Integrated Sachs-Wolfe Figure

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  • The Sloan Digital Sky Survey (SDSS) identifies Galaxy Concentrations and determines their positions on the sky.
  • The Wilkinson Microwave Anisotropy Probe (WMAP) measures the angular pattern of energies of the Cosmic Microwave Background Radiation (CMBR) [reds,yellows, greens, blues, purples, in order of increasing energy].
  • Microwaves (wavey lines) pass through the galaxy concentrations. As they fall in they become more energetic (more blue) and as they climb out they get less energetic (more red).
  • We have determined that the microwaves which pass through galaxy conentrations are slightly more energetic than those which do not. But only by roughly one part in one million.
  • We believe this means that the energy they lose when climbing away from the galaxy concentration is less than the energy they gain while falling in as indicated (the outgoing waves are more blue than the incoming).
  • This will happen if the galaxy concentration is expanding rapidly which, so to speak, dilutes the gravitational forces between the time which the microwaves enter the cluster and the time they exit. This is why one looses less energy climbing out.
  • We believe the reason for this expansion is that within the galaxy concentration there is a type of matter which is gravitationally repulsive (the red arrows) which acts in opposition to the normal gravitational self attraction (the green arrows) of the "normal" matter.
  • Over cosmological timescales (billions of years) the net gravitational repulsion and attraction combining with the normal cosmological expansion initiated at the Big Bang causes these concentrations to expand rapidly enough to lead to the increased energy of the microwaves we observe.
    • Albert Stebbins
    Last modified: Wed Oct 22 16:01:01 CDT 2003