational to learn that ideas like “the multiverse” and “the anthropic principle” aren’t recent inventions of a new generation of postmodern physicists, but in fact have been part of respectable scientific discourse for over a century.

It’s in this chapter that we get to bring up the haunting idea of Boltzmann Brains — observers that fluctuate randomly out of thermal equilibrium, rather than arising naturally in the course of a gradual increase of entropy over billions of years. I tried my best to explain how such monstrosities would be the correct prediction of a model of an eternal universe with thermal fluctuations, but certainly are not observers like ourselves, which lets us conclude that that’s not the kind of world we live in. Hopefully the arguments made sense. One question people often ask is “how do we know we’re not Boltzmann Brains?” The realistic answer is that we can never prove that we’re not; but there is no reliable chain of argument that could ever convince us that we are, so the only sensible way to act is as if we are not. That’s the kind of radical foundational uncertainty that has been with us since Descartes, but most of us manage to get through the day without being overwhelmed by existential anxiety.

Today is the much celebrated pi-day . Ok, perhaps it’s not that big a holiday – I don’t think Hallmark is selling any pi-day cards yet – but anyone who uses google today knows that something mathematical and geeky is being honored. I promise not to go into diatribes about calculations of the first few million digits of pi, or how many digits one needs to keep in order to calculate the radius of the universe to atomic accuracy. Instead, I merely want to relay a simple short story a colleague of mine recounted to me years ago.

Several years ago, before pi-day was famous, a student called the phone number associated with the digits in pi that appear after the decimal point, i.e., 1-415-926-5358. Apparently this is rather common now, and in fact, appears to be promoted as a mnemonic for the first 10 decimal places for those folks we need to have those numbers handy at all times. But this story happened in earlier times, back before the Bay Area split into several area codes. And, as the clever reader has already guessed, that student reached the SLAC main gate. How cool to phone pi and reach the main gate of a major national scientific research laboratory!

Alas, time and phone numbers march on, and nowadays phoning pi yields a “your call cannot be completed as dialed” message. (And I’m told that I cannot publish this post without noting that 3-14-15 will be a more accurate pi day.)

Oh dear. Sometimes it’s so hard to let go.

And most importantly, don’t forget to join us MARCH 13, at 1pm for the PLUTO IS A PLANET PROTEST MARCH AND RALLY. The march starts at the Greenwood Space Travel Supply store (8414 Greenwood Ave N) and will end at Neptune Coffee (8415 Greenwood Ave N).

But really, Greenwood Space Travel Supply is all kinds of awesome, even if they’re weirdly co-dependent with small rocks in the outer solar system. They’re the Seattle branch of the 826 network, which is a non-profit writing center for kids.

They also have cool t-shirts.

Reporting back from a hotel in midtown Manhattan, having made it through the Colbert Report basically unscathed. In fact the experience was great from beginning to end. Update: here is the clip.

Monday morning I talked on the phone with Emily Lazar, a researcher for the show. I was really impressed right from the start: it was clear that she wanted to make it easy for me to get across some substantive message, within the relatively confining parameters of what is basically a comedy show. From start to finish everyone I dealt with was a consummate pro.

We got picked up at our hotel in a car that brought us to the Colbert studio, and hustled inside under relatively high security — people whispering into lapel microphones that we had arrived and were headed to the green room. Very exciting. The green room was actually green, which is apparently unusual. I got pep talks from a couple of the staff people, who encouraged me to keep things as simple as possible. They made an interesting point about scientists: they make the perfect foils for Stephen’s character, since they actually rely on facts rather than opinions.

Stephen himself dropped by to say hi, and to explain the philosophy of his character — I suppose there still are people out there who could be guests on the show who haven’t ever actually watched it. Namely, he’s a complete idiot, and it’s my job to educate him. But it’s not my job to be funny — that’s his bailiwick. The guests are encouraged to be friendly and sincere, but not pretend to be comedians.

We got to sit in the audience as the early segments were taped, which were hilarious. I feel bad that my own interview is going to be the low point of the show, laughs-wise. But I went out on cue, and fortunately I wasn’t at all jittery — too much going on to have time to get nervous, I suppose.

I had some planned responses for what I thought were the most obvious questions. Of which, he asked zero. Right off the bat Colbert managed to catch me off guard by asking a much more subtle question than I had anticipated — isn’t the early universe actually very disorderly? That would be true if you ignored gravity, but a big part of my message is that you can’t ignore gravity! The problem was, I had promised myself that I wouldn’t use the word “entropy,” resisting the temptation to lapse into jargon. But he had immediately pinpointed an example where the association of “low entropy” with “orderly” wasn’t a perfect fit. So I had to go back on my pledge and bring up entropy, although I didn’t exactly give a careful definition.

