The universe wouldn't surprise me at all if it is fundamentally incoherent to it's own content (for example observers) which are restricted to experiencing time and space from a falsely standardised pov. — Benj96

I thinks it definitionally impossible for an event to occur outside of time and space, considering an event is defined as that which occurs somewhere at some time. If I were to tell you that Event A exists nowhere and it occurred at no time, we'd just say that Event A never occurred.

How could we possibly know if it's the beginning of the universe or some stage of a larger multiverse? We have no way of knowing, at least at the moment, maybe even in principle.

Yeah, given our current knowledge and best guesses on that basis, asking about the beginning of the universe makes about as much sense as asking about the edge of the Earth.

And yet, and yet, we have flat earthers. No pics from the edge? Interesting. :joke:

:sweat:

I suppose we can know that there was a big bang, and that its possibility requires something rather than nothing
(or an instable kind of "nothing" a la Krauss & Co). Penrose's idea of cyclic eons seems interesting but I suppose it is too soon to pass it for knowledge.

Philosophy as physics without the maths. — Banno

I think this thread shows that mathematics is insufficient for explaining the reality of physical existence. That's why we've developed philosophy.

I think this thread shows that mathematics is insufficient for explaining the reality of physical existence. That's why we've developed philosophy. — Metaphysician Undercover

The philosophy is being done by the scientists, and some would call it speculation. Philosophical ideas seem to require ream after ream of supporting prattle. Physicists have better things to do. :cool:

Philosophical ideas seem to require ream after ream of supporting prattle. — jgill

This seems to be self-contradictory. If it is supporting the ideas, how could it be called "prattle"? That reams of material is required to support the philosophical ideas is a good thing, isn't it? That support is what makes the philosophy sound.

And without a hierarchy of moral values which only philosophy can provide, your own proposition itself, that "physicists have better things to do", is meaningless prattle. Such a proposition would require reams of support to justify it as sound.

And without a hierarchy of moral values which only philosophy can provide, your own proposition itself, that "physicists have better things to do", is meaningless prattle. Such a proposition would require reams of support to justify it as sound. — Metaphysician Undercover

Point scored for philosophy. :up:

Hi there! I have a PhD in Physics and therefore cannot resist chiming in on this.

While I concede that Science itself is not free from biases, but this is one area where the formal position is pretty respectable. This position defines the confirmed existence of the "Big Bang Theory" by the multiple stages of rapid expansion that we know the universe experienced in its first few seconds, days, and years. So we can (and do) know that the Big Bang happened immediately after the birth of the universe, but our knowledge can only get asymptomatically close to "t=0". Our current mathematical models extrapolate the existence of a singularity at t=0, but in every case where they come up, a singularity represents a transition point where our theories (or maybe just our current system of mathematics, or both) stop working and, as far as we can tell, no longer describe reality.

Not only do we not know if or how reality might work on the "other side" of any singularity, we don't know if or how reality might work *at* a singularity.

My point is that Science communicators may talk about the exciting, other-worldly implications of the extrapolating our mathematical models, the actual dominant position in the scientific community is that we can't say anything for sure about the universe before t = 10^-32 seconds or something like that.

Not only is it possible that we don't actually understand the birth of the universe, it is an established fact that we do not.

There is no shortage of scientific speculation about how the universe began, and what may have come before it, like:
- the implication of string theory (or maybe it was M-theory specifically) that two universes (or "branes") colliding within the multiverse could create a Big Bang event,
- the possibility of a "Big Crunch" end of the universe resulting in a collapse that would pull a universe back into a singularity which then inflates into a new Big Bang (and could do so over and over, maybe even indefinitely),
- I forget the formal name for it (and some of the other specifics), but the idea that the quantum foam that makes up our spacetime may have a Ground Energy level lower than we think, and the energy level of our spacetime itself may drop, thus resetting all universal constants and changing all current physical laws (which I think is somehow an even more drastic "reset" than the Big Crunch and Bang possibility),
- or the comparatively mundane idea that the difficulty of nailing down the ultimate reason for time-asymmetries that are not also space-asymmetries exists because time has a capacity to be spontaneously reversed, on occasion (I think this one is pretty unpopular, but honestly I'm running out of ideas).

However, while these kinds of theories are potentially consistent what we do know, no one yet knows how to prove or disprove any of them.

So my own conclusion - which I hope does not come across as a cop-out - is that the ultimate origin of our universe is unknown, and is potentially unknowable. And what (if anything) came before may have been some kind of reality that was a lot like ours - but considering that the nature of the universe at t=0 is fundamentally different to what our reality currently is, it seems very reasonable to expect that anything on the other side is likely to have been radically different to our current reality. Maybe even so different that we wouldn't even be able to understand it as anything "real".

