Newtonian "schema/paradigm" != Newton's mechanics

[Fra]

As this has been a key point, in several threads in particular the last close one https://www.physicsforums.com/threa...-anticorrelations-inside-spin-theory.1066463/ I though I would clarify what this means becuase it is a pity to confuse it with classical (newtons) mechanics, it causes lots of confusion. I assumed most was familiar with this but I was wrong.

I wrote:

I will just note that Quantum mechanics as well as QFT are STILL in the newtonian paradigm.

Nugatory responded:

Here you have lost me, probably because my definition of that paradigm is more restrictive than yours. I understand it to include that effects have causes (constrained by relativity) and counterfactual definiteness, and I do not see how to reconcile these with Bell-violating QM

Newtonian paradigm or schema here does not refer to "newtons mechanics", I agree the name I think first coined by Lee Smolin is confusing, but I think the name is associated with Newton as one the the founders of calculus and differential equations and system dynamics. Here the concept is that you have a (timeless) state space, initial conditions and (timeless) evolution laws.

Just to give one reference to the terms (ie. i didn't make it up), by smolin uses the term in every other paper as well.

"Isaac Newton taught us some powerful and useful mathematics, dubbed it the “System of the World”, and ever since we’ve assumed that the universe actually runs according to Newton’s overall scheme. Even though the details have changed, we still basically hold that the universe is a computational mechanism that takes some initial state as an input and generates future states as an output.
...
Such a view is so pervasive that only recently has anyone bothered to give it a name: Lee Smolin now calls this style of mathematics the “Newtonian Schema”. Despite the classical-sounding title, this viewpoint is thought to encompass all of modern physics, including quantum theory. This assumption that we live in a Newtonian Schema Universe (NSU) is so strong that many physicists can’t even
articulate what other type of universe might be conceptually possible."
-- https://arxiv.org/abs/1211.7081

This is very true, and the reason why Smolin felt it was necessary to write several books, for example this one just to motivate what is problem with the Newtonian schema - and still - it is admittedly hard to graps the alternative.

/Fredrik

 

[anuttarasammyak]

Just to know what is Newtonian Schema, I would like to know whether there is any other competitive schema in physics. Is there one and what is its name ?

 

[pines-demon]

I think that Smolin missed the mark with the name, I can understand why you gotten some pushback in the wrong direction.

Smolin's Newtonian Schema is too similar to Newtonian paradigm or any other common use of Newtonian "System of the world". When scientists use those terms it refers to the differences between Newton mechanics and modern physics (relativity and quantum mechanics) in terms of both equations and philosophy.

Secondly, why is the Newtonian Schema attributed to Newton? It could be called the Computational Schema or the Causal Schema or anything else, but naming it after Newton is in dissonance with other terms. I know Newton has a weight here for having the most fruitful equations first but cause-effects ideas were discussed before Newton and the idea of the Universe being predictable was discussed in more depth by others like Laplace or 20th century philosophers.

Edit: here is an example of a more common alternative https://en.wikipedia.org/wiki/Digital_physics
Edit2: Other alternatives include older terms like mechanic philosophy or (Newton's) clockwork universe but if these interpretations still apply to modern physics depends on the wording.

 

[Fra]

Just to know what is Newtonian Schema, I would like to know whether there is any other competitive schema in physics. Is there one and what is its name ?

In short, it's the evolutionary perspective. It is the topic in lots of smolins books. His "evoution of law" and "reality of time" elaborates in this. But its on open problem on how to make this work.

The point is not that the alternative is a mature theory. Step one is to see the problem in the newtonian schema. It is of course closely related to the deep problem of time as well. Also the problem of fine tuning is relates to this, it may even follow from forcing the newtonian schema.

/Fredrik

 

[Nugatory]

Even though the details have changed, we still basically hold that the universe is a computational mechanism that takes some initial state as an input and generates future states as an output

I’ll buy that as a definition of the paradigm. But before the discovery of quantum mechanics it would be near impossible to imagine such a mechanism without classical causality and counterfactual definiteness. I consider this to be a much more foundational change than just "the details have changed" - if we're going to extend the definition of "mechanism" that much we've left the paradigm behind.

Perhaps I'm just overreacting to your original statement, which seemed to me to underplay the conceptual shock that comes with QM.

 

[Fra]

I’ll buy that as a definition of the paradigm. But before the discovery of quantum mechanics it would be near impossible to imagine such a mechanism without classical causality and counterfactual definiteness. I consider this to be a much more foundational change than just "the details have changed" - if we're going to extend the definition of "mechanism" that much we've left the paradigm behind.