As everyone warned me, the whole interview went by in an absolute flash, although it really lasts about five minutes. There was a fun moment when we agreed that “Wrong Turn Into Yesterday” would make a great title for a progressive-rock album. Overall, I think I could have done a better job at explaining the underlying science, but at least I hope I successfully conveyed the spirit of the endeavor. We’ll have to see how it comes across on TV.

I shouldn’t end without including some good words about the bag of swag. Not only does every guest get a goodie bag that includes a bottle of excellent tequila, it also includes a $100 gift certificate for Donors Choose. How awesome is that?

And as we left the studio, there were some young audience members lurking around hoping for a glimpse of the great man himself. They had to settle for me, but they sheepishly asked if I would pose for a picture with them. Not yet having perfected my diva act, I happily complied. I hope they take away some great memories of the night.

When we think about the “meaning of life,” we tend to conjure ideas such as love, or self-actualization, or justice, or human progress. It’s an anthropocentric view; try to convince blue-green algae that self-actualization is some sort of virtue. Let’s ask instead why “life,” as a biological concept, actually exists. That is to say: we know that entropy increases as the universe evolves. But why, on the road from the simple and low-entropy early universe to the simple and high-entropy late universe, do we pass through our present era of marvelous complexity and organization, culminating in the intricate chemical reactions we know as life?

Yesterday’s book club post referred to a somewhat-whimsical vision of Maxwell’s Demon as a paradigm for life. The Demon takes in free energy and uses it to maintain a separation between hot and cold sides of a box of gas — a sustained departure from thermal equilibrium. But what if we reversed the story? Instead of thinking that the Demon takes advantage free energy to help advance its nefarious anti-thermodynamic agenda, what if we imagine that the free energy is simply using the Demon — that is, the out-of-equilibrium configurations labeled “life” — for its own pro-thermodynamic purposes?

Energy is conserved, if we put aside some subtleties associated with general relativity. But there’s useful energy, and useless energy. When you burn gasoline in your car engine, the amount of energy doesn’t really change; some of it gets converted into the motion of your car, while some gets dissipated into useless forms such as noise, heat, and exhaust, increasing entropy along the way. That’s why it’s helpful to invent the concept of “free energy” to keep track of how much energy is actually available for doing useful work, like accelerating a car. Roughly speaking, the free energy is the total energy minus entropy times temperature, so free energy is used up as entropy increases.

Because the Second Law of Thermodynamics tells us that entropy increases, the history of the universe is the story of dissipation of free energy. Energy wants to be converted from useful forms to useless forms. But it might not happen automatically; sometimes a configuration with excess free energy can last a long time before something comes along to nudge it into a higher-entropy form. Gasoline and oxygen are a combustible mixture, but you still need a spark to set the fire.

This is where life comes in, at least according to one view. Apparently (I’m certainly not an expert in this stuff) there are two competing theories that attempt to explain the first steps taken toward life on Earth. One is a “replicator-first” picture, in which the key jump from chemistry to life was taken by a molecule such as RNA that was able to reproduce itself, passing information on to subsequent generations. The competitor is a “metabolism-first” picture, where the important step was a set of interactions that helped release free energy in the atmosphere of the young Earth. You can read some background about these two options in this profile of Mike Russell (pdf), one of the leading advocates of the metabolism-first view.

I was reading a bit about this stuff because I wanted to move beyond the fairly simplistic sketch I presented in my book about the relationship between entropy and life. So I did a little research and found some papers by Eric Smith at the Santa Fe Institute. Smith has taken quite an academic path; his Ph.D. was in string theory, working with Joe Polchinski, and now he applies ideas from complexity to questions as diverse as economics and the origin of life.

On Saturday I was on a long plane ride from LA to Bozeman, Montana, via Denver. So I had pulled out one of Smith’s papers and started to read it. A couple sat down next to me, and the husband said “Oh yes, Eric Smith. I know his work well.” This well-read person turned out to be none other than Mike Russell, featured in the profile above. Here I was trying to learn about entropy and the origin of life, and one of the world’s experts sits down right next to me. (Not completely a coincidence; Russell is at JPL, and we were both headed to give plenary talks at the annual IEEE Aerospace Conference.)

So I explained a little to Mike (now we are buddies) what I was trying to understand, and he immediately said “Ah, that’s easy. The purpose of life is to hydrogenate carbon dioxide.” (See figure above, taken from one of Eric Smith’s talks.)

