The great debate: Just how big is the universe?

1. Tools

1.1. Advanced telescopes like the Hooker Telescope at Mount Wilson Observatory, which Harlow Shapley and later Edwin Hubble used for their observations.

1.2. The ovservational power allowed astronomers to see fainter and more distant objects, crucial for observing globular clusters and extragalactic nebulae.

1.3. Edwin Hubble used Cepheid variables in the Andromeda Galaxy to measure its distance, proving it was far outside the Milky Way.

1.4. The long exposure imaging Allowed astronomers to capture faint objects over time, essential for studying distant nebulae and stars.

2. Nebulae

2.1. At the time of the debate, nebulae were broadly defined as cloud-like objects visible in the night sky. Their true nature was unclear, leading to significant debate.

2.2. Heber Curtis argued that spiral nebulae, like Andromeda, were actually separate galaxies, or "island universes," rather than objects within the Milky Way.

2.3. Curtis used the appearance of spiral structures and novae within these nebulae to argue that they were far more distant and external to the Milky Way.

3. Harlow shapely

3.1. Size of the milky way, the milky way is much more larger than previously thought.

3.2. The position of the sun is not at the center of the milky way but located far from it.

3.3. Global clusters are used to the distribution of globular clusters to argue for a larger milky way.

4. Heber Curtis

4.1. The island universe hypothesis, other galaxies exist outside the milky way.

4.2. The size of the universe is much larger than the milky way.

4.3. The used of observation of novae in andromeda to argue that it was a separate galaxy.

5. Edwin Hubble

5.1. Later confirmed the existence of galaxies beyond the milky way.

5.2. His findings resolved the debate.

6. He discovered the expansion of the universe.

7. Scientific developments

7.1. Hubble’s role further solidified the understanding of galaxies and expanding universe.

7.2. The bigbang theory later developments in cosmology built on the understanding from this debate.

8. Key concepts

8.1. The size and the structure debate over whether the milky way encompasses the entire universe or is it just one of many galaxies

8.2. Shapely’s claim that the sun is not at the center of the milky way, challenging earlier views of the milky way’s structure