9 ms·

Julian Barbour’s ideas about time and the universe have roamed free of academia

98 points by dnetesn 5y ago

j7ake 5y ago
Interestingly, it is probably because he was free from academic constraints that would allow him to do his most creative work (long term, book form, philosophical).
dotsam 5y ago
This reminds me of a confusion I have with theoretical physics and mathematically describing a universe without time. I don’t understand how you could use mathematics - numbers and operations on numbers - to specify a timeless universe, given that mathematics has time as a precondition (how can you perform an operation like 1+1 without time?).
- deleted 5y ago
  [deleted]
- madsbuch 5y ago
  It's the difference between the domain of reasoning and complexity of reasoning.
- k1t 5y ago
  Presumably the issue is that you have defined 1+1 as an operation, rather than just an alternative representation (of 2).
  - GlobalFrog 5y ago
    That's interesting actually : isn't that more a philosophical question or just an interpretation ? That is, if 1+1 is just an alternatative representation of '2', you can postulate that the universe is fixed, predefined and timeless. But if you consider that '1 + 1' is not just a representation of '2' but has more information in it, that information could be the dynamic and evolution that we call time. Isn't that linked also to the usual question of the link to reality of Mathematics ?
    - slibhb 5y ago
      It's a philosophical question. Whether 1 + 1 = 2 is a tautology (analytic) or if it "has more information in it" (synthetic) is an open question. This dispute is associated with the analytic-synthetic distinction which has existed since at least Kant.
- nl 5y ago
  > how can you perform an operation like 1+1 without time? 1+1 is a dimensionless operation. Do you mean how it would physically happen without time? It's possible time is just an illusion that emerges from our perception of the universe. See https://www.nature.com/articles/d41586-018-04558-7 https://www.nature.com/articles/d41586-018-04558-7 and https://www.quantamagazine.org/does-time-really-flow-new-clues-come-from-a-century-old-approach-to-math-20200407/ https://www.quantamagazine.org/does-time-really-flow-new-clu... or https://www.npr.org/2013/05/17/184775924/resetting-the-theory-of-time https://www.npr.org/2013/05/17/184775924/resetting-the-theor... for a counter argument.
  - dotsam 5y ago
    My confusion is around the feeling that space and time must be preconditions for numbers and operations. How can you differentiate one number or symbol (or anything) from another without dimensions? It seems to me that you wouldn't be able to have the notion of "1" and "2" unless they can be separated, and to separate them you need dimensions. So for a number to be intelligible at all, it requires dimensions; but how do you get dimensionality in the first place, if your equation is specifying the universe?
    - bourgwaletariat 5y ago
      You need time to differentiate, but the universe does not. The one and the one and the two of them are always here in the universe. You just need time to speak it. You need time to observe the difference between the neuronal pattern between an awareness of one and the other one and the two of them. But they are all at once.
      - dotsam 5y ago
        To have the one and the two in the first place grants spatial dimensions, to separate them. Otherwise you end up with a single point, or maybe not even that. I can't get my head around how anyone can generate time (whether an illusion or not) just from spatial dimensions. If I have to assume spatial dimensions to get anywhere, can I also assume time?
- jl6 5y ago
  Addition is just a function and functions are just sets of pairs and sets can just sit there merrily existing in the abstract without any need for time or flow or movement or such.
  - sharkbot 5y ago
    That is true, but that would be the definition of +. The OP is referring to the application of that operator to its arguments, which (depending on semantics) could also be a set of sets, or it could be a rewriting (ie, time based) process.
    - mannykannot 5y ago
      Anything you can do as a sequence of operations on symbols can be written out, and then there you have it, on the page, all at once! Time does not appear in formal logic or number theory, even though it is convenient to think of a derivation or a calculation as as sequence of steps performed one at a time. it is also very convenient to use mathematics to model a temporal process, but we can, and often do, then show what happened (or will happen) as tables, graphs or other static representations. I know that last sentence presupposes time, but I am not even going to attempt to rewrite it in a way that avoids doing so!
- meroes 5y ago
  Does a triangle have a duration? Does a line? An equation of a line is very close to 1+1=2. X=2 and y=2 are lines. Nothing in math has time or duration. 1+1 = 2 = area of a triangle with base and height 2 = 362/181 = -2(-1). These are timeless relations. If 2 has no duration, none of the others do. They are just statements of relations. In fact ontic structural realism (some versions) says there is only these abstract relations and everything can be reduced to mathematical relations. Spacetime, consciousness, subjecive experience - all of it are just timeless relations like numbers in a table.
  - dotsam 5y ago
    My brain sputters out when I try to go from timeless relations (which assume spatial dimensionality as a given) to a timeless universe within which I sit with the illusion of time! I can't get my mind around anything that doesn't also assume time as a given -- all I end up with is a load of geometry sitting around doing nothing.
    - meroes 5y ago
      No one actually has a working model of consciousness so that programme has a long way to go. But if the only evidence for time is change as Barbour likes to say, and change basically boils down the relative motion of particles, why not describe the whole thing as a timeless table of coordinates essentially? And let psychologists build sensation and a perception of a flow of time from that. It's a tempting view due to its simplicity and the importance of math. But it is extreme, but so is every other theory or metaphysics trying to explain the same stuff!
      - fpoling 5y ago
        This is a circular argument since motion is a change in position. So a change is a motion and a motion is a change. This implicitly refers to personal experience of perception of time flow, but nobody has figured out how to describe it with equations or model without references to that perception. It can be that this is even impossible since as with equations the words of language are static and can only refer to the perception of time without capacity to describe it.
- coldtea 5y ago
  >given that mathematics has time as a precondition Citation needed :-) >(how can you perform an operation like 1+1 without time?). As a long tautology -- all steps exist in advance. There is no "movement" in mathematics. 1+1 is already 2. Same way in e.g. a holographic universe could have all developments present at the "same time" (or rather, in a timeless state). Where time is just the perception of focusing on one or the other pre-existing point (with no actual process of change from one to the other).
- User23 5y ago
  You don’t perform anything it’s just a statement. You’re conflating mathematics and computation.
  - dotsam 5y ago
