Reality Is Not What It Seems – Carlo Rovelli

Milesians – decisive discovery was a different style of thinking, where the disciple no longer had to respect and follow the ideas of the master, but was free to build on the ideas without being afraid to discard or criticize the part that can be improved upon. Basis of scientific thinking. 

Miletus – cradle of philosophy, natural sciences, and geographical and historical studies. City was destroyed by the Persian empire in 494 BC. 

Democritus – believed that the entire universe was made up of space in which innumerable atoms run. Space without limits or boundary. Atoms, no qualities outside of their shape. No weight, color, taste, etc. Invisible, but continually colliding with one another. 

The world, according to Democritus, was built off the constant collisions of atoms. Everything in the universe is the by-product of accidental collision, and subsequent combining of different atoms. Every piece of matter is made up of a finite number of discrete pieces that are indivisible, each one having a finite size: the atoms. 

Plato and Aristotle did not accept this idea since they preferred to believe that everything was finalistic, that is for a purpose. Nothing was dumb luck, chance, or coincidence. 

Galileo – built upon the ideas of Copernicus, which stated that the earth was a part of the universe / heavens, and it’s movements could be predicted using math and geometry. He (Galileo) wanted to understand how objects moved on Earth when they are set free – that is, when they fall. Learned that objects don’t fall at a constant speed. Instead, speed gradually increases during the early part of the fall. Speed increases by 9.8M / second for each second of time while falling. 

Newton – built on Galileo’s work and came up with the idea of gravity. Objects, for example planes, must have an attraction which pulls them towards each other and causes them to orbit (rotate), otherwise they would keep moving apart or collide while moving in a straight line. Gravity – every body attracts every other body. On Earth gravity causes things to fall downwards, in space, it causes planets and stars to orbit. 

19th Century view informed by Newton – the world consists only of a great infinite space where, as time passes, particles move and attract each other by means of forces. 

Electromagnetism – the force that holds together the matter that forms solid bodies, holds together the atoms in molecules, and electrons in atoms. This is what makes chemistry and living matter work. 

Field – bundles of very thin lines (infinitely thin) which fill space and everything around us. These lines transmit the electric and magnetic forces from one body to another. The field is needed to allow forces, as thought of by Newton, to connect and interact. 

Light – the trembling of lines that make up a field. 

Color – the frequency (speed of oscillation) of the electromagnetic wave light is. If the wave vibrates more rapidly, the color is bluer. If it vibrates more slowly, closer to red. Color as we perceive it is the psychophysical reaction of the nerve signal generated by the receptors of our eyes, which distinguish electromagnetic waves of different frequencies. 

We only see lines when they are vibrating, not when they are static. We see things because in between us and what we’re seeing, there are millions of faraday lines vibrating, which in essence allows up to see!

Lines vibrating at very low frequencies become the basis for telecommunications – radio, tv, phones, bluetooth, wifi, etc. 

Special relativity Einstein – comes up with the idea that there is an extended present, which is dependant on how far away you are the origin of an event taking place. The duration of the extended present is longer the further away you are from an event, but this all happens well under our ability to perceive time. You would only notice it if you were on the moon and something was happening on earth for example, where the extended present would be a few seconds. This would later be referred to as spacetime. 

E=mc2. C= speed of light, e= energy, m = mass. Energy and mass are two facets of the spacetime. The energy obtained by transforming one gram of mass is enormous – would become the basis for nuclear power (and bombs). 

General Relativity – Einstein’s most well known work published when he was 35. The most beautiful produced by physics. 

Gravity is a force, as stated by Newton, that allows things to react and be measured in relative terms. However there is a field required, to transmit the force using electromagnetism. The field is comprised of Faraday lines. This system also applied to gravity, and implied that a gravitational field exists which causes things to fall downwards on earth

General Relativity – aimed to describe the gravitational field and define Newton’s space. Answer – on earth they are the same thing. The earth is made up only of particles and fields! Space is no longer different than matter. Space can be curved and bent. 

Curved space – can also be known as spacetime, equals R. Einstein determines that R is proportional to the energy of matter. This is the analog of the Maxwell equation, but for gravity instead of electricity. 

Time, like space, also curves and bends according to general relativity. A ball falls after being thrown upward because it “gains time” on the way up. A ball falls then because it is following a straight trajectory in a space (or spacetime) that is curved. 

General relativity – predicts that the universe is expanding and has emerged from a cosmic explosion fourteen billion years ago. 

The universe is curved, so there are no borders. It can be finite and borderless at the same time, another 

General relativity predicts that the universe will always be contracting or expanding. Einstein would not accept the answer of his own model – he preferred to believe that the universe would always be fixed in size, finite. He would eventually be proven to be incorrect. 

Quanta – small packets, little bricks of energy. First used by Max Planck, eventually led to the creation of a new variable, h, which will later be known as Planck’s constant. 