There's a quote from J. B. S. Haldane that I like: "Not only is the universe queerer than we suppose - it may be queerer than we can suppose."

I thought you and others might enjoy knowing that most physicists regard String Theorists and other specialists in unprovable/unfalsifiable theories as not really being "physicists", and actually being "mathematical philosophers". ;)

It's a distinction that is not usually made with disrespect (philosophy is a huge part of foundational physics) - but as more of a demarcation of what should be allowed to be called "science".

So my own conclusion - which I hope does not come across as a cop-out - is that the ultimate origin of our universe is unknown, and is potentially unknowable. And what (if anything) came before may have been some kind of reality that was a lot like ours - but considering that the nature of the universe at t=0 is fundamentally different to what our reality currently is, it seems very reasonable to expect that anything on the other side is likely to have been radically different to our current reality. Maybe even so different that we wouldn't even be able to understand it as anything "real". — Jaded Scholar

What do you think of proposals such as Roger Penrose's CCC, with his supporting evidence of 'Hawking points?' My quals in physics only go as far as year 1, of my BSc(Hons) in Computing Science, (over 30 years ago). Do you assign any significant credence to any of the cyclical or oscillating universe proposals?

I thought you and others might enjoy knowing that most physicists regard String Theorists and other specialists in unprovable/unfalsifiable theories as not really being "physicists", and actually being "mathematical philosophers". ;)
It's a distinction that is not usually made with disrespect (philosophy is a huge part of foundational physics) - but as more of a demarcation of what should be allowed to be called "science". — Jaded Scholar

As a 'fan' of string theory, I found this quite interesting. I wonder how someone like Brian Greene would respond to it, (if he has not already.)

I found this, based on a google search:
String Theory is currently not falsifiable. It does not make any testable predictions, and in the strictly positivist popperian view, it couldn't even be regarded as science. However, some physicists argue that string theory is falsifiable if an experiment shows quantum mechanics fails.

How would you respond to the last sentence, would your response be anything more than 'yeah ..... IF!'

While I concede that Science itself is not free from biases, but this is one area where the formal position is pretty respectable. This position defines the confirmed existence of the "Big Bang Theory" by the multiple stages of rapid expansion that we know the universe experienced in its first few seconds, days, and years. So we can (and do) know that the Big Bang happened immediately after the birth of the universe, but our knowledge can only get asymptomatically close to "t=0". Our current mathematical models extrapolate the existence of a singularity at t=0, but in every case where they come up, a singularity represents a transition point where our theories (or maybe just our current system of mathematics, or both) stop working and, as far as we can tell, no longer describe reality. — Jaded Scholar

Consider that every time we make a temporal measurement there is necessarily a t=0, the point at which the measurement starts. And, as you explain, "our knowledge can only get asymptomatically close to 't=0'". Because of this, the very same problem which we have in modeling the Big Bang, exists when we model any temporal reality. In Newtonian mechanics it manifests as an infinite acceleration at the precise moment a force is applied, and in wave mechanics it manifests as the uncertainty of the Fourier transform.

Not only do we not know if or how reality might work on the "other side" of any singularity, we don't know if or how reality might work *at* a singularity. — Jaded Scholar

So this is the problem with any supposed "point in time", it is a singularity and we cannot understand what exists at a point in time. Accepted conventions place the limit at about the Planck length, but that is dependent on the conventions.

Not only is it possible that we don't actually understand the birth of the universe, it is an established fact that we do not. — Jaded Scholar

Likewise, as explained above, we do not understand the universe at the present, at every moment of passing time.

I thought you and others might enjoy knowing that most physicists regard String Theorists and other specialists in unprovable/unfalsifiable theories as not really being "physicists", and actually being "mathematical philosophers". ;) — Jaded Scholar

I would classify that as metaphysical speculation. The issue with this speculation which is derived from mathematicians and physicists, is that it tends to rely heavily on the reality of mathematical ideals and geometrical figures. This is known as Pythagorean, or Platonic, idealism.

I thought you and others might enjoy knowing that most physicists regard String Theorists and other specialists in unprovable/unfalsifiable theories as not really being "physicists", and actually being "mathematical philosophers". ;) — Jaded Scholar

As a retired mathematician, a "mathematical philosopher" resonates more as someone indulging in mathematical foundations - a topic at the heart of the subject, but one many if not most practitioners have little concern over.

I would classify that as metaphysical speculation. — Metaphysician Undercover

I agree.

