Scientists estimate that about 35,000 other objects, too small to detect with radar but detectable with powerful Earth-based telescopes, are also circling the Earth at an altitude of 200 to 700 miles. This debris poses little danger to us on the Earth. but since it is traveling at average relative speeds of six miles per second, it can severely damage expensive equipment in a collision. The threat was dramatized by a cavity one-eight of an inch in diameter created in a window of a United States space shuttle in 1983. The pit was determined to have been caused by a collision with a speck of paint treveling at a speed of about two to four miles per second.The window had to be replaced.