    That's a good distinction, thank you. But how would we have mathematics at all, if we could not compute? How can a statement have any meaning if you cannot 'read' it? Both require time to be intelligible. That is the problem I am wrestling with: it is only from within time that we can make sense of something existing timelessly.
    - User23 5y ago
      This is one of those philosophy if mathematics things that people have been debating for a very long time[1]. I don’t have much interest in philosophy of mathematics, so that link isn’t much more than a starting point, but there is plenty to read if you do. [1] https://en.m.wikipedia.org/wiki/Constructivism_(philosophy_of_mathematics) https://en.m.wikipedia.org/wiki/Constructivism_(philosophy_o...
    - jerf 5y ago
      The fact that we can only understand timeless concepts with time is a property of our existence, not a property of the timeless facts. In 0 seconds I can "do" nothing, but that's a property of my existence, not necessarily a universal absolute across the entire Tegmark-ian multiverse.
    - hnjst 5y ago
      I'd say that an important part of mathematics aims at understanding structures and relations between entities in order to avoid inefficient computations. Maybe a trivial example would be multiplication algorithms that allow to bypass costly iterated sums while preserving confidence in the result. Complexity (and entropy) have surely a crucial importance and can't be totally avoided but I think that mathematics precisely work at minimizing their impact.
- fsloth 5y ago
  Mathematics does not have time as a precondition. I think you have confused something somewhere, but I'm not sure what. 1+1 is a dimensionless computation and hence has no notion of time. To use time, we need to add it explicitly as a dimension to the numbers used. We generally use SI units to abbreviate the dimensions. I.e. s = seconds, m = meters. Now 1s + 1s = 2s. There we have used second as the dimension of the unit. We can do the same thing for lengths. 1m + 1m = 2m. Speed is generally expressed as a dimension, that when multiplied by time, gives us the length travelled. speed * time = distance or speed = distance/time If we set time = 1 s, distance 1=m, we can deduce the unit of speed as. speed = 1 m / 1 s = 1 m/s Hence we get the dimension of speed, m/s ,or meters per second. We can now ask time related questions like "How long - how many seconds - does it take to travel 6 meters with speed 3 m/s". We can just observed the dimensions to get the correct calculation: 6m / (3m/s) = (2/1s^-1) = 2s So that is how mathematics and time generally interact. Time is used like a dimension, just like distance or weight. I'm not sure if this is what you meant or something else.
  - dotsam 5y ago
    Performing your dimensionless computations took time -- that's what I mean. And if you don't perform any computations, how can you derive mathematics?
    - fsloth 5y ago
      One way to view this is that while the "act of performing" mathematics happens in a physical world, the results as such are unrelated to time. Below is written from a specific pedestrian view of mathematics, and is partly arm-chair philosophy. Similarly to one playing a specific piece from sheet music, the sheet music is an invariant of time, while the act of performance, is, yes, very much time related. I think what you mean is the act of performing the computation 1+1 always takes some time, what mathematically is generally understood as relevant is the relationship 1+1 itself, which does not really change. We can change the numbers so we don't know the result beforehand, but that does not mean the end result would change - it does not, as long as the rules don't change. The relationship of the diameter of a circle and the the circumference is always pi. We can take any number of of circumferences and diameters, and given one or another is unknown, we may need to do some computations to know for example the circumference of a wheel with a diameter of 2. While we need to perform the computation pi * 2, the result itself actually never changes, and is irrelevant of time -an eternal truth so to speak, crystallized forever in the fundamental logical nature of our reality. Or, another example, if we take a right triangle, say with the Egyptian famous example with side lengths of 3,4, and 5, it gives us many more invariants that don't change no matter how many times you perform any computation. Given a right triangle with non-hypotenuse sides 3 and 4, the hypotenuse is always a length of 5. No matter how many times we perform the computation, for example, sqrt(3*3 + 4*4) - the end result is something timeless. Pythagorean theorem holds for all planar right triangles, for all eternity, and everywhere, Acapulco or for example on a some desolate rock circling a star in Magellanic Clouds 2 million years ago. While "Pythagorean theorem" is just a name given to a specific logical relationship, the logical relationships described by the theorem do not change. They are eternal. Discovering Pythagorean theorem certainly took time. One view of mathematics is that it's just a way to navigate a vast logical landscape of logical relations that are invariant of time or space. That the act of "performing" mathematics is navigating a static landscape crystallized beyond space and time, into a fundament. Others view mathematics as just a logical game. Never the less, even there with fixed rules, specific input will always result in specific output.
- tsimionescu 5y ago
  You are confusing computation, which is a branch of mathematics, with all of mathematics. In general in mathematics, the thinking is equational: equality is absolute. In computation you generally do follow a process which follows from one step to the next. However, this doesn't necessarily imply time in any meaningful way, I think having a countable base like the natural numbers is enough (such that you can meaningfully say 'this is step 1, this is step 2, step 2 comes after step 1 in our ordering').
qlk1123 5y ago
I don't know how to make sense out of this. What about thermodynamics and entropy?
- SiempreViernes 5y ago
  Read his book, then you can feel the same way much more authoritatively! I've only gotten some way into the book, it is very confusing and people who have read it don't see much better off than the rest of us.
- raattgift 5y ago
