January 2008 Archives

Cold Biking


Several of you have probably heard me say at some point that I don't bike below -5 °F. This is purely empirical -- I've never successfully biked at lower temperature, because at -5 I could no longer prevent my breath from freezing onto my glasses.

Until today. New personal best: -9 °F. I used a snorkel.

(The new helmet, which has a coverslip to close the vents, also helped. But it was mostly the snorkel, which kept my exhaled air safely behind my head. I probably looked like a steamship trundling down the street.)


I'm about as big a political nerd as you'll find not actually working in a campaign, and I did not watch the State of the Union address last night. I also turned off the radio this morning when NPR was about to replay it. See, I already knew it would be vacuous and asinine. It is a given that it would leave me angry, and needing a shower to rinse off the stupid. Plus this year, as lame ducks go, last Thanksgiving's Tofurkey is getting around better than President Junior.

Also, now we have people like Obama to tell you all you really needed to know about the speech:

(That, and the magic of the amazing TV-replacing intertubes.)

And now, since it's five below and the windchill just broke -20 °F (And oh, c'mon! The sun just set!) and both are falling fast, I'm going to go catch a bus. And only leave the house again if it's actually on fire. Because at least then my front yard would probably be toasty.

Fine, Fine Line

As a postscript, from Elena (who moonlights, or rather daylights, as a code monkey) on coming home from work in a musical mood:

(Sung, obviously, to the tune of "Fine, Fine line" -- sadly the internets have failed me and I cannot find a video of the original to link to. While the sound is somewhat poor, this gives a general idea.)

There's a fine, fine line
between the database, and a mess
There's a fine, fine line
between it's working, and it ain't
And you don't even know until you've taken your break
if it was even worth it to compile
Because there's a fine, fine line
between the code ... and a waste of my time!

Avenue Q

Back in college when I lived in the dorm, my house made a point of mounting the occasional expedition to a concert or a show, as an exercise in both giving us some culture and getting us out of the books for an evening. As my house here seems to be increasingly emulating the best aspects of that old place (the communal cooking being another prime symptom), we've been making sporadic forays to take in live music of various sorts. In our most ambitious outing to date, last weekend we took the State Theater by storm and partook of Avenue Q.

This is the second time I've seen this particular piece of theater (my sister, awesome girl that she is, took me to see it on Broadway a couple of years back when I was visiting her in NYC), and I would say that it holds up well. The roommates all found it hilarious, each seemed to associate a little too well with at least one song1, and I must say that muppet sex is less awkward with roommates than the baby sister.

Last time I was having too much fun with the novelty to give it much deep thought. This time I left with the nagging concern that the message of the show is a bit too pro-status quo for my tastes. In one sense this is understandable: the core audience is post-collegiate but still young enough to remember, or still inhabit, their years of passionate idealism. For them the show is either a poignant reminder, or a helpful warning, of the painful letdowns and compromises involved in navigating from that place into a real, mundane life. A "BA in English" and strong desire to save the world will not, in general or by themselves, go very far towards paying the bills.

However, the uncomfortable feeling remains that, in laying on the theme as thickly as it does (and in resorting to such a blatant deus ex porn-magnate machina to contrive a happy ending), the show winds up over-fertilizing the very attitudes that lead from wry detachment to ironic disengagement to political apathy, social resignation, and voting Republican. That all our troubles (even George Bush) are "only for now" is cold comfort when you're seeding the logic that brings many of them about -- and implying that the best strategy is to just wait them out and make do for yourself. Idealism, in this show, is a fast track to poverty and dejection.

But the major theme of Avenue Q isn't idealism so much as happiness. Here, the old maxim certainly seems to apply that "most people are about as happy as they make up their mind to be." With the caveat that a sufficient run of misfortune will get most anybody down, of course. That said, it's significant that the two characters who are closest to sublime fulfillment at the final curtain are the Republican investment banker (who just adds a modicum of tolerance to his life) and the idealist who is gifted a million bucks to make her vision come true. Otherwise, the surest road to contentment is not to stress about other people too much -- use a little friendly stereotyping to help everyone get along, use other folks' suffering as a pick-me-up, even use your own generosity primarily as an antidepressant.