Yes sure, the "details" om QM are important change I agree.

But in the perspective of unification and the problem of time, this can be though of as "details". Because the hamiltonian flow of the quantum states, follows the same schema. The different is more in the ontology of the state spaces.

Perhaps I'm just overreacting to your original statement, which seemed to me to underplay the conceptual shock that comes with QM.

I was probably reacting the other way, that when someone wants to understand QM, it is often routinely lumped with the IMO by now old original resistance to QM (of which I play no part). My quest is to understand QM, not dismiss or reject it.

In fact, I would say that the "weirdness" implied by considering the alternative to newtons schema, is much worse than the "weirdness" we often speak about when going from classical mechanics to QM. This is also why Smolins met so much resistance from I think if not most, at least many many physicists.

/Fredrik

 

[PeterDonis]

the hamiltonian flow of the quantum states, follows the same schema. The different is more in the ontology of the state spaces.

Yes, and the weirdness hiding in your innocuous-sounding phrase "ontology of the state spaces" is huge. And I think most people would say that this...

the "weirdness" implied by considering the alternative to newtons schema, is much worse than the "weirdness" we often speak about when going from classical mechanics to QM.

...is backwards, because the quantum "ontology of the state spaces" is way, way more "non-classical" than any alternative to newton's schema.

 

[pines-demon]

In short, it's the evolutionary perspective. It is the topic in lots of smolins books. His "evoution of law" and "reality of time" elaborates in this.

Can you expand on the differences between these two and the Newtonian Schema?

 

[Fra]

Can you expand on the differences between these two and the Newtonian Schema?

In the newtonian schema there is only "parameters time". Like in special realitivity. Meaning it is in a sense "timeless". And the evolution laws are fixed. And what happens is just an arbitrary parameters in the timehistory.

"Reality of time" is opposing the "parameter time" view, arguing that time (one should here read, cosmological time) is objective in the sense that it also parameterizes the evolution of the STATE space. But this "evolution" is not "dynamical". The newtonian schema solution here would be to embedd the original space that evolves into a LARGER space, and apply again a turtle tower of newtonian schemas ontop of each other. But this leads to an unmanagably large superstate space, and a finetuning problem. Where the "explanatory value" rests upon picking an "improbable initial conditions". The argument is that this is a bad explanation.

But smolin explains all of this with lots examples in his books. But this is hard to grasp, and why its considered a pardigm change.

/Fredrik

 

[anuttarasammyak]

In short, it's the evolutionary perspective. It is the topic in lots of smolins books. His "evoution of law" and "reality of time" elaborates in this. But its on open problem on how to make this work.

Thanks for the explanation.

But smolin explains all of this with lots examples in his books. But this is hard to grasp, and why its considered a pardigm change.

Does he show some physical phenomena that represents the evolutionary perspective ?

 

[Fra]

Does he show some physical phenomena that represents the evolutionary perspective ?

The idea is that all the parameters of the standardmodel are the result of evolution, rather than been just fine tuned for no given reason. This is the idea between his CNS (cosmological natural selection). But his idea is that evolution happens just at big bang, where parameters are mutated. And this then spawns more universes via BH production. But that is a more specific alternative.

Which originally was considered as a solutuion to the finetuning problem of the string landscape.

Smolin does not present anywhere imo a satisfactory tentative implementation of what i personally seek, but he has patiently presented and argued at length around it. Which is a good first step to convey to others.

/Fredrik

 

[anuttarasammyak]

Thanks for the interesting explanation. It reminds me of Dirac Large Number Hypothesis https://en.wikipedia.org/wiki/Dirac_large_numbers_hypothesis which also deals with time changing physical constants. May I understand that the evolutionary perspective is mainly for cosmology or standard model, rather than human sized time space phenomena ?

 

[pines-demon]

The idea is that all the parameters of the standardmodel are the result of evolution, rather than been just fine tuned for no given reason. This is the idea between his CNS (cosmological natural selection). But his idea is that evolution happens just at big bang, where parameters are mutated. And this then spawns more universes via BH production. But that is a more specific alternative.

Which originally was considered as a solutuion to the finetuning problem of the string landscape.

Smolin does not present anywhere imo a satisfactory tentative implementation of what i personally seek, but he has patiently presented and argued at length around it. Which is a good first step to convey to others.

/Fredrik

If what we consider the parameters of our universe are dynamical, it still sounds mechanistic, I do not see how that escapes "Newton Schema".

