Reality is Not What it Seems: The Journey to Quantum Gravity
by Carlo Rovelli
30 popular highlights from this book
Key Insights & Memorable Quotes
Below are the most popular and impactful highlights and quotes from Reality is Not What it Seems: The Journey to Quantum Gravity:
“The atoms of our body, as well, flow in and away from us. We, like waves and like all objects, are a flux of events; we are processes, for a brief time monotonous”
“You don’t get to new places by following established tracks.”
“We are all in the depths of a cave, chained by our ignorance, by our prejudices, and our weak senses reveal to us only shadows. If we try to see further, we are confused; we are unaccustomed. But we try. This is science. Scientific”
“I believe that this example demonstrates how great science and great poetry are both visionary, and may even arrive at the same intuitions. Our culture is foolish to keep science and poetry separated: they are two tools to open our eyes to the complexity and beauty of the world.”
“There is a feeling of deep universalism, in the wake of the splendid words of Democritus: “To a wise man, the whole earth is open, because the true country of a virtuous soul is the entire universe.”
“Quantum mechanics extends this relativity in a radical way: all variable aspects of an object exist only in relation to other objects. It is only in interactions that nature draws the world.”
“In the world described by quantum mechanics there is no reality except in the relations between physical systems. It isn’t things that enter into relations but, rather, relations that ground the notion of ‘thing’. The world of quantum mechanics is not a world of objects: it is a world of events. Things are built by the happening of elementary events: as the philosopher Nelson Goodman wrote in the 1950s, in a beautiful phrase, ‘An object is a monotonous process.’ A stone is a vibration of quanta that maintains its structure for a while, just as a marine wave maintains its identity for a while before melting again into the sea.”
“Quantum mechanics reveals to us that the more we look at the detail of the world, the less constant it is. The world is not made up of tiny pebbles. It is a world of vibrations, a continuous fluctuation, a microscopic swarming of fleeting microevents.”
“The incompleteness and the uncertainty of our knowledge, our precariousness, suspended over the abyss of the immensity of what we don’t know, does not render life meaningless: it makes it interesting and precious.”
“Science is a continual exploration of ways of thinking. Its strength is its visionary capacity to demolish preconceived ideas, to reveal new regions of reality, and to construct new and more effective images of the world. This adventure rests upon the entirety of past knowledge, but at its heart is change.”
“Science is born from this act of humility: not trusting blindly in our past knowledge and our intuition. Not believing what everyone says. Not having faith in the accumulated knowledge of our fathers and grandfathers. We learn nothing if we think that we already know the essentials, if we assume that they were written in a book or known by the elders of the tribe. The centuries in which people had faith in what they believed were the centuries in which little new was learned.”
“Things change only in relation to one another. At a fundamental level, there is no time.”
“The most credible answers are the ones given by science, because science IS the search for the most credible answers available, not for answers pretending to certainty.”
“This does not mean that science is just the art of making measurable predictions. Some philosophers of science overly circumscribe science by limiting it to its numerical predictions. They miss the point, because they confuse the instruments with the objectives. Verifiable quantitative predictions are instruments to validate hypotheses. The objective of scientific research is not just to arrive at predictions: it is to understand how the world functions; to construct and develop an image of the world, a conceptual structure to enable us to think about. Before being technical, science is visionary.”
“An elementary structure of the world is emerging, generated by a swarm of quantum events, where time and space do not exist. Quantum fields draw together space, time, matter, and light, exchanging information between one event and another. Reality is a network of granular events; the dynamic that connects them is probabilistic; between one event and another, space, time, matter, and energy melt into a cloud of probability.”
“Science is about reading the world from a gradually widening point of view.”
“The world, particles, light, energy, space, and time—all of this is nothing but the manifestation of a single type of entity: covariant quantum fields.”
“Science is not reliable because it provides certainty. It is reliable because it provides us with the best answers we have at present. Science is the most we know so far about the problems confronting us. It is precisely its openness, the fact that it constantly calls current knowledge into question, which guarantees that the answers it offers are the best so far available: if you find better answers, these new answers become science.”
“But it is not only space that curves: time does too. Einstein predicts that time on Earth passes more quickly at higher altitude, and more slowly at lower altitude. This is measured, and also proves to be the case. Today we have extremely precise clocks, in many laboratories, and it is possible to measure this strange effect even for a difference in altitude of just a few centimeters. Place a watch on the floor and another on a table: the one on the floor registers less passing of time than the one on the table. Why? Because time is not universal and fixed; it is something that expands and shrinks, according to the vicinity of masses: Earth, like all masses, distorts spacetime, slowing down time in its vicinity. Only slightly—but two twins who have lived respectively at sea level and in the mountains will find that, when they meet up again, one will have aged more than the other”
“Space is created by the interaction of individual quanta of gravity.”