The loophole in this whole argument, of course, comes back to the audience. Targeted at the generation of irony, it's impossible these days to lay anything on that thick and be taken seriously. With any luck, the remaining idealists in the audience will leave the theater thinking, well fine, but surely I can do better than those losers!

1 Pretty much in the ways you'd expect, too. The Americorp volunteer with boy troubles: "I'm kinda pretty and pretty damn smart / I like romantic things like music and art / ... So why don't I have a boyfriend!? F#*@ it sucks to be me!"

The variably employed artist: "What do you do with a BA in English? / What is my life meant to be? / Four years of college, and plenty of knowledge / have earned me this useless degree!"

The one with the boyfriend who's afraid of commitment and currently in China: "The more you love someone / the more you want to kill him. / The more you love someone / the more you want him dead!"


For a number of years, the Voices in the News segment of NPR's Weekend Edition Sunday has played an outsized role in my thinking -- far beyond what you'd expect from a 2-3 minute audio montage. But it tends to coincide with when I wake up on a typical Sunday morning, and thus is one of the first things I hear when the clock radio snaps on. Lying in bed as that hauntingly simple background music runs, the week's news distilled and juxtaposed into just a few voices from in media res, is like starting out the week by letting the rest of the world just soak in. Just for a moment. (Here's a good example, from last fall. Close your eyes, imagine the sun rising on the first day of the week, and that you've just woken up.)

So it grieves me considerably that since the new year, the segment has gotten, well, lame. I'm guessing a new producer took it over. It's been cut down to only about a minute or so, and typically features a narrow category of clips, typically political soundbites. This week it was a sentence or so from each of the three nominal winners of Saturday's primary contests. Worse, last week it was predictable and bumbling snippets from Bush's speech in the United Arab Emirates. Perhaps fortunately, it's also been moved to the beginning of the second hour of Weekend Edition instead of the first, so it's no longer the first thing I hear. But I'm sad not to have that anymore, and I really hope it goes back to something closer to what it was.

A Cosmic Focus Knob


There's a general problem in astronomy, which is that we almost totally lack depth perception. This is not to say that we don't know the distances to things, for we frequently do. That's what the cosmic distance ladder is for. However, except for quite nearby things, for which parallax measurements can be done, you're quite some ways up the ladder and you often have only approximate distances only for certain types of objects.

Case in point, at some journal club talk last year a number of interesting conclusions hinged on whether a chunk of radio emission was coming from a particular galaxy however many Megaparsecs distant, or else was far in front of or behind it. For the galaxy, the distance is reasonably well known (certainly via the cosmological redshift, possibly via other means as well). For the radio emission, not so much. It was a continuum source, which means there were no spectral lines to give a redshift, and it wasn't a galaxy, which rules out most of the other higher rungs of the distance ladder.

With present techniques, the Magellanic Clouds are the only galaxies for which one could really conceive of getting parallax measurements. This would have to be done using long-baseline interferometry of radio point sources, of course, using something like the VLBA. The limit is set by the angular resolution of your instrument, since the parallax is nothing more than measuring a (tiny) angle on the sky. For the VLBA, observing at 10 cm from stations around 10,000 km apart, you can get about a milli-arcsecond. Using the Earth's orbit as your separation, that gets you out to a few kiloparsecs.

What could you conceive of building, anyway? If you want a super-long baseline, you need to stick to radio techniques, where you record the waveforms and feed them into a correlator elsewhere. Electronics are getting better, so I can imagine that working up to several hundred GHz, so millimeter waves. We're pretty good at chucking things into solar orbits, and at powering things off solar energy at Earth-like distances from the sun, too. So I can conceive of building a millimeter wavelength interferometer array with a baseline of a couple of AU. And that gets you to about a nanoarcsecond. With this kind of resolution, you could just resolve a penny held up to the sun by an astronaut at Saturn. (Or, someone else with this telescope could see the city lights of Earth from halfway across the Galaxy.)

If you consider that the Solar System moves at about 220 km/s around the galactic center, if you're willing to wait a year as with traditional parallaxes, you get a baseline of 50 AU or so. In principle, you can then measure a parallax out to basically the edge of the universe, 50 Gigaparsecs or so, although you'll have trouble defining a fixed background if you do that. However, this probably wouldn't help with the sort of diffuse source that I started out discussing.

