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Category — observations

Dow Jones and Mathematica

A recent post by economist-blogger Brad DeLong, which was also picked up Matthew Yglesias, mused upon the clustering of the Dow Jones Industrial Average clustered near values starting with 1. He showed a chart with the years 1971–1984, and 1996–2008 circled, when the Dow appeared to fluctuate near 1000 and 10000, respectively. Many commenters quickly jumped to point out that this was an example of Benford’s Law, which says, essentially, that if you’re throwing darts at a logarithmically shaped dartboard, you’re going to hit “1” more often than any other digit. If you pick random values of some phenomenon that is logarithmically distributed, you should get values beginning with “1” about 30% of the time, which makes sense if you’ve ever looked at log scale graph paper.

It occurred to me that this is an easy thing to investigate with Mathematica, much like my earlier post on the Bailout. Mathematica 6 includes access to a huge library of curated data, including historical values of the Dow Jones Industrial average and other indices (and individual stocks, and so forth). The function here is FinancialData, which Wolfram cautions is experimental: I believe they get the data from the same source as, say, Yahoo! Finance, and just do the conversions to make it automatically importable into Mathematica. That is, it is no more reliable than other web-based archives. The computations are absurdly easy, taking only a few lines of Mathematica code. 

The graph I (eventually) produced shows the relative frequencies of first digits that are calculated by Benford’s Law, together with the relative frequencies of the leading digits from the Dow Jones Industrial Average, the S&P 500, the NASDAQ Composite index, the DAX 30, and the Nikkei 225:

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November 1, 2008   No Comments

“We should” vs. “I will”

“We should”: one of the most counter-productive phrases in existence.

As a progressive, and with my student days behind me, I’ve come to feel that civic engagement shouldn’t be considered optional. I’ve looked to local organizations for involvement: while in DC, I’ve volunteered with three organizations, plus one political campaign,  and will probably work with others as my priorities nd responsibilities evolve. 

In every setting that involves a group of volunteers–or more generally, a group of people in which the individuals each decide how they will invest their time–the words “we should” are a sure path to inaction. What the words really mean is “I won’t but hope someone else will,” but without the candor to admit that the speaker, in fact, won’t do whatever it is he is suggesting. 

These words are usually spoken in meetings, gatherings that many people claim to disdain. The fact that nothing actually gets done during meetings compels some to ask if everyone shouldn’t really use their time to actually do something. Someone might suggest meetings every other month, instead of monthly.  If a project does require the input of more than one person, however, you need meetings. In the case of volunteer groups, in which everyone has a myriad of other obligations and interests, the truth is out-of-sight, out-of-mind. Nobody’s time is so carefully managed that he could take the time that would have been spent in a meeting and use it on a project: there are plenty of other things that rush in to fill the temporal void. One might read a few more threads on Daily Kos, or watch the television program that comes on after your favorite program, or skim through catalogs you get in the mail instead of sending them straight to the recycle bin. The way things get done in a volunteer organization is through mutual accountability: we agree to take on tasks, and follow through because we value the value of our word.

Meetings are necessary: the trap is to think that meetings are sufficient. I think that even the complainers like their volunteer meetings, perhaps secretly. For one, it’s a chance to hang out with like-minded people for a few hours. There is also a sort of perverse satisfaction from attending a meeting: you get to feel that you’ve accomplished something but you actually haven’t had to expend much effort. You’ve spent a few hours getting updates and making plans for next steps; you’ve thought about the issues at hand, so it seems like you’ve done your part. 

And truthfully, for many, that’s all they do, as the meeting is the only space they’ve made in their schedules for the issues at hand. Of course, we’re all so busy, and it’s tempting to just be thankful that they care enough to show up, but if everyone at the meeting is like this, nothing will get done. Some would do well to re-evaluate their own priorities–they do so much, they get nothing done.1

Calling out the “we should”s, and insisting on “I will”s is one tool with which to separate the do-ers from the rest. Perhaps meeting organizers should keep tallies of each phrase. Each time “we should” is uttered, put the utterer on the spot, and ask if he’s volunteering to do the task he suggests. Now, this is not to say that someone can’t have good–even inspiring–ideas that he can’t carry out himself,2 but in such cases he should simply say so.

