Preposterous Universe

Sunday, October 31, 2004
Genetic superiority

I don't want to linger too long in the already-disturbed hornet's nest of competition, gender, and physics, but I do want to point to some thoughtful articles by Maire that are worth reading: here, here, and here. We're basically on the same wavelength, but she has the patience to get into some of the details.

Whenever anyone is quick to leap from a fact of our current social arrangements (underrepresentation of group X in occupation Y) to a conclusion about biological inevitability (X's just don't have what it takes to succeed in Y), I can't help but think of the SPHA's -- the South Philadelphia Hebrew Association. The SPHA's were a dominant basketball team back in the 1930's. Indeed, at the time a significant percentage of the best basketball players were Jewish. Are we surprised to learn that it was common for people to attribute this success to the intrinsic superiority of Hebrews when it came to the skills of basketball? From Jon Entine, quoted by Michael Shermer:
"The reason, I suspect, that basketball appeals to the Hebrew with his Oriental background," wrote Paul Gallico, sports editor of the New York Daily News and one of the premier sports writers of the 1930s, "is that the game places a premium on an alert, scheming mind, flashy trickiness, artful dodging and general smart aleckness."
Jews were also thought to possess the genetic advantage of being short, enabling them to dart past the gangly Gentiles for easy buckets. Of course, these days we are enlightened enough to realize that it is actually blacks who are genetically predisposed to have game, not those sneaky Hebrews. Progress marches on.

Friday, October 29, 2004
The blogosphere is insufficiently cynical

Maybe I just haven't noticed, but has anyone pointed out the most obvious possibility? The Bin Laden tape is the October Surprise. Think about it: a good October Surprise will make people rally around the incumbent, without having any obvious fingerprints of political maneuvering all over it. And we don't know where Al-Jazeera got the tape from. Karl Rove is as likely a source as any.

The point of faith

Jack Balkin talks about different sorts of faith, and I nit-pick him on definitions. But it's worth reading.

More shameless than you would have believed possible

From the LA Times, via The Poor Man:
WASHINGTON — Bush administration lawyers argued in three closely contested states last week that only the Justice Department, and not voters themselves, may sue to enforce the voting rights set out in the Help America Vote Act, which was passed in the aftermath of the disputed 2000 election.

Veteran voting-rights lawyers expressed surprise at the government's action, saying that closing the courthouse door to aspiring voters would reverse decades of precedent.
Because, of course, the only person with the requisite wisdom and objectivity to protect the American voter would be John Ashcroft.

Another example of DeLong's Law: The Bush Administration is always worse than one imagines, even when taking into account DeLong's Law.

Arrogance, aggressiveness, competitiveness

No, I'm not talking about politicians -- it's about physicists.

Sometimes, you see a hornet's nest, and some wise part of you knows that you shouldn't go poking it with a stick. But if you were smart enough to resist, you wouldn't have a blog, would you? Peter Woit mentions a recent colloquium at Fermilab by Howard Georgi, in which Georgi discusses the lamentable under-representation of women in physics. Peter says some sensible things about how complicated the problem is, but being a provocateur, he can't resist getting in a dig at Lubos Motl at the end of it. Lubos, getting into the Halloween spirit, dons his caveman costume and responds with an explanation of the situation, which seems to rely on hormones and the fact that women have fewer neurons than men. (He mentions, generously, that women can be both smart and beautiful; this is only fair, as he frequently mentions how this or that male physicist is kind of dreamy.)

I've chatted before about the issue of gender disparity in physics, but there is a separate but related issue worth remarking on: the arrogance, aggressiveness, and competitiveness of many physicists. Of course such a characterization is a careless over-generalization, but there is enough truth to it that it's worth exploring. The fact is, many physicists can be overbearingly macho about their field. Why is that? Is it also true in other fields, to the same extent? My limited experience seems to indicate that other parts of academia are just as competitive as physics is, but somehow don't have quite the arrogance that we often do. I know that academics in the social sciences or humanities will find this hard to believe, but I really do think that physicists are even worse, on average.

We could indulge in some cheap psychology here. Most of these physicists, after all, were not exactly quarterbacking the football team in high school. It would not be a stretch to imagine that many of them were -- what do we say -- kind of nerdy. We may just be dealing with a certain amount of overcompensation. Finding themselves in a relatively isolated community of like-minded folks, where the ability to do integrals is more prized than the ability to do push-ups, it might be natural to deal with some lingering resentment about being picked on as a child by picking on others as a somewhat-developed adult. In other words, the macho posturing of physicists (scoring points by ridiculing the ideas of others, angling to shout the loudest during seminars, looking disdainfully at any sign of weakness or lack of knowledge) may be the same phenomenon that creates schoolyard bullies, played out in a very different arena.

Admittedly, that is some really cheap psychology indeed, and the truth is undoubtedly more complex. For one thing, the field is competitive, whether we like it or not, for the most basic of reasons: too many people chasing too few goods. In the case the goods are positions of various forms -- acceptance at the best graduate schools, getting good postdocs and faculty jobs, winning awards. There are many more people who want to be scientists than there are jobs for them, so competition is inevitable. And that creates an unfortunate situation where everyone is constantly evaluating the worthiness of everyone else, estimating in their own minds where they deserve to be in the hierarchy of desirable goods. I don't see any way to possibly escape that syndrome -- even if we lived in a utopia of wealth where everyone received a substantial stipend to pursue their individual passions, there would still be competition to get located in the best places, which are limited by definition.

But there's a difference between competing for jobs (sad but inevitable) and acting as if doing physics were itself a competition (sad and untrue). Nature is a big complicated thing that is smarter than any of us, and we should all be in this together. Almost everyone will admit under examination that cooperation is a more effective way of doing science than pure competition. And although becoming a professional physicist is by necessity a difficult task, it doesn't have to be torture, or even unfriendly. Too often in my field we mistake aggressiveness for intelligence, or at least refuse to make the effort to nurture talented people who don't push themselves forward as shamelessly as some of their colleagues. Perhaps it's gradually changing for the better, but I have no way of knowing.

I suspect that a large number of people (of any gender) leave the field simply because they look around and think to themselves, "Wow, a substantial number of my colleagues are hyper-competitive jerks, this really isn't worth it." And that's too bad. Fortunately, along with the jerks are a large number of very sweet and supportive individuals who I am happy to call my friends. So if anyone out there is a friendly non-competitive person with a passion and talent for physics -- stick with it, we need more like you.

Thursday, October 28, 2004
Winning the war

John Holbo points to a post by Jim Henley on why libertarians should vote for Kerry. Part of the argument is kind of obvious -- general fears of big-government Democrats aside, why would any libertarian think that George W. Bush would be better? Apart from the general incompetence of the administration at just about everything, they haven't demonstrated any particular tendency toward small government, aside from cutting taxes. Spending is up, foreign policy is willfully interventionist, the deficit is out of control, civil liberties are under assault as never in the past fifty years, and no special effort has been made to promote free trade. But the particular emphasis of Henley's piece is the unrealistic attitude of the administration to the war on terror. Which, although I agree with the critique, raises an interesting rhetorical point, and a valid criticism against both Kerry and Bush.

