Carlo Rovelli – The Order of Time

Books & reading, Project 1: The Shape of Time, Research & Reflection


Lecture Notes

  • What is time? Linear time is wrong. As you go further, time loses its structure. Quantum gravity is at the bottom of what we know and things get complicated! Time is a sequence of moments that is ordered. We intuitively assume it has a direction. The past is known as we can remember it – history. There are traces to evidence it happened. We have memories. The future has nothing, we can measure it with clocks, we have no concrete evidence it will happen. Time is a good concept for our daily lives but it stops working when we look ahead. When we look ahead, the properties don’t work. Time is layered.
  • How do we measure time? Clocks measure time, but they don’t all measure the same. If one goes higher, it measures different. Atomic clocks with precision can measure this error. Your head is older than your feet!
  • General Relativity Einstein predicted and showed that mass slows down time. This means closer to masses like the Earth, time is slower. Hence why our feet age slower than our heads. In our experience, the difference is not noticeable but we can measure it and on an astronomical scale it becomes more important. There is no single time in the universe.
  • What does now mean? We always see things in the past, there is no meaning of now outside small distances because of the speed of light. It takes light time to travel so when we look at an object we are seeing how it looked in the past. Again, significant for astronomical distances. There is no meaning of now outside of the bubble. We are told what is real is now, but how can it be?
  • Thermodynamics and Entropy The past is different from the future. Only one equation in the whole of physics shows this. The 2nd law of thermodynamics with the concept of Entropy (S). Entropy fundamentally is a statistical measure of disorder. Entropy always flows from ordered to less ordered. So it distinguishes past from future. The order is in the eye of who is looking; the order depends on what you are categorising e.g. colour, size. The past looks ordered only because of how we observe it. So, why was the universe ordered in the past? It looks ordered to us as we are the ones categorising it. To someone else with a different set of organised criteria, it may not look it. So, does it really relate to time?
  • Models of Time On the quantum level, it is probability only. Time is the counting of change. We can see this back in Aristotle. Newton introduced the idea of time passing but we now go back to a more Aristotelian model.
  • The brain and time The brain works by anticipating the future and remembering the past. It is a time machine. Does this make time a truly human construct? St Augustine wrote on this back in his Confessions. For example, we only ever hear one musical note at a time but our brain acts as a memory store for the ones we have just heard to piece it together in a phrase. We cannot think without time. In Search of Lost Time – Proust covers some of these themes. Time is always emotionally charged. The Buddhists describe this as the sense of suffering due to impermanence. Time is the root of our suffering as we never beat it.

Book Notes

Perhaps Time is the Greatest Mystery

Perhaps Time is the Greatest Mystery. The universe unfolds into the future, dragged by time, and exists according to the order of time.

In those same books, I also discovered that we still don’t know how time actually works. The nature of time is perhaps the greatest remaining mystery.

Why do we remember the past and not the future? Do we exist in time, or does time exist in us? What does it really mean to say that time ‘ passes ’? What ties time to our nature as persons, to our subjectivity? What am I listening to when I listen to the passing of time?

What we call ‘ time ’ is a complex collection of structures, of two layers

Because the mystery of time is ultimately, perhaps, more about ourselves than about the cosmos.

I believe our knowledge of time has reached: up to the brink of that vast nocturnal and star-studded ocean of all that we still don’t know.

Let’s begin with a simple fact: time passes faster in the mountains than it does at sea level.

Time passes more slowly in some places, more rapidly in others

This modification of the structure of time influences, in turn, the movement of bodies, causing them to ‘ fall ’ towards each other

The Earth is a large mass and slows downtime in its vicinity

If things fall, it is due to this slowing down of time. Where time passes uniformly, in interplanetary space, things do not fall. They float, without falling

time passes more slowly for your feet than it does for your head.

Things are transformed one into another according to necessity and render justice to one another according to the order of time

the whole of our physics, and science in general, is about how things develop ‘ according to the order of time ’.

The equations tell us how things change as the time measured by a clock passes.

times that change relative to each other. Neither is truer than the other.

Times are legion: a different one for every point in space.

Einstein has given us the equations that describe how proper times develop relative to each other.

Time has lost its first aspect or layer: its unity.

