Doctor, farmer, and peace activist Peter Underwood joins Thirty Love host Carl Bialik to talk about his book The Pros: The Forgotten Era Of Tennis. Underwood explains why tennis took so long to go professional, what motivated pros such as Jack Kramer and Rod Laver to endure tough conditions for small purses, and how today's top men would do as barnstormers. Underwood works with the Medical Association for Prevention of War, the founder of ICAN (the International Campaign Against Nuclear Weapons) and the recipient of the 2017 Nobel Peace Prize. His forthcoming book is a collection of poetry. He lives in Perth and runs a small farm in Denmark, West Australia. Have a suggestion for a Thirty Love guest? Email Carl at bialik@pm.me Music by Lee Rosevere: "Credit Roll" and "Glass Android."