alt Hacker NewsSorry, yes, there’s a terminological disconnect here: M31, say, is the “Andromeda Galaxy” to us, but the “Andromeda Nebula” to Hubble’s contemporaries circa 1920. The recognition that at least some of the cloudy (nebulous, literally) stuff in the sky is galaxies (and that the universe fits more than one) was the very point of the fight I mentioned. The world before it was thought to be drastically smaller in a way that I find difficult to think about.
That's right. Historically, nebula was anything that looked cloudy, so a lot of astrophysical objects that we now understand are distinct, were simply labelled as nebulous. M31, as you said, being a great example.
Modern astrophysics still carries the baggage of obsolete terminology to this day, from names of objects to names of units.