Encased in a glass container is the world's most precise gyroscope. This 1.5-inch quartz sphere is less than three ten-millionths of an inch from perfect sphericity and is homogenous to within two parts per million. If enlarged to the size of the Earth, the highest peak and lowest valley would be separated by only 16 feet. This gyroscope will enable Gravity Probe B, a NASA mission, to make the most precise test of Einstein's theory of relativity ever attempted.
Image Credit: NASA