Phil 105: Science and Philosophy - Fall 2004 Lectures
!You will be sorely disappointed if you think that these are a
substitute
for attending class!
Topic Five: Spacetime
Previous Lecture
Lecture 24 – Shrinking (11/18/04)
1. Distances are less in moving frame
- Suppose you were driving in a car and you wanted to compare its
length to that of one driving past in the opposite direction?
front
rear
rear
front
rear
front
front
rear
- Let's do that experiment, in relativity – i.e., in spacetime with
relative simultaneity
- Consider two identical
cars A and B (in particular, the same lengths if they have no relative
motion).
- A: at the instant that the front of B is level with the rear
of A where is the rear of B relative to the front of A? Ahead? Level?
Behind?
- B: at the instant that the front of A is level with the rear
of B where is the rear of A relative to the front of B? Ahead? Level?
Behind?
- That is, in the frame of A, B is shorter than A, while in the
frame of B, A is shorter than A – even though they are identical!
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