- Lake Itasca (/aɪˈtæskə/ eye-TASS-kə) is a small glacial lake, approximately 1.8 square miles (4.7 km2; 1,200 acres) in area. Located in southeastern Clearwater County, in the Headwaters area of north central Minnesota, it is notable for being the headwater of the Mississippi River. The lake is in Itasca State Park. It has an average depth of 20 to 35 feet (6.1 to 10.7 m) and is 1,475 feet (450 m) above sea level.
- n-body problem (Wikipedia)
In physics, the n-body problem is the problem of predicting the individual motions of a group of celestial objects interacting with each other gravitationally. Solving this problem has been motivated by the desire to understand the motions of the Sun, Moon, planets, and visible stars. In the 20th century, understanding the dynamics of globular cluster star systems became an important n-body problem. The n-body problem in general relativity is considerably more difficult to solve due to additional factors like time and space distortions.