Retouch

Retouching Via Marginal Revolution, a link to the Girl Power campaign of the Swedish Ministry of Health and Social Affairs. Click here and wait for it to load; it’s a Flash demonstration of how you turn a photo of an (already attractive) young woman into magazine-cover material.

The campaign is supposed to draw attention and criticism to the overly sexualized nature of advertising and the media more generally. It suffers a bit from the self-undermining impulse of many such campaigns, by itself relying on overly sexual imagery to get attention. But it’s nice to help people distinguish media fantasy from reality.

Update: the site was also linked at Feministe, who point to a couple of other examples — Greg’s Digital Archive and Glenn Feron.

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A good day for science

The verdict in the Dover intelligent-design trial is in! To nobody’s surprise, it’s a rout.

HARRISBURG, Pa. – “Intelligent design” is “a religious alternative masquerading as a scientific theory” and cannot be mentioned in biology classes in a Pennsylvania public school district, a federal judge said Tuesday, ruling in one of the biggest courtroom clashes on evolution since the 1925 Scopes trial.

Dover Area School Board members violated the Constitution when they ordered that its biology curriculum must include the notion that life on Earth was produced by an unidentified intelligent cause, U.S. District Judge John E. Jones III said.

“We find that the secular purposes claimed by the Board amount to a pretext for the Board’s real purpose, which was to promote religion in the public school classroom,” he wrote in his 139-page opinion. “The citizens of the Dover area were poorly served by the members of the Board who voted for the ID Policy,” Jones wrote, adding that several members repeatedly lied to cover their motives even while professing religious beliefs.

Judge Jones’s opinion is online (pdf); commentary from PZ and Ed Brayton. Overall, a huge, unambiguous win: not only were the creationists shot down, but their religious and anti-science agenda was made perfectly clear.

Not that the battles are over just yet. DarkSyde has an interview with Chris Mooney about his book The Republican War on Science. We have a long way to go, but it’s nice to win one decisively once in a while.

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Unsolicited advice, 1: How to get into graduate school

Your humble bloggers here at Cosmic Variance have spent quite a bit of accumulated time in academic and research settings — in fact, my guess is that none of us have spent an entire year away from such a setting since the age of about six or so. That’s a lot of accumulated wisdom right there, and it’s about time we started sharing it. Since it’s that time of year when applications are being sent off to graduate schools, I thought I would start off by letting everyone in on the secret to how to get accepted everywhere you apply. Of course I can only speak for physics/astronomy departments, but the basic lessons should be widely applicable. [Update: see also Choosing a Graduate School and How to Be a Good Graduate Student.]

So, here goes: have great grades, perfect GRE scores, significant research experience, and off-scale letters of recommendation. Any questions?

If, perhaps, it’s a bit too late to put that plan into action, here are some personal answers to questions that come up during the process. Co-bloggers (and anyone else) are free to chime in with their own take on these complicated issues. Keep in mind that every person is different, as is every grad school — in fact, specific schools might behave quite differently from year to year as different people serve on the admissions committee. Don’t sink your sense of self-worth into how you do on these applications; there’s a strong random component in the decisions, and there are a very large number of good schools where you can have a fun and successful graduate career.

