Just a little perspective, the outermost layer of Earth’s atmosphere known as the exosphere is said to extend up to an altitude of 10,000km above the surface of Earth, while the radius of the earth is only around 6,400km. In that sense, if the exosphere is to be considered the outermost shell of the planet, then most of the earth is hollow, aside from a “core” consisting of the crust down to inner core which we humans can stand on without falling through the atmosphere (on average). The volume of the earth is V = (4π(6400km)^3 )/3 = 1.0868 trillion cubic km, while the volume of the atmosphere extending through the outermost part of the exosphere would be V = (4π(10000km)^3 )/3 - (4π(6400km)^3 )/3 = 3.090724 trillion cubic km, nearly 3 times the volume of the crusty/corey part. Somehow, use that to approximate the entire earth as a point source, and poof, your friend is right!