Science & Discovery in the 2nd century

18 sourced entries, 100 CE to 194 CE, oldest first. Also see Science & Discovery across every century or everything else in the 2nd century.

• 100In China, the wheelbarrow makes its first appearance.source
• 104Nijmegen is renamed Ulpia Noviomagus Batavorum.source
• 105Papermaking is refined and officially created by the Chinese eunuch Cai Lun, who receives official praise from the emperor for his methods of making paper from tree bark, hemp, remnant rags, and fish nets. Occasionally, skin from cadavers was also spread as a final layer. Paper had been made in China from the 2nd century BC, but Cai Lun's paper provides a writing surface far superior to pure silk and is much less costly to produce. Bamboo and wooden slips will remain the usual materials for books and scrolls in most of the world for another 200 years, and paper will remain a Chinese secret for 500 years.source
• 120A Kushan ambassadorial contingent visits with Hadrian.source
• 123Chinese scientist Zhang Heng adjusts the calendar to bring it into line with the four seasons.source
• 124Antinous becomes Hadrian's beloved companion on his journeys through the Roman Empire.source
• 130Claudius Ptolemaeus tabulates angles of refraction for several media.source
• 1416th recorded perihelion passage of Halley's Comet.source
• 142The Chinese Taoist alchemist Wei Boyang, author of the Kinship of the Three, is the first to describe an early form of gunpowder solution.source
• 150This is also the approximate date of completion of Ptolemy's monumental work Almagest. The geocentric cosmology contained in it holds sway for 1,400 years.source
• 150Antoninus Liberalis writes a work on mythology (Μεταμορφωσεων Συναγωγη) (approximate date).source
• 156The La Mojarra Stela 1 is produced in Mesoamerica.source
• 161Gaius' Institutiones are published.source
• 179Han dynasty China: The full title of the Nine Chapters on the Mathematical Art appears on two bronze standard measures dated to this year, yet there is speculation that the same book existed beforehand only under different titles. In the 3rd century, Liu Hui would provide commentary on this important early Chinese mathematical treatise.source
• 185A supernova now known as SN 185 is noted by Chinese astronomers in the Astrological Annals of the Houhanshu, making it the earliest recorded supernova.source
• 185Cleomedes discovers the refraction of light by the Earth's atmosphere.source
• 190Cleomedes teaches that the moon does not glow on its own, but rather reflects sunlight.source
• 194Galen writes his manual on pathology, The Art of Curing (approximate date).source