That might be something of a colorful exaggeration, but there’s something fascinating and provocative behind the idea. An extremely simplified version of the story is that the Earth was quite a bit hotter in its early days than it is today, and the atmosphere was full of carbon dioxide. At high temperatures that’s a stable situation; but once the Earth cools, it would be energetically favorable for that CO2 to react with hydrogen to make methane (and other hydrocarbons) and water. That is to say, there is a lot of free energy in that CO2, just waiting to be released.

The problem is that there is a chemical barrier to actually releasing the energy. In physicist-speak: the Earth’s atmosphere was caught in a false vacuum. There’s no reaction that takes you directly from CO2 and hydrogen to methane (CH4) and water; you have to go through a series of reactions to get there. And the first steps along the way constitute a potential barrier: they consume energy rather than releasing it. Here’s a plot from one of Russell’s talks of the free energy per carbon atom of various steps along the way; it looks for all the world like a particle physicist’s plot of the potential energy of a field caught in a metastable vacuum. (Different curves represent different environments.)

Here is the bold hypothesis: life is Nature’s way of opening up a chemical channel to release all of that free energy bottled up in carbon dioxide in the atmosphere of the young Earth. My own understanding gets a little fuzzy at this point, but the basic idea seems intelligible. While there is no simple reaction that takes CO2 directly to hydrocarbons, there are complicated series of reactions that do so. Some sort of membrane (e.g. a cell wall) helps to segregate out the relevant chemicals; various inorganic compounds act as enzymes to speed the reactions along. The reason for the complexity of life, which is low entropy considered all by itself, is that it helps the bigger picture increase in entropy.

In ordinary statistical mechanics, we say that high-entropy configurations are more likely than low-entropy ones because there are simply more of them. But that logic doesn’t quite go through if you can’t get to the high-entropy configurations in any straightforward way. Nevertheless, a sufficiently complicated system can bounce around in configuration space, trying various different possibilities, until it hits on something that looks quite complex and unlikely, but is in fact very useful in helping the system as a whole evolve to a higher-entropy state. That’s life (as it were). It’s not so different from other cases like hurricanes or turbulence where apparent complexity arises in the natural course of events; it’s all about using up that free energy.

Obviously there is a lot missing to this story, and much of it is an absence of complete understanding on my part, although some of it is that we simply don’t know everything about life as yet. For one thing, even if you are a metabolism-first sympathizer, at some point you have to explain the origin of replication and information processing, which plays a crucial role how we think about life. For another, it’s a long road from explaining the origin of life to getting to the present day. It’s true that we know of very primitive organisms whose goal in life seems to be the conversion of CO2 into methane and acetate — methanogens and acetogens, respectively. But animals tend to produce CO2 rather than consume it, so it’s obviously not the whole story.

No surprise, really; whatever the story of life might be, there’s no question it’s a complicated one. But it all comes down to the elementary building blocks of Nature doing their best to fulfill the Second Law.

Welcome to this week’s installment of the From Eternity to Here book club. Now for something of a palate-cleanser, in the form of Chapter Nine, “Information and Life.”

Excerpt:

Schrödinger’s idea captures something important about what distinguishes life from non-life. In the back of his mind, he was certainly thinking of Clausius’s version of the Second Law: objects in thermal contact evolve toward a common temperature (thermal equilibrium). If we put an ice cube in a glass of warm water, the ice cube melts fairly quickly. Even if the two objects are made of very different substances—say, if we put a plastic “ice cube” in a glass of water—they will still come to the same temperature. More generally, nonliving physical objects tend to wind down and come to rest. A rock may roll down a hill during an avalanche, but before too long it will reach the bottom, dissipate energy through the creation of noise and heat, and come to a complete halt before very long.

Schrödinger’s point is simply that, for living organisms, this process of coming to rest can take much longer, or even be put off indefinitely. Imagine that, instead of an ice cube, we put a goldfish into our glass of water. Unlike the ice cube (whether water or plastic), the goldfish will not simply equilibrate with the water—at least, not within a few minutes or even hours. It will stay alive, doing something, swimming, exchanging material with its environment. If it’s put into a lake or a fish tank where food is available, it will keep going for much longer.

This chapter starts with something very important: the relationship between entropy and memory. Namely, the reason why we can “remember” the past and not the future is that the past features a low-entropy boundary condition, while the future does not. I don’t go into great detail about this, and we certainly don’t talk very specifically about how real memories are formed in the brain, or even in a computer. But when we get to the next chapter, about recurrences and Boltzmann brains, it will be crucial to understand how the assumption of a low-entropy boundary condition enables us to reconstruct the past. It’s hard for people to wrap their brains around the fact that, without such an assumption, our “memories” or records of the past will generally be unreliable — knowledge of the current macrostate wouldn’t allow us to reconstruct the past any better than it allows us to predict the future. (Which is only logical, since it’s only this hypothesis that breaks time-reversal symmetry.)

