Harry Hotspur, as we know, was celebrated for his embonpoint. And so, preoccupied no doubt by the unpleasant consequences of his own rotundity, he viewed an earthquake as a symptom of dyspepsia on a planetary scale:
Oft the teeming earth,
Is with a kind of colic pinch'd and vex'd
By the imprisoning of an unruly wind
Within her womb; which, for enlargement striving,
Shakes the old bedlam earth and topples down
The steeples and the moss-grown towers.
Nowadays, of course, we know differently. Our planet is encrusted with a fragmented layer of solid rock whose segments, rather like a cracked eggshell, float as a series of plates on the molten "white" beneath. The edges of these plates - which we know as "faults" - define the major earthquake zones.
In some regions the plates slide past each other smoothly without consequence; in others they do so in a kind of "stickslip" motion. Sometimes they may "stick" for several decades - then slip suddenly by several yards to produce, unexpectedly, an earthquake.
Even without the aid of radio or television, scientists around the world would have been able to pinpoint this week's earthquake in Afghanistan with great precision, since distant tremors are detectable with seismographs.
The very first such instrument appears to have been manufactured around AD 130 by a Chinese astronomer called Chang Heng. It consisted of a copper dome fixed firmly to the ground, inside which, delicately balanced, was an inverted pendulum.
Arranged in a circle around the rim of the dome were eight ornamental dragons, each with a copper ball balanced on the tip of its tongue, protruding from its open mouth. And below each dragon, mouth agape, there sat a toad of bronze. This ornate contraption was so arranged that at the slightest jarring, and consequent disturbance of the pendulum, the latter would cause the balls corresponding to the line of the earthquake to fall from the dragon's tongue, into the mouth of the waiting toad below.
In this way, not only the occurrence, but also the approximate direction, of a distant earthquake could be deduced long before messengers from the stricken zone might arrive with tragic news.
Modern seismographs consist, in essence, of a massive block suspended by a spring from a superstructure firmly embedded in the ground.
When the earth shudders, the superstructure shudders with it, but the suspended block - because of its very great inertia - hardly moves at all. The movement of the two parts of the instrument, relative to one other, provides a record of the tremor's progress.