“Change is ubiquitous. Only: elementary processes cannot be ordered along a common succession of instants. At the extremely small scale of the quanta of space, the dance of nature does not develop to the rhythm kept by the baton of a single orchestral conductor: every process dances independently with its neighbours, following its own rhythm. The passing of time is intrinsic to the world, it is born of the world itself, out of the relations between quantum events which are the world and which themselves generate their own time.”
“The importance of experimental proof, on the other hand, does not mean that without new experimental data we cannot make advances. It is often said that science takes steps forward only when there is new experimental data. If this were true, we would have little hope of finding the theory of quantum gravity before measuring something new, but this is patently not the case. Which new data were available to Copernicus? None. He had the same data as Ptolemy. Which new data did Newton have? Almost none. His real ingredients were Kepler's laws and Galileo's results. What new data did Einstein have to discover general relativity? None. His ingredients were special relativity and Newton's theory. It simply isn't true that physics only advances when it is afforded new data.”
“Quantum mechanics teaches us not to think about the world in terms of "things" that are in this or that state but in terms of "processes" instead. A process is the passage from one interaction to another. The properties of "things" manifest themselves in a granular manner only in the moment of interaction-that is to say , at the edges of the processes-and are such only in relation to other things. They cannot be predicated in an unequivocal way, but only in a probabilisitc one. This is the vertiginous dive taken by Bohr, Heisenberg, and Dirac-into the depth of the nature of things.”
“Clues put us on the right path toward a correct theory. Strong evidence is that which subsequently allows us to trust whether the theory we have built is a good one or not. Without”
“The world is strange, but simple”
“For Aristotle, physics works as follows: first, it is necessary to distinguish between the heavens and Earth. In the heavens, everything is made up of a crystalline substance that moves in a circular motion and turns eternally around Earth in great concentric circles, with the spherical Earth at the center of everything. On Earth, on the other hand, it is necessary to distinguish between forced motion and natural motion. Forced motion is caused by a thrust and ends when the thrust ends. Natural motion is vertical—upward or downward—and depends both on the substance and the location. Each substance has a “natural place,” that is to say, a proper altitude to which it always returns; earth at the bottom, water a little way above it, air a little higher still, and fire even higher. When you pick up a stone and let it fall, the stone moves downward because it wants to return to its natural level. Air bubbles in water, fire in the air, or children’s flying balloons move upward instead, again seeking their natural place.”
“Ami engem illet, én jobban szerek szembenézni tudatlanságunkkal, elfogadni, és egy kevéssel túllátni rajta: megpróbálni megérteni, hogy mi az, amit megérthetünk. Nemcsak azért, mert ennek a tudatlanságnak az elfogadása ad kiutat a babonák és előítéletek fogságából, hanem legfőképpen azért, mert a szememben nem tudásunk elfogadása a legigazabb, a legszebb s főleg a legőszintébb út. Igyekezni minél messzebbre látni, igyekezni minél messzebbre jutni ez azok közé a csodálatos dolgok közé tartozik, amelyek értelmet adnak az életnek. Mint a szerelem, vagy mint nézni az égboltot. A tanulásvágy, a felfedező kíváncsiság, az, hogy tudni akarjuk, mi van a dombokon túl, az, hogy meg akarjuk kóstolni az almát ez tesz emberré bennünket.”
“the possibility that the Big Bang is not a real beginning, that there could have been another universe before it.”
“When Lemaître defends the idea that the universe is expanding, and Einstein does not believe it, one of the two is wrong; the other, right. All of Einstein’s results, his fame, his influence on the scientific world, his immense authority, count for nothing. The observations prove him wrong, and it’s game over. An obscure Belgian priest is right. It is for this reason that scientific thinking has power.”
“Science is born from this act of humility: not trusting blindly in our past knowledge and our intuition. Not believing what everyone says. Not having absolute faith in the accumulated knowledge of our fathers and grandfathers. We learn nothing if we think we already know the essentials, if we assume that they were written in a book or known by the elders of the tribe. The centuries in which people had faith in what they believed were the centuries in which little new was learned. Had they trusted the knowledge of their fathers, Einstein, Newton, and Copernicus would never have called things into question and would never have been able to move our knowledge forward (259, trsl. Carnell & Segre)”
