Hubble began taking spectra of galaxies as well as measuring their distance with Cepheid variables. He found that almost everyone's absorption lines were shifted. The further a galaxy is from Earth, the more its light is redshifted.
The Hubble constant or the Hubble parameter: relating a galaxy's redshift velocity to its distance. Astronomers are strongly divided over the value, or rather over the representative galaxies. Thanks to the HST and the Hipparcos satellite, though, most seem to think it will end up being 75 km/s/Mpc.
Anyway, all this rushing away made everyone aware that the universe was expanding. Explosively, since the further away the faster things went. Ta Da: The Big Bang Theory.
Okay, lab time.
Conclusion for Lab 30
"Spiral arms are where the open clusters and nebulae are most likely to be found. When we look at our Milky Way we see open clusters and nebulosities form a diagonal line in the same place in the sky as the Milky Way. In photos of other galaxies, the blue areas of the open clusters and pink of the hydrogen nebulae are found in the spiral arms, leading us to believe our galaxy is the same. Since the area in the arms consists of more compressed gas and dust than other parts of the galaxy, new stars, massive stars, and supernovae are more likely to be found here."
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