And it continues to this day; William Lane Craig is a particularly egregious case, he continues to deliberately misrepresent contemporary cosmology as providing support for his Kalam cosmological argument, specifically the premise that the world/universe began to exist (and no doubt other apologists/theologians follow his lead here).

Maybe it did. Maybe it didn't. No accepted or established scientific theory tells us anything either way. — Seppo

I guess we could chalk it up to two things:

1. Misunderstanding (communication gaps). Not getting the facts straight.

2. Religious zeal. Some believers are too eager to make a point that they're willing to gloss over important details. Cherry-picking, confirmation bias.

Great! So, I've been wrong all this time — TheMadFool

Strangely enough you didnt accept that when I told you that

Any ideas why space would need to expand? — TheMadFool

Yes.But you would think Im a jackpot!

But let me say this. It could indeed be a scalar field or maybe even the Higgs field as some say. The probllem with the Higgs field, in its present form, is that is has an unreal Mexican hat potential. The zero field energy content is non-zero, which is given as the reason for the expansion. But...The whole Higgs mechanism is ABSENT. The Higgs field is just an ordinary field which emerges from elementsry rishon interactions (6 of them). This means there wasnt such a proposed cause for the inflation of space. Some say God gave the first blow. I dont agree, Naturally!

Great! So, I've been wrong all this time
— TheMadFool

Strangely enough you didnt accept that when I told you that — Prishon

Apologies. My life isn't perfect! G'day!

Apologies. My life isn't perfect! G'day! — TheMadFool

Who's life is? You think mine?

in the case of Craig, I think its quite clearly deliberate, not a good faith misunderstanding. He goes to great lengths to misconstrue contemporary science, despite having received responses from the very scientists he's misquoting/misrepresenting asking him to stop mischaracterizing their work (this happened with his misuse of the Borde-Guth-Vilenkin theorem).

But I don't think this is generally true. Many people just hear the popular science TV shows or Youtube channels refer to the Big Bang as the "beginning of the universe" and so just assume that must be true. But Craig knows better, and does it anyway.

↪TheMadFool in the case of Craig, I think its quite clearly deliberate, not a good faith misunderstanding. He goes to great lengths to misconstrue contemporary science, despite having received responses from the very scientists he's misquoting/misrepresenting asking him to stop mischaracterizing their work (this happened with his misuse of the Borde-Guth-Vilenkin theorem).

But I don't think this is generally true. Many people just hear the popular science TV shows or Youtube channels refer to the Big Bang as the "beginning of the universe" and so just assume that must be true. But Craig knows better, and does it anyway — Seppo

What bothers me is why did cosmologists stop the extrapolation at, to quote Wikipedia, "...hot dense state..." They could've simply drawn the trajectories of all the galaxies back to a point just as William Lane Craig and I thought. It's not that there was a law against it, right?

What bothers me is why did cosmologists stop the extrapolation at, to quote Wikipedia, "...hot dense state..." They could've simply drawn the trajectories of all the galaxies back to a point just as William Lane Craig and I thought. It's not that there was a law against it, right? — TheMadFool

But it makes a big difference whether you are imagining extrapolating a line - a linear relation - or instead an asymptotic curve.

Do the two parts of the cosmic equation - spacetime extent and energy density content - go to infinite value because they trace back all the way through the Planckscale event horizon and meet at a point, the confounding singularity, at some further distance beyond?

Or are the two parts of the equation yoked to each other in reciprocal fashion - as the Planck triad of c, G and h suggest - so that instead they converge asymptotically to create that event horizon that marks the beginning of both spacetime extent and its entropic spreading.

What bothers me is why did cosmologists stop the extrapolation at, to quote Wikipedia, "...hot dense state..." They could've simply drawn the trajectories of all the galaxies back to a point just as William Lane Craig and I thought. It's not that there was a law against it, right?

Because that's where our theories cease to be good descriptions of physical reality. As we rewind the clock backwards and the universe gets smaller and hotter, eventually we reach a point where quantum effects become significant, and general relativity ceases to be a good theory. General relativity is a classical theory, it does not include quantum mechanical effects, so once we reach the point where gravitation dominates on the quantum scale in the very early universe, we need a quantum theory of gravity to describe what is happening... which we don't have. So we can't rewind any further, as we have no description of how physics works in those extreme conditions.