"Terror" is a tactic, not an enemy. You can't "win" the "war" on it, the notion is absurd. The best you can hope to do is to minimize the danger, so that concerns about terror are reasonably contained, just as we hope to do with countless other dramatic dangers. Everybody in their right minds knows this, certainly both candidates do. But you aren't allowed to admit it out loud. It is taken as a given that we must pretend that the goal is to crush terrorism out of existence, and that each candidate has a plan for doing so within four years. The problem is, campaigning is hard and people get tired, so both candidates will occasionally slip. They will admit in moments of weakness that the fight against terror is likely to go on forever, and that really the goal is to minimize the danger. Within minutes the other campaign will be all over them, accusing the momentarily honest politician of insufficient manliness to lead our nation through these perilous times.

Only a few more days before the recounts and court challenges begin in earnest.

Wednesday, October 27, 2004
The Arrow of Time

So I've been busy, but with good reason. Long ago I mentioned some research I have been doing with Jennie Chen, a grad student here, on the arrow of time. And finally the paper is done! We have just submitted the manuscript to the online e-print server at http://arxiv.org/archive/hep-th, where it should appear Thursday evening. (Update: here it is!) Some day we'll even submit it to a journal, although that seems so twentieth-century to me.

As a reward to all our faithful readers at Preposterous Universe, here is the paper itself, revealed a full twenty-four hours before ordinary physicists get to see it! Getting in on the cosmological ground floor, as it were. The paper is available as a postscript file or as a pdf file; unfortunately the pdf version will look crappy on your screen, but it should print okay.

We have a grandiose-sounding goal: to explain the century-old puzzle of why the entropy of the universe was low in the past. The entropy, of course, is a measure of how "disorderly" a system is; more properly, how "generic" or "random" it is. Low-entropy states are suspiciously orderly; the classic example is a box of gas in which all of the gas just happens to be located in one corner. This is a perfectly acceptable configuration, but a statistically very unlikely one; if you let it go, the gas will quickly evolve to fill the room. This is the celebrated Second Law of Thermodynamics -- in closed systems, entropy tends to increase (or stay constant). Long ago Boltzmann developed a mathematical understanding of this phenomenon, by showing how entropy measured the number of equivalent ways we could re-arrange the elements of the system to give a state that was macroscopically indistinguishable. For the box of gas, there aren't that many ways we could re-arrange the molecules to keep them in one corner, but there are many ways we could re-arrange them smoothly throughout the box. It is therefore very natural to evolve from a low-entropy state to a high-entropy state, simply because there are so many more high-entropy states to evolve to.

The fact that entropy increases defines the arrow of time. It is a statistical phenomenon, valid for large systems, and the Second Law looks very different from the "microscopic" laws of physics, which are generally don't care which direction time is running in. Of course, the only reason we see that entropy increases is because it used to be small in the past. Once the gas fills the box, it essentially stays there forever (apart from rare fluctuations).

So, as cosmologists, we have an issue to address -- why was the entropy of our early universe so small? If high-entropy states are "natural," why don't we live in one? You might think to appeal to the dreaded anthropic principle, and argue that life couldn't exist in a state with really high entropy. But that turns out not to be good enough; the entropy of our universe is much much lower than it needs to be to support the existence of life. So we are faced with the "arrow of time problem."

Although there isn't a consensus view of the solution to this problem, most cosmologists would guess that it has something to do with inflation. The idea of inflation states that the very early universe went through a period of incredible acceleration, which smoothed out the bumps and wiggles and gave us the big smooth universe we observe today. If it works, inflation tends to wipe out any pre-existing features and leave us with a universe similar to what we observe today.

But there's a problem -- even though cosmologists think that it's quite natural for inflation to start and leave us with the universe we see, very few would think it was quite natural for a collapsing universe to smooth itself out and anti-inflate; that is, to undergo a process that is the time-reversed version of inflation. So secretly, the very idea of inflation has some time-asymmetry built into it; it makes sense forward but not backward. Therefore it doesn't really count as a solution to the arrow of time problem. We need to explain how the conditions for inflation to start in the first place could naturally arise.

Jennie and I do the following thought experiment -- if it weren't for inflation, what would be a "natural" state for the universe to be in? Different people have addressed this question, with different answers; Roger Penrose, for example, has suggested that it would be a lumpy universe full of black holes. Our answer is almost exactly the opposite -- the only natural state is empty space. This is basically because gravity makes everything unstable, and the entropy of any given configuration can always be increased by just expanding the universe by a huge factor. Sure, black holes will form, but they will ultimately evaporate away. If you let the universe evolve forever, it will ultimately get emptier and emptier (generically).

But we now know that even empty space has energy -- vacuum energy. (Or at least some sort of dark energy.) So when we evolve to "empty space," there is still some energy pushing the universe around; the resulting spacetime is called "de Sitter space." Along with this energy comes a small nonzero temperature, which keeps all the fields in the universe gently fluctuating. Gentle or not, however, if we wait long enough we will find a really big fluctuation -- one that is large enough to make inflation spontaneously begin. In other words, we are suggesting (although it's not original with us) that de Sitter space is unstable; it doesn't last forever, but eventually starts inflating here and there. These little inflationary patches will ultimately convert into ordinary matter and radiation, leaving behind universes just like our own.

And here is the fun part: this story can be told either forward or backward in time. In other words, you give me some state of the universe, chosen however you like. (Maybe you calculated the wavefunction of the universe, who knows.) I evolve it using the laws of physics. If Jennie and I are correct, it first empties out into a cold de Sitter space, dominated by a tiny shred of dark energy. But eventually we get lucky, and a small patch of inflating universe is born within this de Sitter background. This will happen at different places and times, give rise to a fractal distribution of spacetime geometry in the far future. And I can do the same thing going backwards in time from the initial state you gave me; the generic evolution is the same. It will empty out, and eventually begin to spontaneously inflate. So in the super-far past of our universe, before our "Big Bang" (which is nothing special in this picture), we will find other Big Bangs for which the arrow of time is running in the opposite direction. On the very largest scales, the entire universe is symmetric with respect to time.

Is this scenario correct? Interesting? Important? We're not sure yet. This is certainly not one of those brilliant flashes of insight, like the original discovery of inflation was. Rather, it's a concatenation of several intriguing ideas, most of which had already been suggested by someone or another. And there are a million questions remaining to be answered, especially about the onset of inflation in an empty background spacetime. But I like how the whole picture hangs together, and wouldn't be surprised if something like it eventually came to be accepted as a reasonable picture of the universe on the very largest scales.

