Did the Universe Really Start with a ‘Big Bang’ ?

 

A couple of years ago I attempted to answer the question ' Are we alone in the universe'. 

At risk of appearing to be a 'glutton for punishment' I thought it would be useful to follow this up by looking at an even weightier and topical question - 'How did the universe start and how will it end ?'. There is a lot of argument about this currently, with the principal 'Big Bang' theory, until recently taken as gospel by cosmologists, now being challenged in the light of new evidence from the JWST. More evidence suggesting the presence of 'bio-signature' gases in the atmosphere of a nearby exoplanet has also caught the media's attention and promoted discussion about our place in the universe recently.

Read on for a short 'journey into cosmology' to whet your appetite for the arguments to come...

Introduction

The Big Bang theory still remains the favoured explanation for the history of the universe amongst cosmologists. However, in the past few years since data started emerging from the James Webb Space telescope (JWST) in earnest, cracks have started to appear in its support base, and there is even talk of a need for a complete re-think....

As an interested biological scientist with a lifelong interest in things astronomical, I have to confess I’ve always been somewhat skeptical about accepting a theory which effectively proposes a discrete ‘creation event’, without adequately explaining how the vast amounts of matter and energy in the known universe (to say nothing of the bits we think are there but still can’t see!) might have come into existence in the first place.

Let’s take a closer look at the pros and cons….

Principal ‘Pros’

The principal lines of evidence typically quoted in the literature in support of the Big Bang theory are as follows:

·         Red-shift of Galaxies: The light from distant galaxies appears redder than expected, indicating they're all moving away from us. This ‘red-shift’ effect is predicted by the Big Bang theory. It is explained by proposing that space-time itself is expanding rather than just the matter within it (see later for an explanation of why this complication is necessary).

·         Cosmic Microwave Background (CMB): This is a form of faint radiation that is observed in all directions from earth; it's interpreted by Big Bang as being a remnant of the incredibly hot and dense early phase of the universe the theory proposes.

·         Abundance of Light Elements: The observed relative amounts of hydrogen and helium in the universe now closely match what the theory predicts for the early stages of the universe.

 

Principal ‘Cons’

·         Dark Matter: The theory as it stands needs to propose vast amounts of so-called 'dark' matter to explain fully the observed motions and disposition of distant galaxies. We simply haven't directly detected any of it yet.

This doesn’t of course mean that dark matter doesn’t exist, but leaves a definite question mark against the Big Bang argument. Since the dark matter component of the universe would also need to account for at least 80% of the total, we would expect to see some evidence of its existence, even if we can’t actually perceive it directly with our current instrumentation.

·         Universal Constants: Some cosmologists argue that the universal physical constants extrapolated from Big Bang, which we thus assume must apply throughout the universe, do seem suspiciously well-adjusted for life to develop and evolve. The question being asked is effectively why would they be so favourable ?

·         Consistency of Red shifts: Not all objects visible from earth have the same degree of red-shift. Although generally more distant objects tend to have higher red shifts as predicted, this is not universal, and nearer objects in particular are much more variable. Big Bang attempts to explain this by splitting the shift into two components – Cosmological and Doppler. The cosmological component is caused by space-time expansion, whereas Doppler occurs because objects have their own physical motions relative to others (and us). A ‘fundamentalist’ interpretation of  Big Bang would, I suspect, assume that everything was expanding in all directions due to space-time expansion, so red shifts should be much more consistent.  I’ll leave the reader to decide whether this ‘fudge’ is credible.

Other Challenges

Apart from these two key questions, there a few more ‘challenges’ to the theory which I don’t believe have been adequately addressed:

·   How did the most distant galaxies visible via the JWST (ca 13.6Bn light years away from us) get to where they are in the 13.6 Bn years since the Big Bang without actually exceeding the speed of light ? The explanation quoted for this by Big Bang adherents revolves around expansion of the universe itself, rather than true physical motion of galaxies within it. This is a difficult concept for those not familiar with the mathematical basis of the theory understand. AI engines typically try to explain the concept as follows:

“It's space-time itself that is expanding, not the galaxies. Think of it like this: Imagine placing dots on a balloon. As you inflate the balloon, the dots (galaxies) move further apart on the balloon (universe) even though they're staying still relative to the balloon's surface. The expansion of space itself carries these distant galaxies further and further away from us, even though they aren't actually traveling faster than light through space…”

Further explanations expand on it like this:

"..The Big Bang doesn't describe galaxies flying apart through space, but rather space itself stretching and carrying them along. It's the fabric of space-time that's expanding, not the objects within it exceeding the speed of light.

Expansion isn’t from a central point where the original bang occurred, but is occurring in all directions wherever you are in the universe..."

If you accept that space-time can and does expand, this explanation effectively gets round the apparent breach of the universal‘speed limit’ of light.

