Two things are infinite: the universe and human stupidity; and I'm not sure about the universe.
- Albert Einstein
So, along time ago, there was this point - somewhere in the void. The point (a blackhole) exploded in what we call the big bang, and from it came all of the observable universe – and of course, in time, you and me.
From what we can see, detect and measure, the initial explosion will continue to spread the stuff that the point originally contained evermore thinly, and push it all farther apart. The universe will continue to expand, until most of the night sky darkens: the stars outside of our own galaxy will ultimately move so far away from us, that no telescope would ever be able to find them. At the same time, and one by one, nearby stars will consume all of their fuel, and darken – and they too will become lost to us.
However, there is another possibility. Because of gravity (everything attracts everything else), the current expansion will ultimately slow down, stop, and then reverse in direction – the matter in the universe will begin to coalesce, and eventually contract to a single point – and, who knows, maybe that single point will decide to explode (again) - and the whole process will repeat. If this is so, who knows what repeat - or 'cycle' - we might actually be living through at this moment – is this cycle 1, cycle 1,000,000 or cycle impossible-to-comprehend-really-big-number?
However, there's a problem with this second scenario - from our calculations to date, there's just not enough matter about the place to counter the momentum inflicted upon the observable mass by the big bang. However, nature seems to operate very elegantly, and, judging by some of her laws, she also always seems to choose simplicity over complexity. So, what is the most likely scenario – that the universe expands and/or fades to death, or that the universe should continually oscillate in this way? Of course, each can be argued for (or against) – but it seems to me that the latter is the only scenario that shows any form of elegance!
Of course, there are many other possibilities. Maybe our calculations are simply wrong, or maybe the law of gravity is not the same throughout the universe, or maybe it changes over time. The latter is of course something we'll never know unless we visit – um – everywhere - and measure it! Alternatively, the missing matter might not be observable - in any sense that we are able to define such a term - for example, maybe it's in another dimension – a part of the same (but related) void that our senses will never be able perceive?
If the universe does cycle – imagine what the big bang would look like – wouldn't it be something to behold – indeed, could one witness it (and would there be a restaurant there to observe it from)?
Of course, nature, being a tricky mistress, she'll have a twist up her sleeve somewhere.
Imagine that the universe does contract, and that quite sometime before the cycle completes, a sufficiently advanced civilisation sees it coming, and decides to preserve itself, i.e., it doesn't relish the idea of being crushed out of existence. So, being sufficiently advanced, they capture a few uninhabited planets, and move them – and themselves – well clear of the point where the blackhole will ultimately form, and they use their captured planets' mass as fuel – turning it into energy as they require to hold their position.
On the assumption that the next big bang will happen pretty soon after all the matter they don't control collapses into the point, they have of course worked out how much mass they'll need for this necessary station-keeping. Indeed, they have calculated that they have enough energy (and thus time) to watch the new cycle evolve in detail – they will see new suns form, and new galaxies born.
However, and to their surprise, after they witness the blackhole form, it doesn't explode – and they begin to wonder why – and to worry about it. But, then it comes to them. The amount of matter (or, if you prefer, energy or mass) required to kick-start the next cycle is exact! It is exactly the same amount of stuff that was present the last time around, and, as such, it must also include them!
Time passes, and they wait - ever hopeful. However, one day their fuel too runs out, and from that moment on, their fate is sealed. They are now at the mercy of gravity's influence on their precious mass - and they are no longer able to keep themselves at a safe distance.
As they eventually begin to fall in, and to slide down the side of the well, I wonder if they'll hear nature chuckling to herself?