The Perfect Theory

Pedro G. Ferreira “The Perfect Theory: A Century of Geniuses and the Battle over General Relativity”, Houghton Mifflin Harcourt, 2014, 235 pps  

Reading this book uncovered a talent I have: Apparently I can read 235 pages of something I mostly do not understand, yet, enjoy the journey. Author Pedro G. Ferreira is a professor of astrophysics at the University of Oxford. An expert in cosmology, the early universe and general relativity, he writes frequently for trade and academic science publications and is a regular commentator for the BBC.  This book reminds me of the enjoyment I got years ago watching Carl Sagan on TV.

My Notes:

Pg. 8:  In Newtonian gravity, an isolated planet orbiting the sun follows a simple, closed orbit with the shape of a squashed circle, known as an ellipse.  A planet will go around and around, endlessly following the same path, periodically getting closer to and then more distant from the sun.  The point in its orbit at which the planet is closest to the sun—called its perihelion—remains constant over time.  Some planets, like the Earth, have almost circular orbits—the ellipse is barely squashed—while others, like Mercury, follow much more elliptical paths.

Pg. 29:  Einstein first formulated his field equations in 1915 and he wanted to solve them himself.  These equations explain the relationship among gravity, space, and time.

 Finding a solution to his equations that could accurately model the whole universe seemed a good place to start.  In Einstein’s theory, the distribution of matter and energy told space-time what to do.  To model the universe as a whole, he needed to consider all the matter and energy in the universe.  The simplest and most logical assumption, and the one Einstein adopted in his first attempt, was that matter and energy are spread evenly throughout the whole of space.  He was just continuing the Copernican revolution which had made our place in the cosmos more insignificant.  The assumption that the universe was full of stuff, evenly spread out, made the field equations much simpler, but it also led to a very strange result: at some point, all the evenly distributed bits of energy and matter would start moving relative to each other.  Eventually everything could even fall in on itself, pulling space-time along with it and causing the entire universe to collapse out of existence.

Pg. 29:  In 1916 astronomers’ and Einstein’s view of the cosmos was mostly limited to the Milky Way; there was little sense of what lay beyond it.  Observations seemed to show that stars were moving about a little bit, but not dramatically, the sky seemed static, and there was no evidence that the universe was collapsing or expanding.  Letting his intuition get the better of him, Einstein attached a new constant term to his field equations.  This constant would stabilize the universe.  (He later called this constant addition his biggest mistake).

Pg. 33:  Alexander Friedmann ignored Einstein’s results and came up with a startling fact: that one number, the overall curvature of space, evolved with time.  However, Friedmann died in 1925, at the age of thirty-seven, and his mathematical model of an evolving universe was to lie dormant for a number of years.

Pg. 40:  Edwin Hubble in 1925 was able to figure out that Andromeda’s distance from Earth was almost a million light-years, five to ten times more than what was then the estimate of the size of the Milky Way, so it was apparent that Andromeda could not be part of the Milky Way.  The natural explanation was that Andromeda was simply another galaxy, just like the Milky Way.  And if this was true of Andromeda, why shouldn’t it be true of many other nebulae? With that one measurement, Hubble made the universe a much bigger place.

Pg. 93:  Radio waves behave just like light waves, but their wavelengths are a billon times longer than those of visible light.  The light we can actually see, which makes up the bulk of the sun’s rays, has a wavelength that is less than a millionth of a meter.  Radio waves have gigantic wavelengths, ranging from a millimeter all the way up to hundreds of meters.

Pg. 137:  General relativity stood alone in its incompatibility with quantum physics.  The ascent of the quantum after the Second World War led to a completely new and powerful theory that brought together all the forces with the fundamental constituents of matter as a simple, coherent whole—all the forces, that is, except gravity.  So the challenge of unification remained: how to come up with a common way of dealing with all four fundamental forces: gravitational, electromagnetic, weak, and strong.

Pg. 193:  Stephen Hawking in just under two decades of research had made lasting contributions touching on the birth of the universe and black hole physics.  His crowning achievement announced in 1975 had been the proof that black holes would radiate, had entropy and a temperature, and would ultimately evaporate. 

Pg. 211:  General relativity’s prediction that 96 percent of the universe is dark and exotic could just mean that our theory of gravity is breaking down. 

Pg. 216:  Einstein’s theory remained a resounding success if you steered clear of the minefield of quantum gravity and didn’t need to work with the universe right at its beginning, when it was hot, dense, and messy.  On large scales, in astrophysics and cosmology, general relativity kept on giving.