UU Fellowship of North Central Iowa
  Sunday, August 9, 2015
  Title: Dark Matter --  What do we know?

  Blurb: Dark Matter is a huge mystery in Astronomy. The
  observational evidence will be presented, including the
  observations and experiments under way to understand what
  Dark Matter is.

  Bio: Sam Wormley is a retired Associate Scientist and
  Principal Investigator at Iowa State and a retired Adjunct
  Prof of Astronomy at Marshalltown Community College. Sam
  regularly teaches science classes for the Osher Lifelong
  Learning Institute (OLLI) at Iowa State and for the
  RaySociety at Drake University.

  Astronomer's Tools
   - Spectral lines
   - Doppler shift

  Dark Matter
   - Galactic Rotation rates as measured by Doppler Shift of
     stars and gas

   - Motion of Galaxies in a cluster as measured by Doppler
     Shift of stars and gas

   - Gravitational Lensing (to determine mass of a cluster of

   - X-Ray imagery to determine the location and density of hot
     gas in galactic clusters

   - Dark Matter Candidates

  Summary -- the actual observation are of electromagnetic
  radiation, but as you can see above can be used to measure,
  motion within clusters and within galaxies, and gravitation
  effects to measure mass.