Here we have a picture of a guy on the summit of a mountain :

The guy in the picture states :
"On the summit of Weisshorn, August 6, 1974 with Matterhorn as a backdrop. The Matterhorn is lower than the Weisshorn, but because of Earth's curvature, it reaches above the horizon as seen from the Weisshorn."
If the earth was flat, then the mountain in the back ground would not be above the horizon.
Can this be explained by the FE theory?