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.
Bathymetric map showing a global view of the mid-ocean ridge (MOR). The mid-ocean ridge wraps around the globe for more than 65,000 km like the seam of a baseball, with an average depth to the ridge crest of 2500 m. Click image for larger view and image credit.he mid-ocean ridge wraps around the globe for more than 65,000 km like the seam of a baseball. The average depth to the crest (top) of the ridge is 2500 m, but it rises above sea-level in Iceland and is more than 4000 m deep in the Cayman Trough.