I hope you stick around. Actual scientists are a rarity here, as are math people. The intersections of science and philosophy can be an entertaining circus. :cool:

What do you think of proposals such as Roger Penrose's CCC, with his supporting evidence of 'Hawking points?' My quals in physics only go as far as year 1, of my BSc(Hons) in Computing Science, (over 30 years ago). Do you assign any significant credence to any of the cyclical or oscillating universe proposals? — universeness

Overall, I've never found cyclical models particularly appealing, for two (somewhat personal) reasons:
1. It feels... almost anthropocentric to focus too much on the idea that what exists before/after our universe is just a kind of continuation of our universe. It feels a bit like we're just recreating the 19th(?) century assumption that our universe is static and eternal (maybe because that saves us from imagining something different?).
2. Almost all cyclical models I've heard about rely on the assumption that each iteration ends with a big crunch or a big rip (sorry, I'm gonna make any interested parties wiki some things rather than spend even longer defining terms). But the experimental measurements of our universe keep indicating that our fate is *probably* exactly in between those, and unlikely to encounter either. It's very possible that that's not the case, but I think it's too coincidental to not be seen as meaningful that as our measurements get better and better, they generally keep telling us "Yeah, we could be on either side of this knife edge, but it still seems like we're exactly in the middle". So while I think we shouldn't assume every other universe is like we think ours is, it seems even more tenuous to assume that every other universe is unlike ours.

That said, I actually wasn't familiar with Penrose's CCC theory. I've read a bit about it, and can't claim to fully understand it yet, but it's probably my favourite cyclical model so far. It doesn't have problem #2 above, and while it doesn't have any supporting evidence yet (I learned that the "Hawking points" evidence has been refuted as something that is explainable by our current universe's cosmology), the fact that it is potentially provable/falsifiable... doesn't necessarily make it more or less likely to be true, but it does make me like it more.

However, some physicists argue that string theory is falsifiable if an experiment shows quantum mechanics fails.

How would you respond to the last sentence, would your response be anything more than 'yeah ..... IF!' — universeness

Haha, thank you for bringing that up - I hadn't heard that argument before. Your guess at my response is pretty accurate! I've given it some thought, and the best comparison I can think of is that we could say "If someone proves that mathematics itself is broken, that would mean that String Theory is too! So technically, it is falsifiable."

Admittedly, that example gives Quantum Mechanics too much credit (and String Theory too little) but the above statement is much closer to this than it is to any serious claim of falsifiability.

As a retired mathematician, a "mathematical philosopher" resonates more as someone indulging in mathematical foundations - a topic at the heart of the subject, but one many if not most practitioners have little concern over. — jgill

Interesting. That connotation is pretty much what I meant, just with fewer steps - as crucial as mathematics is to literally every area of physics, the only areas where it gets close to centre stage are the foundational ones, generally.

I hope you stick around. Actual scientists are a rarity here, as are math people. The intersections of science and philosophy can be an entertaining circus. :cool: — jgill

Thanks! :)
And I completely agree. I've often enjoyed being able to expand or refine philosophies that touch on my area of expertise, and look forward to finding out how reasonable/full-of-it those ideas are. At any rate, I'm sure it'll be more worthwhile than just privately scoffing at, say, William James, and never finding out if I'm justified in doing so.

Curious, are you familiar with Max Tegmark’s ideas on Levels 1-4 multiverses? His general metaphysical theory is that the physical world (what we human animals perceive anyways) is basically mathematical structure all the way down. He argues further, that ours is a computable mathematical world though this gets thorny when considering Godel’s paradox.





He has ideas on consciousness too, and how it’s about bring a mathematical pattern similar to Tononi’s ideas of integrated information theory or “phi”, but that’s probably stepping further out of his specialty. Perhaps that’s needed though.

it's probably my favourite cyclical model so far. — Jaded Scholar

Ditto!

I tried to read the actual published papers from Penrose and his team but they soon overwhelmed my grasp of physics. I was intrigued by the point that the 4 hawking points he is confident of, are residuals of large galaxy clusters from a previous aeon, and are supported by the WMAP and Planck project data.

I watched the debate between him and Alan Guth:

Really worth the watch, if you have not already watched it. Guth talks about alternative explanations for Hawking points but I think Roger insists that the evidence for these alternatives is not as robust as his evidence for the cause of these hawking points.

I can follow the general logic of CCC and the 'heat death' of the universe via the entropy model.
The difference between 'heat death' and 'big rip' being:
Heat Death is the slow dissipation of all matter into entropy and the Big Rip is the tearing apart of all matter and the fabric of spacetime.
The bit I struggle with, conceptually, is the final 'state' before the 'new Aeon/Big Bang,' begins.
The universe has expanded to the point where any remaining content (energy) is unable to do work.
At this point, the vast size of the universe loses all significance (whatever that means?) and the perception of 'big' and 'small' become indistinguishable. At that moment, time resets to zero and a new big band/Aeon begins? Any thought about that?

Could you also help me understand a little more as to why any loop quantum gravity quanta could not turn out to be just another vibrating string state?