  Entropy works in the same Boltzmannian way - within a shell (a Gaussian surface) one takes a measure of the number of configurations of the enclosed elements which produce the same observables outside the shell. That is, one takes a coarse-grained macrostate "a living human in a functioning spacesuit", a volume (say a cubic metre), and a fine-grained microstate (say a cubic millimetre); the more pairs of microstates one can swap without changing the macrostate, the more the entropy. If you swap part of the living human's aorta with shards of helmet, toenail, or vacuum, you quickly get a non-living, therefore non-metabolizing, therefore observably cooling human, so the entropy is well below a maximum. But if our macrostate is "a cubic metre of vacuum" you can swap any sized microstate around and still get all the same observables as the original "cubic metre of vacuum" -- entropy is therefore maximal for the shell around that volume. We can repeat this procedure for arbitrarily-sized Gaussian surfaces, and arbitrarily fine microstates. We recover the second law of thermodynamics by observing that wherever in the entire cosmos you place your shell, you are more likely to enclose a high entropy region than a low entropy one. In an expanding and diluting universe like ours, where more and more high quality vacuum appears between galaxy clusters, there are more places where one's shell will enclose a very high entropy region than a very low one. We then can consider Boltzmann's view of the second law of thermodynamics as it being infinitely improbable to have a completely dynamically ordered state. Let's contrast the Janus point with a Lemaître style regression cosmology. In the latter we simply look at the expansion history in reverse, and extrapolate through ever denser and hotter and lower-entropy configurations and (following classical General Relativity) end up at an inevitable singularity. This has some problems, mainly that nobody knows how matter works at the much more extreme heats and densities than we can hope to produce in laboratory conditions on Earth, nobody is happy with a singularity because there is no way to predict that an actual singularity will decay into the fields of the Standard Model, and because the singularity contains everything, there is nothing outside the Gaussian surface to make observations of the macrostate. Returning to Boltzmann, the singularity itself must be completely dynamically ordered, because when it breaks down, it must be able to produce dynamical systems like galaxy clusters and cats. However, if we somehow prevent the singularity, we might be able to make that prediction in principle even if we cannot do so now. We substitute the infinitely dense zero entropy singularity for merely extremely dense and extremely low entropy, and can at least in principle evade all of the problems in the previous paragraph. The Janus argument is that a singularity-free entropy minimum is plausible if shared with two regions with much higher entropy everywhere else. A shell around the entropy minimum has much less empty space in it than a shell around anywhere else in the two regions, so we can show this relatively low entropy by doing the swapping procedure above. In both cases we make the argument that we can take a values surface at the entropy minimum and use dynamical laws to predict how that values surface will evolve. In the Lemaître-style system, we get a universe like ours; but in a system with a non-singular entropy minimum, we must have more than one region (one containing a universe like ours, one containing something else that evolved out of the entropy minimum). In neither approach do we have the means to determine what the initial values should be, so abolishing the singularity Janus style doesn't seem to bring that much of practical calculational value. Moreover if we start with some late-time values surface on this side of the Janus point and work backwards, our known time-reversible dynamical laws do not lead to a Janus point but rather to a Lemaître-style singularity. Let's return to recovering thermodynamics from the second-law discussion above. The third law again comes from a statistical mechanics view. There is a unique low-energy state that is perfect vacuum. In an expanding universe, we have regions containing that state after it has been evacuated of galaxy clusters, dust, and gas, and the cosmic microwave radiation has become so sparse and cold as to essentially vanish (a bit technically, we can put in a comoving observer with a Eulerian view of the cosmic microwave background such that the characteristic wavelength of the CMB photons are longer than the observer's Hubble length). Those regions are nowhere near the entropy minimum in either the Janus or in the Lemaître configurations, but are nearly everywhere when sufficiently far in the future. (We somewhat circularly define the past as lowest entropy and future as highest entropy.) At cosmological scales in an expanding universe there is no especially satisfying way to recover the first law of thermodynamics even though it is perfectly reasonable to treat the whole cosmos as the ultimate closed system. One can think of the expansion as an adiabatic and reversible process on the matter content, however, and that is part of the basis for the Lemaître and Janus models. > I don't know how to make sense out of this Well, me neither, frankly. Or rather, I can understand the goal of Barbour's thinking but I think it misses the point. We still have an extremely improbable configuration somewhere when the universe was much smaller and denser, and we have no way to recover that surface using observations made here-and-now. Worse, with what we know of gravitation -- specifically, if we accept Raychaudhuri's focusing theorem (which s a deep and interesting result of General Relativity) -- missing the focusing into a caustic is much less probable than focusing into a caustic. Once you have a caustic, you have a singularity, unless you have some magic means of avoiding it through unknown quantum effects. The Janus point doesn't even seem to open up that option, or rather, it appears to require either insanely good luck or quantum effects modifying General Relativity at energy scales which are astrophysical at modern times. However, maybe just maybe what's on the other side of the Janus point has different physics that makes a Janus point (that produces our side with high probability) likely. And maybe just maybe in the far future when we can make truly enormous gravitational wave detectors we can spot gravitationally-lensed early-cosmos gravitational waves that might distinguish between a Janus-style early configuration and a singularity early configuration (or some other singularity-avoiding early configuration). There are also some theoretical questions. The big one: what constrains the Janus point to having exactly two higher-entropy regions rooted to it? Also: are there false Janus points, i.e., is there a hierarchy of relatively low entropy configurations from which two+ higher-entropy regions sprout, but those regions still have enough entropy coupled with dynamical laws that (quoting the article) "The diameter will shrink to a minimum at some moment in time, then grow again"? I think most working cosmologists would bet [a] a Janus configuration does not seem more probable than any other plausible early-universe configuration and [b] even if it were and thus abolished the singularity, it does not solve the vexing theoretical problems posed by the very early universe's extreme heat and density. Finally, all of this has evaded Barbour's "timelessness" language, since that was largely missing from the Nautilus article, and my comments are instead rooted in the conventional concordance cosmology.
JDEW 5y ago
> He is excited by the possibility that developing this idea will solve the measurement problem of quantum mechanics as well as uniting quantum theory with relativity. He also thinks, even more controversially, that it could identify meaning in the universe. Sigh > But Barbour seems happy to swap the roles of science and the arts. He even suggests that art might provide a better guide to the true nature of the universe than science. What did I just read? > ...he writes that human moments of deep creativity “might be subliminal inspirations from the whole universe,” and that a performance of a great operatic aria can capture something of the cosmos as neatly as any mathematical equation. Riiiight. If I would get a dollar for every story along the lines of "Lone genius... famous university... mumble mumble... quantum gravity... mumble mumble... meaning of life..."... (Not necessarily criticizing Barbour, whose work I haven't read)
