Exploring Cosmology
Start with what was, for a long time, the "standard" cosmology:
H_{o}=50, Omega_{M}=1, Omega_{L}=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 H_{o}=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 H_{0}=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 Omega_{M}=0.5. How and why does the age change?
 Increase the mass density to Omega_{M}=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 1215 billion years old.
Given these ages:
 How big can H_{o} be if Omega_{M}=1?
 If Omega_{M} is lower than 1, say Omega_{M}=0.3, how big can H_{o} be?
 A current estimate of H_{o} is H_{o}=65. Is H_{o}=65, Omega_{M}=0.3 consistent with the age estimates of objects in our galaxy?
Now add a cosmological constant by making Omega_{L} nonzero.
 For a H_{o}=65, Omega_{M}=0.3, what happens to the age of the universe as you increase Omega_{L}? 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?
