Summary

• Einstein's postulates
• Consequence #1: Simultaneity

• Consequence #2: synchronization
  
  
  
• Michelson-Morley experiment applet
  
  
• Consequence #3: time dilation
  • light clock applet
  • derivation of γ
  • time dilation equation
  • Twin Paradox
    Example #1
    
    Example #2
    
  
  
• Consequence #4: Length contraction
  • consequence of time dilation
  • measure a moving rod applet
  • length contraction equation
    Example #3
    
  
  

kw5 10.
Can a person live long enough to make a trip to a star 200 light years away from Earth?
A. YES             B. NO
Answer







kw5 10.
The half life of nuclei measured at rest relative to the nuclei is 920 s. What is the lifetime of nuclei traveling at 0.9999c?
A. 13.0 s           B. 70.7 s
C. 920 s            D. 65,100 s
Answer







kw5 10.
Ed is traveling in a spaceship at half the speed of light relative to Mary. If Ed measures his craft to be 20 m long, what does Mary measure?
A. 1.154 m           B. 17.3 m
C. 20.0 m             D. 23.1 m
Answer







 



A. YES
If the person travels at nearly the speed of light, much less than 200 years elapses on their clocks during their trip to the distant star. However, all their friends back on Earth will grow old and die before the trip is even half over!













 



D. 65,100 s













 



B. 17.3 m