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    MATERIAL FROM CLASS 27: Wednesday December 13

    Explaining sizes of fluctuations in the cosmic microwave background requires dark energy

    Points show the amount that the temperature of the cosmic microwave background changes between points separated by the angle on the top scale. The blue points are from WMAP, red points from other experiments. The largest hot and cold patches are about 1 degree across; a region of this size expands to about 200megaparsecs (700mega-light-years) by the present.
    The solid curve is the prediction including dark energy; the dashed curve is what we expect without dark energy.
    The dotted curve shows what happens if the amount of protons and neutrons is reduced to half of what we think it should be.
    [WMAP fluctuations]

    'Millennium simulation' of galaxies forming

    The Millennium Run used more than 10 billion particles to trace the evolution of the matter distribution in a cubic region of the Universe over 2 billion light-years on a side. It kept busy the principal supercomputer at the Max Planck Society's Supercomputing Centre in Garching, Germany for more than a month. By applying sophisticated modelling techniques to the 25 Tbytes of stored output, Virgo scientists have been able to recreate evolutionary histories both for the 20 million or so galaxies which populate this enormous volume and for the supermassive black holes which occasionally power quasars at their hearts. By comparing such simulated data to large observational surveys, one can clarify the physical processes underlying the buildup of real galaxies and black holes.
    Project webpage: www.mpa-garching.mpg.de/galform/virgo/millennium/

    Pictures in the left column are 7Bly across, and show the largest scale; the middle column zooms in 4 times, and the left one is 440Mly across, magnified another 4 times.
    In the upper rows, pictures from early times are 'blown up' to remove the effect of cosmic expansion.

    The cosmos begins in a nearly uniform state: the first picture is even before the microwave background was produced as we now see it. With time, gravity pulls material into denser regions, to build up clusters of galaxies.
    In the lower right picture, each yellow knot will develop into a cluster of galaxies. That picture is 100 megaparsecs or 325 million light years across. We can't see galaxies themselves on this image because they are too small.

    time = 210Myr, size scale 0.05 (redshift 18.3)
    [z=18.3 biggest] [z=18.3 zoom1] [z=18.3 zoom2]

    time = 1Byr, size scale 0.15 (redshift 5.7)
    [z=5.7 biggest] [z=5.7 zoom1] [z=5.7 zoom2]

    time = 4.7Byr, size scale 0.4 (redshift 1.4)
    [z=1.4 biggest] [z=1.4 zoom1] [z=1.4 zoom2]

    time = 13.6Byr: present day
    [z=0 biggest] [z=0 zoom1] [z=0 zoom2]