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We have been talking about planned cities of the past and of the future. Almost every urban culture in history has fantasized about how to make cities better, and some civilizations have actually put these ideas into practice (or tried to do so). But when it comes to crafting cities in the mind and then actually building them in the real world, nobody rivals China. From the 12th century BC through the present, the world’s most populous city has, more often than not, been Chinese. Densely populated urban environments are a defining feature of Han culture. And during all that time, strong central authority and hierarchical planning of all aspects of society has been an equally prominent aspect of Chinese civilization.
As you might imagine, such a mixture has left a long history in Chinese letters. The Kao Gongji (Kao Gong Ji) was written in the late Spring and Autumn period around 500 BC (although the oldest surviving copy only dates to 1235 AD). The book generalizes about may different sorts of practical skills and trades, but it reserves special attention for how princes should build their capitals.
The style of these ruling cities is as imperious as you would imagine: The Kao Gongji dictates a walled palace/administrative nucleus in the center of a large capital city. This pattern was common in many early states particularly in southern China.
To quote the book directly:
“When the builder constructs the capital, the city should be a fang (a four-sided orthogonal shape) nine li on each side with three gates each. Within the city are nine longitudinal and nine latitudinal streets, each of them 9 carriages wide. On the left (i.e. east) is the Ancestral Temple, on the right (west) are the Altars of Soil and Grain, in front is the Hall of Audience and behind the markets.”
This idea (which literally placed the king/emperor squarely at the center of all aspects of society) was put into practice in the ancient capital of Luoyi, and it manifested again and again in the layout of China’s other capitals. Indeed, although the Mongols and the Qing had moved beyond such rudimentary urban plans, the fundamental concept is even present in Beijing.
Hey, remember the super-massive black hole at the center of the galaxy? Well, scientists have been thinking about it too, and they concluded that other black holes should sink into the middle of the galaxy near to the central monster. To find out if this holds true, they utilized the Chandra X-Ray Observatory (an x-ray telescope located on a satellite in orbit around Earth) to observe stars near to the center of the galaxy. Black holes can’t be detected on their own, but if they interact with nearby stars they produce esoteric x-rays which can be detected (so long as the x-ray telescope is outside of a planetary atmosphere, which absorbs x-rays, thank goodness). Within the tiny (er, relatively tiny) three light year area which they scrutinized, the astronomers discovered dozens of black holes. Extrapolating this data leads them to conclude there are more than 10,000 black holes at the center of our galaxy. I wish I could contextualize this for you, but I just can’t… the concept of 10,000 super-dense gravity wells flattening and tearing all of the spacetime in the center of the galaxy into Swiss cheese is to disturbing for me to deal with (in any other way than blurting it out in a midnight blog). I’m not sure this universe is safe at all. I am going to go lie down.

The constellation Sagittarius (from “Urania’s Mirror” a set of constellation cards published in England circa 1825)
My apologies for the blogging break last week. Usually I try to write a new post every weekday, but last week was a blogging holiday. To reinvigorate things after the lost week, let’s turn to a big subject—in fact a super-massive subject! Long ago, Ferrebeekeeper featured a post about Eta Carinae, a blue hypergiant with a hundred times the mass of the sun (which is itself a million times more massive than Earth). Stars like Eta Carinae are rarely formed and short lived—there are probably less than a dozen in our galaxy. However compared to the most massive object in the galaxy, Eta Carinae is puny and common. Twenty six thousand light years away from the solar system there exists a truly monstrous space object!
In 1974, Astronomers discovered an astronomical feature which was emitting exotic radio waves in the Sagittarius constellation. The scientists named the feature “Sagittarius A” and set out to determine what it was. Part of the feature seems to be the remnants of a star which had gone supernova. A second part of the feature is a cloud of ionized gas surrounded by an even larger torus of molecular gas. In the middle of Sagittarius A is something which is emitting most of the high energy electromagnetic radiation visible to radio telescopes. The cloud of ionized gas seems to be emptying into it and nearby stars orbit it with greater velocity than stars move anywhere else in the galaxy (in fact the object affects the proper motion of thousands of nearby stars). And yet the space object at the center of Sagittarius A has a diameter of only 44 million kilometers–a bit less than the distance between the middle of the sun and Mercury at its perihelion (when the rocky planet is closest to the sun). By calculating the proper motion of thousands of nearby stars, scientists determined that the mysterious object at the center of Sagittarius A (which they took to calling Sagitarrius A*) has mass of 4.31 million suns (i.e. solar masses). Whatever lies at the center of Sagittarius A–which I probably should have mentioned, is also the center of the Milky Way Galaxy–is smaller in volume than a large star, but has a mass which exceeds by many orders of magnitude even exotic hypergiants like Eta Carina.
Of course the only kinds of discrete objects which we know (or even hypothesize) to be capable of attaining such mass are black holes. It is believed that most (indeed probably all) galaxies have super-massive black hole at their centers. Smaller galaxies have small super massive black holes (forgive the oxymoron) but large galaxies have immense central black holes which can equal billions of solar masses. Radio astronomers have observed plumes of exotic electromagnetic radiation coming from the center of other galaxies, and they wondered where the Milky Way’s galactic center was located. It seems that a supernova near the galactic center blew away a great deal of the dust and gas on which the black hole would otherwise “feed” thereby making the galactic center of the Milky Way less energetic than the active center of farther (e.g. older) galaxies.
The super massive black holes which lie at the center of galaxies may be a result of the accretion of matter around stellar-sized black holes (which could grow quickly in matter-rich galactic cores) but most astrophysicists believe they are instead a primordial feature of the Big Bang around which galaxies themselves coalesced. The ultimate nature of super massive black holes remains unknown and seems to be tied to the nature and shape of our universe.