A particularly pernicious form of “we should” are the obstructionist “we should”s–that when person A volunteers to take on some task, person B pipes up with an impractical pre-condition that “we should” do before beginning on person A’s task. More than just a waste of time, this could actually derail a real action. In physics, we are occasionally encouraged to “make mistakes as fast as possible.”3 That is, you won’t learn anything, and you won’t get anything done, without doing something. So do something. Say that you will do something, and do it, and if it turns out to be not quite the right thing, then you can do something else.

  1. One of Paul Sally’s graduate school advisors apparently told this to him, when in his early grad student days he wasn’t getting much mathematics done. []
  2. One idea I’ve had for the organizations I’ve worked with, but can’t do myself, is to create a coloring page based on your organization’s work, so that if you’re tabling an event, and a parent comes by with his or her child, you can let the child color the coloring page (supply crayons) while you talk to the parent about the organization. []
  3. A sentiment attributed to the late John Wheeler. []

June 5, 2008   No Comments

Taking data

By trade, I am a physicist; specifically a condensed-matter experimentalist. More so than other scientists, physicists are rather sharply split into two categories: theorists and experimentalists. Einstein and Feynman were theorists, working with equations and making calculations. Experimentalists work in labs and conduct experiments and analyze data.

A day spent taking data, then, is usually a good day: data is, after all, the lifeblood of experimental physics, and if you’re taking data then that means your apparatus is working, which is always a good thing.

I spent today taking data. Even though the process is heavily automated and computer controlled, the apparatus needs constant supervision. As is the case with most of the experiments I run, there is a very short duty cycle for attention: I’ll need to make an adjustment, then let the experiment run for a few minutes, then make another adjustment, and wait a few minutes, and so forth. And although the taking of data is an inherently good and fulfilling process, the time scale that my experiments work on can be frustrating.

The intervals between which my attention is needed are long enough so that, after a while, it’s sort of boring just to sit there and wait. On the other hand, the intervals are too short to get anything meaningful done. I often think that I should be able to read journal articles in these time spans, and I usually have an article or two with me that I intend to read, but this always fails: reading journal articles must be done in large, uninterrupted time blocks. If I do try to read a journal article, and get in depth reading it, then I’d be likely to let the experiment languish, and in the end that’d be a terribly inefficient way to take data.

As it turns out, surfing the web is the sort of activity that can be broken into minute-long chunks, and since the data taking computer is usually also hooked up to the internet, it actually works out quite well to browse the web during the gaps when the computer is doing all the other work.

Most of the data I take measure some sort of quantity as a function of temperature, and typically the experiment cools to it’s lowest temperature, and then the temperature is raised in steps, with a datum taken at each temperature. A large part of the waiting around I do is waiting for the temperature to stabilize. In many experiments, the speed with which the temperature can be changed and stabilized sets the rate at which I can take data. Inasmuch as I’m browsing the web while I’m waiting for the temperature to stabilize, being lazy and being careful can sometimes look very much like one another. To be careful, you really want to make sure the temperature is stable, that it isn’t drifting or oscillating, and generally, this means waiting longer. But waiting longer also means more time browsing the web and less time doing real physics, so if you’re waiting longer than it takes for the temperature to become as stable as your experiment needs, then you’re being lazy.

April 23, 2008   No Comments

March Meeting observations

This year, I only went to the first three days of the March Meeting; extended trips are less feasible now with a baby at home. The trade show and posters are only Monday–Wednesday, and a fair number of attendees–particularly college faculty with classes to teach–stay for only a few days. So Thursday and Friday the conference is sort of a ghost town, but one thing I’ve heard from quite a few people this year is that it looks like several interesting sessions are scheduled for Thursday and Friday.

