11 ms·

> It may seem eerie to our brains, which process events sequentially, but the history of science is also littered with examples of human biases leading to bad c

> It may seem eerie to our brains, which process events sequentially, but the history of science is also littered with examples of human biases leading to bad conclusions, such as the Earth-centric model of the solar system. Slow down. Assuming that time moves in one direction is not comparable to geocentrism.

whatshisface 4y ago
It is because in both cases, you can work out that you'll never make an observation that really proves it one way or the other, but you might come up with some laws of physics that are more conveniently expressed in one way than another. They're both ultimately questions about your coordinate system, and in fact it is easier to invert time than it is to work out how everything's supposed to function in a rotating+sun-orbiting+precessing+... coordinate system.
- nanidin 4y ago
  If we reverse time and this implies running everything backwards in physics, do we include gravity in the set of things that are reversed? Then everything would fly off the face of the earth in reverse-time.
  - entropicdrifter 4y ago
    Gravity is a universal constant. If you reverse time, you just reverse the order of cause and effect, not what the effect is. Does that make more sense to you?
    - nanidin 4y ago
      If we reverse time, would gravitational waves flow backwards?
      - dekhn 4y ago
        yes. it's literally like playing a movie in reverse.
        nanidin 4y ago
        " it's literally like playing a movie in reverse" seems overly authoritative for something we haven't observed. I have seen Tenet, but it's a work of fiction. Have we observed reflected gravitational waves? In reverse-time, where would they originate from if they presumably rippled out into space and didn't collide with anything in forward-time?
        dekhn 4y ago
        .... they would "originate" from all the locations the gravity waves spread to and converge on the source. Tenet has nothing to do with this- I'm just explaining it as it was covered in my many physics classes that covered the nature of the arrow of time (https://en.wikipedia.org/wiki/Arrow_of_time https://en.wikipedia.org/wiki/Arrow_of_time) and how I interpret it in terms of what seems most likely/least unlikely.
    - bigbacaloa 4y ago
      "gravity is a universal constant" contradicts Newtonian mechanics, special and general relativity.
      - nanidin 4y ago
        In these "it's like taking a video of throwing a ball in the air and allowing it to land on the ground, then playing it in reverse" examples, I can't help but think of Newton's first law. If an object at rest stays at rest, how does the ball leap from the ground? Where does the impulse come from? Reverse time seems too far fetched for me, or at least the simplified naïve version of it does.
        bnralt 4y ago
        It also seems a bit misleading, since in that scenario a ball is intentionally thrown so that it comes down the same way. Let's consider something else - imagine an accretion disk of space dust slowly pulling itself together to form a planet. Play that in reverse, and you have the a planet slowly coming apart piece by piece. Imagine reversing the impact that created the moon. The moon comes apart piece by piece, creating an accretion disk around the earth, which then all moves and hits one area of the earth, and there several parts of it (and part of the earth itself) move together to form a separate planet, which then launches itself from the earths surface into space, flies around the sun a few times, and then slowly breaks apart piece by piece into another accretion disk.
  - whatshisface 4y ago
    Let's check. F = ma F = m dv/dt u = -t dv/dt = -dv/du - F = m dv/du If you stop there it looks like you're right, but you also must change the definition of velocity to account for the new time. v = dx/dt = -dx/du +F = m dx/du So the direction of gravity (the force F) stays the same when you flip time. I can explain that without the math by pointing out that if you took a video of a ball being thrown up and caught and played it in reverse, it would still depict a ball being thrown up and caught.
    - nextaccountic 4y ago
      > I can explain that without the math by pointing out that if you took a video of a ball being thrown up and caught and played it in reverse, it would still depict a ball being thrown up and caught. That's amazing, thanks. The portion where you caught the ball in forward time is equivalent to throwing the ball in reverse time. I need to rewatch Tenet some day
      - novaRom 4y ago
        I watched it 4 times. Only then I started to understand what's happening. How great and unique this movie really is.
        mkl 4y ago
        I felt like I understood it the first time, but didn't think it was very good. Was that your initial reaction?
    - nanidin 4y ago
      If we change the analogy of throwing a ball to firing a gun into the air - does the analogy still work? Since when we fire the gun up, the bullet will travel faster up than it will travel down due to terminal velocity in forward time. How is that phenomenon explained in reverse time?
