1. Herber D. Curtis
1.1. made a technical speech to prove proof
1.2. Milk Way
1.2.1. Galaxies exist outside it
2. 1909
2.1. Velocity
2.1.1. Vesto Slipher
2.1.1.1. Radial Velocity
2.1.1.1.1. rates of movement
2.1.1.1.2. redshift
2.1.1.1.3. blueshift
2.1.1.2. Andromeda Nebula
2.1.1.2.1. moves towards the milky way at the speed of 300 k/ms
3. 1911
3.1. William Wallace Campbell
3.1.1. age of stars and its velocity
3.1.1.1. older star
3.1.1.1.1. higher velocity
3.1.1.2. young stars
3.1.1.2.1. 10km/s
3.1.1.3. andromeda nebula
3.1.1.3.1. 300km/s
4. Capheid variable
4.1. brightness
4.1.1. star (standardize measurement)
4.2. magnitude
4.2.1. 10 parsecs (30 light-years)
4.3. m - M = 5 log r/10
4.3.1. m is magnitude
4.3.2. M is absolute magnitude
4.3.3. r is distance in parsec
4.3.4. log is logarithm
5. Uniformity in Nature
5.1. Occam's Razor
5.1.1. Nebulae
5.1.1.1. external
5.1.1.1.1. galaxy
5.1.1.2. internal
5.1.1.2.1. milky way
6. 1912
6.1. Hanrietta Leavitt
6.1.1. luminosity
6.1.1.1. stars
6.1.1.1.1. standard candles
6.1.1.1.2. to determine distance
7. 1915
7.1. Adrian van Maanen
7.1.1. nebula M101
7.1.1.1. 300,000 light-years
7.1.1.1.1. rarional period of 85,000 years
8. Harlow Shapley
8.1. Island Universes
8.1.1. Andromeda Nebula
8.2. Milky way
8.2.1. 100,000 light-years in diameter
8.3. Globular cluster
8.3.1. 500 light-years in diameter
8.4. drew to provide proof
9. 1700s
9.1. Telescope
9.1.1. nebulae
9.1.1.1. cloud
9.1.1.2. blotches of light
9.1.1.3. spirals
9.1.1.4. globular clusters
9.1.1.5. whirlpool-like object
9.1.1.6. 1840
9.1.1.6.1. Lord Rosse
9.1.1.6.2. John P. Nichol
9.1.1.7. 1864
9.1.1.7.1. William Huggins
9.1.1.8. 1885
9.1.1.8.1. stars
9.1.1.9. 1898
9.1.1.9.1. Julius Scheiner
9.1.1.10. 1900
9.1.1.10.1. 100,000 nebulae had been detected
9.1.2. planets
9.1.3. comets
9.1.4. asteroids
9.1.5. stars
10. Edwin Hubble
10.1. Hubble Space Telescope
10.1.1. Milky Way
10.1.1.1. One of many galaxies
10.2. Evidence can be gathered by locating a variable within a nebula
10.2.1. which could be used to estimate the distance to the nebula
10.3. Andromeda Nebula
10.3.1. cepheid variable in andromeda nebula
10.3.2. M31
10.3.3. 300,000 persecs in over 900,000 light-years
10.3.3.1. 3 times larger than Shapley's Big Galaxy
10.3.4. The universe was expanding
11. Size
11.1. F.W Very
11.1.1. 120 light-years
11.1.1.1. 3800 light-years apart
11.1.1.1.1. milky way
11.1.1.1.2. andromeda nebula
11.2. astronomers from 1910
11.2.1. 30,000 light-years in diameter
11.3. Max Wolf
11.3.1. 1,000 light-years in diameter