  • What do graduate school admissions committees look at?
    Everything. Keep in mind that, unlike being admitted to college (undergrad), at the grad school level the admissions are done by individual departments, with committees comprised of faculty members with different kinds of expertise, and often students as well. They’ll look at your whole application, and in my experience they really take the responsibility seriously, poring over a huge number of applications to make some hard decisions. Still, it’s well-known that careful examination of a thick file of papers is no substitute for five minutes of talking to someone, which schools usually don’t have the luxury of doing, so decisions are always somewhat fickle.
  • Even my personal essay?
    Well, okay. I wouldn’t sweat the personal essay; in my experience it doesn’t have too much impact. Let’s put it this way: an incredibly good essay could help you, but a bad essay won’t do too much harm (unless it’s really bad). To a good approximation, all these essays sound alike after a while; it’s quite difficult to be original and inspiring in that format.
  • Are GRE scores important?
    Yes. At least, in the following sense: while bad GRE’s won’t kill your chances, good GRE’s make it much easier to admit you. (We’re speaking of the Physics GRE, of course; the general tests are completely irrelevant.) It stands to reason: given two applicants from similar schools with similar grades and interests, there’s no reason for a department to choose the student with lower GRE scores. At the same time, you can certainly overcome sub-par GRE’s by being outstanding in other areas; this is particularly true for students who want to do experiment. I know at Chicago that we let in students with quite a range of scores.
  • What about research experience?
    Research can be a big help, although it’s by no means absolutely necessary. These days it seems that more and more undergrads are doing research, to the point where it begins to look unusual when people haven’t done any. There is some danger that people think you must want to keep on doing the kind of research that you did as an undergrad, although I wouldn’t worry too much about that. Mostly it shows some initiative and passion for the field. It can be very difficult to do theoretical research as an undergrad, but that’s okay; even if you eventually want to be a string theorist, it’s still great experience to do some experimental work as an undergrad (in fact, perhaps it’s especially useful).
  • How do I get good letters of recommendation?
    It’s more important to have letters from people who know you well than from people who are well-known themselves. One of the best side benefits of doing research is that you can get your supervisor (who hopefully has interacted with you quite a bit) to write letters for you. It’s really hard to write a good letter for a student who you only know because they took one class from you a year or two ago. Over the course of your undergrad career, you should find some way to strike up a personal relationship with one or more faculty members, if only to sit in their office now and then and ask some physics questions. Then they can write a much more personal and effective letter. Of course, if you are just a bad person who annoys everyone, it would be just as well to stay hidden. (Kidding!)
  • Is it true that the standards are different for theorists and experimenters?
    Typically, yes, although it might be different from place to place. Because a lot of undergrads haven’t been exposed to a wide range of physics research, a large number of them want to be Richard Feynman or Stephen Hawking or Ed Witten. Which is great, since we need more people like that. But even more, we need really good experimenters. Generally the ratio of applicants to available slots is appreciably larger for theorists than for experimenters, and schools do take this into account. Also, of course, the standards are a little different: GRE’s count more for prospective theorists, and research experience counts more for prospective experimenters. And let’s be honest: many schools will accept more prospective theorists than they can possible find advisors for, in the hopes of steering them into experiment once they arrive.
  • So should I claim to be interested in experiment, even if I’m not?
    No. Think about it: given that schools already tend to accept more students who want to do theory than they can take care of, what are your chances of getting a good advisor if you sneak into a department under false pretenses and have to compete with others who came in with better preparation? It makes much more sense to go someplace where they really want you for who you are, and work hard to flourish once you get there.
  • Do I need to know exactly what I will specialize in?
    Not really, although in certain circumstances it can help. Professors like to know that someone is interested in their own area of research, and might push a little harder to accept someone whose interest overlaps with their work; on the other hand, most people understand that you don’t know everything after three and a half years of being an undergraduate, and it can take time to choose a specialization. In particular, at most American physics departments (unlike other countries and some other disciplines), it is generally not expected that you need to know ahead of time who your advisor will be when you arrive, or which “group” you will work in.
  • Should I contact faculty members individually if I’m interested in their research?
    That depends, mostly on whether the person you are contemplating contacting is desperate for more grad students, or is overwhelmed with too many requests as it is. In popular areas (ahem, like theoretical particle physics, string theory, and cosmology), there are generally more applicants than departments have advisors for. In that case, most people who receive random emails from undergraduates will just urge them to wait for the admissions process to take its course; remember that it’s a zero-sum game, and for everyone who gets in there’s someone else who doesn’t, and it would be a little unfair to penalize those applicants who didn’t contact faculty members personally. On the other hand, if you have reason to believe that someone you’re interested in working with is trying to get more students, or if you think your case is somehow unique and requires a bit of attention, feel free to email the appropriate faculty member with a polite inquiry. The worst that can happen is that you get a brush-off; I can’t imagine it would actually hurt your chances.
  • Is my life over if I don’t get into my top grad school?
    Yes. Well, only if you let it be. The truth is, how you do in grad school and beyond (including how you do on the postdoc and faculty job market) depends much more on you than it does on where you go to school. In the next episode of “unsolicited advice,” we’ll think about how to actually choose where to go, including how to get the most out of visiting different schools.

Actually this episode was not completely unsolicited; thanks to Philip Tanedo for suggesting we share some of our invaluable insight. See, sometimes we really do listen.

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The universe is the poor man's particle accelerator

David SchrammOne thing I wanted to add to Mark’s post about the New Views conference. The conference as a whole was dedicated to the memory of David Schramm, whose 60th birthday would have been this year; he died while piloting his own airplane in 1997. Schramm was an enormously influential figure in contemporary cosmology, one of the prime movers in bringing together particle physics and astrophysics in the study of the early universe. In particular, he was a pioneer in the use of Big-Bang Nucleosynthesis as a way to understand both particle physics and cosmology.

