Summary

• Einstein's postulates
• Consequence #3: Time dilation
• Consequence #4: Length contraction

• Spacetime
• pole through barn scenario
• the fourth dimension

Example #1

Example #2



• The Mechanical Universe: Lorentz Transformation video



• Spacetime diagram of twin paradox (Fig. 2.26)

kw5 10
Mary claims that the engine of Ed's fast moving train came out of a tunnel at the same time the caboose entered. Does Ed agree?
A. Yes
B. No - the engine came out first.
C. No - the caboose entered first.
Answer



















kw5 10
According to Ed, which is longer, the train or the tunnel?
A. The train is longer than tunnel.
B. The tunnel is longer than train.
C. They are the same length.
Answer



















 



B. No - the engine came out first.
Mary argues that the Ed only thinks the engine emerged first because he is moving fast toward that signal and away from the caboose signal. Ed claims he's at rest and Mary only thinks the signals are simultaneous because she is moving fast toward the caboose signal and away from the engine signal.

























 



A. The train is longer than tunnel.
Ed sees his train as "normal" in length but the approaching tunnel is contracted and appears shorter than the train. He does not think the train is ever fully in the tunnel, but Mary does.