Anti-de Sitter space bell. It might be described as being the "opposite" of the surface of a sphere, which has a positive curvature. General relativity is a theory of the nature of time, space and gravity in which gravity is a curvature of space and time that results from the presence of matter or energy. Energy and mass are equivalent (as expressed in the equation "E" = "mc"), and space and time can be translated into equivalent units based on the speed of light ("c" in the "E" = "mc" equation). A common analogy involves the way that a dip in a flat
Grumman C-2 Greyhound were ordered under designation "Reprocured C-2A" or C-2A(R). In 2010 all C-2A(R) aircraft received updated propellers (from four to eight blades) and navigational updates (glass cockpit). The C-2 Greyhound, a derivative of the E-2 Hawkeye, shares wings and power plants with the E-2, but has a widened fuselage with a rear loading ramp. The first of two prototypes flew in 1964. After successful testing, Grumman began production of the aircraft in 1965. The C-2 replaced the piston-engined Grumman C-1 Trader in the COD role. The original C-2A aircraft were overhauled to extend their operational life in 1973. Powered by two