To read up on some of the physics presented at the March Meeting, a physics blogger’s account starts here. Physics journalists are blogging from the meeting here. Another attendee’s take is here. (I’ll update periodically if I find new blogged accounts.)
Photographing Talks
One phenomenon that’s becoming more common, and which is at least slightly disturbing, is for audience members to use digital cameras to photograph all the slides that a speaker presents. It’s obnoxious when the camera makes faux-shutter sounds, and it’s really obnoxious when the flash fires. When the flash is used, it’s also a sign that the photographer is an idiot, because the flash will make the image of the projected slide come out worse: physicists should be able to figure this out. If the photographs are unobtrusive, I haven’t quite figured out what the ethics of the situation are. I’d think if you really wanted someone’s viewgraphs, or data, you should just send them an email and ask: I’d share my data and graphs if someone asked for them.

I saw 39 talks this March Meeting, and only one used viewgraphs, and that was after the speaker attempted to use the computer but had some difficulty getting the computer to cooperate with the projector. The APS recommends that speakers have viewgraphs as backups; most don’t, but this speaker did, and the talk otherwise went off without a hitch. One out of 39 is 2.6%, which is a smaller fraction than last year (but not significantly so).

One piece of technology that number of speakers decided to do without was the (supplied) wireless microphone, which is a real shame. Perhaps the folks up front can hear the speaker fine, but there’s always a background rustling of papers and backpacks and schedule books, and people are talking outside the room, and if the doors are open this really filters in, and if the doors are closed then they keep opening and closing as people straggle in. It’s really hard to hear an un-miked speaker in the back of the room.

Because of the 39 parallel sessions, in which you wish you could be two or three places at once, people do lots of session-to-session shuffling. It’s always awkward to squeeze in to the open seats mid-session. The solution to this: more aisle seats! Instead of having two columns of seats, with an aisle down the middle and sometimes aisles down the sides, the APS should have the convention center arrange the seats to be at most 4 across, in 3–5 columns, so that everyone who wants an aisle seat–which is everyone who’s shuffling between sessions–could get one. It would cut down on the capacity a little, but although there are some overflowing sessions, there are plenty that are sparsely attended. To this end, the APS should try a little harder to predict the attendance at the sessions, and put the popular ones in the large rooms. I know this is hard, but isn’t this the sort of problem that physicists should be able to tackle?

New Orleans Convention Center
The March Meeting isn’t like a trade show, where you need lots of floor space, preferably contiguous, for all the vendors to set up their booths. Rather, we need lots and lots of meeting rooms. Convention centers, as a rule, have both, but some do the meeting rooms better than others. The shorter the distances between rooms, the better, because at the March Meeting it is common to try to shuffle between different rooms during a session. In New Orleans, there were two giant rooms on the first floor, and the rest were on the second floor. Most of these were along one long linear corridor, but a handful of rooms were in a parallel corridor on the other side of the center. To get between these corridors you went through an elevated walkway that overlooked the trade show floor. The convention center is along the Mississippi river. Between the center and the river are active railroad tracks. In the rooms on the river side, one could clearly hear the horns of the trains that used this track. I suppose this isn’t a problem inside a noisy trade show floor, but when you’re trying to listen to a talk, it makes you wonder why the architect didn’t specify more robust soundproofing on the walls that face the river.

The trade show:
Trade Show, March Meeting 2008
And the posters:
Posters, March Meeting 2008

The PAR 124 lives!
Perhaps the most exciting development, from my perspective, was the unveiling of the Signal Recovery 7124 Lock-In amplifier, so new it doesn’t appear on their website. Lock-in amplifiers are one of the most useful pieces of equipment in experimental physics research: They perform frequency selective signal detection and amplification, showing the amplitude and phase that appears on a signal in relation to a reference signal. They are tremendously valuable for processing noisy signals.

