 I love old books. I've shown this book on the vlog before. This is a turn of the century, I think first published in 1900, introductory astronomy book. And what I love about it is it's just mostly geometry. It's really simple. And I just love the graphics. Like I don't know if you can see that. Look at these things. One of the fun nerdy things people do when they write their thesis is try to see what the oldest citation they can include is. Now astronomy has been around for a long time, like maybe for all of time. So it's impossible to have read all of the literature. In fact it's impossible to just read all the literature that's coming out right now. Too many papers are being published every month for me to read any appreciable fraction of them. It's super important to read and super important to read old things because so many times the idea you think is fresh and new has been done. And that's okay. It's often okay to redo an idea. Okay I don't have a physical copy of my PhD thesis. I printed at like 50 bucks a pop. I printed like eight copies but I gave them all to like family members and my grandparents and my advisor however. I have a copy of my advisor's thesis which is actually really awesome. Turning to the future work section from 30 years ago it is fun to see how many of these things came true. The oldest citation is 1949. So 40 years before this thesis was published. Not bad. One thing we have in astronomy which makes this whole endeavor a lot easier now is ADS or the Astrophysics Data System. This is like a search engine just for astronomy, primarily for astronomy and physics papers. But it makes searching for these old papers really easy. Look at this. 1600 to 1700. That's nothing. It's so easy to search by year. A lot of interesting names are in here. Rahe, Kama, Tico, Kepler, Galileo, sandwich, Kama, Earl of, I like it, Halley, Huygens, Cassini. I think this one is kind of amusing. Picard, Kama, Jean. When I look through my thesis the oldest citation is Carrington, 1859. That's for the famous Carrington Solar Storm. So it becomes really easy to include these old citations which I think is fun. It helps the literature live. Okay so I asked astronomers on Twitter what the oldest citation in their thesis was. Let's just like look at some of the answers here. Dr. Victoria Greenberg says Roche, 1849. Nice. I like that. Oh, interesting. Oh, interesting. Joey Rodriguez says he's cited work as far back as 1890 thanks to Dash. Keaton Bell says von Zeipel, 1924. That's pretty good. James Paul Mason says Pearson, 1895. Ashley Pagnata says Levin Pickering, 1913. Awesome, awesome. And then Schaunders-Sakar, 1931. Schaunders-Sakar did everything. So my friend Brett Morris who's writing his thesis right now, right now is the current winner with Copernicus 1543 for the Copernican principle and Galileo 1613 for the first observations of sound spots. Some more good ones here, okay. Helen Johnson says Galileo 1610, Milky Way being made up of stars. That's a good citation. Here's one for Hipparchus, 160 BC, but I doubt that's an ADS. One from Stine Sigurdsson says Michael, 1767, arguing that some stars must be binaries based on statistical excesses of close pairs. That's a cool one. Oh, and Chris Lintot, Bessel, 1844 on the variation of proper motions of Procyon and Sirius. That's cool. Oh, okay. This one might be my favorite. Molnart Laszloh says Captain 1890, discovery of variable stars which turn out to be R. L. I. Ray. He says, follow closely by Bailey 1899 and beautiful hand-drawn light curves. Oh, those are cool. I'm going to include this figure. Jason Wright, Galileo 1613 for the sound spot records prior to the Monderminim. Laura Maiorga says Mueller 1893, pretty good. But it's in German and she knows that she technically hasn't read it. I think that's true for a lot of people that these are fun citations that we haven't actually read them. Though I will say I have actually read my oldest citation. These are awesome. Thank you to everybody who participated in this Twitter thread. I'll link the original Twitter thread below. And if you have one from your PhD, go at it. This is really fun. Okay. And besides like weird flexing about how esoteric your citations can be, what's the point? Science in many ways is the literature. Really? And I've said this so many times on this channel. Science is people. But we move on. We die. New generations of scientists come up. And if we don't write it down, then what did we do? In many ways, the literature is science. It is astronomy. By including these old citations in our work, by reflecting on the past, I think in some ways we keep this work alive. It's impossible to look at all of the old work and it's impossible to know every corner of the literature. But by including some of these citations, it helps people go back. It helps us reflect. It helps us relearn what's been known. I think that's important. That to me seems like an important part of science.