Extragalactic background radiation Book

This Calder book is disappointing. The author has a penchant for making bold statements about Einstein's theories on how the cosmos operates, but then he does not provide a clear description about what is meant by such statements. Thus, Calder states that because gravity affects light, gravity also affects time. This statement has a lot of potential but the reader fails to get a description about how, exactly, light is time. Or, in regard to Einstein's theory, the author states that the speed of light is more fundamental than space or time. Yet, how that is so is not clear. In his last chapter, Calder attempts to put Einstein's cosmology into the grandest of perspectives by saying that as time began with the big bang, the word "before" (the big bang) has no meaning. Calder then goes on to say that such insights constitute the convergence of all scientific, philosophical and religious thought. This is probably true, but Calder is not one to describe how this might be so.

To be sure, there is a responsibility of the reader to work at the material to dig out meaning. In this book, we understand that gravity's effect on space and time was central for Einstein. We also understand that gravity therefore abolishes the notion of absolute time and space. Thinking this through, we know that in Einstein's theory mass and energy are equivalent, that light (waves that move across time and space) is energy with some mass and, therefore, subject to gravitation from massive bodies that bend (i.e., make non-absolute) space and time (light). We can understand bit by bit and, given that this is Einstein, perhaps that's all that can be done. Calder takes the reader a few steps further down the road, even though one hoped for more.