David Morin is a Lecturer and the Associate Director of Undergraduate Studies in the Physics Department at Harvard University. He received his A.B. in mathematics from Brown University and his Ph.D. in theoretical particle physics from Harvard University. He is the author of five books, including Introduction to Classical Mechanics (Cambridge University Press, 2008), Electricity and Magnetism (Cambridge University Press, co-author, 2013), and Probability: For the Enthusiastic Beginner (2016). When not writing textbooks, thinking of physics limericks, or conjuring up new problems whose answers involve e or the golden ratio, he can be found running along the Charles River or hiking in the White Mountains of New Hampshire. Resources for his books, along with other educational material, can be found on his Harvard webpage.