Gravity Probe B (opens in new tab)

Wikipedia: «At the time of their manufacture, the gyroscopes were the most nearly spherical objects ever made (two gyroscopes still hold that record, but third place has been taken by the silicon spheres made by the Avogadro project). Approximately the size of ping pong balls, they were perfectly round to within forty atoms (less than 10 nm). If one of these spheres were scaled to the size of the Earth, the tallest mountains and deepest ocean trench would measure only 2.4 m (8 ft) high.»

I wonder how this compares to the sphericity of a neutron star.

The data analysis done to try to salvage results from this mission were nothing short of heroic.

See [1] for more detailed discussion of how the Gravity B team pushed on with analysis in the face of systematic errors much larger than the effect they were trying to measure, to come out in the end with a believable measurement of the incredibly subtle effect of gravitational frame dragging.

[1] https://ddd.uab.cat/pub/tesis/2016/hdl_10803_400663/chev1de1...

Back in the day, I heard it said of the Fairbanks group, that they could have a collective publication career if they did no more than publish all the systematic effect discoveries they made in attempting very difficult experiments.

Same group that "measured" a magnetic monopole and fractional electric charge, IIRC.

Gravity Probe B is my favourite example of scientists spending a lot of money and effort to verify something almost everyone believed to be true, because science.

General relativity remains a marvel of abstract, intuitive thinking that has led to one of the most verified physical theories ever. I'm not sure there is any other theory that stands up to it in this regard. Other thoroughly verified theories, like the standard model, had an extremely tight iterative loop between theory and experiment during their development.

I'm having a hard time understanding this Wikipedia article. Can someone explain like I'm five what this probe actually did/proved? Thanks!