Carlo Rovelli on Einstein's 'stroke of genius' (#43)
The theoretical physicist explains gravity and space-time simpler and more elegantly than anyone before him
There are certain books that, though slight in length, are immense in profundity.
They are the sorts of books best read slowly. The sorts of books that make you feel like you did as a child the moment you were taught some amazing fact—like how rain comes from clouds. Reading these books, you like your father is lifting you above his head and you are, for a short time, able to see a little bit farther.
Carlo Rovelli’s Seven Brief Lessons on Physics is that sort of book.
In just eighty pages, Rovelli explains, with all of the artistry of a novelist, ideas so previously unwieldy (e.g. gravity, relativity, quantum physics, thermodynamics) in such concise, plain terms and imbued with such grandeur, that he makes you feel both smarter and humbler.1
As you read it, you slow down. Not just to grasp what he is saying—and you must do that—but to delay what you fear will soon be the end of the book. The time when you’ll no longer be under the spell of Rovelli’s hypnotic pen.
We might as well begin with the most popular of the theories Rovelli describes: the General Theory of Relativity.
“In his youth,” Rovelli writes, “Albert Einstein spent a year loafing aimlessly. You don't get anywhere by not 'wasting' time- something, unfortunately, that the parents of teenagers tend frequently to forget.”
What did Einstein’s aimless loafing lead to?
That’s the subject of today’s OGT.
Einstein’s ‘Moment of Enlightenment’
Rovelli starts us off from where Einstein did—at Newton’s idea of the world.
Newton had tried to explain the reason why things fall and the planets turn. He had imagined the existence of a 'force' that draws all material bodies toward one another and called it 'the force of gravity.'
How this force was exerted between things distant from each other, without there being anything between them, was unknown -- and the great father of modern science was cautious of offering a hypothesis. Newton had also imagined that bodies move through space and that space is a great empty container, a large box that enclosed the universe, an immense structure through which all objects run true until a force obliges their trajectory to curve.
What this 'space' was made of, this container of the world he invented, Newton could not say.
Then, Rovelli brings in the the key ingredient that when contrasted with Newton’s mysterious force, led Einstein to imagine space differently.
Not as emptiness, but as material— as a kind of web.
But a few years before the birth of Einstein two great British physicists, Michael Faraday and James Maxwell, had added a key ingredient to Newton's cold world: the electromagnetic field.
This field is a real entity that, diffused everywhere, carries radio waves, fills space, can vibrate and oscillate like the surface of a lake, and 'transports' the electrical force. Since his youth Einstein had been fascinated by this electromagnetic field that turned the rotors in the power stations built by his father, and he soon came to understand that gravity, like electricity, must be conveyed by a field as well: a 'gravitational field' analogous to the 'electrical field' must exist.
He aimed at understanding how this 'gravitational field' worked and how it could be described with equations.
With the two ideas—gravitational force and the electromagnetic field, Einstein had an epiphany—they’re the same.
And it is at this point that an extraordinary idea occurred to him, a stroke of pure genius: the gravitational field is not diffused through space; the gravitational field is that space itself. This is the idea of the general theory of relativity. Newton's 'space,' through which things move, and the 'gravitational field' are one and the same thing.
It’s a moment of enlightenment. A momentous simplification of the world: space is no longer something distinct from matter—it is one of the “material” components of the world. An entity that undulates, flexes, curves, twists...
We are not contained within an invisible, rigid infrastructure: we are immersed in a gigantic, flexible snail shell. The sun bends space around itself, and Earth does not turn around it because of a mysterious force but because it is racing directly in a space that inclines, like a marble that rolls in a funnel. There are no mysterious forces generated at the center of the funnel; it is the curved nature of the walls that causes the marble to roll. Planets circle around the sun, and things fall, because space curves.
The OGT
Do I fully understand the General Theory of Relativity after reading this tiny book? Probably not.
But I have a stronger hold than I did before. And, better, I can start to ask the right questions—which is the beginning of understanding.2
If you’re trying to understand the basics about the less intuitive topics of the world in which you have no background—e.g. quantum mechanics, temperature, or genetics— Rovelli is the sort of writer to read. Someone who knows that esoteric subject matter so well, as Einstein once said, that he could explain it to a 6th grader.
What makes Rovelli even more compelling, is that like Siddhartha Mukherjee or Rachel Carson, he can simplify complexity and make it sing like a story.
Smarter for your new knowledge you once thought inaccessible. Humbler because, with the veil lifted, the universe has grown larger and stranger.
It also allows me to learn more about it. I really like this channel for a visual explanation.