Reality is not what it seems

by Carlo Rovelli

Introduction

  I like the physics because it opens a window through which we can see further.

  In the course of the centuries, we have come to realize just how very many wrong ideas we had

  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. → is there any possible of invisible hand?

  Latest indications given by nature, such as the confirmation of the cosmological Standard Model obtained from the Planck satellite and the failure at CERN to observe the supersymmetric particles that many expected. → it discusses consequences of these ideas; the granular structure of space; the disappearance of time at small scale, the physics of the Big Bang; the origin of black hole heat

  ## like an escaped caveman, Christianity must tell about the light, - life, truth. In other words, they must provide us with window to see outside the cave. But just tell about deadness, untruth, trivial. Reality was changed by sciences. What it seems is not reality, but they just tell what it seems. They also restrain our thinking instead of freeing from prejudice, absurdity. Narrowing point of view instead of widening.

Part one: Roots

Grains

The Milesians understand that by shrewdly using observation and reason, rather than searching for answers in fantasy, ancient myths, or religion – and above all by using critical thought in a discriminating way – it is possible to repeatedly correct our world view and to discover new aspects of reality that are hidden to the common view. It is possible to discover the new.

The decisive discovery is that of a different style of thinking where the disciple is no longer obliged to respect and share the ideas of the master but is free to build on those ideas without being afraid to discard or criticize the part that can be improved. This is a novel middle way, placed between full adherence to a school and generic deprecation of ideas.

Anaximander understand that Earth floats in the sky and the sky continues beneath Earth; that rainwater comes from the evaporation of water on Earth; that the variety of substances in the world must be susceptible to being understood in terms of a single, unitary, and simple constituent, which he calls apeiron, the indistinct: that animals and plants evolve and adapt to changes in the environment, and that man must have evolved from other animals.

For the first time men doubt that only the gods are capable of accounting for the mysteries of the world.

Atoms have no qualities at all, apart from their shape. They have no weight, no color, no taste. “Sweetness is opinion, bitterness is opinion; heat, cold and color are opinion; in reality only atoms. And vacuum”

Nature continues to experiment with forms and structures; and we, like the animals, are the products of a selection that is random and accidental, over the course of eons of time. Our life is a combination of atoms, our thoughts are made up of thin atoms, our dreams are the products of atoms; our hopes and our emotions are written in a language formed by combinations of atoms; the light that we see is composed of atoms, which brings us images.

The thought that thus emerges is a kind of intense humanism rationalist and materialist.

Plato and Aristotle understand the world in finalistic terms → everything that happens has a purpose, a way of thinking that would reveal itself to be very misleading for understanding the ways of nature. He wanted to know what good it was for Earth to be round

1-1 Is there a limit to divisibility?

All scientific knowledge was to be destroyed, and only one sentence passed on to the next generation of creatures→ all things are made of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another.

Could small particles of extended dimension remain? No because if this were the case the piece of matter would not yet broken up to infinity.

Zeno of pupil of Parmenides support fundamentalist rationalism: Zeno’s paradox → infinite number of strings can make a finite string, an infinite number of increasingly short time may make a finite time, → will end up catching the tortoise

Leucippus suggests, noting arbitrarily small exists there is a lower limit to divisibility. The extension of string must be formed by a finite number of finite objects with finite size. → the string cannot be cut as many times as we want; matter is not continuous, it is made of individual atoms of a finite sized. 

Water is composed of two parts hydrogen and one part oxygen.

1905: the definitive proof of the atomic hypothesis by Einstein   by Brownian motion  

1-2 the nature of things

If all the works of Democritus had survived, and nothing of Aristotle’s, the intellectual history of our civilization would have been better. But centuries dominated by monotheism have not permitted the survival of Democritus’s naturalism. Plato and Aristotle, pagans who believed in the immortality of the soul or in the existence of a Prime Mover could be tolerated by a triumphant Christianity. Not Democritus.

Epicurus →→ pupil of a pupil of Democritus and Lucretius

Lucretius:  do you not see that nature is clamoring for two things only a body free from pain, a mind released from worry and fear for the enjoyment of pleasurable sensations?

