Albert Einstein and other physicists at Paul Ehrenfest's home, Leyden, Netherlands. [Getty Images]

Albert Einstein and other physicists at Paul Ehrenfest's home, Leyden, Netherlands. Einstein (1879-1955) (left) with Paul Ehrenfest, Paul Langevin (1872-1946) (centre), Kamerlingh Onnes and Pierre Weiss. (Photo by Oxford Science Archive/Print Collector/Getty Images)

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