And the fact that GR spits out an evident absurdity- the "Big Bang singularity", where all the mass in the universe occupies a 0-dimensional point where density, temperature, and spacetime curvature run to infinity- in precisely the situation where we expect it to cease to be applicable is no doubt why the overwhelming majority of cosmologists don't believe there was any such thing- the singularity is an artifact of a theory pushed past its breaking point- and that a successful theory of quantum gravity will remove such singularities (which is exactly what happens in candidate theories of quantum gravity like string/M-theory and loop quantum gravity/loop quantum cosmology).

we need a quantum theory of gravity to describe what is happening... which we don't have. So we can't rewind any further, as we have no description of how physics works in those extreme conditions. — Seppo

Do you see how you just confused the expectation of being able to rewind (in linear fashion) beyond the Planckscale event horizon with the acceptance that it is the actual limit of such rewinding?

You have been very dogmatic about the Big Bang not counting as the actual beginning of the Universe, but that is just a failure to rid your metaphysics of this assumption about linearity - the ability to extend any straight line to infinity.

What QM tells us about GR is that its straight lines become eventually so completely curved that they turn into little circles. You wind up with a description of a spacetime foam that is populated by blackholes and wormholes. A mess of naked and disconnected fluctuations, in other words.

So the Universe - as we understand it to be, via our models - is this classical realm dominated by its Euclidean flatness. We then look a little closer and have to come up with further models like GR and QFT that introduce some curvature and uncertainty. Then we track those speed wobbles in our initial Newtonian determinism and find eventually it all goes completely out of control. All the straight lines turn into curves so tight they are a foam of circles. All the uncertainty becomes so great that all that exists is naked fluctuation with no grounding context.

QG might be regarded as a project that restores linearity to the physics in a way that will let us punch right on through the Planckscale event horizon and see what lies "beyond" ... as some extrapolatable continuation of a spacetime extent and its energy density content. But as with the Hartle–Hawking imaginary time proposal, everything we know and love as the metaphysically taken-for-granted might just curve into each other and thus vanish up its own collective arse. :razz:

So the problem lies with projecting linear expectations onto GR and QM, which are already themselves frameworks for dealing with the gathering curvature and uncertainty of reality, and then expecting QG to be the triumphant return of Newtonian straight-line metaphysics.

GR works because it uncouples the connection between spacetime extent and local energy density. So in a Universe that is generally large, cold and empty - which means what, about at least 10^-10 seconds old and down to barely 10^15 degrees? - the two halves of the one reciprocal deal can seem clearly separated. You have a backdrop of flattish spacetime in which reasonably well located events are taking place. The electroweak symmetry has cracked. The Higgs field is on. Particles now have a mass that means they can go much slower than light, even if they are still a long way from being at any kind of rest.

But as we wind the clock back towards the Big Bang, we see all that familiar asymmetry being swallowed up into the anonymity of an increasingly more general set of symmetries, until we arrive at a vanilla GUT force and a matchingly vanilla notion of a relativistic quark-gluon soup, just before everything merges into the one cosmic vagueness of an event horizon, beyond which lurks only our notions about a quantum foam of fluctuations that could also be described in GR terms as a host of tiniest possible circularities - a hot mess of spatial blackholes and temporal wormholes.

So quit holding out hope that a QG theory will restore linearity and so discover a time and a place (and a higher heat or energy density) that lies over the well-demarcated Planckscale event horizon. That will enable you to be less dogmatic in your proclamations about the Big Bang not marking the beginnings of metaphysical linearity as we know and love it. The Universe that is generally large, cold and just about empty. :smile:

So the Universe - as we understand it to be, via our models - is this classical realm dominated by its Euclidean flatness. We then look a little closer and have to come up with further models like GR and QFT that introduce some curvature and uncertainty. — apokrisis

They've actually looked to see if the universe shows overall curvature, and it doesn't. As far as we can see a modified Euclidean geometry does work. That doesn't mean that there couldn't be curvature that's just so vast we can't see it.

You have been very dogmatic about the Big Bang not counting as the actual beginning of the Universe, b — apokrisis

That's the prevailing view in physics right now. No singularity.

QG might be regarded as a project that restores linearity to the physics in a way that will let us punch right on through the Planckscale event horizon and see what lies "beyond" ... as some extrapolatable continuation of a spacetime extent and its energy density content. But as with the Hartle–Hawking imaginary time proposal, everything we know and love as the metaphysically taken-for-granted might just curve into each other and thus vanish up its own collective arse.

Sure, that's perfectly fair. I'm mostly just stating what is the conventional wisdom, and I'm aware that the hope in QG allowing us to peek behind the curtain and tell the rest of this story is only one among many. I think there's a lot of value to the suggestion that we've pushed this type of program to its limit, and we have to think outside the box to really move past the present stalemate. We're well past holding our breath for string/superstring theory to yield any testable (let alone actually confirmed) predictions, so may as well bang our head against a different wall, for something new and different if nothing else.

