What a nonsense.
1. When was the last time this Doctor of Philosophy looked up in the sky and found a non spherical planet?
2. All spheres objects have a curvature.
3. When you travel on land tall buildings are not visible until you reach within a certain distance from them. (This phenomena is more visible in sea voyages). The earth curves out of sight at a distance of over 3 miles.
4. One can literally go around the world by travelling in one direction.