Microwave background: Looking back in time to the Big Bang
Recently somebody asked me for my assessment of Big Bang Theory. I'm no ball of knowledge on Big Bang, but I do have a few notions on the subject that I relate here. That the cosmos has its origins in a hot dense continuum seems a very likely scenario given the state of astronomical observation, but this very general idea can be the front for a huge amount of detail: it seems that those details are far less settled. Anyway, below are my comments on Big Bang that I returned to the inquirer:
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Inflation was an idea that was generated by the need to explain why opposite ends of the universe show the same temperature and density given that without inflation they wouldn't have been in thermal contact at the beginning. Inflation also explained the observation that the universe looks to be flat to a very good approximation.
But Inflation theory is far from confirmed: The source of the energy needed to generate inflation is unknown, although there is some speculative talk about it being "dark energy". There is also the problem of unifying gravity and quantum mechanics which inflationary theory doesn't pretend to solve....as the inflation is wound back one reaches the so called "quantum gravity" limit where space-time curvature is so great that one must take into account the uncertainty principle - what happens here given that gravity hasn't yet been successfully quantized is anybody's guess.
What we are fairly sure about is that to all intents and purposes we can only wind the clock back 13 odd billion years to the very hot & dense big bang before we hit the "unknown physics barrier".
We can of course imagine the graticules of time measurement extending before that, but since time is actually measured using the physical ticks provided by material standards (such as vibrations) then given that as we go back in time gravity modifies these ticks by slowing them to near zero it follows that time just about stops at t=0 simply because there is no physical standard which remains ticking to measure it.
We are very far from understanding the big bang in terms of absolute origins. Hence the actual details on the other side of the big bang are up for the philosophical grabs. Atheists who don't like the idea that the big bang was an absolute beginning can speculate about previous universes or a multiverse of continuous inflationary bubbles or play philosophical word games with the meaning of nothing. Alternatively theists can speculate about it being an absolute beginning; that is the mathematical edge of a grand logical hiatus....this is the point at which our ability to carry out algorithmic compression via the annunciation of general physical equations stops. See the epilogue of my book on randomness where I discuss this:(see footnote)
My money is on this argument running and running because of epistemic distance: There seem to be insurmountable epistemic barriers in the two areas where we can attempt to make observations to test origins theories: Viz: 1) The microwave background yields limited data and only extends back so far. 2) Particle accelerators are unlikely to reach the colossal energies needed to recapitulate the very early universe. Of course there may always be observational & theoretical wild cards out there somewhere, but I'm not banging banking on it!
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?
Endnotes
Contingency and the Grand Logical Hiatus
Endnote 1: (Added 03/10/2021) It ought to be fairly self evident that an ultimate Logical Hiatus in our so-called "explanations" is forever going to be an irreducible feature of our attempts to account for the cosmos. For those explanations find their expression in succinct mathematical laws as algorithmic ways of encoding descriptive information about the ordered dynamic that pervades our world. A hard core of contingency, then, can never be eliminated as the algorithmic nature of these laws means that as a matter of logical inevitability they must start from a set of given mathematically stated conditions. The laws of physics, then, amount to a form of algorithmic compression and as such lead back to an irreducible kernel of enigmatic simplicity. So, if we are looking for an ultimate "explanation" in some deeper sense than mere description, it's not going to be found in the simplicity of physics; more likely in complexity; perhaps the complexity of a Godhead. (See here where I first mooted this idea)
So leaving aside the silly word games with the meaning of "nothing", those who dislike the mystery of an irreducibly particular contingency find that their best shot is to postulate some version of multiverse theory, a theory which in its most extreme form posits the existence of just about every logically possible contingency. This tactic works by attempting to neutralize the mystery of a kernel of particular contingency by eliminating selective contingency (which is in fact what our cosmos, on the face of it, presents us with) by spreading the existential butter over a huge range of possibility. Needless to say, our instincts suggest that behind selective contingency is an intentionality. That there is such a concerted effort to eliminate selective contingency with multiverse notions is a sign that these instincts, even among disbelievers, are alive and well.
Endnote 2: (added 19/10/2021) One of the bugbears with the common concept of "mechanism" is that it is conceived as entirely a matter of local interactions between the parts of the mechanism. Those parts, such as atoms or fundamental particles, have a few relatively simple rules governing their near-neighbor interactions and it is thought that these "mindless" rules are then the source from which all else incidentally and purely fortuitously emerges. It is assumed then that these rules are the fundamental & primary reality of the cosmos and all else is secondary and ephemeral. No further questions are then asked about whether this system of rules, if it supports the development and maintenance of life, must therefore be algorithmically pre-biased. Moreover, it is further assumed that these rules do not include global teleological constraints, constraints which (amounting to action at a distance) would really blow away any semblance of local interaction completeness & primacy. The oft overriding and superficial response to this picture of local mechanical interactions is that it is entirely mindless in that clearly in and of themselves these interactions have no sentient apprehension of what they are doing and therefore any complex development built on them (such as life) is purely accidental and incidental. It is ironic that this superficial response is endemic among the de-facto Intelligent Design community of North America. But then there is this.
OK, the mechanical picture of cosmic development with its purely bottom-up as opposed to top-down vision is at first sight a challenge to an anthropocentric view of the cosmos. But if one starts to push a little harder the wall of that challenge starts to crumble.