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The Physics and Philosophy of Time – with Carlo Rovelli

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From Boltzmann to quantum theory, from Einstein to loop quantum gravity, our understanding of time has been undergoing radical transformations. Carlo Rovelli brings together physics, philosophy and art to unravel the mystery of time.
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Watch the Q&A: https://youtu.be/FIgYmNYXMas

Time is a mystery that does not cease to puzzle us. Philosophers, artists and poets have long explored its meaning while scientists have found that its structure is different from the simple intuition we have of it. Time flows at a different speed in different places, the past and the future differ far less than we might think, and the very notion of the present evaporates in the vast universe.

Carlo Rovelli is a theoretical physicist who has made significant contributions to the physics of space and time. He has worked in Italy and the US, and is currently directing the quantum gravity research group of the Centre de physique théorique in Marseille, France. His books ‘Seven Brief Lessons on Physics’ and ‘Reality Is Not What It Seems’ are international bestsellers translated into forty-one languages.

This talk and Q&A was filmed in the Ri on 30 April 2018.

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38 thoughts on “The Physics and Philosophy of Time – with Carlo Rovelli”

  3. Here is my understanding of what TIME is:
    First of all, we have to go down to a level, deep into quantum realm, where there is no time. Let’s take a photon as an example. A photon is a massless particle, which does NOT experience time at all, nor space. It knows only two things, its creation, and its destruction, and nothing in between. The only important thing is the order of the two, the destruction comes AFTER its creation. The photon is basically nothing more than a cause-effect relationship between two points in the universe. Time and space between them is irrelevant.
    Let’s step up, and see that there is not one, but many photons out there. One photon equals one cause-effect pair, but there are many causes and effects, affecting each other. So we need an ordering amongst them, to know what other causes and effects are happening between the cause and effect of a single photon. We need a distance between them. Time is basically the absolute ordering of all events in the universe. Without events, there is no time either. (That’s why we say there might’ve been no time before big bang). And the distance defines how many other events are happening between them. Time and space are the same things here. We can directly convert one into the other, and the conversion ratio is C. That’s why we call the distance “lightyear”.
    C is not the speed of light, C is the speed of CAUSALITY, as described above. Everything is happening with the speed of C (which is the measure of both time, and space). Photon is just a great example, because it is easy to observe. But what’s up with the other particles. All higher particles can be described as a virtual box of photon (or an equal other force-carrying particle), where the photon is oscillating within the walls of this virtual box. If we try to move the box, it hits the opposite wall of the box more, slowing it down, giving it a resistace against acceleration, giving it MASS. It still travels with C, back and forth between the walls. This essentially makes it a clock. If we move the box (move the particle), the speed of movement counts into the movement of the photon, as it still moves with C, so it hits the wall less frequently. Therefore, its time slowed down, just as Einstein predicted.
    So with the above (bit oversimplified) model, we went from having no time just cause and effect, into explaining relativity.

    Of course the real world is more complex than that (many types of particles, not just photons),but I think the above might be the basic mechanic of it.

  4. I disagree with the conclusion of the lecture a bit. It is not really scientific, but its okay, even the title says it’s phylosophy:)
    However it says that the universe not special, we are special, our understanding of the universe makes what it is. But I say we are not special. There is only one universe, but many living beings. And as far as we know, all living being experience time in the same way. Otherwise it would imply, that there might be a lifeform out there, which senses the universe differently, senses the entropy not as the order of the particles of standard model, but something different. And by that, maybe the time flows in the other directon for them, or something even more different.
    Okay, that’s not unreasonable or impossible, but we have zero signs of that so far, and we also cannot test it. So as the title says, it is completely phylosophical, and nothing scientific.
    These are valuable thoughts nonetheless, so it is nice to think about that. But let’s be clear about where science and knowledge ends, and where philosophy and spirituality begins.

