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.
GPS Master Plan. The launch of the 24th block II satellite in March of 1994 completed the GPS constellation. Four additional satellites are in reserve to be launched on need. The spacings of the satellites are arranged so that a minimum of five satellites are in view from every point on the globe. On the ground all GPS receivers have an almanac programmed into their computers that tells them where in the sky each satellite is, moment by moment.