And there is a serene acceptance of the inevitability of death, which cancels every evil, and about which there is nothing to feat.  For Lucretius, religion is ignorance; reason is the torch that enlightens. → there is the simple idea of the finite divisibility of things. The granular quality of the world. 

2.The Classics

2-1 Isaac and the little moon

	Pythagoras		BC 570 ~ 495	Number governs forms and ideas
	Plato		BC 428 ~ 348
	Socrates		BC 469 ~ 399
	Aristoteles		BC 384 ~ BC 302
	Leucippus		BC 450 ~370	Teacher of Democritus
Euclid		BC mid 4th ~ mid 3rd		Element of Euclid
Ptolemy		AD 100 - 170
Copernicus		1473 ~ 1543
Galileo		1564~ 1642
Kepler		1571 ~ 1630
Newton		1642~1726

Pythagoras:  number governs forms and ideas

Plato:  carved on the door of his school the phrase: “let no one enter here who is ignorant of geometry”

Aristotle: Physics

Ptolemy: Almagest of Ptolemy is triumphs of this science.  Mathematics allows the world to be described and the future to be predicted: apparently wandering and disorderly movements of the planets can be precisely predicted by using mathematical formulas that Ptolemy, presents in a systematic and masterly way.

Copernicus made the leap forward that generations of Indian, Arab, and Persian astronomers had not been able to make.

Kepler: mathematical laws described with exactitude the movement of the planets around the sun.

Galilei: telescope, logical deduction from the cosmic revolution brought about by Copernicus. Experimental science begins with Galileo. Object do not fall always at a constant speed, that is constant is the acceleration.   9.8 meters per second per second.  

Newton: little moon that complete its orbit around Earth every hour and a half.  An object that orbits does not go straight; it continually changes direction, and a change of direction is an acceleration.  9.8 meter per second per second. The force causing objects to fall is same gravity that makes the little moon turn around Earth.

There is no longer separation between the heavens and Earth; there is no natural level for thins, there is no center to the world, no natural place →  subversion of the conceptual structure of the Aristotelian world.

The world of Newton is the world Democritus, rendered mathematical.

Newton’s equations→ build bridges, trains, and skyscrapers, engines and hydraulic systems

The world consists only of a great infinite space where, as time passes, particles move and attract one another by means of forces.

2-2 Michael: field and light

Electromagnetism is the force that hold together the matter that form solid bodies holds together atoms in molecules and electron in atoms. This is what makes chemistry and living matter work

Michael Faraday is an impoverished Londoner without formal education who works first in a bookbindery. He sees physics with his mind’s eye. And his mind’s eye creates worlds.

Line of forces →→ Maxwell’s equation describe the behavior of the electric and the magnetic fields. Mathematical version of the Faraday lines.  → design antennae, radios, electric engines, and computers.

    These same equations are needed to explain how atoms function (they are held together by electrical forces) why the particles of the material that forms a stone adhere together, or how the sun works.

    Light is nothing other than this rapid trembling of Faraday’s lines. Color is the frequency of the electromagnetic wave light is.  the wave vibrates rapidly, → blue, more slow → redder

    Faraday’s lines can also vibrate at much lower frequencies→ move electrical charges →build the radio.

Outstanding power of theoretical physics.

The world has changed no longer made up of particles in space, but of particles and fields in space.

Part two   The beginning of the revolution

3.Albert

3-1 the extended present

Maxwell equation determine a velocity

Newton’s equation is acceleration

Special relativity:  on the moon the duration of this intermediate zone is few seconds, on the mars quarter of hours. This means on the Mars there are events that in this precise moment have already happened, events that are yet to happen, but also a quarter of an hour of events during which things occur that are neither in our past nor in our future.

Space and time fuse together in a single concept of spacetime so electric and magnetic fields fuse together in the same way → electromagnetic field.

Concept of energy and mass get combined in the same way as time and space. Electric and magnetic fields are fused together. Energy and mass are two facets of the same entity, electric and magnetic fields are two facets of the same field and space and time are two facets of the one thing, spacetime. Space does not exist independently from time. Our intuitive idea of the present, the ensemble of all events happening now in the universe, is an effect of our blindness: our inability to recognize small temporal intervals.  The present is like the flatness of Earth: an illusion.

There isn’t an up and a down in the universe. Similarly, there isn’t always a before and an after between two events in the universe.   

