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Introduction Newton's
laws of motion give us a complete description of the behavior moving objects at
low speeds. The laws are different at speeds reached by the particles at SLAC. Einstein's
Special Theory of Relativity describes the motion of particles moving at close
to the speed of light. In fact, it gives the correct laws of motion for any
particle. This doesn't mean Newton was wrong, his equations are contained within
the relativistic equations. Newton's "laws" provide a very good
approximate form, valid when v is much less than c. For
particles moving at slow speeds (very much less than the speed of light), the
differences between Einstein's laws of motion and those derived by Newton are
tiny. That's why relativity doesn't play a large role in everyday life.
Einstein's theory supercedes Newton's, but Newton's theory provides a very good
approximation for objects moving at everyday speeds. Einstein's
theory is now very well established as the correct description of motion of
relativistic objects, that is those traveling at a significant fraction of the
speed of light. Because
most of us have little experience with objects moving at speeds near the speed
of light, Einstein's predictions may seem strange. However, many years of high
energy physics experiments have thoroughly tested Einstein's theory and shown
that it fits all results to date. |