Bob Nichols's Reviews > Einstein's Universe

This is the third time around on this book - each time you move ahead just a wee bit more in trying to crack the Einstein code. There's much in the way to recommend in this book, but it's interspersed with weak spots for the general reader on several important questions, particularly related to the General Theory (Calder begins with Einstein's 1915 General Theory and only then goes back to the 1905 Special Theory). Regarding the weak spots:

1. In the reference to "falling objects," "falling" suggests downward, but Wheeler says objects free float in space and that Einstein did away with gravitational "pull" so what does it mean to say an object "falls"? For that matter, if there is no up and down in space (no fixed reference point), why doesn't an object "move upward?" Calder leaves it to the reader to figure something out. In warped space, there's always movement toward depressions in space (massive bodies). Is that "falling"?

2. Calder doesn't explain why a falling body doesn't always move into a larger body. What keeps them apart? Does the speed of a moving body, which Calder mentions almost incidentally, play a key role in keeping a body falling at the same rate as another (hence, orbits), and is there a balance" or equilibrium between having too much speed (escaping influence) or too little speed (falling into another body)?

3. Related to # 2, why does matter congeal to form mass? Does the lack of speed have a role. The author does not say.

4. Calder refers numerous times to "empty space". If space is a "fabric," what does it consist of? If space stretches due to a massive body, what is it that "stretches?" Calder is silent, although perhaps his answer is implicit as he does note that space is filled ("crisscrossed with") photons and we speculate now about dark energy and matter. Is all of this the "something" of space?

5. The author says space is dense near a massive body and that this slows down the speed of light. How is it that space both stretches (around a mass) and is also denser? Does a massive body create both effects?

6. Does a smaller mass moving toward a larger mass accelerate (move faster "downhill")? With acceleration, is there a gain of mass ("energy of motion") per Einstein, and an increased gravitational effect because of additional mass?

7. If under Einstein, there's a gain in mass with increased speed (energy of motion), does a runner then gain mass and not expend or shed energy as we believe to be the case? There's something wrong here.