Book Reviewed: Seven Brief Lessons on Physics, by Carlo Rovelli

A simplified introduction to physics and reality for a non-cognoscente

Theoretical physicist Carlo Rovelli has condensed physics ideas into this 78 pages book. This work is the result of a series of articles published in an Italian newspaper. Building basic concepts to comprehend the nature of reality has not been simple for theoretical physicists, but the author has spared the narratives for leaner and lucid descriptions in the hopes that these ideas stir up some interest among readers. There is no math and no heavy discussion of relativity or quantum physics. String physics is not included in this discussion. This is certainly a good way to bring modern physics for general readers. This reminds me of Nobel Laureate Richard Feynman’s “Six Easy Pieces: Essentials of Physics Explained.” This book has appeared in many versions and captured the minds of readers in theoretical physics. But Rovelli covers only seven topics that include relativity, quantum physics, particle physics and black holes.

The author is one of the inventors of loop quantum gravity which says that space is not continuous but it is made of grains, significantly smaller than an electron, and they are linked to each other forming a network. Quantum gravity essentially refers to quantum properties of space-time and not the quantum behavior of matter in spacetime. But the author has not discussed loop quantum gravity theory in any depth in this book.

A brief summary of the book is as follows: In quantum physics, you can be at two places at the same time but in relativity or Newtonian physics this is crazy. In quantum physics a conscious observes creates perceived reality, but it is impossible according our common sense. Physicists are also divided about the concept of space and time. Some believe that space is real, and time is an illusion; but others argue that time is real, and space is an illusion. The very fabric of spacetime has been investigated in string/brane physics and loop quantum gravity to determine if space is continuous or it exists in discrete quanta like matter at the quantum level. Rovelli suggests that time is not real and he says that it exists because of thermodynamics. In fact there is no such thing as past or future either in relativity or quantum physics. The physics formulas do not contain the time parameter. Rovelli says that flow of time is a matter of statistics.

One of Einstein’s predictions is that gravity slows down time; hence time dilation occurs for individuals at two different levels of gravity. In the film “Interstellar,” an hour on a planet orbiting a black hole is equivalent to seven years on Earth! Now some physicists argue that gravity produces the physical reality we observe in a quantum physics experiments. Through its effect on time dilation, which effectively produces decoherence of matter, a conscious observer is not needed to collapse a wave function such as in a Schrodinger’s Cat thought experiment. In essence gravitational decoherence is responsible for physical reality and not a conscious observer!

The author muses on human existence and our perception of physical reality. It is a song of god in which matter (energy) behave in spacetime guided by a set of physical laws. According to Isaac Newton, space was the “sensorium of God”, the organ through which He surveyed the creation; it is absolute, unchanging, and infinite. In our current understanding of things, somehow Newtonian physics, relativistic physics, quantum physics and thermodynamics connect with each other to create the nature of reality. But we are further away in comprehending it, and author Rovelli understands this better than many physicists.