The rest of the chapter, meanwhile, is more about having fun and mentioning some ideas that are not directly related to our story, but certainly play a part in understanding the arrow of time. Information theory, life, complexity. I’m not an expert in any of these fields, but it was a lot of fun reading about them to pick out some things that fit into the broader narrative. The Maxwell’s Demon story, in particular, is one that every physicist should know (up through it’s relatively modern resolution), but relatively few do. And I think Jason Torchinsky did a great job with the illustrations of the Demon.

A lot of big ideas here, of course, and much of this stuff is still very much in the working-out stage, not the settled-understanding stage. We’re still arguing about basic things like the definition of “complexity” and “life.” It’s relatively easy to state the Second Law and explain how the arrow of time is related to the growth of entropy, but there’s a tremendous amount of work still to be done before we completely understand the way in which the universe actually evolves from low entropy to high.

In honor of the Oscars, I spent last night watching a movie. It was set on another world, populated by exotic flora and fauna (e.g., a blue creature with a long tail). The good inhabitants of this world live as one with all nature, and refuse to kill or do harm. A caucasian human shows up, and saves the world from disaster by being brave enough to kill. The movie was in 3-D, creatively combining real-action and animation, and was lushly filmed with dramatic scenes of waterfalls and forests and mountains. The movie’s title starts with the letter “A”.

Of course, I’m talking about Alice in Wonderland. What, is there some other movie you were thinking of? Spoilers follow (although it’s not the type of movie that gets spoiled), so if you’re hyper-sensitive about such things (as I am), cease reading now.

Alice and Avatar make an excellent study in contrasts. They both use the same canvas, and there are remarkable superficial similarities between the two. However, I found Alice to be much more interesting and satisfying as a film. Avatar, as the entire world seems to have noted, has a completely mundane and predictable story, with a sound-byte message. Within about ten minutes of the film, you know more-or-less the full arc. It’s a reasonable story, with lots of visual candy, and I can’t say I was bored (which is saying a lot for a three hour film). But, at least for me, it left little mark. To go to such great lengths to build up an entire world, you’d think you’d have something profoundly new and interesting to say. Sean does a nice job of summarizing some of Avatar’s failings.

I found Alice, on the other hand, to be much more entertaining. For any self-respecting science geek, having a movie which revolves around a vorpal sword has to warm the cockles of your heart. But there’s substance behind all of the talking flowers and Jabberwocks. For example, consider the good and bad queens. They had interesting, quirky personalities, and didn’t play directly to stereotype. In Avatar, these roles would have been completely one dimensional. In Alice, the Red Queen has moments of doubt, and seems genuinely surprised that she is not loved. Images of hearts proliferate, to no avail. The White Queen, meanwhile, swats at “dragonflies” while professing her love for all creatures. She seems somewhat annoyed that she’s not allowed to wreak mayhem on her rival, as if she’s struggling within the bounds of the “good queen” convention. There are subtle physical manifestations as well: her snow white hair is dark underneath, and she has slightly dark circles about her eyes. The distance between the two queens (and sisters) is not as great as it initially appears. These satisfying levels of grey give the characters more depth and nuance (something that is completely absent in Avatar). Alice demands that the viewer do some work; the movie does not present everything neatly wrapped with a bow. The moral of the film is left a bit hazy. It has something to do with letting your imagination run wild. Resisting convention. Living in the world you want, rather than the one you find. At the end of Avatar, the main character remains on Pandora. Alice, on the other hand, chooses to leave Wonderland and return to London. Which film is more courageous?

We’ve been studied. Bora points to a new paper by Inna Kouper in the Journal of Science Communication. The title is “Science blogs and public engagement with science: Practices, challenges, and opportunities,” which pretty much explains what it’s about. The author picks out a collection of eleven blogs — Pure Pedantry, Synthesis, MicrobiologyBytes, Bioethics, Wired Science, DrugMonkey, Scientific Activist, Pharyngula, Panda’s Thumb, and our own humble offering — and analyzes posts and comments to judge how effective these sites are at promoting science communication.

The list of blogs chosen is — okay, I guess. I have no idea how it was constructed, and the paper doesn’t seem to provide much guidance. Bora has a critique of the methodology that wonders about that, and about exactly how objective the study is. It’s very hard to assign numbers to things like “ratio of informative posts vs. rants,” or “degree to which the cause of collegial communication was harmed by use of intemperate language.” The paper reads like someone read a bunch of blogs and typed up their personal impressions.