If the world is upheld by the dancing Shiva, there must be ten thousand such dancing Shivas, like the dancing figures painted by Matisse …H

Past and future are different from each other. Cause precedes effect. Pain comes after a wound, not before it.

We cannot change the past; we can have regrets, remorse, memories. The future instead is uncertainty, desire, anxiety, open space, destiny

Time is not a line with two equal directions: it is an arrow with different extremities.

Rebellion is perhaps among the deepest roots of science: the refusal to accept the present order of things.

All of the sons of Adam are part of one single body, They are of the same essence. When time afflicts us with pain In one part of that body All the other parts feel it too. If you fail to feel the pain of others You do not deserve the name of man.

poetry is another of science’s deepest roots: the capacity to see beyond the visible.

Rudolf Clausius. It is he who grasps the fundamental issue at stake, formulating a law that was destined to become famous: if nothing else around it changes

heat cannot pass from a cold body to a hot one.

This is the only basic law of physics that distinguishes the past from the future.

one of these equations distinguishes the past from the future.

In the elementary equations of the world, 5 the arrow of time appears only where there is heat.fn1 The link between time and heat is therefore fundamental: every time a difference is manifested between the past and the future, heat is involved. In every sequence of events that becomes absurd if projected backwards, there is something that is heating up

Only where there is heat is there a distinction between past and future.

‘ the second principle of thermodynamics ’

heat passes only from hot bodies to cold, never the other way round.

heat passes from hot to cold, and not vice versa: by shuffling, by the natural disordering of everything. The growth of entropy is nothing other than the ubiquitous and familiar natural increase of disorder.

If we think about it carefully, every configuration is particular, every configuration is singular, if we look at all of its details, since every configuration always has something about it that characterizes it uniquely. Just as, for its mother, every child is particular and unique

Yes. If I observe the microscopic state of things, then the difference between past and future vanishes.

In a microscopic description, there can be no sense in which the past is different from the future.

the difference between the past and the future refers only to our own blurred vision of the world.

there is nothing intrinsic about the flowing of time. That it is only the blurred reflection of a mysterious improbability of the universe at a point in the past.

The consequence of this discovery for our basic intuitive perception of time is the most devastating of all.

Time passes more slowly for the one who keeps moving

For everything that moves, time passes more slowly.

Nobody had imagined previously that time could be different for a stationary watch and one that was being moved.

Not only is there no single time for different places – there is not even a single time for any particular place

‘ Now ’ Means Nothing

The light takes time to reach you, let’s say a few nanoseconds – a tiny fraction of a second – therefore, you are not quite seeing what she is doing now but what she was doing a few nanoseconds ago.

The truth of the matter is that we need to give up asking the question

The notion of ‘ the present ’ refers to things that are close to us, not to anything that is far away

Our ‘ present ’ does not extend throughout the universe. It is like a bubble around us

As humans, we distinguish tenths of a second only with great difficulty; we can easily consider our entire planet to be like a single bubble where we can speak of the present as if it were an instant shared by us all.

The idea that a well-defined now exists throughout the universe is an illusion, an illegitimate extrapolation of our own experience

there is no such thing as “ the same moment ” definable in the universe

A partial order establishes a relation of before and after between certain elements, but not between any two of them.

The temporal structure of the universe is very similar to this one. It is also made of cones.

defines an order between the events of the universe that is partial, not complete.

The expanded present is the set of events that are neither past nor future

Every event has its past, its future and a part of the universe that is neither past nor future, just as every person has forebears, descendants and others who are neither forebears nor descendants.

Light travels along the oblique lines that delimit these cones. This is why we call them ‘ light cones

This is the structure of spacetime that Einstein understood when he was twenty-five years old

When a gravitational wave passes, for example, the small light cones oscillate together from right to left, like ears of wheat blown by the wind.

In this way, a continuous trajectory towards the future returns to the originating event, to where it began.

This is because the mass of the black hole slows time to such a degree that, at its border ( called the ‘ horizon ’ ), time stands still

So, to exit from a black hole, you would need to move ( like the trajectory marked in black in the following diagram ) towards the present rather than towards the future!