I often wonder if this would work. Measure distance by defocusing an interferometer. By this I mean, interferometric correlators work on the assumption that the incoming wavefronts are flat. The constant-phase surface of a radio signal leaving a point source is actually a sphere (usually), but at a distance of light years, you don't especially care. But I guarantee that you have seen this effect before.

Turn the focus knob of a pair of binoculars, or one of those old cameras that actually made you focus it yourself. Objects at one distance will appear crisply, while objects in the foreground and background become fuzzy. The optics of the focus mechanism are compensating for a specific amount of this wavefront curvature. You would be correct in imagining that this could be used to measure distance, but only out to a certain maximum.

If you push the focus knob all the way to one end, generally marked as "infinity", then everything beyond some distant point will be in focus. Past that is the far field of your device, beyond which the wavefront curvature doesn't matter, and because of which nobody worries about depth of field when photographing landscapes or nebulae. The far field distance is roughly the square of your aperture size divided by wavelength. For your binoculars (3 cm, 550 nm) it's a kilometer or so. For the VLBA (10,000 km, 10 cm) this is about a tenth of a light year, but for our really ambitious yet conceivable telescope (2 AU, 1 mm) this becomes a few Gigaparsecs.

Now, I think an algorithm based on this technique would probably work, even on the diffuse cloud discussed above. You just have to adjust the depth of field until the cloud is at its smallest. You also wouldn't need a fixed background against which to compare (usually distant quasars today, but they probably wouldn't be distant enough for this kind of work). Now, it's rather complex to make a good interferometric image of a spread-out thing, but my understanding is that it's possible. Maybe some of the radio astronomers reading this will set me straight if not.

Arrow of Time

Yesterday, Jess took and ran with my analogy between extreme cold and radiation. (Although I think that entry is locked, so not everyone will be able to see it.) At one point she says, "the Second Law of Thermodynamics, the law of increase of entropy that, in a way, defines the direction of time for the universe...".

This refers to the open question regarding why time appears to flow in one direction only, often called the Arrow of Time Problem. One of my old cosmology profs is now out in California, blogging and thinking about the Arrow of Time. Probably not in that order. But Jess' post reminded me of a recent post of his, an Arrow of Time FAQ.

Not Brrr -- Ouch


The thermometer outside my window read -1°F when I started getting dressed, and the weather pages said it was two degrees warmer than that when I got to the lab. Not far from my house, there's a section of sidewalk that got covered in slush during the thaw, which is now frozen into a rock hard uneven and cratered moonscape. Biking over it this morning, I figured I'm pretty much just an air tank away from riding on the surface of Europa. (No, I don't generally bike on sidewalks; this is the sidewalk that runs in front of my house, which I take for a block when there's too much frozen muck plowed up in the driveway.)

It occurred to me that this is why Arctic cultures have umpteen words for things like cold, and snow. Because what it is outside just now, is a completely different thing than what I grew up calling "cold." Cold was when you put on thick socks and a jacket before going to school, when you could see your breath and if you stood around outside too long you'd start to shiver. Biking on a sunny subzero day there's no danger of shivering if you're dressed at all appropriately (which is to say, a bit like an astronaut). Outside the cold is like a form of radiation that you must shield yourself against. Choosing what to wear becomes a tradeoff between the ability to see and the fact that your face will hurt when you arrive from exposure to the outside, the ability to operate brake levers versus fingertips that will be red and stinging as though scalded.

Tomorrow it will be even colder, and if I go out I'll take my chances with the brakes, and wear the big warm gauntlets.


The trouble with the sort of experimental science that I do is that you tend to go a while between publications. The vast majority of your time being consumed by, for instance, making sure that your telescope doesn't turn right in response to a command to go up. (So far as I know, it doesn't.) This is in marked contrast to my observer friends down the hall, who appear to spend more time trying to corral their results into papers than they do actually obtaining said results. On the third hand, I have no clear idea of how exactly the theorists upstairs spend their days, except that it seems to involve more coffee than the rest of us put together.

Point being, last year I successfully scored another paper, which came out this month. By all means check out the January issue of Applied Optics if you're into that sort of thing. Here's the abstract, with the full PDF text available from there as well.