      - whatshisface 4y ago
  - theemathas 4y ago
    Reversing time on an attracting force still gives you an attractive force. Velocity is reversed, but acceleration isn't. Imagine a ball being thrown up and then falling down, in a parabola. Reversing a video of that still gives you a video of a ball in a normal parabola trajectory.
    - deleted 4y ago
      [deleted]
    - pixl97 4y ago
      The history of the universe channel on YouTube has an episode called 'what is time' that goes over symmetries like this. Lots of atomic/quantum scale interactions are time reversible like this, but not quote all, and that may be where time arrives from. Well worth watching that episode as it does far better explaining than I do.
- sidlls 4y ago
  It isn't because we have the observations we have. It might be mathematically easy to invert time, but empirically it's not so simple. Mathematical symmetries and expressions are nice, but then the actual physical consequences and requirements (e.g., material, time, energy inputs) sort of force one's hand. Also, geocentrism is actually disproven by numerous observations, which in fact guided the mathematical formulation of our current physics. One thing is (almost) certain: the laws of physics as we know them (i.e. the Standard Model and General Relativity) are incomplete ("wrong"). That doesn't mean any old model is equivalent or as useful as either, though.
  - whatshisface 4y ago
    >Also, geocentrism is actually disproven by numerous observations, which in fact guided the mathematical formulation of our current physics. The validity of a coordinate system with the earth stationary at the center is guaranteed by the general principle of relativity. To get the stars to circle around it you would add a radially increasing potential in classical mechanics, or some coordinate shenanigans in GR. These coordinate systems are used in aerospace engineering to get convenient expressions of L1 points, etc. I know it sounds hard to believe, but if you're willing to bite the bullet that "the center of the universe" has no physical meaning, then earth can't be not the center of the universe any more than it can be.
    - prerok 4y ago
      To be honest, I have no idea what you are talking about. Certainly, there is merit in practical calculations when we are all this close to the ground where it all seems either flat or at least geo-centric. But... the movements of the other planets in our solar system were really strange to model in geo-centric models. In short, each of the other planets should rotate around an imaginary axis to compensate for their changing positions in the sky. Of course, all this is talk about in the context of our solar system. As for us being the center of the universe, well, the same argument holds for any other point in the universe. So, I think it's less likely than me winning the lottery in the next five minutes :)
epgui 4y ago
I disagree, I think the comparison is pretty reasonable. Your entire experience of the world is defined and limited by the fact that your brain "only processes information in one direction of time" (for lack of better wording). Your personal experience does not necessarily map correctly to the real world. The same is true for both examples.
- brwck 4y ago
  It's not just a matter of our subjective experience of time, it's a matter of the laws of thermodynamics and entropy. Time moves in one direction is another way of saying entropy always increases. If time could move in the opposite direction, then entropy decreases which breaks our understanding of physics.
  - VeninVidiaVicii 4y ago
    It's really interesting to think about how we struggle to express the idea of the future having a causal impact on the past. I reckon this is because our language and our understanding of time are limited. Our brains like to process events in a linear sequence, from past to present to future, but this view of time might not fully capture how everything in the universe is interconnected. It's possible that our language just can't handle these complex concepts. So, I don't think anything mentioned in this thread contradicts the idea that "time always moves in one direction" and "entropy always increases".
    - dasil003 4y ago
      Right. "Time only moves in one direction" is not saying much more than "our consciousness experience time moving in one direction". The very idea that time "moves" is entirely related to our vantage point. If our perception were not bound to time, then the nature of cause and effect might look completely different.
  - Trasmatta 4y ago
    I don't think the idea that "the future can influence the past" is the same thing as saying that entropy decreases or that time can move in the opposite direction. I think these are different concerns
7thaccount 4y ago
Yep. Someone else already pointed out the well known counterargument to symmetry below regarding thermodynamics. You typically don't see scrambled eggs become whole again. I think that's pretty hard evidence to overcome. Granted, I'm not a physicist and I'm sure any physicist working on this totally understands that. Just wanted to point it out.
- kridsdale1 4y ago
