How far is the horizon, if a $r=2 m$ tall man watches to the sea?
I have calculated that it would be even just about 6 km. if R = radius of earth( $6370 \cdot10^3$ m ). By pythagorean theorem we get. $(r+R)^2 = x^2 + R^2$ => $\sqrt((r+R)^2 - R^2) = \sqrt((2+6370 \cdot 10^3)^2 - (6370x10^3)^2) = 5048$ m ~ $5$ km = x Is this right?