The headline seems a bit click-baity, as it refers to the Page-Wooters mechanism which was introduced 30 years ago, and as mentioned in the paper has been extensively studied.
A brief and accessible overview can be found here[2].
However this paper seeks to provide a more concrete and less constrained implementation of the Page-Wooters mechanism in order to connect it to our classical world better that previous attempts.
So while probably not a breakthrough paper, a solid step in an interesting direction.
His book From Eternity to Here on the subject of time is one of the very best science trade books I have ever read. It is chock full of end notes too which are a must read so bring two bookmarks to that party :)
I suspect though he would take issue with the description “illusion”. An illusion implies a trick, believing something that isn’t real. I think he would say emergent phenomena are real phenomena that we really experience and that time while it might not be fundamental it is very real.
The idea that time is emergent is considered unproven by most scientists. However, I personally believe there is some validity to it, even though I haven't found a single paper that convincingly supports this idea. I must admit that even some papers that are widely accepted as accurate are difficult for me to grasp and believe, as they are beyond my understanding and knowledge.
He came up with a framework where time is real (assumed), and then the laws of physics evolve with time, and then goes on to develop an evolutionary theory of universes, where universes reproduce by producing black holes, which spawn baby universes, with slightly different laws of physics. He then predicts that it should tend to produce universes that are optimized to produce black holes.
I'd recommend Henri Bergson's Time and Free Will for mind opening view of time. Imo it elaborates on the distinction between space time and our temporal experience.
Rovelli is an absolutely wonderful author - you’ll arrive at the end of that book maybe not actually understanding quantum mechanics fully, but at least feeling like you’ve been given a glimpse of them.
Fantastic book, from what I remember it was more of an autobiography with some math sprinkled in. But he's a really good writer and seems like a wonderful person.
Shook my foundations a little, I remember my partner and I were hiking for a few days at the time I was reading it and I recall having to drag myself back out of my head to experience the mountains
When they built up this physical theory, they assumed things about time, like that one thing happens after another, countless -- well -- countless times.
There is no way to not do that.
So it's pointless to say "time is an illusion". It's a basic category of thought.
But whatever to get hype for your paper, I guess...
You can "assume things about time" while writing a paper (including when it's due for sunmission), while still investigating whether the object of those assumptions has some fundamental properties, or whether it is just an emergent phenomenon from more fundamental things with no specific substance to it.
Same way we can assume things about color, but still come to the conclusion that the qualia of color are just manufactured in our brain, and that the reality behind color, as far as the universe is concerned, is electromagnetic radiation at various frequences.
Not really. The paper referenced in this article basically says "time" for a quantum system emerges from entanglement between that system and a clock. What is a clock? A system that, um, keeps time. Circular reasoning.
> So it's pointless to say "time is an illusion". It's a basic category of thought
If you think it’s pointless, it’s going to be pointless to you whether it’s true or not
However, to give an alternative point of view. If you can model time differently and provide some predictions or enable some technology, then having a different understanding of time might be very useful. Even if we still need to use time in the models
And that’s been the case with general relativity. For a long time, and for many physical phenomena, Newton laws and models are just fine. But relativity has enabled a lot of better technologies and finer understanding of some things, through re-defining how we model time
My intuitive, but not mathematical, model is that time is an illusion created by our perception “sampling reality”
It’s like when it looks like wheels are spinning backwards, or when using a stroboscopic light you see something different
“Time” is just flowing everywhere, not in any particular direction. But our perception assigns things an order, which gives us the impression of direction
We are also perceiving multiple times simultaneously. Consider that whatever is on your ears right now, will be converted to electrical signals and then loop through your brain, and potentially trigger a conscious reaction, but right now you have some other signals from some “previous” sound on your brain. So technically, your whole body is perceiving things at different times and trying to blend it all together in an illusion of “present time” that “moves forward”
My own, very personal opinion, is that there is no causality, only correlation
Well, if you believe in causality, everything that happens in a certain progression might seem as the consequence of a previous event
And that seems totally right and it’s a great model to understand our everyday life
Now imagine for a second, that the whole universe was a big cycle, and that you are going to be repeating this very same life in a “future” cycle, and maybe infinitely many times
Which one of those times is the first one? And what is happening first? Did you die first and then were born again, or were you born first before dying? If it’s a never ending cycle, would you know, or would you just be picking a point that seems convenient to you?
At another extreme, when you feel like you are hungry, what is the cause for being hungry? Is it a certain signal in your brain, is a special hormone, is it because you have a habit of eating at a certain time? When exactly do you get hungry and what is the cause? There are pretty much infinite many possible causes to choose, because there are an infinite way of understanding and modeling the meaning of the question and how to answer it
Usually we just take the fastest, “most reasonable” explanation as the reason, but it is arbitrary and subjective. Causes are agreements expressed in language and our models, they are not an absolute unbreakable order of reality
We all share a single photon in some theories. When time has no meaning, it can run through the whole universe in a strobe.