  Scrambled eggs can become whole again by being consumed by insects, who are then consumed by chickens, who then lay eggs. The biological processes enabling that sequence can be said to have negative entropy.
  - dekhn 4y ago
    Negative entropy (also called negentropy) isn't really a well-defined concept. Instead, better to say that biological processes harvest free energy to maintain order in the face of increasing entropy.
- resource0x 4y ago
  If the direction of time is reversed, the eggs become whole again, but your memory of them once being scrambled is reversed, too, so you don't notice anything unusual. (It's like a rollback of database transaction, where not only the database state, but also the state of everything, including your brain, is getting rolled back)
  - fortyseven 4y ago
    That would suggest a kind of "super timeline" I'd imagine.
  - 7thaccount 4y ago
    But is there any evidence of that? Or is it just a thought experiment? I need to read more of the article, but appreciate you giving me some food for thought.
seydor 4y ago
Assuming that time "moves" kinda is
- weknowbetter 4y ago
  Nothing actually moves according to Zeno's paradox.
  - Ygg2 4y ago
    Zeno's paradox assumes space is infinitely divisible.
    - kelseyfrog 4y ago
      they didn't understand limits
      - deleted 4y ago
        [deleted]
      - Ygg2 4y ago
        You don't understand physics. Or logic. Nature doesn't have to obey any particular set of axiom you adopt.
        kelseyfrog 4y ago
        Can you make your point without a personal slight?
    - edgyquant 4y ago
      can you profe to me that the physical space between everything isn’t?
      - Ygg2 4y ago
        Planck length.
macrolocal 4y ago
It's comparable to GPT4 being shocked that we can read backwards!
0xBABAD00C 4y ago
Here's the analogy, per Sean Carroll [1]: - There seems to be a special direction "down", where things fall by default, because we live in the vicinity of an influential object in space, called Earth - There seems to be a special direction "forward in time", where things happen by default, because we live in the vicinity of an influential event in time, called Big Bang If we had stuck to the local Earth context and geocentrism, the objectivity of the "down" direction would remain unquestioned. It's when we started modeling other things outside of Earth, it became clear there's no objective "down" direction, just a more general concept of Gravity. Carroll's argument is that it's the Big Bang, an extremely low-entropy configuration of the universe, that gives rise to the 2nd Law of Thermodynamics and the resulting emergence of an arrow of time in the forward direction. It's purely a statistical phenomenon at larger scales, and attributable to being "next to an influential event", according to him. [1] https://www.youtube.com/watch?v=AZsmyTE3j9o https://www.youtube.com/watch?v=AZsmyTE3j9o
- photochemsyn 4y ago
  It's difficult to see how such a hypothesis could be tested either experimentally or observationally. Sounds more like metaphysics? Stars shine until they run out of fuel, and the age of a star - the status of its fuel, the buildup of fusion products - happens as time passes. Life on planets taps into the flow of sunlight from the star (and/or the flow of heat and chemical energy from the a hot planetary core) to generate complex structures in defiance of the regular direction of entropy (not violating conservation of energy, though). So... life reverses the arrow of time?
  - prerok 4y ago
    Well, of course not :) Entropy as direction of time just means that the chaos on the whole increases. So, to create an ordered structure, like a cell organism, the by-product is more chaos around it.
    - ashirviskas 4y ago
      To add, life just speeds up the chaos by orders of magnitude, it's a perfect entropy catalyst.
yyyk 4y ago
The comparison is bad all around. Geocentrism actually had decent reasoning and was not a superstition. It's just we couldn't see the parallax with then-current instruments. As soon as instruments allowed, humanity changed rather quickly.
- Notatheist 4y ago
  Time moving in one direction actually has decent reasoning and is not a superstition. It's just we can't detect time moving backwards with now-current instruments. As soon as instruments allow, humanity will change rather quickly.
  - yyyk 4y ago
    The problem with the comparison is what it's used to imply. The popular understanding* is that scientists believed in religious dogma, and that led them to 'unscientific' geocentrism and believing that time has only one direction. It's a backhanded accusation of superstition, and that's unfair towards both current scientists and past scientists. (On a personal note, I'm actually sympathetic to the article's retrocasual proposition. I suspect reality is non-local and TSVF etc. naturally tend towards non-locality.) * This is Vice, of course they use the popular understanding and not something more sophisticated.
    - stametseater 4y ago
      It seems to me that the popular understanding is influenced by grossly misleading 20th century anti-religious propaganda. The geocentric model is not something the Catholic Church plucked out of the bible; they got it from Ptolemy and other 'heathen' classical thinkers, whom the Catholic Church considered meritorious despite not being Christians. Sure, they then found some biblical citations to back themselves up in this, but the idea was never their own in the first place.
