1 Hardness: cubic zirconia has a rating of approximately 8 on Mohs hardness scale vs. a rating of 10 for diamond. 2  Specific gravity: the density of cubic zirconia is about 1.7 times that of diamond. 3  Refractive index: cubic zirconia has a refractive index of 2.15â2.18, compared to a diamond's 2.42.he synthesized material is hard, optically flawless and usually colorless, but may be made in a variety of different colors. It should not be confused with zircon, which is a zirconium silicate (ZrSiO 4).
When GPS service was first made available for civilians in 1983, for national security reasons, the U.S. military decided to scramble the signal, making it a little too inaccurate to be reliable. This practice, also known as selective availability, was aimed at preventing military use of GPS by the enemies.
Originally consisting of 11 orbiting satellites, the GPS--official name NAVSTAR (Navigation System with Timing And Ranging)--was launched by DOD in 1978 strictly for military use. The idea for the system began much, much earlier. The technology of GPS history, however, first emerged in the 1950s. In 1957, Russia launched a satellite (Sputnik) into space. After the launch, MIT researchers noticed that as Sputnik orbited the planet, its radio signal varied in strength.