- tgv 5y ago
  I agree. That's pretty nonsensical. "[A] performance of a great operatic aria can capture something of the cosmos as neatly as any mathematical equation." The amount of assumptions and reinterpretation of common language that have to be made for that statement is staggering.
  - zenron 5y ago
    Is it nonsensical? Does it need a lot of assumptions? TLDR - The Earth is a breadboard and humans decided to arrange themselves in such a way that they created an immense circuit that could be made into a schematic to be replicated. It data packs every choice each performer makes(singer, composer, carpenter, painter, marketer, observer) in their lives over a duration until observation. Is it safe to consider this is an analog what they meant? - A great operatic area is the product of many threads of choices from composers (tone arranger), singers (tone generators), carpenters (set creators), painters (set decorators), etc. that over their lives chose to develop talents (some internal arousal). Then you have the observers who view the operation. For replication, depending on the era that the opera was created and first rendered the replication and want to re-view it or expand viewership the adding more observers would be word to mouth. In a modern era that moment of orchestration could be captured on video and marketed online. This opens even MORE human interaction and duration because the humans over time moved technology to the point where the quality of sampling rate has moved from poor audio to obscenely realistic video. Then there are people who may have heard it at a lower sample rate and prefer it vs new sampling rates which are incidental data inputs in and of themselves. And as people die new generations pick up positions in the orchestration the decisions they chose, the biological improvements for tone generations one person may have, or a more expressive actor may impact the observers more than a previous one. That last aspect, is very much like iteration over PCB designs where you may swap out an old technology for a new one that does the job more efficiently. Or maybe I am way off and my exercise at Duck Typing the humanities to circuit design is whimsical and lacking… edit: for some clarity around word to mouth and modern marketing
T-A 5y ago
Barbour’s thesis is that the Big Bang, which he calls the Janus Point, seeded the flow of time in two directions. Time “no longer has one direction, from past to future, but instead has two: from a common past at the Janus point to two futures in the two directions away from it,” Barbour writes. From 2018: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.251301 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.12... https://physicsworld.com/a/our-universe-has-antimatter-partner-on-the-other-side-of-the-big-bang-say-physicists/ https://physicsworld.com/a/our-universe-has-antimatter-partn...
- nabla9 5y ago
  Sean Carroll has also proposed two headed arrow of time. If the direction of time is towards increasing entropy, the starting point of time is the lowest entropy configuration in the universe. The arrow of time is pointing away from that point. https://www.preposterousuniverse.com/blog/2004/10/27/the-arrow-of-time/ https://www.preposterousuniverse.com/blog/2004/10/27/the-arr... Spontaneous Inflation and the Origin of the Arrow of Time https://arxiv.org/abs/hep-th/0410270 https://arxiv.org/abs/hep-th/0410270 >Sean M. Carroll, Jennifer Chen >We suggest that spontaneous eternal inflation can provide a natural explanation for the thermodynamic arrow of time, and discuss the underlying assumptions and consequences of this view. In the absence of inflation, we argue that systems coupled to gravity usually evolve asymptotically to the vacuum, which is the only natural state in a thermodynamic sense. In the presence of a small positive vacuum energy and an appropriate inflaton field, the de Sitter vacuum is unstable to the spontaneous onset of inflation at a higher energy scale. Starting from de Sitter, inflation can increase the total entropy of the universe without bound, creating universes similar to ours in the process. An important consequence of this picture is that inflation occurs asymptotically both forwards and backwards in time, implying a universe that is (statistically) time-symmetric on ultra-large scales
- arthurcolle 5y ago
  So Tenet actually may have made sense? After multiple rewatchings I just thought the mechanics were completely nonsensical.
doctoboggan 5y ago
Greg Egan has written a series called Orthogonal which explores a universe that contains different rules for the time dimension than ours. http://www.gregegan.net/ORTHOGONAL/00/PM.html http://www.gregegan.net/ORTHOGONAL/00/PM.html
- untoxicness 5y ago
  Another book by Greg Egan exploring different metrics of spacetime is Dichronauts. In Orthogonal the metric signature explored is (+,+,+,+). In Dicronauts the metric signature explored is (-,-,+,+). (We live in a universe with metric signature (-,+,+,+).) http://gregegan.net/DICHRONAUTS/DICHRONAUTS.html http://gregegan.net/DICHRONAUTS/DICHRONAUTS.html
  - snarfy 5y ago
    What would the difference between (-,+,+,+) and (+,-,-,-) be? It seems like they are the same except for choice of labels. I guess the main difference is where speed of light fits in. In (-,+,+,+) the - is multiplied by c.
    - untoxicness 5y ago
      You are right, there is no difference. As a matter of fact, many physicists work with a signature of (+,-,-,-) to describe the spacetime of our universe. https://en.wikipedia.org/wiki/Sign_convention#Relativity https://en.wikipedia.org/wiki/Sign_convention#Relativity
- choxi 5y ago
  I'm most of the way through Diaspora where he invents a new theory of physics to drive the plot, he also elaborates on some existing theories and their philosophical implications to an advanced civilization. It's great, definitely recommend it.
mcshicks 5y ago
Barbour's work had a big influence on science fiction writer Neal Stephenson. https://www.nealstephenson.com/acknowledgments.html https://www.nealstephenson.com/acknowledgments.html
kleiba 5y ago
He asked an acquaintance what would be expected of him if he took a research post. The answer—to publish one or two good papers a year. Oh man... I wish it was that easy.
rini17 5y ago
Off topic: Do people actually appreciate to be eased into the topic by tangents like "It’s not hard to imagine a young Hugh Grant rushing through the churchyard in a morning suit and mumbling apologies for being late again." ? It distracted me, i absentmindedly switched the tab and later remembered to read it further.
YeGoblynQueenne 5y ago
>> In December, 2020, he published The Janus Point, his first book since The End of Time. It’s named after the two-headed Roman god who simultaneously looks forward and backward. Dammit. I thought I was going to read an engaging discussion about the philosophy of physics, say. Instead, it seems I'm once again sucked into an advert for someone's book. An advertisement, even complete with endorsements as one expects to find in the inner cover: >> Lee Smolin, a faculty member at the Perimeter Institute of Theoretical Physics, called The Janus Point “simply the most important book I have read on cosmology in several years … both a work of literature and a masterpiece of scientific thought.” Very frustrating.