- TheSpiceIsLife 4y ago
  We've always been able to detect that some celestial objects appear to move backwards at times.
bsder 4y ago
> Slow down. Assuming that time moves in one direction is not comparable to geocentrism. Why not? The "arrow of time" almost always requires thermodynamic arguments. And that requires a concentration of "low entropy" to move toward "high entropy". Which, by definition, are "boundary conditions" and not a fundamental part of your physical rules. If, for example, your universe is entropically uniform, is there an "arrow of time"? And, even if there were, could you detect it? However, I would like to point out that it's not like we haven't had this kind of issue before. The Bohr-Einstein debates were a good example. Einstein favored a "fields" interpretation of quantum mechanics. Unfortunately, Einstein's interpretation predicted that atomic states wouldn't decay, and that was clearly, obviously wrong, and Bohr very much hammered on that. Except that Einstein wasn't "clearly, obviously wrong." As you increasingly isolate excited atoms, their atomic states take longer and longer to decay. The problem was that the experiments of the day couldn't create these kinds of singular quantum state systems--they were stuck with systems that were contaminated with lots of thermodynamic interactions. We may be seeing something similar here. We are just starting to be able to put together the experiments that can probe things like Bell's Inequality. As we isolate these systems, we may find that the systems were contaminated with statistical time and that we get different results when we can isolate them.
- febusravenga 4y ago
  > If, for example, your universe is entropically uniform, is there an "arrow of time"? And, even if there were, could you detect it? Would we have fluctuations in that state? In which directions they would... Progress? Isn't what you describe an anomaly like black hole or division by zero, where we cannot understand what actually happens because normal laws break because they are unsolvable with current models?
- kgwgk 4y ago
  > If, for example, your universe is entropically uniform, is there an "arrow of time"? And, even if there were, could you detect it? What does that even mean? If your universe is entropically uniform there is no “you”.
- Barrin92 4y ago
  >If, for example, your universe is entropically uniform, is there an "arrow of time"? Nope, and there's a really great 'physics slam' about this, sadly only in German but auto-translate seems fine. https://youtu.be/z64PJwXy--8?t=519 https://youtu.be/z64PJwXy--8?t=519
deleted 4y ago
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CuriouslyC 4y ago
Geocentrism seemed reasonable until it didn't. If time is a true dimension rather than just something we model as a dimension, it's not unreasonable to think that outcomes in the present could be influenced by constraints that exist in the future - if the "universe" function must be valid according to some constraints at all points in the time dimension, "past" states that lead to invalid future states will never occur. The idea of invalid universe states is of course purely fun conjecture, but this same concept also maps to probable vs improbable universe states as well. If a future state is improbable (in the sense of a Bayesian prior according to some underlying distribution of energy in the universe) that might cause the universe to evolve in a way that seems improbable at the moment by moment level, but is actually the most probable sequence of events when integrated over the entire duration of the universe.
- deleted 4y ago
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willis936 4y ago
Time could move backwards if we lived in a time symmetric universe. We don't. Maybe if you flipped the charge and handedness of the entire universe you could also reverse time, but that's yet to be tested. https://youtu.be/L2idut9tkeQ https://youtu.be/L2idut9tkeQ
lxgr 4y ago
How so? The idea doesn't seem so different from matter being the default (vs. antimatter), relative speeds much closer to zero than to the speed of light being what's commonly observable etc.
fdsafsd34 4y ago
I think the actual assumption is that we are currently seeing just one direction of the arrow of time, but if there is no arrow of time, maybe we are already seeing the future and not realizing it is the future. I commented further in this line of though in another comments, about a probable (ironically), "Inverted 2nd. Law of Thermodynamics" of sorts, which it would be basically just the Law of Probability, interpreted from the point of view of not having an actual arrow of time and the fact that we have - all the time, again ironically - the information of what happens in the future (the one probability in the range which ends being the right one, actually ocurring). Yeah, I know it would be another Law, and the universe would upside down once again for us the poor meatbags, but we were already in this position several times, discovering the electricity, quantum mechanics, relativiy, you name it.

