The graph below shows historical estimates of the speed of light, c, alongside uncertainty intervals (Klein & Roodman, 2005, Figure 1). The horizontal line shows the currently agreed value, now measured with high precision.
Note the area I’ve pointed to with the pink arrow, between 1930 and 1940. These estimates are around 17km/sec too slow relative to what we know now, but with relatively high precision (narrow uncertainty intervals). Some older estimates were closer! What went wrong? Klein and Roodman (2005, p.143) cite a post-mortem offering a potential explanation:
“the investigator searches for the source or sources of […] errors, and continues to search until he [sic] gets a result close to the accepted value.
“Then he [sic] stops!”
Fantastic case study illustrating the social construction of scientific knowledge, even in the “hard” sciences.
References
Klein, J. R., & Roodman, A. (2005). Blind analysis in nuclear and particle physics. Annual Review of Nuclear and Particle Science, 55, 141–163. doi: 10.1146/annurev.nucl.55.090704.151521 [preprint available]