For the most part I don’t disagree too strongly with the impressions, with the obvious caveat that it’s almost completely useless to study “science blogs” as a group. People don’t read randomly chosen collections of blogs; they read very intentionally chosen subsets that appeal to their own interests, and different reading lists will lead to wildly divergent impressions about what blogs are really like.

More significantly, though, I can’t really agree with the moral that the author draws from these experiences. Here is the telling quote from the paper:

The blogs employ a variety of writing and authoring models, and no signs of emerging or stabilizing genre conventions could be observed. Even though all blogs mentioned science or a particular scientific discipline in their descriptions, they differed in their voice representations, points of view, and content orientation.

It’s hard to disagree with that, but I think it’s a good thing, and the author clearly does not. Blogs differ in many ways, and happily avoid the encroachment of stabilizing genre conventions. That’s one of the biggest benefits of opening up communication channels to a tremendous variety of content providers, rather than restricting things to just a few mainstream outlets; writers can have their voices, and readers can choose who to read, and everyone is happy.

It’s clear that a lot of people want blogs to be just like some pre-existing communication medium, just with comments and occasional expertise. And there are blogs like that, if that’s what you’re into. And there are blogs that aren’t, likewise. I hope it stays that way.

The New York Times has an article about stand-up paddleboarding. I guess that means it’s now officially mainstream? It’s weird to have seen a sport arise completely from scratch, over a period of just a few years. Five years ago paddleboarders were basically freaks. Now every break is teeming with them, and there’s a whole industry specifically for stand-up. Even the gray lady herself is in on the game.

For the uninitiated: imagine an oversized longboard (over 10 feet long), with extra width and stability. You stand up on the board, and use a long-handled paddle to propel yourself through the water. Sort of like a canoe, only standing up. It’s good exercise. It’s also really fun. You can really cruise. And you can enjoy it even if it’s totally flat (although the real fun is to take the big boards into the surf).

The rapid rise in popularity is almost certainly due to the fact that the learning curve for stand-up paddleboarding is shallow. The average person can be up and going in about 10 minutes. And it’s almost like they’re surfing. After all, they’re standing on a surfboard, moving through the water. However, this is a pale imitation. Until you actually get the board out in the surf, and feel the acceleration of a drop, and the exhilaration as you glide down a wall of water, you have no idea what it’s all about. Good paddleboarders can go out in big surf. But that part of the learning curve is Jaws steep.

I was in Maui this past January, and my favorite break (Kanaha) was overrun by paddleboards. At least half the people out there were doing stand-up. For a “conventional” surfer it’s a bummer, since the paddleboards catch waves early, and there’s no room to drop in, even if you wanted to. But if you can’t beat ‘em….

About a year ago I had my initiation, doing a down-winder from past Ho’okipa to Spreckelsville. It took a while to get the balance down, but eventually you figure out where to stand, and how to use the paddle for stability. And then you’re cruising. You can paddle into reasonable breaking surf, since the board has a tendency to keep going and remain unperturbed. You cut right through waves that would have tossed a longboard. However, I can tell you from painful experience that it really sucks to get Maytagged while doing stand-up. I have a nice fin-shaped scar to prove it.

I did my graduate work at the University of Chicago, and lived in Hyde Park. On occasion I would take the bus (the #6 Jeffery Express) to downtown. Although the buses were scheduled to run every 15 minutes, I would invariably end up waiting a half hour. Sometimes more. Often in the freezing cold, or the sweltering heat. Most infuriatingly, when the bus finally arrived, there was always another one immediately behind it! The buses inevitably came in pairs. Sometimes even in triples or quads.

Let’s assume that the buses are supposed to arrive every 15 minutes. If the buses adhered to their schedule, and I showed up at a random time, I should generally have to wait roughly half the mean bus arrival time: 7.5 minutes. If the buses were totally random, then I would have to wait the average time between bus arrivals: 15 minutes (if you haven’t thought about this before, this statement should sound crazy; perhaps I’ll do a future post on it). So the question is: why did I always end up waiting roughly 30 minutes or more?

I always assumed that the Universe was conspiring against me. This is a common feeling in graduate school. However….

I just stumbled across a blog post of a friend of mine from graduate school, Alex Lobkovsky. In it, he discusses precisely this problem, and presents various reasons for the bunching of buses. I have no doubt that he was inspired from similar suffering. Perhaps at the very same bus stop.

