Better Appreciating the Scale of It: Lemaître and de Sitter at the BAAS Centenary

In September 1931, a panel discussion was convened at Central Hall Westminster on the subject of the ‘evolution of the universe’ at the centenary meeting of the British Association for the Advancement of Science. Center stage was what to do about the evolving universe being younger than the stars, evidently a paradox in the relativistic study of the evolving universe at the time. Here, we discuss two diametrically opposed reactions to the paradox, which were each broadcast at the meeting by Lemaître and de Sitter, respectively. As we argue, that both could be projected to the public as viable reflects an unsettled question at the foundations of the then-nascent discipline: What is the role for considerations of scale in relativistic cosmology?