A fun tradition among astronomers is trying to include the oldest citation possible in your work, especially in your PhD Thesis/dissertation/viva. I love this, as it helps keep our published history alive. Today I asked Astronomers on Twitter to dig out their PhDs and find their oldest references - I was very impressed with what they reported! My oldest reference was for the Carrington solar storm (1859), but other people's responses were a fascinating walk through history! Twitter thread for "What is your oldest citation?" https://twitter.com/jradavenport/status/1098270382182682627 MUSIC: David Miner https://www.youtube.com/daveminer87 https://ift.tt/2tUfAFu VLOG GEAR: Nikon D7500 Sigma 17-50mm f/2.8 Nikon 70-300mm AF-P VR Takstar SGC-598Be sure to SUBSCRIBE for more videos!