3-2 the most beautiful of theories

The force of gravity must have its Faraday lines as well. → by analogy the force of attraction between the sun and Earth or between Earth and falling objects, must be attributed to a field “gravitational field.”

Space: Newton and Democritus : large empty container, a rigid box for the universe.  Democritus Atoms are being(full) and space nonbeing(empty), Newton arguing that space was God’s sensorium.

Two problems : first, How can we describe the gravitational field?  Second, what is Newton’s space?  → Newton’s space is nothing more than gravitational field. The world is made up of particles + fields and nothing else.

Space is no longer different from matter. It is one of the material components of the world, akin to the electromagnetic field. It is real entity that undulates, fluctuates, bends, and contorts. We are not contained within an invisible, rigid scaffolding. We are immersed in a gigantic, flexible mollusk.

It is the curved nature of the funnel wall that guides the rotation of the bead. Planets circle around the sun and things fall, because space around them is curved.  A little more precisely, what curves is not space but spacetime.

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.  Fig 3.8

Black hole stars burn as long as they have available hydrogen then die out. → the remaining material is no longer supported by the pressure of the heat and collapses under its own weight. → when this happens to a large enough star, the weight is so strong that matter is squashed down to an enormous degree and space curves so intensely as to plunge down into an actual hole.

Spacetime and the gravitational field are one and the same thing.

3-3 Mathematics or physics?

Einstein had a unique capacity to imagine how the world might be constructed, to see it in his mind. → for Einstein, the theory of general relativity is not a collection of equations; it is a mental image of the world arduously translated into equations.

3-4 the cosmos

The universe can be finite and at the same time have no boundary.

If infinite → there are not sufficient combinations of atoms to fill it with things always different from one another.  → there must exist somewhere a reader just like you who is reading the very same book.

3-sphere: something with a finite volume(sum of the volume of the two balls)but without borders.

Traditional representation of Dante’s universe fig 3-13

Everything attracts, therefore the only way for a finite universe not to collapse on itself is to be expanding. Universe is expanding, exactly as the equations predicted. Fourteen billion years ago, the universe was concentrated almost to a singly, furiously hot point. From there it expanded in a colossal cosmic explosion – this is the Big Band.

Space time is a field: world is made only of fields and particles.

4.Quanta

3 aspects of reality: granularity, indeterminism, and relationality

 4-1 albert again

      E = hv

It happens or does not happen depending on the color of light(the frequency) rather than its intensity(energy)

 4-2 Niels, Werner, and Paul

Since color is the frequency of light, light is emitted by substance at certain fixed frequencies. Color is the

      speed at which Faraday’s lines vibrate, and this is determined by the vibrations of the electric charges that

emit light

 

 4-3 Fields and Particles are the same thing

Convergence between the notion of particles used by Newton, and the notion of fields introduced by Faraday. → the notions of fields and particles, separated by Faraday and Maxwell, end up merging in quantum mechanics. → field behaves like a set of packets of energy.

Quantum mechanics → the world is not made up of fields and particles but of a single type of entity: quantum field. There is no longer particles that move in space with the passage of time, but quantum fields whose elementary events happen in spacetime.

  

4-4 Quanta 1: information is finite

Existence of a fundamental granularity in nature.

 

4-5 Quanta 2: indeterminacy

It is a world of vibrations, a continuous fluctuation, a microscopic swarming of fleeting microevents.

4-6 Quanta 3: reality is relational

The theory does not describe things as they are: it describes how things occur, and how they interact with each other. It doesn’t describe where there is a particle but how the particle shows itself to others.

4-7 but do we really understand?

It seems absurd to Einstein who had taught us that time is not universal and space bends

I think that the obscurity of the theory is not the fault of quantum mechanics but is rather duet to the limited capacity of our imagination.

To the very last, the desire to debate, to understand more. The very last doubt. This permanent doubt, the deep source of science.

Part three Quantum space and relational time

5.Spacetime is quantum

Einstein understood that spacetime squashes like a mollusk, time passes differently in different place.

 

 5-1 Matvei

The smaller the region where we try to locate particle, the greater the velocity at which it escapes.: Heisenberg’s uncertainty principle. → energy makes space curve (Einstein) a lot of energy in a small region results in curving space so much that it collapses into a black hole, like a collapsing star.

