The Biggest Bang

I saw an interesting blog on the big bang - it was Tim Reeves' response to astrophysicist Ethan Siegal's Big Think Article stating that the big bang isn't the beginning of the universe anymore. I'll paste Tim's article below, and I'll add my response to the responses.

SIEGEL: Extrapolating beyond the limits of your measurable evidence is a dangerous, albeit tempting, game to play. After all, if we can trace the hot Big Bang back some 13.8 billion years, all the way to when the universe was less than 1 second old, what's the harm in going all the way back just one additional second: to the singularity predicted to exist when the universe was 0 seconds old? The answer, surprisingly, is that there's a tremendous amount of harm - if you're like me in considering "making unfounded, incorrect assumptions about reality" to be harmful. The reason this is problematic is because beginning at a singularity - at arbitrarily high temperatures, arbitrarily high densities, and arbitrarily small volumes - will have consequences for our universe that aren't necessarily supported by observations. For example, if the universe began from a singularity, then it must have sprung into existence with exactly the right balance of "stuff" in it - matter and energy combined - to precisely balance the expansion rate. If there were just a tiny bit more matter, the initially expanding universe would have already recollapsed by now. And if there were a tiny bit less, things would have expanded so quickly that the universe would be much larger than it is today. And yet, instead, what we're observing is that the universe's initial expansion rate and the total amount of matter and energy within it balance as perfectly as we can measure. Why? If the Big Bang began from a singularity, we have no explanation; we simply have to assert "the universe was born this way," or, as physicists ignorant of Lady Gaga call it, "initial conditions. Similarly, a universe that reached arbitrarily high temperatures would be expected to possess leftover high-energy relics, like magnetic monopoles, but we don't observe any. The universe would also be expected to be different temperatures in regions that are causally disconnected from one another - i.e., are in opposite directions in space at our observational limits - and yet the universe is observed to have equal temperatures everywhere to 99.99%+ precision. We're always free to appeal to initial conditions as the explanation for anything, and say, "well, the universe was born this way, and that's that." But we're always far more interested, as scientists, if we can come up with an explanation for the properties we observe.

REEVES: Siegel is warning us against the extrapolating right back to a space-time singularity. That makes sense to me on this basis: I always have doubts when a theory predicts an infinity and I'm inclined to believe that this is a sign of an incomplete theory that is being pushed too far.  But in the above quote Siegel's reason for rejecting an initial singularity is to do with scientific prediction: For unless one is to engage in the ad hoc business of patching in arbitrary initial conditions, a cosmos that starts with an arbitrarily high temperature doesn't perform well on the prediction front. Siegel then goes on to tell us that a good origins theory would predict important cosmic features like the  flatness of space, the absence of magnetic monopoles, and the uniformity of temperature and density across the observable universe. As we shall see Siegel doesn't contradict Einstein's great theory of gravitation which predicts the possibility of a space-time singularity. Instead he conveniently side steps the question of whether space time space-time singularities are physical by telling us to stop yourself before you go all the way back to a singularity.

My Comment: The universe is a mathematical object, and mathematics is more primary than physics, and God is more primary than mathematics. So while the notion of a singularity may be a difficult concept in physics, it is less difficult as a comprehension of the creation of God the cosmic mathematician. We shouldn't use theology to answer scientific questions, but equally we shouldn't rob the universe of theological gravitas by attempting to explain it only with scientific concepts, because science is only confined to physical descriptions. We've been doing sophisticated science for a few hundred years now, and have a deep understanding of much of the universe. But there will always be a hiatus in certain areas of potential discovery, and it's in those areas where the tools of science are going to remain too blunt - because if the observable universe has its origin in a singularity, it is likely to be something akin to God speaking it into being, rather how Genesis conveys. But, as we'll see below, the singularity isn't the end of the consideration, even in physics.

