Since my undergraduate days, I have been puzzled by the fact that we have Newton’s laws of motion but only Einstein’s theory of special relativity. We have finished celebrating the 100th anniversary of the publication of the theory of special relativity, and it seems to me that after a century of validation, it’s time to rename it as more than just a theory.
I propose that we, as physicists, define a set of Einstein’s laws, just as we have Newton’s laws, Coulomb’s law, or Faraday’s law. I begin the discussion by offering the following three laws:
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▸ The laws of physics are identical in all non-accelerating (that is, inertial) frames.
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▸ The vacuum speed of light, c, is the same for all inertial frames.
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▸ The total energy E of a body of mass m and momentum p is given by . In particular, the energy of a body measured in its own rest frame is given by E = mc 2, and the energy of a massless body is E = pc.
Collectively, these laws should, in my opinion, be called Einstein’s laws of special relativity. Others may prefer slightly different wording, or more lawyerly definitions; with that I have no quibble. Time dilation, length contraction, and the relativity of simultaneity could be considered corollaries of these laws.
Some may ask what is the consequence of renaming a “theory” to a “law”; obviously Nature does not care. To my way of thinking a theory is speculation based on incomplete knowledge, and a law is valid in all cases where the appropriate circumstances apply. I believe that the special theory of relativity falls into the latter category equally with Newton’s laws, Coulomb’s law, or Faraday’s law. If nothing else, this change would help us impress upon students and nonscientists (a) the importance of special relativity to our understanding of nature and (b) the multitude of advances in science made possible as a consequence of its formulation.
