• Mark Trodden Video about Expanding Galaxies and Types of Matter/Energy
  Research summary of old notions of the expanding universe and newer approach to explain how galaxies can to continue moving away from each other at ever-increasing velocities. Talks about Einstein's general theory of relativity -- movement being a curvature of space/time continuum (or something like this)
  in Public bookmarks with cosmology dark_energy dark_matter elementary gravity particle relativity video
  Note: Video spends too much time focused on Trodden and not enough on his slides, so you lose focus (and interest) while staring at him talking.
• Chandra :: Galaxy Clusters and Dark Energy
  A galaxy cluster is comprised on hundreds of galaxies embedded in a cloud of extremely hot gas and dark matter. Dark matter, an invisible and unknown type of material, is postulated to hold clusters together. X-ray observations have the unique ability to determine the ratio of the mass of the hot gas and the mass of the dark matter in a cluster. The observed values of the gas fraction depend on the assumed distance to the cluster.
  in Public bookmarks with cloud clusters dark_energy dark_matter galaxies invisible x-ray
• Dark Energy, Dark Matter - NASA Science
  Eventually theorists came up with three sorts of explanations. Maybe it was a result of a long-discarded version of Einstein's theory of gravity, one that contained what was called a "cosmological constant." Maybe there was some strange kind of energy-fluid that filled space. Maybe there is something wrong with Einstein's theory of gravity and a new theory could include some kind of field that creates this cosmic acceleration. Theorists still don't know what the correct explanation is, but they have given the solution a name. It is called dark energy.
  in Public bookmarks with acceleration dark_energy dark_matter expanding gravity theory universe

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