More than a hundred years have passed since we learned that the ‘ present of the universe ’ does not exist. And yet this continues to confound us and still seems difficult to conceptualize

If the present has no meaning, then what ‘ exists ’ in the universe? Is not what ‘ exists ’ precisely what is here ‘ in the present ’?

‘ How long is forever ? ’ asks Alice. ‘ Sometimes, just one second, ’ replies the White Rabbit.

Time is elastic in our personal experience of it.

On the one hand, time is structured by the liturgical calendar

For centuries, we have divided time into days. The word ‘ time ’ derives from an Indo – European root – di or dai – meaning ‘ to divide ’.

Sundials, hourglasses and water clocks already existed in the ancient world

It is only in the fourteenth century in Europe that people’s lives start to be regulated by mechanical clocks.

Gradually, time slips from the hands of the angels and into those of the mathematicians

For centuries, as long as travel was on horseback, on foot or in carriages, there was no reason to synchronize clocks between one place and another.

It is in the United States that the first attempt is made to standardize time.

In 1883 a compromise is reached with the idea of dividing the world into time zones

Einstein worked in the Swiss Patent Office, dealing specifically with patents relating to the synchronization of clocks at railway stations.

The rhythm of the day followed by night also regulates the lives of plants and animals.

Diurnal rhythms are ubiquitous in the natural world. They are essential to life,

Living organisms are full of clocks of various kinds – molecular, neuronal, chemical, hormonal – each of them more or less in tune with the others

The diurnal rhythm is an elementary source of our idea of time

In the ancient consciousness of humanity, time is, above all, this counting of days.

counting how things change.

Aristotle is the first we are aware of to have asked himself the question ‘ What is time? ’

time is the measurement of change.

Time is the measure of change: 8 if nothing changes, there is no time.

the existence of a time that is uniform, independent of things and of their movement which today seems so natural to us is not an ancient intuition that is natural to humanity itself. It’s an idea of Newton’s.

Legend has it that Leibniz, whose name is still occasionally spelt with a ‘ t ’ ( Leibnitz ), had deliberately dropped the letter from his name following his belief in the nonexistence of the absolute Newtonian time t.

Don’t take your intuitions and ideas to be ‘ natural ’: they are often the products of the ideas of audacious thinkers who came before us.

That which seems intuitive to us now is the result of scientific and philosophical elaborations in the past.

Remember the clocks in Chapter 1 that slow down in the vicinity of a mass? They slow down because there is, in a precise sense, ‘ less ’ gravitational field there. There is less time there.

Time thus becomes part of a complicated geometry woven together with the geometry of space.

the residual temporal scaffolding of general relativity, illustrated in the previous chapter, also falls away if we take quanta into account.

The time measured by a clock is ‘ quantified ’, that is to say, it acquires only certain values and not others. It is as if time were granular rather than continuous.

A minimum interval of time exists. Below this, the notion of time does not exist – even in its most basic meaning.

A Reflection on Time

Coursework, Creative Arts 1.1 Experience Creative Arts, Creative Arts BA (Hons), Project 1: The Shape of Time

Time remains a mystery to us. From the dawn of humans, it seems to have fascinated us, and humans of all eras seem to have been occupied with marking its passing but we still don’t understand it or can be even sure if it exists. Through science, philosophy, and the creative arts, we can explore time and what it means to us but any true definition still eludes us. On many levels, it appears to be a purely human construct that comes about from the experience of change, sensory or otherwise. Perhaps it is the mysterious nature and our lack of fundamental understanding that leads it to be a source of inspiration across the creative arts? Will exploration in this creative way lead us any closer to what time actually is? This reflection takes a look at how the sciences, philosophy, literature, film, art, and music engage with or use time to explore our understanding and experience of it.

When I think about what time is, my first thoughts take me back to learning about time as a young child. From an early age, we are taught to “tell the time” on a clock and the concept of time is broken down for us into units of seconds, hours, years. We mark the passing of time by learning about seasons and expectedly count down the days to birthdays and Christmas. All through high school science, we treat time as a fundamental measurement, we use equations with t in them to calculate the time in the standard unit of seconds. We use it to measure the speed of something, how much an object accelerates, and other basic calculations. Then, when we get to a certain level of science learning, we discover Einstein and how he blew the notion of time to pieces. Through his work on special and general relativity, we know that there is no absolute time. Time is not constant like we intuitively assume. There are mind-boggling ideas of time being slowed down by mass and it changes depending on how fast an object is moving. That in fact time is linked to space through the concept of ‘spacetime’. The more we learn, the less we seem to understand and we yearn for those simpler days of moving hands on a clock to learn how to tell the time. 

