Einstein and Relativity: The Big Idea Book

This is a short book (87 pages). Much of it is biographical information on Einstein, so now the book is even shorter. Substantive ideas are repeats - same thoughts, same wording - of what has been said before. If the reader wishes for a fresh explanation, this is not the book to read.

Strathern states that Einstein's E=MC2 "implied that matter is solidified energy." Strathern doesn't explain why he uses "matter" as opposed to mass, or explain the significance of light squared. If matter is solidified energy, is light to be understood as its counterpart: purified (of mass) energy? As light is a massless particle, and as gravity pulls light, is it accurate to say that gravity acts on (pure) energy as well as mass?* While mass and energy are equivalent, where does a light particle fit in? How is a light particle different from mass since it is massless and how is it different from energy as it's a particle?

Strathern writes that "Einstein showed that when a particle traveled at a speed approaching that of light its mass increased, requiring ever vaster amounts of energy to propel it." We know about Einstein's thought experiments, but this still prompts a question: What particle? As light is a (massless) particle that travels at light speed, how would it increase its mass if it is massless? And, just to throw this in, what "propels" light?

Strathern says of Einstein that time becomes "zero at the speed of light." As time involves duration, how does it become zero (no duration) when, for example, light is used to measure time across light years, which involves extensive duration? And, what is the distinction between speed of light and time when Strathern writes that "our entire notion of ultimate speed (and thus space, and thus time) depended upon the speed of light," which ties them together? This exemplifies a problem with this book. Strathern makes many bottom-line statements without explaining how he got there.

*N.B. In his Lectures on Physics, Feynman writes: "Even light, which as an energy, has a 'mass.' When a light beam, which has energy in it, comes past the sun there is an attraction on it by the sun."