Five years ago, I announced a popular science book project with Tanya Klowden on the cosmic distance ladder, in which we released a sample draft chapter of the book, covering the “fourth rung” of the ladder, which for us meant the distances to the planets. In the intervening time, a number of unexpected events have slowed down this project significantly; but I am happy to announce that we have completed a second draft chapter, this time on the “seventh rung” of measuring distances across the Milky Way, which required the maturation of the technologies of photography and spectroscopy, as well as the dawn of the era of “big data” in the early twentieth century, as exemplified for instance by the “Harvard computers“.

We welcome feedback of course, and are continuing to work to complete the book despite the various delays. In the mean time, you can check out our instagram account for the project, or the pair of videos that Grant Sanderson (3blue1brown) produced with us on this topic, which I previously blogged about here.

Thanks to Clio Cresswell and Noah Klowden for comments and corrections.