In the 1900s, Hungarian physicist Theodore von Kármán determined the boundary to be around 50 miles up, or roughly 80 kilometers above sea level ... at an average height of 240 miles—would ...

The seawall was built after that, to a height of 5.5 meters ... Much of the city stands less than 15 feet above sea level. The waves could inundate nearly everything within roughly a mile of ...