A brood comb

….philosophical and other notes….

How To Impress Girls If You Have A Time Machine

Posted by Tanas Gjorgoski on June 27, 2007

I was reading the paper What lies beneath? Understanding the limits of understanding by Keil, F.C., Rozenblit, L.R. and Mills, C. the other day. In that work the authors analyze the phenomenon of “illusion of explanatory depth” – the phenomenon where people usually overestimate their knowledge of how things work. The whole paper is interesting, but I thought that the following part was quite interesting and thought provoking on its own:

One way to get a sense of people’s limitations is to consider how much they underestimate the work involved in construction and design of everyday devices This error is vividly demonstrated by the popularity of various novels about people transported back in time (or to a primitive planet) who then proceed to re-create much of the technology of their own civilization in situ. The original instance of this plot device, quite familiar to readers of the science fiction genre, can be found in Mark Twain’s classic novel A Connecticut Yankee in King Arthur’s Court. These stories of individuals single-handedly rebuilding high technology are engaging, but they are almost always utterly implausible to anyone who has a sense of the intense division of labor (including cognitive labor) on which a technological civilization depends. The history of technological progress and the individual experience of those of us who have tried their hand at design show that development from concept to prototype takes an enormous amount of trial and error.

Consider gunpowder, for example. How likely is is that an average citizen of 2004, thrust into a low-technology world, would be able to reinvent gunpowder as a propellant for cannon balls? The process of making gunpowder itself seems easy enough on the surface. Many of us have learned in high school chemistry that it is made by mixing carbon, sulfur and saltpeter in the right proportions. Even if we do not remember the correct proportions for rapid-burning black powder (75% saltpeter; 14% carbon; and 11% sulfur), the ratios seem easy enough to derive through some elementary experimentation. Ignore, for the moment, and difficulties we might have in figuring out how to obtain the ingredients (how many of us know what saltpeter is, let alone where we might find it?). Also ignore the considerable problems of constructing cannon barrels strong enough to contain an explosion, of devising a reliable firing mechanism, and of making cannon balls of appropriate size, weight, and composition. Consider only the problems of making gunpowder function as a propellant for cannon balls.

History gives some clues as to how difficult the problem really is. The formula though well known to the Chinese since at least the tenth century, did not arrive in Europe until the early fourteenth century. The first cannons, however were quite ineffective as siege devices (their primary use for the next 300 years), compared to the advanced trebuchet catapults of the period, and were even less effective on the battlefield. Indeed, gunpowder-propelled cannon balls would not become central to European warfare until the early sixteenth century.

Obviously, knowing the formula for gunpowder does not translate into a decisive military advantage in any direct sense. One problem is that simply mixing the components of the high school chemistry gunpowder formula produces an inefficient and unpredictable propellant, “serpentine” black powder, which tends to separate into its constituent parts during transportation Nearly 200 years of development passed before gunpowder became a sufficiently effective propellant for cannons to compete with catapults. A key insight was that wetting the gunpowder, then drying it into cakes, which were then granulated ,produced several desirable properties. Granulated or “corned” gunpowder is much more stable and produces a substantially more powerful propulsive force. More importantly, by controlling the size of the granules, the manufacturer could control the burn rate, and produce different powder for different-sized cannons.

Granulated gunpowder powder, when combined with advanced in cannon manufacturing (e.g., the development of blast furnaces permitted casting of iron cannons) enabled artillery to destroy standing walls, thus changing the face of European warfare at the very end of the fifteenth century. Further advances in cannon design made gunpowder the central force on the battlefield by the early sixteenth century. But how many time travelers, armed with the high school chemistry formula, would be able to re-create the 200 years of research and development in their lifetimes? we would venture, “Not many”.

So keep a copy of this page handy! You can never know when time-travel vortex will suck you in, or have the mad scientist neighbor invite you to try his time-travel machine.


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