Hubble Law Example using relative vr and relative d
Car “B” is the Highway Patrol – using a radar gun which can find
speed and distance to other cars – but can’t see the ground.
Car
d
vr
t0 = 1/H0
d  relative to B
vr  relative to B
t0 = 1/H0
A
 30 miles
15 miles/hr
2 hr
-70 miles
-35miles/hr
2 hr
B
100 miles
50 miles/hr
2 hr
   0 miles
   0 miles/hr
 ----
C
120 miles
60 miles/hr
2 hr
 20 miles
 10 miles/hr
2 hr
D
140 miles
70 miles/hr
2 hr
 40 miles
 20 miles/hr
2 hr
You get the same result whether you use “absolute” velocities and
distances, or measure velocities relative to any arbitrary car.
Every driver thinks they are at the center of the “car universe” and
the other cars are just heading away from them, all having left at
some common start time.