April 4, 2005

Solar Eclipse

Click this image for an expanded view of NASA's map of total solar eclipses, 2001-2025.

April 8 is the first new moon following the spring solstice, which means that solar eclipse season is once again upon us. NASA, as always, has all your eclipse info. U.S. residents are mostly out of luck on this one, although those of you in Texas will get 20-30% eclipsing goodness. If you happened to be in Venezuela or out in the middle of the south Pacific, you'd be treated to a rare hybrid solar eclipse, which begins and ends as an annular eclipse but becomes total in the middle.

Also from this NASA site, I found this map, showing the paths of all solar eclipses predicted between 2001 and 2025. I'll have to be sure to head back to San Antonio for spring break in 2024; looks like the total eclipse path passes right over my home town April 8 of that year. In the meanwhile, I need to come up with a good excuse to be in Turkey next spring. (Incidentally, next year's Africa-Mideast eclipse is the Saros precursor to the 2024 North American one.)

In principle, you can look directly at a total solar eclipse, and it's supposed to be a very beautiful sight. Some care is required, though, because it may seem plenty dark while there's still a small sliver of the Sun's photosphere exposed. Look then and you can console yourself with the knowledge that you're only irreversibly grilling a small part of your retina! Even during totality, though, I'd suggest you wear UV-resistant glasses if you've got them, since the solar corona is much brighter in the ultraviolet portion of the spectrum than in the visible.

You can only look directly at a partial solar eclipse through a solar filter. There's cheap ones to be had, and I trust them about as far as I'd trust a used bargin-basement bike helmet. Aluminized mylar is apparently okay if you don't feel like shelling out for a real filter or some welder's goggles, provided you get the good stuff, but traditional things like smoked glass are next to useless.

For a partial eclipse, I've always been preferential to projection, anyway. As a kid, I'd turn my little potbelly Cassegrain on it's side and point the smallest eyepiece I had at the sun. The barrel of the telescope would then project a big image of the sun onto a wall. I'm not certain that this was necessarily the best way to treat my telescope, but at least it wasn't dangerous to me. In theory you could do with with binoculars, too, except that their ocular lenses are generally fairly large, so I'd be concerned about overheating and cracking something.

The easiest thing though, especially for those of you who don't have a telescope lying around, is just to make a pinhole camera. Fun fact about ray optics: if you have two surfaces, and put a hole in one surface that is much smaller than the distance between the two, light passing through the hole will automatically form an in-focus image on the other side. Practical application here: put a small hole in a piece of cardboard, and you can project the sun onto the ground. Magnification (or the lack thereof) is the key here, as the resulting image will be 9/1000 times the distance from the hole to the image, or just under a centimeter across per meter separation (half an inch per yard).

In fact, nature does this quite nicely on its own. In most parts of the world (and everywhere that this eclipse will be visible, I think) trees will have put on leaves by now. Look underneath; during a partial eclipse the spots of sunlight shining through the leaves will take on a distinct crescent shape. That's because the gaps that the sun does manage to shine through make rather bad, but all-natural, pinhole cameras.

Posted by Milligan at 7:47 PM | Comments (2) | TrackBack

March 25, 2005


Abandoned British munitions dumps stretching across a dusty field near Gaza. If the rains keep up long enough, it might just yield a wheat harvest. 2005:02:19 15:18:44

Astro-Tiyul continued on from Pura to Kibbutz Be'eri and the nearby nature reserve.

An excerpt from the notes I took on the road back home illustrates my impressions:

...fields dotted with raised berms, abandoned ammunition dumps of the British army. The roads also clearly dated back to the Mandate, too. Even older, Byzantine cisterns poked from one hill, near an improbable -- if very small -- waterfall.

I could see Gaza in the distance, faint through dust-bleached sky. I could probably have walked up to the fence.

The Gaza Strip is hardly Mordor, but sometimes it might as well be, spoken of as it is, as a bogeyman land of danger and foes. So this verdant land between the road and the fence, littered with the detrius of old rulers and past wars, has a distinctly Ithilien quality.