"Comparison of the crossed and the Gregorian Mizuguchi-Dragone for wide-field millimeter-wave astronomy" by H. Tran, A. Lee, S. Hanany, M. Milligan, and T. Renbarger grew out of some work I was involved in a couple of years back when we were hammering out the optical design for the EBEX telescope. We found that a wide swath of the design space could be collapsed down to a choice between two different classes of telescope geometry, and that the pros and cons of that choice weren't well understood, at least for millimeter-waves. These frequencies roughly straddle the worlds of radio astronomy (where telescopes are designed using well understood principles of antenna physics) and optical astronomy (which relies upon the similarly well understood field of optics). As a result, to really understand the trade-offs, we needed to consider both worlds. Add to that the fact that we're interested in really high-precision polarization measurements, which is considered a rather quirky subfield on its own. Then it's easy to understand how we'd stumbled onto a problem that had barely been considered before, but has become quite important in recent years as the significance to cosmology of the polarization of the CMB has been recognized, and numerous teams have joined the race to observe it.

New Year

I suppose global warming can mostly be said to be rendering Minnesota more habitable. Still, it was pretty weird spending yesterday morning slogging around in ankle-deep ice water trying to clear melting slush from the walks. With limited success, I should note: you could definitely ice skate in the breezeway beside my house.

While it's maybe a little late for new year's memes, since I've been doing this one for a couple of years now, I feel like keeping up the tradition.

So, to summarize EGAD's year, in 2007 I published 108 posts, a little under half of which were categorized as Narrative (then, in descending order, Politics, Science, and Entrances to the Labyrinth). EGAD got 15,308 hits, probably one-third of which was my dozen or so regular readers. Most of the rest came from Google. For most of the year, the top draw appears to have been my maps and photographs from the trip to the Sinai back in 2005, but starting in November I started getting a lot of visitors looking for information about Comet Holmes. The internets at large continue to care not one whit about my musings on grad student life, politics, or science. That's pretty unsurprising, as Jorge Cham takes care of the first, and there's whole blogospheres devoted to the latter two.

And as for every year, here we have the first and last sentence of each month of 2007:


... I apparently was on blog-vacation all month.


First: Groundhog Day... ...is as good a day as any to bring my blog-vacation to a close.
Last: Via Pandagon, because cows with guns are catchy:


First: So it looks like the Duluth zoo's porcupine was right -- here we are in our fourth week of rather conspicuous winter since the conflicting predictions of Groundhog's Day.
Last: In an effort to keep you folks up-to-date, let's assume a couple-posts-per-week schedule for now while things percolate.


First: I am, however, amused by the fact that the United States Postal Service webpage now has a "Star Wars Experience" on/off button.
Last: The list also includes a bunch of medieval European inns and breweries, which pretty much tells you all you need to know about Europe.


First: I was probably six or eight when I picked up Azimov's Foundation trilogy.
Last:: Just a quick question to brighten your Sunday morning: does it invoke Godwin's Law to point out that the Bush administration is actually lifting its doublespeak from the Gestapo?


First: Collaborators leave town tomorrow; then I rejoin the outside world.
Last: Okay, I'll go to bed now.


First: Life with the CSA has been an adventure so far -- you don't realize the degree to which laziness nudges variety out of your diet until you're confronted with eating from a box full of whatever happens to be ripe this week.
Last: And finally, I would be remiss if I failed to cite the newly-discovered Cheney Superposition (via Dean)


First: So first of all, I was nowhere near the bridge.
Last: Best of luck to Sean Fritz and Tim McQuillan; I think the next few months will be very interesting for them.


First: Friday night I was out at O'Brien running a Universe in the Park event, and throughout the evening I and the attendees kept noticing a highly unusual number of bright meteors in the sky.
Last: I also learned some trivia about brown eggs.


First: No, I haven't abandoned the blog.
Last: Since we've got clear skies here, I plan to take the telescope for another spin, even despite the cold I'm battling.


First: It's Guy Fawkes, er ... Counterterrorism Day.
Last: Which might explain why I enjoy cranking up the old refractor and fiddling around until I can take acceptable photos with whatever cheap equipment I have handy. It's just fun.


First: First of December, and right on cue it's snowing.
Last: I'll be here in Texas, thawing out, for the next week.

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