Monday, October 25, 2004
Predicting the election

Honestly, I think it's a dead heat -- a statistical tie, too close to call, too uncertain to prognosticate. And wishful thinking is a powerful drug. But I'm not too proud to take heart in this graph, from Andrea Moro at the University of Minnesota.

Cosmology primer

Here's a homework assignment for you folks out there in internet-land. As my own assignment as a member of the Kavli Institute for Cosmological Physics here at Chicago, I've written a Cosmology Primer meant to explain the basic features of the universe to people on the street. It's very much in rough draft form at present, but has nevertheless gone live. I'd be very interested in what people think -- not about stylistic questions, since the look and feel will undoubtedly evolve, but whether the level is appropriate, and if the important questions are addressed, and if so if the answers make sense. Let me know.

Saturday, October 23, 2004
I just can't help it

Nobody with any pretensions to originality would quote Fafblog. It's just too cheap and easy. But downright irresistible.
Some other candidates say they are steady but are they really? Or are they just suspiciously french an ketchupy? "Sacre bleu, vive le France," say some other candidates. "Ceci n'est pas une pipe."

Friday, October 22, 2004
What He Thought

By Heather McHugh. I've had this one linked to my home page for a while, but I'm not above recycling.
We were supposed to do a job in Italy
and, full of our feeling for
ourselves (our sense of being
Poets from America) we went
from Rome to Fano, met
the mayor, mulled
a couple matters over (what's
a cheap date, they asked us; what's
flat drink). Among Italian literati

we could recognize our counterparts:
the academic, the apologist,
the arrogant, the amorous,
the brazen and the glib --- and there was one

administrator (the conservative), in suit
of regulation gray, who like a good tour guide
with measured pace and uninflected tone narrated
sights and histories the hired van hauled us past.
Of all, he was most politic and least poetic,
so it seemed. Our last few days in Rome
(when all but three of the New World Bards had flown)
I found a book of poems this
unprepossessing one had written: it was there
in the pensione room (a room he'd recommended)
where it must have been abandoned by
the German visitor (was there a bus of them?)
to whom he had inscribed and dated it a month before.
I couldn't read Italian, either, so I put the book
back into the wardrobe's dark. We last Americans

were due to leave tomorrow. For our parting evening then
our host chose something in a family restaurant, and there
we sat and chatted, sat and chewed,
till, sensible it was our last
big chance to be poetic, make
our mark, one of us asked
                     ``What's poetry?
Is it the fruits and vegetables and
marketplace of Campo dei Fiori, or
the statue there?'' Because I was

the glib one, I identified the answer
instantly, I didn't have to think --- ``The truth
is both, it's both,'' I blurted out. But that
was easy. That was easiest to say. What followed
taught me something about difficulty,
for our underestimated host spoke out,
all of a sudden, with a rising passion, and he said:

The statue represents Giordano Bruno,
brought to be burned in the public square
because of his offense against
authority, which is to say
the Church. His crime was his belief
the universe does not revolve around
the human being: God is no
fixed point or central government, but rather is
poured in waves through all things. All things
move. ``If God is not the soul itself, He is
the soul of the soul of the world.'' Such was
his heresy. The day they brought him
forth to die, they feared he might
incite the crowd (the man was famous
for his eloquence). And so his captors
placed upon his face
an iron mask, in which

he could not speak. That's
how they burned him. That is how
he died: without a word, in front
of everyone.
               And poetry ---
                              (we'd all
put down our forks by now, to listen to
the man in gray; he went on
softly) ---
               poetry is what
he thought, but did not say.

Thursday, October 21, 2004
All-In for Kerry

Normally I pride myself on being more of an idea person than a man of action. Action can be exhausting, after all. But sometimes circumstances force you to move against your natural inclinations. So, recently Chris Lackner and I combined two of our favorite activities -- poker and Bush-bashing -- into a small but rewarding fundraising event for the Kerry campaign. We held a No-Limit Texas Hold'Em tournament, with proceeds going to the campaigns in Midwest battleground states.

Physicists constituted a minority of the participants -- only four of the sixteen -- but dominated in the late stages, including three of the top four finishers. Must be that special combination of mathematical wizardry and deep psychological insight that makes people successful in both science and poker. In a tense showdown stretching into the late hours of the evening, string theorist Jeff Harvey defeated cosmologist Risa Wechsler to take first place. (And they say that string theorists are disconnected from the real world.)

How often do you get to see a picture of internationally renowned theoretical physicists staring each other down over a flop? The role of the button (indicating the dealer) was played by a small Albert Einstein action figure. Note also the abundance of alcoholic beverages -- well-known to increase one's poker skills.

So we raised a little money and had a lot of fun. These events are also good because they give people a feeling of being involved in the process; empirically, anyone who goes to a fundraiser is more likely to actually vote on Election Day. (Hopefully, even if they didn't do well in the tournament.)

Tangled Bank appears

The 14th edition of Tangled Bank (just as fascinating as the 13th, if not officially as lucky) is now up at Prashant Mullick's weblog. It involves a bacterium named Wigglesworthia, so you know it will be good.

Wednesday, October 20, 2004
The endorsement race

Since choosing between presidential candidates can be hard, it's often wise to turn to newspaper endorsements to decide how to vote. George W Bush's landslide victory over Al Gore in 2000 can be largely attributed to his over 2-1 lead in newspaper endorsements (an amazing accomplishment for the liberal media, we must admit). This year looks less promising for the President, as John Kerry seems to be kicking his butt in the endorsement race. Even the President's hometown paper would rather see him return to Crawford.

But we have to take into account quality, not just quantity. Before anyone makes any hasty decisions, keep in mind the keen judgment of these world opinion leaders who have looked carefully at the record and come out for Bush:
  • Al-Quaeda is for Bush!
    The statement said Abu Hafs al-Masri needs what it called Bush's "idiocy and religious fanaticism" because they would "wake up" the Islamic world.
    Can't ask for a more clear-eyed policy analysis than that.

  • Vladimir Putin ("Vladimir" to his friends) is for Bush!
    The courageous leader who has brought peace and democracy to a Russian nation still in the delicate stages of post-Communism understands what it takes to be resolute in the face of annoying international pressures.

  • Iran's National Security Council is for Bush!
    The mullahs understand that, loose talk about axes of evil notwithstanding, those Democrats tend to frown upon so-called "human rights violations," which tends to get in the way of sensible realpolitik.
So I'm sure the President isn't losing any sleep. Who needs the Albuquerque Tribune, anyway?

Amputee football

I noticed this striking image in this month's University of Chicago Magazine -- a rainy training session for the Sierra Leone Amputee Football Team. Captain M'byo Conteh is in the center.