Map of Gaza and the northern Negev illustrating Be'eri and Pura. For scale, S'derot is about 10 kilometers from Gaza City.

Even during the supposed "greening" of the desert, the Negev around Gaza is still desolate country. While we found a good deal of grass and flowering near the seasonal streams, the fields in between are a dusty, dry affair. This is an ecologically curious observation, since the Strip is beachfront property. My understanding is that the prevailing winds tend to blow either due east or due west. Farther north, such as around Tel Aviv and Haifa, this means that dry mountain air alternates with Mediterranean moisture, and the ecology is appropriately subtropical. Here in the Negev, though, the changing weather merely switches between Arabian and Sahara dessication. (See here for a map of the wider region.)

The combination of lots of Egyptian tanks and a large Palestinian city kept Israel from conquering Gaza in '48, but it and the Sinai Peninsula fell in the war of '67. Egypt eventually agreed to make nice with Israel in exchange for the peninsula, which was fine by Sharon and company since that had never really been considered part of the Land of Israel. Even so, the howls of protest over uprooting the Sinai settlements apparently bore striking resemblance to today's state of affairs.

A recently planted grove. The straight rows of relatively young trees are dead giveaway. Almost certainly about 50 years old, it would have been planted on the remains of a destroyed Arab village to prevent its former occupants ever returning. 2005:02:19 14:44:33
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February 23, 2005



Click above for an expanded view of this CIA map of the Middle East (Greater Near East, Southwest Asia, whatever you want to call it), from the University of Texas PCL Map Collection.

Over the weekend, journalist Scott Ritter gave a speech asserting that inside sources tell him that the Bush administration has already signed off on plans to bomb Iran in June, and that it manipulated the January elections in Iraq. It would seem that the story has been noticed, since I've seen it on half a dozen web pages and in my email this morning. The folks breathlessly declaring these to be historic revelations need to get a grip, immediately. Though it says something that it's now a notable event for someone stating the obvious to be taken seriously.

So this week's map is presented so as to provide a bit of geographic context to current events.

Sez the article, "Ritter said that U.S. authorities in Iraq had manipulated the results in order to reduce the percentage of the vote received by the United Iraqi Alliance from 56% to 48%." Quite the accomplishment, it would seem, especially after the U.S. bombed the Sunnis into boycotting the election, which undoubtedly boosted the UIA from around 30% to an absolute majority for the Shiites in the Iraqi parliament. Which is a huge setback both to Bush's petroleum cronies and the Iraqi feminists. And Rumsfeld, for that matter, is suddenly quite unlikely to get to keep those permanent bases he so desperately wants. But hey, at least the Iranians won't complain about the outcome. So, nice work there.

I don't know whether Bush has signed off on a particular invasion plan, but I'd be very suprised if the Pentagon hasn't put one together. The DoD, after all, can see the writing on the wall, and they'd like very much to be a bit better prepared for Iran than they were for Iraq. But let us, for a moment, look at the map I posted. Long sea coast, which means that in the event of hostilities a considerable presence in the Gulf would be needed just to keep the fleet marginally safe. And then take note of where all the major Mideastern mountain ranges are. Correct, they pretty much define Iran's borders. No blitzkreig dash from the sea to Tehran, I'm thinking. No wonder Iran has been independent for most of the past 2,600 years. Persia has been called the most defensible territory on the planet. And that was before they had a modern military.

On the other hand, nobody should be in the least suprised if Bush really does have another war in the works. The Iraq war was just about a done deal at this point in the game last time around, and all the signs indicate that the administration's following the same quite successful playbook. We've already got the agitation about links to terrorism -- I'm just waiting for the first Fox anchor to suggest that it was actually the Hizbullah behind 9/11. Then there's the hysteria over Iran's 'nukular' bombs that are, no doubt, just about to start rolling off the assembly line of evil. Some neocons have even gone so far as to trot out the cannard about how shaking things up with a few precision missile strikes will cause the oppressed people rising up against the tyrannical clerics. And in case you hadn't noticed, Israel is once again none too subtley hinting that they'd really, really like Iran out of the way.