As Carlo Rovelli talks about in The Order of Time (2019) and his Royal Institution lecture, time’s properties mean very strange things occur, such that our head ages at a faster rate than our feet! Scientists now are pretty unanimous that there is no actual concept of “now”; what we consider now is actually not now on a distant planet lightyears away. Just take that as an idea, the fact that we are measuring a distance using a time measure of a year shows how intricately linked space and time are. We also know that the only equation in the whole of the body of science that even considers time to have a direction is the second law of thermodynamics. For everything else, we can seemingly work with time that does not need to flow from the past to the present to the future. It is only through our understanding of entropy needing to flow from the past of order to the future of randomness that we consider time to have this directional nature. The more we discover in science, especially on the quantum level, the more our intuitions about time are proved wrong. Is it this when we turn to other disciplines outside of science?

There is no question that science must work alongside philosophy especially when dealing with time. Time is one of those bones of contention that has been argued about for centuries. In the Hellenic period, there was a split between those who saw the world as a static place (e.g. Archimedes) and those who saw it as essentially flux (e.g. Aristotle). Aristotle was a great thinker about time, it is from him that this idea of time being the counting of change started and science has come back to this model of time. Philosophers have battled to find the answer to the question “what is time?” and like the scientists, no definitive answer has arisen. Plotinus considered the nature of time and stated “Time is the moving image of eternity” and “time is not something separate from soul, not the same as soul; it is the energy of the soul”. This Neoplatonic view has heavily influenced many in the creative arts such as T.S. Eliot who I will consider later in this reflection.

Various religions have their interpretations of time and how it was created by whom. Some see time as a linear process with a creator God starting time and that we follow a line from His creation along the timeline that He has mapped out for us. Other religions see time as a more circular path. In Buddhism, the idea of time and as a result, impermanence is what results in suffering. Ancient religions such as the Celtic Druids held time as important, the root of many festivals still celebrated today, was in the marking of time, with huge structures such as Stonehenge built to mark the seasons and the wheel of the year.

Literature has always tried to explore time. The most famous literary novel exploration is probably Prousts’ In Search of Lost Time which is a fictional piece of work heavily influenced by thoughts of philosophy of time. Other pieces of work such as Garcia Marquez’s One Hundred Years of Solitude explore how time feels to pass. Children’s literature too such as Alice’s Adventures in Wonderland explores time more fantastically with some of the best-known quotes about time.

Poetry too not only explores time and the human perception such as the famous line ‘Stop all the clocks’ by WH Auden, but perhaps in a more direct way than longer pieces of prose, they use time as a poetic method.TS Eliot is one poet who, as mentioned earlier, due to his philosophical background contemplates the nature of time, and many of his poems reflect this. Some emphasise the individual experience of time such as his earlier ‘Prufrock and Other Observations’ and the experience of timelessness, others look at the fundamental nature of time, particularly in his later poems, the question of time is increasingly religious such as in ‘A Song for Simeon’. There is a lot of evidence in the poems that Eliot is influenced by Plotinus’ view of time. In his earlier poems, there is a consistent emphasis on daily routine, the cycle of the morning, afternoons and evenings and this comparison of the external world of time passing and the human consciousness of time.

 “And indeed there will be time
For the yellow smoke that slides along the street,
Rubbing its back upon the window-panes;
There will be time, there will be time
To prepare a face to meet the faces that you meet;
There will be time to murder and create,
And time for all the works and days of hands
That lift and drop a question on your plate;
Time for you and time for me,
And time yet for a hundred indecisions,
And for a hundred visions and revisions,
Before the taking of a toast and tea.” (TS Eliot)

There is a sense of preoccupation with time and its control but also patterned by the cycle of seasons. It leads back to this human conflict between us wanting to be in control of something and understand something that seems to just pass us by and nothing we can do can alter that. In Four Quartets memory becomes a far more powerful key, retaining in time, timeless moments. This links to the idea that Rovelli talks about in his Royal Institute Lecture, that it is really our brains that are the ultimate time machine of deciphering what is past, present and future.