At the end of the day, there’s a fairly straightforward solution. Imagine all of the buses are roughly on time. Now imagine that one bus (call it bus S) happens to fall behind. Because S is running behind, more time has elapsed since the previous bus has passed. This means that more waiting passengers have accumulated, at more bus stops. This in turn means that bus S has to stop more often, and has to pick up more people at each stop. Hence, bus S falls even farther behind. Which means even more people accumulate at each stop. Which means the bus falls even farther behind. And so on. In short: a slow bus gets slower and slower.

Now let us consider the bus behind bus S; we’ll call it bus F. Bus F starts out roughly on schedule. But because bus S is running late, less time than average has elapsed between when bus S last passed and when bus F arrives. This means fewer people have accumulated, at fewer stops. Which means bus F makes fewer stops, and picks up fewer people. Which means that it starts to run faster than average. Which means even fewer people accumulate. Which means it runs even faster. And so on. In short: a fast bus gets faster and faster.

Putting this all together: if a random fluctuation creates a slow bus, then it will get slower and slower, and the bus behind it will get faster and faster, until the two buses meet up. At this point, the buses stick together, and are essentially incapable of separating. Thus, in general, buses will bunch up. This will usually happen in pairs, though on occasion triples and even quads may occur. This argument predicts that the arrival of buses will be random, with pairs of buses arriving more often than not, being separated by on average double the mean bus separation. And this is precisely what I discovered, the hard way, shivering at the corner of 55th St. and Hyde Park Boulevard. (N.B. I spent a year in Berlin. There, the buses are fermions, and always arrive exactly on time. It’s the stereotype, but it turns out to be true.)

After writing this post, I found that wikipedia has already figured it all out. Regardless, it’s nice to know that my suffering was due to statistics, and not because the Universe is out to get me.

First a programming notice: turns out I will not be on the Colbert Report tonight. Never fear — I was just bumped back to next week, Wednesday March 10 (11:30 p.m., 10:30 Central). Business as usual in TV land, no big deal. I was hoping that I was nudged in favor of a newly medaled Olympic hero, or at least minor royalty, but it looks like tonight’s guest will be Garry Wills. He’s one of my favorite writers, but still. Obviously some Catholic favoritism going on here.

Small scheduling glitches aside, the Colbert Report and the Daily Show remain two of the best places to hear interviews with interesting academics on TV, especially with scientists. In USA Today, Dan Vergano writes about this curious state of affairs. Neil deGrasse Tyson brings up a good point, that Johnny Carson’s version of the Tonight Show used to feature interviews with heavyweights such as Carl Sagan and Margaret Mead. These days, not many non-satirical network news shows bring on scientists (or anthropologists, or for that matter philosophers or English professors) as a regular event.

When Conan O’Brian took over the Tonight Show, the Science and Entertainment Exchange received a request from the producers to suggest some entertaining (and hopefully enlightening) scientists they could consider bringing on as guests. I don’t know if they ever followed up on that idea, and now I guess we’ll never know. Hopefully the success of Stewart and Colbert will convince the networks that Americans don’t necessarily turn the channel when faced with people who think carefully about the universe.

A physics student here at UC Davis, Austin Sendek, has launched a campaign to add another designator to the list of numeric SI prefixes such as kilo-, mega-, etc. to cover 1027: hella. For example, 1 hellagram would be 1027 grams, or 1000 yottagrams.

The term “hella” is one I first heard my sister-in-law utter in the context “that ski run was hella fun!”, which I immediately took as a shorthand for “a hell of a lot of”. I’ve since learned that it originated, reportedly, in San Francisco to mean just that, or “very” in general, as in “that tee shirt is hella awesome” – it’s not an uncommon utterance to hear here in northern California.

And, 1027 is hella big, to be sure. A hellasecond is ten billion times the age of the universe, and the mass of the earth is about 6 hellagrams.

It seems that hella is poised to go viral…there are nearly 24,000 fans of the facebook petition, and it even made the local news last night in Sacramento.

Who decides such things? The International Bureau of Weights and Measures, that’s who. They added yotta in 1991. Sign the petition to them at the facebook site!

Welcome to this week’s installment of the From Eternity to Here book club. Finally we dig into the guts of the matter, as we embark on Chapter Eight, “Entropy and Disorder.”

Excerpt:

Why is mixing easy and unmixing hard? When we mix two liquids, we see them swirl together and gradually blend into a uniform texture. By itself, that process doesn’t offer much clue into what is really going on. So instead let’s visualize what happens when we mix together two different kinds of colored sand. The important thing about sand is that it’s clearly made of discrete units, the individual grains. When we mix together, for example, blue sand and red sand, the mixture as a whole begins to look purple. But it’s not that the individual grains turn purple; they maintain their identities, while the blue grains and the red grains become jumbled together. It’s only when we look from afar (“macroscopically”) that it makes sense to think of the mixture as being purple; when we peer closely at the sand (“microscopically”) we see individual blue and red grains.