  5. So time is created by and effected by gravity, entropy and speed. Our perception of time is erroneously caused by our brain ?. I am confused ?‍♀️ by what this all means in regards to the reality of cause and effect. It sounds like some scientists are implying that perhaps the future already exists, and that our actions are predetermined and we don’t really have a conscious choice in what we do, our brains are simply causing us to interpret these predetermined actions as our choices. I don’t know what to make of this. Perhaps we don’t have the mental ability to experience this predetermined road we are on in any other way. Mind blown ?!

  8. So….time is illusion because it's our imagining of entropy? Then why can't we imagine entropy going forward instead, and get actual reversal of times effects? Oh wait, just imagining it doesn't make it real. Verifiable scientific evidence states all matter, apparently everything but energy, from galaxy sized gravitational singularities to quarks, has a birth and a death. Entropy is the gradual degradation of the fundamental particle fields that make up the fabric of our known universe. In that sense, mankind uses time as a measuring tool to describe what's going on in ways we, as limited as we are, can understand. Although I`m no Nicola Tesla, that's what makes the most sense to me.

  11. I have an opinion on what time is, if the listeners will indulge my naivete. I am not a scientist, not a theoretical physicist but I do engage in a little light reading on physics from time to time. My thought is this time is the proof that we are actually holograms created by one dimensional strings. The vibration of quantum strings create what we call reality or 4 dimensional space/time, can only be accomplished in a quantum manner this we experience as time. The creation of these particles is quantum, the subatomic motion of these particles is quantum, but on a large scale the quantum effects get lost so that we no longer see the discreet motion but rather the smooth flow of what we call time, and finally at the very large scale we see relativistic effects in the motion of particles and thus relativistic time. Therefore, it might be said that time is the proof that on the smallest scales there is no such thing as a smooth flow of energy only energy delivered in discreet packets the sum total of these produce motion and thus time.

  15. And it's always goes back to the concept of buddhism. Because meditation is the tool that helps us pass each moment with awareness. The more you are in the moment the less you suffer from the suffer from the pass and the closer you are to the real enlightenment. At one point we practice until we always dwell in the instant and no memory or the past that can hurt us. I always imagine that is called enlightenment. But I can't imagine how are we going to live in that state or even how we can attain that state of mind.
    Just my two cents. I'm not even good at Physics. Just wanted to share what I think.

  19. Professor Rovelli,

    Thank you for your great presentation on 'time'. I very much appreciate that you presented this in English with such professional video and audio. I noticed that you had a full house except for one seat. I suspect the person belonging to that seat had heard all of this before.

    There are few people who so thoroughly and successfully combine philosophy with physics in forming their world views. I appreciate that you appear to view time as a sequencing of events. It can be challenging to think flexibly enough to adopt this view.

    You emphasize that one's experience strongly affects their perceptions. This runs much deeper than you may expect. Think of space as consisting of the fabric of space. All of physics and all of our life experiences occur as a result of how the fabric of space responds when we interact with it.

    There is a deeper level that falls outside of physics and outside of our experiences. The deeper level consists of the operation of the fabric of space itself. How can space be built and how can space be maintained? Since this falls outside of our experience we do not know a priori the metaphysical laws that prevail in the fabric of space. We only experience the laws of interacting with the fabric.

    It is possible to understand the operation of the fabric of space itself. In order to do this many of the philosophical things you mention must be considered. In the end, one must take their best guess and see where it leads. Most often it will lead down a path that conflicts with reality. In that case one must try a different thought path.

    Over four decades ago I started on a thought journey. Very early in the journey it seemed that Something and Nothing were a likely candidate for the starting point. Never in my wildest imagination did I guess where it would lead.

    The most direct result from this thought process was an understanding of gravity. I know it is presumptive to talk about gravity with someone so skilled in it as yourself. I mean no disrespect. Quite the contrary, it is your depth of understanding that appeals to me. My understanding of gravity runs contrary to deeply embedded concepts in physics. I know from your presentation that you give a great deal of consideration to embedded thoughts.

    First, General Relativity (GR) and space-time are only local approximations to reality. They are very good, but hide the true nature of space and time. There is no four dimensional space-time continuum. Time is continually slowing down, that is what prevents a space-time continuum as we understand it.

