The Big Bang Theory – Part II

After reading a paper by Ashtekar on quantum gravity and thinking about it, I realized what my trouble with the Big Bang theory was. It is more on the fundamental assumptions than the details. I thought I would summarize my thoughts here, more for my own benefit than anybody else’s.

Classical theories (including SR and QM) treat space as continuous nothingness; hence the term space-time continuum. In this view, objects exist in continuous space and interact with each other in continuous time.

Although this notion of space time continuum is intuitively appealing, it is, at best, incomplete. Consider, for instance, a spinning body in empty space. It is expected to experience centrifugal force. Now imagine that the body is stationary and the whole space is rotating around it. Will it experience any centrifugal force?

It is hard to see why there would be any centrifugal force if space is empty nothingness.

GR introduced a paradigm shift by encoding gravity into space-time thereby making it dynamic in nature, rather than empty nothingness. Thus, mass gets enmeshed in space (and time), space becomes synonymous with the universe, and the spinning body question becomes easy to answer. Yes, it will experience centrifugal force if it is the universe that is rotating around it because it is equivalent to the body spinning. And, no, it won’t, if it is in just empty space. But “empty space” doesn’t exist. In the absence of mass, there is no space-time geometry.

So, naturally, before the Big Bang (if there was one), there couldn’t be any space, nor indeed could there be any “before.” Note, however, that the Ashtekar paper doesn’t clearly state why there had to be a big bang. The closest it gets is that the necessity of BB arises from the encoding of gravity in space-time in GR. Despite this encoding of gravity and thereby rendering space-time dynamic, GR still treats space-time as a smooth continuum — a flaw, according to Ashtekar, that QG will rectify.

Now, if we accept that the universe started out with a big bang (and from a small region), we have to account for quantum effects. Space-time has to be quantized and the only right way to do it would be through quantum gravity. Through QG, we expect to avoid the Big Bang singularity of GR, the same way QM solved the unbounded ground state energy problem in the hydrogen atom.

What I described above is what I understand to be the physical arguments behind modern cosmology. The rest is a mathematical edifice built on top of this physical (or indeed philosophical) foundation. If you have no strong views on the philosophical foundation (or if your views are consistent with it), you can accept BB with no difficulty. Unfortunately, I do have differing views.

My views revolve around the following questions.

These posts may sound like useless philosophical musings, but I do have some concrete (and in my opinion, important) results, listed below.

There is much more work to be done on this front. But for the next couple of years, with my new book contract and pressures from my quant career, I will not have enough time to study GR and cosmology with the seriousness they deserve. I hope to get back to them once the current phase of spreading myself too thin passes.


2 thoughts on “The Big Bang Theory – Part II”

  1. It’s quite rewarding when someone with a solid grounding in science introduces the same problem as a laymen like myself has always had with the Big Bang theory.
    i.e. that space is not really part of the equation in the pre-BB ‘universe.’

    The other issue I’ve had is also connected to the points you have raised.
    i.e. if time didn’t exist pre-BB, yet time is required for any chemical reaction then how did the BB actually take place given that there can’t be any preparatory events leading to the reaction that caused the BB. In fact if time didn’t exist then the BB can’t be said to have even taken place (as there was no time)

    I know it’s probably amusing to hear a laymen pondering these two elements, having no solid grounding in science, but I’d love to hear your thoughts on this further

    1. Thanks for your comment, Trent.

      Although I have some background in physics, I am pretty much a beginner when it comes to BB cosmology.

      I think where people like you and me have trouble is when physicists treat their theories as “real,” or when we think they do. I guess the smarter ones do not think of their theories as anything more than mathematical models. I remember reading Feynman once describe an electron as possibly a mathematical concept — after having developed QED! Similarly, BB is perhaps only a framework that seems to hold a few observed properties together in neat equations.

      I still have problems with the assumptions at its foundation though. Space and time, in my view, are a cognitive representation of our senses. Saying that they started from a singularity (or small region) is as silly as saying that sound and smell started from a small region! IMHO…

      – cheers,
      – Manoj

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