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    MATERIAL FROM CLASS 24: Monday December 4

    Distances to galaxies, Hubble's "law", expansion and the Big Bang, dark energy

    Hubble's own plot of galaxy distances and speeds: from 'The Realm of the Nebulae', Yale, 1936.
    Remember that 1 parsec = 3.26 light years.
    The lowest black circle above the word 'distance' is the Andromeda galaxy, which is approaching us.
    The most distant objects here are in the Virgo cluster, now reckoned to be about 15Mpc distant, not 2Mpc as Hubble shows.
    [Hubble's Hubble diagram]

    Dark energy is not well covered in the text: see the Wikipedia article.