Due to the curvature of Earth, assuming a flat plane (such as the ocean), can you tell me the distance to what we see as the horizon?
The distance depends on the height of your eyes. Measure the distance to eye level in feet, multiply by three, divide by two, and take the square root of the answer. The result is the number of miles to the horizon. For example, if your eyes are about six feet above the ground or water level of a flat plane, the horizon is almost three miles away. If your eyes were exactly at ground or water level, there would be no distance at all; the horizon would be directly in front of you.