Large correlated events need to exist because smaller correlations do. It only makes logical sense if you try to remedy the movement / distance paradoxes.
There’s probably an information density limit, which is why far away galaxies will never have their information reach us after a certain point. They might as well not exist to us, because their information will never be useable in a correlated way.
Maybe I understand it wrong, but if time is not an illusion, does that mean the past still exists? Hypothetically, if we could reverse the flow of time, would that mean we could travel into the past?
I ask this because I have a bit of a paradox regarding time travel. It's pretty simple, presumably we're all sentient beings, and our consciousness is here, now, in the present. The science fiction portrayal of time travel suggests that we could travel into the past and interact with our former selves. But if my conscious mind is here now in the year 2024, then what conscious mind are you talking to in the past? Surely my conscious mind cannot exist in two different eras simultaneously.
This little "paradox" of mine has made me ponder the true nature of time. Though more likely these are just the ramblings of a person who has a poor understanding of physics.
>Surely my conscious mind cannot exist in two different eras simultaneously.
mentally I think of it more like save/restore states.
the future-person meeting the past person would just be past person+future person as a merged state, the past person would just be a working snapshot of everything before it without the accrued knowledge of future-person.
if you're someone who believe in an untouchable intangible non-duplicable 'soul', then it breaks the framework. I see myself more as a collection of experiences, so it jibes well into that concept.
A more interesting idea is whether "you" cease to exist in the present while "you" travel back in time to meet "you" in the past. Ie, If time travel is possible, are there "yous" spread across every moment of your existence?
That asks questions of our idea of timeless self-identity or "soul" if you like. Like Trigger's Broom [1], are we the same person as we were yesterday?
The idea of "block universe" follows from special relativity and suggests that not only the past "still" exists, but also the future "already" exists. In other words, all the states of the Universe from all times are physically "there". Here is a great i troduction to this concept:
There is no past you. You travel along the time axis at one speed, other things travel at other speeds. So something could take off from earth at the speed of light and come back further ahead down your line, but nothing can go back in time.
Time is a result of entropy. Which is an inherent property of everything in the universe. From when light transmits the first existence of anything to when it returns to nothing after entropy runs its course. Time is just a measurement of degradation.
I have never understood this, it seems backwards to me. We notice that entropy tends to increase over time, and then say that entropy is a fundamental cause of time?
The increase of entropy is a statistical certainty given a causal ordering of events, no new fundamental properties required.
It is certainly true that the increase of entropy gives a measurable direction to the arrow of time, i.e. the future is where entropy is higher. But I cannot fathom how entropy is anything more than a statistical effect.
Readit News
The headline seems a bit click-baity, as it refers to the Page-Wooters mechanism which was introduced 30 years ago, and as mentioned in the paper has been extensively studied.
A brief and accessible overview can be found here[2].
However this paper seeks to provide a more concrete and less constrained implementation of the Page-Wooters mechanism in order to connect it to our classical world better that previous attempts.
So while probably not a breakthrough paper, a solid step in an interesting direction.
[1]: https://arxiv.org/abs/2310.13386
[2]: https://quantum-journal.org/views/qv-2019-07-21-16/
https://www.preposterousuniverse.com/blog/2016/07/18/space-e...
I suspect though he would take issue with the description “illusion”. An illusion implies a trick, believing something that isn’t real. I think he would say emergent phenomena are real phenomena that we really experience and that time while it might not be fundamental it is very real.
He came up with a framework where time is real (assumed), and then the laws of physics evolve with time, and then goes on to develop an evolutionary theory of universes, where universes reproduce by producing black holes, which spawn baby universes, with slightly different laws of physics. He then predicts that it should tend to produce universes that are optimized to produce black holes.
https://bookshop.org/p/books/the-order-of-time-carlo-rovelli...
Rovelli is an absolutely wonderful author - you’ll arrive at the end of that book maybe not actually understanding quantum mechanics fully, but at least feeling like you’ve been given a glimpse of them.
Shook my foundations a little, I remember my partner and I were hiking for a few days at the time I was reading it and I recall having to drag myself back out of my head to experience the mountains
There is no way to not do that.
So it's pointless to say "time is an illusion". It's a basic category of thought.
But whatever to get hype for your paper, I guess...
You can "assume things about time" while writing a paper (including when it's due for sunmission), while still investigating whether the object of those assumptions has some fundamental properties, or whether it is just an emergent phenomenon from more fundamental things with no specific substance to it.