whatshisface 4y ago

It is because in both cases, you can work out that you'll never make an observation that really proves it one way or the other, but you might come up with some laws of physics that are more conveniently expressed in one way than another. They're both ultimately questions about your coordinate system, and in fact it is easier to invert time than it is to work out how everything's supposed to function in a rotating+sun-orbiting+precessing+... coordinate system.

nanidin 4y ago
If we reverse time and this implies running everything backwards in physics, do we include gravity in the set of things that are reversed? Then everything would fly off the face of the earth in reverse-time.
- entropicdrifter 4y ago
  Gravity is a universal constant. If you reverse time, you just reverse the order of cause and effect, not what the effect is. Does that make more sense to you?
  - nanidin 4y ago
    If we reverse time, would gravitational waves flow backwards?
    - dekhn 4y ago
      yes. it's literally like playing a movie in reverse.
      - nanidin 4y ago
        " it's literally like playing a movie in reverse" seems overly authoritative for something we haven't observed. I have seen Tenet, but it's a work of fiction. Have we observed reflected gravitational waves? In reverse-time, where would they originate from if they presumably rippled out into space and didn't collide with anything in forward-time?
        dekhn 4y ago
        .... they would "originate" from all the locations the gravity waves spread to and converge on the source. Tenet has nothing to do with this- I'm just explaining it as it was covered in my many physics classes that covered the nature of the arrow of time (https://en.wikipedia.org/wiki/Arrow_of_time https://en.wikipedia.org/wiki/Arrow_of_time) and how I interpret it in terms of what seems most likely/least unlikely.
  - bigbacaloa 4y ago
    "gravity is a universal constant" contradicts Newtonian mechanics, special and general relativity.
    - nanidin 4y ago
      In these "it's like taking a video of throwing a ball in the air and allowing it to land on the ground, then playing it in reverse" examples, I can't help but think of Newton's first law. If an object at rest stays at rest, how does the ball leap from the ground? Where does the impulse come from? Reverse time seems too far fetched for me, or at least the simplified naïve version of it does.
      - bnralt 4y ago
        It also seems a bit misleading, since in that scenario a ball is intentionally thrown so that it comes down the same way. Let's consider something else - imagine an accretion disk of space dust slowly pulling itself together to form a planet. Play that in reverse, and you have the a planet slowly coming apart piece by piece. Imagine reversing the impact that created the moon. The moon comes apart piece by piece, creating an accretion disk around the earth, which then all moves and hits one area of the earth, and there several parts of it (and part of the earth itself) move together to form a separate planet, which then launches itself from the earths surface into space, flies around the sun a few times, and then slowly breaks apart piece by piece into another accretion disk.
- whatshisface 4y ago
  Let's check. F = ma F = m dv/dt u = -t dv/dt = -dv/du - F = m dv/du If you stop there it looks like you're right, but you also must change the definition of velocity to account for the new time. v = dx/dt = -dx/du +F = m dx/du So the direction of gravity (the force F) stays the same when you flip time. I can explain that without the math by pointing out that if you took a video of a ball being thrown up and caught and played it in reverse, it would still depict a ball being thrown up and caught.
  - nextaccountic 4y ago
    > I can explain that without the math by pointing out that if you took a video of a ball being thrown up and caught and played it in reverse, it would still depict a ball being thrown up and caught. That's amazing, thanks. The portion where you caught the ball in forward time is equivalent to throwing the ball in reverse time. I need to rewatch Tenet some day
    - novaRom 4y ago
      I watched it 4 times. Only then I started to understand what's happening. How great and unique this movie really is.
      - mkl 4y ago
        I felt like I understood it the first time, but didn't think it was very good. Was that your initial reaction?
  - nanidin 4y ago
    If we change the analogy of throwing a ball to firing a gun into the air - does the analogy still work? Since when we fire the gun up, the bullet will travel faster up than it will travel down due to terminal velocity in forward time. How is that phenomenon explained in reverse time?
    - whatshisface 4y ago
- theemathas 4y ago
  Reversing time on an attracting force still gives you an attractive force. Velocity is reversed, but acceleration isn't. Imagine a ball being thrown up and then falling down, in a parabola. Reversing a video of that still gives you a video of a ball in a normal parabola trajectory.
  - deleted 4y ago
    [deleted]
  - pixl97 4y ago
    The history of the universe channel on YouTube has an episode called 'what is time' that goes over symmetries like this. Lots of atomic/quantum scale interactions are time reversible like this, but not quote all, and that may be where time arrives from. Well worth watching that episode as it does far better explaining than I do.
sidlls 4y ago
It isn't because we have the observations we have. It might be mathematically easy to invert time, but empirically it's not so simple. Mathematical symmetries and expressions are nice, but then the actual physical consequences and requirements (e.g., material, time, energy inputs) sort of force one's hand. Also, geocentrism is actually disproven by numerous observations, which in fact guided the mathematical formulation of our current physics. One thing is (almost) certain: the laws of physics as we know them (i.e. the Standard Model and General Relativity) are incomplete ("wrong"). That doesn't mean any old model is equivalent or as useful as either, though.
- whatshisface 4y ago
  >Also, geocentrism is actually disproven by numerous observations, which in fact guided the mathematical formulation of our current physics. The validity of a coordinate system with the earth stationary at the center is guaranteed by the general principle of relativity. To get the stars to circle around it you would add a radially increasing potential in classical mechanics, or some coordinate shenanigans in GR. These coordinate systems are used in aerospace engineering to get convenient expressions of L1 points, etc. I know it sounds hard to believe, but if you're willing to bite the bullet that "the center of the universe" has no physical meaning, then earth can't be not the center of the universe any more than it can be.
  - prerok 4y ago
    To be honest, I have no idea what you are talking about. Certainly, there is merit in practical calculations when we are all this close to the ground where it all seems either flat or at least geo-centric. But... the movements of the other planets in our solar system were really strange to model in geo-centric models. In short, each of the other planets should rotate around an imaginary axis to compensate for their changing positions in the sky. Of course, all this is talk about in the context of our solar system. As for us being the center of the universe, well, the same argument holds for any other point in the universe. So, I think it's less likely than me winning the lottery in the next five minutes :)

