Most spherical manmade object

According to Official Guinness Records,

The most perfect manmade spheres constructed to date are the fused solid quartz gyroscopic rotors built for NASA's Gravity Probe B spacecraft. There are four spheres onboard, each measuring 3.81 cm (1.5 in) across. Their average departure from mathematically perfect sphericity is 1.8 X10-7 of the diameter. This means that, if scaled up to the size of the Earth, the maximum height/depth of topographic features would be 1.5 m (4.92 ft). Gravity Probe B was launched on 20 April 2004 and will spend 16 months testing Albert Einstein's General Theory of Relativity.

For a complete list of 2004 records, please visit 2004 Guinness Records in United States.

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