The enormous pondering of 1920

At 8:15, April 26th 1920 at the national academy of sciences in Washington D.C. two men, Harlow Shapley and Heber Curtis both spoke about one subject with the title “The scale of the Universe.” The evening’s events have pasted into history to be known as “The great debate.”

The great debate was first proposed by George Ellery Hale in late 1919. Hale wanted the next National Academy meeting to include a evening debate about the island universe theory of spiral nebulae or relativity, in short time it was decided that the debate would be about island universe theory.

Shipley’s main point was that the Milky Way is very large and that spiral nebulae’ are a part of it: where-as; Curtis argued that the Milky Way is small and there may be other galaxies like it. Both agreed that there was a general structure to the galaxy, contains billions of stars, which are distributed uniformly, and is shaped like a lens, much like other spiral nebulae.

They disagreed about how large the Milky-way galaxy is, and on how big and how far away other spiral nebulae are, other wise (now) known as Galaxies. The problem though was that may of the observations and data of the day was inconclusive and even just plan wrong. For example Shapley thought that the edges of some spirals orbited around there centers at speeds faster then the speed of light. Curtis also made mistakes, over estimating the distance to the Andromeda spiral nebula, because the concept of a super-nova wasn’t conceived yet. It wasn’t until later that Edwin Hubble was able to measure the distances to the observed spiral nebula that conclusive measurements could be made. Proving that they were indeed, galaxies in there own right, thus ending the “Great Debate” and Shipley’s and Curtis’s enormous pondering.

Sources

Kaiser, Christian: The Shapley-Curtis debate, 2001-09-18 http://www.astro.umn.edu/~larry/CLASS/AST2001/shapleycurtis.html Bonnell, Jerry & Nemiroff, Robert: Why the `Great Debate' Was Important http://antwrp.gsfc.nasa.gov/diamond_jubilee/1920/cs_why.html CURTIS, HEBER D. & SHAPLEY, HARLOW: THE SCALE OF THE UNIVERSE [*] http://antwrp.gsfc.nasa.gov/diamond_jubilee/1920/cs_nrc.html Michael A. Hoskin: The 'Great Debate': What Really Happened, http://antwrp.gsfc.nasa.gov/htmltest/gifcity/cs_real.html

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