The Hubble Space Telescope, viewed by many scientists as perhaps the most valuable scientific instrument ever developed, is about to complete its 100,000th orbit of the Earth, which will bring its total mileage to 2.72 billion miles. The HST was launched on April 24, 1990, and has been sailing through space about 380 miles overhead at a pace of just less than five miles per second ever since. In celebration of the 100,000 orbit mark, which happened at 7:42 a.m. EDT on August 11, the Space Telescope Science Institute in Baltimore calculated that 2.72 billion miles is the equivalent of 5,700 round trips to the moon. It is also, according to STSI, the number of miles that will be driven by vehicles in the U.S. every three hours. The Hubble, they note, uses gravity, not fuel, to move through space.