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
C. E. Hooper of the New Yorker depicts a speeding automobile with a radio antenna being overtaken by a Hooper employee in the sidecar of a motorcycle who is shouting "We're from the Hooper Survey, sir. Do you have your radio on, and if so what program are you listening to?" A 1947 radio skit has Henry Morgan and Arnold Stang sarcastically discussing each other's radio shows. Morgan says " . . . by the way, how's your Hooper rating?", to which Stang replies "Wells, it's eh...ehh...aw, that rating doesn't mean a thing...". C. E. Hooper The C. E. Hooper Company was an