Between a few seconds and a few minutes after the Big Bang, the universe was a nuclear reactor, converting nucleons (neutrons and protons) into nuclei of helium, lithium, and deuterium. At very high temperatures the nucleons can’t bind together without being knocked apart; at low temperatures they would like to be bound into their lowest-energy state, which would be iron nuclei. But the universe is rapidly expanding, so we get a competition: as the temperature declines and it’s possible to form nuclei, the density is also falling, making reactions less frequent. We end up with several light nuclei, but don’t have enough time to make anything heavier.

The relic abundances of these nuclei depend on everything about physics when the universe was one minute old: particle physics parameters that govern the reaction rates, the number of species that governs the energy density, and the laws of general relativity that govern the expansion of the universe. (For example, if the universe were expanding a little bit faster, the reactions would happen a little bit earlier, implying that fewer neutrons would have decayed, allowing for the production of more helium.) Miraculously, the observed abundances fit precisely onto the predictions that come from extrapolating what we know about physics here and now all the way back to a minute after the Big Bang. The helium abundance provided the first empirical evidence that there were only three families of matter particles, long before Earth-based particle accelerators verified the result. And BBN assures us that Einstein’s general relativity works without modification in the very early universe; in particular, we know that Newton’s constant of gravitation had the same value then as it does now to within about twenty percent.

Personally, I find the success of BBN to be one of the most impressive feats in all of modern science. Here we are, 7,000,000,000,000,000 minutes after the Big Bang, making quantitative statements about what was going on 1 minute after the Big Bang — and it’s a perfect fit. I’ll never cease to be amazed that we know exactly what the universe was doing when it was one minute old.

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Bloggy B. Blog McBlog

It’s the time of the year when the liberal blogosphere takes a breather from waging the War on Christmas to pause and hand itself some awards. The Koufax awards, in particular — named after one of the greatest left-handed pitchers of all time. The reason for separate awards for the liberal blogosphere is simply that, a couple of years ago when blogs became popular enough to start giving awards to each other, the sphere as a whole had a decided rightward tilt, and conservative blogs would always win all the awards. Liberals have by now caught up, and the recent Weblog Awards witnessed lefty blogs dominating in all the interesting categories. But it’s still fun to pal around with our friends here in the attractive and friendly half of the blogosphere, so the Koufax awards are continuing to go strong.

The awards are run by the selfless folks at Wampum; anyone can submit nominations, just by visiting Wampum and looking for the most recent “Koufax nominations post.” Here are my own nominations. I am too shy and self-effacing to nominate CV for anything, although in principle we would fit into various categories: Best Blog, Best Expert, Best Group Blog, Best New Blog. (Nothing to stop anyone else from nominating us, I suppose.)

None of my entries for “Deserving wider recognition” have a snowball’s chance, with the possible exception of 3 Quarks; the others are just my idiosyncratic favorites. I largely agree with Ezra’s take on the whole affair; the winner is determined by who funnels in the most votes, not necessarily which blogs are actually the best. But it’s very fruitful to peruse the nominations, as you might uncover some hidden gems. The blogosphere is (happily) by now so large that there are just too many good blogs out there, and even those of us who read quite a few of them basically find some favorites and stick to them. I’m chagrined to see that I didn’t have any worthy nominations for the “Best New Blog” category. Feel free to make nominations in the comments.

Speaking of good blogging, you probably know that Daily Kos is the most popular blog on all the internets, with somewhere between 500,000 and a million hits per day. (We’re not at that level yet, but we’re young.) In addition to Kos himself, there are numerous diarists on the site, and every year a handful are chosen to be front-page posters. This year promises to see a significant uptick in the science content (!) of Daily Kos, as DarkSyde of Unscrewing the Inscrutable fame has been chosen as one of the front-pagers. He’s already instituted a “Science Friday” feature, and the first installment is a well-written tour through the powers of ten.

Finally, if you find all these blogs kind of overwhelming (and you don’t already use an RSS reader such as Bloglines), you can get a collection of physics blog content all in one place at Mixed States. I have mixed feelings about these things (although I use Bloglines myself) — on the one hand, it’s a vastly more efficient way to read multiple content sources; on the other, you lose the individual presentations of the sites themselves. It’s the wave of the future, though.

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Next step: political action committees

Congratulations to the people of Iraq, who held an historic vote yesterday. Regardless of the wisdom of our choice to invade the country, we can all be happy to see the first steps toward what hopefully becomes a functioning democracy, complete with campaign-finance laws and gerrymandering. I can’t imagine what it must feel like to go to a polling place and cast a meaningful ballot after a lifetime of dictatorship, but I imagine it must be a remarkable feeling.