I have to confess that I didn't even know there was such a team, nor that there was a UK National Amputee Team for them to play against, as explained in this page at Polaris Images. (UofC alumnus Adam Nadel took the award-winning pictures.) The team formed a couple of years ago, in an attempt to look beyond the grinding poverty and constant war that plague the country. The UK tour was organized by charitable organization Action for Children in Conflict.

Amadu Kamara celebrates a goal. The team didn't fare well against their British counterparts, but they were pleasantly surprised by the warmth with which they were greeted on the tour.

Tuesday, October 19, 2004

Two different views of the same event. The event being a Bush rally in Oregon, featuring a celebration of moral values and the expulsion of three local teachers with tickets to the event who were wearing T-shirts carrying the motto "Protect Our Civil Liberties."

One article about the event seems to be derived almost exclusively from a Democratic Party press release.
Responding to the number of examples of American voters being turned away, or removed from George W. Bush’s visits to their cities and states, Democratic National Committee Chairman Terry McAuliffe hosted a national conference call with Oregon teachers who were kicked out of an Oct. 14 Medford Bush rally for wearing T-shirts saying, "Protect Our Civil Liberties."

McAuliffe released the following statement Sunday:

“"The President has stripped his events of anyone who might disagree with him, which is completely un-American. It is dangerous for a President to be the bubble boy of American politics. But it might explain why the President can’t admit the problems of people without jobs, without health care, without prescription drugs, or trying to put their kids through college. He doesn’t know about them because he refuses to even see them."
But those of us who think that people should be able to wear whatever T-shirts they like (although "protect our civil liberties" is pushing the irony envelope a little far, I must admit) have heard so many of these stories that it's too exhausting to gather our outrage once more. And the President's supporters are able to overlook little events like this. He is, after all, resolute in the face of threats, both real and imagined. And Kerry is a flip-flopper! If stifling a little dissent is the price we have to pay for security, so be it.

The interesting thing is the local paper's pro-Bush take on the same event, sporting the title "Crowd lauds Bush for conviction, 'his word'." The story about the teachers is relegated to a passing mention in the second half of the article. It's the pro-Bush story that is scarier to those of us who are on the anti-theocracy side of our great national debate.
Applegate Christian Fellowship pastor Rev. Peter John Courson gave an invocation, urging onlookers to pray for the president and to bless the troops.

"In Jesus'’ name, thank you for being here," he said.

During the Pledge of Allegiance, the crowd emphasized the words "under God."

Applegate resident Tustin Ellison, who said he'’s as conservative as "Attila the Hun," said he doesn'’t agree with everything the president has done, but supports the invasion of Iraq.


Medford resident Rochelle Lovlin said she supported the president because he conveys a sense of morality.

"He knows how to quote scripture better than Kerry," she said.
Who was it again who was famously able to quote scripture for his own purpose?

Monday, October 18, 2004
Escape from the negativity

Don't let the sorry state of our political discourse get you down. Head over to Luboš's blog for a fair and balanced review of an important piece of world literature (my GR book).

I don't know if Luboš can keep up the pace of posting, but he deserves an entry on the blogroll. (Who says I can't be bought?) Other worthy new additions: 3quarksdaily, Trish Wilson, and BlogBites.

Reality-Based Communitarians

Why blog about Godzilla when the country (and by extension the world) is being destroyed by a cabal of faith-based nutjobs? Because I feel myself in weird sympathy with the Bushies -- reality is just too depressing. For comments from folks with stronger constitutions, see Majikthise, Matthew Yglesias, Matt McIrvin, Michael Bérubé, Chris C Mooney, or best of all Cosma Shalizi.

Ahead of the curve

And here I thought it was just me who thought about the scientific issues raised by Godzilla. No, there are a bunch of people interested in this and all other sorts of Godzilla issues; they're getting together this week to exchange ideas.
The University of Kansas plans to pay homage to the giant lizard later this month, organizing a three-day scholarly conference for the 50th anniversary of his first film.

It's not just about celebrating campy creature features. Planners want to provoke discussion of globalization, Japanese pop culture and Japanese-American relations after World War II.


The movie - in which H-bomb testing disturbs Godzilla's undersea habitat and transforms him into a behemoth with fiery, radioactive breath - reflects anxiety and a feeling of helplessness in the face of a nuclear threat, Igarashi said.

The franchise was widely known for its campy special effects. Godzilla films featured men in dinosaur suits stomping around miniature urban landscapes and some monster battles that, Tsutsui acknowledged in his book, seem more like professional wrestling matches.

When an American version of the first film was released in 1956 - re-edited to include new scenes featuring Raymond Burr of "Perry Mason" fame - the New York Times dismissed it as "cheap cinematic horror-stuff."

"It is true there were some bad, bad films produced, particularly in the late '60s and early '70s," said Igarashi, who plans to lecture at the conference on the 1964 movie "Godzilla vs. the Thing," in which Godzilla battles the giant moth, Mothra, and its offspring.
I don't know why I wasn't invited to the conference. Maybe the organizers thought I was already traveling too much.

Friday, October 15, 2004
The anthropic principle

Greetings from Baltimore, where I just gave a talk on the accelerating universe at Johns Hopkins. (After giving a similar talk at Penn the day before, and Urbana last week, and Brandeis and Arizona the week before that. I have to start increasing my speaker fees [from zero] or this will get ridiculous.)

Our universe is accelerating and we don't know why. So my talk goes through a little flowchart of all the possibilities, similar to the approach in this paper. The leading candidate, of course, is a small vacuum energy, or cosmological constant -- a tiny, persistent energy density inherent in space itself, rather than being associated with some particle or field. But this possibility raises two huge questions: why is the vacuum energy much smaller than it naturally should be (by a factor of 10-120), and why is the vacuum energy density comparable to that in matter today, even though they evolve rapidly with respect to each other as the universe expands?

What everyone would like to have is a formula that predicts the correct value of the vacuum energy in terms of other measured quantities. But we don't seem to have any clue how to find such a formula, or even if it exists. So various people (I don't know the history well, so won't attempt to attach names to ideas) have suggested that the vacuum energy is not a constant of nature, but rather an environmental variable that can be different from place to place in the universe. It seems quite constant over our observable universe, so this scenario needs to posit the existence of regions of space far outside our observable universe, which we can't see and which have very different conditions. The part of the universe that we observe is certainly finite, but it's quite big -- tens of billions of light-years across. Still, there's nothing to stop us from imagining other regions, just as big, which are outside what we can observe -- it would be inappropriately anthropocentric to imagine that the entire universe resembles our little piece of it.

So the idea is that the vacuum energy is a consequence of local conditions, rather than a fundamental number -- much like, for example, the temperature of the Earth's atmosphere. If we imagine some primitive physicists living in a region of Earth that was perpetually cloudy and with a very mild climate, they might expend a great deal of effort trying to predict the temperature from a theory of everything. But we know better; outside the atmosphere the temperature is very different. Further, we are not really surprised to find ourselves here on Earth, rather than on the surface of Saturn or the Sun, even though the Earth is quite tiny compared to them; the conditions are just more hospitable here.

