How The Universe Got Its Spots

Janna Levin, “How The Universe Got Its Spots”, Princeton Univ. Press, 2002, 197 Pages

Some months ago, I was listening to an NPR interview of this author and this led me to reading this book. Janna Levin (Ph.D) is an Advanced Fellow in the Department of Applied Mathematics and Theoretical Physics at Cambridge University. This book is allegedly written as a diary of unsent letters to her mother describing what the author knows about the shape and extent of the universe. It is written so the unwashed (that’s me) can follow along. It turns out that we still do not know whether the universe is infinite or finite but there is hope that more discoveries will lead us to the answer. I found the book very interesting in parts and baffling in others.

My Notes:

Pg. 26: If Newtonian mechanics was correct, we would find by charting the earth’s motion through the invisible ether that we could identify the state of absolute rest. One way to measure our relative motion is to measure the speed of light as the earth orbits the sun. The speed of light should increase in one direction and decrease in the other, just like a train approaches faster if you run towards it than if you run away. Michelson and Morley devised experiment to accurately measure the speed of light and discovered that, contrary to the Newtonian prediction, the speed of light was exactly the same in all directions and at all points along the earth’s orbit. It always moves and always at the same speed, c, which equals 300,000 km per second. So, the speed of light refuses to depend on the observer’s speed. The absolute structure of space and time and the relative speed of light switched places in Einstein’s theory of special relativity. In special relativity, and in reality as far as we can assess it, the speed of light is an absolute constant and the structure of space and time is relative.

It was really Einstein who stood strong when he came to the idea that there was no absolute time and no absolute space. We cannot measure our velocity relative to absolute space because absolute space does not exist. The laws of physics must therefore be the same for all observers in relative motion, since these observers are truly equivalent. Light requires no medium, no ether. It is pure energy and propels itself forward as the oscillation of an electromagnetic field.

Pg. 29: The principle of relativity asserts that the laws of physics must be the same for all inertial observers, for all observers moving freely in the absence of forces. All observers will experience the same consequences of atomic interactions. All that matters is relative motion. No observer could ever prove it is the other that is moving. The constancy of the speed of light in conjunction with the principle of relativity forces two observers in relative motion to disagree on their measures of space and time.

Pg. 35: To make gravity and special relativity consistent, Feinstein invented the general theory of relativity. He discarded the notion of gravity as a force and replaced it with a theory of curved space. Matter and energy curve space, and our experience of gravity is our fall along these natural curves. Action at a distance was overthrown and in its place emerged a theory of geometry: that is, a theory of curved spaces. Spacetime itself became something.

Pg. 44 Newton’s laws assert that in the absence of forces an object will move along a straight line. In Einstein’s theory of curved space, objects and light beams follow the straightest path they can find. Light and matter are lazy and take the path of least resistance, and on a curved space, the path of least resistance will not be strictly straight.

Pg. 70: If Jupiter were a bit more massive it would be able to ignite nuclear reactions and light up as a star.

Pg 74: No one foresaw that black holes as extravagant as 100 million suns could burgeon from the cores of galaxies, but now we think they do reside there in nearly every galaxy including our own. Black holes are a portal to a fundamental theory of physics beyond Einstein, beyond quantum mechanics. Giving us these clues, black holes press us to pursue that final theory of quantum gravity. The other doorway to quantum gravity is the big bang.

Pg. 79: Is it possible to have all galaxies appear to recede from every other galaxy? The answer is yes, but only if we accept that it is not the galaxies that are moving but the space between them which is stretching.