Later, as the months wear on, a series of additional messages arrive from Gerry -- always delivered in the most remarkable and surprising of ways. With each new message comes a new adventure, and each letter signs off in the same familiar way: P.S. I love you..
For a person standing at sea level, however, the horizon is only about 3 miles away. Lets do the calculations. The figure below shows an observer whose eyes are a distance E above sea level. A straight line drawn from the observers eyes tangent to the seas surface touches it at the distance d1, which is the distance to the horizon. If R is the radius of the earth, then, to first order in E/R, it is easy to show that.
If you stand on the beach, your eyes are probably between 5 and 6 feet above the sandy beach (depending on your height). From there you can see about 2.7 miles across the ocean. Now, let's say you go up on a sand dune next to the beach, taking your eyeballs 50 feet into the air. Then, you can see about 8.37 miles across the ocean. Now, let's say that you are staying in a beachfront hotel on the 20th floor, 250 feet above sea level. Then you can see 18.71 miles across the ocean.