Years ago, a company called Princeton Applied Research (PAR) produced a truly amazing lock-in, the PAR 124. Built with all analog electronics, and mostly from discrete components, it was very sensitive, very quiet, and had been a staple of low-temperature research labs for decades. Contemporary lock-ins are, as a rule, digital, making use of Digital Signal Processing (DSP) to process the input signals, and do more with them than ever possible with analog electronics. But the digitization process itself is noisy, sending a sort of switching noise back up the input line to the experiment. This added noise and energy is very much unwanted in low-temperature experiments, so low-temperature labs kept PAR 124s around and sought them out from second-hand equipment dealers.

(I’ve used them in many of the mechanical oscillator projects I’ve worked on, but for a slightly different reason. Even when you use an external signal for the reference channel of the 124, the internal oscillator locks to your external reference and then this internal oscillator is used for signal processing. Because of the way this locking is accomplished, the 124 can be used to implement a phase-locked loop, by driving the mechanical oscillator with the reference signal output.)

Princeton Applied Research was bought by EG&G, who was then bought by Perkin-Elmer, then became Ametek, and who finally decided to call themselves Signal Recovery. And whenever they showed up at a trade show, such as at the March Meeting, low temperature physicists (including myself) would always ask if the PAR 124 would ever come back. “We’re working on it,” was always the answer.

And so they were. This March Meeting, they had on display the 7124 lock-in. It uses an all-analog front end, to which you connect your experimental signal. It’s connected by a 5-meter fiber optic cable to a digital DSP lock-in, so you can take advantage of all the advanced features of a DSP lock-in without the digitizing noise getting back to your sample. If I had a spare $15000 sitting around, I might buy one.

March 13, 2008   3 Comments


For Presidents’ Day, the Washington Post reports: banks are closed, courts are closed, local government offices are closed, schools are closed, libraries are closed. There is no trash pickup on Presidents’ Day, and Sunday traffic and parking regulations are in effect. 

But the lotteries have regular drawings! Can’t stop the lottery for a holiday.

The lottery is a tax on hopelessness, at a dollar a prayer. The church stopped such selling of indulgences in the sixteenth century, that our governments do so today is shameful.

February 17, 2008   No Comments

Another holiday flies by

One of the biggest changes moving from academia to being an employee of the U.S. Government was that I now have to keep track of vacation days–I get 19.5 per year, in addition to the 10 federal holidays. So I don’t always take the entire week between Christmas and New Year’s off, but this year I did, using up four vacation days to get an 11-day stretch at home. (The President was gracious enough to give Federal employees Christmas Eve day off.)

As with most vacations, I had anticipated making progress on a whole list of projects, but, as is also usually the case, I hardly touched most of them.

Let me say right off that the first problem is that the ‘to-do list’ mentality is not really the appropriate way to describe spending time with my son. I played with him and photographed him and read to him, and the fact that I didn’t get to cross any of these things off a project list is really irrelevant.

But still, it does seem like a whole bunch of time went by without much productive being done. And I think it’s partly because even though I do have some to-do lists made up, I didn’t really plan my vacation.

Planning might seem line anathema for vacations, an unwelcome imposition of order onto what ought to be relaxing, but I’ve come to differ. You must, at some point, plan your time: one way or the other, you’re going to have to figure out what you want to do. At the most inefficient, you can use up your vacation time deciding what to do, and in the end I think I don’t think that ends up very satisfying.

I think our sense of elapsed time–whether a vacation has flown by, or seemed like a good break–is strongly correlated with the number of changes we experience throughout. A “leisurely” day–getting up late, eventually eating and getting dressed, thumbing through the newspaper, and then thinking about what to do, to be followed, perhaps, by actually doing something in the afternoon–does not put one through very many changes, and seems to go by quickly. (This does describe a large number of my eleven days off.)

By contrast, I think of two-day conferences I’ve been to, with separate events in the mornings, afternoons, and evenings–lots of changes–and recall that they usually end up feeling satisfying, or at least, I can’t recall feeling like time flew by with nothing being done.

Planning out vacation time in advance becomes more important if you’re traveling somewhere, because then, your time at your destination is very rare and very expensive. What a waste to spend your time sitting in a hotel room flipping through a guidebook!

