Standing on a flat plateau, you look ahead toward the horizon. You strain your eyes, then take out your favorite binoculars and stare through them, as far as your eyes (with the help of the binocular lenses) can see.
Next, climb up the closest treeโthe higher the better, just be careful not to drop those binoculars and break their lenses. Then look again, strain your eyes, and stare through the binoculars out to the horizon.
The higher up you climb, the farther you will see. Usually, we tend to relate this to Earthly obstaclesโlike the fact we have houses or other trees obstructing our vision on the ground, and climbing upwards we have a clear viewโbut thatโs not the true reason. Even if you stood on a completely clear plateau with no obstacles between you and the horizon, you would see much farther from the greater height than you would on the ground.
This phenomenon is caused by the curvature of the Earth as well, and would not happen if the Earth was flat:
