Blogs / Cosmic Variance

You know, other people talk a lot about time, too — it’s not just me. Here’s a great video from Nature, featuring a conversation between David Gross and Itzhak Fouxon about the existence of time. (Via Sarah Kavassalis.) Itzhak plays the role of the starry-eyed young researcher — he opens the video by telling us how he originally went into physics to impress girls, although apparently he has stuck with it for other reasons. Gross, of course, shared a Nobel Prize for asymptotic freedom, and has become one of the most influential string theorists around. David plays the role of the avuncular elder statesman (I’ve seen him be somewhat more acerbic in his criticisms) — but he’s one of the smartest people in physics, and his admonitions are well worth listening to. He gives some practical advice, but also advises young people to think big.

Unfortunately the video doesn’t seem to be embeddable, but you can go to the video page and click on the “David Gross” entry. (The others are good, too!)

You all know my perspective here — time probably exists, and we should try to understand it rather than replace it. But I’ll agree with David — let’s not ignore more “practical” problems, but not be afraid to tackle the big ideas!

Uncertain Chad is, well, uncertain, about how best to deal with two competing ideals when using Powerpoint (or Keynote) for lecture classes.

On the one hand, nobody likes a cluttered slide. In science lectures it’s much better to show a single plot augmented with a verrrry limited amount of text. The clarity focuses the student on the most important point, and frees them to actually listen to what you’re saying.

On the other hand, it’s useful for the students to have a more detailed record of what you discussed while explaining the plot. Yes, they can and should take notes, but there is a natural tendency for students to write down Every. Word. You. Say., since they have no context for prioritizing the importance of the information spewing forth. I prefer to be explicit about what the key points are.

My trick for balancing this is using black text on a black background. The text doesn’t show on the screen, but it does show up when printed as a handout, since the black background defaults back to white. Thus, you get the following:

Pretty much every successful proposal starts with a variant of the following structure:

1. Topic X is important and interesting.

2. But.

3. This is how we will address “But.”

The rest of the proposal reiterates those three points with enough detail to make it believable.

In a short proposal, the structure fills a paragraph. In a long proposal, it’s three paragraphs, and shouldn’t go past the first page.

The abstract is a 1 paragraph version of the same structure, with the addition of a closing rah rah rah sentence.

If you can’t bludgeon your introduction into this form, you might want to step back and regroup.

I am just back from Princeton where we held the annual meeting of the GRE Physics Committee of Examiners, a group of six, ahem, distinguished professors (we have grey hair) who sit around a conference table working through hundreds of potential and actual Physics GRE problem. Each year new exam forms are completed, new questions added to the pool, statistics reviewed, and a good time is generally had by all.

This was my last meeting – I have served on the committee for six years. The membership rotates roughly every two years. I had been an external reviewer and problem writer for a couple years, and was then asked to serve on the committee. I am sworn to secrecy about a lot of the details, for good reason, but let me try to tell you from my perspective as an exam writer how to study for this dreaded event in your physics education.

Firstly, there’s the format. The exam is 100 questions long, and you have 170 minutes to do it. This is, therefore, different from just about every other physics exam you have had in college, where you have, say, four to six problems in an hour-long exam. The GRE Physics problems (or “items” in assessment world jargon) are short, to-the-point questions, and just about all of them are short calculations, if any, and take little time once you see what to do. Writing such questions is a difficult thing to do, let me tell you. We are continually amazed how, after about six levels of review, we can find issues of clarity, reasoning, and even sometimes basic physics correctness in the items submitted to the pool. All the committee members spend a lot of time each year reviewing hundreds of problems, looking for flaws, but more often than you would think the face-to-face meeting in Princeton with the ETS folks reveals something previously overlooked. It’s a really interesting process.
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As Mark recently mentioned, we are deep in recommendation letter season. I’ve been in the biz long enough that I’ve probably written at least a hundred letters (estimating more than ten a year for more than a decade), and read far more than that.

After you read enough letters, they can start blend together. But, in a big stack of applications, there are usually a few letters that stand out as risible, causing a good chuckle and round of comment from the committee.

And they are almost always letters written on behalf of women.

In a standard letter of recommendation at the postdoc/faculty level, there is frequently a comparison to other successful scientists. The letter usually reads something like “reminds me of person X, Y, or Z at a similar level of their career” or “shows the same persistence and insight as person Q, and stronger big picture thinking than person P”. These comparisons are almost always favorable, saying that the applicant is in the same league as other people who are recognized as having had a significant scientific impact.

But, for some reason, some fraction of letter writers insist upon doing these comparisons only within a single gender, when the applicant is a woman. In other words, “(woman) X shows a similar level of insight as (woman) Y and (woman) Z”. I’m not saying that these comparisons are not favorable — they’re usually comparing a strong female applicant favorably with other successful female scientists. Their praise is genuine and well meant. However, one can’t but help perceive that they see women as somehow swimming in a different pool than the rest of the guys.

