Down memory lane…
“As to relativity, I must confess that I would rather have a subject in which there would be a half dozen members of the Academy competent enough to understand at least a few words of what the speakers were saying if we had a symposium upon it. I pray to God that the progress of science will send relativity to some region of space beyond the fourth dimension, from whence it may never return to plague us.”
Letter of C.G. Abbot (Home Secretary of the National Academy of Science) to G.E. Hale (Director of Mount Wilson Observatory), 20 January 1920
The subject of the symposium eventually agreed upon was the so-called “Great Debate”
https://en.wikipedia.org/wiki/Great_Debate_(astronomy)
The Great Debate, also called the Shapley–Curtis Debate, was held on 26 April 1920 at the Smithsonian Museum of Natural History, between the astronomers Harlow Shapley and Heber Curtis. It concerned the nature of so-called spiral nebulae and the size of the universe; Shapley believed that distant nebulae were relatively small and lay within the outskirts of Earth’s home galaxy, while Curtis held that they were in fact independent galaxies, implying that they were exceedingly large and distant.
Incidentally, the controversy was finally settled by E. Hubble using the 100 inch Hooker reflector at Mt Wilson, just a few years later. At the time, the Hooker was the largest telescope in the world, and its aperture was the same as the Hubble Space Telescope (2.5 meters).
Of course, Hubble didn’t stop there. Not only did he demonstrate that those dim fuzzy spiral nebulae were not just little local objects scattered around the edges of our Milky Way universe, but that they were other island universes not unlike our Milky Way stretching out for as far as we could see; and as if that weren’t enough, the whole shebang was expanding, faster and faster, to the edge of infinity.
You can get some idea of the scale by the chairs by the control console in the lower right corner of the image, and the railing surrounding the telescope pit.