@johncarlosbaez

This reminds me of Gravity Probe B, which was (for its time) a similarly awe-inspiring piece of engineering — they had to craft two spheres that were, back then, the smoothest objects humanity had ever produced, then start them spinning eternally to become precise gyroscopic measurements of “frame dragging”, or, the relativistic propensity of the earth to slightly drag and deform the shape of spacetime around it as it rotates

Love projects like this so much