- #1
ehrenfest
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Homework Statement
http://books.google.com/books?id=Xm...5Dw&sig=6cUrZKqmPMoe0QBRTSYNnipNRw4#PPA114,M1
For problem 6.5 I did a lot of manipulation and I get that the following holds at the endpoints of an open string:
[tex]c = |\frac{\partial{\vec{X}}}{\partial{t}}| [/tex]
This probably seems like silly intuitive queston, but I cannot explain why this implies that the string endpoints move at the speed of light. Since X is a four-vector not a three-vector, why can we draw that conclusion?