Seems like the vote went fairly smoothly, at least by local standards, although there were some unfortunate incidents. Even the Aljazeera account was largely indistinguishable from those in the Western press, except for these short paragraphs near the end:

After casting his vote in the western city of Ramadi, 21-year-old Jamal Mahmoud said: “I’m delighted to be voting for the first time because this election will lead to the American occupation forces leaving Ramadi and Iraq,” echoing a belief common among voters across the war-torn country.

In the holy city of Najaf, stronghold of the ruling Shia Islamist Alliance’s list No. 555, 40-year-old Abdullah Abdulzahra said: “I’ll vote for 555 because they’ll kill all Baathists.”

I think that Ann Coulter might have a future in Iraqi punditry.

The best news is that the Sunnis turned out in large numbers, indicating a willingness to join the new government as full participants. How smoothly that will go remains to be seen; some prognostications at Crooked Timber by Kieran Healy and Daniel Davies. Regardless, an historic occasion, hopefully the first of many in the region.

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Susskind interview

While we’re getting the multiverse out of our system, let me point to this interview with Leonard Susskind by Amanda Gefter over at New Scientist (also noted at Not Even Wrong). I’ve talked with Amanda before, about testing general relativity among other things, and she was nice enough to forward the introduction to the interview, which appears in the print edition but was omitted online.

Ever since Albert Einstein wondered whether the world might have been different, physicists have been searching for a “theory of everything” to explain why the universe is exactly the way it is. But one of today’s leading candidates, string theory, is in trouble. A growing number of physicists claim it is ill-defined, based on crude assumptions and hasn’t got us any closer to a theory of everything. Something fundamental is missing, they say (see New Scientist, 10 December, p 5).

The main complaint is that rather than describing one universe, the theory describes some 10500, each with different kinds of particles, different constants of nature, even different laws of physics. But physicist Leonard Susskind, who invented string theory, sees this huge “landscape” of universes not as a problem, but as a solution.

If all these universes actually exist, forming a huge “multiverse,” then maybe physicists can explain the way things are after all. According to Susskind, the existence of a multiverse could answer the most perplexing question in physics: why the value of the cosmological constant, which describes how rapidly the expansion of the universe is accelerating, appears improbably fine-tuned to allow life to exist. A little bigger and the universe would have expanded too fast for galaxies to form; a little smaller and it would have collapsed into a black hole. With an infinite number of universes, says Susskind, there is bound to be one with a cosmological constant like ours.

The idea is controversial, because it changes how physics is done, and it means that the basic features of our universe are just a random luck of the draw. He explains to Amanda Gefter why he’s defending it, and why it’s a possibility we simply can’t ignore.

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Is our universe natural?

Hey, has anyone heard about this string theory landscape business, and the anthropic principle, and some sort of controversy? Hmm, I guess they have. Perhaps enough that whatever needs to be said has already been thoroughly hashed out.

But, hey! It’s a blog, right? Hashing stuff out is what we like to do. So I’ll modestly point to my own recent contribution to the cacophony: Is Our Universe Natural?, a short review for Nature. To give you an idea of the gist:

If any system should be natural, it’s the universe. Nevertheless, according to the criteria just described, the universe we observe seems dramatically unnatural. The entropy of the universe isn’t nearly as large as it could be, although it is at least increasing; for some reason, the early universe was in a state of incredibly low entropy. And our fundamental theories of physics involve huge hierarchies between the energy scales characteristic of gravitation (the reduced Planck scale, 1027 electron volts), particle physics (the Fermi scale of the weak interactions, 1011 eV, and the scale of quantum chromodynamics, 108 eV), and the recently-discovered vacuum energy (10-3 eV). Of course, it may simply be that the universe is what it is, and these are brute facts we have to live with. More optimistically, however, these apparently delicately-tuned features of our universe may be clues that can help guide us to a deeper understanding of the laws of nature.

The article is not strictly about the anthropic principle, but about the broader question of what kinds of explanations might account for seemingly “unnatural” features of the universe. The one thing I do that isn’t common in these discussions is to simultaneously contemplate both the dynamical laws that govern the physics we observe, and the specific state in which we find the universe. This lets me tie together the landscape picture with my favorite ideas about spontaneous inflation and the arrow of time. In each case, selection effects within a multiverse dramatically change our naive expectation about what might constitute a natural situation.