Thing is, the facts on the ground are wildly different this time around, so the playbook should probably have been modified to reflect that. For one thing, there's that pesky defensible geography protected by a military that, interestingly enough, hasn't been under embargo for the past decade1. The Europeans are wise(r) to Bush this time around, so America can't expect even the flimsy diplomatic cover that it got in Iraq; there's not so much as a decade-old Security Council resolution that can be spun to authorize a war. Most important, though, is the you-and-what-army? factor. Also stated as, gee golly, our entire army is either tied down in Iraq or recouperating and in no condition to fight elsewhere, and the reserves seem to be running dry pretty fast.

1 Okay, actually the U.S. has had sanctions against Iran for some time, but since nobody in Eurasia, nor even our own Halliburton, seems to have followed suit, let's assume it can buy anything it wants.

Posted by Milligan at 12:08 PM | Comments (0) | TrackBack

February 15, 2005

Map of the Week: The Old City

Click the image for an expanded view of this map of Jerusalem's Old City, Aer Atika. Never mind its efforts at a "vintage" look; this comes from the map they hand out at the Tourist Information Bureau at the Jaffa Gate.

I've always enjoyed poring over a good map. I can tell a good map because, after studying one, I come away with the feeling that I know something about the place depicted, that I have the beginnings of a feeling for what it would be like to be there. A good map invites the eye to an open-ended narrative of exploration, and in so doing distills the notions of Place and Journey.

It may come as no suprise, then, to hear that I've accumulated a fair collection of the things since I left the States. Since this blog is partly about digging into the various forms of locality, and partly about communicating my travels to the folks back home, I think it makes sense to share some of these maps. Let's try weekly.

Today, to add a bit of context to my peregrinations in Jerusalem documented last week, I chose a map of Aer Atika, the Old City of Jerusalem. For a tourist-oriented freebie, it's a suprisingly good one. Notice that the grey boxes between the major roads are meant to represent individual buildings -- not something to be attempted in the average city map. On the other hand, there isn't a whole lot of major construction going on here, so the buildings do mostly stay put. The density is overwhelming, even before taking into account the fact that in reality, many of the buildings are indistinguishably joined by common walls or roofs, and frequently vault across the road on stone archways. Moreover, the main market roads are generally covered by awnings, probably more to keep off the summer heat than the rain.

In theory, cars are only allowed a short way in through the Jaffa Gate, to a parking lot in the Armenian Quarter, and through the Dung Gate to the Western Wall parking lot. Actually, cars seem to penetrate much farther than I would have even thought practical on the narrow and frequently stair-stepped paths, much less allowed. I also note that, in blatant contradiction to my understanding of the posted regulations, this map indicates some kind of parking lot near almost every one of the gates. On the other hand, the vast quantity of goods sold in the Suks must get in somehow. Sure, rugs may sell slowly enough that they could be carried in -- but the dozen lamb carcasses I passed hanging in one shop?

The reason so many roads are stepped is because, not indicated by the map, the Old City is far from flat. In fact, it straddles the flanks of Mount Zion to the south, and Mount Moria (the Temple Mount) to the east, which are both decent sized hills (but far from being mountains, traditional names aside). As a result, the area slopes modestly down into the Muslim Quarter. I would speculate that this is was intentional in the layout established under the Ottomans, as it would give the Muslims the best sources of water. The downside, which I got to witness, is that the area really gets quite soggy when it rains.

If you've read this far, thanks. As your reward, I give you this article from the January 2005 notices of the American Mathematical Society. A brief quote to demonstrate why you should give it a perusal:

Q: What's hot, chunky, and acts on a polygon?
A: Dihedral soup.

Ba-dum-ching. Thanks, I'm here till, oh, whenever. Enjoy the soup.