    What does it mean for time to continually slow down? Matter works as the brakes on time that is what creates time dilation. If we were able to separate a piece of space that contained no energy or matter, we could consider this to be a clock that does not slow down. Relative to that separated space we would find the clocks in our universe were slowing down. This is not a convergent series so readers should not be concerned.

    Time slows down at the same extremely low rate everywhere in the universe. This is why we have no perception of it locally. MOND gravity provides evidence of this slowdown at a distance, but we choose to ignore it and introduce Dark Matter.

    If we were allow ourselves to be objective, we might raise some questions about GR. It does not apply on the quantum level; nor, does it apply on the cosmological level. The cosmological failure is evidenced by Mordehai Milgrom's MOND work. Even black holes raise philosophical questions. If GR doesn't apply on the quantum level then how can we possibly deduce pure black holes from the continuous formula. At some point we get close enough to where time stands still that we are into the quantum area. I do understand that quantum effects are being considered, but the whole premise of time standing still should be rejected.

    In this view of gravity, space acts as a flywheel and matter acts as the brakes. This closely matches GR locally.

    There are many more philosophical conclusions that one gets from understanding Something and Nothing. Alas, nobody seems to believe such an understanding is possible. This is a difficult enough journey to make that it possibly would not happen again.

    Thank you for listening.

    Richard Marker

  20. Sorry. Interesting man but a terrible presentation. He could learn a few things from Ted talks. Lots of rambling here. I wanted to watch it but after 13 minutes I had enough.

  21. Wow science has become a religion. There is no time, effect can come before cause, might as well believe in the tooth fairy. Brainwashing at it's best. What happened to questioning everything?

  23. Time does not exist. Space does not exist. Spacetime exists, but only as a concept in our minds. When you watch a second hand move around a clock, you generate the concept of time because you have a memory of where the second hand was some "time" previously. TIme is simply how you acount for your memories. Space likewise – just relative changes in patterns of energy around you that you can remember and compare because unlike ants, you can recognize patterns and remember sequences. The fabric of reality is nothing more than information.

  25. Carlo. I almost agree with you about the time doesn´t really exist and is just a result of the way we perceive the universe. The only reason why i don't accept this as a true is the real impact of gravity on entropy velocity explained by Einstein and also you mentioned. That is something real, out of us and a property of the velocity of change in the universe that we call "time". So i conclude that time must be real and a part of the universe structure. Some times i wonder if this property "time" is just a part of something bigger that we as three dimensional beings are not able to know or imagine.

  26. Frank De Silva, a Sri Lankan born Australian, has discovered the theory as described by himself as "A description of consciousness leads to a contradiction with the postulation from special relativity that there can be no connections between simultaneous events. This contradiction points to consciousness involving quantum level mechanisms. The Quantum level description of the universe is re-evaluated in the light of what is observed in consciousness namely 4 Dimensional objects." The full paper can be found: https://philpapers.org/rec/DESCAS.

    Frank has discovered this theory more than 20 years ago in 1996, however, until today, it has been totally ignored by the utterly arrogant, sometimes even prejudicial physics world. His paper has caught no physicists' attention simply because that Frank is not an academic, most of all, he's not a Ph.D. or professor that listed on the physicist celebrity list. After his revolutionary discovery, Frank has since devoted his time in computer programming in solving the real-world problems. As such, he remains totally unknown in the physics world. However, if any of the physicists could be humble enough to take a read of his theory, they would soon realize that the problems plagued the physics world for decades had been resolved. This is a revolutionary and Nobel Prize worthy discovery! Let's hope that the truth will eventually prevail.

    If mankind could let go of their pride and prejudice, the world would a different and better world.

