9. [S] In the now-decommissioned Stanford Linear Collider, electrons and positrons were accelerated to energies of approximately 40 GeV in a beam pipe 2 mi long but only a few centimeters in diameter. Steering an electron through through such a narrowly defined path over such a distance sounds like a daunting task. But how long is the accelerator in the rest frame of the electron when it has this energy?
