The phrase "century physicists" refers to the scientists who made significant contributions and breakthroughs in the field of physics during a particular century. Full definition
It was invisible, ubiquitous, and in the late 19th century every physicist believed in it. (newscientist.com)
Through the nineteenth century physicists believed that atoms were, as the name implies, tiny pellets of matter not susceptible of further analysis or division. (religion-online.org)
Hence the Boltzmann Brain proposed by super famous 19th century physicist Ludwig Boltzmann the father of statistical mechanics. (judithcurry.com)