98 points by dnetesn 5y ago

Interestingly, it is probably because he was free from academic constraints that would allow him to do his most creative work (long term, book form, philosophical).

dotsam 5y ago

This reminds me of a confusion I have with theoretical physics and mathematically describing a universe without time. I don’t understand how you could use mathematics - numbers and operations on numbers - to specify a timeless universe, given that mathematics has time as a precondition (how can you perform an operation like 1+1 without time?).

deleted 5y ago
[deleted]
madsbuch 5y ago
It's the difference between the domain of reasoning and complexity of reasoning.
k1t 5y ago
Presumably the issue is that you have defined 1+1 as an operation, rather than just an alternative representation (of 2).
- GlobalFrog 5y ago
  That's interesting actually : isn't that more a philosophical question or just an interpretation ? That is, if 1+1 is just an alternatative representation of '2', you can postulate that the universe is fixed, predefined and timeless. But if you consider that '1 + 1' is not just a representation of '2' but has more information in it, that information could be the dynamic and evolution that we call time. Isn't that linked also to the usual question of the link to reality of Mathematics ?
  - slibhb 5y ago
    It's a philosophical question. Whether 1 + 1 = 2 is a tautology (analytic) or if it "has more information in it" (synthetic) is an open question. This dispute is associated with the analytic-synthetic distinction which has existed since at least Kant.
nl 5y ago
> how can you perform an operation like 1+1 without time? 1+1 is a dimensionless operation. Do you mean how it would physically happen without time? It's possible time is just an illusion that emerges from our perception of the universe. See https://www.nature.com/articles/d41586-018-04558-7 https://www.nature.com/articles/d41586-018-04558-7 and https://www.quantamagazine.org/does-time-really-flow-new-clues-come-from-a-century-old-approach-to-math-20200407/ https://www.quantamagazine.org/does-time-really-flow-new-clu... or https://www.npr.org/2013/05/17/184775924/resetting-the-theory-of-time https://www.npr.org/2013/05/17/184775924/resetting-the-theor... for a counter argument.
- dotsam 5y ago
  My confusion is around the feeling that space and time must be preconditions for numbers and operations. How can you differentiate one number or symbol (or anything) from another without dimensions? It seems to me that you wouldn't be able to have the notion of "1" and "2" unless they can be separated, and to separate them you need dimensions. So for a number to be intelligible at all, it requires dimensions; but how do you get dimensionality in the first place, if your equation is specifying the universe?
  - bourgwaletariat 5y ago
    You need time to differentiate, but the universe does not. The one and the one and the two of them are always here in the universe. You just need time to speak it. You need time to observe the difference between the neuronal pattern between an awareness of one and the other one and the two of them. But they are all at once.
    - dotsam 5y ago
      To have the one and the two in the first place grants spatial dimensions, to separate them. Otherwise you end up with a single point, or maybe not even that. I can't get my head around how anyone can generate time (whether an illusion or not) just from spatial dimensions. If I have to assume spatial dimensions to get anywhere, can I also assume time?
jl6 5y ago
Addition is just a function and functions are just sets of pairs and sets can just sit there merrily existing in the abstract without any need for time or flow or movement or such.
- sharkbot 5y ago
  That is true, but that would be the definition of +. The OP is referring to the application of that operator to its arguments, which (depending on semantics) could also be a set of sets, or it could be a rewriting (ie, time based) process.
  - mannykannot 5y ago
    Anything you can do as a sequence of operations on symbols can be written out, and then there you have it, on the page, all at once! Time does not appear in formal logic or number theory, even though it is convenient to think of a derivation or a calculation as as sequence of steps performed one at a time. it is also very convenient to use mathematics to model a temporal process, but we can, and often do, then show what happened (or will happen) as tables, graphs or other static representations. I know that last sentence presupposes time, but I am not even going to attempt to rewrite it in a way that avoids doing so!
meroes 5y ago
Does a triangle have a duration? Does a line? An equation of a line is very close to 1+1=2. X=2 and y=2 are lines. Nothing in math has time or duration. 1+1 = 2 = area of a triangle with base and height 2 = 362/181 = -2(-1). These are timeless relations. If 2 has no duration, none of the others do. They are just statements of relations. In fact ontic structural realism (some versions) says there is only these abstract relations and everything can be reduced to mathematical relations. Spacetime, consciousness, subjecive experience - all of it are just timeless relations like numbers in a table.
- dotsam 5y ago
  My brain sputters out when I try to go from timeless relations (which assume spatial dimensionality as a given) to a timeless universe within which I sit with the illusion of time! I can't get my mind around anything that doesn't also assume time as a given -- all I end up with is a load of geometry sitting around doing nothing.
  - meroes 5y ago
    No one actually has a working model of consciousness so that programme has a long way to go. But if the only evidence for time is change as Barbour likes to say, and change basically boils down the relative motion of particles, why not describe the whole thing as a timeless table of coordinates essentially? And let psychologists build sensation and a perception of a flow of time from that. It's a tempting view due to its simplicity and the importance of math. But it is extreme, but so is every other theory or metaphysics trying to explain the same stuff!
    - fpoling 5y ago
      This is a circular argument since motion is a change in position. So a change is a motion and a motion is a change. This implicitly refers to personal experience of perception of time flow, but nobody has figured out how to describe it with equations or model without references to that perception. It can be that this is even impossible since as with equations the words of language are static and can only refer to the perception of time without capacity to describe it.