So while I think we shouldn't assume every other universe is like we think ours is, it seems even more tenuous to assume that every other universe is unlike ours. — Jaded Scholar

Does this mean you favour the many worlds proposal, supported by such as Sean Carroll and Alan Guth et al.

I love listening to Max Tegmark, he is a fascinating thinker. I think he is, however considered very fringe, by the physics/cosmology community. I have watched a few youtube videos about his 4 levels of multiverse. Including this discussion between him and Brian Greene:

All I can honestly say is that I prefer the musings of max, regarding reality, compared to the insistences that theists claim are facts about the universe/multiverse. They will always add 'yeah and if Max turns out to be correct, then that's just the way god made it.'
Exemplified by the theist who recently quoted a line at me, from 'all things bright and beautiful,' when I asked for a comment about his god, and the proposal that a multiverse existed.
"Well, if the multiverse exists, then 'The lord god made them all'" :broken:

A lot of scientists other than neuroscientists seem to be jumping on and off the 'consciousness' bandwagon. Have you watched any of the youtube stuff with Roger Penrose and Stuart Hameroff on consciousness and quantum mechanics? Such as:

I want to give a disclaimer that your comment irked me. I'm not certain exactly why, therefore I'm not sure if it was for a good reason or a bad one, hence the disclaimer.

I think it's because I think everything you said is generally on the right track, but is either not entirely accurate or not entirely applicable to what *I* said.

For instance:

Consider that every time we make a temporal measurement there is necessarily a t=0, the point at which the measurement starts ... the very same problem which we have in modeling the Big Bang, exists when we model any temporal reality. — Metaphysician Undercover

When I say "t=0" in this case, I'm using it as a shorthand for the much more difficult-to-characterise hypothetical boundary where our mathematical models interpolate the existence of spacetime itself, as we know it, to exist on this side, and to not be able to exist on the other side. This is very different from what you are talking about; the arbitrary assignment of t=0 on a number line to define the subset of a Cartesian plane that we care about. Though I admit that I did not communicate that at all (in fact, I deliberately avoided it).

In Newtonian mechanics it manifests as an infinite acceleration at the precise moment a force is applied, and in wave mechanics it manifests as the uncertainty of the Fourier transform. — Metaphysician Undercover

This claim about Newtonian mechanics does not make sense. It confused me so much that I honestly think you can't be as wrong as I think and you are more likely to be referring to something I'm not getting. One of the biggest benefits of Newtonian mechanics over pre-Newtonian classical mechanics was that the second law eliminated the artefact of infinite acceleration (except for massless particles).

But I am confident that in your next line you really are just misinterpreting the nature of wave mechanics and/or Fourier transformation. The temporal uncertainty you refer to here has nothing to do with time itself, and is a straightforward result of transformation between any given noncommutative dimensions - none of which are *necessarily* time.

So this is the problem with any supposed "point in time", it is a singularity and we cannot understand what exists at a point in time. Accepted conventions place the limit at about the Planck length, but that is dependent on the conventions. — Metaphysician Undercover

I don't want to say that it's not worthwhile to argue about the physical reality/unreality of "a point in time", and reference the suggested limits of its quantisation, but I do think that it's not actually relevant to what I was talking about.

Likewise, as explained above, we do not understand the universe at the present, at every moment of passing time. — Metaphysician Undercover

Again, I agree, but do not think this is actually meaningful here, and comes across as actively un-meaningful. Along the lines of: "Sure, we don't understand the Big Bang, but like, do we really understand ANYTHING, man?".

I would classify that as metaphysical speculation. The issue with this speculation which is derived from mathematicians and physicists, is that it tends to rely heavily on the reality of mathematical ideals and geometrical figures. This is known as Pythagorean, or Platonic, idealism. — Metaphysician Undercover

I am happy to end on this note, because although your specific criticism is several centuries out of date, I agree completely with the general spirit of this objection.

Most modern physics is grounded in the mathematical framework of Complex Theory, which requires having no hierarchy of validity - real and imaginary numbers have no distinction except the planes they define (sadly, though, the label of "imaginary numbers" has still stuck, despite that name being given to them not by their creators, but by critics who wanted to ridicule the idea of unphysical numbers), and the dimensionalities of objects and planes that get discussed most are discussed because they're most interesting and strange. In Physics, we get mathematical results that can be called "unphysical", but I don't recall any such qualification given a single time in my Complex Theory lectures.

But even in Physics, there is no arrogance behind this label - such a finding is not unwelcome, but rather, is often the most exciting thing. Many unphysical results are known to model phenomena that really exist, and we just don't fully understand yet - like quantum tunnelling, where a particle can bypass any otherwise impenetrable barrier if the circumstances allow it to have a speed that is an imaginary number.

So I'm incredibly confident that the problem of Platonic idealism has been solved, as far as it applies to our mathematical and scientific culture.