  30. He says that the universe is events, but what is an event if it isn't something that occurs in time? The Big Bang was an event that occurred some 13.7 billion years ago. The formation of the earth is an event that occurred some 4.5 billion years ago. There was our galaxy before this solar system formed, there was our galaxy while this solar system was forming, there is our galaxy as it exists "now," and there will be our galaxy as it will exist after the sun has exhausted its hydrogen and the earth is no more. Perhaps time is unecessary – perhaps even nonexistent – at the quantum level, but it makes little sense to say that at the macroscopic level time exists merely in our heads because we have evolved into beings that remember the past and plan for the future. I have no idea whether the second law of thermodynamics holds at the quantum level, but it certainly holds at the level at which we perceive the universe, and at that level time exists, if only as a measure of increasing entropy.

  31. Physicists never understand time and time is a so-called fundamental variable that has never been defined by physicists. For physicists, time is nothing more than some measurement by a clock. To Einstein, time is something that can be measured by a local clock. And time measurement by different clocks will be different. So, what is time? Isn't that obvious? There is no such thing as time. No one will ever agree upon its measurement and hence it is a different concept to everyone. There is NO time. You can read some numbers from your clock but those numbers have no meaning really. It is like turning on your TV and let the show runs. What if there is no clock or no TV? Then time ceases to exist cause it needs to be measured to have a meaning. Thanks to Einstein! LOL

  32. Time is simply a measure of change (action), and there is no cosmic clock. I don't think there is actually a smallest increment of time (or anything else), but there certainly is a greatest distance in size (etc.) from us. The bottom of reality is like a muddy river — there is no bottom, but merely a point where you can no longer distinguish a part from a whole. The quanta are merely our best possible view of something else — and we cannot know what else other than by observing their effects.

  34. What is Time?
     
    1. Assume the three dimensional
    Universe is inside a three dimensional photo Frame. Everything in this universe
    is dynamic and changing in relative to other things and itself. Entropy is
    changing also.

    2. The whole Universe inside the
    frame marked as Now Moment is separated from previous Now Moment by shortest
    possible separator Planck-time.

    3. Last Now Moments are Record,
    History, Memory or Information. Next Now Moments are next changed states of the
    Universe inside Frame.  

    4. Only Now Moment Exist. Past and
    Future do not exist. Flow of Time forward or backward does not exist. No arrow
    of time. It is arrow of Change with elapse of Time. Moment is ticking
    repeatedly at Planck-Time interval with a new 3D-Photo of the Universe whether any change or not. If no change, then can describe "no change for certain number of ticking Moments". Time is universal.

    5. Conscious Mind can make
    predictions of next Moments from experience and can plan events for next
    Moments.

    6. Every Planck-Volume’s “Now” of
    the Universe including space and stuffs in it is always in the same Now Moment
    Frame of the Universe. Relative Clock ticking, fast or slow, at different planck-volume for different conditions does not shift anything to previous or next Moment Frames of the Universe. Because clocks ticking slow or fast does not mean Time elapsing slow or fast. It is error of the clock for certain condition which need to be adjusted. All points Now remain in the Now Moment Frame of the Universe. That is why twins of paradox can meet at any ones Now though
    relatively they are backward or forward in respect of amount of time elapsed.
    Time travel is not possible. Our invented Clocks and Calendars are misleading
    us about time in the repetition of day & night and seasons.

    7. The Unit by Clock is three dimensional at any
    point of the Universe. X axis: Universal Period of Time, Y axis: Passage or
    Elapse of Time and Z axis: Local Present or Now. Our Clocks only show one
    dimension: passage of Time. Clocks are good measuring device with a Unit but that is not Time.

  37. I think, when you speed up or go to some higher gravity place or planet(n also maybe gravity effects everything(matter,charges,etc)), then weight of the matter increases, charges between those matter gets slower(for some reason like weight of the matter effects movement of the matter maybe) and movement of the matter gets slower and not the time itself because i think time is imaginary line of events. time is not physical entity. you cannot mold it because time does not exist, it is imaginary.

    I am not an expert but this is just my maybe theory. i don't know how to prove or disapprove it.

    Lets assume there is a box and you put a clock and a dog in it. and, you created a device which controls gravity and you can increased the gravity of that box and everything in it and after few years you open the box and probably you see clock is showing past date n time n dog is still young and healthy. so that means maybe everything(physically existing thing) in it slows down and not the time.

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