But I do object to the suggestion that there's anything "dogmatic" about pointing out that the parts of the BBT which are widely-accepted and observationally-corroborated don't include any beginning or origin of the universe. We can't test the relevant physics, can't re-create the relevant conditions even at the LHC (not by several orders of magnitude), so we're purely shooting in the dark in those earliest stages of the universe. And I'm not claiming that there was no beginning or origin of the universe; I'm certainly not ruling that out at all. My only purpose is to counter the familiar and misleading talking point (found mostly in popular-level content on cosmology/BBT) that this is a generally accepted or observationally well-established part of the standard cosmological model accepted by most cosmologists, or that the BBT is primarily a theory of the origin of the universe (rather than of its development). It just isn't.

They've actually looked to see if the universe shows overall curvature, and it doesn't. — frank

But they looked and found it has dark energy and so an "internal pressure" that means spacetime isn't contracting, nor even coasting to a gravitational halt, but is undergoing open-ended acceleration.

So there are three generalised curvatures the Universe could have had - closed and hyperspheric, flat and Euclidean, and open and hyperbolic. The surprise is that it looks to be hyperbolic and so the event horizon of the Big Bang can be matched by its inverse of the event horizon of a de Sitter space Heat Death.

The end of the Universe is also a problem. It was hard to believe it could actually be so finally balanced in terms of its gravitational contraction and thermal expansion that it might indeed just coast towards a stop over infinite time - another singularity! And if it had too much gravity, too little matter, then it is almost just as improbable that it would have lasted the 14 billion years until now without collapsing.

So a faint positive curvature allows the Universe to stay open and yet come to an eventual Heat Death halt in terms of its cosmological event horizon – the size of the region that counts as the observable Universe.

The source of that dark energy or cosmological constant still has to be explained. It would be nice if the simple theory - that it is curvature contribution from the quantum fluctuations of the vacuum itself - pans out. That would make the force something internal to the fabric of spacetime itself - all part of the Big Bang deal.

That's the prevailing view in physics right now. No singularity. — frank

Well singularity is a technical term in maths for some kind of radical break or discontinuity in the smooth continuity of a function. So it can take many shapes.

Folk who were rewinding the GR-regulated evolution of the Cosmos past the Planckscale were aiming at a singularity shaped like a zero-D point. They wanted to shrink things to where spacetime was infinitely small. But QM said that meant it also had to be infinitely hot - as such complete certainty about location was a matchingly complete uncertainty about momentum.

But actually tie to the two curves together by inserting all three Planck constants into your cosmological equations - as QG would have to do - and you get instead (hopefully) a smooth transition in terms of a singularity-masking event horizon.

So there are three generalised curvatures the Universe could have had - closed and hyperspheric, flat and Euclidean, and open and hyperbolic. The surprise is that it looks to be hyperbolic a — apokrisis

No, it's flat and Euclidean.

Well singularity is a technical term in maths for some kind of radical break or discontinuity in the smooth continuity of a function. So it can take many shapes. — apokrisis

As I said, the prevailing view now is that there was no singularity of any kind. Big bangs happen from time to time in a greater universe that could be without limits.

So, what you're saying is the backwards extrapolation of matter and energy in the universe approaches a single point but never really reaches it (asymptote). :ok:

Thanks! :up:

They've actually looked to see if the universe shows overall curvature, and it doesn't. — frank

How can you know that if we see only a minor part of that universe. It can be locally flat and globally curved.

, what you're saying is the backwards extrapolation of matter and energy in the universe approaches a single point but never really reaches it (asymptote). :ok: — TheMadFool

The "point" is that there IS no such point.You can say that that point lays an infinite amount of time away and thus asking about the time before makes no sense but a black hole has a beginning too.

How can you know that if we see only a minor part of that universe. It can be locally flat and globally curved. — Prishon

We don't know. What we see is flat. Read my whole post.

The "pont" is that there IS no such point. — Prishon

:ok:

It could be that the fluctuating quantum fields are the source of dark energy (virtual particle pairs to use a popular but quite imaginative view; it shows a classical view of particles though and how the hell can a particle and its anti companion appear like that? But for the argument the image fits as long as you remember that it is a small part of the whole of virtuality). The fluctuating fields are always there. They even represent scalar particles (total spin 0 or 1, though they not are fundamental). Dark energy curves spacetime negatively. But what "normal" particle could THAT? There are scalar mesons but they dont curve spacetime negatively. Not even virtual ones.

It could be that the universe is a bunch of particles moving away from each other on a static, spatially 4d substrate, giving the illusion of expansion in our 3d space. The problem is though how to keep all that matter on the 3d manifold. But there, the structure of particles can come to the rescue.

But I do object to the suggestion that there's anything "dogmatic" about pointing out that the parts of the BBT which are widely-accepted and observationally-corroborated don't include any beginning or origin of the universe. — Seppo

The dogmatism relates to the assumption of a beginning/origin having to exist at some smaller scale/hotter temperature beyond the Planckscale event horizon of the Big Bang.

