|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
� |
Look
�into the past� to see if expansion rate was faster in
|
|
|
early
history.
|
|
|
� |
To �look into the past�� look very far away:
|
|
|
|
� |
Find �Ho� for very
distant objects, compare that to �Ho� for
|
|
|
closer objects
|
|
|
� |
Remember � we found Ho by
plotting velocity (vr) vs.
|
|
|
|
|
distance
|
|
|
|
� |
We found velocity vr from the red shift
(z)
|
|
|
|
� |
We found distance by measuring apparent magnitude (mv)
|
|
|
of known brightness objects
|
|
|
|
� |
We can test for changing Ho by measuring
mv vs. z
|
|