Shown here refracting a classic image of Einstein himself, is what was, up until 2008, the closest thing to a perfect sphere ever made by humankind.
Crafted from fused quartz (which is made by melting down and further refining high quality quartz crystal, resulting in a much more consistent and pure form of glass than is achieved by standard means), four of these spheres went up in 2004 as components of four gyroscopes on Gravity Probe B, a satellite designed to test Einstein’s theories on the effects that large spinning objects, such as Earth, have on space and time. The precision of the measurements that were to be taken, required each sphere to be engineered to as close to perfection as was possible with technology available at the time. Even advanced high-end gyroscopes used here on Earth are millions of times too inaccurate to perform these kinds of measurements, due to the slightest imperfections in their design and production. The meticulous construction of these spheres, for the most part, overcomes those issues, being near perfectly round to within just forty atoms. This means if you were to scale one up to the size of Earth, the tallest peak would be 2.4m high.
However during 2008, in a bid to redefine how a kilogram is measured, a new standard was set when a number of teams, including CSIRO and the Australian Centre for Precision Optics, crafted spheres of silicon-28 so near perfectly smooth, that if one were scaled up to the size of Earth, the most noticeable imperfections would be slight ripples of about 12 to 15mm. This feat is perhaps only topped in nature by objects like neutron stars or single electrons.