G: newton constant

C: speed of light

h: Panck constant

Matvei : points out that quantum mechanics and general relativity , taken together are incompatible with our customary idea of space as an infinitely divisible continuum

  

    

 5-2 John

He imagined it as a cloud of superimposed geometries, just as we can think of a quantum electron as a cloud of positions.

Wheeler’s equation →→ no longer contains the time variable.

 

 5-3 the loops’ first steps

Loop theory or loop quantum gravity : it is not the only direction explored in the search for a quantum theory of gravity, but it is the one I consider the most promising.

  

6.Quanta of space

Nodes: Lines intersect

Links: lines between nodes

Graph:  what a set of intersecting lines forms, a combination of nodes connected by links

It is in the nodes of the graph, not in the lines, that the volume of space resides.

    

    

 6-1 spectra of volume and area

The nodes of the graph represent the discrete packets of volume. The nodes are the elementary quanta of which physical space is made. Every node of the graph is a quantum particle of space.

Link is an individual quantum of a Faraday line.

Space appears continuous to us only because we cannot perceive the extremely small scale of these individual quanta of space, just as when we look closely at the cloth of a T-shirt, we see that it is woven from small threads.

General relativity taught us the space is something dynamic, like the electromagnetic field: in immense, mobile mollusk in which we are immersed, which stretches and bends.

Quantum mechanics teaches us that every field of this sort is made of quanta, has a fine, granular structure. It follows that physical space being a field, is made of quanta, as well. The same granular structure characterizing the other quantum fields also characterized the quantum gravitational field, and therefore space.

 

 6-2 atoms of space

There is a lower limit to the divisibility of space.

      

    

 6-3 spin networks

A spin network represents a quantum state of the gravitational field: a quantum state of space, a granular space in which area and volume are discrete.

The crucial difference between photons, the quanta of the electromagnetic  field, and the nodes of the graph, the quanta of gravity, is that photons exist in space, whereas the quanta of gravity constitute space itself.

Two nodes connected by a link are two nodes in proximity. They are two grains of space in contact with each other: this touching constructs the structure of space.

The quanta of gravity, this is are not in space; they are themselves space.

Physical space is the fabric resulting from the ceaseless swarming of this web of relations. The lines themselves are nowhere – they are not in a place but rather create places through their interactions. Space is created by the interaction of individual quanta of gravity.

    

7.Time does not exist

Special and general relativity made The inadequacy of our common-sense view of time explicit.

    

Things do not inhabit space; they dwell one over the other, and space is the fabric of their neighboring relations.

Time no longer exists in the fundamental theory: the quanta of gravity do not evolve in time. Time just counts their interrelations.  The fundamental equation (Wheeler-DeWitt) no longer contain the time variable. Time emerges, like space, from the quantum gravitational field. Time too must have those aspects of probabilistic indeterminacy, granularity and relationality, which are common to all of reality.

      

 

 7-1 time is not what we think it is

Special and general relativity made the inadequacy of our common sense view of time explicit.

Gravitational time dilatation: the closer you get to Earth, where gravity is more intense, the slower time passes

Every object in the universe has its own time, running at a pace determined by the local gravitational field. → this notion of a localized time no longer works. → quantum events are no longer ordered by the passage of time, the Planck scale. Time, in a sense, ceases to exist.

Absence of the variable time from the fundamental equations does not imply that everything is immobile, and that change does not happen. → it means that change is ubiquitous.  → every process dances independently with its neighbors, following its own rhythm.

 

 7-3 The candle Chandelier and the pulse

Galileo: oscillation of a pendulum all have the same duration by Galileo pulses. → measure pulse by clock(pendulum) → we never measure time itself → the existence of the variable time is a useful assumption, not the result of an observation.

That is to say, equations that tell us directly how many pulse-beats there are in an oscillation, without mentioning t.  → physics without time is physics where we speak only of the pulse and the chandelier, without mentioning time.

Things change only in relation to one another.   We must learn to think of the world not as something that changes in time, but in some other way.

The world described by the theory is far from the one we are familiar with. There is no longer space that contains the world, and no longer time during the course of which events occur.

