•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
•
•