coldtea 5y ago
>given that mathematics has time as a precondition Citation needed :-) >(how can you perform an operation like 1+1 without time?). As a long tautology -- all steps exist in advance. There is no "movement" in mathematics. 1+1 is already 2. Same way in e.g. a holographic universe could have all developments present at the "same time" (or rather, in a timeless state). Where time is just the perception of focusing on one or the other pre-existing point (with no actual process of change from one to the other).
User23 5y ago
You don’t perform anything it’s just a statement. You’re conflating mathematics and computation.
- dotsam 5y ago
  That's a good distinction, thank you. But how would we have mathematics at all, if we could not compute? How can a statement have any meaning if you cannot 'read' it? Both require time to be intelligible. That is the problem I am wrestling with: it is only from within time that we can make sense of something existing timelessly.
  - User23 5y ago
    This is one of those philosophy if mathematics things that people have been debating for a very long time[1]. I don’t have much interest in philosophy of mathematics, so that link isn’t much more than a starting point, but there is plenty to read if you do. [1] https://en.m.wikipedia.org/wiki/Constructivism_(philosophy_of_mathematics) https://en.m.wikipedia.org/wiki/Constructivism_(philosophy_o...
  - jerf 5y ago
    The fact that we can only understand timeless concepts with time is a property of our existence, not a property of the timeless facts. In 0 seconds I can "do" nothing, but that's a property of my existence, not necessarily a universal absolute across the entire Tegmark-ian multiverse.
  - hnjst 5y ago
    I'd say that an important part of mathematics aims at understanding structures and relations between entities in order to avoid inefficient computations. Maybe a trivial example would be multiplication algorithms that allow to bypass costly iterated sums while preserving confidence in the result. Complexity (and entropy) have surely a crucial importance and can't be totally avoided but I think that mathematics precisely work at minimizing their impact.
fsloth 5y ago
Mathematics does not have time as a precondition. I think you have confused something somewhere, but I'm not sure what. 1+1 is a dimensionless computation and hence has no notion of time. To use time, we need to add it explicitly as a dimension to the numbers used. We generally use SI units to abbreviate the dimensions. I.e. s = seconds, m = meters. Now 1s + 1s = 2s. There we have used second as the dimension of the unit. We can do the same thing for lengths. 1m + 1m = 2m. Speed is generally expressed as a dimension, that when multiplied by time, gives us the length travelled. speed * time = distance or speed = distance/time If we set time = 1 s, distance 1=m, we can deduce the unit of speed as. speed = 1 m / 1 s = 1 m/s Hence we get the dimension of speed, m/s ,or meters per second. We can now ask time related questions like "How long - how many seconds - does it take to travel 6 meters with speed 3 m/s". We can just observed the dimensions to get the correct calculation: 6m / (3m/s) = (2/1s^-1) = 2s So that is how mathematics and time generally interact. Time is used like a dimension, just like distance or weight. I'm not sure if this is what you meant or something else.
- dotsam 5y ago
  Performing your dimensionless computations took time -- that's what I mean. And if you don't perform any computations, how can you derive mathematics?
  - fsloth 5y ago
    One way to view this is that while the "act of performing" mathematics happens in a physical world, the results as such are unrelated to time. Below is written from a specific pedestrian view of mathematics, and is partly arm-chair philosophy. Similarly to one playing a specific piece from sheet music, the sheet music is an invariant of time, while the act of performance, is, yes, very much time related. I think what you mean is the act of performing the computation 1+1 always takes some time, what mathematically is generally understood as relevant is the relationship 1+1 itself, which does not really change. We can change the numbers so we don't know the result beforehand, but that does not mean the end result would change - it does not, as long as the rules don't change. The relationship of the diameter of a circle and the the circumference is always pi. We can take any number of of circumferences and diameters, and given one or another is unknown, we may need to do some computations to know for example the circumference of a wheel with a diameter of 2. While we need to perform the computation pi * 2, the result itself actually never changes, and is irrelevant of time -an eternal truth so to speak, crystallized forever in the fundamental logical nature of our reality. Or, another example, if we take a right triangle, say with the Egyptian famous example with side lengths of 3,4, and 5, it gives us many more invariants that don't change no matter how many times you perform any computation. Given a right triangle with non-hypotenuse sides 3 and 4, the hypotenuse is always a length of 5. No matter how many times we perform the computation, for example, sqrt(3*3 + 4*4) - the end result is something timeless. Pythagorean theorem holds for all planar right triangles, for all eternity, and everywhere, Acapulco or for example on a some desolate rock circling a star in Magellanic Clouds 2 million years ago. While "Pythagorean theorem" is just a name given to a specific logical relationship, the logical relationships described by the theorem do not change. They are eternal. Discovering Pythagorean theorem certainly took time. One view of mathematics is that it's just a way to navigate a vast logical landscape of logical relations that are invariant of time or space. That the act of "performing" mathematics is navigating a static landscape crystallized beyond space and time, into a fundament. Others view mathematics as just a logical game. Never the less, even there with fixed rules, specific input will always result in specific output.
tsimionescu 5y ago
You are confusing computation, which is a branch of mathematics, with all of mathematics. In general in mathematics, the thinking is equational: equality is absolute. In computation you generally do follow a process which follows from one step to the next. However, this doesn't necessarily imply time in any meaningful way, I think having a countable base like the natural numbers is enough (such that you can meaningfully say 'this is step 1, this is step 2, step 2 comes after step 1 in our ordering').