Previously energy was thought to vary in continuous manner, and there was no reason to treat it like it was made up of grains. Planck’s idea was in direct opposition to this view. 

Photoelectric effect – light is made up of small particles of light. There are substances that generate a weak electric current when light shines on them. They emit electrons when light shines on them. But surprisingly, it’s the frequency (color) and not the intensity of the light creates the photoelectric effect. The intensity of energy in each particle is the determining factor, not the absolute number of particles. 

Photons – packets of energy noted above. Light is a wave in an electromagnetic field made up of photons. Implies that there is a fundamental granularity in all things, including light. 

Atoms – mass is concentrated in the heavy central nucleus, around which light electrons revolve. 

Spectrum – the set of frequencies that characterize a given substance. Studying spectra allow us to understand how electrons move around nuclei. 

Color – determined by the speed at which faraday lines vibrate. 

Quantum leaps – electrons can move between one orbit to another when they permit energy and transfer it. The frequency at which electron moves on these orbits determines the frequency of the emitted light, and explains why only certain frequencies are emitted. 

Heisenberg – trying to explain quantum leaps, states that the location of particles should not be monitored on a minute-by-minute, second-by-second, etc scale, but only when they interact with something else. He is uncovering the relational aspect of everything in the universe, another key tenet of quantum mechanics along with granularity. 

Indeterminacy – chance operates at the atomic level. The third tentpole of quantum mechanics. By taking a weighted average of all possible outcomes, we can create estimates for probability of events, but never predict with certainty a specific outcome. 

Quantum Field Theory – particles are quanta of a field, just as photons are quanta of light. All fields display a granular structure in their interactions. 

Quantum mechanics – the world isn’t made of distinct fields and particles, but of a single entity – the quantum field. Elementary events in quantum mechanics happen in spacetime

Granularity – puts an end to the idea of infinite. It limits the amount of information that can exist within a system.

Indeterminacy – the world is a sequence of granular quantum events. Individual interactions between one physical system and another. The future is genuinely unpredictable. The world is made up of tiny vibrations and continuous vibrations.  

Relational – reality is relational. The world of existent things is reduced to a realm of possible interactions. There is no reality except in the relations between physical systems. 

Quantum mechanics – does not describe objects: it describes processes and events that are junction points between processes. Process – the passage from one interaction to another. 

Einstein struggled to accept quantum mechanics – why? Because he believed that there was an object reality, not just reality manifests itself through interactions, like it’s being rendered in front of you. 

General relativity and quantum mechanics seem to contradict each other – general relativity ignores that a field is a quantum field (qm idea). And qm ignores that spacetime bends and bends (gr idea). This is the problem of quantum gravity. 

Loop quantum gravity – brings together general relativity and qm. General relativity – shows us that space is dynamic, it stretches and bends. QM – shows that every field is made of quanta, it has a fine granular structure. The same granular structure of any quantum field also applies to a quantum gravitational field, and therefore space. Space is granular. Space is formed by “atoms of space”, a billion billion times smaller than the smallest of atomic nuclei. It describes the granular quantum structure of space in a precise mathematical form. 

Space – created by the interaction between the individual quanta of gravity.  

Time – is not a great cosmic clock that marks the life of the universe. It is a localized phenomenon; every object in the universe has it’s own time, running at a pace determined by the local gravitational field. 

Time doesn’t exist – it is a useful assumption, not the result of an observation. We use time as a way to measure the duration of other things. Heartbeats, oscillation, etc. If we stop using time as the baseline for comparison, we have to start measuring the other variables against each other. 

The illusion of being surrounded by a continuous space and time – the product of a farsighted vison of a dense swarming of elementary processes. 

Galaxies – small opalescent clouds among stars when looked at through a telescope.

Universe – constantly expanding and contracting, as predicted, but not accepted by him, in General relativity (Einstein). The universe swells like a balloon. It has expanded over time – in a far distant past, it was compact and extremely hot. There is no reason to believe that there is only one universe. We just see our own. 

Black holes – regions in which space is so curved as to collapse in on itself, and where time continues to stand still. The black hole in the center of our galaxy has a mass a million times greater than the sun. It can swallow up other stars that get too close. The gravitational pull of the hole causes time to slow down considerably around it. 

Information – can be defined as the capacity to distinguish between alternatives. In the context of physics, it is critical to our understanding of the world because it measures the ability of one physical system to communicate with another physical system. 

In quantum mechanics, a physical system manifests itself only in interacting with another. A description of a system is therefore always a description of the information a system has about another system, that is the correlation between the two systems. 

The description is nothing more than a way of summarizing past interactions, and using them to predict future ones. 

Thermal time – heat and time are linked. Only heat distinguishes the past from the future. (?) We live and get old, producing heat. A candle burns creating fire and smoke. The notion of time comes from the fact that we interact only with the averages of many variables. 

Time is not real, but comes from the fact we aren’t able to see or comprehend the numerous micro-activities happening all around us. Time is an effect of our overlooking the physical microstates of things.

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