Seven Brief Lessons on PhysicsBook - 2016 | First American edition
The architecture of the cosmos
Grains of space
Probability, time, and the heat of black holes
From Library Staff
A homage to Hawking's Brief History of Time, Rovelli's Brief Lessons is also very much an updated version of Hawking's bestseller. Reviewers have called Rovelli's prose poetic.
From the critics
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The heat of black holes is a quantum effect upon an object, the black hole, which is gravitational in nature. It is the individual quanta of space, the elementary grains of space, the vibrating “molecules,” that heat the surface of black holes and generate black hole heat.
Nature is our home, and in nature we are at home. This strange, multicolored, and astonishing world that we explore— where space is granular, time does not exist, and things are nowhere— is not something that estranges us from our true selves, for this is only what our natural curiosity reveals to us about the place of our dwelling. About the stuff of which we ourselves are made. 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.
If we are special, we are only special in the way that everyone feels themselves to be, like every mother is for her child. Certainly not for the rest of nature.
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.
All of our cousins are already extinct. What’s more, we do damage. The brutal climate and environmental changes that we have triggered are unlikely to spare us. For Earth they may turn out to be a small irrelevant blip, but I do not think that we will outlast them unscathed— especially since public and political opinion prefers to ignore the dangers that we are running, hiding our heads in the sand.
There are frontiers where we are learning, and our desire for knowledge burns. They are in the most minute reaches of the fabric of space, at the origins of the cosmos, in the nature of time, in the phenomenon of black holes, and in the workings of our own thought processes.
the difference in the passage of time is enormous, and what for the observer on the star would seem an extremely rapid bounce would appear, seen from outside it, to take place over a very long time. This is why we observe black holes remaining the same for long periods of time: a black hole is a rebounding star seen in extreme slow motion.
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...
The flow of time emerges thus from physics, but not in the context of an exact description of things as they are. It emerges, rather, in the context of statistics and of thermodynamics.
A university student attending lectures on general relativity in the morning and others on quantum mechanics in the afternoon might be forgiven for concluding that his professors are fools or have neglected to communicate with one another for at least a century. In the morning the world is curved space where everything is continuous; in the afternoon it is a flat space where quanta of energy leap.
It is not the first time that physics finds itself faced with two highly successful but apparently contradictory theories. The effort to synthesize has in the past been rewarded with great strides forward in our understanding of the world. Newton discovered universal gravity by combining Galileo’s parabolas with the ellipses of Kepler. Maxwell found the equations of electromagnetism by combining the theories of electricity and of magnetism. Einstein discovered relativity by way of resolving an apparent conflict between electromagnetism and mechanics.
Minuscule moving wavelets. They disappear and reappear according to the strange laws of quantum mechanics, where everything that exists is never stable and is nothing but a jump from one interaction to another.
It’s clear that there is something there, but we don’t know what. Nowadays it is called “dark matter.” Evidence indicates that it is something not described by the Standard Model; otherwise we would see it. Something other than atoms, neutrinos, or photons . . .
For now, this is what we know of matter: 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.
... general relativity is a compact gem: conceived by a single mind, that of Albert Einstein, it’s a simple and coherent vision of gravity, space, and time. Quantum mechanics, or “quantum theory,” on the other hand, has gained unequaled experimental success and led to applications that have transformed our everyday lives ...
Einstein's words on photon:
In accordance with the assumption to be considered here, the energy of a light ray spreading out from a point source is not continuously distributed over an increasing space but consists of a finite number of “energy quanta” which are localized at points in space, which move without dividing, and which can only be produced and absorbed as complete units.
Science begins with a vision. Scientific thought is fed by the capacity to “see” things differently than they have previously been seen.
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.
...here the magical richness of the theory opens up into a phantasmagorical succession of predictions that resemble the delirious ravings of a madman but have all turned out to be true.
Equation of the general theory of relativity (GTR) described by the curvature of space-time (ab are subs:)
Rab - ½ R gab = Tab
Murray Gell-Mann named “quarks,” inspired by a seemingly nonsensical word in a nonsensical phrase in James Joyce’s Finnegans Wake: “Three quarks for Muster Mark!”
SummaryAdd a Summary
For Carlo Rovelli, a theoretical physicist, the thrill of discovering how the universe functions, does not fade. The first six chapters celebrate Rovelli's awe of the beauty of the laws of nature. In the seventh chapter, he explores the relationship between human nature and these natural laws. When we consider gravity, or the structure of the atom for example, we automatically think of what's going to happen. If we drop a ball, or react two chemicals together, the exact same thing is always going to happen. Predictability is a critical feature of nature's laws. How is it that humans are objects within the universe, and thus, subject to natural law, yet their behavior seems so unpredictable? Perhaps our conception of the predictability of human behavior is too narrow? Rovelli's final observation is that the human species seems inexorably bent on self-destruction. As he says, "The...climate and environmental changes that we have triggered are unlikely to spare us." Nevertheless, acknowledging the possibility of this outcome is not discouraging to Rovelli in the ending of the book.
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