 

[Fra]

If what we consider the parameters of our universe are dynamical, it still sounds mechanistic, I do not see how that escapes "Newton Schema".

Good reflevtion and Smolin also brings this up for reflection. He asks, if the laws evolve, and there is a meta law for this; we can enlarge the space and get bsvk to the same newtonian schema. But the key is, "evolution" is not same as "dynamics". To explan he takes example by analogy from complex systems such as biology.

In dynamics "timevolution" follows a timeless law in a given timeless statespace.

The evolution smolin speaks about is not one that follows a meta law, but where the state and statespace both change. Here the "effective law" governing the apparent or short scale "dynamics" within the effective state spaces are considered subject to variation and evolution, and are effectively emergent.

So insteade of a "timless world" where time is an arbitrary parameter, one has an evolving world wher "effective laws" are selected by some yet not known principle of selforganisation and selfpreservation.

In this schema no a prioro "improbable" initial conditions in a superspace is required to "explain" the effective laws what we infer today.

/Fredrik

 

[Fra]

Btw, smolins ideas are in perfect harmony of the idea that all laws as we known them are "effective". This applies also to standardmodel. In his work he also makes clear compelling arguments that the success of timeless mathematics of newtonian schema is precisely because it is inferred from "short time scales". So even if you reject newtonian scheme at fundamental it is expected that any statistical abduction of law of short lived processes; will produced an "effective law" in the newtonian schema. So we need not abandon newtonian schema for practical work, but may help to see thay it is an effective framework. Extrapolation this in absurdum due to its success at short timescales may produce problems of finetuning

I can recommen hos books, they offer a healthy dose of provocative perspectives that comea both with promises but also new problems.

/Fredrik

 

[Fra]

Thanks for the interesting explanation. It reminds me of Dirac Large Number Hypothesis https://en.wikipedia.org/wiki/Dirac_large_numbers_hypothesis which also deals with time changing physical constants. May I understand that the evolutionary perspective is mainly for cosmology or standard model, rather than human sized time space phenomena ?

The evolutuonary theory is accepted in biology already. Rats arent magically "fine tuned", they are evolved.

In this context, the idea is o apply the same idea to the fundamental levels of physics, ie the particle phenomenology, "tuning" of parameters. So that standard model can be understood as tuned by evolution - rather than unnaturally "fine tuned" without explanation.

/Fredrik

 

[PeterDonis]

The evolutuonary theory is accepted in biology already.

Yes, but that's because there is abundant evidence for the necessary requirements: replication with variation, and different variations having different fitness in the presence of selection pressures.

The corresponding requirements for evolution of universes or natural laws are pure speculation; we have no evidence for them.

 

[gentzen]

Just to give one reference to the terms (ie. i didn't make it up), by smolin uses the term in every other paper as well.

"...
Such a view is so pervasive that only recently has anyone bothered to give it a name: Lee Smolin now calls this style of mathematics the “Newtonian Schema”. Despite the classical-sounding title, this viewpoint is thought to encompass all of modern physics, including quantum theory. This assumption that we live in a Newtonian Schema Universe (NSU) is so strong that many physicists can’t even articulate what other type of universe might be conceptually possible."
-- https://arxiv.org/abs/1211.7081

That name Ken Wharton sounded oddly familiar to me. So I clicked on his name to see which other papers he has on arXiv: Many papers together with Huw Price, a well known philosopher! Judging from the arXiv abstracts, this Ken Wharton seems to be all over the place, when it comes to foundations of QM. (I guess I had seen his name before on scirate, because his papers sometimes get scited. For example the paper you cited has 5 scites: https://scirate.com/arxiv/1211.7081)
Do you have an opinion on Ken Wharton, and the specific paper you cited?

His proposed alternative to the NSU in this paper is the Lagrangian Schema Universe (LSU), which seems completely unrelated to the alternatives proposed by Smolin. His reasons and arguments feel to me mostly like "if you want to follow the math, then take the courage to really follow it".

I decided to also read a "recent" paper by Huw Price on foundations of QM without Ken Wharton as coauthor:
https://arxiv.org/abs/2102.02392
Somehow its arguments feel more compelling to me, from a philosophical POV. But Huw Price is a philosopher, so I guess this should not really surprise me.

 

[physika]

...that the universe is a computational mechanism...

Perhaps the "Laws" are "derived" computationally (itself).


....

