Cosmology Applet - Lab Applications Cosmo Home
Exploring Cosmology

Start with what was, for a long time, the "standard" cosmology: Ho=50, OmegaM=1, OmegaL=0

  • What is the current age of this universe; ie, how old is this universe at a redshift z=0?
  • If we change the Hubble constant to Ho=100, how does this change the age of the Universe? Why does the age of the Universe change?
  • Hubble's initial estimate (in 1929) of the current expansion rate was H0=500 km/s/Mpc. What is the age of the Universe under this model? Is that reasonable?
  • Now reduce the mass density of the Universe to OmegaM=0.5. How and why does the age change?
  • Increase the mass density to OmegaM=2.0. Again, how and why does the age change?
Now put some data points on the age plot. Try these:
  • The sun is currently about 5 billion years old.
  • The age of the disk of the galaxy is about 10 billion years old.
  • The oldest globular clusters in the galaxy are 12-15 billion years old.
Given these ages:
  • How big can Ho be if OmegaM=1?
  • If OmegaM is lower than 1, say OmegaM=0.3, how big can Ho be?
  • A current estimate of Ho is Ho=65. Is Ho=65, OmegaM=0.3 consistent with the age estimates of objects in our galaxy?
Now add a cosmological constant by making OmegaL nonzero.
  • For a Ho=65, OmegaM=0.3, what happens to the age of the universe as you increase OmegaL? Why does the age change?
Finally, put data for LBDS 53W091 on the age plot. It is a galaxy at a redshift of 1.552, and a preliminary estimate of its age was 3 Gyr.
  • How does adding this point constrain cosmology? Show an example of a cosmology that was consistant with the galaxy age data but is inconsistent with the 3 Gyr age of LBDS 53W091.
More recent estimates of the age of LBDS 53W091 suggest it is younger, only 1.5 Gyr old at its redshift of 1.552.
  • How does this change the allowed cosmologies?