Spherical geometry other geometric concepts are defined as in plane geometry, but with straight lines replaced by great circles. Thus, in spherical geometry, angles are defined between great circles, resulting in a spherical trigonometry that differs from ordinary trigonometry in many respects; for example, the sum of the interior angles of a triangle exceeds 180 degrees. Spherical geometry is "not" elliptic geometry, but is rather a "subset" of elliptic geometry. For example, it shares with that geometry the property that a line has no parallels through a given point. Contrast this with Euclidean geometry, in which a line has one parallel through
Medvedev–Sponheuer–Karnik scale 1980s, the MSK scale became widely used in Europe and the USSR. In early 1990s, the European Seismological Commission (ESC) used many of the principles formulated in the MSK in the development of the European Macroseismic Scale, which is now a "de facto" standard for evaluation of seismic intensity in European countries. MSK-64 is still being used in India, Israel, Russia, and throughout the Commonwealth of Independent States. The Medvedev–Sponheuer–Karnik scale is somewhat similar to the Modified Mercalli (MM) scale used in the United States. The MSK scale has 12 intensity degrees expressed in Roman numerals (to prevent the use