Same way we can assume things about color, but still come to the conclusion that the qualia of color are just manufactured in our brain, and that the reality behind color, as far as the universe is concerned, is electromagnetic radiation at various frequences.
Not really. The paper referenced in this article basically says "time" for a quantum system emerges from entanglement between that system and a clock. What is a clock? A system that, um, keeps time. Circular reasoning.
If you think it’s pointless, it’s going to be pointless to you whether it’s true or not
However, to give an alternative point of view. If you can model time differently and provide some predictions or enable some technology, then having a different understanding of time might be very useful. Even if we still need to use time in the models
And that’s been the case with general relativity. For a long time, and for many physical phenomena, Newton laws and models are just fine. But relativity has enabled a lot of better technologies and finer understanding of some things, through re-defining how we model time
https://www.youtube.com/watch?v=KpMGbjvBXSE
It’s like when it looks like wheels are spinning backwards, or when using a stroboscopic light you see something different
“Time” is just flowing everywhere, not in any particular direction. But our perception assigns things an order, which gives us the impression of direction
We are also perceiving multiple times simultaneously. Consider that whatever is on your ears right now, will be converted to electrical signals and then loop through your brain, and potentially trigger a conscious reaction, but right now you have some other signals from some “previous” sound on your brain. So technically, your whole body is perceiving things at different times and trying to blend it all together in an illusion of “present time” that “moves forward”
My own, very personal opinion, is that there is no causality, only correlation
And that seems totally right and it’s a great model to understand our everyday life
Now imagine for a second, that the whole universe was a big cycle, and that you are going to be repeating this very same life in a “future” cycle, and maybe infinitely many times
Which one of those times is the first one? And what is happening first? Did you die first and then were born again, or were you born first before dying? If it’s a never ending cycle, would you know, or would you just be picking a point that seems convenient to you?
At another extreme, when you feel like you are hungry, what is the cause for being hungry? Is it a certain signal in your brain, is a special hormone, is it because you have a habit of eating at a certain time? When exactly do you get hungry and what is the cause? There are pretty much infinite many possible causes to choose, because there are an infinite way of understanding and modeling the meaning of the question and how to answer it
Usually we just take the fastest, “most reasonable” explanation as the reason, but it is arbitrary and subjective. Causes are agreements expressed in language and our models, they are not an absolute unbreakable order of reality
There’s probably an information density limit, which is why far away galaxies will never have their information reach us after a certain point. They might as well not exist to us, because their information will never be useable in a correlated way.
Time exists to prevent everything happening at once.
I ask this because I have a bit of a paradox regarding time travel. It's pretty simple, presumably we're all sentient beings, and our consciousness is here, now, in the present. The science fiction portrayal of time travel suggests that we could travel into the past and interact with our former selves. But if my conscious mind is here now in the year 2024, then what conscious mind are you talking to in the past? Surely my conscious mind cannot exist in two different eras simultaneously.
This little "paradox" of mine has made me ponder the true nature of time. Though more likely these are just the ramblings of a person who has a poor understanding of physics.
mentally I think of it more like save/restore states.
the future-person meeting the past person would just be past person+future person as a merged state, the past person would just be a working snapshot of everything before it without the accrued knowledge of future-person.
if you're someone who believe in an untouchable intangible non-duplicable 'soul', then it breaks the framework. I see myself more as a collection of experiences, so it jibes well into that concept.
That asks questions of our idea of timeless self-identity or "soul" if you like. Like Trigger's Broom [1], are we the same person as we were yesterday?
[1] https://youtu.be/LAh8HryVaeY?si=5_URpP6si31KWIWD
https://youtu.be/Md6DkWF2T-A
If you are in a higher dimension, maybe you can physically see our entire timeline of our universe.
Deleted Comment
Aside from the obvious, why not? See quantum teleportation thought experiments.
The increase of entropy is a statistical certainty given a causal ordering of events, no new fundamental properties required.
It is certainly true that the increase of entropy gives a measurable direction to the arrow of time, i.e. the future is where entropy is higher. But I cannot fathom how entropy is anything more than a statistical effect.
This is famously referred to as "The Last Question" by Isaac Asimov
> noun
> UK /ɪˈluː.ʒən/ US /ɪˈluː.ʒən/
> an idea or belief that is not true:
> have no illusion about He had no illusions about his talents as a singer.
> under no illusion I'm under no illusions (= I understand the truth) about the > man I married.
> be labouring under the illusion My boss is labouring under the illusion that > > (= wrongly believes that) the project will be completed on time.
> something that is not really what it seems to be:
> create the illusion of A large mirror in a room can create the illusion of space.
> The impression of calm in the office is just an illusion
The backpain I started to have since few years tells me that time isn't an illusion