Likewise with vacuum energy. If the vacuum energy were very large and positive, life could not exist, since the huge acceleration that would result would make it impossible for individual atoms to form, much less stars and galaxies. If the vacuum energy were large and negative, it would likewise squeeze things together, collapsing the entire universe in a tiny fraction of a second. From this point of view, it's not a surprise that we measure such a mild vacuum energy -- if the magnitude of the vacuum energy were anywhere near its "natural" value, we would not be here to measure it.

Of course, it's never a surprise to find that a quantity takes on a value that allows us to exist -- it's kind of necessary, when you think about it. The question is, did we just get lucky enough that it worked out that way, or does this true statement actually count as an explanation for something? If our observable universe is just a small patch of a larger ensemble in which the vacuum energy takes on all sorts of values, there is no point in looking for a unique formula that determines its observed value; we are constrained to measuring only those parts of the ensemble that are hospitable to the existence of intelligent life. This approach to understanding the vacuum energy or other constants of nature is sometimes called the anthropic principle (and sometimes called other things, so please let's not argue about the terminology).

I don't think anything I have just said should be controversial in any way; it's essentially a long string of tautologies. Nevertheless, people get rather emotional about this issue. Some folks are quite fervently in favor of the anthropic approach, some are equally strongly against it. I find myself disagreeing with just about everybody.

For the people who like the anthropic approach, it's necessary to believe that there really are all those regions of universe out there with different values of the vacuum energy (and presumably, of all the other parameters of physics). Remarkably, this is not an implausible idea. Our best candidate for a reconciliation of gravity with quantum mechanics is string theory, which predicts that there are really eleven dimensions of spacetime. We look around and only see four dimensions, so the extra ones are somehow hidden -- probably by being "compactified" into a tiny ball that is so small we can't see it. Each different way of compactifying would give rise to different physics in four dimensions, including a different value of the vacuum energy. How many different ways might there be? This is currently under investigation, but the numbers being bandied about look like 10500 or worse. (For purposes of comparison, the number of particles in the observable universe is only 1088.) So, many different compactifications, and likewise many possible values of the vacuum energy -- that's the celebrated "string theory landscape." But that doesn't do us any good unless those possibilities are actually realized somewhere out there. No problem; inflation allows us to take a tiny region of space and boost it up to a universe-like size. Therefore it's by no means impossible that the combination of inflation and string theory has indeed given us a huge collection of many different "universes" with different values of the vacuum energy.

Of course, there's a long road from "by no means impossible" to "likely true." The fact is we understand precious little about the string theory landscape, and not that much about the process of inflation. Even if we did, we're pretty clueless about how to turn such an understanding into a computation of what the vacuum energy should be. The problem is that we'd like to know what a "typical observer" in this baroque ensemble of universes is likely to measure. That's nearly hopeless, as we don't know what "observers" would be like if the laws of physics were dramatically different. Since what we actually want to do is hopeless, some people try to do a much simpler thing, which is just to count the number of vacuum states with a given vacuum energy. That's nice, but unless we understand all of the physical process in these states, we don't know what "life" would be like there. Not to mention that the total number of observers in the entire spacetime is likely to be infinite.

So, even if the anthropic principle is right, in the sense that our observed vacuum energy is simply an environmental variable whose observed value can be attributed to anthropic selection, we're extremely far away from being able to use such a scheme to predict anything. People try, but I don't think the results should be taken seriously at this point.

On the other end of the spectrum are people who think the whole idea is completely non-scientific, or even anti-scientific. As far as I can tell, their objections generally come in two forms -- either that it's "giving up" to attribute the observed value of a parameter to a selection effect rather than as derivable from the laws of nature, or that all these extra universes are unobservable in principle, therefore shouldn't count as part of a truly scientific description of the world.

I honestly don't see why either objection makes sense. The fact is, those extra parts of the universe might really be there, whether we can observe them or not. And if they are, it's completely possible that the vacuum energy really does change from place to place, rather than obeying some fundamental formula. To me, science doesn't proceed by first deciding how the world works, and then forcing it to conform; we keep an open mind, and try our best to understand how our actual universe behaves. If our best theories predict that the universe has very different conditions outside our observable patch, and that there is no unique prediction for the vacuum energy, than we have to learn to deal with it, even if those conditions will never be directly observed. The universe doesn't really care how we would like it to behave.

Of course, that is no reason to give up the search for a more traditional calculation of the value of the vacuum energy. As I just said, we are extremely far away from having any confidence that there are multiple domains, and even farther away from using that knowledge to reliably predict anything. We don't usually accuse our fellow scientists of "giving up" on one hypothesis whenever they propose an alternative; we usually have lots of different hypotheses floating around, and try our best to see which ones work and which ones don't. There is plenty of real science remaining to be done before we have any reason to accept the anthropic idea to the exclusion of others -- we need to verify that the dark energy is truly constant rather than dynamical, we need to search for supersymmetry and extra dimensions at particle accelerators, we need to develop our theoretical understanding of string theory and inflation to the point where we can begin to make sensible predictions. The great adventure is far from over -- it's very much in full swing.

Update: Peter Woit and Luboš Motl both write substantial blog posts in response to this one, so you can read some other perspectives on the issue. Luboš is a vocal proponent of string theory and Peter is a vocal critic, so they are both concerned with the specific implementation of the anthropic principle in the context of the string theory landscape. Most of what they each say about the anthropic principle itself is perfectly sensible; neither of them are big fans, but admit that it might ultimately be relevant to reality. Hopefully at some point I'll get around to talking about string theory in its own right.

I should also have mentioned the post by Ted Woollett that was part of Tangled Bank #13. Ted points to a dialogue at Edge between pro-anthropic string theorist Lenny Susskind and anti-anthropic loop quantizer Lee Smolin.

Wednesday, October 13, 2004

Wikipedia is a free web-based encyclopedia, constructed entirely out of contributions from folks out there on the internets. A nice idea, but obviously you need some mechanisms for quality control, not to mention resolving disputes over how to present certain material. Consequently, there is a long list of entries that are currently in "NPOV Dispute," for "Neutral Point of View." Leaving aside the issue of whether such a thing is philosophically possible, it is extremely illuminating to have a look at the topics currently under dispute -- it's a reflection of what issues are currently regarded as controversial in the world.
This is a partial list, but you get the idea. Mostly the standard stuff -- religion, sex, Wal-Mart, the Middle East, wars just about anywhere. But there are a few surprises -- Henry James? Catherine Zeta-Jones? Loop quantum gravity? Okay, that last one makes sense. (Especially for readers of Luboš Motl's new blog.)

Tuesday, October 12, 2004
Globular cluster

Sorry for the big picture file, but it's worth it.

