Galaxies and the Expanding Universe

These links relate to the discovery that the universe is expanding, plus the birth of the Big Bang theory.

Vesto Slipher discovered that Andromeda was coming toward us, and other objects were receding.

http://www.roe.ac.uk/~jap/slipher/

http://www2.lowell.edu/workshops/slipher/

Henrietta Swan Leavitt discovered a way to determine how far away other galaxies are.

http://www.famousscientists.org/henrietta-swan-leavitt/

http://www.encyclopedia.com/topic/Henrietta_Leavitt.aspx

http://www.womanastronomer.com/hleavitt.htm

http://www.windows2universe.org/people/leavitt.html

Edwin Hubble determined that more distant galaxies were moving faster, and that meant the universe itself was expanding

https://www.spacetelescope.org/about/history/the_man_behind_the_name/

https://cosmology.carnegiescience.edu/timeline/1929

Georges Lemaitre: Father of the Big Bang
http://www.amnh.org/education/resources/rfl/web/essaybooks/cosmic/p_lemaitre.html