 

[Fra]

That name Ken Wharton sounded oddly familiar to me. So I clicked on his name to see which other papers he has on arXiv: Many papers together with Huw Price, a well known philosopher! Judging from the arXiv abstracts, this Ken Wharton seems to be all over the place, when it comes to foundations of QM. (I guess I had seen his name before on scirate, because his papers sometimes get scited. For example the paper you cited has 5 scites: https://scirate.com/arxiv/1211.7081)
Do you have an opinion on Ken Wharton, and the specific paper you cited?

His proposed alternative to the NSU in this paper is the Lagrangian Schema Universe (LSU), which seems completely unrelated to the alternatives proposed by Smolin. His reasons and arguments feel to me mostly like "if you want to follow the math, then take the courage to really follow it".

Actually I simply picked a paper as a reference to the therm of the newtonian schema/paradigm and pay no attention to the rest. I agree, that the rest of the paper does not seem clearly related to Smolins ideas, and it doesnt align well with my own thinking either. His actual objections to newtonian schema are also very different than mine.

What paradigm to try instead of that, probably has several possible answers! But if we start to discuss that we are most definitely going into explicit speculation, which we can't do. As I see it, the preferred paradigm should the in future demonstrate it's power by making things easier and solving some open problems. And until we get there, then all is speculation. I see the benefit of "speculation" in research similar to variability in evolution. It is necessary, but must be tamed so we also have stability.

/Fredrik

 

[Fra]

Perhaps the "Laws" are "derived" computationally (itself).....

Given that noone has the answer, this paper of Mueller contains some very good components and good idea that are at least partly in the direction of my thinking...

Law without law: from observer states to physics via algorithmic information theory
"to start with the first-person (the observer) rather than the third-person perspective (the world)
...
universal induction determines the chances of what any observer sees next. That is, instead of a world or physical laws, it is the local state of the observer alone that determines those probabilities. Surprisingly, despite its solipsistic foundation, I show that the resulting theory recovers many features of our established physical worldview: it predicts that it appears to observers as if there was an external world that evolves according to simple, computable, probabilistic laws."
-- https://arxiv.org/abs/1712.01826

To connect to Smolin, this relates to one of smolins paper

Precedence and freedom in quantum physics
"A new interpretation of quantum mechanics is proposed according to which precedence, freedom and novelty play central roles. This is based on a modification of the postulates for quantum theory given by Masanes and Mueller
...
We also propose that laws of quantum evolution arise from a principle of precedence, according to which the outcome of a measurement on a quantum system is selected randomly from the ensemble of outcomes of previous instances of the same measurement on the same quantum system. This implies that dynamical laws for quantum systems can evolve as the universe evolves, because new precedents are generated by the formation of new entangled states. "
-- https://arxiv.org/abs/1205.3707

/Fredrik

 

[pines-demon]

Just to clash again a bit on the terminology. I checked Kuhn's work who is the one that introduced the concept of paradigms shifts in science. Newtonian paradigm is mentioned many times in different ways, mostly to say that it is different from that of Einstein and Aristotle. However Kuhn himself recognizes that he is sometimes not clear if "Newton's paradigm" includes or not all classical mechanics, in the postcript on his own book, Kuhn says

Turn now to paradigms and ask what they can possibly be. My original text leaves no more obscure or important question. One sympathetic reader, who shares my conviction that ‘paradigm’ names the central philosophical elements of the book, prepared a partial analytic index and concluded that the term is used in at least twenty-two different ways. Most of those differences are, I now think, due to stylistic inconsistencies (e.g., Newton’s Laws are sometimes a paradigm, sometimes parts of a paradigm, and sometimes paradigmatic), and they can be eliminated with relative ease.

He then continues with long sections to explain the difference, but I cannot tell if I am unable to understand it or if he does not solve it either in the postcript.
Source: T. Kuhn, The Structure of Scientific Revolutions, 2ed..

 

[anuttarasammyak]

The evolutuonary theory is accepted in biology already. Rats arent magically "fine tuned", they are evolved.

A physical approach to explain evolution of lives is dissipative structure. Is thermodynamics, including its second law, is categorized in Newton Schema ?

 

[gentzen]

A physical approach to explain evolution of lives is dissipative structure. Is thermodynamics, including its second law, is categorized in Newton Schema ?

No, it is not a Newton Schema, because there is not necessarily a dynamical law. However, some sort of kinematical structure should be there, and some "arrow" of time is assumed too. In many respects, the requirements are similar to Smolin's requirements for evolution.

 

[physika]

"start with the first-person (the observer) rather than the third-person perspective (the world)"

Imo, that is a false dichotomy or a circular infinite regress.
What is first the "observer" or the "observed"...

