What if humans were cold-blooded like reptiles? What if the Earth got too close to a black hole? What if the speed of light were only four miles per hour? These are just a few of the questions explored on What the If?, a podcast that envisions science fiction scenarios and uses real science to follow them to their logical conclusion. Launched in 2017, What the If? is hosted by Philip Shane, a documentary filmmaker who also studied astrophysics and engineering, and Matthew Stanley, a professor of the history and philosophy of science at New York University. Each episode imagines a single hypothetical change to the universe, and many episodes are just Shane and Stanley riffing together in bantering conversation about what the consequences of that change might be. The hosts are also frequently joined in their speculations by guests such as science journalist Carl Zimmer, science fiction author Paul McAuley, and theoretical physicist Sean Carroll. Episodes typically range from about 40 to 60 minutes in length. Interested readers can stream What the If? online at the link above, and they can also find it on Apple Podcasts, Google Podcasts, Stitcher, and other platforms.