This is today's Astronomy Picture of the Day, an image of the globular cluster M3 taken by Joel Hartman and Krzysztof Stanek at the Harvard-Smithsonian Center for Astrophysics. Take the time to let it fully load; it's not just a still picture, but a short movie that shows the "twinkling" of variable stars in the cluster. (Details here.)

Globular clusters are bound systems of very old stars, orbiting around (and often passing through) the main disk of our galaxy. The variable stars in the above image are RR Lyrae variables, single stars that pulsate with periods of about half a day. This is a highly sped-up view, compressing images taken over the course of a single night into a few seconds. Fun to look at, but also a sign of the times: astronomers are increasingly using modern technology to extend wide-field imaging from static images into the time domain.

If you like the twinkling stars, check out movies of motions in the center of our galaxy, showing stars moving rapidly around a heavy, invisible mass -- in fact, a million-solar-mass black hole.

Monday, October 11, 2004
Worldline demographics

I've often thought, looking around my neighborhood on Chicago's North Side, that there must be some obscure city ordinance that force people to move out once they either hit the age of 40 or have kids. I found a way to quantify just how tightly bunched the local demographics of my neighborhood really are: City-Data.com gives you the raw data about the composition of anywhere in the U.S., and some fascinating graphical representations of who lives there.

So I studied my personal history as told through the demographics of the zip codes in which I lived (somewhat streamlined for dramatic purposes). You can't really choose where you are born, and I grew up in the depths of the Philadelphia suburbs, in 19067. Here is a graph of the number of people in the zip code as a function of their age; black for males, magenta for females (hey, I don't pick the color schemes).

You can tell instantly that it's a middle-class child-raising family community; a bunch of kids, most of whom flee at the age of 18 to go to college, then gradually trickle back to buy homes and raise their own kids -- if not the exact same people who grew up there, then their demographic equivalents. As they become slightly more prosperous or the kids move out and they don't need a three-bedroom house with a yard, they decamp to more appropriate locales.

Next it was on to college at Villanova, in the scenic zip of 19085.

Clearly, nobody lives there but the college students. It must be that the zip code only includes the university proper, as the surrounding area was populated by the old-money upper class of Philadelphia's Main Line.

Then to grad school at Harvard and the celebrated destination of 02138, where they used to sell T-shirts proudly proclaiming it as "The Most Opinionated Zip Code in America."

Dominated by college students, but somewhat more inclusive; faculty, researchers, grad students, and sundry folks who just enjoyed the atmosphere of Harvard Square.

After graduating, I took the easy way out and stayed in Cambridge for my first postdoc at MIT. But with my spiffy new postdoctoral salary I could move across the river to the South End in Boston, landing in 02116.

A noticeably urban environment (thank God), one with a healthy dose of post-high-school students lurking around (not exactly sure why), certainly youthful but not like being in college any more.

But alas, the academic wheel of fortune turns in mysterious ways, and my next stop was at the Institute for Theoretical Physics in Santa Barbara. As I hoped to be spirited away by an attractive faculty offer at any moment, I chose not to bother to find a place in SB proper but rather live in Isla Vista, 93117.

IV is an entire municipality surrounded on three sides by the UCSB campus and on the fourth by the Pacific Ocean; nobody in their right mind lives there but students and surfers. Not an environment devoted to the life of the mind, but the weather was awfully nice.

Finally I was spirited away to the Windy City, where I live in the Lakeview section of Chicago, 60613.

Truly in my yuppie-metrosexual element, short on students but heavy on post-college strivers making the gradual transition from apartments to condos. And yes, there does seem to be some sort of upper age limit. I wonder where they all go? And will they drag me physically away, or is it a more subtle mind-control sort of thing?

Sunday, October 10, 2004

Jacques Derrida, French philosopher and originator of deconstruction, passed away this Friday. Obituaries at the Guardian and the New York Times; blog posts by Michael Bérubé and Jack Balkin and Brian Leiter; comments at Crooked Timber; a nice encyclopedia article. A quick perusal is enough to give an impression of how controversial Derrida was!

Derrida is one of those intellectual figures who is arguably more important as a symbol than for his actual work. In Derrida's case, in the minds of many people he has come to represent a perspective that is deeply anti-intellectual, or at least anti-Enlightenment and anti-rationality. This is a completely misguided impression, but a persistent one nonetheless. Derrida enjoyed the project of undermining conventional Western metaphysics, emphasizing gaps and contradictions in the writings of major players of the philosophical tradition. More significantly (for the critics), he also enjoyed playful and elliptical language, especially in his own writings, although he could be quite straightforward in speech.

I am by no means an expert on Derrida's work, although I have read a couple of things and can vouch that he was not nearly as impenetrable as his reputation suggests. I couldn't tell you whether deconstruction will end up being counted as a productive moment in the history of philosophy, but the simple caricatures of his enemies tend to make me sympathetic to Derrida's side of the controversies. I take Derrida to be interested in highlighting the weak points and inconsistencies in grand meta-narrative systems. The question would be, do we do no more than delight in the failings of the system-builders, or do we try to nurture what remains valid, reconstructing after deconstructing? Derrida's critics would argue that he is nothing but a nihilist, while he prefers to place himself squarely in the Enlightenment tradition of questioning authority and dispelling mysteries. Consistent with this stance, his later writings and activities had become increasingly political; a recent book describes interviews with Derrida and Jurgen Habermas over the significance of the September 11th attacks.

You might think that scientists, who take a noisy pride in the self-critical techniques of their own disciplines, would be sympathetic to the search for weak points in philosophical theories, even if those theories were implicitly subscribed to by the scientists themselves. Okay, maybe you wouldn't; scientists have never been excessively fond of criticism from non-scientists. Derrida rarely addressed science directly (although his brother Bernard is a well-known condensed matter physicist), but his status as a symbol of anti-reason drew substantial attention from defenders of objective truth. A famous example was of course the Sokal affair, in which physicist Alan Sokal parodied postmodern jargon in an article he managed to get published in the journal Social Text. Just like it's more fun to attack the wingnuts at Little Green Footballs than it is to attack more respectable conservative thinkers, the critics would gleefully (and correctly) highlight the most ridiculous statements of self-described postmodernists, without bothering to engage carefully with the better thinkers on their own terms.

Time will tell what Derrida's legacy ultimately becomes. Deconstruction was a technique rather than a system, but not everyone needs to build a system. My guess is that, two hundred years from now, some of Derrida's writings will be ignored as misguided or silly, while some basic insights of deconstruction will be acknowledged as useful tools for probing the limitations of ideas. And everyone will wonder what all the fuss was about.

Update: Have to include a small joke that Ed Cohn noticed in the BBC obituary:
He was so influential that last year a film was made about his life - a biographical documentary.

At one point, wandering through Derrida's library, one of the filmmakers asks him: "Have you read all the books in here?"