epgui 4y ago

I disagree, I think the comparison is pretty reasonable. Your entire experience of the world is defined and limited by the fact that your brain "only processes information in one direction of time" (for lack of better wording). Your personal experience does not necessarily map correctly to the real world. The same is true for both examples.

brwck 4y ago
It's not just a matter of our subjective experience of time, it's a matter of the laws of thermodynamics and entropy. Time moves in one direction is another way of saying entropy always increases. If time could move in the opposite direction, then entropy decreases which breaks our understanding of physics.
- VeninVidiaVicii 4y ago
  It's really interesting to think about how we struggle to express the idea of the future having a causal impact on the past. I reckon this is because our language and our understanding of time are limited. Our brains like to process events in a linear sequence, from past to present to future, but this view of time might not fully capture how everything in the universe is interconnected. It's possible that our language just can't handle these complex concepts. So, I don't think anything mentioned in this thread contradicts the idea that "time always moves in one direction" and "entropy always increases".
  - dasil003 4y ago
    Right. "Time only moves in one direction" is not saying much more than "our consciousness experience time moving in one direction". The very idea that time "moves" is entirely related to our vantage point. If our perception were not bound to time, then the nature of cause and effect might look completely different.
- Trasmatta 4y ago
  I don't think the idea that "the future can influence the past" is the same thing as saying that entropy decreases or that time can move in the opposite direction. I think these are different concerns

7thaccount 4y ago

Yep. Someone else already pointed out the well known counterargument to symmetry below regarding thermodynamics. You typically don't see scrambled eggs become whole again. I think that's pretty hard evidence to overcome. Granted, I'm not a physicist and I'm sure any physicist working on this totally understands that. Just wanted to point it out.