Just as a calm and clear Alpine lake is made up of a rapid dance of a myriad of minuscule water molecules, the illusion of being surrounded by continuous space and time is the product of a farsighted vision of a dense swarming of elementary processes.

 

 7-4 spacetime sushi

Space and time are the gravitational field, Einstein’s mollusk: we are also including the gravitational field – that is to say, a piece of the mollusk – in the process. Everything is immersed in Einstein’s great mollusk: here, imagine that you are slicing a small, finite portion of it, like a piece of sushi, which encompasses the collision and what surrounds it.

Spacetime box

 

 7-5 spinfoams

Form because it is name of surfaces that meet on lines, which in turn meet on vertices, resembling a foam of soap bubbles.

Spinform because the faces of the foam carry spins, as the links of the graphs whose evolution they describe.

Space is a spin network whose nodes represent its elementary grains, and whose links describe their proximity relations. Space time is generated by processes in which these spin networks transform into one another, and these processes are described by sums over spinfoams. A spinform represents a history of a spin network, hence a granular spacetime where the nodes of graph combine and separate.

This microscopic swarming of quanta, which generates space and time, underlies the calm appearance of the macroscopic reality surrounding us. → every cubic centimeter of space, and every second that passes, is the result of this dancing foam of extremely small quanta.

 

   

 7-6 what is the world made of?

The answer now is simple: the particles are quanta of quantum fields: light is formed by quanta of a field; space is nothing more than a field, which is also made of quanta; and time emerges from the processes of this same field. In other words, the world is made entirely from quantum fields. Fig 7.8.  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. Covariant quantum fields have become today the best description that we have of the απειρογ    the apeiron, the primal substance of which everything is formed,

The wave gives an approximate large-scale vision of photons. Photons are the way I which waves interact. Continuous space and time are an approximate large-scale vision of the dynamic of quanta of gravity. The quanta of gravity are the way in which space and time interact. the same mathematics coherently describes the quantum gravitational field as the other quantum fields.

  

     

Part four Beyond space and time

8.Beyond the big bang

8-1 the master

Gorges Lemaitre: the younger Belgian priest suggests that the universe was originally extremely small and compressed and started its expansion in a gigantic explosion.  

Even the greatest make mistakes and are prey to preconceived ideas. (Einstein)

The Bible knows nothing about physics, and physics knows nothing about God.

There is a point at which they reach the Planck scale, fourteen billion years ago. At that point, the equations of general relativity are no longer valid, because it is no longer possible to ignore quantum mechanics.

8-2 Quantum Cosmology

According to classical mechanics, an electron falling straight into an atomic nucleus would be swallowed by the nucleus and disappear. But this is not what happens in reality(quantum repulsion pushes away the electron when it gets too close to the center.

Big bounce instead of Big Bang

9. Empirical confirmation

We can check whether these are correct, or not. This is the power of science, that which grounds its reliability and allows us to trust it with confidence. We can check whether a theory is right or wrong. This is what distinguishes science form other kinds of thinking, where deciding who is right and who is wrong is usually a much thornier question, sometimes even devoid of meaning.

Clue 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.

9-1 Signs from Nature

String theory: supersymmetric particles. But the supersymmetric particles were not observed.

    

There have been 3 major experimental results in fundamental physics in recent years.

1)          Higgs boson at CERN in Geneva: confirmation of the validity of the ideas behind the Standard model elementary particle based on quantum mechanism.

2)          Planck satellite measurements: conforming standard cosmological model

3)          First detection of gravitational waves announced in first months of 2016   → a spectacular confirmation of general relativity

What nature is confirming is general relativity, quantum mechanics. And within quantum mechanism the Standard model.

9-2        A window onto Quantum Gravity

10.Quantum black holes

Black holes populate our universe in great number. They are regions in which space is so curved as to collapse in on itself, and  where time comes to a standstill.

The surface of a black hole is like the present: it 추 be crossed in only one direction. From the future, there is no return..

For  black hole, the past is the outside, the future is the inside

On the horizon itself, time stops: if we get extremely close to it and then move away after a few of our minutes, a million years might have elapsed in the rest of the universe.

11.The end of infinity

Quantum gravity is the discovery that no infinitely small point exists.

Singularity: pathological situation predicted by general relativity, where the theory give infinite quantities.