But humans still have limits to our imagination, even if we have pushed those limits farther than our predecessors.

We can imagine living on a mobius strip or a cyclical universe. But can we imagine what an "imaginary number" would even mean in the world of our every day existence? What does an "imaginary velocity" actually represent? Or what would our perceptions be like if they could undergo a Fourier transformation (or other dimensional transformation) just like our numbers?

There are clearly limits to what we can imagine. And it follows that there are also greater limits to reality than what we can currently imagine. Mathematics provides a powerful bridge between what we can imagine and what is real. But I think we should assume that there are limits on what mathematics we can imagine, and on how well the nature of the universe itself can fit within any framework constructed from our invented mathematics.

I think it is both safe and responsible to assume that one of the fundamental barriers to our full understanding of the universe is that mathematics itself may not yet be sophisticated enough.

Whatever the gaps are, they are not what you described - if we could label them, we could have fixed them by now. But I think the general principle that our blind spots are probably rooted in our difficulty understanding things that don't exist in our macroscopic perceptions of the world (and/or the often-accompanying unwillingness to accept such things as potentially "real") - which I take to be part of the spirit behind your objection - is a very, very good guess.

I have heard about Tegmark's 4 levels of multiverses. It seems like a worthwhile classification system for how different kinds of mathematical models nest within each other, but it's never really struck me as anything more significant than that.

I appreciate that Tegmark seems dedicated to anti-dualism (I was about to say "Monism", but after a quick search, I think that term has more baggage than I want to accidentally reference), especially given the human history of dualistic metaphysics always[citation needed] smuggling in some kind of cultural virtue disguised as a law of nature, and given the power of mathematics to describe reality more accurately than literally any non-mathematical approach. But I think he goes a little too far, and in doing so, glosses over too many flaws and incompatibilities within the mathematical models that he just assumes are going to work themselves out at some point (or so I gather).

The power of modern maths is unprecedented, and I am happy to have science popularisers talking about that, but ... less happy to have them included in academia, where I think more people should be realistically considering that some of our gaps could be the result of fundamental problems with mathematics itself.

Similarly, his (and Tononi's) ideas on consciousness seem like they provide interesting opportunities to quantify our observations in a sophistocated way, but if they are useful at all, I think it will be in identifying the specific kinds of mathematics we observe, and allowing us to use that to infer the underlying mechanisms - and nothing like the validation of the metaphysics used to construct those models.

Thanks - I will check out that debate between Penrose and Guth.

The bit I struggle with, conceptually, is the final 'state' before the 'new Aeon/Big Bang,' begins. — universeness

To be honest, I still do not understand it either. I have read a little more about it, and I'm pretty sure that it would take a lot more work than I'm able to put in (certainly in the short term). I'm a quantum physicist, and while I have a passable understanding of general relativity, the only time where I have ever felt like I fully understood general relativity was during the year where I intensively studied it in my Honours degree. It takes a LOT of work to really get your head around space and time being the same thing, and gain an intuition for what the dynamics are that the field equations are describing (it did for me, anyway), and I feel like that's basically what I'd need to do to understand how that conformal boundary trick works.

Could you also help me understand a little more as to why any loop quantum gravity quanta could not turn out to be just another vibrating string state? — universeness

This one, I actually can!

String theory was really born out of QM particle physics, where the quantisation of universal forces (like gravity) results in them being mediated by messenger particles (the messenger particle for gravity being the graviton, as I'm sure you know). Obviously, in String Theory, these are constructed from strings using more complex laws, but still, these messenger particles and the strings themselves are objects that travel through spacetime (and/or other available degrees of freedom).

But LQG is based on a modification of general relativity, and in GR, gravity is a force both created and enacted by spacetime itself. In a sense, it's not even accurate to describe gravity as a "force" in this setting. LQG attempts to unify GR with QM by quantising spacetime itself. So LQG quanta are not just the mediators of gravity, they are also, in a way, the origin of gravity and the medium in which its effects occur.

So the results they generate should be the same, but the mathematical mechanisms they use to do so are almost mutually exclusive. If one of them really exists, the other won't.

Does this mean you favour the many worlds proposal, supported by such as Sean Carroll and Alan Guth et al. — universeness

I'm sorry, but I don't. I enjoy scientific speculation about what multiverses might exist, but in much the same way that I enjoy other speculation of what's technically possible, within what we know. (One of my favourite speculations is Feynmann's idea that, because a positron effectively behaves the same as a time-reversed electron, it's technically possible that what we perceive as annihilation events are actually time-reversal events, and there is actually only one electron in the entire universe, just flipping between going backwards and forwards through time on a number of events somewhere between 10^80 and infinity - which would explain why all electrons are identical.)

