Edward Carr argues that, as the first tool, the blade opened up a new world bursting with unimagined possibilities ...

From INTELLIGENT LIFE magazine, January/February 2012

Go into the kitchen and find a chopping board, a tomato—not too ripe—and your favourite knife. To be sure that the knife is sharp, run the tip of your finger down the edge and feel it catch the tiny ridges on your skin. Place the tomato on the board and draw the blade across it. At first, you will sense the surface resistance, then a slight give as blade eases through flesh to the board beneath, like the keel of a boat running into the sand.

The stainless-steel blade in your hand barely differs from the sharp-edged flint and obsidian that our ancestors knapped from a core of rock two or three million years ago. The first flints were scrapers and knives for skinning and butchering animals. Larger stones, fixed to wooden handles, served as axes for chopping and adzes for smoothing rough wood. The smallest became arrowheads and spear-tips. From the beginning, technology both brought life and took it away.

The blade is so familiar that we tend to overlook its technical refinement. Pressure equals force divided by area: the thin surface at the cutting edge concentrates moderate forces into extreme pressures. By minimising the area, the teeth of a serrated blade concentrate the force still further. With a blunt knife, you have to exert a large force to make a cut—and you have a squashed tomato. But a sharp one can give us a surgeon’s incision; axes and saws generate enough pressure to slice through trees and rock; fine wires shave off a wafer of silicon for etching integrated circuits. 

Some technologies, like steam-power and the candle, have come and mostly gone. Others have been optional—the Incas, Aztecs and Native Americans got by without the wheel. Only the blade has been with people everywhere and throughout history. In fact, as the first tool, the blade opened a new world bursting with unimagined possibilities—and we are not done exploring them yet. Elegant and enduring, the blade was the breakthrough on which everything else is built.

Edward Carr is editorial director of Intelligent Life and foreign editor of The Economist

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