 

[apostolosdt]

With due respect to all the members who have contributed to the present thread, this is not the physics I've been taught or the physics I've been teaching.

 

[Nugatory]

With due respect to all the members who have contributed to the present thread, this is not the physics I've been taught or the physics I've been teaching.

That’s a fair reaction to many interpretation/foundations threads, and why they’re in their own subforum.

 

[Fra]

Just wanted to make a short comment on this.

A physical approach to explain evolution of lives is dissipative structure. Is thermodynamics, including its second law, is categorized in Newton Schema ?

No, it is not a Newton Schema, because there is not necessarily a dynamical law. However, some sort of kinematical structure should be there, and some "arrow" of time is assumed too. In many respects, the requirements are similar to Smolin's requirements for evolution.

IMO, the idea to explain the non-dynamical evolution as an entropic flow, still shares a problem with the newtonian schema, which is that it's explanatory value builds on that we have an low entropy initial condition in a timeless statespace, but where the statistical average may imply a hamiltonian flow on the macrostate levels.

Just like dynamical law in chemistry (which can be said to have a dissipative explanation) also follows the newtonian schema.

For me this problematic, because the "explanation" presumes and improbable (low entropy) premise and "true" evolution that I think is the deeper sense Smolin refers aims to explain more without that premise. My firm opinion is that trying to "solve this" but thinking it's just emergence in terms of entropic flows is really missing part oft he core issue.

I still add that I think the ideas of entropic flow to explain dynamics, has place and is likely part of the solution, but there is one more component to the puzzle than to consider this happening in a fixed statespace; and that point relates to at least my own critique against the newtonian schema.

But here we get into various reasons why newtonian schema is problematic and there I think we again get many interpretations on this. An example is already the paper I randomly cited to describe the term, Ken Wharton argues in ways I wouldn't but that is a seaparate discussion I think.

/Fredrik

 

[Fra]

Imo, that is a false dichotomy or a circular infinite regress.
What is first the "observer" or the "observed"...

I understand how you think, I do, because even given my current stance, I come from the same thinking! But this is not how this is supposed to be understood.

I would put like it like this:

The conclusion that this is "circular infinite regress" is due to analysing things while beeing constrained to the newtonian paradigm.

To see that it is rather an evolutionary progression (not circular regress), one must step outside the problematic paradigm. The concept of evolutionary progressing can't even be grasped in the newtonian paradigm, that is the point.

/Fredrik

 

[physika]

....

Time will tell, whether or not such an approach survives or whether it becomes part of the necropolis of failed ideas in Physics.

.....

 

[gentzen]

Just wanted to make a short comment on this.


IMO, the idea to explain the non-dynamical evolution as an entropic flow, still shares a problem with the newtonian schema, which is that it's explanatory value builds on that we have an low entropy initial condition in a timeless statespace, but where the statistical average may imply a hamiltonian flow on the macrostate levels.

IMO, most of us here (me included) are more interested in the exact meaning of Newtonian "schema/paradigm" than in its supposed problems. Can we just agree that stuff like David Deutsch's constructor theory does not follow the Newtonian scheme? And that thermodynamics and its second law is maybe only halfway as different from the Newtonian scheme, but still different?

For me this problematic, because the "explanation" presumes and improbable (low entropy) premise and "true" evolution that I think is the deeper sense Smolin refers aims to explain more without that premise. My firm opinion is that trying to "solve this" but thinking it's just emergence in terms of entropic flows is really missing part oft he core issue.

The past entropy doesn't need to be extremely low, it only needs to be noticably lower than the current entropy. And like David Wallace observed, it would actually be more surprising if this were not the case. So no fine tuning is required for that assumption/premise.

But here we get into various reasons why newtonian schema is problematic and there I think we again get many interpretations on this. An example is already the paper I randomly cited to describe the term, Ken Wharton argues in ways I wouldn't but that is a seaparate discussion I think.

Exactly!

 

[Fra]

IMO, most of us here (me included) are more interested in the exact meaning of Newtonian "schema/paradigm" than in its supposed problems. Can we just agree that stuff like David Deutsch's constructor theory does not follow the Newtonian scheme? And that thermodynamics and its second law is maybe only halfway as different from the Newtonian scheme, but still different?

Yes.

Deutsch also likes to contrast his constructor theory with this himself

Constructor Theory of Information
"...The basic principle of constructor theory is that

I. All other laws of physics are expressible entirely in terms of statements about which physical transformations are possible and which are impossible, and why.

