Lessons of Physics

I read 7 Brief Lessons on Physics by Carlo Rovelli over the weekend. A short read, but jam packed with essential concepts in Physics explained in simple English. The book has a very poetic and philosophical feel, and contains lots of dramatic passages, that a sceptic might think are woo-woo or imaginary. But the book is based on pure scientific facts which are so fascinating that it needs no other imagination or creativity. Here is a summary of my Kindle Highlights and quotes I found interesting.

Light is made up of photons, the particles of light intuited by Einstein. The things we see are made of atoms. Every atom consists of a nucleus surrounded by electrons. Every nucleus consists of tightly packed protons and neutrons.

Quantum mechanics and experiments with particles have taught us that the world is a continuous, restless swarming of things, a continuous coming to light and disappearance of ephemeral entities. A world of happenings, not of things.

We are made of the same stardust of which all things are made, and when we are immersed in suffering or when we are experiencing intense joy, we are being nothing other than what we can’t help but be: a part of our world.

A handful of types of elementary particles, which vibrate and fluctuate constantly between existence and nonexistence and swarm in space, even when it seems that there is nothing there, combine together to infinity like the letters of a cosmic alphabet to tell the immense history of galaxies; of the innumerable stars; of sunlight; of mountains, woods, and fields of grain; of the smiling faces of the young at parties; and of the night sky studded with stars.

A physicist is only too happy when he finds a conflict of this kind between successful theories: it’s an extraordinary opportunity. Can we build a conceptual framework for thinking about the world that is compatible with what we have learned about it from both theories?

The equations describing grains of space and matter no longer contain the variable “time.” This doesn’t mean that everything is stationary and unchanging. On the contrary, it means that change is ubiquitous.

What we find is that when the universe is extremely compressed, quantum theory generates a repulsive force, with the result that the great explosion, or “big bang,” may have actually been a “big bounce.” Our world may have actually been born from a preceding universe that contracted under its own weight until it was squeezed into a tiny space before “bouncing” out and beginning to re-expand, thus becoming the expanding universe that we observe around us.

In every case in which heat exchange does not occur, or when the heat exchanged is negligible, we see that the future behaves exactly like the past.

The difference between past and future exists only when there is heat. The fundamental phenomenon that distinguishes the future from the past is the fact that heat passes from things that are hotter to things that are colder.

But many times in the past we have realized that it is our immediate intuitions that are imprecise: if we had kept to these we would still believe that Earth is flat and that it is orbited by the sun. Our intuitions have developed on the basis of our limited experience. When we look a little further ahead, we discover that the world is not as it appears to us: Earth is round, and in Cape Town their feet are up and their heads are down. To trust immediate intuitions rather than collective examination that is rational, careful, and intelligent is not wisdom: it is the presumption of an old man who refuses to believe that the great world outside his village is any different from the one that he has always known.

“what’s non-apparent is much vaster than what’s apparent.” From this limited, blurred focus we get our perception of the passage of time. Is that clear? No, it isn’t. There is so much still to be understood.

We are an integral part of nature; we are nature, in one of its innumerable and infinitely variable expressions. This is what we have learned from our ever-increasing knowledge of the things of this world.

Who knows how many and which other extraordinary complexities exist, in forms perhaps impossible for us to imagine, in the endless spaces of the cosmos? There is so much space up there that it is childish to think that in a peripheral corner of an ordinary galaxy there should be something uniquely special. Life on Earth gives only a small taste of what can happen in the universe. Our very soul itself is only one such small example.