Just a quick school update

Tomorrow (Monday the 30th) is my first day of classes here at Stony Brook. Now, I only have one class, as it turns out, but it also promises to be a really good one.

People always say that, especially as a graduate student, you shouldn't necessarily take a course because of the topic, or because you feel like you "have to,"  but because of the professor. They say you should ask around the department, find out who the coolest teachers are, and then just sign up for whatever they're teaching. Well, here's one such guy:

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∫ Finally, a math puzzle I can use!

After much thought, I've hit upon a math puzzle that will work for my friend's little neighbor, the aspiring mathematician. Actually, I'm going to give her a two-part puzzle: a more straightforward version of the "littler math puzzle"  posted below, and this little guy that I came up with yesterday while exploring the behavioral sciences building. Incidentally, why do "people scientists"  and "medical scientists" always have such nicer buildings than "hard scientists?"

Anyway, here's the puzzle:

Most small numbers are pretty close to a prime number. For example, the number 22 isn't prime, but if I just change the second 2 into a 9, then it is (because 29 is prime). Similarly, 310 isn't prime, but 313 is. So it seems like often, all I have to do is change one digit in a number and I can make it into a prime number.

Unfortunately, that's not true for ALL numbers. There are some numbers that can't be made into a prime number just by changing one (and only one) digit. The question is, what is the smallest of these numbers?

Answer and explanation below the fold, as always.

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If America wants to be like Rome, we have to start paying our athletes more

That's the message I take from this post by Peter Struck, a professor at U Penn who writes a blog about interesting things from history. Struck is writing in response to the news a year or so ago that Tiger Woods has become the first athlete to earn $1 billion in the course of his career. For comparison, he points us to the charioteers of ancient Rome, who were apparently the absolute hottest attraction in the Roman entertainment scene.

No, this is not a picture of Gaius Appuleius Diocles.

The hottest of the hot, a Spaniard named Gaius Appuleius Diocles, apparently earned so much money that after his retirement--at age 42--a monument was erected to immortalize the staggering amount of his collective winnings. As Struck writes:

His total take home amounted to five times the earnings of the highest paid provincial governors over a similar period—enough to provide grain for the entire city of Rome for one year, or to pay all the ordinary soldiers of the Roman Army at the height of its imperial reach for a fifth of a year. By today’s standards that last figure, assuming the apt comparison is what it takes to pay the wages of the American armed forces for the same period, would cash out to about $15 billion. Even without his dalliances, it is doubtful Tiger could have matched it.

I'm a little skeptical of Struck's strategy for translating Diocles' earnings, as it seems to me there are a lot of variables about the size and cost of the armed forces that are uncontrolled for. I think in terms of comparing him to modern athletes, a better strategy might be to ask what percentile of earners he fell into against the percentile rank of Woods and the like. But whatever his actual  "adjusted" salary turned out to be, its pretty clear it would have been far more than what our average athlete makes today. I think it's even possible that by this metric, he would project out to have made a lot more than $15 billion, quite a feat given the fact that the general public in this day and age probably has a lot more disposable income to put into seeing athletic competitions than the amount that was available when just a few wealthy statesmen were organizing these things.

In other words, the next time someone tells you that the US is on its way to becoming "just a modern Roman empire,"  make sure to include in your rebuttal the fact that we aren't yet nearly obsessed enough with sport.

Mark Wahlberg and an eggplant teach me to enjoy action flicks

I watched "Shooter" last night while I made eggplant curry. The curry turned out really well--turns out the missing ingredient last time I made it was coconut milk-- but the really interesting part of the evening was the experience I had watching the movie. By most accounts, "Shooter" was a pretty bad movie, or at least pretty mediocre, but I really enjoyed it. And I think the reason was, I wasn't really paying attention.

I'm not trying to rip on the movie. I've always believed that the so-called "mindless action flick" was a perfectly defensible art form. It's just like I always appreciated the music of folks like Justin Timberlake and the Black Eyed Peas. I think they're geniuses: they are legitimately some of the best in the world at crafting catchy beats, hooks, and melodies. You just can't go to them expecting depth and introspection. That would be foolish. You go to them when you need to be emotionally manipulated by music on a deep level. And I'm not so snobby as to think there's anything wrong with that on any level. Sometimes you need to be tricked into feeling happy, sad, hopeful, whatever. We do this all the time by turning to friends, starting leading conversations, et cetera. So there's no reason to feel bad doing it with music.

For some reason, though, I've always had trouble letting movies do this to me.
Action films in particular get on my nerves when they try to provoke an emotional response. They always try really hard to get me to have a gut-level, testosterone laced level of support for the hero, and they often try to get me to join in on the his righteous anger against whatever evildoers he's battling, too. And for some reason, even though I know the trick to enjoying such movies is not to expect any deep revelations about the state of humanity, and not to expect any magical, arts camera work, et cetera, I always manage to get angry at the shallowness of the movie.

