"It is now known that the Milky Way is only one of hundreds of billions of galaxies in the visible universe, proving Curtis the more accurate party in the debate in that respect."
Statements like this are a bit ironic. When Shapely was arguing, he was arguing from what was 'known' in his time.
Furthermore, nothing in science is 'known' or 'proven'. What we have are theories that to lesser or greater degrees explain the known evidence. Cosmology is the one area in science in which such statements are most mortally dangerous... because it's in worse shape right now than its ever been.
It's a good thing that what Shapely 'knew' didn't stop Hubble from deciding otherwise, right? Let's hope that what we 'know' isn't keeping us in the dark. Twang (talk) 07:53, 26 November 2009 (UTC)
You are right that there are a great many things in cosmology which are up in the air, and not known in any concrete sense. Among these are the nature of dark energy and dark matter, perhaps their existence at all, although we have compelling evidence for both. However, that the Milky Way is only one of hundreds of billions of galaxies is in no way in doubt. In the 1920s, no one knew whether the Milky Way was one of many island universes or the entire universe - there was evidence for both conjectures. The situation is much different now. -Thucydides411 (talk) 11:25, 5 December 2009 (UTC)