Posted by Milligan at 11:22 PM | Comments (1) | TrackBack

February 7, 2005

Milligan: 1, Weather: 2

Click above for an expanded view of this road map of central Israel; the route taken by my bus to Jerusalem is highlighted in light blue. The total distance covered from Rehovot to Jerusalem is about 30 km. Just take a moment to really appreciate the settlement density implied by this map.

With my advisor out of the country and the usual Sunday seminar moved to Tuesday, yesterday seemed an ideal opportunity to poke my head up out of Rehovot and survey something. Only having time for a day trip, I decided to take a proper look around the Old City in Jerusalem (i.e. without spending most of my time in shops picking up Christmas gifts). This is absurdly easy to do as, despite Rehovot's diminuitive stature, there are no less than two inter-city bus routes directly connecting the two cities.

The Rehovot central bus station is in the Rehovot mall (every town of more than about 35 people here has a mall), about a 15-minute walk from my dorm. Generally a pleasant walk, especially if breakfast is a pastry from the bakery next door. However, a cold front blew through over the weekend, which in this case meant that it started pouring quite chilly rain about halfway there. Fine, I thought, score 1 for the weather. I put up my hood and figured I'd dry out on the bus.

[Ed. update: lest you think it's just me]

Two fields that are functionally pretty similar except for the time at which the pictures are taken, midway between Rehovot and Jerusalem (probably somewhere near Latrun). Above, a pleasant day in December. 2004:11:28 13:21:02 Below, a thoroughly cold and damp day in February. 2005:02:06 10:48:44

Israel in the rainy season is really quite a different animal from other times of year. See, from early January through sometime in February this curious liquid substance called water tends to fall out of the sky in rather large quantities with some regularity. The plants seem to love this. Not so great for the cats and people caught near the event. (My friend Naomi's advice to Israeli urban planners: "Less cats, more gutters." Very insightful. My nigh-waterproof hiking boots are still drying out from all the flooded streets I crossed.) Later this month we've planned an outing to the Negev (the southern desert), which is evidently in full blossom right about now.

Anyhow, I arrived in the Jerusalem central bus station in a reasonably dry state, and after the usual frisking, wanding, and special to Jerusalem x-raying of my backpack, the lot of us were admitted to the mall to which this bus station is attached. (Pattern, anyone?) I chalked this up as a point in my favor. However, it's worth noting that, based on past experience, since Rehovot was wet and cool, I'd been expecting Jerusalem to be dry and cooler. Not this time. It was raining here too, and cold as well.

The Old City ramparts manage to look decidedly more desolate and windswept -- and thus somehow more Medieval -- when accompanied by rain, fog, and a healthy dose of wind as well. Don't be fooled, though. I'm practically in somebody's back yard taking this shot. This is an actual, functioning Medieval city, and the population density is stupendous. 2005:02:06 12:14:58

Getting to the Old City is a matter of a quick bus ride down Jaffa Street, which I can even do without embarassing myself now that I know how much the bus fare is. The rain didn't stop, but since many of the streets in the Old City are covered, it wasn't all that bad. Although they're not especially well-covered. Sure, the merchandise mostly stays dry, but pedestrians get liberally dripped upon, and the walkways can get quite brookish. Altogether worth it, though. Not just for the sightseeing, which I'll go into in another post, but I should emphasize that genuine Arab falafel not only beats the pants off the weak Israeli stuff, but on a nasty day like yesterday was darn near one of the best things I've ever put in my mouth.

Then, however, the wind picked up and the rain turned to a lovely mix of wet sleet and hail. Observing that my coat was completely soaked through by this point, I declared lack of pneumonia to be the better part of valour, and hailed a cab to take me back to the bus station. Point and match to the weather, I'm afraid.

Pictured here, the Jaffa Gate has been the traditional point of entrance for pilgrims to Jerusalem for a thousand years or so. Archeological evidence indicates that, although the boundaries of the Old City have migrated considerably over the millenia, this particular segment of wall has pretty much always been part of the wall's route, and that there has likewise always been a gate here. The automotive traffic, on the other hand, is a much more recent feature. And might I add, the camera really makes it look more pleasant out than it was. 2005:02:06 12:18:58
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