Olvasd el a Stephenson könyv első fejezetét. 

Elolvastam... 

A rövid kivonat; 

„Numerous observations of the Moon, Sun and planets are recorded in ancient and medieval history. These observation – which include many eclipses and lunar and planetary conjunctions – frequently attract the interest of historians of astronomy. If the positions of the Moon and Sun (and to a lesser extent the planets) int he historical past are to be computed with high precision, it is usually necessary to make satisfactory allowance for the effect of variations int he Earth’s rate of rotation, or equivalently, the length of the day (LOD).

Long –term variations int he LOD are mainly produced by lunar and solar tides, but other causes –such  as the continuing rise of land that was glaciated during the last ice-age –are also significant. Although actual changes int he LOD amount to only a few hundredths of a second over several thousend years, the cumulative effect (know as Delta T) of these minute changes can be very large. For instance, the estimated value of Delta T at the epoch 1000 B.C. as much as 7 hours.”