This is in contrast with the prevailing conception of fundamental physics,which seeks to explain the
world in terms of initial conditions and laws of motion, and whose basic dichotomy is therefore between what happens and what does not.

Constructor theory describes the world in terms of transformations involving two kinds of physical systems, playing different roles. One is the agent causing the transformation, which we refer to as the constructor, whose defining characteristic is that it remains unchanged in its ability to cause the transformation again. The other consists of the subsystems—which we refer to as the substrates—which are transformed from having some physical attribute to having another."
-- https://royalsocietypublishing.org/doi/10.1098/rspa.2014.0540

This is indeed the newtonian schema/paradigm, although he doesn't label it as such.

So loosely speaking he instead of a "statespace" and a "lawspace", he seems to entertain some "set of possible substrates" and "set of possible constructors".

The past entropy doesn't need to be extremely low, it only needs to be noticably lower than the current entropy. And like David Wallace observed, it would actually be more surprising if this were not the case. So no fine tuning is required for that assumption/premise.

I can't comment on what Wallace arguments was I am not familiar with it, but it's not just about the entropy associated to the initial condition of the state space or phase space, but also about the priori probability of having all the laws tuned, to what they are in "theory space". The latter contains massive amounts of prior information that is tactically hidden and not made explicit in the fine tuning of the laws temselves, in the newtonian schema.

/Fredrik

 

[Morbert]

The past entropy doesn't need to be extremely low, it only needs to be noticably lower than the current entropy. And like David Wallace observed, it would actually be more surprising if this were not the case. So no fine tuning is required for that assumption/premise.

In Penrose's Conformal Cyclic Cosmology (CCC) treatise, he makes the argument that symmetry implies we should expect entropy to increase both into the past and the future. E.g. our evolutionary history is more surprising than a history where we spontaneously came into existence as our physical state moves from a higher-entropy to a lower-entropy region. This is one of his motivations for CCC as it would predict a low entropy early universe and hence a breaking of this symmetry.

Does Wallace argue that no such explanation is necessary and we should just expect our past to be lower entropy anyway?

 

[gentzen]

The past entropy doesn't need to be extremely low, it only needs to be noticably lower than the current entropy. And like David Wallace observed, it would actually be more surprising if this were not the case. So no fine tuning is required for that assumption/premise.

I can't comment on what Wallace arguments was I am not familiar with it, but it's not just about the entropy associated to the initial condition of the state space or phase space, but also about the priori probability of having all the laws tuned,

Does Wallace argue that no such explanation is necessary and we should just expect our past to be lower entropy anyway?

David Wallace simply said that he doesn’t understand why such an explanation should be necessary.
https://www.preposterousuniverse.com/podcast/2021/08/02/158-david-wallace-on-the-arrow-of-time/

0:43:31.7 SC: Good. ... There’s this feeling that you say something like, “Look, it’s just a black body radiation, that’s high entropy. How could it… It had the highest entropy it could have had, given that it was tiny,” but when you turn on gravity, that’s not true. So am I right to say that it’s fair to say the early universe had low entropy compared to what it could have had?

0:44:10.6 DW: Yeah.

0:44:11.2 SC: And gravity had something to do with that.

0:44:12.7 DW: But look, here’s something I don’t understand about this, these conversations with cosmologists. Absolutely, the early universe had low entropy compared to what it could have, but one really quick way to tell that is the early universe had low entropy compared to the current universe. If it didn’t, the second law of thermodynamics is empirically wrong. And no one thinks that.

0:44:34.1 SC: Well, yes, but the…

0:44:35.4 DW: So it’d really better be the case that the early universe was lower entropy than the present universe. We shouldn’t need to give some subtle transcendental argument as to why it must be lower. It’d better be lower in order not to blow our entire thermodynamic theory out of the water.

The main argument Sean Carroll advanced against this was that the empircally observed entropy of the early universe is even lower than can be explained by this "of course the entropy in the early universe had to be noticably lower than in the current universe".

 

[physika]

The Borde–Guth–Vilenkin theorem poses insurmountable obstacles to cyclic universe models.

Vilenkin:
"A cyclic universe runs into the second law of thermodynamics, which says that any system left to itself eventually reaches the state of maximum disorder, called thermal equilibrium. So if the universe were cyclic, then in every cycle, the disorder in the universe would increase. Eventually the universe would reach this thermal equilibrium state, which is a totally featureless mixture of everything—this is not what we see around us."



.....