kridsdale1 4y ago
Scrambled eggs can become whole again by being consumed by insects, who are then consumed by chickens, who then lay eggs. The biological processes enabling that sequence can be said to have negative entropy.
- dekhn 4y ago
  Negative entropy (also called negentropy) isn't really a well-defined concept. Instead, better to say that biological processes harvest free energy to maintain order in the face of increasing entropy.
resource0x 4y ago
If the direction of time is reversed, the eggs become whole again, but your memory of them once being scrambled is reversed, too, so you don't notice anything unusual. (It's like a rollback of database transaction, where not only the database state, but also the state of everything, including your brain, is getting rolled back)
- fortyseven 4y ago
  That would suggest a kind of "super timeline" I'd imagine.
- 7thaccount 4y ago
  But is there any evidence of that? Or is it just a thought experiment? I need to read more of the article, but appreciate you giving me some food for thought.

seydor 4y ago

Assuming that time "moves" kinda is

weknowbetter 4y ago
Nothing actually moves according to Zeno's paradox.
- Ygg2 4y ago
  Zeno's paradox assumes space is infinitely divisible.
  - kelseyfrog 4y ago
    they didn't understand limits
    - deleted 4y ago
      [deleted]
    - Ygg2 4y ago
      You don't understand physics. Or logic. Nature doesn't have to obey any particular set of axiom you adopt.
      - kelseyfrog 4y ago
        Can you make your point without a personal slight?
  - edgyquant 4y ago
    can you profe to me that the physical space between everything isn’t?
    - Ygg2 4y ago
      Planck length.

macrolocal 4y ago

It's comparable to GPT4 being shocked that we can read backwards!

0xBABAD00C 4y ago

Here's the analogy, per Sean Carroll [1]: - There seems to be a special direction "down", where things fall by default, because we live in the vicinity of an influential object in space, called Earth - There seems to be a special direction "forward in time", where things happen by default, because we live in the vicinity of an influential event in time, called Big Bang If we had stuck to the local Earth context and geocentrism, the objectivity of the "down" direction would remain unquestioned. It's when we started modeling other things outside of Earth, it became clear there's no objective "down" direction, just a more general concept of Gravity. Carroll's argument is that it's the Big Bang, an extremely low-entropy configuration of the universe, that gives rise to the 2nd Law of Thermodynamics and the resulting emergence of an arrow of time in the forward direction. It's purely a statistical phenomenon at larger scales, and attributable to being "next to an influential event", according to him. [1] https://www.youtube.com/watch?v=AZsmyTE3j9o https://www.youtube.com/watch?v=AZsmyTE3j9o

photochemsyn 4y ago
It's difficult to see how such a hypothesis could be tested either experimentally or observationally. Sounds more like metaphysics? Stars shine until they run out of fuel, and the age of a star - the status of its fuel, the buildup of fusion products - happens as time passes. Life on planets taps into the flow of sunlight from the star (and/or the flow of heat and chemical energy from the a hot planetary core) to generate complex structures in defiance of the regular direction of entropy (not violating conservation of energy, though). So... life reverses the arrow of time?
- prerok 4y ago
  Well, of course not :) Entropy as direction of time just means that the chaos on the whole increases. So, to create an ordered structure, like a cell organism, the by-product is more chaos around it.
  - ashirviskas 4y ago
    To add, life just speeds up the chaos by orders of magnitude, it's a perfect entropy catalyst.

yyyk 4y ago

The comparison is bad all around. Geocentrism actually had decent reasoning and was not a superstition. It's just we couldn't see the parallax with then-current instruments. As soon as instruments allowed, humanity changed rather quickly.

Notatheist 4y ago
Time moving in one direction actually has decent reasoning and is not a superstition. It's just we can't detect time moving backwards with now-current instruments. As soon as instruments allow, humanity will change rather quickly.
- yyyk 4y ago
  The problem with the comparison is what it's used to imply. The popular understanding* is that scientists believed in religious dogma, and that led them to 'unscientific' geocentrism and believing that time has only one direction. It's a backhanded accusation of superstition, and that's unfair towards both current scientists and past scientists. (On a personal note, I'm actually sympathetic to the article's retrocasual proposition. I suspect reality is non-local and TSVF etc. naturally tend towards non-locality.) * This is Vice, of course they use the popular understanding and not something more sophisticated.
  - stametseater 4y ago
    It seems to me that the popular understanding is influenced by grossly misleading 20th century anti-religious propaganda. The geocentric model is not something the Catholic Church plucked out of the bible; they got it from Ptolemy and other 'heathen' classical thinkers, whom the Catholic Church considered meritorious despite not being Christians. Sure, they then found some biblical citations to back themselves up in this, but the idea was never their own in the first place.
TheSpiceIsLife 4y ago
We've always been able to detect that some celestial objects appear to move backwards at times.