SIEGEL: Inflation accomplishes [(correct) predictions] by postulating a period, prior to the hot Big Bang, where the universe was dominated by a large cosmological constant (or something that behaves similarly): : the same solution found by de Sitter way back in 1917. This phase stretches the universe flat, gives it the same properties everywhere, gets rid of any pre-existing high-energy relics, and prevents us from generating new ones by capping the maximum temperature reached after inflation ends and the hot Big Bang ensues. Furthermore, by assuming there were quantum fluctuations generated and stretched across the universe during inflation, it makes new predictions for what types of imperfections the universe would begin with.

REEVES: So, inflation theory predicts a) a near enough flat universe, b) the absence of high energy relics (like magnetic monopoles), c) essentially a uniform distribution and d) makes predictions about the magnitude of fluctuations away from perfect uniformity.  Sounds good so far.

My Comment: Yes, inflationary theory purports to explain why opposite ends of the universe exhibit the same temperature and density, without which they wouldn't have been in thermal contact at the point of origin. Inflation theory also purports to explain the observation that, to a very good approximation, the universe appears to be flat. Inflation theory is still tentative: we don't know the source of the energy needed to generate inflation (although it could be dark energy). There is also the long-standing matter of unifying gravity and quantum mechanics, and that's probably not an area for Inflation or dark energy to solve, because when the inflation is pegged back, we hit the discrete barrier of the so-called quantum gravity limit, when space-time curvature is in the order of the uncertainty principle, prior to gravity being formally quantised.

SIEGEL: But things get really interesting if we look back at our idea of "the beginning." Whereas a universe with matter and/or radiation - what we get with the hot Big Bang - can always be extrapolated back to a singularity, an inflationary universe cannot. Due to its exponential nature, even if you run the clock back an infinite amount of time, space will of time, space will only approach infinitesimal sizes and infinite temperatures and densities; it will never reach it. This means, rather than inevitably leading to a singularity, inflation absolutely cannot get you to one by itself. The idea that "the universe began from a singularity, and that's what the Big Bang was," needed to be jettisoned the moment we recognized that an inflationary phase preceded the hot, dense, and matter-and-radiation-filled one we inhabit today. This new picture gives us three important pieces of information about the beginning of the universe that run counter to the traditional story that most of us learned. First, the original notion of the hot Big Bang, where the universe emerged from an infinitely hot, dense, and small singularity - and has been expanding and cooling, full of matter and radiation ever since - is incorrect. The picture is still largely correct, but there's a cutoff to how far back in time we can extrapolate it.

REEVES: Yes, I get the point: Running a positive exponent exponential backwards means that it never reaches that mathematically mysterious singularity.  And yes we may well need to jettison the singularity postulate. I for one regard it as ontologically suspicious and unlikely to be physical.

My Comment: At the big bang, the universe inflated with astounding rapidity, but we don't know what set up the conditions for the big bang. We know about the big, but not exactly what caused the bang, because we don't know everything about what inflated the inflation. What they call cosmic inflation is supposed to have lasted only a trillionth of a second, and is supposed to be an even more rapid event than the big bang itself. And then there is conjecture about what they call a 'reheating' process, where the relatively cooler matter became hot enough to bang and set the universe in motion. Whichever way we cut the cloth, the beginning of the universe required extreme energy, and astounding mathematical complexity in the initial conditions.

Moreover, I think some physicists are being a bit slippery here, talking about what's prior to the big bang here. Considering what short timescales we are dealing with here, in terms of kickstarting the universe, they can for all intents and purposes be treated as two parts of the same event. Furthermore, the singularity or cause of the universe is ultimately theological in nature. Being physical beings, we are locked in physical descriptions of science - and it seems certain that we can only wind the clock back 14 billion years to the very hot & dense big bang, beyond which we stop describing reality using a physics we've been built to understand. This is compounded by the fact that time itself is measured using the physical ticks provided by the material substrate (such as vibrations), and given that gravity modifies these ticks by slowing them to zero, time for us reaches a cul-de-sac at t=0 because there is no up and running physical standard by which it can be measured (the cosmic microwave background provides limited data on this as it only extends back to just after the big bang, and even future sophisticated particle accelerators are unlikely to ever reach the astronomical energies needed to recapitulate the very early universe).

