Map showing the expansion of Han dynasty in the 2nd century BC

Rome and Han China were the two biggest empires on the planet at the same time. Together they ruled something like half the people alive. And for about 200 years they knew each other almost entirely through rumors, middlemen, and one fabric. The Romans called the Chinese the "Seres," the silk people. Nobody in Rome had any idea how silk was made. Virgil and Pliny the Elder both wrote that it was combed off the leaves of trees. What Romans did know was that they wanted it. Silk got so fashionable that in 14 AD the Senate banned men from wearing it because it was seen as effeminate. Seneca complained that silk dresses were so sheer a woman wearing one might as well be naked. Pliny griped that India, China, and Arabia were draining 100 million sesterces a year out of the empire for luxuries. The Chinese, meanwhile, called Rome "Daqin," roughly "Great Qin." The Han histories said its people were tall and upright and resembled the Chinese, which is how it got the name. They described 400 walled cities, stone buildings, relay stations for messengers, and gold and silver coins. They also got some things beautifully wrong. One Chinese account says the king of Daqin is not permanent. Worthy men are chosen to rule, and if there's a disaster or bad weather, the king is replaced, and the one removed accepts it without complaint. Somewhere in there is a garbled echo of Roman politics passed down through a dozen translators. In 97 AD the Han general Ban Chao sent an envoy named Gan Ying west to actually find Rome. He made it as far as the coast of the Persian Gulf. There, Parthian sailors told him the voyage could take up to two years, that crews packed three years of supplies, and that men at sea got so homesick some of them died. Gan Ying turned around. The Chinese later figured out why. Their own history says the Parthians wanted to control the silk trade and deliberately blocked contact between the two empires. The middlemen had every reason to make the ocean sound terrifying. It took until 166 AD for someone to get through. A group arrived at the Han court by sea, through what is now Vietnam, claiming to be sent by "Andun," almost certainly Emperor Marcus Aurelius Antoninus. They brought ivory, rhino horn, and tortoiseshell. The Chinese historians noted there were no jewels at all and suspected the stories about Daqin's wealth had been exaggerated. Most historians today think these "ambassadors" were enterprising merchants. And no, a lost Roman legion from the Battle of Carrhae did not end up founding a town in China. That theory was popular for decades, but DNA studies of the people of Liqian found no Roman ancestry. Two superpowers, roughly 5,000 miles apart, each one sure the other was fabulously rich and a little bit strange. One envoy got close enough to smell the ocean and got talked out of it.