Okay cats and kittens, now we’re really cooking. We haven’t exactly been reluctant throughout the book to talk about entropy and the arrow of time, but now we get to be precise. Not only do we explain Boltzmann’s definition of entropy, but we give an example with numbers, and even use an equation. Scary, I know. (In fact I’d love to hear opinions about how worthwhile it was to get just a bit quantitative in this chapter. Does the book gain more by being more precise, or lose by intimidating people away just when it was getting good?)

In case you’re interested, here is a great simulation of the box-of-gas example discussed in the book. See entropy increase before your very eyes!

Explaining Boltzmann’s definition of entropy is actually pretty quick work; the substantial majority of the chapter is devoting to digging into some of the conceptual issues raised by this definition. Who chooses the coarse graining? (It’s up to us, but Nature does provide a guide.) Is entropy objective, or does it depend on our subjective knowledge? (Depends, but it’s as objective as we want it to be.) Could entropy ever systematically decrease? (Not in a subsystem that interacts haphazardly with its environment.)

We also get into the philosophical issues that are absolutely inevitable in sensible discussions of this subject. No matter what anyone tells you, we cannot prove the Second Law of Thermodynamics using only Boltzmann’s definition of entropy and the underlying dynamics of atoms. We need additional hypotheses from outside the formalism. In particular, the Principle of Indifference, which states that we assign equal probability to every microstate within any given macrostate; and the Past Hypothesis, which states that the universe began in a state of very low entropy. There’s just no getting around the need for these extra ingredients. While the Principle of Indifference seems fairly natural, the Past Hypothesis cries out for some sort of explanation.

Not everyone agrees. Craig Callender, a philosopher who has thought a lot about these issues, reviewed my book for New Scientist and expresses skepticism that there is anything to be explained. (A minority view in the philosophy community, for what it’s worth.) He certainly understands the need to assume that the early universe had a low entropy — as he says in a longer article, “By positing the Past State the puzzle of the time asymmetry of thermodynamics is solved, for all intents and purposes,” with which I agree. Callender is simply drawing a distinction between positing the past state, which he’s for, and trying to explain the past state, which he thinks is a waste of time. We should just take it as a brute fact, rather than seeking some underlying explanation — “Sometimes it is best not to scratch explanatory itches,” as he puts it.

While it is absolutely possible that the low entropy of the early universe is simply a brute fact, never to be explained by any dynamics or underlying principles, it seems crazy to me not to try. If we picked a state of the universe randomly out of a hat, the chances we would end up with something like our early universe are unimaginably small. To most of us, that’s a crucial clue to something deep about the universe: it’s early state was not picked randomly out of a hat! Something should explain it. We can’t be completely certain that such an explanation exists, but cosmology is hard enough without choosing to ignore the most blatant clues that nature is sticking under our noses.

This chapter and the next two are the heart and soul of the book. I hope that the first part of the book is interesting enough that people are drawn in this far, because this is really the payoff. It’s all interesting and fun, but these three chapters are crucial. Putting it into the context of cosmology, as we’ll do later in the book, is indispensable to the program we’re outlining, but the truth is that we don’t yet know the final answers. We do know the questions, however, and here is where they are being asked.

It’s generally easy to write a damning book review. It’s much harder to write a positive and enthusiastic one. So how about a review that includes this paragraph?:

I put down Rebecca Skloot’s first book, “The Immortal Life of Henrietta Lacks,” more than once. Ten times, probably. Once to poke the fire. Once to silence a pinging BlackBerry. And eight times to chase my wife and assorted visitors around the house, to tell them I was holding one of the most graceful and moving nonfiction books I’ve read in a very long time.

That’s Dwight Garner reviewing the book for the New York Times. What’s more, this is a nonfiction book revolving around science! Henrietta Lacks died at age 31 of cervical cancer. She was relatively poor, and completely unknown. No tombstone marks her grave. Without any sort of consent or awareness, some of her cells were “stolen” during her treatment. It turned out that the cells could be cultured, and they rapidly became a key tool in biomedicine. Salk used her cells to develop a vaccine for polio. The cells are ubiquitous, living on and thriving half a century after Henrietta Lacks’ death. Although this was all news to me, apparently any self-respecting biologist has heard of HeLa. Her full story has plenty of moral and philosophical implications, as well as basic science. Henrietta Lacks has had a profound, and completely unwitting, impact on our lives. Wired magazine has a chart:

Garner ends his review with:

This is the place in a review where critics tend to wedge in the sentence that says, in so many words, “This isn’t a perfect book.” And “The Immortal Life of Henrietta Lacks” surely isn’t. But there isn’t much about it I’d want to change. It has brains and pacing and nerve and heart, and it is uncommonly endearing. You might put it down only to wipe off the sweat.

