Universe is Expanding
![Hubble diagram](images/hubble_diagram_sm.png)
Using the 100-inch Hooker Telescope at Mount Wilson Observatory, Dr. Edwin Hubble has studied many spiral nebulae. He has discovered they are moving away from us at a rapid pace. This is strong evidence of an expanding universe. He has further determined that the farther the nebula, the faster it moves away.
The Minds atop Mount Wilson
![Mount Wilson 100-inch Hooker telescope](images/hooker_telescope_tn.jpg)
High above Pasadena, California in the San Gabriel Mountains, the astronomers at the Carnegie Institution's Mount Wilson Observatory are changing our view of the Universe. Who are these scientists?
Classifying Nebulae
![Hubble 'tuning fork' diagram of galaxy classification](images/hubble_tuning_fork_tn.jpg)
For over a thousand years, astronomers wondered about the nature and development of nebulae. Nebulae appear to be faint clouds of gas and dust in the distant universe. Until recently, there have not been enough observations to classify nebulae based on their features or qualities.
In Their Own Words
![Image of Albert Einstein](images/einstein_1921_tn.jpg)
![Image of Edwin Hubble](images/hubble_office_tn.jpg)
Read quotes from Albert Einstein and Edwin Hubble about our changing understanding of the universe.
Andromeda Nebula Lies Outside Milky Way Galaxy
![annotated image of Andromeda showing variable star locations](images/andromeda_hubble_annotated.png)
Astronomer Edwin Hubble, of the Mount Wilson Observatory at Pasadena, California, has solved the mystery of the spiral nebulae. The spiral nebulae look like hazy pin-wheels in the sky. He has determined that these objects are much more distant than previously thought. Therefore, they are distant galaxies and not part of our own Milky Way galaxy. In the process, Dr. Hubble was also able to determine the distance to the spiral Andromeda nebula.
"Great Debate" Resolved
![Image of Heber Curtis](images/curtis_1918_tn.jpg)
![Image of Willem de Sitter](images/shapley_1935_tn.gif)
Dr. Hubble's discovery settles the "Great Debate" over the size of our own Milky Way galaxy. It also settles the distance to spiral nebulae and what they are.