There is a strong exploration of the concept of time in art and photography. Both in terms of exploring the nature of time and using time to help portray the meaning behind the picture. We use time to date art, such is our need as humans to categorise things due to the time in which they were made. We can do this in art by looking at the materials used but also the style and techniques that were used at the time of the creation. For example, we can look at a cave painting and know it was from a different era to an impressionist piece. On the next level, we can help deduce from a painting, what time of year or even time of day a painting is portraying. For example, in Canaletto’s View of Venice with St Mark’s (1735) he conveys that it is late afternoon by painting long shadows that stretch across the square. It is this linking to a certain time of day that helps give Canaletto’s work a strong sense of place as time is such an important theme to portray. A piece that isn’t linked to a time would not appear to have as strong of a connection to the real place. However, Van Gogh subverts this and deliberately paints the night sky in Café Terrace at Night in vibrant blues, violets and greens which seems to highlight the concept of the time of day being night even more. As well as time being used to indicate the time of day in paintings, there are examples of symbols that are used to discuss the idea of time. One such symbol is the skull which is used to indicate the time of passing into death. One interesting use of this is in Holbein the Younger’s The Ambassador (1533) which has a large distorted skull in the foreground. Could this be an early sign of the ambiguity of time? More traditional symbols appear in Vanitas paintings. We see skulls, candles, hourglasses to indicate time throughout still life compositions. In Waterhouse’s The Lady of Shalott (1888) three candles appear on the boat with her to show the passing of time on her journey.

The bizarreness of time has been explored in art too. The most famous example is probably Dali’s The Persistence of Memory (1931) which is said to have been influenced by Einstein’s work of a similar time on relativity and the nature of time. Einstein described how time bends due to gravity and Dali made the step to showing if time bends, do watches too?

Photographs too often are set up with the premise of capturing “a moment in time”. By the very nature of them, in contrast to moving film, a photograph is a snapshot of time. However, there have been cases of photographs not necessarily portraying the moment in time the viewer is led to believe. One example is Capa’s The Falling Soldier (1936) an early war photograph that depicts a soldier falling backwards after being shot and is said to depict the moment of his death. However, the image is controversial as it has been suggested it was staged and that it is instead a posed photo. Another example perhaps of time not always being what we think it is!

The use of special effects play with time. In the media of film, we can view things faster or slower than we perceive them normally. With super slow motion cameras, we can slow events that happen in milliseconds right down to see in more detail than ever before the mechanisms of things such as explosions.

Few would disagree with the idea that music has a special relationship with time. This time connection is not without parallel in other expressive arts; drama, film, dance and performance art all involve time performances. We know that the ear is a better device than other sensory organs for extracting many types of temporal nuance from perceptions. Music parallels science in that musical events have a unique time ordering. One is that musical time, except that, found measured out in the metronome markings of scores, has a subjective, experienced, psychological component. This much-discussed subjective impression of time is affected by various qualities of the musical texture, notably activity level, and to a lesser extent, timbre, pitch, etc. This dichotomy between clock or objective time and experienced or subjective time has had considerable discussion in music. Musical time is designed by the composer and articulated by the performer, not empirically received by the listener as the result of natural processes governed by physical laws. Some composers have subverted this, such as John Cage’s Piano Concert (1957) where the order and inclusion of parts are at the performer’s discretion. Music also continues to show this fascination we have as humans as marking the passing of time. The classic example is Vivaldi’s popular ‘The Four Seasons’ which honours similarly that the ancients did the passing of the seasons and the magic which is the wheel of the year.

Through this rather jumbled reflection of some of the ways, humans interact with the concept of time has confirmed to me the wonder of the human mind. We can take something that on one level seems so intuitive to us and expand our knowledge radially to the point where we realise that we don’t understand anything at all. Time is truly an interdisciplinary topic that shows the importance of all disciplines working together to form collective knowledge. We can never truly understand anything if we narrow our focus on one academic subject. At the same time, do we ever truly understand anything?