"Although Heisenberg began thinking about an electron track in a , he came to realize that the problem of locating an electron is not one of instrumentation... [H]e found that it was never possible... to measure the precise path of an electron: for example, the droplet size is too large in a cloud chamber. Or if you try to "see" an electron with light (or x-rays), then the light photons strike the electron like billiard balls and randomly change the electron's position. ...It was ...a limit in principle on the accuracy ...a theoretical limit—an irreducible degree of uncertainty or Indeterminacy—in measuring the simultaneous position and motion of an electron. ...[T]he two measurements—of position and motion—counterbalance one another. The better you measure the position, the worse you will be able to measure the motion, and vice versa. If you could measure the position (or motion) perfectly, you would know nothing about the motion (position). The uncertainty principle thus seems to reconcile the particle-wave duality. The better you know the position... the more localized... the more it seems to act like a particle. Alternatively, if you know the motion or speed very well... [position] is diffuse, like a wave. ...[A] different point of view on duality but still ...a paradoxical fact of life."