In terms of actual interpretations of quantum mechanics, I'm fairly vanilla, and am most happy with the Copenhagen interpretation. Overall, I'm not really a fan of manyworlds interpretations of QM because they seem to be based on a desire to eliminate the reality of quantum uncertainty (the original german term translates more closely to "indeterminability" than "uncertainty", which I would prefer, but I don't want to be confusing by not using the accepted name). I think it's kind of profound to observe that quantum randomness seems to be a real thing - that the universe doesn't bother figuring out the result of *any* random event until some physical process needs to actually use that result. There have been several interpretations of QM that seek to eliminate this unintuitive feature, the earliest being Einstein's Local Hidden Variable theory, which was experimentally disproven in 1987 when we were first able to confirm the existence of quantum entanglement. But many other theories - like manyworlds, pilot wave theory/other Bohmian interpretations, and certainly several others I can't remember - are still based on this same idea that we need to find some way around the "unnatural" implication that quantum randomness and quantum nonlocality are real (those quote marks apply to Einstein's description, not just me transcribing air-quotes ... in this case). In the case of manyworlds (Everett's original version, and most, but not all, other variants), this is done by simply shifting the causality of the dice-roll: the universe assigns "real" values to every aspect of a quantum object at its creation, and doesn't actually procrastinate on deciding any of them only at the point where they are measured - it actually just creates a new universe for every possible value. The randomness that gets resolved at measurement is not quantum uncertainty - it's simply the uncertainty of which one of the infinite number of universes we are in. This seems to me like a whole lot more complication purely for the sake of not accepting that reality itself is not as "real" as we like to think it is.

I think that being a good scientist has the same fundamental ingredients as being a good philosopher - to be always be open to the possibility that you are wrong about something (or everything), and to not complicate things any more (or any less) than is necessary. So I much prefer interpretations that accept the possible reality of bizarre mathematical implications, and don't spend any mathematical overhead on merging those implications into a kind of reality that is more intuitive to humans (instead of actually challenging those intuitions).

When I say "t=0" in this case, I'm using it as a shorthand for the much more difficult-to-characterise hypothetical boundary where our mathematical models interpolate the existence of spacetime itself, as we know it, to exist on this side, and to not be able to exist on the other side. This is very different from what you are talking about; the arbitrary assignment of t=0 on a number line to define the subset of a Cartesian plane that we care about. Though I admit that I did not communicate that at all (in fact, I deliberately avoided it). — Jaded Scholar

What I\m talking about is better understood through principles of calculus. The "t=0" represents the limit, and the problem is in approaching the limit. We use a t=0 for any type of temporal measurement, so any measurement made very close to t=0, i.e. a short period of time, has that problem.

This claim about Newtonian mechanics does not make sense. It confused me so much that I honestly think you can't be as wrong as I think and you are more likely to be referring to something I'm not getting. One of the biggest benefits of Newtonian mechanics over pre-Newtonian classical mechanics was that the second law eliminated the artefact of infinite acceleration (except for massless particles). — Jaded Scholar

Suppose something is at rest. Then it is moving because it has been subjected to a force. There is a point in time, when it changes from being at rest, to being in motion. At this point in time, its rate of acceleration must be infinite.

But I am confident that in your next line you really are just misinterpreting the nature of wave mechanics and/or Fourier transformation. The temporal uncertainty you refer to here has nothing to do with time itself, and is a straightforward result of transformation between any given noncommutative dimensions - none of which are *necessarily* time. — Jaded Scholar

I believe the uncertainty is based in a time/frequency relation.

Again, I agree, but do not think this is actually meaningful here, and comes across as actively un-meaningful. Along the lines of: "Sure, we don't understand the Big Bang, but like, do we really understand ANYTHING, man?". — Jaded Scholar

Exactly, our understanding of anything is incomplete, therefore deficient, lacking,

So I'm incredibly confident that the problem of Platonic idealism has been solved, as far as it applies to our mathematical and scientific culture. — Jaded Scholar

I don't think so. Set theory in general, presupposes that numbers are objects, Platonic Idealism. This results in numerous problems starting with the empty set, and the infinite set, and stuff like Russel's paradox. Set theory is relatively modern, the problems have not been solved only made more complex by attempts to cover them up through the introduction of more and more axioms.

I think it is both safe and responsible to assume that one of the fundamental barriers to our full understanding of the universe is that mathematics itself may not yet be sophisticated enough. — Jaded Scholar

I agree with this to an extent. But I do not think that it is sophistication which makes good math, I think the opposite. Good math is based in simple principles with universal applicability. When the principles are lacking in universal applicability, instead of throwing them away and starting at the bottom with more applicable ones, the tendency is just to adapt the old, add a few new axioms to make things work in the difficult areas. This works for a while, until new problems present themselves, so new axioms are added. The mathematics gets more and more sophisticated, but the sophistication is not evidence of good principles, but the contrary, it is evidence of basic principles which are faulty, not universally applicable. So they require addendums to work in different areas.