SIEGEL:  Lastly, and perhaps most importantly, we can no longer speak with any sort of knowledge or confidence as to how - or even whether - the universe itself began. By the very nature of inflation, it wipes out any information that came before the final few moments: where it ended and gave rise to our hot Big Bang. Inflation could have gone on for an eternity, it could have been preceded by some other nonsingular phase, or it could have been preceded by a phase that did emerge from a singularity. Until the day comes where we discover how to extract more information from the universe than presently seems possible, we have no choice but to face our ignorance. The Big Bang still happened a very long time ago, but it wasn't the beginning we once supposed it to be.

REEVES: Yes, I can accept Siegel's talk about our ignorance: in fact Siegel himself doesn't comment on two outstanding questions: Viz: What provides the energy for inflation? The nearest he gets to this question is a reference to a the cosmological constant which is another patch-in not greatly different to patching in initial conditions to fix the problems. The other baffling issue is this: As we follow the shrinking exponential of inflation back in time there comes a point where the scales of gravity and quantum theory collide: What happens then?   But quoting Siegel once more we've at least got this to hang onto: The [Big Bang] picture is still largely correct, but there's a cutoff to how far back in time we can extrapolate it. So further extrapolation beyond the hot big bang period is an extrapolation into the dark unknown. Therefore, apart from speculation on all sides, I guess that is how the situation will remain for some time to come. As I said in my last post on Big Bang: People still hanker and yearn after the idea that there was something  before the big bang. But what was it? Was it God or just more  algorithmically compressible bytes and bits?  It might help when the incommensurability of gravitational theory and quantum theory is sorted.

My Comment: As above, I think any notion of before the big bang is so distinctly minuscule that it's ostensibly part of the same physical process - where, what sits outside of it, belongs in the realms of the mathematical algorithms that bootstrap the event, and ultimately thoughts in God's mind. The upshot is, not only do we reach a natural limit with physics, we also have every reason to believe that the physics we have been bestowed is expressed with Intelligence at the heart of its mathematical engine. As mathematics is more primary than physics, then the way we view quantum mechanics is as a form of mathematical information signalling that channels a form of random walk, but in a way in which it imposes a restriction (a mathematical bias, described in this blog post) on the combinatorial search space in which the walk can take place - a bit like putting up barriers in a city so when the drunk man stumbles out of the pub he has restricted pathways that favour a route in which he will eventually find his hotel. As I said in my book on God's Genius:

"This is a truly astonishing element for God to have incorporated into creation. It's so profound that we have to ask: which is real, the practical limit on the physics of the body, or the infinite equations that embed the reality? And here we return to the primacy of mathematics, in that the physical truths are accurate through the physical lens, and the theoretical parts (zeros, infinities, and difficult to interpret negative numbers) tap us into the more complex reality of mathematics that exists over and above the physical universe. This is a mindblowing example of how we dance with the finite and the eternal in one complex embrace. What the above shows is that we are forced to dance with eternity. Here's another one to consider; take the example of gravitational singularities in black holes. Suppose an object was approaching the black hole; the object would be torn apart by tidal forces. As the debris settled into the event horizon, time would pass much more slowly for the stuff than it passes for an outside observer of the stuff. But then the debris would be trapped in a 'forever falling around the hole' situation, never making it into the hole, because time becomes distorted at the event horizon and approaches infinity as a limit (for anything to happen in the event horizon). This propounding shows another clear discontinuity between the theoretical and the actual; terms like 'event horizon' and even 'infinity' or even time coming to a stand still at c cannot really be literally true in a finite spatio-temporal cosmos. They are only useful as theoretical approximations, not as actual facts about physical reality. Although current physics does come up with two infinities in the form of gravitational singularities and in re-normalisation in quantum field theory, this involves the hypothetical subtraction of one infinity from another, so it is only applicable as a concept of ideals rather than as practically useful in dealing with nature. There are no such things as physical infinities. Imagination is not merely a way of transcending reality - the imagined is our ability to dance with a part of reality at an eternal conceptual level, where the real and the imagined lock horns and give us a glimpse of a greater reality outside of spacetime, and of what is to come."