"No," he replies impishly, "only four of them. But I read those very, very carefully".

Friday, October 08, 2004
May 24, 1980

By Joseph Brodsky. Translated from Russian by the author.
I have braved, for want of wild beasts, steel cages,
carved my term and nickname on bunks and rafters,
lived by the sea, flashed aces in an oasis,
dined with the-devil-knows-whom, in tails, on truffles.
From the height of a glacier I beheld half a world, the earthly
width. Twice have drowned, thrice let knives rake my nitty-gritty.
Quit the country the bore and nursed me.
Those who forgot me would make a city.
I have waded the steppes that saw yelling Huns in saddles,
worn the clothes nowadays back in fashion in every quarter,
planted rye, tarred the roofs of pigsties and stables,
guzzled everything save dry water.
I've admitted the sentries' third eye into my wet and foul
dreams. Munched the bread of exile; it's stale and warty.
Granted my lungs all sounds except the howl;
switched to a whisper. Now I am forty.
What should I say about my life? That it's long and abhors transparence.
Broken eggs make me grieve; the omelette, though, makes me vomit.
Yet until brown clay has been rammed down my larynx,
only gratitude will be gushing from it.

Thursday, October 07, 2004
I would totally pay for that

I can't even resist the ordinary greasy Philly cheesesteaks, going so far as to search out good ones here in Chicago. (Clark Street Dog does an acceptable job.) Now they've gone upscale.

To quote the article:
Served with a small bottle of champagne, Barclay Prime's cheesesteak is made of sliced Kobe beef, melted Taleggio cheese, shaved truffles, sauteed foie gras, caramelized onions and heirloom shaved tomatoes on a homemade brioche roll brushed with truffle butter and squirted with homemade mustard.
Perfectly calibrated, in other words, to appeal all at once to both the shameless hedonist side and the scruffy Philadelphian within me. (Although they should skip the mustard and go with gourmet ketchup instead.) Hmm, I'm visiting Penn next week to give a colloquium; think they'll spring for dinner?

Wednesday, October 06, 2004
Hawking bests Beckham

... as a role model for British youth. But Hawking didn't take first prize; he lost out to rugby hero Johnny Wilkinson. What all this means, I have no idea.

Tangled Bank #13

Welcome to the Lucky Thirteenth edition of Tangled Bank! A carnival of bloggy excellence in which we collect some of the best science-oriented posts of the previous two weeks. (We have taken a loose interpretation of the "previous two weeks" requirement, to feature some worthy authors that don't have a recent science post. As you will see, we have even taken a loose interpretation of the "science" requirement!)

The next Tangled Bank will be hosted by Prashant Mullick, and is scheduled to appear on October 20th. You can email your contribution directly to Prashant at mullickprashant@gmail.com, or to host@tangledbank.net. We are always looking for new hosts (it's really not so hard); if you're interested, email PZ Myers at pzmyers@pharyngula.org.

This edition's nineteen (count 'em!) entries will be listed in apparently-random order, according to a convoluted algorithm known only to me.

From Richard Hoppe at The Panda's Thumb we have an Introduction to Multiple Designers Theory. When advocates of the Intelligent Design movement claim to be thinking purely scientifically rather than theologically, what if they were telling the truth? What conclusions would they be drawn to?
Mainstream Intelligent Design is proving itself to be scientifically vacuous. While Dembski has his Explanatory Filter and Complex Specified Information and Specified Complexity, and Behe has his Irreducible Complexity, no actual research program utilizing those concepts has emerged from the mainstream Intelligent Design movement. Therefore a revolutionary change in the conception of ID is necessary to rouse it from its empirical and theoretical slumber and to provide appropriate material for school boards and legislatures who want an alternative to modern evolutionary theory to be taught in secondary schools. Multiple Designers Theory is that revolutionary change.
From Selva at The Scientific Indian we have The Story of Shit. No comment on this, I'm getting in enough trouble already.
I cooked up this story at a lighter moment (pun intended). Shit is second law of thermodynamics in action. Looking at feces from a thermodynamical perspective may somewhat unburden our mind from the inherent unpleasantness of the subject matter. Besides, I have been mulling over the second law of thermodynamics, evolution and human form for a while now. All these different ideas are connected in strange ways. As part of the story of shit I am going to explain the connections I see.
From Chris Clarke Creek Running North we have Puma, an essay on predation including a personal account of a puma encounter.
As I rounded yet another bend in the road, the wind picked up. The breeze off the ocean had been a little gusty that afternoon, more so as I got deeper into the ravines on the east side of the ridge. That's the only way I can explain what happened next; that the wind was too loud for the puma to hear me walking down the road. It must not have known I was there. Why else would it have leapt the guardrail to cross the road at precisely the time I arrived at said guardrail?
From Samuel Conway we have PSA: Save a life while you sleep! It's a personal story of bone marrow donation.
What is the first thing that pops into your mind when I say the words "bone marrow donation"?

I'll tell you what it is: PAIN. That is what everyone always talks about. We read stories about donors, usually in places like Readers' Digest, and we shudder and squirm at the thought of how agonizing it must be. My word, we say, aren't these people heroic? The truth, however, is that the majority of donors experience only moderate discomfort, and some report feeling little or no pain at all. True, for some the procedure can be painful, but even those donors say that they would be ready to do it again in a heartbeat.
From George Wilkinson at Keats' telescope we have Grab that glutamate, about the natural history of GLUD2.
This month's Nature Genetics (subscription required) has a cool short communication by Fabien Burki and Henrik Kaessmann about a gene that is most likely only expressed in the brain, and is only found in humans and apes. This gene, GLUD2, and its more widespread relative, GLUD1, encode proteins which help break down glutamate. Glutamate is an important neurotransmitter in the brain, and can be released in large amounts during intense neural activity. However too much released glutamate can be toxic, and these two genes are important for control of glutamate levels.
From ema at The Well-Timed Period we have Womanhood and Menses. "Having a menstrual period does not make women inferior, nor does it empower them to rule the world."
There is a tendency to infuse the menstrual period with all sorts of societal meanings of almost mythical proportions (e.g., the essence of womanhood, woman power, etc.). This is detrimental, especially when it comes to women making informed period-related health decisions. Why? Because, by definition, myths aren't to be explained; they're to be believed. This is a dangerous proposition when it comes to your health.
From Prashant Mullick we have Fibonacci Spiral Phyllotaxis. He must be reading the Da Vinci Code!
Phyllotaxis is the arrangement of leaves on a stem. There are several types of arrangements. One of them is a spiral pattern.