bsder 4y ago

> Slow down. Assuming that time moves in one direction is not comparable to geocentrism. Why not? The "arrow of time" almost always requires thermodynamic arguments. And that requires a concentration of "low entropy" to move toward "high entropy". Which, by definition, are "boundary conditions" and not a fundamental part of your physical rules. If, for example, your universe is entropically uniform, is there an "arrow of time"? And, even if there were, could you detect it? However, I would like to point out that it's not like we haven't had this kind of issue before. The Bohr-Einstein debates were a good example. Einstein favored a "fields" interpretation of quantum mechanics. Unfortunately, Einstein's interpretation predicted that atomic states wouldn't decay, and that was clearly, obviously wrong, and Bohr very much hammered on that. Except that Einstein wasn't "clearly, obviously wrong." As you increasingly isolate excited atoms, their atomic states take longer and longer to decay. The problem was that the experiments of the day couldn't create these kinds of singular quantum state systems--they were stuck with systems that were contaminated with lots of thermodynamic interactions. We may be seeing something similar here. We are just starting to be able to put together the experiments that can probe things like Bell's Inequality. As we isolate these systems, we may find that the systems were contaminated with statistical time and that we get different results when we can isolate them.

febusravenga 4y ago
> If, for example, your universe is entropically uniform, is there an "arrow of time"? And, even if there were, could you detect it? Would we have fluctuations in that state? In which directions they would... Progress? Isn't what you describe an anomaly like black hole or division by zero, where we cannot understand what actually happens because normal laws break because they are unsolvable with current models?
kgwgk 4y ago
> If, for example, your universe is entropically uniform, is there an "arrow of time"? And, even if there were, could you detect it? What does that even mean? If your universe is entropically uniform there is no “you”.
Barrin92 4y ago
>If, for example, your universe is entropically uniform, is there an "arrow of time"? Nope, and there's a really great 'physics slam' about this, sadly only in German but auto-translate seems fine. https://youtu.be/z64PJwXy--8?t=519 https://youtu.be/z64PJwXy--8?t=519

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CuriouslyC 4y ago

Geocentrism seemed reasonable until it didn't. If time is a true dimension rather than just something we model as a dimension, it's not unreasonable to think that outcomes in the present could be influenced by constraints that exist in the future - if the "universe" function must be valid according to some constraints at all points in the time dimension, "past" states that lead to invalid future states will never occur. The idea of invalid universe states is of course purely fun conjecture, but this same concept also maps to probable vs improbable universe states as well. If a future state is improbable (in the sense of a Bayesian prior according to some underlying distribution of energy in the universe) that might cause the universe to evolve in a way that seems improbable at the moment by moment level, but is actually the most probable sequence of events when integrated over the entire duration of the universe.

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willis936 4y ago

Time could move backwards if we lived in a time symmetric universe. We don't. Maybe if you flipped the charge and handedness of the entire universe you could also reverse time, but that's yet to be tested. https://youtu.be/L2idut9tkeQ https://youtu.be/L2idut9tkeQ

lxgr 4y ago

How so? The idea doesn't seem so different from matter being the default (vs. antimatter), relative speeds much closer to zero than to the speed of light being what's commonly observable etc.

fdsafsd34 4y ago

I think the actual assumption is that we are currently seeing just one direction of the arrow of time, but if there is no arrow of time, maybe we are already seeing the future and not realizing it is the future. I commented further in this line of though in another comments, about a probable (ironically), "Inverted 2nd. Law of Thermodynamics" of sorts, which it would be basically just the Law of Probability, interpreted from the point of view of not having an actual arrow of time and the fact that we have - all the time, again ironically - the information of what happens in the future (the one probability in the range which ends being the right one, actually ocurring). Yeah, I know it would be another Law, and the universe would upside down once again for us the poor meatbags, but we were already in this position several times, discovering the electricity, quantum mechanics, relativiy, you name it.