qlk1123 5y ago

I don't know how to make sense out of this. What about thermodynamics and entropy?

SiempreViernes 5y ago
Read his book, then you can feel the same way much more authoritatively! I've only gotten some way into the book, it is very confusing and people who have read it don't see much better off than the rest of us.
raattgift 5y ago
Entropy works in the same Boltzmannian way - within a shell (a Gaussian surface) one takes a measure of the number of configurations of the enclosed elements which produce the same observables outside the shell. That is, one takes a coarse-grained macrostate "a living human in a functioning spacesuit", a volume (say a cubic metre), and a fine-grained microstate (say a cubic millimetre); the more pairs of microstates one can swap without changing the macrostate, the more the entropy. If you swap part of the living human's aorta with shards of helmet, toenail, or vacuum, you quickly get a non-living, therefore non-metabolizing, therefore observably cooling human, so the entropy is well below a maximum. But if our macrostate is "a cubic metre of vacuum" you can swap any sized microstate around and still get all the same observables as the original "cubic metre of vacuum" -- entropy is therefore maximal for the shell around that volume. We can repeat this procedure for arbitrarily-sized Gaussian surfaces, and arbitrarily fine microstates. We recover the second law of thermodynamics by observing that wherever in the entire cosmos you place your shell, you are more likely to enclose a high entropy region than a low entropy one. In an expanding and diluting universe like ours, where more and more high quality vacuum appears between galaxy clusters, there are more places where one's shell will enclose a very high entropy region than a very low one. We then can consider Boltzmann's view of the second law of thermodynamics as it being infinitely improbable to have a completely dynamically ordered state. Let's contrast the Janus point with a Lemaître style regression cosmology. In the latter we simply look at the expansion history in reverse, and extrapolate through ever denser and hotter and lower-entropy configurations and (following classical General Relativity) end up at an inevitable singularity. This has some problems, mainly that nobody knows how matter works at the much more extreme heats and densities than we can hope to produce in laboratory conditions on Earth, nobody is happy with a singularity because there is no way to predict that an actual singularity will decay into the fields of the Standard Model, and because the singularity contains everything, there is nothing outside the Gaussian surface to make observations of the macrostate. Returning to Boltzmann, the singularity itself must be completely dynamically ordered, because when it breaks down, it must be able to produce dynamical systems like galaxy clusters and cats. However, if we somehow prevent the singularity, we might be able to make that prediction in principle even if we cannot do so now. We substitute the infinitely dense zero entropy singularity for merely extremely dense and extremely low entropy, and can at least in principle evade all of the problems in the previous paragraph. The Janus argument is that a singularity-free entropy minimum is plausible if shared with two regions with much higher entropy everywhere else. A shell around the entropy minimum has much less empty space in it than a shell around anywhere else in the two regions, so we can show this relatively low entropy by doing the swapping procedure above. In both cases we make the argument that we can take a values surface at the entropy minimum and use dynamical laws to predict how that values surface will evolve. In the Lemaître-style system, we get a universe like ours; but in a system with a non-singular entropy minimum, we must have more than one region (one containing a universe like ours, one containing something else that evolved out of the entropy minimum). In neither approach do we have the means to determine what the initial values should be, so abolishing the singularity Janus style doesn't seem to bring that much of practical calculational value. Moreover if we start with some late-time values surface on this side of the Janus point and work backwards, our known time-reversible dynamical laws do not lead to a Janus point but rather to a Lemaître-style singularity. Let's return to recovering thermodynamics from the second-law discussion above. The third law again comes from a statistical mechanics view. There is a unique low-energy state that is perfect vacuum. In an expanding universe, we have regions containing that state after it has been evacuated of galaxy clusters, dust, and gas, and the cosmic microwave radiation has become so sparse and cold as to essentially vanish (a bit technically, we can put in a comoving observer with a Eulerian view of the cosmic microwave background such that the characteristic wavelength of the CMB photons are longer than the observer's Hubble length). Those regions are nowhere near the entropy minimum in either the Janus or in the Lemaître configurations, but are nearly everywhere when sufficiently far in the future. (We somewhat circularly define the past as lowest entropy and future as highest entropy.) At cosmological scales in an expanding universe there is no especially satisfying way to recover the first law of thermodynamics even though it is perfectly reasonable to treat the whole cosmos as the ultimate closed system. One can think of the expansion as an adiabatic and reversible process on the matter content, however, and that is part of the basis for the Lemaître and Janus models. > I don't know how to make sense out of this Well, me neither, frankly. Or rather, I can understand the goal of Barbour's thinking but I think it misses the point. We still have an extremely improbable configuration somewhere when the universe was much smaller and denser, and we have no way to recover that surface using observations made here-and-now. Worse, with what we know of gravitation -- specifically, if we accept Raychaudhuri's focusing theorem (which s a deep and interesting result of General Relativity) -- missing the focusing into a caustic is much less probable than focusing into a caustic. Once you have a caustic, you have a singularity, unless you have some magic means of avoiding it through unknown quantum effects. The Janus point doesn't even seem to open up that option, or rather, it appears to require either insanely good luck or quantum effects modifying General Relativity at energy scales which are astrophysical at modern times. However, maybe just maybe what's on the other side of the Janus point has different physics that makes a Janus point (that produces our side with high probability) likely. And maybe just maybe in the far future when we can make truly enormous gravitational wave detectors we can spot gravitationally-lensed early-cosmos gravitational waves that might distinguish between a Janus-style early configuration and a singularity early configuration (or some other singularity-avoiding early configuration). There are also some theoretical questions. The big one: what constrains the Janus point to having exactly two higher-entropy regions rooted to it? Also: are there false Janus points, i.e., is there a hierarchy of relatively low entropy configurations from which two+ higher-entropy regions sprout, but those regions still have enough entropy coupled with dynamical laws that (quoting the article) "The diameter will shrink to a minimum at some moment in time, then grow again"? I think most working cosmologists would bet [a] a Janus configuration does not seem more probable than any other plausible early-universe configuration and [b] even if it were and thus abolished the singularity, it does not solve the vexing theoretical problems posed by the very early universe's extreme heat and density. Finally, all of this has evaded Barbour's "timelessness" language, since that was largely missing from the Nautilus article, and my comments are instead rooted in the conventional concordance cosmology.

JDEW 5y ago

> He is excited by the possibility that developing this idea will solve the measurement problem of quantum mechanics as well as uniting quantum theory with relativity. He also thinks, even more controversially, that it could identify meaning in the universe. Sigh > But Barbour seems happy to swap the roles of science and the arts. He even suggests that art might provide a better guide to the true nature of the universe than science. What did I just read? > ...he writes that human moments of deep creativity “might be subliminal inspirations from the whole universe,” and that a performance of a great operatic aria can capture something of the cosmos as neatly as any mathematical equation. Riiiight. If I would get a dollar for every story along the lines of "Lone genius... famous university... mumble mumble... quantum gravity... mumble mumble... meaning of life..."... (Not necessarily criticizing Barbour, whose work I haven't read)

