Many of you will have come across the 'birthday puzzle' that went viral this week:
Proving that philosophical logicians can make real contributions to serious, societal problems, my colleague Barteld Kooi has made a video where he explains how the puzzle can be solved with the help of dynamic epistemic logic. (Barteld is one of the most prominent researchers working in the field -- in particular, he is one of the authors of Dynamic Epistemic Logic (2008) and one of the editors of the much more reasonably priced Handbook of Epistemic Logic (2015).) Here is the video:
Moreover, logician and ninja-woman Audrey Yap of University of Victoria has also provided a solution to the puzzle using similar tools, which is represented in a series of pictures; the series can be found in this post by Richard Zach.
Homework for M-Phi readers (please comment below for your answers): how are the two solutions, Barteld's and Audrey's, related? Are they similar, are they different? If different, how so? Let us know!