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