When my wife and my mother-in-law and I went to Korea, we did a lot of planning: to know what the bus and train schedules were, and what days the museums we wanted to see were open, and how to get from a hotel to a site of interest. And the planning paid off: we still marvel at how much we saw in ten days. Quite a contrast to this year’s eleven days of holidays.

January 2, 2008   No Comments

Spontaneity on Metro

When asked if the Washington Metro is “safe,” this is how I’ve responded:

Yes, absolutely. Inside the system–on trains and in stations, generally anywhere inside the faregates, the system is safe for everyone at all hours. I even consider the station platform areas to be safe for those stations that are in neighborhoods that tend towards rough. The system was designed and built in the 1970s, and has a much cleaner, space-age, modernist feel than the older systems of New York, Chicago, or Boston. The stations are open and airy, creating far fewer places for hoodlums to hide. Almost all the entrances and exits are supervised at all times by a station manager: there are no cage-like revolving door exits and no lonely staircases framed by rusting steel girders. On the trains, its very rare to encounter a bum or panhandler or street preacher or some sketchy guy selling socks and batteries.

Metro’s first general manager was a retired army general, Jackson Graham, whose military background contributed much to the culture that grew around Metro. Metro is safe and comfortable, and clean and uniform, and slightly dull. There are no abandoned stations or little-known gems or interesting or historic artwork. Metro is straightforward: unlike New Yorkers, who can have endless discussions about the most efficient way to get from one part of Manhattan to another, Metro riders have little lore to learn and share. Riding Metro is, generally, uneventful.

So we were pleasantly surprised today when a talented accordionist boarded our Metro train and played as we rode. Like most Washingtonians, it took me a while to realize how fortunate we were, and what a joyous addition to an otherwise cold and gloomy day his music was. (Read Post columnist Gene Weingarten’s brilliant social experiment, to see how Washingtonians react to a busking Joshua Bell.) (See also the followup discussion, which describes the unimaginative intransigence of Metro in preparations for the experiment.)

The accordionist rode a few stops, by which point I’d lost any unexpected-event-induced grumpiness, and I happily contributed when he came by with his outstretched hat. He was very gracious, smiling at our son and playing a few notes for him. While he was playing, I took a picture.

Accordionist on Metro

December 16, 2007   3 Comments

The time of day

At some point each day, there is a transition between “early in the day” and “late in the day.” If I manage to get something done while it’s still “early in the day,” then I’m happy; if I don’t finish until it’s “late in the day,” then I feel that I’ve spent the entire day on that task and don’t really have much time left to accomplish anything else. This is true whether at home or at work. Of course I hardly ever get things done “early in the day.” 

Presently, I think that the transition point is 2:30pm.

Along similar lines, I think the boundary between “late at night” and “early in the morning” is 3:30am. Or at least now that I’ve left graduate school, I hope never to have to stay up past or wake up before this point. 

November 29, 2007   2 Comments

Magic words

There are magic words in our society, words whose utterance casts a spell over all those who hear them. No, this isn’t about any supernatural hogwash.Two magic words–there may be more–are liability and security. “Liability” has been with us for decades now, but the magical effects of “security” were only discovered post 9/11.When these words are uttered, and the spells cast, those under the spell temporarily lose the ability to think. The usual context is something like this: several people are gathered in a meeting. One of them suggests doing something that would be enlightening, entertaining, or otherwise innovative. Someone else, feeling threatened by this idea, will respond by chanting the spell, along the lines of “What about our liability?” or “that brings up security issues.” At this point, instead of a discussion about the actual potential legal liabilites, or of what, specifically, the security concerns are–it does not matter if there are no genuine experts at either liability or security in the meeting–the idea dies. (I do not wish to imply here that I necessarily believe in the existence of genuine security experts.) The other people at the meeting are under the spell, so great is their fear of being personally responsible for the next multi-million dollar lawsuit, or the next 9/11.I do not know of effective ways to counter these spells: perhaps to call out “Abracadabra” and demand specifics?

November 25, 2007   1 Comment