Einstein has found the way of thinking of a finite cosmos without borders.      

The book of Ecclesiasticus: who can number the san of the sea, and the drops of rain and the days of eternity? Who can find out the height of heaven, and the breath of the earth, and the deep and wisdom?

The sand reckoner by Archimedes : some think, O king Hiero, that the grains of sand cannot be counted. He does so in order to demonstrate that their number is large but finite. Develop a new system of numbering. His central point is rebellion against the renunciation of the desire to know.

Archimedes was slaughtered by the Romans during the sacking of Syracuse.

A vast cosmos, but a finite one. The only truly infinite thing is our ignorance.

12.Information

Information is the measure of the number of possible alternatives for something. (by Claude  Shannon) S= log 2 N(N: number of alternative , S: Shannon information)

Let’s imagine a world formed of an interminable sea of atoms that bounce, attract, and cling together, and of nothing else. Aren’t we missing something?

Plato and Aristotle insisted on the fact that something was indeed missing; they thought that the form of things was this something extra that had to be    added to the substance of which things were made, in order to understand the world. For Plato, forms exist by themselves, in an ethereal ideal world for forms, a world of ideas. For Plato, a real horse is nothing but a pale reflection of the idea of a horse. The atoms that make up the horse count for little what counts is the “horseness”, the abstract form.

Democritus materialism.: there is more than just atoms in this idea: what counts is the way in which they are combined, on in relation to another. The way in which the atoms arrange themselves is correlated with the way other atoms arrange themselves. → therefore, a set of atoms can have information. (like genetic code)

The world isn’t then just a network of colliding atoms: it is also a network of correlations between sets of atoms, a network of real, reciprocal information between physical system. (like brain neuron)

Heat : is random , microscopic movement of molecules → the molecules of tea are extremely numerous and extremely small, and we don’t know their precise movement. Therefore, we lack information → missing information.

Entropy is missing information. The total amount of entropy can only increase, because information can only diminish.

The relevant information in any physical system is finite.

You can always obtain new information on a physical system

The notion of information was fundamental to the understanding of quantum reality was John Wheeler.  “everything is information”

When information enters into a black hole, it is no longer recoverable from outside. Viewed from outside, the information lost in the black hole now appears as entropy associated with the area of the hole.

In order to grasp the basic grammar of the world, we need to merge three basic ingredients, not just two not just general relativity and quantum mechanics, but also the theory of heat. → everything is still confused, and there is a very great deal that remains to b understood.

   

12-1 Thermal time

If notion of time has no role to play at an elementary level, it certainly plays a significant role in our lives, jus as up and hot do.

Time comes from averages of many microscopic variables. → the salient characteristic of time is that it moves forward and not backward, there are irreversible phenomena.

The sum too is getting older and in fact produces heat. → whenever you consider a phenomenon certifying the passage of time, it is through the production of heat that it does so. There is no preferred direction of time without heat.

We are always correlated with averages. Averages behave like averages: they disperse heat and, intrinsically, generate time.

Time is an effect of our overlooking the physical microstates of things. Time is information we don’t have. Time is our ignorance.

Instead of inquiring how time produces dissipation in heat, it asks how heat produces time.

 12-2 Reality and Information

Reality is this network of relations, of reciprocal information, what weaves the world.

A living organism is system that continually re-forms itself in order to remain itself, interacting ceaselessly with the external world.

The finalistic aspects of the biological world are therefore the result of the selection of complex forms effective in persisting. But the effective way of continuing to exist in a changing environment is to better manage correlations with the external world, that is to say, information: to collect, store, transmit, and elaborate information. 

Atoms are like the letters in an alphabet (genetic code)

As humans we are that which others know of us, that which we know of ourselves, and that which others know about our knowledge. We are complex nodes in a rich web of reciprocal information. 

Order of orders of orders

13.Mystery

Only by keeping mind that our beliefs may turn out to be wrong is it possible to free ourselves from wrong ideas, and to learn. To learn something, it is necessary to have the courage to accept that what we think we know, including our most rooted convictions, may be wrong, or at least naive: shadows on the wall of Plato’s cave

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.

If no one had raised doubts, we would be still worshipping pharaohs and thinking that Earth is supported on the back of a giant turtle.