This has made a lot of my friends angry to no end. So many of them got a huge rush out of "Quantum of Solace," but I was busy being mad that it didn't live up to the emotional complexity of "Casino Royale." A good number of them managed to get a kick out of the fight sequences in "G.I. Joe," whereas I couldn't get over the fact that it contains some of the most unrealistic science, most incoherent plot "twists," and most densely-packed clichés of all time.

Well now I've learned the trick, courtesy of Mark Wahlberg.

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∫ Things I learned from teaching undergraduates: Tennis Ball Topspin Edition

The Youtube clip above shows Roger Federer hitting a topspin forehand in slow motion. The ball is moving too fast after he hits it for you to be able to see the direction of its spin, but you can tell pretty clearly from the motion of his racket that he's hitting a little bit beneath the ball and then sliding the racket upwards along the backside of the ball at the same time as he follows through. The result is the the ball will be spinning with what tennis players call "Topspin."  It's a rotation where the ball the top of the ball is moving in the same direction as the ball is flying, and the bottom of the ball is moving the opposite way.

Topspin is a huge deal. Part of the reason Roger Federer is so good is that he hits with 2,500 RPM of topspin, which is more than either Pete Sampras or Andre Agassi (only Rafael Nadal hits with more, although it's been argued that he actually hits with too much!)

Now, like anyone who's ever taken a tennis lesson, I know tennis reasons the pros hit most of their shots with topspin. Coach after coach after coach has told me over the years that there are basically two principal reasons: first, a ball with topspin will "kick" upwards when it bounces (I think it's pretty easy to see why) and that can make it harder for your opponent to hit, because they wind up having to hit it up around their ears. But then there's this second reason: Topspin is supposed to make the ball "drop" sooner, meaning you can hit it higher over the net and still get it to land inside the court. Being able to hit higher  in turn means you have less chance of hitting it into the net, and it means that you can hit it a little harder. Seems like a good deal all around.


But one thing I definitely did not know until a couple of days ago is why topspin causes the ball to move like this. After all, why would spinning make a ball want to fall downward faster? It's not like it makes it any heavier.

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My first research job offer. Sort of.

I was at a departmental welcome barbecue (yes, physicists can have social events!) and I wound up talking to Chan Kee Jung, a professor here at Stony Brook who's well known in the world of neutrino physics (he headed up the experiment that first showed evidence of neutrino oscillation, but that's another story). When I first saw him, however, I had no idea who it was, because as far as I could tell, it was just some big, stocky Korean with a pony tail, a Hawaiian shirt and a hotdog in each hand, talking to a handful of physics students about why a follow-through is important if you want to punch someone.

I crashed the conversation and discovered that Dr. Jung teaches a course called "The physics of sports" for nonscience students at Stony Brook. As the rest of the students wandered off to have another go at the mango salsa, he and I wound up having a one on one conversation, during which we talked about everything from the spin of tennis balls to the sweet spot of a baseball bat (thank you, COMAP competition!) I also found out we cheer for a lot of the same teams in college basketball.

Next thing I know, Dr. Jung was asking me to be a TA for his Physics of Sports class (I get the impression that the guy who's supposed to do it didn't know much about sports). I told him I'd look into it and see if it would work with my schedule (I've since found out it won't) and I decided to try to steer the conversation towards his current neutrino research, which is a really cool project called T2K, in which a neutrino beam detected on one sideof Japan is detected and studied 300 miles away, on the other side. We had a fun conversation about that, too, and then suddenly, he was suggesting that I should join his research group and come with them to Japan this summer.

I have to say, I was pretty flattered, except for the obvious fact that his favorite thing about me was that I liked Duke and knew the rules of soccer. So it seems the sad fact is this: after all the time I've spent honing my interview skills and my professional persona so that I can appear like a promising job applicant, it turns out the real trick is to get your future employer a beer and a couple of Brooklyn-style hotdogs, and start chatting him up about his favorite sports teams.

A non-math puzzle

Here's a puzzle of a different sort:

It's been a while since I wrote one of these, but I think I'm getting better at it. It's still not up to NYT standards, but I'm making progress. And more importantly, I'm getting faster at it. The first crossword I ever wrote took me pretty much an entire summer. I finished this one in a week and a half, partly thanks to the fact that I'm now using some software to do the grid-setup and to keep track of the numbers and clues. Anyhow, here's the puzzle, have at it. I think it should be about equivalent to a hard Tuesday Times puzzle, but it may be a little harder than that.

In case you need it, or if you find a place I made a mistake, you can check the solution below the fold:

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