About the anthropic principle itself (or, as I much prefer, “environmental selection”), I don’t say much that I haven’t said before. I’m not terribly fond of the idea, but it might be right, and if so we have to deal with it. Or it might not be right. The one thing that I hammer on a little is that we do not already have any sort of “prediction” from the multiverse, even Weinberg’s celebrated calculation of the cosmological constant. These purported successes rely on certain crucial simplifying assumptions that we have every reason to believe are wildly untrue. In particular, if you believe in eternal inflation (which you have to, to get the whole program off the ground), the spacetime volume in any given vacuum state is likely to be either zero or infinite, and typical anthropic predictions implicitly assume that all such volumes are equal. Even if string theorists could straightforwardly catalogue the properties of every possible compactification down to four dimensions, an awful lot of cosmological input would be necessary before we could properly account for the prior distribution contributed by inflation. (If indeed the notion makes any sense at all.)

I was asked to make the paper speculative and provocative, so hopefully I succeeded. The real problem is that draconian length constraints prevented me from making arguments in any depth — there are a lot of contentious statements that are simply thrown out there without proper amplification. But hopefully the main points come through clearly: calculating probabilities within an ensemble of vacua may some day be an important part of how we explain the state of our observed universe, but we certainly aren’t there yet.

Here’s the conclusion:

The scenarios discussed in this paper involve the invocation of multiple inaccessible domains within an ultra-large-scale multiverse. For good reason, the reliance on the properties of unobservable regions and the difficulty in falsifying such ideas make scientists reluctant to grant them an explanatory role. Of course, the idea that the properties of our observable domain can be uniquely extended beyond the cosmological horizon is an equally untestable assumption. The multiverse is not a theory; it is a consequence of certain theories (of quantum gravity and cosmology), and the hope is that these theories eventually prove to be testable in other ways. Every theory makes untestable predictions, but theories should be judged on the basis of the testable ones. The ultimate goal is undoubtedly ambitious: to construct a theory that has definite consequences for the structure of the multiverse, such that this structure provides an explanation for how the observed features of our local domain can arise naturally, and that the same theory makes predictions that can be directly tested through laboratory experiments and astrophysical observations. Only further investigation will allow us to tell whether such a program represents laudable aspiration or misguided hubris.

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Where the dark matter is

Dark Matter Map Just because you can’t see the dark matter doesn’t mean you can’t take a picture of it. Via Universe Today, here’s a press release from Johns Hopkins announcing a beautiful new image of the reconstructed dark matter density in cluster CL 0152-1357 by Jee et al. (I couldn’t find the paper online, but you can get a higher-resolution version of the picture at Myungkook Jee’s home page.) The dark matter is in purple, the galaxies are in yellow.

How do you do that? It’s not because we’ve detected some form of light coming from the dark matter. Rather, we’ve detected (once again) its gravitational field — this time, via the tiny distortions in the shapes and positions of background galaxies (weak lensing). This is a form of gravitational lensing that is so subtle you could never detect it happening to a single galaxy — it would be impossible to distinguish between lensing and the intrinsic shape of the galaxy. But if you have a large number of background galaxies (which the universe is kind enough to provide us), you can use statistics to reconstruct the gravitational field through which the light travels, and hence figure out where the dark matter must be.

Of course we’re still trying to detect the dark matter, both directly (in ground-based experiments) and indirectly (looking for high-energy radiation produced by annihilating dark matter particles), not to mention using particle accelerators to actually produce candidate dark matter particles. Over the next ten or twenty years, probing the properties of dark matter is going to be one of the top priorities at the particle/astrophysics interface.

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Hostility to atheists

While I’m shirking my blogging responsibilities by linking to series of posts elsewhere, there’s an interesting discussion about hostility to atheists at the Volokh Conspiracy: see here, here, here, and here. You’d be unsurprised (I suspect) to learn that Americans find atheists to be one of the most untrustworthy brands of people around. Just to get an idea, here are the answers from a 2005 poll that asked whether “your overall opinion of [the group] is very favorable, mostly favorable, mostly unfavorable, or very unfavorable?”

Group

Very favorable (%)

Mostly favorable

Mostly unfavorable

Very unfavorable

“Catholics”

24

49

10

4

“Jews”

23

54

5

2

“Evangelical Christians”

17

40

14

5

“Muslim Americans”

9

46

16

9

“Atheists, that is, people who don’t believe in God”

7

28

22

28

Well, I suppose it’s understandable, since atheists are constantly killing innocent members of other sects in the name of their belief system. Oh wait, no they’re not. Must be the War On Xmas that is hurting our ratings.

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