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.
The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. The first GPS satellite was launched in 1978. 2  A full constellation of 24 satellites was achieved in 1994. 3  Each satellite is built to last about 10 years. 4  Replacements are constantly being built and launched into orbit.