Spacetime and energy density are so yoked together that going "smaller" and getting "hotter" really doesn't make sense if curvature reaches its maximum at that scale. We arrive at a "just before" that is all blackholes and wormholes – a quantum foam at best.

That might be still a "something" we can model as a pre-Bang state. It just wouldn't be any kind of time, place, or state of materiality, as we claim to know it from this side of the cosmological event horizon.

So the Big Bang would in that view be the start of the Universe in the sense that the term has any useful meaning.

After all, I'm sure you would agree with the conventional reply when folk ask what is the Universe expanding into. Very quickly you will say it is just the expansion of the metric itself. The Universe is not embedded in some larger space.

But why doesn't the same logic apply to the origin of the Universe? Why does it have to be developing out of something? Why can't the development itself be what produces a developed something?

My only purpose is to counter the familiar and misleading talking point (found mostly in popular-level content on cosmology/BBT) that this is a generally accepted or observationally well-established part of the standard cosmological model accepted by most cosmologists, or that the BBT is primarily a theory of the origin of the universe (rather than of its development). It just isn't. — Seppo

I'm trying to highlight the problem with what you say is the generally accepted metaphysics.

It could be the case that Universe didn't start at the "point in time" that is its Planckscale event horizon. It could be true that there is a lengthy pre-bang story along the lines of Linde’s eternal inflation or Big Bounce cosmology. It may well be that QG is a theory that sees beyond the Planckscale and finds some kind of spacetime/energy density story that pushes the origin of that spacetime/energy density story into realms that are simply just smaller and hotter.

But these ideas are speculative, simplistic, and don't even tackle the essential questions about why there are these things of spacetime and energy density. Again, we pull folk up who ask what space our Universe is growing into, yet seem untroubled by bouncing cosmologies or branching inflation fields that presume a familiar notion of passing time as the place in which our Big Bang universe appears as just another material development.

Nothing useful is added by these kinds of linear extrapolations. The question is why spacetime and energy density are even a thing that came into being. Telling people not to bother so much with the Big Bang, wait for the full story of the "universe" beyond the Planckscale, is buying into the bad metaphysics that simply makes good careers for mathematical physicists looking to stay relevant in a time where there is little actual progress to report.

My inclination is instead to turn things around, take the Big Bang seriously as its own origin point, and see how that fits what we already know in terms of GR, QFT, the Planck triad of constants, and general symmetry breaking and condensed matter physics principles.

The Planckscale describes the first moment when spacetime as the backdrop, and energy density as its contents, could be told apart. It's a tale of co-dependent arising. And that is already the story the Big Bang theory tells in its talk of a beginning that was a relativistic realm of vanilla GUT force fluctuations. In what sense did either distinct particles or a background vacuum exist when the world was still so hot that the void was completely filled by its own wild fluctuations? Big Bang theory then says that was the initial lack of proper separation that became fairly quickly an expanding~cooling process of increasing separateness.

You don't have to like the scenario. But again, the point is that we agree not much progress has been made these past 20 years or so. Conventional thinking might be that we just need to be able to punch through the Planckscale event horizon to discover what further cosmological structure lies beyond its veil. I say the event horizon most likely simply marks an actual limit on counterfactual being. And that is at least an alternative worth being discussed - as has indeed happened with some of the loop and condensed matter models.

No, it's flat and Euclidean. — frank

You might be thinking just of space and not spacetime. Inertial expansion is flat but accelerating expansion is curved.

As I said, the prevailing view now is that there was no singularity of any kind. Big bangs happen from time to time in a greater universe that could be without limits. — frank

But even Linde’s eternal inflation is a story about a fractally branching multiverse so it indeed all branches from one initial starting point. There is a singularity in the need to explain why there was the first Planckian shoot that became the vast tree.

But if I had to pick a pre-Bang cosmology, an inflating multiverse seems the best candidate. It at least provides an anthropic reason why we live in a branch that happens to have the “right” randomly chosen physical constants - I mean all the constants besides the three key Planck ones the multiverse must also presume. :grin:

most of that dust has coalesced to form planets and other objects in the universe...including you and me.

most of that dust has coalesced to form planets and other objects in the universe...including you and me. — Michael Zwingli

What caused that to happen?

the answer seems to be simple probability. With localized random intensifications of energy in pre-universal space having occurred throughout "time", there was bound, "sooner or later" as they say, to be an intesification profound enough to begin the inverse reaction of the mass-energy equivalence reaction described by E=mc^2.

the force of gravity over a long time in the environment of space, which is of course, a function of the matter itself.