It’s still getting bigger

In episode 42, we learned that in 1923, Hubble found out that spiral nebula are actually spiral galaxies, changing our understanding of the size of our universe. In 1929, using spectral lines, (see episode 44 and episode 46,) and building off of work previously done by Vesto Slipher, he discovered that the universe is not only bigger than we thought; it’s still getting bigger. This provided supporting evidence for the theory of the big bang.