What it doesn’t explain is how the universe is managing to expand at, or even faster than the speed of light – and in all directions at once, as it would need to have done for us to detect galaxies at 13.6 Bn light years distance now…indeed, the ‘offending’ distant  galaxies may now actually be much farther away from us than this, given that the light we are now seeing left them 13.6 Bn years ago. Unless space-time expansion has slowed down radically in the meantime, they will have been carried a lot further away, assuming expansion has continued everywhere at the same rate since then. (It would seem to have done so, locally at least, going by the continuing red shift of much less distant objects).

Last, but certainly not least, it doesn’t explain why space-time would need to expand at all or how the expansion process actually works. The proposed idea of everything expanding in all directions at once, rather than from the central point where the big bang occurred is a particularly difficult concept to rationalise for the layman, to say the least, and thus stretches credibility even further. (The fact that the word ‘incredibly’ occurs as frequently as it does in most explanations of how the universe started says it all…..)

Could matter ever exist as a super-dense singularity of the type suggested by ‘big bang’ without flying apart long before it did so?

Another key issue is how the vast and unquantifiable amounts of matter and energy (in the form that we know it at least!) could possibly all be squeezed into a single point at the centre of the primeval universe.         

To get round this one, you would have to propose that the current universe started in a form quite different to conventional matter, where the conventional laws of Physics as we understand them simply didn’t apply. As yet, no one has explained how this might have happened. 

Here’s yet another key question, which in my opinion is probably one of the biggest unanswered challenges to Big Bang:

Where did all the matter and energy in the primeval ‘pre-big bang’ universe come from ?

The theory seems to suggest the singularity just 'appeared' from nowhere, and offers no explanation as to how this might have happened. Unless we call upon the theologians for help and propose some form of divine intervention, we're stuck for an explanation, and the theory as it stands 'singularly' fails to offer one (see what I did there ?). Some cosmologists admit that this is a major flaw and are increasingly tending towards a more ‘continuous cycle’ approach. Although matter and energy are interchangeable to some extent (and this needs to be done on earth with great care if you’re trying to convert matter to energy!) neither can be created de novo by any means we're aware of.  This is one of the most difficult conundrums to reconcile with our ‘common sense’ criterion, and is arguably the ‘Achilles heel’ of the theory.

 A related problem is:

How does the theory propose the universe will end ? 

Presumably an ‘end to everything’ would be a necessary part of Big Bang, if nothing else for the sake of symmetry – in the words our hypothetical 'universal creator' might employ, “…I’ve started, so I‘ll finish…”. This is perhaps an even more difficult one to explain…apart from some form of cataclysmic ‘de-creation’ event, the only winding-up option available to the theory as it stands would be continued expansion into an infinitely large space-time ‘vault’ such that its overall density tended towards zero. Even this wouldn’t, of course, be a discrete ‘end’ as such, just an infinitely slow dilution process resulting ultimately in an effectively empty universe.

Final thoughts

As someone who likes to try to find reasonable explanations for ‘life, the universe and everything’ as Douglas Adams so eloquently put it, the Big Bang theory as it stands has too many unanswered questions, and doesn’t really ‘make sense’ overall. I suspect I’m not alone in identifying this problem….

I much prefer an explanation involving a continuous universe, with periodic expansion and contraction built in to its architecture.  This fits better with what seems conceptually reasonable, and avoids the difficult question of where everything came from in the first place. It also bypasses the need for a ridiculously dense and overheated singularity, since the contraction cycles could only occur down to a point where repulsion outweighed attraction, and the whole lot would then simply start expanding again.

It would also explain why we can see objects at 13.6Bn light years distance with the JWST without resorting to 'trekkie'-style warp speed expansion of the whole universe. Since the universe is infinitely old, there has been plenty of time for galaxies to travel that far (and much further) without any need to physically exceed ‘c’.

Neither would we need to propose that space-time itself  has to expand continuously to explain current observations – the present pattern of observable red shifts seen in the spectra of distant objects could be explained in other ways, allowing true relative motions alone to account for this.

Last but not least, the awkward question of the invisible dark matter could be persuaded to go away in a continuous cycle universe. There might simply not be any…..which would explain why we can’t see it.

The only difficulty with an everlasting universe is a conceptual one – as humans we are hard-wired to want to define things as having discrete beginnings and ends, and the idea of ‘for ever’ is a more difficult one to accept when it comes to something as fundamental as our universe.

Interestingly, though, most of the major religious doctrines presented propose a continuous after-life (some with occasional reincarnations along the way) as an explanation of what happens after our physical deaths; many billions in our world happily accept that concept as the basis of their religious faiths. 

Why ? - perhaps it's because it enables the faithful to ‘leave it in God’s hands’ rather than worrying about it themselves. There’s yet another conundrum for you to ponder !....

First published 28.4.24