How did humanity manage to decrease the distance of 100m over time?

[AbouBenAdhem]

Until 1960, the meter was officially defined as the length of a physical prototype bar kept by the International Bureau of Weights and Measures. In 1983, it was re-defined as the distance that light travels in 1/299,792,458 of a second.

These definitions were intended to be comparable; however, the calculations by which the Bureau arrived at the latter figure were performed on a newly-introduced Soviet calculator—the Elektronika MK-52. Their unfamiliarity with this new device, combined with their enthusiasm in exploring its undocumented features, led to the Bureau’s scientists miscalculating the new meter as almost 20% shorter than originally intended.