tgv 5y ago
I agree. That's pretty nonsensical. "[A] performance of a great operatic aria can capture something of the cosmos as neatly as any mathematical equation." The amount of assumptions and reinterpretation of common language that have to be made for that statement is staggering.
- zenron 5y ago
  Is it nonsensical? Does it need a lot of assumptions? TLDR - The Earth is a breadboard and humans decided to arrange themselves in such a way that they created an immense circuit that could be made into a schematic to be replicated. It data packs every choice each performer makes(singer, composer, carpenter, painter, marketer, observer) in their lives over a duration until observation. Is it safe to consider this is an analog what they meant? - A great operatic area is the product of many threads of choices from composers (tone arranger), singers (tone generators), carpenters (set creators), painters (set decorators), etc. that over their lives chose to develop talents (some internal arousal). Then you have the observers who view the operation. For replication, depending on the era that the opera was created and first rendered the replication and want to re-view it or expand viewership the adding more observers would be word to mouth. In a modern era that moment of orchestration could be captured on video and marketed online. This opens even MORE human interaction and duration because the humans over time moved technology to the point where the quality of sampling rate has moved from poor audio to obscenely realistic video. Then there are people who may have heard it at a lower sample rate and prefer it vs new sampling rates which are incidental data inputs in and of themselves. And as people die new generations pick up positions in the orchestration the decisions they chose, the biological improvements for tone generations one person may have, or a more expressive actor may impact the observers more than a previous one. That last aspect, is very much like iteration over PCB designs where you may swap out an old technology for a new one that does the job more efficiently. Or maybe I am way off and my exercise at Duck Typing the humanities to circuit design is whimsical and lacking… edit: for some clarity around word to mouth and modern marketing

T-A 5y ago

Barbour’s thesis is that the Big Bang, which he calls the Janus Point, seeded the flow of time in two directions. Time “no longer has one direction, from past to future, but instead has two: from a common past at the Janus point to two futures in the two directions away from it,” Barbour writes. From 2018: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.251301 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.12... https://physicsworld.com/a/our-universe-has-antimatter-partner-on-the-other-side-of-the-big-bang-say-physicists/ https://physicsworld.com/a/our-universe-has-antimatter-partn...

nabla9 5y ago
Sean Carroll has also proposed two headed arrow of time. If the direction of time is towards increasing entropy, the starting point of time is the lowest entropy configuration in the universe. The arrow of time is pointing away from that point. https://www.preposterousuniverse.com/blog/2004/10/27/the-arrow-of-time/ https://www.preposterousuniverse.com/blog/2004/10/27/the-arr... Spontaneous Inflation and the Origin of the Arrow of Time https://arxiv.org/abs/hep-th/0410270 https://arxiv.org/abs/hep-th/0410270 >Sean M. Carroll, Jennifer Chen >We suggest that spontaneous eternal inflation can provide a natural explanation for the thermodynamic arrow of time, and discuss the underlying assumptions and consequences of this view. In the absence of inflation, we argue that systems coupled to gravity usually evolve asymptotically to the vacuum, which is the only natural state in a thermodynamic sense. In the presence of a small positive vacuum energy and an appropriate inflaton field, the de Sitter vacuum is unstable to the spontaneous onset of inflation at a higher energy scale. Starting from de Sitter, inflation can increase the total entropy of the universe without bound, creating universes similar to ours in the process. An important consequence of this picture is that inflation occurs asymptotically both forwards and backwards in time, implying a universe that is (statistically) time-symmetric on ultra-large scales
arthurcolle 5y ago
So Tenet actually may have made sense? After multiple rewatchings I just thought the mechanics were completely nonsensical.

doctoboggan 5y ago

Greg Egan has written a series called Orthogonal which explores a universe that contains different rules for the time dimension than ours. http://www.gregegan.net/ORTHOGONAL/00/PM.html http://www.gregegan.net/ORTHOGONAL/00/PM.html

untoxicness 5y ago
Another book by Greg Egan exploring different metrics of spacetime is Dichronauts. In Orthogonal the metric signature explored is (+,+,+,+). In Dicronauts the metric signature explored is (-,-,+,+). (We live in a universe with metric signature (-,+,+,+).) http://gregegan.net/DICHRONAUTS/DICHRONAUTS.html http://gregegan.net/DICHRONAUTS/DICHRONAUTS.html
- snarfy 5y ago
  What would the difference between (-,+,+,+) and (+,-,-,-) be? It seems like they are the same except for choice of labels. I guess the main difference is where speed of light fits in. In (-,+,+,+) the - is multiplied by c.
  - untoxicness 5y ago
    You are right, there is no difference. As a matter of fact, many physicists work with a signature of (+,-,-,-) to describe the spacetime of our universe. https://en.wikipedia.org/wiki/Sign_convention#Relativity https://en.wikipedia.org/wiki/Sign_convention#Relativity
choxi 5y ago
I'm most of the way through Diaspora where he invents a new theory of physics to drive the plot, he also elaborates on some existing theories and their philosophical implications to an advanced civilization. It's great, definitely recommend it.

mcshicks 5y ago

Barbour's work had a big influence on science fiction writer Neal Stephenson. https://www.nealstephenson.com/acknowledgments.html https://www.nealstephenson.com/acknowledgments.html

kleiba 5y ago

He asked an acquaintance what would be expected of him if he took a research post. The answer—to publish one or two good papers a year. Oh man... I wish it was that easy.

rini17 5y ago

Off topic: Do people actually appreciate to be eased into the topic by tangents like "It’s not hard to imagine a young Hugh Grant rushing through the churchyard in a morning suit and mumbling apologies for being late again." ? It distracted me, i absentmindedly switched the tab and later remembered to read it further.

YeGoblynQueenne 5y ago

>> In December, 2020, he published The Janus Point, his first book since The End of Time. It’s named after the two-headed Roman god who simultaneously looks forward and backward. Dammit. I thought I was going to read an engaging discussion about the philosophy of physics, say. Instead, it seems I'm once again sucked into an advert for someone's book. An advertisement, even complete with endorsements as one expects to find in the inner cover: >> Lee Smolin, a faculty member at the Perimeter Institute of Theoretical Physics, called The Janus Point “simply the most important book I have read on cosmology in several years … both a work of literature and a masterpiece of scientific thought.” Very frustrating.