The Han Dynasty was a time of enormous progress in every area of knowledge and civilization. The travel along the Silk Road to India and beyond both brought new ideas from other cultures and great wealth. The stability of the period allowed attention to be paid to the growth of knowledge and the finer arts with the resources to support these endeavors.

Zhang Heng soaked in the influences from every source and excelled in most fields. In mathematics he estimated the value of π pi as the square root of 10 or 3.1622. He invented a cart to measure lǐ 里, the Chinese mile. (Three Chinese li are roughly equivalent to an English mile.) It was the first odometer.

In his treatise, Líng Xiàn (灵宪 Mystical Laws), he proposed a theory of the universe that compared it to an egg. "The sky is like a hen's egg and is as round as a crossbow pellet. The Earth is like the yolk of the egg, lying alone at the center. The sky is large and the Earth is small." The universe originated from chaos or yuánqì (元气). He said that the sun, moon, and planets were on the inside of the sphere and moved at different rates. He explained lunar eclipses and demonstrated the process with an armillary such as the one shown below. He demonstrated that the moon did not have independent light but that it merely reflected the light from the sun. He showed that lunar eclipses occurred relatively frequently because the moon moved faster within the sphere of the heavens.

China has been plagued by quakes through history. The most recent major quake was the Tangshan earthquake in 1976 measuring 8.2 on the Richter scale. Tangshan is on the north China plane. The quake killed more than a quarter million people. There is frequent activity along the Gansu Corridor, the Shanxi plateau, the Xi'an (Chang'an) area, the Beijing area, and the western and northern edges of the north China plain. In the east, from Shenyang in the north to Nanjing in the south, there are moderately frequent quakes. The western provinces of Sichuan, Yunnan, Tibet, and Xinjiang also have high levels of quake activity. In the south quakes are centered on the Fujian coast and Taiwan. For that reason, China is a major source of earthquake detection and prediction research. Historical records are of great interest to study both the risk level and to look for patterns over time. As part of that research, Feng Rui and Yu Yan-xiang (2006, Institute of Geophysics, China Earthquake Administration) concluded that the earthquake that first set off Zhang Heng's seismograph was magnitude 7 in Longxi with an epicenter at Tianshui on December 13, 134 AD.