I think he liked the book. Other reviews have been similarly enthusiastic (see Skloot’s blog for links). “Immortal Life” is definitely heading to my bedside table. But apparently one of my co-bloggers has recently published a book, and I should probably read that one first. If only I could find time.

Jane McGonigal thinks they can help. She’s a game designer who gave a talk at the TED conference this year (although her talk isn’t up yet).

McGonigal makes some good points in this short video, especially about how dealing with things in a video-game environment — like failure, or social interactions — can be greatly helpful when one eventually has to deal with them in the real world. She also helped put together Urgent Evoke, a large-scale multiperson game where you collect achievements by performing world-saving tasks.

The kids these days, they love their gaming. So it makes sense to ask how that passion can be put to good use. Personally I’m fascinated by the prospects of using games to teach people science. Not just facts and features of the real world — although those are important — but the scientific method of hypothesis-testing and experiment. Games already feature exactly those features, of course; everyone who figures out the “laws of nature” in the game world is secretly doing science. It wouldn’t be that hard to tweak things here and there so that the techniques they were practicing connected more directly with science in the non-virtual reality.

I spent last week attending the “Formation and Evolution of Black Holes” conference at the Aspen Center for Physics, organized by Andrea Ghez, Vicky Kalogera, Fred Rasio, and Steinn Sigurdsson (who blogs over at the Dynamics of Cats). It was a great mix of observers and theorists, and we covered the full range, from stellar-mass black holes in our galaxy to supermassive black holes on the far side of the Universe. I was particularly interested in two topics: gravitational-wave recoil and black hole binary inspiral (I’ll blog about both soon enough). And I made another pilgrimage to the Highlands bowl, this time with 15″ of virgin powder.

The Aspen Center runs a public lecture series in conjunction with each conference. So last Wednesday Andrea Ghez gave a lecture on the black hole at the center of our galaxy. It’s our closest big black hole, roughly 25,000 light years (2×1017 kilometers) away, and four million times the mass of our Sun. Andrea has been leading a team studying the motion of stars orbiting around this black hole. These orbits are one of the best ways (short of the detection of gravitational waves from black hole mergers) of confirming that black holes exist. The orbits tell us the mass of the central object. And the innermost passage of the closest orbit gives us an upper limit on the size of the central object. Combining these numbers gives us a lower limit to the density of the “dark object” at the center of our galaxy. At this point, a black hole is the only viable model for what we see. There is no way to make sense of the orbits using a cluster of (dark) stars at the center, or a massive gas cloud, or anything else we can think of. Gravity tells us that any normal stuff we put there (including “conventional” dark matter) will evaporate or collapse to a black hole. We are not yet probing the horizon of the black hole (in some sense, its surface), but we are getting closer and closer with each passing year.

But, more importantly, Andrea is responsible for one of the coolest movies in all of science:

This shows the orbits of stars around our galactic center. This isn’t an artist’s conception. This isn’t some abstraction of other data. This is a real movie of stars circling the black hole over the last 15 years. In particular, watch S-02. It loops around the black hole, and closes its orbit; we have watched it over one full S-02 “year”. It is an incredible feat of observational astronomy to make these movies. It requires adaptive optics on the largest telescopes in the world (the Keck telescopes on Mauna Kea). We used to think of the heavens as eternal and unchanging. Now we watch movies of stars orbiting black holes.

It’s walking cats that is truly problematic.

Feel free to construct your own similes. (Via Cynical-C.)

Everyone is linking to this Guardian article collecting advice from fiction writers. My favorite list comes from Richard Ford — not that I necessarily agree with every rule:

1 Marry somebody you love and who thinks you being a writer’s a good idea.

2 Don’t have children.

3 Don’t read your reviews.

4 Don’t write reviews. (Your judgment’s always tainted.)

5 Don’t have arguments with your wife in the morning, or late at night.

6 Don’t drink and write at the same time.

7 Don’t write letters to the editor. (No one cares.)

8 Don’t wish ill on your colleagues.

9 Try to think of others’ good luck as encouragement to yourself.

10 Don’t take any shit if you can ­possibly help it.

There’s an entire blog devoted to listing the daily routines of writers. It’s a funny business — the people who do it can’t imagine doing anything else, but they still rely on all sorts of gimmicks to keep their work flowing smoothly. Maybe that’s part of the difference between styling one’s self as a writer and actually writing.