It turns out that among plants displaying spiral phyllotaxis about 92% of them have Fibonacci phyllotaxis - the number of visible spirals are two successive elements of the Fibonacci sequence.
From PZ Myers at Pharyngula we have PZ Myers' Own Original, Cosmic, and Eccentric Analogy for How the Genome Works -OR- High Geekology. Is the genome a recipe, or a village of idiots? Nope, it's a power spectrum.
I'm a long-time microscopy and image processing geek, and you know what that means: Fourier transforms (and if you don't know what it means, I'm telling you now: Fourier transforms). I'm going to be kind and spare you all mathematics of any kind and do a simplified, operational summary of what they're all about, but if bizarre transformations of images aren't your thing, you can bail out now.
(By the way, a Fourier transform is just a change of basis in the space of functions, from one where the basis functions are delta-functions to one where they are sines and cosines. Clear now?)

From Charlie Wagner we have A Scientific Case for Intelligent Input. Not our usual Tangled Bank fare -- it's an apologia for intelligent design, included here in the spirit of the free market of ideas. (Without any implied promise to include pseudoscience posts in future editions!)
As you probably know, empirical data can be either observational or experimental. Observations usually come first, and hypotheses are developed. When a sufficient number of observations are collected, a pattern emerges and a theory is formulated. Additional experiments are then performed in an attempt to falsify the theory. After numerous attempts to falsify the theory, it may be elevated to the status of Law. Of course, any theory or law is subject to new data which may or may not overturn it. I have proposed Nelson's Law and, so far as I can tell, it has not been falsified by any observational or experimental data and must be assumed to be highly likely to be true.
From Radagast at Rhosgobel we have a set of three connected posts -- They're not so little anymore, More Manduca Pictures: Spiracles and Tracheae, and Manduca Update: They're Wandering! I have to admit, those caterpillars are pretty cute.
You may or may not know that insects are supposed to have three pairs of legs (six legs total), while spiders have four pairs of legs (eight legs total). Knowing this, let's count the legs on the caterpillar pictured above. A quick count reveals that the caterpillar has sixteen legs (eight pairs), significantly more than the six it's supposed to have. Are caterpillars not insects? Have we been wrong all along in believing that insects have six legs?
From Jenn at Invasive Species Weblog we have Invasive Species: The Newest Threat to Property...Rights? Science meets the pervasive phenomenon of annoying neighbors.
Invasive species, indeed any weedy species, don't give a hoot about your property boundaries. Sometimes things that happen on your property affect others, and it's not fair to say tough luck just because you own that plot of land. I'm sorry, but if someone notices that a bunch of trees on your property are infested with Asian longhorn beetles, I don't think you have a right to not do anything about it. I also don't think you should have to pay to remove the trees, and I would like to see the government help you out by maybe replanting or giving you some money. But unless you're going to build a biodome over your land, this is about more than you and what you "own."
From Stephen Brophy we have Meaning Well is No Excuse. Following Richard Dawkins, he argues that it's not okay to make people feel better by giving them false hope.
So, the news that yet another Cancer remedy has been touted should really come as no surprise. Nevertheless, the sight of this article made my blood boil. The con-artist pushing this particular miracle cure seems to be claiming that "It works by creating an alkaline environment in which acidic cancer cells cannot survive" (So there you have it dear reader, curing cancer turns out to be one of the many uses of baking soda!). The individual making the above quoted claim is apparently a doctor. This is obscene, and the fool should be kept away from patients (It seems clear to me that his treatment represents a gross violation of his Hippopotamus Oath).
From Ted Woollet at Dark Energy2 we have The Anthropic Principle: Good Physics or Not?? With the surprising observational result that the universe is dominated by vacuum energy that has a much smaller value than it should, cosmologists have been tempted by the idea that our observable universe is just one of many.
According to these ideas, we exist in a "pocket universe" with a tiny (but non-zero) effective cosmological constant. Without the cosmological constant having a value in a small range around a tiny number, our variety of intelligent observers could not have evolved to a state like the present. The tiny non-zero value of the effective cosmological constant is hard to understand using traditional particle physics arguments.
From John Fleck at inkstain we have Extinction. Can major extinctions of 10,000 years ago be blamed on weather, or are they our fault?
One of the classic scientific debates, on a par with "nature vs. nurture," albeit far more obscure, is the question of what caused the great megafaunal extinction at the end of the Pleistocene.

Pretty much everywhere you look, you find evidence of big critters roaming the earth - mastodons, mammoths, big camels, and my favorite, beavers the size of black bears. And then they "blink out," to borrow a lovely phrase I heard a biologist use recently. In a very short period of time in geologic terms, they're gone.
From me at Preposterous Universe we have What is this quintessence of dust? A needlessly showy quote from Hamlet, by way of introduction to different possibilities for what dark energy might be.
I think it was Tolstoy who said, "Cosmological constants are all alike; every model of dynamical dark energy is dynamical in its own way." Tautological enough, but it points to an important feature of dynamical dark energy candidates -- because they have more features than simply their energy density, there are more ways they could be detected and thus more parameters you need to fine-tune to explain why we haven't noticed them yet.
From David Winter at Science and Sensibility we have the Plight of a Bumble Bee, Part One and Part Two. This is why other people can't understand scientists -- when confronted with a bumblebee infestation, they contemplate the essence of bees rather than just spraying them dead.
Over the last few weeks my flat has been beset by slow, confused looking bumble bees. Most days at least one gets itself stuck in the house, usually trying valiantly but ultimately futilely to fly through one of our closed windows. Of course I usually try and help these wayfarers out but I was too late for one, which I found dead in our living room. I have tried to get a photo of the unfortunate bumble bee for you but technology has conspired against me, so here is one of the same species.
From Mike at 10,000 Birds we have Flyways And Byways. Examining the remarkably well-defined migration corridors of North American birds.
You don't need to be a birder to know that most birds fly from temperate northern climes to more tropical southern locales for the winter. Changes in light, temperature, and food availability trigger the instinct to migrate, an urge so powerful that only a really well-stocked backyard bird feeder can override it. Migratory birds follow a variety of routes, most of which are are far more complicated than just due south. Every species has its own path.
From Pyracantha at Electron Blue we have One of those little victories which keep me going. Pyracantha is an artist who is teaching herself math and physics.
The fireworks are out and it's back to math. I'm working my way through lots of logarithm problems. As you may remember from last time, I spoke in a rather agricultural way about "raising" and "rooting" numbers. How would I describe a logarithm, then? It's a number seed which when planted, both raises and roots at the same time.
From Wolverine Tom we have San Andreas Fault. I was only in an earthquake once, and it was a tiny one -- as if the building was suddenly floating on water rather than anchored to dry land, and just as suddenly back again.
A few days ago, a 6.0 magnitude earthquake occurred in the San Andreas Fault out in California. For those people living in the area, this is a common occurance. But why is this area so prone to earthquakes? To understand this, the geologic of the area must be known.
Many thanks to everyone (most of whom I didn't get a chance to thank individually) for contributing. And if I've left anyone out, it was just an email snafu, not a cold-hearted editorial decision -- so please let me know.

Ideas on culture, science, politics.
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