Whatever the gaps are, they are not what you described - if we could label them, we could have fixed them by now. — Jaded Scholar

The problem is that no one wants to fix them. The principles work in most situations, so they do not need fixing. Then for the places where they do not work, keep using them and add some more principles to make them sort of work. Look, thousands of years ago Pythagoras label pi and the diagonal of a square as "irrational". To me, this indicates that there is something fundamentally wrong with the dimensional representation of space. But who cares, the principles work, and when it turns out that real circles in the real world are not actually circular, but ellipses and things like that, we just adapt "the circle" and pi principles to make them work in the real world. But you cannot say that these problems haven't been labeled.

When I say "t=0" in this case, I'm using it as a shorthand for the much more difficult-to-characterise hypothetical boundary where our mathematical models interpolate the existence of spacetime itself, as we know it, to exist on this side, and to not be able to exist on the other side — Jaded Scholar

I have never thought of boundaries of spacetime. Since both space and time are in essence metaphysical concepts through which we nevertheless function, the idea of "boundaries" might refer mostly to mathematical models. The Big Bang being possibly an exception. MU has argued before about the notion of a point in time, and his arguments are similar to those of Peter Lynds, who denies the existence of such points in favor of duration or intervals, somewhat like Bergson.

In Physics, we get mathematical results that can be called "unphysical", but I don't recall any such qualification given a single time in my Complex Theory lectures. — Jaded Scholar

That's something for me to chew on. Fifty years ago I wrote a paper concerning limits of infinite compositions of Mobius transformations. There was a strong connection with analytic continued fractions, and these can be used somewhere in physics. Later, I found that such expansions might be accelerated or analytically continued through fixed points. If you think infinite compositions of complex functions theory might find a niche in physics, let me know!

But I think we should assume that there are limits on what mathematics we can imagine, — Jaded Scholar

Perhaps. But ArXiv.org receives hundreds of original math papers each day, every day. 26,000 math topics in Wikipedia. However, applications to the "real" world is another matter. I never went that direction.

Since you both brought up consciousness, I wanted to talk about that too - but also wanted to stress from the beginning that while I have been fascinated by this subject since first-year university, I have not done any actual research in this field, and the views I hold are mostly the result of recreational reading and not actual scientific experience. But now that I been responsible and warned you of the possibility that this might be a Sermon from Mount Stupid:

I think my own views on consciousness have been shaped most by two things:
1. A series of philosophers and physicists that can't seem to analyse the concept without introducing something innately "special", and devolving into ridiculous theories like panpsychism.
2. A single biology paper I read last year about sleep (after that ranty intro about intellectual honesty, I guess I should admit that I read a series of articles on it and just skimmed the paper itself).
https://www.science.org/content/article/if-alive-sleeps-brainless-creatures-shed-light-why-we-slumber

A key quote being:
“I think if it’s alive, it sleeps,” says Paul Shaw, a neuroscientist from Washington University in St. Louis. The earliest life forms were unresponsive until they evolved ways to react to their environment, he suggests, and sleep is a return to the default state. “I think we didn’t evolve sleep, we evolved wakefulness.”

This was one of those revelations to me that I had never come close to realising, but once I heard it, it made perfect sense to me.

Conscious interaction with the world is a more resource-intensive and more adaptive extension of unconscious interaction with the world, observed only in living things, and - if you allow a generously broad definition - is observed in all living things, to an extent. The thing I find beautiful about this interpretation is that I think it fits so well into what life itself is: a complex chemical reaction that is particularly persistent because it is particularly adaptive. In that sense, consciousness is just "the same, but moreso".

So I think the question "what is consciousness?" can only be answered as an extension of the question "what is life?". We have some definitions for that, but they're all incredibly post-hoc, and I have found them to be either so specific as to be meaningless or so vague as to be meaningless (as much as I like it, I do have to admit the the one I gave in the last paragraph does fall into the latter category).

The question "what is life?" is an enormous one that I think does not get as much attention as it deserves - maybe because it's so easy to be shuffled into the category of "I don't know but I know it when I see it", and there's not much attention to be gained by treating it like a mystery just because we can't actually define it well. Whatever the reason, I think it makes complete sense that any complete definition of consciousness will involve little to no extra "specialness" than a complete definition of life - and if I'm right, then it's a sign of pretty slow progress that our culture is supposedly on the brink of creating artificial life forms, yet our discourse is focussed almost entirely on consciousness instead of life.

