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!

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:

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.

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.

For each new exam form we eventually arrive at 100 items that test mastery of a clear physics concept or idea, and there is, yes, a certain amount of memorization required in terms of the basic equations learned in undergraduate physics. But there are many problems that can be done using just concepts, and many that can be done with simple dimensional analysis. When there are numerical solutions (and many if not most are in that category) the numbers are chosen so as to allow easy arithmetic – no calculators are allowed.

My first piece of advice to students studying for this exam is to focus on reviewing the textbook from your freshman introductory physics course. In my years on the GRE committee, when I have needed to consult a text, it is that text at least 80% of the time. If you master every example in there and review the basic equations, you will do really well on the GRE. I have found that only a small fraction of the items on the GRE are actually from upper-level topics like stat mech, quantum, and special topics (solid state, nuclear, particle, cosmology, etc.) And presumably you have been studying the advanced topics more recently anyway. I think the single biggest mistake students make in studying for the GRE is to focus on too-advanced subjects.

The other piece of advice I give students is to be disciplined in your approach to actually taking the exam. You only have an average of 1.7 minutes per problem! If you get bogged down on a long algebraic calculation, you risk not being able to complete the exam, including items that you would correctly answer in a few seconds. So when you take the exam, read each problem, answer it if you can do so reasonably quickly and then put an X on the problem number. If you think the problem will take some time or a long calculation, put a circle around the number and come back to it in a second pass through the whole thing. But pIck off the easy ones first! It also helps build confidence as you go through.

Also realize that the GRE penalizes random guessing: your raw score is the number correct minus the 1/4 times the number incorrect. As a result it’s no better to guess than to leave an answer blank if you cannot eliminate some of the five choices. But if you can eliminate some, then by all means guess! Look carefully at the possible answers – sometimes just the units, or magnitude, or mathematical form can give you a way to guess more astutely.

So just what is the GRE measuring? A critic might point out that it measures the ability to work under pressure, memorization, and quick mathematical reasoning and calculation. Though these are good qualities for a physicist to have, they are by no means the only qualities required for a successful career. I would argue further, though, that the Physics GRE really does test knowledge about basic physics and the ability to analyze physical situations accurately.

So then how important is the Physics GRE for your career? It turns out that it is in fact quite important. Some of the top programs in the US even go to the extent of requiring a GRE score above some threshold for considering the applicant. I have served on our graduate admissions committee for five years now, and I can tell you that we regard the GRE as just one piece of information telling us how likely a student is to thrive in our program. We do see a clear correlation between an incoming graduate student’s Physics GRE score and their score on the other dreaded exam in a physics student’s career, the Ph.D. written preliminary exam, which is a very different beast. (There was, a few years back, some lore that the GRE Verbal score was a better predictor than the GRE Physics score, and there is a correlation, but not as strong as with the GRE Physics score.)

In considering an applicant we look at a number of things, including the applicant’s own statement, experience, letters of recommendation, and their undergraduate transcript, in addition to the GRE general and subject scores, to get an idea of the whole student. My own observation is that students below about the 30% level have a very hard time attaining a Ph.D., though this is by no means absolute. I am sure there are tons of very successful physicists out there who, for whatever reason, scored poorly on this peculiar exam and went on to great careers.

So, to of those of you facing this exam in a few weeks, I wish you good luck! Review your intro course, get a good night’s sleep before the exam, and make sure you pick off all the easy problems that you can!

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.

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)

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…

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.

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!

• “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.