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The Cosmological Constant
Cosmic Inventory

Basic Idea: Contents: where and what, scales

The measured effects of the cosmological constant are primarily in the field of cosmology, the study of the universe as a physical system. In order to provide a context for the various subsequent sections, this section will describe many of the objects in the universe and relative sizes, and the next section will very briefly summarize the current paradigm for the history of the universe. Note that cosmological inventory is still underway at the frontiers of cosmological research.


Interest here is in subset of astronomical objects, many of which are quite large.

Cosmic Voyage and powers of 10: relative sizes

Some Objects and Scales

  • nearby objects
    • earth
    • sun
    • solar system
    • next nearest star
    • milky way
  • cosmological objects
    • galaxies
    • cluster
    • super cluster
  • note: mapping out the universe locally and beyond is a major current research project
What are they made of?
  • familiar matter: baryons, photons, neutrinos
  • dark matter
    • evidence
    • Types: hot, cold
    • Exotic particle candidates--particle physics has many possible suggestions but no particle physics detections either direct or indirect yet. Many searches are underway.
      Difficult-not clear where to look given their weak interactions
      Current issues: self interactions, how light traces mass
  • Combined matter content picture
Some other objects used in later sections:
  • globular clusters
  • black holes/supermassive black holes/quasars
  • supernovae
  • Cepheids
  • LMC
  • lyman alpha forests

Wavelengths/observations: radiation is all around us!

  • photons: spectrum
    finite speed of light: look at large distances, seeing back in time
    examples--how far corresponds to how long ago in terms of z, pc
    distance to farthest visible objects
    search for earliest objects (farthest) underway by many groups
  • neutrinos
  • cosmic rays
  • gravity waves

Some references.

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