Of course I may not be right. But of course, being human, I think I probably am.

it's so easy to be shuffled into the category of "I don't know but I know it when I see it" — Jaded Scholar

Along with its bed mate? :cool:

The power of modern maths is unprecedented, and I am happy to have science popularisers talking about that, but ... less happy to have them included in academia, where I think more people should be realistically considering that some of our gaps could be the result of fundamental problems with mathematics itself. — Jaded Scholar

Could you elaborate a bit on that on what that means conceptually? Are we just talking the inability to unify GR math and QM math?

Similarly, his (and Tononi's) ideas on consciousness seem like they provide interesting opportunities to quantify our observations in a sophistocated way, but if they are useful at all, I think it will be in identifying the specific kinds of mathematics we observe, and allowing us to use that to infer the underlying mechanisms - and nothing like the validation of the metaphysics used to construct those models. — Jaded Scholar

Indeed, this seems to be the weird difference. What does Tegmark mean that the unvierse IS math rather than just a model of the terrain? What does it mean for mathematical structures to be "real"?

What does it mean for mathematical structures to be "real"? — schopenhauer1

From the perspective of a mathematician, I would say examples exist. Not necessarily physical. If a function is "real" (not a real function) examples within mathematics must exist.

Physics? Well, we will see . . .

For me, it's such a pleasant breeze of cool fresh air on a hot and sticky day, to read your posts.

and the strings themselves are objects that travel through spacetime (and/or other available degrees of freedom). — Jaded Scholar

That's not something I had considered before. I assumed some string or perhaps superstring states, were responsible for the actual (for want of a better term) 'fabric' of spacetime itself. I thought that's part of the reason why supersymmetric particles were so sought after at the LHC?
String theory/Mtheory was/is a possible t.o.e, is it not, and as such, does it not also suggest that spacetime is quantisable? If QFT is correct, is it not that string states, would be the same as field disturbances, rather than be free travelling particles/strings? Rather than the concept of a single electron (as such), we would have an electron as a string state/field disturbance?

I hope I am not frustrating you too much with my poor grasp of the details involved here.
Can you explain a little more about where I maybe making mistakes above in my attempts to connect string theory with QFT, for example?

But LQG is based on a modification of general relativity, and in GR, gravity is a force both created and enacted by spacetime itself. In a sense, it's not even accurate to describe gravity as a "force" in this setting. LQG attempts to unify GR with QM by quantising spacetime itself. So LQG quanta are not just the mediators of gravity, they are also, in a way, the origin of gravity and the medium in which its effects occur. — Jaded Scholar

So is the difference between String theory and LQG, your earlier point that in string theory, all proposed string states exist WITHIN spacetime. Spacetime would thus be a 'container,' for all string/superstring states, so, LQG includes spacetime and string/superstring theory does not? This seems to clash with my own (probably incorrect) interpretations of the Sabine Hossenfelder article below:

The article from Sabine. String Theory Meets Loop Quantum Gravity. Two leading candidates for a “theory of everything,” long thought incompatible, may be two sides of the same coin.

She makes the following comments:
"Among the attempts to unify quantum theory and gravity, string theory has attracted the most attention. Its premise is simple: Everything is made of tiny strings. The strings may be closed unto themselves or have loose ends; they can vibrate, stretch, join or split. And in these manifold appearances lie the explanations for all phenomena we observe, both matter and space-time included."


"Loop quantum gravity, by contrast, is concerned less with the matter that inhabits space-time than with the quantum properties of space-time itself. In loop quantum gravity, or LQG, space-time is a network. The smooth background of Einstein’s theory of gravity is replaced by nodes and links to which quantum properties are assigned. In this way, space is built up of discrete chunks. LQG is in large part a study of these chunks."

As Sabine goes on to describe the main differences between the two theories, such as string theory suggests supersymmetry and vibrations in 10 dimensions, whereas LQG suggests neither of these.
I can grasp these basic differences, but I don't get the node/link network imagery of LQG! I am a computer scientist, I understand network topologies very well, computers can be nodes in a network and can be connected via links, but such a notion occurs 'within a container,' within a space and cannot describe that space itself. So again, I get lost!

I read Sabines article 4 times and tried to grasp the main points she was making in paragraphs such as:

But this isn’t a conundrum only for string theorists. “This whole discussion about the black hole firewalls took place mostly within the string theory community, which I don’t understand,” Verlinde said. “These questions about quantum information, and entanglement, and how to construct a [mathematical] Hilbert space – that’s exactly what people in loop quantum gravity have been working on for a long time.”

My grasp of physics was just not up to the task, even with Sabine's attempt to simplify the concepts involved for folks like me.
It's not a long article, so it would be great if you could have a look at it and give your opinion on it.

I absolutely understand, if you just don't have the time to try to explain this stuff in lay terms, when folks like Sabine have already attempted to do so. I am willing to plod on in my running through strong setting glue, towards my own eureka moments, on this stuff, that always seem just a bit beyond my abilities in physics. :blush: