How astronomers came to accept other galaxies in the 1920s

[hankaaron]

I found this 1926 news article on Google News archives
http://news.google.com/newspapers?i...BAJ&pg=3525,5055158&dq=galaxy+telescope&hl=en

In it Hubble originally perceived distant galaxies as an "external" universe. Actually, it seems that was also the conventional wisdom of astronomers at that time. Some time later, the concept of other galaxies within our universe rightfully began to take hold.

hankaaron.

 

[Drakkith]

What is your point?

 

[hankaaron]

What is your point?

The point, or rather the narrative, is how the scope of the universe was so different 100 years ago. Astronomers had become so accustomed to the Milky was being synonymous with the Universe, that when another galaxy was resolved by Hubble- he and other astronomers considered it as being a separate Universe.

I don't know about you, but I find that fascinating.

 

[Steely Dan]

What do you think that astronomers of that era thought that the term "universe" meant?

 

[hankaaron]

What do you think that astronomers of that era thought that the term "universe" meant?

The Milky Way.

 

[Steely Dan]

The Milky Way.

If they thought the definition of "universe" was "The Milky Way," why were they calling other galaxies "island universes?"

What I'm getting at is that you are thinking of the contemporary definition of "universe," which describes all of the matter and energy that we can conceivably interact with; anything else would exist in a separate universe. Clearly the astronomers in Hubble's era were not using the term in the same way, since they could indeed actually see the light from those galaxies.

 

[hankaaron]

If they thought the definition of "universe" was "The Milky Way," why were they calling other galaxies "island universes?"

Clearly the astronomers in Hubble's era were not using the term in the same way, since they could indeed actually see the light from those galaxies.

Yes. That is exactly my point.

 

[phyzguy]

There was a 'Great Debate' at the time as to whether the 'Spiral Nebulae' were simply part of the Milky Way, or whether they were separate entities like the Milky Way. Obviously the latter viewpoint won, but it was not clear for many years. Many people though that the spiral nebulae were solar systems in the process of forming.

 

[D H]

If they thought the definition of "universe" was "The Milky Way," why were they calling other galaxies "island universes?"

The issue was whether those spiral nebulae were a part of our galaxy or beyond it. The term "island universe" went way back to Kant. The "island universe theory" (which predated Kant) hypothesized that they were outside of our galaxy.

 

[Steely Dan]

Yes. That is exactly my point.

OK, so you've admitted that your only argument is that they had a different definition of the word universe than we do now. I'm not understanding whether you're trying to make a point here, or not.

 

[russ_watters]

Did anyone actually read the article? It does not quote Hubble using the word "universe". That's the writer's word: Hubble uses the word "galaxy". Looks to me like just bad science writing, using an archaic and irrelevant definition of "universe" interchangeable with "galaxy". Some things never change.

In any case, I echo the earlier question: What's your point? The title implies an issue much bigger than a writing/wording/definition problem...

 

[D H]

Hubble did use the words "island universe." A spiral nebula as a stellar system: Messier 33., Astrophysical Journal, 63, 236-274 (1926). That phrase, "island universe" was old, 170 years old, at Hubble's time, and was originated by Immanuel Kant. The "island universe theory" as espoused by Kant and many others since Kant said that spiral nebula such as Messier 33 were external to rather than a part of the Milky Way.

 

[russ_watters]

Fair enough: it just didn't say it in the article linked - I didn't realize the paper did use those words. So it is just an issue of evolving definitions then?

 

[Dickfore]

The term 'Universe' is used in the title and the opening of the newspaper article. However, if you find where 'external' is used, you will see it used in conjunction with galaxy.

 

[D H]

It's a newspaper article, for crying out loud. Does the media get anything right with respect to science today? (No.) Why would anyone expect the media of 1926 to get things straight?