What are the three Han innovations?

The three significant innovations of the Han dynasty include the creation of paper, the development of the seismograph, and advancements in iron casting techniques. Paper, invented by Cai Lun, revolutionized record-keeping and literature. The seismograph, attributed to Zhang Heng, allowed for the detection of earthquakes. Improved iron casting techniques enabled the production of stronger tools and weapons, contributing to agricultural and military advancements.