
50 Questioning the Universe: Concepts in Physics
taking some time to inform the distant eld there has been a change; therfore, there
must be a time delay that depends on distance.
6.3.2.1 The Speed and Identity of the Kink
As stated above, the kink travels at a de nite speed. That speed is 186,000 miles/s,
or 3 × 10
8
m/s. Some of you may recognize this as the speed of light. In fact, that is
exactly what light is: the readjustment of the electric eld when charged particles are
accelerated. So, not only does the eld concept predict the correct time delay, but it
predicts and explains what light is. To emphasize this point, light is only ...