how far can a human standing on the surface of the earth see in the distance
Since there are 360 degrees in a circle, this angle is about is about 1/7930 of the circumference of the circle. And the circle in question, the earth, has an average circumference of 40,041,470 meters. Dividing by 7930 results in 5048.88 meters, or a little over 5 kilometers. Remember, however, that this is based on an assumed height of 2 meters, which is very tall for a human. A shorter person would not be able to see as far; a taller person could see farther. But there are diminishing returns. For example, a 4 meter-tall person can't see twice as far as a 2-meter-tall person, but a 1-meter-tall person can see more than half as far as a 2-meter-tall person. Or...