I just watched the documentary "Fastball". It's great. It's narrated by Kevin Costner and has major leaguers and HOFers talking about the best fastball pitchers in the game. Lots of good stories and info. Have you ever heard of Steve Dalkowski? The intimidation factor of Gossage and Gibson. The argument between player and scientist about the "rising/riding" 4 seam fastball. The Koufax perfect game. The difference between 92 and 100 is 4.5 feet, but that's all the difference in the world. Lots of great stuff in this doc.
The comparisons between who are considered the best fastball pitchers in each era is interesting. They used army ballistic equipment to measure Big Train Johnson and Bob Feller and have estimated adjustments compared to Aroldis Chapman's best pitch measured at 105.1 MPH at 50 feet.
Walter Johnson 93.8 MPH
Bob Feller 107.6 MPH
But it's Nolan Ryan declared the winner. Nolan regularly gunned over a 100, but adjusted to today's measurements, they're giving his best pitch at 108.5 MPH. Loved watching Nolan pitch, so him getting GOAT made me smile.
This is a really good documentary. History and science make baseball great.