The search for knowledge is not nourished by certainty: it is nourished by a radical distrust in certainty. This means not giving credence to those who say they are in possession of the truth. For this reason, science and religion frequently find themselves on a collision course.

It is a world that does not exist in space and does not develop in time. A world made up solely of interacting quantum fields, the swarming of which generates- through a dense network of reciprocal interactions – space, time particles, waves, and light

Phrases to think

1. I like the physics because it opens a window through which we can see further

2. 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. → is there any possible of invisible hand?

3. The world has changed no longer made up of particles in space, but of particles and fields in space.

4. There isn’t an up and a down in the universe. Similarly, there isn’t always a before and an after between two events in the universe.

5. Space is no longer different from matter. It is one of the material components of the world, akin to the electromagnetic field. It is real entity that undulates, fluctuates, bends, and contorts. We are not contained within an invisible, rigid scaffolding. We are immersed in a gigantic, flexible mollusk.

6. Spacetime and the gravitational field are one and the same thing

7. Einstein had a unique capacity to imagine how the world might be constructed, to see it in his mind. → for Einstein, the theory of general relativity is not a collection of equations; it is a mental image of the world arduously translated into equations.

8. The universe can be finite and at the same time has no boundary.

9. 3 aspects of reality: granularity, indeterminism, and relationality

10. physical space being a field, is made of quanta, as well. The same granular structure characterizing the other quantum fields also characterized the quantum gravitational field, and therefore space.

11. Physical space is the fabric resulting from the ceaseless swarming of this web of relations. The lines themselves are nowhere – they are not in a place but rather create places through their interactions. Space is created by the interaction of individual quanta of gravity.

12. Absence of the variable time from the fundamental equations does not imply that everything is immobile, and that change does not happen. → it means that change is ubiquitous.  → every process dance independently with its neighbors, following its own rhythm.

0. spacetime: time이 space에 종속되어 있다. time의 상대성 extended present.  상대성이론

13-1 공간에 많은 입자들이 있는 것이 아니라.  공간들이 입자들의 운동으로 만들어진다. 마치 사람들이 특별한 입자(양자)들의 운동으로 사람처럼 보이는 것처럼 공간도 역시 입자들의 운동으로 만들어졌으며 그렇게 보일 뿐이다.

13. There is no longer space that contains the world, and no longer time during the course of which events occur.

14. Covariant quantum fields have become today the best description that we have of the απειρογ the apeiron, the primal substance of which everything is formed,

15. For Plato, forms exist by themselves, in an ethereal ideal world for forms, a world of ideas. For Plato, a real horse is nothing but a pale reflection of the idea of a horse. The atoms that make up the horse count for little what counts is the “horseness”, the abstract form.

16. A vast cosmos, but a finite one. The only truly infinite thing is our ignorance.

17. Reality is this network of relations, of reciprocal information, what weaves the world.

18. A living organism is system that continually re-forms itself in order to remain itself, interacting ceaselessly with the external world.

19. Atoms are like the letters in an alphabet (genetic code)

19. 아직 우리가 그 문법을 알지 못한다.

20. Only by keeping mind that our beliefs may turn out to be wrong is it possible to free ourselves from wrong ideas, and to learn. To learn something, it is necessary to have the courage to accept that what we think we know, including our most rooted convictions, may be wrong, or at least naive: shadows on the wall of Plato’s cave

21. 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.

22. The search for knowledge is not nourished by certainty: it is nourished by a radical distrust in certainty. This means not giving credence to those who say they are in possession of the truth.  For this reason, science and religion frequently find themselves on a collision course.

23. It is a world that does not exist in space and does not develop in time. A world made up solely of interacting quantum fields, the swarming of which generates- through a dense network of reciprocal interactions – space, time particles, waves, and light

24. information: is the measure of the number of possible alternatives for something. 경우수  

  

Briefer history of time by Stephen hawking

1.     Thinking about the universe

2.     Our evolving picture of the universe

3.     The nature of a scientific theory

4.     \Newton’s Universe

5.     Relativity

6.     Curved Space

7.     The expanding universe

8.     The big Bang, black holes, and the evolution of the Universe

9.     Quantum Gravity

10.  Wormholes and time travel

11.  The forces of nature and the unification of Physics

12.  Conclusion