Now the good news is that most committees that I’ve been on have seen right through this. We note it, and have a small laugh at the letter writer’s expense. In addition, it’s not common — usually only affecting a couple of letters in an applicant pool.

So, if you’re writing a letter for someone in an underrepresented group, please save yourself from mockery by examining exactly how you perceive the applicant’s comparison sample.

This is transcendently ridiculous.

For the many international CV readers, today is the US’s Independence Day celebration, which is in large part an excuse to bar-b-que meat products, blow up fireworks, and drink beer. If you’re tuning in from abroad, you are probable sober enough to read Daniel’s upcoming post on gravitational waves. For the rest of the drunken US crew, you can probably handle the Muppets.

PS. While we’re talking beer, I must recommend the current Full Sail Limited Edition L.T.D. (Recipe No. 3), sold in bottles with the pale blue label. Seriously. Try some.

(h/t: Again with the CakeWrecks)

Not to be a harbinger of doom, but this one sounds bad. There are some 6-15 million computers out there running Windows which are infected with a computer virus, dubbed Conficker C. The recent report by SRI makes for some chilling reading. On April 1 (that is, next Wednesday!) the virus is set to…well…do something. It’s not clear what, but with so many millions of computers will do it. The report concludes:

We present an analysis of Conficker Variant C, which emerged on the Internet at roughly 6 p.m. (PST) on 4 March 2009. This variant incorporates significant new functionality, including a new domain generation algorithm and a new peer-to-peer file sharing service. Absent from our discussion has been any reference to the well-known attack propagation vectors (RCP buffer overflow, USB, and NetBios Scans) that have allowed C’s predecessors to saturate so much of the Internet. Although not present in C, these attack propagation services are but one peer upload away from any C infected host, and may appear at any time. C is, in fact, a robust and secure distribution utility for distributing malicious content and binaries to millions of computers across the Internet. This utility incorporates a potent arsenal of methods to defend itself from security products, updates, and diagnosis tools. It further demonstrates the rapid development pace at which Conficker’s authors are maintaining their current foothold on a large number of Internet-connected hosts. Further, if organized into a coordinated offensive weapon, this multimillion-node botnet poses a serious and dire threat to the Internet.

Yikes! Whoever wrote this thing is not a very nice person…or persons. The C variant apparently managed to upgrade itself over the network, and disables security anti-virus software. If I were you (and I am apparently not because I use only OS X and Unix) I would update my antivirus software every day and scan my machine. And leave it off next Wednesday if possible.

Pass the word…

Via Slashdot, I came across the following question

Troy writes:

“I’m a high school math teacher who is trying to assemble an extra-credit reading list. I want to give my students (ages 16-18) the opportunity/motivation to learn about stimulating mathematical ideas that fall outside of the curriculum I’m bound to teach. I already do this somewhat with special lessons given throughout the year, but I would like my students to explore a particular concept in depth. I am looking for books that are well-written, engaging, and accessible to someone who doesn’t have a lot of college-level mathematical training. I already have a handful of books on my list, but I want my students to be able to choose from a variety of topics. Many thanks for all suggestions!”

There are some good suggestions in the comments, and some not so good ones. Surely our wise and mathematically sophisticated readers will be able to help. Add what you can there, and in the comments here if you like.

Given the current DEFCON 1 level of anxiety about recommendation letters, and my belief that more transparency is usually a good thing, I thought it would be informative to assemble a word cloud of about 10 years of recommendation letters written for undergraduates applying to graduate schools or fellowships (with names and schools omitted).

As you can see, the top three themes are “research”, “project”, and “work” indicating that the letters are highly weighted towards what students have actually accomplished, rather than just pure intellectual firepower. The cloud for graduate students applying to postdoctoral positions would be more biased towards words like “thesis” and “papers”, but would again emphasize what one has done, not how intelligent one is.

So, if you are a student thinking about graduate school, you should make sure you get involved in research, and, when you do, make sure you get something done!

Here are some of the things from various admissions files that have made me sad (details changed to preserve anonymity)

• “I’m sure Stu Dent could do well in graduate school, provided you can get him to talk to you more than I ever could.”

• Transcripts with three times the number of courses (and substantially better grades) in music than in physics.

• Deep, Meaningful quotes from rock bands and dead hip-hop artists in the footer of the applicant’s cover letter.

• “No other institution would benefit more from my presence than yours.”

• “I only want to work on Topic X! Nothing is cooler than Topic X! My intellectual life is a shrine to Topic X.” Except, our department has no relevant work on Topic X.

• “Stu Dent has excellent physical intuition and will undoubtedly succeed in graduate school”. Except, Stu has mostly B’s and C’s in their physics courses and a 15th percentile on the physics GRE.

• Students who have taken no math beyond calculus.